Penn State – 3D Imaging Technique Unlocks Properties of Perovskite Crystals – Applications for Perovskite Solar Cells


A reconstruction of a perovskite crystal (CaTiO3) grown on a similar perovskite substrate (NdGaO3) showing electron density and oxygen octahedral tilt. (insert) Artist’s conception of the interface between substrate and film. Credit: Yakun Yuan/Penn State

A team of materials scientists from Penn State, Cornell and Argonne National Laboratory have, for the first time, visualized the 3D atomic and electron density structure of the most complex perovskite crystal structure system decoded to date.

Perovskites are minerals that are of interest as electrical insulators, semiconductors, metals or superconductors, depending on the arrangement of their atoms and electrons.

Perovskite crystals have an unusual grouping of oxygen atoms that form an octahedron, an eight-sided polygon. This arrangement of oxygen atoms acts like a cage that can hold a large number of the elemental atoms in the periodic table. Additionally, other atoms can be fixed to the corners of a cube outside of the cage at precise locations to alter the material’s properties, for instance in changing a metal into an insulator, or a non-magnet into a ferromagnet.

In their current work, the team grew the very first discovered perovskite crystal, called calcium titanate, on top of a series of other perovskite crystal substrates with similar but slightly different oxygen cages at their surfaces. Because the thin film perovskite on top wants to conform to the structure of the thicker substrate, it contorts its cages in a process known as tilt epitaxy.

The researchers found this tilt epitaxy of calcium titanate caused a very ordinary material to take on the property of ferroelectricity, a spontaneous polarization, and to remain ferroelectric up to 900 Kelvin, around three times hotter than room temperature. They were also able to visualize the three-dimensional electron density distribution in calcium titanate thin film for the first time.

“We have been able to see atoms for quite some time, but not map them and their electron distribution in space in a crystal in three dimensions,” said Venkat Gopalan, professor of materials science and physics, Penn State. “If we can see not just where atomic nuclei are located in space, but also how their electron clouds are shared, that will tell us basically everything we need to know about the material in order to infer its properties.”

That was the challenge the team set for itself over five years ago when Gopalan gave his student and lead author of a new report in Nature Communications, Yakun Yuan, the project.

Based on a rarely used x-ray visualization technique called COBRA, for coherent Bragg rod analysis, originally developed by a group in Israel, Yuan figured out how to expand and modify the technique to analyze one of the most complicated, least symmetrical material systems studied to date: the strained three-dimensional perovskite crystal with octahedral tilts in all directions, grown on another equally complex crystal structure.

“To reveal 3D structural details at the atomic level, we had to collect extensive datasets using the most brilliant synchrotron X-ray source available at Argonne National Labs and carefully analyze them with the COBRA analysis code modified for accommodating the complexity of such low symmetry,” said Yakun Yuan.

Gopalan went on to explain that very few perovskite oxygen cages are perfectly aligned throughout the material. Some rotate counterclockwise in one layer of atoms and clockwise in the next. Some cages are squeezed out of shape or tilt in directions that are in or out of plane to the substrate surface.

From the interface of a film with the substrate it is grown on, all the way to its surface, each atomic layer may have unique changes in their structure and pattern.  All of these distortions make a difference in the material properties, which they can predict using a computational technique called density functional theory (DFT).

“The predictions from the DFT calculations provide insights that complement the experimental data and help explain the way that material properties change with the alignment or tilting of the perovskite oxygen cages,” said Prof. Susan Sinnott, whose group performed the theoretical calculations.

The team also validated their advanced COBRA technique against multiple images of their material using the powerful Titan transmission electron microscope in the Materials Research Institute at Penn State.  Since the electron microscopes image extremely thin electron transparent samples in a 2-dimensional projection, not all of the 3-dimensional image could be captured even with the best microscope available today and with multiple sample orientations.

Why Perovskite Solar Cells Are So Efficient

This is an area where 3-dimensional imaging by the COBRA technique outperformed the electron microscopy in such complex structures.

The researchers believe their COBRA technique is applicable to the study of many other three-dimensional low-symmetry atomic crystals.

Additional authors on “Three-dimensional atomic scale electron density reconstruction of octahedral tilt epitaxy in functionals perovskites” are Yanfu Lu, a Ph.D. student in Sinnott’s group, Greg Stone, Gopalan’s former postdoctoral scholar, Ke Wang, a staff scientist in Penn State’s Materials Research Institute, Darrell Schlom and his Ph.D. student Charles Brooks, Cornell University, and Hua Zhou, staff scientist, Argonne National Laboratory.

img_0885-1Penn State University

Funding was provided by the National Science Foundation with additional support provided through the Department of Energy and the Penn State 2D Crystal Consortium, a NSF Materials Innovation Platform, and the Penn State institute for CyberScience.

