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Locking in Solar Power: How a Stronger Interlayer Boosts Perovskite Cell Durability

Daniel Morton — Mon, 05 Jan 2026 19:31:00 +0000

Locking in Solar Power: How a Stronger Interlayer Boosts Perovskite Cell Durability Daniel Morton Mon, 01/05/2026 - 12:31

New Molecular Designs Extend the Life and Efficiency of Next-Generation Solar Cells

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Posted on the RASEI website with permission and minor modifications from the piece published by David DeFusco on the UNC Chapel Hill Applied Physical Sciences Site here.

A new study published in Science led by researchers at UNC-Chapel Hill, with collaborators from the Renewable and Sustainable Energy Institute (RASEI), explains why perovskite solar cells—fast-rising rivals to traditional silicon panels—tend to break down under prolonged heat and sunlight, especially ultraviolet light, and reveals a promising strategy to dramatically slow that damage.

The work focuses on a thin “interlayer” that sits between the electrode and the perovskite material inside a solar cell. This layer is only a single molecule thick, but it plays an outsized role in how long the device lasts.

“These interlayers are meant to help charges move efficiently out of the perovskite and into the circuit,” said Chengbin Fei, first author of the study and a postdoctoral researcher in UNC’s Department of Applied Physical Sciences. “But we found that some of the same chemical features that make them useful can also cause long-term damage if they’re not tightly attached to the electrode.”

Many high-performance perovskite solar cells use interlayers based on phosphonic acids. These molecules stick to a transparent electrode made of indium tin oxide, or ITO, and help pull positive charges out of the perovskite. Until now, most researchers assumed these layers were harmless once installed. Fei and his colleagues discovered that this is not always true.

The researchers found that some of these tiny helper molecules aren’t firmly stuck to the solar cell’s surface. When the cell gets hot or sits in sunlight that includes ultraviolet rays, those that are loosely attached molecules can break free. Once that happens, they start interfering with the solar material itself. They trigger harmful changes inside the cell: key ingredients fall apart, iodine-related components react in damaging ways and lead turns into a form that no longer works properly. Over time, all of this damage adds up and causes the solar cell to produce less and less electricity.

“In simple terms, the acid part of these molecules can act like a slow poison,” said Fei. “At high temperatures and under UV light, it accelerates chemical reactions that the perovskite just can’t tolerate.”

To understand what was happening, the researchers used a range of techniques, including spectroscopy and X-ray measurements, to watch how the materials changed over time. They found that stronger acids caused faster damage and that UV light made the reactions much worse. This explained why devices that look stable at first can fail after hundreds or thousands of hours outdoors.

The key advance came when the researchers at UNC and the �� created a new version of this thin helper layer containing a combination of two molecules that sticks much more tightly to the electrode surface. Seth Marder, the senior author at the University of Colorado-Boulder and Director of the Renewable and Sustainable Energy Institute (RASEI) says “the molecule our team developed was designed to not only interact with the electrode surface but more strongly with its neighboring molecules. Consequently the molecules stay more securely in place, reducing the reactive parts that can break away and damage the solar material that is deposited on top ”. As a result, the layer still helps charges flow out of the cell, but it no longer triggers the damaging reactions that shorten the cell’s lifetime.

Simply put, “when the molecule is firmly locked onto the surface, it can’t wander into the perovskite and cause trouble,” said Fei. “That simple change makes a huge difference over time.”

Solar cells made with the new interlayer design showed striking improvements and met a key performance milestone. Under harsh test conditions—85 degrees Celsius, continuous bright light that included UV and constant operation—the devices ran for nearly 3,000 hours before losing just 10 percent of their efficiency. That level of durability has not been reported before for this type of perovskite solar cell.

The molecule our team developed was designed to not only interact with the electrode surface but more strongly with its neighboring molecules. Consequently the molecules stay more securely in place, reducing the reactive parts that can break away and damage the solar material that is deposited on top.
- Seth Marder

The researchers also scaled up their approach to small solar modules, closer to what might be used in real products. These “minimodules,” about the size of a postcard, reached power conversion efficiencies above 22 percent and kept working for more than 2,000 hours under the same stressful conditions, which is considered very high performance for this type of solar technology.

Jinsong Huang, senior author of the paper and UNC Louis D. Rubin Distinguished Professor, said the results address one of the most important barriers to commercialization. “Efficiency alone is not enough,” he said. “For perovskite solar technology to succeed outside the lab, it must survive heat, light and time. This work shows a clear chemical pathway to make that happen.”

Beyond improving one specific material, the study sends a broader message to the field. Tiny details at buried interfaces—places that are hard to see and easy to overlook—can control the lifetime of an entire solar module. By understanding and managing these details, researchers can design devices that last far longer.

“This study reminds us that stability is a chemistry problem as much as an engineering one,” said Wei You, a co-author of the study and UNC Cary C. Boshamer Distinguished Professor of Chemistry and Applied Physical Sciences. “Once you understand the chemistry, you can start to fix it.”

JANUARY 2026

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The Filament Factory: How two specialized cells team up to build microscopic rock and drive carbon capture

Daniel Morton — Mon, 05 Jan 2026 17:26:55 +0000

The Filament Factory: How two specialized cells team up to build microscopic rock and drive carbon capture Daniel Morton Mon, 01/05/2026 - 10:26

Daniel Morton

In the tiny, beaded chain of the cyanobacterium Anabaena sp. ATCC 33047, two different cells, the photosynthetic factory worker and the nitrogen-fixing specialist, play distinct and powerful roles in creating solid minerals.

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A team led by Renewable And Sustainable Energy Institute (RASEI) Fellow Jeff Cameron and Nature, Environment, Science & Technology (NEST) Studio co-founder Erin Espelie, used advanced high-resolution microscopy to capture the key moments; the factory worker leaks materials when stressed, and the specialist accelerates crystal growth through contact, proving that single-cell behaviors are a vital trigger for biomineralization. Understanding the cellular processes could inform large-scale applications, from oceanic buffering and soil improvement to mineral formation, and living building materials that sequester carbon.

