Papers by Keyword: Dye-Sensitized

Abstract: AbstractTitanium dioxide nanoparticles are great boosters for better sunlight absorption by plants. However, their band gap is so wide that they can only absorb UV light, which is a small portion of the sunlight. To improve the absorption of visible light, in this work, titanium nanoparticles were sensitized by saffron dye and the effect of foliar application of the dyed nanoparticles on growth parameters and enzymatic properties of sorghum was investigated and the results were compared with those of conventional titanium dioxide nanoparticles. The experiment was conducted in Zabol region, Iran. Saffron, a natural organic dye, was used as a sensitizer because of its availability and high extinction coefficient in the visible regions. To perform sensitization, titanium dioxide nanoparticles were immersed in saffron dye solution to absorb the dye on their surface. Then different concentrations of the sensitized nanoparticles were applied on plants by foliar spraying. The most improved growth parameters including root and shoot lengths, shoot fresh and dry weights, root fresh and dry weights were obtained after application of dye-sensitized TiO₂ nanoparticles. Zinc and iron are the elements highly affected by the application of new nanoparticles. Enzyme activities of catalase, ascorbate peroxidase and guaiacol peroxidase were also increased significantly. Chlorophyll a and Chlorophyll a/b ratio showed the highest values in 500 ppm dye-sensitized TiO₂ nanoparticles. The obtained results confirm the improvement in growth parameters and enzymatic properties of Sorghum after application of the new TiO₂ nanoparticles.

Abstract: Dye-sensitizer is heart of dye-sensitized solar cell which is an electron donor when receiving irradiation on the surface. Dye can be classified as synthesized dye or natural dye. Natural dye can be obtained colourfully from various plants such as tomato, carrot, grapes, chili, and so on. In this work, three selected plants which are locally available were chosen for three different colours. Green colour was extracted from leaves of Tiliacora triandra (Ya-nang). Red colour was from flower of Hibiscus sabdariffa (Rosella), and purple colour was from fruits of Morus alba (Mulberry). They were dried and ground into powder and their colour was extracted using 95%-ethanol. The concentrations of solution were 5, 10, and 20 g of powder per 200 ml for solvent extraction of each colour. These three colours were tested for absorbance index indicating ability of light absorption. The absorbance index curves showed that Ya-nang in green colour gave the best absorbance index having several peaks at 458 and 675 nm wavelengths for the 20 g/200 ml solution. While Rosella in red colour showed the peak at 534 nm wavelength and Mulberry in purple colour gave peak at 666 nm wavelength. The characteristics from the absorbance index curves also revealed the type of colour pigment in the dye. It was found that Ya-nang in green dye, Rosella in red dye and Mulberry in purple dye contained “Chlorophyll”, “Anthocyanin” and “Betacyanin” pigments respectively. Moreover, the area under the curves obviously indicated that the area of the green colour from Ya-nang was higher than those of Rosella and Mulberry. This implied that Ya-nang had higher potential to be dye-sensitizer and would give better dye sensitized solar performance compared with Rosella and Mulberry.

Abstract: Silicon nanowires (SiNWs) are important candidate for high performance electronic and optoelectronic devices due to their unique structures, electrical and optical properties. SiNWs were fabricated by silver-assisted electroless etching of Si wafer. Vertically aligned SiNW arrays with length about 8.75 μm and diameter of less than 90 nm have been fabricated. The reflectance of SiNWs without dye (12%) is greatly lower compared to bare Si wafer (25%). Therefore, SiNWs on Si substrate can be used as a good anti-reflection layer for a wide range of incident light. The reflectance of dye-sensitized SiNWs with red, green and blue dyes is 7%, 5.5%, and 5% respectively. The results confirmed that the reflectance of SiNWs with dye is much lower compared to SiNWs without dye and bare Si wafer. It was proven that dye on SiNWs can be used to reduce the reflectance (improved absorption) about 40% compared to SiNWs without dye.

Abstract: A multilayer TiO₂ film featured with gradual scattering structure was developed and used as photoelectrode for dye-sensitized solar cells. This structure of film consists of P25 nanoparticles and TiO₂ aggregate which was synthesized by micro-emulsion method as scattering centers The scattering centers were deposited by gradually increasing the amount from the film’s bottom to its top. The special films were used for the studies on the photovoltaic performance of N719 and Zn-3, and their photoelectric conversion efficiencies were 7.34% and 4.04%, respectively. Furthermore, more improvement of the conversion efficiency is realized for Zn-3 than for N719 by using our newly developed multilayer films as photoelectrode compared with ordinary photoelectrode.

Abstract: The process of TiCl₄ treatment on the FTO substrate of DSSC were analyzed and the microstructures of substrates before and after treatment were observed. Further more, the influence of TiCl₄ treatment on the substrate of Dye-sensitized solar cell to photo-current voltage performance was numerical analyzed.

Abstract: In this work, ZnO nanorod has been grown by hydrothermal solution method. The samples were prepared by two stages. The first stage was seeding process where the ZnO nanoparticles are spin-casted onto ITO coated glasses and the second stage was hydrothermal process. The morphology of nanorods were investigated by using scanning electron microscope (SEM) and different of length and diameter of nanorods with different growth durations have been observed. The differences of diameters and aspect ratio of nanorods have affected the optical and electrical properties of the ZnO-coated thin film with dye due to its surface area and morphologies of growth rod. Aspect ratio of ZnO nanorods increases by increasing the reaction time (growth time). From the band gap energy study, the thin film with the longest ZnO nanorods growth time has the lowest band gap energy (3.55 eV). The higher aspect ratio of the nanorod affected the conductivity, by increasing the conductivity when combined with N3 dye.

Abstract: Highly ordered closely packed TiO2 nanotubes were successfully fabricated by anodization of Ti foils in ethylene glycol-based electrolytes. For an identified electrolyte, the dependence manner of the nanotube dimension to the anodization parameters, including anodization voltage and time were systematically investigated. The inner diameter depends linearly on the anodization voltage but is time independent. The morphology of the tube is relative to the anodization voltage. The tube length is closely relative to the anodization time. Keeping the anodization voltage, the length will increase with the time rising to an extent and then maintain a relatively steady value. Longer nanotubes will be obtained when the anodization voltage is higher for a determined time. TiO2 nanotube-based dye-sensitized solar cells (DSSCs) were fabricated. The results showed that the conversion efficiency was related to the tube dimension. The optimum efficiency of 4.25% is obtained.

Abstract: This review covers recent research on counter electrodes using platinum (Pt), carbon and conducting polymers as catalysts for the reduction of triiodide in the dye-sensitized solar cell. Different types of counter electrode preparation methods and their advantages and disadvantages are compared. The inadequacy of the counter electrode with the precious metals and the advantages of the non-metallic-type counter electrode are pointed out. Especially, recent research on the Pt counter electrode in our group is discussed concerning with the reaction mechanism of the triiodide (I3-)/ iodide (I-) redox couple on the Pt counter electrode.

Abstract: Highly conductive and well-aligned ZnO nanowhisker films which can be used to optoelectronic devices have been fabricated on conductive F-doped SnO2 coated glass substrates using aqueous solutions with the addition of polyethylenimine at a lower temperature. ZnO nanowhiskers with well crystalline and hexagonal morphology were grown with high orientation along the c-axis. The electrical properties were investigated by a low intensity red laser irradiation (6 mW), after DNA molecules labeled with dye molecules were absorbed on the nanowhiskers. Enhanced photocurrent was detected.