Boosting the efficiency of silicon solar cells

The efficiency of a solar cell is one of its most important parameters.

It indicates what percentage of the solar energy radiated into the cell is converted into electrical energy. The theoretical limit for silicon solar cells is 29.3 percent due to physical material properties. In the journal Materials Horizons, researchers from Helmholtz-Zentrum Berlin (HZB) and international colleagues describe how this limit can be abolished. The trick: they incorporate layers of organic molecules into the solar cell. These layers utilise a quantum mechanical process known as singlet exciton fission to split certain energetic light (green and blue photons) in such a way that the electrical current of the solar cell can double in that energy range.

The principle of a solar cell is simple: per incident light particle (photon) a pair of charge carriers (exciton) consisting of a negative and a positive charge carrier (electron and hole) is generated. These two opposite charges can move freely in the semiconductor. When they reach the charge-selective electrical contacts, one only allows positive charges to pass through, the other only negative charges. A direct electrical current is therefore generated, which can be used by an external consumer.

>Read more on the BESSY II at Helmholtz-Zentrum Berlin website

Picture: Darstellung des Prinzips einer Silizium-Multiplikatorsolarzelle mit organischen Kristallen
Credit: M. Künsting/HZB

How did humans live 5000 years ago?

Researchers from the Cyprus Institute, in collaboration with the Iranian Center of Archaeological Research, have worked around the clock for a week on ID16A to discover more about the lifestyle of our ancestors.

How did people live 5000 years ago? What did they eat? What can we learn of their health? Were they exposed to contaminants? To answer these questions with various techniques researchers first need to understand more about the preservation state of ancient human hair. In order to do this, a team from Cyprus Institute is  scanning hair remains found within burials at the ancient site of Shahr-I-Sokhta, in Iran.
In this urban settlement, at a crossroads of important ancient trade routes that later became part of the Silk Road, there was busy commercial and manufacturing activity around metal and precious materials as evidenced by the  artifacts found onsite during archaeological excavations. Archaeologists have also found remains of the inhabitants of the city dating to the 3rd millennium BC, and their state of preservation is remarkable. “The climate in this area is very arid and hot, and this has led to preservation of body tissues not often found with human skeletons, including hair”, explains Kirsi Lorentz, assistant professor at the Cyprus Institute.

>Read more on the European Synchrotron (ESRF) website

Image: Aerial view of the Shahr-I-Sokhta site, in Iran.
Credit: Media Rahmani

Nanotechnology in oil exploration

Research investigates use of nanoparticles for advanced oil recovery.

Brazil is a pioneering country in the exploration of oil in deep waters and a great quantity of this fossil fuel is stored in the porous space of carbonate rocks, especially in the pre-salt layer. These rocks are very heterogeneous and have complex pore systems, bringing great challenges to the extraction of oil and gas.
After drilling an oil or gas reservoir, the natural pressure inside it causes the contents to flow naturally to the surface where the fluid is collected and directed to a tanker. However, a few years after the opening of the well, the amount of oil extracted daily tends to decrease due to the drop in internal well pressure.

One of the ways to continue the exploration is by the injecting water or gas into the well, which helps in the transport of fluids and increases oil production, allowing it to be explored for several years. A more efficient way is, however, through the injection of surfactants, which facilitate the remobilization of oil, even in regions where water and gas have no further effect.
Recently, Tannaz Pak and collaborators from Brazil and the United Kingdom investigated [1] the use of nanoparticles to improve the advanced recovery of oil in carbonate rocks. By means of time-resolved X-ray microtomography, the research showed for the first time how oil droplets, retained in the pores of carbonate rocks, change shape when interacting with silica nanoparticles suspended in water, making it again available for extraction.

>Read more on the Brazilian Synchrotron Light Laboratory website

Image Credit: Geraldo Falcão / Banco de Imagens Petrobras

X-rays uncover a hidden property that leads to failure in a lithium-ion battery material

Experiments at SLAC and Berkeley Lab uproot long-held assumptions and will inform future battery design.

