This book gives a comprehensive view of ?-conjugated light-emitting semiconductors, including conventional fluorescence materials and the new generation of high-efficiency organic emitters capable of competing against organometallic phosphors in device efficiency. After an introduction to the fundamentals of organic semiconductors, this book discusses different kinds of organic light-emitting semiconductors, classified according to their radiation mechanisms. The topics covered in detail in this book include conventional fluorescence materials and devices, triplet-triplet annihilation, radical emitters with doublet characteristics, room temperature organic phosphorescence, organic chromophores with aggregation-induced emission properties, solution-processed polymer light-emitting materials and devices, and more. The book explicitly discusses the principles and processes of light-emitting diodes, transistors, and laser diodes. In today's technologically evolving world, this book is a must read for understanding the latest information on organic light-emitting semiconductors.