Triazatruxene-based small molecules with thermally activated delayed fluorescence, aggregation-induced emission and mechanochromic luminescence properties for solution-processable nondoped OLEDs

Two solution processable triazatruxene-based small molecules (TATC-BP and TATP-BP) with thermally activated delayed fluorescence (TADF), aggregation-induced emission (AIE), and mechanochromic luminescence (MCL) properties are synthesized and characterized. Compared with phenyl-substituted TATP-BP, TATC-BP with hexyl substituents showed a clearer MCL with a larger emission color change from 483 to 542 nm upon mechanical grinding. On the other hand, the solution processed nondoped OLED of TATP-BP showed a better EL performance with a maximal current efficiency of 18.9 cd A⁻¹, a maximum external quantum efficiency (EQE) of 6.0%, and a remarkable small roll-off of 3.3% in EQE even at a luminance of 1000 cd m⁻².