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The presence of the detrimental PbI2 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 PbI2 has been rarely investigated, despite its critical significance for high-efficiency and stable PSCs. Here, we investigated the formation and elimination mechanism of residual PbI2 at the buried interface influenced by citric acid (CA) and found that CA can quickly remove the PbI2·DMSO complex through a competitive adsorption mechanism by forming highly crystallized PbI2. This promotes the subsequent intercalation of amine cations into the PbI2 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 cm2 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.
Zhao et al. (Fri,) studied this question.