探花直播 of Cambridge - Akshay Rao

Cambridge researchers awarded European Research Council Consolidator Grants

cg605 — Tue, 31 Jan 2023 16:00:25 +0000

探花直播ERC is the premier European funding organisation for excellent frontier research. This year it has awarded 鈧�657m in grants to 321 researchers across Europe.

Consolidator grants are given to excellent scientists, who have 7 to 12 years鈥� experience after their PhDs, to pursue their most promising ideas.

鈥淓RC Consolidator grants support researchers at a crucial time of their careers, strengthening their independence, reinforcing their teams and helping them establish themselves as leaders in their fields,鈥� said President of the European Research Council Professor Maria Leptin. 鈥淎nd this backing above all gives them a chance to pursue their scientific dreams.鈥�

Cambridge awardees:

Dr Eloy de Lera Acedo, STFC Ernest Rutherford Fellow at Cavendish Astrophysics and the Kavli Institute for Cosmology of the Department of Physics, has been awarded a grant for REACH_21: Probing the Cosmic Dawn and Epoch of Re-ionization with the REACH experiment.

De Lera Acedo said: 鈥淩EACH_21 aims to unveil the mysteries of the infant universe. We want to answer the question: how did the cosmos, that evolved from the Big Bang, become the complex and luminous realm of celestial objects we can see from planet Earth today?

鈥淭his unknown missing piece in the puzzle of the history of the universe is now closer to being understood thanks to a new experimental approach that attempts to observe extremely faint radio signals emitted nearly 13.5 billion years ago by the most abundant element at that time: Neutral Hydrogen.鈥�

鈥淭his is amazing news for the REACH collaboration. We have been designing our experiment for over five years and are currently awaiting the start of scientific observations in South Africa. 探花直播ERC grant is going to allow me to use the REACH telescope, analyse its data, and hopefully access a whole new world of information about the early evolution of the cosmos.鈥�

Dr Daniel Hodson, of the Department of Haematology, has been awarded a grant for Unwind-Lymphoma: RNA helicases; switched paralogue dependency as an exploitable vulnerability in aggressive B cell lymphoma.

Hodson聽said: 鈥淭his ERC-funded project, Unwind Lymphoma, will explore sex-specific, cancer cell addiction to the DDX3 family of RNA helicases, proteins that unwind secondary structure in mRNA.

鈥淲e will develop recent findings from our lab showing that whilst most male Burkitt lymphoma cells have deleted the X-chromosome gene DDX3X, they instead become uniquely addicted to the Y-chromosome paralogue DDX3Y, a related protein that is silenced in most normal cells. By unravelling the molecular basis of this 鈥榮witched paralogue dependency鈥� we will expose a potential therapeutic Achilles Heel in this devastating form of blood cancer.

鈥淚 am thrilled to receive this award, which I hope will take me one step closer to a tenured position in Cambridge or beyond.鈥�

Sohini Kar-Narayan, Professor of Device and Energy Materials of the Department of Materials Science and Metallurgy, has been awarded a grant for BIOTRONICA: Bio-Electronic Integrated Devices for Healthcare Applications.

Kar-Narayan said: 鈥淢y research focuses on the development and characterisation of novel functional polymers and nanocomposites, and their application in functional devices using microscale additive manufacturing methods. It covers novel energy harvesting nanomaterials to microfluidic biosensors, to materials and devices for next-generation flexible and wearable electronics.

鈥淚 am absolutely delighted to have been awarded a Consolidator Grant to develop new tools for remote health monitoring and personalised medicine. These include novel non-invasive 鈥榩oint-of-care鈥� biosensors, which could potentially be self-powered through energy harvested from the body, thus enabling a step change in health monitoring and patient care.鈥�

Dr Elisa Laurenti, 探花直播 Associate Professor in Stem Cell Medicine and Wellcome Royal Society Sir Henry Dale Fellow of the Wellcome Medical Research Council Cambridge Stem Cell Institute and Department of Haematology, has been awarded a grant for HEXAGEN: Harnessing haematopoietic stem cell EX vivo Adaptation for GENe therapy.

Laurenti said: 鈥淏lood stem cell-based gene therapy has the potential to cure an expanding range of debilitating genetic diseases. HEXAGEN seeks to further improve gene therapies and their outcomes by overcoming the loss of stem cell function observed in current clinical protocols. Using cutting edge single cell technologies, we aim to identify how blood stem cells adapt to the invitro environment, dissect how this negatively impacts their function, and design new strategies to improve gene therapy.

鈥淭his award gives my team the unique opportunity to be ambitious and complete a full circle from basic stem cell biology to improving gene therapy for patients with many diseases. I am very excited, because unlocking blood stem cell behaviour outside our bodies will also drive many other clinical applications.鈥�

Dr Naomi McGovern, of the Department of Pathology and the Centre for Trophoblast Research, has been awarded a grant for PMDR: Placental macrophages: Their development and role in the placenta.

McGovern said: 鈥淢y team鈥檚 research focus is human placental macrophage biology. We are interested in determining the role of these cells in mediating healthy placental function and in protecting the placenta from infection. By developing our understanding of these cells, we will be able to provide new insight into pregnancy disorders.

