الفهرس 
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Abstract
In recent years the greatest problem focused on the energy due to high cost and unrenewable energy sources. So recently, use of solar cells as clean renewable energy utilization is proposed as one of the main potential solutions for global warming.
Therefor the objective of this work is to try to fabricate low cost dye sensitized solar cell to produce electricity from the sun.
This thesis consists of three chapters:
Chapter 1 deals with a general introduction of the subject and a literature review is given.
Chapter 2 includes the materials, experimental procedures, instrumentation and the different advanced methods of
data analysis and data transfer using Origin vergion 6.1.
Chapter 3 deal with the results and discussion that are reported as follows:
Part I: the effect of various types of TiO2 on photodegradation of three dyes (CFL, CR, AO) under different conditions to select the suitable type of TiO2 and the obtained results are:
-The effect of TiO2 (P25) on photodegradation of dyes in acidic, basic and neutral media, and found that the photodegradation for CFL and CR in acidic medium is greatest compare with the results in basic and neutral media,and this is opposite to that of AO.
The effect of NaCl and Na2CO3 on photodegradation of dyes using TiO2 (P25) in neutral medium, shows that photodegradation rate is smaller in case of CFL and CR than in the case of AO.
-The effect of TiO2 colloidal on photodegradation of dyes, in case of CFL and CR shows that the absorption maximum is shifted to longer wavelength upon addition of TiO2 colloidal nanoparticle. This behaviour can be explained in terms of complex formation as well as charge transfer transition via electron transfer between TiO2 and the dye molecules because CFL and CR are adsorbed on the surface of semiconductor nanoparticle through its anchoring group ( –COO−, -SO3−) respectively.
But for AO which does not have any anchoring group with TiO2. In AO-TiO2 system upon increasing the concentration of colloidal TiO2 nanoparticles there is no change in the absorption spectrum of AO indicating that the interaction between AO and surface of the semiconductor nanoparticles is not possible. Thus, the rate of photodegradation increases in the order:
CFL<CR<AO.
-Preparation and characterization of TiO2 and Gd(III)
TiO2 sol- gel.
-Effect of TiO2 and Gd(III)-TiO2 on photodegradation
dyes.
-photodegradation of CFL, CR and AO in presence of different types of TiO2 , it has been found that photodegradation rate is small in case of using TiO2 and Gd(III)-TiO2 thus are suitable for dye sensitized solar cell fabrication.
Part II: Fabrication of Dye-Sensitized Solar Cell (DSSC).
-Fabrication of dye-sensitized solar cell: we have designed successfully solar cells by using TiO2 and Gd(III)-TiO2 as anode.
-We determined the various factors for the cells as: electricity conversion efficiency η and fill factor F.F and hence it was found that the photovoltaic efficiency of the solar cell based on Gd-doped titania thin films was twice higher than that of the solar cell based on pure titania thin film electrode. This is because the Gd form surface complex with dye and thus increase adsorption efficiency. Moreover the surface area of Gd(III)-TiO2 higher than that of pure TiO2.
We conclude:
-The photolysis of CFL, CR and AO results in a decrease in the absorbance with no new absorption bands appear in either the visible or ultraviolet regions (about 15.9%, 2.4% and 1.0% CFL, CR and AO respectively).
-The photodegradability of the different dyes was tested by using another TiO2 sol prepared by sol-gel methods.
-The photostability of the different dye sensitizers was tested using a new prepared Gd-doped TiO2, nanomaterials prepared by simple sol-gel methods and which was compared with the pure titania. It was found that the stability of the three dye-sensitizers was higher in case of pure titania rather than in presence of Gd-doped TiO2 only under UV-irradiation.
-Successful fabrication of dye-sensitized solar cell using CFL as dye sensitizer and titania (Gd-doped and pure) thin film electrodes was obtained with a fair efficiency.