The UK uses about a fifth of the electricity it generates on lighting.
Part of the reason for this is that much of our lighting is so inefficient. A conventional incandescent lightbulb emits 98% of the energy input as heat. Over its lifetime, it will use the same amount of energy as there is in three metric tonnes of coal.
So there are great carbon savings to be made by developing more efficient lighting.
Light-emitting diodes (LEDs) are an energy efficient way of producing light, with only 10% of the carbon footprint of a conventional lightbulb.
But they’re expensive to produce. Modern LED bulbs typically contain four to six chips, but cost four to six times more than traditional bulbs. So, to reduce costs, and increase competitiveness, manufacturers require LED bulbs with just one chip – which requires significant increases in the efficiency of LED chips.
Researchers at the University of Bath are part of a consortium looking at solving fundamental problems that limit take-up of today’s LEDs.
- Increasing efficiency – not all the light emitted by an LED chip makes it out. Better engineering of the materials that go into LEDs should get more light out of each individual chip.
- Decreasing costs – finding viable alternatives to expensive LED components could drastically reduce their manufacturing cost.
Embedding nanostructures into LEDs
LEDs are made from layers of different semi-conducting material, all put together in the same chip. When combined, defects are generated, and these defects reduce the quality of the light.
Incorporating nanostructures into the LED chips encourages the semi-conductor materials to grow in a much more regular crystal structure.
Fewer defects are created, which means that the light output is better, the efficiency is better and there is less wasted light.
The nanostructures allow the researchers to have much more control over the direction of light produced by LEDs, allowing them to focus beams of light, which will be of use in projectors or car headlights.
Replacing sapphire with silicon
There's no point in making the most perfect LED if no one can afford to buy it.
At the moment most LEDs are made on sapphire wafers, which are very expensive – and also in very limited supply.
"We’re now trying to develop processes, in conjunction with partners in industry, to make LEDs on silicon," says Dr Duncan Allsopp, from the Department of Electronic & Electrical Engineering. Silicon is very cheap, it is also widely available, and it is also very well established technology, so the processing is very well developed."
Lighting the future
The intended outcome is more efficient LEDs – which will help reduce carbon emissions, and make LED lighting more cost effective for consumers.
This isn’t the end goal, instead it’s a beginning – as new lighting technologies, and new ideas of how we could use lighting, will also spring from this research.