An organic light-emitting diode (OLED or organic LED), also known as organic electroluminescent (organic EL) diode, is a
light-emitting diode
A light-emitting diode (LED) is a semiconductor device that emits light when current flows through it. Electrons in the semiconductor recombine with electron holes, releasing energy in the form of photons. The color of the light (cor ...
(LED) in which the
emissive electroluminescent
Electroluminescence (EL) is an optical and electrical phenomenon, in which a material emits light in response to the passage of an electric current or to a strong electric field. This is distinct from black body light emission resulting from h ...
layer is a film of
organic compound
In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. The ...
that emits light in response to an electric current. This organic layer is situated between two
electrode
An electrode is an electrical conductor used to make contact with a nonmetallic part of a circuit (e.g. a semiconductor, an electrolyte, a vacuum or air). Electrodes are essential parts of batteries that can consist of a variety of materials de ...
s; typically, at least one of these electrodes is transparent. OLEDs are used to create
digital display
A display device is an output device for presentation of information in visual or tactile form (the latter used for example in tactile electronic displays for blind people). When the input information that is supplied has an electrical signal the ...
s in devices such as
television
Television, sometimes shortened to TV, is a telecommunication medium for transmitting moving images and sound. The term can refer to a television set, or the medium of television transmission. Television is a mass medium for advertisin ...
screens,
computer monitor
A computer monitor is an output device that displays information in pictorial or textual form. A discrete monitor comprises a visual display, support electronics, power supply, housing, electrical connectors, and external user controls.
The di ...
s, and portable systems such as
smartphone
A smartphone is a portable computer device that combines mobile telephone and computing functions into one unit. They are distinguished from feature phones by their stronger hardware capabilities and extensive mobile operating systems, whic ...
s and
handheld game console
A handheld game console, or simply handheld console, is a small, portable self-contained video game console with a built-in screen, game controls and speakers. Handheld game consoles are smaller than home video game consoles and contain the cons ...
s. A major area of research is the development of white OLED devices for use in
solid-state lighting
Solid-state lighting (SSL) is a type of lighting that uses semiconductor light-emitting diodes (LEDs), organic light-emitting diodes (OLED), or polymer light-emitting diodes (PLED) as sources of illumination rather than electrical filaments, pla ...
applications.
There are two main families of OLED: those based on small molecules and those employing
polymer
A polymer (; Greek '' poly-'', "many" + ''-mer'', "part")
is a substance or material consisting of very large molecules called macromolecules, composed of many repeating subunits. Due to their broad spectrum of properties, both synthetic a ...
s. Adding mobile
ion
An ion () is an atom or molecule with a net electrical charge.
The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by conven ...
s to an OLED creates a
light-emitting electrochemical cell A light-emitting electrochemical cell (LEC or LEEC) is a solid-state device that generates light from an electric current (electroluminescence). LECs are usually composed of two metal electrodes connected by (e.g. sandwiching) an organic semiconduc ...
(LEC) which has a slightly different mode of operation. An OLED display can be driven with a
passive-matrix (PMOLED) or
active-matrix Active matrix is a type of addressing scheme used in flat panel displays. In this method of switching individual elements (pixels), each pixel is attached to a transistor and capacitor ''actively'' maintaining the pixel state while other pixels are ...
(
AMOLED
AMOLED (active-matrix organic light-emitting diode, ) is a type of OLED display device technology. OLED describes a specific type of thin-film-display technology in which organic compounds form the electroluminescence, electroluminescent materia ...
) control scheme. In the PMOLED scheme, each row and line in the display is controlled sequentially, one by one, whereas AMOLED control uses a
thin-film transistor
A thin-film transistor (TFT) is a special type of field-effect transistor (FET) where the transistor is thin relative to the plane of the device. TFTs are grown on a supporting (but non-conducting) substrate. A common substrate is glass, becaus ...
(TFT) backplane to directly access and switch each individual pixel on or off, allowing for higher resolution and larger display sizes.
OLED is fundamentally different from
LED
A light-emitting diode (LED) is a semiconductor Electronics, device that Light#Light sources, emits light when Electric current, current flows through it. Electrons in the semiconductor recombine with electron holes, releasing energy i ...
which is based on a
p-n diode structure. In LEDs
doping is used to create p- and n- regions by changing the conductivity of the host
semiconductor
A semiconductor is a material which has an electrical resistivity and conductivity, electrical conductivity value falling between that of a electrical conductor, conductor, such as copper, and an insulator (electricity), insulator, such as glas ...
. OLEDs do not employ a p-n structure. Doping of OLEDs is used to increase radiative efficiency by direct modification of the quantum-mechanical optical recombination rate. Doping is additionally used to determine the
wavelength
In physics, the wavelength is the spatial period of a periodic wave—the distance over which the wave's shape repeats.
It is the distance between consecutive corresponding points of the same phase on the wave, such as two adjacent crests, tro ...
of photon emission.
An OLED display works without a
backlight
A backlight is a form of illumination used in liquid crystal displays (LCDs). As LCDs do not produce light by themselves—unlike, for example, cathode ray tube (CRT), plasma (PDP) or OLED displays—they need illumination ( ambient light or a ...
because it emits its own
visible light
Light or visible light is electromagnetic radiation that can be perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 nanometres (nm), corresponding to frequencies of 750–420 te ...
. Thus, it can display deep
black level
Video black level is defined as the level of brightness at the darkest (black) part of a visual image or the level of brightness at which no light is emitted from a screen, resulting in a pure black screen.
Video displays generally need to be cal ...
s and can be thinner and lighter than a
liquid crystal display
A liquid-crystal display (LCD) is a flat panel display, flat-panel display or other Electro-optic modulator, electronically modulated optical device that uses the light-modulating properties of liquid crystals combined with polarizers. Liqui ...
(LCD). In low
ambient light conditions (such as a dark room), an OLED screen can achieve a higher
contrast ratio
The contrast ratio (CR) is a property of a display system, defined as the ratio of the luminance of the brightest shade (white) to that of the darkest shade (black) that the system is capable of producing. A high contrast ratio is a desired aspec ...
than an LCD, regardless of whether the LCD uses
cold cathode fluorescent lamps or an
LED backlight
A backlight is a form of illumination used in liquid crystal displays (LCDs). As LCDs do not produce light by themselves—unlike, for example, cathode ray tube (CRT), plasma (PDP) or OLED displays—they need illumination ( ambient light or a sp ...
. OLED displays are made in the same way as LCDs, but after TFT (for active matrix displays), addressable grid (for passive matrix displays) or indium-tin oxide (
ITO
Ito may refer to:
Places
* Ito Island, an island of Milne Bay Province, Papua New Guinea
* Ito Airport, an airport in the Democratic Republic of the Congo
* Ito District, Wakayama, a district located in Wakayama Prefecture, Japan
* Itō, Shizuo ...
) segment (for segment displays) formation, the display is coated with hole injection, transport and blocking layers, as well with electroluminescent material after the first 2 layers, after which ITO or metal may be applied again as a
cathode
A cathode is the electrode from which a conventional current leaves a polarized electrical device. This definition can be recalled by using the mnemonic ''CCD'' for ''Cathode Current Departs''. A conventional current describes the direction in whi ...
and later the entire stack of materials is encapsulated. The TFT layer, addressable grid or ITO segments serve as or are connected to the
anode
An anode is an electrode of a polarized electrical device through which conventional current enters the device. This contrasts with a cathode, an electrode of the device through which conventional current leaves the device. A common mnemonic is ...
, which may be made of ITO or metal. OLEDs can be made flexible and transparent, with
transparent display
A see-through display or ''transparent display'' is an electronic display that allows the user to see what is shown on the screen while still being able to see through it. The main applications of this type of display are in head-up displays, augme ...
s being used in smartphones with optical fingerprint scanners and
flexible display
A flexible display or rollable display is an electronic visual display which is flexible in nature, as opposed to the traditional flat screen displays used in most electronic devices. In recent years there has been a growing interest from nume ...
s being used in
foldable smartphone
A foldable smartphone (also known as a foldable phone or simply foldable) is a smartphone with a folding form factor. Some variants of the concept use multiple touchscreen panels on a hinge, while other designs utilise a flexible display. Conce ...
s.
History
André Bernanose
André Bernanose (17 June 1912 – 18 March 2002) was a 20th-century French physicist, chemist and pharmacologist.
He studied chemiluminescence during the late 1940s - early 1950s, which led him to discover the electroluminescence. He is for thi ...
and co-workers at the
Nancy-Université
Nancy-Université federated the three principal institutes of higher education of Nancy, France, Nancy, in Lorraine (region), Lorraine, France before their merger into the University of Lorraine:
* Henri Poincaré University (UHP, also known as ...
in France made the first observations of
electroluminescence
Electroluminescence (EL) is an optical phenomenon, optical and electrical phenomenon, in which a material emits light in response to the passage of an electric current or to a strong electric field. This is distinct from black body light emissi ...
in organic materials in the early 1950s. They applied high alternating
voltage
Voltage, also known as electric pressure, electric tension, or (electric) potential difference, is the difference in electric potential between two points. In a static electric field, it corresponds to the work needed per unit of charge to m ...
s in air to materials such as
acridine orange
Acridine orange is an organic compound that serves as a nucleic acid-selective fluorescent dye with cationic properties useful for cell cycle determination. Acridine orange is cell-permeable, which allows the dye to interact with DNA by intercala ...
dye, either deposited on or dissolved in
cellulose
Cellulose is an organic compound with the formula , a polysaccharide consisting of a linear chain of several hundred to many thousands of β(1→4) linked D-glucose units. Cellulose is an important structural component of the primary cell wall ...
or
cellophane
Cellophane is a thin, transparent sheet made of regenerated cellulose. Its low permeability to air, oils, greases, bacteria, and liquid water makes it useful for food packaging. Cellophane is highly permeable to water vapour, but may be coated w ...
thin film
A thin film is a layer of material ranging from fractions of a nanometer (monolayer) to several micrometers in thickness. The controlled synthesis of materials as thin films (a process referred to as deposition) is a fundamental step in many ap ...
s. The proposed mechanism was either direct excitation of the dye molecules or
excitation of electrons.
In 1960,
Martin Pope
Martin Pope (born Isidore Poppick; August 22, 1918March 27, 2022) was an American physical chemist and professor at New York University.
His discoveries of ohmic contacts and research in the fields of organic insulators and semiconductors led ...
and some of his co-workers at
New York University
New York University (NYU) is a private research university in New York City. Chartered in 1831 by the New York State Legislature, NYU was founded by a group of New Yorkers led by then-Secretary of the Treasury Albert Gallatin.
In 1832, the ...
developed
ohmic dark-injecting electrode contacts to organic crystals. They further described the necessary energetic requirements (
work function
In solid-state physics, the work function (sometimes spelt workfunction) is the minimum thermodynamic work (i.e., energy) needed to remove an electron from a solid to a point in the vacuum immediately outside the solid surface. Here "immediately" m ...
s) for hole and electron injecting electrode contacts. These contacts are the basis of charge injection in all modern OLED devices. Pope's group also first observed direct current (DC) electroluminescence under vacuum on a single pure crystal of
anthracene
Anthracene is a solid polycyclic aromatic hydrocarbon (PAH) of formula C14H10, consisting of three fused benzene rings. It is a component of coal tar. Anthracene is used in the Economic production, production of the red dye alizarin and other dyes ...
and on anthracene crystals doped with
tetracene
Tetracene, also called naphthacene, is a polycyclic aromatic hydrocarbon. It has the appearance of a pale orange powder. Tetracene is the four-ringed member of the series of acenes.
Tetracene is a molecular organic semiconductor, used in organic ...
in 1963 using a small area silver electrode at 400
volt
The volt (symbol: V) is the unit of electric potential, electric potential difference (voltage), and electromotive force in the International System of Units (SI). It is named after the Italian physicist Alessandro Volta (1745–1827).
Defi ...
s. The proposed mechanism was field-accelerated electron excitation of molecular fluorescence.
Pope's group reported in 1965 that in the absence of an external electric field, the electroluminescence in anthracene crystals is caused by the recombination of a thermalized electron and hole, and that the conducting level of anthracene is higher in energy than the
exciton
An exciton is a bound state of an electron and an electron hole which are attracted to each other by the electrostatic Coulomb force. It is an electrically neutral quasiparticle that exists in insulators, semiconductors and some liquids. The ...
energy level. Also in 1965,
Wolfgang Helfrich
Wolfgang Helfrich (born 25 March 1932) is a German physicist and inventor recognized for his contributions to twisted-nematic liquid crystal technology, which is used to produce a variety of modern LCD electronic displays.
Career
Helfrich s ...
and W. G. Schneider of the
National Research Council National Research Council may refer to:
* National Research Council (Canada), sponsoring research and development
* National Research Council (Italy), scientific and technological research, Rome
* National Research Council (United States), part of ...
in Canada produced double injection recombination electroluminescence for the first time in an anthracene single crystal using hole and electron injecting electrodes, the forerunner of modern double-injection devices. In the same year,
Dow Chemical
The Dow Chemical Company, officially Dow Inc., is an American multinational chemical corporation headquartered in Midland, Michigan, United States. The company is among the three largest chemical producers in the world.
Dow manufactures plastics ...
researchers patented a method of preparing electroluminescent cells using high-voltage (500–1500 V) AC-driven (100–3000Hz) electrically insulated one millimetre thin layers of a melted phosphor consisting of ground anthracene powder, tetracene, and
graphite
Graphite () is a crystalline form of the element carbon. It consists of stacked layers of graphene. Graphite occurs naturally and is the most stable form of carbon under standard conditions. Synthetic and natural graphite are consumed on large ...
powder. Their proposed mechanism involved electronic excitation at the contacts between the graphite particles and the anthracene molecules.
