posted on 2022-07-15, 16:09authored byYaxin Wang, Zilong Guo, Yixuan Gao, Yiran Tian, Yingyi Deng, Xiaonan Ma, Wensheng Yang
Delayed fluorescence (DF) emitters with high color purity
are of
high interest for applications in high-resolution displays. However,
the charge transfer required by high emitting efficiency usually conflicts
with the expected color purity. In this work, we investigated the
S1/S0 conformational relaxation, spin–orbital
coupling (SOC), and vibronic coupling of hot-exciton emitters while
hybrid local and charge transfer (HLCT) state tuning was achieved
by a structural meta-effect. The meta-linkage leads to suppressed S1/S0 conformational
relaxation and weakened vibronic coupling, while the unsacrificed
emitting efficiency is largely ensured by multiple rISC channels (Tn → Sm)
with thermally accessible triplet–singlet energy gap (ΔEST) and effective SOC. We demonstrated that
the unique excited-state mechanism provides opportunities to improve
the emitting color purity of hot-exciton emitters without sacrificing
emitting efficiency by HLCT state tuning with simple chemical structural
modification, for which hot-exciton emitters might play a more important
role for high-resolution organic light-emitting diode displays.