White-light electroluminescent organic devices based on efficient energy harvesting of singlet and triplet excited states using blue-light exciplex

In this study, blue exciplex electroluminescence was observed under both optical and electrical excitation during mixing of the extensively used hole-transport material tris(4-carbazoyl-9-ylphenyl)amine and electron-transport material, 4,7-diphenyl-1,10-phenanthroline. Comprehensive experiments demonstrated efficient energy transfer from the blue exciplex to the green and red phosphors. We successfully introduced a unique white organic light-emitting device that used a singlet state exciplex as the blue emitter in combination with green and red phosphors to yield white light with an external quantum efficiency of 10.5% at 1000 cd/m(2) and satisfied Commission Internationale de l'Eclairage color coordinates of (0.38, 0.43) and the corresponding color rendering index of 81. (C) 2014 The Japan Society of Applied Physics