Heavy-Atom-Linker Engineering of Dual Multiresonance Emitters for High-Efficiency Solution-Processed Organic Light-Emitting Diodes

A highly efficient solution-processed organic light-emitting diode (OLED) based on multiresonance thermally activated delayed fluorescence (MR-TADF) emitters remains challenging because of the MR-TADF skeleton’s poor solubility. Herein, a heavy-atom-included linker strategy was proposed to construct a solution-processable boron–nitrogen (BN)-based MR-TADF emitter, in which a dibenzothiophene-based linker is introduced to connect two MR units, affording the emitter DBT-BN and its oxidized derivative DBTO-BN. The sulfur-containing linker not only enhances the spin–orbit coupling but also modulates the short-range and long-range charge transfer character. Both DBT-BN and DBTO-BN show emission at 491 and 503 nm in toluene, with a high photoluminescence quantum yield of 92% and 95%, respectively. A relatively fast reverse intersystem crossing rate of ca. 0.6 × 10 5 s –1 is obtained for the emitters. Solution-processed OLEDs based on DBTO-BN achieve a maximum external quantum efficiency of 26%. This research demonstrates the effectiveness of a heavy-atom linker for developing solution-processable MR-TADF emitters.