Photonic crystal LEDs

Research at Southampton has led to energy efficient, long-lasting, super bright LED lights that are used in digital displays, traffic signs, household appliances and automobile products around the world.

Research challenge

Light emitting diodes (LEDs) are one of the most energy-efficient lighting technologies.

As well as consuming less energy, they last longer, are smaller, more durable, and offer comparable or better light quality than other incandescent energy sources.

However, a typical semiconductor material used in the production of LEDs has a high refractive index, limiting the amount of light that can be extracted.

The challenge was to harness the capabilities of photonic quasi-crystals to create technologies that could improve the light extraction and efficiency of LEDS.

Context

Globally a wealth of real-world applications rely on the use of LEDs due to the multitude of advantages they have over incandescent energy sources. The US Department of Energy advocated the use of LEDs saying the widespread use of LED lighting has the greatest potential impact on energy savings in the United States. It predicted that use of LEDs could save the US more than $30b at today’s electricity prices and save 348TWh of electricity by 2027 – the equivalent of the annual electrical output of 44 large electric power plants.

Our solution

Researchers at Southampton discovered that creating an array of microscopic holes a couple of hundred nanometres deep in dielectric layers of silicon nitride substrate allowed them to bend light around corners at sub-millimetre scale while avoiding light escaping at the corners and weakening the signal.

Further research revealed that multiple optical functions and complex systems could be implemented at high density on a single silicon chip, paving the way for the low-cost, high-volume production of integrated optical devices.

The research results led to the creation of spin-out company Mesophotonics Ltd to develop and market the photonic crystal devices.

What was the impact?

Southampton’s research into the use of photonic crystals in LEDs has had a significant impact on the global manufacture of photonic crystal LED devices and an international move towards more energy efficient lighting.

As a direct result of its research, Mesophotonics Ltd successfully developed a range of products that incorporated photonic crystals into LEDs and offered increased brightness over other LEDs.

In 2008 this commercial success led to Mesophotonics Ltd being acquired by Taiwanese LED manufacturer Luxtaltek Corporation.

Luxtaltek currently employs more than 300 people and manufactures and supplies LED chips and crystalline grains that are used in digital displays, traffic signs, household electrical appliances, and automobile products all over the world. From 2008-12 the company made total profits of £35m on LEDs with photonic quasi-crystals.