Exciton regeneration at polymeric semiconductor heterojunctions.
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.
Morteani
Arne C
AC
Cavendish Laboratory, University of Cambridge, Madingley Road, Cambridge CB3 0HE, United Kingdom.
Sreearunothai
Paiboon
P
Herz
Laura M
LM
Friend
Richard H
RH
Silva
Carlos
C