PbS Quantum Dots/ZnO Nanosheets Composite Films:Preparation and Photoelectrochemical Performance

PbS quantum dots(QDs)/ZnO nanosheets composite films were synthesized via a two-step method.ZnO nanosheet films were firstly grown on fluorine-doped SnO2 conducting glass(FTO) by electrodeposition techniques,then PbS QDs were decorated on ZnO nanosheets to form composite films by sequential chemical bath deposition.The morphology and crystalline phase of obtained films were detailedly characterized by scanning electron microscope(SEM),X-ray diffraction(XRD).The UV-Vis absorption,photoelectrochemical and surface photovoltage properties of ZnO nanosheets and PbS QDs/ZnO nanosheets composite films were investigated respectively.The results show that the absorption and surface photovoltage response region of PbS QDs/ZnO nanosheets composite films are more abroad than that of pristine ZnO nanosheets,extended from UV to visible light region.The photoelectrochemical property of PbS QDs/ZnO nanosheets composite films is dramatically enhanced compared to non-decorated ZnO nanosheets films,from 0.1 to 0.7 mA/cm2 of short circuit current density(Jsc),from 0.04% to 0.57% of convert efficiency.Compared with ZnO nanosheets,the surface photovoltage response intensity is enhanced in PbS QDs/ZnO nanosheets,indicating heterojunction formed between PbS and ZnO.Photo-generated charge can effectively separate through this heterojunction,that is the reason for enhancement in photoelectric properties of PbS QDs/ZnO nanosheets composite films.