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.
  • 2017-11-14 10:05:00
  • Article ID: 685154

Twisting Molecule Wrings More Power from Solar Cells

Readily rotating molecules let electrons last, resulting in higher solar cell efficiency.

  • Credit: Image courtesy of Seunghun Lee, University of Virginia

    The atomic structure of organic-inorganic perovskite transitions from a tetragonal structure (top left) to a cubic structure (top right) upon heating. Black and purple spheres represent lead and iodine atoms, respectively. Also shown are the positively charged organic molecules (cations) and the rotational degrees of freedom (preferential or random). The cations in the cubic structure have more rotational freedom than in the tetragonal structure. Photoluminescence measurements (bottom left) and lifetimes (bottom right, t, nanoseconds) show the longer lasting the excited charge carriers in the cubic phase correlate well with higher rotational freedom.

The Science

Inside a solar cell, sunlight excites electrons. But these electrons often don’t last long enough to go on to power cell phones or warm homes. In a promising new type of solar cell, the solar-excited electrons have better odds going on to work. Why? Scientists revealed the dominant force behind the higher efficiency of these promising hybrid organic-inorganic perovskite solar cells. They found that positively charged molecules rotate in the cell. In moving, the molecules screen the excited charge carriers — electrons and holes (missing electrons) — from annihilation. How far the molecules can rotate determines how long the excited electrons and holes last.

The Impact

Solar cells could yield more electricity from the sunshine they harvest. Cells made from hybrid organic-inorganic perovskites are promising. They are highly efficient and low cost. The issue was knowing how the perovskites worked in detail. Discovering this new microscopic mechanism offers a rational path to design novel materials for higher solar cell efficiency.


Upon exposure to sunlight, electrons in a semiconducting material are excited from their normal to higher energy states, forming photo-excited electron and hole pairs. (A hole is an empty state left over by the excited electron.) In general, these charge carriers (the excited electrons and holes) will quickly recombine and annihilate each other. However, if they are made to survive long enough to be collected in an external circuit, they can produce electricity. This is the basis for producing electricity from solar energy. Hybrid organic-inorganic perovskites are among the most promising materials for next-generation solar cells because they combine high efficiency and low cost. The lifetime of the charge carriers in hybrid organic-inorganic perovskites is among the highest of all solar cell materials and hence considered to be the major contributor for their higher efficiencies. However, the microscopic mechanism for the high charge carrier lifetimes in these perovskites is under debate.

A team led by researchers at the University of Virginia discovered the dominant mechanism for the higher carrier lifetime that is responsible for the superior hybrid organic-inorganic perovskite solar cell performance. The mechanism involves screening excited charge carriers by the rotating positively charged (cationic) organic molecules in the crystal. The extent of rotational freedom available for the cations determines the magnitude of the lifetime of the photo-excited charge carriers. By combining neutron and x-ray diffraction, high-performance computing, and opto-electronic measurements, the excited carrier lifetimes were found to dramatically increase whenever the system enters from a phase with a lower number of configurations of rotating cations (called rotational entropy) to a phase with a higher value. The lifetime increases upon transition from a tetragonal with constrained orientation for the cation to a cubic phase with random orientation. The enhanced rotational entropy screens the charge carriers, thereby extending their lifetimes. This discovery points out that searching for hybrid organic-inorganic perovskites with high rotational entropy over a wide temperature range may be a key to further improve solar cell performance.


U.S. Department of Energy, Office of Science, Basic Energy Sciences (University of Virginia plus research at the Center for Nanophase Materials Sciences, an Office of Science user facility) and Advanced Scientific Computing Research (the National Energy Research Scientific Computing Center, also an Office of Science user facility); Ministry of Science and Technology of Taiwan (National Taiwan University); and the National Science Foundation and National Institute for Health (Cornell High Energy Synchrotron Source).   


