Xing Zengshan, Qammar Memoona, Sergeev Aleksandr A, Zhou Zhicong, Geng Pai, Chan Christopher C S, Halpert Jonathan E, Wong Kam Sing
Department of Physics, The Hong Kong University of Science and Technology, Clear water bay, Kowloon, Hong Kong 999077, P. R. China.
Department of Chemistry, The Hong Kong University of Science and Technology, Clear water bay, Kowloon, Hong Kong 999077, P. R. China.
J Phys Chem Lett. 2024 Oct 10;15(40):10146-10152. doi: 10.1021/acs.jpclett.4c02046. Epub 2024 Sep 30.
Zero-dimensional CsCuX (X=Cl, Br, or I), the intensively studied light-emitting materials, generally exhibit single-band emissions from intrinsic self-trapped excitons (STEs), while defect-induced (extrinsic) STEs were considered nonemissive. Herein, we observed a dual-band emission from intrinsic and extrinsic STEs for CsCuBr at low temperature, and their emission mechanisms are elucidated. The intrinsic and extrinsic STEs are trapped from different initial states, with remarkably large trapping depths (>900 meV) evaluated at 50 K, indicating their negligible detrapping rates. In addition, the stronger electron-phonon coupling for extrinsic STE could shift the extrinsic STE band to intersect with the ground state in the configuration coordinate diagram, acting as a nonradiative pathway. This explains the vanishment of extrinsic STE emission at room temperature and the reported low photoluminescence quantum yields (<50%). With growing efforts to obtain multiple-band emitters, our insights into the emission mechanisms of intrinsic and extrinsic STEs provide valuable bases for further material engineering.
零维CsCuX（X = Cl、Br或I）是经过深入研究的发光材料，通常表现出源自本征自陷激子（STE）的单带发射，而缺陷诱导（非本征）的STE被认为是无发射的。在此，我们观察到CsCuBr在低温下本征和非本征STE的双带发射，并阐明了它们的发射机制。本征和非本征STE从不同的初始状态被俘获，在50 K时评估出其俘获深度非常大（>900 meV），这表明它们的去俘获率可忽略不计。此外，非本征STE更强的电子 - 声子耦合可使非本征STE带在组态坐标图中与基态相交，从而形成一条非辐射途径。这解释了非本征STE发射在室温下的消失以及报道的低光致发光量子产率（<50%）。随着获取多带发射体的努力不断增加，我们对本征和非本征STE发射机制的见解为进一步的材料工程提供了有价值的基础。
