(85f) Designing Copper Zinc Oxide as a P-Type Transparent Conducting Oxide for Photovoltaic Applications

Transparent conducting oxides (TCOs) are electrically conductive materials that are used in thin-film opto-electronic applications, such as solar cells, but major improvements in performance and cost are necessary for TCOs to be used on a commercial scale. We present Copper-doped Zinc Oxide as a low-cost TCO candidate.  We determined how the electrical transport properties and optical properties vary with composition by performing density functional theory calculations, including gradient-corrected, hybrid, and Green’s functions.  With increasing Cu concentration (x), the band gap of Copper-doped Zinc Oxide (Zn_1-xCu_xO) decreases due to the down shift of the valence band. However, the optimal value of x is determined by the balance between the increase in electrical conductivity and the decrease in optical absorption.  We also compare our results to ternary oxides formed from zinc and copper, and discuss strategies for designing materials with desirable properties.