Solvent Baths Promise Better Perovskite Crystals and Better Solar Energy

With the coming of spring, and the looming global warming ever at our odds, it's clear that there's enough heat already out in the world. So why would you want your "green" energy practices to contribute ever more to that heat? Current methods, for example, in the production of solar cells used to capture energy require an intense recrystallization process that comes at the price of a drastic raise in the temperature of the substance-perovskite. But now, thanks to chemists at Brown University, the green energy movement may soon be equated with a cooler movement, as well.

In a new study published this week in the Royal Society of Chemistry's Journal of Materials Chemistry A, Yuanyuan Zhou of Brown University and his advisor Nitin Padture describe a new method of making perovskite films for solar cells that will be especially effective in creating ultra-thin films that are semi-transparent. By using a room-temperature solvent bath to create perovskite crystals, rather than the blast of heat used in current crystallization methods, the new technique produces high-quality films with precise control that is perfect for mass production methods.

"Using other methods, when the thickness gets below 100 nanometers you can hardly make full coverage of film. You can make a film, but you get lots of pinholes" Zhou says. "In our process, you can form the film evenly down to 20 nanometers because the crystallization at room temperature is much more balanced and occurs immediately over the whole film upon bathing."

Current methods used in the production of solar cells have been effective, however, the level of efficiency is far too low and the end product comes at too high a price for the average consumer. In spite of government programs and initiatives put in place to encourage the movement towards massive production and use of solar cells, often the clean-energy products require too far a deductible that makes consumers shy away from the long-term savings. But Zhou's methods will now undoubtedly change that.

"People have made good films over relatively small areas-a fraction of a centimeter or so square" Padture says. "But they've had to go to temperatures from 100 to 150 degrees Celcius, and that heating process causes a number of problems."

Now, without the heat, and the added ability of being able to create perovskite crystals/films on any width or thickness of a solar cell, the researchers believe that their new process may help solar energy enter a new era of production.