1 research outputs found
Accelerating Intersystem Crossing in Multiresonance Thermally Activated Delayed Fluorescence Emitters via Long-Range Charge Transfer
Multiresonance thermally activated delayed fluorescence
(MR-TADF)
emitters are excellent candidates for high-performance organic light-emitting
diodes (OLEDs) due to their narrowband emission properties. However,
the inherent mechanism of regulating the rate of intersystem crossing
(ISC) is ambiguous in certain MR-TADF skeletons. Herein, we propose
a mechanism of accelerating ISC in B/S-based MR-TADF emitters by peripheral
modifications of electron-donating groups (EDGs) without affecting
the narrowband emission property. The long-range charge transfer (LRCT)
stems from the introduced EDG leading to high-lying singlet and triplet
excited states. The ISC process is accelerated by the enhanced spin–orbital
coupling (SOC) between the singlet short-range charge transfer (SRCT)
and triplet LRCT manifolds. Meanwhile, the narrowband emission derived
from the MR-type SRCT state is well retained as expected in the peripherally
modified MR-TADF emitters. This work reveals the regulation mechanism
of photophysical properties by high-lying LRCT excited states and
provides a significant theoretical basis for modulating the rate of
ISC in the further design of MR-TADF materials