Contact Venkat Gopalan at vxg8@psu.edu or Hua Zhou at hzhou@aps.anl.gov.

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Quantum Dots leader completes deal to manufacture NextGen Cadmium Free QD’s in Asia


A leading US quantum dot and nanomaterials manufacturer has announced a licensing and manufacturing deal in Assam, India.

The company, Quantum Materials Corp (QMC), has a range of products which can be used to make anything from superior Ultra High Definition television displays to ultra-thin solar cells and more efficient batteries.

The agreement will not only lead to significant job opportunities in the locality of Assam, but is also a major step in deploying QMC’s extraordinary technologies in the region.

There is the opportunity to adopt next-generation solar photovoltaic technology in the area, after the implementation of recent tariffs on imported photovoltaics into India.

QMC’s cadmium-free quantum dots offer a less hazardous and eco-friendlier alternative for producers and consumers, providing them with the color benefit without the risks of toxicity or liability.

The incorporation of cadmium in quantum dots has restricted their adoption, keeping manufacturers from leveraging the benefits of the technology. Restriction of Hazardous Substances regulations currently state that 1,000 parts per million (ppm) cadmium can be used, however this exception will soon expire and only 100 ppm of cadmium will be acceptable. In 2015, the European Parliament banned the continued use of cadmium in display and lighting devices.

img_0866Read More: What are quantum dots? The Science and Applications

Furthermore, controls and regulations are growing in Asia, with China implementing new laws of its own.

QMC signed the License and Development Agreement with Amtronics CC to allow for the establishment of large scale, low cost quantum dot production for the development and future commercial manufacture of: ultra-high definition display panels, solid state lighting LEDs and quantum dot driven thin-film solar cells.

The Agreement provides Amtronics CC with the right to manufacture quantum dots and thin-film quantum dot solar cells for commercial supply in India, as well as the right to use the QDXTM trademark and technical data to support its marketing initiatives. Under the terms of the Agreement, QMC receives an immediate upfront license fee of US$1,000,000 in addition to technology development funding, scheduled milestone payments and royalties on all quantum dots/solar cells produced.

The 12,000 square feet nanotech-focused facility is being established as the anchor project within the recently announced Electronics Manufacturing Cluster in the Guwahati Tech City.

“We are extremely pleased to partner with Amtronics CC and Amtron as they establish the necessary infrastructure to support large scale thin-film, quantum dot based solar cell production in Assam India using QMC patented technologies” explained Stephen B. Squires, President and CEO of Quantum Materials Corp.

“India’s recent implementation of tariffs applied to imported solar photovoltaics creates an ideal opportunity to establish QMC’s next generation thin-film photovoltaics for broad adoption in the region. I am highly confident that our technologies will help India fulfill its goal to deploy low cost renewables as a significant step toward energy independence”

Dr. George Anthony Balchin, Managing Director of Amtronics CC added, “We are pleased to be involved and provide the initial US $20,000,000 in funding for this enterprise and are anxious to see these extraordinary technologies deployed in a region that will benefit from both the end product as well as the significant potential for job creation.

The initial capital infusion will be used to build out the facility, purchase all the production and process equipment, including the micro reactors, train the staff and provide the initial working capital. It is very rare and rewarding to be involved with a project that is the culmination of a group of like-minded individuals striving for a common goal that has so much potential to enhance the lives of so many.”

Commenting further QMC CEO Squires stated: “As India represents one of the largest renewable energy and consumer electronics markets in the world, our partnership with Amtronics CC is an important step in expanding the value of the QMC franchise globally. This partnership will allow us to address global challenges such as rising energy costs, energy security, increasing power consumption and environmental quality on a more rapid basis.”

Graphene takes a Step Toward Renewable Fuel – Converting water and carbon dioxide to the renewable energy of the future


graphenetakeJianwu Sun at Linköping University inspecting the growth reactor for growth of cubic silicon carbide. Credit: Thor Balkhed/LiU

Using the energy from the sun and graphene applied to the surface of cubic silicon carbide, researchers at Linköping University, Sweden, are working to develop a method to convert water and carbon dioxide to the renewable energy of the future.

They have now taken an important step toward this goal, reporting a method that makes it possible to produce graphene with several layers in a tightly controlled process. The researchers have also shown that graphene acts as a superconductor in certain conditions. Their results have been published in the scientific journals Carbon and Nano Letters.

