Quinoxaline-based thermally activated delayed fluorescence emitters for highly efficient organic light-emitting diodes

Thermally activated delayed fluorescence (TADF) materials are regarded as the most promising next-generation emitters in organic light-emitting diodes (OLEDs). In this work, three TADF compounds were designed and synthesized based on 1,2,3,4-tetrahydrophenazine as acceptor and 9,9-dimethyl-9,10-dihydroacridine (DMAC-TTPZ), phenoxazine (PXZ-TTPZ), and phenothiazine (PTZ-TTPZ) as donors. Wherein, cyclohexane was introduced to the acceptor segment to improve solubility and weaken the conjugate degree to realize blue-shifted emission. Due to the twisted conformation, the frontier molecular orbital (FMO) overlap was largely minimized, resulting in small singlet-triplet energy splitting (Delta E-ST) of 0.15, 0.09, and 0.07 eV for DMAC-TTPZ, PXZ-TTPZ, and PTZ-TTPZ, respectively. Taking these compounds as emitters for OLEDs, maximum brightness, power efficiency (PE), and external quantum efficiency (EQE) of up to 36 480 cd m(-2), 41.0 lm W-1, and 15.3% were achieved, demonstrating their potential in OLEDs.

Automated summary

Thermally activated delayed fluorescence (TADF) materials based on three designed and synthesized compounds showed promising potential as emitters in OLEDs, with blue-shifted emission achieved by introducing cyclohexane. The small singlet-triplet energy splitting and twisted conformation of the compounds minimized frontier molecular orbital overlap. OLEDs using these compounds as emitters achieved high brightness, power efficiency, and external quantum efficiency, demonstrating their potential in OLED applications.