Properties of white organic electroluminescent device with double light-emitting layers based upon different hosts

A novel phosphorescent white organic light-emitting device (WOLED) with configuration of ITO/NPB/CBP:TBPe:rubrene/ BAlq:Ir(piq)(2)(acac)/BAlq/Alq(3)/Mg:Ag was fabricated successfully, where the phosphorescent dye Ir(piq)(2)(acac) was doped into BAlq (electron transport material) as the red emitting layer, and fluorescent dye TBPe and together with rubrene was doped into CBP (ambipolar conductivity material) as the blue and orange emitting layer, respectively. The emitting layers were sandwiched between the undoped NPB and BALq layers. We also discussed how to achieve the bright pure white light with high stability through optimizing the doping concentration of each dopant and employing the balanced charges distribution for the introduction of the heterojunctions between the different hosts in detail. This device turns on at the driving voltage of 4.2 V. It presents a maximum external quantum efficiency and brightness of 1.5% and 15000 cd/m(2), respectively. The Commission Internationale de l'Eclairage (CIE) coordinates varies from (0.368, 0.389) at 10 V to (0.314, 0.327) at 15 V, and the best point is located at (0.334, 0.339) at 13 V. With the good EL performance, this kind of WOLED are particular suited for working as the backlight in LCD in combination with color filters to achieve the full color display.