Effects of charge rearrangement on interfacial contact resistance of TiO2/graphite from first-principles calculations.

The results show that the Schottky barrier depends on the charge distribution induced by graphite. When the charge depletion and accumulation layer are mainly distributed in the space-charge region, the contact resistance is determined by the conductivity of the doped TiO 2. For example, the n-type Schottky barrier is formed between graphite and the n-type of Sb-doped TiO 2. In the contrast, if the charge rearrangement occurs in the heterojunction as a whole, the contact resistance relies on the electronic injection of graphite. For instance, the n-type Schottky barrier is formed between graphite and the p-type of Ge-doped TiO 2. We hope that the formation mechanisms and the control strategies of the contact resistance between titanium oxides and graphite can be used to develop new materials with a high conductivity. [Display omitted] • The effects of thirty-five metallic dopants on the interfacial contact resistance and electrical conductivity of TiO 2 /graphite were studied. • The effects of charge rearrangement on interfacial contact resistance of TiO 2 /graphite is revealed. The contact resistance is significantly affected by the charge rearrangement. • Graphite has a good conductivity because the Fermi-Dirac cone is not destroyed in the heterojunctions. Titanium bipolar plates have been widely employed in fuel cells, due to the high resistance achieved by the oxide film (TiO 2). However, that also results in high interfacial contact resistance between the titanium and the gas diffusion layer of graphite, reducing the cells' efficiency significantly. To improve the conductivity properties, the effects of thirty-five metallic dopants on the contact resistance and electrical conductivity were studied based on the first-principles merged with the Schottky-Mott theory and Boltzmann transport equation. The results show that the contact resistance depends on the charge distribution induced by graphite. The contact resistance depends on the conductivity when the charge depletion and accumulation layer are distributed in the space-charge region. If the charge rearrangement occurs in the heterojunction as a whole, the contact resistance is determined by the electronic injection. In addition, the single conduction path between titanium, oxygen and graphite atoms disappears in the TiO 2 doped with Zn, Cd, etc., because those dopants have stronger electron affinity in the heterojunction. While a stronger built-in electric field is formed that can further enhance the electronic conductivity. [ABSTRACT FROM AUTHOR]