A central enabling technology to lower pollution and reduce carbon emissions is developing clever ways to capture, and handle carbon dioxide. One avenue of investigation is to use processes already developed by Nature. There is significant research focused on using one of the Earth’s oldest and powerful processes: Microbiologically Induced Calcium Carbonate Precipitation, or MICP for short. Bacteria and algae through their normal life functions naturally create rock, specifically calcium carbonate, the main component of limestone. This process is a critical process in oceanic buffering and holds immense potential promise for green technologies. If we can understand, and harness this process, we could use such bacteria for a broad range of applications. We could create “living” cements for self-healing concrete, stabilize fragile soils, even enhance industrial carbon dioxide sequestration. However, to control this process we first need to understand the specific cellular blueprints that guide these microbial construction projects. Until now, those blueprints have been frustratingly fuzzy.

To better understand the puzzle of biomineralization the team explored the cellular structure of the cyanobacteria Anabaena sp. ATCC 33047 (hereafter Anabaena). Think of this organism as a tiny “Filament Factory”, one that grows as a string of cells, essentially a beaded green chain (they show up as red in the images because of the microscopy technique), where labor is divided in specific jobs. The links in the chain are not identical, it contains two specialized cell types that perform distinct, but equally important tasks.

First, let’s consider the Vegetative Cells, which are like tireless “Photosynthetic Factory Workers”. These are the green, abundant cells with the primary job of harvesting solar energy to convert carbon dioxide into sugars (Photosynthesis). This process has long been proposed as the main cause for triggering rock formation through MICP, as it raises the local pH, making the environment more alkaline, which encourages calcium carbonate to precipitate.

The other kind of cells, which can be found scattered along the filament, are called Heterocysts. These are like “Nitrogen-Fixing Specialists”. These cells are slightly larger, more solidly built, and specialize in converting atmospheric nitrogen gas into a usable form for the entire filament. This requires an extremely lo-oxygen environment, distinguishing the heterocysts and giving them a significant influence over the cells surrounding chemical environment.

To understand the process in a stepwise fashion the team were able to treat the bacterial system with a specific nutrient cocktail that essentially “turned off” the generalized photosynthesis-driven precipitation and instead focus solely on the effects of these two specialized cells. By developing approaches to shutdown specific parts of the process the team could use advanced microscopy techniques to better pin-point the single-cell behaviors responsible for triggering the formation and growth of microscopic rock.

Unlocking this level of detail in the cellular workings of a cyanobacteria requires specialized tools. The researchers used a suites of powerful high-resolution techniques to interrogate the bacteria, including Quantitative Fluorescence Microscopy and Raman Microscopy, that enabled them to watch the action unfold. The ability to directly observe the single-cell processes was critical to determining how the “Filament Factory” uses two distinct mechanisms for biomineralization.

The first observation centers around the Vegetative Cells, or the “Photosynthetic Factory Workers”. While the cells are usually busy using solar energy to capture carbon dioxide the high-resolution microscopy captured what happens when these cells are under mechanical stress, such as when they are bent by other cells, or squashed against an existing mineral structure. The team were able to watch in real-time as this physical pressure caused the cells membrane to rupture. This breach of the membrane releases, or leaks, a key chemical, the sequestered inorganic carbon (bicarbonate) that the cell was holding inside. This rapid, localized surge of carbon creates excellent conditions for the formation of a new crystal at the leakage site. This reframes the start of the process. It is not just a passive gradual change in the environment that causes crystal growth, instead it can be caused by an active, stress-induced cell failure that is a trigger for calcite crystal nucleation.

The second observation concerns the actions of the Heterocyst Cells, or the “Nitrogen-Fixing Specialists”. Using the powerful techniques that enabled the researchers to peer into the inner workings of the cells the team were able to confirm that when a heterocyst cell came into direct contact with an existing calcite crystal “seed”, the crystal experienced rapid and dramatic growth. Crucially, this accelerated growth did not happen when a vegetative cell touched the crystal.

The team proposes that this dramatic crystal growth is connected to the function of Heterocyst Cell. Nitrogen fixation is a chemical transformation that consumes protons (H⁺). By pulling these protons out of the surrounding water, the heterocyst locally, and rapidly, increases the pH (alkalinity) of the microenvironment, which is amplified at the point of contact. This sudden shift in pH provides ideal conditions to effectively “glue” dissolved ions onto the existing crystal, resulting in rapid growth.

These findings describe how these two specialized cells have complementary roles. One is the nucleation trigger when stressed, and the other is the growth accelerator when in contact.

This detailed observation and analysis of the processes happening at the single-cell level shifts our understanding around the processes involved in biomineralization. Instead of thinking of microbial rock formation as a slow and uniform chemical reaction driven by large-scale phenomena like photosynthesis, this work illustrates mechanisms that are controlled and function-specific processes that are dictated by the precise cellular roles and localized behavior of individual cells.

The understanding building from these findings has the potential to inform a wide-range of applications. By isolating the “stress leak” trigger in vegetative cells and the growth accelerator from the heterocysts, researchers could design systems that intentionally apply mechanical stress, triggering crystal formation and accelerating the growth of carbon dioxide sequestering materials. This could have application in oceanic buffering and technologies for bio-concrete and soil rectification.

The development and application of advanced microscopic techniques has provided the bio-engineering world a new set of variable that they can use in bacterial engineering. By moving from a vague knowledge of “microbes make rock”, to a precise understanding of how the “Filament Factory” uses specialized cells to build, and grow, calcite crystals, the field is a step closer to harnessing this powerful natural approach for using carbon dioxide in a cleaner, more efficient way.

January 2026

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New window insulation blocks heat, but not your view

Daniel Morton — Thu, 11 Dec 2025 16:24:44 +0000

New window insulation blocks heat, but not your view Daniel Morton Thu, 12/11/2025 - 09:24

Physicists at CU Boulder, led by RASEI Fellow Ivan Smalyukh, have designed a new material for insulating windows that could improve the energy efficiency of buildings worldwide—and it works a bit like a high-tech version of Bubble Wrap.

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The team’s material, called Mesoporous Optically Clear Heat Insulator, or MOCHI, comes in large slabs or thin sheets that can be applied to the inside of any window. So far, the team only makes the material in the lab, and it’s not available for consumers. But the researchers say MOCHI is long-lasting and is almost completely transparent.

CU Boulder Today have put together a feature article that has been picked up by a number of other news outlets. Check out the feature and the follow ups with the links to the right.

