title: Large electronic bandwidth in solution-processable pyrene crystals: the role of close-packed crystal structure.
abstract: We examine the interdependence of structural and electronic properties of two substituted pyrene crystals by means of combined spectroscopic probes and density-functional theory calculations. Substituted pyrenes are useful model systems to unravel the interplay of crystal structure and electronic properties in organic semiconductors. To study the effect of steric encumbrance on the crystalline arrangement of two 1,3,6,8-tetraalkynylpyrene derivatives, one features linear n-hexyl side groups while the other contains branched trimethylsilyl groups. Both derivatives form triclinic crystal structures when grown from solution, but the electronic dispersion behavior is significantly different due to differences in π-π overlap along the π-stacking axis. Both systems display dispersion of around 0.45 eV in the valence band, suggesting a high intrinsic hole mobility. However, the direction of the dispersion is different: it is primarily along the π-stacking axis in the trimethylsilyl-substituted derivative, but less aligned with this crystal axis in the hexyl-substituted molecule. This is a direct consequence of the differences in co-facial π electron overlap revealed by the crystallographic studies. We find that photophysical defects, ascribed to excimer-like states, point to the importance of localized trap states.
authors: Département de Physique et Regroupement Québécois sur les Matériaux de Pointe, Université de Montréal, C.P. 6128, Succursale Centre-Ville, Montréal (Québec) H3C 3J7, Canada.
authors: Françoise
authors: F
authors: Provencher
authors: Nicolas
authors: N
authors: Bérubé
authors: Jean-Frédéric
authors: JF
authors: Laprade
authors: Gabrielle
authors: G
authors: Simard
authors: Julien
authors: J
authors: Tant
authors: Véronique
authors: V
authors: de Halleux
authors: Yves
authors: Y
authors: Geerts
authors: Carlos
authors: C
authors: Silva
authors: Michel
authors: M
authors: Côté