Zinc-oxide microwires improve the efficiency of UV LEDs

The devices are believed to be the first LEDs that have had their performance enhanced by using the so-called piezo-phototronic effect.

‘By utilising this effect, we can enhance the external efficiency of these devices by a factor of more than four times, up to eight per cent,’ said Prof Zhong Lin Wang of the Georgia Institute of Technology’s School of Materials Science and Engineering.

‘From a practical standpoint, this new effect could have many impacts for electro-optical processes — including improvements in the energy efficiency of lighting devices.’

High-efficiency UV emitters are needed for applications in chemical, biological, aerospace, military and medical technologies. Although the internal quantum efficiencies of these LEDs can be as high as 80 per cent, the external efficiency for a conventional single p-n junction thin-film LED is currently only about three per cent.

By applying mechanical strain to the microwires, the researchers the created a piezoelectric potential in the wires, and that potential was used to tune the charge transport and enhance carrier injection in the LEDs.