IREDs or InfraRed Emitting Diodes are a type of LEDs which emit light in the infrared range of the electromagnetic spectrum. IREDs are widely used in process control, optical switching circuits and Logic circuits.

Like LEDs, Infrared Emitting Diodes are PN junctions which emit light when connected in a forward bias.  Under forward bias conditions, the carriers are given energy to cross the depletion layer.  On crossing the depletion layer, the carriers, both holes and electrons recombine.  Energy is released in the process of recombination in the form of a photon.

One common application where Infrared Emitting Diodes are used is the TV remote

Infrared Emitting Diodes are made of materials such as Gallium Arsenide (GaAs) and Gallium Aluminium Arsenide (GaAlAs). 

IREDs emit radiation at wavelengths such as 880nm and 940 nm (nanometres).  Thus, they are ideal for switching on phototransistors which are sensitive to electromagnetic radiation at such wavelengths.

A British Company, has developed a simple, low cost light which can be used by remote communities isolated from the main electricity grid.  This simple low cost light source can be an alternative to the kerosene lamp which is polluting and expensive as it consumes kerosene which consumes a significant part of the family's income. Kerosene has also been linked to accidents.

The Gravity lamp is powered by a dynamo which is drive by a weight (a bag of sand) which is raised to a certain level.  As the weight gradually descends, it drives the dynamo which powers the LED.

This gravity powered light can last for half an hour by when the weight comes to its lowest position.  After that, it has to be lifted to its higher position which takes about 3 seconds.  It then starts again.  The power from this dynamo can be used to power LEDs for illumination, to charge batteries or to power a radio.

This lamp would ideal for households in remote communities.

The company says that with increased research and production, the efficiency and cost would improve further..