Sharif Digital Repository

A new strategy for enhancing the efficiency of TiO2 dye sensitized solar cells (DSSCs) doped with Ni ions with different molar percentages (i.e., 0, 0.5, 1, 5 and 10 mol%) was reported. The samples were prepared by sol-gel route and characterized by means of XRD, DRS, UV-visible, FESEM and photovoltaic measurment techniques. It was found that Ni-doped TiO2 nanoparticles had a mixture of anatase, rutile and brookite crystal structures. Moreover, the band gap energy was decreased with increasing Ni molar ratio, The highest cell efficiency of 5.4% was achieved for 1mol% Ni-doped TiO2, being 42% greater than that of pure TiO2 nanoparticles  

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... 

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... 

The aim of this thesis was to study and fabricate stable inks of Cu2SnS3 (CTS), Cu2ZnSnS4 (CZTS) and Cu3SbS4 (CAS) copper-based chalcogenide nanoparticles (NPs) and their application in solar cells. Inorganic semiconductors with p-type conductivity, high stability, high hole mobility (compared to organic type), and the ability to synthesize and deposition by simple low temperature solution-based methods have the potential to provide suitable alternative for hole-transporting material (HTM) in perovskite solar cells (PSCs) and the photo-absorbers in thin film solar cells (TFSCs). The ability to adjust energy levels and optoelectrical properties is another advantage of these compounds. In... 

According to Iran's proper location to take advantage of solar energy and the ability of nanostructured solar cells fabrication in the country, in this study, the manufacturing problems and complexities of nanostructured solar cells such as dye solar cells and perovskite-based solar cells are investigated. The chromium metal as an alternative to the transparent conductive substrates in order to reduce the manufacturing cost of dye solar cells (DSCs) and reducing series resistance is introduced in this study. In case of utilizing chromium as a substrate for photoanode, the thickness of CrxOy layer is controlled by depositing TiO2 compact layer and the efficiency of DSC is increased from 2.6%... 

Luminescence down shifting (LDS) of the incident spectrum is a practical strategy that helps to increase the light harvesting efficiency by manipulating the incident spectrum instead of interfering with the active material inside the cell. In this research, for a dye-sensitized solar cell with a near-infrared sensitizer, the photovoltaic performance was enhanced remarkably with a reflective luminescent down-shifting (R-LDS) layer. Different inorganic phosphors with different luminescent quantum efficiencies have been used as the down shifting materials to increase the light-harvesting efficiency of DSSCs sensitized with TT1 and SQ1 dyes. Four different structures were examined to find the... 

Dye-sensitized solar cells (DSCs) are third generation of solar cells, which composed of a porous layer of wide band gap semiconductor such as TiO2, covered with a molecular dye that absorbs sunlight, and a counter electrode contacted by a liquid redox electrolyte. Photovoltaic performance is the collective measure of light harvesting, charge separation and charge collection efficiencies. Light harvesting has a significant role in improvement of photovoltaic performance. Molecular engineering of dyes to improve absorption spectrum or to have a broad absorption spectrum,andlight scattering layes are approaches for this porpuse. This research is focused on photon management in DSCs using... 

Dye-sensitized solar cells were introduced by M. Gratzel in 1991. These solar cells have a power conversion efficiency of about 12% over the AM1.5 full sun. Traditionally, a liquid electrolyte redox system is used to regenerate the dye. Due to stability issues, a solid hole transport material has been employed to replace the liquid electrolyte as an attempt to create solid-state Dye-sensitized solar cell (ssDSC). Over past few years power conversion efficiency of ssDSCs has improved considerably and reached over 7%.
Here, ss-DSCs based on TiO2 nanoparticles as photoelctrode and P3HT as hole transport material were fabricated and characterized. We used three different methods; dip... 

In this research we focus on fabrication and characterization of Dye and Cadmium based Quantum Dot Sensitized Solar Cells (QDSCs) based on TiO2 nanostructures. TiO2 nanorods were synthesized with a simple chemical method. TiO2 nanorods, TiO2 nanorod/TiO2 and ZnO nanoparticle composite structures were integrated as photoanode in dye sensitized solar cells (DSSCs). Incorporation of TiO2 nanoparticles into the bare nanorods increased the efficiency more than 45%. Monitoring electron transport properties of the cells, pointed out the crucial role of electronic structure of composite film components on the performance of cells. Suitable morphology of TiO2 nanorods, led us to use them, to make a... 

Dye sensitized solar cells (DSCs) are among the 3rd generation solar cells which their mechanism of light absorption is similar to chlorophyll in green leafs and is based on photo-excitation of dyes. The electron-hole pairs of photo-excited dye separate at the interface of mesoporous semiconductor-dye-electrolyte. One of the approaches to increase the light path length and therefore the light harvesting efficiency in DSC is the addition of light scatterers inside the mesoporous semiconductor (photoanode).In this research, nanoparticulated hollow TiO2 fibers are introduced as novel light scatterers in DSCs with simultaneous light scattering, light trapping and high surface area. Light... 

