The increasing world population and expanding economy demand a steady and reliable power supply. Most of the power supply comes from fossil fuels, raising concerns regarding environmental issues, natural disasters, and diseases. Therefore, the search for alternative fuel is highly crucial, and timely essential to save our planet. The United Nations (UN) declared the SDG goal 2030, whereas goal 7 emphasized the use and accessibility of clean and sustainable energy technologies. For instance, hydrogen fuel could be considered a blessing to achieve this goal due to its lightweight atom, requiring less energy to dissociate from naturally abundant water sources, high energy density comparable to fossil fuel, and zero emission. At present, hydrogen fuel is mainly produced through non-renewable routes such as steam methane reforming, nuclear energy, coal gasification, and other hydrocarbon. In contrast, all methods are neither eco-friendly nor sustainable. Hence, the available suitable options are electrolysis or photolysis of water to produce eco-friendly hydrogen fuel. The electrolysis of water requires a semiconductor, where electrical power serves as the input energy to split water and produce hydrogen. It should be noted that the semiconductor used in this process is called an electrocatalyst. Although the production of hydrogen fuel through electrocatalyst is clean and environmentally safe, the direct consumption of electrical energy is not considered a viable option. On the other hand, solar-driven hydrogen production, also known as solar water splitting, photolysis of water, or photoelectrochemical (PEC) water splitting, is regarded as a promising approach, attracting researchers and scientists worldwide. PEC water splitting requires only a semiconductor (serve as a photocatalyst), a counter electrode, and water. When sunlight strikes the (either n-type or p-type) semiconductor surface, it generates electron–hole pairs, which are efficiently separated. The charge carriers flow through an external circuit to the counter electrode, leading to the production of hydrogen fuel. Here, the most important work is to develop an efficient semiconductor that can absorb a large portion of the light, split the water, and achieve the benchmark solar-to-hydrogen (STH) conversion efficiency. Since the invention of PEC hydrogen production, numerous semiconductor materials extensively explored to reach the benchmark efficiency but no semiconductor achieved the goal till now because of various limitations such as large bandgap, unavailability, slower oxygen evolution reaction kinetics, and less stability. In this chapter, we discussed the fundamental principles of PEC solar water splitting, focusing on both three-electrode and two-electrode system mechanisms. We also explored the various semiconductor material, synthesis methods for various semiconductor nanostructures, along with their modification techniques and inherent limitations. Additionally, an overview of solar-to-hydrogen (STH) evaluation techniques also provided, offering valuable insights for beginners and researchers into PEC materials.