鈥淚 am delighted that our proposal was selected for an ERC Consolidator Award. It is an acknowledgement of the exciting research my team carries out. 探花直播hard work of my team and the additional expertise provided by our supportive collaborators all helped to form the basis for this proposal. 探花直播award will provide my group with the time and resources to undertake high-risk research to inform on placental biology. It is now up to us to deliver on this generous investment.鈥�

Professor Robert Phipps, of the Yusuf Hamied Department of Chemistry, has been awarded a grant for IonPairEnantRadical: Transforming Enantioselective Radical Chemistry using Ion-Pairing Catalysis.

Phipps said: 鈥淐hemical reactions that are driven by radical mechanisms are rapidly growing in importance, but it is an ongoing challenging to control enantioseletivity in those that form stereocentres. This grant will fund an ambitious program which will apply innovative and unexplored ion-pairing strategies to control enantioselectivity in a variety of important radical chemistries for which there are no or limited existing methods for imposing enantiocontrol.

鈥淚 am extremely grateful that my proposal was selected for funding in this very competitive call. I am excited about the chemistry that my group will be able to explore over the coming five years with this fantastic opportunity!鈥�

Akshay Rao, Professor of Physics of the Cavendish Laboratory in the Department of Physics, has been awarded a grant for SPICE: Spin-Exchange and Energy Transfer at Hybrid Molecular/Lanthanide Nanoparticle Interfaces to Control Triplet Excitons.

Rao聽said: 鈥淥ur project, SPICE, will explore the physics and chemistry of a new class of hybrid materials, organic molecules connected to lanthanide doped nanoparticles.

鈥淎lthough we are still at an early stage of research, if we succeed it may create transformative applications in areas ranging from optoelectronics, data communication, photocatalysis, optogenetics and 3D bio-printing. Over the long term this kind of blue-sky science is what drives technological innovation helping to drive improved productivity in industry, but also directly tacking major societal challenges such as climate change and health.

鈥淲e are delighted that our project has received the support of the European Research Council. This is a great opportunity for us to pursue high-risk high-gain blue-sky science and push the limits of our understanding of these materials and take them towards application. 探花直播award also serves as recognition of the excellent science done by our PhD students and postdoctoral researchers, who鈥檚 tireless efforts to push the scientific frontier have made possible the breakthroughs that have brought us here.鈥�

Dr Milka Sarris, Assistant Professor of the Department of Physiology, Development and Neuroscience, was awarded a grant for LongWayFromFlam: 探花直播uncharted journeys of inflammatory cells and their functional implications.

Sarris said: 鈥淢y group studies how cells of the immune system move in the body to generate and resolve inflammatory responses. To study these processes, we use state of the art microscopy techniques and genetic approaches in zebrafish, a small vertebrate model organism.

鈥淚 am absolutely thrilled to have won this award at a key stage of my career and to be able to pursue an ambitious new line of fundamental research. It was a long process and I remain very grateful to my university colleagues, the peer reviewers and the evaluation committee for their feedback.鈥�

Eight researchers from the 探花直播 of Cambridge have won European Research Council (ERC) Consolidator Grants

Photos provided by winners

From clockwise: Eloy de Lera Acedo, Daniel Hodson, Sohini Kar-Narayan, Elisa Laurenti, Naomi McGovern, Robert Phipps, Akshay Rao and Milka Sarris.

探花直播text in this work is licensed under a Creative Commons Attribution 4.0 International License. Images, including our videos, are Copyright 漏探花直播 of Cambridge and licensors/contributors as identified.聽 All rights reserved. We make our image and video content available in a number of ways 鈥� as here, on our main website under its Terms and conditions, and on a range of channels including social media that permit your use and sharing of our content under their respective Terms.

Yes

Watching lithium in real time could improve performance of EV battery materials

sc604 — Fri, 14 Oct 2022 13:46:50 +0000

探花直播team, led by the 探花直播 of Cambridge, tracked the movement of lithium ions inside a promising new battery material in real time.

It had been assumed that the mechanism by which lithium ions are stored in battery materials is uniform across the individual active particles. However, the Cambridge-led team found that during the charge-discharge cycle, lithium storage is anything but uniform.

When the battery is near the end of its discharge cycle, the surfaces of the active particles become saturated by lithium while their cores are lithium deficient. This results in the loss of reusable lithium and a reduced capacity.

探花直播research, funded by the Faraday Institution, could help improve existing battery materials and could accelerate the development of next-generation batteries. 探花直播results are published in Joule.

Electrical vehicles (EVs) are vital in the transition to a zero-carbon economy. Most electric vehicles on the road today are powered by lithium-ion batteries, due in part to their high energy density.

However, as EV use becomes more widespread, the push for longer ranges and faster charging times means that current battery materials need to be improved, and new materials need to be identified.

Some of the most promising of these materials are state-of-the-art positive electrode materials known as layered lithium nickel-rich oxides, which are widely used in premium EVs. However, their working mechanisms, particularly lithium-ion transport under practical operating conditions, and how this is linked to their electrochemical performance, are not fully understood, so we cannot yet obtain maximum performance from these materials.

