Highly efficient green phosphorescent organic light-emitting diodes with simplified device geometry

We report on the performance of green phosphorescent organic light-emitting diodes based on the well-known host 4,4′-di(carbazol-9-yl)-biphenyl and the green phosphor emitter fac tris(2-phenylpyridinato-N,C2′) iridium. Using a spin-coated hole-injection/transport layer of poly(N-vinyl-carbazole) and a hole-blocking/electron-transport layer of 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline, devices with efficiencies of 21.2% and 72cd∕A at 100cd∕m2 were obtained in a simplified device geometry that requires the deposition of only two organic layers from the vapor phase.