Organic-inorganic hybrid halide perovskites are proven to be a promising semiconductor material as the absorber layer of solar cells. However, the perovskite films always suffer from nonuniform coverage or high trap state density due to the polycrystalline characteristics, which degrade the photoelectric properties of thin films. Herein, the alkali metal ions which are stable against oxidation and reduction are used in the perovskite precursor solution to induce the process of crystallization and nucleation, then affect the properties of the perovskite film. It is found that the addition of the alkali metal ions clearly improves the quality of perovskite film: enlarges the grain sizes, reduces the defect state density, passivates the grain boundaries, increases the built-in potential (Vbi), resulting to the enhancement in the power conversion efficiency of perovskite thin film solar cell.

中文翻译：

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碱金属掺杂用于改进CH3NH3PbI3钙钛矿太阳能电池。

有机-无机杂化卤化物钙钛矿被证明是一种有前途的半导体材料，可作为太阳能电池的吸收层。然而，由于多晶特性，钙钛矿膜总是遭受不均匀覆盖或高陷阱态密度的困扰，这降低了薄膜的光电性能。在此，在钙钛矿前体溶液中使用对氧化和还原稳定的碱金属离子，以诱导结晶和成核过程，然后影响钙钛矿膜的性能。发现添加碱金属离子明显改善了钙钛矿膜的质量：增大了晶粒尺寸，降低了缺陷态密度，钝化了晶界，增加了内在电势（Vbi），