Carbon, oxygen and hydrogen are the three elements obtained by taking apart molecules of carbon dioxide and water. The same elements are the building blocks of chemical substances used for fuel, such as ethanol and methane. The conversion of carbon dioxide and water to renewable fuel could provide an alternative to fossil fuels and contribute to reducing carbon dioxide emissions into the atmosphere. Jianwu Sun, senior lecturer at Linköping University, is trying to find a way to do just that.

Researchers at Linköping University have previously developed a world-leading method to produce cubic silicon carbide, which consists of silicon and carbon. The cubic form has the ability to capture energy from the sun and create charge carriers. This is, however, not sufficient. Graphene, one of the thinnest materials ever produced, plays a key role in the project. The material comprises a single  of  atoms bound to each other in a hexagonal lattice. Graphene has a high ability to conduct an electric current, a property that would be useful for solar energy conversion. It also has several unique properties, and possible uses of graphene are being extensively studied all over the world.

jianwu-sun-ifm-liu-tb-dsc2960Read Original Post from Linkoping University

In recent years, the researchers have attempted to improve the process by which graphene grows on a surface in order to control the properties of the graphene. Their recent progress is described in an article in the scientific journal Carbon.

“It is relatively easy to grow one layer of graphene on silicon carbide. But it’s a greater challenge to grow large-area uniform graphene that consists of several layers on top of each other. We have now shown that it is possible to grow uniform graphene that consists of up to four layers in a controlled manner,” says Jianwu Sun of the Department of Physics, Chemistry and Biology at Linköping University.

One of the difficulties posed by multilayer graphene is that the surface becomes uneven when different numbers of layers grow at different locations. The edge when one layer ends has the form of a tiny, nanoscale staircase. Flat layers are desirable, so these steps are a problem, particularly when the steps accumulate in one location, like a wrongly built staircase in which several steps have been united to form one large step. The researchers have now found a way to remove these large, united steps by growing the graphene at a carefully controlled temperature. Furthermore, the researchers have shown that their method makes it possible to control how many layers the graphene will contain. This is the first key step in an ongoing research project whose goal is to make fuel from water and .

In a closely related article in the journal Nano Letters, the researchers describe investigations into the electronic properties of multilayer graphene grown on cubic silicon carbide.

“We discovered that multilayer graphene has extremely promising electrical properties that enable the material to be used as a superconductor, a material that conducts electrical current with zero electrical resistance. This special property arises solely when the graphene layers are arranged in a special way relative to each other,” says Jianwu Sun.

Theoretical calculations had predicted that multilayer  would have superconductive properties, provided that the layers are arranged in a particular way. In the new study, the researchers demonstrate experimentally for the first time that this is the case. Superconducting magnets are extremely powerful magnets used in medical magnetic resonance cameras and in particle accelerators. There are many potential areas of application for superconductors, such as electrical supply lines with zero energy loss, and high-speed trains that float on a magnetic field. Their use is currently limited by the inability to produce superconductors that function at room temperature. Currently available superconductors function only at extremely low temperatures.

 Explore further: Atoms use tunnels to escape graphene cover

More information: Yuchen Shi et al, Elimination of step bunching in the growth of large-area monolayer and multilayer graphene on off-axis 3C SiC (111), Carbon (2018). DOI: 10.1016/j.carbon.2018.08.042

Weimin Wang et al. Flat-Band Electronic Structure and Interlayer Spacing Influence in Rhombohedral Four-Layer Graphene, Nano Letters (2018). DOI: 10.1021/acs.nanolett.8b02530

 

Will Drexel’s Discovery Enable a Lithium-Sulfur ‘Battery (R)evolution’?


Lithium-sulfur batteries could be the energy storage devices of the future, if they can get past a chemical phenomenon that reduces their endurance. Drexel researchers have reported a method for making a sulfur cathode that could preserve the batteries’ exceptional performance. (Image from Drexel News)

Drexel’s College of Engineering reports that researchers and the industry are looking at Li-S batteries to eventually replace Li-ion batteries because a new chemistry that theoretically allows more energy to be packed into a single battery.

img_0808This improved capacity, on the order of 5-10 times that of Li-ion batteries, equates to a longer run time for batteries between charges.

However, the problem is that Li-S batteries have trouble maintaining their superiority beyond just a few recharge cycles. But a solution to that problem may have been found with new research.

The new approach, reported by in a recent edition of the American Chemical Society journal Applied Materials and Interfaces, shows that it can hold polysulfides in place, maintaining the battery’s impressive stamina, while reducing the overall weight and the time required to produce them.

