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Chemists ID Catalytic 'Key' for Converting CO2 to Methanol

Results from experiments and computational modeling studies that definitively identify the "active site" of a catalyst commonly used for making methanol from CO2 will guide the design of improved catalysts for transforming this pollutant to useful chemicals.

Cryo-Electron Microscopy Achieves Unprecedented Resolution Using New Computational Methods

Cryo-electron microscopy (cryo-EM)--which enables the visualization of viruses, proteins, and other biological structures at the molecular level--is a critical tool used to advance biochemical knowledge. Now Berkeley Lab researchers have extended cryo-EM's impact further by developing a new computational algorithm instrumental in constructing a 3-D atomic-scale model of bacteriophage P22 for the first time.

New Study Maps Space Dust in 3-D

A new Berkeley Lab-led study provides detailed 3-D views of space dust in the Milky Way, which could help us understand the properties of this dust and how it affects views of distant objects.

Single-Angle Ptychography Allows 3D Imaging of Stressed Materials

Scientists have used a new X-ray diffraction technique called Bragg single-angle ptychography to get a clear picture of how planes of atoms shift and squeeze under stress.

New Feedback System Could Allow Greater Control Over Fusion Plasma

A physicist has created a new system that will let scientists control the energy and rotation of plasma in real time in a doughnut-shaped machine known as a tokamak.

Towards Super-Efficient, Ultra-Thin Silicon Solar Cells

Researchers from Ames Laboratory used supercomputers at NERSC to evaluate a novel approach for creating more energy-efficient ultra-thin crystalline silicon solar cells by optimizing nanophotonic light trapping.

Study IDs Link Between Sugar Signaling and Regulation of Oil Production in Plants

UPTON, NY--Even plants have to live on an energy budget. While they're known for converting solar energy into chemical energy in the form of sugars, plants have sophisticated biochemical mechanisms for regulating how they spend that energy. Making oils costs a lot. By exploring the details of this delicate energy balance, a group of scientists from the U.

High-Energy Electrons Probe Ultrafast Atomic Motion

A new technique synchronized high-energy electrons with an ultrafast laser pulse to probe how vibrational states of atoms change in time.

Rare Earth Recycling

A new energy-efficient separation of rare earth elements could provide a new domestic source of critical materials.

Two-Dimensional MXene Materials Get Their Close-Up

Researchers have long sought electrically conductive materials for economical energy-storage devices. Two-dimensional (2D) ceramics called MXenes are contenders.


Three SLAC Employees Awarded Lab's Highest Honor

At a March 7 ceremony, three employees of the Department of Energy's SLAC National Accelerator Laboratory were awarded the lab's highest honor ­- the SLAC Director's Award.

Dan Sinars Represents Sandia in First Energy Leadership Class

Dan Sinars, a senior manager in Sandia National Laboratories' pulsed power center, which built and operates the Z facility, is the sole representative from a nuclear weapons lab in a new Department of Energy leadership program that recently visited Sandia.

ORNL, HTS International Corporation to Collaborate on Manufacturing Research

HTS International Corporation and the Department of Energy's Oak Ridge National Laboratory have signed an agreement to explore potential collaborations in advanced manufacturing research.

Jefferson Lab Director Honored with Energy Secretary Award

Hugh Montgomery, director of the Department of Energy's Thomas Jefferson National Accelerator Facility (Jefferson Lab), was awarded The Secretary's Distinguished Service Award by the Secretary of Energy earlier this year.

New Projects to Make Geothermal Energy More Economically Attractive

Geothermal energy, a clean, renewable source of energy produced by the heat of the earth, provides about 6 percent of California's total power. That number could be much higher if associated costs were lower. Now scientists at the Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab) have launched two California Energy Commission-funded projects aimed at making geothermal energy more cost-effective to deploy and operate.

Southern Research Project Advances Novel CO2 Utilization Strategy

The U.S. Department of Energy's Office of Fossil Energy has awarded Southern Research nearly $800,000 for a project that targets a more cost-efficient and environmentally friendly method of producing some of the most important chemicals used in manufacturing.

Harker School Wins 2017 SLAC Regional Science Bowl Competition

After losing its first match of the day to the defending champions, The Harker School's team won 10 consecutive rounds to claim victory in the annual SLAC Regional DOE Science Bowl on Saturday, Feb. 11.

Francis Alexander Named Deputy Director of Brookhaven Lab's Computational Science Initiative

Alexander brings extensive management and leadership experience in computational science research to the position.

Kalinin, Paranthaman Elected Materials Research Society Fellows

Two researchers at Oak Ridge National Laboratory, Sergei Kalinin and Mariappan Parans Paranthaman, have been elected fellows of the Materials Research Society.

Two PNNL Researchers Elected to Membership in the National Academy of Engineering

Two scientists at the Pacific Northwest National Laboratory will become members of the prestigious National Academy of Engineering.


