title: Recent advances in singlet fission.
abstract: A survey is provided of recent progress in the understanding of singlet fission, a spin-allowed process in which a singlet excited molecule shares its energy with a ground-state neighbor to produce two triplet excited molecules. It has been observed to occur in single-crystal, polycrystalline, and amorphous solids, on timescales from 80 fs to 25 ps, producing triplet yields as high as 200%. Photovoltaic devices using the effect have shown external quantum efficiencies in excess of 100%. Almost all the efficient materials are alternant hydrocarbons of the acene series or their simple derivatives, and it is argued that a wider structural variety would be desirable. The current state of the development of molecular structure design rules, based on first-principles theoretical considerations, is described along with initial examples of implementation.
authors.affiliation: Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309-0215, USA.
authors.forename: Millicent B
authors.initials: MB
authors.lastname: Smith
authors.forename: Josef
authors.initials: J
authors.lastname: Michl