Halide perovskites are strongly influenced by large amplitude anharmonic lattice fluctuations at room temperature. We develop a tight-binding model for dynamically disordered ${\mathrm{MAPbI}}_3$ based on density functional theory calculations to calculate electronic structure for finite temperature crystal structures at the length scale of thermal disorder and carrier localization. The model predicts individual Hamiltonian matrix elements and band structures with high accuracy, owing to the inclusion of additional matrix elements and descriptors for non-Coulombic interactions. We apply this model to electronic structure at length and timescales inaccessible to first-principles methods, finding an increase in band gap, carrier mass, and the subpicosecond fluctuations in these quantities with increasing temperature as well as the onset of carrier localization in large supercells induced by thermal disorder at 300 K. We identify the length scale $L^{*}=5$ nm as the onset of localization in the electronic structure, associated with decreasing band edge fluctuations, increasing carrier mass, and Rashba splitting approaching zero.

中文翻译：

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由基于第一性原理的紧束缚模型描述的 MAPbI3 中动态无序引起的热波动和载流子定位

卤化物钙钛矿在室温下受到大振幅非谐晶格波动的强烈影响。我们为动态无序开发了一个紧束缚模型${\mathrm{MAPbI}}_3$基于密度泛函理论计算，在热无序和载流子定位的长度尺度上计算有限温度晶体结构的电子结构。由于包含额外的矩阵元素和非库仑相互作用的描述符，该模型可以高精度地预测单个哈密顿矩阵元素和能带结构。我们将该模型应用于第一性原理方法无法达到的长度和时间尺度的电子结构，发现带隙、载流子质量和这些量的亚皮秒波动随着温度的升高以及大型超级单元中载流子定位的开始而增加通过 300 K 的热无序。我们确定了长度尺度${升}^{*}=5$ nm 作为电子结构中定位的开始，与带边缘波动的减少、载流子质量的增加和 Rashba 分裂接近零相关。