No. 16
Light-emitting Diodes (LEDs)
LED technology is developing rapidly. As a consequence we are likely to see considerably more LED applications in
the near future. Unfortunately not all LED product matches suppliers’ claims and purchasers need to be cautious.
Nevertheless there is some excellent LED technology available from reputable suppliers and new applications are
being developed and refined both in Australia and overseas. This edition of Light Technical provides an introduction to
LEDs and lists some of the technology’s lighting applications.
What is an LED and how does it work?
An LED is a semiconductor diode that emits light. It consists of
a chip of semiconducting material treated to create a structure
called a p-n (positive/negative) junction. When connected to
a power source, current flows from the p-side or anode to the
n-side, or cathode, but not in the reverse direction. Chargecarriers (electrons and electron holes) flow into the junction from
electrodes. When an electron meets a hole, it falls into a lower
energy level, and releases energy in the form of a photon (light).
The specific colour emitted by the LED depends on the materials
used to make the diode. Red LEDs are based on aluminum
indium gallium phosphide (AlInGaP). Blue and green LEDs
use indium gallium nitride (InGaN). ‘White’ light is created by
combining the light from red, green and blue (RGB) LEDs or by
coating a blue LED with yellow phosphor.
Benefits of LEDs
LEDs can be highly efficient, with a promise of consuming
considerably less energy than other light sources. In addition
good quality LEDs have a very long life – 50,000 hours is
common – compared to around 1,000 hours for a GLS lamp.
LED terminology
Solid-state lighting (SSL) technology uses semi-conducting
materials to convert electricity into light. SSL is an umbrella
term encompassing both light-emitting diodes (LEDs) and
organic light emitting diodes (OLEDs).
Organic light-emitting diodes (OLEDs) are based on organic
(carbon based) materials – as opposed to LEDs which are based
on inorganic materials. In contrast to LEDs, which are small
point sources, OLEDs are made in sheets which provide a diffuse
area light source. OLED technology is developing rapidly and is
increasingly used in display applications such as mobile phones
and PDA screens.
Discotheque illuminated by dimmable, colour-changing LEDs
LED technology is becoming increasingly cost-effective,
particularly in the following areas:
• Undercabinet lighting
• Step and path lighting
• In-cabinet accent lighting
• Cove lighting
• Adjustable task lighting
• Spaces with occupancy
sensors
• Refrigerated case lighting
LED applications
• Outdoor area lighting
The first commercial LEDs were commonly used in laboratory
and electronics test equipment, then later in appliances and
applications such as TVs, radios, telephones, calculators,
watches and motor vehicle brake lights. These red LEDs were
bright enough only for use as indicators, as the light output was
not enough to illuminate an area. Later, other colours became
available and also appeared in appliances and equipment. As
LED materials technology became more advanced, light output
was increased, causing LEDs to become bright enough to be
used for illumination.
• Elevator lighting
• Recessed downlights
• Accent lights
• Food preparation areas
• Retail display cases
• Art display lighting
• Illuminated signage
LEDs will find increasing application in commercial buildings
where high maintenance costs and energy performance are
important factors.
For more information see LED Fact Sheets on Lighting Council Australia’s website www.lightingcouncil.com.au
The information in this newsletter has been prepared in good faith by Lighting Council Australia. However:
- The information is not intended to constitute advice and persons should seek professional advice before relying on the information.
- Lighting Council Australia does not warrant the accuracy of the information, and to the extent permitted by law, disclaims responsibility for any loss or damage of any nature whatsoever which may be suffered by
any person directly or indirectly through relying upon it, whether that loss or damage is caused by any fault or negligence of Lighting Council Australia or otherwise.
For more details please contact: Lighting Council Australia T: +61 2 6247 8011 F: +61 2 6162 3457 E: info@lightingcouncil.com.au W: www.lightingcouncil.com.au