Research On Highly Efficient Solution Processed Organic Light Emitting Devices Based On Thermally Activated Delayed Fluorescence

Organic light-emitting diodes?OLEDs?have important application prospects in the field of flat panel display and solid-state light sources.How to improve device performance and reduce device fabrication costs is the key to the research of this technology.For the method,the solution process is considered to be a very important way to reduce costs.For the emitting materials,thermally activated delayed fluorescence?TADF?materials are the third generation of high efficiency organic light-emitting materials after fluorescent materials and phosphorescent materials.In this thesis,a low-cost solution process was combined with TADF emitting materials to study the high efficiency OLEDs based on TADF materials,and a series of research results were obtained.1.Blue OLEDs based on TADF material 2CzPN was prepared by solution process.Based on the bipolar material POBPCz,the maximum external quantum efficiency?EQE?of the blue OLED is 12.9%,the current efficiency CE is 33.0 cd/A,the power efficiency PE is 12.7 lm/W,and the CIE color coordinates are?0.19,0.37?.The efficiency of this device is the highest of 2CzPN-based blue OLEDs prepared by solution process in the reported literature.2.Based on the high efficiency blue TADF device,high efficiency white OLEDs were further fabricated by solution process.Two-color white emitting was achieved by the combination of 2CzPN and the orange phosphorescent material Ir?MDQ?₂?acac?.The best device achieved a maximum EQE of 12.4%with a CIE color coordinate of?0.36,041?.And the device has good spectral stability.From low brightness of 100cd/m² to high brightness of 1000 cd/m²,the CIE coordinates only change?0.01,0.01?.3.The effect of an additive in TADF devices prepared by solution process was studied.High efficiency TADF OLEDs of yellow,green and blue were fabricated by solution method.Different percentages of additives 1,8 octanediol?ODO?were added to each emitting layer to compare the device performance.The devices with low percentages of 0.5 to 2 wt%ODO are compared to the standard devices without ODO.The turn-on voltages are decreased by 0.1 to 0.2 V and the EQEs are increased by 5.3 to11.6%.More importantly,the devices with additive exhibit a significant increase in air stability.In this work,high efficiency TADF OLEDs were fabricated by solution process,and the efficiency and stability of TADF devices were improved by additive,which promoted the development of high performance OLEDs fabricated by solution process.