EXPERIMENTAL. The. The light light emitting emitting diodes diodes (LEDs) .... modulation technique technique with with 33 VV AC. AC susu perposed.
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optic Materials (CEEM) and our industrial partner, Ohmtek, Inc., of Niagara Falls, NY. We also rec ognize technical discussions with Dr. Robert Ham ilton and Dr. Frank Collins.
REFERENCES 1. W. R. Buessem, L. E. Cross and A. K. Groswami, J. Am.
Ceram. Soc. 49, 33 (1966). 2. C. A. T. Salama and E. Sicinaus, J. Vac. Sci. Technol. 9, 91 (1971).
3. R. Vu Huy Dat and C. Baumberger, Phys, Status Solidi 22,
67 (1967).
4. 1. H. Pratt, Proc. IEEE 59, 1440 (1971). 5. T. Nagatomo, T. Kosaka and O. Omoto, Ferroelectric 37,681
(1981).
6. K. Sreenivas, A. Mansingh and M. Sayer, J. Appl. Phys. 62,
4475 (1987).
7. Y. Shintani and O. Tada, J. Appl. Phys. 41, 2376 (1970). 8. T. L. Rose, E. M. Kelliher, A. N. Scoville and S. E. Stone, J.
Appl. Phys. 55, 3706 (1984).
9. Q. X. Jia and W. A. Anderson, Appl. Phys. Lett. 57, 304 (1990). 10. P. J. Harrop and D. S. Campbell, Thin Solid Films, 2, 273 (1968).
Improved Efficiency in Semiconducting Polymer Light-Emitting Diodes D. BRAUN and A. J. HEEGER D. Institute for Polymers and Organic Solids, University of California California
93106
Santa Barbara, California 93106 H. KRaEMER KROEMER H. Department of Electrical and Computer Engineering, University of California Santa Barbara, California 93106 We report visible light emission from metal-polymer diodes made from semiconducting oxide as the "ohmic" ~ontact, ~ontact, and a variety ?f metals as the polymers, with indium-tin oxid.e which confirm the dIscovery by the Cambndge group [Na [Na barrier metal. Our results, whIch cast ture 347, 539 (1990)], demonstrate that light-emitting diodes can be fabricated by cast fr~m solution ~ith. no subseque.nt subseque:nt polymer ing the polymer film on indium-t.in oxide fr~m processing or heat treatment reqmred. reqUIred. ElectrIcal characterIzatIOn chara:terIzatI.on reveals dlOde dIOde behav behav ior with rectification ratios greater than 105 at sufficiently suffiCIently high hIgh voltages. Use of ?f an magmtude electrode material with low work function leads to more than an order of magnitude room-temperature efficien~y ?f the device~. For exa~ple~ the most improvement in the room-temp~rature calcium as the rectlfymg rectIfymg contact dIsplay effiCIencIes of 0.01 efficient devices made with calclUm photons per electron. Key words: Barium, calcium, electroluminescence, indium, ligh~-emitting ligh~-emitting dio~e dio~e (LED), magnesium, poly(2-methoxy,5-(2' semIconduct poly(2-methoxy,5-(2' -ethy -ethy1-hexoxy )-1,4- phenylene-vmylene), semIconduct ing polymer
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