Over the past three decades, lithium-ion batteries, rechargeable batteries that move lithium ions back and forth to charge and discharge, have enabled smaller devices that juice up faster and last longer.
Now, X-ray experiments at the Department of Energy’s SLAC National Accelerator Laboratory and Lawrence Berkeley National Laboratory have revealed that the pathways lithium ions take through a common battery material are more complex than previously thought. The results correct more than two decades worth of assumptions about the material and will help improve battery design, potentially leading to a new generation of lithium-ion batteries.

An international team of researchers, led by William Chueh, a faculty scientist at SLAC’s Stanford Institute for Materials & Energy Sciences and a Stanford materials science professor, published these findings today in Nature Materials.
“Before, it was kind of like a black box,” said Martin Bazant, a professor at the Massachusetts Institute of Technology and another leader of the study. “You could see that the material worked pretty well and certain additives seemed to help, but you couldn’t tell exactly where the lithium ions go in every step of the process. You could only try to develop a theory and work backwards from measurements. With new instruments and measurement techniques, we’re starting to have a more rigorous scientific understanding of how these things actually work.”

>Read more on the SLAC website

Image: When lithium ions flow into the battery’s solid electrode – illustrated here in hexagonal slices – the lithium can rearrange itself, causing the ions to clump together into hot spots that end up shortening the battery lifetime.
Credit: Stanford University/3Dgraphic

X-rays reveal L-shape of scaffolding protein

Structural biologists discover unexpected results at PETRA III at DESY in Germany.

An investigation at DESY’s X-ray light source PETRA III has revealed a surprising shape of an important scaffolding protein for biological cells. The scaffolding protein PDZK1 is comprised of four so-called PDZ domains, three linkers and a C-terminal tail. While bioinformatics tools had suggested that PDZK1’s PDZ domains and linkers would behave like beads on a string moving around in a highly flexible manner, the X-ray experiments showed that PDZK1 has a relatively defined L-shaped conformation with only moderate flexibility. The team led by Christian Löw from the Centre for Structural Systems Biology CSSB at DESY and Dmitri Svergun from the Hamburg branch of the European Molecular Biology Laboratory EMBL report their results in the journal Structure.

Similar to metal scaffolding which provides construction workers with access points to a building, scaffolding proteins mediate interactions between proteins situated on the membrane of the human cell. While the molecular structure of each of PDZK1’s four individual PDZ domains has been solved using X-ray crystallography and NMR spectroscopy, the overall arrangement of the domains in the protein as well as their interactions was not yet understood.

>Read more on the PETRA III at DESY website

Image: Artistic shape interpretation of the scaffolding protein PDZK1. (Credit: Manon Boschard)tistic shape interpretation of the scaffolding protein PDZK1.
Credit: Manon Boschard

A closer look of zink behaviour under extreme conditions

Researchers have explored the phase diagram of zinc under high pressure and high temperature conditions, finding evidence of a change in its structural behaviour at 10 GPa. Experiments profited from the brightness of synchrotron light at ALBA and Diamond.

These results can help to understand the processes and phenomena happening in the Earth’s interior.

The field of materials science studies the properties and processes of solids to understand and discover their performances. Synchrotron light techniques permit to analyse these materials at extreme conditions (high pressure and high temperature), getting new details and a deep knowledge of them.

Studying the melting behaviours of terrestrial elements and materials at extreme conditions, researchers can understand the phenomena taking place inside them. This information is of great value for discovering how these materials react in the inner core of Earth but also for other industrial applications. Zinc is one of the most abundant elements in Earth’s crust and is used in multiple areas such as construction, ship-building or automobile.

>Read more on the ALBA website

Figure: P-T phase diagram of zinc for P<16 GPa and T<1600K. Square data points correspond to the X-ray diffraction measurements. Solid squares are used for the low pressure hexagonal phase (hcp) and empty symbols for the high pressure hexagonal phase (hcp’). White, red and black circles are melting points from previous studies reported in the literature. The triangles are melting points obtained in the present laser-heating measurements. In the onset of the figure is shown the custom-built vacuum vessel for resistively-heated membrane-type DAC used in the experiments at the ALBA Synchrotron. 