By tracking how light interacts with active particles during battery operation under a microscope, the researchers observed distinct differences in lithium storage during the charge-discharge cycle in nickel-rich manganese cobalt oxide (NMC).

鈥淭his is the first time that this non-uniformity in lithium storage has been directly observed in individual particles,鈥� said co-first author Alice Merryweather, from Cambridge鈥檚 Yusuf Hamied Department of Chemistry. 鈥淩eal time techniques like ours are essential to capture this while the battery is cycling.鈥�

Combining the experimental observations with computer modelling, the researchers found that the non-uniformity originates from drastic changes to the rate of lithium-ion diffusion in NMC during the charge-discharge cycle. Specifically, lithium ions diffuse slowly in fully lithiated NMC particles, but the diffusion is significantly enhanced once some lithium ions are extracted from these particles.

鈥淥ur model provides insights into the range over which lithium-ion diffusion in NMC varies during the early stages of charging,鈥� said co-first author Dr Shrinidhi Pandurangi from Cambridge鈥檚 Department of Engineering. 鈥淥ur model predicted lithium distributions accurately and captured the degree of heterogeneity observed in experiments. These predictions are key to understanding other battery degradation mechanisms such as particle fracture.鈥�

Importantly, the lithium heterogeneity seen at the end of discharge establishes one reason why nickel-rich cathode materials typically lose around ten percent of their capacity after the first charge-discharge cycle.

鈥淭his is significant, considering one industrial standard that is used to determine whether a battery should be retired or not is when it has lost 20 percent of its capacity,鈥� said co-first author Dr Chao Xu, from ShanghaiTech 探花直播, who completed the research while based at Cambridge.

探花直播researchers are now seeking new approaches to increase the practical energy density and lifetime of these promising battery materials.

探花直播research was supported in part by the Engineering and Physical Sciences Research Council (EPSRC), part of UK Research and Innovation (UKRI). Alice Merryweather is jointly supervised by Professor Dame Clare Grey and Dr Akshay Rao, who are both co-authors on the current paper.聽聽

Reference:
Chao Xu et al. 鈥�Operando visualization of kinetically induced lithium heterogeneities in single-particle layered Ni-rich cathodes.鈥� Joule (2022). DOI: 10.1016/j.joule.2022.09.008

For more information on聽energy-related research in Cambridge, please visit聽Energy聽IRC, which brings together Cambridge鈥檚 research knowledge and expertise, in collaboration with global partners, to create solutions for a sustainable and resilient energy landscape for generations to come.聽

Researchers have found that the irregular movement of lithium ions in next-generation battery materials could be reducing their capacity and hindering their performance.

Andrew Roberts via Unsplash

Electric car charging

Yes

Researchers identify and clear efficiency hurdle for organic solar cells

sc604 — Wed, 29 Sep 2021 15:00:00 +0000

探花直播researchers, led by the 探花直播 of Cambridge, identified a loss pathway in organic solar cells which makes them less efficient than silicon-based cells at converting sunlight into electricity. In addition, they identified a way to suppress this pathway by manipulating molecules inside the solar cell to prevent the loss of electrical current through an undesirable state, known as a triplet exciton.

Their results, reported in the journal Nature, suggest that it could be possible for organic solar cells to compete more closely with silicon-based cells for efficiency.

Organic solar cells, which are flexible, semi-transparent, and cheap, can greatly expand the range of applications for solar technology. They could be wrapped around the exteriors of buildings and can be used for the efficient recycling of the energy used for indoor lighting, neither of which are possible with conventional silicon panels. They are also far more environmentally friendly to produce.

鈥淥rganic solar cells can do lots of things that inorganic solar cells can鈥檛, but their commercial development has plateaued in recent years, in part due to their inferior efficiency,鈥� said Dr Alexander Gillett from Cambridge鈥檚 Cavendish Laboratory, the paper鈥檚 first author. 鈥淎 typical silicon-based solar cell can reach efficiencies as high as 20 to 25%, while organic solar cells can reach efficiencies of around 19% under laboratory conditions, and real-world efficiencies of about 10 to 12%.鈥�

Organic solar cells generate electricity by loosely mimicking the natural process of photosynthesis in plants, except they ultimately use the energy of the sun to create electricity rather than convert carbon dioxide and water into glucose. When a light particle, or photon, hits a solar cell, an electron is excited by the light and leaves behind a 鈥榟ole鈥� in the material鈥檚 electronic structure. 探花直播combination of this excited electron and hole is known as an exciton. If the mutual attraction between the negatively charged electron and the positively charged hole in the exciton, akin to the attraction between the positive and negative poles of a magnet, can be overcome, it is possible to harvest these electrons and holes as an electrical current.

However, electrons in solar cells can be lost through a process called recombination, where electrons lose their energy - or excitation state - and fall back into the empty 鈥榟ole鈥� state. As there is a stronger attraction between the electron and hole in carbon-based materials than in silicon, organic solar cells are more prone to recombination, which in turn affects their efficiency. This necessitates the use of two components to stop the electron and hole from recombining rapidly: an electron 鈥榙onor鈥� material and an electron 鈥榓cceptor鈥� material.

