Nav: Home

Treating solar cell materials reveals formation of unexpected microstructures

July 30, 2019

WASHINGTON, D.C., July 30, 2019 -- Recent advances in solar cell technology use polycrystalline perovskite films as the active layer, with an increase to efficiency of as much as 24.2%. Hybrid organic-inorganic perovskites are especially successful, and they have been used in optoelectronic devices including solar cells, photodetectors, light-emitting diodes and lasers.

But the surface of hybrid perovskites is prone to surface defects, or surface traps, where charge carriers are trapped in the semiconducting material. To solve this problem and reduce the number of traps, the crystal surface must be passivated.

Before use, perovskites can be treated with chemical solutions, vapors and atmospheric gases to remove defects that make the material less effective. Benzylamine is one particularly successful molecule for this purpose. A detailed understanding of the physical and chemical mechanisms by which these treatments work is key to increasing the collection of charge carriers in solar cells.

In their article in this week's Applied Physics Reviews, from AIP Publishing, the authors describe their work testing hybrid organic-inorganic perovskite crystals treated with benzylamine to investigate the mechanisms by which the surface of the crystal is passivated, and traps states are reduced.

"This molecule has been used in polycrystalline fields in solar cells, and people have demonstrated that the solar cells were improved," author Maria A. Loi said. "We wanted to study, in a clean system, why the solar cells were improving and understand why adding this molecule makes the devices better."

The experiments revealed benzylamine enters into the surface of the crystal to create a new, two-dimensional material -- 2D perovskite -- on the surface of the three-dimensional crystal. Where the 2D version forms and later breaks away from the surface, a terraced etching pattern occurs.

"The main purpose was to passivate the surface to reduce defect states," Loi said. "To our surprise, we found out the surface was modified, which was not an expected mechanism. People report that this molecule can improve the quality of devices, but nobody has reported that, in reality, it was creating a two-dimensional layer and could also restructure the material."

The authors also discovered the combination of benzylamine and atmospheric gases is most effective for passivation. That could mean, Loi said, that more than one type of trap state exists. Further investigation of multiple types of trap states could enable precise tuning of the mechanisms involved in preparing crystals for efficient optoelectronic devices.
-end-
The article, "Mechanism of surface passivation of methylammonium lead tribromide single crystals by benzylamine," is authored by Herman Duim, Hong-Hua Fang, Sampson Adjokatse, Gert H. ten Brink, Miguel A. L. Marques, Bart J. Kooi, Graeme R. Blake, Silvana Botti and Maria A. Loi. The article will appear in Applied Physics Reviews on July 30, 2019 (DOI: 10.1063/1.5088342). After that date, it can be accessed at http://aip.scitation.org/doi/full/10.1063/1.5088342.

ABOUT THE JOURNAL

Applied Physics Reviews publishes on important and current topics in experimental or theoretical research in applied physics or applications of physics to other branches of science and engineering. See https://aip.scitation.org/are.

American Institute of Physics

Related Science Articles:

75 science societies urge the education department to base Title IX sexual harassment regulations on evidence and science
The American Educational Research Association (AERA) and the American Association for the Advancement of Science (AAAS) today led 75 scientific societies in submitting comments on the US Department of Education's proposed changes to Title IX regulations.
Science/Science Careers' survey ranks top biotech, biopharma, and pharma employers
The Science and Science Careers' 2018 annual Top Employers Survey polled employees in the biotechnology, biopharmaceutical, pharmaceutical, and related industries to determine the 20 best employers in these industries as well as their driving characteristics.
Science in the palm of your hand: How citizen science transforms passive learners
Citizen science projects can engage even children who previously were not interested in science.
Applied science may yield more translational research publications than basic science
While translational research can happen at any stage of the research process, a recent investigation of behavioral and social science research awards granted by the NIH between 2008 and 2014 revealed that applied science yielded a higher volume of translational research publications than basic science, according to a study published May 9, 2018 in the open-access journal PLOS ONE by Xueying Han from the Science and Technology Policy Institute, USA, and colleagues.
Prominent academics, including Salk's Thomas Albright, call for more science in forensic science
Six scientists who recently served on the National Commission on Forensic Science are calling on the scientific community at large to advocate for increased research and financial support of forensic science as well as the introduction of empirical testing requirements to ensure the validity of outcomes.
More Science News and Science Current Events

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

Rethinking Anger
Anger is universal and complex: it can be quiet, festering, justified, vengeful, and destructive. This hour, TED speakers explore the many sides of anger, why we need it, and who's allowed to feel it. Guests include psychologists Ryan Martin and Russell Kolts, writer Soraya Chemaly, former talk radio host Lisa Fritsch, and business professor Dan Moshavi.
Now Playing: Science for the People

#537 Science Journalism, Hold the Hype
Everyone's seen a piece of science getting over-exaggerated in the media. Most people would be quick to blame journalists and big media for getting in wrong. In many cases, you'd be right. But there's other sources of hype in science journalism. and one of them can be found in the humble, and little-known press release. We're talking with Chris Chambers about doing science about science journalism, and where the hype creeps in. Related links: The association between exaggeration in health related science news and academic press releases: retrospective observational study Claims of causality in health news: a randomised trial This...