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Polarized photovoltaic properties emerge

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Polarized photovoltaic properties emerge

For the first time, researchers have discovered a way to obtain polarity and photovoltaic behavior from certain nonphotovoltaic, atomically flat (2D) materials. The key lies in the special way in which the materials are arranged. The resulting effect is different from, and potentially superior to, the photovoltaic effect commonly found in solar cells.

Solar power is considered a key technology in the move away from fossil fuels. Researchers continually innovate more efficient means to generate solar energy. And many of these innovations come from the world of materials research.

Research Associate Toshiya Ideue from the University of Tokyo’s Department of Applied Physics and his team are interested in the photovoltaic properties of 2D materials and their interfaces where these materials meet.

“Quite often, interfaces of multiple 2D materials exhibit different properties to the individual crystals alone,” said Ideue. “We have discovered that two specific materials which ordinarily exhibit no photovoltaic effect do so when stacked in a very particular way.”

The two materials are tungsten selenide (WSe2) and black phosphorus (BP), both of which have different crystal structures. Originally, both materials are nonpolar (do not have a preferred direction of conduction) and do not generate a photocurrent under light.

However, Ideue and his team found that by stacking sheets of WSe2 and BP together in the right way, the sample exhibited polarization, and when a light was cast on the material, it generated a current. The effect takes place even if the area of illumination is far from the electrodes at either end of the sample; this is different from how the ordinary photovoltaic effect works.

Key to this behavior is the way the WSe2 and BP are aligned. The crystalline structure of BP has reflective, or mirror, symmetry in one plane, whereas WSe2 has three lines of mirror symmetry. When the symmetry lines of the materials align, the sample gains polarity. This kind of layer stacking is delicate work, but it also reveals to researchers new properties and functions that could not be predicted just by looking at the ordinary form of the materials.

“The biggest challenge for us will be to find a good combination of 2D materials with higher electric-generation efficiency and also to study the effect of changing the angles of the stacks,” said Ideue.

“But it’s so rewarding to discover never-before-seen emergent properties of materials. Hopefully, one day this research could improve solar panels. We would like to explore more unprecedented properties and functionalities in nanomaterials.”

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Solar Energy

Project receives funding for advanced solar-thermal research

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Project receives funding for advanced solar-thermal research


Project receives funding for advanced solar-thermal research

by Sophie Jenkins

London, UK (SPX) Apr 12, 2024






The University of Surrey, leading a collaboration with the University of Bristol and Northumbria University, has received a GBP 1.1 million grant from the Engineering and Physical Sciences Research Council (EPSRC) to develop solar-thermal devices. These devices aim to revolutionize the way we heat homes and generate power, differing from traditional solar cells by converting sunlight into heat for energy production.

The research focuses on creating surfaces that selectively absorb sunlight and emit heat through near-infrared radiation. This project leverages the combined expertise of the institutions in photonics, advanced materials, applied electromagnetics, and nanofabrication to address a global need for efficient solar energy utilization.



Professor Marian Florescu, Principal Investigator from Surrey, highlighted the importance of the project: “The sun provides an immense amount of energy daily, much more than we currently harness. By advancing these solar-absorbing surfaces, we aim to transform solar energy use into a sustainable powerhouse for our increasing energy needs.”



Goals of the project include developing high-temperature solar absorbers, enhancing the efficiency of solar-absorbing structures, and improving the management of heat generated from sunlight. Prototypes will be constructed to demonstrate these technologies.



Professor Marin Cryan, Co-Principal Investigator from the University of Bristol, explained their focus on thermionic solar cell technology, which uses concentrated sunlight to initiate electron emission for high-efficiency solar cells.



Dr. Daniel Ho, Co-Principal Investigator from Northumbria University, added: “Our university leads in thermophotovoltaic research, utilizing advanced thermal analysis techniques. We’re excited to contribute to groundbreaking developments in renewable energy.”


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Improving Solar and Wind Power Integration in the U.S. Grid

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Improving Solar and Wind Power Integration in the U.S. Grid


Improving Solar and Wind Power Integration in the U.S. Grid

by Clarence Oxford

Los Angeles CA (SPX) Apr 11, 2024






The Midcontinent Independent System Operator manages a high-voltage electricity network spanning from Manitoba to Louisiana, serving 45 million users. This vast operation requires maintaining a balance between the energy generated and the demand across its regions.

