This review discusses the development of photoelectrochemical (PEC) devices for solar water splitting, focusing on materials and challenges. It begins with an understanding of semiconductor properties and charge transfer processes in PEC devices. Various configurations of PEC devices, including single light-absorber cells and multi-light-absorber devices (PEC, PV-PEC, and PV/electrolyser tandem cells), are described. Recent progress on photoelectrode materials (light absorbers) and electrocatalysts is summarized, along with important factors that dominate photoelectrode performance, such as light absorption, charge separation and transport, surface chemical reaction rate, and the stability of the photoanode. Strategies to address challenges in materials development, such as smart architectures, innovative device configuration design, co-catalyst loading, and surface protection layer deposition, are outlined to deliver a highly efficient and stable PEC device for water splitting. Key learning points include the fundamental aspects of semiconductor physics and the behavior of photoexcited carriers during PEC water splitting processes, the design concept of different configurations in an efficient PEC device and criteria for evaluating PEC water splitting performance, the most important photoanode/photocathode materials developed to date (e.g., TiO₂, BiVO₄, Fe₂O₃, CdS, Cu₂O, Si and III-V materials), the most important earth-abundant co-catalysts/electrocatalysts developed recently, and combination strategies for highly efficient and stable photoelectrodes. The review discusses the principles of PEC water splitting, including semiconductor band bending and the space charge region, and the processes involved in PEC water splitting. It covers the energy and quantum conversion efficiencies of PEC cells, the importance of photoelectrode materials, and the challenges in developing efficient and stable PEC devices for solar water splitting. The review also highlights the potential of various materials, such as TiO₂, α-Fe₂O₃, BiVO₄, and CdS, for PEC water splitting, along with strategies to improve their performance. The review concludes with the importance of developing efficient and stable PEC devices for solar water splitting to achieve sustainable energy solutions.This review discusses the development of photoelectrochemical (PEC) devices for solar water splitting, focusing on materials and challenges. It begins with an understanding of semiconductor properties and charge transfer processes in PEC devices. Various configurations of PEC devices, including single light-absorber cells and multi-light-absorber devices (PEC, PV-PEC, and PV/electrolyser tandem cells), are described. Recent progress on photoelectrode materials (light absorbers) and electrocatalysts is summarized, along with important factors that dominate photoelectrode performance, such as light absorption, charge separation and transport, surface chemical reaction rate, and the stability of the photoanode. Strategies to address challenges in materials development, such as smart architectures, innovative device configuration design, co-catalyst loading, and surface protection layer deposition, are outlined to deliver a highly efficient and stable PEC device for water splitting. Key learning points include the fundamental aspects of semiconductor physics and the behavior of photoexcited carriers during PEC water splitting processes, the design concept of different configurations in an efficient PEC device and criteria for evaluating PEC water splitting performance, the most important photoanode/photocathode materials developed to date (e.g., TiO₂, BiVO₄, Fe₂O₃, CdS, Cu₂O, Si and III-V materials), the most important earth-abundant co-catalysts/electrocatalysts developed recently, and combination strategies for highly efficient and stable photoelectrodes. The review discusses the principles of PEC water splitting, including semiconductor band bending and the space charge region, and the processes involved in PEC water splitting. It covers the energy and quantum conversion efficiencies of PEC cells, the importance of photoelectrode materials, and the challenges in developing efficient and stable PEC devices for solar water splitting. The review also highlights the potential of various materials, such as TiO₂, α-Fe₂O₃, BiVO₄, and CdS, for PEC water splitting, along with strategies to improve their performance. The review concludes with the importance of developing efficient and stable PEC devices for solar water splitting to achieve sustainable energy solutions.