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SUMMARY:Charge separation in bulk heterojunctions - Dr. Martijn Kemerink\,
   Department of Applied Physics\, Eindhoven University of Technology\, The
  Netherlands
DTSTART:20130219T143000Z
DTEND:20130219T153000Z
UID:TALK43080@talks.cam.ac.uk
CONTACT:Dr. Girish Lakhwani
DESCRIPTION:Despite the poor screening of the Coulomb potential in organic
  semiconductors\, excitons can dissociate efficiently into free charges at
  a donor-acceptor heterojunction. In the first part of this colloquium I w
 ill present a kinetic two-particle Monte Carlo model that quantitatively e
 xplains this high efficiency as a two-step hopping process. Driven by the 
 band offset between donor and acceptor\, one of the charge carriers first 
 hops across the interface\, forming a charge transfer (CT) complex. Since 
 the electron and hole forming the CT complex have typically not relaxed wi
 thin the disorder-broadened density of states (DOS)\, the remaining Coulom
 b binding energy can be overcome by further relaxation in the DOS. As this
  process is driven by the internal energy of the non-relaxed system the di
 ssociation yield therefore only shows a moderate thermal activation and a 
 weak dependence on electric field. The model predicts dissociation yields 
 in excess of 90% for a prototypical heterojunction. In the second part of 
 the colloquium I will address charge sepa-ration in the more realistic sit
 uation where free charges and excitons are simultaneously present.
LOCATION:Kapitza Building Seminar Room\, Cavendish Laboratory\, Department
  of Physics
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