Evidence of environmental strains on charge injection in silole based organic light emitting diodes.

Nolwenn Huby (1) , Lionel Hirsch (1) , Laurent Aubouy (2) , Philippe Gerbier (2) , Arie van Der Lee (3) , Fabrice Amy (4) , Antoine Kahn (4)

1 IMS - Laboratoire de l'intégration, du matériau au système
2 ICGM ICMMM - Institut Charles Gerhardt Montpellier - Institut de Chimie Moléculaire et des Matériaux de Montpellier
3 IEM - Institut Européen des membranes
4 Princeton University

Using d. functional theory (DFT) computations, the authors demonstrated a substantial skeletal relaxation when the structure of 2,5-bis-[4-anthracene-9-yl-phenyl]-1,1-dimethyl-3,4-diphenyl-silole (BAS) is optimized in the gas-phase comparing with the mol. structure detd. from monocrystal x-ray diffraction. The origin of such a relaxation is explained by a strong environmental strains induced by the presence of anthracene entities. Also, the estn. of the frontier orbital levels showed that this structural relaxation affects mainly the LUMO that is lowered of 190 meV in the gas phase. To check if these theor. findings would be confirmed for thin films of BAS, the authors turned to UV photoemission spectroscopy and/or inverse photoemission spectroscopy and electrooptical measurements. The study of the c.d. or voltage and luminance or voltage characteristics of an ITO/PEDOT/BAS/Au device clearly demonstrated a very unusual temp.-dependent behavior. Using a thermally assisted tunnel transfer model, this behavior likely originated from the variation of the electronic affinity of the silole deriv. with the temp. The thermal agitation relaxes the mol. strains in thin films as it is shown when passing from the cryst. to the gas phase. The relaxation of the intramol. thus induces an increase of the electronic affinity and, as a consequence, the more efficient electron injection in org. light-emitting diodes.

Mots clés: Silole; OLED; DFT; Supramolecular effects; Charge injection

Domaines: Chimie organique; Science des matériaux [cond-mat.mtrl-sci]; Chimie théorique et/ou physique

Nolwenn Huby, Lionel Hirsch, Laurent Aubouy, Philippe Gerbier, Arie van Der Lee, et al.. Evidence of environmental strains on charge injection in silole based organic light emitting diodes.. Physical Review B: Condensed Matter and Materials Physics (1998-2015), 2007, 75 (11), pp.115416/1. ⟨10.1103/PhysRevB.75.115416⟩. ⟨hal-00186586⟩