Electronic Structure, Defect Formation Energy, And Photovoltaic Properties Of Wurtzite-Derived Cugao2

Wurtzite-derived CuGaO2 (beta-CuGaO2) is a recently synthesized oxide and expected as a candidate material for photovoltaic solar cells. In this paper, we propose computational material design concerning beta-CuGaO2 based on the first-principles calculations. We perform hybrid calculations by using the VASP code. It is predicted that beta-CuGaO2 has a direct bandgap (E-g = 1.56 eV), which is nearly optimal for high efficiency solar cells. The calculated formation energy of Cu vacancy (V-Cu) is very small and can be negative depending on the Fermi level. This result reasonably explains the observed p-type conduction in this material. As for the n-type doping, Cd doping could be suitable; however, VCu formation needs to be repressed in order to realize n-type beta-CuGaO2. It is also shown that halogen impurities are not suitable for n-type beta-CuGaO2 because of their large formation energy. Band alignment between beta-CuGaO2 and ZnO is predicted to be type-II, leading to a suggestion of photovoltaic device based on the heterojunction. Published by AIP Publishing.