Sharif Digital Repository

This research is focused on fabrication of TiO2 layers by electrophoretic deposition (EPD) for application as photoanode in Dye Sensitized Solar Cell (DSC). DSCs are third generation of solar cells, also known as the Grätzel cell, after its inventor Michael Grätzel. A DSC is composed of a porous layer of wide band gap semiconductor such as TiO2 and ZnO, covered with a molecular dye that absorbs sunlight, and a counter electrode contacted by a liquid redox electrolyte. Dye Sensitized semiconductor (photoanode) has important role in conversion of photon to electricity. To achieve higher efficiency, preparation of photoanode with high surface area resulted to enough dye adsorption is necessary.... 

Counter electrode of dye sensitized solar cell is prepared by deposition of a thin catalytic layer onto a conducting substrate and is responsible for reduction of iodide/triiodide redox electrolyte. Conventionally, counter electrode is made of platinum.
Depending on the method of deposition, the thickness of Pt layer varies. The Pt layer may be so thick that it acts as reflector and returns the incident light back to the cell. In this case, large amount of Pt is used and a rise in cost is been made, but only the Pt particles in the interface of counter electrode/electrolyte take part in the reduction reaction.
The aim of this project is optimization of making a counter electrode,... 

Increasing of human demanding for energy and limiting of fossil fuels and bio-logical problems, it seems necessary to access new and clean source of ener-gy. For instance, one of these sources of energy is sun. If we can impart from this infinite energy source so health and natural life can be pictured for human. Nanostructure dye sensitized solar cells in compare with other photovoltaic cells are more economical and practical as a result of lower material cost and simpler manufacturing process. In general, a typical dye sensitized solar cell is a sandwich structure based on two transparent conducting oxide (FTO) glasses. The FTO glass substrates are expensive and account for most of... 

In this research we focus on study and fabrication of titanium dioxide nanofibers and their application in preparation of dye sensitized solar cell’s photo anode in order to improve optical and electrical properties. Titanium dioxide nanofibers was prepared by electroespinning method. To investigate the effect of nanofiber diameter on optical and electrical properties of photo anode, three different diameter of titanium dioxide nanofibers with diameters of 100-200 nm, 200-300 nm and 500-600 nm was prepared by varying the type or amount of polymer in the electrospinning solution and fixing other conditions of electrospinning process. By use of these structures, paste of pure fibers in form of... 

Dye–sensitized solar cell (DSSC) includes (a) A transparent conductive oxide coated glass substrate, (b) Semi conductive film, (c) Dye adsorbed on this film, (d) Redox couple electrolyte and (e) A counter electrode which can reduce redox couple.In this study, selection of a nanostructured pattern for increasing absorption efficiency of a DSSC based on TiO2 has been considered. For this purpose, using carbon nanotubes (CNTs) in fabrication of photoelectrode has been proposed. Therefore, at the first TiO2–CNT nanocomposites contained various percent of carbon nanotube was coated on fluorinated tin oxide (FTO) conductive glasses via sol–gel dip coating method. Then DSSCs were assembled by... 

In this research, the synthesis of the electrospum nano fiber doped zinc oxide and its photocatalyst usage was investigated. The band gap of the zinc oxide in the area of UV leads to deactivation of this material at the visible light. With due the attention to sunny weather in Iran and the fact that about 50 percentage of sunlight is visible light, producing and usage of catalyst materials actived at visible light is economical. Doping is one of the ways of activating ZnO at visible light, so in this research thiourea is used as the source of ZnO doping. The results of the expriments done at visible light and also spectrums of DRS, XPS and XRD prove that the doping is happened. Also, in this... 

Dye-sensitized solar cells (DSSCs) are Photoelectrochemical cells using wide band gap nanoporous oxide semiconductors sensitized by dye molecules. For achieving high efficiency DSSCs preparation of photoanode electrode with high surface aea which leads to adequate dye absorption is necessary. In order to achieve proper morphology, thickness, particles size and porosity, producing a TiO2 nano-structured paste is required. TiO2 powder was prepared using sol-gel method. following a calcination process at 300 degrees, XRD patterns showed presence of anatase and brookite structures with average crystallite size of 9 nm. Additives such as diethylene glycol, acetylacetone and Triton X-100 were used... 

