This book elucidates the concepts and innovative models around prospective developments with respect to photodetectors. It talks in detail about the various concepts and theories related to this subject. Photodetectors refer to the sensors that sense light and electromagnetic energy. It has various types like polarization photodetector, photoemission photodetector, photovoltaic, and photochemical photodetectors, etc. The aim of this text is to equip students with the fundamental techniques and methods used in this area. Most of the topics introduced in the book cover new techniques and the applications of photodetectors. Through this book, we attempts to further enlighten the readers about the new concepts in this field. Coherent flow of topics, student-friendly language and extensive use of examples make this textbook an invaluable source of knowledge.