Piezo-phototronic Effect Improves LED Efficiency
Researchers at the Georgia Institute of Technology have added a piezoelectric material to an LED and found greatly improved performance by stressing the added material. Light emitting diodes work by causing the positive holes in the semiconductor to be filled with negative electrons. The interaction causes the release of photons at specific wavelengths. The piezoelectric material, zinc-oxide microwires specifically, acted as the source of the electrons, the “n” part of a p-n junction, while gallium nitride was the “p” part. The strain on the microwires caused a charge to build up on their edge, which aided in the transport of the electrons and holes at the p-n junction. The result was increased emission intensity by a factor of 17 and improved injection current by a factor of four. All together the energy conversion was increased by a factor of 4.25. The LEDs in the experiment produced light in the ultra-violet range, but the researchers believe visible light can be produced by other LEDs to benefit from this piezo-phototronic effect.