Just like lego – studying flexible protein for drug delivery

Researchers from the Sapienza University of Rome and its spin-off company MoLiRom (Italy) are spending the weekend at the ESRF to study a protein that could potentially transport anticancer drugs.

Ferritin is a large spherical protein (20 times bigger than haemoglobin) that stores iron within its cavity in every organism. Just like a lego playset, Ferritin assembles and disassembles. It is also naturally targeted to cancer cells. These are the reasons why Ferritin is a great candidate as a drug-transport protein to fight cancer. An international team of scientists from “Sapienza” University of Rome and the SME MoLiRom (Italy) came to the ESRF to explore a special kind of ferritin that shows promising properties. “This is an archaebacterial ferritin that have transformed into a humanised ferritin to try to tackle cancer cells”, explains Matilde Trabuco, a scientist at the Italian SME MoLiRom.

The mechanism looks simple enough: “Ferritin has a natural attraction to cancer cells. If we encapsulate anti-cancer drugs inside it, it will act as a Trojan horse to go inside cells, then it will open up and deliver the drug”.

Ferritins have been widely used as scaffolds for drug-delivery and diagnostics due to their characteristic cage-like structure. Most ferritins are stable and disassemble only by a harsh pH jump that greatly limits the type of possible cargo. The humanised ferritin was engineered to combine assembly at milder conditions with specific targeting of human cancer cells.

 

>Read more on the European Synchrotron Website

 

SRI 2018 in Taipei

The 13th International Conference on Synchrotron Radiation Instrumentation (SRI 2018), attended by more than 850 participants from 25 countries, was hosted by the National Synchrotron Radiation Research Center (NSRRC) between June 10 to 15 at the Taipei International Convention Center. On the 11th, the Conference Chair, Director Shangjr Gwo of NSRRC, opened the conference, followed by a speech given by the vice president of the nation, Dr. Chien-Jen Chen.

The triennial SRI conference is a large and the most significant international forum, organized by the community of worldwide X-ray free electron laser (XFEL) and synchrotron radiation (SR) facilities, to provide opportunities for discussions and collaborations among scientists and engineers around the world involved in development of new concepts, techniques, and instruments related to SR and XFEL research. Subsequent meetings were hosted by countries with the most advanced light source facilities in Europe, America and Asia-Pacific region.

>Read more on the NSRRC website

Image: Vice President Chien-Jen Chen gave a speech in the opening session.

Demonstrating a new approach to lithium-ion batteries

A team of researchers from the University of Cambridge, Diamond Light Source and Argonne National Laboratory in the US have demonstrated a new approach that could fast-track the development of lithium-ion batteries that are both high-powered and fast-charging.

In a bid to tackle rising air pollution, the UK government has banned the sale of new diesel and petrol vehicles from 2040, and the race is on to develop high performance batteries for electric vehicles that can be charged in minutes, not hours. The rechargeable battery technology of choice is currently lithium-ion (Li-ion), and the power output and recharging time of Li-ion batteries are dependent on how ions and electrons move between the battery electrodes and electrolyte. In particular, the Li-ion diffusion rate provides a fundamental limitation to the rate at which a battery can be charged and discharged.

>Read more on the Diamond Light Source website

Scientists unravel mechanism for body odour in armpits

British researchers from the University of York and the University of Oxford have shown the mechanism that leads to body odour in armpits by studying the molecular process at the ESRF and other lightsources.

Stepping into a cramped bus on a hot summer day can sometimes translate into having to hold your breath and a very unpleasant experience. Sweat production increases in hot weather, and, with it, body odour. Despite much research and antiperspirant deodorants, scientists still haven’t managed to selectively block body odour.

Researchers from the University of York and the University of Oxford have recently used the ESRF and Diamond Lightsource to find out what happens at a molecular level when we smell badly. They focused on the apocrine gland, which is found only in the armpit, genitalia and ear canal. It secrets an odourless lipid-rich viscous secretion, which is likely to play a role in scent generation, but it is not involved in thermoregulation.

It all comes down to bacteria. “The skin of our underarms provides a unique niche for bacteria,” explains investigator Gavin Thomas, professor in the department of biology at the University of York and co-leader of the study. “Through the secretions of various glands that open onto the skin or into hair follicles, this environment is nutrient-rich and hosts its own microbial community, the armpit microbiome, of many species of different microbes.”

