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Download fileEffective Design Strategy for Aggregation-Induced Emission and Thermally Activated Delayed Fluorescence Emitters Achieving 18% External Quantum Efficiency Pure-Blue OLEDs with Extremely Low Roll-Off
journal contribution
posted on 2021-11-23, 21:06 authored by Jinshan Wang, Jianfeng Zhang, Cuifeng Jiang, Chuang Yao, Xinguo XiHigh-color
purity organic emitters with a simultaneous combination
of aggregation-induced emission (AIE) and thermally activated delayed
fluorescence (TADF) characteristics are in great demand due to their
excellent comprehensive performances toward efficient organic light-emitting
diodes (OLEDs). In this work, two D−π–A-structure
emitters, ICz-DPS and ICz-BP, exhibiting AIE and TADF properties were
developed, and both the emitters have narrow singlet (S1)–triplet (T1) splitting (ΔEST) and excellent photoluminescence (PL) quantum yields
(ΦPL), derived from the distorted configurations
and weak intra/intermolecular interactions, suppressing exciton annihilation
and concentration quenching. Their doped OLEDs based on ICz-BP provide
an excellent electroluminescence external quantum efficiency (ηext) and current efficiency (ηC) of 17.7%
and 44.8 cd A–1, respectively, with an ηext roll-off of 2.9%. Their nondoped OLEDs based on ICz-DPS
afford high efficiencies of 11.7% and 30.1 cd A–1, with pure-blue emission with Commission Internationale de l’Éclairage
(CIE) coordinates of (0.15, 0.08) and a low roll-off of 6.0%. This
work also shows a strategy for designing AIE–TADF molecules
by rational use of steric hindrance and weak inter/intramolecular
interactions to realize high ΦPL values, fast reverse
intersystem crossing process, and reduced nonradiative transition
process properties, which may open the way toward highly efficient
and small-efficiency roll-off devices.
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