Two-dimensional (2D) lead halide perovskites represent an emerging class of materials given their tunable optoelectronic properties and long-term stability in perovskite solar cells. In order to assess the halide ion mobility, we have tracked the changes in the bromide and iodide composition in physically paired 2D lead halide perovskite films of different layer numbers (n = 10–1). These low-dimensional perovskites suppressed halide ion migration as a result of their intercalated spacer ligands and their strong van der Waals interactions. The rate constants for halide exchange of low dimensionality perovskites follow the Arrhenius relationship with thermal activation energy ranging from 58 kJ/mol (n = 10) to 72 kJ/mol (n = 1). The suppression of halide ion mobility (and diffusion coefficient) with modulating perovskite layer number (n) provides further insight into the role of 2D perovskites in improving the performance of photovoltaic devices.

中文翻译：

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抑制2D卤化钙钛矿中卤离子的迁移

二维（2D）卤化铅钙钛矿代表了新兴的一类材料，因为它们具有可调节的光电性能和钙钛矿太阳能电池的长期稳定性。为了评估卤化物离子的迁移率，我们跟踪了物理配对的不同层数（n = 10-1）的二维配对卤化钙钛矿钙钛矿膜中溴化物和碘化物组成的变化。这些低维钙钛矿由于嵌入了间隔基配体和强大的范德华相互作用而抑制了卤离子的迁移。低维钙钛矿卤化物交换的速率常数遵循Arrhenius关系，热活化能为58 kJ / mol（n = 10）至72 kJ / mol（n= 1）。通过调节钙钛矿层数（n）抑制卤化物离子迁移率（和扩散系数），可以进一步了解2D钙钛矿在改善光伏器件性能中的作用。