No abstract

Dye-sensitized solar cells (DSSCs) are a feasible option for photovoltaic energy. Zinc oxide is an n-type semiconductor employed as photoanode on DSSCs. ZnO thin films were electrodeposited to study the effects of different potentials applied during deposition. SEM images, XRD and UV-Vis analysis were conducted to reveal the morphologic, structural and optical properties of the films at three potentials. DSSCs were assembled and the photovoltaic parameters were obtained through J-V plots. DSSC with 0.031% of efficiency was demonstrated at -1.4 V of deposition potential.

The aim of this research was to estimate the production of hydrogen, organic acids and alcohols by the strain of Clostridium acetobutylicum ATCC 824 using residual glycerol as a carbon source. The experiments were carried out in pure and mixed cultures in batch experiments. Three different sources of inocula for mixed culture were used. Ruminal liquid from goats and sludge collected from two upflow anaerobic sludge blanket reactors treating municipal wastewater and brewery effluent were tested for hydrogen, organic acids and alcohols production with or without C. acetobutylicum ATCC 824. The main detected end-products from the glycerol fermentation were hydrogen, organic acids (acetic, propionic, butyric and caproic) and alcohol (ethanol and 1,3-propanediol - 1,3PD). High hydrogen (0.44 mol H2/mol glycerol consumed) and 1,3PD (0.32 mol 1,3PD/mol glycerol consumed) yields were obtained when the strain C. acetobutylicum ATCC 824 was bioaugmented into the sludge from municipal wastewater using 5 g/L of glycerol. Significant concentrations of n-caproic acid were detected in the ruminal liquid when amended with C. acetobutylicum ATCC 824. The results suggest that glycerol can be used for the generation of H2, 1,3PD and n-caproic acid using C. acetobutylicum ATCC 824 as agent in pure or mixed cultures.

Semiconductors, such as zinc oxide (ZnO), are used in different scientific fields, including energy. This study applied ZnO thin films on a photovoltaic cell, specifically a dye-sensitized solar cell (DSSC). ZnO was used in solar cells due to its characteristics such as electronic mobility. Electrophoretic deposition (EPD) is an efficient method to deposit thin films since it can be done at room temperature and its parameters can be easily controlled. ZnO thin films were deposited on fluorine-doped tin oxide (FTO) glass, changing the tension parameter, and used in a DSSC, with different dye immersion times, between 7 and 24 h, to observe time effects on cell efficiency. For lower tension, 30 and 40 V, 7 h improved the cell efficiency, and at 50 V, 24 h favored the current density and efficiency. The highest efficiency was for the photoanode EPD deposited at 50 V, for 24 h dye immersion, at about 2.68%, and photocurrent of 13.55 mA/cm 2 .

Tin Zinc Oxide thin films were deposited on transparent conductive oxide by chemical bath, at percentages of 5, 10 and 15% of tin (Sn) on the zinc oxide (ZnO) structure. All films were thermally treated to improve its crystallinity. The produced films with tin were characterized by x-ray diffraction and optical measurements, such as absorbance, transmittance and reflectance. The x-ray spectrum showed the formation of the ZnO wurtzite and the crystallite size of the films were calculated to be 53.74; 79.59 and 66.38 nm for the photoanodes at 5, 10 and 15% of tin (Sn), respectively, on the zinc oxide structure. The calculated band gap energy of the films revealed that the presence of tin can reduce the band gap energy to about 3.2 eV. Those films were used as photoanodes on dye sensitized solar cells (DSSC) to observe the effects of the tin (Sn) on the photovoltaic activity of the zinc oxide (ZnO) semiconductor. Parameters such as efficiency and short circuit current density were particularly affected by the presence of tin in the composition, with the 5% Sn ZnO film presenting the best results of 7.56 % efficiency and 34.35 mA/cm2, short circuit current density, the other films presented lower values for efficiency, which can be attributed to lower values of short-current density.