A co-adsorbed strategy using a small molecule, 2-chloro-5-(trifluoromethyl)isonicotinic acid (PyCA-3F), was employed to enhance the performance of self-assembled monolayers (SAMs) in perovskite and organic solar cells (PSCs and OSCs). This approach significantly reduced the aggregation of 2PACz, improved surface smoothness, and increased the work function of the modified SAM layer, leading to a flattened buried interface with favorable heterointerface properties. The resulting improvements in crystallinity, minimized trap states, and enhanced hole extraction and transfer capabilities led to power conversion efficiencies (PCEs) exceeding 25% in PSCs with a p-i-n structure (certified at 24.68%). OSCs using the CA strategy achieved a PCE of 19.51% based on the PMI:PTQ10:m-BTP-PhC6 photoactive system. After 1000 hours of maximal power point tracking, encapsulated PSCs and OSCs retained approximately 90% and 80% of their initial PCEs, respectively. The CA strategy demonstrated significant improvements in both PSCs and OSCs, with enhanced operational stability. The study highlights the effectiveness of the CA approach in enhancing the performance of SAM-based devices, achieving efficiency breakthroughs and improved stability in both PSCs and OSCs. The co-adsorbed strategy effectively reduces interfacial energy losses, enhances crystallinity, and minimizes trap states, leading to improved device performance and stability. The results demonstrate the potential of the CA approach in advancing the development of high-performance, stable photovoltaic devices.A co-adsorbed strategy using a small molecule, 2-chloro-5-(trifluoromethyl)isonicotinic acid (PyCA-3F), was employed to enhance the performance of self-assembled monolayers (SAMs) in perovskite and organic solar cells (PSCs and OSCs). This approach significantly reduced the aggregation of 2PACz, improved surface smoothness, and increased the work function of the modified SAM layer, leading to a flattened buried interface with favorable heterointerface properties. The resulting improvements in crystallinity, minimized trap states, and enhanced hole extraction and transfer capabilities led to power conversion efficiencies (PCEs) exceeding 25% in PSCs with a p-i-n structure (certified at 24.68%). OSCs using the CA strategy achieved a PCE of 19.51% based on the PMI:PTQ10:m-BTP-PhC6 photoactive system. After 1000 hours of maximal power point tracking, encapsulated PSCs and OSCs retained approximately 90% and 80% of their initial PCEs, respectively. The CA strategy demonstrated significant improvements in both PSCs and OSCs, with enhanced operational stability. The study highlights the effectiveness of the CA approach in enhancing the performance of SAM-based devices, achieving efficiency breakthroughs and improved stability in both PSCs and OSCs. The co-adsorbed strategy effectively reduces interfacial energy losses, enhances crystallinity, and minimizes trap states, leading to improved device performance and stability. The results demonstrate the potential of the CA approach in advancing the development of high-performance, stable photovoltaic devices.