Regulation of Buried Interface through the Rapid Removal of PbI₂·DMSO Complex for Enhancing Light Stability of Perovskite Solar Cells

The presence of the detrimental PbI 2 residue at the buried interface negatively affects the photovoltaic performance of perovskite solar cells (PSCs). However, the underlying mechanism involved in the formation and elimination of residual PbI 2 has been rarely investigated, despite its critical significance for high-efficiency and stable PSCs. Here, we investigated the formation and elimination mechanism of residual PbI 2 at the buried interface influenced by citric acid (CA) and found that CA can quickly remove the PbI 2 ·DMSO complex through a competitive adsorption mechanism by forming highly crystallized PbI 2 . This promotes the subsequent intercalation of amine cations into the PbI 2 framework by forming a stable perovskite. Consequently, the best-performing target PSC achieves an efficiency of 25.19% (a certified efficiency of 24.64%) and 23% from a 1 cm 2 PSC. Additionally, the target PSC also demonstrates improved light stability after 200 h of UV light soaking by maintaining 94.21% of its initial efficiency compared with only 70.76% for the control PSC.