Colloidally uniform single-crystal precursors enable uniform FAPbI₃ films for efficient perovskite submodules

With the unprecedented research development on lead halide perovskite photovoltaics, scaling up fabrication while comprehensively understanding the properties of cost-effective and highly uniform precursor films has become critical for their practical application. When enlarging the device area, good precursor purity serves as the first step in ensuring the uniformity of the perovskite film. Chemical purity and colloidal uniformity in the precursor solution both play important roles in dictating film uniformity and defect density. Here, for the first time, we explored the colloidal behavior of FAPbI₃ precursors using different preparatory materials of varied costs but with similar metal purity. As the colloidal size of regular PbI₂ + FAI powder precursors increased compared to that of PbI₂ colloids, the FAPbI₃ single-crystal precursor synthesized from low-purity chemicals exhibited a generally smaller and more uniform colloidal size, which yielded perovskite films with improved uniformity and reduced defect density at lower cost. The colloidally uniform single-crystal precursors led to photovoltaics with higher power conversion efficiency and better long-term operational stability. More importantly, the uniformity in the precursor and film was found to be beneficial for large-area fabrication, where the scaling-up production of 30 cm × 30 cm perovskite submodules based on single-crystal precursors achieved an impressive 20.7% efficiency.