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 (Vbi), 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.