The first Polymer LED (PLED) to be created was by Roger Partridge at the
National Physical Laboratory in the United Kingdom. It used a film of poly(
N-vinylcarbazole) up to 2.2 micrometers thick located between two charge-injecting electrodes. The light generated was readily visible in normal lighting conditions though the polymer used had 2 limitations; low conductivity and the difficulty of injecting electrons. Later development of conjugated polymers would allow others to largely eliminate these problems. His contribution has often been overlooked due to the secrecy NPL imposed on the project. When it was patented in 1974 it was given a deliberately obscure "catch all" name while the government's Department for Industry tried and failed to find industrial collaborators to fund further development. As a result publication was delayed until 1983.
Practical OLEDs
Chemists
Ching Wan Tang
Ching Wan Tang (; born July 23, 1947) is a Hong Kong–American physical chemist. He was inducted into the National Inventors Hall of Fame in 2018 for inventing OLED (together with Steven Van Slyke), and was awarded the 2011 Wolf Prize in Chemi ...
and
Steven Van Slyke
Steven Van Slyke (born July 19, 1956) is an American chemist, best known for his co-invention of the Organic Light Emitting Diode (OLED) and his contributions to the commercial development of OLED displays. Van Slyke is currently the Chief Techn ...
at
Eastman Kodak
The Eastman Kodak Company (referred to simply as Kodak ) is an American public company that produces various products related to its historic basis in analogue photography. The company is headquartered in Rochester, New York, and is incorpor ...
built the first practical OLED device in 1987.
[ This device used a two-layer structure with separate hole transporting and electron transporting layers such that recombination and light emission occurred in the middle of the organic layer; this resulted in a reduction in operating voltage and improvements in efficiency.
Research into polymer electroluminescence culminated in 1990, with J. H. Burroughes ''et al.'' at the ]Cavendish Laboratory
The Cavendish Laboratory is the Department of Physics at the University of Cambridge, and is part of the School of Physical Sciences. The laboratory was opened in 1874 on the New Museums Site as a laboratory for experimental physics and is named ...
at Cambridge University
, mottoeng = Literal: From here, light and sacred draughts.
Non literal: From this place, we gain enlightenment and precious knowledge.
, established =
, other_name = The Chancellor, Masters and Schola ...
, UK, reporting a high-efficiency green light-emitting polymer-based device using 100nm thick films of poly(p-phenylene vinylene)
Poly(''p''-phenylene vinylene) (PPV, or polyphenylene vinylene) is a conducting polymer of the rigid-rod polymer family. PPV is the only polymer of this type that can be processed into a highly ordered crystalline thin film. PPV and its derivat ...
. Moving from molecular to macromolecular materials solved the problems previously encountered with the long-term stability of the organic films and enabled high-quality films to be easily made. Subsequent research developed multilayer polymers and the new field of plastic electronics
Organic electronics is a field of materials science concerning the design, synthesis, characterization, and application of organic molecules or polymers that show desirable electronic properties such as conductivity. Unlike conventional inorga ...
and OLED research and device production grew rapidly. White OLEDs, pioneered by J. Kido ''et al.'' at Yamagata University
is a national university located in the Japanese cities of Yamagata, Yonezawa, and Tsuruoka in Yamagata Prefecture.
The Times Higher Education released World University Rankings 2016–2017. Yamagata University ranked 600-800th out of the top ...
, Japan in 1995, achieved the commercialization of OLED-backlit displays and lighting.
In 1999, Kodak and Sanyo
, stylized as SANYO, is a Japanese electronics company and formerly a member of the Fortune Global 500, ''Fortune'' Global 500 whose headquarters was located in Moriguchi, Osaka, Moriguchi, Osaka prefecture, Japan. Sanyo had over 230 subsidiari ...
had entered into a partnership to jointly research, develop, and produce OLED displays. They announced the world's first 2.4-inch active-matrix, full-color OLED display in September the same year. In September 2002, they presented a prototype of 15-inch HDTV format display based on white OLEDs with color filters at the CEATEC Japan.
Manufacturing of small molecule OLEDs was started in 1997 by Pioneer Corporation
commonly referred to as Pioneer, is a Japanese multinational corporation based in Tokyo, that specializes in digital entertainment products. The company was founded by Nozomu Matsumoto in January 1, 1938 in Tokyo as a radio and speaker repair s ...
, followed by TDK
is a Japanese multinational electronics corporation that manufactures electronic components and recording and data-storage media. Its motto is "Contribute to culture and industry through creativity".
"TDK" is an initialism of the original Ja ...
in 2001 and Samsung
The Samsung Group (or simply Samsung) ( ko, 삼성 ) is a South Korean multinational manufacturing conglomerate headquartered in Samsung Town, Seoul, South Korea. It comprises numerous affiliated businesses, most of them united under the ...
-NEC
is a Japanese multinational corporation, multinational information technology and electronics corporation, headquartered in Minato, Tokyo. The company was known as the Nippon Electric Company, Limited, before rebranding in 1983 as NEC. It prov ...
Mobile Display (SNMD), which later became one of the world's largest OLED display manufacturers - Samsung Display, in 2002.
The Sony XEL-1
The XEL-1 is the world's first organic light-emitting diode (OLED) television, designed by Sony in 2007 and produced for sale the following year. It was also the world's thinnest television during its production, at 3 mm. It has a screen siz ...
, released in 2007, was the first OLED television. Universal Display Corporation
Universal Display Corporation is a developer and manufacturer of organic light emitting diodes (OLED) technologies and materials as well as provider of services to the display and lighting industries. It is also an OLED research company. Founded ...
, one of the OLED materials companies, holds a number of patents concerning the commercialization of OLEDs that are used by major OLED manufacturers around the world.
On 5 December 2017, JOLED
is a Japanese display technology company headquartered in Tokyo, Japan, incorporated in 2015 as the result of a consolidation of the OLED business units of Panasonic and Sony. Notable for pioneering an inkjet printing process for coating emissi ...
, the successor of Sony
, commonly stylized as SONY, is a Japanese multinational conglomerate corporation headquartered in Minato, Tokyo, Japan. As a major technology company, it operates as one of the world's largest manufacturers of consumer and professional ...
and Panasonic
formerly between 1935 and 2008 and the first incarnation of between 2008 and 2022, is a major Japanese multinational corporation, multinational Conglomerate (company), conglomerate corporation, headquartered in Kadoma, Osaka, Kadoma, Osaka P ...
's printable OLED business units, began the world's first commercial shipment of inkjet-printed OLED panels.
Working principle
A typical OLED is composed of a layer of organic materials situated between two electrodes, the anode
An anode is an electrode of a polarized electrical device through which conventional current enters the device. This contrasts with a cathode, an electrode of the device through which conventional current leaves the device. A common mnemonic is ...
and cathode
A cathode is the electrode from which a conventional current leaves a polarized electrical device. This definition can be recalled by using the mnemonic ''CCD'' for ''Cathode Current Departs''. A conventional current describes the direction in whi ...
, all deposited on a substrate. The organic molecules are electrically conductive as a result of delocalization
In chemistry, delocalized electrons are electrons in a molecule, ion or solid metal that are not associated with a single atom or a covalent bond.IUPAC Gold Boo''delocalization''/ref>
The term delocalization is general and can have slightly diff ...
of pi electrons
In chemistry, pi bonds (π bonds) are covalent chemical bonds, in each of which two lobes of an orbital on one atom overlap with two lobes of an orbital on another atom, and in which this overlap occurs laterally. Each of these atomic orbitals ...
caused by conjugation
Conjugation or conjugate may refer to:
Linguistics
* Grammatical conjugation, the modification of a verb from its basic form
* Emotive conjugation or Russell's conjugation, the use of loaded language
Mathematics
* Complex conjugation, the chang ...
over part or all of the molecule. These materials have conductivity levels ranging from insulators to conductors, and are therefore considered organic semiconductor
Organic semiconductors are solids whose building blocks are pi-bonded molecules or polymers made up by carbon and hydrogen atoms and – at times – heteroatoms such as nitrogen, sulfur and oxygen. They exist in the form of molecular crystals or ...
s. The highest occupied and lowest unoccupied molecular orbitals (HOMO and LUMO
In chemistry, HOMO and LUMO are types of molecular orbitals. The acronyms stand for ''highest occupied molecular orbital'' and ''lowest unoccupied molecular orbital'', respectively. HOMO and LUMO are sometimes collectively called the ''frontie ...
) of organic semiconductors are analogous to the valence and conduction
Conductor or conduction may refer to:
Music
* Conductor (music), a person who leads a musical ensemble, such as an orchestra.
* Conductor (album), ''Conductor'' (album), an album by indie rock band The Comas
* Conduction, a type of structured f ...
bands of inorganic semiconductors.[Kho, Mu-Jeong, Javed, T., Mark, R., Maier, E., and David, C. (2008) ''Final Report: OLED Solid State Lighting – Kodak European Research,'' MOTI (Management of Technology and Innovation) Project, Judge Business School of the University of Cambridge and Kodak European Research, Final Report presented on 4 March 2008, at Kodak European Research at Cambridge Science Park, Cambridge, UK., pp. 1–12]
Originally, the most basic polymer OLEDs consisted of a single organic layer. One example was the first light-emitting device synthesised by J. H. Burroughes ''et al.'', which involved a single layer of poly(p-phenylene vinylene)
Poly(''p''-phenylene vinylene) (PPV, or polyphenylene vinylene) is a conducting polymer of the rigid-rod polymer family. PPV is the only polymer of this type that can be processed into a highly ordered crystalline thin film. PPV and its derivat ...
. However multilayer OLEDs can be fabricated with two or more layers in order to improve device efficiency. As well as conductive properties, different materials may be chosen to aid charge injection at electrodes by providing a more gradual electronic profile, or block a charge from reaching the opposite electrode and being wasted. Many modern OLEDs incorporate a simple bilayer structure, consisting of a conductive layer and an emissive layer. Developments in OLED architecture in 2011 improved quantum efficiency
The term quantum efficiency (QE) may apply to incident photon to converted electron (IPCE) ratio of a photosensitive device, or it may refer to the TMR effect of a Magnetic Tunnel Junction.
This article deals with the term as a measurement of ...
(up to 19%) by using a graded heterojunction. In the graded heterojunction architecture, the composition of hole and electron-transport materials varies continuously within the emissive layer with a dopant emitter. The graded heterojunction architecture combines the benefits of both conventional architectures by improving charge injection while simultaneously balancing charge transport within the emissive region.
During operation, a voltage is applied across the OLED such that the anode is positive with respect to the cathode. Anodes are picked based upon the quality of their optical transparency, electrical conductivity, and chemical stability. A current of electron
The electron ( or ) is a subatomic particle with a negative one elementary electric charge. Electrons belong to the first generation of the lepton particle family,
and are generally thought to be elementary particles because they have no kn ...
s flows through the device from cathode to anode, as electrons are injected into the LUMO of the organic layer at the cathode and withdrawn from the HOMO at the anode. This latter process may also be described as the injection of electron hole
In physics, chemistry, and electronic engineering, an electron hole (often simply called a hole) is a quasiparticle which is the lack of an electron at a position where one could exist in an atom or atomic lattice. Since in a normal atom or ...
s into the HOMO. Electrostatic forces bring the electrons and the holes towards each other and they recombine forming an exciton
An exciton is a bound state of an electron and an electron hole which are attracted to each other by the electrostatic Coulomb force. It is an electrically neutral quasiparticle that exists in insulators, semiconductors and some liquids. The ...
, a bound state of the electron and hole. This happens closer to the electron-transport layer part of the emissive layer, because in organic semiconductors holes are generally more mobile
Mobile may refer to:
Places
* Mobile, Alabama, a U.S. port city
* Mobile County, Alabama
* Mobile, Arizona, a small town near Phoenix, U.S.
* Mobile, Newfoundland and Labrador
Arts, entertainment, and media Music Groups and labels
* Mobile ( ...
than electrons. The decay of this excited state results in a relaxation of the energy levels of the electron, accompanied by emission of radiation
In physics, radiation is the emission or transmission of energy in the form of waves or particles through space or through a material medium. This includes:
* ''electromagnetic radiation'', such as radio waves, microwaves, infrared, visi ...
whose frequency
Frequency is the number of occurrences of a repeating event per unit of time. It is also occasionally referred to as ''temporal frequency'' for clarity, and is distinct from ''angular frequency''. Frequency is measured in hertz (Hz) which is eq ...
is in the visible region
The visible spectrum is the portion of the electromagnetic spectrum that is visible to the human eye. Electromagnetic radiation in this range of wavelengths is called ''visible light'' or simply light. A typical human eye will respond to wav ...
. The frequency of this radiation depends on the band gap
In solid-state physics, a band gap, also called an energy gap, is an energy range in a solid where no electronic states can exist. In graphs of the electronic band structure of solids, the band gap generally refers to the energy difference (in ...
of the material, in this case the difference in energy between the HOMO and LUMO.
As electrons and holes are fermion
In particle physics, a fermion is a particle that follows Fermi–Dirac statistics. Generally, it has a half-odd-integer spin: spin , spin , etc. In addition, these particles obey the Pauli exclusion principle. Fermions include all quarks an ...
s with half integer spin
Spin or spinning most often refers to:
* Spinning (textiles), the creation of yarn or thread by twisting fibers together, traditionally by hand spinning
* Spin, the rotation of an object around a central axis
* Spin (propaganda), an intentionally b ...
, an exciton may either be in a singlet state
In quantum mechanics, a singlet state usually refers to a system in which all electrons are paired. The term 'singlet' originally meant a linked set of particles whose net angular momentum is zero, that is, whose overall spin quantum number s=0. A ...
or a triplet state
In quantum mechanics, a triplet is a quantum state of a system with a spin of quantum number =1, such that there are three allowed values of the spin component, = −1, 0, and +1.
