Liang Ningning, Liu Guogang, Hu Deping, Wang Kai, Li Yan, Zhai Tianrui, Zhang Xinping, Shuai Zhigang, Yan He, Hou Jianhui, Wang Zhaohui
College of Physics and Optoelectronics, Faculty of Science, Beijing University of Technology, Beijing, 100124, P. R. China.
Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190, P. R. China.
Adv Sci (Weinh). 2022 Jan;9(3):e2103975. doi: 10.1002/advs.202103975. Epub 2021 Nov 23.
Organic phosphorescence, originating from triplet excitons, has potential for the development of new generation of organic optoelectronic materials. Herein, two heavy-atom-free room-temperature phosphorescent (RTP) electron acceptors with inherent long lifetime triplet exctions are first reported. These two 3D-fully conjugated rigid perylene imide (PDI) multimers, as the best nonfullerene wide-bandgap electron acceptors, exhibit a significantly elevated T of ≈2.1 eV with a room-temperature phosphorescent emission (τ = 66 µs) and a minimized singlet-triplet splitting as low as ≈0.13 eV. The huge spatial congestion between adjacent PDI skeleton endows them with significantly modified electronic characteristics of S and T . This feature, plus with the fully-conjugated rigid molecular configuration, balances the intersystem crossing rate and fluorescence/phosphorescence rates, and therefore, elevating E to ≈2.1 from 1.2 eV for PDI monomer. Meanwhile, the highly delocalized feature enables the triplet charge-transfer excitons at donor-acceptor interface effectively dissociate into free charges, endowing the RTP electron acceptor based organic solar cells (OSCs) with a high internal quantum efficiency of 84% and excellent charge collection capability of 94%. This study introduces an alternative strategy for designing PDI derivatives with high-triplet state-energy and provides revelatory insights into the fundamental electronic characteristics, photophysical mechanism, and photo-to-current generation pathway.
源自三重态激子的有机磷光在新一代有机光电子材料的开发方面具有潜力。在此，首次报道了两种具有固有长寿命三重态激子的无重原子室温磷光（RTP）电子受体。这两种三维完全共轭的刚性苝酰亚胺（PDI）多聚体作为最佳的非富勒烯宽带隙电子受体，展现出显著提高的约2.1电子伏特的三线态能量，具有室温磷光发射（τ = 66微秒）以及低至约0.13电子伏特的最小单重态-三重态分裂。相邻PDI骨架之间巨大的空间拥挤赋予它们显著改变的单重态（S）和三重态（T）电子特性。这一特性，加上完全共轭刚性分子构型，平衡了系间窜越速率与荧光/磷光速率，因此，将PDI单体的三线态能量从1.2电子伏特提高到约2.1电子伏特。同时，高度离域的特性使供体-受体界面处的三重态电荷转移激子有效解离为自由电荷，赋予基于RTP电子受体的有机太阳能电池（OSC）84%的高内部量子效率和94%的优异电荷收集能力。本研究介绍了一种设计具有高三重态能量的PDI衍生物的替代策略，并为基本电子特性、光物理机制以及光生电流产生途径提供了启发性见解。
