Solar Energy

‘Twisting’ atomic materials may convert light into electricity

Published

4 years ago

May 2, 2021

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‘Twisting’ atomic materials may convert light into electricity

A pair of physicists at the University of California, Riverside, are aiming to convert light falling on atomically thin semiconductor materials into electricity, having received more than $582,000 in funding from the U.S. Department of the Army.

Nathaniel Gabor and Vivek Aji, both associate professors of physics and astronomy, will focus on how the fundamental science of light and its interaction with matter enables new sensing capabilities in layered and twisted vertical structures of stacked monolayer semiconductors. The researchers aim to understand how electronic excitations influence the flow of photo-absorbed energy in ultrasmall semiconducting optoelectronic materials.

“”This research effort has the potential to impact fundamental science and technology, involving physics of quantum processes in light-sensing and deeper knowledge of novel optoelectronic properties in 2D quantum materials,” said Tania Paskova, program manager of the U.S. Army Combat Capabilities Development Command, known as DEVCOM, Army Research Laboratory. “A successful execution will open new opportunities for quantum enhanced sensors that could usher a new era of night vision technology and quantum communication networks, both of significant importance for the Army.”

Gabor and Aji expect their stacking and twisting approach will spawn a new generation of quantum photodiodes that operate at room temperature, next-generation photovoltaics, single photon sensors, and light-emitting diodes, or LEDs. They will be among the first to explore the ability to stack-engineer the interaction between vibrational motion and electronic states, heralding a new era of quantum sensor science.

“We think this project will give us a deep understanding of fast and highly sensitive quantum coherent electron-hole separation in light sensing,” said Gabor, the three-year grant’s principal investigator. “”It also promises rapid future advancement of precisely engineered materials and devices for advanced light-sensing technologies.””

Using theoretical modeling as a tool, Gabor and Aji have already begun experiments with atomically thin semiconductors tungsten diselenide and molybdenum diselenide. When such semiconductors absorb a photon, a bound electron can be freed, leaving behind an electron vacancy, or hole. As the hole behaves like an electron with positive charge, the electron and hole can attract each other to form a bound state called an exciton.

“Today, we understand better even at just the stacking level how these materials behave,” said Aji, a theoretical physicist and the grant’s co-principal investigator. “In twisting, you arrive at a series of ‘magic angles’ where certain aspects repeat. Twisting is the future in this line of research.”

Gabor explained that materials scientists are now easily able to isolate individual atomically thin materials and also control how they’re twisted relative to each other. Engineering the interactions in these “twistronic” materials between atomic motion and excitons, however, is challenging since the interaction strength is fixed by atomic-scale configuration and electronic structure.

“Imagine a layer of red atoms on top of a layer of blue atoms,” Gabor said. “By twisting these against each other, you finely manipulate the distance between the red and blue atoms and the atoms’ allowed vibrations get affected in unusual ways. As you continue to make these twists … their behavior, in turn, becomes more complex, affecting properties such as magnetism, superconductivity, and optical effects.

“With just one layer, you have a very narrow absorption of an exciton. When you start to stack and twist the layers, you can find new ways to absorb light and efficiently generate current from it.”

When stacking tungsten diselenide and molybdenum diselenide layers, an electrical field may form between them. Light shining on this stack forms a bound exciton, which is then converted directly into electrons and holes with remarkable efficiency. Gabor suspects some unique quantum mechanical effects may be occurring in the tungsten diselenide-molybdenum diselenide system. Only a few materials systems behave in this manner, he said.

“It has to do with the way the atoms are vibrating and how that interacts with light,” he added. “We may be seeing vibronic physics here. The ultimate goal from the Army’s perspective is to find such new ways of increasing efficiency that take advantage of quantum mechanical effects. We have a whole suite of semiconductors that behave like tungsten diselenide and molybdenum diselenide to experiment with.”

Aji explained that when light is absorbed in a semiconductor, some excitation is created in the system that often dissipates away.

“But if you could control the electronic properties of the materials systematically, then you could tune the materials to respond to light in just the ways you want,” he said. “The stacking and twisting of semiconducting layers allow just that.”

The researchers acknowledge twisting two semiconductors against each other places their work in the “Stone Age” of this research endeavor.

“Our collaborative work so far has only scratched the surface of this vast landscape,” Gabor said. “”With three, four, or 10 monolayers, we have a humongous parameter space to study. The good news is we will have a lot of work to do, which should keep my lab busy for long. The bad news is with many layers it gets much harder to understand what exactly is happening.”

Unlike other research groups working on stacking and twisting semiconducting materials, Gabor and Aji are interested in demonstrating devices, such as room temperature vibronic sensors, from an experimental perspective.

