title: External quantum efficiency above 100% in a singlet-exciton-fission-based organic photovoltaic cell.
abstract: Singlet exciton fission transforms a molecular singlet excited state into two triplet states, each with half the energy of the original singlet. In solar cells, it could potentially double the photocurrent from high-energy photons. We demonstrate organic solar cells that exploit singlet exciton fission in pentacene to generate more than one electron per incident photon in a portion of the visible spectrum. Using a fullerene acceptor, a poly(3-hexylthiophene) exciton confinement layer, and a conventional optical trapping scheme, we show a peak external quantum efficiency of (109 ± 1)% at wavelength λ = 670 nanometers for a 15-nanometer-thick pentacene film. The corresponding internal quantum efficiency is (160 ± 10)%. Analysis of the magnetic field effect on photocurrent suggests that the triplet yield approaches 200% for pentacene films thicker than 5 nanometers.
authors.affiliation: Energy Frontier Research Center for Excitonics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
authors.forename: Daniel N
authors.initials: DN
authors.lastname: Congreve
authors.forename: Jiye
authors.initials: J
authors.lastname: Lee
authors.forename: Nicholas J
authors.initials: NJ
authors.lastname: Thompson
authors.forename: Eric
authors.initials: E
authors.lastname: Hontz
authors.forename: Shane R
authors.initials: SR
authors.lastname: Yost
authors.forename: Philip D
authors.initials: PD
authors.lastname: Reusswig
authors.forename: Matthias E
authors.initials: ME
authors.lastname: Bahlke
authors.forename: Sebastian
authors.initials: S
authors.lastname: Reineke
authors.forename: Troy
authors.initials: T
authors.lastname: Van Voorhis
authors.forename: Marc A
authors.initials: MA
authors.lastname: Baldo