Organic-inorganic hybrid perovskites exhibiting exceptional photovoltaic and optoelectronic properties are of fundamental and practical interest, owing to their tunability and low manufacturing cost. For practical applications, however, challenges such as material instability and the photocurrent hysteresis occurring in perovskite solar cells under light exposure need to be understood and addressed. While extensive investigations have suggested that ion migration is a plausible origin of these detrimental effects, detailed understanding of the ion migration pathways remains elusive. Here, we report the characterization of photo-induced ion migration in perovskites using in situ laser illumination inside a scanning electron microscope, coupled with secondary electron imaging, energy-dispersive X-ray spectroscopy and cathodoluminescence with varying primary electron energies. Using methylammonium lead iodide and formamidinium lead iodide as model systems, we observed photo-induced long-range migration of halide ions over hundreds of micrometers and elucidated the transport pathways of various ions both near the surface and inside the bulk of the samples, including a surprising finding of the vertical migration of lead ions. Our study provides insights into ion migration processes in perovskites that can aid perovskite material design and processing in future applications.

有机-无机杂化钙钛矿具有优异的光伏和光电特性，由于其可调性和低制造成本，具有基础和实际意义。然而，对于实际应用，需要了解和解决诸如材料不稳定性和钙钛矿太阳能电池在光照下发生的光电流滞后等挑战。虽然广泛的调查表明离子迁移是这些有害影响的合理来源，但对离子迁移途径的详细了解仍然难以捉摸。在这里，我们报告了使用扫描电子显微镜内的原位激光照明以及二次电子成像对钙钛矿中光诱导离子迁移的表征，具有不同初级电子能量的能量色散 X 射线光谱和阴极发光。我们使用甲基铵碘化铅和甲脒碘化铅作为模型系统，观察了光诱导的卤化物离子在数百微米范围内的远程迁移，并阐明了样品表面附近和主体内部各种离子的传输路径，包括铅离子垂直迁移的惊人发现。我们的研究提供了对钙钛矿中离子迁移过程的见解，可以帮助钙钛矿材料在未来应用中的设计和加工。我们观察了光诱导的卤化物离子在数百微米范围内的远距离迁移，并阐明了样品表面附近和主体内部各种离子的传输路径，包括铅离子垂直迁移的惊人发现。我们的研究提供了对钙钛矿中离子迁移过程的见解，可以帮助钙钛矿材料在未来应用中的设计和加工。我们观察了光诱导的卤化物离子在数百微米范围内的远距离迁移，并阐明了样品表面附近和主体内部各种离子的传输路径，包括铅离子垂直迁移的惊人发现。我们的研究提供了对钙钛矿中离子迁移过程的见解，可以帮助钙钛矿材料在未来应用中的设计和加工。