Intrinsic Halide Segregation at Nanometer Scale Determines the High Efficiency of Mixed Cation/Mixed Halide Perovskite Solar Cells

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• 作者：Paul Gratia ; Giulia Grancini ; Jean-Nicolas Audinot ; Xavier Jeanbourquin ; Edoardo Mosconi ; Iwan Zimmermann ; David Dowsett ; Yonghui Lee ; Michael Grätzel ; Filippo De Angelis ; Kevin Sivula ; Tom Wirtz ; Mohammad Khaja Nazeeruddin
• 刊名：Journal of the American Chemical Society
• 出版年：2016
• 出版时间：December 14, 2016
• 年：2016
• 卷：138
• 期：49
• 页码：15821-15824
• 全文大小：333K
• ISSN：1520-5126

文摘

Compositional engineering of a mixed cation/mixed halide perovskite in the form of (FAPbI₃)_0.85(MAPbBr₃)_0.15 is one of the most effective strategies to obtain record-efficiency perovskite solar cells. However, the perovskite self-organization upon crystallization and the final elemental distribution, which are paramount for device optimization, are still poorly understood. Here we map the nanoscale charge carrier and elemental distribution of mixed perovskite films yielding 20% efficient devices. Combining a novel in-house-developed high-resolution helium ion microscope coupled with a secondary ion mass spectrometer (HIM-SIMS) with Kelvin probe force microscopy (KPFM), we demonstrate that part of the mixed perovskite film intrinsically segregates into iodide-rich perovskite nanodomains on a length scale of up to a few hundred nanometers. Thus, the homogeneity of the film is disrupted, leading to a variation in the optical properties at the micrometer scale. Our results provide unprecedented understanding of the nanoscale perovskite composition.