The effect of substrate temperature on the spray-deposited TiO2 nanostructured films for dye-sensitized solar cells.

The nanostructured TiO2 films have deposited on SnO2:F (FTO) coated glass substrate by spray pyrolysis technique at different substrate temperatures of 200-500 degrees C. The structural, surface morphological and optical properties of TiO2 films significantly vary with the substrate temperature. The surface of the TiO2 films deposited at 400 degrees C shows the nanoflakes and short nanorods (approximately 130 nm) like structures while the TiO2 films prepared at 500 degrees C shows only the nanoflakes like structures. The band gap of the TiO2 films prepared at higher temperatures (300-500 degrees C) becomes narrow due to presence the rutile phases in their crystal structure. Ruthenium (II) complex as a dye, KI/I2 as an electrolyte and carbon on FTO glass as a counter electrode has used to fabricate the dye-sensitized solar cell (DSC). The TiO2 film deposited at 400 degrees C has showed the best photovoltaic performance in DSC with the efficiency of 3.81%, the photovoltage of 773 mV, the photocurrent of 8.34 mA/cm2, and the fill factor of 56.17%. The photovoltage of the DSC increases with the increase of substrate temperature during the deposition of TiO2 films. Moreover, all the DSCs exhibit reasonably high fill factor value.

Gas phase photocatalytic activity of ultrathin Pt layer coated on alpha-Fe2O3 films under visible light illumination.

In this paper, the alpha-Fe(2)O(3) (hematite) films were reactively prepared by dc facing targets sputtering method. The ultrathin Pt layer with thickness of around 2 nm was deposited on the surface of alpha-Fe(2)O(3) films by dc diode sputtering method. X-ray diffraction, spectrophotometer, scanning electron microscopy, energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy were used to study the structural, optical, surface morphological, and chemical composition properties of the as-deposited films. The gas phase photocatalytic activities of the alpha-Fe(2)O(3) films coated with Pt ultrathin layer (Pt/Fe(2)O(3)) were evaluated by decomposition of volatilized methanol under illumination of visible light. The variation of photocatalytic activity was depended on the sputtering conditions of Pt/Fe(2)O(3) films, and the Pt/Fe(2)O(3) deposited in low sputtering pressure showed the best photocatalytic performance, which was mainly attributed to the different size of grain boundary and carrier mobility. The mechanism of methanol decomposition on the surface of Pt/Fe(2)O(3) was also discussed in detail.

Facing-target sputtering deposition of ZnO films with Pt ultra-thin layers for gas-phase photocatalytic application.

In this paper, various zinc oxide (ZnO) films are deposited by a versatile and effective dc-reactive facing-target sputtering method. The ratios of Ar to O(2) in the mixture gas are varied from 8:2 to 6:4 at a fixed sputtering pressure of 1.0 Pa. X-ray diffraction, spectrophotometer and scanning electron microscope are used to study the crystal structure, optical property and surface morphology of the as-deposited films. The Pt ultra-thin layer, approximately 2 nm thick, is deposited on the surface of ZnO film by dc diode sputtering with a mesh mask controlling the coated area. The photocatalytic activity of ZnO films and Pt-ZnO films is evaluated by decomposition of methanol under UV-vis light irradiation. The variation of photocatalytic activity depends on the ratios of Ar to O(2), which is mainly attributed to the different grain size and carrier mobility. Though the pure ZnO film normally shows a low gas-phase photocatalytic activity, its activity is significantly enhanced by depositing Pt ultra-thin layer.