Combined post-modification of iodide ligands and wide band gap ZnS in quantum dot sensitized solar cells

Abstract

Combined post-modification strategy of iodide ligands and wide band gap ZnS layer were employed in quantum dot sensitized solar cells. J–V curves show that the combined post-modification could improve the photoconversion efficiency compared to the single post-modification of ZnS because of the more effective passivation. CdS-sensitized and CdS/CdSe-co-sensitized solar cells both reveal that the assembly structure of QDs/I⁻/ZnS is more beneficial for the efficiency of solar cells than that of QDs/ZnS/I⁻. EIS results show that the former structure exhibit higher interface resistance and could suppress electron recombination more powerfully. XPS results reveal that the iodide ligands have different binding energy, which indicates a different coordination state of the iodide atom in these two structures. Finally, 3.28% efficiency and 18.16 mA cm⁻² were achieved for CdS/CdSe QDSCs by applying this combined post-modification.