Compound semiconductors have long been an integral part of everyday life. Recent progress on their potential as emitters, sensing devices in biological and chemical environments, and high-efficiency power devices demonstrates their impact on energy and environment. Compound-semiconductor-based photovoltaic systems are emerging as an economical means of generating renewable energy through the use of concentrator technologies. However, while solid-state lighting devices have shown energy-saving and environmental benefits, much still needs to be done to realize their full potential. This book contains reports from internationally known experts on the state of compound-semiconductor-based devices with application in environmental conservation and energy saving challenges. Topics include: compound semiconductors for PV applications; compound semiconductors for lighting; compound semiconductors for lighting, power and sensing; compound semiconductors for energy; compound semiconductors for sensing; and materials growth and characterization. An appendix, with select papers from Symposium S, Materials in Photocatalysis and Photochemistry for Environmental Applications and H2 Generation, is also included in the book.