Chapter 12: Fullerene Derivatives for Organic Photovoltaics

Since the discovery of fullerene C₆₀ in 1985 and its behaviour to act as an electron acceptor in photoinduced electron-transfer processes ten years later, intensive research programs have focused on the use of fullerene derivatives as acceptors in organic solar cells. After only fifteen years of studies, it is now clearly established that fullerene-based materials are among the most important candidates able to promote the expansion of plastic solar cells. In this chapter, we focus on the recent improvement in the efficiency of these solar cells, essentially developed during the last five years, thanks to the synthesis of new p-type donors and n-type C₆₀ derivatives. In the field of accepting materials, the molecules [60]PCBM and [70]PCBM are now considered by physicists as the references. However, whereas there is no clear reason for not supposing that another C60 derivative will reach or surpass [60]PCBM and [70]PCBM, intensive research effort is being made by creative synthetic chemists to offer new C₆₀ derivatives but also carbon nanotubes as potential electronic acceptors. These different strategies are overviewed in this chapter in terms of approaches for organic chemists to synthesise new fullerene derivatives as accepting materials for solar cells.