Solar Perovskites Could Revolutionize Panel Technology
New Solar technology is in the pipeline as solar perovskites are moving from lab to production across the world. Compared to traditional silicon panels, these panels are peaking at more than 28 percent efficiency for turning light into power, versus the record for silicon photovoltaics of 26.7 percent. Additionally, they have the potential for greater flexibility, greater consistency, and lower cost, according to industry experts. This could be the future of solar, and it could be a dominant one.
Perovskites are a mineral compounds with the formula shorthand AMX3. A represents an organic molecule, M represents a metal, and X3 represents three halogens. They were first discovered in 1839 but were not used for capturing solar power until 2009. For these compounds, the ability to capture energy comes from structure, rather than the exact makeup. As a resut there are many competing formulas for the compounds, and large room for improvement. The first lab prototypes were unstable, and had an efficiency of just 3.8 percent. On the other hand, Oxford PV, a startup spun-out from the University of Oxford, reported in 2018 an efficiency of 28 percent.
The main reason solar panels are currently made out of silicon is because of built-up knowledge from the semi-conductor industry. There was already a large amount of industry experience in working with silicon and in the manufacturing processes associated with using silicon at small scale. However, that does not mean silicon is always the optimal choice for solar panel material. Pure and perfect silicon is required in order to have the right properties for use as solar panels. Additionally, silicon naturally has a lower peak efficiency than some other materials, due to the atomic properties of the material.
High-quality solar panels may hit an efficiency of just 20 percent, with typical numbers around 15-17 percent. This means there is a big leap when moving to perovskites. Silicon is difficult to work with; silicon can suffer greatly from mild imperfections, so it's much more common to produce panels with lower efficiency than their 26.7 percent lab peak. Perovskites are much more defect tolerant, according to researcher Joseph Berry of the National Renewable Energy Laboratory.
The manufacturing process for silicon is deeply ingrained in solar panel production. This means that any new material will have to be able to be manufactured in the same way silicon currently is. This is one of the big advantages of perovskites, which lend themselves to spin coating and roll-to-roll printing, according to Berry. Because they can piggyback on already refined manufacturing techniques, and require less precision in production, they have the potential to be much cheaper than current solar panels. Berry predicts a large scale factory could cost as little as one-tenth what a current, silicon factory would.
Image Source: Dennis Schroeder of NREL
Pure perovskites could be flexible, even made into an ink as seen above.
However, most people looking for near term commercialization are not looking at totally replacing silicon panels. That path to commercialization would be long and uncertain, so instead many are looking towards making hybrid, or tandem perovskite panels. This would involve placing a top conductive layer, followed a perovskite layer that would capture 15-17 percent of light energy, (mainly at the bluer end of the spectrum) before finally hitting a silicon solar layer. By adding an additional layer to the panel, the properties of both silicon and perovskites could be optimized for, all while retaining the current structure and low cost. This would be added for well under the cost of making a new solar panel, greatly reducing cost per watt.
Many players, including both startups and big firms such as Toshiba and Panasonic, are working on the technology. Oxford PV is planning on fielding their first perovskite module in 2019, partnering with an as yet unknown manufacturer. However, many researchers are still warning to take it slow and make sure all the kinks are worked out. "There is a real opportunity for this technology to change the world. That’s not an opportunity you get every day, and you certainly don’t want to mess it up.”