Photoelectrochemical (PEC) water splitting is a promising technology for converting solar photons to H2 fuel, which is carbon-free and suitable for transportation, storage, and consumption. The PEC reactions for water splitting are driven by successive processes such as light absorption, generation of electron-hole pairs, separation of the generated charges and charge transfer to the electrolyte. In order to address each of these aspects, as well as to prevent (photo-)chemical corrosion of the electrodes, the development of multi-layered structures consisting of various functional layers is generally required (e.g. light-absorbing semiconductors, selective contacts, protective layers, and catalysts).