Papers by Keyword: Transparent Electrode

Abstract: Transparent conducting oxides (TCOs) are widely used as a transparent electrode in various fields of opto-and semiconductor electronics. The main materials used today are indium-tin oxide, tin-antimony oxide and zinc-aluminum oxide. The authors have developed and improved the spray-pyrolysis method, which is one of the most promising methods of implementation in production. In this work, the study of tin dioxide doped with antimony coatings and the development of a methodology for the controlled synthesis of TCO, taking into account the effect of technological modes of deposition on the TCO parameters. The results of the performed studies contribute to the development of an automated technology for the synthesis of transparent conducting oxides with desired properties.

Abstract: In this work, we fabricated a flexible silver nanowires (Ag NWs)/graphene transparent conducting film on polyethylene terephthalate (PET) substrate, which was applied in an electrochromic device. The graphene layer was coated on the surface of the Ag NW film utilizing the electrostatic adsorption in order to improve the stability of the metallic nanowire layer and the performance of the electrochromic device. The Ag NWs/graphene composite film exhibited an optical transmittance of 82.5% at 550 nm and a sheet resistance of 57.5 Ω/sq. With the concentration of the adsorbed graphene increased, the transmittance and conductivity of the composite film both decreased. Furthermore, the lifetime of the electrochromic devices based on the tungsten oxide (WO₃) thin film and the Ag NW/graphene composite electrodes was greatly extended, compared to that utilizing the pristine Ag NW electrodes. The results indicate that the introduction of the graphene layer could protect the Ag NW film from corrosion of the electrolyte layer, and greatly improve the lifetime and cycle numbers of the electrochromic device. Key words: silver nanowire; graphene; transparent electrode; electrochromic devices

Abstract: We report our investigation of roles of polyvinyl alcohol (PVA) as a high-performance capping agent in synthesizing silver nanowires (AgNWs) using polyol method. For this purpose, we varied the concentration of silver nitrate (AgNO3), from 0.3 M to 1.0 M, and molar ratios of [PVA:AgNO3] from 2 to 6. The UV-vis spectra show the AgNWs growth optimally at a molar ratio of 4.5 with the absorbance peaks of 378 nm and 380 nm. Meanwhile, from XRD patterns, it was found that the crystal structure of the AgNWs can be identified as a face-centered cubic (fcc) with a lattice constant according to the spacing distance between the {111} planes of 4.087 Å. Finally, scanning electron microscopy (SEM) and transmission electron microscopy TEM images show the diameter and length of the AgNRs are 150 to 230 nm and 50 to 120 µm, respectively. These results show that the AgNWs synthesized using PVA having a long size.

Abstract: We demonstrated a metal-semiconductor-metal type GaN UV sensor for the first time by using multi-layer graphene as a Schottky electrode. Multi-layer graphene shows good Schottky electrode characteristic and fabricated UV sensor shows good UV response characteristics. The maximum dark current density and photo-responsive current density were 6.42 × 10^-9 A/cm² and 5.57 × 10^-5 A/cm² at the 10 V bias, respectively. UV/visible rejection ratios were higher than 10³ with each applied bias from 1 V to 15 V.

Abstract: A facile and rapid deposition process is developed for the fabrication of large-area graphene films by scalpel technology using graphene nanopartical as material. Graphite oxide (GO) was synthesized using modified Hummers method. Graphene nanopartical was fabricated by a reducing process in which GO was well reduced by hydrazine hydrate. The crystal structure and photoelectric properties of graphene and graphene films were investigated by X-ray diffraction. The composition of production (GO and graphene) is investigated by Fourier Transform Infrared Spectroscopy (FTIR) and Raman spectroscopy technology. Surface morphology of graphene layers were observed by SEM. Then, the semitransparent conductive films were applied to backside illumination DSSC. As a result, the maximum power conversion efficiency (PCE) is as high as 0.2558% and the fill factor is 30.97%.

Abstract: The characteristics of Ga-doped zinc oxide (GaZnO) thin films deposited at different substrate temperatures (TS~250 to 550oC) on 4H-SiC have been investigated. Structural and electrical properties of GaZnO thin film on n-type 4H-SiC (100)were investigated by using x-ray diffraction, atomic force microscopy (AFM), Hall effect measurement, and Auger electron spectroscopy (AES). Hall mobility is found to increase as the substrate temperature increase from 250 to 550 oC, whereas the lowest resistivity (~3.3 x 10-4 Ωcm) and highest carrier concentration (~1.33x1021cm-3) values are observed for the GaZnO films deposited at 400 oC. It has been found that the c-axis oriented crystalline quality as well as the relative amount of activated Ga3+ Introduction ions may affect the electrical properties of GaZnO films on SiC.

