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Total 128 records

    Improved efficiency of dye-sensitized solar cells based on a single layer deposition of skein-like TiO 2 nanotubes

    , Article Journal of the American Ceramic Society ; Vol. 97, issue. 9 , 2014 , pp. 2873-2879 ; ISSN: 00027820 Mojaddami, M ; Mohammadi, M. R ; Madaah Hosseini, H. R ; Sharif University of Technology
    Abstract
    We present a new TiO2 morphology, featuring high surface area and open structure, synthesized by a two-step chemical route for the manufacture of dye-sensitized solar cells (DSSCs). This construct is sets of intertwined one-dimensional (1D) nanostructures (i.e., nanotubes), so-called skein-like nanotubes (NTs). Such morphology is produced by a combination of TiC oxidation and hydrothermal processes. The mesoporous TiO2 nanoparticles, as the product of TiC oxidation operation, is used as the precursor of hydrothermal process to grow the skein-like NTs. The effect of processing parameters of TiC oxidation and hydrothermal processes is studied. The skein-like morphology enables to eliminate the... 

    Double-Layer TiO2 Electrodes with Controlled Phase Composition and Morphology for Efficient Light Management in Dye-Sensitized Solar Cells

    , Article Journal of Cluster Science ; Vol. 25, issue. 4 , 2014 , p. 1029-1045 Abdi-Jalebi, M ; Mohammadi, M. R ; Fray, D. J ; Sharif University of Technology
    Abstract
    The light-scattering effect in the dye-sensitized solar cells (DSCs) was studied by controlling TiO2 phase composition and morphology by fabrication of double-layer cells with different arrangement modes. The starting material for preparation of TiO2 cells was synthesized by an aqueous sol-gel process. X-ray diffraction and field emission scanning electron microscopic analyses revealed that TiO2 nanoparticles had particle size ranging between 18 and 44 nm. The optical property and band gap energy of TiO2 nanoparticles were studied through UV-Vis absorption. The indirect optical band gap energy of anatase and rutile nanoparticles was found to be 3.47 and 3.41 eV, respectively. The... 

    Assessment of luminescent downshifting layers for the improvement of light-harvesting efficiency in dye-sensitized solar cells

    , Article ChemPhysChem ; Vol. 15, issue. 17 , 2014 , pp. 3791-3799 ; ISSN: 14394235 Hosseini, Z ; Diau, E. W. G ; Mehrany, K ; Taghavinia, N ; Sharif University of Technology
    Abstract
    Luminescence downshifting (LDS) of light can be a practical photon management technique to compensate the narrow absorption band of high-extinction-coefficient dyes in dye-sensitized solar cells (DSSCs). Herein, an optical analysis on the loss mechanisms in a reflective LDS (R-LDS)/DSSC configuration is reported. For squaraine dye (550-700 nm absorption band) and CaAlSiN3:Eu2+ LDS material (550-700 nm emission band), the major loss channels are found to be non-unity luminescence quantum efficiency (QE) and electrolyte absorption. By using an ideal LDS layer (QE=100 %), a less absorbing electrolyte (Co-based), and antireflection coatings, approximately 20% better light harvesting is obtained.... 

    Defect study of TiO2 nanorods grown by a hydrothermal method through photoluminescence spectroscopy

    , Article Journal of Luminescence ; Volume 157 , January , 2015 , Pages 235-242 ; 00222313 (ISSN) Rajabi, M ; Shogh, S ; Iraji Zad, A ; Sharif University of Technology
    Elsevier  2015
    Abstract
    This paper describes the photoluminescence study of titanium dioxide (TiO2) nanorods grown by a hydrothermal synthesis method on the surface of fluorine doped tin oxide (FTO) coated glass. The effects of growth conditions including: reaction time, precursor concentration and adding NaCl to hydrothermal solution on the structural and optical properties of productions are examined by using SEM, XRD, TEM and room temperature photoluminescence measurements. Also, the performance of the TiO2 nanorods as a photoanode of dye sensitized solar cells is investigated. The different excitation energies and intensities are chosen to verify the discrete electronic state of radiative recombination centers... 

    A review of 2D-based counter electrodes applied in solar-assisted devices

    , Article Coordination Chemistry Reviews ; Volume 324 , 2016 , Pages 54-81 ; 00108545 (ISSN) Irani, R ; Naseri, N ; Beke, S ; Sharif University of Technology
    Elsevier  2016
    Abstract
    The alarming energy and environmental crisis of our modern era necessitates scientists to propose alternatives to replace the scarce and harmful fossil fuels. The Sun, as a free, and abundant clean energy resource, presents a motivation for researchers to convert the sunlight to electrical power and store the H2 as an energy carrier by developing solar cells as well as water splitting devices, respectively. One of the fundamental parts of a solar energy convertor (solar cell/photoelectrochemical device), where the reduction reaction occurs, is the counter electrode (CE); the CE is commonly based on rare Pt. It is critical to substitute costly CEs with efficient, low-cost replacements, which... 

