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.
A low cost spin coater was constructed in this work for the deposition of thin films of titanium dioxide (TiO 2 ) on conductive substrate of FTO (fluoride doped tin oxide) with application on dye sensitized solar cells. The results showed a 95% precision between the speed values obtained by the software of C#sharp language and the spin values observed directly on the device. The TiO 2 films deposited through the spin coater with different angular speeds were characterized by UV-Vis optical spectrum, scanning electron microscopy (SEM), atomic force microscopy (AFM) and electrical measurements on an active area of 0.25 cm 2 . The DSSCs assembled with the TiO 2 films of double layer deposited by the spin coater had an efficiency value of 12.74%, while the cell with a single layer presented 4.05% efficiency. Therefore, it is concluded that the spin coater assembled in this study at low costs successfully can produce TiO 2 electrodes for DSSCs.
For oxide semiconductors for application in dye-sensitized solar cells (DSSCs), titanium dioxide conjugated with zinc oxide thin films was synthesized and characterized. The UV (ultraviolet) spectrum characterization showed a peak of absorbance at around 355 nm, with a band gap of 3.25 eV and reflectance around 85%. Such characteristics allowed the fabrication of DSSCs with N719 dye, under simulated light of 100 mW/cm 2 . The highest efficiency of 1.17% was at 5% titanium dioxide and 4 h of dye immersion.
This work deals with the synthesis of superparamagnetic cobalt ferrite (CoFe 2 O 4 ) nanoparticles, via a sol-gel method that uses gelatin as an organic precursor and a rapid thermal processing furnace with halogen lamps as a heat source. TEM, HRTEM, XRD, VSM and Mössbauer spectroscopy measurements were performed, at room temperature, to characterize the samples. Nanoparticles with an average size of 5-10 nm and microstrain of the order of 10 −4 -10 −3 were obtained. Magnetic hardening was also observed with increased nanoparticle size, in addition to an increase in the anisotropy constant, which ranged from 1.7 to 4.7•10 6 erg/cm 3 . The saturation magnetization decreased with decreasing size due to the formation of a magnetically dead layer on the surface (thickness = 0.6-0.7 nm). The Mössbauer spectra showed an increase in the superparamagnetic phase for samples with smaller nanoparticles and less dispersion.
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