Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

It's a trap!

29.03.2018

When a solar cell absorbs a photon of light, it starts an electronic race against time. Two particles -- a negatively charged electron and positively charged "hole" -- generate electricity if they fully separate.

However, when these particles become trapped within a solar material before they can fully separate, it can diminish the ability of the material to convert light into electricity.


Argonne researchers helped identify the process by which holes get trapped in nanoparticles made of zinc oxide, a material of potential interest for solar applications because it absorbs ultraviolet light.

Credit: Image by Christopher Milne

Scientists at the U.S. Department of Energy's (DOE) Argonne National Laboratory have published a new study that identifies the process by which holes get trapped in nanoparticles made of zinc oxide, a material of potential interest for solar applications because it absorbs ultraviolet light.

"If you are making a solar cell, you want to avoid trapping holes; but if you're making a photocatalyst, you want to trap them." -- X-ray scientist Christopher Milne of Switzerland's Paul Scherrer Institute.

... more about:
»Nanoparticles »X-ray »solar cell »spectroscopy »trap »zinc

Using X-rays produced by Argonne's Advanced Photon Source (APS), the researchers were able to see the trapping of holes in specific regions of the nanoparticle. This represents a notable advance, as previous experiments were able to detect the migration and trapping of electrons but not holes.

According to Stephen Southworth, an author of the study, some have considered zinc oxide as a possible alternative to titanium dioxide, the most commonly used photovoltaic material. Understanding the hole trapping behavior is necessary to evaluate the viability of the material in solar energy applications, he said.

Although hole trapping impairs the performance of photovoltaic devices, it can improve the ability of zinc oxide to act as a photocatalyst, as positive charges stored in the traps within the material can go on to act as participants in chemical reactions.

"If you are making a solar cell, you want to avoid trapping holes; but if you're making a photocatalyst, you want to trap them," said project lead Christopher Milne, an X-ray scientist at the Paul Scherrer Institute in Switzerland. "Regardless, understanding how these atoms get trapped -- and for how long -- is crucially important for making functional materials that convert light into usable energy."

The researchers determined that the holes became trapped in "oxygen vacancies" -- places within the crystal lattice where an oxygen atom is missing. Zinc oxide, Milne said, has a crystalline structure that allows it to have many of these vacancies. The trapping happens because the vacancies have a lower energy level than the surrounding environment, creating an energetic crevasse for passing holes.

To make their measurements, the researchers combined two different X-ray techniques: X-ray absorption spectroscopy and resonant X-ray emission spectroscopy. "Combining these techniques is uniquely possible with the setup we have at the APS, giving us a view that shows us both the atomic geometry and the electronic structure of the material," said Argonne X-ray physicist Gilles Doumy, an author of the study, which used the 7ID-D beamline at the APS.

"APS was one of the only places in the world we could have done this experiment. It was a very fruitful collaboration," said Milne. The APS is a DOE Office of Science User Facility.

The researchers indicated that future studies of the system could benefit from having the ability to take extremely quick snapshots of the trapping behavior. Such an experiment could be conducted at X-ray free-electron laser facilities like SLAC's Linac Coherent Light Source, also a DOE Office of Science User Facility.

"Essentially, we want to see the same process but have the ability to take images a thousand times faster," said Southworth.

"The functionality of the material is always going to rely on how behavior at early times in the process influences the behavior at later and longer times," added Doumy. "We need both pictures for a comprehensive understanding."

###

An article based on the research, "Revealing hole trapping in zinc oxide nanoparticles by time-resolved X-ray spectroscopy," appeared in the February 2 online issue of Nature Communications. Argonne physicist Anne Marie March also co-wrote the paper.

The work was sponsored, in part, by the DOE's Office of Science.

Argonne National Laboratory seeks solutions to pressing national problems in science and technology. The nation's first national laboratory, Argonne conducts leading-edge basic and applied scientific research in virtually every scientific discipline. Argonne researchers work closely with researchers from hundreds of companies, universities, and federal, state and municipal agencies to help them solve their specific problems, advance America's scientific leadership and prepare the nation for a better future. With employees from more than 60 nations, Argonne is managed by UChicago Argonne, LLC for the U.S. Department of Energy's Office of Science.

The U.S. Department of Energy'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, visit the Office of Science website.

Media Contact

Jared Sagoff
jsagoff@anl.gov
630-252-5549

 @argonne

http://www.anl.gov 

Jared Sagoff | EurekAlert!
Further information:
http://www.anl.gov/articles/it-s-trap
http://dx.doi.org/10.1038/s41467-018-02870-4

Further reports about: Nanoparticles X-ray solar cell spectroscopy trap zinc

More articles from Materials Sciences:

nachricht Graphene origami as a mechanically tunable plasmonic structure for infrared detection
25.04.2018 | University of Illinois College of Engineering

nachricht Scientists create innovative new 'green' concrete using graphene
24.04.2018 | University of Exeter

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Why we need erasable MRI scans

New technology could allow an MRI contrast agent to 'blink off,' helping doctors diagnose disease

Magnetic resonance imaging, or MRI, is a widely used medical tool for taking pictures of the insides of our body. One way to make MRI scans easier to read is...

Im Focus: BAM@Hannover Messe: innovative 3D printing method for space flight

At the Hannover Messe 2018, the Bundesanstalt für Materialforschung und-prüfung (BAM) will show how, in the future, astronauts could produce their own tools or spare parts in zero gravity using 3D printing. This will reduce, weight and transport costs for space missions. Visitors can experience the innovative additive manufacturing process live at the fair.

Powder-based additive manufacturing in zero gravity is the name of the project in which a component is produced by applying metallic powder layers and then...

Im Focus: Molecules Brilliantly Illuminated

Physicists at the Laboratory for Attosecond Physics, which is jointly run by Ludwig-Maximilians-Universität and the Max Planck Institute of Quantum Optics, have developed a high-power laser system that generates ultrashort pulses of light covering a large share of the mid-infrared spectrum. The researchers envisage a wide range of applications for the technology – in the early diagnosis of cancer, for instance.

Molecules are the building blocks of life. Like all other organisms, we are made of them. They control our biorhythm, and they can also reflect our state of...

Im Focus: Spider silk key to new bone-fixing composite

University of Connecticut researchers have created a biodegradable composite made of silk fibers that can be used to repair broken load-bearing bones without the complications sometimes presented by other materials.

Repairing major load-bearing bones such as those in the leg can be a long and uncomfortable process.

Im Focus: Writing and deleting magnets with lasers

Study published in the journal ACS Applied Materials & Interfaces is the outcome of an international effort that included teams from Dresden and Berlin in Germany, and the US.

Scientists at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) together with colleagues from the Helmholtz-Zentrum Berlin (HZB) and the University of Virginia...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Invitation to the upcoming "Current Topics in Bioinformatics: Big Data in Genomics and Medicine"

13.04.2018 | Event News

Unique scope of UV LED technologies and applications presented in Berlin: ICULTA-2018

12.04.2018 | Event News

IWOLIA: A conference bringing together German Industrie 4.0 and French Industrie du Futur

09.04.2018 | Event News

 
Latest News

World's smallest optical implantable biodevice

26.04.2018 | Power and Electrical Engineering

Molecular evolution: How the building blocks of life may form in space

26.04.2018 | Life Sciences

First Li-Fi-product with technology from Fraunhofer HHI launched in Japan

26.04.2018 | Power and Electrical Engineering

VideoLinks
Science & Research
Overview of more VideoLinks >>>