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Bridging Small Molecules to Conjugated Polymers: Efficient Thermally Activated Delayed Fluorescence with a Methyl‐Substituted Phenylene Linker
Author(s) -
Rao Jiancheng,
Liu Xinrui,
Li Xuefei,
Yang Liuqing,
Zhao Lei,
Wang Shumeng,
Ding Junqiao,
Wang Lixiang
Publication year - 2020
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.201912556
Subject(s) - conjugated system , phenylene , quantum efficiency , fluorescence , electroluminescence , photochemistry , excited state , linker , polymer , delocalized electron , chemistry , materials science , polymer chemistry , optoelectronics , organic chemistry , physics , layer (electronics) , quantum mechanics , computer science , nuclear physics , operating system
Based on a “TADF + Linker” strategy (TADF=thermally activated delayed fluorescence), demonstrated here is the successful construction of conjugated polymers that allow highly efficient delayed fluorescence. Small molecular TADF blocks are linked together using a methyl‐substituted phenylene linker to form polymers. With the growing number of methyl groups on the phenylene, the energy level of the local excited triplet state ( 3 LE b ) from the delocalized polymer backbone gradually increases, and finally surpasses the charge‐transfer triplet state ( 3 CT). As a result, the diminished delayed fluorescence can be recovered for the tetramethyl phenylene containing polymer, revealing a record‐high external quantum efficiency (EQE) of 23.5 % (68.8 cd A −1 , 60.0 lm W −1 ) and Commission Internationale de l′Eclairage (CIE) coordinates of (0.25, 0.52). Combined with an orange‐red TADF emitter, a bright white electroluminescence is also obtained with a peak EQE of 20.9 % (61.1 cd A −1 , 56.4 lm W −1 ) and CIE coordinates of (0.36, 0.51).