Efficient white electroluminescence based on a single multi-resonance TADF emitter with dual emission feature

Pure organic white organic light-emitting diodes (WOLEDs) based on a single dopant offer distinct advantages over traditional WOLEDs with RGB emitters, especially in terms of simple fabrication process and low cost. However, the maximum external quantum efficiency (EQEmax) of the reported pure organic single-dopant WOLED devices remains below 15%, which could be attributed to insufficient exciton utilization. Herein, a multi-resonance thermally activated delayed fluorescence (MR-TADF) molecule (Th-DBN) with extended π-conjugation is reported, along with highly efficient excimer emission and dual TADF features. The single-dopant WOLEDs based on Th-DBN deliver outstanding performance, achieving a record EQEmax of 27.1%, Commission Internationale de l’Eclairage (CIE) coordinates of (0.35, 0.50), and a significant operational lifetime (LT80) of 398 h at 1000 cd m−2, which are among the best reported results of pure organic single-dopant WOLEDs. This work not only provides the first example of a single-dopant WOLED based on an MR-TADF molecule, but also paves the way to designing pure organic WOLEDs with a single dopant and efficient exciton utilization.