Using a combination of spectroscopy and computer modelling, the researchers were able to track the mechanisms at work in organic solar cells, from the absorption of photons to recombination. They found that a key loss mechanism in organic solar cells is caused by recombination to a particular type of exciton, known as a triplet exciton.

In organic solar cells, triplet excitons present a difficult problem to overcome, as it is energetically favourable for them to form from the electrons and holes. 探花直播researchers found that by engineering strong molecular interactions between the electron donor and electron acceptor materials, it is possible to keep the electron and hole further apart, preventing recombination into triplet excitons from occurring.

Computational modelling suggests that by tuning the components of the organic solar cells in this way, the timescales of recombination to these triplet exciton states could be reduced by an order of magnitude, allowing for more efficient solar cell operation.

鈥� 探花直播fact that we can use the interactions between components in a solar cell to turn off the triplet exciton loss pathway was really surprising,鈥� said Gillett. 鈥淥ur method shows how you can manipulate molecules to stop recombination from happening.鈥�

鈥淣ow, synthetic chemists can design the next generation of donor and acceptor materials with strong molecular interactions to suppress this loss pathway,鈥� said co-author Dr Thuc-Quyen Nguyen from the 探花直播 of California, Santa Barbara, USA. 鈥� 探花直播work shows the path forward to achieve higher device efficiency.鈥�

探花直播researchers say their method provides a clear strategy to achieve organic solar cells with efficiencies of 20% or more by stopping recombination into triplet exciton states. As part of their study, the authors were also able to provide design rules for the electron donor and electron acceptor materials to achieve this aim. They believe that these guidelines will allow chemistry groups to design new materials which block recombination into triplet excitons, enabling organic solar cells with efficiencies closer to silicon to be realised.

聽

Reference:
Alexander J聽Gillett et al. 鈥� 探花直播role of charge recombination to triplet excitons in organic solar cells.鈥� Nature (2021). DOI: 10.1038/s41586-021-03840-5

Researchers have identified a key mechanism responsible for the lower efficiencies of organic solar cells and shown a way that this hurdle might be overcome.

Organic solar cells can do lots of things that inorganic solar cells can鈥檛, but their commercial development has plateaued in recent years, in part due to their inferior efficiency

Alexander Gillett

Akshay Rao

Lasers in the Optoelectronics Lab

Yes

Low-cost imaging technique shows how smartphone batteries could charge in minutes

sc604 — Wed, 23 Jun 2021 15:00:00 +0000

Using the low-cost technique, the researchers identified the speed-limiting processes which, if addressed, could enable the batteries in most smartphones and laptops to charge in as little as five minutes.

探花直播researchers, from the 探花直播 of Cambridge, say their technique will not only help improve existing battery materials, but could accelerate the development of next-generation batteries, one of the biggest technological hurdles to be overcome in the transition to a fossil fuel-free world. 探花直播results are reported in the journal Nature.

While lithium-ion batteries have undeniable advantages, such as relatively high energy densities and long lifetimes in comparison with other batteries and means of energy storage, they can also overheat or even explode, and are relatively expensive to produce. Additionally, their energy density is nowhere near that of petrol. So far, this makes them unsuitable for widespread use in two major clean technologies: electric cars and grid-scale storage for solar power.

鈥淎 better battery is one that can store a lot more energy or one that can charge much faster 鈥� ideally both,鈥� said co-author Dr Christoph Schnedermann, from Cambridge鈥檚 Cavendish Laboratory. 鈥淏ut to make better batteries out of new materials, and to improve the batteries we鈥檙e already using, we need to understand what鈥檚 going on inside them.鈥�

To improve lithium-ion batteries and help them charge faster, researchers need to follow and understand the processes occurring in functioning materials under realistic conditions in real time. Currently, this requires sophisticated synchrotron X-ray or electron microscopy techniques, which are time-consuming and expensive.

鈥淭o really study what鈥檚 happening inside a battery, you essentially have to get the microscope to do two things at once: it needs to observe batteries charging and discharging over a period of several hours, but at the same time it needs to capture very fast processes happening inside the battery,鈥� said first author Alice Merryweather, a PhD student at Cambridge鈥檚 Cavendish Laboratory.

探花直播Cambridge team developed an optical microscopy technique called interferometric scattering microscopy to observe these processes at work. Using this technique, they were able to observe individual particles of lithium cobalt oxide (often referred to as LCO) charging and discharging by measuring the amount of scattered light.

They were able to see the LCO going through a series of phase transitions in the charge-discharge cycle. 探花直播phase boundaries within the LCO particles move and change as lithium ions go in and out. 探花直播researchers found that the mechanism of the moving boundary is different depending on whether the battery is charging or discharging.

鈥淲e found that there are different speed limits for lithium-ion batteries, depending on whether it鈥檚 charging or discharging,鈥� said Dr Akshay Rao from the Cavendish Laboratory, who led the research. 鈥淲hen charging, the speed depends on how fast the lithium ions can pass through the particles of active material. When discharging, the speed depends on how fast the ions are inserted at the edges. If we can control these two mechanisms, it would enable lithium-ion batteries to charge much faster.鈥�

鈥淕iven that lithium-ion batteries have been in use for decades, you鈥檇 think we know everything there is to know about them, but that鈥檚 not the case,鈥� said Schnedermann. 鈥淭his technique lets us see just how fast it might be able to go through a charge-discharge cycle. What we鈥檙e really looking forward to is using the technique to study next-generation battery materials 鈥� we can use what we learned about LCO to develop new materials.鈥�

鈥� 探花直播technique is a quite general way of looking at ion dynamics in solid-state materials, so you can use it on almost any type of battery material,鈥� said Professor Clare Grey, from Cambridge鈥檚 Yusuf Hamied Department of Chemistry, who co-led the research.

