This volume is devoted exclusively to the interfacial photoelectronic properties of the inorganic layered semiconductors investigated in solid state (Schottky and p-n) photovoltaic and photoelectrochemical (solid/electrolyte) cells. The results of extensive studies on the various interfacial and surface electronic characteristics, interfacial photoreactions and materials aspects of the layered semiconductors reported in the last fifteen years have been reviewed. The layered transition metal dichalcogenides have served as model compounds for the investigation of the details of photoelectrochemical processes and related studies involving surfaces. The layered semiconducting materials have been found to be promising solar cell materials. Significant energy conversion efficiencies have been realized in photoelectrochemical solar cells and in solid state photovoltaic cells. Novel studies including quantum size effects in layered semiconductors have been reported. UHV spectroscopic studies of the surfaces of important layered semiconductors have been given. Recent developments in the preparation of the layered materials have been summarized. New insights into the physical and chemical characteristics of this class of materials have been gained by the studies reported in this book. Highlights include: -- Data on optical and electronic properties of layered semiconductors; -- Solid state and semiconductor/electrolyte junction characteristics; -- Photovoltaic and photoelectrochemical solar cells based on layered materials; -- UHV spectroscopic studies of surfaces of layered semiconductors; -- Quantum size effects in layered semiconductor colloids; -- Novel layered material preparation techniques.