15. Singlet Fission Solar Cells

The high-energy (blue) part of the solar spectrum is inefficiently converted in conventional solar cells, mainly because the high-energy excitations thermalize to the bandgap before they are extracted. Several strategies have been devised to tackle these thermalization losses, most prominently tandem solar cells. However, these tandem cells require an intricate device design and current matching in case of a series connection. Downconversion via singlet fission and quantum cutting promise a better use of the high-energy photons, avoiding a large fraction of the thermalization losses, but without the intricate fabrication and design constraints of tandem cells. In this chapter we review the progress made towards efficient singlet fission and quantum cutting downconversion. We start with the potential for solar cell integration, reviewing the different integration schemes and their efficiency potential. In the second part we review the progress towards solar cells that utilize singlet fission and quantum cutting from all-organic devices to hybrid two-bandgap devices and fully optical integration. Finally, we lay out the challenges for using these downconversion schemes in commercial solar cells.