Hypophosphorous Acid Additive Engineering for Efficient Cu2AgBiI6 Solar Cells

Abstract

Perovskite solar cells have demonstrated significant performance advancements over the past decade, characterized by their low-cost fabrication and compatibility with both rigid and flexible substrates. Despite their potential, challenges such as long-term instability and the toxicity of lead in high-performance devices hinder their commercialization. Recently, the perovskite-inspired material Cu₂AgBiI₆ (CABI) is explored as a light absorber due to its promising optoelectronic properties. However, its wide bandgap and difficulties in producing high-quality films limit its photovoltaic performance. In this study, hypophosphorous acid (H₃PO₂) is introduced to the CABI precursor solution, generating in situ silver nanoparticles that enhance light absorption through localized surface plasmon resonance. The incorporation of H₃PO₂ improved the crystallinity and surface morphology of CABI films while reducing defect states. Solvent vapor annealing is further employed to optimize the film quality. As a result, the optimal CABI solar cell achieved a power conversion efficiency of 2.22%, a fourfold increase over the pristine film (0.55%). Additionally, the CABI device demonstrated an efficiency of 5.66% under 1000 lux 6000 K indoor illumination, showcasing its potential for powering Internet of Things devices. This strategy is further validated in the CuAgBiI₅ system, offering a pathway to enhance the performance of perovskite-inspired solar cells.