Extending Self-Assembled Monolayer Interface Engineering to Carbon-Based Perovskite Solar Cells

Printable carbon-based perovskite solar cells (C-PSCs) offer a low-cost and durable photovoltaic platform but remain limited by poor interfacial charge extraction and substantial nonradiative recombination at the perovskite/carbon junction suppressing open-circuit voltage (VOC). While phosphonic acid-based self-assembled monolayers (SAMs) are widely used in p-i-n devices, their application in mesoscopic carbon architectures remains unexplored. Here, we report a simple post-treatment based on the molecular self-assembled monolayer MeO-2PACz to address these bottlenecks in triple-mesoscopic TiO2/ZrO2/carbon architectures. MeO-2PACz treatment modulates the perovskite/carbon interface, improving energy-level alignment and passivating undercoordinated Pb2+ sites. Transient photocurrent and transient photovoltage analyses show accelerated charge extraction and extended recombination lifetimes. Consequently, the SAM-treated devices achieve enhanced VOC (0.90 V), fill factor (70.7%), and a champion power conversion efficiency (PCE) of 14.7%, along with suppressed hysteresis and improved stability, retaining 98% of initial PCE after 2400 h under controlled humidity without encapsulation.