The current picture of ion transport in the solar-cell absorber material CH₃NH₃PbI₃ (MAPbI₃) suffers from a disturbing lack of clarity. In this study, we demonstrate that, with knowledge of the jump rate of iodine vacancies and with a defect chemical model, various experimental data reported in the literature for the ionic conductivity of MAPbI₃ can be reconciled. A quantitative expression for the vacancy jump rate was obtained by studying iodine tracer diffusion as a function of temperature and iodine-vacancy concentration by means of classical molecular-dynamics simulations. The defect-chemical model yields acceptor concentrations in experimental samples of 10¹⁵ cm⁻³ and lower, and the enthalpy and entropy of anti-Frenkel disorder. We also demonstrate that the generation of additional iodine vacancies can explain quantitatively the increase in the ionic conductivity under illumination. Finally, the consequences for devices under bias and for grain-boundary transport are discussed.

中文翻译：

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钙钛矿杂化甲基铵碘化铅中碘空位的热力学和动力学

离子迁移的太阳能电池的当前图片吸收剂材料CH ₃ NH ₃碘化铅₃（MAPbI ₃）遭受来自干扰缺乏清晰度。在这项研究中，我们证明，借助对碘空位的跃迁速率的了解以及具有缺陷化学模型，可以对文献中报道的MAPbI ₃的离子电导率的各种实验数据进行核对。通过经典分子动力学模拟研究碘示踪剂扩散随温度和碘空位浓度的变化，获得了空位跃迁速率的定量表达式。缺陷化学模型在实验样品中产生的受主浓度为10 ¹⁵ cm ^-3以及更低的抗弗伦克尔病的焓和熵。我们还证明了额外碘空位的产生可以定量解释光照下离子电导率的增加。最后，讨论了在偏压下器件的影响以及对晶界传输的影响。