December 2025

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The Grid’s New Shock Absorber: ‘Droop-e’ Control tames frequency swings and keeps renewable energy flowing smoothly

Daniel Morton — Tue, 09 Dec 2025 16:00:00 +0000

The Grid’s New Shock Absorber: ‘Droop-e’ Control tames frequency swings and keeps renewable energy flowing smoothly Daniel Morton Tue, 12/09/2025 - 09:00

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Electricity is crucial to modern life. We rely on being able to plug devices in to the outlet in the wall, flipping a switch, and things working without a problem. But it is not that simple, the power grid, all of the infrastructure that delivers energy from the power plant to your home, is something of a balancing act.

In order for a grid to operate safely, supply must equal demand. The flow of electricity through the grid in the United States flows at a frequency of 60 Hz, if the supply increases more than the demand, the frequency will increase, while if the demand increases, or the supply dips, the frequency decreases. The vast array of hardware that makes up the grid and in electrical devices, such as transformers, motors, or electronics, have been designed to operate at a specific frequency. If the grid is unbalanced, and the frequency changes too much, equipment can be damaged, efficiency is reduced, and it can lead to overheating, system failures, and blackouts. Keeping the grid online, and safe, is a balancing act that requires sophisticated controls systems to make sure that supply always equals demand.

Think of the electric grid like a high-speed train system. In order for the train system to operate effectively all the trains need to maintain consistent speeds and keep to schedule, so passengers are not left waiting on the platform, or miss their trains because they left too early. Traditional power plants are like massive freight trains, that are super heavy and take a long time to speed up or slow down. These massive freight trains provide a kind of inertia to the whole system. They are hard to disrupt, which results in a consistent speed. Renewable energy sources, such as solar and wind, are more like fast, light commuter trains, that can change speed essentially instantly. They lack the inertia of the massive freight trains, but they can change fast. If it were up to just human conductors and train line controllers to regulate how the trains are running, having the freight trains and the commuter trains on the same lines would be near impossible, the difference in speed and inertia would make it really hard to reconcile. This is where advanced computer-driven control systems come into play. In the train analogy the smart predictive system would predictively control the brake and throttle of the commuter trains to ensure a simple constant speed. How would the grid be impacted if we developed a smart control system?

This new report details work led by RASEI Fellow Bri-Mathias Hodge, and discloses a new approach for smart control in the grid. The grid is already full of control systems, with the standard way power generators respond to frequency events being via linear droop control. This would be like a simplistic cruise control for one of the Commuter Trains in the above analogy. If the frequency drops a little, the system increases the power proportionately. The problem with this approach is that it often doesn’t use the inverters full capacity fast enough. The innovation described in this work is an update called Droop-e, a non-linear control based on an exponential function. Think of it like replacing the trains cruise control, which previously had a simple on/off switch, with a smart responsive gas pedal, that can speed up, or slow down, on a curve.

This change, from an on/off control to a responsive curve, has the potential to have significant impacts on the grid. By using the available power reserves more effectively, Droop-e reduces the number of severe power swings in the system, and results in a slower rate of change of frequency (ROCOF), which can buy grid operators valuable time to react to changes in frequency.

The benefits from the ‘shock-absorber’ properties that Droop-e offers could help prevent blackouts before they start, help stabilize the grid and improve integration of renewable energy sources, and create a smarter, more responsive grid, future-proofing systems by replacing the software, and not the hardware, a significant cost saving.

The simulations from this study confirm that this new control approach could improve the stability of grids that include a combination of traditional power plants and renewable energy generators. If a major power plant trips offline, this sophisticated control system activates un-tapped power reserves in batteries and renewables, acting as a hyper responsive shock absorber to protect the entire grid system. For grid operators, it means more time to react. For everyone with devices plugged into a power outlet, it means improved stability, and less equipment damage. It also provides a more effective mechanism to integrate different power sources, improving reliability, security, and affordability.

December 2025

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New ‘Molecular Dam’ Stops Energy Leaks in Nanocrystals

Daniel Morton — Tue, 21 Oct 2025 19:17:19 +0000

New ‘Molecular Dam’ Stops Energy Leaks in Nanocrystals Daniel Morton Tue, 10/21/2025 - 13:17

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A molecular engineering breakthrough could make key light-driven reactions over 40 times more efficient.

A collaborative team of scientists from the ��, the University of California Irvine, and Fort Lewis College, led by RASEI Fellow Gordana Dukovic, has found a way to slow energy leaks that have impeded the use of tiny nanocrystals in light-driven chemical and energy applications. As described in a new article published in the journal Chem, the team has used a molecule that strongly binds to the nanocrystal’s surface, essentially acting like a ‘dam’ to hold back the energy stored in the charge-separated state formed after light absorption. This technique extends the lifetime of the charge separation to the longest recorded for these materials, providing a pathway to improved efficiencies and more opportunities to put this energy to work in chemical reactions. This collaboration is part of the U.S. Department of Energy funded Energy Frontier Research Center: Ensembles of Photosynthetic Nanoreactors (EPN).

Harnessing Light to Power Chemistry

Many of the products we rely on today, from plastics, to fertilizers, and pharmaceuticals, are created, or synthesized, through industrial chemical reactions that can often require immense heat and pressure, typically generated by burning fossil fuels. For decades there has been research exploring a less harsh and theoretically more efficient alternative: Photocatalysis. The goal is to use a compound, a “photocatalyst”, that can harness the energy in light and use it to power chemical reactions at room temperature. Semiconductor nanocrystals, particles that are over a thousand times smaller than the width of a human hair, are a leading candidate for this job. When exposed to light these nanocrystals generate a short-lived spark of energy, in the form of a separated negative charge (an electron) and a positive charge (called a “hole”, due to the absence of an electron). A key challenge in this area is that this spark disappears quickly, because the electron and the hole recombine, and the energy is lost before it can be put to good use.

Building a Molecular Dam

To solve this problem the team focused on building what we might call a ‘molecular dam’, something that helps prevent, or at least slow down, the electron and the hole from recombining. This research started with cadmium sulfide (CdS) nanocrystals and designed a molecule (in this case a phenothiazine derivative) with two key features; first the incorporation of a chemical group that acts as a ‘sticky anchor’ (in this case a carboxylate group), which binds strongly to the nanocrystal surface, and second, a molecular structure that quickly accepts the positive charge (the hole), from the nanocrystal to realize the light-driven charge separation event.

