305 Copyright © 2018, IGI Global. Copying or distributing in print or electronic forms without written permission of IGI Global is prohibited. Chapter 9 DOI: 10.4018/978-1-5225-5170-6.ch009 ABSTRACT Considering the imminent global energy crisis and inefcient energy utilization, energy-efcient organic light-emitting diodes (OLEDs) are considered one of the most competitive candidates for displays and particularly for future energy-saving lighting sources. Full color displays require all primary colors: red, green, and blue (RGB). In recent decades, numerous phenanthroimidazole (PI) RGB-emitting materials have been developed for efcient OLEDs. In organic electronics, considerable interest is shown on PI, due to ease in fuorophore modifcation. This chapter focuses on the design and synthesis of PI-based materials and their applications in OLEDs. At frst, some nondoped blue, green, and yellow fuorescent materials are comprehensively studied. Then attention has been paid for typical blue, green, yellow, orange, and red PhOLEDs of PI-based fuorophores as a host materials are briefy presented. The mo- lecular design concept, general synthetic routes for PI materials, and the applications of fuorophores in fuorescent OLEDs and host materials in PhOLEDs are reviewed. INTRODUCTION Organic light-emitting diodes (OLEDs) are competitive candidates for the next generation flat-panel displays and solid state lighting sources since the pioneering work by Tang et al., in 1987 (Tang, & VanSlyke, 1987). Extensive research has been carried out to promote OLEDs into commercial appli- cations as solid-state lighting resources and smart displays (Kamtekar, Monkman, & Bryce, 2010). A Phenanthroimidazole-Based Organic Fluorophores for Organic Light-Emitting Diodes: An Overview Sivakumar Vaidyanathan National Institute of Technology Rourkela, India Jairam Tagare National Institute of Technology Rourkela, India