Fabrication and characterization of metal-oxide semiconductors for energy harvesting applications

One of the most important requirements of current and the near future is clean and environmentally friendly energy. Because of the greenhouse gases, arising from fossil fuels, natural life is coming across with global warming and climate change threat. So that, clean energy generation systems as solar cells can be a good alternative to attain cleaner and low-cost energy. Dye-sensitized solar cells (DSSCs) have attracted remarkable attention from the energy sector and researchers thanks to the multiple advantages in terms of diversity in material selection, low-cost and chemical stability. The efficiency of a solar cell can be tailored by changing semiconducting oxide layer or adding an extra metal-oxide layer among this sandwich system. In addition to these methods, doping titanium oxide layer with an intrinsic material or designing the solar cell structure in a different way can be also included. In this thesis, firstly, a brief information about solar cells was given and working principle of them is introduced. Then, studies carried out to investigate the effects of different approaches on the performance of DSSCs and collected under three different sections are given. In the sixth chapter, the effect of the acceleration of the spin coating device on the light absorption parameter of a solar cell was investigated and it was recognized that the opto-electrical properties of the samples could be enhanced if the device was operated with the ideal rotational acceleration. In the seventh chapter, the effect of using gallium nitrate as a blocking layer was investigated and it was observed that the electron recombinations of the samples decreased in consequence of employing the gallium nitrate. Finally, in the eighth chapter; the effect of adding multi-walled carbon nanotubes (MWCNTs) into the titanium oxide layer on the charge transfer kinetics of a solar cell was examined and it was obtained that the electron diffusion length and charge collection efficiency increased due to the decrease in the charge transfer resistance of the samples with adding trace amounts of these particles.