A Review on Development of White Light Sources

Many researchers are concerned about the light sources development to consider in the economic and commercial aspects of lighting supply. Initially, the bulb lamps were gradually replaced by fluorescent lamps with higher energy efficiency to reduce in conversion of electrical energy to thermal energy. Afterwards, the need of more energy saving caused the development of the solid state white lights with low consumption energy. These solid-state white light emitting diods are sufficiently durable and competent to apply for home and general usages. In addition, the high energy saving of solid state white light emitting diods headed them to replace incandescent bulbs. In the first part of this paper, the history of the light source development has been considered and then the white solid state properties and applications are described. Incidentally, the structure and performance of organic and inorganic light emitting diods are explained and the solid state lighting devices developments are clarified. Futhermore, some quantization methods to characterise the light emitting diods and investigation on their color effect with some ideas introduce to improve the LEDs lightness performance and durability have been reviewed.