Spin, in the context of quantum mechanics, is not a mechanical ...
depending on how the spins of the electron and hole have been combined. Statistically three triplet excitons will be formed for each singlet exciton. Decay from triplet states (phosphorescence
Phosphorescence is a type of photoluminescence related to fluorescence. When exposed to light (radiation) of a shorter wavelength, a phosphorescent substance will glow, absorbing the light and reemitting it at a longer wavelength. Unlike fluo ...
) is spin forbidden, increasing the timescale of the transition and limiting the internal efficiency of fluorescent devices. Phosphorescent organic light-emitting diode Phosphorescent organic light-emitting diodes (PHOLED) are a type of organic light-emitting diode (OLED) that use the principle of phosphorescence to obtain higher internal efficiencies than fluorescent OLEDs. This technology is currently under deve ...
s make use of spin–orbit interaction
In quantum physics, the spin–orbit interaction (also called spin–orbit effect or spin–orbit coupling) is a relativistic interaction of a particle's spin with its motion inside a potential. A key example of this phenomenon is the spin–orbi ...
s to facilitate intersystem crossing Intersystem crossing (ISC) is an isoenergetic radiationless process involving a transition between the two electronic states with different spin multiplicity.
Excited Singlet and Triplet States
When an electron in a molecule with a singlet ground ...
between singlet and triplet states, thus obtaining emission from both singlet and triplet states and improving the internal efficiency.
Indium tin oxide Indium tin oxide (ITO) is a ternary composition of indium, tin and oxygen in varying proportions. Depending on the oxygen content, it can be described as either a ceramic or an alloy. Indium tin oxide is typically encountered as an oxygen-saturated ...
(ITO) is commonly used as the anode material. It is transparent to visible light and has a high work function
In solid-state physics, the work function (sometimes spelt workfunction) is the minimum thermodynamic work (i.e., energy) needed to remove an electron from a solid to a point in the vacuum immediately outside the solid surface. Here "immediately" m ...
which promotes injection of holes into the HOMO level of the organic layer. A second conductive (injection) layer is typically added, which may consist of PEDOT:PSS, as the HOMO level of this material generally lies between the work function of ITO and the HOMO of other commonly used polymers, reducing the energy barriers for hole injection. Metals such as barium
Barium is a chemical element with the symbol Ba and atomic number 56. It is the fifth element in group 2 and is a soft, silvery alkaline earth metal. Because of its high chemical reactivity, barium is never found in nature as a free element.
Th ...
and calcium
Calcium is a chemical element with the symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar to ...
are often used for the cathode as they have low work function
In solid-state physics, the work function (sometimes spelt workfunction) is the minimum thermodynamic work (i.e., energy) needed to remove an electron from a solid to a point in the vacuum immediately outside the solid surface. Here "immediately" m ...
s which promote injection of electrons into the LUMO of the organic layer. Such metals are reactive, so they require a capping layer of aluminium
Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. I ...
to avoid degradation. Two secondary benefits of the aluminum capping layer include robustness to electrical contacts and the back reflection of emitted light out to the transparent ITO layer.
Experimental research has proven that the properties of the anode, specifically the anode/hole transport layer (HTL) interface topography plays a major role in the efficiency, performance, and lifetime of organic light-emitting diodes. Imperfections in the surface of the anode decrease anode-organic film interface adhesion, increase electrical resistance, and allow for more frequent formation of non-emissive dark spots in the OLED material adversely affecting lifetime. Mechanisms to decrease anode roughness for ITO/glass substrates include the use of thin films and self-assembled monolayers. Also, alternative substrates and anode materials are being considered to increase OLED performance and lifetime. Possible examples include single crystal sapphire substrates treated with gold (Au) film anodes yielding lower work functions, operating voltages, electrical resistance values, and increasing lifetime of OLEDs.
Single carrier devices are typically used to study the kinetics
Kinetics ( grc, κίνησις, , kinesis, ''movement'' or ''to move'') may refer to:
Science and medicine
* Kinetics (physics), the study of motion and its causes
** Rigid body kinetics, the study of the motion of rigid bodies
* Chemical ki ...
and charge transport mechanisms of an organic material and can be useful when trying to study energy transfer processes. As current through the device is composed of only one type of charge carrier, either electrons or holes, recombination does not occur and no light is emitted. For example, electron only devices can be obtained by replacing ITO with a lower work function metal which increases the energy barrier of hole injection. Similarly, hole only devices can be made by using a cathode made solely of aluminium, resulting in an energy barrier too large for efficient electron injection.
Carrier balance
Balanced charge injection and transfer are required to get high internal efficiency, pure emission of luminance layer without contaminated emission from charge transporting layers, and high stability. A common way to balance charge is optimizing the thickness of the charge transporting layers but is hard to control. Another way is using the exciplex. Exciplex formed between hole-transporting (p-type) and electron-transporting (n-type) side chains to localize electron-hole pairs. Energy is then transferred to luminophore and provide high efficiency. An example of using exciplex is grafting Oxadiazole and carbazole side units in red diketopyrrolopyrrole-doped Copolymer main chain shows improved external quantum efficiency and color purity in no optimized OLED.
Material technologies
Small molecules
Organic small-molecule electroluminescent materials have the advantages of a wide variety, easy to purify, and strong chemical modifications. In order to make the luminescent materials to emit light as required, some chromophores or unsaturated groups such as alkene bonds and benzene rings will usually be introduced in the molecular structure design to change the size of the conjugation range of the material, so that the photophysical properties of the material changes. In general, the larger the range of π-electron conjugation system, the longer the wavelength of light emitted by the material. For instance, with the increase of the number of benzene rings, the fluorescence emission peak of benzene
Benzene is an organic chemical compound with the molecular formula C6H6. The benzene molecule is composed of six carbon atoms joined in a planar ring with one hydrogen atom attached to each. Because it contains only carbon and hydrogen atoms, ...
, naphthalene
Naphthalene is an organic compound with formula . It is the simplest polycyclic aromatic hydrocarbon, and is a white crystalline solid with a characteristic odor that is detectable at concentrations as low as 0.08 ppm by mass. As an aromati ...
, anthracene
Anthracene is a solid polycyclic aromatic hydrocarbon (PAH) of formula C14H10, consisting of three fused benzene rings. It is a component of coal tar. Anthracene is used in the Economic production, production of the red dye alizarin and other dyes ...
, and butyl gradually red-shifted from 283 nm to 480 nm. Common organic small molecule electroluminescent materials include aluminum complexes, anthracenes
Anthracene is a solid polycyclic aromatic hydrocarbon (PAH) of formula C14H10, consisting of three fused benzene rings. It is a component of coal tar. Anthracene is used in the production of the red dye alizarin and other dyes. Anthracene is color ...
, biphenyl acetylene aryl derivatives, coumarin derivatives, and various fluorochromes. Efficient OLEDs using small molecules were first developed by Ching W. Tang
Ching Wan Tang (; born July 23, 1947) is a Hong Kong Americans, Hong Kong–American Physical chemistry, physical chemist. He was inducted into the National Inventors Hall of Fame in 2018 for inventing OLED (together with Steven Van Slyke), and ...
''et al.'' at Eastman Kodak
The Eastman Kodak Company (referred to simply as Kodak ) is an American public company that produces various products related to its historic basis in analogue photography. The company is headquartered in Rochester, New York, and is incorpor ...
. The term OLED traditionally refers specifically to this type of device, though the term SM-OLED is also in use.[Kho, Mu-Jeong, Javed, T., Mark, R., Maier, E., and David, C. (2008) ''Final Report: OLED Solid State Lighting – Kodak European Research,'' MOTI (Management of Technology and Innovation) Project, Judge Business School of the University of Cambridge and Kodak European Research, Final Report presented on 4 March 2008, at Kodak European Research at Cambridge Science Park, Cambridge, UK., pp. 1–12]
Molecules commonly used in OLEDs include organometallic chelates
Chelation is a type of bonding of ions and molecules to metal ions. It involves the formation or presence of two or more separate coordinate bonds between a polydentate (multiple bonded) ligand and a single central metal atom. These ligands are ...
(for example Alq3, used in the organic light-emitting device reported by Tang ''et al.''), fluorescent and phosphorescent dyes and conjugated dendrimers
Dendrimers are highly ordered, branched polymeric molecules. Synonymous terms for dendrimer include arborols and cascade molecules. Typically, dendrimers are symmetric about the core, and often adopt a spherical three-dimensional morphology. The ...
. A number of materials are used for their charge transport properties, for example triphenylamine
Triphenylamine is an organic compound with formula (C6H5)3N. In contrast to most amines, triphenylamine is nonbasic. At room temperature it appears as a colorless crystalline solid, with monoclinic structure. It is well miscible in diethyl ether a ...
and derivatives are commonly used as materials for hole transport layers. Fluorescent dyes can be chosen to obtain light emission at different wavelengths, and compounds such as perylene
Perylene or perilene is a polycyclic aromatic hydrocarbon with the chemical formula C20H12, occurring as a brown solid. It or its derivatives may be carcinogenic, and it is considered to be a hazardous pollutant. In cell membrane cytochemistry, ...
, rubrene
Rubrene (5,6,11,12-tetraphenyltetracene) is a red colored polycyclic aromatic hydrocarbon. Rubrene is used as a Photosensitizer, sensitiser in chemoluminescence and as a yellow light source in lightsticks.
Electronic properties
As an organic semi ...
and quinacridone
Quinacridone is an organic compound used as a pigment. Numerous derivatives constitute the quinacridone pigment family, which finds extensive use in industrial colorant applications such as robust outdoor paints, inkjet printer ink, tattoo inks, ...
derivatives are often used. Alq3 has been used as a green emitter, electron transport material and as a host for yellow and red emitting dyes.
Because of the structural flexibility of small-molecule electroluminescent materials, thin films can be prepared by vacuum vapor deposition, which is more expensive and of limited use for large-area devices. The vacuum coating system, however, can make the entire process from film growth to OLED device preparation in a controlled and complete operating environment, helping to obtain uniform and stable films, thus ensuring the final fabrication of high-performance OLED devices.However, small molecule organic dyes are prone to fluorescence quenching in the solid state, resulting in lower luminescence efficiency. The doped OLED devices are also prone to crystallization, which reduces the luminescence and efficiency of the devices. Therefore, the development of devices based on small-molecule electroluminescent materials is limited by high manufacturing costs, poor stability, short life, and other shortcomings. Coherent emission from a laser dye-doped tandem SM-OLED device, excited in the pulsed regime, has been demonstrated. The emission is nearly diffraction limited with a spectral width similar to that of broadband dye lasers.
Researchers report luminescence from a single polymer molecule, representing the smallest possible organic light-emitting diode (OLED) device. Scientists will be able to optimize substances to produce more powerful light emissions. Finally, this work is a first step towards making molecule-sized components that combine electronic and optical properties. Similar components could form the basis of a molecular computer.
Polymer light-emitting diodes
Polymer light-emitting diodes (PLED, P-OLED), also light-emitting polymers (LEP), involve an electroluminescent
Electroluminescence (EL) is an optical and electrical phenomenon, in which a material emits light in response to the passage of an electric current or to a strong electric field. This is distinct from black body light emission resulting from h ...
conductive polymer
Conductive polymers or, more precisely, intrinsically conducting polymers (ICPs) are organic polymers that conduct electricity. Such compounds may have metallic conductivity or can be semiconductors. The biggest advantage of conductive polymer ...
that emits light
Light or visible light is electromagnetic radiation that can be perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 nanometres (nm), corresponding to frequencies of 750–420 tera ...
when connected to an external voltage. They are used as a thin film
A thin film is a layer of material ranging from fractions of a nanometer (monolayer) to several micrometers in thickness. The controlled synthesis of materials as thin films (a process referred to as deposition) is a fundamental step in many ap ...
for full-spectrum Full-spectrum light is light that covers the electromagnetic spectrum from infrared to near-ultraviolet, or all wavelengths that are useful to plant or animal life; in particular, sunlight is considered full spectrum, even though the solar spectral ...
colour displays. Polymer OLEDs are quite efficient and require a relatively small amount of power for the amount of light produced.
Vacuum deposition is not a suitable method for forming thin films of polymers. If the polymeric OLED films are made by vacuum vapor deposition, the chain elements will be cut off and the original photophysical properties will be compromised. However, polymers can be processed in solution, and spin coating
Spin coating is a procedure used to deposit uniform thin films onto flat substrates. Usually a small amount of coating material is applied on the center of the substrate, which is either spinning at low speed or not spinning at all. The substrate ...
is a common method of depositing thin polymer films. This method is more suited to forming large-area films than thermal evaporation. No vacuum is required, and the emissive materials can also be applied on the substrate by a technique derived from commercial inkjet
Inkjet printing is a type of computer printing that recreates a digital image by propelling droplets of ink onto paper and plastic substrates. Inkjet printers were the most commonly used type of printer in 2008, and range from small inexpensi ...
printing. However, as the application of subsequent layers tends to dissolve those already present, formation of multilayer structures is difficult with these methods. The metal cathode may still need to be deposited by thermal evaporation in vacuum. An alternative method to vacuum deposition is to deposit a Langmuir-Blodgett film.
Typical polymers used in PLED displays include derivatives of poly(''p''-phenylene vinylene) and polyfluorene
Polyfluorene is a polymer with formula , consisting of fluorene units linked in a linear chain — specifically, at carbon atoms 2 and 7 in the standard fluorene numbering. It can also be described as a chain of benzene rings linked in ''para'' p ...
