This book intends to publish the concept of the sharp lined red emitting phosphors based on polyborate materials for light emitting application. The basic needs of red emitters for white light emission are explained on the basis of the history of light emission. The spectroscopic behavior and the color characteristics are discussed in details for different kinds of polyborate materials. The occurrence of charge transfer band and its effect on LEDs has also been explained in the book. And the best polyborate material has been proposed on the basis of thermal stability and color purity for red light emission. The process of fabrication of LED is also incorporated elaborately. White light emitting diodes are fabricated using the previously developed red emitter and the enhancement in color rendering and improvement in color temperature are discussed in this book. And finally the book will reveal not only the best materials for red emission in white light emitting diodes, but also the basics knowledge of the fabrication of LEDs and phosphors.