White Organic Light Emitting Devices Based on Multiple Emissive Nanolayers

In this paper, a white organic light-emitting device (WOLEDs) with multiple-emissive-layer structure has been fabricated. The device has a simple structure of indium tin oxide (ITO)/NPB (20 nm)//DPVBi(20 nm)/CDBP:xIr(btp)2acac(10 nm)/Alq3(25 nm)/BCP (5 nm)/CsF (1 nm)/Al (150 nm) (x= 0.15, 2.5 and 3.0 wt%), where NPB and BCP are used as the hole-injecting layer, electron transporting and hole blocking layer, respectively. White light emission was realized in an OLED with 2.5% Ir(btp)2acac doping concentration. The device exhibits peak efficiency of 1.93 cd/A at 9 V and maximum brightness of 7005 cd/m(2) at 14 V. The Commission International de I'Eclairage (CIE)(1931) coordinates of white emission are well within the white zone, which moves from (0.35,0.33) to (0.26,0.30) when the applied voltage is varied from 5 V to 14 V.