. Substitution
Substitution may refer to:
Arts and media
*Chord substitution, in music, swapping one chord for a related one within a chord progression
* Substitution (poetry), a variation in poetic scansion
* "Substitution" (song), a 2009 song by Silversun Pi ...
of side chains onto the polymer backbone may determine the colour of emitted light or the stability and solubility of the polymer for performance and ease of processing.
While unsubstituted poly(p-phenylene vinylene) (PPV) is typically insoluble, a number of PPVs and related poly(naphthalene vinylene)s (PNVs) that are soluble in organic solvents or water have been prepared via ring opening metathesis polymerization
Ring-opening metathesis polymerization (ROMP) is a type of olefin metathesis chain-growth polymerization. The driving force of the reaction is relief of ring strain in cyclic olefins (e.g. norbornene or cyclopentene). A variety of heterogeneo ...
. These water-soluble polymers or conjugated poly electrolytes (CPEs) also can be used as hole injection layers alone or in combination with nanoparticles like graphene.
Phosphorescent materials
Phosphorescent organic light-emitting diodes use the principle of electrophosphorescence to convert electrical energy in an OLED into light in a highly efficient manner, with the internal quantum efficiencies of such devices approaching 100%.
Typically, a polymer such as poly( N-vinylcarbazole) is used as a host material to which an organometallic complex
Complex commonly refers to:
* Complexity, the behaviour of a system whose components interact in multiple ways so possible interactions are difficult to describe
** Complex system, a system composed of many components which may interact with each ...
is added as a dopant. Iridium complexes such as Ir(mppy)3 as of 2004 were a focus of research, although complexes based on other heavy metals such as platinum have also been used.
The heavy metal atom at the centre of these complexes exhibits strong spin-orbit coupling, facilitating intersystem crossing Intersystem crossing (ISC) is an isoenergetic radiationless process involving a transition between the two electronic states with different spin multiplicity.
Excited Singlet and Triplet States
When an electron in a molecule with a singlet ground ...
between singlet and triplet states. By using these phosphorescent materials, both singlet and triplet excitons will be able to decay radiatively, hence improving the internal quantum efficiency of the device compared to a standard OLED where only the singlet states will contribute to emission of light.
Applications of OLEDs in solid state lighting require the achievement of high brightness with good CIE coordinates (for white emission). The use of macromolecular species like polyhedral oligomeric silsesquioxanes (POSS) in conjunction with the use of phosphorescent species such as Ir for printed OLEDs have exhibited brightnesses as high as 10,000cd/m2.
Device architectures
Structure
Bottom emission
The bottom-emission organic light-emitting diode (BE-OLED) is the architecture that was used in the early-stage AMOLED
AMOLED (active-matrix organic light-emitting diode, ) is a type of OLED display device technology. OLED describes a specific type of thin-film-display technology in which organic compounds form the electroluminescence, electroluminescent materia ...
displays. It had a transparent anode fabricated on a glass substrate, and a shiny reflective cathode. Light is emitted from the transparent anode direction. To reflect all the light towards the anode direction, a relatively thick metal cathode such as aluminum is used. For the anode, high-transparency indium tin oxide (ITO) was a typical choice to emit as much light as possible. Organic thin-films, including the emissive layer that actually generates the light, are then sandwiched between the ITO anode and the reflective metal cathode. The downside of bottom emission structure is that the light has to travel through the pixel drive circuits such as the thin film transistor (TFT) substrate, and the area from which light can be extracted is limited and the light emission efficiency is reduced.
Top emission
An alternative configuration is to switch the mode of emission. A reflective anode, and a transparent (or more often semi-transparent) cathode are used so that the light emits from the cathode side, and this configuration is called top-emission OLED (TE-OLED). Unlike BEOLEDs where the anode is made of transparent conductive ITO, this time the cathode needs to be transparent, and the ITO material is not an ideal choice for the cathode because of a damage issue due to the sputtering process. Thus, a thin metal film such as pure Ag and the Mg:Ag alloy are used for the semi-transparent cathode due to their high transmittance
Transmittance of the surface of a material is its effectiveness in transmitting radiant energy. It is the fraction of incident electromagnetic power that is transmitted through a sample, in contrast to the transmission coefficient, which is th ...
and high conductivity
Conductivity may refer to:
*Electrical conductivity, a measure of a material's ability to conduct an electric current
**Conductivity (electrolytic), the electrical conductivity of an electrolyte in solution
**Ionic conductivity (solid state), elec ...
. In contrast to the bottom emission, light is extracted from the opposite side in top emission without the need of passing through multiple drive circuit layers. Thus, the light generated can be extracted more efficiently.
Improvements
Micro-cavity theory
When light waves meet while traveling along the same medium, wave interference
In physics, interference is a phenomenon in which two waves combine by adding their displacement together at every single point in space and time, to form a resultant wave of greater, lower, or the same amplitude. Constructive and destructive ...
occurs. This interference can be constructive or destructive. It is sometimes desirable for several waves of the same frequency to sum up into a wave with higher amplitudes.
Since both electrodes are reflective in TEOLED, light reflections can happen within the diode, and they cause more complex interferences than those in BEOLEDs. In addition to the two-beam interference, there exists a multi-resonance interference between two electrodes. Because the structure of TEOLEDs is similar to that of the Fabry-Perot resonator or laser resonator An optical cavity, resonating cavity or optical resonator is an arrangement of mirrors or other optical elements that forms a cavity resonator for light waves. Optical cavities are a major component of lasers, surrounding the gain medium and provi ...
, which contains two parallel mirrors comparable to the two reflective electrodes), this effect is especially strong in TEOLED. This two-beam interference and the Fabry-Perot interferences are the main factors in determining the output spectral intensity of OLED. This optical effect is called the "micro-cavity effect."
In the case of OLED, that means the cavity in a TEOLED could be especially designed to enhance the light output intensity and color purity with a narrow band of wavelengths, without consuming more power. In TEOLEDs, the microcavity effect commonly occurs, and when and how to restrain or make use of this effect is indispensable for device design. To match the conditions of constructive interference, different layer thicknesses are applied according to the resonance wavelength of that specific color. The thickness conditions are carefully designed and engineered according to the peak resonance emitting wavelengths of the blue (460 nm), green (530 nm), and red (610 nm) color LEDs. This technology greatly improves the light-emission efficiency of OLEDs, and are able to achieve a wider color gamut due to high color purity.
Color filters
In " white + color filter method," red, green, and blue emissions are obtained from the same white-light LEDs using different color filters. With this method, the OLED materials produce white light which is then filtered to obtain the desired RGB colors. This method eliminated the need to deposit three different organic emissive materials so only one kind of OLED material is used to produce white light. It also eliminated the uneven degradation rate of blue pixels vs. red and green pixels. Disadvantages of this method are low color purity and contrast. Also, the filters absorb most of the light waves emitted, requiring the background white light to be relatively strong to compensate for the drop in brightness, and thus the power consumption for such displays can be higher.
Color filters can also be implemented into bottom- and top-emission OLEDs. By adding the corresponding RGB color filters after the semi-transparent cathode, even purer wavelengths of light can be obtained. The use of a microcavity in top-emission OLEDs with color filters also contributes to an increase in the contrast ratio by reducing the reflection of incident ambient light. In a conventional panel, a circular polarizer was installed on the panel surface. While this was provided to prevent the reflection of ambient light, it also reduced the light output. By replacing this polarizing layer with color filters, the light intensity is not affected, and essentially all ambient reflected light can be cut, allowing a better contrast on the display panel. This potentially reduced the need for brighter pixels, and can lower the power consumption.
Other architectures
Transparent OLEDs
Transparent OLEDs use transparent or semi-transparent contacts on both sides of the device to create displays that can be made to be both top and bottom emitting (transparent). TOLEDs can greatly improve contrast, making it much easier to view displays in bright sunlight. This technology can be used in Head-up display
A head-up display, or heads-up display, also known as a HUD (), is any transparent display that presents data without requiring users to look away from their usual viewpoints. The origin of the name stems from a pilot being able to view informa ...
s, smart windows or augmented reality
Augmented reality (AR) is an interactive experience that combines the real world and computer-generated content. The content can span multiple sensory modalities, including visual, auditory, haptic, somatosensory and olfactory. AR can be de ...
applications.
Graded heterojunction
Graded heterojunction OLEDs gradually decrease the ratio of electron holes to electron transporting chemicals. This results in almost double the quantum efficiency of existing OLEDs.
Stacked OLEDs
Stacked OLEDs use a pixel architecture that stacks the red, green, and blue subpixels on top of one another instead of next to one another, leading to substantial increase in gamut
In color reproduction, including computer graphics and photography, the gamut, or color gamut , is a certain ''complete subset'' of colors. The most common usage refers to the subset of colors which can be accurately represented in a given circ ...
and color depth, and greatly reducing pixel gap. Other display technologies with RGB (and RGBW) pixels mapped next to each other, tend to decrease potential resolution.
Inverted OLED
In contrast to a conventional OLED, in which the anode is placed on the substrate, an Inverted OLED uses a bottom cathode that can be connected to the drain end of an n-channel TFT especially for the low cost amorphous silicon
Amorphous silicon (a-Si) is the non-crystalline form of silicon used for solar cells and thin-film transistors in LCDs.
Used as semiconductor material for a-Si solar cells, or thin-film silicon solar cells, it is deposited in thin films onto ...
TFT backplane useful in the manufacturing of AMOLED
AMOLED (active-matrix organic light-emitting diode, ) is a type of OLED display device technology. OLED describes a specific type of thin-film-display technology in which organic compounds form the electroluminescence, electroluminescent materia ...
displays.
All OLED displays (passive and active matrix) use a driver IC, often mounted using Chip-on-glass (COG), using an Anisotropic conductive film
Anisotropic conductive film (ACF), is a lead-free and environmentally friendly adhesive interconnect system that is commonly used in liquid crystal display manufacturing to make the electrical and mechanical connections from the driver electronics ...
.
Color patterning technologies
Shadow mask patterning method
The most commonly used patterning method for organic light-emitting displays is shadow masking during film deposition, also called the "RGB side-by-side" method or "RGB pixelation" method. Metal sheets with multiple apertures made of low thermal expansion material, such as nickel alloy, are placed between the heated evaporation source and substrate, so that the organic or inorganic material from the evaporation source is deposited only to the desired location on the substrate. Almost all small OLED displays for smartphones have been manufactured using this method.
Fine metal masks (FMMs) made by photochemical machining
Photochemical machining (PCM), also known as photochemical milling or photo etching, is a chemical milling process used to fabricate sheet metal components using a photoresist and etchants to corrosively machine away selected areas. This process ...
, reminiscent of old CRT shadow mask
The shadow mask is one of the two technologies used in the manufacture of cathode-ray tube (CRT) televisions and computer monitors which produce clear, focused color images. The other approach is the aperture grille, better known by its t ...
s, are used in this process. The dot density of the mask will determine the pixel density of the finished display. Fine Hybrid Masks (FHMs) are lighter than FFMs, reducing bending caused by the mask's own weight, and are made using an electroforming process.
This method requires heating the electroluminescent materials at 300 °C using a thermal method in a high vacuum of 10Pa. An oxygen meter ensures that no oxygen enters the chamber as it could damage (through oxidation) the electroluminescent material, which is in powder form. The mask is aligned with the mother substrate before every use, and it is placed just below the substrate. The substrate and mask assembly are placed at the top of the deposition chamber. Afterwards, the electrode layer is deposited, by subjecting silver and aluminum powder to 1000 °C, using an electron beam. Shadow masks allow for high pixel densities of up to . High pixel densities are
necessary for virtual reality headset
A virtual reality headset (or VR headset) is a head-mounted device that provides virtual reality for the wearer. VR headsets are widely used with VR video games but they are also used in other applications, including simulators and trainers. VR ...
s.
White + color filter method
Although the shadow-mask patterning method is a mature technology used from the first OLED manufacturing, it causes many issues like dark spot formation due to mask-substrate contact or misalignment of the pattern due to the deformation of shadow mask. Such defect formation can be regarded as trivial when the display size is small, however it causes serious issues when a large display is manufactured, which brings significant production yield loss. To circumvent such issues, white emission devices with 4-sub-pixel color filters (white, red, green and blue) have been used for large televisions. In spite of the light absorption by the color filter, state-of-the-art OLED televisions can reproduce color very well, such as 100% NTSC
The first American standard for analog television broadcast was developed by National Television System Committee (NTSC)National Television System Committee (1951–1953), Report and Reports of Panel No. 11, 11-A, 12–19, with Some supplement ...
, and consume little power at the same time. This is done by using an emission spectrum with high human-eye sensitivity, special color filters with a low spectrum overlap, and performance tuning with color statistics into consideration.
This approach is also called the "Color-by-white" method.
Other color patterning approaches
There are other types of emerging patterning technologies to increase the manufacturabiltiy of OLEDs.
Patternable organic light-emitting devices use a light or heat activated electroactive layer. A latent material (PEDOT-TMA
Poly(3,4-ethylenedioxythiophene)-tetramethacrylate or PEDOT-TMA is a p-type conducting polymer based on 3,4-ethylenedioxylthiophene or the EDOT monomer. It is a modification of the PEDOT structure. Advantages of this polymer relative to PEDOT (o ...
) is included in this layer that, upon activation, becomes highly efficient as a hole injection layer. Using this process, light-emitting devices with arbitrary patterns can be prepared.
Colour patterning can be accomplished by means of a laser, such as a radiation-induced sublimation transfer (RIST).
Organic vapour jet printing (OVJP) uses an inert carrier gas, such as argon
Argon is a chemical element with the symbol Ar and atomic number 18. It is in group 18 of the periodic table and is a noble gas. Argon is the third-most abundant gas in Earth's atmosphere, at 0.934% (9340 ppmv). It is more than twice as abu ...
or nitrogen
Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...
