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Tailoring Excited State Properties and Energy Levels Arrangement via Subtle Structural Design on D‐π‐A Materials
Author(s) -
Liang Xiaoming,
Wang Zhiheng,
Wang Liangxuan,
Hanif Muddasir,
Hu Dehua,
Su Shijian,
Xie Zengqi,
Gao Yu,
Yang Bing,
Ma Yuguang
Publication year - 2017
Publication title -
chinese journal of chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.28
H-Index - 41
eISSN - 1614-7065
pISSN - 1001-604X
DOI - 10.1002/cjoc.201700211
Subject(s) - chemistry , intersystem crossing , excited state , acceptor , singlet state , band gap , oled , triplet state , photochemistry , homo/lumo , chemical physics , molecule , optoelectronics , atomic physics , materials science , physics , organic chemistry , layer (electronics) , condensed matter physics
The donor‐π‐conjugated‐acceptor (D‐π‐A) structure is an important design for the luminescent materials because of its diversity in the selections of donor, π‐bridge and acceptor groups. Herein, we demonstrate two examples of D‐π‐A structures capable to finely modulate the excited state properties and arrangement of energy levels, TPA‐AN‐BP and CZP‐AN‐BP , which possess the same acceptor and π‐bridge but different donor. The investigation of their photophysical properties and DFT calculation revealed that the D‐π‐A structure with proper donor, π‐bridge and acceptor can result in separation of frontier molecular orbitals on the corresponding donor and acceptor with an obvious overlap on the π‐bridge, resulting in a hybridized local and charge‐transfer ( HLCT ) excited state with high photoluminescent ( PL ) efficiencies. Meanwhile, their singlet and triplet states are arranged on corresponding moieties with large energy gap between T 2 and T 1 , and a small energy gap between S 1 and T 2 , which favor the reverse intersystem crossing ( RISC ) from high‐lying triplet levels to singlet levels. As a result, the sky‐blue emission non‐doped OLED based on the TPA‐AN‐BP reached maximum external quantum efficiency ( EQE ) of 4.39% and a high exciton utilization efficiency ( EUE ) of 77%. This study demonstrates a new strategy to construct highly efficient OLED materials.