Nanowires have been the center of attention for the past few years. By enabling scientists to produce devices that were never thought to be possible, the nanowires made investments flow into this area and bring even more discoveries of their potential.
As the solar industry is statistically evolving faster than ever, nanowires found themselves an application in solar cells. PhD student Peter Krogstrup, from the University of Copenhagen, have developed a method of producing nanowires that would benefit future solar cells and various devices using them.
“We have changed the recipe for producing nanowires. This means that we can produce nanowires that contain two different semiconductors, namely gallium indium arsenide and indium arsenide. It is a big breakthrough, because for first time on a nanoscale, we can combine the good characteristics of the two materials, thus gaining new possibilities for the electronics of the future,” explains Peter Krogstrup.
“Different materials capture energy from the sun in different and quite specific absorption areas. When we manufacture nanowires of gallium indium arsenide and indium arsenide, which each have their own absorption area, they can collectively capture energy from a much wider area. We can therefore utilize more solar energy, if we produce nanowires from the two semiconductors and use them for solar cells,” he explains.
The nanowire production takes place in a vacuum chamber. A gold droplet is laid on a thin disc made of the semiconductor and the nanowire grows up from below. In the transition between the two semiconductor materials in the gold droplet there was previously a mixing between the materials in the gold droplet and there was a soft transition between the materials.
With the method they invented, both of the materials from the gold droplet can go from the top of it or from its bottom side. When the material comes from the bottom, no mixing of the semiconductor materials occur. Therefore, there’s an atomic-level sharp transition between the gallium indium arsenide and indium arsenide.
“This sharp transition between the two semiconductors is necessary for the current — in the form of electrons, to be able to travel with high efficiency between the two materials. If the transition is soft, the electrons can easily get caught in the border area. The new mixed nanowire can be beneficial for many areas of nano research around the world,” says Krogstrup, who has been working at the Danish III-V Nanolab, operated in collaboration between the University of Copenhagen and the Technical University of Denmark.
Capturing different wavelenghts of light is the aim of many researchers in the solar cells field. Some have achieved improvements by using coating materials that have an extremely low reflection factor and direct the light inside the cell, while others make innovations on the core side. If combined, both methods may render better and cheaper solar cells for the hungry energy market.