, to transport evaporated organic molecules (as in organic vapour phase deposition). The gas is expelled through a micrometre
The micrometre ( international spelling as used by the International Bureau of Weights and Measures; SI symbol: μm) or micrometer (American spelling), also commonly known as a micron, is a unit of length in the International System of Unit ...
-sized nozzle or nozzle array close to the substrate as it is being translated. This allows printing arbitrary multilayer patterns without the use of solvents.
Like ink jet material deposition
Ink jet material deposition is an emerging manufacturing technique in which ink jet technology is used to deposit materials on substrates. The technique aims to eliminate fixed costs of production and reduce the amount of materials used.
Uses
An ...
, inkjet etching (IJE) deposits precise amounts of solvent onto a substrate designed to selectively dissolve the substrate material and induce a structure or pattern. Inkjet etching of polymer layers in OLED's can be used to increase the overall out-coupling efficiency. In OLEDs, light produced from the emissive layers of the OLED is partially transmitted out of the device and partially trapped inside the device by total internal reflection
Total internal reflection (TIR) is the optical phenomenon in which waves arriving at the interface (boundary) from one medium to another (e.g., from water to air) are not refracted into the second ("external") medium, but completely reflected b ...
(TIR). This trapped light is wave-guided along the interior of the device until it reaches an edge where it is dissipated by either absorption or emission. Inkjet etching can be used to selectively alter the polymeric layers of OLED structures to decrease overall TIR and increase out-coupling efficiency of the OLED. Compared to a non-etched polymer layer, the structured polymer layer in the OLED structure from the IJE process helps to decrease the TIR of the OLED device. IJE solvents are commonly organic
Organic may refer to:
* Organic, of or relating to an organism, a living entity
* Organic, of or relating to an anatomical organ
Chemistry
* Organic matter, matter that has come from a once-living organism, is capable of decay or is the product ...
instead of water-based due to their non-acidic nature and ability to effectively dissolve materials at temperatures under the boiling point of water.
Transfer-printing is an emerging technology to assemble large numbers of parallel OLED and AMOLED devices efficiently. It takes advantage of standard metal deposition, photolithography
In integrated circuit manufacturing, photolithography or optical lithography is a general term used for techniques that use light to produce minutely patterned thin films of suitable materials over a substrate, such as a silicon wafer, to protect ...
, and etching to create alignment marks commonly on glass or other device substrates. Thin polymer adhesive layers are applied to enhance resistance to particles and surface defects. Microscale ICs are transfer-printed onto the adhesive surface and then baked to fully cure adhesive layers. An additional photosensitive polymer layer is applied to the substrate to account for the topography caused by the printed ICs, reintroducing a flat surface. Photolithography and etching removes some polymer layers to uncover conductive pads on the ICs. Afterwards, the anode layer is applied to the device backplane to form the bottom electrode. OLED layers are applied to the anode layer with conventional vapor deposition
Vacuum deposition is a group of processes used to deposit layers of material atom-by-atom or molecule-by-molecule on a solid surface. These processes operate at pressures well below atmospheric pressure (i.e., vacuum). The deposited layers can r ...
, and covered with a conductive metal electrode layer. transfer-printing was capable to print onto target substrates up to 500mm × 400mm. This size limit needs to expand for transfer-printing to become a common process for the fabrication of large OLED/AMOLED displays.
Experimental OLED displays using conventional photolithography techniques instead of FMMs have been demonstrated, allowing for large substrate sizes (as it eliminates the need for a mask that needs to be as large as the substrate) and good yield control.
Thin-film transistor backplanes
For a high resolution display like a TV, a thin-film transistor
A thin-film transistor (TFT) is a special type of field-effect transistor (FET) where the transistor is thin relative to the plane of the device. TFTs are grown on a supporting (but non-conducting) substrate. A common substrate is glass, becaus ...
(TFT) backplane is necessary to drive the pixels correctly. As of 2019, low-temperature polycrystalline silicon Low-temperature polycrystalline silicon (LTPS) is polycrystalline silicon that has been synthesized at relatively low temperatures (~650 °C and lower) compared to in traditional methods (above 900 °C). LTPS is important for display ind ...
(LTPS)– TFT is widely used for commercial AMOLED
AMOLED (active-matrix organic light-emitting diode, ) is a type of OLED display device technology. OLED describes a specific type of thin-film-display technology in which organic compounds form the electroluminescence, electroluminescent materia ...
displays. LTPS-TFT has variation of the performance in a display, so various compensation circuits have been reported. Due to the size limitation of the excimer laser
An excimer laser, sometimes more correctly called an exciplex laser, is a form of ultraviolet laser which is commonly used in the production of microelectronic devices, semiconductor based integrated circuits or "chips", eye surgery, and microm ...
used for LTPS, the AMOLED
AMOLED (active-matrix organic light-emitting diode, ) is a type of OLED display device technology. OLED describes a specific type of thin-film-display technology in which organic compounds form the electroluminescence, electroluminescent materia ...
size was limited. To cope with the hurdle related to the panel size, amorphous-silicon/microcrystalline-silicon backplanes have been reported with large display prototype demonstrations. An indium gallium zinc oxide
Indium gallium zinc oxide (IGZO) is a semiconducting material, consisting of indium (In), gallium (Ga), zinc (Zn) and oxygen (O). IGZO thin-film transistors (TFT) are used in the TFT backplane of flat-panel displays (FPDs). IGZO-TFT was developed b ...
(IGZO) backplane can also be used.
Advantages
The different manufacturing process of OLEDs has several advantages over flat panel display
A flat-panel display (FPD) is an electronic display used to display visual content such as text or images. It is present in consumer, medical, transportation, and industrial equipment.
Flat-panel displays are thin, lightweight, provide better li ...
s made with LCD technology.
; Lower cost in the future: OLEDs can be printed onto any suitable substrate by an inkjet printer or even by screen printing, theoretically making them cheaper to produce than LCD or plasma display
A plasma display panel (PDP) is a type of flat panel display that uses small cells containing plasma: ionized gas that responds to electric fields. Plasma televisions were the first large (over 32 inches diagonal) flat panel displays to be release ...
s. However, fabrication of the OLED substrate as of 2018 is costlier than that for TFT LCDs. Roll-to-roll vapor-deposition methods for organic devices do allow mass production of thousands of devices per minute for minimal cost; however, this technique also induces problems: devices with multiple layers can be challenging to make because of registration
Register or registration may refer to:
Arts entertainment, and media Music
* Register (music), the relative "height" or range of a note, melody, part, instrument, etc.
* ''Register'', a 2017 album by Travis Miller
* Registration (organ), th ...
— lining up the different printed layers to the required degree of accuracy.
; Lightweight and flexible plastic substrates: OLED displays can be fabricated on flexible plastic substrates, leading to the possible fabrication of flexible organic light-emitting diode
A flexible organic light-emitting diode (FOLED) is a type of organic light-emitting diode (OLED) incorporating a flexible plastic substrate on which the electroluminescent organic semiconductor is deposited. This enables the device to be bent or ...
s for other new applications, such as roll-up displays embedded in fabrics or clothing. If a substrate like polyethylene terephthalate
Polyethylene terephthalate (or poly(ethylene terephthalate), PET, PETE, or the obsolete PETP or PET-P), is the most common thermoplastic polymer resin of the polyester family and is used in fibres for clothing, containers for liquids and foods ...
(PET) can be used, the displays may be produced inexpensively. Furthermore, plastic substrates are shatter-resistant, unlike the glass displays used in LCD devices.
; Better picture quality: OLEDs enable a greater contrast ratio
The contrast ratio (CR) is a property of a display system, defined as the ratio of the luminance of the brightest shade (white) to that of the darkest shade (black) that the system is capable of producing. A high contrast ratio is a desired aspec ...
and wider viewing angle compared to LCDs, because OLED pixels emit light directly. This also provides a deeper black level
Video black level is defined as the level of brightness at the darkest (black) part of a visual image or the level of brightness at which no light is emitted from a screen, resulting in a pure black screen.
Video displays generally need to be cal ...
, since a black OLED display emits no light. Furthermore, OLED pixel colors appear correct and unshifted, even as the viewing angle approaches 90° from the normal Normal(s) or The Normal(s) may refer to:
Film and television
* ''Normal'' (2003 film), starring Jessica Lange and Tom Wilkinson
* ''Normal'' (2007 film), starring Carrie-Anne Moss, Kevin Zegers, Callum Keith Rennie, and Andrew Airlie
* ''Norma ...
.
; Better power efficiency and thickness: LCDs filter the light emitted from a backlight
A backlight is a form of illumination used in liquid crystal displays (LCDs). As LCDs do not produce light by themselves—unlike, for example, cathode ray tube (CRT), plasma (PDP) or OLED displays—they need illumination ( ambient light or a ...
, allowing a small fraction of light through. Thus, they cannot show true black. However, an inactive OLED element does not produce light or consume power, allowing true blacks. Removing the backlight also makes OLEDs lighter because some substrates are not needed. When looking at top-emitting OLEDs, thickness also plays a role when talking about index match layers (IMLs). Emission intensity is enhanced when the IML thickness is 1.3–2.5nm. The refractive value and the matching of the optical IMLs property, including the device structure parameters, also enhance the emission intensity at these thicknesses.
; Response time: OLEDs also have a much faster response time
Response time may refer to:
*The time lag between an electronic input and the output signal which depends upon the value of passive components used.
* Responsiveness, how quickly an interactive system responds to user input
* Response time (biolog ...
than an LCD. Using response time compensation technologies, the fastest modern LCDs can reach response times as low as 1ms for their fastest color transition, and are capable of refresh frequencies as high as 240Hz. According to LG, OLED response times are up to 1,000 times faster than LCD, putting conservative estimates at under 10μs (0.01ms), which could theoretically accommodate refresh frequencies approaching 100kHz (100,000Hz). Due to their extremely fast response time, OLED displays can also be easily designed to be strobed, creating an effect similar to CRT flicker in order to avoid the sample-and-hold
In electronics, a sample and hold (also known as sample and follow) circuit is an analog device that samples (captures, takes) the voltage of a continuously varying analog signal and holds (locks, freezes) its value at a constant level for a ...
behavior seen on both LCDs and some OLED displays, which creates the perception of motion blur
Motion blur is the apparent streaking of moving objects in a photograph or a sequence of frames, such as a film or animation. It results when the image being recorded changes during the recording of a single exposure, due to rapid movement or lo ...
.
Disadvantages
Lifespan
The biggest technical problem for OLEDs is the limited lifetime of the organic materials. One 2008 technical report on an OLED TV panel found that after 1,000hours, the blue luminance degraded by 12%, the red by 7% and the green by 8%. In particular, blue OLEDs at that time had a lifetime of around 14,000hours to half original brightness (five years at eight hours per day) when used for flat-panel displays. This is lower than the typical lifetime of LCD, LED or PDP technology; each rated for about 25,000–40,000hours to half brightness, depending on manufacturer and model. One major challenge for OLED displays is the formation of dark spots due to the ingress of oxygen and moisture, which degrades the organic material over time whether or not the display is powered. In 2016, LG Electronics reported an expected lifetime of 100,000 hours, up from 36,000 hours in 2013. A US Department of Energy paper shows that the expected lifespans of OLED lighting products goes down with increasing brightness, with an expected lifespan of 40,000 hours at 25% brightness, or 10,000 hours at 100% brightness.
Cause of degradation
Degradation occurs because of the accumulation of nonradiative recombination
In the solid-state physics of semiconductors, carrier generation and carrier recombination are processes by which mobile charge carriers (electrons and electron holes) are created and eliminated. Carrier generation and recombination processes ar ...
centers and luminescence quenchers in the emissive zone. It is said that the chemical breakdown in the semiconductors occurs in four steps:
# recombination of charge carriers through the absorption of UV light
Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nm (with a corresponding frequency around 30 PHz) to 400 nm (750 THz), shorter than that of visible light, but longer than X-rays. UV radiation i ...
# homolytic dissociation
# subsequent radical addition reactions that form radicals
# disproportionation between two radicals resulting in hydrogen-atom transfer reactions
However, some manufacturers' displays aim to increase the lifespan of OLED displays, pushing their expected life past that of LCD displays by improving light outcoupling, thus achieving the same brightness at a lower drive current. In 2007, experimental OLEDs were created which can sustain 400cd/m2 of luminance
Luminance is a photometric measure of the luminous intensity per unit area of light travelling in a given direction. It describes the amount of light that passes through, is emitted from, or is reflected from a particular area, and falls withi ...
for over 198,000hours for green OLEDs and 62,000hours for blue OLEDs. In 2012, OLED lifetime to half of the initial brightness was improved to 900,000hours for red, 1,450,000hours for yellow and 400,000hours for green at an initial luminance
Luminance is a photometric measure of the luminous intensity per unit area of light travelling in a given direction. It describes the amount of light that passes through, is emitted from, or is reflected from a particular area, and falls withi ...
of 1,000cd/m2. Proper encapsulation is critical for prolonging an OLED display's lifetime, as the OLED light emitting electroluminescent materials are sensitive to oxygen and moisture. When exposed to moisture or oxygen, the electroluminescent materials in OLEDs degrade as they oxidize, generating black spots and reducing or shrinking the area that emits light, reducing light output. This reduction can occur in a pixel by pixel basis. This can also lead to delamination of the electrode layer, eventually leading to complete panel failure.
Degradation occurs three orders of magnitude faster when exposed to moisture than when exposed to oxygen. Encapsulation can be performed by applying an epoxy adhesive with dessicant, by laminating a glass sheet with epoxy glue and dessicant followed by vacuum degassing, or by using Thin-Film Encapsulation (TFE), which is a multi-layer coating of alternating organic and inorganic layers. The organic layers are applied using inkjet printing, and the inorganic layers are applied using Atomic Layer Deposition
Atomic layer deposition (ALD) is a thin-film deposition technique based on the sequential use of a gas-phase chemical process; it is a subclass of chemical vapour deposition. The majority of ALD reactions use two chemicals called precursors (also ...