>Read more on the European Synchrotron (ESRF) website

Image: Picture showing how body odour is produced in armpits.
Credit: University of York and Oxford. 

Insight into catalysis through novel study of X-ray absorption spectroscopy

An international team has made a breakthrough at BESSY II.

For the first time, they succeeded in investigating electronic states of a transition metal in detail and drawing reliable conclusions on their catalytic effect from the data. These results are helpful for the development of future applications of catalytic transition-metal systems. The work has now been published in Chemical Science, the Open Access journal of the Royal Society of Chemistry.

Many important processes in nature depend on catalysts, which are atoms or molecules that facilitate a reaction, but emerge from it themselves unchanged. One example is photosynthesis in plants, which is only possible with the help of a protein complex comprising four manganese atom sites at its centre. Redox reactions, as they are referred to, often play a pivotal role in these types of processes. The reactants are reduced through uptake of electrons, or oxidized through their release. Catalytic redox processes in nature and industry often only succeed thanks to suitable catalysts, where transition metals supply an important function.

>Read more about on the BESSY II at HZB website

Image: Manganese compounds also play a role as catalysts in photosynthesis.
Credit: HZB

Experts disscuss about the future of European particle accelerators

On 19 and 20 July, the ALBA Synchrotron is hosting the 102nd Plenary ECFA meeting, with the participation of 70 researchers, including Dr. Fabiola Gianotti, CERN’s Director-General.

The European Committee for Future Accelerators (ECFA) is an advisory body for CERN Management, CERN Council and its Committees, and to other national and international organizations, on the long-term planning of European High-Energy Physics (HEP) facilities, accelerators and equipment adequate for the conduction of a valid high energy research program.

The participants of the plenary meeting will discuss, during two days, about different topics on high energy physics and the main HEP accelerator facilities in Europe will report on their activities. Fabiola Gianotti, CERN’s Director-General, will report on CERN activities and perspectives. The role of ECFA is of particular relevance in the period 2018-2020 due to the on-going update of the European Strategy for Particle Physics, which will shape the future of the HEP community in Europe and, in particular, what lays ahead for CERN after the High Luminosity LHC project (the upgrade of the Large Hadron Collider (LHC) that aims to increase its luminosity such that the accumulated data will be 10 times larger than with the present configuration).

>Read more on the ALBA website

Helmholtz International Fellow Award for N. Mårtensson

The Helmholtz Association has presented the Swedish physicist Nils Mårtensson with a Helmholtz International Fellow Award. 

The synchrotron expert of the University of Uppsala, who heads the nobel comitee for physics, cooperates closely with the HZB-Institute Methods and Instrumentation for Synchrotron Radiation Research. Nils Mårtensson is a professor at Uppsala University. He directed the development of the Swedish synchrotron radiation source Max IV and received a grant from the European Research Council (ERC) in 2013. Mårtensson is a member of the Swedish Academy of Sciences and chairman of the Nobel Committee for Physics. At HZB, he cooperates with Alexander Föhlisch’s team at HZB-Institute Methods and Instrumentation for Synchrotron Radiation Research. Together they run the Uppsala Berlin Joint Laboratory (UBjL) to further develop methods and instruments.

Image: Nils Mårtensson, University of Uppsala, cooperates closely with HZB.

Diamond celebrates publication of its 7000th paper

A paper in PNAS by an international scientific collaboration from the UK, Germany and Switzerland is the 7000th to be published as a result of innovative research conducted at Diamond Light Source, the UK’s Synchrotron.

This new paper reveals details of the 3D spin structure of magnetic skyrmions, and will be of key importance for storing digital information in the development of next-generation devices based on spintronics.

Laurent Chapon, Diamond’s Physical Sciences Director, explains the significance of these new findings:  “A skyrmion is similar to a nanoscale magnetic vortex, made from twisted magnetic spins, but with a non-trivial topology that is ‘protecting them’. They are therefore stable, able to move, deform and interact with their environment without breaking up, which makes them very promising candidates for digital information storage in next-generation devices. For years, scientists have been trying to understand the underlying physical mechanisms that stabilise magnetic skyrmions, usually treating them as 2D objects. However, with its unique facilities and ultra-bright light, Diamond has provided researchers the tools to study skyrmions in 3D revealing significant new data.”

