Highly efficient ternary polymer-based solution-processable exciplex with over 20% external quantum efficiency in organic light-emitting diode

To develop high-performance solution-processed thermally activated delayed fluorescence (TADF) organic light-emitting diodes (OLED5) based on exciplex emitters, a novel strategy was present to develop ternary polymer-based exciplex emitter by introducing the third small-molecule constituent material into binary polymer-based exciplex in this work. Compared with common binary polymer-based exciplex emitters, such ternary polymer-based exciplex emitters could not only enhance up-conversion of nonradiative triplet excitons and realize higher exciton utilization, but also maintain the superiorities of polymers in solution processing, like excellent film-forming ability and thermal stability. Based on our strategy, a highly efficient ternary polymer-based exciplex PVK:PO-T2T:mCP was developed. As expected, PVK:PO-T2T:mCP successfully realizes much higher photoluminescence quantum yield of 82.0% and rate constant of RISC process of 2.62 x 10(5) than PVK:PO-T2T. In the solution-processed OLED5, interfacial PVK:PO-T2T:mCP exhibits a record-high maximum external quantum efficiency of 21.9% for polymer-based exciplexes, demonstrating the superiorly of our strategy for further development of solution-processed TADF-OLED5.