![NREL PV Cell Record Efficiency Chart](https://upload.wikimedia.org/wikipedia/commons/b/b0/NREL_PV_Cell_Record_Efficiency_Chart.png)
Solar-cell efficiency refers to the portion of energy in the form of sunlight that can be converted via
photovoltaics into electricity by the
solar cell
A solar cell, or photovoltaic cell, is an electronic device that converts the energy of light directly into electricity by the photovoltaic effect, which is a physical and chemical phenomenon. .
The efficiency of the solar cells used in a
photovoltaic system, in combination with latitude and climate, determines the annual energy output of the system. For example, a solar panel with 20% efficiency and an area of 1 m
2 will produce 200 kWh/yr at Standard Test Conditions if exposed to the Standard Test Condition solar irradiance value of 1000 W/m
2 for 2.74 hours a day. Usually solar panels are exposed to sunlight for longer than this in a given day, but the solar irradiance is less than 1000 W/m
2 for most of the day. A solar panel can produce more when the sun is high in the sky and will produce less in cloudy conditions or when the sun is low in the sky, usually the sun is lower in the sky in the winter.
Two location dependant factors that affect solar PV efficiency are the dispersion and intensity of solar radiation. These two variables can vary greatly between each country.
The global regions that have high radiation levels throughout the year are the middle east, Northern Chile, Australia, China, and Southwestern USA.
In a high-yield solar area like central Colorado, which receives annual
insolation of 2000 kWh/m
2/year,
a panel can be expected to produce 400
kWh of energy per year. However, in Michigan, which receives only 1400 kWh/m
2/year,
annual energy yield will drop to 280 kWh for the same panel. At more northerly European latitudes, yields are significantly lower: 175 kWh annual energy yield in southern England under the same conditions.
![Solartce3](https://upload.wikimedia.org/wikipedia/commons/b/be/Solartce3.gif)
Several factors affect a cell's conversion efficiency, including its
reflectance
The reflectance of the surface of a material is its effectiveness in reflecting radiant energy. It is the fraction of incident electromagnetic power that is reflected at the boundary. Reflectance is a component of the response of the electronic ...
,
thermodynamic efficiency
In thermodynamics, the thermal efficiency (\eta_) is a dimensionless performance measure of a device that uses thermal energy, such as an internal combustion engine, steam turbine, steam engine, boiler, furnace, refrigerator, ACs etc.
For a ...
,
charge carrier separation efficiency, charge carrier collection efficiency 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 ...
efficiency values.
Because these parameters can be difficult to measure directly, other parameters are measured instead, including
quantum efficiency,
open-circuit voltage
Open-circuit voltage (abbreviated as OCV or VOC) is the difference of electrical potential between two terminals of an electronic device when disconnected from any circuit. There is no external load connected. No external electric current f ...
(V
OC) ratio, and . Reflectance losses are accounted for by the quantum efficiency value, as they affect "external quantum efficiency". Recombination losses are accounted for by the quantum efficiency, V
OC ratio, and fill factor values. Resistive losses are predominantly accounted for by the fill factor value, but also contribute to the quantum efficiency and V
OC ratio values. In 2019, the world record for solar cell efficiency at 47.1% was achieved by using
multi-junction Multi-junction (MJ) solar cells are solar cells with multiple p–n junctions made of different semiconductor materials. Each material's p-n junction will produce electric current in response to different wavelengths of light. The use of multiple ...
concentrator In the evolution of modern telecommunications systems there was a requirement to connect large numbers of low-speed access devices with large telephone company 'central office' switches over common paths. During the first generations of digital netw ...
solar cells, developed at National Renewable Energy Laboratory, Golden, Colorado, USA.
Factors affecting energy conversion efficiency
The factors affecting
energy conversion efficiency were expounded in a landmark paper by
William Shockley
William Bradford Shockley Jr. (February 13, 1910 – August 12, 1989) was an American physicist and inventor. He was the manager of a research group at Bell Labs that included John Bardeen and Walter Brattain. The three scientists were jointl ...
and
Hans Queisser
Hans-Joachim Queisser (born 6 July 1931, Berlin, Germany) is a solid-state physics, solid-state physicist. He is best known for co-authoring the 1961 work on solar cells that detailed what is today known as the Shockley–Queisser limit, which is n ...
in 1961.
