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2 February 2001 High-efficiency organic electrophosphorescent devices
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We have fabricated saturated red, orange, yellow and green OLEDs, utilizing phosphorescent dopants. Using phosphorescence based emitters we have eliminated the inherent 25% upper limit on emission observed for traditional fluorescence based systems. The quantum efficiencies of these devices are quite good, with measured external efficiencies > 15% and > 40 lum/W (green) in the best devices. The phosphorescent dopants in these devices are heavy metal containing molecules (i.e. Pt, and Ir), prepared as both metalloporphyrins and organometallic complexes. The high level of spin orbit coupling in these metal complexes gives efficient emission from triplet states. In addition to emission from the heavy metal dopant, it is possible to transfer the exciton energy to a fluorescent dye, by Forster energy transfer. The heavy metal dopant in this case acts as a sensitizer, utilizing both singlet and triplet excitons to efficiently pump a fluorescent dye. We discuss the important parameters in designing electrophosphorescent OLEDs as well as their strengths and limitations. Accelerated aging studies, on packaged devices, have shown that phosphorescence based OLEDs can have very long device lifetimes.
© (2001) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Mark E. Thompson, Sergey Lamansky, Peter Djurovich, Drew Murphy, Feras Abdel-Razaq, Stephen R. Forrest, Marc A. Baldo, Paul E. Burrows, Chihaya Adachi, Theodore X. Zhou, Lech A. Michalski, Kamala Rajan, and Julie J. Brown "High-efficiency organic electrophosphorescent devices", Proc. SPIE 4105, Organic Light-Emitting Materials and Devices IV, (2 February 2001);

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