An accessible and pedagogical introduction to photovoltaics, Harvesting Sunshine presents the solar cell as a multifaceted device that can be viewed as an electronic energy converter, an absorber and emitter of light, and a thermodynamic heat engine, while also outlining its links with the most ancient of solar energy converters: photosynthesis. Beginning with a simple introduction to photovoltaics, suitable as a stand-alone basic primer, the text goes on to explain the solar cell operation in more detail, outlining the electrical characteristics linked to the balance and reciprocity between electrical currents across a semiconductor junction. At a more fundamental level, the book then looks at the Shockley-Queisser limit and its physical foundations, underpinned by Kirchhoff's and Planck's radiation laws linked by photon recycling, moving the discussion into the realm of thermodynamics. A thermodynamic analysis of thermalization reveals an intimate link between the photovoltaic and thermoelectric energy conversion. A discussion of ultimate limits leads to the Landsberg efficiency, and provides a basis for exploring next-generation devices, such as multispectral converters and hot-carrier solar cells. With focus on basic concepts, Harvesting Sunshine explains how solar cells work using simple calculations, illustrated by exercises. The book requires no specific prerequisites other than those acquired in most undergraduate courses in physics, chemistry, or engineering, and will be of interest to all students with an interest in delving deeper into the foundations of photovoltaics.