Transformation from Nonthermally Activated Delayed Fluorescence Molecules to Thermally Activated Delayed Fluorescence Molecules

A novel molecular design approach transforming nonthermally activated delayed fluorescence (TADF) molecules to TADF molecules is developed for high external quantum efficiencies in TADF devices by utilizing an opened double emission process through selective twisting of the donor structure. Two non-TADF type donor–acceptor molecules are coupled together to selectively twist the donor structure for enhanced charge transfer character. Selective twisting of the donor is achieved by simultaneously coupling the opened reverse intersystem crossing channel for TADF emission and the double emission process to achieve high external quantum efficiencies. Two emitters are created based on the molecular design concept demonstrating high external quantum efficiencies of 27.8% for sky blue TADF devices.