Study On The Structure Improvement And The Performance Enhancement Of White Organic Light-Emitting Devices

White organic light-emitting devices (WOLEDs) have been attracting worldwide interest for their potential applications as backlights for liquid crystal displays and solid state lighting (SSL). The efficiency, brightness, lifetime and color stability to applied voltage are all key parameters that must be optimized for the commercialization of WOLEDs. The brightness and efficiency of the devices has increased markedly with the introduction of phosphorescent materials. At the same time, many methods to improve the color stability have been reported in the literature. These include the control of the exciton recombination zone by introducing a carrier blocking layer and the fabrication of a single-emitting-layer device. Our work are mainly on the performance enhancement including the efficiency, color stability and CRI of the WOLEDs:Firstly, by employing a phosphorescent dye Ir(piq)2(acac) as a red emitter and TBPe as blue emitter, a high efficiency WOLED was fabricated successfully. On one hand, the introduction of red phosphorescent enhance the efficiency, on the other hand, the blue fluorescent dye employed as blue emitting dye avoided the flaw of the short lifetime for blue phosphorescent. The device show a maximum external efficiency of 1.7% with the brightness of 1020 cd/m2 at 8 V. The brightness reaches 11500 cd/m2 at 17 V.Secondly, by the introduction of a phosphorescent dye (Ir(ppy)3) as a sensitizer, fluorescent dyes (Rubrene and TBPe) as yellow and blue emitter respectively, a high efficiency WOLED device is fabricated sucessfuly. The charges distribution and the CIE coordinate of the device could be well controlled by the BCP layer between the two emitting layers.Thirdly, a single emitting layer WOLED and a bright multilayer WOLED with high color stability to applied voltage is fabricated, respectively. We provide a feasible way to fabricate mutilyer white device with high color stability to applied voltage. The mutilayer device is fabricated by introducing a hole blocking layer and adjusting the doping concentration. The CIE coordinates varies only from (0.3108, 0.3803) at 5 V to (0.3089, 0.3771) at 17 V and the EL spectrum shows very slight change.The end, a novel phosphorescent white organic light-emitting device (WOLED) with configuration of ITO/NPB/NPB:Ir(piq)2(acac)/CBP:TBPe/BAlq:rubrene/BAlq/Alq3/Mg:Ag is fabricated successfully. The device shows a CRI of 92 which is raletivly high, compared with both the other white OLED and the other kind of light source. The white device shows a maximum external quantum efficiency of 1.5 % at 9 V, and a high brightness of 16260 cd/m2 at 20 V. For the emission spectra of the white OLED are mainly consist of blue (464 nm), green (552 nm) and red (620 nm) emissions, which are particular suitable to be combined with color filters to obtain the three primary colors for the full color display.