Boziki Ariadni, Dar M Ibrahim, Jacopin Gwénolé, Grätzel Michael, Rothlisberger Ursula
Laboratory of Computational Chemistry and Biochemistry, Institute of Chemical Sciences and Engineering, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland.
Laboratory of Photonics and Interfaces, Institute of Chemical Sciences and Engineering, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland.
J Phys Chem Lett. 2021 Mar 18;12(10):2699-2704. doi: 10.1021/acs.jpclett.1c00263. Epub 2021 Mar 11.
CsPbBr has received wide attention due to its superior emission yield and better thermal stability compared to other organic-inorganic lead halide perovskites. In this study, through an interplay of theory and experiments, we investigate the molecular origin of the asymmetric low-temperature photoluminescence spectra of CsPbBr. We conclude that the origin of this phenomenon lies in a local dipole moment (and the induced Stark effect) due to the preferential localization of Cs in either of two off-center positions of the empty space between the surrounding PbBr octahedra. With increasing temperature, Cs ions are gradually occupying positions closer and closer to the center of the cavities. The gradual loss of ordering in the Cs position with increasing temperature is the driving force for the formation of tetragonal-like arrangements within the orthorhombic lattice.
与其他有机-无机铅卤化物钙钛矿相比，CsPbBr因其优异的发射产率和更好的热稳定性而受到广泛关注。在本研究中，通过理论与实验的相互作用，我们研究了CsPbBr不对称低温光致发光光谱的分子起源。我们得出结论，这种现象的起源在于由于Cs优先定位于周围PbBr八面体之间空隙的两个偏心位置之一而产生的局部偶极矩（以及诱导斯塔克效应）。随着温度升高，Cs离子逐渐占据越来越靠近空腔中心的位置。随着温度升高，Cs位置有序性的逐渐丧失是在正交晶格内形成类似四方排列的驱动力。
