Researchers at the Division of Solid State Physics and NanoLund at LTH have developed a new type of light-emitting diode (LED) built from branched nanostructures. The technology could pave the way for LEDs that are both more energy efficient and less costly to manufacture than those available today. By controlling exactly where light is produced within the structure, the team has reduced the losses that normally restrict light output, enabling more of the generated light to be utilised.
In the materials used for conventional light-emitting diodes – such as the LED bulbs found in most households – a large proportion of the light is trapped inside the material due to what is known as total internal reflection. This phenomenon means that only a small proportion of the light comes out, even though it is generated inside the material. This new design aims to overcome this problem. This method is based on the fact that light is emitted from very thin side branches that extend from a central nanowire. “If the structures are made thin enough – thinner than the wavelength of light – the light cannot be trapped inside the material in the same way. Theoretically, this could enable a very high light output. In principle, it would be possible to release virtually all the light,” says Magnus Borgström, professor of solid-state physics at Lund University.
In the materials used for today’s LEDs, only around four per cent of the light is emitted without additional surface treatment. To improve efficiency, various techniques and methods of processing the material are therefore used to increase light extraction. If the new technology proves successful, it would be possible to avoid these costly processes. Although LEDs are already inexpensive, any improvement in efficiency is important for industrial production.
