It gives me immense pleasure to introduce readers a book about chalcogenides (especially, sulphides and their composites), their physical properties as well as possible applications. Interesting and fascinating material properties of II-VI, V-VI semiconductor compounds and their composites for futuristic developments of photosensors have been put forth in this book. This book is an outcome of author s extensive research experience and rigorous studies in chalcogenide thin films, photosensor, opto-electronic, and solar cell device applications.