The traditional reliance on coal and natural gas power plants is changing. For example, wind farms in Iowa now generate over 64% of the state’s electricity, and recent initiatives like the Alliant Energy Solar Farm at Iowa State University represent the shift towards renewable energy sources. These sources, however, introduce variability and uncertainty into grid management.



Zhaoyu Wang, a Northrop Grumman associate professor of electrical and computer engineering at Iowa State, emphasized, The power system seeks certainty which is challenging with unpredictable natural resources like sun and wind.



Wang is leading the MODERNISE project, aimed at modernizing grid operations. The U.S. Department of Energy has earmarked a $3 million grant over three years for this initiative, with an additional $1.1 million coming from project collaborators including Argonne National Laboratory and Siemens Corp.



The project, titled Modernizing Operation and Decision-Making Tools Enabling Resource Management in Stochastic Environment, involves developing computational tools that allow for better integration and management of renewable energy sources into the grid.



Jennifer M. Granholm, U.S. Secretary of Energy, supported this initiative stating that effective integration of renewable resources is essential for deploying clean energy. The project is part of a larger $34 million investment by the DOE to develop technologies that enhance grid reliability and efficiency.



By aggregating smaller renewable energy resources into larger operational blocks, MODERNISE aims to improve grid stability and predictability. Bai Cui, project co-leader and assistant professor at Iowa State, explained that this approach allows operators to manage grid operations more effectively by understanding and handling the uncertainties of renewable supply sources.



This initiative promises to make grid operations more adaptable and efficient, critical for accommodating the increasing reliance on renewable energy.


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Quantum Material Achieves Up to 190% Efficiency in Solar Cells

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Quantum Material Achieves Up to 190% Efficiency in Solar Cells


Quantum Material Achieves Up to 190% Efficiency in Solar Cells

by Clarence Oxford

Los Angeles CA (SPX) Apr 11, 2024






Researchers from Lehigh University have developed a material that significantly enhances the efficiency of solar panels.

A prototype incorporating this material as the active layer in a solar cell displays an average photovoltaic absorption rate of 80%, a high rate of photoexcited carrier generation, and an external quantum efficiency (EQE) reaching up to 190%. This figure surpasses the theoretical Shockley-Queisser efficiency limit for silicon-based materials, advancing the field of quantum materials for photovoltaics.



This work signifies a major advance in sustainable energy solutions, according to Chinedu Ekuma, professor of physics at Lehigh. He and Lehigh doctoral student Srihari Kastuar recently published their findings in the journal Science Advances. Ekuma highlighted the innovative approaches that could soon redefine solar energy efficiency and accessibility.



The material’s significant efficiency improvement is largely due to its unique intermediate band states, which are energy levels within the material’s electronic structure that are ideally positioned for solar energy conversion.



These states have energy levels in the optimal subband gaps-energy ranges capable of efficiently absorbing sunlight and producing charge carriers-between 0.78 and 1.26 electron volts.



Moreover, the material excels in absorbing high levels in the infrared and visible regions of the electromagnetic spectrum.



In traditional solar cells, the maximum EQE is 100%, which corresponds to the generation and collection of one electron for each photon absorbed. However, newer materials and configurations can generate and collect more than one electron per high-energy photon, achieving an EQE over 100%.



Multiple Exciton Generation (MEG) materials, though not yet widely commercialized, show immense potential for enhancing solar power system efficiency. The Lehigh-developed material utilizes intermediate band states to capture photon energy typically lost in traditional cells, including energy lost through reflection and heat production.



The research team created this novel material using van der Waals gaps, atomically small spaces between layered two-dimensional materials, to confine molecules or ions. Specifically, they inserted zerovalent copper atoms between layers of germanium selenide (GeSe) and tin sulfide (SnS).



Ekuma developed the prototype based on extensive computer modeling that indicated the system’s theoretical potential. Its rapid response and enhanced efficiency strongly indicate the potential of Cu-intercalated GeSe/SnS as a quantum material for advanced photovoltaic applications, offering a path for efficiency improvements in solar energy conversion, he stated.



While the integration of this quantum material into existing solar energy systems requires further research, the techniques used to create these materials are already highly advanced, with scientists mastering precise methods for inserting atoms, ions, and molecules.



Research Report:Chemically Tuned Intermediate Band States in Atomically Thin CuxGeSe/SnS Quantum Material for Photovoltaic Applications


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