Since the realization of the imperative need to reduce our dependence on fossil fuels, we have witnessed an unprecedented enthusiasm in the scientific community for the design of photovoltaic cells. Indeed, the possibility of using sunlight on a large scale as a major source of primary energy could become a reality in the course of this lecture century. Unlike conventional silicon-based cells, the operating principle of dye cells is inspired by the natural process of photosynthesis . In other words, the processes of light absorption and charge separation are differentiated and carried out by separate materials. Each molecular component performs just one function for which it is optimized. Another advantage of these cells is their low cost, based as they are on inexpensive materials and low-cost technology.
This paper presents the principles governing the operation of photovoltaic cells based on the sensitization of a semi-conducting mineral oxide with a wide bandgap. The first part deals with so-called " Grätzel-type cells ", i.e. cells whose mechanism is based on the injection of electrons into the conduction band of an n-type semiconductor (typically TiO2 or ZnO). The second part concerns a new photovoltaic technology based on the use of p-type semiconductors (SC-p), whose operating principle is reversed, since the photo-excited dye injects a gap into the valence band of the SC-p. Major contributions and prospects in this field are presented.
