Triazatruxene-based thermally activated delayed fluorescence small molecules with aggregation-induced emission properties for solution-processable nondoped OLEDs with low efficiency roll-off

Abstract

In this work, two thermally activated delayed fluorescence (TADF) fluorophores (TAT-BP and TAT-2BP) based on triazatruxene (TAT) and benzophenone (BP) have been successfully prepared. While both compounds show similar green emission and typical AIE behaviors, TAT-2BP with two BP units exhibits a shorter delay fluorescence lifetime (0.54 μs) than TAT-BP with one BP unit (0.79 μs) in neat films. In solution-processable non-doped organic light-emitting diodes (OLEDs), TAT-2BP shows a better EL performance with a turn-on voltage of 2.5 V, a maximum current efficiency of 32.3 cd A⁻¹, a maximum power efficiency of 33.0 lm W⁻¹, and a maximum external quantum efficiency of 9.8%. Remarkably, very small efficiency roll-offs of 1.0% at 1000 cd m⁻² and 2.0% at 2000 cd m⁻² are realized for TAT-2BP based devices, which are also much lower than those of TAT-BP (10.9% at 1000 cd m⁻² and 28.0% at 2000 cd m⁻²), indicating that the utilization of TAT-2BP with a shorter delay fluorescence lifetime can efficiently retard the efficiency decline.