“We are focusing on semiconductor devices with applications in photo detection and optoelectronics,” Gabor said. “These devices can theoretically operate at speeds inaccessible to LEDs and lasers, promising high-speed communication. One thing worth noting is that the experiments and theory are presently moving at the same pace in this field. This is really unusual in science. What sets us apart from other research groups is that we are already building these semiconductor devices.”

Gabor and Aji will be assisted in the research by two graduate students. The project, titled “Stacking and twisting van der Waals heterostructures for ultrafast and ultrasensitive vibronic sensors,” begins Sept. 1.

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Solar Energy

Breakthrough new material brings affordable, sustainable future within grasp

Published

4 hours ago

December 22, 2024

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Breakthrough new material brings affordable, sustainable future within grasp

by Rashda Khan for Canepa News

Houston TX (SPX) Dec 23, 2024

While lithium-ion batteries have been the go-to technology for everything from smartphones and laptops to electric cars, there are growing concerns about the future because lithium is relatively scarce, expensive and difficult to source, and may soon be at risk due to geopolitical considerations. Scientists around the world are working to create viable alternatives.

An international team of interdisciplinary researchers, including the Canepa Research Laboratory at the University of Houston, has developed a new type of material for sodium-ion batteries that could make them more efficient and boost their energy performance – paving the way for a more sustainable and affordable energy future.

The new material, sodium vanadium phosphate with the chemical formula NaxV2(PO4)3, improves sodium-ion battery performance by increasing the energy density – the amount of energy stored per kilogram – by more than 15%. With a higher energy density of 458 watt-hours per kilogram (Wh/kg) compared to the 396 Wh/kg in older sodium-ion batteries, this material brings sodium technology closer to competing with lithium-ion batteries.

“Sodium is nearly 50 times cheaper than lithium and can even be harvested from seawater, making it a much more sustainable option for large-scale energy storage,” said Pieremanuele Canepa, Robert Welch assistant professor of electrical and computer engineering at UH and lead researcher of the Canepa Lab. “Sodium-ion batteries could be cheaper and easier to produce, helping reduce reliance on lithium and making battery technology more accessible worldwide.”

From Theory to Reality

The Canepa Lab, which uses theoretical expertise and computational methods to discover new materials and molecules to help advance clean energy technologies, collaborated with the research groups headed by French researchers Christian Masquelier and Laurence Croguennec from the Laboratoire de Rea’ctivite’ et de Chimie des Solides, which is a CNRS laboratory part of the Universite’ de Picardie Jules Verne, in Amiens France, and the Institut de Chimie de la Matie`re Condense’e de Bordeaux, Universite’ de Bordeaux, Bordeaux, France for the experimental work on the project. This allowed theoretical modelling to go through experimental validation.

The researchers created a battery prototype using the new material, NaxV2(PO4)3, demonstrating significant energy storage improvements. NaxV2(PO4)3, part of a group called “Na superionic conductors” or NaSICONs, is designed to let sodium ions move smoothly in and out of the battery during charging and discharging.

Unlike existing materials, it has a unique way of handling sodium, allowing it to work as a single-phase system. This means it remains stable as it releases or takes in sodium ions. This allows the NaSICON to remain stable during charging and discharging while delivering a continuous voltage of 3.7 volts versus sodium metal, higher than the 3.37 volts in existing materials.

While this difference may seem small, it significantly increases the battery’s energy density or how much energy it can store for its weight. The key to its efficiency is vanadium, which can exist in multiple stable states, allowing it to hold and release more energy.

“The continuous voltage change is a key feature,” said Canepa. “It means the battery can perform more efficiently without compromising the electrode stability. That’s a game-changer for sodium-ion technology.”

Possibilities for a Sustainable Future

The implications of this work extend beyond sodium-ion batteries. The synthesis method used to create NaxV2(PO4)3 could be applied to other materials with similar chemistries, opening new possibilities for advanced energy storage technologies. That could in turn, impact everything from more affordable, sustainable batteries to power our devices to help us transition to a cleaner energy economy.

“Our goal is to find clean, sustainable solutions for energy storage,” Canepa said. “This material shows that sodium-ion batteries can meet the high-energy demands of modern technology while being cost-effective and environmentally friendly.”

A paper based on this work was published in the journal Nature Materials. Ziliang Wang, Canepa’s former student and now a postdoctoral fellow at Northwestern University, and Sunkyu Park, a former student of the French researchers and now a staff engineer at Samsung SDI in South Korea, performed much of the work on this project.

