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2008-03-19 - Article/Dans un journal avec peer-review - Anglais - 8 page(s)

Difley S., Beljonne David , Van Voorhis T., "On the Singlet-Triplet Splitting of Geminate Electron-Hole Pairs in Organic Semiconductors" in Journal of the American Chemical Society, 130, 11, 3420-3427

  • Edition : American Chemical Society, Washington (DC)
  • Codes CREF : Physique de l'état condense [struct., électronique, etc.] (DI1266), Physique de l'état solide (DI1261)
  • Unités de recherche UMONS : Chimie des matériaux nouveaux (S817)
  • Instituts UMONS : Institut de Recherche en Science et Ingénierie des Matériaux (Matériaux)
Texte intégral :

Abstract(s) :

(Anglais) Because of their unique photophysical properties, organic semiconductors have shown great promise in both light-emitting devices (LEDs) and photovoltaic systems. In particular, the question of spin statistics looms large in these applications: the relative energetics and rates of formation for singlet versus triplet excited states can have a significant impact on device efficiency. In this Article, we study the singlet and triplet charge-transfer (CT) configurations that can be thought of as the immediate precursors to the luminescent states in organic LEDs. In particular, we find that the CT singlet-triplet energy gap (?EST) of organic dyes and oligomers depends sensitively on both the material and the relative orientation of the donor/acceptor pair. Furthermore, in contrast with the commonly held view, we find that the singlet CT states nearly always lie energetically below the triplet CT states (?EST < 0). This trend is attributed to two physical sources. First, the relatively close contact between the donor and acceptor leads to a strong kinetic exchange component that favors the singlet. Second, Coulombic attraction between the separated charges favors inner-sphere reorganization that brings the donor and acceptor closer together, further enhancing the kinetic exchange effect. We discuss the implications of these results on the design of organic LEDs.

Notes :
  • (Anglais) Publié en ligne le 21 février 2008
Identifiants :
  • DOI : 10.1021/ja076125m