Abstract: The performance of SnO2/SiO2/n-Si solar cells was studied by considering various transport mechanisms including minority-carrier diffusion, carrier recombination, and tunneling through insulating layer. The tunneling current through the SiO2 layer was obtained by employing the Airy-wavefunction approach. The efficiency was calculated to determine the performance of the cells under AM1 illumination for different values of insulating layer thickness, interface state density, hole life-time, doping density of silicon substrate, and cell thickness. It was shown that the efficiency increases as the insulating layer becomes thinner due to the decrease of short-circuit current. It was also shown that the efficiency increases as the doping density increases up to 6x1022/m3 and it then decreases for higher doping densities. As the interface state density decreases, the efficiency becomes higher. In addition, the increases in the hole lifetime and cell thickness enhance the efficiency of the solar cell.
Abstract: The color elimination of real tea wastewater by the electrocatalytic system was investigated. The electrocatalytic system composed IrO2 electrode as the anode and DSA electrode as the cathode under the current density of 40 mA cm-2. Various concentrations of NaCl and wastewater volumes were tested to understand their effects. For the effect of NaCl addition, the color removal efficiency increased 25% under the condition of NaCl addition. The relatively proper operation was 0.25 M NaCl and 1.0 liter wastewater, which caused the color removal efficiency up to 85%. Based on this color removal efficiency, the tea wastewater of 1.0 L consumed the electricity of 0.03KWh.
Abstract: Beta-carotene dye which is extracted from daucus carota material was used as sensitizer to fabricate dye-sensitized solar cell (DSSC). DSSCs were arranged in a sandwich structure consisting of fluorine-doped tin oxide (FTO) as a transparent conducting oxide (TCO), titanium dioxide (TiO2) layer, beta-carotene dye, iodide/tri-iodide redox electrolyte, and carbon layer as a counter electrode. Beta-carotene dye has an absorbance in wavelength zones from 415 to 508 nm. Meanwhile, it has the largest photoconductivity of 28.3×10-4 and 8.2×10-4 (Ω.m)-1 in dark and bright conditions, respectively. Moreover, the photoelectrochemical performance of the DSSC based on beta-carotene dye showed that the maximum voltage of 23.9×10-2 V and the maximum current of 3.3×10-5 A. However, the photo-to-electric conversion efficiency of this DSSC was very low i.e. 12.5×10-4 %.
Abstract: A blue luminescent of ZnO:Zn nanocrystal has been successfully prepared by one step spray pyrolysis method without reducing gas atmosphere. Zinc acetate dihydrate aqueous solutions (0.05 M) were atomized by ultrasonic atomizer. The atomizer used an air as carrier gas with 1, 3 and 5 L/min flowrate. The tubular reactor was set at 500, 600 and 700oC. As prepared samples were characterized by means of x-ray diffraction spectroscopy and scanning electron microscope-energy dispersive x-ray spectroscopy (SEM-EDS). The crystal size of as prepared particles calculated by Scherrer’s equation give 10-20 nm. The luminescent properties of as prepared particles were measured using spectrofluorophotometer. The highest photoluminescent intensity of particles irradiated with excited wavelength of 250 nm was obtained from samples prepared using 5 L/min carrier gas with temperature of tubular reactor 700oC. High intensity of blue luminescent was obtained due to oxygen vacancy in ZnO:Zn.
Abstract: ZnO nanorods were deposited on ITO glass substrate via chemical bath deposition at low temperature of 90°C. The seeding solution was made by dissolving zinc nitrate tetrahydrate and methenamine in cool water (5°C). The as-synthesized ZnOs were further subjected to post-hydrothermal treatment series. The results of scanning electron microscope (SEM) studies showed that the ZnO nanorods were grown as vertically-aligned hexagonal structure, while x-ray diffraction (XRD) patterns showed a high intensity of  peak. The absorption spectra of the as-synthesized sample indicated a strong absorption peak near the UV region. After post-hydrothermal treatments, the absorption was slightly shifted to visible region. The ZnO nanorods sample derived from post-hydrothermal treatment at 150°C for 12 hours has the largest crystallite size of 269.402 nm and the lowest band gap energy, Eg value of 3.205 eV.
