Thermally activated delayed fluorescence: exploring the past to get insights into reverse and forward intersystem crossing

The early history of thermally activated delayed fluorescence (TADF) studies is summarized prior to the popularization of TADF-based materials by Adachi and his group for organic light-emitting diodes (OLEDs) in the third-generation of OLEDs. Then, some insights into reverse and forward intersystem crossing (RISC and ISC) in TADF are argued based on earlier experimental results.