Targeted PbI₂ Removal Unlocks 31.71% Efficiency Perovskite‐Silicon 2T Tandem Solar Cells

Perovskite‐silicon tandem solar cells (PSTSCs) represent one of the most promising candidates for next‐generation photovoltaics, offering the potential to surpass the Shockley–Queisser efficiency limit of single‐junction devices due to their tunable bandgap and strong light absorption. However, residual PbI 2 formed from incomplete crystallization in the perovskite top subcell introduces nonradiative recombination centers, structural inhomogeneity, and interfacial instability, thereby limiting device performance. In this work, we proposed a chemical polishing strategy based on a dimethyl sulfoxide and chlorobenzene mixed solvent system that selectively removes surface PbI 2 without disrupting the perovskite lattice. This approach effectively reduces trap‐state density, promotes grain boundary fusion, enhances photoluminescence intensity, and extends carrier lifetime. As a result, the fabricated PSTSCs achieve a certified power conversion efficiency of 31.71%, accompanied by an increase in open‐circuit voltage from 1.821 V to 1.839 V and a marked suppression of interface‐related recombination losses. This study highlights a facile yet effective interfacial engineering strategy that mitigates residual PbI 2 and supports the development of high‐efficiency, stable perovskite‐silicon tandem photovoltaics.