Solar Energy

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

Published

4 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

DGIST enhances quantum dot solar cell performance

Published

13 hours ago

October 4, 2024

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DGIST enhances quantum dot solar cell performance

by Riko Seibo

Tokyo, Japan (SPX) Oct 04, 2024

A research team led by Professor Jongmin Choi from the Department of Energy Science and Engineering at DGIST, in collaboration with Gyeongsang National University’s Professor Tae Kyung Lee and Kookmin University’s Professor Younghoon Kim, has developed a new method that significantly boosts the performance and longevity of perovskite quantum dot solar cells. Their innovative approach addresses a key issue: surface distortions on quantum dots that hinder solar cell efficiency.

Perovskite quantum dots are widely regarded as essential for next-generation solar cells due to their high light-to-electricity conversion efficiency and scalability. However, the process of replacing the “ligands” on their surface often causes distortions, akin to crumpled paper, that degrade solar cell performance.

The research team tackled this problem by introducing short ligands that firmly grip both sides of the quantum dots. This method effectively restores the quantum dot’s distorted surface, resembling the process of flattening crumpled paper. By smoothing the surface, they significantly reduced defects and improved both the performance and the stability of the solar cells. The power conversion efficiency rose from 13.6% to 15.3%, and the cells maintained 83% of their performance over 15 days, marking a major advancement in solar cell technology.

“Through this research, we could minimize surface defects on the quantum dots and stabilize their surfaces by newly adopting these amphiphilic ligands, thereby significantly improving the efficiency and stability of the solar cells,” explained Professor Jongmin Choi. He also noted the team’s intention to extend this approach to other photoelectric devices in the future.

This study, a collaborative effort by DGIST, Gyeongsang National University, and Kookmin University, was supported by the National Research Council of Science and Technology, the DGIST R and D Program, and the New Faculty Research Foundation at Gyeongsang National University. The findings were published in the ‘Chemical Engineering Journal’ on September 15, 2024.

Research Report:Multifaceted anchoring ligands for uniform orientation and enhanced cubic-phase stability of perovskite quantum dots

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Solar Energy

Philippines’ Marcos opens first EV battery plant

Published

3 days ago

October 1, 2024

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Philippines’ Marcos opens first EV battery plant

by AFP Staff Writers

Manila (AFP) Sept 30, 2024

President Ferdinand Marcos inaugurated on Monday the first factory for electric vehicle batteries in the Philippines, calling it the “future” of clean energy.

The Australian-owned lithium-iron-phosphate factory aims to produce two gigawatt-hours of batteries per year by 2030, powering about 18,000 electric vehicles or nearly half a million home battery systems.

“We have worked very hard and tried to do our best to bring this kind of technology to the Philippines with a clear recognition that this is the future,” Marcos said in a livestreamed speech.

“As the first manufacturing plant in the Philippines for advanced iron phosphate batteries… (it) sets the stage for the Philippines to become a player in clean energy storage in our part of the world.”

Located in New Clark city north of Manila, the StB Giga Factory Inc. facility will create 2,500 local jobs and channel five billion pesos ($89.2 million) into the economy each year, Marcos said.

The investment aligns with the government’s efforts to “transition our country to renewable energy”, and would help Manila “entice more investors in renewable energy facilities in the country”, he added.

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Solar Energy

Fire breaks out at Chinese battery giant CATL plant

Published

4 days ago

October 1, 2024

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Fire breaks out at Chinese battery giant CATL plant

by AFP Staff Writers

Beijing (AFP) Sept 29, 2024

A fire broke out Sunday at a factory belonging to Chinese battery giant CATL, which supplies electric vehicle makers including Tesla, but only a “relatively small” impact on operations is expected, the company said.

A CATL spokesperson said no injuries or casualties had occurred at the plant in the coastal city of Ningde, and that “the reasons behind this accident are still under investigation”.

Emergency services were sent to the plant to fight the fire and to organise the evacuation of any people who were inside the 15,000 square metre (160,000 square feet) site, a statement by the Dongqiao Economic and Technological Development Zone said.

Firefighters were alerted to the blaze just before 11:30 AM local time (0330 GMT).

It was not immediately clear what was produced at the plant, CATL’s base in the eastern province of Fujian, but the company said the effect of the now extinguished fire would not be significant.

“The impact to CATL’s overall production operation is relatively small,” the spokesperson said.

Videos published by the Chinese business media outlet Cailianshe, and posted on the Weibo social network, showed parts of a large white building in flames with thick gray smoke rising into the air.

AFP could not immediately verify the authenticity of the images.

CATL was founded in 2011 and produces more than a third of the electric vehicle batteries sold worldwide for automakers that include Mercedes-Benz, BMW, Volkswagen, Toyota, Honda and Hyundai.

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