Ultrathin lead-free double perovskite cesium silver bismuth bromide nanosheets

Two-dimensional (2D) lead halide perovskites nanostructures have drawn great fundamental interest and displayed excellent properties for various optoelectronic applications. However, the toxicity of lead remains a concern for their large-scale utilizations. Bismuth halide double perovskites stand out as a class of promising candidates for lead-free halide perovskites. In this work, we demonstrate the first synthesis of lead-free 2D halide double perovskite nanosheets. The synthesized Cs2AgBiBr6 nanosheets exhibited thicknesses in the range of 3-5 nm and lateral dimensions of similar to 200 nm. The nanosheets showed a strong absorption peak centered at similar to 430 nm and the photoluminescence emission observed at similar to 630 nm. We also explored dimensionality control from zero-dimensional nanocubes to 2D nanosheets and investigated the preferential growth of Cs2AgBiBr6 over other related compounds such as Cs3Bi2Br9 and CsAgBr2. Our study reveals that Cs2AgBiBr6 nanosheets are interesting 2D material for potential optoelectronic applications and provides a guideline for the controllable synthesis of multi-component compounds with tunable morphology, dimensionality and phase.