Diverse sources of energy are becoming increasingly significant in today's world. The most common source of energy today is fossil fuels, such as coal, oil, and gas. While this energy source has many advantages, it also comes with many problems. In order to meet this demand, environmentally friendly and sustainable alternatives to energy are urgently needed. Renewable energy such as hydro, wind, photovoltaics, biomass, and geothermal is an attractive and promising kind of energy. Solar energy is among the most efficient, cleanest, and cheapest sources of energy. In this thesis, two photoprocesses are utilized to produce solar energy using nanostructured materials. One is photocatalysis, mainly photoelectrochemical (PEC) water splitting for hydrogen production and photodegradation of organic dyes, and another is a sunlight-powered photovoltaic cell.In this thesis, we aim to demonstrate optimized low-cost sustainable electrodes based on nanostructured materials for solar energy applications. For PEC water splitting two materials namely ZnO NRs and CuO NLs are fabricated by hydrothermal methods followed by deposition of different materials such as Ag2WO4 and AgBr. These materials show relatively high PEC water splitting efficiency using sunlight. Similarly, for the photodegradation of II organic dyes Ta2O5 is used with the addition of Ag/AgCl nanoparticles (Ag/AgCl NPs), which results in an effective plasmonic photocatalyst for the removal of water-soluble Congo red (CR) dye compounds. For high-efficiency solar cells two methods are applied. Firstly, a FDTD simulation method was applied to study the plasmon enhancement of light absorption from p-i-n junction GaAs nanowires. Secondly a study of anisotropic deformation of colloidal particles exposed to heavy ions irradiation. Finally, a novel low-cost template-assisted method was used in order to improve the alignment of ZnO NRs grown on Si substrates.