Defect Chemistry of Novel Transparent Conductors

The combination of optical transparency and metallic-like conductivity in a single material is unusual, such that only a handful of transparent conductors have been discovered in the last century. However, they play a crucial rôle as transparent electrodes in the operation of modern devices such as display screens and solar cells. The increasing ubiquity of opto-electronic technology therefore motivates the continued development and discovery of transparent conductors. This work uses computational methods to investigate the defect chemistry and rationalise the performance of a wide variety of transparent conducting materials. The insights from this project will guide the optimisation of existing technologies through alternative doping strategies, and act as a stepping stone towards the development of new materials for transparent conducting applications. An overview of the electronic structure requirements and some applications of transparent conducting materials are offered in Chapter 1. Next, the computational theory that enables the calculation of electronic structure is presented in Chapter 2, followed by a section on methodology and implementation in Chapter 3. Chapter 4 introduces a selection of post-transition metal oxides (ZnO, In₂O₃, Ga₂O₃ and ZnSb₂O₆) as n-type transparent conductors and investigates doping strategies for achieving metallic-like conductivity. This is followed by Chapter 5, which examines CaCuP and CuI as potential p-type transparent conductors, with a focus on their defect chemistry (specifically the copper vacancy) and charge transport behaviour. Finally, p-type doping strategies are considered in the transparent perovskite BaSnO₃ in Chapter 6, followed by a summary of the results and suggestions of future work in Chapter 7