“We have created freestanding porous titanium monoxide nanofiber mat as a cathode host material in lithium-sulfur batteries,” said Vibha Kalra, PhD, an associate professor in the College of Engineering who led the research.

img_0810

“This is a significant development because we have found that our titanium monoxide-sulfur cathode is both highly conductive and able to bind polysulfides via strong chemical interactions, which means it can augment the battery’s specific capacity while preserving its impressive performance through hundreds of cycles.

We can also demonstrate the complete elimination of binders and current collector on the cathode side that account for 30-50 percent of the electrode weight — and our method takes just seconds to create the sulfur cathode, when the current standard can take nearly half a day.”

img_0811

Please find the full report here: LINK
TiO Phase Stabilized into Free-Standing Nanofibers as Strong Polysulfide Immobilizer in Li-S Batteries: Evidence for Lewis Acid-Base Interactions
Arvinder Singh and Vibha Kalra

ACS Appl. Mater. Interfaces, Just Accepted Manuscript

DOI: 10.1021/acsami.8b11029

We report the stabilization of titanium monoxide (TiO) nanoparticles in nanofibers through electrospinning and carbothermal processes and their unique bi-functionality – high conductivity and ability to bind polysulfides – in Li-S batteries. The developed 3-D TiO/CNF architecture with the inherent inter-fiber macropores of nanofiber mats provides a much higher surface area (~427 m2 g-1) and overcomes the challenges associated with the use of highly dense powdered Ti-based suboxides/monoxide materials, thereby allowing for high active sulfur loading among other benefits.

The developed TiO/CNF-S cathodes exhibit high initial discharge capacities of ~1080 mAh g-1, ~975 mAh g-1, and ~791 mAh g-1 at 0.1C, 0.2C, and 0.5C rates, respectively with long term cycling. Furthermore, free-standing TiO/CNF-S cathodes developed with rapid sulfur melt infiltration (~5 sec) eradicate the need of inactive elements viz. binders, additional current collectors (Al-foil) and additives. Using postmortem XPS and Raman analysis, this study is the first to reveal the presence of strong Lewis acid-base interaction between TiO (3d2) and Sx2- through coordinate covalent Ti-S bond formation.

Our results highlight the importance of developing Ti-suboxides/monoxide based nanofibrous conducting polar host materials for next-generation Li-S batteries.

“Reprinted with permission from (DOI: 10.1021/acsami.8b11029). Copyright (2018) American Chemical Society.”

 

 

The Future Of Energy Isn’t Fossil Fuels Or Renewables, It’s Nuclear Fusion (Really?)


 

Co State Nuc Fussion 2Colorado State University scientists, using a compact but powerful laser to heat arrays of ordered nanowires, have demonstrated micro-scale nuclear fusion in the lab.

Let’s pretend, for a moment, that the climate doesn’t matter. That we’re completely ignoring the connection between carbon dioxide, the Earth’s atmosphere, the greenhouse effect, global temperatures, ocean acidification, and sea-level rise. From a long-term point of view, we’d still need to plan for our energy future. Fossil fuels, which make up by far the majority of world-wide power today, are an abundant but fundamentally limited resource. Renewable sources like wind, solar, and hydroelectric power have different limitations: they’re inconsistent. There is a long-term solution, though, that overcomes all of these problems: nuclear fusion.

Even the most advanced chemical reactions, like combusting thermite, shown here, generate about a million times less energy per unit mass compared to a nuclear reaction.

Even the most advanced chemical reactions, like combusting thermite, shown here, generate about a million times less energy per unit mass compared to a nuclear reaction.NIKTHESTUNNED OF WIKIPEDIA

It might seem that the fossil fuel problem is obvious: we cannot simply generate more coal, oil, or natural gas when our present supplies run out. We’ve been burning pretty much every drop we can get our hands on for going on three centuries now, and this problem is going to get worse. Even though we have hundreds of years more before we’re all out, the amount isn’t limitless. There are legitimate, non-warming-related environmental concerns, too.

Even if we ignored the CO2-global climate change problem, fossil fuels are limited in the amount Earth contains, and also extracting, transporting, refining and burning them causes large amounts of pollution.

Even if we ignored the CO2-global climate change problem, fossil fuels are limited in the amount Earth contains, and also extracting, transporting, refining and burning them causes large amounts of pollution.GREG GOEBEL

The burning of fossil fuels generates pollution, since these carbon-based fuel sources contain a lot more than just carbon and hydrogen in their chemical makeup, and burning them (to generate energy) also burns all the impurities, releasing them into the air. In addition, the refining and/or extraction process is dirty, dangerous and can pollute the water table and entire bodies of water, like rivers and lakes.

