14 DAY TRIAL // At this point, nanowire technology counts as one of the most promising in the world, with enormous potential applications for a wide array of fields. Usually made out of alloy materials, these very thin wires can be used in the electronics industry, or for designing new medical tools and new processors. In recent advancements, a group of investigators form the Arizona State University (ASU) managed to produce a new alloy for nanowire synthesis. This promises to lead to new generations of light-emitting diodes (LED) – to replace less energy-efficient incandescent light bulbs – and also to highly-efficient photovoltaic cells for renewable energy production.
The ASU group, led by electrical engineers Cun-Zheng Ning and Alian Pan, is working on many fronts at once. They are developing new materials, striving to improve their performances, while at the same time obtaining a wider band gap – which would enable the alloys to be used for even more practical applications. The main target of study are quaternary alloy semiconductor nanowire materials, which are basically wires tens of nanometers thick and several microns long, that are produced from four different types of semiconductor materials.
Semiconductors represent the basis for much of today's advancements, ranging from the development of computers, LED and even light detectors working in either visible light of infrared wavelengths. The most important property any semiconductor can exhibit, and the one that dictates what material can be used, is the band gap. In solar cells for example, this determines which wavelengths of the sunlight' electromagnetic spectrum will be absorbed by the photovoltaic cells, and which will be left unchanged as they pass through. In this particular instance, increasing the band gap makes the cells all the more efficient. In LED, the band gap range dictates which color the light they emit will take.
But producing semiconductors with custom, or arbitrary, band gaps is very difficult, as combining various materials in alloys can only be done following very specific rules. “This is why we cannot grow alloys of arbitrary compositions to achieve arbitrary band gaps. This lack of available band gaps is one of reasons current solar cell efficiency is low, and why we do not have LED lighting colors that can be adjusted for various situations,” Ning says. But the ASU team took a new approach towards accomplishing this, by creating the first-ever continuously-varying composition substrate. This is the first time such a quaternary semiconductor material has been shaped like a nanowire or nanoparticle.