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The history of the LED

The light-emitting diode (LED) is one of the fastest developing lighting technologies today. A type of solid-state lighting, LEDs use a semiconductor to convert electricity into light and emit that light in a specific direction. This reduces the need for reflectors and diffusers that can trap light. From their humble beginnings as indicator lights to an energy-efficient, connected option for owners of smart home hubs, take a walk down memory lane and explore the history of the LED.

Early LEDs

The first LEDs were red, and they got their start as indicator lights for circuit boards and small electrical equipment for this reason.

LEDs consist of layers of semiconductor crystals stacked on a wafer. As layers are added, dopants are incorporated to determine the color of the LED. Next, the tiny wafer is placed into molten liquid, and metal contacts and leads are added. The mixture used in the first LEDs produced a natural red color. Today, new processes make it possible to deliver a variety of colors. (Wired

One of the next stages in LED history featured the development of high-brightness LEDs. As LEDs were developed, the light levels increased to the extent that they could be considered for applications outside simple indicator lamps. By 1987, AlGaAs (aluminium gallium arsenide) diodes were bright enough for the first applications within lighting. (Electronics Notes)

The first applications for these diodes was within the automotive industry, where red LEDs were used for vehicle brake lights and traffic lights. Here, LEDs were of particular interest, because they offered increased reliability over the incandescent lights that had been previously used. (Electronics Notes)

A year after the introduction of the first AlGaAs LEDs, another variant, AlInGaP (aluminium Indium Gallium Phosphide), appeared. These LEDs represented a significant improvement over the previous AlGaAs diodes, because they doubled the light output. 

Second-generation LED technology included the ability to string multiple LEDs into a single circuit. Over time, LEDs became more suitable for outdoor use. Widespread adoption by municipalities followed, as the LEDs provided a superior alternative to incandescent bulbs in traffic lights. LEDs also saw limited success as a replacement for fluorescent bulbs and neon in lighted signs.

In 1993, Shuji Nakamura achieved a breakthrough in doping (the name for the process by which manufacturers introduce impurities in an LED to change its color properties) that led to bright blue LEDs. Blue LEDs with yellow phosphor coatings gave us the white LED and a whole host of new applications. (Wired

LED technology today

As LEDs grew brighter, the flashlight industry switched to LEDs from incandescent lights. The new flashlights used less power, and the bulbs never had to be replaced. Now, it’s difficult to find a flashlight without LED bulbs. (Wired

The optical mouse was invented in the early 1980s. But it wasn’t until 1999, when Microsoft introduced the IntelliMouse Optical, that the technology became widely available. The mouse replaced the filth-attracting roller ball with a bright LED. The LED mouse used image sensors in conjunction with an LED to track the movements of the mouse on any surface. (Wired

Today's LED technology supports commercialindustrial and residential applications. LED technology has grown across the board, with exponential improvements in lifespan, brightness and energy efficiency.