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Promoting through-space charge transfer-based TADF via rational alignment of quasi-planar donor and acceptor in solid state

固态下给体和受体的合理排列促进空间电荷转移型热激活延迟荧光

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Abstract

Through-space charge transfer (TSCT)-based thermally activated delayed fluorescence (TADF) materials have attracted widespread attention due to their great potential in simultaneously possessing small singlet-triplet splitting energy (ΔEST) and rapid radiative rate (kf), but it remains a great challenge for the rational design of such materials. In this work, we perform a theoretical investigation on the photophysical properties of carbazole-based TSCT TADF materials both in solvent and solid phase using the polarizable continuum model and the combined quantum mechanics and molecular mechanics method to rationalize their experimental performance difference and reveal the molecular design principles. The results indicate that the molecules with gradually enhanced planarity of donor (D) or/and acceptor (A) units exhibit decreased distance and enhanced intramolecular interactions between D and A units originated from the intermolecular interactions of compact molecular arrangement, leading to favorable radiative rate process in solid phase compared with the situation in toluene. And the enhancement of planarity of D and A units significantly restricts the molecular stretching and rotation vibrations and decreases the non-radiative processes, which mainly contributes to the improved performance of the molecules. Moreover, such TSCT-based molecules show an obvious separation of the highest occupied molecular orbital and lowest unoccupied molecular orbital distributions, which is beneficial to achieving small ΔEST values. These theoretical understandings could give an in-depth physical insight into the structure-property relationship of such TSCT-based materials, providing quasi-planar controlled strategies for the exploration of high-performance TADF materials.

摘要

基于空间电荷转移(TSCT)的热激活延迟荧光(TADF)材料因其可同时实现小的单重态-三重态分裂能(ΔEST)和快速的辐射速率(kf)而受到广泛关注, 但对这类材料的合理设计仍面临挑战. 本工作使用极化连续介质模型和量子力学与分子力学结合的方法, 对咔唑基TSCT-TADF材料在液相和固相中的光物理性质进行了理论研究, 阐明其实验性能的差异并揭示分子设计规则. 研究表明给体(D)、 受体(A)单元平面度逐渐增强的分子表现出D和A单元之间的距离减小、 分子内相互作用增强, 导致其在固相中有利的辐射过程; 并且A单元平面度的增强显著限制了分子的拉伸和旋转振动, 减少了非辐射损失, 有助于分子性能的提高. 此外, 这类分子的前线轨道分布显示出明显的分离, 有利于实现较小的ΔEST. 这些新的理论认识可以对TSCT-TADF材料的结构-性能关系提供深入的光物理见解, 为设计和探索高性能TADF材料提供有效策略.

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Acknowledgements

This work was supported by the National Natural Science Foundation of China (22275097, 61875090, 21772095, and 91833306), the Key Giant Project of Jiangsu Educational Committee (19KJA180005), the Fifth 333 Project of Jiangsu Province of China (BRA2019080), the 1311 Talents Program of Nanjing University of Posts and Telecommunications, the Natural Science Foundation of Jiangsu Higher Education Institutions (22KJB150030), the Scientific Starting Fund from Nanjing University of Posts and Telecommunications (NUPTSF) (NY219160), the Natural Science Foundation of Nanjing University of Posts and Telecommunications (NY221092 and NY222148), and the Open Research Fund of State Key Laboratory of Organic Electronics and Information Displays.

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Authors and Affiliations

  1. State Key Laboratory of Organic Electronics and Information Displays & Jiangsu Key Laboratory for Biosensors, Institute of Advanced Materials (IAM), Nanjing University of Posts & Telecommunications, Nanjing, 210023, China

    Ping Li  (李平), Cefeng Zhou  (周策峰), Wenjing Li  (李文静), Yewen Zhang  (张业文), Jie Yuan  (袁杰) & Runfeng Chen  (陈润锋)

  2. School of Materials Science and Engineering, Zhejiang Sci-Tech University, Hangzhou, 310018, China

    Runfeng Chen  (陈润锋)

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  1. Ping Li  (李平)
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  2. Cefeng Zhou  (周策峰)
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  3. Wenjing Li  (李文静)
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  4. Yewen Zhang  (张业文)
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  5. Jie Yuan  (袁杰)
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  6. Runfeng Chen  (陈润锋)
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Contributions

Author contributions Li P and Zhou C carried out the theoretical calculations and wrote the draft; Li W, Zhang Y, and Yuan J discussed the results; Chen R provided guidance on calculations and revised the manuscript. All authors contributed to the general discussion.

Corresponding author

Correspondence to Runfeng Chen  (陈润锋).

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Conflict of interest The authors declare that they have no conflict of interest.

Additional information

Ping Li received her PhD degree from Jilin University in 2019. She joined Nanjing University of Posts and Telecommunications as a lecture in 2019. Her research is focused on the theoretical investigations on organic optoelectronic materials.

Cefeng Zhou is a Master student of Nanjing University of Posts and Telecommunications. His research is focused on the theoretical simulations on the through-space charge transfer-based thermally activated delayed fluorescence materials.

Runfeng Chen received his PhD degree from Fudan University and did his postdoctoral work at the National University of Singapore. He joined Nanjing University of Posts and Telecommunications in 2006. His research interest focuses on the development of optoelectronic materials and devices.

Supplementary information Supporting data are available in the online version of the paper.

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Promoting through-space charge transfer-based TADF via rational alignment of quasi-planar donor and acceptor in solid state

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Li, P., Zhou, C., Li, W. et al. Promoting through-space charge transfer-based TADF via rational alignment of quasi-planar donor and acceptor in solid state. Sci. China Mater. 66, 3958–3967 (2023). https://doi.org/10.1007/s40843-023-2563-2

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