We report almost perfectly vertically aligned ZnO nanorod arrays synthesized by the hydrothermal route at considerably lower temperature on a sputtered Al:ZnO seed layer using different growth strategies. The nanorod arrays demonstrate remarkable alignment along the c-axis over a large area. Several barrier layers, such as ZnO, Al2O3, BaTiO3 and SiO2, were introduced to form the p-i-n junction to reduce the leakage current. The photocurrent is significantly reduced in nanorod arrays on AZO/SiO2/p-Si heterojunction due to multiple scattering phenomena from ZnO hexagonal facets associated with the nanorod arrays. This research may open up venues for various optical and opto-electronic applications where highly aligned nanostructures are desired. (C) 2012 Elsevier B.V. All rights reserved.