White Light Emission from Polymer Electrophosphorescent Light-Emitting Devices Doped with Iridium Complexes

Abstract

We have fabricated simple polymer electrophosphorescent light-emitting devices based on a single emitting layer containing a hole-transporting host polymer, poly(N-vinylcarbazole), and an electron-transporting 1,3-bis[(4-tert-butylphenyl)-1,3,4-oxadiazolyl]phenylene, doped with iridium complexes. We obtained a white light emission, whose Commission Internationale de l'Eclairage color coordinates are x=0.33 and y=0.36, by double-doping with phosphorescent materials: 11.8 wt% blue-light-emitting bis[(4,6-difluorophenyl)-pyridinato-N,C2'](picolinate) iridium(III) and 0.2 wt% red-light-emitting bis[2-(2'-benzothienyl)pyridinato-N,C3'](acetylacetonate) iridium(III). At a practical luminance of 100 cd/m2, the external quantum efficiency of electroluminescence and the power luminous efficiency were 4.9% and 2.6 lm/W, respectively. This work demonstrates that high-efficiency white-light-emitting devices can be constructed from polymers and phosphorescent materials by using simple wet fabrication processes.