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THESIS DR. GOPALA KRISHNA THALLURI - SYNOPSIS

"Preparation and Characterization of Novel and Eco-Friendly Hybrid Organic: Inorganic Solar Cells."

Emerging alternative photovoltaic (PV) technologies like Grätzel and polymer based solar cells offer an alluring way for simple and low cost PV production. In the photovoltaics research and development area, the main goal is to fabricate a low cost photovoltaic device with a sufficient stability and high efficiency. The organic:inorganic hybrid solar cells (HSCs) containing inorganic nanoparticles such as TiO2/ZnO and semiconducting polymers such as P3HT are still behind emerging alternative photovoltaics. In spite of that, hybrid solar cells have the potential to grow towards better performance. They offer several benefits compared to polymer based solar cells such as low-cost, thin and easy to produce. Furthermore TiO2/ZnO, are abundant materials.

The goal of this dissertation was the preparation and characterization of hybrid polymer:metal oxide solar cells. An important aspect of this work was the realization of an efficient 3-dimensional interpenetration nano-network of polymers as hole conductors/photo-active layer and metal oxides as electron acceptors/conductors. Initially, in this research the mesoporous TiO2 nanostructured oxide layer electrodes were prepared and sensitized with different dyes. Poly-3(hexylthiophene) (P3HT) was deposited above metal oxide electrodes as a photoactive and hole transporting material and a structured way of complete device fabrication was developed. IV-characterizations and various opto-electrical measurements were performed for better understanding the physical properties of these nanostructured devices.

As an alternative approach, copper phthalocyanine (CuPc) as a hole conductor/photo active layer was vacuum sublimated above TiO2 electrodes with and without dye sensitization. In these types of structured devices the IV-characterizations along with charge transport and charge separation properties were investigated by using a variety of opto-electrical characterization techniques.

Towards the development and preparation of eco-friendly hybrid solar cells, the dye and P3HT were replaced by water soluble conjugated polymer. The water soluble polymer was used as a hole transporting and photo-active layer. The opto-electric and morphological properties were systematically studied for some of the water soluble conjugated polymers. The best-performing polymer was processed by an alternative new processing method and introduced above different TiO2 electrodes. Complete solar cells were built in this way and IV-characteristics were investigated.

Towards the end of this work, conclusions are summarized and as an outlook the poly(isothianaphthene) (PITN) oligomer precursor solution polymerization into the metal oxide layers was studied. This stands as a principle for future development of solar cells by using this novel photo-active and hole transporting material for the complete filling of mesoporous nano-oxide layers with polymers.