Approach using the electrical structure and optical properties of aluminium-doped zinc oxide for solar cells

Abstract

Aluminium-doped zinc oxide (AZO) is attracting a continuously increasing amount of attention because of its potential as a solar cell material. To analyze the effect of the concentration of doped Al (set as x) on AZO, we investigated properties such as band structure, electronic conductivity, absorption and reflectivity under different doping concentrations by using a first-principles method based on density functional theory (DFT). The results demonstrated Al_xZn_1−xO (for x = 0.0625, 0.125, or 0.1875) to be an n-type degenerate semiconductor. The band gaps as well as electric conductivities decreased as x was increased. Meanwhile, the real part ε₁(ω) and imaginary part ε₂(ω) of dielectric function were investigated. The ε₂(ω) and ε₁(ω) were only slightly different with those of pure ZnO and positioned at higher energy direction in the concentrations of 0.0625 and 0.125, while yielded lower energy directions as x increasing to 0.1875. The reflectivity was found to be lowest for x = 0.125. This result may provide a theoretical reference for solar cells based on Al-doped n-type ZnO.