title: Exciton fission and charge generation via triplet excitons in pentacene/C60 bilayers.
abstract: Organic photovoltaic devices are currently studied due to their potential suitability for flexible and large-area applications, though efficiencies are presently low. Here we study pentacene/C(60) bilayers using transient optical absorption spectroscopy; such structures exhibit anomalously high quantum efficiencies. We show that charge generation primarily occurs 2-10 ns after photoexcitation. This supports a model where charge is generated following the slow diffusion of triplet excitons to the heterojunction. These triplets are shown to be present from early times (<200 fs) and result from the fission of a spin-singlet exciton to form two spin-triplet excitons. These results elucidate exciton and charge generation dynamics in the pentacene/C(60) system and demonstrate that the tuning of the energetic levels of organic molecules to take advantages of singlet fission could lead to greatly enhanced photocurrent in future OPVs.
authors.affiliation: Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, UK.
authors.forename: Akshay
authors.initials: A
authors.lastname: Rao
authors.forename: Mark W B
authors.initials: MW
authors.lastname: Wilson
authors.forename: Justin M
authors.initials: JM
authors.lastname: Hodgkiss
authors.forename: Sebastian
authors.initials: S
authors.lastname: Albert-Seifried
authors.forename: Heinz
authors.initials: H
authors.lastname: Bässler
authors.forename: Richard H
authors.initials: RH
authors.lastname: Friend
mesh_terms: D037741:Fullerenes / Q000737:chemistry*; D009279:Naphthacenes / Q000737:chemistry*; D011789:Quantum Theory
chemical_list: D037741:Fullerenes; D009279:Naphthacenes; C523499:pentacene; C069837:fullerene C60