Abstract: We have designed new coating equipment for applying nanoparticles of TiO2 on nylon fiber surfaces. A roll hot press with a motor speed of 1740 rpm was able to synthesis ±227 cm/min coated fibers. This equipment is simple and does not require any adhesive materials for attaching Ti02 nanoparticles on the fiber surface. The fiber was passed through a dispersion of TiO2 nanoparticles and then passed through a roll hot press at heating temperature between 600C and 700C. The TiO2-coated fibers were then used for decomposing rhodB-solutions under solar illumination. We observed the TiO2-coated fibers did not affect to properties of TiO2 as catalyst in photocatalysis. The best result was observed when 0,5 gr TiO2-coated fibers were suspended into 250 ml of rhodB-solution in water with a concentration of 1,6 %w/v.
Abstract: Micro to nano scale study of dendrite structure is important in order to have better properties control of casting product. The present study concerns on the morphological study of dendrite structure by phase-field simulation, in order to obtain the morphological growth of this structure that close its real morphology. Focus was given on the morphological growth of dendrite structure of Al-Si cast alloys, therefore thermodynamic data were taken for this type of materials. Anisotropy noise, strength of anisotropy and different undercooled conditions were applied as the variable parameters in the present works. It was observed that by introducing higher anisotropy noise, higher degree fragmentation of dendrite structure was obtained. Similar condition was obtained by introducing higher strength of anisotropy value, that higher degree of fragmentation was obtained. Both of these phenomena was also supported by the heat flux rate features of these variations that higher heat flux rate to almost all direction was obtained with the higher value of anisotropy noise and strength of anisotropy. In addition it was also observed that higher degree fragmentation of dendrite only possible to occur if sufficient undercooled condition established.
Abstract: Dye-sensitized solar cell (DSSC) which employed natural dye from black rice has been successfully fabricated and improved its performance by depositing interconnected copper (copper bridge) on the space between TiO2. The copper bridge has significant role in minimizing recombination of electron-hole which occurred in TiO2 surface by trapping electron and facilitating to anode. The presence of interconnected copper nanoparticle in the space between TiO2 nanoparticle was confirmed by Scanning Electron Microscopy (SEM) and X-Ray Diffractometer (XRD). The current-voltage (I-V) characterization of DSSC solar cells by using Keithley 617 was also performed to investigate performance of solar cells under sun illumination in varying intensities. It is found that performance of copper coated DSSC solar cells (efficiency 0.35% and fill factor 0.35) is higher than DSSC without copper coating (efficiency 0.17% and fill factor 0.35). This result is consistent with impedance spectroscopy analyzing where the internal resistance of copper coated DSSC solar cells is lower than DSSC without coated. It is concluded that performance of DSSC increasing with decreasing of internal resistance. Our finding is higher than other researcher reports in Ref.  and  with similar structure and kind of natural dye. In addition, this paper also reports the use of polymer electrolyte which employing polyvinyl acetate (PVA) containing lithium ion to maintain long-term stability of device.
Abstract: The present work concerns on preparing suitable titanium alloy substrate that might induce better characteristic of titanium oxide layer on the substrate. Different degree of cold rolling treatments were applied on Ti6Al4V alloy before thermal-electrochemical anodizing processes. The later processes were performed to produce titanium oxide layer which combines thermal process by heat treatment and followed with electrochemical anodizing process. After thermal heat treatment process, it was observed more homogeneous titanium oxide layer for the samples given cold rolling treatment as compared with sample without the treatment. This condition is believed due to the finer substrate surface after cold rolling treatment as observed from surface roughness measurement. Similar situation was observed after anodizing process that irregular oxidized layer was observed for sample without cold rolling treatment, whereas more homogenous layer was observed for sample with cold rolling treatment. Except for sample without cold rolling treatment, anodizing treatment tends to create finer oxidized layer. Therefore, it can be concluded that cold rolling treatment on titanium substrate before oxidizing process induces the formation of homogeneous oxide layer, whereas additional anodizing process create finer titanium oxide layer.