Loading...

The Effect of Surface, Morphology, and Composition of Semiconductor Layer on the Back Reaction of Electrons in Dye Sensithized Solar Cells:Theoritical and Experimental Investigation

Pazoki, Meysam | 2012

1273 Viewed
  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 43807 (04)
  4. University: Sharif University of Technology
  5. Department: Physics
  6. Advisor(s): Taghavinia, Nima; Nafari, Nasser
  7. Abstract:
  8. This thesis deals with a theoretical and experimental investigation of different approaches for reduction of electronic recombination in the semiconductor/Dye interface of dye sensitized solar cells (DSSC) including dye coverage, core-shell structures and energy level distributions. Interface of ZnO/TiO2 in the core-shell structure have been studied by density functional theory and the energy level distribution of surface atoms, recombination and Fermi level changes, open circuit voltage and surface dipole distributions have been discussed.
    The presence of TiO2 shell increases the ZnO surface dipole moment, and shifts the ZnO conduction and valence bands to higher energies. Also, it raises the Fermi level and improves the electron injection efficiency. In order to investigate of the effect of semiconductor growth method on the recombination, chemical vapor deposition was used for the growth of TiO2 spherical nanostructures and the effect of growth method on the distribution of bulk traps, electron lifetime and transport time was studied. Rapid growth of spheres leads to an increase in bulk traps and consequently electron lifetime and transport time is increased.
    The effect of trap depths on the electronic lifetime and recombination was studied by the investigation of microbead structures. TiO2 microbead structure as a new and highly efficient structure was applied in the DSSCs based on the cobalt electrolyte and a high efficiency of 7.5% was obtained. Morphology and configuration of these structures results in the improvement of electronic and ionic transport and light harvesting in comparison to the common standard cells. The depth of the traps was higher than standard layers. As an example of physical separation of ions and electrons, the effect of D35 dye coverage on the electron recombination and lifetime was investigated. By increasing the dye coverage, electron lifetime, transport time, Helmholtz layer capacitance and the dye regeneration time was increased. Physical sep aration and changing the energy level distributions will improve the electronic transport and reduce the recombination.
  9. Keywords:
  10. Density Functional Theory (DFT) ; Dye Sensitized Solar Cells ; Core-Shell Structure ; Electron Transition ; Chemical Vapor Deposition (CVD) ; Electron Recombination ; Cobalt Electrolyte

 Digital Object List

  • محتواي پايان نامه
  •   view

 Bookmark