Interface‐Enriched Fluorinated Covalent Organic Framework Enables Stable, High‐Performance n‐i‐p Perovskite Solar Cells

Abstract

ABSTRACT Buried interfacial integrity remains a major bottleneck limiting both the efficiency and long‐term stability of perovskite solar cells (PSCs). Existing surface‐modification strategies often introduce additional interfacial discontinuities, thereby exacerbating rather than alleviating buried‐interface vulnerabilities. Here, we report an in situ buried‐interface modification strategy that reinforces the SnO 2 /perovskite interface using a fully conjugated covalent organic framework (COF) grafted with polyfluoroalkyl side chains. During perovskite crystallization, strong dipolar interactions between the polyfluoroalkyl chains and the SnO 2 drive the COF toward the buried SnO 2 /perovskite interface. The COF anchors at the SnO 2 /perovskite interface and forms a robust and functionally active interlayer. This dynamic interfacial assembly simultaneously 1) establishes a continuous, graded energy landscape that enhances electronic coupling and accelerates charge extraction; 2) induces facet‐selective SnO 2 ‐COF‐perovskite interactions that guide the oriented growth of perovskite grains; and 3) suppresses interfacial defects and halide migration, thereby stabilizing carrier transport. Consequently, n‐i‐p PSCs achieve a power conversion efficiency of 26.24% with a fill factor of 85.4%, and retain 86% of their initial efficiency after 2000 h of continuous operation. By transforming spontaneous molecular self‐assembly into a processing advantage, this work establishes a new materials paradigm for achieving high‐efficiency, stable, and scalable perovskite photovoltaics.