To address the slow recombination of photogenerated charges in tetragonal CH₃NH₃PbI₃, the evolution of extra electrons and holes is simulated through advanced ab initio molecular dynamics. We show that the localization of the charge carriers and their hopping from one polaronic state to another occur on a subpicosecond time scale. The localization, attended by weak bond contractions and elongations in the inorganic sublattice, is induced by thermal vibrations and only moderately perturbed by the disordered field generated by the organic cations. The simultaneous simulation of extra electrons and holes shows that they preferentially localize in spatially distinct regions. As determined by the overlap between the electron and hole wave functions, the probability of radiative bimolecular recombination is lowered by two orders of magnitude compared with that of optical generation. The separate polaronic localization of electrons and holes emerges as the key feature for achieving exceptional photovoltaic properties.

中文翻译：

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金属卤化物钙钛矿中低电子-空穴复合速率的起源†

为了解决四方CH ₃ NH ₃ PbI ₃中光生电荷的缓慢重组，通过先进的从头算来模拟多余电子和空穴的演化分子动力学。我们表明，载流子的定位及其从一种极化状态到另一种极化状态的跳跃发生在皮秒以下的时间尺度上。局部化由无机亚晶格中弱的键收缩和伸长引起，是由热振动引起的，并且仅受到有机阳离子产生的无序场的轻微扰动。额外的电子和空穴的同时仿真表明，它们优先位于空间上不同的区域。由电子和空穴波函数之间的重叠确定，辐射双分子复合的可能性比光学产生的可能性降低了两个数量级。电子和空穴的分开的极化子局部化成为实现优异光伏性能的关键特征。