A light-emitting electrochemical cell (LEC or LEEC) is a solid-state device that generates light from an electric current (
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 emission ...
). LECs are usually composed of two metal electrodes connected by (e.g. sandwiching) an
organic semiconductor containing mobile ions. Aside from the mobile ions, their structure is very similar to that of an
organic light-emitting diode (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 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 or a blend of
carbon nanotube
A carbon nanotube (CNT) is a tube made of carbon with a diameter in the nanometre range ( nanoscale). They are one of the allotropes of carbon. Two broad classes of carbon nanotubes are recognized:
* ''Single-walled carbon nanotubes'' (''S ...
s and polymers have been used as electrodes, eliminating the need for using
indium tin oxide 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 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.
See also
*
Electrochemical cell
An electrochemical cell is a device that either generates electrical energy from chemical reactions in a so called galvanic cell, galvanic or voltaic cell, or induces chemical reactions (electrolysis) by applying external electrical energy in an ...
*
Electrochemiluminescence
*
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 (corre ...
*
Organic light-emitting diode
*
Photoelectrolysis
References
Display technology
Molecular electronics
Conductive polymers
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