and MR-TADF emitter MR-T4 combination. With an aim of developing an efficient TADF emitter, a sterically congested TADF emitter, T20 with multiple donor groups was developed. The presence of multiple donor-acceptor moieties in the same molecule supported the orbital mixing of LE and CT states, ensuing a high kRISC of 2.36 × 10 6 s -1 .