CHAPTER 5: Design and Synthesis of Small Molecule Donors for High Efficiency Solution Processed Organic Solar Cells

Solution processed small molecule bulk-heterojunction solar cells have emerged as one of the most promising approaches to the development of organic photovoltaic technology. The design of these solar cells is based on an active layer that is comprised entirely of discrete molecular systems. To date, the best performance has been realized using donor–acceptor type active layers, employing small molecule donors and fullerene acceptors. Through rational molecular design strategies, improvements in the small molecule donor architecture have resulted in solar cells reaching power conversion efficiencies in excess of 10%. This chapter briefly describes the evolution of small molecule donors for use in organic solar cells and details key materials properties. The bulk of the chapter highlights the synthesis and structure of several important classes of small molecule donors that have enabled the fabrication of highly efficient devices, including diketopyrrolopyrrole, isoindigo, porphyrins, and donor–acceptor type oligothiophene-based materials.