A hydrogen-bonding anchoring strategy for buried interface passivation toward enhanced efficiency and stability of inverted perovskite solar cells

Abstract

Buried interface defects in perovskite solar cells (PSCs) remain one of the key factors limiting the efficiency and stability of the devices. Various passivation strategies for reducing buried interface defects have been explored. However, the strong solvation capability of perovskite precursor solvents (e.g., DMF/DMSO) often causes passivation molecules to diffuse the into perovskite bulk. This adversely affects perovskite film crystallization or degrades the passivation layer, ultimately undermining the passivation efficacy. Herein, we developed an effective anchoring strategy for buried interface passivation in inverted PSCs by leveraging the hydrogen bonding between a cross-linked P-TSPA [3-(triethoxysilyl)propylamine] polymer and thenoyltrifluoroacetone (TTFA) passivation molecules. The P-TSPA layer, stabilized by “Si–O” bonding with NiOx, resists solvent dissolution, while TTFA forms multiple hydrogen bonds with P-TSPA and passivates undercoordinated Pb2+ defects at the buried interface. Characterizations confirmed that TTFA passivation remains localized at the buried interface without perturbing the perovskite lattice structure. This approach enhances grain growth, reduces defect density, and prolongs carrier lifetime, enabling inverted PSCs (ITO/NiOx/P-TSPA/TTFA/MAPbClxI3−x/PEAI/C60/BCP/Ag) to achieve a champion efficiency of 20.07% (vs 16.21% for controls) via suppressed interfacial recombination. Further optimization with FA+ doping improves efficiencies to 20.30% (FA0.1MA0.9PbClxI3−x) and 20.83% (FA0.2MA0.8PbClxI3−x). The modified devices also exhibit exceptional stability, retaining 85.3% of their initial performance after 50 days (12% humidity, low O2), compared to 53.1% for controls, due to enhanced hydrophobicity and strong Pb coordination at the buried interfaces. This work demonstrates a scalable interface engineering strategy for high-performance, industrially viable PSCs.