Graphene quantum dots (GQDs) hold promise as co-sensitizers in dye-sensitized solar cells (DSSCs) due to their excellent light-harvesting capabilities. However, their intrinsic limitations in electron transport can hinder overall device performance. This study investigates the impact of heteroatom-doping with nitrogen (N), fluorine (F), and sulfur (S) on the performance of GQDs as co-sensitizers for N719 dye in DSSCs. The heteroatom-doped GQDs (NFS-GQDs) enhance light harvesting compared to pristine GQDs, extending absorption into the UV region. Photoluminescence quenching data confirms efficient electron injection from both GQDs and NFS-GQDs to the TiO2 conduction band, exhibiting superior electron injection efficiency. Among the co-sensitized cells, 20 wt.% doping level achieves the highest power conversion efficiency of 4.33 %. Besides, electron transport and electronic structure were investigated in detail to understand the interaction of the TiO2/NFS-GQDs+N719 interface. The findings suggest that NFS-doping GQDs offer a promising strategy for developing efficient co-sensitizers for DSSCs.
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