By anchoring this molecule to the surface of the nanocrystal the team created a highly efficient and stable pathway. As soon as exposure to light creates the electron-hole pair in the nanocrystal, the anchored molecule shuttles the hole away, physically separating it from the electron. This physical separation of the electron and the hole prevents the two from quickly snapping back together and wasting the energy. This results in a charge-separated state that lasts for microseconds, which is an eternity in the world of photochemistry, creating a much larger window of time for future researchers to work with in terms of harnessing this captured light-driven energy for useful chemical reactions. The team was able to prove the significance of the ‘sticky anchor’ carboxylate, by comparing their derivative to a phenothiazine that lacked the anchor, which was shown to be far less effective at holding the energy, demonstrating that this anchoring to the surface was key to this system’s performance.

This collaborative work was done as part of the U.S. Department of Energy funded Energy Frontier Research Center (EFRC) Ensembles of Photosynthetic Nanoreactors (EPN). EPN consists of 17 senior investigates located across 9 universities and 3 U.S. national laboratories. The goal of EPN is to provide a forum for collaboration, bringing together expertise to advance the frontiers of discovery and fundamental knowledge in photochemical energy conversion. The aim is to not only foster new discoveries and applications, but in doing so, train the researchers who will build knowledge and advances that will benefit the United States innovation and economy.

This project took advantage of the different areas of expertise of each team to generate ideas and quickly execute them. Kenny Miller’s group of dedicated undergraduate researchers at Fort Lewis College synthesized the carboxylated phenothiazine derivative (and a slew of others). Miller then sent the derivative to Jenny Yang’s group of inorganic electrochemists at UC Irvine for advanced electrochemical characterization. Gordana Dukovic’s group here at CU Boulder synthesized the nanocrystals, tested their compatibility with the derivative, characterized the binding, and undertook the advanced laser spectroscopy study to see how the electrons and holes behaved.

“The first time I saw the results-saw how effective our ‘molecular dam’ was at slowing charge recombination-I knew we had struck gold” explained Dr. Sophia Click, a lead author on the study. “To slow charge recombination from nanoseconds to microseconds, and with a molecule that can be paired with so many existing photocatalyst systems, makes this work vital to share with as many researchers as possible.”

Development of this ‘molecular dam’ could have implications for the future design of catalysts for light-driven chemistry. By increasing the efficiency of the initial energy-capture step, this system improves the efficiency of the entire process. This could improve not just one specific reaction, but rather, benefit a broad range of light-driven chemical reactions. A key technology this could enhance is the development of light-driven creation of chemical commodities or high-value chemicals. This research provides a more robust and versatile chemical toolkit for exploring these possibilities.

This discovery in controlling charge-separation, and energy, at the nanoscale is an important design parameter into developing light-driven chemistry, and hopefully light-driven chemical manufacturing. Imagine a future where materials, such as plastics, and even pharmaceuticals, are not made in energy inefficient high-temperature reactors powered by fossil fuels but instead are synthesized directly and efficiently using the power of light. While this vision is still on the horizon, the work done in this collaboration provides an important piece of the scientific puzzle, constituting a huge leap toward one day achieving these goals.

The study, “Exceptionally Long-Lived Charge Separated States in CdS Nanocrystals with a Covalently Bound Phenothiazine Derivative” was published in the journal Chem. This work was supported by the U.S. Department of Energy, Office of Science, as part of the Energy Frontier Research Center: Ensembles of Photosynthetic Nanoreactors (EPN; DE-SC0023431), with additional experiments on nanorods supported by Air Force Office of Scientific Research under AFOSR (FA9550-22-1-0347).

October 2025

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Fixing Solar’s Weak Spot: Why a tiny defect could be a big problem for perovskite cells

Daniel Morton — Mon, 15 Sep 2025 15:25:36 +0000

Fixing Solar’s Weak Spot: Why a tiny defect could be a big problem for perovskite cells Daniel Morton Mon, 09/15/2025 - 09:25

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Solar energy is a crucial part of our clean energy future, but a new, highly efficient solar material has a hurdle that needs to be addressed. A recent study reveals how a microscopic weak spot can lead to total device failure and what we can do about it.

A collaboration between a team led by RASEI Fellow Mike McGehee and scientists at the National Renewable Energy Laboratory (NREL), just published in the scientific journal Joule, provides evidence to help solve one of the key hurdles to large-scale manufacture of next generation perovskite solar cells.

Imagine you have a series of hoses connected end-to-end to water your garden. The water flows from the faucet, through each hose, and out the last nozzle. When every hose is getting enough water, the flow is strong and steady. This is like how a string of solar cells works on a solar panel; the sun’s energy makes electrons (the “water”) that flow through each cell, creating electricity.

But what happens if a single section of the hose gets kinked? The water can’t flow through it anymore, but there is still a lot of pressure coming from the faucet. The pressure will build up and eventually burst the weak spot in the kinked section. This is analogous to what happens when a section of the solar panel is shaded --- the cell becomes ‘kinked’. When just one part of a panel is shaded, the unshaded cells still generate electricity and “force” current backward through the non-producing shaded cell. This is known as reverse bias, and it can cause the shaded cell to permanently degrade and fail.

For conventional silicon-based solar cells, reverse bias is a known problem and engineers have developed a solution: a bypass diode. You can think of this as a small side-channel that allows the water to flow around the kinked hose, keeping the rest of the system running smoothly without building up damaging pressure.

However, the bypass diode solution doesn’t work for perovskite-based solar cells, a leading candidate for the next generation of more efficient and more affordable solar cells, because they are often too “weak”. One of the key pieces in the puzzle to solving this reverse bias problem in perovskite solar cells is understanding how the cell degrades when under reverse bias, and that is the focus of this research collaboration.

The McGehee group has a long history of success in creating and optimizing perovskite solar cells. Beginning in 2018, their focus shifted to a critical challenge: what happens when these cells are in the shade? Many researchers had already observed that even a small amount of reverse bias caused the materials to heat up and "melt," leading to rapid and permanent degradation of the perovskite.

While these observations were widely accepted, the exact reason for the degradation was a mystery and a subject of much debate. "These are complex systems, and it can be very hard to untangle what is going on," explained Ryan DeCrescent, one of the study's lead researchers. This is where the McGehee group's work came in—they set out to find the specific mechanism behind this destructive behavior.

