Scalable post-treatment for improved self-assembled monolayer coverage in perovskite solar cells†

Perovskite solar cells (PSCs) are rapidly emerging as a next-generation photovoltaic technology due to their tunable band gap, low-temperature processing, and high power conversion efficiency (PCE). Achieving uniform and effective coverage of self-assembled monolayers (SAMs) on transparent conducting oxides (TCOs) is critical for optimizing PSC performance, as non-uniform SAM coverage can lead to surface recombination, higher leakage currents, and reduced efficiency. In this study, we introduce a low-cost, air-processible method—Cooled Moisture Condensation (CMC)—to enhance the coverage of MeO–2PACz SAMs on fluorine-doped tin oxide (FTO) substrates. By cooling the FTO in ambient air, moisture condenses uniformly, increasing surface hydroxyl (–OH) groups and reducing oxygen vacancies, which improves SAM bonding and coverage. Conductive Atomic Force Microscopy (C-AFM) and Scanning Electron Microscopy (SEM) confirm enhanced SAM coverage, reduced leakage current, and improved perovskite film quality. Capacitance–voltage (C–V) measurements reveal a higher built-in potential (V_bi), while open-circuit voltage decay (OCVD) and transient photocurrent decay (TPC) analyses demonstrate more efficient charge extraction and reduced recombination in CMC-treated devices. As a result, PSCs fabricated with CMC-treated substrates exhibit superior performance and reproducibility, highlighting the potential of this method for scalable, high-efficiency solar cell production.