Dye-Sensitized Solar Cells: Photophysics of Coordination Complex

In the past decades, dye-sensitized solar conversion technologies have gained more and more interest in the scientific community. Dye-sensitized solar cells (DSCs) are a very promising technology that can combine the high-stability features common to the inorganic semiconductors and the wide flexibility of the organic compounds. Indeed, these novel solar cells are multi-component devices that can be prepared using different metal oxides as charge transport materials in combination with organometallic or organic sensitizers as absorber. Because of their great flexibility, they immediately became a source of great interest from different points of view, especially with regard to the studies of the phenomena of charge generation and transport. These phenomena are strictly related to the structure of the cell itself and the nature of the sensitizers.These cells can be made as n-type or p-type with a passive counter electrode, depending on the metal oxide semiconductor, as well as in combination in a tandem configuration with both active anode and cathode. However, the most important part of the cell is the sensitizer. Indeed, since their report, the rush to find novel more efficient sensitizers started. From the first ruthenium complex, the rush to more efficient and more stable dyes led to the production of a plethora of different molecular sensitizers, either organometallic and organic, capable of astonishing properties setting higher and higher the attainable efficiency and improving, the stability of the overall device. In this chapter, after a presentation of the main type of DSCs, attention will be paid to the photophysics of devices sensitized with metallo-porphyrins based dyes and the effect of the different functionalzation of their tetra-aryl porphyrinic core. Different techniques have been used to evaluate the main photophysics parameters to point out the critical effect of proper functionalization over the final efficiency of the devices.