"These are complex systems, and it can be very hard to untangle what is going on," explained Ryan DeCrescent

The perovskite layer is formed through an approach called solution processing. Solution processing is kind of like making a pancake, you make your batter and when you pour it onto a hot griddle several things happen: the water evaporates, the solids set, the thickness is determined by how much you add, and you often get gaps, or holes in your pancake. In these devices, the perovskite ingredients are put into a solvent. The solvent is then dropped onto the earlier layers of the device and warmed up, whereby the solvent evaporates and a film is formed, but often with defects, or gaps. Defects and pinholes are easily formed in such films. This is a particular issue for perovskites, since the precursor solution has low viscosity and during the heating stage defect formation is common.

To better understand the impact of these defects on the performance of the solar cells under reverse bias you need to take a really good look at them. Central to this work is a suite of tools that enabled exceptional examination of the perovskite layer. “A large part of this work was really setting ourselves up to look very carefully at these surfaces” said DeCrescent. Four main techniques were employed to better understand the defects: Electroluminescence (EL) imaging with a high-resolution camera, Scanning Electron Microscopy (SEM), Laser-Scanning Confocal Microscopy (LSCM) and Video Thermography. The strategy was to compare ‘before, during, and after’ pictures of devices that had been exposed to reverse bias. The high-resolution camera showed that “weak spots” in the device were the origin of degradation. To better understand “perfect” device behavior and efficiently scan a large number of samples (~100), the team setup a large number of very small devices, creating thin films with an area of just 0.032 mm^2. To put that in perspective, each device was about the width of two human hairs. The small size of these devices meant that it was possible to create devices that were defect-free, since it is hard to create defect-free films on a larger scale. Through this combination of a large sample size, and advanced imaging, the team was able to rapidly explore many different types of defects.

This approach of using advanced imaging proved to be an incredibly effective way not only to identify the defects but also to understand exactly what happens to them. "Video thermography and electroluminescence imaging are really powerful techniques for such devices; for example, defects that are sometimes difficult to spot really stand out using these approaches," explained Ryan. Using the thermography technique the defects glow brightly, and in the electroluminescence technique the defects show as dark. Using these techniques in combination provided a very reliable and effective way of mapping the defects. The techniques clearly revealed where the degradation was occurring.

The team’s evidence strongly supports the argument that defects, like pinholes and thin spots in the perovskite layer, are the precise locations where reverse-bias breakdown begins. The thermography images showed that these sites are where the material rapidly heats up and melts, essentially shorting between the two contact layers. In contrast, defect-free devices showed remarkable stability, surviving hours of reverse bias without any significant degradation.

This level of detailed understanding is crucial for the future of this technology. The team's research provides a clear path forward for scientists and engineers: to develop more robust and stable perovskite solar cells, they must prioritize making pinhole-free films and using more robust contact layers to prevent this kind of abrupt and permanent thermal damage.

This work represents a critical step in the journey toward commercializing perovskite solar cells. It highlights the fact that detail-driven, rigorous scientific approaches are needed to understand complex problems. With this knowledge in hand, scientists can now engineer devices that are designed for longevity, ensuring these promising materials can fulfill their potential.

September 2025

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Liquid Crystals that Keep Time: Scientists Create Matter that Dances to Its Own Beat

Daniel Morton — Fri, 05 Sep 2025 19:29:45 +0000

Liquid Crystals that Keep Time: Scientists Create Matter that Dances to Its Own Beat Daniel Morton Fri, 09/05/2025 - 13:29

Adapted from an article run in CU Boulder Today by Daniel Strain

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A team led by RASEI Fellow Ivan Smalyukh has discovered a new type of liquid crystal that exists in perpetual, rhythmic motion, creating, for the first time, time crystals visible to the naked eye.

Reporting their findings in Nature Materials, the team demonstrates how liquid crystals, the same materials found in your phone display, can form a phase of matter that spontaneously breaks both space and time symmetries. Unlike previous time crystals that existed only in quantum systems invisible to the naked eye, these can be observed directly under a microscope.

The researchers designed special glass cells filled with liquid crystals and coated with light-sensitive dye molecules. When illuminated with blue light, something remarkable happens: like dancers following a lead, the liquid crystal molecules respond to cues from the dye molecules, creating an elaborate molecular waltz that repeats its steps over and over.

Here's how the molecular choreography works: The azobenzene dye molecules at the surface respond to light by rotating, which then guides neighboring liquid crystal molecules to reorient. This creates a feedback loop where the changing liquid crystal orientation affects how light polarizes as it passes through, which then influences more dye molecules at the bottom surface. The result is a self-sustaining temporal rhythm.

The researchers discovered that these time crystals are built from special molecular arrangements called ‘topological solitons’, think of it like stable whirlpools in a stream that maintain their shape while the water flows around them. These soliton "particles" interact with each other through the liquid crystal's elasticity, forming arrays that oscillate in time with remarkable precision.

What makes these time crystals remarkable is their resilience, similar to a heartbeat that continues despite disturbances, these patterns persist even when perturbed. The team demonstrated that the crystals maintain their rhythm when subjected to random light fluctuations and recover their ordered state after disruptions, meeting stringent criteria that distinguish true time crystals from simple periodic behavior.

The temporal periods can be tuned from milliseconds to tens of seconds by adjusting temperature and light intensity, while the spatial patterns can extend over areas larger than a square millimeter—making them easily visible and potentially practical for applications.

There are many potential applications, particularly in optoelectronics and security. The time crystals could serve as dynamic optical elements that modulate light in both space and time, enable new forms of optical communication, or provide sophisticated anti-counterfeiting features through their unique spatiotemporal "fingerprints." The ability to create 2+1 dimensional barcodes (two spatial dimensions plus time) could revolutionize information storage and encoding.

As is often found with breakthrough discoveries, the most transformative applications are likely yet to be imagined. But for now, scientists have created matter that literally keeps time.

September 2025

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Breakthroughs in materials science are helping to improve tomorrows energy storage

Daniel Morton — Fri, 15 Aug 2025 15:18:38 +0000

Breakthroughs in materials science are helping to improve tomorrows energy storage Daniel Morton Fri, 08/15/2025 - 09:18

Daniel Morton

The future of energy storage is being written at the molecular level. As renewable energy is transforming how we generate electricity, battery storage technologies are emerging as the backbone of a resilient, flexible power grid. Advances in materials science are key to unlocking their massive potential to change the way we interact with energy.

Effective and sustainable energy storage is critical to a modern and resilient power grid. Independent of how the electrons are generated, the ability to flexibly store and supply electricity strengthens the grid and improves our energy security.

