Xiaoming Liang1, Zhiheng Wang1, Liangxuan Wang1, Muddasir Hanif1, Dehua Hu1, Shi‐Jian Su1, Zengqi Xie1, Yu Gao2, Bing Yang2, Yuguang Ma1
1Institute of Polymer Optoelectronic Materials and Devices, State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou, Guangdong 510640 China
2State Key Laboratory of Supramolecular Structure and Materials, Jilin University, Changchun, Jilin 130012 China
Tóm tắt
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 T2 and T1, and a small energy gap between S1 and T2, 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.
