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CATEGORIES:Optoelectronics Group
SUMMARY:Charge transport in supramolecular assemblies: An 
 atomistic description - Dr. Jerome Cornil\, Univer
 site de Mons-Hainaut\, Belgium
DTSTART;TZID=Europe/London:20090217T143000
DTEND;TZID=Europe/London:20090217T153000
UID:TALK15796AThttp://talks.cam.ac.uk
URL:http://talks.cam.ac.uk/talk/index/15796
DESCRIPTION:Charge transport plays a key role in defining the 
 performance of organic-based devices such as light
 -emitting diodes\, solar cells\, or field-effect t
 ransistors. Transport is typically described in tw
 o extreme cases\, namely the band regime versus th
 e hopping regime. I will argue in the first part o
 f the talk that many electronic effects in organic
  semiconductors tend to favor a hopping picture in
  devices at room temperature. In this context\, ma
 croscopic models have been developed over the year
 s to characterize the influence of several paramet
 ers (such as temperature\, electric field amplitud
 e\, disorder\, charge carrier density) on the mobi
 lity values. Most of them have in common to involv
 e effective parameters that do not take fully into
  account the nature and relative position of the i
 nteracting molecules. On the other hand\, quantum-
 chemical calculations have been extensively used r
 ecently to calculate all parameters governing the 
 rate of charge transfer between two interacting mo
 lecules in the hopping regime\; such an approach e
 xplicitly takes into account the chemical structur
 e and actual packing of the molecules. I will surv
 ey some of our recent studies aiming at the descri
 ption of the various transport parameters in a lar
 ge variety of systems. I will also show that a bri
 dge can be established between the molecular and m
 acroscopic worlds by performing Monte-Carlo (MC) s
 imulations based on the calculated transfer rates 
 to be in position to evaluate charge mobility with
 in the hopping regime in supramolecular assemblies
  from calculated molecular parameters\; recent app
 lications of this approach will be shown\, for ins
 tance to characterize the anisotropy of charge tra
 nsport in molecular crystals or the electric-field
  dependence of the mobility. Such simulations are 
 typically performed nowadays on frozen structures\
 , thus neglecting the impact of lattice dynamics. 
 In the last part of the talk\, I will show very re
 cent results examining the way intermolecular vibr
 ations modulate the key transport parameters and I
  will discuss the implications for charge transpor
 t properties. \n\n
LOCATION:Kapitza Building Seminar Room\, Cavendish Laborato
 ry\, Department of Physics
CONTACT:Dr. Z Chen
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