Tianjin Key Laboratory of Molecular Optoelectronic Sciences, Department of Chemistry, National Demonstration Center for Experimental Chemistry & Chemical Engineering Education, School of Science, Tianjin University, Tianjin 300354, China.
J Phys Chem Lett. 2023 Jan 12;14(1):164-169. doi: 10.1021/acs.jpclett.2c03482. Epub 2022 Dec 29.
In this work, we first developed CsKBiCl cubic double perovskite nanocrystals and a series of morphologically isotropic double perovskite nanocrystals. Different contributions of different elements to self-trapped states were revealed by density functional theory. Meanwhile, these double perovskite nanocrystals exhibit the coexistence of free and self-trapped exciton dual-color photoluminescence. Femtosecond transient absorption spectroscopy can confirm that the double perovskite nanocrystals produce a relatively obvious structural deformation in the excited state. We infer that this can lead to a large deviation of the excitation and emission transition dipoles, thus causing large photoluminescence anisotropy. Most importantly, we observe for the first time that both free exciton emission and self-trapped exciton emission are highly anisotropic, which are comparable to or even better than that of lead halide perovskites. This research paves the way for exploring more possibilities and practical applications.
在这项工作中，我们首先开发了 CsKBiCl 立方双钙钛矿纳米晶体和一系列形态各向同性的双钙钛矿纳米晶体。通过密度泛函理论揭示了不同元素对自陷态的不同贡献。同时，这些双钙钛矿纳米晶体表现出自由激子和自陷激子双颜色光致发光的共存。飞秒瞬态吸收光谱可以证实双钙钛矿纳米晶体在激发态下产生相对明显的结构变形。我们推断这可能导致激发和发射跃迁偶极子的大偏差，从而导致大的光致发光各向异性。最重要的是，我们首次观察到自由激子发射和自陷激子发射都是高度各向异性的，与卤化铅钙钛矿相比具有可比性，甚至更好。这项研究为探索更多可能性和实际应用铺平了道路。
