Colloidally Uniform Single Crystal Precursors Enable Uniform FAPbI3 Films for Efficient Perovskite Submodules

Abstract

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