探花直播high throughput nature of the methodology allows many particles to be sampled across the entire electrode and, moving forward, will enable further exploration of what happens when batteries fail and how to prevent it.

鈥淭his lab-based technique we鈥檝e developed offers a huge change in technology speed so that we can keep up with the fast-moving inner workings of a battery,鈥� said Schnedermann. 鈥� 探花直播fact that we can actually see these phase boundaries changing in real time was really surprising. This technique could be an important piece of the puzzle in the development of next-generation batteries.鈥�

聽

Reference:
Alice J. Merryweather et al. 鈥�Operando optical tracking of single-particle ion dynamics in batteries.鈥� Nature (2021). DOI: 10.1038/s41586-021-03584-2

Researchers have developed a simple lab-based technique that allows them to look inside lithium-ion batteries and follow lithium ions moving in real time as the batteries charge and discharge, something which has not been possible until now.

This technique could be an important piece of the puzzle in the development of next-generation batteries

Christoph Schnedermann

Image by Alexandra_Koch from Pixabay

Batteries charging

Yes

Researchers road-test powerful method for studying singlet fission

tdk25 — Mon, 17 Oct 2016 15:00:00 +0000

Physicists have successfully employed a powerful technique for studying electrons generated through singlet fission, a process which it is believed will be key to more efficient solar energy production in years to come.

Their approach, reported in the journal Nature Physics, employed lasers, microwave radiation and magnetic fields to analyse the spin of excitons, which are energetically excited particles formed in molecular systems.

These are generated as a result of singlet fission, a process that researchers around the world are trying to understand fully in order to use it to better harness energy from the sun. Using materials exhibiting singlet fission in solar cells could make energy production much more efficient in the future, but the process needs to be fully understood in order to optimize the relevant materials and design appropriate technologies to exploit it.

In most existing solar cells, light particles (or photons) are absorbed by a semiconducting material, such as silicon. Each photon stimulates an electron in the material's atomic structure, giving a single electron enough energy to move. This can then potentially be extracted as electrical current.

In some materials, however, the absorption of a single photon initially creates one higher-energy, excited particle, called a spin singlet exciton. This singlet can also share its energy with another molecule, forming two lower-energy excitons, rather than just one. These lower-energy particles are called spin "triplet" excitons. Each triplet can move through the molecular structure of the material and be used to produce charge.聽

探花直播splitting process - from one absorbed photon to two energetic triplet excitons - is singlet fission. For scientists studying how to generate more solar power, it represents a potential bargain - a two-for-one offer on the amount of electrical current generated, relative to the amount of light put in. If materials capable of singlet fission can be integrated into solar cells, it will become possible to generate energy more efficiently from sunlight.

But achieving this is far from straightforward. One challenge is that the pairs of triplet excitons only last for a tiny fraction of a second, and must be separated and used before they decay. Their lifespan is connected to their relative "spin", which is a unique property of elementary particles and is an intrinsic angular momentum. Studying and measuring spin through time, from the initial formation of the pairs to their decay, is essential if they are to be harnessed.

In the new study, researchers from the 探花直播 of Cambridge and the Freie Universit盲t Berlin (FUB) utilised a method that allows the spin properties of materials to be measured through time. 探花直播approach, called electron spin resonance (ESR) spectroscopy, has been used and improved since its discovery over 50 years ago to better understand how spin impacts on many different natural phenomena.聽

It involves placing the material being studied within a large electromagnet, and then using laser light to excite molecules within the sample, and microwave radiation to measure how the spin changes over time. This is especially useful when studying triplet states formed by singlet fission as these are difficult to study using most other techniques.聽

Because the excitons' spin interacts with microwave radiation and magnetic fields, these interactions can be used as an additional way to understand what happens to the triplet pairs after they are formed. In short, the approach allowed the researchers to effectively watch and manipulate the spin state of triplet pairs through time, following formation by singlet fission.

探花直播study was led by Professor Jan Behrends at the Freie Universit盲t Berlin (FUB), Dr Akshay Rao, a College Research Associate at St John's College, 探花直播 of Cambridge, and Professor Neil Greenham in the Department of Physics, 探花直播 of Cambridge.

Leah Weiss, a Gates-Cambridge Scholar and PhD student in Physics based at Trinity College, Cambridge, was the paper's first author. "This research has opened up many new questions," she said. "What makes these excited states either separate and become independent, or stay together as a pair, are questions that we need to answer before we can make use of them."聽

探花直播researchers were able to look at the spin states of the triplet excitons in considerable detail. They observed pairs had formed which variously had both weakly and strongly-linked spin states, reflecting the co-existence of pairs that were spatially close and further apart. Intriguingly, the group found that some pairs which they would have expected to decay very quickly, due to their close proximity, actually survived for several microseconds.

