Understanding the properties of the interface between graphene and transition metal oxide thin films using first principle approaches

Abstract

Recently, carbonaceous nanomaterials such as carbon nanotubes and two-dimensional graphene have attracted the attention of the scienti c community in probes to improve energy conversion and storage technologies. The graphene sheet is preferred due to its large speci c area, exible structure, high transparency, excellent mobility of charge carriers and is expected to be able to slow the charge recombination. Graphene/transition metal oxides nanocomposite study has become much of a wide interest recently with metal oxides like TiO2, ZnO, SnO2, etc. These metal oxides are used as thin lms in photovoltaic technology to harness energy. The nal composite embodies both the transport properties of the former and the semiconducting properties of the latter species. This work describes an analysis of the electronic and optical properties of the nal composite studied using the Density Functional Theory (DFT) in application to dye-sensitized solar cells (DSSCs). The study aims to slow charge recombination in DSSCs and improve the e ciency of the cell. The geometry optimizations for the electronic and optical properties were performed by the rst principle calculations based on density functional theory. Various supercells of graphene were modelled and, optimized and their properties were calculated. The results show that different graphene supercells have di erent electronic and optical properties. When graphene is incorporated into a brookite TiO2, the composite results show a reduced energy band gap compared to that of a brookite TiO2 without a graphene on it. The optical properties showed graphene/TiO2 increases absorption in the infrared region.