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 PbI₂ 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 PbI₂ 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 PbI₂ and supports the development of high-efficiency, stable perovskite-silicon tandem photovoltaics.