The chapter discusses the development and challenges of photoelectrochemical (PEC) devices for solar water splitting, aiming to convert sunlight into chemical fuels. It highlights the importance of efficient semiconductor materials and low-cost, earth-abundant co-catalysts to enhance the performance of PEC devices. The review covers fundamental aspects of semiconductor properties, charge transfer processes, and various configurations of PEC devices, including single and multi-light-absorber systems. Recent advancements in photoelectrode materials and electrocatalysts are discussed, along with key factors affecting photoelectrode performance, such as light absorption, charge separation, transport, and surface chemical reaction rates. The text emphasizes the need for controlling semiconductor properties to improve the efficiency and stability of PEC devices, and outlines strategies for addressing these challenges, including smart architectures, innovative device design, co-catalyst loading, and surface protection layer deposition. The chapter also provides an overview of the principles of PEC water splitting, including semiconductor band-bending and the space charge region, and discusses the energy and quantum conversion efficiencies of PEC devices. Finally, it reviews promising photoanode materials, such as TiO2, α-Fe2O3, BiVO4, CdS, and Group III-V compounds, and strategies to enhance their performance.The chapter discusses the development and challenges of photoelectrochemical (PEC) devices for solar water splitting, aiming to convert sunlight into chemical fuels. It highlights the importance of efficient semiconductor materials and low-cost, earth-abundant co-catalysts to enhance the performance of PEC devices. The review covers fundamental aspects of semiconductor properties, charge transfer processes, and various configurations of PEC devices, including single and multi-light-absorber systems. Recent advancements in photoelectrode materials and electrocatalysts are discussed, along with key factors affecting photoelectrode performance, such as light absorption, charge separation, transport, and surface chemical reaction rates. The text emphasizes the need for controlling semiconductor properties to improve the efficiency and stability of PEC devices, and outlines strategies for addressing these challenges, including smart architectures, innovative device design, co-catalyst loading, and surface protection layer deposition. The chapter also provides an overview of the principles of PEC water splitting, including semiconductor band-bending and the space charge region, and discusses the energy and quantum conversion efficiencies of PEC devices. Finally, it reviews promising photoanode materials, such as TiO2, α-Fe2O3, BiVO4, CdS, and Group III-V compounds, and strategies to enhance their performance.