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2010-07-07 - Colloque/Présentation - communication orale - Français - 28 page(s)

Olivier Yoann , "Molecular Insights on Charge Transport in Conjugated Materials for Applications in Organic Electronics" in 12ème Rencontre des Chimistes Théoriciens Francophones , Namur, Belgique, 2010

  • Codes CREF : Physico-chimie générale (DI1320), Chimie quantique (DI1321)
  • Unités de recherche UMONS : Chimie des matériaux nouveaux (S817)
  • Instituts UMONS : Institut de Recherche en Science et Ingénierie des Matériaux (Matériaux)

Abstract(s) :

(Anglais) Charge transport plays a key role in defining the performance of organic-based devices such as light-emitting diodes, solar cells, or field-effect transistors. Transport is typically described in two extreme cases, namely the band regime versus the hopping regime. Many electronic effects in organic semiconductors tend to favor a hopping picture in devices at room temperature. In this regime, macroscopic models have been developed over the years to characterize the influence of several parameters (such as temperature, electric field amplitude, disorder, charge carrier density) on the mobility values. Most of them have in common to involve effective parameters that do not take fully into account the nature and relative position of the interacting molecules. On the other hand, quantum-chemical calculations have been extensively used recently to calculate all parameters governing the rate of charge transfer between two interacting molecules in the hopping regime, thus with an explicit account of the chemical structure and actual packing of the molecules [1,2]. We will first survey some of our recent studies aiming at the description of the various transport parameters in a large variety of systems [2,3]. We will then show that a bridge can be established between the molecular and macroscopic worlds by performing Monte-Carlo (MC) simulations based on the calculated transfer rates in order to evaluate charge mobility values within the hopping regime in supramolecular assemblies from calculated molecular parameters [4]. However, such simulations are often performed on frozen structures, thus neglecting the impact of lattice dynamics. In the last part of the talk, we will examine the way intermolecular vibrations modulate the key transport parameters and the implications for charge transport properties [5,6].