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 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 ...

containing mobile ions. Aside from the mobile ions, their structure is very similar to that of an

organic light-emitting diode An organic light-emitting diode (OLED or organic LED), also known as organic electroluminescent (organic EL) diode, is a light-emitting diode (LED) in which the emissive electroluminescent layer is a film of organic compound that emits light i ...

(OLED). LECs have most of the advantages of OLEDs, as well as additional ones: * The device is less dependent on the difference in

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" ...

of the electrodes. Consequently, the electrodes can be made of the same material (e.g. gold). Similarly, the device can still be operated at low voltages. * Recently developed materials such as

graphene Graphene () is an allotrope of carbon consisting of a single layer of atoms arranged in a hexagonal lattice nanostructure.

or a blend of carbon nanotubes and polymers have been used as electrodes, eliminating the need for using

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 ...

for a transparent electrode. * The thickness of the active electroluminescent layer is not critical for the device to operate. This means that: *LECs can be printed with relatively inexpensive printing processes (where control over film thicknesses can be difficult). *In a planar device configuration, internal device operation can be observed directly. There are two distinct types of LECs, those based on inorganic transition metal complexes (iTMC) or light emitting polymers. iTMC devices are often more efficient than their LEP based counterparts due to the emission mechanism being phosphorescent rather than fluorescent. While electroluminescence had been seen previously in similar devices, the invention of the polymer LEC is attributed to Pei et al. Since then, numerous research groups and a few companies have worked on improving and commercializing the devices. In 2012 the first inherently stretchable LEC using an elastomeric emissive material (at room temperature) was reported. Dispersing an ionic transition metal complex into an elastomeric matrix enables the fabrication of intrinsically stretchable light-emitting devices that possess large emission areas (∼175 mm2) and tolerate linear strains up to 27% and repetitive cycles of 15% strain. This work demonstrates the suitability of this approach to new applications in conformable lighting that require uniform, diffuse light emission over large areas. In 2012 fabrication of organic light-emitting electrochemical cells (LECs) using a

roll-to-roll In the field of electronic devices, roll-to-roll processing, also known as web processing, reel-to-reel processing or R2R, is the process of creating electronic devices on a roll of flexible plastic, metal foil, or flexible glass. In other fields p ...

compatible process under ambient conditions was reported. In 2017, a new design approach developed by a team of Swedish researchers promised to deliver substantially higher efficiency: 99.2 cd A⁻¹ at a bright luminance of 1910 cd m⁻².

References

Display technology Molecular electronics Conductive polymers {{electronics-stub

See also

References