As spintronic devices rely on effects that occur in the surface layers of materials, the team was investigating the influence of surfaces on the twisted spin structure. It is commonly assumed that surface effects only modify the properties of stable materials within the top few atomic layers, and investigating 3D magnetic structures is a challenging task. However, using the powerful circularly polarised light produced at Diamond, the researchers were able to use resonant elastic X-ray scattering (REXS) to reconstruct the full 3D spin structure of a skyrmion below the surface of Cu2OSeO3.

>Read more on the Diamond Light Source website

Image: (extract) Illustration of a ‘Skyrmion tornado’. The skyrmion order changes from Néel-type at the surface to Bloch-type deeper in the sample. On the right hand side, the corresponding stereographic projections of these two boundary skyrmion patterns are shown. Full image and detailed article here.

Maria Faury appointed new chair of the European XFEL Council

As of the 1 July 2018, Maria Faury is the new chair of the European XFEL council, the highest governing body of the company. Maria Faury has an engineering background and is Director of International Affairs and Large Research Infrastructures of the Fundamental Research Division at the Commissariat à l’Énergie Atomique et aux Énergies Alternatives (CEA) in France. She has represented CEA, one of the two European XFEL partners in France, on the council since 2014. She will succeed Prof. Martin Meedom Nielsen from the Technical University of Denmark (DTU), who, having served two terms as chair, will continue to support the work of European XFEL as vice chair. The current vice chair, Prof. Lars Börjesson from Chalmers University of Technology in Gothenburg, will again become a member of the Swedish delegation on the council.

Maria Faury said: “It will be an honor, and a real pleasure for me to chair the European XFEL Council. Since 2014, I have had the chance to witness the progress in the construction of the facility and have been impressed by the unwavering involvement of the staff, the management and the stakeholders. European XFEL is now operating and attracting scientists from all over the world, starting to deliver excellent science. The coming years will be very exciting and all together we will ensure that European XFEL remains a world-leading facility. I fully trust Robert Feidenhans’l and his team and I am very happy to work more closely with them in the future. I would like to thank Martin Meedom Nielson who has chaired the council in such a nice, open and positive way. He has been very inspiring to us and I am happy he will continue as vice chair.”

>Read more on the European XFEL website

Picture: Maria Faury, new chair of the European XFEL Council

Redox-transformation kinetics of aqueous thio-arsenic species…

… determining arsenic sequestration by organic thiol groups of peat.

Arsenic (As) is a toxic metalloid which has attracted the attention of the general public because of its natural toxic concentrations in drinking water of millions of people around the world.  The mobility and bioavailability of As thereby strongly depends on redox conditions, often linked to the redox cycles of sulfur (S), iron (Fe), and carbon (C). In reducing systems such as wetlands (swamps, peatlands, paddy fields etc.) As is thought to be mainly present in its reduced trivalent form as arsenite. Naturally, these systems are rich in natural organic matter (NOM) because mineralization of carbon is delayed under anoxic, reducing conditions. Furthermore sulfur, which acts as a main nutrient for plants, can also be present in its reduced forms as e.g. organic thiol groups in NOM-rich environments after anoxic decomposition of plant debris or reduction of released sulfate.

>Read more on the Stanford Synchrotron Radiation Lightsource (SSRL) website

Figure: (extract) Proposed conceptual model for the As-S chemistry in the minerotrophic peatland Gola di Lago, Switzerland. Scenario 1: arsenate and arsenite prevail as long as no reduced inorganic sulfur is present. Scenario 2: monothioarsenate formation from arsenite and surface-bound zerovalent sulfur species. Scenario 3: formation of higher thiolated arsenates from monothioarsenate under conditions of available free sulfide. (…)  Entire figure and information here
Credit: Besold et al. 2018, ES&T, DOI: 10.1021/acs.est.8b01542, Copyright 2018, American Chemical Society.