Compositional engineering for lead-free antimony bismuth alloy-based halide perovskite solar cells

Owing to their low toxicity and remarkable stability, perovskites based on antimony and bismuth have garnered significant interest in recent years. However, A3B2X9 perovskite materials derived from antimony and bismuth face several challenges, including excessively wide band gaps, elevated defect densities, and suboptimal film quality, all of which hinder advancements in device efficiency. While extensive studies have been undertaken to investigate the effects of modulating the A-site and X-site elements in lead-free A3B2X9 perovskites, there remains a notable scarcity of reports addressing the impact of modifications to the B-site element. In this study, we investigated the alloying of antimony and bismuth within the 2D Cs3B2I6Br3 perovskite. By systematically varying the ratios of two elements, we found that the incorporation of both antimony and bismuth at the B-site significantly enhances the quality of the perovskite films. Our findings indicate that a 1 : 1 ratio of antimony to bismuth produces the densest films, the highest photoluminescence intensity, and superior photovoltaic performance. Ultimately, the devices fabricated using this optimal ratio achieved an open-circuit voltage (VOC) of 1.01 V and a power conversion efficiency (PCE) of 0.645%.