Controlled Synthesis of Composition Tunable Formamidinium Cesium Double Cation Lead Halide Perovskite Nanowires and Nanosheets with Improved Stability

Lead halide perovskites with well-defined morphology have attracted attention for their unique properties as a promising new class of semiconductor materials in photovoltaics and optoelectronics. However, controlling morphologies and compositions of perovskite nanostructures with improved stability, especially for double cation lead halide perovskite, still remains a challenge. Here, we demonstrate a colloidal synthetic approach for direct synthesis of stable single crystal formamidinium (FA) cesium double cation lead halide FA(0.33)Cs(0.67)PbBr(3-x)I(x)(0 <= x <= 3) perovskite nanostructures with controllable morphology over a wide range of halide compositions, without using a previous anion-exchange process. The presence of FA alloyed in the A site for the pure cesium lead halide perovskite structure can stabilize the nanocrystals while delivering a better balance between structure and composition. On the basis of the FA(0.33)Cs(0.67)PbBr(3-x)I(x) alloy perovskite system, we achieved nanowires and nanosheets with high yield of various halide compositions by tuning the ligand participating in the reaction. These new perovskite nanostructures with well-defined morphology and compositions demonstrated improved stability and fluorescent and optoelectronic properties, which may allow them to find application as replacements for conventional semiconductor nanostructures in nanoscale devices.