Thin-film compound semiconductor photovoltaic solar cells have demonstrated efficiencies of nearly 20% and are leading candidates to provide lower-cost energy due to potential advantages in manufacturing and materials costs. To fulfill the promise, a number of technical issues are being addressed, including a lack of fundamental understanding of these unique materials, devices and processes for large-area deposition. This book focuses on advances in the materials science, chemistry, processing and device issues of thin-film compound semiconductor materials that are used, or have potential use, in photovoltaic solar cells and related applications. Topics include: growth and performance of compound thin-film solar cells; novel materials and processes; defects and impurities; industrial perspectives; contacts and interfaces; grain boundaries and inhomogeneities; and structural, optical and electronic characterization.