See
Shockley–Queisser limit
In physics, the radiative efficiency limit (also known as the detailed balance limit, Shockley–Queisser limit, Shockley Queisser Efficiency Limit or SQ Limit) is the maximum theoretical efficiency of a solar cell using a single p-n junction ...
for more detail.
Thermodynamic-efficiency limit and infinite-stack limit
![ShockleyQueisserFullCurve](https://upload.wikimedia.org/wikipedia/commons/4/4c/ShockleyQueisserFullCurve.svg)
If one has a source of heat at temperature and cooler heat sink at temperature , the maximum theoretically possible value for the ratio of work (or electric power) obtained to heat supplied is , given by a
Carnot heat engine
A Carnot heat engine is a heat engine that operates on the Carnot cycle. The basic model for this engine was developed by Nicolas Léonard Sadi Carnot in 1824. The Carnot engine model was graphically expanded by Benoît Paul Émile Clapeyron in 1 ...
. If we take 6000 K for the temperature of the sun and 300 K for ambient conditions on earth, this comes to 95%. In 1981, Alexis de Vos and Herman Pauwels showed that this is achievable with a stack of an infinite number of cells with band gaps ranging from infinity (the first cells encountered by the incoming photons) to zero, with a voltage in each cell very close to the open-circuit voltage, equal to 95% of the band gap of that cell, and with 6000 K
blackbody radiation
Black-body radiation is the thermal electromagnetic radiation within, or surrounding, a body in thermodynamic equilibrium with its environment, emitted by a black body (an idealized opaque, non-reflective body). It has a specific, continuous spe ...
coming from all directions. However, the 95% efficiency thereby achieved means that the electric power is 95% of the ''net'' amount of light absorbed – the stack ''emits'' radiation as it has non-zero temperature, and this radiation has to be subtracted from the incoming radiation when calculating the amount of heat being transferred and the efficiency. They also considered the more relevant problem of maximizing the power output for a stack being illuminated from all directions by 6000 K blackbody radiation. In this case, the voltages must be lowered to less than 95% of the band gap (the percentage is not constant over all the cells). The maximum theoretical efficiency calculated is 86.8% for a stack of an infinite number of cells, using the incoming concentrated sunlight radiation.
When the incoming radiation comes only from an area of the sky the size of the sun, the efficiency limit drops to 68.7%.
Ultimate efficiency
Normal photovoltaic systems however have only one
p–n junction and are therefore subject to a lower efficiency limit, called the "ultimate efficiency" by Shockley and Queisser. Photons with an energy below the band gap of the absorber material cannot generate an
electron-hole pair, so their energy is not converted to useful output, and only generates heat if absorbed. For photons with an energy above the band gap energy, only a fraction of the energy above the band gap can be converted to useful output. When a photon of greater energy is absorbed, the excess energy above the band gap is converted to kinetic energy of the carrier combination. The excess kinetic energy is converted to heat through
phonon interactions as the kinetic energy of the carriers slows to equilibrium velocity. Traditional single-junction cells with an optimal
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 ( ...
for the solar spectrum have a maximum theoretical efficiency of 33.16%, the
Shockley–Queisser limit
In physics, the radiative efficiency limit (also known as the detailed balance limit, Shockley–Queisser limit, Shockley Queisser Efficiency Limit or SQ Limit) is the maximum theoretical efficiency of a solar cell using a single p-n junction ...
.
Solar cells with multiple band gap absorber materials improve efficiency by dividing the solar spectrum into smaller bins where the thermodynamic efficiency limit is higher for each bin.
Quantum efficiency
As described above, when a photon is absorbed by a solar cell it can produce an electron-hole pair. One of the carriers may reach the p–n junction and contribute to the current produced by the solar cell; such a carrier is said to be ''collected''. Or, the carriers
recombine with no net contribution to cell current.
Quantum efficiency refers to the percentage of photons that are converted to electric current (i.e., collected carriers) when the cell is operated under short circuit conditions. There are two types of quantum that are usually referred to when talking about solar cells. The external quantum efficiency, that relates to the external measurable properties of the solar cell. The "external" quantum efficiency of a
silicon
Silicon is a chemical element with the symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic luster, and is a tetravalent metalloid and semiconductor. It is a member of group 14 in the periodic ta ...
solar cell includes the effect of optical losses such as transmission and reflection. In particular, some measures can be taken to reduce these losses. The reflection losses, which can account for up to 10% of the total incident energy, can be dramatically decreased using a technique called texturization, a light trapping method that modifies the average light path.
