Postprint version. Published in Journal of Electronic Materials, Volume 20, Issue 11, November 1, 1991, pages 945-948.
NOTE: At the time of publication, the author David Braun was not yet affiliated with Cal Poly.
The definitive version is available at https://doi.org/10.1007/BF02816037.
We report visible light emission from metal-polymer diodes made from semiconducting polymers, with indium-tin oxide as the “ohmic” contact, and a variety of metals as the barrier metal. Our results, which confirm the discovery by the Cambridge group [Nature347, 539 (1990)], demonstrate that light-emitting diodes can be fabricated by casting the polymer film on indium-tin oxide from solution with no subsequent polymer processing or heat treatment required. Electrical characterization reveals diode behavior with rectification ratios greater than 105 at sufficiently high voltages. Use of an electrode material with low work function leads to more than an order of magnitude improvement in the room-temperature efficiency of the devices. For example, the most efficient devices made with calcium as the rectifying contact display efficiencies of 0.01 photons per electron.
Electrical and Computer Engineering