Doe Science news source
The DOE Science News Source is a Newswise initiative to promote research news from the Office of Science of the DOE to the public and news media.
  • 2017-07-24 17:05:29
  • Article ID: 678363

Atomic Movies May Help Explain Why Perovskite Solar Cells Are More Efficient

SLAC's Ultrafast 'Electron Camera' Captures Surprising Atomic Motions in these Next-Generation Materials

  • Credit: SLAC National Accelerator Laboratory

    According to a new SLAC study, atoms in perovskites respond to light with unusual rotational motions and distortions that could explain the high efficiency of these next-generation solar cell materials.

  • Credit: SLAC National Accelerator Laboratory

    Light separates electric charges in a solar cell material by displacing negatively charged electrons. This also creates electron deficiencies, called “electron holes,” with a positive charge. Electrons and holes migrate to opposite sides of the material, generating a voltage for electrical appliances.

  • Credit: SLAC National Accelerator Laboratory

    Illustration of the ultrafast electron diffraction (UED) experiment used to capture the rapid atomic response to light in perovskites. An electron beam (blue) is deflected as it passes through the perovskite sample, generating an intensity or diffraction pattern on a detector that allows the reconstruction of the sample’s atomic structure. By measuring how the pattern changes over time after the sample was hit by a laser pulse (red), researchers can create an ultrafast movie of the atomic response.

  • Credit: Te Hu/Xiaoxi Wu/SLAC National Accelerator Laboratory

    At left: The SLAC study looked at atomic motions in a perovskite solar cell material made of lead (black spheres), iodine (purple) and methylammonium (red and blue). The atomic arrangement is typical for all perovskites, named after a naturally occurring mineral of titanium, oxygen and calcium. At right: Scanning electron microscope image of a thin perovskite film used in the study, showing grains of the material with a size of 50 to 100 nanometers.

  • Credit: SLAC National Accelerator Laboratory

    Iodine atoms, which surround lead atoms in a perovskite solar cell material studied at SLAC, respond to light in a surprising manner: Within 10 trillionths of a second after a light pulse, iodine atoms rotate around every lead atom as if they are moving on the surface of a sphere with the lead atom at the center. These motions could potentially explain the material’s high efficiency in converting light into electricity.

  • Credit: SLAC National Accelerator Laboratory

    From left: SLAC researchers Xijie Wang, Aaron Lindenberg and Xiaoxi Wu at the lab’s experimental station for ultrafast electron diffraction (UED).

In recent years, perovskites have taken the solar cell industry by storm. They are cheap, easy to produce and very flexible in their applications. Their efficiency at converting light into electricity has grown faster than that of any other material – from under four percent in 2009 to over 20 percent in 2017 – and some experts believe that perovskites could eventually outperform the most common solar cell material, silicon. But despite their popularity, researchers don’t know why perovskites are so efficient.

 Now experiments with a powerful “electron camera” at the Department of Energy’s SLAC National Accelerator Laboratory have discovered that light whirls atoms around in perovskites, potentially explaining the high efficiency of these next-generation solar cell materials and providing clues for making better ones.

“We’ve taken a step toward solving the mystery,” said Aaron Lindenberg from the Stanford Institute for Materials and Energy Sciences (SIMES) and the Stanford PULSE Institute for ultrafast science, which are jointly operated by Stanford University and SLAC. “We recorded movies that show that certain atoms in a perovskite respond to light within trillionths of a second in a very unusual manner. This may facilitate the transport of electric charges through the material and boost its efficiency.”

The study was published today in Science Advances.

Light Sets Atomic Structure in Motion 

When light shines on a solar cell material, its energy displaces some of the material’s negatively charged electrons. This leaves behind “electron holes” with a positive charge where the electrons were originally located. Electrons and holes migrate to opposite sides of the material, creating a voltage that can be used to power electrical devices.

A solar cell’s efficiency depends on how freely electrons and holes can move in the material. Their mobility, in turn, depends on the material’s atomic structure. In silicon solar cells, for example, silicon atoms line up in a very orderly fashion inside crystals, and even the smallest structural defects reduce the material’s ability to efficiently harvest light. 

As a result, silicon crystals must be grown in costly, multistep procedures under extremely clean conditions. In contrast, “Perovskites are readily produced by mixing chemicals into a solvent, which evaporates to leave a very thin film of perovskite material,” said Xiaoxi Wu, the study’s lead author from SIMES at SLAC. “Simpler processing means lower costs. Unlike silicon solar cells, perovskite thin films are also lightweight and flexible and can be easily applied to virtually any surface.”

