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

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 AlxZn1-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 epsilon(1)(omega) and imaginary part 32(omega) of dielectric function were investigated. The epsilon(2)(omega) and epsilon(1)(omega) 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.