π-Conjugated donor-acceptor small molecule thin-films on gold electrodes for reducing the metal work-function

Publication date: 1 October 2016
Source:Thin Solid Films, Volume 616
Author(s): Naved Azum, Layla Ahmad Taib, Yasser Mohammed Al Angari, Abdullah M. Asiri, Mitchel Denti, Wei Zhao, Hakan Usta, Antonio Facchetti
This paper reports the design, facile synthesis and purification of four π-conjugated donor-acceptor small molecules comprising heteroaromatic units, DA-1–DA-4, for surface and electronic structure modification of gold thin film. These molecules were characterized by ¹H/¹³C nuclear magnetic resonance spectroscopy, cyclic voltammetry, UV–Vis spectroscopy, and single-crystal X-ray diffraction. Morphologically smooth thin-films (~5nm) of DA-1–DA-4 were deposited onto Au thin films via thermal evaporation and characterized by atomic force-microscopy, θ–2θ X-ray diffraction and ultraviolet photoelectron spectroscopy. The work functions of the small molecule coated Au electrodes are shifted to lower energies by ~0.1–0.3eV, compared to that of the bare Au film measured as a reference. The vapor-deposition of structurally simple small molecules developed here shows great promise as a facile approach to reduce gold work function for electron injection/extraction between organic semiconductors and Au contacts in various opto-electronic devices.