Femtosecond Laser Spectroscopy and Singlet Fission

Singlet exciton fission or singlet fission (SF) is a process in which a singlet excited molecule, usually in a densely packed organic solid or in a polymer, shares its energy with a neighboring molecule in its electronic ground state, both molecules forming a pair of triplet states in a spin allowed process. SF was first proposed in 1965 to explain the delayed fluorescence in anthracene crystal [1]. It was further proven by the magnetic field effect on tetracene crystal [2,3]. Interest towards SF rises in recent years due to its potential applications in photovoltaics. SF may dramatically increase efficiency of the solar cells.