But what exactly is it about perovskites that allows some of them to harvest light very efficiently? Scientists think that one of the keys is how their atoms move in response to light.

To find out more, Wu and her colleagues studied these motions in a prototype material made of iodine, lead and an organic molecule called methylammonium. The iodine atoms are arranged in octohedra – eight-sided structures that look like two pyramids joined at their bases. The lead atoms sit inside the octohedra and the methylammonium molecules sit between octohedra (see diagram below). This architecture is common to many of the perovskites investigated for solar cell applications.

“Previous studies have mostly explored the role of the methylammonium ions and their motions in transporting electric charge through the material,” Wu said. “However, we’ve discovered that light causes large deformations in the network of lead and iodine atoms that could be crucial for the efficiency of perovskites.”     

Unusual Distortions May Enhance Efficiency   

At SLAC’s Accelerator Structure Test Area (ASTA), the researchers first hit a perovskite film, less than two millionths of an inch thick, with a 40-femtosecond laser pulse. One femtosecond is a millionth of a billionth of a second. To determine the atomic response, they sent a 300-femtosecond pulse of highly energetic electrons through the material and observed how the electrons were deflected in the film. This technique, called ultrafast electron diffraction (UED), allowed them to reconstruct the atomic structure.

“By repeating the experiment with different time delays between the two pulses, we obtained a stop-motion movie of the lead and iodine atoms’ motions after the light hit,” said co-author Xijie Wang, SLAC’s lead scientist for UED. “The method is similar to taking a series of ultrafast X-ray snapshots, but electrons give us much stronger signals for thin samples and are less destructive.”   

The team expected that the light pulse would affect atoms evenly in all directions, causing them to jiggle around their original positions.

“But that’s not what happened,” Lindenberg said. “Within 10 trillionths of a second after the laser pulse, the iodine atoms rotated around each lead atom as if they were moving on the surface of a sphere with the lead atom at the center, switching each octahedron from a regular shape to a distorted one.”

The surprising deformations were long-lived and unexpectedly large, similar in size to those observed in melting crystals. 

“This motion could alter the way charges move,” Wu said. “This response to light could enhance efficiency, for instance by allowing electric charges to migrate through defects and protecting them from being trapped in the material.”

“The results from the Lindenberg group provide fascinating first-time insights into the properties of hybrid perovskites using ultrafast electron diffraction as a unique tool,” according to Felix Deschler, an expert in the field of light-induced physics of novel materials and a researcher at Cambridge University’s Cavendish Lab.

“Knowledge about the detailed atomic motion after photoexcitation yields new information about their performance and can provide new guidelines for material development.”

This work was funded by the DOE Office of Science through SIMES.  Other contributors came from the University of Pennsylvania, Columbia University and the Weizmann Institute of Science in Israel.

SLAC is a multi-program laboratory exploring frontier questions in photon science, astrophysics, particle physics and accelerator research. Located in Menlo Park, California, SLAC is operated by Stanford University for the U.S. Department of Energy Office of Science. To learn more, please visit www.slac.stanford.edu.

SLAC National Accelerator Laboratory is supported by the Office of Science of the U.S. Department of Energy. 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 science.energy.gov.

X
X
X
  • Filters

  • × Clear Filters

Biomass-Produced Electricity in the US Possible, but It'll Cost

If the U.S. wants to start using wood pellets to produce energy, either the government or power customers will have to pay an extra cost, a new University of Georgia study has found.

Scientists Make Atoms-Thick Post-It Notes for Solar Cells and Circuits

In a study published Sept. 20 in Nature, UChicago and Cornell University researchers describe an innovative method to make stacks of semiconductors just a few atoms thick. The technique offers scientists and engineers a simple, cost-effective method to make thin, uniform layers of these materials, which could expand capabilities for devices from solar cells to cell phones.

Titan Helps Researchers Suck Mystery Out of Cell's 'Vacuum Cleaners'

In cancer cells, a membrane transport protein called P-glycoprotein, or Pgp, actively pumps anticancer drugs out of the cell, contributing to multidrug resistance. Recently, a team led by computational biophysicist Emad Tajkhorshid from the University of Illinois at Urbana-Champaign (UIUC) used the Titan supercomputer to uncover new details about Pgp that could help the drug discovery community manipulate Pgp function.

Laser-Free Method of Ion Cooling Has Range of Potential Uses

Prof. Daniel Zajfman's universal ion trap cools to a tenth of a degree above absolute zero. The new method does not depend on the type or the weight of the ion and, thus, might be used to investigate the properties of large biological molecules or nanoparticles, among other things.