Wind farms, like many other sources of renewable energy, are dependent on the environment in an inconsistent, uncontrollable way.

Wind farms, like many other sources of renewable energy, are dependent on the environment in an inconsistent, uncontrollable way.WINCHELL JOSHUA, U.S. FISH AND WILDLIFE SERVICE

On the other hand, renewable energy sources are inconsistent, even at their best. Try powering your grid during dry, overcast (or overnight), and drought-riddled times, and you’re doomed to failure. The sheer magnitude of the battery storage capabilities required to power even a single city during insufficient energy-generation conditions is daunting. Simultaneously, the pollution effects associated with creating solar panels, manufacturing wind or hydroelectric turbines, and (especially) with creating the materials needed to store large amounts of energy are tremendous as well. Even what’s touted as “green energy” isn’t devoid of drawbacks.

Reactor nuclear experimental RA-6 (Republica Argentina 6), en marcha. The blue glow is known as Cherenkov radiation, from the faster-than-light-in-water particles emitted.

Reactor nuclear experimental RA-6 (Republica Argentina 6), en marcha. The blue glow is known as Cherenkov radiation, from the faster-than-light-in-water particles emitted.CENTRO ATOMICO BARILOCHE, VIA PIECK DARÍO

But there is always the nuclear option. That word itself is enough to elicit strong reactions from many people: nuclear. The idea of nuclear bombs, of radioactive fallout, of meltdowns, and of disasters like Chernobyl, Three Mile Island, and Fukushima — not to mention residual fear from the Cold War — make “NIMBY” the default position for a large number of people. And that’s a fear that’s not wholly without foundation, when it comes to nuclear fission. But fission isn’t the only game in town.

Watch the Video: Nuclear Bomb – The First H Bomb Test

 

In 1952, the United States detonated Ivy Mike, the first demonstrated nuclear fusion reaction to occur on Earth. Whereas nuclear fission involves taking heavy, unstable (and already radioactive) elements like Thorium, Uranium or Plutonium, initiating a reaction that causes them to split apart into smaller, also radioactive components that release energy, nothing involved in fusion is radioactive at all. The reactants are light, stable elements like isotopes of hydrogen, helium or lithium; the products are also light and stable, like helium, lithium, beryllium or boron.

 

The proton-proton chain responsible for producing the vast majority of the Sun's power is an example of nuclear fusion.

The proton-proton chain responsible for producing the vast majority of the Sun’s power is an example of nuclear fusion.BORB / WIKIMEDIA COMMONS

So far, fission has taken place in either a runaway or controlled environment, rushing past the breakeven point (where the energy output is greater than the input) with ease, while fusion has never reached the breakeven point in a controlled setting. But four main possibilities have emerged. img_0787

  1. Inertial Confinement Fusion. We take a pellet of hydrogen — the fuel for this fusion reaction — and compress it using many lasers that surround the pellet. The compression causes the hydrogen nuclei to fuse into heavier elements like helium, and releases a burst of energy.
  2. Magnetic Confinement Fusion. Instead of using mechanical compression, why not let the electromagnetic force do the confining work? Magnetic fields confine a superheated plasma of fusible material, and nuclear fusion reactions occur inside a Tokamak-style reactor.
  3. Magnetized Target Fusion. In MTF, a superheated plasma is created and confined magnetically, but pistons surrounding it compress the fuel inside, creating a burst of nuclear fusion in the interior.
  4. Subcritical Fusion. Instead of trying to trigger fusion with heat or inertia, subcritical fusion uses a subcritical fission reaction — with zero chance of a meltdown — to power a fusion reaction.

The first two have been researched for decades now, and are the closest to the coveted breakeven point. But the latter two are new, with the last one gaining many new investors and start-ups this decade.

The preamplifiers of the National Ignition Facility are the first step in increasing the energy of laser beams as they make their way toward the target chamber. NIF recently achieved a 500 terawatt shot - 1,000 times more power than the United States uses at any instant in time.