The path to a reliable and sustainable energy economy runs directly through better, more efficient batteries. Today’s power grid demands storage solutions that are more efficient, built from materials that are abundant, affordable and environmentally responsible. This intersection of performance and sustainability presents one of the most exciting tensions in modern energy research.

In the last six months RASEI Fellows have publish more than ten research articles that explore a range of materials science challenges associated with battery storage, developing solutions at the molecular level that could have profound impacts on how we store energy on the grid-scale, here we highlight a selection of this recent work.

Why Batteries Are Essential For Grid Flexibility

Battery storage offers exceptional flexibility to a modern power grid, providing rapid response capabilities that can balance supply and demand within seconds rather than minutes or hours. A key benefit of battery systems is that they can be deployed virtually anywhere, from urban centers to remote locations, creating opportunities for more resilient and distributed grids that adapt to local needs and conditions.

Materials Science Engineering Charges Innovation

At its core, battery performance is fundamentally about engineering better materials: how molecules are structured, how electricity flows, and how charged particles travel through carefully designed and engineered structures. This is where cutting-edge materials science research is essential, providing the tools to better design battery components at the molecular scale to achieve faster charging, longer lifespans, and higher energy storage. These are features that will be critical as we scale up to grid-level storage.

Consider how a typical rechargeable battery, such as a lithium-ion battery, works: charged particles (such as lithium ions) move between the two sides of the battery during charging and discharging. Think of it like cars moving between parking lots (the two sides of the battery, the positive and negative electrodes). The ability to park more cars represents the ability to carry more energy. When you use the battery the cars (the lithium ions) travel between the lots through a highway (the electrolyte). To use the highway, they have to pay a toll. In this case they give up an electron, which produces the electricity that powers your device. When you charge the battery the cars move back to the original lot, but you have to give them an electron to go back through the toll.

Repeated charging and discharging can cause damage to the parking lots, the highway between them, and the cars can even get stuck. Building better electrodes (parking lots), more effective electrolytes (the highway) and better understanding of how the charged particles act (the cars), teams can develop more effective and robust energy storage.

Recent Research Highlights

Boron-Alloyed Silicon Nanoparticle Anodes can improve the performance for lithium-Ion Batteries.

Read the article here

By mixing some boron with your silicon you can make a more robust battery electrode!

With a theoretical energy density ten times higher than graphite, Silicon (Si) has inspired interest as a next generation anode active material for lithium-ion batteries. In the general analogy, this is building a more robust parking lot for the charged state. When you charge and discharge a lithium-ion battery, on a molecular scale this is achieved by the pumping in, and pumping out of lithium ions (cars going in and out of the parking lot), which come with a significant volume change. (This would be like the floors of a multi-story parking lot changing size as cars drive in and out. Realistic on the atomic scale, not so much on the car-scale…) Silicon-based anodes have been found to be unstable to this constant change in volume which can lead to instability and failure. One strategy to address this is to move from having the silicon anode being a solid slab, to being a series of nanoparticles, which helps to reduce this mechanical stress, but this comes with another problem, the increased surface area of the particles allows more chemical side reactions, which is another big problem. There has been much research investigating the materials science and surface chemistry to reduce the unwanted side reactions. A key finding from recent research is that the best way to prevent unwanted side reactions is to essentially isolate the silicon surface from the electrolyte media it is in. This is where this research, led by RASEI Fellow Nate Neale, comes in.

By mixing, or alloying, the silicon with boron, the anodes were found to perform better and last longer. The more boron added to the nanoparticles, the more robust they were. In fact, the team saw a 3x improvement in lifetime by incorporating boron. The team proposes that by making the nanoparticles out of a mixture of silicon and boron, the presence of the boron creates an “electric double layer” effect, essentially providing a protective layer at the surface of the nanoparticle, shielding from the unwanted side reactions. This saw some real improvements in the performance of the electrolytes, not just a 3x improvement in the calendar lifetime, but an 82.5% capacity retention after 1000 cycles, the pure silicon electrodes reached the end-of-life (<80% capacity retention) in fewer than 400 cycles under similar conditions.

Boron creates a strong electrical field at the nanoparticle surface that attracts and concentrates ions from the surrounding electrolyte, forming a stable, dense layer that acts like a permanent shield. This work reveals an underexplored parameter in the design and optimization of silicon anodes that could prove valuable in the next-generation of lithium-ion batteries.

This breakthrough could accelerate the adoption of silicon anodes in battery applications, such as electric vehicles, where longer-lasting batteries are essential to address range anxiety. The research team is now working to identify the optimal silicon-boron ratio that maximizes both capacity and longevity, potentially bringing us closer to the next generation of high-performance lithium-ion batteries.

How Molecular Shape Impacts Battery Performance: New Insights for Flow Batteries

Read the article here

Making seemingly minor molecular changes to the structure of charge storage chemicals can have significant impacts on the performance of redox flow batteries.

Redox Flow Batteries offer a promising solution for large-scale energy storage. Unlike the lithium-ion batteries in your phone, flow batteries store energy in liquid electrolytes that flow through the system. This design allows them to store massive amounts of energy for long periods, making them ideal for stabilizing electrical grids.

However, making these batteries practical requires finding the right chemical compounds that are stable, efficient, and cost effective. This article describes collaborative research that includes teams led by RASEI Fellow Mike Toney and former RASEI Fellow Mike Marshak. The teams were exploring the optimization of chromium-based compounds as charge carriers. The aim was that by changing the structure of the organic chelate ligand that surrounds the chromium atom, they could better understand the relationship between structure and performance and use that understanding to design more efficient systems.

Two very similar chromium compounds were prepared; CrPDTA and CrPDTA-OH, which differ only by the addition of a single hydroxyl group (-OH) on the organic framework. Hydroxy groups are often added to compounds to improve their solubility in water, but in this case the team observed a drop in the performance of the molecule. The hydroxylated compound showed:

Slower reaction rates – The CrPDTA-OH transferred electrons 100 times more slowly than the non-hydroxylated.
Reduced efficiency – battery efficiency dropped from 99.3% to 98.2%.
Increased hydrogen gas production – more energy was wasted producing unwanted hydrogen gas in a side reaction instead of being stored.

It’s kind of like if some of the cars had one flat tire. They are going to be worse at transporting charge back and forth, and they might do things you don’t want them to.

