Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

New ORNL method could unleash solar power potential

16.03.2016

Measurement and data analysis techniques developed at the Department of Energy's Oak Ridge National Laboratory could provide new insight into performance-robbing flaws in crystalline structures, ultimately improving the performance of solar cells.

While solar cells made from light-harvesting perovskite (an organic-inorganic hybrid) materials have recently eclipsed the 20 percent efficiency mark, researchers believe they could do better if they had a clearer picture of energy flow at the nanometer scale.


(Top) A phasor plot of the transient absorption data shows the presence of free charges and excitons; a false colored image shows their contributions at different spatial positions.

Credit: ORNL

The ORNL discovery, described in a paper published in ACS Photonics, synchronizes microscopy, ultra-short pulses of laser light and data analytics to extract images with single-pixel precision, providing unprecedented detail.

"If we can see exactly and in real time what is happening, we can map out the electronic processes in space instead of relying on snapshots gleaned from spatial averages," said Benjamin Doughty, one of the authors and a member of ORNL's Chemical Sciences Division.

Armed with information about what electrons are doing inside the material, researchers believe they can make improvements that lead to solar cells that are more efficient and potentially less expensive.

"With conventional approaches of studying photovoltaic materials, we are unable to accurately map out electronic processes and how electrons are getting lost," Doughty said. "Those processes can translate into losses in efficiency."

The experiment consists of optically pumping the thin film sample with a 50 femtosecond -- or 50 millionths of a billionth of a second -- laser pulse and then measuring changes in light absorption with a second laser pulse in the material. The technique, called femtosecond transient absorption microscopy, consists of a tabletop of lasers, optics and a microscope. The net result is a pixel-by-pixel map of the material being studied and information researchers can use to improve performance.

"The ability to identify what will be created after the solar cell absorbs a photon, either a pair of free charges or their bound form called an exciton, is crucial from both fundamental and applied perspectives," said co-author Yingzhong Ma, who led the research team. "We found that both free charges and excitons are present, and the strength of our approach lies in not only identifying where they are but also determining what their relative contributions are when they are both present at a given spatial location."

A key remaining challenge is to understand what causes the observed spatial difference, said Ma, so he and colleagues are exploring an all-optical imaging approach that would allow them to correlate electronic dynamics with underlying structural information. This approach may also help researchers map and understand perovskite degradation issues associated with moisture. Ma noted that this must be resolved before solar cells based on this class of materials can be successful.

###

Other team members were Mary Jane Simpson, the lead author and a postdoctoral research associate in the Chemical Sciences Division, and Bin Yang and Kai Xiao of ORNL's Center for Nanophase Materials Science. The paper, titled "Separation of Distinct Photoexcitation Species in Femtosecond Transient Absorption Microscopy," is available at http://pubs.acs.org/doi/abs/10.1021/acsphotonics.5b00638.

This research was funded by DOE's Office of Science. Perovskite sample preparation was done at the Center for Nanophase Materials Sciences, a DOE Office of Science User Facility.

UT-Battelle manages ORNL for the DOE's Office of Science. The 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 http://science.energy.gov/.

Image: https://www.ornl.gov/sites/default/files/news/images/Phasor.jpg

Cutline: (Top) A phasor plot of the transient absorption data shows the presence of free charges and excitons; a false colored image shows their contributions at different spatial positions.

NOTE TO EDITORS: You may read other press releases from Oak Ridge National Laboratory or learn more about the lab at http://www.ornl.gov/news. Additional information about ORNL is available at the sites below:

Twitter -- http://twitter.com/ornl

RSS Feeds -- http://www.ornl.gov/ornlhome/rss_feeds.shtml

Flickr -- http://www.flickr.com/photos/oakridgelab

YouTube -- http://www.youtube.com/user/OakRidgeNationalLab

LinkedIn -- http://www.linkedin.com/companies/oak-ridge-national-laboratory

Facebook -- http://www.facebook.com/Oak.Ridge.National.Laboratory

Ron Walli | EurekAlert!

More articles from Materials Sciences:

nachricht New materials: Growing polymer pelts
19.11.2018 | Karlsruher Institut für Technologie (KIT)

nachricht Why geckos can stick to walls
19.11.2018 | Jacobs University Bremen gGmbH

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: First diode for magnetic fields

Innsbruck quantum physicists have constructed a diode for magnetic fields and then tested it in the laboratory. The device, developed by the research groups led by the theorist Oriol Romero-Isart and the experimental physicist Gerhard Kirchmair, could open up a number of new applications.

Electric diodes are essential electronic components that conduct electricity in one direction but prevent conduction in the opposite one. They are found at the...

Im Focus: Nonstop Tranport of Cargo in Nanomachines

Max Planck researchers revel the nano-structure of molecular trains and the reason for smooth transport in cellular antennas.

Moving around, sensing the extracellular environment, and signaling to other cells are important for a cell to function properly. Responsible for those tasks...

Im Focus: UNH scientists help provide first-ever views of elusive energy explosion

Researchers at the University of New Hampshire have captured a difficult-to-view singular event involving "magnetic reconnection"--the process by which sparse particles and energy around Earth collide producing a quick but mighty explosion--in the Earth's magnetotail, the magnetic environment that trails behind the planet.

Magnetic reconnection has remained a bit of a mystery to scientists. They know it exists and have documented the effects that the energy explosions can...

Im Focus: A Chip with Blood Vessels

Biochips have been developed at TU Wien (Vienna), on which tissue can be produced and examined. This allows supplying the tissue with different substances in a very controlled way.

Cultivating human cells in the Petri dish is not a big challenge today. Producing artificial tissue, however, permeated by fine blood vessels, is a much more...

Im Focus: A Leap Into Quantum Technology

Faster and secure data communication: This is the goal of a new joint project involving physicists from the University of Würzburg. The German Federal Ministry of Education and Research funds the project with 14.8 million euro.

In our digital world data security and secure communication are becoming more and more important. Quantum communication is a promising approach to achieve...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Optical Coherence Tomography: German-Japanese Research Alliance hosted Medical Imaging Conference

19.11.2018 | Event News

“3rd Conference on Laser Polishing – LaP 2018” Attracts International Experts and Users

09.11.2018 | Event News

On the brain’s ability to find the right direction

06.11.2018 | Event News

 
Latest News

Removing toxic mercury from contaminated water

21.11.2018 | Life Sciences

New China and US studies back use of pulse oximeters for assessing blood pressure

21.11.2018 | Medical Engineering

Exoplanet stepping stones

21.11.2018 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>