Dual-functional 2-mercaptopyridine-N-oxide doping for simultaneous electronic optimization and silver electrode stabilization in inverted perovskite solar cells

Abstract 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.