We report on the thermal conductivities of two-dimensional metal halide perovskite films measured by time domain thermoreflectance. Depending on the molecular substructure of ammonium cations and owing to the weaker interactions in the layered structures, the thermal conductivities of our two-dimensional hybrid perovskites range from 0.10 to 0.19 W m-1 K-1, which is drastically lower than that of their three-dimensional counterparts. We use molecular dynamics simulations to show that the organic component induces a reduction of the stiffness and sound velocities along with giving rise to vibrational modes in the 5-15 THz range that are absent in the three-dimensional counterparts. By systematically studying eight different two-dimensional hybrid perovskites, we show that the thermal conductivities of our hybrid films do not depend on the thicknesses of the organic layers and instead are highly dependent on the relative orientation of the organic chains sandwiched between the inorganic constituents.

中文翻译：

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二维金属卤化物钙钛矿的超低导热系数。

我们报告通过时域热反射率测量的二维金属卤化物钙钛矿薄膜的热导率。取决于铵阳离子的分子亚结构，并且由于层状结构中的相互作用较弱，我们的二维杂化钙钛矿的导热系数在0.10至0.19 W m-1 K-1范围内，大大低于其钙钛矿的导热系数。三维对应。我们使用分子动力学模拟表明有机成分会导致刚度和声速降低，并引起三维对应物所没有的5-15 THz范围内的振动模式。通过系统地研究八种不同的二维杂化钙钛矿，