Solar Energy

Squeezing a rock-star material could make it stable enough for solar cells

Published

3 years ago

February 8, 2021

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Squeezing a rock-star material could make it stable enough for solar cells

Among the materials known as perovskites, one of the most exciting is a material that can convert sunlight to electricity as efficiently as today’s commercial silicon solar cells and has the potential for being much cheaper and easier to manufacture.

There’s just one problem: Of the four possible atomic configurations, or phases, this material can take, three are efficient but unstable at room temperature and in ordinary environments, and they quickly revert to the fourth phase, which is completely useless for solar applications.

Now scientists at Stanford University and the Department of Energy’s SLAC National Accelerator Laboratory have found a novel solution: Simply place the useless version of the material in a diamond anvil cell and squeeze it at high temperature. This treatment nudges its atomic structure into an efficient configuration and keeps it that way, even at room temperature and in relatively moist air.

“This is the first study to use pressure to control this stability, and it really opens up a lot of possibilities,” said Yu Lin, a SLAC staff scientist and investigator with the Stanford Institute for Materials and Energy Sciences (SIMES).

“Now that we’ve found this optimal way to prepare the material,” she said, “there’s potential for scaling it up for industrial production, and for using this same approach to manipulate other perovskite phases.”

A search for stability

Perovskites get their name from a natural mineral with the same atomic structure. In this case the scientists studied a lead halide perovskite that’s a combination of iodine, lead and cesium.

One phase of this material, known as the yellow phase, does not have a true perovskite structure and can’t be used in solar cells. However, scientists discovered a while back that if you process it in certain ways, it changes to a black perovskite phase that’s extremely efficient at converting sunlight to electricity. “This has made it highly sought after and the focus of a lot of research,” said Stanford Professor and study co-author Wendy Mao.

Unfortunately, these black phases are also structurally unstable and tend to quickly slump back into the useless configuration. Plus, they only operate with high efficiency at high temperatures, Mao said, and researchers will have to overcome both of those problems before they can be used in practical devices.

There had been previous attempts to stabilize the black phases with chemistry, strain or temperature, but only in a moisture-free environment that doesn’t reflect the real-world conditions that solar cells operate in. This study combined both pressure and temperature in a more realistic working environment.

Pressure and heat do the trick

Working with colleagues in the Stanford research groups of Mao and Professor Hemamala Karunadasa, Lin and postdoctoral researcher Feng Ke designed a setup where yellow phase crystals were squeezed between the tips of diamonds in what’s known as a diamond anvil cell. With the pressure still on, the crystals were heated to 450 degrees Celsius and then cooled down.

Under the right combination of pressure and temperature, the crystals turned from yellow to black and stayed in the black phase after the pressure was released, the scientists said. They were resistant to deterioration from moist air and remained stable and efficient at room temperature for 10 to 30 days or more.

Examination with X-rays and other techniques confirmed the shift in the material’s crystal structure, and calculations by SIMES theorists Chunjing Jia and Thomas Devereaux provided insight into how the pressure changed the structure and preserved the black phase.

The pressure needed to turn the crystals black and keep them that way was roughly 1,000 to 6,000 times atmospheric pressure, Lin said – about a tenth of the pressures routinely used in the synthetic diamond industry. So one of the goals for further research will be to transfer what the researchers have learned from their diamond anvil cell experiments to industry and scale up the process to bring it within the realm of manufacturing.

The researchers described their results in Nature Communications.

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Solar Energy

Momentus and Ascent Solar Technologies announce new solar array partnership

Published

19 hours ago

April 18, 2024

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Momentus and Ascent Solar Technologies announce new solar array partnership

by Staff Writers

Momentus

by Clarence Oxford
Los Angeles CA (SPX) Apr 18, 2024
Momentus Inc. (NASDAQ: MNTS) and Ascent Solar Technologies (Nasdaq: ASTI) has unveiled their partnership aimed at jointly marketing innovative solar arrays that integrate Momentus’s low-cost Tape Spring Solar Array (TASSA) technology and Ascent’s advanced, flexible photovoltaic modules.

The surge in satellite production and deployment underscores a critical demand for affordable and efficient solar arrays. This collaboration will deliver a solar solution offering significant benefits including cost-effectiveness, durability under extreme space conditions, and high power output capabilities.

Following the successful initial demonstration of TASSA in orbit, launched via the Vigoride-6 mission, Momentus is enhancing the system with Ascent’s newer, more efficient Titan Module solar blankets. These upgrades aim to optimize power generation while reducing costs, with TASSA designed to support high-volume satellite operations by accommodating multiple units within standard launch payload configurations.

Rob Schwarz, CTO of Momentus, noted, “TASSA aims to empower small satellites with substantial power capabilities without compromising on mass, thermal management, or budget. This innovation not only maximizes space utilization within launch vehicles but also expedites satellite constellation deployment.”

The system’s adaptability includes retractable features to minimize exposure to space debris and adverse weather, potentially extending mission lifespans and operational reliability.

Paul Warley, CEO of ASTI, highlighted the suitability of their photovoltaic technology for space applications, emphasizing its durability and lightweight attributes which are critical in harsh orbital environments. “Our technology is designed to deliver sustained power output over time with significantly reduced mass, which is fundamental for successful long-term missions,” said Warley.

This partnership is set to streamline satellite array systems, making prolonged, cost-efficient space missions feasible.

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Solar Energy

Quantum material achieves up to 190% efficiency in solar cells

Published

20 hours ago

April 18, 2024

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Quantum material achieves up to 190% efficiency in solar cells

by Clarence Oxford

Los Angeles CA (SPX) Apr 17, 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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Solar Energy

Project receives funding for advanced solar-thermal research

Published

7 days ago

April 12, 2024

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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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