History, development, and applications of high-brightness visible light-emitting diodes

In a practical sense, the development of high-performance visible-spectrum light-emitting diodes (LEDs) has occurred over a period of over 60 years, beginning with the discovery of the first semiconductor p-n junction in 1940, the development of solid-state electronic band theory in the 1940s, the invention of the first bipolar transistor in 1947, and the demonstration of efficient light generation from III-V alloys in the 1950s and 1960s. This paper reviews some of the major scientific and technological developments and observations that have created the materials and device technologies currently used in the commercial mass production of high-brightness visible-spectrum LEDs and that have culminated in white-light sources exhibiting luminous efficacies of over 150 lm/W, far beyond what has been achieved with conventional lighting technologies.