Efficient white organic light-emitting diodes based on iridium complex sensitized copper complex

Abstract

Efficient double emission-layer white organic light-emitting diodes comprising a yellow emission from bis[(4,6-difluorophenyl)-pyridinato-N,C2](picolinato)Ir(III) (FIrpic) sensitized [Cu(bis[2-(diphenylphosphino)phenyl]ether) (6,7-Dicyanodipyrido[2,2-d : 2′, 3′-f] quinoxaline)]BF4(CuI complex) and a blue emission from 4, 4′-bis(2,2′-diphenylvinyl)-1, 1′-biphenyl (DPVBi) were demonstrated. The emission spectrum can be fine tuned by effectively controlling the thicknesses of the two emission layers. The optimized device with 18 nm FIrpic and the CuI complex codoped 4, 4′-N,N′-dicarbazole-biphenyl layer and 12 nm DPVBi layer shows a maximum current efficiency of 8.5 cd A−1, a maximum power efficiency of 5.3 lm W−1 and a maximum luminance of 3290 cd m−2. Moreover, the device exhibits a CIE coordinate of (0.345, 0.357) at a bias of 8 V and a slight colour variation with increased voltage from 6 to 16 V.