T. Chen, W.L. Chen, B.J. Foley, J. Lee, J.P.C. Ruff, J.Y.P. Ko, C.M. Brown, L.W. Harriger, D. Zhang, C. Park, M. Yoon, Y.M. Chang, J.J. Choi, and S.H. Lee, “Origin of long lifetime of band-edge charge carriers in organic-inorganic lead iodide perovskites.” Proceedings of the National Academy of Sciences USA 114, 7519-7524 (2017). [DOI: 10.1073/pnas.1704421114]

  • Filters

  • × Clear Filters

Solar Cell Discovery Opens a New Window to Powering Tomorrow's Cities

Windows that generate electricity may have a clearer path to prominent roles in buildings of the future due to an Argonne-led discovery.

How the Earth Stops High-Energy Neutrinos in Their Tracks

A research collaboration including scientists from Berkeley Lab has demonstrated that the Earth stops high-energy neutrinos - particles that only very rarely interact with matter.

Kentucky Researchers First to Produce High Grade Rare Earths From Coal

University of Kentucky researchers have produced nearly pure rare earth concentrates from Kentucky coal using an environmentally-conscious and cost-effective process, a groundbreaking accomplishment in the energy industry.

Watching Atoms Move in Hybrid Perovskite Crystals Reveals Clues to Improving Solar Cells

The discovery of nanoscale changes deep inside hybrid perovskites could shed light on developing low-cost, high-efficiency solar cells. Using X-ray beams and lasers, a team of researchers led by the University of California San Diego discovered how the movement of ions in hybrid perovskites causes certain regions within the material to become better solar cells than other parts.

Quantum Dots Amplify Light with Electrical Pumping

In a breakthrough development, Los Alamos scientists have shown that they can successfully amplify light using electrically excited films of the chemically synthesized semiconductor nanocrystals known as quantum dots.

The Challenge of Estimating Alaska's Soil Carbon Stocks

A geospatial analysis determined the optimal distribution of sites needed to reliably estimate Alaska's vast soil carbon.

Strain-Free Epitaxy of Germanium Film on Mica

Germanium was the material of choice in the early history of electronic devices, and due to its high charge carrier mobility, it's making a comeback. It's generally grown on expensive single-crystal substrates, adding another challenge to making it sustainably viable for most applications. To address this aspect, researchers demonstrate an epitaxy method that incorporates van der Waals' forces to grow germanium on mica. They discuss their work in the Journal of Applied Physics.

Unplugging the Cellulose Biofuel Bottleneck

Molecular-level understanding of cellulose structure reveals why it resists degradation and could lead to cost-effective biofuels.

Detailed View of Immune Proteins Could Lead to New Pathogen-Defense Strategies

Biologists at Berkeley Lab and UC Berkeley used cryo-EM to resolve the structure of a ring of proteins used by the immune system to summon support when under attack, providing new insight into potential strategies for protection from pathogens. The researchers captured the high-resolution image of a protein ring, called an inflammasome, as it was bound to flagellin, a protein from the whiplike tail used by bacteria to propel themselves forward.

Unlocking the Secrets of Ebola

Scientists have identified a set of biomarkers that indicate which patients infected with the Ebola virus are most at risk of dying from the disease. The results come from one of the most in-depth studies ever of blood samples from patients with Ebola.

  • Filters

  • × Clear Filters

Five Brookhaven Lab Scientists Named 2017 American Physical Society Fellows

Anatoly Frenkel, Morgan May, Rachid Nouicer, Eric Stach, and Peter Steinberg were recognized for their outstanding contributions to astrophysics, materials physics, and nuclear physics.

Argonne Appoints Chief of Staff

Megan Clifford has been named Chief of Staff at the U.S. Department of Energy's (DOE) Argonne National Laboratory, effective January 1, 2018.

Jefferson Lab Scientist Selected to Receive Francis Slack Award

Dr. Hari Areti, has been selected to receive the Francis G. Slack Award, established by the Southeastern Section of the American Physical Society, to honor excellence in service to Physics in the Southeastern U.S.

