Nav: Home

New perovskite research discoveries may lead to solar cell, LED advances

September 07, 2016

"Promising" and "remarkable" are two words U.S. Department of Energy's Ames Laboratory scientist Javier Vela uses to describe recent research results on organolead mixed-halide perovskites.

Perovskites are optically active, semiconducting compounds that are known to display intriguing electronic, light-emitting and chemical properties. Over the last few years, lead-halide perovskites have become one of the most promising semiconductors for solar cells due to their low cost, easier processability and high power conversion efficiencies. Photovoltaics made of these materials now reach power conversion efficiencies of more than 20 percent.

Vela's research has focused on mixed-halide perovskites. Halides are simple and abundant, negatively charged compounds, such as iodide, bromide and chloride. Mixed-halide perovskites are of interest over single-halide perovskites for a variety of reasons. Mixed-halide perovskites appear to benefit from enhanced thermal and moisture stability, which makes them degrade less quickly than single-halide perovskites, Vela said. He added they can be fine-tuned to absorb sunlight at specific wavelengths, which makes them useful for tandem solar cells and many other applications, including light emitting diodes (LEDs).Using these compounds, scientists can control the color and efficiency of such energy conversion devices.

Speculating that these enhancements had something to do with the internal structure of mixed-halide perovskites, Vela, who is also an associate professor of chemistry at Iowa State University (ISU), worked with scientists with expertise in solid-state nuclear magnetic resonance (NMR) at both Ames Laboratory and ISU. NMR is an analytical chemistry technique that provides scientists with physical, chemical, structural and electronic information about complex samples.

"Our basic question was what it is about these materials in terms of their chemistry, composition, and structure that can affect their behavior," said Vela.

Scientists found that depending on how the material is made there can be significant nonstoichiometric impurities or "dopants" permeating the material, which could significantly affect the material's chemistry, moisture stability and transport properties.

The answers came via the combination of the use of optical absorption spectroscopy, powder X-ray diffraction and for the first time, the advanced probing capabilities of lead solid-state NMR.

"We were only able to see these dopants, along with other semicrystalline impurities, through the use of lead solid-state NMR," said Vela.

Another major discovery scientists made was that solid state synthesis is far superior to solution-phase synthesis in making mixed-halide perovskites. According to Vela, the advanced spectroscopy and materials capabilities of Ames Laboratory and ISU were critical in understanding how various synthetic procedures affect the true composition, speciation, stability and optoelectronic properties of these materials.

"We found you can make clean mixed halide perovskites without semi-crystalline impurities if you make them in the absence of a solvent," Vela said.

According to Vela, the significance of their findings is multifold and they are only beginning to grasp the implications of those findings.

"One obvious implication is that our understanding of the amazing opto-electronic properties of these semiconductors was incomplete," said Vela. "We're dealing with a compound that is not inherently as simple as people thought."

The research is further discussed in a paper, "Persistent Dopants and Phase Segregation in Organolead Mixed-Halide Perovskites," authored by Vela, Bryan A. Rosales, Long Men, Sarah D. Cady, Michael P. Hanrahan, and Aaron J. Rossini; and published online in Chemistry Materials. The work was supported by DOE's Office of Science.
Ames Laboratory is a U.S. Department of Energy Office of Science national laboratory operated by Iowa State University. Ames Laboratory creates innovative materials, technologies and energy solutions. We use our expertise, unique capabilities and interdisciplinary collaborations to solve global problems.

DOE's Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit

DOE/Ames Laboratory

Related Chemistry Articles:

The chemistry of olive oil (video)
Whether you have it with bread or use it to cook, olive oil is awesome.
With more light, chemistry speeds up
Light initiates many chemical reactions. Experiments at the Laser Centre of the Institute of Physical Chemistry of the Polish Academy of Sciences and the University of Warsaw's Faculty of Physics have for the first time demonstrated that increasing the intensity of illumination some reactions can be significantly faster.
The chemistry of whiskey (video)
Derby Day means it's time to recognize the chemical process of distillation, which makes bourbon possible.
Restoration based on chemistry
Considered the pinnacle of mediaeval painting, the Ghent Altarpiece was painted around 1432 by Jan van Eyck and probably his brother Hubert.
The chemistry of redheads (video)
The thing that sets redheads apart from the crowd is pigmentation.
Scientists discover helium chemistry
The scientists experimentally confirmed and theoretically explained the stability of Na2He.
What might Trump mean for chemistry? (video)
Donald Trump is now the 45th president of the US.
Chemistry on the edge
Defects and jagged surfaces at the edges of nanosized platinum and gold particles are key hot spots for chemical reactivity, researchers confirmed using a unique infrared probe at Berkeley Lab.
Light powers new chemistry for old enzymes
Princeton researchers have developed a method that irradiates biological enzymes with light to expand their highly efficient and selective capacity for catalysis to new chemistry.
Better chemistry through...chemistry
Award-winning UCSB professor Bruce Lipshutz is out to make organic chemistry better for the planet

Related Chemistry Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Do animals grieve? Do they have language or consciousness? For a long time, scientists resisted the urge to look for human qualities in animals. This hour, TED speakers explore how that is changing. Guests include biological anthropologist Barbara King, dolphin researcher Denise Herzing, primatologist Frans de Waal, and ecologist Carl Safina.
Now Playing: Science for the People

#SB2 2019 Science Birthday Minisode: Mary Golda Ross
Our second annual Science Birthday is here, and this year we celebrate the wonderful Mary Golda Ross, born 9 August 1908. She died in 2008 at age 99, but left a lasting mark on the science of rocketry and space exploration as an early woman in engineering, and one of the first Native Americans in engineering. Join Rachelle and Bethany for this very special birthday minisode celebrating Mary and her achievements. Thanks to our Patreons who make this show possible! Read more about Mary G. Ross: Interview with Mary Ross on Lash Publications International, by Laurel Sheppard Meet Mary Golda...