Recent Advances in SnO2 Electron Transport Layers for Perovskite Solar Cells.

Metal halide perovskites exhibit great application potential in various next-generation optoelectronic devices, and perovskite solar cells (PSCs) have become a core photovoltaic research hotspot owing to their high efficiency and low cost; poor stability and efficiency decay during large-area manufacturing remain key industrial bottlenecks. As a core functional layer, the electron transport layer (ETL) determines the efficiency and stability of PSCs. Tin oxide (SnO2) stands out as an ideal ETL candidate with high electron mobility, wide band gap, low-temperature processability, and superior chemical stability, outperforming traditional materials like TiO2 and ZnO. This review systematically summarizes research advances in SnO2 electron transport layers (SnO2 ETLs) spanning 2020 to 2026, covering their crystal structures, optoelectronic properties, and defect characteristics, fabrication routes (solution-processed, vacuum-deposited, and scalable large-area techniques), modification tactics (elemental doping, surface/interface engineering, and nanostructure modulation), as well as their implementation in various perovskite solar cell architectures, including normal n-i-p structures, inverted p-i-n structures, all-inorganic devices, flexible cells, and large-area photovoltaic modules. It also points out the core challenges in defect control, interfacial stability, and scalable fabrication, and prospects future directions such as synergistic modification, green scalable preparation, and adaptation to lead-free PSCs. This work provides theoretical and technical support for the performance optimization and industrialization of SnO2-based PSCs.