Preparation And Photoelectronic Properties Of SnS/TiO₂（Nb₂O₅） Nanocomposites

Titanium dioxide(TiO2) is an inorganic functional semiconductor materials,widely used as photocatalyst because of its non-toxicity,high chemical stability, high photocatalytic activity and low cost.Among all of the TiO2nanomaterials, TiO2nanotube arrays prepared by electrochemical anodization of titanium has attracted great attention due to their advantages of highly ordered array structure, the larger specific surface area and efficient electron transport. Niobium oxide (Nb2O5), an important functiona semiconductor materials, has a higher conduction band edge than TiO2, and therefore, it is possible to attain higher open circuit voltage and photo-conversion efficiency (η). Both TiO2and Nb2O5are wide gap semiconductors and efficiently absorb only a very small UV part (approximately5%) of solar light. Coupling TiO2nanotube and Nb2O5nanorod with low-band-gap is an efficient way to extend the range of light response. Tin suifide (SnS) was choosed as the narrow-band-gap semiconductor.It is a candidate for the absorber materials because there are many advantages of SnS such as proper bangdgap (1.32eV),high absorption coefficient in the visible solar spectrum.In this article, SnS/TiO2nannotube arrays composite materials were prepared through a successive ionic layer adsorption and reaction process.The photoelectrochemical property and surface photovoltaic response of the SnS/TiO2nanotube arrays composites have been improved due to the enhanced electron-hole separation that because heterojunctions between SnS and TiO2could provide the driving force. SnS/TiO2heteroj unction nanotube arrays with different deposition cycles were elevated in terms of morphology and photoelectrochemical property of the composites. Ultimately the optimum number of cycles was obtained.Before the preparation of surface SnS/Nb2O5nanorodcompositis,filed-induced photovoltage response of the different morphology of Nb2O5nano-powder under the positive and negative external electric field was analyzed. These flake-like structures Nb2O5nano-powder demonstrated higher surface photovoltage response due to its advantages of electronic transmission. In addition,Nb2O5nanorods were also prepared by using the niobium foil as a precursor via hydrothermal method. In view of its wide band gap (Eg=3.4eV), SnS nanoparticles was used to sensitize Nb2O5nanorods to improve the optical absorption property.The SnS/Nb2O5nanorod composites with the successive ionic layer adsorption and reaction process were obtained. Then the morphology and photoelectrochemical properties of the composites were analyzed and discussed, and found that the composite structure has a higher short-circuit current and photoelectric conversion efficiency than pure Nb2O5nanorod structure.