Nav: Home

Just like toothpaste: fluoride radically improves the stability of perovskite solar cells

May 13, 2019

Solar cells made of perovskite hold much promise for the future of solar energy. The material is cheap, easy to produce and almost as efficient as silicon, the material traditionally used in solar cells. However, perovskite degrades quickly, severely limiting its efficiency and stability over time. Researchers from Eindhoven University of Technology, energy research institute DIFFER, Peking University and University of Twente have discovered that adding a small amount of fluoride to the perovskite leaves a protective layer, increasing stability of the materials and the solar cells significantly. The solar cells retain 90 percent of their efficiency after 1000 hours operation at various extreme testing conditions. The findings are published today in the leading scientific journal Nature Energy.

Because they are so cheap to make, perovskite solar cells have been at the center of much recent solar research. As a consequence, their efficiency has risen from less than 4 percent in 2009 to over 24 percent at present, which is close to traditional silicon cells. So-called tandem cells, which combine silicon and perovskite cells, achieve an efficiency of more than 28 percent.

Despite this success, perovskite has a number of defects due to the nature of the material and the way it is manufactured. Over time, vacancies in the atomic structure of the metal halide trigger the degradation of the perovskite under the influence of moisture, light and heat.

Protective layer

The researchers in Eindhoven, Twente and Beijing have experimented with a new type of perovskite, by adding a small amount of fluoride in the production process. Just like fluoride in toothpaste, the fluoride ions form a protective layer around the crystal, preventing the diffusion of the harmful defects.

"Our work has improved the stability of perovskite solar cells considerably", says Shuxia Tao, assistant professor at the Center for Computational Energy Research, a joint center of the Department of Applied Physics of TU/e and DIFFER, and co-author of the paper. "Our cells maintain 90 percent of their efficiency after 1000 hours under extreme light and heat conditions. This is many times as long as traditional perovskite compounds. We achieve an efficiency of 21.3 percent, which is a very good starting point for further efficiency gains".

Due to its high eletronegativity, fluoride stabilizes the perovskite lattice by forming strong hydrogen bonds and ionic bonds on the surface of the material.

Much of the work of the team from Eindhoven has gone into explaining why fluoride is such an effective ingredient compared to other halogens. Using computer simulations they conclude that part of its success is due to the small size and high electronegativity of fluoride ions. The higher the electronegativity of an element, the easier it attracts electrons of neighbouring elements. This helps fluoride ions to form strong bonds with the other elements in the perovskite compound, forming a stable protective layer.

Future research

The study is seen as an important step towards the successful implementation of perovskite solar cells in the future. However, much work remains to be done. The gold standard in the solar industry is a retention rate of at least 85 percent of original efficiency after ten to fifteen years, a standard which is still some way off for perovskite cells.

"We expect it will take another five to ten years for these cells to become a commercially viable product. Not only do we need to further improve their efficiency and stability, we also need to gain a better theoretical understanding of the relevant mechanisms at the atomic scale. We still don't have all the answers to why some materials are more effective than others in increasing the long-term stability of these cells", says Tao.
-end-


Eindhoven University of Technology

Related Solar Cells Articles:

Next gen solar cells perform better when there's a camera around
A literal ''trick of the light'' can detect imperfections in next-gen solar cells, boosting their efficiency to match that of existing silicon-based versions, researchers have found.
On the trail of organic solar cells' efficiency
Scientists at TU Dresden and Hasselt University in Belgium investigated the physical causes that limit the efficiency of novel solar cells based on organic molecular materials.
Exciting tweaks for organic solar cells
A molecular tweak has improved organic solar cell performance, bringing us closer to cheaper, efficient, and more easily manufactured photovoltaics.
For cheaper solar cells, thinner really is better
Researchers at MIT and at the National Renewable Energy Laboratory (NREL) have outlined a pathway to slashing costs further, this time by slimming down the silicon cells themselves.
Flexible thinking on silicon solar cells
Combining silicon with a highly elastic polymer backing produces solar cells that have record-breaking stretchability and high efficiency.
Perovskite solar cells get an upgrade
Rice University materials scientists find inorganic compounds quench defects in perovskite-based solar cells and expand their tolerance of light, humidity and heat.
Can solar technology kill cancer cells?
Michigan State University scientists have revealed a new way to detect and attack cancer cells using technology traditionally reserved for solar power.
Solar cells with new interfaces
Scientists from NUST MISIS (Russia) and University of Rome Tor Vergata found out that a microscopic quantity of two-dimensional titanium carbide called MXene significantly improves collection of electrical charges in a perovskite solar cell, increasing the final efficiency above 20%.
Welcome indoors, solar cells
Swedish and Chinese scientists have developed organic solar cells optimised to convert ambient indoor light to electricity.
Mapping the energetic landscape of solar cells
A new spectroscopic method now makes it possible to measure and visualize the energetic landscape inside solar cells based on organic materials.
More Solar Cells News and Solar Cells Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Climate Mindset
In the past few months, human beings have come together to fight a global threat. This hour, TED speakers explore how our response can be the catalyst to fight another global crisis: climate change. Guests include political strategist Tom Rivett-Carnac, diplomat Christiana Figueres, climate justice activist Xiye Bastida, and writer, illustrator, and artist Oliver Jeffers.
Now Playing: Science for the People

#562 Superbug to Bedside
By now we're all good and scared about antibiotic resistance, one of the many things coming to get us all. But there's good news, sort of. News antibiotics are coming out! How do they get tested? What does that kind of a trial look like and how does it happen? Host Bethany Brookeshire talks with Matt McCarthy, author of "Superbugs: The Race to Stop an Epidemic", about the ins and outs of testing a new antibiotic in the hospital.
Now Playing: Radiolab

Speedy Beet
There are few musical moments more well-worn than the first four notes of Beethoven's Fifth Symphony. But in this short, we find out that Beethoven might have made a last-ditch effort to keep his music from ever feeling familiar, to keep pushing his listeners to a kind of psychological limit. Big thanks to our Brooklyn Philharmonic musicians: Deborah Buck and Suzy Perelman on violin, Arash Amini on cello, and Ah Ling Neu on viola. And check out The First Four Notes, Matthew Guerrieri's book on Beethoven's Fifth. Support Radiolab today at Radiolab.org/donate.