Tiny Lasers from a Gallery of Whispers

Whispering gallery mode resonators rely on a phenomenon similar to an effect observed in circular galleries, and the same phenomenon applies to light. When light is stored in ring-shaped or spherical active resonators, the waves superimpose in such a way that it can result in laser light. This week in APL Photonics, investigators report a new type of dye-doped WGM micro-laser that produces light with tunable wavelengths.

Copper Catalyst Yields High Efficiency CO2-to-Fuels Conversion

Berkeley Lab scientists have developed a new electrocatalyst that can directly convert carbon dioxide into multicarbon fuels and alcohols using record-low inputs of energy. The work is the latest in a round of studies coming out of Berkeley Lab tackling the challenge of a creating a clean chemical manufacturing system that can put carbon dioxide to good use.

Solar-to-Fuel System Recycles CO2 to Make Ethanol and Ethylene

Berkeley Lab scientists have harnessed the power of photosynthesis to convert carbon dioxide into fuels and alcohols at efficiencies far greater than plants. The achievement marks a significant advance in the effort to move toward sustainable sources of fuel.

New Evidence for Small, Short-Lived Drops of Early Universe Quark-Gluon Plasma?

UPTON, NY--Particles emerging from even the lowest energy collisions of small deuterons with large heavy nuclei at the Relativistic Heavy Ion Collider (RHIC)--a U.S. Department of Energy Office of Science User Facility for nuclear physics research at DOE's Brookhaven National Laboratory--exhibit behavior scientists associate with the formation of a soup of quarks and gluons, the fundamental building blocks of nearly all visible matter.

New Insights Into Nanocrystal Growth in Liquid

PNNL researchers have measured the forces that cause certain crystals to assemble, revealing competing factors that researchers might be able to control. The work has a variety of implications in both discovery and applied science. In addition to providing insights into the formation of minerals and semiconductor nanomaterials, it might also help scientists understand soil as it expands and contracts through wetting and drying cycles.

Discovery Could Reduce Nuclear Waste with Improved Method to Chemically Engineer Molecules

A new chemical principle discovered by scientists at Indiana University has the potential to revolutionize the creation of specially engineered molecules whose uses include the reduction of nuclear waste and the extraction of chemical pollutants from water and soil.


  • Filters

  • × Clear Filters

Los Alamos Gains Role in High-Performance Computing for Materials Program

A new high-performance computing initiative announced this week by the U.S. Department of Energy will help U.S. industry accelerate the development of new or improved materials for use in severe environments.

UK Commits $88 Million to LBNF/DUNE in First-Ever Umbrella Science Agreement with U.S.

The UK has committed $88 million to the Long-Baseline Neutrino Facility and Deep Underground Neutrino Experiment as part of an umbrella science and technology agreement with the United States.

Wayne State Receives $1.2 Million NSF Grant to Develop Autonomous Battery Operating System

Researchers at Wayne State University led by Nathan Fisher, associate professor of computer science in the College of Engineering, received a $1.2 million grant from the National Science Foundation to address the need for effective, integrative battery operating systems that provide sustained and reliable power.

UAH leads effort that secures $20 million grant from the National Science Foundation

A partnership comprising nine universities in Alabama, including The University of Alabama in Huntsville (UAH) as the lead institution, has been awarded a $20 million, five-year grant by the National Science Foundation's Experimental Program to Stimulate Competitive Research (EPSCoR).

Sandia Labs Wins 5 Regional Technology Transfer Awards

Sandia National Laboratories won five awards from the 2017 Federal Laboratory Consortium for its work to develop and commercialize innovative technologies.

Tulane Receives Grant to Reduce Auto Emissions

Members of Tulane University's Shantz Lab will work with industrial scientists to assist in the development of next-generation materials designed to reduce harmful automotive emissions. The three-year old lab and its group of students have received a grant and equipment resources from SACHEM, Inc., a chemical science company.

Lab Leads New Effort in Materials Development

Lawrence Livermore National Lab will be part of a multi-lab effort to apply high-performance computing to US-based industry's discovery, design, and development of materials for severe environments under a new initiative announced by the Department of Energy (DOE) on Sept. 19.

ORNL Innovation Crossroads Program Opens Second Round of Energy Entrepreneurial Fellowships

Entrepreneurs are invited to apply for the second round of Oak Ridge National Laboratory's Innovation Crossroads program.

