Discotic liquid crystals are

mesophase In chemistry and chemical physics, a mesophase is a state of matter intermediate between liquid and solid. Gelatin is a common example of a partially ordered structure in a mesophase. Further, biological structures such as the lipid bilayers of cel ...

s formed from disc-shaped molecules known as "discotic mesogens". These phases are often also referred to as

columnar phase The columnar phase is a class of mesophases in which molecules assemble into cylindrical structures to act as mesogens. Originally, these kinds of liquid crystals were called discotic liquid crystals or bowlic liquid crystals because the columnar s ...

s. Discotic mesogens are typically composed of an aromatic core surrounded by flexible alkyl chains. The aromatic cores allow charge transfer in the stacking direction through the π conjugate systems. The charge transfer allows the discotic

liquid crystal Liquid crystal (LC) is a state of matter whose properties are between those of conventional liquids and those of solid crystals. For example, a liquid crystal may flow like a liquid, but its molecules may be oriented in a crystal-like way. T ...

s to be electrically semiconductive along the stacking direction. Applications have been focusing on using these systems in photovoltaic devices, organic

light emitting diodes 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 ...

(OLED), and molecular wires. Discotics have also been suggested for use in compensation films, for LCD displays.

Photovoltaic devices

Discotic liquid crystals have similar potential to the

conducting polymers 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 ...

for their use in

photovoltaic cells 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.

, they have the same technical challenges of low conductivity and sensitivity to UV damage as the polymer designs. However one advantage is the

self-healing Self-healing refers to the process of recovery (generally from psychological disturbances, trauma, etc.), motivated by and directed by the patient, guided often only by instinct. Such a process encounters mixed fortunes due to its amateur nature, ...

properties of the discotic mesogens. So far the photovoltaic applications have been limited, using a

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, ...

and

hexabenzocoronene Hexa-peri-hexabenzocoronene (HBC) is a polycyclic aromatic hydrocarbon with the molecular formula C42H18. It consists of a central coronene molecule, with an additional benzene ring fused between each adjacent pair of rings around the periphery. I ...

mesogens in a simple two layer systems has only resulted in ~2% power efficiency.

Organic light emitting diodes

So far the study into discotic liquid crystals for light emitting diodes are still in its infancy, but there have been some examples produced; a

triphenylene Triphenylene is an organic compound with the formula (C6H4)3. A flat polycyclic aromatic hydrocarbon (PAH), it consists of four fused benzene rings. Triphenylene has delocalized 18-''π''-electron systems based on a planar structure, correspondin ...

and

mesogen A mesogen is a compound that displays liquid crystal properties. Mesogens can be described as disordered solids or ordered liquids because they arise from a unique state of matter that exhibits both solid- and liquid-like properties called the liq ...

combination can be used to make a red LED. The

self-assembly Self-assembly is a process in which a disordered system of pre-existing components forms an organized structure or pattern as a consequence of specific, local interactions among the components themselves, without external direction. When the ...

properties make them more desirable for manufacturing purposes when producing commercial electronics, than the currently used

small molecule Within the fields of molecular biology and pharmacology, a small molecule or micromolecule is a low molecular weight (≤ 1000 daltons) organic compound that may regulate a biological process, with a size on the order of 1 nm. Many drugs ar ...

crystals in Sony’s new OLED displays. Also they have the added benefit of the self-healing properties that both the small molecule and the polymers lack as conductors, potentially being beneficial for longevity OLED products.

References

{{reflist Solar energy Liquid crystals