    Molecular engineering of bithiazole-based organic dyes with different electron-rich linkers toward highly efficient dye-sensitized solar cells

    , Article Journal of Photochemistry and Photobiology A: Chemistry ; Volume 349 , 2017 , Pages 171-182 ; 10106030 (ISSN) Hosseinzadeh, E ; Hadipour, N. L ; Parsafar, G ; Sharif University of Technology
    Abstract
    A series of bithiazole-based dye sensitizers have been designed by employing various electron-rich moieties as π-spacer, which are based on the reported experimentally synthesized dye T-BT, to shed a light on the impact of both the nature and position of electron-rich moiety on the efficiency of dyes in DSSCs. To evaluate the efficiency of these dyes, various key parameters associated with overall conversion efficiency (η), including electronic and optical properties of free dyes are calculated, based on the computational methods. Besides, the dye/TiO2 structures have been taken into account to investigate the interfacial features of the dye sensitizers adsorbed on TiO2 semiconductor and... 

    Luminescent Spectral Conversion to Improve the Performance of Dye-Sensitized Solar Cells

    , Article ChemPhysChem ; Volume 18, Issue 23 , 2017 , Pages 3292-3308 ; 14394235 (ISSN) Hosseini, Z ; Taghavinia, N ; Wei Guang Diau, E ; Sharif University of Technology
    Abstract
    Relative to the broadband solar spectrum, a narrow range of spectral absorption of photovoltaic (PV) devices is considered an important determinant that the efficiency of light harvesting of these devices is less than unity. Having the narrowest spectral response to solar radiation among all PV devices, dye-sensitized solar cells (DSSCs) suffer severely from this loss. Luminescent spectral conversion provides a mechanism to manipulate and to adapt the incident solar spectrum by converting, through photoluminescence, the energies of solar photons into those that are more effectively captured by a PV device. This mechanism is particularly helpful for DSSCs because there is much flexibility in... 

    Dye-sensitized solar cells based on TiO2 particulate gels: Impact of gel formation mechanism on photovoltaic performance

    , Article Journal of Photochemistry and Photobiology A: Chemistry ; Volume 338 , 2017 , Pages 104-114 ; 10106030 (ISSN) Emami Kervee, S. E ; Mohammadi, M. R ; Sharif University of Technology
    Elsevier B.V  2017
    Abstract
    In this work the influence of different particulate gels on morphology and photoelectric performance of TiO2 dye-sensitized solar cells (DSCs) is studied. Two coagulant and flocculant agents are used to convert a TiO2 particulate sol into the gels using double layer compression and charge neutralization mechanisms. One more TiO2 particulate gel is also prepared by changing the pH of the sol using acid: alkoxide molar ratio higher than the critical ratio to obtain an unstable sol. Based on X-ray diffraction (XRD) analysis, the films contain primary nanoparticles with average crystallite size of 13–15 nm. Field emission scanning electron microscopy (FE-SEM) images show uniform, nanostructured... 

    Enhanced light harvesting with a reflective luminescent down-shifting layer for dye-sensitized solar cells

    , Article ACS Applied Materials and Interfaces ; Volume 5, Issue 12 , 2013 , Pages 5397-5402 ; 19448244 (ISSN) Hosseini, Z ; Huang, W. K ; Tsai, C. M ; Chen, T. M ; Taghavinia, N ; Diau, E. W. G ; Sharif University of Technology
    2013
    Abstract
    For a dye-sensitized solar cell with a near-infrared squaraine (SQ1) sensitizer, the photovoltaic performance was enhanced remarkably with a reflective luminescent down-shifting (R-LDS) layer to increase the light-harvesting efficiency at the wavelength region 400-550 nm where the SQ1 dye has weak absorption. Relative enhancements greater than 200% in IPCE near 500 nm and 40-54% in JSC were achieved with red phosphor CaAlSiN 3:Eu2+ as the LDS material, attaining 5.0 and 4.8% overall efficiencies of power conversion for the R-LDS layer coated on the counter electrode (front illumination) and working electrode (back illumination), respectively  

    Improved charge collection efficiency of hollow sphere/nanoparticle composite TiO 2 electrodes for solid state dye sensitized solar cells