Los Alamos Recognized as Top Diversity Employer

For the second straight year, Los Alamos National Laboratory was recognized as a top diversity employer by LATINA Style and STEM Workforce Diversity magazine.

SLAC-Led Project Will Use Artificial Intelligence to Prevent or Minimize Electric Grid Failures

A project led by the Department of Energy's SLAC National Accelerator Laboratory will combine artificial intelligence with massive amounts of data and industry experience from a dozen U.S. partners to identify places where the electric grid is vulnerable to disruption, reinforce those spots in advance and recover faster when failures do occur.


  • Filters

  • × Clear Filters

Fungi: Gene Activator Role Discovered

Specific modifications to fungi DNA may hold the secret to turning common plant degradation agents into biofuel producers.

First Look at a Living Cell Membrane

Neutrons provide the solution to nanoscale examination of living cell membrane and confirm the existence of lipid rafts.

High Yield Biomass Conversion Strategy Ready for Commercialization

Researchers convert 80 percent of biomass into high-value products with strategy that's ready for commercialization.

Consequences of Drought Stress on Biofuels

Switchgrass cultivated during a year of severe drought inhibited microbial fermentation and resulting biofuel production.

Clay Minerals and Metal Oxides Change How Uranium Travels Through Sediments

Montmorillonite clays prevent uranium from precipitating from liquids, letting it travel with groundwater.

Tundra Loses Carbon with Rapid Permafrost Thaw

Seven-year-study shows plant growth does not sustainably balance carbon losses from solar warming and permafrost thaw.

Crystals Grow by Twisting, Aligning and Snapping Together

Van der Waals force, which that enables tiny crystals to grow, could be used to design new materials.

Vitamin B12 Fuels Microbial Growth

Scarce compound, vitamin B12, is key for cellular metabolism and may help shape microbial communities that affect environmental cycles and bioenergy production.

Carbon in Floodplain Unlikely to Cycle into the Atmosphere

Microbes leave a large fraction of carbon in anoxic sediments untouched, a key finding for understanding how watersheds influence Earth's ecosystem.

Bacterial Cell Wall Changes Produce More Fatty Molecules

New strategy greatly increases the production and secretion of biofuel building block lipids in bacteria able to grow at industrial scales.


Spotlight

Thursday September 07, 2017, 02:05 PM

Students Discuss 'Cosmic Opportunities' at 45th Annual SLAC Summer Institute

SLAC National Accelerator Laboratory

Thursday August 31, 2017, 05:05 PM

Binghamton University Opens $70 Million Smart Energy Building

Binghamton University, State University of New York

Wednesday August 23, 2017, 05:05 PM

Widening Horizons for High Schoolers with Code

Argonne National Laboratory

Saturday May 20, 2017, 12:05 PM

Rensselaer Polytechnic Institute Graduates Urged to Embrace Change at 211th Commencement

Rensselaer Polytechnic Institute (RPI)

Monday May 15, 2017, 01:05 PM

ORNL, University of Tennessee Launch New Doctoral Program in Data Science

Oak Ridge National Laboratory

Friday April 07, 2017, 11:05 AM

Champions in Science: Profile of Jonathan Kirzner

Department of Energy, Office of Science

Wednesday April 05, 2017, 12:05 PM

High-Schooler Solves College-Level Security Puzzle From Argonne, Sparks Interest in Career

Argonne National Laboratory

Tuesday March 28, 2017, 12:05 PM

Champions in Science: Profile of Jenica Jacobi

Department of Energy, Office of Science

Friday March 24, 2017, 10:40 AM

Great Neck South High School Wins Regional Science Bowl at Brookhaven Lab

Brookhaven National Laboratory

Wednesday February 15, 2017, 04:05 PM

Middle Schoolers Test Their Knowledge at Science Bowl Competition

Argonne National Laboratory

Friday January 27, 2017, 04:00 PM

Haslam Visits ORNL to Highlight State's Role in Discovering Tennessine

Oak Ridge National Laboratory

Tuesday November 08, 2016, 12:05 PM

Internship Program Helps Foster Development of Future Nuclear Scientists

Oak Ridge National Laboratory

Friday May 13, 2016, 04:05 PM

More Than 12,000 Explore Jefferson Lab During April 30 Open House

Thomas Jefferson National Accelerator Facility

Monday April 25, 2016, 05:05 PM

Giving Back to National Science Bowl

Ames Laboratory

Friday March 25, 2016, 12:05 PM

NMSU Undergrad Tackles 3D Particle Scattering Animations After Receiving JSA Research Assistantship

Thomas Jefferson National Accelerator Facility

Tuesday February 02, 2016, 10:05 AM

Shannon Greco: A Self-Described "STEM Education Zealot"

Princeton Plasma Physics Laboratory

Monday November 16, 2015, 04:05 PM

Rare Earths for Life: An 85th Birthday Visit with Mr. Rare Earth

Ames Laboratory

Tuesday October 20, 2015, 01:05 PM

Meet Robert Palomino: 'Give Everything a Shot!'

