An ultrafast method for manufacturing and assembling stable perovskite solar modules has been developed at Stanford University. The technique, according to study author Reinhold Dauskardt, resolves some of the most formidable barriers to module-scale manufacturing that have vexed researchers for years. To address the problem of large-scale production, the researchers deployed a technology they recently developed and patented called rapid-spray plasma processing. The method uses a robotic device equipped with two nozzles to quickly produce thin films of perovskite. One nozzle spray coats a liquid solution of perovskite chemical precursors onto a pane of glass, while the other releases a burst of highly reactive ionized gas known as plasma. A perovskite solar module produced by rapid-spray plasma processing. Stanford professor Reinhold Dauskardt's lab has shown that perovskite modules can be produced cheaper and four times faster than conventional silicon panels. Courtesy of Nick Rolston. “Conventional processing requires you to bake the perovskite solution for about half an hour,” said Nick Rolston, a postdoctoral scholar at Stanford. “Our innovation is to use a plasma high-energy source to rapidly convert liquid perovskite into a thin-film solar cell in a single step.” Using rapid-spray processing, the Stanford team was able to produce 12 m of perovskite film per minute — about four times faster than it takes to manufacture a silicon cell. “We achieved the highest throughput of any solar technology,” Rolston said. “You can imagine large panels of glass placed on rollers and continuously producing layers of perovskite at speeds never accomplished before.” The team estimated that the modules can be manufactured for about 25 cents per sq ft, as opposed to approximately $2.50 per sq ft for a silicon module. The modules achieved an efficiency of approximately 18%. Previously developed perovskite cells have clocked in at 25% efficiency, though those cells are unlikely to be found on rooftops any time soon. “Most work done on perovskites involves really tiny areas of active, usable solar cell. They’re typically a fraction of the size of your pinky fingernail,” Rolston said. Attempts to make bigger cells have produced defects and pinholes that significantly decrease cell efficiency. Thin-film perovskites, unlike silicon cells, which last for 20 to 30 years, tend to degrade when exposed to heat and moisture. “Perovskite solar technology is at a crossroads between commercialization and flimflammery,” Rolston said. “Millions of dollars are being poured into startups. But I strongly believe that in the next three years, if there isn't a breakthrough that extends cell lifetimes, that money will start to dry up.” Silicon solar cells are connected together in encapsulated modules to boost power output and withstand harsh weather. To compete with silicon, the researchers are exploring new encapsulation technologies and other ways to improve durability. “If we can build a perovskite module that lasts 30 years, we could bring down the cost of electricity below 2 cents per kilowatt-hour,” Rolston said. “At that price, we could use perovskites for utility-scale energy production. For example, a 100-megawatt solar farm.” The research was published in Joule (www.doi.org/10.1016.joule.2020.11.001).