Rational design of efficient orange-red to red thermally activated delayed fluorescence emitters for OLEDs with external quantum efficiency of up to 26.0% and reduced efficiency roll-off

A class of novel donor–acceptor orange-red to red thermally activated delayed fluorescence (TADF) emitters with a maximum external quantum efficiency (EQE) of up to 26.0% and extremely low efficiency roll-off have been designed and synthesized.