Research Report:Obtaining V2(PO4)3 by sodium extraction from single-phase NaxV2(PO4)3 (1 < x < 3) positive electrode materials

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Solar Energy

Pioneering advancements in solid-state battery technology for energy storage

Published

5 hours ago

December 22, 2024

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Pioneering advancements in solid-state battery technology for energy storage

by Riko Seibo

Tokyo, Japan (SPX) Dec 23, 2024

Recent strides in solid-state battery technology are setting the stage for a transformative era in energy storage. These advancements hold promise for revolutionizing electric vehicles and renewable energy systems through improved performance and safety. A focus on electrolyte innovation has been key to this progress, enabling the development of high-performance all-solid-state batteries (ASSBs).

A new review paper provides a comprehensive summary of advancements in inorganic solid electrolytes (ISEs), materials that are central to ASSBs. Researchers examined the roles of oxides, sulfides, hydroborates, antiperovskites, and halides not only as electrolytes but also as catholytes and interface layers, which collectively enhance battery performance and safety.

“We highlighted the recent breakthroughs in synthesizing these materials, honing our attention on the innovative techniques that enable the precise tuning of their properties to meet the demanding requirements of ASSBs,” said Eric Jianfeng Cheng, associate professor at Tohoku University’s Advanced Institute for Materials Research (AIMR). “Precise tuning is crucial for developing batteries with higher energy densities, longer life cycles, and better safety profiles than conventional liquid-based batteries.”

The review also delves into the electrochemical properties of ISEs, including ionic conductivity, stability, and electrode compatibility. Researchers evaluated current ASSB models and suggested emerging strategies that could drive the next generation of energy storage solutions.

However, challenges persist in the development of ASSBs, notably the limited compatibility between ISEs and electrodes, which can trigger interfacial reactions. Addressing these compatibility issues is vital to improving battery efficiency and longevity. The review outlines these challenges and provides insights into efforts aimed at overcoming them.

“Our comprehensive review underscores the importance of continued research and development in the field of solid-state batteries. By developing new materials, improving synthesis methods, and overcoming compatibility issues, current efforts are driving innovation toward practical ASSBs that could transform how we store and use energy,” Cheng added.

Research Report:Inorganic solid electrolytes for all-solid-state lithium/sodium-ion batteries: recent developments and applications

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Solar Energy

Buried interface engineering drives advances in tin-lead perovskite solar cell efficiency

Published

2 days ago

December 20, 2024

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Buried interface engineering drives advances in tin-lead perovskite solar cell efficiency

by Simon Mansfield

Sydney, Australia (SPX) Dec 20, 2024

A team led by Prof. Meng Li from Henan University’s School of Nanoscience and Materials Engineering has unveiled an innovative approach to overcoming stability and efficiency challenges in tin-lead (Sn-Pb) perovskite solar cells. The researchers’ work focuses on optimizing the buried hole-selective interface using a specially designed self-assembled material, offering major implications for single-junction and tandem solar cell technologies.

Tin-lead perovskites are valued for their narrow bandgap properties, which position them as key materials for producing high-efficiency solar cells. However, energy level mismatches and degradation at the buried interface have constrained both their performance and long-term stability. Addressing these issues, Prof. Meng’s team designed a boronic acid-anchored hole-selective contact material, 4-(9H-carbazole-9-yl)phenylboronic acid (4PBA).

Compared to conventional materials, 4PBA demonstrated superior stability and compatibility at the substrate surface. Its high adsorption energy of -5.24 eV and significant molecular dipole moment (4.524 D) improved energy level alignment between the substrate and perovskite layer, facilitating efficient charge extraction. Additionally, the interface engineered using 4PBA improved perovskite crystallization and substrate contact, reducing defects and non-radiative recombination.

These advancements enabled Sn-Pb perovskite solar cells incorporating 4PBA to achieve a power conversion efficiency (PCE) of 23.45%. The material’s reduced corrosiveness also mitigated the degradation effects typically caused by PEDOT:PSS, a widely used hole-transport material, enhancing chemical stability and storage durability. The cells retained 93.5% of their initial efficiency after 2,000 hours of shelf storage.

“This approach offers a practical path to enhancing both the efficiency and stability of Sn-Pb perovskite solar cells, addressing energy level mismatches and interfacial stability concerns,” the research team commented.

The findings provide a foundation for advancing efficient and stable Sn-Pb perovskite solar cells and highlight the importance of interface engineering in next-generation photovoltaic technologies.

Research Report:Buried Hole-Selective Interface Engineering for High-Efficiency Tin-Lead Perovskite Solar Cells with Enhanced Interfacial Chemical Stability