title: Exciton regeneration at polymeric semiconductor heterojunctions.
abstract: Control of the band-edge offsets at heterojunctions between organic semiconductors allows efficient operation of either photovoltaic or light-emitting diodes. We investigate systems where the exciton is marginally stable against charge separation and show via E-field-dependent time-resolved photoluminescence spectroscopy that excitons that have undergone charge separation at a heterojunction can be efficiently regenerated. This is because the charge transfer produces a geminate electron-hole pair (separation 2.2-3.1 nm) which may collapse into an exciplex and then endothermically (E(A)=100-200 meV) back transfer towards the exciton.
authors.affiliation: Cavendish Laboratory, University of Cambridge, Madingley Road, Cambridge CB3 0HE, United Kingdom.
authors.forename: Arne C
authors.initials: AC
authors.lastname: Morteani
authors.forename: Paiboon
authors.initials: P
authors.lastname: Sreearunothai
authors.forename: Laura M
authors.initials: LM
authors.lastname: Herz
authors.forename: Richard H
authors.initials: RH
authors.lastname: Friend
authors.forename: Carlos
authors.initials: C
authors.lastname: Silva