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

Samadpour, Mahmoud | 2011

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 42663 (48)
  4. University: Sharif University of Technology
  5. Department: Institute for Nanoscience and Nanotechnology
  6. Advisor(s): Iraji Zad, Azam; Taghavinia, Nima
  7. Abstract:
  8. 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 new cell structure aiming to decrease the rate of CdTe corrosion in QDSSCs using corrosive I-/I-3 electrolyte. A thin gold layer was sputtered on the TiO2 electrode to act as a protective layer against the I-/I-3 corrosive electrolyte. The mechanism of the charge transfer in the presence of gold layer was discussed and our results show that the photostability of solar cells made by TiO2/CdTe/Au photoanode has increased. High surface area (82.83 m2/gr) TiO2 hollow fibers were manufactured by a simple synthesizing method, using natural cellulose fibers as a template. By optimizing anode structure, high power conversion efficiencies were obtained, 3.24%, and a clear correspondence of the cell performance with the photoanode structure was observed. The unique properties of these fibers and the rather high efficiencies obtained here suggest that hollow fibers can be introduced as promising nanostructures to make high efficient QDSCs. We have carried out a general study for studying the effect of TiCl4 surface treatment of QDSCs using CdS, CdSe and PbS/CdS as light absorbing materials. No significant effect on QDSC performance has been observed after this treatment on the nanostructured TiO2 electrode, conventionally used for DSCs. However, a fluorine treatment, with NH4F or HF, of the TiO2 electrodes produces a general enhancement of QDSCs performance. Although a general increase has been observed, after F treatment, for the three kinds of analyzed QDSCs (CdS, CdSe and PbS/CdS), the origin of the enhancement is different depending on the semiconductor material. This general study indicates that F treatment can be systematically used in QDSCs to increase cell performance, playing an analogous role to the TiCl4 treatment in DSCs
  9. Keywords:
  10. Nanorod ; Dye Sensitized Solar Cells ; Quantum Dot ; Impedance Spectroscopy ; Titanium Oxide Nanofiber

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