2,3-Dimethylindole as Donor for Novel Thermally Activated Delayed Fluorescence Emitters
A couple of indole derivatives based light-emitting molecules were synthesized and studied. They shared the same donor unit, 2,3-dimethylindole, were quite similar in emission color. In addition, they possessed almost the same lowest unoccupied molecular orbital (LUMO) and highest occupied molecular orbital (HOMO) energy levels. However, their discrepancy in the amount of 2,3-dimethylindole donor units resulted in different energy gaps between singlet and triplet states as well as efficiency of reverse intersystem crossing (RISC) process. OLED device based on these 2,3-dimethylindole compounds displayed external quantum efficiencies of 6.3% and 16.5% with greenish blue emission, respectively.