Highly rigid polycyclic acceptors by incorporating quinoxaline and naphthalimideacridine towards red TADF emitters

Abstract

The development of red thermally activated delayed fluorescence (TADF) emitters with the emission peak above 600 nm remains far behind blue and green emitters. Herein, the highly rigid polycyclic acceptors with strong electron-withdrawing ability, integrated by quinoxaline and 1,8-naphthalimideacridine units, were utilized to construct two new red emitters with emission peak at 640 nm. Both target molecules display the twisted configuration to decrease singlet-triplet splitting energy (ΔEST) for the TADF property. Red organic light-emitting diodes (OLEDs) employing the emitters achieve the maximum external quantum efficiencies of 5.2% with electroluminescence peaks over 600 nm. This work provides a feasible strategy of the new polycyclic acceptors for developing efficient red TADF emitters.