Optical properties of undoped and Al-doped ZnO nanostructures grown from aqueous solution on glass substrate

The paper presents the optical properties of undoped and aluminium-doped zinc oxide nanostructures grown on glass substrates using the hydrothermal method. The obtained ZnO-based nanostructures showed optical transmittance over 75% and low reflectance in the visible domain. The increasing of optical transmittance of Al-doped ZnO nanostructures with increased doping concentrations was observed. The optical constants such as index of refraction, extinction coefficient, dielectric constants and optical conductivity were determined using the transmission and the reflection at normal incidence of light in the wavelength range of 200–1100 nm. The band gap broadens with increasing dopant concentration from 2% to 4%. The obtained nanostructured layers with size in the range of subwavelength of visible light can act as anti-reflective coating that reduces reflectance based on the Moth Eye principle.

► The Al doping affects the morphology and optical properties of ZnO-based 1D nanostructures.
► Optical transmittance of Al-doped ZnO nanostructures increases when increasing Al doping.
► Band gap broadens if the doping concentration increases.
► Blueshift of the absorption edge of ZnO with increasing Al doping.
► The obtained nanostructured layers can act as anti-reflective coating.