The preamplifiers of the National Ignition Facility are the first step in increasing the energy of laser beams as they make their way toward the target chamber. NIF recently achieved a 500 terawatt shot – 1,000 times more power than the United States uses at any instant in time.DAMIEN JEMISON/LLNL

Even if you reject climate science, the problem of powering the world, and doing so in a sustainable, pollution-free way, is one of the most daunting long-term ones facing humanity. Nuclear fusion as a power source has never been given the necessary funding to develop it to fruition, but it’s the one physically possible solution to our energy needs with no obvious downsides. If we can get the idea that “nuclear” means “potential for disaster” out of our heads, people from all across the political spectrum just might be able to come together and solve our energy and environmental needs in one single blow. If you think the government should be investing in science with national and global payoffs, you can’t do better than the ROI that would come from successful fusion research. The physics works out beautifully; we now just need the investment and the engineering breakthroughs.

Special Contribution to Forbes by: Ethan Siegel 

The $80 Trillion World Economy in One Chart: The World Bank View


The latest estimate from the World Bank puts global GDP at roughly $80 trillion in nominal terms for 2017.

Today’s chart from HowMuch.net uses this data to show all major economies in a visualization called a Voronoi diagram – let’s dive into the stats to learn more.

THE WORLD’S TOP 10 ECONOMIES

Here are the world’s top 10 economies, which together combine for a whopping two-thirds of global GDP.

Rank Country GDP % of Global GDP
#1 United States $19.4 trillion 24.4%
#2 China $12.2 trillion 15.4%
#3 Japan $4.87 trillion 6.1%
#4 Germany $3.68 trillion 4.6%
#5 United Kingdom $2.62 trillion 3.3%
#6 India $2.60 trillion 3.3%
#7 France $2.58 trillion 3.3%
#8 Brazil $2.06 trillion 2.6%
#9 Italy $1.93 trillion 2.4%
#10 Canada $1.65 trillion 2.1%

In nominal terms, the U.S. still has the largest GDP at $19.4 trillion, making up 24.4% of the world economy.

While China’s economy is far behind in nominal terms at $12.2 trillion, you may recall that the Chinese economy has been the world’s largest when adjusted for purchasing power parity (PPP) since 2016. 

The next two largest economies are Japan ($4.9 trillion) and Germany ($4.6 trillion) – and when added to the U.S. and China, the top four economies combined account for over 50% of the world economy.

MOVERS AND SHAKERS

Over recent years, the list of top economies hasn’t changed much – and in a similar visualization we posted 18 months ago, the four aforementioned top economies all fell in the exact same order.

However, look outside of these incumbents, and you’ll see that the major forces shaping the future of the global economy are in full swing, especially when it comes to emerging markets.

Here are some of the most important movements:

India has now passed France in nominal terms with a $2.6 trillion economy, which is about 3.3% of the global total. In the most recent quarter, Indian GDP growth saw its highest growth rate in two years at about 8.2%.

Brazil, despite its very recent economic woes, surpassed Italy in GDP rankings to take the #8 spot overall. 

Turkey has surpassed The Netherlands to become the world’s 17th largest economy, and Saudi Arabia has jumped past Switzerland to claim the 19th spot.

And what about the Future?

Read About How China will lead the world by 2050 Photo: REUTERS/Stringer

How a ‘solar battery’ could bring electricity to rural areas – A ‘solar flow’ battery could “Harvest (energy) in the Daytime and Provide Electricity in the Evening


New solar flow battery with a 14.1 percent efficiency. Photo: David Tenenbaum, UW-Madison

Solar energy is becoming more and more popular as prices drop, yet a home powered by the Sun isn’t free from the grid because solar panels don’t store energy for later. Now, researchers have refined a device that can both harvest and store solar energy, and they hope it will one day bring electricity to rural and underdeveloped areas.

The problem of energy storage has led to many creative solutions, like giant batteries. For a paper published today in the journal Chem, scientists trying to improve the solar cells themselves developed an integrated battery that works in three different ways.

It can work like a normal solar cell by converting sunlight to electricity immediately, explains study author Song Jin, a chemist at the University of Wisconsin at Madison. It can store the solar energy, or it can simply be charged like a normal battery.

“IT COULD HARVEST IN THE DAYTIME, PROVIDE ELECTRICITY IN THE EVENING.”

It’s a combination of two existing technologies: solar cells that harvest light, and a so-called flow battery.

The most commonly used batteries, lithium-ion, store energy in solid materials, like various metals. Flow batteries, on the other hand, store energy in external liquid tanks.

What is A ‘Flow Battery’

This means they are very easy to scale for large projects. Scaling up all the components of a lithium-ion battery might throw off the engineering, but for flow batteries, “you just make the tank bigger,” says Timothy Cook, a University at Buffalo chemist and flow battery expert not involved in the study.

“You really simplify how to make the battery grow in capacity,” he adds. “We’re not making flow batteries to power a cell phone, we’re thinking about buildings or industrial sites.

