Covalent Organic Framework‐Enabled SAM Co‐Assembly for Efficient and Stable Inverted Perovskite Solar Cells

ABSTRACT Self‐assembled monolayers (SAMs) serve as efficient hole transport layers (HTLs) in inverted perovskite solar cells due to tunable work function and favorable energy alignment. However, the widely used MeO‐4PACz tends to aggregate during film formation, causing nonuniform coverage, limited conductivity, and increased interfacial defects that hinder device performance. Herein, we propose a co‐assembly strategy incorporating custom‐designed, fully sp 2 ‐carbon‐linked 2D covalent organic frameworks ( sp 2 c ‐COFs: g‐TBH‐COF and g‐TBY‐COF ) with MeO‐4PACz for SAM homogenization and deep interfacial passivation. The highly extended planar π‐conjugated sp 2 c ‐COFs facilitate charge transport and suppress MeO‐4PACz aggregation via intermolecular hydrogen bonding and π–π interactions, yielding a homogeneous, highly conductive HTL. Dense pyrimidine and bipyridine Lewis basic sites form strong coordination bonds with the perovskite, deeply regulating crystallization dynamics, achieving efficient defect passivation, and optimizing energy alignment. Concurrently, the ordered COF framework reconstructs stress distribution, alleviating residual tensile strain within the perovskite lattice. Consequently, the champion device ultimately achieves an exceptional power conversion efficiency of 26.51%, the highest reported for COF‐modified PSCs, and exhibits outstanding long‐term operational stability under various stringent conditions. This study demonstrates the potential of sp 2 c ‐COFs to homogenize SAMs and improve perovskite film quality, offering a promising strategy for efficient and stable inverted PSCs.