Enhanced electrophosphorescence of copper complex based devices by codoping an iridium complex

Evidently enhanced electrophosphorescence of [Cu(bis[2-(diphenylphosphino)phenyl] ether)(6,7-dicyanodipyrido [2,2-d:2′,3′-f] quinoxaline)] BF4 (CuI complex) by codoping bis[(4,6-difluorophenyl)-pyridinato-N, C2](picolinato)Ir(III) (FIrpic) into the same host, 4,4′-N,N′-dicarbazole-biphenyl, was demonstrated. The device codoped with 8wt% FIrpic and 2wt% CuI complex shows a maximum current efficiency and power efficiency of 26.6cd∕A and 17.8lm∕W, respectively, which were increased by factors of 2.6 and 2.1 compared with the 2wt% CuI complex monodoped device. The improvements of the devices were testified to the efficient energy transfer from FIrpic to the CuI complex. The detail of the energy transfer mechanism between the two phosphors was also proposed.