Research On Phosphorescent Organic Light-Emitting Devices Based On A New Host-Guest Doping System

In recent years, a new type of display technology based on organic light-emitting devices has been more and more attention of scientific research institutions and enterprises. To make the OLED lighting and display products more meet the demand of the market, improves the performance of the light-emitting device is particularly important. In OLED, the choosing of appropriate emission layer structure and material is essential to enhance the efficiency of the whole device and work stability. We have employed a host-guest doping system and researched the performance of OLED basing on a yellow-green guest material(Ir(β-Phppy)3) and three kinds of host materials(FIrpic, FIr6, DBTPhPm).First of all, a theoretical simulation of correlated color temperature and color rendering index is designed using the electroluminescence spectra of eight kinds of phosphorescent materials. The simulation result shows that the yellow-green has a positive effect on improving color rendering index. In order to demonstrate the simulation, a white OLED is fabricated basing on the structure of ITO/Mo O3/TAPC / TCTA/ Bepp2 /Bepp2: Ir(β-Phppy)3(10%) /Bepp2: Ir(pmiq)2(acac)(5%)/ BmPyPb/ LiF /Mg:Ag(15:1). At the driving voltage of 8V, the device owns a color rendering index of 87, a special color rendering index of 92, and a maximum power efficiency of 10.4 lm/W.And then, we employ two kinds of phosphorescent materials(FIrpic, FIr6) as host, and obtain a series highly efficient, low-voltage monochromatic OLEDs. The devices using FIrpic or FIr6 as the host have higher power efficiency than the device with the conventional host CBP. The enhancement of the maximum power efficiency in green phosphorescent device can reach 37.2%. Further, a two color-based white OLED is fabricated by simply reducing the concentration of the guest. At a brightness of 1000 cd/m2, the power efficiency of the white device is 8.4 lm/W with a color rendering index of 76.Finally, highly efficient monochromatic and white OLEDs with low turn-on voltage and low efficiency roll-off have been achieved based on a new bipolar host material DBTPhPm. The green device owns a low turn-on voltage of 2.4V due to the bipolar property and the energy matching between interfaces, and at the same time, the device has a rather high current efficiency of 40.3 cd/A at the brightness of 1000 cd/m2 which is only 1% roll-off from the maximum current efficiency of 40.7 cd/A. Moreover, we designed a two color-based white OLED with the structure of ITO /MoO3/TAPC/TCTA/DBTPhPm:Firpic(10%)/DBTPhPm:PO-01(7%)/TmPyPB/LiF/M g:Ag(15:1). The maximum power efficiency and the maximum current efficiency of the device can reach to 26.4 lm/W and 25.6 cd/A, respectively.