Regulated Crystallization of FASnI₃ Films through Seeded Growth Process for Efficient Tin Perovskite Solar Cells

Although rapid progress has been made in tin-based perovskite solar cells (PSCs), the inferior film qualities of the solution-processed perovskites always lead to poor reproducibility and instability. Herein, we present a simple seeded growth (SG) approach to obtain high-quality tin-based perovskite films with preferred crystal orientation, large grain sizes, and fewer apparent grain boundaries. High-quality tin-based perovskite films fabricated through this SG process could greatly reduce the nonradiative recombination centers and inhibit the oxidation of Sn²⁺. Using formamidinium tin tri-iodide (FASnI₃) perovskites, the SG-PSCs exhibit a much improved efficiency from 5.37% (control) to 7.32% with all improved photovoltaic parameters. Moreover, this SG strategy is easily applicable to other tin-based perovskite compositions. The PSC based on methylammonium (MA) doped mixed-cation perovskite (FA_0.75MA_0.25SnI₃) exhibited a power conversion efficiency (PCE) of 8.54% with an improvement of 19.3% in the photovoltaic performance, making it a general approach for achieving efficient tin-based PSCs.