Understanding ion migration in two-dimensional (2D) perovskite materials is key to enhancing halide perovskite device performance and stability. However, prior studies have been primarily limited to heat- and light-induced ion migration. In this work, to investigate electrically induced ion migration in 2D perovskites, we construct a high-quality, single-crystal, 2D perovskite heterostructure device platform with near-defect-free van der Waals contact. While achieving real-time visualization of halide anions migrating toward the positive bias, defined here as directional ion migration, we also uncover the unique behavior of halide anions interdiffusing toward the opposite direction under prolonged bias. Confocal microscopy imaging reveals a halide migration channel that aligns with the crystal and heterojunction edges. After a sustained ion migration, stable junction diodes exhibiting an up to ∼1,000-fold forward-to-reverse current ratio are realized. This study unveils important fundamental insights into halide migration under electrical bias, paving the way toward high-performance devices.

了解二维 (2D) 钙钛矿材料中的离子迁移是提高卤化物钙钛矿器件性能和稳定性的关键。然而，先前的研究主要限于热和光诱导的离子迁移。在这项工作中，为了研究二维钙钛矿中的电诱导离子迁移，我们构建了具有近乎无缺陷的范德华接触的高质量、单晶、二维钙钛矿异质结构器件平台。在实现卤化物阴离子向正偏压迁移（此处定义为定向离子迁移）的实时可视化的同时，我们还揭示了卤化物阴离子在长时间偏压下向相反方向相互扩散的独特行为。共焦显微镜成像揭示了与晶体和异质结边缘对齐的卤化物迁移通道。经过持续的离子迁移，实现了正向与反向电流比高达 ∼1,000 倍的稳定结二极管。这项研究揭示了电偏压下卤化物迁移的重要基本见解，为高性能器件铺平了道路。