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  1. ساخت پوشش کامپوزیتی بر پایه کیتوسان با قابلیت رهایش آنتی بیوتیک به روش رسوب دهی الکتروفورتیک برای کاربرد در ایمپلنت های استخوانی

The Evaluation of Titanium Oxide-Aluminum Oxide-Aluminum Titanate Nanocomposite (TiO2-Al2O3-Al2TiO5) as a Novel Material for Solar Cells

Ghorbani Moghadam, Amir | 2025

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 58628 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Madaah Hosseini, Hamid Reza
  7. Abstract:
  8. This study investigates titanium oxide–aluminum oxide–aluminum titanate (TiO2–Al2O3–Al2TiO5) nanocomposites as a novel candidate electron-transport material for solar cells. The nanocomposite was synthesized via a sol–gel method using aluminum chloride and titanium tetra(isopropoxide) as precursors and citric acid as a chelating agent under a nitrogen atmosphere. The resulting gel was dried and then calcined at temperatures ranging from 750 to 1050 °C. A paste prepared from the nanocomposite was coated onto transparent conductive glass by the doctor-blading method to evaluate its performance as an electron-transport layer in a DSSC. SEM images and XRD patterns revealed that, within the applied calcination temperature range, the anatase, rutile, α-alumina, and tialite phases formed in different proportions. Additionally, at lower temperatures, crystallites with an average size of ~30–40 nm were obtained. Based on DRS-derived Tauc plots, the estimated optical band gaps for most samples were in the range 3.0–3.2 eV, whereas the sample calcined at 900 °C exhibited a slightly smaller band gap of ~2.8 eV. This reduction in band gap may be associated with the formation of band-tail states and a shift of the conduction-band edge, which may correlates with a decrease in the open-circuit voltage and an increase in the short-circuit current of the corresponding DSSC. BET analysis revealed that, with increasing calcination temperature, the specific surface area decreased due to enhanced particle growth, leading to a lower concentration of adsorbed dye and a reduced short-circuit current density. PL analysis indicated that, with increasing temperature, radiative recombination initially decreases, likely due to passivation and reduction of radiative trap levels, and then increases as a result of greater incorporation of aluminum ions into the rutile lattice. Photovoltaic measurements showed that, for samples calcined between 750 and 900 °C, the conversion efficiency decreased from ~5.42% to ~4.44%, while for samples calcined at higher temperatures it dropped to below 1%. The higher current density for the 900 °C sample suggests that the α-alumina and tialite phases, despite their low carrier density, may influence electron transport by modifying the electron percolation pathways and reducing the probability of radiative recombination within this intermediate calcination range. Overall, these auxiliary phases, present at intermediate calcination temperatures, appear to act in combination with titanium oxide to modify the electron-transport layer and contribute to improved DSSC performance compared with samples calcined at higher temperatures
  9. Keywords:
  10. Titanium Oxide ; Aluminum Oxides ; Aluminum Titanate ; Nanocomposite ; Solar Cells ; Electron Transporting Layer

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