(ALD). The encapsulation process is carried out under a nitrogen environment, using UV-curable LOCA glue and the electroluminescent and electrode material deposition processes are carried out under a high vacuum. The encapsulation and material deposition processes are carried out by a single machine, after the Thin-film transistor
A thin-film transistor (TFT) is a special type of field-effect transistor (FET) where the transistor is thin relative to the plane of the device. TFTs are grown on a supporting (but non-conducting) substrate. A common substrate is glass, becaus ...
s have been applied. The transistors are applied in a process that is the same for LCDs. The electroluminescent materials can also be applied using inkjet printing.
Color balance
The OLED material used to produce blue light degrades much more rapidly than the materials used to produce other colors; in other words, blue light output will decrease relative to the other colors of light. This variation in the differential color output will change the color balance
In photography and image processing, color balance is the global adjustment of the intensities of the colors (typically red, green, and blue primary colors). An important goal of this adjustment is to render specific colors – particularly neu ...
of the display, and is much more noticeable than a uniform decrease in overall luminance. This can be avoided partially by adjusting the color balance, but this may require advanced control circuits and input from a knowledgeable user. More commonly, though, manufacturers optimize the size of the R, G and B subpixels to reduce the current density through the subpixel in order to equalize lifetime at full luminance. For example, a blue subpixel may be 100% larger than the green subpixel. The red subpixel may be 10% larger than the green.
Efficiency of blue OLEDs
Improvements to the efficiency and lifetime of blue OLEDs is vital to the success of OLEDs as replacements for LCD technology. Considerable research has been invested in developing blue OLEDs with high external quantum efficiency
The term quantum efficiency (QE) may apply to incident photon to converted electron (IPCE) ratio of a photosensitive device, or it may refer to the TMR effect of a Magnetic Tunnel Junction.
This article deals with the term as a measurement of ...
, as well as a deeper blue color.
Since 2012, research focuses on organic materials exhibiting thermally activated delayed fluorescence (TADF), discovered at Kyushu University OPERA and UC Santa Barbara CPOS. TADF would allow stable and high-efficiency solution processable (meaning that the organic materials are layered in solutions producing thinner layers) blue emitters, with internal quantum efficiencies reaching 100%. Early in 2017, TADF materials based on oxygen-based fully bridged boron-type electron accepttors had achieved huge breakthrough in their proprities. The external quantum efficiency of TADF-OLED for blue and green light had achieved 38%, with thin full-width half-maximum and high color purity. In 2022, Han et al. synthesized a new D-A type luminescent material, TDBA-Cz, and used the m-AC-DBNA synthesized by Meng et al. as a control to investigate the effect of the substitution site of the carbazole unit as an electron donor on the oxygen-bridged triphenylboron electron acceptor unit on the photophysical properties of the overall molecule. It was found that the introduction of two carbazole units into the same benzene ring of the oxygen-bridged triphenylboron electron acceptor unit could effectively suppress the conformational relaxation of the molecule during the radiative transition, resulting in narrow bandwidth blue light emission. In addition, TDBA-Cz is the first reported blue material to achieve both a FWHM down to 45 nm and a maximum EQE of 21.4% in a non-doped TADF-OLED.
Blue TADF emitters are expected to market by 2020 and would be used for WOLED displays with phosphorescent color filters, as well as blue OLED displays with ink-printed QD color filters.
Water damage
Water can instantly damage the organic materials of the displays. Therefore, improved sealing processes are important for practical manufacturing. Water damage especially may limit the longevity of more flexible displays.
Outdoor performance
As an emissive display technology, OLEDs rely completely upon converting electricity to light, unlike most LCDs which are to some extent reflective. E-paper
Electronic paper, also sometimes electronic ink, e-ink or electrophoretic display, are display devices that mimic the appearance of ordinary ink on paper. Unlike conventional flat panel displays that emit light, an electronic paper display re ...
leads the way in efficiency with ~ 33% ambient light reflectivity, enabling the display to be used without any internal light source. The metallic cathode in an OLED acts as a mirror, with reflectance approaching 80%, leading to poor readability in bright ambient light such as outdoors. However, with the proper application of a circular polarizer
A polarizer or polariser is an optical filter that lets light waves of a specific polarization pass through while blocking light waves of other polarizations. It can filter a beam of light of undefined or mixed polarization into a beam of wel ...
and antireflective coating
An antireflective, antiglare or anti-reflection (AR) coating is a type of optical coating applied to the surface of lenses, other optical elements, and photovoltaic cells to reduce reflection. In typical imaging systems, this improves the effici ...
s, the diffuse reflectance can be reduced to less than 0.1%. With 10,000 fc incident illumination (typical test condition for simulating outdoor illumination), that yields an approximate photopic contrast
Photopic vision is the vision of the eye under well-lit conditions (luminance levels from 10 to 108 cd/m2). In humans and many other animals, photopic vision allows color perception, mediated by cone cells, and a significantly higher visu ...
of 5:1. Advances in OLED technologies, however, enable OLEDs to become actually better than LCDs in bright sunlight. The AMOLED
AMOLED (active-matrix organic light-emitting diode, ) is a type of OLED display device technology. OLED describes a specific type of thin-film-display technology in which organic compounds form the electroluminescence, electroluminescent materia ...
display in the Galaxy S5
The Samsung Galaxy S5 is an Android-based smartphone unveiled, produced, released and marketed by Samsung Electronics as part of the Samsung Galaxy S series. Unveiled on 24 February 2014 at Mobile World Congress in Barcelona, Spain, it was rele ...
, for example, was found to outperform all LCD displays on the market in terms of power usage, brightness and reflectance.
Power consumption
While an OLED will consume around 40% of the power of an LCD displaying an image that is primarily black, for the majority of images it will consume 60–80% of the power of an LCD. However, an OLED can use more than 300% power to display an image with a white background, such as a document or web site. This can lead to reduced battery life in mobile devices when white backgrounds are used.
Screen flicker
OLEDs use pulse width modulation to show colour/brightness gradations, so even if the display is at 100% brightness, any pixel that's, for example, 50% grey will be off for 50% of the time, making for a subtle strobe effect. The alternative way to decrease brightness would be to decrease the constant power to the OLEDs, which would result in no screen flicker, but a noticeable change in colour balance, getting worse as brightness decreases.
Manufacturers and commercial uses
Almost all OLED manufacturers rely on material deposition equipment that is only made by a handful of companies, the most notable one being Canon Tokki
Canon Tokki Corporation is a Japanese manufacturer of material deposition equipment for making OLED displays. It is a wholly owned subsidiary of Canon Inc. and has a near-monopoly in its main business field.
History
The company began producing ...
, a unit of Canon Inc.
is a Japanese multinational corporation headquartered in Ōta, Tokyo, Japan, specializing in optical, imaging, and industrial products, such as lenses, cameras, medical equipment, scanners, printers, and semiconductor manufacturing equipment. Canon Tokki is reported to have a near-monopoly of the giant OLED-manufacturing vacuum machines, notable for their size. Apple
An apple is an edible fruit produced by an apple tree (''Malus domestica''). Apple fruit tree, trees are agriculture, cultivated worldwide and are the most widely grown species in the genus ''Malus''. The tree originated in Central Asia, wh ...
has relied solely on Canon Tokki in its bid to introduce its own OLED displays for the iPhones released in 2017. The electroluminescent materials needed for OLEDs are also made by a handful of companies, some of them being Merck, Universal Display Corporation and LG Chem. The machines that apply these materials can operate continuously for 5–6 days, and can process a mother substrate in 5 minutes.
OLED technology is used in commercial applications such as displays for mobile phones and portable digital media player
A digital media player (also sometimes known as a streaming device or streaming box) is a type of consumer electronics device designed for the storage, playback, or viewing of digital media content. They are typically designed to be integra ...
s, car radios and digital camera
A digital camera is a camera that captures photographs in digital memory. Most cameras produced today are digital, largely replacing those that capture images on photographic film. Digital cameras are now widely incorporated into mobile device ...
s among others, as well as lighting. Such portable display applications favor the high light output of OLEDs for readability in sunlight and their low power drain. Portable displays are also used intermittently, so the lower lifespan of organic displays is less of an issue. Prototypes have been made of flexible and rollable displays which use OLEDs' unique characteristics. Applications in flexible signs and lighting are also being developed. OLED lighting offers several advantages over LED lighting, such as higher quality illumination, more diffuse light source, and panel shapes. Philips
Koninklijke Philips N.V. (), commonly shortened to Philips, is a Dutch multinational conglomerate corporation that was founded in Eindhoven in 1891. Since 1997, it has been mostly headquartered in Amsterdam, though the Benelux headquarters i ...
Lighting has made OLED lighting samples under the brand name "Lumiblade" available online and Novaled AG based in Dresden, Germany, introduced a line of OLED desk lamps called "Victory" in September, 2011.
Nokia
Nokia Corporation (natively Nokia Oyj, referred to as Nokia) is a Finnish multinational corporation, multinational telecommunications industry, telecommunications, technology company, information technology, and consumer electronics corporatio ...
introduced OLED mobile phones including the N85 and the N86 8MP, both of which feature an AMOLED display. OLEDs have also been used in most Motorola
Motorola, Inc. () was an American Multinational corporation, multinational telecommunications company based in Schaumburg, Illinois, United States. After having lost $4.3 billion from 2007 to 2009, the company split into two independent p ...
and Samsung
The Samsung Group (or simply Samsung) ( ko, 삼성 ) is a South Korean multinational manufacturing conglomerate headquartered in Samsung Town, Seoul, South Korea. It comprises numerous affiliated businesses, most of them united under the ...
color cell phones, as well as some HTC
HTC Corporation ( zh, t=宏達國際電子股份有限公司, s=宏达国际电子股份有限公司, p=Hóngdá Guójì Diànzǐ Gǔfèn Yǒuxiàn Gōngsī, first=t) or High Tech Computer Corporation, (literally ''Hongda International Electron ...
, LG and Sony Ericsson
Sony Mobile Communications Inc. ( ja, ソニーモバイルコミュニケーションズ株式会社) was a multinational telecommunications company founded on October 1, 2001, as a joint venture between Sony Group Corporation and Ericsson. I ...
models.[Electronic News]
OLEDs Replacing LCDs in Mobile Phones
, 7 April 2005. Retrieved 5 September 2016. OLED technology can also be found in digital media players such as the Creative ZEN V, the iriver clix, the Zune HD
The Zune HD is a portable media player in the Zune product family released on September 15, 2009, by Microsoft. It was a direct competitor with Apple's iPod Touch series of mobile devices. It was initially released in 16 and 32 GB capacities. A ...
and the Sony Walkman X Series.
The Google
Google LLC () is an American multinational technology company focusing on search engine technology, online advertising, cloud computing, computer software, quantum computing, e-commerce, artificial intelligence, and consumer electronics. ...
and HTC Nexus One
The Nexus One (codenamed HTC Passion) is an Android smartphone designed and manufactured by HTC as Google's first Nexus smartphone. The Nexus became available on January 5, 2010, and features the ability to transcribe voice to text, an addition ...
smartphone includes an AMOLED screen, as does HTC's own Desire
Desires are states of mind that are expressed by terms like "wanting", "wishing", "longing" or "craving". A great variety of features is commonly associated with desires. They are seen as propositional attitudes towards conceivable states of aff ...
and Legend
A legend is a Folklore genre, genre of folklore that consists of a narrative featuring human actions, believed or perceived, both by teller and listeners, to have taken place in human history. Narratives in this genre may demonstrate human valu ...
phones. However, due to supply shortages of the Samsung-produced displays, certain HTC models will use Sony's SLCD displays in the future, while the Google and Samsung Nexus S
The Nexus S 4G is a smartphone co-developed by Google and Samsung and manufactured by Samsung Electronics for release in 2010. It was the first smartphone to use the Android 2.3 "Gingerbread" operating system, and the first Android device to su ...
smartphone will use "Super Clear LCD" instead in some countries.
OLED displays were used in watches made by Fossil (JR-9465) and Diesel (DZ-7086). Other manufacturers of OLED panels include Anwell Technologies Limited
Anwell Technologies Limited was a Hong Kong multinational manufacturing company. Founded in 2000, the company initially designed machines that mass-produced optical discs, but later began manufacturing thin-film solar cells and organic light-em ...
(Hong Kong), AU Optronics
AUO Corporation (AUO; ) is a Taiwanese company that specialises in optoelectronic solutions. It was formed in September 2001 by the merger of Acer Display Technology, Inc. (the predecessor of AUO, established in 1996) and Unipac Optoelectronics Cor ...
(Taiwan), Chimei Innolux Corporation
Innolux Corporation () is a company producing TFT LCD panels, established in 2003 and located in Taiwan.
Overview
Innolux Display Corp., following its merger with Chi Mei Optoelectronics and TPO Displays Corp., began operating under the name In ...
(Taiwan), LG (Korea), and others.
DuPont
DuPont de Nemours, Inc., commonly shortened to DuPont, is an American multinational chemical company first formed in 1802 by French-American chemist and industrialist Éleuthère Irénée du Pont de Nemours. The company played a major role in ...
stated in a press release in May 2010, that they can produce a 50-inch OLED TV in two minutes with a new printing technology. If this can be scaled up in terms of manufacturing, then the total cost of OLED TVs would be greatly reduced. DuPont also states that OLED TVs made with this less expensive technology can last up to 15 years if left on for a normal eight-hour day.
