Simultaneously addressing nanoscale interfacial charge transport inefficiency and Ag electrode diffusion remains a critical bottleneck for scalable inverted perovskite solar cells (PSCs). Herein, we report a dual-functional molecular engineering strategy by doping 2-mercaptopyridine-N-oxide (2-MPNO) into the 10 nm-thick nanoscale bathocuproine (BCP) cathode buffer layer, achieving synergistic optimization of interfacial energy alignment and Ag⁺ diffusion inhibition. The n-type doping effect of 2-MPNO triples the electron mobility of the [6,6]-phenyl-C61-butyric acid methyl ester (PCBM)/BCP layer (via space-charge-limited current measurements), with ultraviolet photoelectron spectroscopy confirming a 0.37 eV upward Fermi level shift to optimize nanoscale interfacial energy alignment. Owing to the incomplete coverage of PCBM on the perovskite surface, 2-MPNO molecules infiltrate the perovskite interface, effectively passivating defects and reducing non-radiative recombination. Concurrently, the –SH and N–O groups of 2-MPNO form bidentate coordination with Ag at the nanoscale Ag/BCP interface, constructing a molecular barrier to block Ag⁺ migration. As a result, the optimized device exhibits an improvement in efficiency from 23.56% to 25.31%. More importantly, unencapsulated devices maintain 97.4% of their original efficiency after 2115 h stored in air with a relative humidity of 15% ± 5% and retain 94.0% of their initial efficiency following thermal aging at 65 °C for 1256 h in a nitrogen environment.

In inverted perovskite solar cells (PSCs), effective modification of the interface between the metal cathode and electron transport layer (ETL) is crucial for achieving high performance and stability. Herein, sulfonated bathocuproine, commonly known as disodium bathocuproine disulfonate (BCDS), was employed as a cathode buffer layer to address the interfacial issues at the [6,6]-phenyl-C61-butyric acid methyl ester (PCBM)/Ag interface. BCDS possesses the ability to form coordinate bonds with Ag electrodes. The utilization of the BCDS buffer layer enhanced the charge extraction capability at the cathode interface while simultaneously achieving interfacial defect passivation, improving interfacial contact and increasing the built-in electric field. Consequently, a power conversion efficiency (PCE) of 25.06% was achieved. Furthermore, owing to the excellent film-forming uniformity of BCDS on PCBM, the stability of the device was also improved. After storage in dry air for more than 2000 h, the device maintained 96% of its initial efficiency. This work underscores the remarkable potential of tailoring coordination groups to enhance charge extraction efficiency at the ETL–cathode interface, unveiling a promising new frontier in buffer layer development and performance optimization strategies for PSCs.