Synthesis of CuInS₂ Quantum Dots/In₂S₃/ZnO Nanowire Arrays with High Photoelectrochemical Activity

Decoration of CuInS₂ (CIS) quantum dots (QDs) on ZnO nanowires (NWs) with an interlayer of In₂S₃ as photoelectrode has been successfully fabricated on FTO via the simple solution routes for photoelectrochemical (PEC) application. Scanning electron microscopy, transmission electron microscopy, and X-ray diffraction are utilized to systematically analyze the morphology and structure of the CIS QD/In₂S₃/ZnO NWs heterostructure. The composition of this multilayer heterostructure and the removal of QD ligands by a thermal process are confirmed by X-ray photoelectron spectra. In comparison with CIS QDs/ZnO NWs, the CIS QD/In₂S₃/ZnO heterostructural photoelectrode displays an efficient charge separation and carrier transport path for photocurrent up to 2.4 mA·cm^-2 that is competitive with other Cd- and Pb-free QD-based materials. In addition, Mott-Schottky analysis demonstrates the negative shift of the flat band in the CIS QD/In₂S₃/ZnO, which benefits the early onset potential. Significantly, this hierarchical photoelectrode shows the improvement the absorption and conversion of solar light in the visible region obtained using a pristine ZnO structure. Our research paves the way for exploring lead-free and lead-free sulfide materials in the new category of solar applications.