Beneficial microstructured TiO₂ photoanodes for improving DSSC performance

Critical assessment of economically viable renewable energy sources is essential for the development of a globally sustainable society. Dye sensitized solar cells (DSSCs) offer a viable alternative to traditional silicon and thin film photovoltaic (PV) technologies owing to their potential low cost and facile manufacturing. The two main challenges in enhancing device cell performance lie in improving the open circuit voltage (VOC), and suppressing recombination in the semiconductor TiO₂ matrix. This thesis explores the latter challenge through investigation of a novel microstructured TiO₂ photoanode system. In this research, we have synthesized CTAB-templated mesoporous, anatase, high surface area TiO₂. Through simple supramolecular self-assembly of the TiO₂ particles during the synthesis, we have discovered a self-assembled system of TiO₂ nanocrystallites, which when applied as the photoanode in DSSCs, result in a novel high-roughness film beneficial for dye adsorption, and also lead to enhanced intrinsic light-scattering within the film itself. The TiO₂ nanocrystallites are highly crystalline, with good interconnectivity for improved electron conduction. The novel photoanode film also shows hierarchical meso- and macro-porosity, enabling better access of electrolyte to dye molecules, and thereby improving dye regeneration capacity. In all, we have fabricated a TiO₂ system through a one-step process that incorporates key beneficial microstructural features crucial for enhancing DSSC behavior. TiCl₄ surface treatment studies of this novel TiO₂ microstructure led to deeper insight and improvement of recombination kinetics in the photonanode film matrix, together with enhancement in the intrinsic light harvesting features. Improved efficiency was observed when compared to cells prepared using standard Degussa P25 TiO₂ electrodes of similar thickness. In the last endeavor of this thesis, we have incorporated graphene oxide (GO) in the TiO₂ photoanode films in an effort to gain further insight into recombination kinetics of the novel TiO2 microstructure. Upon heat treatment of the photoanodes, reduced GO (rGO) was obtained. It was found that rGO was incorporated in a much more uniform and effective manner within the novel TiO₂ microstructure compared to its P25 counterpart – likely due to its highly porous structure. Overall, the rGO incorporated novel TiO₂ cells outperformed the P25 TiO₂ cells in solar and optoelectronic properties.Ph. D.Includes bibliographical referencesby Saquib Ahme