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arXiv 2104.01455cond-mat.mtrl-sci
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卤代钙钛矿降解的原子观研究:反应力场分子动力学研究

Atomistic insights into the degradation of halide perovskites: a reactive force field molecular dynamics study

Mike Pols, José Manuel Vicent-Luna, Ivo Filot, Adri C. T. van Duin, Shuxia Tao

摘要:

卤化物钙钛矿由于其特殊的光电性质而制成高效的太阳能电池,但存在若干稳定性问题。由于实验中时空分辨率的限制以及缺乏有效的计算方法来研究反应过程,降解过程的表征具有挑战性。在这里,我们提出的第一个努力,在发展反应力场的大规模分子动力学模拟的相不稳定性和缺陷诱导的降解反应在无机CsPbI $_{3}$。我们发现,相变的钙钛矿晶格的非谐性与热熵的组合驱动。在相对低的温度下,Cs阳离子倾向于远离与周围金属卤化物骨架良好接触的优先位置,潜在地导致其转化为非钙钛矿相。我们的缺陷结构的模拟表明,虽然碘空位和杂质在钙钛矿晶格中是非常移动的,但空位对稳定性有不利影响,引发钙钛矿分解反应为PbI $_{2}$。我们的工作提出ReaxFF作为一个有效的计算框架,研究反应过程中的卤化物钙钛矿。

英文摘要:

Halide perovskites make efficient solar cells due to their exceptional optoelectronic properties, but suffer from several stability issues. The characterization of the degradation processes is challenging because of the limitations in the spatio-temporal resolution in experiments and the absence of efficient computational methods to study the reactive processes. Here, we present the first effort in developing reactive force fields for large scale molecular dynamics simulations of the phase instability and the defect-induced degradation reactions in inorganic CsPbI$_{3}$. We find that the phase transitions are driven by a combination of the anharmonicity of the perovskite lattice with the thermal entropy. At relatively low temperatures, the Cs cations tend to move away from the preferential positions with good contacts with the surrounding metal halide framework, potentially causing its conversion to a non-perovskite phase. Our simulations of defective structures reveal that, although both iodine vacancies and interstitials are very mobile in the perovskite lattice, the vacancies have a detrimental effect on the stability, initiating the decomposition reactions of perovskites to PbI$_{2}$. Our work puts ReaxFF forward as an effective computational framework to study reactive processes in halide perovskites.

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