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2008-10-30 - Article/Dans un journal avec peer-review - Anglais - 10 page(s)

Karsten B.P., Viani Lucas, Gierschner J., Cornil Jérôme , Janssen R.A.J., "An Oligomer Study to Small Band Gap Polymers" in Journal of Physical Chemistry A, 112, 43, 10764-10773

  • Edition : American Chemical Society, Washington (DC)
  • Codes CREF : Chimie quantique (DI1321), Spectroscopie [électromagnétisme, optique, acoustique] (DI1255), Chimie générale (DI1310)
  • 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) Small band gap polymers may increase the energy conversion efficiency of polymer solar cells by increased absorption of sunlight. Here we present a combined experimental and theoretical study on the optical and electrochemical properties of a series of well-defined, lengthy, small band gap oligo(5,7-bis(thiophen-2-yl)thieno[3,4-b]pyrazine)s (Eg = 1.50 eV) having alternating donor and acceptor units. The optical absorptions of the ground state, triplet excited state, radical cation, and dication are identified and found to shift to lower energy with increasing chain length. The reduction of the band gap in these alternating small band gap oligomers mainly results from an increase of the highest occupied molecular orbital (HOMO) level. The S1-T1 singlet-triplet splitting is reduced from 0.9 eV from the trimeric monomer to –0.5 eV for the pentamer. This significant exchange energy is consistent with the fact that both the HOMO and the lowest unoccupied molecular orbital (LUMO) remain distributed over virtually all units, rather than being localized on the D and A units.

Notes :
  • (Anglais) Publié en ligne le 1 octobre 2008
Identifiants :
  • DOI : 10.1021/jp805817c