This study presents a solvent engineering strategy for the scalable fabrication of perovskite/silicon tandem solar cells in ambient air. The key finding is that n-butanol (nBA), with its low polarity and moderate volatility, effectively mitigates moisture-induced degradation during the fabrication process and enhances the uniformity of perovskite films. This approach enables the fabrication of high-efficiency perovskite/silicon tandem solar cells with a power conversion efficiency (PCE) of 29.4% (certified 28.7%) for 1.044 cm² devices and 26.3% for 16 cm² devices. The encapsulated devices retained 96.8% of their initial output after 780 hours of maximum power point tracking. Additionally, a conversion efficiency of 25.9% was achieved for 16 cm² devices fabricated via slot-die coating, demonstrating the feasibility of commercial perovskite/silicon tandem solar cells. The study highlights the importance of understanding the influence of air moisture on perovskite crystallization, which is critical for achieving high-quality perovskite films. The research demonstrates that nBA not only reduces the detrimental effects of moisture but also promotes the uniformity of perovskite films on large-scale silicon substrates. The results show that nBA-based solvents lead to improved performance, with lower non-radiative recombination and higher uniformity compared to other solvents like ethanol and isopropyl alcohol. The study also shows that nBA-based perovskite films exhibit a lower intensity of PbI₂ peaks, indicating minimal perovskite decomposition. The study further demonstrates that nBA-based perovskite/silicon tandem solar cells exhibit superior photovoltaic performance and photostability compared to those fabricated in nitrogen environments. The devices achieved a PCE of 29.4% for 1.044 cm² and 26.3% for 16 cm², with a certified PCE of 28.7% for 1.044 cm². The encapsulated devices retained 96.8% of their initial output after 780 hours of maximum power point tracking. The study also shows that nBA-based perovskite/silicon tandem solar cells have excellent stability under ambient conditions, with a PCE of 25.9% for 16 cm² devices fabricated via slot-die coating. The study provides a new solution for the large-scale practical production of perovskite/silicon tandem solar cells, which is beneficial to realize the commercialization of perovskite/silicon tandem solar cells. The results demonstrate the feasibility of commercial perovskite/silicon tandem solar cells and highlight the importance of solvent engineering in achieving scalable fabrication in ambient conditions.This study presents a solvent engineering strategy for the scalable fabrication of perovskite/silicon tandem solar cells in ambient air. The key finding is that n-butanol (nBA), with its low polarity and moderate volatility, effectively mitigates moisture-induced degradation during the fabrication process and enhances the uniformity of perovskite films. This approach enables the fabrication of high-efficiency perovskite/silicon tandem solar cells with a power conversion efficiency (PCE) of 29.4% (certified 28.7%) for 1.044 cm² devices and 26.3% for 16 cm² devices. The encapsulated devices retained 96.8% of their initial output after 780 hours of maximum power point tracking. Additionally, a conversion efficiency of 25.9% was achieved for 16 cm² devices fabricated via slot-die coating, demonstrating the feasibility of commercial perovskite/silicon tandem solar cells. The study highlights the importance of understanding the influence of air moisture on perovskite crystallization, which is critical for achieving high-quality perovskite films. The research demonstrates that nBA not only reduces the detrimental effects of moisture but also promotes the uniformity of perovskite films on large-scale silicon substrates. The results show that nBA-based solvents lead to improved performance, with lower non-radiative recombination and higher uniformity compared to other solvents like ethanol and isopropyl alcohol. The study also shows that nBA-based perovskite films exhibit a lower intensity of PbI₂ peaks, indicating minimal perovskite decomposition. The study further demonstrates that nBA-based perovskite/silicon tandem solar cells exhibit superior photovoltaic performance and photostability compared to those fabricated in nitrogen environments. The devices achieved a PCE of 29.4% for 1.044 cm² and 26.3% for 16 cm², with a certified PCE of 28.7% for 1.044 cm². The encapsulated devices retained 96.8% of their initial output after 780 hours of maximum power point tracking. The study also shows that nBA-based perovskite/silicon tandem solar cells have excellent stability under ambient conditions, with a PCE of 25.9% for 16 cm² devices fabricated via slot-die coating. The study provides a new solution for the large-scale practical production of perovskite/silicon tandem solar cells, which is beneficial to realize the commercialization of perovskite/silicon tandem solar cells. The results demonstrate the feasibility of commercial perovskite/silicon tandem solar cells and highlight the importance of solvent engineering in achieving scalable fabrication in ambient conditions.