Architectures for efficient electrophosphorescent organic light-emitting devices

We discuss several device architectures leading to high-efficiency organic electrophosphorescent (EP) light emission. An external electroluminescence efficiency (/spl eta//sub ext/) of (10.0 /spl plusmn/ 0.5) % was realized by doping fac-tris(2-phenylpyridine)iridium (Ir(ppy)/sub 3/) into a 2,9-dimethyl-4,7-diphenyl-1,10-phenenthroline (BCP) electron transport layer. Direct exciton formation on the phosphor dopant avoids exciplex formation at the interface of unipolar hole and electron transport layers. Further, triplet exciton and carrier dynamics in a double heterostructure were investigated to determine the location and width of the exciton formation zone. High-efficiency EP is also demonstrated in a simplified two layer architecture using a 4,4'-N, N'-dicarbazole-biphenyl (CBP) ambipolar carrier transport host.