An in situ crosslinked fluorene polymer for efficient perovskite photovoltaics with mitigated lead leakage

Perovskite solar cells (PSCs) suffer from interfacial defects, mechanical instability, and lead leakage. Here, a fluorene-based bisacrylate monomer (BPEFDA) is in situ polymerized to form a crosslinked interlayer (P-BPEFDA), enhancing interfacial adhesion and shear strength. Its carbonyl/ether groups and conjugated backbone passivate defects through Lewis acid-base and metal-π interactions, while facilitating hole extraction and suppressing ion migration. Consequently, PSCs and modules achieve efficiencies of 26.19% and 22.24%, respectively, with enhanced operational stability and ∼97% suppression of lead leakage. This work establishes a multifunctional interfacial strategy for efficient, stable, and environmentally sustainable perovskite photovoltaics.