Promoting optoelectronic properties of Cs₂AgBiBr₆ nanocrystals by formation of heterostructures with BiOCl nanosheets

Lead halide perovskite nanocrystals and their heterostructures have achieved substantial advances in optoelectronics; however, their inherent material instability and lead toxicity have driven research on alternative material systems. Herein, solution-processable heterostructures composed of lead-free double perovskite Cs₂AgBiBr₆ nanocrystals and BiOCl nanosheets were prepared through a colloidal synthesis method. Defect states were present in BiOCl and benefited carrier generation, recombination and transport in Cs₂AgBiBr₆. As a result, the light emission of the Cs₂AgBiBr₆ nanocrystals was greatly enhanced at low temperatures, and the photodetector based on the Cs₂AgBiBr₆/BiOCl heterostructure exhibited a much improved on-off ratio compared to the device based on Cs₂AgBiBr₆ alone. Our work highlights the complex nature and impact of two-dimensional heterostructure assembly on the optoelectronic properties of lead-free double perovskites and demonstrates their great potential toward environmentally friendly optoelectronic devices.