Improved optical transmittance of Al-doped ZnO thin films by use of ZnO nanorods

We have investigated the optical transmittance of Al-doped ZnO films improved by the use of ZnO nanorods prepared by the aqueous chemical growth method. In this study, ZnO nanorods were synthesized on the Al doped ZnO transparent conducting oxide layer. The length and diameter of the rods were controlled by the OH− concentration of hexa-methenamine in the solution. The transmittance of Al-doped ZnO films with post-grown ZnO nanorods is clearly improved at wavelengths between 400 and 850 nm by modulating the air volume ratio of the rod densities and by the variation in the diameter of the rods. In this study, the resultant refractive index of ZnO nanorods with varied diameters is also evaluated by using the effective medium approximation. In our further study, this approach may be used to improve the optical transmittance of the transparent conducting electrodes used in optoelectronics, such as amorphous Si thin film solar cells, for increasing the short-circuit current density at the specific wavelength region.