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 ~ 200 nm. The nanosheets showed a strong absorption peak centered at ~ 430 nm and the photoluminescence emission observed at ~ 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.