Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Watching atoms move in hybrid perovskite crystals reveals clues to improving solar cells

22.11.2017

A team of researchers led by the University of California San Diego has for the first time observed nanoscale changes deep inside hybrid perovskite crystals that could offer new insights into developing low-cost, high-efficiency solar cells.

Using X-ray beams and lasers, researchers studied how a new promising class of solar cell materials, called hybrid perovskites, behaves at the nanoscale level during operation. Their experiments revealed that when voltage is applied, ions migrate within the material, creating regions that are no longer as efficient at converting light to electricity.


The inside back cover image of the Nov. 20, 2017 issue of Advanced Materials illustrates how ion migration in a hybrid perovskite crystal affects solar cell performance in different areas of the crystal.

Credit: AMOLF

"Ion migration hurts the performance of the light absorbing material. Limiting it could be a key to improving the quality of these solar cells," said David Fenning, a professor of nanoengineering and member of the Sustainable Power and Energy Center at UC San Diego.

The team, led by Fenning, includes researchers from the AMOLF Institute in the Netherlands and Argonne National Laboratory. Researchers published their findings in Advanced Materials.

Hybrid perovskites are crystalline materials made of a mixture of both inorganic and organic ions. They are promising materials for making next-generation solar cells because they are inexpensive to manufacture and are considerably efficient at converting light to electricity.

However, hybrid perovskites are not very stable, which can make them difficult to study. Microscopic techniques typically used to study solar cells often end up damaging the hybrid perovskites or can't image beyond their surfaces.

Now, a UC San Diego-led team has shown that by using a technique called nanoprobe X-ray fluorescence, they can probe deep into hybrid perovskite materials without destroying them. "This is a new window to peer inside these materials and see precisely what's going wrong," Fenning said.

The researchers studied a type of hybrid perovskite called methylammonium lead bromide, which contains negatively charged bromine ions. Like other hybrid perovskites, its crystalline structure contains many vacancies, or missing atoms, which have been suspected to allow ions to move readily within the material when a voltage is applied.

The researchers first performed nanoprobe X-ray fluorescence measurements on the crystals to create high-resolution maps of the atoms inside the material. The maps revealed that when voltage is applied, the bromine ions migrate from negatively charged areas to positively charged areas.

Next, the researchers shined a laser on the crystals to measure a property called photoluminescence--the material's ability to emit light when excited by a laser--in different areas of the crystals. A good solar cell material emits light very well, so the higher the photoluminescence, the more efficient the solar cell should be. The areas with higher bromine concentrations had up to 180 percent higher photoluminescence than areas depleted of bromine ions.

"We watch the bromine ions migrate within minutes and see that the resulting bromine-rich areas have the potential to become better solar cells while the performance is degraded in bromine-poor areas," Fenning said. Fenning and his team are now exploring ways to limit bromine migration in methylammonium lead bromide and other hybrid perovskites. Researchers say that one potential option would be growing hybrid perovskite crystals in different conditions to minimize the number of vacancies and limit ion migration in the crystalline structure.

###

This work was supported in part by the University of California Carbon Neutrality Initiative, UC San Diego startup funds, the Hellman Foundation, the European Research Council under the European Union's Seventh Framework Programme and the U.S. Department of Energy, Office of Science, Basic Energy Sciences (award no. DE-SC0012118). This work used computing resources provided by Triton Shared Computing Cluster (TSCC) at UC San Diego, the National Energy Research Scientific Computer Center (NERSC) and the Extreme Science and Engineering Discovery Environment (XSEDE) supported by the National Science Foundation (grant no. ACI-1053575). The X-ray measurements were performed at the Advanced Photon Source, a U.S. Department of Energy Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory (contract no. DE-AC02-06CH11357).

Paper title: "Direct Observation of Halide Migration and its Effect on the Photoluminescence of Methylammonium Lead Bromide Perovskite Single Crystals." Authors of the study are Yanqi Luo*, Zhuoying Zhu, Shyue Ping Ong and David P. Fenning of UC San Diego; Parisa Khoram*, Sarah Brittman and Erik C. Garrett of AMOLF, Netherlands; and Barry Lai of Argonne National Laboratory.

*These authors contributed equally to this work.

Media Contact

Liezel Labios
llabios@ucsd.edu
858-246-1124

 @UCSanDiego

http://www.ucsd.edu 

Liezel Labios | EurekAlert!

Further reports about: Energy X-ray bromine crystalline crystals ions perovskites solar cell solar cells

More articles from Materials Sciences:

nachricht One in 5 materials chemistry papers may be wrong, study suggests
15.12.2017 | Georgia Institute of Technology

nachricht Scientists channel graphene to understand filtration and ion transport into cells
11.12.2017 | National Institute of Standards and Technology (NIST)

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-of-its-kind chemical oscillator offers new level of molecular control

DNA molecules that follow specific instructions could offer more precise molecular control of synthetic chemical systems, a discovery that opens the door for engineers to create molecular machines with new and complex behaviors.

Researchers have created chemical amplifiers and a chemical oscillator using a systematic method that has the potential to embed sophisticated circuit...

Im Focus: Long-lived storage of a photonic qubit for worldwide teleportation

MPQ scientists achieve long storage times for photonic quantum bits which break the lower bound for direct teleportation in a global quantum network.

Concerning the development of quantum memories for the realization of global quantum networks, scientists of the Quantum Dynamics Division led by Professor...

Im Focus: Electromagnetic water cloak eliminates drag and wake

Detailed calculations show water cloaks are feasible with today's technology

Researchers have developed a water cloaking concept based on electromagnetic forces that could eliminate an object's wake, greatly reducing its drag while...

Im Focus: Scientists channel graphene to understand filtration and ion transport into cells

Tiny pores at a cell's entryway act as miniature bouncers, letting in some electrically charged atoms--ions--but blocking others. Operating as exquisitely sensitive filters, these "ion channels" play a critical role in biological functions such as muscle contraction and the firing of brain cells.

To rapidly transport the right ions through the cell membrane, the tiny channels rely on a complex interplay between the ions and surrounding molecules,...

Im Focus: Towards data storage at the single molecule level

The miniaturization of the current technology of storage media is hindered by fundamental limits of quantum mechanics. A new approach consists in using so-called spin-crossover molecules as the smallest possible storage unit. Similar to normal hard drives, these special molecules can save information via their magnetic state. A research team from Kiel University has now managed to successfully place a new class of spin-crossover molecules onto a surface and to improve the molecule’s storage capacity. The storage density of conventional hard drives could therefore theoretically be increased by more than one hundred fold. The study has been published in the scientific journal Nano Letters.

Over the past few years, the building blocks of storage media have gotten ever smaller. But further miniaturization of the current technology is hindered by...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

See, understand and experience the work of the future

11.12.2017 | Event News

Innovative strategies to tackle parasitic worms

08.12.2017 | Event News

AKL’18: The opportunities and challenges of digitalization in the laser industry

07.12.2017 | Event News

 
Latest News

Engineers program tiny robots to move, think like insects

15.12.2017 | Power and Electrical Engineering

One in 5 materials chemistry papers may be wrong, study suggests

15.12.2017 | Materials Sciences

New antbird species discovered in Peru by LSU ornithologists

15.12.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>