In the present work, one dimensional ZnO nanostructures were grown by seed-assisted hydrothermal method. Hydrothermal processing parameters were controlled to obtain ZnO nanorods with diameter lower than 120 nm. The products were characterized by FE-SEM, EDAX, XRD, PL, and ATR-FTIR analyses. ZnO nanoparticles were also synthesized via a simple solvothermal method and their photo peropeties were compared with onedimensional nanostructures. Thereafter dye-sensitized solar cells based on TiO2-ZnO double layer nanostructured film were fabricated. It was observed that DSSC efficiency increased with decreasing the thickness of the film. The highest efficiency of 2.41% was obtained  

In the current research, Anatase-Rutile Titania hollow spheres were synthesized using hydrothermally prepared carbon spheres as template. Different calcination temperatures were used to remove carbon template and crysalized Titania. The characterizations for the physicochemical properties of prepared samples were carried out by XRD, FESEM, XPS, DRS, UV-Vis and FTIR.It is found that doping of carbon in the crystal structure of Titania hollow sphere, cause red shift in band gap wavelenght and the absorption wavelength edge was expanded to the visible light region and the additional diffusive electronic states were observed on the valence band spectra of samples.The photoelectric conversion... 

Different types of morphologies and phase structures of crystalline TiO2 were synthesized by hydrothermal methods. For the first time, dandelion-like rutile TiO2 powder composed of numerous single crystalline nanorods was synthesized using TiCl4 as the main precursor. TiO2 Nanoparticles were produced using TTIP and 2-propanol, as precursor and solvent, respectively. Field emission scanning electron microscopy analyses revealed that the synthesized TiO2 nanoparticles had average crystallite size in the range 21–70 nm, whereas dandelion-like TiO2 showed diameter in the range 2-10 µm. According to the significant refractive index of TiO2, in particular rutile phase, it can be used in the... 

There are many industries in the world that produce colorized wastewater. Because of the complex structure and good solubility of dyes, such industries have problem treating this wastewaters. On the other hand, because of the toxicity of these materials for water living, dye removal from discharged wastewater of these industries is very important. In recent years, researchers have become interested in the synthesis of dye Nano adsorbents and they have published many works on this subject. The important parameters in the synthesis of such adsorbent include; non-toxicity, high adsorption capacity and easy separation. In this project, cellulose was extracted from bagasse and then CMC was... 

Many efforts have been put into increasing the efficiency of dye-sensitized solar cells that part of it has been devoted to structure and chemical composition of photoanode electrode. In this thesis, the effect of changes in the composition and its influence on light scattering ability in photoanode of dye sensitized solar cells was studied.First, the nanoparticles of titanium dioxide powder through solvothermal method as well as spherical particle and barium titanate powder by sol-gel method were synthesized. XRD and FE-SEM analyses indicated that synthesized powders are in good size and morphology regarding the intended chemical composition. Optical properties of TiO2 particles were... 

The Dye-sensitizers loading on TiO2 is decreasing the electron excitation energy and therefore improving the photocatalytic performance from the increasing the sensitivity under visible light irradiation.in this project CoPCTS , Mordant dye and N3(Ruthenium 535) used as dye-sensitizers. Also The addition of VIII group metals on TiO2 is improving the photocatalytic activity that increasing the photocatalytic reaction rate because of the intermediation role of them for moving the conduction band electrons to electron acceptors and increasing the pair electron-holes long-life that in this case Pt loading used as a VIII group metal. In this project Titanium Isopropoxide as a precursore and... 

