In situ Crosslinked Robust Molecular Zipper at the Buried Interface for Perovskite Photovoltaics

The brittle buried interface, characterized by weak adhesion to the substrate, numerous imperfections, and unfavorable strain, poses a significant challenge that impairs the overall performance and long-term stability of perovskite solar cells (PSCs). Herein, a robust molecular zipper is constructed through in situ polymerization of self-assembly monomer 4-vinylbenzoic acid (VA), to tightly link the buried interface to the substrate in n-i-p PSCs with an adhesive strength as high as 10.77 MPa. The modified buried interface exhibits improved morphology, suppressed defects, released strain, and matched energy level alignment. The resulting PSCs deliver an absolute gain of ≥1.67% in champion power conversion efficiency based on both one-step deposition protocol and two-step one, demonstrating the universality of this strategy across different film-processing scenarios. The unencapsulated PSCs can retain 94.2% of their initial efficiency after 550 h with a linear extrapolated T₉₀ value of 1230 h, as per the ISOS-L-2 protocol. This work provides a facile strategy to reinforce the buried interface of PSCs.