The role of a vapor-assisted solution process on tailoring the chemical composition and morphology of mixed-halide perovskite solar cells

Abstract

Herein, we report a modified two-step method to construct a uniform and pinhole-free polycrystalline perovskite film with large grains up to the microscale using lead mixed-halide (PbI₂–PbCl₂) precursor solutions to guarantee the device functioning. Commonly used sequential deposition methods based on dip- and spin-coatings are combined with a vapor-assisted solution process to improve the perovskite morphology and tune the residual lead mixed-halides. These can enhance the optical absorption and efficiency of perovskite solar cell (PSC) devices. The impact of the Cl content in the lead mixed-halide precursors and the employed preparation methods on the photovoltaic performance of PSCs are studied. The highest performance of PSC is obtained for a vapor-treated film containing 2 mol% PbCl₂ deposited by spin-coating, showing a 56% increase in photoconversion efficiency compared to the pristine PbI₂-based device.