The use of OLEDs may be subject to patent
A patent is a type of intellectual property that gives its owner the legal right to exclude others from making, using, or selling an invention for a limited period of time in exchange for publishing an enabling disclosure of the invention."A p ...
s held by Universal Display Corporation
Universal Display Corporation is a developer and manufacturer of organic light emitting diodes (OLED) technologies and materials as well as provider of services to the display and lighting industries. It is also an OLED research company. Founded ...
, Eastman Kodak
The Eastman Kodak Company (referred to simply as Kodak ) is an American public company that produces various products related to its historic basis in analogue photography. The company is headquartered in Rochester, New York, and is incorpor ...
, DuPont
DuPont de Nemours, Inc., commonly shortened to DuPont, is an American multinational chemical company first formed in 1802 by French-American chemist and industrialist Éleuthère Irénée du Pont de Nemours. The company played a major role in ...
, General Electric
General Electric Company (GE) is an American multinational conglomerate founded in 1892, and incorporated in New York state and headquartered in Boston. The company operated in sectors including healthcare, aviation, power, renewable energ ...
, Royal Philips Electronics
Koninklijke Philips N.V. (), commonly shortened to Philips, is a Dutch multinational conglomerate corporation that was founded in Eindhoven in 1891. Since 1997, it has been mostly headquartered in Amsterdam, though the Benelux headquarters is ...
, numerous universities and others. By 2008, thousands of patents associated with OLEDs, came from larger corporations and smaller technology companies.[
Flexible OLED displays have been used by manufacturers to create curved displays such as the ]Galaxy S7 Edge
The Samsung Galaxy S7, Samsung Galaxy S7 Edge and Samsung Galaxy S7 Active are Android-based smartphones manufactured, released and marketed by Samsung Electronics. The S7 series serves as the successor to the Galaxy S6, S6 Edge, S6 Edge+ and ...
but they were not in devices that can be flexed by the users. Samsung demonstrated a roll-out display in 2016.
On 31 October 2018, Royole, a Chinese electronics company, unveiled the world's first foldable screen phone featuring a flexible OLED display. On 20 February 2019, Samsung
The Samsung Group (or simply Samsung) ( ko, 삼성 ) is a South Korean multinational manufacturing conglomerate headquartered in Samsung Town, Seoul, South Korea. It comprises numerous affiliated businesses, most of them united under the ...
announced the Samsung Galaxy Fold
The Samsung Galaxy Fold is an Android-based foldable smartphone developed by Samsung Electronics. Unveiled on March 20, 2019, it was released on September 6, 2019 in South Korea. The device is capable of being folded open to expose a 7.3-inch ...
with a foldable OLED display from Samsung Display, its majority-owned subsidiary. At MWC 2019 on 25 February 2019, Huawei
Huawei Technologies Co., Ltd. ( ; ) is a Chinese multinational technology corporation headquartered in Shenzhen, Guangdong, China. It designs, develops, produces and sells telecommunications equipment, consumer electronics and various smar ...
announced the Huawei Mate X
The Huawei Mate X is an Android-based high end foldable smartphone produced by Huawei. It was unveiled at MWC 2019 on 25 February 2019 and was originally scheduled to launch in June 2019, but the launch was pushed back to allow for extensive te ...
featuring a foldable OLED display from BOE
BOE, BoE or Boe may refer to:
Abbreviations, acronyms or initialisms
* Bank of England, the central bank of the United Kingdom
* Bank of English, a representative subset of the 4.5 billion words COBUILD corpus
* Barrel of oil equivalent, a uni ...
.
The 2010s also saw the wide adoption of ''tracking gate-line in pixel'' (TGP), which moves the driving circuitry from the borders of the display to in between the display's pixels, allowing for narrow bezels.
Fashion
Textiles incorporating OLEDs are an innovation in the fashion world and pose for a way to integrate lighting to bring inert objects to a whole new level of fashion. The hope is to combine the comfort and low cost properties of textile with the OLEDs properties of illumination and low energy consumption. Although this scenario of illuminated clothing is highly plausible, challenges are still a road block. Some issues include: the lifetime of the OLED, rigidness of flexible foil substrates, and the lack of research in making more fabric like photonic textiles.
Automotive
The number of automakers using OLEDs is still rare and limited to the high-end of the market. For example, the 2010 Lexus RX
The is a luxury crossover SUV sold since 1998 by Lexus, a luxury division of Toyota. Originally released in its home market of Japan in late 1997 as the Toyota Harrier, export sales began in March 1998 as the Lexus RX. Considered as the first ...
features an OLED display instead of a thin film transistor (TFT-LCD) display.
A Japanese manufacturer Pioneer Electronic Corporation
commonly referred to as Pioneer, is a Japanese multinational corporation based in Tokyo, that specializes in digital entertainment products. The company was founded by Nozomu Matsumoto in January 1, 1938 in Tokyo as a radio and speaker repair ...
produced the first car stereos with a monochrome OLED display, which was also the world's first OLED product. The Aston Martin DB9 incorporated the world's first automotive OLED display, which was manufactured by Yazaki
is a global automotive parts supplier with a focus on wire harnesses, instruments and components such as connectors and terminals. The company's origin and headquarters are in Japan, but in 2011, roughly 90% of its employees were outside the home ...
, followed by the 2004 Jeep Grand Cherokee and the Chevrolet Corvette C6. The 2015 Hyundai Sonata
The Hyundai Sonata is a mid-size car that has been manufactured by Hyundai since 1985. The first generation Sonata, which was introduced in 1985, was a facelifted Hyundai Stellar with an engine upgrade, and was withdrawn from the market in two ...
and Kia Soul
The Kia Soul is a subcompact crossover SUV manufactured and marketed worldwide by Kia, currently in its third generation.
Designed at Kia's design center in California, the Soul debuted at the 2008 Paris Motor Show and is manufactured in South Ko ...
EV use a 3.5-inch white PMOLED display.
Company-specific applications
Samsung
By 2004, Samsung Display, a subsidiary of South Korea
South Korea, officially the Republic of Korea (ROK), is a country in East Asia, constituting the southern part of the Korea, Korean Peninsula and sharing a Korean Demilitarized Zone, land border with North Korea. Its western border is formed ...
's largest conglomerate and a former Samsung-NEC
is a Japanese multinational corporation, multinational information technology and electronics corporation, headquartered in Minato, Tokyo. The company was known as the Nippon Electric Company, Limited, before rebranding in 1983 as NEC. It prov ...
joint venture, was the world's largest OLED manufacturer, producing 40% of the OLED displays made in the world, and as of 2010, has a 98% share of the global AMOLED
AMOLED (active-matrix organic light-emitting diode, ) is a type of OLED display device technology. OLED describes a specific type of thin-film-display technology in which organic compounds form the electroluminescence, electroluminescent materia ...
market. The company is leading the world of OLED industry, generating $100.2million out of the total $475million revenues in the global OLED market in 2006. As of 2006, it held more than 600 American patents and more than 2800 international patents, making it the largest owner of AMOLED technology patents.
Samsung SDI announced in 2005, the world's largest OLED TV at the time, at . This OLED featured the highest resolution at the time, of 6.22million pixels. In addition, the company adopted active matrix-based technology for its low power consumption and high-resolution qualities. This was exceeded in January 2008, when Samsung showcased the world's largest and thinnest OLED TV at the time, at 31inches (78cm) and 4.3mm.
In May 2008, Samsung unveiled an ultra-thin 12.1inch (30cm) laptop OLED display concept, with a 1,280×768 resolution with infinite contrast ratio. According to Woo Jong Lee, Vice President of the Mobile Display Marketing Team at Samsung SDI, the company expected OLED displays to be used in notebook PCs as soon as 2010.
In October 2008, Samsung showcased the world's thinnest OLED display, also the first to be "flappable" and bendable. It measures just 0.05mm (thinner than paper), yet a Samsung staff member said that it is "technically possible to make the panel thinner". To achieve this thickness, Samsung etched an OLED panel that uses a normal glass substrate. The drive circuit was formed by low-temperature polysilicon TFTs. Also, low-molecular organic EL materials were employed. The pixel count of the display is 480 × 272. The contrast ratio is 100,000:1, and the luminance is 200cd/m2. The colour reproduction range is 100% of the NTSC standard.
As of 2020, the world's largest OLED television is an 88-inch with a 8K resolution, frame rate up to 120 fps and cost of 34,676 US Dollars.
At the Consumer Electronics Show (CES) in January 2010, Samsung demonstrated a laptop computer with a large, transparent OLED display featuring up to 40% transparency and an animated OLED display in a photo ID card.
Samsung's 2010 AMOLED smartphones used their Super AMOLED
AMOLED (active-matrix organic light-emitting diode, ) is a type of OLED display device technology. OLED describes a specific type of thin-film-display technology in which organic compounds form the electroluminescent material, and active matrix ...
trademark, with the Samsung Wave S8500
The Samsung Wave (or Samsung Wave GT-S8500) is a smartphone developed and produced by Samsung Electronics. It is the first smartphone to run the Bada operating system developed by Samsung Electronics, which was commercially released on May 24, 201 ...
and Samsung i9000 Galaxy S being launched in June 2010. In January 2011, Samsung announced their Super AMOLED Plus displays, which offer several advances over the older Super AMOLED
AMOLED (active-matrix organic light-emitting diode, ) is a type of OLED display device technology. OLED describes a specific type of thin-film-display technology in which organic compounds form the electroluminescent material, and active matrix ...
displays: real stripe matrix (50% more sub pixels), thinner form factor, brighter image and an 18% reduction in energy consumption.
At CES 2012, Samsung introduced the first 55" TV screen that uses Super OLED technology.
On 8 January 2013, at CES Samsung unveiled a unique curved 4K Ultra S9 OLED television, which they state provides an "IMAX-like experience" for viewers.[Rougeau, Michael (2013-01-08)]
Samsung's curved OLED TV provides an 'IMAX-like' experience
. Techradar. Retrieved 2013-01-08.
On 13 August 2013, Samsung announced availability of a 55-inch curved OLED TV (model KN55S9C) in the US at a price point of $8999.99.
On 6 September 2013, Samsung launched its 55-inch curved OLED TV (model KE55S9C) in the United Kingdom with John Lewis.
Samsung introduced the ''Galaxy Round'' smartphone in the Korean market in October 2013. The device features a 1080p screen, measuring , that curves on the vertical axis in a rounded case. The corporation has promoted the following advantages: A new feature called "Round Interaction" that allows users to look at information by tilting the handset on a flat surface with the screen off, and the feel of one continuous transition when the user switches between home screens.
Samsung released a new line of OLED TVs in 2022, its first using the technology since 2013. They use panels sourced from Samsung Display; previously, LG was the sole manufacturer of OLED panels for TVs.
Sony
The Sony CLIÉ PEG-VZ90 The Clie PEG-VZ90 is a Personal Digital Assistant (PDA) made by Sony. It ran the Palm OS (version 5) and was the last of the CLIÉ line. The PEG-VZ90 was released in 2004, only in Japan, and was made in the form of a Mini Tablet PC. It was the firs ...
was released in 2004, being the first PDA to feature an OLED screen. Other Sony products to feature OLED screens include the MZ-RH1 portable minidisc recorder, released in 2006 and the Walkman X Series.
At the 2007, Las Vegas
Las Vegas (; Spanish for "The Meadows"), often known simply as Vegas, is the 25th-most populous city in the United States, the most populous city in the state of Nevada, and the county seat of Clark County. The city anchors the Las Vegas ...
Consumer Electronics Show
CES (; formerly an initialism for Consumer Electronics Show) is an annual trade show organized by the Consumer Technology Association (CTA). Held in January at the Las Vegas Convention Center in Winchester, Nevada, United States, the event typi ...
(CES), Sony showcased a , (resolution 960×540) and , full HD resolution at OLED TV models. Both claimed 1,000,000:1 contrast ratio
The contrast ratio (CR) is a property of a display system, defined as the ratio of the luminance of the brightest shade (white) to that of the darkest shade (black) that the system is capable of producing. A high contrast ratio is a desired aspec ...
s and total thicknesses (including bezels) of 5mm. In April 2007, Sony announced it would manufacture 1000 OLED TVs per month for market testing purposes. On 1 October 2007, Sony announced that the model XEL-1, was the first commercial OLED TV[Sony XEL-1:The world's first OLED TV](_blank)
, OLED-Info.com (2008-11-17). and it was released in Japan in December 2007.
In May 2007, Sony publicly unveiled a video of a flexible OLED screen which is only 0.3 millimeters thick. At the Display 2008 exhibition, Sony demonstrated a 0.2mm thick display with a resolution of 320×200 pixels and a 0.3mm thick display with 960×540 pixels resolution, one-tenth the thickness of the XEL-1.
In July 2008, a Japanese government body said it would fund a joint project of leading firms, which is to develop a key technology to produce large, energy-saving organic displays. The project involves one laboratory and 10 companies including Sony Corp. NEDO said the project was aimed at developing a core technology to mass-produce 40inch or larger OLED displays in the late 2010s.
In October 2008, Sony published results of research it carried out with the Max Planck Institute
Max or MAX may refer to:
Animals
* Max (dog) (1983–2013), at one time purported to be the world's oldest living dog
* Max (English Springer Spaniel), the first pet dog to win the PDSA Order of Merit (animal equivalent of OBE)
* Max (gorilla) (1 ...
over the possibility of mass-market bending displays, which could replace rigid LCDs and plasma screens. Eventually, bendable, see-through display
A see-through display or ''transparent display'' is an electronic display that allows the user to see what is shown on the screen while still being able to see through it. The main applications of this type of display are in head-up displays, augme ...
s could be stacked to produce 3D images with much greater contrast ratios and viewing angle
In display technology parlance, viewing angle is the angle at which a display can be viewed with acceptable visual performance. In a technical context, the angular range is called viewing cone defined by a multitude of viewing directions. The vie ...
s than existing products.
