Epoxy Click‐Linking of Hole‐Transport Self‐Assembled Monolayers for Robust Efficient Perovskite Solar Cells

ABSTRACT Self‐assembled monolayers (SAMs) have been widely explored as hole‐transporting layers for inverted perovskite solar cells (PSCs). Their uneven substrate coverage and interfacial instability remain, however, as key factors in determining device efficiency and long‐term operation. Herein, we propose an epoxy‐amine click strategy for crosslinking SAMs into a robust covalent network interface for high‐performance PSCs. The epoxy ring‐opening afforded the in situ crosslinked HTL with excellent solvent resistance and unchanged optoelectronic properties even under extreme conditions. Importantly, meticulously designed cross‐linking SAMs endow the covalent network with abundant functional groups for effective passivation of interfacial defects, optimization of energy level alignment, and boosting hole extraction. Benefiting from these merits, the crosslinked SAMs based PSCs achieve a champion power conversion efficiency of 26.38%, and 84.7% of efficiency retention after 984 h continuous operation in air at 65 ± 5°C without encapsulation. This work provides an effective material‑design and cross‑linking strategy for constructing high‑performance and stable interfacial layers in perovskite photovoltaics.