Solar cells based on organic-inorganic halide perovskites have recently shown rapidly rising power conversion efficiencies, but exhibit unusual behaviour such as current-voltage hysteresis and a low-frequency giant dielectric response. Ionic transport has been suggested to be an important factor contributing to these effects; however, the chemical origin of this transport and the mobile species are unclear. Here, the activation energies for ionic migration in methylammonium lead iodide (CH3NH3PbI3) are derived from first principles, and are compared with kinetic data extracted from the current-voltage response of a perovskite-based solar cell. We identify the microscopic transport mechanisms, and find facile vacancy-assisted migration of iodide ions with an activation energy of 0.6 eV, in good agreement with the kinetic measurements. The results of this combined computational and experimental study suggest that hybrid halide perovskites are mixed ionic-electronic conductors, a finding that has major implications for solar cell device architectures.

中文翻译：

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混合碘化铅钙钛矿太阳能电池中的离子传输。

最近，基于有机-无机卤化物钙钛矿的太阳能电池显示出快速提高的功率转换效率，但表现出不寻常的行为，例如电流-电压磁滞和低频巨介电响应。离子传输被认为是造成这些影响的重要因素。但是，这种运输的化学起源和流动物种尚不清楚。在此，从第一原理中导出甲基铵碘化铅（CH3NH3PbI3）中离子迁移的活化能，并将其与从钙钛矿型太阳能电池的电流-电压响应中提取的动力学数据进行比较。我们确定了微观的运输机制，并发现具有0.6 eV活化能的碘离子的空位辅助迁移，与动力学测量结果非常吻合。