New insights in Dye-sensitized Solar Cells: novel nanostructured photoanodes, metal-free dye, quasi-solid electrolytes and physics-based modeling

The main objective of this thesis is to develop and optimize innovative materials for Dye-sensitized Solar Cells application, with the aim of overcoming the drawbacks highlighted by the conventional ones. In particular, it is well known from the literature that TiO2 presents the disadvantage of a reduced charge transport due to a long pathway for the electron diffusion within the semiconductor network; Ru-based sensitizers exhibit the important limits of expensive synthesis process, relatively low molar extinction coefficient in the visible region, limited availability of precursors and waste disposal troubles; finally, the main issues when exploiting liquid solvent-based electrolytes are their limited long-term stability, difficulty in sealing and leakage, which prevent the realization of devices having a high and constant-over-time efficiency. Within this framework, sponge-like and flower-like ZnO nanostructures have been employed as alternative photoanode materials, hemi-squaraine organic sensitizer (CT1) has been exploited in substitution of Ru-based N719 dye, and UV-crosslinked polymer membrane and cellulose-based gel have been proposed in quality of quasi-solid electrolytes. In the fascinating but at the same time complex Dye-sensitized Solar Cells’ research world, a theoretical support often reveals necessary to clarify and corroborate some experimental evidences. In this context, a physical model able to explain the aggregation phenomenon typically shown by organic dye molecules and an opto-electronic model applied to build a consistent picture of the static and dynamic small-signal performances of nanocrystalline TiO2-based DSCs under different incident illumination intensities and directions will be presented.