So there’s this thing in solar power called the Shockley Queisser Efficiency, which states that a one-layered solar cell can only be roughly 33.7 percent efficient at converting the sun’s light into electricity. As of July 2016 the most efficient single-junction cell is a 28.8 percent efficient gallium arsenide test cell developed by Alta Devices. But research from the Department of Energy’s Lawrence Berkeley National Laboratory show that perovskite solar cells, one of the newer solar technologies being explored, could reach efficiency levels of 31 percent—knocking on the door of that theoretical limit.
Not bad considering that the National Renewable Energy Laboratory showed that the most efficient perovskite solar cells are currently 22.1 percent efficient—even better when considering that when NREL started tracking the technology in 2013, its efficiency levels were closer to 13.7 percent. The cells that are 22.1 percent efficient are already more efficient than most of the commercial silicon solar cells and panels on the market today. The most efficient silicon solar test panels are about 24.1 percent today.
“The efficiency at which perovskite solar cells convert photons to electricity has increased more rapidly than any other material to date, starting at three percent in 2009,” the lab stated. For comparison it took more than 15 years—from 1977 to 1993—for silicon solar cells to rise from 13 percent efficiency to 22 percent efficiency.
Based on the newly published research It looks like perovskite’s rapid increase in efficiency is likely to continue, too. The Joint Center for Artificial Photosynthesis and the Molecular Foundry, both part of the Berkeley lab, found that a perovskite solar cell could be manipulated to reach efficiency levels of up to 31 percent.
“I thought perovskites are the most exciting thing in solar right now, and I really wanted to see how they work at the nanoscale, which has not been widely studied,” said Sibel Leblebici, a postdoctoral researcher at the Molecular Foundry.
Using atomic force microscopes the researchers realized that certain parts of perovskite crystal already was converting 31 percent of the sun’s energy into electricity. However, other parts were much less efficient. “If the material can be synthesized so that only very efficient facets develop, then we could see a big jump in the efficiency of perovskite solar cells, possibly approaching 31 percent,” Leblebici explained.
What they found is that the facets of the perovskite crystals behave like billions of tiny solar cells connected in parallel. Some of these microcells convert sunlight extremely well while others do it very poorly. Since the current flows towards the poor cells it lowers the performance of the material overall. “If the material can be optimized so that only highly efficient facets interface with the electrode, the losses incurred by the poor facets would be eliminated,” the lab stated.
“This means, at the macroscale, the material could possibly approach its theoretical energy conversion limit of 31 percent,” said Ian Sharp a scientist at the Joint Center for Artificial Photosynthesis, who coauthored the research, which was published in Nature Energy.Tweet