GaAs can be used to create highly efficient solar cells, and researchers have found a way to combine GaAs nanowires with standard Si-based solar cells. What challenges do solar panels face, what did the researchers achieve, and could this technology help improve renewable energy moving forwards?

What challenges do solar panels face?

When it comes to renewable energy, solar panels are one of the top players (next to wind) thanks to their ability to be deployed in most places around the world and their ability to convert sunlight directly into electricity (specifically, photovoltaic types). However, like most renewable energies, solar is far from perfect and suffers from many setbacks. One of these is the inability to generate energy at night, and energy usage can be high, especially during winter.

Photovoltaic solar panels (directly producing electricity from sunlight) also suffer from price and efficiency challenges. On average, the amount of solar energy that reaches the earth’s surface is 1000W per square meter. A 100% efficient solar panel would produce 1000W of electricity for every square meter of ground covered. In reality, solar cells made from silicon rarely have efficiency above 15%, meaning that most of the solar energy collected is wasted in the form of heat and reflection.

Another challenge faced by solar panels is their price. Solar panels made with alternative materials such as GaAs can be far more efficient, but they are often more expensive, meaning that cheaper materials such as silicon are preferred. Solar panels are still costly to produce, which results in solar energy being an expensive form of power. Recent studies suggest that solar energy is cheaper than coal, but this does not consider the inability of solar to produce energy at night, its inability to store energy, and the ability to react to demand.

Researchers combined GaAs nanowires with silicon solar cells

Recently, researchers from the Norwegian University of Science and Technology have developed a technology that combines the benefits of GaAs solar technology with silicon solar technology. GaAs is a well-known material for making high-efficiency solar panels (greater than 40%). Still, its high cost often restricts it to advanced applications such as space missions involving rovers and satellites.

Thus, the researchers decided to explore if GaAs could be combined with Si to create solar panels with greater efficiency while reducing their costs. The solution developed by the team came from GaAs nanowires that were grown on top of a standard silicon solar cell. These vertically grown wires avoid the need for an entire GaAs substrate which reduces the overall amount of GaAs used while enabling the silicon substrate to operate as a solar panel.

The team has estimated that their device will push solar panel efficiencies to 40%, doubling the efficiency of commonly used panels. Research is still being done into the device developed by NTNU, but if the concept can be scaled to mass-production sizes, future solar panels could be a hybrid between GaAs and Si.

Will such technology help renewable energies in the future?

Undoubtedly, increasing solar efficiency will help the world move away from fossil fuels and closer to fully renewable sources. Greater efficiency not only helps to reduce the cost of panels per watt but also helps to reduce the overall land needed to install solar panels. A doubling of panel efficiency would see a solar installation doubling its power output, which would be immense on the scale.

However, this is all dependent on the ability to mass-produce the new panels at acceptable prices. A panel that is twice as efficient but more expensive may not be seen as worth it, especially if the price per watt is higher than that of Si panels.

The other challenge introduced by such panels is that the energy storage problem is still not solved. A solar farm that can double its output may not store the unused energy for when it is needed, and thus non-renewable sources will be required to pick up the slack when solar energy output is at its lowest.

It appears that nanostructures and nanotechnology, in general, shows great promise in improving current technologies. Nanostructures allow for smaller transistors that improve computing performance, nanowires increase the efficiency of standard Si solar panels, and nanomachines may even one day help cure diseases currently impossible with modern medicine.