The second type is the internal quantum efficiency, this measurement of the internal quantum efficiency gives a deeper insight of the internal material parameters like the absorption coefficient or internal luminescence quantum efficiency.
The internal quantum efficiency is mainly used when it comes to the understanding of the potential of a certain material rather than a device.
Quantum efficiency is most usefully expressed as a ''spectral'' measurement (that is, as a function of photon wavelength or energy). Since some wavelengths are absorbed more effectively than others, spectral measurements of quantum efficiency can yield valuable information about the quality of the semiconductor bulk and surfaces. However, the quantum efficiency alone is not the same as overall energy conversion efficiency, as it does not convey information about the fraction of power that is converted by the solar cell.
Maximum power point
![Dust on the a solar panel](https://upload.wikimedia.org/wikipedia/commons/4/4a/Dust_on_the_a_solar_panel.jpg)
A solar cell may operate over a wide range of
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 ...
s (V) and
currents
Currents, Current or The Current may refer to:
Science and technology
* Current (fluid), the flow of a liquid or a gas
** Air current, a flow of air
** Ocean current, a current in the ocean
*** Rip current, a kind of water current
** Current (stre ...
(I). By increasing the resistive load on an irradiated cell continuously from zero (a ''
short circuit
A short circuit (sometimes abbreviated to short or s/c) is an electrical circuit that allows a current to travel along an unintended path with no or very low electrical impedance. This results in an excessive current flowing through the circui ...
'') to a very high value (an ''open circuit'') one can determine the
maximum power point, the point that maximizes V×I; that is, the load for which the cell can deliver maximum electrical power at that level of irradiation. (The output power is zero in both the short circuit and open circuit extremes).
The maximum power point of a solar cell is affected by its temperature. Knowing the technical data of certain solar cell, its power output at a certain temperature can be obtained by
, where
is the power generated at the standard testing condition;
is the actual temperature of the solar cell.
A high quality, monocrystalline silicon solar cell, at 25 °C cell temperature, may produce 0.60
V open-circuit (''V
OC''). The cell temperature in full sunlight, even with 25 °C air temperature, will probably be close to 45 °C, reducing the open-circuit voltage to 0.55 V per cell. The voltage drops modestly, with this type of cell, until the short-circuit current is approached (''I
SC''). Maximum power (with 45 °C cell temperature) is typically produced with 75% to 80% of the open-circuit voltage (0.43 V in this case) and 90% of the short-circuit current. This output can be up to 70% of the ''V
OC x I
SC'' product. The short-circuit current (''I
SC'') from a cell is nearly proportional to the illumination, while the open-circuit voltage (''V
OC'') may drop only 10% with an 80% drop in illumination. Lower-quality cells have a more rapid drop in voltage with increasing current and could produce only 1/2 ''V
OC'' at 1/2 ''I
SC''. The usable power output could thus drop from 70% of the ''V
OC x I
SC'' product to 50% or even as little as 25%. Vendors who rate their solar cell "power" only as ''V
OC x I
SC'', without giving load curves, can be seriously distorting their actual performance.
The maximum power point of a
photovoltaic varies with incident illumination. For example, accumulation of dust on photovoltaic panels reduces the maximum power point. Recently, new research to remove dust from solar panels has been developed by utilizing electrostatic cleaning systems. In such systems, an applied electrostatic field at the surface of the solar panels causes the dust particles to move in a "flip-flop" manner.
Then, due to gravity and the fact that the solar panels are slightly slanted, the dust particles get pulled downward by gravity.
These systems only require a small power consumption and enhance the performance of the solar cells, especially when installed in the desert, where dust accumulation contributes to decreasing the solar panel's performance. Also, for systems large enough to justify the extra expense, a
maximum power point tracker
Maximum power point tracking (MPPT) or sometimes just power point tracking (PPT), is a technique used with variable power sources to maximize energy extraction as conditions vary. The technique is most commonly used with photovoltaic (PV) solar s ...
tracks the instantaneous power by continually measuring the voltage and
current
Currents, Current or The Current may refer to:
Science and technology
* Current (fluid), the flow of a liquid or a gas
** Air current, a flow of air
** Ocean current, a current in the ocean
*** Rip current, a kind of water current
** Current (stre ...
(and hence, power transfer), and uses this information to dynamically adjust the load so the maximum power is ''always'' transferred, regardless of the variation in lighting.
