In what is being called a "surprise discovery," researchers at the U.S. Department of Energy's Lawrence Berkeley National Laboratory have found they may be able to boost energy conversion rates in one type of solar module by as much as 40%.
The research was published in the peer-reviewed journal Nature Energy.
Using an atomic microscope, the researchers observed multifaceted surfaces like a gemstone in solar cells made with the mineral perovskite. Some of the grains, which were about 200 microns in width, had sharply formed multi-angled facets, while others were poorly formed. The poorly formed facets had energy conversion efficiencies approaching 31%, which beats today's top photovoltaic efficiency rates of 22%.
The top-performing facets of perovskite-based solar cells could hold the secret to highly efficient solar cells, "although more research is needed," according to the scientists from the Berkley Labs' Molecular Foundry and the Joint Center for Artificial Photosynthesis.
"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," Sibel Leblebici, a researcher at the Molecular Foundry, said in a news release.
This atomic force microscopy image of the grainy surface of a perovskite solar cell reveals a new path to much greater efficiency. Individual grains are outlined in black, low-performing facets are red and high-performing facets are green. A big jump in efficiency could possibly be obtained if the material can be grown so that more high-performing facets develop.
Like organic solar cells made of carbon-based materials combined with various metals, perovskite cells are inexpensive and easy to fabricate, the researchers said.
The vast majority of solar modules being manufactured for rooftop and other use today have a light-conversion efficiency rating of 15% to 17%; the rating refers to the percentage of photons striking the modules that can be turned into electric current.
Even more interesting, the researchers added, is that the efficiency at which perovskite solar cells convert photons to electricity has increased more rapidly than any other material to date, starting with 3% in 2009 -- when research first began -- to 22% today. Twenty-two percent is roughly the same solar efficiency rate as crystalline silicon-based solar cells, which are, by far, the most prevalent material used to manufacture solar cells today.
MJ Shiao, director of solar research at GTM Research, explained that in large solar power systems, such as utility-scale power plants, photovoltaic modules make up over 50% of system costs and technology gains like improved efficiency can help reduce solar energy costs.
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