Introduction to the issue on high-efficiency light-emitting diodes

Since their inception in the 1960s, light-emitting diodes (LEDs) have enjoyed sustained rapid development in terms of efficiency, available emission spectrum, higher power, higher speed, and application methods. These improvements, coupled with the inherent properties of solid-state devices-ruggedness, low-voltage operation, high reliability, and low cost-have catapulted LEDs into a wide range of applications, from telecommunications, to solid-state lighting, to displays. In each case, LEDs are increasingly replacing the conventional technologies. Even more exciting is the fact that progress in LED technology in each of these areas is continuing at very rapid rate, ensuring that LEDs will continue to see accelerated growth in new and emerging markets, and will find use in applications that would have been considered impossible just a few years ago. Indeed, in this special issue, Watt-class visible-spectrum LEDs are presented for the first time. Here we have 9 invited and 13 contributed papers that give a comprehensive cross-sectional view of the current state-of-the-art in LED technology. The papers are grouped into four main areas: communications, solid-state lighting, ultraviolet emitters, and organic LEDs.