Brookhaven National Laboratory

Tuesday April 22, 2014, 11:30 AM

University of Utah Makes Solar Accessible

University of Utah

Wednesday March 06, 2013, 03:40 PM

Student Innovator at Rensselaer Polytechnic Institute Seeks Brighter, Smarter, and More Efficient LEDs

Rensselaer Polytechnic Institute (RPI)

Friday November 16, 2012, 10:00 AM

Texas Tech Energy Commerce Students, Community Light up Tent City

Texas Tech University

Wednesday November 23, 2011, 10:45 AM

Don't Get 'Frosted' Over Heating Your Home This Winter

Temple University

Wednesday July 06, 2011, 06:00 PM

New Research Center To Tackle Critical Challenges Related to Aircraft Design, Wind Energy, Smart Buildings

Rensselaer Polytechnic Institute (RPI)

Friday April 22, 2011, 09:00 AM

First Polymer Solar-Thermal Device Heats Home, Saves Money

Wake Forest University

Friday April 15, 2011, 12:25 PM

Like Superman, American University Will Get Its Energy from the Sun

American University

Thursday February 10, 2011, 05:00 PM

ARRA Grant to Help Fund Seminary Building Green Roof

University of Chicago

Tuesday December 07, 2010, 05:00 PM

UC San Diego Installing 2.8 Megawatt Fuel Cell to Anchor Energy Innovation Park

University of California San Diego

Monday November 01, 2010, 12:50 PM

Rensselaer Smart Lighting Engineering Research Center Announces First Deployment of New Technology on Campus

Rensselaer Polytechnic Institute (RPI)

Friday September 10, 2010, 12:40 PM

Ithaca College Will Host Regional Clean Energy Summit

Ithaca College

Tuesday July 27, 2010, 10:30 AM

Texas Governor Announces $8.4 Million Award to Create Renewable Energy Institute

Texas Tech University

Friday May 07, 2010, 04:20 PM

Creighton University to Offer New Alternative Energy Program

Creighton University

Wednesday May 05, 2010, 09:30 AM

National Engineering Program Seeks Subject Matter Experts in Energy

JETS Junior Engineering Technical Society

Wednesday April 21, 2010, 12:30 PM

Students Using Solar Power To Create Sustainable Solutions for Haiti, Peru

Rensselaer Polytechnic Institute (RPI)

Wednesday March 03, 2010, 07:00 PM

Helping Hydrogen: Student Inventor Tackles Challenge of Hydrogen Storage

Rensselaer Polytechnic Institute (RPI)

Thursday February 04, 2010, 02:00 PM

Turning Exercise into Electricity

Furman University

Thursday November 12, 2009, 12:45 PM

Campus Leaders Showing the Way to a Sustainable, Clean Energy Future

National Wildlife Federation (NWF)

Tuesday November 03, 2009, 04:20 PM

Furman University Receives $2.5 Million DOE Grant for Geothermal Project

Furman University

Thursday September 17, 2009, 02:45 PM

Could Sorghum Become a Significant Alternative Fuel Source?

Salisbury University

Wednesday September 16, 2009, 11:15 AM

Students Navigating the Hudson River With Hydrogen Fuel Cells

Rensselaer Polytechnic Institute (RPI)

Wednesday September 16, 2009, 10:00 AM

College Presidents Flock to D.C., Urge Senate to Pass Clean Energy Bill

National Wildlife Federation (NWF)

Wednesday July 01, 2009, 04:15 PM

Northeastern Announces New Professional Master's in Energy Systems

Northeastern University

Friday October 12, 2007, 09:35 AM

Kansas Rural Schools To Receive Wind Turbines

Kansas State University

Thursday August 17, 2006, 05:30 PM

High Gas Prices Here to Stay, Says Engineering Professor

Rowan University

Wednesday May 17, 2006, 06:45 PM

Time Use Expert's 7-Year Fight for Better Gas Mileage

University of Maryland, College Park





Showing results

0-4 Of 2215