posted on 2024-03-15, 23:29authored byKun Shi, Yanchao Xie, Lei Hua, Shengyu Li, Zhi Yang, Yuwei Yin, Zhi Wang, Shian Ying, Yuchao Liu, Zhongjie Ren, Shouke Yan
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.