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Sterically‐Locked Donor–Acceptor Conjugated Polymers Showing Efficient Thermally Activated Delayed Fluorescence
Author(s) -
Rao Jiancheng,
Yang Liuqing,
Li Xue,
Zhao Lei,
Wang Shumeng,
Tian Hongkun,
Ding Junqiao,
Wang Lixiang
Publication year - 2021
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.202016428
Subject(s) - conjugated system , steric effects , acceptor , photochemistry , polymer , materials science , fluorescence , planarity testing , doping , chemistry , crystallography , stereochemistry , optoelectronics , physics , quantum mechanics , composite material , condensed matter physics
Donor–acceptor (D–A) conjugated polymers often possess a significant frontier molecular orbital overlap because of the conjugation elongation, leading to no thermally activated delayed fluorescence (TADF) caused by a large singlet‐triplet energy splitting (▵ E ST ). Herein a novel steric locking strategy is proposed by incorporating methyl groups into D–A conjugated polymers. Benefitting from the methyl hindrance, the torsion between the donor and acceptor can be well tuned to form a sterically‐locked conformation, so that the unwanted relaxation toward planarity and thus conjugation elongation is prevented to boost hole–electron separation. The resultant D–A conjugated polymer achieves an extremely low Δ E ST of 0.09 eV to enable efficient TADF. The corresponding doped and non‐doped devices are fabricated via a solution process, revealing a record‐high external quantum efficiency (EQE) of 24.0 % (79.4 cd A −1 , 75.0 lm W −1 ) and 15.3 % (50.9 cd A −1 , 47.3 lm W −1 ).