Researchers, engineers and students engaged in researching/teaching PEC cells or knowledge of our sun, its energy, and its distribution to the earth will find essential topics such as the physics of semiconductors, the electrochemistry of semiconductors, p:n junctions, Schottky junctions, the concept of Fermi energy, and photochromism and its industrial applications. "The topics in this book are explained with clear illustration and indispensable terminology. It covers both fundamental and advanced topics in photoelectrochemistry and I believe that the content presented in this monograph will be a resource in the development of both academic and industrial research". , President, Tokyo University of Science, and Director, Photocatalysis International Research Center, Tokyo University of Science, Japan