Light-emitting Electrochemical Cell

A light-emitting electrochemical cell (LEC or LEEC) is a solid-state devices that generates light from an electric current (electroluminesces). They are usually composed of two metal electrodes connected by (e.g. sandwiching) an organic semiconducting material that contains mobile ions. Aside from the ions, their structure is very similar to that of an Organic light-emitting diode (OLED).

LECs have most of the advantages of OLEDs and several more:
* The device does not depend on the difference in work function of the electrodes, which means that the electrodes can be made of the same material (e.g. Gold), and the device can still be operated at low voltages. [Citation
last1 = Gao | first1 = J.
last2 = Dane | first2 = J.
contribution = Planar polymer light-emitting electrochemical cells with extremely large interelectrode spacing
title = Applied Physics Letters
year = 2003
doi = 10.1063/1.1618948 ] [Citation
last1 = Shin | first1 = J.-H.
last2 = Dzwilewski | first2 = A.
last3 = Iwasiewicz | first3 = A.
last4 = Xial | first4 = S.
last5 = Fransson | first5 = A.
last6 = Ankah | first6 = G.N.
last7 = Edman | first7 = L.
contribution = Light emission at 5 V from a polymer device with a millimeter-sized interelectrode gap
title = Applied Physics Letters
year = 2006
doi = 10.1063/1.2219122 ]
* The thickness of the active electroluminescent layer is not critical for the device to operate. This means that:
**LECs can be printed [Citation
last1 = Mauthner | first1 = G.
last2 = Landfester | first2 = K.
last3 = Kock | first3 = A.
last4 = Bruckl | first4 = H.
last5 = Kast | first5 = M.
last6 = Stepper | first6 = C.
last7 = List | first7 = E.J.W.
contribution = Inkjet printed surface cell light-emitting devices from a water-based polymer dispersion
title = Organic Electronics
year = 2008
doi = 10.1016/j.orgel.2007.10.007 ] with relatively inexpensive printing processes (where control over film thicknesses can be difficult).
**Internal device operation can be observed directly. [Citation
last1 = Gao | first1 = J.
last2 = Dane | first2 = J.
contribution = Visualization of electrochemical doping and light-emitting junction formation in conjugated polymer films
title = Applied Physics Letters
year = 2004
doi = 10.1063/1.1702126 ]

History

The invention of the polymer LEC is attributed to Pei et al. [Citation
last1 = Pei | first1 = Q.B.
last2 = Yu | first2 = G.
last3 = Zhang | first3 = C.
last4 = Yang | first4 = Y.
last5 = Heeger | first5 = A.J.
contribution = Polymer Light-Emitting Electrochemical-Cells
year = 1995
title = Science
doi = 10.1126/science.269.5227.1086] Since then, numerous research groups, and even a few companies, have worked on improving and commercializing the devices.

References