Improved efficiency in semiconducting polymer light-emitting diodes
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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.
Key wordsBarium calcium electroluminescence indium light-emitting diode (LED) magnesium poly(2-methoxy,5-(2’-ethyl-hexoxy)-l,4-phenylene-vinylene) semiconducting polymer
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- 2.F. Wudl, P.-M. Allemand, G. Srdanov, Z. Ni and D. Mc- Branch, in Materials for Non-linear Optics: Chemical Per- spectives, eds. S. R. Marder, J. E. Sohn and G. D. Stucky, (The American Chemical Society, 1991), p. 683.Google Scholar
- 3.T. W. Hagler, K. Pakbaz, J. Moulton, F. Wudl, P. Smith and A. J. Heeger, Polym. Commun.32, 339 (1991) in press.Google Scholar
- 4.J. I. Pankove, Electroluminescence (Springer-Verlag, Berlin, 1977).Google Scholar
- 5.T. W. Hagler, K. Pakbaz, K. Voss and A. J. Heeger, Phys. Rev. B44, (1991) in press.Google Scholar
- 9.Handbook of Chemistry and Physics, ed. R. C. Weast (The Chemical Rubber Co., Cleveland, 1980).Google Scholar
- 10.Proceedings of the 1990 International Conference on the Sci- ence and Technology of Synthetic Metals, Synth. Met.41- 43 (1991).Google Scholar