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Acridan‐Grafted Poly(biphenyl germanium) with High Triplet Energy, Low Polarizability, and an External Heavy‐Atom Effect for Highly Efficient Sky‐Blue TADF Electroluminescence
Author(s) -
Hung MiaoKen,
Tsai KuenWei,
Sharma Sunil,
Wu JunYi,
Chen ShowAn
Publication year - 2019
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.201904433
Subject(s) - electroluminescence , polarizability , intersystem crossing , materials science , germanium , atom (system on chip) , photochemistry , oled , exciton , quantum efficiency , optoelectronics , chemistry , singlet state , atomic physics , molecule , nanotechnology , physics , silicon , excited state , organic chemistry , layer (electronics) , quantum mechanics , computer science , embedded system
Abstract We propose the novel σ–π conjugated polymer poly(biphenyl germanium) grafted with two electron‐donating acridan moieties on the Ge atom for use as the host material in a polymer light‐emitting diode (PLED) with the sky‐blue‐emitting thermally activated delayed fluorescence (TADF) material DMAC‐TRZ as the guest. Its high triplet energy ( E T ) of 2.86 eV is significantly higher than those of conventional π–π conjugated polymers ( E T =2.65 eV as the limit) and this guest emitter ( E T =2.77 eV). The TADF emitter emits bluer emission than in other host materials owing to the low orientation polarizability of the germanium‐based polymer host. The Ge atom also provides an external heavy‐atom effect, which increases the rate of reverse intersystem crossing in this TADF guest, so that more triplet excitons are harvested for light emission. The sky‐blue TADF electroluminescence with this host/guest pair gave a record‐high external quantum efficiency of 24.1 % at maximum and 22.8 % at 500 cd m −2 .