Pre-Embedded Potassium Acetate-Modified SnO₂ Electron Transfer Layer for Efficient and Durable Perovskite Solar Cells

Perovskite solar cells (PSCs) have garnered significant attention due to their exceptional photovoltaic performances. However, their power conversion efficiency and stability are significantly hindered by lattice defects and nonradiative recombination losses at the interface between the perovskite film and electron transport layer (ETL). Herein, we report the incorporation of multifunctional potassium acetate (KAc) into SnO₂ ETL. Through thermal diffusion of K⁺ and CH₃COO^- during annealing, these ions electrostatically penetrate the surface and grain boundary, effectively passivating the formation of bulk defects. The resulting KAc-SnO₂ ETL exhibited uniformity, low defect density, and high conductivity, providing an ideal ETL film for the subsequent deposition of perovskite films, thereby enhancing interfacial charge transfer and device efficiency. The optimized device achieved a PCE of 21.76%, a 14% increase over the control device (19.16%), and retained 88.9% of its initial PCE after 1000 h, offering a promising approach for scalable manufacturing in the perovskite industry.