Review—White Light-Emitting Diodes: Past, Present, and Future

With the advancement in technology of efficient and high-quality lighting, white light-emitting diodes (WLEDs) are gradually gaining ground with their ever-increasing high efficiency, energy density excitation, high device stability, and high output power. In this review, various technological approaches that are used to produce white light are presented. The progress made in improving the efficiency of white LEDs, using different phosphors along with a blue LED chip, is discussed. Phosphor-based approach is better and efficient in comparison to other approaches to generate white light. Using different phosphors, the improvement in luminous efficacy of white LEDs is reviewed. This review may serve as a roadmap for easily-fabricated, low-cost, and a longer lifespan white light-emitting diodes for indoor and outdoor applications.