Phase Segregation Dynamics in Mixed-Halide Perovskites Revealed by Plunge-Freeze Cryogenic Electron Microscopy

Qingyuan Fan; Yi Cui; Yanbin Li; Julian A. Vigil; Zhiqiao Jiang; Partha Nandi; Robert Colby; Chensong Zhang; Hemamala I. Karunadasa; Aaron M. Lindenberg

arXiv · 2412.13004

Phase Segregation Dynamics in Mixed-Halide Perovskites Revealed by Plunge-Freeze Cryogenic Electron Microscopy

Qingyuan Fan·Yi Cui·Yanbin Li·Julian A. Vigil·Zhiqiao Jiang·Partha Nandi·Robert Colby·Chensong Zhang·Hemamala I. Karunadasa·Aaron M. Lindenberg

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Abstract

Mixed-halide lead perovskites, with photoexcited charge-carrier properties suitable for high-efficiency photovoltaics, hold significant promise for high-efficiency tandem solar cells. However, phase segregation under illumination, where an iodide-rich phase forms carrier trap states, remains a barrier to applications. This study employs plunge-freeze cryogenic electron microscopy to visualize nanoscale phase segregation dynamics in CsPb(Br,I) films. By rapidly freezing the illuminated samples, we preserve transient photoexcited ion distributions for high-resolution structural and compositional analysis at the nanoscale. Cryogenic scanning transmission electron microscopy techniques (EELS, 4D-STEM) captured the dynamics of photo-induced iodine migration from grain boundaries to centers, identified the buildup of anisotropic strain, and captured the heterogeneous evolution of this process within a single grain. These findings provide new insights into microscopic phase segregation mechanisms and their dynamics, enhancing our understanding of mixed-halide perovskite photostability.

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Qingyuan Fan, Yi Cui, Yanbin Li, Julian A. Vigil, Zhiqiao Jiang, Partha Nandi, Robert Colby, Chensong Zhang, Hemamala I. Karunadasa, Aaron M. Lindenberg. 2024-12-17. Phase Segregation Dynamics in Mixed-Halide Perovskites Revealed by Plunge-Freeze Cryogenic Electron Microscopy. https://arxiv.org/abs/2412.13004

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