We fabricated the CH₃NH₃PbI_3-XCl_X perovskite crystalline films by solution processed method in air and nitrogen ambience to investigate the impact of the growth conditions on surface morphology and interface properties of the films. The surface morphology of CH₃NH₃PbI_3-XCl_X thin films are captured by scanning electron microscopy (SEM) and fractal analysis is performed on SEM micrographs. The value of fractal dimension/hurst exponent is found to be larger/smaller in N₂ environment as comparison to open air environment. The greater value of fractal dimension is corresponding to larger surface jaggedness which plays a crucial role for improving the interface between the perovskite and hole transportation layer. Furthermore, this analytical prediction is confirmed by photovoltaic devices fabricated on these films and observed a 60% enhancement in power conversion efficiency (PCE)  of N₂ environment based thin films as compare to open air processed films. This may be due to the formation of compact and voids free perovskite self-affine fractal surfaces under nitrogen environment as compare to open air environment. Our findings represent a step forward to the realization of the peculiar morphological behaviour of the mixed halide perovskite fabricated in different environmental conditions.

中文翻译：

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CH ₃ NH ₃ PbI _3-X Cl _X薄膜的表面演化和分形维数及其光伏性能

我们在空气和氮气环境中通过溶液处理方法制备了 CH ₃ NH ₃ PbI _3-X Cl _X钙钛矿晶体薄膜，以研究生长条件对薄膜表面形貌和界面特性的影响。CH ₃ NH ₃ PbI _3-X Cl _X薄膜的表面形貌通过扫描电子显微镜(SEM) 捕获并且在SEM 显微照片上进行分形分析。发现分形维数/赫斯特指数的值在 N _{2 中}更大/更小环境与露天环境相比。分形维数越大，表面锯齿状越大，这对改善钙钛矿和空穴传输层之间的界面起着至关重要的作用。此外，在这些薄膜上制造的光伏器件证实了这一分析预测，并观察到 ​​N _{2 的}功率转换效率 (PCE) 提高了 60%与露天加工薄膜相比，基于环境的薄膜。这可能是由于与露天环境相比，在氮气环境下形成了致密且无空隙的钙钛矿自仿射分形表面。我们的发现代表了实现在不同环境条件下制造的混合卤化物钙钛矿的特殊形态行为迈出的一步。