Q. Alan Xu, Ciyu Ge, Bokai Hao, Aoyue Chen, Peiyan Zhang, Xiaodong Li, Ying Zhou, Qiansong Deng, Ping Fu, Long Hu, Hongyan Lu, Sheng He, Shuping Pang, Haisheng Song, Chao Chen, Jiang Tang
Vacuum-assisted growth is promising for scalable halide perovskite solar cells, yet its application to Sn–Pb narrow-band gap systems is hindered by the skin effect, where rapid surface solvent extraction induces buried voids and defective films. Here, we quantitatively elucidate the skin-effect formation through a microscopic solvent-dynamics model, revealing that it emerges when the surface extraction rate exceeds internal diffusion by over 3-fold. A low-temperature vacuum-assisted growth strategy is developed to rebalance surface extraction and internal diffusion, reducing the surface extraction rate by 5.8 times and suppressing the skin effect. This approach lowers film defect density at surface by 2 orders of magnitude. Consequently, Sn–Pb perovskite solar cells achieve efficiencies of 23.44% (0.0768 cm 2 ) and 22.18% (1 cm 2 ), representing the highest reported performance for anti-solvent-free Sn–Pb systems.