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Aluminium and tungsten co-doped vanadium dioxide (VO2:W:Al) thin films were deposited by DC reactive magnetron sputtering technique. In this work we report on the effects of aluminium and tungsten co–doping on the optical properties of vanadium dioxide (VO2) based thin films with a view of combining both increased luminous transmittance (Tlum) and lowered transition temperature (τc). The effect of aluminium and tungsten co-doping on semiconductor-metal transition of vanadium dioxide films was investigated and compared with tungsten doped and undopedVO2films. Spectral transmittances of the films were obtained using Shimadzu SolidSpec-3700 DUV UV-VIS-NIR spectrophotometer. The results revealed that the transmittance of tungsten and aluminium co–doped vanadium dioxide using two Al pellets showed a peak at about 54% in the visible spectral range with fairly good switching characteristics and a transition temperature of 61 oC.Keywords: Transition temperature, luminous transmittance; tungsten-aluminium co-doping; vanadium dioxid

This study investigated the effects of selenized DC sputtered precursor stacking orders on the structural, electrical and optical properties of copper zinc tin selenide (CZTSe) absorber layer for thin film solar cells. The precursors were deposited sequentially on the soda lime glass substrate at room temperature by DC magnetron sputtering. The precursors were selenized by annealing in an atmosphere containing selenium pellets and nitrogen gas. The structural, morphological, optical and electrical properties were respectively characterized using X-Ray Diffractometer (XRD), atomic force microscopy (AFM), UV/VIS/NIR lambda 9/19 spectrophotometer, Hall Effect measurement system (HMS 3000) and a four point probe system. CZTSe samples made up of three different stacking orders with configuration Mo/Cu/Zn/Sn (stack A), Mo/Cu/Sn/Zn (stack B) and Mo/Zn/Sn/Cu (stack C) were prepared. All the films showed kesterite peaks with major peak oriented along (112) plane at an angle of 2q ≈ 27.2°. Stack C was a best stacking order since it had the largest grain size 67 nm, highest carrier concentration 3.4 1020 cm–3 and the lowest sheet resistance of 6.4 W/□. Also this film demonstrated higher average absorption coefficient of about 6.84 104 cm–1. Furthermore, the films were observed to have a smooth surface and well compacted with average surface roughness of about 16 nm without voids.Keywords: CZTSe, stacking orders, DC sputtering, optical, electrical and structural properties

The Hall Effect parameters of Al and W co-doped VO2 thin films were studied in order to explain the effect of co-doping on the electrical properties of thermochromic VO2 films. The carrier concentrations and conductivity of the films were found to increase with increase in temperature while carrier mobility decreased reaching a minimum around the transition temperature then slightly rose and became stable at high temperatures. Tungsten doped films displayed higher carrier concentrations and conductivity on both sides of the metal insulator transition and lower mobility compared to undoped and Al and W co-doped VO2 thin films.Keywords: Vanadium dioxide; Hall effect; Career concentration; career mobility

CZTS thin films were deposited by sol–gel spin coating method using precursor solutions prepared by dissolving copper acetate dihydrate, zinc acetate dihydrate, tin chloride and thiourea in methanol and monoethylamine then annealed in RTP furnace at 500 °C. Sol–gel precursor solutions were prepared with different Zn/Sn in a precursor solution and were annealed at different time intervals; and their effects on the optical and electrical properties of CZTS (Cu2ZnSnS4) films were investigated. The optical band-gap values were estimated to be between 1.30 and 1.88 eV while the absorption coefficients were in the range of 104 cm–1 in the visible region. The resistivity and carrier concentrations ranged from 13.12 to 2634 kΩ/□ and 1017 to 1020 cm−3,respectively. The influence of Zn/Sn ratio and annealing time on structural properties of CZTS thin films are also discussed.Keywords: CZTS; Cu2ZnSnS4; Kesterite; Zn/Sn ratio