Dual Shielding Balanced Stable Photoluminescence and High Photoresponsivity in MAPbX3–MAPbBrnX3–n@PbBr(OH) Core–Shell Single Crystals

Organic–inorganic lead halide perovskite (MAPbX₃, X = Cl, Br, I) single crystals exhibit superior optoelectrical and physical characteristics and have been developed in various optical and electrical applications. However, the poor stability against moisture and light remains the most critical demerit of perovskite materials. In this work, light- and waterproof MAPbBr₃-MAPbBr₃@PbBr(OH) core–shell single crystals were successfully synthesized by surface engineering-induced transformation from MAPbBr₃ to MAPbBr₃@PbBr(OH). In addition, an in situ electrode preparation method was developed to construct the Ag/MAPbBr₃-MAPbBr₃@PbBr(OH)/Ag structure during the crystal growing process. The thickness-adjustable MAPbBr₃@PbBr(OH) shell can present dual shielding effects and not only sustains the MAPbBr₃ single crystal core with the highest responsivity of 31 mA W^1–, response time ∼47 ms, and a detection rate of 4.8 × 10¹¹ Jones but also achieves the embedded MAPbBr₃ nanocrystal with bright photoluminescence (quantum yield of 56.1%). Moreover, the similar MAPbCl₃-MAPbBr_nCl_3–n@PbBr(OH) and MAPbI₃-MAPbBr_nI_3–n@PbBr(OH) core–shell single crystals have been prepared, which also exhibit excellent photoresponsivity and high emission. This work provides an effective strategy for the fabrication of high-performance and environmentally stable photodetectors.