With a big assist from the National Renewable Energy Laboratory in Colorado, a team of Brown University researchers has developed a new process for making solar cells based on the crystalline material perovskite. Early testing shows a solar conversion efficiency of more than 15%, which is pretty impressive for a first try, and to ice the cake, the process can be used to make a semitransparent solar cell film that could be used in windows and other see-through applications.
If Brown University isn’t the first institution that pops up when you think of clean energy, no worries. Compared to some other institutions, the school has been flying under our radar, but we have covered its forays into tidal energy and graphene, so now let’s give perovskite a go.
What Is This Perovskite You Speak Of?
For those of you new to the topic, perovskite refers to a class of crystals that are among the most abundant materials in the world, if not the most abundant. The first example was discovered in the Ural mountains back in 1839.
Conventional solar cells are based on silicon, and perovskites could offer a much cheaper way to get the same — or better — conversion efficiency, so if you think solar energy is giving fossil fuels a run for the money now, just wait until researchers work out some of the kinks involved in making perovskite solar cells.
We went to our friends over at the University of Surrey for some more details about perovskite. Here is a relevant snippet:
Some Perovskites are superconductors! This is where a material can conduct electricity with no resistance at all — it would revolutionalise technology if a room-temperature superconductor was found — at the moment they all operate at very low temperatures.
Perovskites could also be useful in advanced fuel cells and batteries for electric vehicles, but we digress.
The Brown University Perovskite Breakthrough
Typically, perovskite thin-film solar cells are made with an energy-intensive high-temperature process. It’s a finicky, time-consuming approach that can leave “pinholes” in the film, cutting down on efficiency.
Since the film is built up from a substrate, the high temperature also means that you can’t use low-cost, flexible materials like plastics.
The new Brown University perovskite solar cell process goes in an entirely different direction.
The team developed a way to fabricate a thin-film solar cell at room temperature, which they’re calling SSE for solvent-solvent extraction.
Don’t try this at home, but the steps look simple enough:
...perovskite precursors are dissolved in a solvent called NMP and coated onto a substrate. Then, instead of heating, the substrate is bathed in diethyl ether (DEE), a second solvent that selectively grabs the NMP solvent and whisks it away. What’s left is an ultra-smooth film of perovskite crystals.
According to Brown, the entire process only takes a couple of minutes, compared to the hour-long range required for high-temperature processes.
The result is a high-quality thin film without pinholes down to the 20-nanometer range, compared to 300 nanometers required for typical perovskite solar cell films.
At 80 nanometers, the Brown researchers also claim that their perovskite thin-film is more efficient than any other ultra-thin film.
The film is transparent enough to use as a building-integrated solar substitute for windows or glass walls. The team has already tweaked the solvents to create different colors, which would open up a wider range of applications to attract architects and designers.
Also helping things along is the team’s assertion that the process easily lends itself to an assembly line setup, which would help cut manufacturing costs to the bone.
Many Paths To A Perovskite Future
If only Mr. McGuire had said “perovskites” instead of “plastics” way back in 1967, Benjamin and all the rest of us could be swimming in perovskite solar products by now, but instead we’ll have to wait a few more years.
Meanwhile, speaking of group hugs for US taxpayers, the National Renewable Energy Laboratory is just one of several publicly funded R&D facilities working on perovskites.
Over at Los Alamos National Laboratory, for example, researchers are developing a perovskite solar cell approaching 18% efficiency, and they are also working on a low-cost, high-efficiency process for “growing” perovskite solar cells.
The rapid drop in the cost of solar over the past few years is clearly making the fossil competition nervous. If you then consider up-and-coming research like Brown’s, it looks like it’s going to get very interesting soon.
Photo Credit (photo enhanced): Courtesy of Padture Lab/Brown University.