ZnO nano particles and mordnite zeolite nano particles were prepared by precipitation method and hydrothermal method,respectively. The influence of solvent and surfactant in ZnO nano particles synthesis were studied to reform the structure of nano particles.These nano particles were based on different supports to improve and enhance their photocatalytic activities. Synthesized catalysts characterized by X-ray diffraction (XRD), Scanning electron microscopy (SEM), Fourier transform-infra red spectra (FTIR), UV-Vis spectroscopy and BET techniques. To investigated photocatalytic activity of the synthesized catalysts under UV irradiation, they were used to degradation bio-environmental... 

Azo dyes that are the most common dyes in textile industries, are toxic and stable complex compounds. Release of this dyes in environment disturb the ecosystem and endanger human health. So selection of an appropriate method for treatment of them is a sensitive work. photocatalytic degradation is one of the best promising methods because of its perfect mineralization, middle condition and lack of creating the secondary pollutant. In this research CuO/CNT nanocomposite was synthesized and used as a photocatalyst. The surface features of CuO/CNT were surveyed by using Fourier transform infrared(FTIR), X-ray diffraction (XRD) and Scanning electron microscopy (SEM). Photocatalytic efficiency of... 

Dye-sensitized solar cell (DSSCS) is the third-generation of solar cells based on semiconductors formed between a photo sensitized anode and counter cathode which make a photo electrochemical system. They haven’t been commercially marketed due to their lower efficiency than the previous generations. In order to achieve the higher efficiency, the electron injection and light absorption must be increased. One way to increase electron injection is doping the semiconductor with an external ion to reduce lattice band gap. In this work, we made powder and Nano-structured film of titanium dioxide doped with various molar ratios of Mg by the sol-gel process. The effect of Mg:Ti molar ratio on... 

Structure and morphology of titanium dioxide have an excessive effect on the photovoltaic properties of dye-sensitized solar cells (DSCs). Different approaches have been used to improve the efficiency of these cells. One is using a scattering layer. Studies have been shown that properties of scattering layer such as composition and morphology have great effect on photovoltaic properties of solar cell. In this project, the effect of cubic morphology of TiO2 as a scattering agent in photoanode of DSCs is studied. Titanium dioxide with various morphologies including nanoparticles, solid and hollow cubic structures have been synthesized by solvothermal and hydrothermal methods, respectively. The... 

In this project single sided dye sensitized solar cell is introduced as a new design that has both of electrodes in one side. These electrodes can be separated vertically by a thin insulator layer such as SiO2 or horizontally by lithographic method. First a metallic thin film is patterned by lithography, and then thickened by electrochemical deposition of Chromium. Platinum is electrodeposited on the substrate of counter electrode and a thin spacer layer is deposited on Platinum layer to separate it from Titanium dioxide layer.
In Chapters 1, 2 & 3 basic science and methods which are needed for doing this project is introduced. In chapter 1 material for making a standard dye sensitized... 

Dye-sensitized solar cells (DSSCs) have been intensively studied duringthe last decade as a promising third solar cellgeneration due to their potential low-cost manufacturingprocess. DSSCsare based on a semiconductor (i.e., TiO2), formed between a photo-sensitized anode and an electrolyte. In order to reach high conversion efficiencies, it isimportant to increase the electron injection and opticalabsorption. One promising solution to increase the electroninjection is to decrease the large band gap of TiO2 bydoping a foreign ion into TiO2 lattice.
In the present study, Ag- doped TiO2 powders and films with different Ag:Ti molar ratios are reported. The effect of dopant at.%, annealing... 

In this thesis, we focus on studying and fabrication of doped titanium dioxide electrodes and their application in nanostructured dye sensitized solar cells (DSSCs). For this purpose, non-metallic nitrogen (N) and metallic neodymium (Nd) elements were selected. N-doped titanium dioxide nanoparticles were synthesized via solvothermal method and their structural and optoelectrical properties were investigated in comparison to undoped titanium dioxide synthesized by the same method. Based on the obtained results, doping of titanium dioxide by nitrogen resulted in shifting the Fermi level up-ward, increase in charge carriers density, shift of optical absorbance to higher wavelength, and decrease...