Solar energy technology has revolutionized how we think about energy production. Solar panels are used to provide energy for everything from houses to satellites and will certainly play an important role in combating the effects of climate change, not to mention providing a sustainable source of energy for the future. Before we get there, there are still downsides to the technology keeping it from seeing wider commercial adoption. Scientists are diligently researching new ways to build solar panels that will make them cheaper and just as, if not more, efficient than those currently in use.
In the most recent history of solar panel technology, the two most common materials used to build solar panels are silicon (Si) and gallium arsenide (GaAs). Both are expensive materials to work with in terms of mass-producing highly technical equipment like solar panels, and both have unique drawbacks. Though gallium arsenide is something of a wunderkind in this story - being able to produce extremely efficient solar panels - the material itself is extremely difficult to manufacture, especially to mass-produce. This makes it extremely expensive and thus not the most commercially viable option. On the other hand, silicon is also expensive, especially since any silicon used to build solar panels has to be extremely pure. High demand for silicon in computer chips has also led to technological breakthroughs that have made it cheaper to mass-produce, so silicon has risen to become the dominant material for solar panel manufacturing worldwide.
Much of the greatest progress in solar panel R+D has come from research teams discovering new, more efficient materials with which to construct solar panels that are cheaper to mass-produce than those made of silicon or gallium arsenide. One candidate that shows the most promise is called perovskite. No, it’s not the nickname of a Russian space vessel - though it is named after their discoverer, Russian mineralogist L. A. Perovski. Perovskites are naturally occurring minerals found in the Earth’s crust. They’re made of calcium titanium oxide, CaTiO₃. They’re very conductive and are easily combined with other materials, like silicon. Perovskite solar panel research has been progressing at an astounding pace.
In 2012, researchers at L'Ecole Polytechnique Fédérale de Lausanne (EPFL) in Switzerland discovered how to make the first stable perovskite cells. Since then, research institutes around the world have seen an incredible amount of progress in such a relatively short time. I spoke with a researcher at the University of Colorado, Boulder, who has been researching the application of perovskites in solar panel manufacturing. “Perovskites have gone from 13 percent to 24 percent efficient in 5 years,” said Orion Pearce, graduate research assistant at the University of Colorado, Boulder. “It took silicon 40 years to do that.”
Although the original perovskite PV panels were only 10 percent efficient, Pearce told me that breakthroughs in perovskite fabrication have led to the creation of solar panels made of both silicon and perovskites that have reached efficiency ratings of as high as 27 percent - almost as high as the highest level ever reached by GaAs (28.8 percent efficient).
There are, of course, downsides to the material besides its status as relatively new technology. Perovskites tend to erode quickly when exposed to moisture. Unfortunately, that means no floating perovskite solar panels will be seen in Holland or elsewhere anytime soon. According to Pearce, ultra-waterproof materials will need to be developed so they can stand up to the elements. Perovskites also contain lead, which makes them potentially hazardous to work with. “Some groups have started replacing the lead with tin and have already gotten around 10% efficient cells, but a lot more work needs to be done,” he said.
While perovskites are currently the darling of the cutting-edge PV tech world, scientists are still exploring the viability of other materials hoping for a breakthrough that will leave more established, silicon-based PV technology in the dust. Yongsheng Chen, a chemist at Nankai University, has been leading a group dedicated to this task for years. Together they developed O6T-4F (F-M for short), which they believe could reach 17.3 percent efficiency - promising results, considering most commercial silicon panels are around 18-22 percent efficient.
Originally published in Electrical Apparatus Magazine. Print only.