Heterojunction Perovskite Microrods Prepared by Remote‐Controlled Vacancy Filling and Halide Exchange

Abstract Anion exchange reaction tunes the band gap of halide perovskites, which proceeds by the migration of the ions through the halide vacancies. This study reports the preparation of the heterojunction perovskite microrods by optically controlled localized halide vacancy filling, and halide exchange leading to color tuning in the MAPbBr₃ microrod crystals. The exchange reaction is homogeneously suppressed by treating the crystal with a halide precursor solution, whereas the reaction is locally inhibited at the specific site of a crystal by filling the halide vacancies using a tightly focused beam of a near‐infrared laser. By controlling the density of halide vacancies at the specific site of the crystal, the rate of nonradiative recombination of charge carriers in the crystal is controlled. This halide vacancy filling by the remote‐controlled reaction helps to locally control the crystal quality and photoluminescence for designing perovskite‐based high‐quality photovoltaic and optoelectronic devices.