Negative giant surface potential of vacuum-evaporated tris(7-propyl-8-hydroxyquinolinolato) aluminum(III) [Al(7-Prq)(3)] film

Abstract

Negative giant surface potential was realized in a vacuum-evaporated film of tris(7-propyl-8-hydroxyquinolinolato) aluminum(III) [Al(7-Prq)(3)]. Electroabsorption response of the film presented an inverted polarity to that of tris(8-hydroxyquinolinolato) aluminum (Alq(3)), suggesting opposite noncentrosymmetry of molecular orientation. Asymmetric dice model with molecular geometric effect has been proposed, and propyl substitution at 7 position of the ligands was indicated to affects the molecular posture on the surface to invert the polarity of noncentrosymmetry. Our results opened a new possibility of controlling molecular orientation in a film for device applications. (C) 2013 Elsevier B.V. All rights reserved.