Achieving Buried Interface/Bulk Synergistic Passivation via Chlorophyll Derivative for Efficient Inverted Perovskite Solar Cells

Buried interfacial engineering is crucial for NiO_x-based inverted perovskite solar cells (PSCs), while most passivation measures focus only on the interface and neglect the perovskite bulk. In this work, a stable free-base chlorin possessing an amino acid terminal (serinyl pyropheophorbide-a, SPPa) was synthesized as a functional chlorophyll derivative, and its trifluoroacetic acid and hydrogen chloride salts (SPPaX; X = TFA, HCl) were introduced into the NiO_x/perovskite interface. Thanks to the high solubility in N,N-dimethylformamide and dimethyl sulfoxide, SPPaX can diffuse into the perovskite through the precursor. Insertion of SPPaX optimizes the interfacial energy band bending and minimizes interfacial defects, while the growth sites provided by SPPaX facilitate the formation of high-quality perovskite film with less lattice strain and high crystal orientation. Additionally, diffused SPPaX molecules in perovskite improve the crystallization process and decrease the internal defects of perovskite films. As a result, the SPPaX distributed throughout perovskite achieves a bulk/interface synergistic passivation effect at both the bulk and buried interface of the perovskite film. SPPaTFA-modified PSCs deliver a champion power conversion efficiency of 25.54% with a superior long-term stability under both light and thermal stress.