title: Activated singlet exciton fission in a semiconducting polymer.
abstract: Singlet exciton fission is a spin-allowed process to generate two triplet excitons from a single absorbed photon. This phenomenon offers great potential in organic photovoltaics, but the mechanism remains poorly understood. Most reports to date have addressed intermolecular fission within small-molecular crystals. However, through appropriate chemical design chromophores capable of intramolecular fission can also be produced. Here we directly observe sub-100 fs activated singlet fission in a semiconducting poly(thienylenevinylene). We demonstrate that fission proceeds directly from the initial 1Bu exciton, contrary to current models that involve the lower-lying 2Ag exciton. In solution, the generated triplet pairs rapidly recombine and decay through the 2Ag state. In films, exciton diffusion breaks this symmetry and we observe long-lived triplets which form charge-transfer states in photovoltaic blends.
authors.affiliation: Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, United Kingdom. am956@cam.ac.uk
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Musser
authors.forename: Mohammed
authors.initials: M
authors.lastname: Al-Hashimi
authors.forename: Margherita
authors.initials: M
authors.lastname: Maiuri
authors.forename: Daniele
authors.initials: D
authors.lastname: Brida
authors.forename: Martin
authors.initials: M
authors.lastname: Heeney
authors.forename: Giulio
authors.initials: G
authors.lastname: Cerullo
authors.forename: Richard H
authors.initials: RH
authors.lastname: Friend
authors.forename: Jenny
authors.initials: J
authors.lastname: Clark