Suppressing Skin Effect toward Efficient Sn–Pb Perovskite Solar Cells

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.