Physics researchers at Lund University in Sweden have succeeded in building microscopic solar radiation-collecting antennas called nanowires out of three distinct materials that are more suited to the sun spectrum than today’s silicon solar cells. Because the nanowires are light and need minimal material per unit of area, they are currently being tested on satellites powered by solar cells, where efficiency, in conjunction with low weight, is the most critical aspect. A few days ago, the new solar cells were launched into orbit.
Last year, a group of Lund University nanoengineering researchers working on solar cells achieved a breakthrough when they succeeded in creating photovoltaic nanowires with three distinct band gaps. This implies that a single nanowire is made up of three separate materials that respond to various sections of solar radiation. The findings were first reported in Materials Today Energy and then expanded upon in Nano Research.
“The main issue was getting the current to flow between the materials. It took more than ten years, but it was eventually successful “According to Magnus Borgström, professor of solid state physics, who co-authored the papers with then-doctoral student Lukas Hrachowina.
Around the globe, 10 research teams are currently working on nanowire solar cells.
“The issue has been to integrate distinct band gaps in solar cells, and that door has now been opened,” Magnus Borgström explains.
In the future, an alternative to silicon
Tandem solar cells, which have differing band gaps, have so far been seen mostly on satellites and are the focus of much investigation. The goal of the project is to significantly boost efficiency, maybe to double that of today’s commercial silicon solar cells (about 20%).
“Silicon solar cells are rapidly approaching their maximum efficiency. As a result, the emphasis has turned to building tandem solar cells. The variations installed on satellites are too costly to instal on a roof “Magnus Borgström explains.
The most popular method for creating tandem solar cells is to layer distinct semiconducting materials that absorb different sections of the sunlight spectrum on top of each other. Silicon-based tandem solar cells, which entail stacking thin, semi-transparent layers of other light-capturing material on top of the silicon, are gaining popularity.
Lund researchers use a somewhat different strategy. They invented a technique for fabricating exceedingly thin rods of semiconducting material on a substrate. The benefit is that it requires less material per unit area, which might lower manufacturing costs and make it a more sustainable option.
The nanometer-thick rods are made of three materials with varying concentrations of indium, arsenic, gallium, and phosphorus. The researchers have so far reached a 16.7% efficiency in the lab. Yang Chen, a colleague, demonstrated that utilising the existing structure, nanowire solar cells have the potential to achieve 47% efficiency. More band gaps are required to achieve even better efficiency.
In the following phase, he and his colleagues will improve the triple diodes by optimising the tunnel junctions that link the various materials in the structure and attempting to lessen the influence of the surface of the nanowires, which is critical on a nanoscale.
Aside from greater light absorption, nanowire solar cells are distinguished by their longevity, since they can tolerate damaging radiation in space better than film-based tandem solar cells.
“A sheet of nanowires is analogous to a sparse bed of nails. If any aggressive protons came along, which occurs from time to time, they would most likely fall between the wires, and if they occurred to remove some wires, it would be insignificant. If they hit a standard thin coating, the harm might be far severe.”
During the spring, there will be space testing.
These benefits led to the nanowire solar cells being installed on a research spacecraft recently launched into orbit by the researchers’ partnership partners at the California Institute of Technology, Caltech, in the United States.
“Satellites, which are powered by solar cells, govern most of our digital communication. Satellites provide GPS signals, TV broadcasts, data traffic, mobile phone calls, and meteorological information.”
The satellite will remain in orbit throughout the spring, with findings likely to be received on a regular basis.
Tandem solar cells, according to Magnus Borgström, will eventually end up on Earth, but for the time being, silicon-free solar cells will be employed in niche applications such as clothing, windows, and décor.
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