There is an alarming increase of energy issues due to significant fossil fuel consumption. Some progress has been made to replace fossil fuels with renewable sources, among which, solar energy has always been considered as the ultimate solution to solve these problems. As a relatively new evolved type of solar cell, Dye-sensitized solar cells (DSSC), have been investigated intensively in recent years and they are very promising for their cost-effectiveness properties. Zinc oxide (ZnO) is one of best candidates for DSSC due to its low cost and high electron mobility, amongst others. In this thesis, highly branched ZnO nanostructures are synthesized with biologically inspired methods to control the crystal growth and the mechanism by which these grow are investigated. Further explorations of the structure-function relationships reveal potential pathways towards the improvement of DSSC performance.Besides DSSC, it is necessary to transform the solar energy to storable energy so it can be utilized during the night. Titanium dioxide (TiO2) for hydrogen generation through photoelectrolysis is one of the most promising candidates. We synthesize TiO2 nanowire arrays by homoepitaxial growth on templates, and precisely control the nanostructured properties such as nanowire diameter, length, density, etc.. In addition, photoelectrochemical performance has been conducted on TiO2 thin films with different nanostructures to investigate structure-function relationships.Another significant concern involves environmental pollution due to the discharge or emission of a variety of new chemicals, which are threatening environmental and public health. ZnO, as a photocatalytic material, can effectively degrade organic pollutants without byproducts. In this work, we utilized biologically inspired methods to template the synthesis of Zn-organic compound materials using organic scaffolds. The complex material was heat-treated to produce a ZnO-carbon composite material. The processing conditions have been extensively studied and it has been demonstrated that the composite material can effectively improve the photocatalytic performance versus carbon-free ZnO nanostructured materials.