"Finding those pairs in particular was completely unexpected," Weiss added. We think that they could be protected by their overall spin state, making it harder for them to decay. Continued research will focus on making devices and examining how these states can be harnessed for use in solar cells."

Professor Behrends added: "This interdisciplinary collaboration nicely demonstrates that bringing together expertise from different fields can provide novel and striking insights. Future studies will need to address how to efficiently split the strongly-coupled states that we observed here, to improve the yield from singlet fission cells."

Beyond trying to improve photovoltaic technologies, the research also has implications for wider efforts to create fast and efficient electronics using spin, so-called "spintronic" devices, which similarly rely on being able to measure and control the spin properties of electrons.聽

探花直播research was made possible with support from the UK Engineering and Physical Sciences Research Council (EPSRC) and from the Freie Universit盲t Berlin (FUB). Weiss and colleague Sam Bayliss carried out the spectroscopy experiments within the laboratories of Professor Jan Behrends and Professor Robert Bittl at FUB. 探花直播work is also part of the Cambridge initiative to connect fundamental physics research with global energy and environmental challenges, backed by the Winton Programme for the Physics of Sustainability.

探花直播study, Strongly exchange-coupled triplet pairs in an organic semiconductor, is published in Nature Physics. DOI: 10.1038/nphys3908.

In a new study, researchers measure the spin properties of electronic states produced in singlet fission 鈥� a process which could have a central role in the future development of solar cells.

Future research will focus on making devices and examining how these states can be harnessed for use in solar cells

Leah Weiss

Spin, an intrinsic property of electrons, is related to the dynamics of electrons excited as a result of singlet fission 鈥� a process which could be used to extract energy in future solar cell technologies.

探花直播text in this work is licensed under a Creative Commons Attribution 4.0 International License. For image use please see separate credits above.

Yes

Entanglement at heart of 'two-for-one' fission in next-generation solar cells

sc604 — Mon, 26 Oct 2015 16:15:13 +0000

An international team of scientists have observed how a mysterious quantum phenomenon in organic molecules takes place in real time, which could aid in the development of highly efficient solar cells.

探花直播researchers, led by the 探花直播 of Cambridge, used ultrafast laser pulses to observe how a single particle of light, or photon, can be converted into two energetically excited particles, known as spin-triplet excitons, through a process called singlet fission. If singlet fission can be controlled, it could enable solar cells to double the amount of electrical current that can be extracted.

In conventional semiconductors such as silicon, when one photon is absorbed it leads to the formation of one free electron that can be harvested as electrical current. However certain materials undergo singlet fission instead, where the absorption of a photon leads to the formation of two spin-triplet excitons.

Working with researchers from the Netherlands, Germany and Sweden, the Cambridge team confirmed that this 鈥榯wo-for-one鈥� transformation involves an elusive intermediate state in which the two triplet excitons are 鈥榚ntangled鈥�, a feature of quantum theory that causes the properties of each exciton to be intrinsically linked to that of its partner.

By shining ultrafast laser pulses 鈥� just a few quadrillionths of a second 鈥� on a sample of pentacene, an organic material which undergoes singlet fission, the researchers were able to directly observe this entangled state for the first time, and showed how molecular vibrations make it both detectable and drive its creation through quantum dynamics. 探花直播results are reported today (26 October) in the journal Nature Chemistry.

鈥淗arnessing the process of singlet fission into new solar cell technologies could allow tremendous increases in energy conversion efficiencies in solar cells,鈥� said Dr Alex Chin from the 探花直播鈥檚 Cavendish Laboratory, one of the study鈥檚 co-authors. 鈥淏ut before we can do that, we need to understand how exciton fission happens at the microscopic level. This is the basic requirement for controlling this fascinating process.鈥�

探花直播key challenge for observing real-time singlet fission is that the entangled spin-triplet excitons are essentially 鈥榙ark鈥� to almost all optical probes, meaning they cannot be directly created or destroyed by light. In materials like pentacene, the first stage 鈥� which can be seen 鈥� is the absorption of light that creates a single, high-energy exciton, known as a spin singlet exciton. 探花直播subsequent fission of the singlet exciton into two less energetic triplet excitons gives the process its name, but the ability to see what is going on vanishes as the process take place.

To get around this, the team employed a powerful technique known as two-dimensional spectroscopy, which involves hitting the material with a co-ordinated sequence of ultrashort laser pulses and then measuring the light emitted by the excited sample. By varying the time between the pulses in the sequence, it is possible to follow in real time how energy absorbed by previous pulses is transferred and transformed into different states.

Using this approach, the team found that when the pentacene molecules were vibrated by the laser pulses, certain changes in the molecular shapes cause the triplet pair to become briefly light-absorbing, and therefore detectable by later pulses. By carefully filtering out all but these frequencies, a weak but unmistakable signal from the triplet pair state became apparent.

探花直播authors then developed a model which showed that when the molecules are vibrating, they possess new quantum states that simultaneously have the properties of both the light-absorbing singlet exciton and the dark triplet pairs. These quantum 鈥榮uper positions鈥�, which are the basis of Schr枚dinger鈥檚 famous thought experiment in which a cat is 鈥� according to quantum theory 鈥� in a state of being both alive and dead at the same time, not only make the triplet pairs visible, they also allow fission to occur directly from the moment light is absorbed.