Using a suite of advanced characterization techniques the team discovered that the addition of the hydroxyl group caused a distortion of the molecular shape around the central chromium ion. This distorted shape weakened the bonds between the metal atom and the organic chelate ligand, which reduced the efficiency of electron transfer.

This research reveals a fundamental principle for designing redox flow battery materials: molecular geometry matters immensely. The chromium atom needs to adopt an octahedral arrangement to work efficiently. Any distortion of this shape leads to reduced performance. This study also confirms why maintaining the precise structure is so important. It prevents water molecules from interfering with the chromium atom, which would cause the unwanted production of hydrogen gas instead of energy storage.

Researchers Discover The Hidden ‘Dance’ Of Ions That Could Inform The Design Of Grid-Scale Energy Storage

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Insights into the processes of charge movement in the electrolyte could inform future battery design

The electrolyte of the battery is the highway that connects the two parking lots together. This research that brings together an international collaborative team, including researchers from three US universities, three National labs, and researchers from the United Kingdom and Switzerland, and RASEI Fellow Mike Toney, reveals important features of this highway in zinc-ion based batteries.

While most people are familiar with lithium-ion batteries in their phones and devices, zinc-ion batteries offer compelling advantages for large-scale electricity storage. Zinc is more abundant and thus affordable, zinc-ion batteries use water-based electrolytes that are much less likely to overheat or explode, Zinc-ion batteries can pack a lot of energy into a small space, they are very energy dense.

The electrolyte is the media through which the charged ions pass through during charge and discharge cycles. In our metaphor the electrolyte is the highway on which the cars travel back and forth. The properties of the electrolyte can dictate a number of features of the batteries performance, how fast it charges, how long it lasts, and how much energy it can store. This research has explored how these ions, or ‘cars’, act during transport, and they have observed that it is not plain driving, the ions cluster and form convoys as they move through the electrolyte. The way the zinc sulfate ions travel is far more dynamic and complex than previously understood.

Using advanced x-ray techniques in combination with advanced computer modeling the team were able to explore the molecular structure of the electrolyte at different stages of the charge / discharge cycle. They found that the ions don’t just float around independently, instead they form clusters, like cars forming a convoy. It was observed that the zinc ions surround themselves with exactly six water molecules and clusters formed in a range of sizes, from just 2 ions all the way up to 22 ions.

You might expect that they clusters would move more slowly, like a traffic jam on the highway, but the team found that while the clusters do reduce conductivity, the battery still works. Critical to this is the timing of the clusters. The clusters are incredibly short lived, existing for only picoseconds (trillionths of a second) at a time. Instead of having a traffic jam, it is like having really busy traffic that is moving so fast that it is constantly reorganizing itself and so it never actually gets stuck.

This offers insights that can be applied in future battery designs; Ions form diverse, temporary partnerships that vary in size and composition, the system is constantly undergoing reorganization, transport happens both through vehicular motion (cars moving through the highway), and hopping between clusters (it would be like someone jumping from car to car in an action movie). These insights could improve future electrolyte design which could improve battery performance and potentially open the door to new battery chemistries that could be used for a broader range of applications, such as grid-scale storage.

By developing a more informed understanding of how charge is transported in electrolytes we can improve our designs in the future. Instead of trying to avoid cluster, we can harness it to improve the efficiency of charge transport in battery technologies.

Inside the battery: X-Ray Vision Reveals How Sodium Really Moves and Stores Energy

Read the article here

Sodium-ion batteries have the potential to be game changers for grid-scale storage with their abundance, low cost, and sustainability advantages over existing lithium-ion technologies. A key hurdle in their development is that we don’t yet fully understand how sodium actually moves and stores energy on the molecular level. This international collaboration, led by RASEI Fellow Mike Toney, uses cutting-edge X-ray techniques and computational modeling, provides insight into these promising battery chemistries.

Sustainable battery technologies are central to the modern power grid and meeting the growing demand of electrification technologies, such as electric vehicles. Among the growing array of battery chemistries Sodium-Ion Batteries (NIBs) address many of the challenges associated with lithium-ion batteries, and can even benefit from the work done to bring lithium-ion technologies to scale. This is swapping out the cars in our analogy from lithium-ions to more affordable sodium-ions. Sodium is one of the most abundant elements on Earth, making it dramatically more affordable and sustainable than lithium. While NIBs don’t yet match the energy density of lithium-ion based designs, they are ideal for grid storage applications where space is less constrained, but cost and sustainability matter enormously. Furthermore, NIBs can be produced using lithium-ion manufacturing facilities, enabling rapid deployment without the associated infrastructure costs.

The main hurdle has been developing anode materials that efficiently store and release sodium ions. Hard carbon shows promise but understanding exactly how sodium storage works at the molecular level remained elusive—a critical gap for large-scale manufacturing.

This research uses a combination of advanced X-ray spectroscopy techniques and computational modeling to peer inside the electrodes of a working NIB to watch the storage process unfold in real-time. Put simply they explored the details of a three step system where sodium ions first attach to surface defects in the hard carbon, then squeeze between the carbon layers, and finally cluster into the pores of the anode, providing insights and a road map for the design of NIBs in the future.

To gain more information about the details of these processes the team using X-ray total scattering, a technique that bounces high-energy X-rays off atoms and analyzes the scattered pattern to map exactly where atoms are positioned relative to each other. Think of it like echolocation to see in the dark, but for atomic structures! By taking a series of ‘snapshots’ of the NIBs at different stages of charging, the researchers could track how sodium atoms moved and arranged themselves during the process. The X-ray data reveals amazing levels of detail, revealing distinct signatures for different types of sodium storage, distinguishing between sodium atoms stuck to the surface defects of the hard carbon and those squeezed between carbon sheets, and those atoms clustered in pores.

Through a combination of these experimental results and advanced computational modeling the team were able to piece together a three-stage sequence to better understand the movement of sodium ions during charging. First, the sodium ions target high-energy defect sites on the hard carbon surfaces, like easy to access parking spots with the strongest attraction. In the second stage, as the prime parking spots fill up, sodium begins what the researchers call “defect-assisted intercalation’, where the defects are used as entry points to slip between the carbon layer (like cars going to other levels of a multistory parking lot), causing the carbon layers to expand slightly. In the third stage, in the low-voltage plateau region, sodium continues to intercalating between the layers, while also filling up the nanoscale pores and forming metallic clusters. Crucially the evidence from the X-ray analysis shows that the size of these clusters is dependent on the pore size – larger pores in the carbon processed at higher temperatures produced bigger sodium clusters, directly linking the battery’s microstructure to its storage capacity.

