Atomic layer deposition of materials for solar water splitting

The atomic layer deposition (ALD) is not only an ultrathin film technology used in semiconductor industries. Lately, it has been found in many applications in the renewable energy field due to its precise control of thickness of up to a few angstroms and its unique characteristic of grown conformal and uniform films in any 3D structure of random geometry. ALD has long-range applications in this field, including electrochemical storage, fuel cells, photovoltaic solar energy, and photoelectrochemical (PEC) water splitting to produce hydrogen as a green fuel. In PEC water splitting, ALD is now being extensively used as an efficient tool to deposit surface passivation layers, absorber, and barrier and buffer layers in several kinds of PEC cells. This chapter aims to briefly review PEC technology, as well as to introduce the main ALD-based materials used to improve the solar-to-hydrogen efficiency that help to make this technology commercially viable.