Nav: Home

Researchers sew atomic lattices seamlessly together

March 08, 2018

Joining different kinds of materials can lead to all kinds of breakthroughs. It's an essential skill that allowed humans to make everything from skyscrapers (by reinforcing concrete with steel) to solar cells (by layering materials to herd electrons).

In electronics, joining different materials produces heterojunctions - the most fundamental components in solar cells, LEDs and computer chips. The smoother the seam between two materials, the more easily electrons flow across it, which is essential for how well electronic devices function. But they're made up of crystals - rigid lattices of atoms - and they don't take kindly to being mashed together.

In a study published March 8 in Science, Cornell University and University of Chicago scientists revealed a technique to "sew" two patches of crystals seamlessly together to create atomically thin fabrics.

The team wanted to do this by stitching different fabric-like, three-atom-thick crystals. "Usually these are grown in stages under very different conditions; grow one material first, stop the growth, change the condition, and start it again to grow another material," said Jiwoong Park, professor of chemistry at the University of Chicago, and a senior author on the study.

The resulting single-layer materials are the most perfectly aligned ever grown, according to the researchers. The gentler transition means that at the points where the two lattices meet, one lattice stretches or grows to meet the other - instead of leaving holes or other defects.

"If you think of the materials as two different types of fabric, with two different thread counts, where each row of atoms represents a thread, then we are trying to join them thread-to-thread with no loose threads," said David A. Muller, Cornell professor of applied and engineering physics and co-director of the Kavli Institute at Cornell for Nanoscale Science, and a senior author on the study. "Using a new type of electron detector - basically a super-fast, super-sensitive camera - we were able to measure the stretching of the materials from where it joined at the atomic scale to how the whole sheet fitted together, and do so with a precision better than one third of one percent of the distance between atoms."

The atomic seams are so tight, the microscope revealed the larger of the two materials puckers a little around the joint.

"The formation of ripples in these strained 2-D materials provided us with fertile ground for exploring how macroscopic models for the elastic energy can be combined with microscopic theories for the strong underlying van der Waals interactions," said Robert A. DiStasio Jr., assistant professor in Cornell's Department of Chemistry and Chemical Biology in the College of Arts and Sciences, and one of the paper's senior authors.

They decided to test its performance in one of the most widely used electronic devices: a diode. Two kinds of material are joined, and electrons are supposed to be able to flow one way through the "fabric," but not the other.

The diode lit up. "It was exciting to see these three-atom-thick LEDs glowing. We saw excellent performance - the best known for these types of materials," said Saien Xie, a Cornell graduate student in engineering and first author on the paper.

The discovery opens up some interesting ideas for electronics. Devices like LEDs are currently stacked in layers - 3-D versus 2-D - and are usually on a rigid surface. But the new technique could allow new configurations, like flexible LEDs or atoms-thick 2-D circuits that work horizontally and laterally.

Park noted that the stretching and compressing changed the color of the crystals due to the quantum mechanical effects. This suggests potential for light sensors and LEDs that could be tuned to different colors, for example, or strain-sensing fabrics that change color as they're stretched.

"This is so unknown that we don't even know all the possibilities it holds yet," Park said. "Even two years ago it would have been unimaginable."
Other coauthors included postdoctoral scholars Kibum Kang, Ka Un Lao, and Chibeom Park, and graduate students Lijie Tu, Yimo Han, Lujie Huang, and Preeti Poddar.

This study received support from the Cornell Center for Materials Research (CCMR) and the Platform for the Accelerated Realization, Analysis, and Discovery of Interface Materials (PARADIM) at Cornell, as well as the U.S. Air Force Office of Scientific Research, the National Science Foundation, and the Samsung Advanced Institute of Technology. Computational resources were provided by the National Energy Research Scientific Computing Center and the Argonne National Laboratory.

Cornell University

Related Solar Cells Articles:

Record efficiency for printed solar cells
A new study reports the highest efficiency ever recorded for full roll-to-roll printed perovskite solar cells.
Next gen solar cells perform better when there's a camera around
A literal ''trick of the light'' can detect imperfections in next-gen solar cells, boosting their efficiency to match that of existing silicon-based versions, researchers have found.
On the trail of organic solar cells' efficiency
Scientists at TU Dresden and Hasselt University in Belgium investigated the physical causes that limit the efficiency of novel solar cells based on organic molecular materials.
Exciting tweaks for organic solar cells
A molecular tweak has improved organic solar cell performance, bringing us closer to cheaper, efficient, and more easily manufactured photovoltaics.
For cheaper solar cells, thinner really is better
Researchers at MIT and at the National Renewable Energy Laboratory (NREL) have outlined a pathway to slashing costs further, this time by slimming down the silicon cells themselves.
Flexible thinking on silicon solar cells
Combining silicon with a highly elastic polymer backing produces solar cells that have record-breaking stretchability and high efficiency.
Perovskite solar cells get an upgrade
Rice University materials scientists find inorganic compounds quench defects in perovskite-based solar cells and expand their tolerance of light, humidity and heat.
Can solar technology kill cancer cells?
Michigan State University scientists have revealed a new way to detect and attack cancer cells using technology traditionally reserved for solar power.
Solar cells with new interfaces
Scientists from NUST MISIS (Russia) and University of Rome Tor Vergata found out that a microscopic quantity of two-dimensional titanium carbide called MXene significantly improves collection of electrical charges in a perovskite solar cell, increasing the final efficiency above 20%.
Welcome indoors, solar cells
Swedish and Chinese scientists have developed organic solar cells optimised to convert ambient indoor light to electricity.
More Solar Cells News and Solar Cells Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Warped Reality
False information on the internet makes it harder and harder to know what's true, and the consequences have been devastating. This hour, TED speakers explore ideas around technology and deception. Guests include law professor Danielle Citron, journalist Andrew Marantz, and computer scientist Joy Buolamwini.
Now Playing: Science for the People

#576 Science Communication in Creative Places
When you think of science communication, you might think of TED talks or museum talks or video talks, or... people giving lectures. It's a lot of people talking. But there's more to sci comm than that. This week host Bethany Brookshire talks to three people who have looked at science communication in places you might not expect it. We'll speak with Mauna Dasari, a graduate student at Notre Dame, about making mammals into a March Madness match. We'll talk with Sarah Garner, director of the Pathologists Assistant Program at Tulane University School of Medicine, who takes pathology instruction out of...
Now Playing: Radiolab

What If?
There's plenty of speculation about what Donald Trump might do in the wake of the election. Would he dispute the results if he loses? Would he simply refuse to leave office, or even try to use the military to maintain control? Last summer, Rosa Brooks got together a team of experts and political operatives from both sides of the aisle to ask a slightly different question. Rather than arguing about whether he'd do those things, they dug into what exactly would happen if he did. Part war game part choose your own adventure, Rosa's Transition Integrity Project doesn't give us any predictions, and it isn't a referendum on Trump. Instead, it's a deeply illuminating stress test on our laws, our institutions, and on the commitment to democracy written into the constitution. This episode was reported by Bethel Habte, with help from Tracie Hunte, and produced by Bethel Habte. Jeremy Bloom provided original music. Support Radiolab by becoming a member today at     You can read The Transition Integrity Project's report here.