The effect of gold interlayers on the interfacial electronic structure of copper phthalocyanine/indium tin oxide

Gold (Au) nanoparticles have been frequently used in the optoelectronic devices owing to their surface plasmon resonance properties. In this article, the electronic structures at copper phthalocyanine (CuPc)/indium tin oxide (ITO) interface with/without Au oxides interlayers have been investigated using ultraviolet photoelectron spectroscopy (UPS). Based on the UPS data, the interfacial energy levels between CuPc and ITO are aligned with/without the presence of Au interlayers. The experimental results indicate that the height of the hole injection barrier from ITO to CuPc decreases from 0.44 eV to 0.22 eV owing to the existence of 0.5 nm Au oxides layers. The electrical conductivity may also increase at the CuPc/ITO interface due to the insertion of Au layers possessing rather high electrical conductivity.