Wu Yu, Ji Jialin, Ding Yimin, Yang Jiong, Zhou Liujiang
Yangtze Delta Region Institute (Huzhou), University of Electronic Science and Technology, Huzhou, Zhejiang, 313001, China.
College of Biological, Chemical Sciences and Engineering, Jiaxing University, Jiaxing, Zhejiang, 314001, China.
Adv Sci (Weinh). 2024 Nov;11(42):e2406380. doi: 10.1002/advs.202406380. Epub 2024 Sep 18.
Understanding the origin of ultralow lattice thermal conductivity κ of halide perovskites is of great significance in the energy conversion field. The soft phonon modes and the large anharmonicity corresponding to the dynamic rotation of halogen atoms play an important role in limiting the thermal transport of halide perovskites. The dynamic rotation has long been thought to originate from the electrostatic repulsion of lone pairs around halogen atoms. Here, by studying the layered perovskite CsBiICl, it is found that the interaction between the lone pairs contributed by the s bands of halogen atoms is short-range, and the dynamic rotation is really driven by the occupied p-band electrons. It dominates CsBiICl with ultralow κ, < 0.2 W mK at 300 K. Moreover, soft optical phonons are presented ≈1 and 2.2 THz that constitute relatively flat and dense bands due to the rattling Cs and Cl atoms, contributing a large glass-like component to the κ. The results have important implications for understanding the origin of the ultralow κ in halide perovskites and for designing novel perovskites to serve the energy conversion field.
了解卤化物钙钛矿超低晶格热导率κ的起源在能量转换领域具有重要意义。与卤素原子动态旋转相对应的软声子模式和大的非谐性在限制卤化物钙钛矿的热传输中起着重要作用。长期以来，人们一直认为动态旋转源于卤素原子周围孤对电子的静电排斥。在此，通过研究层状钙钛矿CsBiICl，发现由卤素原子的s能带贡献的孤对电子之间的相互作用是短程的，而动态旋转实际上是由占据的p带电子驱动的。它主导了具有超低κ（300 K时<0.2 W mK）的CsBiICl。此外，由于Cs和Cl原子的晃动，出现了频率约为1和2.2 THz的软光学声子，它们构成了相对平坦且密集的能带，对κ贡献了很大的类似玻璃的成分。这些结果对于理解卤化物钙钛矿中超低κ的起源以及设计用于能量转换领域的新型钙钛矿具有重要意义。
