This book highlights the synthesis, luminescence, and applications of rare earth-doped phosphors materials for solid-state lighting. Solid-state lighting is turning into a leading technology in the lighting industry, permitting improvement in the fields from architectural to domestic applications. Driven with the aid of using ongoing multi-field research, solid-state lighting needs an improvement of various technologies: efficient and reliable light-emitting devices, devices for new functionalities, and optical solutions for beam shaping. Noteworthy research endeavors were aimed to find out eco-friendly, better performance, cost, and energy-efficient phosphor materials for the application in solid-state lighting devices. Power phosphor materials with advanced optical and photoluminescence properties in a wide range of areas have shared the research efforts in this sector aimed in the direction of achieving better material features. Rare earth ion-doped phosphor materials have been the subject of scientific interest because of their significant applications in a variety of fields such as display devices, temperature sensors, solar cells, bio-imaging, and optoelectronics devices. This book covers the broad aspects of organic and inorganic materials based on phosphor materials and is beneficial to researchers involved in these areas. This book is specially designed to provide an introductory concept of luminescent materials, particularly man-made (artificial) phosphors in a language comprehensible to beginners and students. The book also includes some new materials with promising technologies and upgraded properties that expose new potential possibilities are also highlighted.