Effects of growth duration on the structural and optical properties of ZnO nanorods grown on seed-layer ZnO/polyethylene terephthalate substrates

► ZnO nanorods were well-formed for up to 5 h, but leaned and agglomerated after 5 h of growth. ► The structural and optical properties of ZnO nanorods were improved after 5 and 6 h, respectively. ► The growth properties of ZnO nanorods are dependent on growth duration in hydrothermal method.