High-Energy Electrons Probe Ultrafast Atomic Motion

A new technique synchronized high-energy electrons with an ultrafast laser pulse to probe how vibrational states of atoms change in time.

Rare Earth Recycling

A new energy-efficient separation of rare earth elements could provide a new domestic source of critical materials.

Modeling the "Flicker" of Gluons in Subatomic Smashups

A new model identifies a high degree of fluctuations in the glue-like particles that bind quarks within protons as essential to explaining proton structure.

Rare Nickel Atom Has "Doubly Magic" Structure

Supercomputing calculations confirm that rare nickel-78 has unusual structure, offering insights into supernovas.

Microbial Activity in the Subsurface Contributes to Greenhouse Gas Fluxes

Natural carbon dioxide production from deep subsurface soils contributes significantly to emissions, even in a semiarid floodplain.

Stretching a Metal Into an Insulator

Straining a thin film controllably allows tuning of the materials' magnetic, electronic, and catalytic properties, essential for new energy and electronic devices.

How Moisture Affects the Way Soil Microbes Breathe

Study models soil-pore features that hold or release carbon dioxide.

ARM Data Is for the Birds

Scientists use LIDAR and radar data to study bird migration patterns, thanks to the Atmospheric Radiation Measurement (ARM) Climate Research Facility.

The Future of Coastal Flooding

Better storm surge prediction capabilities could help reduce the impacts of extreme weather events, such as hurricanes.

Estimating Global Energy Use for Water-Related Processes

Scientists find that water-related energy consumption is increasing across the globe, with pronounced differences across regions and sectors.


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Middle Schoolers Test Their Knowledge at Science Bowl Competition

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Friday January 27, 2017, 04:00 PM

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

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Internship Program Helps Foster Development of Future Nuclear Scientists

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

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

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

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University of Utah Makes Solar Accessible

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New Understanding Could Result in More Efficient Organic Solar Cells

Article ID: 613227

Released: 2014-02-03 13:00:00

Source Newsroom: Penn State Materials Research Institute

  • Credit: Giebink, Penn State

    An electron wave function, indicated by orange shading, spreads across several nanocrystalline fullerene molecules in this representation of an organic solar cell heterojunction.

The goal of making cheap organic solar cells may have gotten a little more approachable with a new understanding of the basic science of charge separation presented in a paper published online today, February 3, in Nature Communications. Co-authored by Penn State electrical engineer Noel Giebink with lead author Bethany Bernardo, an undergraduate in his group, and colleagues at IMEC in Belgium, Argonne National Lab, Northwestern, and Princeton, the paper suggests design rules for making more efficient solar cells in the future.

Organic solar cells currently have a top efficiency of approximately 10 percent in the laboratory, much less than inorganic single crystal silicon. One of the challenges to realizing efficient organic cells lies in separating the strongly bound pairs made up of a negatively charged electron and its positively charged hole that result from light absorption, collectively referred to as an exciton. The electron and hole need to be separated in order to make a current.

The way this is done is by creating a heterojunction, which is two different organic semiconductors next to each other, one of which likes to give up an electron and the other which accepts the electron, thereby splitting the original exciton into an electron and hole residing on nearby molecules. A long-standing question in the field, however, is how the nearby electron and hole – still strongly attracted to each other at this stage – manage to separate completely in order to generate current with the efficiency observed in most solar cells.

Over the past few years, a new perspective has proposed that the high separation efficiency relies on a quantum effect – the electron or hole can exist in a wavelike state spread out over several nearby molecules at the same time. When the wave function of one of the carriers collapses at a location far enough away from its partner, the charges can separate more easily. Giebink and colleagues’ work provide compelling new evidence to support this interpretation and identify nanocrystallinity of the common acceptor material made of C60 molecules (also known as fullerenes or buckyballs) as the key that allows this delocalization effect to take place.

This local crystalline order appears to be critical to efficient photocurrent generation in organic solar cells, says Giebink. “A common view in the community is that it takes a bunch of excess energy to break apart the exciton, which meant that there had to be a large energy level difference between the donor and acceptor materials. But that big energy offset reduces the voltage of the solar cell. Our work dispels this perceived tradeoff in light of the impact that wavefunction delocalization and local crystallinity have on the charge separation process. This result should help people design new molecules and optimize donor and acceptor morphologies that help increase solar cell voltage without sacrificing current.”

The team used various luminescence and electroabsorption spectroscopic techniques together with X-ray diffraction to reach their conclusion. Their results, detailed in the paper titled “Delocalization and dielectric screening of charge transfer states in organic photovoltaic cells,” will provide other groups with a better understanding of charge separation as they design and model more efficient organic solar cells.

Noel (Chris) Giebink is assistant professor of electrical engineering and a faculty member in the Materials Research Institute at Penn State. He can be contacted at ncg2@psu.edu.