A photovoltaic cell is consisted of electron accepting/donating materials as the photoactive layer. In electron donating material, light absorption results to the creation of bound electron-hole pairs called excitons. The excitons have to be separated at the interface between an electron donating and accepting material in order to create mobile charge carriers. The efficiency of photovoltaic cell depends on the number of excitons created during light emission on the photoactive layer. Moreover, the average interfacial distance between electron donor and acceptor greatly affect the photovoltaic efficiency. Therefore by maximizing the reaction area and by assuring that the interfacial distance between the donor and acceptor surfaces is within the exciton diffusion length, improved photovoltaic cell efficiency is expected. Titania (TiO2) is a widely used material as an electron recipient medium. The most attractive aspect of using titania with a conjugated polymer in a photovoltaic cell is the fact that titania can be easily patterned into a continuous network for electron transport.
In this work, the surface to volume ratio of titania surface can be increased by creating nanocrystal structures. This is accomplished by sintering at 500 oC for 30 min after spin coating with a mixture of titania sol-gel solution (titanium ethoxide (IV), HCl, 2-propanol) and Poly(methylmethacrylate) (PMMA) on the ITO substrate. Poly(3-hexylthiophene) (P3HT) was spin coated on the nanocrystal titania and gold counter electrode was deposited by vacuum evaporation. The potential of the fabricated composite nanocrystal titania-P3HT structures on photovoltaic cell synthesis is currently under investigation. Comparative studies with the conventional smooth titania films will be conducted hereafter.
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