This book provides a semi-quantitative approach to understanding and applications of charge carriers in inorganic and organic opto-electronic and photonic devices. Featuring contributions by noted experts in the field of optoelectronics, materials and photonics, this book describes the importance of charge carriers in the operation of optoelectronic and photonic devices of both inorganic and organic semiconductors. An Introduction to Charge Carriers starts with the concept of charge carriers and their involvement in a few inorganic and organic devices, like solar cells and organic light emitting diodes (OLEDs), including those based on thermally activated and delayed fluorescence (TADF). Then it discusses the applications of charge carriers in silicon p-n junction, nanomaterials, wurtzite phases of gallium, aluminium and indium nitride devices, ion conducting polymer electrolytes, rare-earth doped glasses, organic photodetectors, and several aspects of organic and perovskite solar cells. An Introduction to Charge Carriers is an ideal book for senior undergraduate and postgraduate students and teaching and research professionals in the field of solid-state physics, material science and engineering.