Sony exhibited a 24.5" (62cm) prototype OLED 3D television during the Consumer Electronics Show in January 2010.
In January 2011, Sony announced the PlayStation Vita
The PlayStation Vita (PS Vita, or Vita) is a handheld video game console developed and marketed by Sony Interactive Entertainment. It was first released in Japan on December 17, 2011, and in North America, Europe, and other international territo ...
handheld game console (the successor to the PSP) will feature a 5-inch OLED screen.
On 17 February 2011, Sony announced its 25" (63.5cm) OLED Professional Reference Monitor aimed at the Cinema and high end Drama Post Production market.
On 25 June 2012, Sony and Panasonic announced a joint venture for creating low cost mass production OLED televisions by 2013.
Sony unveiled its first OLED TV since 2008 at CES 2017
CES (; formerly an initialism for Consumer Electronics Show) is an annual trade show organized by the Consumer Technology Association (CTA). Held in January at the Las Vegas Convention Center in Winchester, Nevada, United States, the event typi ...
called A1E. It revealed two other models in 2018 one at CES 2018
CES (; formerly an initialism for Consumer Electronics Show) is an annual trade show organized by the Consumer Technology Association (CTA). Held in January at the Las Vegas Convention Center in Winchester, Nevada, United States, the event typ ...
called A8F and other a Master Series TV called A9F. At CES 2019
CES (; formerly an initialism for Consumer Electronics Show) is an annual trade show organized by the Consumer Technology Association (CTA). Held in January at the Las Vegas Convention Center in Winchester, Nevada, United States, the event typi ...
They unveiled another two models one the A8G and the other another Bravia Series TV called A9G. Then, at CES 2020
CES (; formerly an initialism for Consumer Electronics Show) is an annual trade show organized by the Consumer Technology Association (CTA). Held in January at the Las Vegas Convention Center in Winchester, Nevada, United States, the event typi ...
, they revealed the A8H, which was effectively a A9G in terms of picture quality but with some compromises due to its lower cost. At the same event, they also revealed a 48-inch version of the A9G, making this its smallest OLED TV since the XEL-1.
LG
On 9 April 2009, LG acquired Kodak
The Eastman Kodak Company (referred to simply as Kodak ) is an American public company that produces various products related to its historic basis in analogue photography. The company is headquartered in Rochester, New York, and is incorpor ...
's OLED business and started to utilize white OLED technology. As of 2010, LG Electronics
LG Electronics Inc. () is a South Korean multinational electronics company headquartered in Yeouido-dong, Seoul, South Korea. LG Electronics is a part of LG Corporation, the fourth largest '' chaebol'' in South Korea, and often considered a ...
produced one model of OLED television, the 15EL9500[LG 15EL9500 OLED Television](_blank)
. Lg.com. Retrieved 2011-10-04. and had announced a OLED 3D television for March 2011. On 26 December 2011, LG officially announced the "world's largest OLED panel" and featured it at CES 2012. In late 2012, LG announces the launch of the 55EM9600 OLED television in Australia.
In January 2015, LG Display signed a long-term agreement with Universal Display Corporation for the supply of OLED materials and the right to use their patented OLED emitters.
Mitsubishi
Lumiotec is the first company in the world developing and selling, since January 2011, mass-produced OLED lighting panels with such brightness and long lifetime. Lumiotec is a joint venture of Mitsubishi Heavy Industries, ROHM, Toppan Printing, and Mitsui & Co.
On 1 June 2011, Mitsubishi Electric
, established on 15 January 1921, is a Japanese multinational electronics and electrical equipment manufacturing company headquartered in Tokyo, Japan. It is one of the core companies of Mitsubishi. The products from MELCO include elevators an ...
installed a 6-meter OLED 'sphere' in Tokyo's Science Museum.
Recom Group
On 6 January 2011, Los Angeles-based technology company Recom Group introduced the first small screen consumer application of the OLED at the Consumer Electronics Show in Las Vegas. This was a 2.8" (7cm) OLED display being used as a wearable video name tag. At the Consumer Electronics Show in 2012, Recom Group introduced the world's first video mic flag incorporating three 2.8" (7cm) OLED displays on a standard broadcaster's mic flag. The video mic flag allowed video content and advertising to be shown on a broadcasters standard mic flag.
Dell
On 6 January 2016, Dell announced the Ultrasharp UP3017Q OLED monitor at the Consumer Electronics Show in Las Vegas. The monitor was announced to feature a 4K UHD OLED panel with a 120Hz refresh rate, 0.1 millisecond response time, and a contrast ratio of 400,000:1. The monitor was set to sell at a price of $4,999 and release in March, 2016, just a few months later. As the end of March rolled around, the monitor was not released to the market and Dell did not speak on reasons for the delay. Reports suggested that Dell canceled the monitor as the company was unhappy with the image quality of the OLED panel, especially the amount of color drift that it displayed when you viewed the monitor from the sides. On 13 April 2017, Dell finally released the UP3017Q OLED monitor to the market at a price of $3,499 ($1,500 less than its original spoken price of $4,999 at CES 2016). In addition to the price drop, the monitor featured a 60Hz refresh rate and a contrast ratio of 1,000,000:1. As of June, 2017, the monitor is no longer available to purchase from Dell's website.
Apple
Apple
An apple is an edible fruit produced by an apple tree (''Malus domestica''). Apple fruit tree, trees are agriculture, cultivated worldwide and are the most widely grown species in the genus ''Malus''. The tree originated in Central Asia, wh ...
began using OLED panels in its watches in 2015 and in its laptops in 2016 with the introduction of an OLED touchbar to the MacBook Pro. In 2017, Apple announced the introduction of their tenth anniversary iPhone X
The iPhone X (Roman numeral "X" pronounced "ten", also known as iPhone 10) is a smartphone designed, developed and marketed by Apple Inc. It is part of the 11th generation of the iPhone. Available for pre-order from October 27, 2017, it was re ...
with their own optimized OLED display licensed from Universal Display Corporation. Apple has continued the use of the technology in the iPhone X's successors, such as the iPhone XS and iPhone XS Max, and iPhone 11 Pro
The iPhone 11 Pro and iPhone 11 Pro Max are smartphones designed, developed and marketed by Apple Inc. Serving as the Apple's flagship models of the 13th-generation of iPhones, they succeeded the iPhone XS and iPhone XS Max, respectively, ...
and iPhone 11 Pro Max
The iPhone 11 Pro and iPhone 11 Pro Max are smartphones designed, developed and marketed by Apple Inc. Serving as the Apple's flagship models of the 13th-generation of iPhones, they succeeded the iPhone XS and iPhone XS Max, respectively, ...
.
Nintendo
A third model of Nintendo
is a Japanese Multinational corporation, multinational video game company headquartered in Kyoto, Japan. It develops video games and video game consoles.
Nintendo was founded in 1889 as by craftsman Fusajiro Yamauchi and originally produce ...
's Switch
In electrical engineering, a switch is an electrical component that can disconnect or connect the conducting path in an electrical circuit, interrupting the electric current or diverting it from one conductor to another. The most common type of ...
, a hybrid gaming system, features an OLED panel in replacement of its current LCD
A liquid-crystal display (LCD) is a flat-panel display or other electronically modulated optical device that uses the light-modulating properties of liquid crystals combined with polarizers. Liquid crystals do not emit light directly but in ...
panel. Announced in the summer of 2021, it was released on 8 October 2021.
Research
In 2014, Mitsubishi Chemical Corporation
, or MCC, is a subsidiary of Mitsubishi Chemical Holdings Corporation. It is a Japanese corporation, that merged with Mitsubishi Pharma Corporation in 2005 to create Mitsubishi Chemical Holdings Corporation. Mitsubishi Chemical is the largest ...
(MCC), a subsidiary of Mitsubishi Chemical Holdings
is a Japanese company formed in October 2005 from the merger of Mitsubishi Chemical Corporation and Mitsubishi Pharma Corporation. The company is based in Tokyo and is one of the core Mitsubishi companies.
History
On December 4, 2021, the compan ...
, developed an OLED panel with a 30,000-hour life, twice that of conventional OLED panels.
The search for efficient OLED materials has been extensively supported by simulation methods; it is possible to calculate important properties computationally, independent of experimental input, making materials development cheaper.
On 18 October 2018, Samsung
The Samsung Group (or simply Samsung) ( ko, 삼성 ) is a South Korean multinational manufacturing conglomerate headquartered in Samsung Town, Seoul, South Korea. It comprises numerous affiliated businesses, most of them united under the ...
showed of their research roadmap at their 2018 Samsung OLED Forum. This included Fingerprint on Display (FoD), Under Panel Sensor (UPS), Haptic on Display (HoD) and Sound on Display (SoD).
Various venders are also researching cameras under OLEDs (Under Display Cameras). According to IHS Markit Huawei
Huawei Technologies Co., Ltd. ( ; ) is a Chinese multinational technology corporation headquartered in Shenzhen, Guangdong, China. It designs, develops, produces and sells telecommunications equipment, consumer electronics and various smar ...
has partnered with BOE
BOE, BoE or Boe may refer to:
Abbreviations, acronyms or initialisms
* Bank of England, the central bank of the United Kingdom
* Bank of English, a representative subset of the 4.5 billion words COBUILD corpus
* Barrel of oil equivalent, a uni ...
, Oppo with China Star Optoelectronics Technology (CSOT), Xiaomi
Corporation (; ), commonly known as Xiaomi and registered as Xiaomi Inc., is a Chinese designer and manufacturer of consumer electronics and related software, home appliances, and household items. Behind Samsung, it is the second largest ma ...
with Visionox.
In 2020, researchers at the Queensland University of Technology
Queensland University of Technology (QUT) is a public research university located in the urban coastal city of Brisbane, Queensland, Australia. QUT is located on two campuses in the Brisbane area viz. Gardens Point and Kelvin Grove. The univ ...
(QUT) proposed using human hair
Hair is a protein filament that grows from follicles found in the dermis. Hair is one of the defining characteristics of mammals.
The human body, apart from areas of glabrous skin, is covered in follicles which produce thick terminal and f ...
which is a source of carbon and nitrogen to create OLED displays.
See also
*
*
*
*
* Flexible organic light-emitting diode
A flexible organic light-emitting diode (FOLED) is a type of organic light-emitting diode (OLED) incorporating a flexible plastic substrate on which the electroluminescent organic semiconductor is deposited. This enables the device to be bent or ...
* List of emerging technologies
This is a list of emerging technologies, in-development technical innovations with significant potential in their applications. The criteria for this list is that the technology must:
# Exist in some way; purely hypothetical technologies can ...
* List of flat panel display manufacturers
Flat-panel displays are thin panels of glass or plastic used for electronically displaying text, images, or video. Liquid crystal displays (LCD), OLED (organic light emitting diode) and microLED displays are not quite the same; since LCD uses a ...
*
*
*
*
*
* (Dark Mode)
*
* LED display
A LED display is a flat panel display that uses an array of light-emitting diodes as pixels for a video display. Their brightness allows them to be used outdoors where they are visible in the sun for store signs and billboards. In recent y ...
* microLED
microLED, also known as micro-LED, mLED or µLED, first invented in 2000 by the research group of Hongxing Jiang and Jingyu Lin of Texas Tech University while they were at Kansas State University, is an emerging flat-panel display technology. mic ...
* Mini LED
An LED-backlit LCD is a liquid-crystal display that uses LEDs for backlighting instead of traditional cold cathode fluorescent (CCFL) backlighting. LED-backlit displays use the same TFT LCD (thin-film-transistor liquid-crystal display) techno ...
Further reading
* T. Tsujimura, ''OLED Display Fundamentals and Applications'', Wiley-SID Series in Display Technology, New York (2017). .
* P. Chamorro-Posada, J. Martín-Gil, P. Martín-Ramos, L.M. Navas-Gracia, ''Fundamentos de la Tecnología OLED'' (''Fundamentals of OLED Technology''). University of Valladolid, Spain (2008). . Available online, with permission from the authors, at the webpage
Fundamentos de la Tecnología OLED
*
* Shinar, Joseph (Ed.), ''Organic Light-Emitting Devices: A Survey''. NY: Springer-Verlag (2004). .
* Hari Singh Nalwa (Ed.), ''Handbook of Luminescence, Display Materials and Devices'', Volume 1–3. American Scientific Publishers, Los Angeles (2003). . Volume 1: Organic Light-Emitting Diodes
* Hari Singh Nalwa (Ed.), ''Handbook of Organic Electronics and Photonics'', Volume 1–3. American Scientific Publishers, Los Angeles (2008). .
* Müllen, Klaus (Ed.), ''Organic Light Emitting Devices: Synthesis, Properties and Applications''. Wiley-VCH (2006).
* Yersin, Hartmut (Ed.), ''Highly Efficient OLEDs with Phosphorescent Materials''. Wiley-VCH (2007).
* Kho, Mu-Jeong, Javed, T., Mark, R., Maier, E., and David, C. (2008) 'Final Report: OLED Solid State Lighting – Kodak European Research' MOTI (Management of Technology and Innovation) Project, Judge Business School of the University of Cambridge and Kodak European Research, Final Report presented on 4 March 2008 at Kodak European Research at Cambridge Science Park, Cambridge, UK., pages 1–12.
*
References
External links
08. Juli 2020
* ttp://www.ewh.ieee.org/soc/cpmt/presentations/cpmt0401a.pdf Structure and working principle of OLEDs and electroluminescent displays
MIT introduction to OLED technology
(video)
Historical list of OLED products from 1996 to present
{{Authority control
American inventions
Conductive polymers
Display devices
Display technology
Emerging technologies
Energy-saving lighting
Flexible electronics
Light-emitting diodes
Molecular electronics
Optical diodes
Organic electronics