Fill factor
Another defining term in the overall behaviour of a solar cell is the ''fill factor'' (''FF''). This factor is a measure of quality of a solar cell. This is the available ''power'' at the ''maximum power point'' (''P
m'') divided by the ''open circuit voltage'' (''V
OC'') and the ''short circuit current'' (''I
SC''):
:
The fill factor can be represented graphically by the IV sweep, where it is the ratio of the different rectangular areas.
The fill factor is directly affected by the values of the cell's series,
shunt resistances and diodes losses. Increasing the shunt resistance (R
sh) and decreasing the
series resistance (R
s) lead to a higher fill factor, thus resulting in greater efficiency, and bringing the cell's output power closer to its theoretical maximum.
Typical fill factors range from 50% to 82%. The fill factor for a normal silicon PV cell is 80%.
Comparison
Energy conversion efficiency is measured by dividing the electrical output by the incident light power. Factors influencing output include spectral distribution, spatial distribution of power, temperature, and resistive load.
IEC
The International Electrotechnical Commission (IEC; in French: ''Commission électrotechnique internationale'') is an international standards organization that prepares and publishes international standards for all electrical, electronic and r ...
standard 61215 is used to compare the performance of cells and is designed around standard (terrestrial, temperate) temperature and conditions (STC):
irradiance of 1 kW/m
2, a spectral distribution close to solar radiation through AM (
airmass
In astronomy, air mass or airmass is a measure of the amount of air along the line of sight when observing a star or other celestial source from below Earth's atmosphere ( Green 1992). It is formulated as the integral of air density along the lig ...
) of 1.5 and a cell temperature 25 °C. The resistive load is varied until the peak or maximum power point (MPP) is achieved. The power at this point is recorded as
Watt-peak (Wp). The same standard is used for measuring the power and efficiency of PV modules.
Air mass affects output. In space, where there is no atmosphere, the spectrum of the sun is relatively unfiltered. However, on earth, air filters the incoming light, changing the solar spectrum. The filtering effect ranges from
Air Mass
In meteorology, an air mass is a volume of air defined by its temperature and humidity. Air masses cover many hundreds or thousands of square miles, and adapt to the characteristics of the surface below them. They are classified according to l ...
0 (AM0) in space, to approximately Air Mass 1.5 on Earth. Multiplying the spectral differences by the quantum efficiency of the solar cell in question yields the efficiency. Terrestrial efficiencies typically are greater than space efficiencies. For example, a silicon solar cell in space might have an efficiency of 14% at AM0, but 16% on earth at AM 1.5. Note, however, that the number of incident photons in space is considerably larger, so the solar cell might produce considerably more power in space, despite the lower efficiency as indicated by reduced percentage of the total incident energy captured.
Solar cell efficiencies vary from 6% for amorphous silicon-based solar cells to 44.0% with multiple-junction production cells and 44.4% with multiple dies assembled into a hybrid package. Solar cell energy conversion efficiencies for commercially available ''multicrystalline Si'' solar cells are around 14–19%. The highest efficiency cells have not always been the most economical – for example a 30% efficient multijunction cell based on exotic materials such as gallium arsenide or indium selenide produced at low volume might well cost one hundred times as much as an 8% efficient amorphous silicon cell in mass production, while delivering only about four times the output.
However, there is a way to "boost" solar power. By increasing the light intensity, typically photogenerated carriers are increased, increasing efficiency by up to 15%. These so-called "
concentrator systems" have only begun to become cost-competitive as a result of the development of high efficiency GaAs cells. The increase in intensity is typically accomplished by using concentrating optics. A typical concentrator system may use a light intensity 6–400 times the sun, and increase the efficiency of a one sun GaAs cell from 31% at AM 1.5 to 35%.
A common method used to express economic costs is to calculate a price per delivered
kilowatt-hour (kWh). The solar cell efficiency in combination with the available irradiation has a major influence on the costs, but generally speaking the overall system efficiency is important. Commercially available solar cells (as of 2006) reached system efficiencies between 5 and 19%.