This molecular-level understanding has the potential to transform NIB development from educated guesswork into precision engineering. Guided by this three stage roadmap, battery researchers can now strategically design hard carbon materials, altering defect concentrations to optimize initial storage, controlling pore sizes to maximize capacity, while balancing these factors to minimize the irreversible trapping that reduces overall battery lifetimes. The combined X-ray spectroscopy and computational modeling technique demonstrated in this research has the potential to provide a powerful new toolkit for studying other battery chemistries in the future. By revealing more about how sodium energy storage works, this research brings us closer to sustainable solutions for grid-scale energy storage, a critical piece in the puzzle for a modern, resilient, and sustainable energy economy.

August 2025

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Finding the On switch for more efficient light-driven chemistry

Daniel Morton — Mon, 07 Jul 2025 16:34:22 +0000

Finding the On switch for more efficient light-driven chemistry Daniel Morton Mon, 07/07/2025 - 10:34

Daniel Morton

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Collaboration led by RASEI members Obadiah Reid and Garry Rumbles solves a long-standing puzzle in important organic chemical transformation.

In the world of organic chemistry, making new molecules, the building blocks for everything from advanced electronic materials to pharmaceuticals, is a bit like being a chef. Chemists are always looking to improve the recipe, to make it faster, cheaper, more efficient, and produce less waste. In recent years one of the most exciting new ‘cooking techniques’ is nickel photocatalysis, which uses abundant, low-cost nickel and the power of light to enable chemists to build complex molecules under mild conditions.

This technique has emerged as something of a game-changer in building molecules, but it comes with a significant puzzle. The nickel catalyst, as it is normally added to a reaction, is in a dormant state (called a ‘pre-catalyst’). To get the reaction moving, the catalyst needs to be ‘woken up’. For years, scientists were not sure what the wake-up call was. The activation from pre-catalyst to the functioning catalyst was something of a black box, with numerous theories for what was happening. This led to the assumption that each reaction was unique, and each reaction required its own individual and complicated startup sequence. This has often required a lot of work to find the right ‘On switch’.

This collaborative study, led by RASEI researchers Obadiah Reid and Garry Rumbles at the National Renewable Energy Laboratory (NREL), brings together expertise from the SLAC National Accelerator Laboratory, Brookhaven National Laboratory, Argonne National Laboratory and Northeastern University. Together, the scientists have identified key features of the transformation from pre-catalyst to active catalyst. In the report, just published in Nature Communications, the team shows that there is a universal ‘On switch’ to start these powerful reactions, and the key to this transformation is light.

Imagine a high-tech machine delivered in a locked crate. You know that once you get it out and get it running, it can do amazing things, but you don’t have the key. For years, chemists were essentially trying to pick the lock in different ways every time they wanted to use it. This study describes a universal key for getting the crate open.

It was found that light, either directly, or transferred from another light-absorbing molecule, provide a jolt of energy that breaks a bond in the nickel pre-catalyst structure. This process, which is called photolysis, activates the nickel complex, getting it ready to do the chemistry. This initial step is something that has previously been proposed but never fully proven.

The team brought together a sophisticated array of tools to effectively investigate this mechanism, including incredibly fast laser systems that can watch chemical changes happen in fractions of a second. This allowed them to witness the ‘unlocking’ process in real-time and identify the exact sequence of events. They observed that after the initial light-induced bond breaking, the catalyst can then interact with molecules in the surrounding solvent, forming a temporary ‘reservoir’ that holds the catalyst in a state ready for the main reaction.

Building this body of evidence and developing these findings required a significant team effort, bringing together scientists from across the country, from multiple national labs and universities. RASEI Scientists at CU Boulder and NREL used advanced spectroscopy to track the catalyst’s behavior, while researchers at SLAC used high-powered X-rays to confirm changes in the structure of the nickel complex. This combination of knowledge and experience with cutting-edge instrumentation was essential in providing a complete understanding of these reactions begin.

Development of a unified explanation for how one of the most important tools in an organic chemist’s toolbox is initiated has important implications. Understanding this fundamental activation step allows chemists to move from guessing to designing. Not only does this support improvement in the activation of existing reactions, it also provides opportunities to design new transformations, all of which will streamline the manufacture of chemical commodities, such as pharmaceuticals and materials.

JULY 2025

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Light-powered reactions could make the chemical manufacturing industry more energy-efficient

Daniel Morton — Thu, 26 Jun 2025 22:25:34 +0000

Light-powered reactions could make the chemical manufacturing industry more energy-efficient Daniel Morton Thu, 06/26/2025 - 16:25

Daniel Morton

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The Conversation Highlight

SuPRCat

Research Article

Chemistry World Highlight

Colorado Arts & Sciences Magazine Highlight

A recent collaborative report, published in Science, including RASEI Fellow Niels Damrauer, addresses a key issue for light-driven chemistry, potentially opening up possibilities for future energy-efficient chemical manufacturing.

Chemical reactions typically require an input of energy to proceed, this can be through heating, or introduction of chemical energy in the form of reactive chemicals. Recently, light-driven chemistry has emerged as a more energy efficient alternative. The principle is to use energy from light, which is absorbed by a catalyst. Excited by the light energy the catalyst can then donate an electron to the chemicals undergoing the desired chemical transformation.

This sounds great – light-driven reactions? One of the key issues in this class of chemistry is back transfer of the electron. This means that after the catalyst donates the electron to the reagents, instead of doing the desired reaction, the reagent gives the electron back to the catalyst. This can significantly slow down the desired reaction, even sometimes shutting it down.

This report details a new type of catalyst that can overcome this back transfer of electrons. Through rationale design of the catalyst the new system uses a chemical reaction as a catch, preventing the back transfer from the reagent and strongly favoring the desired reaction.

To highlight the impact of this work, which was completed as part of the NSF Center for Chemical Innovation Center for Sustainable Photoredox Catalysis (SuPRCat), CU Boulder student Arindam Sau, a member of the Damrauer group, teamed up with a graduate student and postdoc from Colorado State University to put together a review and summary of this work that was recently published in The Conversation. Check out the highlight to get a full picture of the impact of this work.

June 2025

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