Jin and his team were the first to combine the two features. They have been working on the battery for years, and have now reached 14.1 percent efficiency.

Jin calls this “round-trip efficiency” — as in, the efficiency from taking that energy, storing it, and discharging it. “We can probably get to 20 percent efficiency in the next few years, and I think 25 percent round-trip is not out of the question,” Jin says.

Apart from improving efficiency, Jin and his team want to develop a better design that can use cheaper materials.

The invention is still at proof-of-concept stage, but he thinks it could have a large impact in less-developed areas without power grids and proper infrastructure. “There, you could have a medium-scale device like this operate by itself,” he says. “It could harvest in the daytime, provide electricity in the evening.” In many areas, Jin adds, having electricity is a game changer, because it can help people be more connected or enable more clinics to be open and therefore improve health care.

And Cook notes that if the solar flow battery can be scaled, it can still be helpful in the US.

The United States might have plenty of power infrastructure, but with such a device, “you can disconnect and have personalized energy where you’re storing and using what you need locally,” he says. And that could help us be less dependent on forms of energy that harm the environment.

“Harvesting Energy from Light” – ORNL: Multimodal imaging shows strain can drive chemistry in a photovoltaic material –


In a thin film of a solar-energy material, molecules in twin domains (modeled in left and right panels) align in opposing orientations within grain boundaries (shown by scanning electron microscopy in the center panel). Strain can change chemical segregation and may be engineered to tune photovoltaic efficiency. Credit: Stephen Jesse/Oak Ridge National Laboratory, U.S. Dept. of Energy (hi-res image)

OAK RIDGE, Tenn., Sept. 25, 2018—A unique combination of imaging tools and atomic-level simulations has allowed a team led by the Department of Energy’s Oak Ridge National Laboratory to solve a longstanding debate about the properties of a promising material that can harvest energy from light.

The researchers used multimodal imaging to “see” nanoscale interactions within a thin film of hybrid organic–inorganic perovskite, a material useful for solar cells.

They determined that the material is ferroelastic, meaning it can form domains of polarized strain to minimize elastic energy. This finding was contrary to previous assumptions that the material is ferroelectric, meaning it can form domains of polarized electric charge to minimize electric energy.

“We found that people were misguided by the mechanical signal in standard electromechanical measurements, resulting in the misinterpretation of ferroelectricity,” said Yongtao Liu of ORNL, whose contribution to the study became a focus of his PhD thesis at the University of Tennessee, Knoxville (UTK).

Olga Ovchinnikova, who directed the experiments at ORNL’s Center for Nanophase Materials Sciences (CNMS), added, “We used multimodal chemical imaging—scanning probe microscopy combined with mass spectrometry and optical spectroscopy—to show that this material is ferroelastic and how the ferroelasticity drives chemical segregation.”

The findings, reported in Nature Materials, revealed that differential strains cause ionized molecules to migrate and segregate within regions of the film, resulting in local chemistry that may affect the transport of electric charge.

The understanding that this unique suite of imaging tools enables allows researchers to better correlate structure and function and fine-tune energy-harvesting films for improved performance.

“We want to predictively make grains of particular sizes and geometries,” Liu said. “The geometry is going to control the strain, and the strain is going to control the local chemistry.”

For their experiment, the researchers made a thin film by spin-casting a perovskite on an indium tin oxide–coated glass substrate. This process created the conductive, transparent surface a photovoltaic device would need—but also generated strain.

To relieve the strain, tiny ferroelastic domains formed. One type of domain was “grains,” which look like what you might see flying over farmland with patches of different crops skewed in relation to one another. Within grains, sub-domains formed, similar to rows of two plant types alternating in a patch of farmland. These adjacent but opposing rows are “twin domains” of segregated chemicals.

The technique that scientists previously used to claim the material was ferroelectric was piezoresponse force microscopy (“piezo” means “pressure), in which the tip of an atomic force microscope (AFM) measures a mechanical displacement due to its coupling with electric polarization—namely, electromechanical displacement. “But you’re not actually measuring the true displacement of the material,” Ovchinnikova warned. “You’re measuring the deflection of this whole ‘diving board’ of the cantilever.” Therefore, the researchers used a new measurement technique to separate cantilever dynamics from displacement of the material due to piezoresponse—the Interferometric Displacement Sensor (IDS) option for the Cypher AFM, developed by co-author Roger Proksch, CEO of Oxford Instruments Asylum Research.

They found the response in this material is from cantilever dynamics alone and is not a true piezoresponse, proving the material is not ferroelectric.

