Π-Conjugated Donor-Acceptor Small Molecule Thin-Films on Gold Electrodes for Reducing the Metal Work-Function

Abstract

This paper reports the design, facile synthesis and purification of four pi-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 H-1/C-13 nuclear magnetic resonance spectroscopy, cyclic voltammetry, UV-Vis spectroscopy, and single-crystal X-ray diffraction. Morphologically smooth thin-films (similar to 5 nm) of DA-1-DA-4 were deposited onto Au thin films via thermal evaporation and characterized by atomic force microscopy, theta-2 theta X-ray diffraction and ultraviolet photoelectron spectroscopy. The work functions of the small molecule coated Au electrodes are shifted to lower energies by similar to 0.1-03 eV, 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. (C) 2016 Elsevier B.V. All tights reserved.