This book covers the basic principles and applications of photonic interactions for solar energy conversion (i.e., "solar photonics"). It begins with an overview of device texturing, light concentration, bandgap engineering, and other classical techniques for light trapping. It explains their limitations and then discusses essential nanophotonic approaches that allow for enhanced light absorption and energy extraction. It shows how plasmonic materials and metamaterials are used in photovoltaics and photocatalysis. Computational and experimental examples illustrate the breakthrough efficiency enhancements achievable.