Synthesis of Lead‐free CsGeI₃ Perovskite Colloidal Nanocrystals and Electron Beam‐induced Transformations

Abstract

Colloidal nanocrystals (NCs) of metal halide perovskite have recently aroused great research interest, due to their remarkable optical and electronic properties. We report a solution synthesis of a new member in this category, that is, all-inorganic lead-free cesium germanium iodine (CsGeI₃ ) perovskite NCs. These CsGeI₃ colloidal NCs are confirmed to adopt a rhombohedral structure. Moreover, the electron beam-induced transformations of these lead-free perovskite NCs have been investigated for the first time. The fracture of single-crystalline CsGeI₃ nanocubes occurs first, followed by the emergence and growth of cesium iodine (CsI) single crystals and the final fragmentation into small debris with random orientations. Notably, the electron-reduced Ge species in CsGeI₃ nanocubes exhibit a distinctive transformation path, compared to heavier Pb atoms in lead halide perovskite NCs.