Applying the Density Function Theory (DFT) combined with LCAO basis set and employing the B3LYP hybrid functional, the optimized geometrical parameters, electronic properties, as well as the Infrared and Raman spectra...Applying the Density Function Theory (DFT) combined with LCAO basis set and employing the B3LYP hybrid functional, the optimized geometrical parameters, electronic properties, as well as the Infrared and Raman spectra for wurtzite-ZnO structure were investigated. Prior to computing, ZnO thin film prepared by the spray pyrolysis method is characterized by X-ray diffraction using Rietveld refinement. This analysis shows that ZnO has hexagonal wurtzite structure (P6<sub>3</sub>mc) with lattice parameters, a = 3.2467 and c = 5.2151 Åin good agreement with our predicted optimized geometry. Atomic force microscopy (AFM), Raman spectroscopy and UV-Vis-NIR spectrophotometry techniques are used to explore morphological, optical and vibrational properties of the sprayed ZnO thin film. The computed band gap is in excellent agreement with that deduced from UV-Vis transmission . The simulated infrared and Raman spectra were also calculated, and a good agreement with the measured spectra is obtained. Finally, a detailed interpretation of the infrared and Raman spectra is reported.展开更多
This paper deals with the effect of Cr content on photocatalytic activity of TiO2 thin films deposited on quartz and intrinsic silicon substrates by using the RF magnetron co-sputtering process. Some physical investig...This paper deals with the effect of Cr content on photocatalytic activity of TiO2 thin films deposited on quartz and intrinsic silicon substrates by using the RF magnetron co-sputtering process. Some physical investigations on such sputtered films were made by means of X-ray Diffraction (XRD), atomic force microscopy (AFM), Raman spectroscopy as well as UV-Vis-IR absorption techniques. The heat treatment under oxygen atmosphere at 550°C reveals that the crystalline structure of TiO2: Cr depends on Cr content. Anatase-to-rutile phase transformation occurs at a Cr content of about 7%. On the other hand, the band gap energy value of annealed TiO2: Cr films varies in terms of Cr doping and a transition around 7% of Cr is accrued. The photocatalytic activity of undoped and doped TiO2 films was evaluated by photo-degrading of the amido black under UV light irradiation. Modification of the chemical structure of titanium dioxide by Cr doping allows moving the photocatalytic activity of titanium dioxide towards visible light. The results indicate that films doped with 2% Cr exhibit the highest UV and visible light photocatalytic activity.展开更多
We simulate the conception parameters of a model of a silicon multilayer solar cell. The cell is composed by four layers of opposite conductivities forming three junctions inside the cell. The electric contacts are ta...We simulate the conception parameters of a model of a silicon multilayer solar cell. The cell is composed by four layers of opposite conductivities forming three junctions inside the cell. The electric contacts are tailored vertically to collect the minority carrier generated under illumination. We developed the equations giving the output power, the fill factor and the efficiency of the cell, taking into account the series resistances of each layer. We optimized, using MATLAB software, the thicknesses of the layers, the impurity concentration level and the distance between the electric contacts. We showed that the optimized photovoltaic structure, with the silicon properties published at the Ioffe institute website, gives an efficiency of 20.66%. The n-p-n-p silicon cell delivers a short circuit current Icc = 45.3 mA/cm2, an open circuit voltage V oc= 0.746 V and an output power of 28.5 mW/cm2. The corresponding fill factor is FF = 84.29%.展开更多
文摘Applying the Density Function Theory (DFT) combined with LCAO basis set and employing the B3LYP hybrid functional, the optimized geometrical parameters, electronic properties, as well as the Infrared and Raman spectra for wurtzite-ZnO structure were investigated. Prior to computing, ZnO thin film prepared by the spray pyrolysis method is characterized by X-ray diffraction using Rietveld refinement. This analysis shows that ZnO has hexagonal wurtzite structure (P6<sub>3</sub>mc) with lattice parameters, a = 3.2467 and c = 5.2151 Åin good agreement with our predicted optimized geometry. Atomic force microscopy (AFM), Raman spectroscopy and UV-Vis-NIR spectrophotometry techniques are used to explore morphological, optical and vibrational properties of the sprayed ZnO thin film. The computed band gap is in excellent agreement with that deduced from UV-Vis transmission . The simulated infrared and Raman spectra were also calculated, and a good agreement with the measured spectra is obtained. Finally, a detailed interpretation of the infrared and Raman spectra is reported.
基金This work was financed by the Ministry of Higher Education,Scientific Research and Technology of Tunisia and Institut National de la Recherche Scientifique Canada,INRS-Énergie,Matériauxet Télécommunications(INRS-EMT).
文摘This paper deals with the effect of Cr content on photocatalytic activity of TiO2 thin films deposited on quartz and intrinsic silicon substrates by using the RF magnetron co-sputtering process. Some physical investigations on such sputtered films were made by means of X-ray Diffraction (XRD), atomic force microscopy (AFM), Raman spectroscopy as well as UV-Vis-IR absorption techniques. The heat treatment under oxygen atmosphere at 550°C reveals that the crystalline structure of TiO2: Cr depends on Cr content. Anatase-to-rutile phase transformation occurs at a Cr content of about 7%. On the other hand, the band gap energy value of annealed TiO2: Cr films varies in terms of Cr doping and a transition around 7% of Cr is accrued. The photocatalytic activity of undoped and doped TiO2 films was evaluated by photo-degrading of the amido black under UV light irradiation. Modification of the chemical structure of titanium dioxide by Cr doping allows moving the photocatalytic activity of titanium dioxide towards visible light. The results indicate that films doped with 2% Cr exhibit the highest UV and visible light photocatalytic activity.
文摘We simulate the conception parameters of a model of a silicon multilayer solar cell. The cell is composed by four layers of opposite conductivities forming three junctions inside the cell. The electric contacts are tailored vertically to collect the minority carrier generated under illumination. We developed the equations giving the output power, the fill factor and the efficiency of the cell, taking into account the series resistances of each layer. We optimized, using MATLAB software, the thicknesses of the layers, the impurity concentration level and the distance between the electric contacts. We showed that the optimized photovoltaic structure, with the silicon properties published at the Ioffe institute website, gives an efficiency of 20.66%. The n-p-n-p silicon cell delivers a short circuit current Icc = 45.3 mA/cm2, an open circuit voltage V oc= 0.746 V and an output power of 28.5 mW/cm2. The corresponding fill factor is FF = 84.29%.
