Zinc oxide has a large energy gap and thus it has potential application in the field of solar cells by tuning the absorption of sunlight.In order to enhance its absorption of sunlight,dark color zinc oxides have been prepared by traditional hydrothermal method directly using a zinc foil as both source and substrate.We found that we could tune the optical properties of ZnO samples by changing the temperature.In particular,increasing temperature could significantly reduce the reflectivity of solar energy in the visible range.We speculate that the phenomenon is relevant to the sharp cone morphology of the ZnO nanorods grown on the surface of Zn foils,which furthermore enhance refraction and reflection of light in the nanorods.The capacity to improve the light absorption of ZnO may have a bright application in raising the efficiency of solar cells.