Singlet Fission for Solar Cells

One strategy to overcome the single-threshold efficiency limit of solar cells includes is twofold carrier multiplication for photons more energetic than about twice the band gap. In organic molecules, this may be achieved by the process of singlet fission, a strategy that is limited to 45.9% efficiency and could realistically exceed 30% with minimal re-engineering of the underlying structure. This chapter introduces the reader to the singlet fission concept, leading through the most basic theory needed to understand the electronic structure of the large organic chromophores usually invoked. The reader is provided with a tutorial in excitonic coupling and molecular photophysics before being exposed to the state-of-the-art theoretical thinking behind singlet fission. The chapter concludes by sketching the anticipated benefits of singlet fission and a brief review of the current state-of-the-art with respect to device implementation and prospects.