An introduction to the physics of the photovoltaic cell. It should appeal to undergraduate physicists, graduate students and researchers who want an introduction to the subject. The text covers the ground from the fundamental principles of semiconductor physics to the simple models used to describe solar cell operation. It presents theoretical approaches to efficient solar cell design as well as the features of the main practical types of solar cell. A set of exercises and worked solutions dealing with the text are included to aid in assimilation and teaching. It should enable the reader to understand how solar cells work, to be familiar with the terms and concepts of solar cell device physics, and to formulate and solve relevant physical problems.