CsCl Seed Layer Strategy for Enhanced Fabrication Yield and Device Performance of Solution-Based Two-Step Processed Perovskite Solar Cells

Inverted perovskite solar cells (PSCs) are promising top-cell candidates for 2T perovskite/silicon tandem devices; however, achieving uniform and defect-free perovskite coverage on industrially relevant textured silicon bottom cells remains a major challenge for conventional solution-based perovskite deposition. Here, we introduce a vapor-deposited CsCl seed layer at the hole transport layer/perovskite interface in a solution-based two-step deposition method. This strategy promotes nucleation and improves perovskite film formation, particularly in regions where solution processing alone is insufficient. When implemented in wide-bandgap ($\mathrm{\textit{E}_{g}}$ = 1.67 eV) $\textit{p-i-n}$ PSCs, the approach significantly enhances device performance and long-term operational stability, achieving power conversion efficiencies of 19% and retaining 83% of initial device performance after 1000 h of continuous illumination at 25 $^{\circ}$C in a nitrogen atmosphere. In 2T perovskite/silicon tandem architectures, the CsCl seed layer strategy markedly enhances process repeatability and fabrication yield – particularly on textured silicon bottom cells – achieving yields exceeding 70% across different silicon bottom cell surface structures. These findings demonstrate a simple and scalable strategy to improve the reliability of perovskite film formation, supporting the industrial implementation of 2T perovskite/silicon tandem solar cells.