    , Article Current Applied Physics ; Volume 13, Issue 2 , March , 2013 , Pages 371-376 ; 15671739 (ISSN) Sadoughi, G ; Mohammadpour, R ; Irajizad, A ; Taghavinia, N ; Dadgostar, S ; Samadpour, M ; Tajabadi, F ; Sharif University of Technology
    2013
    Abstract
    The photoanodes of solid state dye sensitized solar cells (ss-DSCs) embedded with different contents of TiO 2 hollow spheres (HSs) were prepared and the photovoltaic performances were systematically characterized. TiO 2 hollow spheres were synthesized by a facile sacrificial templating method, grounded and added in different ratios to TiO 2 nanoparticle (NP) paste, from which composite HS/NP electrodes were fabricated. The composite photoanodes include hollow spheres of 300-700 nm with enhanced light scattering characteristics in visible range which leads to improved light absorption in conventional thin film electrodes of ss-DSC. By optimizing the amount of HSs in the paste, 40% improvement... 

    Ni-doped TiO2 Photoanode Electrodes for Dye-sensitized Solar Cells Applications

    , M.Sc. Thesis Sharif University of Technology Honarvar, Marjan (Author) ; Mohammadi, Mohammad Reza (Supervisor)
    Abstract
    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  

    Novel organic dyes with anchoring group of barbituric/thiobarbituric acid and their application in dye-sensitized solar cells

    , Article Synthetic Metals ; Volume 209 , November , 2015 , Pages 1-10 ; 03796779 (ISSN) Hosseinzadeh, B ; Salimi Beni, A ; Najafi Chermahini, A ; Ghahary, R ; Teimouri, A ; Sharif University of Technology
    Elsevier Ltd  2015
    Abstract
    Abstract New bi-anchoring donor-π-acceptor metal-free organic dyes based on diphenylamine as donor, and barbituric acid and thiobarbituric acid as the acceptor/anchor were synthesized, characterized and used in dye-sensitized solar cells applications. Among the fabricated dye sensitized solar cells, device based on the diphenylamine as donor, and barbituric acid as the acceptor exhibits a high power conversion efficiency of 1.53% with a short circuit current density of 3.71 mA cm-2, an open-circuit photo voltage of 0.55 V and a fill factor of 0.75% under AM 1.5 illumination (85 mW cm-2) compared to the other fabricated devices. The structure of synthesized dyes was optimized and their... 

    Electrophoretic Deposition of Titanium Dioxide for Fabrication of Photoanode of Dye Sensitized Solar Cell

    , M.Sc. Thesis Sharif University of Technology Sedighi, Rahime (Author) ; Taghavinia, Nima (Supervisor)
    Abstract
    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.... 

    Optimized Pt Coating for High Charge Transfer- High Transparency Cathodes of Dye Sensitized Solar Cell

    , M.Sc. Thesis Sharif University of Technology Mashhoun, Sara (Author) ; Taghavinia, Nima (Supervisor)
    Abstract
    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,... 

    Fabrication of one Dimensional Nano-Structured of Titanium Dioxide and their Application in Dye Sensitized Solar Cells

    , M.Sc. Thesis Sharif University of Technology Rahimi, Sanam (Author) ; Iraji Zad, Azam (Supervisor)
    Abstract
    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... 

    Morphological Manipulation of Photo-Anode Electrode of Nano-Structured TiO2 Dye-Sensitized Solar Cells

    , M.Sc. Thesis Sharif University of Technology Moradzaman, Mozhgan (Author) ; Mohammadi, Mohammad Reza (Supervisor)
    Abstract
    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... 

    Fabrication of Dye-Sensitized Solar Cells Based on TiO2-ZnO Double Layer Nanostructured Film

    , M.Sc. Thesis Sharif University of Technology Rostami, Parand (Author) ; Mohammadi, Mohammad Reza (Supervisor)
    Abstract
    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  

    Improvement of Light Scattering Effect of Dye –sensitized Solar Cells Aided by Different Structures of Titanium Dioxide

    , M.Sc. Thesis Sharif University of Technology Sarvari, Najmeh (Author) ; Mohammadi, Mohammad Reza (Supervisor)
    Abstract
    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... 

    Preparation of Ag-doped TiO2 Nanostructured Films for Dye-Sensitized Solar Cells Applications

    , M.Sc. Thesis Sharif University of Technology Rahnejat, Bibi (Author) ; Mohammadi, Mohammad Reza (Supervisor)
    Abstract
    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... 

    Dye and Cadmium Based Quantum dot Sensitized Solar Cells Based on TiO2 Nanostructures

    , Ph.D. Dissertation Sharif University of Technology Samadpour, Mahmoud (Author) ; Iraji Zad, Azam (Supervisor) ; Taghavinia, Nima (Supervisor)
    Abstract
    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...