This book covers topics related to photovoltaic generations, its unique scientific ideas and technical solutions. Issues related to the capability of solar cells and the hydrogen productions in photoelectrochemical solar cells have also been discussed. Usage of advanced materials, like the oxide of copper as an active substance for solar cells, InP in solar cells with MIS arrangement, AlSb for use as an absorber layer, among others, have been discussed. Furthermore, other significant topics such as the analysis of both the status and prospects of organic photovoltaics such as polymer/fullerene solar cells, poly (p-phenylene-vinylene) derivatives, etc. have also been included.