鈥淭his work shows that optimised fission in real materials requires us to consider more than just the static arrangements and energies of molecules; their motion and quantum dynamics are just as important,鈥� said Dr Akshay Rao, from the 探花直播鈥檚 Cavendish Laboratory. 鈥淚t is a crucial step towards opening up new routes to highly efficiency solar cells.鈥�

探花直播research was supported by the European LaserLab Consortium, Royal Society, and the Netherlands Organization for Scientific Research. 探花直播work at Cambridge forms part of a broader initiative to harness high tech knowledge in the physical sciences to tackle global challenges such as climate change and renewable energy. This initiative is backed by the UK Engineering and Physical Sciences Research Council (EPSRC) and the Winton Programme for the Physics of Sustainability.

Reference:
Bakulin, Artem et. al. 鈥�Real-time observation of multiexcitonic states in ultrafast singlet fission using coherent 2D electronic spectroscopy.鈥� Nature Chemistry (2015). DOI: 10.1038/nchem.2371

探花直播mechanism behind a process known as singlet fission, which could drive the development of highly efficient solar cells, has been directly observed by researchers for the first time.

Harnessing the process of singlet fission into new solar cell technologies could allow tremendous increases in energy conversion efficiencies in solar cells

Alex Chin

Lawrence W Chin, David Turban and Alex W Chin

Pentacene molecules convert a single photon into two molecular excitations via the quantum mechanics of singlet fission

探花直播text in this work is licensed under a Creative Commons Attribution 4.0 International License. For image use please see separate credits above.

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Scientists move closer to 鈥渢wo for one deal鈥� on solar cell efficiency

tdk25 — Mon, 16 Mar 2015 16:00:54 +0000

探花直播underlying mechanism behind an enigmatic process called 鈥渟inglet exciton fission鈥�, which could enable the development of significantly more powerful solar cells, has been identified by scientists in a new study.

探花直播process is only known to happen in certain materials, and occurs when they absorb light. As the light particles come into contact with electrons within the material, the electrons are excited by the light, and the resulting 鈥渆xcited state鈥� splits into two.

If singlet exciton fission can be controlled and incorporated into solar cells, it has the potential to double the amount of electrical current produced from highly energetic blue and green light, capturing a great deal of energy that would normally be wasted as heat and significantly enhancing the efficiency of solar cells as a source of green energy. Until now, however, scientists have not really understood what causes the process, and this has limited their ability to integrate it into solar devices.

Writing in the journal Nature Physics, a team of researchers shows that there is an unexpected link between the splitting process and the vibration of the molecule that occurs when light comes into contact with the electrons. This vibration is thought to drive the production of two excited electrons, revealing for the first time how singlet exciton fission happens.

探花直播study was carried out by researchers from the Cavendish Laboratory at the 探花直播 of Cambridge, and the 探花直播 of Oxford. As well as solving a hitherto mysterious problem of quantum physics, it potentially provides a basis on which new singlet fission materials could be developed for use in solar cells.

Dr Andrew Musser, a post-doctoral research associate and former PhD student at St John鈥檚 College, 探花直播 of Cambridge, who co-authored the research paper, said: 鈥淲e tend to characterise singlet exciton fission as a sort of two for the price of one deal on electrons, because you get twice as much electrical current. 探花直播problem is that if we want to implement this in a solar cell, the material needs to be engineered so that it is compatible with all the other components in the device. That means that we need to design a range of materials that could be used, and to do that, we need to understand more about why and how singlet exciton fission occurs in the first place.鈥�

At its most basic, singlet exciton fission is a product of the fact that when light particles, or photons, come into contact with an electron, the electron is excited by the light and moves. In doing so, it leaves a 鈥渉ole鈥� in the material鈥檚 electronic structure. 探花直播electron and the hole are still connected, however, by a state of mutual attraction, and the two together are referred to by physicists as an 鈥渆xciton鈥�.

These excitons come in two very different flavours: spin-singlet and spin-triplet, and in rare circumstances, they can convert from one to the other.

In the natural world, spin-singlet excitons are a part of photosynthesis in plants, because the light absorbed by pigments in the plant generates excitons which then carry energy throughout it. Solar cells imitate this process to generate and drive an electrical current. Conventional solar cells are silicon-based, and the absorption of a single photon leads to the formation of a single, excited electron that can be harvested as electrical current.

In a handful of materials, however, singlet exciton fission occurs instead. Rather than producing just one spin-singlet exciton, two spin-triplets appear when a photon is absorbed. This offers the tantalising prospect of a 100% increase in the amount of electrical current generated.

Researchers attempting to solve the puzzle of why the process happens at all, and why only in certain materials, have typically looked at how the electrons behave when they absorb light. In the new study, however, the team instead focused on the fact when the electrons move in response to the light, the molecule of which they are a part vibrates.

