Consecutive Interfacial Transformation of Cesium Lead Halide Nanocubes to Ultrathin Nanowires with Improved Stability

Although all-inorganic CsPbX₃ (X = Cl, Br, I) nanocrystals (NCs) have been considered as a promising material for photoelectronic devices, their applications are still limited because of their poor stability and the lack of in-depth understanding. Here, we demonstrate a post-treatment method for the preparation of ultrathin CsPbX₃ nanowires (NWs) by treating CsPbBr₃ nanocubes with thiourea solution. A systematic study showed a consecutive interfacial transformation process, in which CsPbBr₃ nanocubes were first converted to Cs₄PbBr₆ NCs in the presence of thiourea, followed by a further transformation to CsPbBr₃ NCs through an interfacial CsX-stripping process. To reduce the surface energy, an oriented attachment process has been realized and CsPbBr₃ NCs aggregated to form ultrathin NWs. The ultrathin CsPbBr₃ NWs exhibited high photoluminescence quantum yield (up to 60%) and high resistance to water treatment, which can be attributed to the surface passivation by thiourea. In addition to thiourea, cysteine and thioacetamide that contain the thiol group can also be used to trigger this transformation. This work can not only offer a facile method for the synthesis of efficient and stable ultrathin CsPbBr₃ NWs but also help to reveal the in-depth mechanisms which may be very useful in the field of metal halide perovskite NCs.