Lead-Free Perovskite Solar Cells with Over 10% Efficiency and Size 1 cm2 Enabled by Solvent–Crystallization Regulation in a Two-Step Deposition Method

The efficiency of tin perovskite solar cells (TPSCs) decreases largely with increased cell area because of the inhomogeneity of the tin perovskite films formed by a one-step deposition method. Here, we apply a two-step deposition method that is rarely used in TPSCs to solve this problem. We study the steric hindrance of four different solvent molecules in the second step on the crystallization process of tin perovskites and find that the increased steric hindrance to hydroxyl in solvent molecules contributes to dense and homogeneous tin perovskite films. In comparison to the films fabrication by a one-step deposition, the tin perovskite films fabricated by the two-step deposition exhibit a higher uniformity in both the horizontal and longitudinal directions. As a result, over 10% power conversion efficiency of TPSCs was achieved with a cell size of over 1 cm 2 . The cell maintained over 92% of its initial efficiency after operation under 1 sun illumination for 1000 h.