High-Efficiency Asymmetric TADF Dendrimers via Promoting Mixing of Multiple Excited States toward Solution-Processed OLEDs with Low Efficiency Rolloff

Abstract

Thermally activated delayed fluorescence (TADF) dendrimers are emerging as promising candidates for solution-processed organic light-emitting diodes (OLEDs), but it is still challenging to produce high-efficiency TADF dendrimer-based OLEDs with low efficiency roll-off. Herein, we propose three asymmetric TADF dendrimers, unveiling that the radiative decay and exciton upconversion avenues are susceptible to the regulation of peripheral dendrons for these asymmetric TADF dendrimers. Especially for the second-generation dendrimer of DMAC-BP-tBu3Cz, photoluminescence quantum yields can reach 94%, together with rate constant of reverse intersystem crossing of 1.3 × 106 s–1. Additionally, it exhibits an excellent electroluminescence properties with maximum external quantum efficiency (EQE) of 28.0%, and maintaining a value of 24.9% at 1000 cd m–2, which is the highest efficiency of TADF dendrimer-based OLED at such a high luminescence. Meanwhile, the hyper-fluorescence ternary OLEDs employing DMAC-BP-tBu3Cz as a TADF sensitizing dopant exhibit a boosted EQE value of 18.4% and greatly alleviative efficiency rolloff of only 4.9% with 17.5% EQE at 1000 cd m–2, accompanied by pure green emission with a full-width-at-half-maximum of 39 nm.