Preparation And Photoelectric Properties Of CuInS₂/TiO₂Nanocomposite Films

An oriented single-crystalline TiO₂is one of the most significant semiconductor materials extensivelyused in the field of photovoltaic and photocatalytic because of its high chemical stability, a long lifetime ofphoton-generated carriers and strong catalytic activity. It is well known that the large band gap of TiO₂（3.2eV） limits its absorption in the ultraviolet region which takes only about5%of the solar spectrum. Variousmethods have been developed to improve the photoresponse of TiO₂in the visible region and then increasethe photoelectrochemical efficiency. Although, dye-sensitized solar cell （DSSC） achieved a high efficiency,but organic dye has disadvantages such as high cost, short age, and unstable performance. Now, muchattention has been focused on using inorganic narrow band-gap semiconductor to substitute organic dye. Toimprove this condition, we prepared TiO₂nanorod array, CuInS₂/TiO₂composite film. The work mainlycontains following three aspects.The TiO₂nanorod array film was grown directly on transparent conductive glass （FTO） by a simplehydrothermal method. The morphologic and structure were investigated by SEM, XRD, TEM respectively,The results showed that TiO₂oriented growth was very favorable by the lattice match between TiO₂andSnO2. On this basis, we prepared crystalline rutile TiO₂wedgy NTs with rectangular cross-sections ontransparent conductive fluorine-doped tin oxide substrates by hydrothermal.Vertically oriented single-crystalline TiO₂nanorod arrays sensitized with CuInS₂quantum dots （QDs）were synthesized directly on （FTO） substrates by two-step solvothermal method. The as-preparednanostructure assembly was characterized by X-ray diffraction （XRD） and scanning electron micro-scope（SEM）. The results indicated that CuInS₂QDs were uniformly covering on the surface of thesingle-crystalline TiO₂nanorods. Ultraviolet visible （UV-Vis） absorption spectra showed that theabsorbance of the TiO₂/CuInS₂nanocomposite film was extended to the visible region. The conversionefficiency was best when the CuInS₂QDs solvothermal deposited on TiO₂nanorods film about6h. Theresults demonstrate that the composite films are excellent with respect to photovoltaic conversion.The sensitization of the TiO₂nanorod array with CuInS₂quantum dots is performed by successiveionic layer adsorption and reaction （SILAR） technique, in which, the In₂（SO₄）₃、CuSO₄、Na₂S are used asthe ion resources in different solvents. The results showed the amount of CuInS₂quantum dots deposited by using the ethylalcohol and methanol as the solvent are more than the water，and the size of CuInS₂quantumdots is5nm. After7cycle deposition, the performance of the CuInS₂quantum dots sensitized TiO₂nanorods arrays are best.