White light‐emitting diodes: History, progress, and future

TLDR

White LEDs first appeared in 1996 and replaced less efficient incandescent and fluorescent lamps. The paper reviews the history, development, and commercialization of white LEDs and outlines future opportunities with smart LED technology. The review discusses advances in blue LED chips, device architecture, light extraction, and phosphors. Early white LEDs surpassed low‑wattage incandescent lamps in efficiency, and significant progress has occurred over the past two decades. An image is included.

Abstract

Abstract About twenty years ago, in the autumn of 1996, the first white light‐emitting diodes (LEDs) were offered for sale. These then‐new devices ushered in a new era in lighting by displacing lower‐efficiency conventional light sources including Edison's venerable incandescent lamp as well as the Hg‐discharge‐based fluorescent lamp. We review the history of the conception, improvement, and commercialization of the white LED. Early models of white LEDs already exceeded the efficiency of low‐wattage incandescent lamps, and extraordinary progress has been made during the last 20 years. The review also includes a discussion of advances in blue LED chips, device architecture, light extraction, and phosphors. Finally, we offer a brief outlook on opportunities provided by smart LED technology. image