Triarylboron-Based Dual Thermally Activated Delayed Fluorescence Emitter for Single Molecule White Light-Emitting Diodes

Single-molecule emitters with dual thermally activated delayed fluorescence (TADF) characteristics are very promising for application in organic light-emitting diodes (OLEDs). Rarely reported, organic dual-TADF materials, especially mechanochromic materials, are in demand. We present two donor–acceptor emitters, Mes*BA-Ac and FXylBA-Ac, which exhibit dual-TADF in the solid state due to the separation of HOMO and LUMO and strong intermolecular interactions. Their phase transition from amorphous to crystalline under stimuli leads to switchable TADF emissions. By blending Mes*BA-Ac with poly(methyl methacrylate), we achieve pure white light with Commission Internationale de l’Eclairage (CIE) coordinates of (0.33, 0.32). Furthermore, single-molecule white organic light-emitting diodes (SM-WOLEDs) using Mes*BA-Ac have been fabricated, reaching a maximum external quantum efficiency (EQEmax) of 1.65% with CIE coordinates of (0.30, 0.31). More importantly, the dual-TADF emission mechanism enables the devices to maintain stable white-light emission across a relatively wide voltage range, providing valuable insights for the advancement of pure organic SM-WOLEDs.