Oxygen plasma surface-modifying SnO2 ETL for near-infrared quantum dots photovoltaics

SnO 2 is considered an ideal electron transport layer (ETL) material for solar cells due to its excellent stability, high transparency, and high electron mobility, however, its performance in near-infrared quantum dots photovoltaics has remained unsatisfactory. This underperformance is mainly linked to generally-used chemical bath deposition (CBD) method of SnO 2 ETLs which is prone to incomplete oxidation of Sn 2+ precursor. The resulting Sn 2+ residues and oxygen vacancy (Ov) induce severe interfacial traps limiting further efficiency gains. In this study, we utilized dielectric barrier discharge technology to generate high-activity oxygen plasma for gas-phase post-treating the CBD-SnO 2 surface. This oxygen plasma reduced the amount of Sn 2+ and Ov by ~20%, which suppressed trap-assisted recombination and collectively reduced interfacial energy band alignment offset. Compared with untreated devices (efficiency: 11.32%), PbS QDSCs with optimized SnO 2 ETL increased carrier lifetime by nearly twofold and enhanced interfacial carrier collection efficiency by 10.7%, significantly raising efficiency to 13.28%. This distinctive gas-phase post-treatment method, which introduces no additional chemicals and leaves no residues, offers a new technical avenue for developing high-performance ETL.