Light-emitting electrochemical cell

A light-emitting electrochemical cell (LEC or LEEC) is a solid-state device that generates light from an electric current (electroluminescence). LEC's 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 does not depend 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.^[1][2]
• Recently developed materials such as graphene^[3] or a blend of carbon nanotubes and polymers^[4] 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^[5] with relatively inexpensive printing processes (where control over film thicknesses can be difficult).
• Internal device operation can be observed directly.^[6]

While electroluminescence had been seen previously in similar devices, the invention of the polymer LEC is attributed to Pei et al.^[7] Since then, numerous research groups and a few companies have worked on improving and commercializing the devices.

In 2012 the first inherently stretchable LEEC 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.^[8]

In 2012 fabrication of organic light-emitting electrochemical cells (LECs) using a roll-to-roll compatible process under ambient conditions was reported.^[9]

See also

• Electrochemical cell
• Electrochemiluminescence
• Light-emitting diode
• Organic light-emitting diode
• Photoelectrolysis

References

1. Gao, J.; Dane, J. (2003). "Planar Polymer Light-Emitting Electrochemical Cells with extremely Large Interelectrode Spacing". Applied Physics Letters 83 (15): 3027. doi:10.1063/1.1618948.
2. Shin, J.-H.; Dzwilewski, A.; Iwasiewicz, A.; Xiao, S.; Fransson, Å.; Ankah, G. N.; Edman, L. (2006). "Light Emission at 5 V from a Polymer Device with a Millimeter-Sized Interelectrode Gap". Applied Physics Letters 89 (1): 013509. doi:10.1063/1.2219122.
3. Matyba, P.; Yamaguchi, H.; Eda, G.; Chhowalla, M.; Edman, L.; Robinson, N. D. (2010). "Graphene and Mobile Ions: The Key to All-Plastic, Solution-Processed Light-Emitting Devices". ACS Nano 4 (2): 637–42. doi:10.1021/nn9018569. PMID 20131906.
4. Yu, Z.; Hu, L.; Liu, Z.; Sun, M.; Wang, M.; Grüner, G.; Pei, Q. (2009). "Fully Bendable Polymer Light Emitting Devices with Carbon Nanotubes as Cathode and Anode". Applied Physics Letters 95 (20): 203304. doi:10.1063/1.3266869.
5. Mauthner, G.; Landfester, K.; Kock, A.; Bruckl, H.; Kast, M.; Stepper, C.; List, E. J. W. (2008). "Inkjet Printed Surface Cell Light-Emitting Devices from a Water-Based Polymer Dispersion". Organic Electronics 9 (2): 164–70. doi:10.1016/j.orgel.2007.10.007.
6. Gao, J.; Dane, J. (2004). "Visualization of Electrochemical Doping and Light-Emitting Junction Formation in Conjugated Polymer Films". Applied Physics Letters 84 (15): 2778. doi:10.1063/1.1702126.
7. Pei, Q. B.; Yu, G.; Zhang, C.; Yang, Y.; Heeger, A. J. (1995). "Polymer Light-Emitting Electrochemical-Cells". Science 269 (5227): 1086–8. doi:10.1126/science.269.5227.1086. PMID 17755530.
8. Filiatrault, H. L.; Porteous, G. C.; Carmichael, R. S.; Davidson, G. J. E.; Carmichael, T. B. (2012). "Stretchable Light-Emitting Electrochemical Cells Using an Elastomeric Emissive Material". Advanced Materials 24 (20): 2673–8. doi:10.1002/adma.201200448.
9. Sandström, A.; Dam, H. F.; Krebs, F. C.; Edman, L. (2012). "Ambient Fabrication of Flexible and Large-Area Organic Light-Emitting Devices Using Slot-Die Coating" (PDF). Nature Communications 3: 1002. doi:10.1038/ncomms2002.