Venture capital as a mean of innovation financing in conditions of investment climate volatility in Ukraine

The energy conversion efficiency of a conventional pn junction solar cell decreases as the temperature increases, and this may eventually lead to failures in the photovoltaic system, especially if it uses concentrated solar radiation. In this work, we show that spectrally selective reflector (SSR) surfaces can be important for reducing the heat buildup on passively cooled solar cells. We outline a computational scheme for optimizing DC magnetron-sputtered TiO(2):Nb-based SSRs tailored for silicon solar cells and find good agreement of the reflectance with an experimental realization of the optimal SSR. A figure of merit for SSRs has also been derived and applied to the experimental data

Fabrication and Characterization of Cobalt Pigmented Anodized Zinc for Photocatalytic Application

ZnO is an n-type oxide semiconductor with a direct wide band gap greater than 3 eV. Like any other semiconductor, the optical and electrical characteristics can be influenced by doping or adjusting process conditions which broaden its applications. In this work, varying amounts of Cobalt (0.01g-0.04g) were electrodeposited on anodized Zinc thin films (ZnO) followed by heat treatment to about 2500C. Optical characterization was performed in the range 300-2500 nm to obtain reflectance data which aided in defining the absorption coefficient and band gap of the films. Photocatalytic activity of the films was explored in Methylene Blue solution degradation under UV light irradiation. Analyzed data revealed a band gap shift to the red, i.e. from 3.34 eV to 3.10 eV for pure ZnO and 0.04g-Cobalt pigmented ZnO thin films respectively. Moreover, absorption coefficient increased with pigmentation attributed to the band shrinkage effect which elucidates that ZnO:Co thin films serve as good candidates for application in photocatalysis. All the fabricated films were photocatalytic but ZnO thin films containing 0.02g of Cobalt was the most photocatalytic

Spectrally selective reflector surfaces for heat reduction in concentrator solar cells : modeling and applications of TiO(2):Nb-based thin films

The energy conversion efficiency of a conventional pn junction solar cell decreases as the temperature increases, and this may eventually lead to failures in the photovoltaic system, especially if it uses concentrated solar radiation. In this work, we show that spectrally selective reflector (SSR) surfaces can be important for reducing the heat buildup on passively cooled solar cells. We outline a computational scheme for optimizing DC magnetron-sputtered TiO(2):Nb-based SSRs tailored for silicon solar cells and find good agreement of the reflectance with an experimental realization of the optimal SSR. A figure of merit for SSRs has also been derived and applied to the experimental data

Room temperature magnetization in Co-doped anatase phase of TiO

CoxTi1–xO2 films were deposited by spray pyrolysis technique on Si(1 0 0) substrates at 475 °C. A hydro-alcoholic solution containing titanium (iv) isopropoxide and Co(NO3)2 with various Co doping levels from x = 0–0.015 in solution was used as spray solution. Grazing incident angle of X-ray diffraction illustrates that the CoxTi1–xO2 films are single phase and polycrystal with mixed orientations. Study of surface morphology of the films by atomic force microscope reveals that the annealing atmosphere does not significantly affect the grain size and the microstructure of the films. This study provides further insight into the importance of annealing atmosphere on magnetization of the films. Room temperature magneto-optical Kerr measurement was employed in polar mode. A hysteresis loop and a paramagnetic behavior have been recorded for samples annealed in H2 ambient gas and air, respectively. Chemical composition analysis by X-ray photo-electron spectroscopy showed that Co atoms are bounded to oxygen and no metallic clusters are present. Moreover, it indicates the formation of high spin Co2+ for the sample x = 0.008 annealed in H2 ambient gas. The origin of magnetization can be attributed to the contribution of oxygen vacancies in the spin polarization of the structure

Optical characterization of photocatalytic copper doped thin films of anodized titanium

Titanium oxide is used in a myriad of applications such as in capacitors, insulation paints among others. It is a prime candidate for water splitting due to its photocatalytic properties. In this work, undoped TiO _2 thin films were prepared by anodizing titanium foils cut into pieces measuring 60 mm by 20 mm. The specimens were anodized in an electrolyte consisting of 0.5 M H _2 SO _4 and 0.075% wt HF at room temperature. The anodizing voltages ranged from 50 V to 100 V. Anion doping of copper in as anodized TiO _2 was done electrochemically. The as anodized Ti foils were dipped in a 1 M Cu _2 SO _4 solution. All samples were annealed at 450 °C for 3 h. Near-normal total reflectance was measured on as anodized and copper pigmented samples in the solar (300–2500 nm) wavelength range. Spectrophotometric reflectance data was analyzed to obtain the absorption coefficient and using the same to determine the band gap of the films. It was noted that the films exhibited reduced solar integrated reflectance for TiO _2 samples prepared at lower anodic voltages of 50, 60 and 70 V. The copper pigmented, and annealed, TiO _2 samples exhibited both direct and indirect energy band gaps in the ranges, 3.38–3.86 and 2.50–2.74, respectively. Further, annealing and copper doping of the films lead to increased absorption. The photocatalytic activity of the films was assessed by measuring the rate of degradation of 10ppm methylene blue in UV light source. Copper doped TiO _2 exhibited enhanced photocatalytic performance in compared to pure TiO _2 . An increase in the anodization voltage caused subsequent increase in photocatalytic activity of films with 70 V as the optimum voltage above which photo degradation of methylene blue decreased