探花直播team used thin samples of TIPS-pentacene, a semiconducting material in which singlet exciton fission is known to occur. They then fired ultra-fast pulses of laser light at the samples, each pulse lasting just 10 鈥渇emtoseconds鈥�, or 10 quadrillionths of a second. 探花直播miniscule timescale was necessary so that large numbers of molecules could be vibrated synchronously, enabling the researchers to measure the response of the molecule and the resulting effect on the electrons as light hit the material. 探花直播measurements themselves were made using ultra-fast vibronic spectroscopy.

To the researchers鈥� surprise, they found that the molecules in the pentacene samples not only vibrated as singlet exciton fission occurred, but also continued to do so afterwards. This implies that the formation of two spin-triplet excitons is stimulated by the vibrations themselves, and the resulting tiny, fast changes in the shape of the molecules.

鈥淲e are fairly confident that this underlies all ultrafast singlet fission,鈥� Dr Akshay Rao, a Research Associate at St John鈥檚 College, Cambridge, who led the Cambridge team, said. 鈥� 探花直播picture that emerges is that when they are excited by light, the intrinsic vibrations drive the development of a new electronic state.鈥�

By understanding the fundamentals of singlet exciton fission, the study opens up the possibility of designing new singlet fission materials that would enable the process to be effectively integrated into a new generation of highly efficient solar cells. Future research is already being planned in which the group will examine the precise vibrational states that are required for singlet exciton fission to happen, which will further add to this knowledge.

探花直播work at Cambridge forms part of a broader initiative to harness high tech knowledge in the physical sciences to tackle global challenges such as climate change and renewable energy. This initiative is backed by the UK Engineering and Physical Sciences Research Council (EPSRC) and the Winton Programme for the Physics of Sustainability.

探花直播causes of a hitherto mysterious process that could enhance the power of solar cells have been explained in a new study.

If we want to implement this in a solar cell, we need to understand more about why and how singlet exciton fission occurs in the first place.

Andrew Musser

Martin Abegglen on Flickr

"Green Power". While conventional solar cells use silicon, it is possible that other materials could eventually be used that would increase their efficiency.

探花直播text in this work is licensed under a Creative Commons Licence. If you use this content on your site please link back to this page. For image rights, please see the credits associated with each individual image.

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Hybrid materials could smash the solar efficiency ceiling

sc604 — Thu, 09 Oct 2014 07:00:00 +0000

Researchers have developed a new method for harvesting the energy carried by particles known as 鈥榙ark鈥� spin-triplet excitons with close to 100% efficiency, clearing the way for hybrid solar cells which could far surpass current efficiency limits.

探花直播team, from the 探花直播 of Cambridge, have successfully harvested the energy of triplet excitons, an excited electron state whose energy in harvested in solar cells, and transferred it from organic to inorganic semiconductors. To date, this type of energy transfer had only been shown for spin-singlet excitons. 探花直播results are published in the journal Nature Materials.

In the natural world, excitons are a key part of photosynthesis: light photons are absorbed by pigments and generate聽excitons, which then carry the associated energy throughout the plant. 探花直播same process is at work in a solar cell.

In conventional semiconductors such as silicon, when one photon is absorbed it leads to the formation of one free electron that can be extracted as current. However, in pentacene, a type of organic semiconductor, the absorption of a photon leads to the formation of two electrons. But these electrons are not free and they are difficult to pin down, as they are bound up within 鈥榙ark鈥� triplet exciton states.

Excitons come in two 鈥榝lavours鈥�: spin-singlet and spin-triplet. Spin-singlet excitons are 鈥榖right鈥� and their energy is relatively straightforward to harvest in solar cells. Triplet-spin excitons, in contrast, are 鈥榙ark鈥�, and the way in which the electrons spin makes it difficult to harvest the energy they carry.

鈥� 探花直播key to making a better solar cell is to be able to extract the electrons from these dark triplet excitons,鈥� said Maxim Tabachnyk, a Gates Cambridge Scholar at the 探花直播鈥檚 Cavendish Laboratory, and the paper鈥檚 lead author. 鈥淚f we can combine materials like pentacene with conventional semiconductors like silicon, it would allow us to break through the fundamental ceiling on the efficiency of solar cells.鈥�

Using state-of-art femtosecond laser spectroscopy techniques, the team discovered that triplet excitons could be transferred directly into inorganic semiconductors, with a transfer efficiency of more than 95%. Once transferred to the inorganic material, the electrons from the triplets can be easily extracted.

鈥淐ombining the advantages of organic semiconductors, which are low cost and easily processable, with highly efficient inorganic semiconductors, could enable us to further push the efficiency of inorganic solar cells, like those made of silicon,鈥� said Dr Akshay Rao, who lead the team behind the work.

探花直播team is now investigating how the discovered energy transfer of spin-triplet excitons can be extended to other organic/inorganic systems and are developing a cheap organic coating that could be used to boost the power conversion efficiency of silicon solar cells.聽

A new method for transferring energy from organic to inorganic semiconductors could boost the efficiency of widely used inorganic solar cells.

探花直播key to making a better solar cell is to be able to extract the electrons from these dark triplet excitons

Maxim Tabachnyk

When light is absorbed in pentacene, the generated singlet excitons rapidly undergo fission into pairs of triplets that can be efficiently transfered onto inorganic nanocrystals.

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