Undoped crystalline silicon devices are approaching the theoretical limiting efficiency of 29.43%.
In 2017, efficiency of 26.63% was achieved in an amorphous silicon/crystalline silicon heterojunction cell that place both positive and negative contacts on the back of the cell.
Energy payback
The energy payback time is defined as the recovery time required for generating the energy spent for manufacturing a modern photovoltaic module. In 2008, it was estimated to be from 1 to 4 years
depending on the module type and location. With a typical lifetime of 20 to 30 years, this means that modern solar cells would be net energy producers, i.e., they would generate more energy over their lifetime than the energy expended in producing them.
Generally,
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 ...
technologies—despite having comparatively low conversion efficiencies—achieve significantly shorter energy payback times than conventional systems (often < 1 year).
A study published in 2013 which the existing literature found that energy payback time was between 0.75 and 3.5 years with thin film cells being at the lower end and multi-si-cells having a payback time of 1.5–2.6 years. A 2015 review assessed the energy payback time and
EROI
EROI or the Eastman Rochester Organ Initiative is a project run by the Eastman School of Music with the goal of creating a unique collection of organ instruments in Rochester, New York.
The Italian Baroque organ
The first milestone of the proje ...
of solar photovoltaics. In this meta study, which uses an insolation of 1,700 kWh/m
2/year and a system lifetime of 30 years, mean harmonized EROIs between 8.7 and 34.2 were found. Mean harmonized energy payback time varied from 1.0 to 4.1 years.
Crystalline silicon
Crystalline silicon or (c-Si) Is the crystalline forms of silicon, either polycrystalline silicon (poly-Si, consisting of small crystals), or monocrystalline silicon (mono-Si, a continuous crystal). Crystalline silicon is the dominant semiconduc ...
devices achieve on average an energy payback period of 2 years.
Like any other technology, solar cell manufacture is dependent on the existence of a complex global industrial manufacturing system. This includes the fabrication systems typically accounted for in estimates of manufacturing energy; the contingent mining, refining and global transportation systems; and other energy intensive support systems including finance, information, and security systems. The difficulty in measuring such energy overhead confers some uncertainty on any estimate of payback times.
Technical methods of improving efficiency
Choosing optimum transparent conductor
The illuminated side of some types of solar cells, thin films, have a transparent conducting film to allow light to enter into the active material and to collect the generated charge carriers. Typically, films with high transmittance and high electrical conductance such as indium tin oxide, conducting polymers or conducting nanowire networks are used for the purpose. There is a trade-off between high transmittance and electrical conductance, thus optimum density of conducting nanowires or conducting network structure should be chosen for high efficiency.
Promoting light scattering in the visible spectrum
Lining the light-receiving surface of the cell with nano-sized metallic studs can substantially increase the cell efficiency. Light reflects off these studs at an oblique angle to the cell, increasing the length of the light path through the cell. This increases the number of photons absorbed by the cell and the amount of current generated.
The main materials used for the nano-studs are
silver
Silver is a chemical element with the symbol Ag (from the Latin ', derived from the Proto-Indo-European ''h₂erǵ'': "shiny" or "white") and atomic number 47. A soft, white, lustrous transition metal, it exhibits the highest electrical ...
,
gold
Gold is a chemical element with the symbol Au (from la, aurum) and atomic number 79. This makes it one of the higher atomic number elements that occur naturally. It is a bright, slightly orange-yellow, dense, soft, malleable, and ductile me ...
, and
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 ...
. Gold and silver are not very efficient, as they absorb much of the light in the visible spectrum, which contains most of the energy present in sunlight, reducing the amount of light reaching the cell.
Aluminium absorbs only ultraviolet radiation, and reflects both visible and infra-red light, so energy loss is minimized. Aluminium can increase cell efficiency up to 22% (in lab conditions).
Radiative cooling
An increase in solar cell temperature of approximately 1 °C causes an efficiency decrease of about 0.45%. To prevent this, a transparent
silica
Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , most commonly found in nature as quartz and in various living organisms. In many parts of the world, silica is the major constituent of sand. Silica is ...
crystal layer can be applied to solar panels. The silica layer acts as a
thermal black body which emits heat as
infrared radiation
Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from around ...
into space, cooling the cell up to 13 °C. Radiative cooling can thus extend the life of solar cells.
