Light Harvesting Properties of Photoactive and Nanostructured Materials

The main idea of this work is based on characterization of nanostructured and photoactive materials and their utilization in solar energy conversion devices. Experimental details are given on the characterization techniques; the fabrication procedures and the electric characterizations employed for the dye sensitized solar cells (DSSCs) are described. The description of morphological, structural and optical properties of different metal-oxide nanostructures for DSSC photoanodes fabricated in our labs (TiO2 nanoparticles, TiO2 nanotubes array, sponge-like ZnO and flower-like ZnO films) is included. The study of the dye-impregnation mechanisms with both metal-organic and organic molecules in DSSC photoanodes is also reported. The obtained experimental results show a very good agreement with data obtained from ab-initio modeling and give useful insights for understanding the measured electrical properties of the final device. The studied online dye impregnation monitoring techniques are useful to explore novel dyes and nanostructured semiconducting oxide films. Ultrafast sensitization of photoanodes using microfluidic chamber can help in fabrication of DSSCs at large scales. Moreover a physical model appropriately elaborated for interpretation of the dye adsorption process is presented. The properties of a new quasi-solid state electrolyte for DSSC are discussed; in particular the effect of γ-Al2O3 nanoparticles (NPs) addition into a traditional iodine-based liquid electrolyte is reported. Also the fabrication and the electrical characterization of DSSCs exploiting NPs-based electrolyte are explained. DSSCs based on such quasi solid state electrolytes have shown long term stability in performance as compared to the ones based on liquid electroolyte. Furthermore the IR-reflecting and self-cleaning nanostructured coatings, obtained in our labs with a cheap and easy-to-scale process, are characterized in order to evidence a multi-functional behavior. These coatings have been applied on a crystalline silicon solar cell for evaluating their efficacy in decreasing the cell working temperature during simulated solar-irradiation. Finally the demonstration of room temperature crystallization of TiO2 nanotubes into anatase phase after only 30 minutes of exposure to water vapor and their utilization in photocatalysis of methylene blue is included. This crystallization process provides a cost effective strategy to allow the integration of ordered TiO2 nanotube carpets on temperature sensitive substrates which is a crucial step for the fabrication of flexible and lightweight devices