Fabrication of a new organic multilayer phosphorescent white-light-emitting device and evaluation of its characteristics

A novel organic phosphorescent white-light-emitting device (WOLED) with configuration of ITO/NPB/NPB:Ir(piq)2 (acac)/ CBP:TBPe /BAIq: rubrene/BAlq/Alq(3)/Mg: Ag is fabricated successfully, in which the phosphorescent dye (Ir(piq)2 ( acac)) doped into NPB ( hole transport material), fluorescent dye ( TBPe) doped into CBP ( ambipolar conductivity material) and another fluorescent dye (rubrene) doped into BALq (electron transport material) work as the red, blue and green emitting layer, respectively. The emitting layers are sandwiched between the undoped NPB and BALq layers. The charge distribution has been balanced for the introduction of heterojunctions between the different emitting layers, which results in a high fabrication reproducibility of the device. White emission is obtained by tuning the thickness and doping proportions of each layer. The device turns on at the driving voltage of 4.5 V. It shows a maximum external quantum efficiency and brightness of 1.5 % and 16260 cd/m(2), respectively. The Commission Internationale de 1' Eclairage (CIE) coordinates varies from (0.396, 0.432) at 5 V to (0.411, 0.414) at 20 V. The emission spectra of the device mainly consist of blue (464 nm), green (552 nm) and red (620 nm) emissions peaks, which are particular suitable to be combined with color filters to obtain the three primary colors and further achieve full color displays.