Abstract: Fluorine doped tin oxide (FTO) thin films have been developed as alternatives to ITO for thin film transparent electrode applications. In this works, the FTO thin films were deposited using inkjet printing technique since the technique is a promising deposition method to fabricate low-cost devices. The FTO precursor was prepared by reacting SnCl4•5H2O and NH4F at 60oC in a sealed container. The thin films were deposited on glass substrates at 40oC with variations of printing layers. The optical and electrical properties of the films were affected by the number of printed layers. It was observed the four layers film has the optimum optical transmittance and sheet resistance which were 96 %T and 16.4 Ω/□ respectively.

Abstract: In dye sensitized solar cell structure, the transparent electrodes of tin oxide doped fluorine (SnO2:F) was coated by titanium dioxide (TiO2) and platinum (Pt) for cathode and anode electrodes, respectively. In order to achieve high efficiency solar cell, both electrodes are required to have proper crystal structure size and morphology. These can be modified during the annealing process therefore the effects of electrode annealing on their crystal structure and surface modification were investigated in this study. Thick films of TiO2 and Pt were deposited by screen printing method on 3mm thick glass substrate (Nippon Sheet Glass) coated with 500nm thick SnO2:F. The glass substrate has sheet resistance of 20 ohm/square with the optical transmission of about 70%. The mixed TiO2 powder has the diameter of about 20 nm. The screen print structure was heated for drying in the oven at 150oC for 1 hour. Then the TiO2 thick films were annealed at various temperatures from 400 to 550oC for 2 hours, while the Pt films were annealed at lower temperature from 300 to 500oC. The obtained thickness of TiO2 and Pt film after annealing become about 10 and 3 µm, respectively. The crystallinity of the films was examined by x-ray diffraction while the surface morphology of both films was determined by atom force microscopy. To investigate the relation between material structure and the performance of the solar cell, the annealed electrodes at different temperature were used to fabricate the dye sensitized solar cell structure with standard rutherium(II) (N719) dye and then the current voltage characteristic was measured under light with air mass of 1.5. It found that the structure with higher anneal temperature electrode exhibited higher power conversion efficiency originating from the higher short circuit current density of better crystallinity and higher surface area.

Abstract: Al-doped ZnO (ZnO:Al) films for transparent electrode applications in dye-sensitized solar cells and thin film solar cells were fabricated and characterized. In order to investigate the effect of crystallinity of the ZnO:Al films to the morphology and optical properties of the etched surface, the ZnO:Al films were deposited with varying substrate temperature by rf magnetron sputtering system and then films’ surface was etched in diluted hydrochloric acid (HCl) solution. Surface morphology of the amorphous ZnO:Al film deposited at room temperature was controllable to have large surface area, but it was not appropriate for transparent electrode layers due to high electrical resistivity. However, the resistivities of the ZnO:Al films deposited at the substrate temperatures of 150 and 300 oC were as low as 1.50×10-3
cm. In addition, the surface morphologies of the films deposited at 150 and 300 oC showed larger surface area for dye-sensitized cells and crater shape for light diffusion through the films, respectively. The surface morphologies and optical properties of the etched ZnO:Al films are attributed to the crystallinity of the as-fabricated films.

Abstract: One of obstacles hindering a realization of large area size twisted nematic liquid crystal display (TN-LCD) flat panel (for example, 1100 x 1250 mm) is a slow response time. The slow response time is due to the inverse proportionality of turn on time with the frame frequency and pixel number (number of gate lines) in the twisted nematic liquid crystal system. It is known that the slow response time in the active matrix system of LCD be solved by reducing the sheet resistance of color filter electrodes. In this paper, we report on the processing details of the deposition of transparent ITO films using a DC sputtering system. The thickness of ITO layer was set for high transmittance and good conductivity and the films were characterized with respect to the transmittance and sheet resistance. The deposited ITO films show a good uniformity across the whole area and the average thickness of the ITO is about 1350 Å under the DC power of 10.7 kW. The transmittance is increased from 72.5 to about 93 % as the oxygen content is increased to 2.5 sccm for the samples without annealing. It was found that the transmittance is significantly improved by the annealing process at 220 oC for 40 min. up to 94 %. The sheet resistance is decreased with the DC power and exhibits below 22
/ after the samples were annealed.