In this research we focus on study and fabrication of ordered nanotube arrays of titanium oxide and their applications in photoelectrochemical cell. Nanotubular films of titanium oxide have been fabricated using anodization method. Short-length nanotubes, less than one micrometer, have been synthesized in aqueous electrolyte containing deionized water, hydrofluoric acid and phosphoric acid. To get Micron-length nanotubes, we have employed organic electrolyte containing ethylene glycol, deionized water and fluoride ammonium. After fabrication, the photo-catalytic activity of nanotubular structures was evaluated by measuring the rate of degradation of in methylene blue aqueous solution. The... 

In recent years, because of the increase in population and more accessibility of health facilities for people, an increase has occurred in water resources consumption. Recycling water has become so much valuable as the freshwater of the world is limited. Besides the advantages of treated water has for people, discharging the untreated wastewater to the rivers could cause many problems for human health. Many kinds of pollutions, such as textile effluent, are not easy to be treated by traditional methods because of their resistance to them. As these types of wastewater have severe negative effects on living things (both humans and animals), new treatment technologies should be considered. The... 

Textile industry is one of the biggest consumers of water in the world. Effluents of textile industry ordinarily have huge rate of dye compounds which are toxic and persistent in environment. In case which they did not treat and discharged in the environment, they can create cancer, poisoning and etc. Finding efficient, economic and fast method for treating of these effluents is an important factor on the management. Combination of ultrafiltration membrane and reverse osmosis processes, has taken into consideration as an efficient and fast method of treatment of textile effluents in recent years. One of the fundamental problems of this process is the high costs of operation and chemical... 

The N-doped rGO/NiFe2O4@Ti-doped ZnO as a novel ternary nanocomposite with magnetic recyclable was obtained by a facile and low-cost hydrothermal method. The structure, morphology, and optical as well as magnetic properties of synthesized nanocomposite were analyzed using the X-ray diffraction (XRD), Fourier-transform infrared spectra (FTIR), Raman spectroscopy, Emission scanning electron microscopy (FESEM) with Energy dispersive spectra, Transmission electron microscopy (TEM), UV-vis diffusive reflectance spectra, and Vibrating sample magnetometer (VSM). The photocatalytic activity was determined by the degradation of Methylene blue (MB) and Methylene orange (MO) dyes under visible light... 

This study presents a facile sol-gel template-assisted route to prepare CNT-TiO2 hybrid structures (CTH) for dye-sensitized solar cell (DSSC) applications. Non-covalent functionalized multi-walled carbon nanotubes (CNTs) with average diameter of 80 nm are used as the template for TiO2 deposition. The X-ray diffraction reveals that the hybrid structures are composed of primary anatase TiO2 nanoparticles with the average crystallite size of 12 nm, after heat treatment at 450°C in air atmosphere. TEM and FESEM images show that the shell thickness of the coated TiO2 on CNTs’ outmost walls varies between 60 to 120 nm, when the ratio of CNTs:TiO2 is 10wt. %. Photovoltaic measurements demonstrate... 

Dye-Sensitized solar cells are the third generation of solar cells that have the potential to increase efficiency as much as solar cells of previous generations, along with lower prices. The cathode electrode of the pigmented solar cell as one of the essential components of the cell plays the role of accelerating the oxidation reaction reduction of the electrolyte. Platinum often is used as a catalyst layer. To reduce production costs and maintain cell viability, platinum should replace with other materials at a lower cost and higher electrochemical activity. Recently, carbon materials have been considered for the production of inexpensive solar cells with suitable performance. Among... 

Nowadays, dye-sensitized solar cells (DSSCs) are highly regarded as a cheap alternative for conventional silicon-based solar cells. Improvements of their efficiency and performance sustainability are two major challenges of their commercialization. Engineering of the photoanode electrode by controlling its thickness, chemical composition, and morphology was proposed as effective method in increasing the light conversion efficiency of the cells. In the present study, mesoporous TiO2 beads with different arrangements including pristine mesoporous beads, mixtures of mesoporous beads with nanoparticles, and in the form of two-layer structure of nanoparticles (as an active layer) and mesoporous... 

In the present study, TiO2-reduced graphene oxide (T-RGO) nanocomposites were synthesized via various in-situ and ex-situ methods, then their photovoltaic performance was examined as photoanode and mesoporous layers in dye-sensitized Solar Cells (DSSCs) and perovskite Solar Cells (PSCs), respectively. Graphene oxide (GO) was prepared using Hummer’s method with some modifications. Both thermal and hydrothermal processes were used to reduce GO. Structural and optical characterization was analytically demonstrated by subjecting of the obtained materials by several techniques, including X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman, thermogravimetric analysis (TGA),... 

In this thesis, pure –known as T- and chromium doped titanium dioxide nanoparticles –known as -CTx- with different dopant atomic ratio (0.1 to 5 %at.) were synthesized using a facile, fast and efficient method. FESEM and XRD studies showed no morphologic and structural change via Cr doping of nanoparticles (size in the range of 20-30 nm). However, according to DRS analysis, Cr intrusion in TiO2 crystal structure, drastically reduced band gap energy of pure TiO2 from 3.14 eV to 1.81 eV for CT3 powder and improved absorption range of UV-Vis spectrum. Mott-Schottky plots indicated that, Cr doping, caused reduction in donor density of TiO2 and an upward shift in the conduction band edge....