Bifunctional Interface Passivation via Copper Acetylacetonate for Efficient and Stable Perovskite Solar Cells

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Manipulating interface defects can minimize interfacial nonradiative recombination, thus increasing the stability and performance of perovskite solar cells (PSCs). Here, copper acetylacetonate [Cu(acac) 2 ] as a passivator is used to treat the interface between Spiro-OMeTAD and perovskite. Owing to the strong chelation, the uncoordinated Pb 2+ could react with –C═O/–COH functional groups, firmly anchoring acetylacetonate at this interface or the grain boundaries (GBs) of perovskite films to construct multiple ligand bridges, accompanied by the p-type copper iodide formation with copper substituting lead. Simultaneously, Cu + –Cu 2+ pairs transfer electrons from Pb 0 to I 0, suppressing deep level defects of Pb 0 and I 0 near the perovskite interface. These can be beneficial to hole-transferring. Moreover, the Schiff base complexes with hydrophobicity, from the reaction of acetylacetonate with perovskite, can lead to tightly packed adjacent perovskite surfaces and self-seal the GBs of the perovskite, inhibiting moisture diffusion for long-term stability. Consequently, the Cu(acac) 2 -based PSC has achieved more than 24% champion efficiency while retaining ca. 92% of the initial power conversion efficiency after 1680 h of storage.