Design of Blue Thermally Activated Delayed Fluorescent Emitter with Efficient Exciton Gathering Property for High-Performance Fully-Solution-Processed Hybrid White OLEDs

摘要： The blue TADF emitters are highly attractive in the fields of constructing hybrid white organic light-emitting diodes (WOLEDs) due to its high efficiency and color stability. However, few of blue TADF emitters can withstand sequential orthogonal solvents, making it impossible to fabricate the fully-solution-processed hybrid WOLEDs. Here, two TADF materials, PCz-4CzCN and TPA-4CzCN, were designed and synthesized by equipping the emissive core with nonconjugated bulky units, which can effectively enhance the solvent resistance ability without disturbing the TADF feature. The photophysical investigation indicates that phenylcarbazole unit can efficiently block the electromer formation to enhance the energy transfer and exciton utilization of the emitter. Accordingly, the blue OLEDs of PCz-4CzCN shows higher external quantum efficiency (EQE) of 22.6%, which is the best performance recorded among the fully-solution-processed blue OLEDs. Upon further doping the yellow phosphor PO-01, the fully-solution-processed TADF-phosphor (T-P) hybrid WOLEDs was successfully obtained with high performance for the first time. Thanks to the efficient exciplex formation, the turn on voltage of the white device are only 2.8 V, and the maximum brightness and power efficiency are as high as 53300 cd m-2 and 38.5 lm W-1, respectively, which are even higher than the previous reported T-P hybrid WOLEDs with a vacuum-deposited electron transfer layer.