ORNL Wins Nine R&D 100 Awards

Researchers at the Department of Energy's Oak Ridge National Laboratory have received nine R&D 100 Awards in recognition of their significant advancements in science and technology.

Argonne Scientists Capture Several R&D 100 Awards

Innovative technologies developed by researchers at the U.S. Department of Energy's (DOE) Argonne National Laboratory recently earned several R&D 100 Awards.

Eight Los Alamos innovations win R&D 100 Awards

Eight Los Alamos National Laboratory technologies won R&D 100 Awards last week at R&D Magazine's annual ceremony in Orlando, Florida.

Physicist David Gates Named Editor-in-Chief of Plasma, a New Online Journal

Article announces David Gates' appointment as editor-in-chief of Plasma magazine

Argonne to Install Comanche System to Explore ARM Technology for High-Performance Computing

Argonne National Laboratory is collaborating with Hewlett Packard Enterprise (HPE) to provide system software expertise and a development ecosystem for a future high-performance computing (HPC) system based on 64-bit ARM processors.

CANDLE Shines in 2017 HPCwire Readers' and Editors' Choice Awards

Argonne National Laboratory has been recognized in the annual <em>HPCwire</em> Readers' and Editors' Choice Awards, presented at the 2017 International Conference for High Performance Computing, Networking, Storage and Analysis (SC17), in Denver, Colorado.

SLAC's Helen Quinn Honored with 2018 Benjamin Franklin Medal in Physics

Helen Quinn, a professor emerita at the Department of Energy's SLAC National Accelerator Laboratory and Stanford University, will receive the 2018 Benjamin Franklin Medal in Physics - one of eight prestigious Franklin Institute Awards that will be handed out in Philadelphia next April.

  • Filters

  • × Clear Filters

The Challenge of Estimating Alaska's Soil Carbon Stocks

A geospatial analysis determined the optimal distribution of sites needed to reliably estimate Alaska's vast soil carbon.

Unplugging the Cellulose Biofuel Bottleneck

Molecular-level understanding of cellulose structure reveals why it resists degradation and could lead to cost-effective biofuels.

How Fungal Enzymes Break Down Plant Cell Walls

Lignocellulose-degrading enzyme complexes could improve biofuel production.

Stretching to Perfection of 2-D Semiconductors

Scientists use heat and mismatched surfaces to stretch films that can potentially improve the efficient operation of devices.

Simple is Beautiful in Quantum Computing

Defect spins in diamond were controlled with a simpler, geometric method, leading to faster computing.

The Effect of Hurricanes on Puerto Rico's Dry Forests

More frequent storms turn forests from carbon source to sink.

A Chemical Thermometer for Tropical Forests

Monoterpene measures how certain forests respond to heat stress.

Where a Leaf Lands and Lies Influences Carbon Levels in Soil for Years to Come

Whether carbon comes from leaves or needles affects how fast it decomposes, but where it ends up determines how long it's available.

Twisting Molecule Wrings More Power from Solar Cells

Readily rotating molecules let electrons last, resulting in higher solar cell efficiency.

Rules Are Only Suggestions in Heavy Elements

The arrangement of electrons in an exotic human-made element shows that certain properties of heavy elements cannot be predicted using lighter ones.


Tuesday October 03, 2017, 01:05 PM

Stairway to Science

Argonne National Laboratory

Thursday September 28, 2017, 12:05 PM

After-School Energy Rush

Argonne National Laboratory

Thursday September 28, 2017, 10:05 AM

Bringing Diversity Into Computational Science Through Student Outreach

Brookhaven National Laboratory

Thursday September 21, 2017, 03:05 PM

From Science to Finance: SLAC Summer Interns Forge New Paths in STEM

SLAC National Accelerator Laboratory

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

Showing results

0-4 Of 2215