Combinatorial donor engineering for highly efficient blue thermally activated delayed fluorescence emitters with low efficiency roll-off

Abstract

A thermally activated delayed fluorescence (TADF) molecule with high reverse intersystem crossing rate accompanied by high photoluminescence quantum yield was developed by combinatorial donor engineering of bicarbazole and 12H-benzofuro[3,2-a]carbazole. The donor was designed to have strong donor character, rigidity and large twisted angle with the acceptor moiety by combining the merits of bicarbazole and benzofurocarbazole. The TADF emitter derived from the new donor achieved high external quantum efficiencies of up to 23.3% and largely suppressed efficiency roll-off at high luminance relative to the control TADF emitters. Therefore, the combinatorial donor approach was effective to trigger the synergistic effect on the device performances of the TADF devices.