Full-system integration of solar energy and radiative cooling is referred to as a combined SE–RC system, which have demonstrated higher energy gain per unit area when compared to non-integrated systems.
Anti-reflective coatings and textures
Antireflective coatings could result in more destructive interference of incident light waves from the sun. Therefore, most of the sunlight would be transmitted into the photovoltaic. There are a few anti-reflective coatings types, some of which can be based on the layer composition or the surface topography. Many architectures of these anti-reflective coats are inspired by nature.
For example, the nipple-array, a hexagonal array of subwavelength conical nanostructures, can be seen at the surface of the moth's eyes.
It was reported that utilizing this sort of surface architecture minimizes the reflection losses by 25%, converting the additional captured photon to a 12% increase in a solar cell's energy.
Texturizing can also be used as a method to achieve anti-reflectiveness in which the surface of a solar cell is altered so that the reflected light strikes the surface again. These surfaces can be created by etching or using lithography. Adding a flat back surface in addition to texturizing the front surface helps to trap the light within the cell, thus providing a longer optical path.
Rear surface passivation
Surface passivation
A surface, as the term is most generally used, is the outermost or uppermost layer of a physical object or space. It is the portion or region of the object that can first be perceived by an observer using the senses of sight and touch, and is ...
is critical to solar cell efficiency. Many improvements have been made to the front side of mass-produced solar cells, but the aluminium back-surface is impeding efficiency improvements. The efficiency of many solar cells has benefitted by creating so-called passivated emitter and rear cells (PERCs). The chemical deposition of a rear-surface dielectric passivation layer stack that is also made of a thin
silica
Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , most commonly found in nature as quartz and in various living organisms. In many parts of the world, silica is the major constituent of sand. Silica is ...
or
aluminium oxide film topped with a
silicon nitride
Silicon nitride is a chemical compound of the elements silicon and nitrogen. is the most thermodynamically stable and commercially important of the silicon nitrides, and the term "silicon nitride" commonly refers to this specific composition. It ...
film helps to improve efficiency in
silicon
Silicon is a chemical element with the symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic luster, and is a tetravalent metalloid and semiconductor. It is a member of group 14 in the periodic ta ...
solar cells. This helped increase cell efficiency for commercial
Cz-Si wafer material from just over 17% to over 21% by the mid-2010s, and the cell efficiency for quasi-mono-Si to a record 19.9%.
Concepts of the rear surface passivation for silicon solar cells has also been implemented for CIGS solar cells. The rear surface passivation shows the potential to improve the efficiency. Al
2O
3 and SiO
2 have been used as the passivation materials. Nano-sized point contacts on Al
2O
3 layer and line contacts on SiO2 layer provide the electrical connection of CIGS absorber to the rear electrode
Molybdenum. The point contacts on the Al
2O
3 layer are created by e-beam lithography and the line contacts on the SiO
2 layer are created using
photolithography. Also, the implementation of the passivation layers does not change the morphology of the CIGS layers.
Thin film materials
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 ...
materials show a lot of promise for solar cells in terms of low costs and adaptability to existing structures and frameworks in technology.
[Da, Yun, and Yimin Xuan. "Role of Surface Recombination in Affecting the Efficiency of Nanostructured Thin-Film Solar Cells .” Osapublishing, 2013, www.osapublishing.org/DirectPDFAccess/F1E0036E-C63D-5F6F-EA52FF38B5D1786D_270075/oe-21-S6-A1065] Since the materials are so thin, they lack the optical absorption of bulk material solar cells. Attempts to correct this have been tried, more important is thin film surface recombination. Since this is the dominant recombination process of nanoscale thin-film solar cells, it is crucial to their efficiency. Adding a passivating thin layer of silicon dioxide could reduce recombination.
See also
*
Environmental impact of the energy industry
The environmental impact of the energy industry is significant, as energy and natural resource consumption are closely related. Producing, transporting, or consuming energy all have an environmental impact. Energy has been harnessed by human bei ...
*
Energy efficiency
Energy efficiency may refer to:
* Energy efficiency (physics), the ratio between the useful output and input of an energy conversion process
** Electrical efficiency, useful power output per electrical power consumed
** Mechanical efficiency, a ra ...
References
External links
*
*
*
{{Solar energy
Solar cells
Photovoltaics