Design, synthesis and photovoltaic properties of [60]fullerene based molecular materials

The possibility to use new organic semiconductor materials, in place of silicon wafers, in the fabrication of photovoltaic devices on substrates offer the prospect of lower manufacturing costs, particularly for large area applications. Thus, one of the most promising areas in fullerene research involves its potential application, mixed with conjugated polymers, in mimicking photosynthesis and in the related solar energy conversion. The tendency to phase segregation in blends of C60 derivatives and conjugated polymers has to be optimized to improve both charge photogeneration and transport in photovoltaic devices. In order to optimize device performances, a great deal of work has been devoted to the development of new device architectures and to elucidating the photophysical processes underlying the photovoltaic response. However, optimization of cells has been carried out with just a few materials and recent findings show that new developments can be very successful if a broader scope of materials in the composite layers becomes accessible. Thus, in this communication we present new approaches toward the synthesis of [60]fullerene derivatives specifically designed to be used in the fabrication of photovoltaic devices. (i) the first approach involves the synthesis of functionalized C60 and C70 derivatives with enhanced solubility; (ii) the second approach is directed to the synthesis of systems containing a conjugated moiety antenna covalently linked to the C60 unit. Together with the synthesis of these new materials, electrochemical and photophysical investigations have been also carried out. Photovoltaic devices have been fabricated with selected materials.