We consider Carbon Nanotube (CNTs) counter electrode as alternative material to Platinum counter electrode for dye sensitized solar cells (DSSCs). Also, CNT counter electrodes having different visible light transmittance were prepared on fluorine-doped tin oxide (FTO) glass substrates by spray coating method. Microstructural images show that there are CNT-tangled layers coated on FTO glass substrates. Using such CNT counter electrodes and screen printed TiO2 electrodes, DSSCs were assembled and its I-V characteristics have been studied and compared. Light energy conversion efficiency of DSSCs increased with decreasing in light transmittance of CNT counter electrode. Our result shows that CNT counter electrode is compatible to Pt counter electrode.
Upscaling the dye sensitized solar cell (DSSC) is a key issue that confronting the entry of this type cells in commercial market. Performance of large size DSSCs is always poor than small size cells because of high resistive losses associated with sheet resistance of conducting glass substrates. Here we show a simple method to reduce resistive loss, also, efficient collection of photo generated carriers through silver current collectors which are prepared on both
working electrode and counter electrode substrates by screen printing method in analogy to conventional silicon solar cells. For long-term stability, to protect corrosion and to avoid charge recombination, silver current collectors were laminated by surlyn sheet. Using these substrates, DSSCs were prepared and their I-V characteristics have been studied as a function of light intensity and compared with normal cells which don't have silver carrier collectors.
The electronic state of Y doped ZnO (YZO) was calculated using the density functional theory. In this study, the program used for the calculation on theoretical structures of ZnO and YZO was Vienna Ab-initio Simulation Package (VASP), which is a sort of pseudo potential method. The detail of electronic structure was obtained by the discrete variational Xα (DV-Xα) method, which is a sort of molecular orbital full potential method. The density of state and energy levels of dopant elements was shown and discussed in association with optical properties, especially related to down-conversion effect. The down-conversion effect of YZO was experimentally investigated by preparing thin films deposited on F doped SnO2 (FTO) glass substrates by sol-gel method using the spin-coating system. A homogeneous and stable solution was prepared by dissolving acetates in the solution added diethanolamine as sol-gel stabilizer. In order to confirm a ultraviolet ray interruption and down-conversion effects, the transmission spectrum and the fluorescent spectrum of YZO films were estimated. The results obtained by experiment were compared with the calculated structure.
For improving solar efficiencies, down conversion of high-energy photons to visible lights is discussed. The losses due to thermalization of charge carriers generated by the absorption of high-energy photons, can largely be reduced in a solar cell if more than one electron-hole pair can be generated per incident photon. The solar cell consists of dye-sensitized anatase-based TiO2, approximately 30 nm particle size, 6 μm thickness, and 6 x 6 mm2 active area, Pt counter electrode and T3/T2 electrolyte. Down conversion phosphor LiGdF4:Eu(LGF) located on the front surface of the solar cells. And we measured the photo-current, current-voltage characteristics, and down-characteristics, and down-conversion efficiency of the down conversion system.
Photo decomposition ability of ultra-fine rutile TiO2 powder was investigated using the photo-catalytic reaction in
aqueous 1.0 mmol 4-chlorophenol (4CP) solutions with pH-controlled conditions. Its photo-catalytic characteristics were
then compared with those of commercial P-25 powder having mainly anatase phase. When 4CP was completely
decomposed by the photo-catalytic reaction, HPPLTed TiO2 powder was more effective than the P-25 powder regardless
of the crystalline structures. As the photo-catalytic reaction time increased, the decomposition of 4CP in the aqueous
solution was accompanied with much consumption of OH- ions. However, in the case of the aqueous solution at pH=4
naturally obtained by mixing of water and 4CP, the photo-catalytic reaction of the HPPLTed TiO2 powder occurred more
actively, compared with in the cases of the more acidic and caustic aqueous solutions. Therefore, it is thought that the
decomposition of non-degradable 4CP would take place well at a certain amount of OH- ion concentration in the aqueous
solution, considering to show no difference in the adsorption of 4CP on the surface of TiO2 particle with various pHs of
the solution, when the HPPLTed TiO2 powder with high surface areas more than 180 m2/g was used.
Great interest is given in developing magnetoresistance(MR) sensor, using ferromagnetic, electrically non-magnetic conducting and antiferromagnetic films, especially for the use in weak magnetic fields. Here, we report single and Wheatstone-bridge type of MR sensors made in Si(001)/NiO(300A)/NiFe bilayers. Angular dependence of MR profiles was measured in Si(001)/NiO(300A)/NiFe(450A) films as a function of an angle between current and applied field direction, also, linearity was determined. AMR characteristics of single MR sensors was well explained with single domain model. Good linearity in 45 degree(s) Wheatstone-bridge type of MR sensors consisting of 4 single MR sensors made in Si(001)/NiO(300A)/NiFe(450A) was shown in the range of about +/- 50 Oe.
Angular-dependent magnetoresistance characteristics in Si(001)/NiO(300A)/NiFe(tequals450, 1000, 1350A) thin films was investigated in terms of an angle between current and applied magnetic field. The samples were grown by RF-sputtering and DC-sputtering methods on naturally oxidised Si(001) substrates. First, NiO layer(300A) was grown on Si substrate, followed by the deposition of NiFe layers as a function of NiFe thickness under the condition of in-situ magnetic bias-field of approximately 500G. The measurement of angular magnetoresistance in Si(001)/NiO(300A)NiFe(tequals450, 1000, 1350A) thin films were carried out in variation of an angle between current direction and external magnetic field. Also, on the base of single magnetic domain model, the comparison between the measured and the calculated MR profiles was made. For tNiFe equals 450A, symmetrical MR characteristics were observed as sweeping external magnetic field proceed. However, for tNiFe equals 1000A, asymmetric MR profiles were shown.
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