“Our work shows the effect believed due to ferroelectric polarization can be explained by chemical segregation,” Liu said.

The study’s diverse microscopy and spectroscopy measurements provided experimental data to validate atomic-level simulations. The simulations bring predictive insights that could be used to design future materials.

We’re able to do this because of the unique environment at CNMS where we have characterization, theory and synthesis all under one roof,” Ovchinnikova said.

“We didn’t just utilize mass spectrometry because [it] gives you information about local chemistry. We also used optical spectroscopy and simulations to look at the orientation of the molecules, which is important for understanding these materials. Such a cohesive chemical imaging capability at ORNL leverages our functional imaging.”

Collaborations with industry allow ORNL to have unique tools available for scientists, including those that settled the debate about the true nature of the light-harvesting material. For example, an instrument that uses helium ion microscopy (HIM) to remove and ionize molecules was coupled with a secondary ion mass spectroscopy (SIMS) to identify molecules based on their weights.

The HIM-SIMS instrument ZEISS ORION NanoFab was made available to ORNL from developer ZEISS for beta testing and is one of only two such instruments in the world. Similarly, the IDS instrument from Asylum Research, which is a laser Doppler vibrometer, was also made available to ORNL for beta testing and is the only one in existence.

“Oak Ridge National Laboratory researchers are naturally a good fit for working with industry because they possess unique expertise and are able to first use the tools the way they’re meant to,” said Proksch of Asylum. “ORNL has a facility [CNMS] that makes instruments and expertise available to many scientific users who can test tools on different problems and provide strong feedback during beta testing as vendors develop and improve the tools, in this case our new IDS metrological AFM.”

The title of the paper is “Chemical Nature of Ferroelastic Twin Domains in CH3NH3PbI3 Perovskite.”

The research was supported by ORNL’s Laboratory Directed Research and Development Program and conducted at CNMS, a DOE Office of Science User Facility at ORNL.

UT-Battelle manages ORNL for DOE’s Office of Science. The single largest supporter of basic research in the physical sciences in the United States, the Office of Science is working to address some of the most pressing challenges of our time. For more information, please visit https://science.energy.gov/.

Lithium leader S Korea funds 4MWh vanadium trial that targets doubled energy density


Protean/KORID’s V-KOR vanadium redox flow battery (VRFB) stack. Image: Protean Energy.

With a view to creating a mass market design for vanadium flow batteries, Australia’s Protean Energy will deploy a 4MWh battery energy storage project in South Korea that will be researched over eight years of operation.

The ASX-listed company is involved both with vanadium resources as well as creating energy storage systems using vanadium pentoxide electrolyte, producing its own stack technology, V-KOR.

V-KOR ‘stacks’ individual vanadium redox flow battery (VRFB) cells within a main system stack, unlike most vanadium flow battery designs in which the whole system is one large ‘cell’. Protean claims this lowers manufacturing costs and improves battery performance. The company connected its first project to the grid in Australia in August, a 100kWh system in Western Australia.

Protean, via its’ 50%-owned Korean subsidiary, KORID ENERGY, has been awarded AU$3 Million in funding towards a trial 1MW/4MWh system by the Korean Institute of Energy Technology Evaluation and Planning (KETEP).

KETEP’s various areas of research and development include extensive focus on renewables and advancing energy technologies overall including the Energy Storage System (ESS) Technology Development Program.

The award to Protean is part of a wider AU$9 million project in this area.

The institute selected the provider through a competitive process for the project, which is anticipated to run for 96 months. It is hoped the trial will double the energy density of vanadium electrolyte, in turn reducing the physical footprint of Protean’s V-KOR battery.

South Korea is best known as home to some of the world’s biggest lithium battery suppliers including Samsung SDI, LG Chem and SK Innovation but this project aims to develop a mass production VRFB through lowering costs and improving manufacturing processes for Protean’s 25kW V-KOR stack.

Protean said KORID’s commercialisation strategy will include targeting the market for large-scale commercial and industrial (C&I) projects.

South Korean chemical company Chemtros will manufacture and supply electrolytes, while other partners are:

Electrolyte chemistry – UniPlus

Power conditioning equipment – EKOS

System development – H2

Sungkyunkwan University

Read Long Time Coming, a feature article published across two quarterly editions of PV Tech Power, looking at the tech, the ambitions and strategies of four flow battery makers, here on the site, or download it as a free PDF from ‘Resources’ to keep and carry (subscription details required).

Read Genesis Nanotech News Online: Our Latest Edition


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