Graphene has many unique properties that have generated tremendous interest in the scientific community and make it suitable for several applications. The tuning of graphene's Fermi level by the modulation of its charge carriers is an important factor in determining the successful operation of electronic/optoelectronic devices.This book focuses on different methods of performing carrier modulation in graphene and the application of doped graphene in diodes, field-effect transistors, solar cells, transparent conducting electrodes, and supercapacitors. It discusses the current status of the research and development in graphene and will be helpful for readers who want to know about graphene and its applications and also other 2D nanomaterials.