This is an intermediate course directed at developing a thorough understanding of the operation of semiconductor p-n junctions and hence solar cells. Emphasis is upon developing an understanding of the relevant properties of semiconductors and how these affect the photovoltaic properties of solar cells. Based on the understanding of cell properties developed in the first half of the course, the second half of the course explores design, fabrication and operational issues relevant to the photovoltaic technologies of current interest: silicon, III-V compound, cadmium telluride, copper indium selenide, amorphous silicon and nanocrystalline dye cells.