posted on 2020-03-13, 12:34authored byBin Huang, Xiaomin Gu, Yan Feng, Ying Zhang, Dawei Jiang, Wen-Cheng Chen, Gu Dai, Yigang Ji, Qiang Zhao, Chun-Sing Lee
A novel
light-emitting material 4-(4-diphenylaminophenyl)-benzo[d,e]benzo[4,5]imidazo[2,1-a]isoquinolin-7-one
(4-TPA-BBI) is synthesized and characterized.
4-TPA-BBI exhibits excellent polymorphism, mechanochromic luminescence
(MCL), and electroluminescence properties. It can form three different
aggregate species: yellow rod-like crystal (Y-crystal), orange needle-like
crystal (O-crystal), and red solid (R-solid). It is observed that
the Y-crystal can be reversibly changed to R-solid upon external stimuli,
while O-crystal can be irreversibly transformed to R-solid via sublimation
under a vacuum. Crystallographic and photophysical studies indicate
that the Y-crystal featuring loose molecular packing demonstrates
a high photoluminescence quantum yield (ΦPL ≈
1) and obvious MCL property, while the compactly packed O-crystal
shows a lower ΦPL of 0.646 with negligible MCL. A
nondoped light-emitting device based on 4-TPA-BBI as an emitter exhibits
bright orange emission with a peak at 588 nm, a high external quantum
efficiency of 4.4%, and a maximum luminance of 22470 cd m–2.