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Al doped ZnO NanoStructures by Electrodeposition & Solvothermal for Dye Sensitized Solar Cells Application

Ghahary, Raheleh | 2012

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 42973 (04)
  4. University: Sharif University of Technology
  5. Department: Physics
  6. Advisor(s): Taghavinia, Nima
  7. Abstract:
  8. ZnO semiconductor has a wide band gap (3.3eV) and high electron mobility, making it a possible candidate for an effective structure-based Dye-sensitized solar cell (DSSC) semiconductor. Efficiency of DSSC based on ZnO is lower than TiO2 due to its low chemical satability. It is well known that the energy conversion efficiency of DSSC depends on the electron transport in the photoelectrode so in this investigation we fabricated high transport photoelectrode by doping Al in ZnO nanostructures. DSSC based on Al doped and undoped ZnO nanosheet synthesized by electrochemical deposition. Current density-voltage (J-V) characterizations indicate that Al-doping in ZnO crystal structure increases current density about 50%. IMPS & EIS also confirms that Al-doping decreases electron transport time & the resistance of charge transfer process occurring at the ZnO/dye/electrolyte interface. Using acetonitrile based dye solution; dye loading on ZnO nanosheet was controlled in order to prevent dye aggregation. 0.5% efficiency and 50% fill factor were achieved for the cells with more than 12 hours dye loading time, which is the highest efficiency and fill factor reported for DSSC based on ZnO nanosheets by electrochemical deposition. Al doped photoelectrodes show more recombination of electrons with electrolyte. Therefore ZnO:Al nanosheets were coated with TiO2 nanoparticles with liquid phase deposition method. Using these nanosheets dye loaded in acetonitrile based dye solution, efficiency of DSSC based on ZnO nanosheets increased about two times. ZnO aggregated nanoparticles were synthesized with solvothermal method. Then the nanoparticles were doped with Al and led to the formation of an amorphous Al shell on the ZnO nanoparticles. This shell makes electron transport in photoanode difficult. So it will not increase the DSSC efficiency. The best efficiency (about 4%) was achieved using ZnO aggragated nanoparticles.

  9. Keywords:
  10. Electrodeposition ; Doping ; Dye Sensitized Solar Cells ; Zinc Oxide ; Electrochemistry ; Nanosheet

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