Solar Energy

Major advance in fabrication of low-cost solar cells also locks up greenhouse gases

Published

4 years ago

June 5, 2021

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Major advance in fabrication of low-cost solar cells also locks up greenhouse gases

Perovskite solar cells have progressed in recent years with rapid increases in power conversion efficiency (from 3% in 2006 to 25.5% today), making them more competitive with silicon-based photovoltaic cells. However, a number of challenges remain before they can become a competitive commercial technology.

Now a team at the NYU Tandon School of Engineering has developed a process to solve one of them, a bottleneck in a critical step involving p-type doping of organic hole-transporting materials within the photovoltaic cells. The research, “CO2 doping of organic interlayers for perovskite solar cells,” appears in Nature.

Currently, the p-doping process, achieved by the ingress and diffusion of oxygen into the hole transporting layer, is time intensive (several hours to a day), making commercial mass production of perovskite solar cells impractical.

The Tandon team, led by Andre D. Taylor, an associate professor, and Jaemin Kong, a post-doctoral associate, along with Miguel Modestino, assistant professor – all in the Department of Chemical and Biomolecular Engineering – discovered a method of vastly increasing the speed of this key step through the use of carbon dioxide (CO2) instead of oxygen.

In perovskite solar cells, doped organic semiconductors are normally required as charge-extraction interlayers situated between the photoactive perovskite layer and the electrodes. The conventional means of doping these interlayers involves the addition of lithium bis(trifluoromethane)sulfonimide (LiTFSI), a lithium salt, to spiro-OMeTAD, a p-conjugated organic semiconductor widely used for a hole-transporting material in perovskite solar cells. The doping process is then initiated by exposing spiro-OMeTAD:LiTFSI blend films to air and light.

Not only is this method time consuming, it largely depends on ambient conditions. By contrast, Taylor and his team reported a fast and reproducible doping method that involves bubbling a spiro-OMeTAD:LiTFSI solution with CO2 under ultraviolet light. They found that their process rapidly enhanced electrical conductivity of the interlayer by 100 times compared to that of a pristine blend film, which is also approximately 10 times higher than that obtained from an oxygen bubbling process. The CO2 treated film also resulted in stable, high-efficiency perovskite solar cells without any post-treatments.

“Besides shortening the device fabrication and processing time, application of the pre-doped spiro-OMeTAD in perovskite solar cells makes the cells much more stable,” explained Kong, the lead author. “That’s partly because most of the detrimental lithium ions in the spiro-OMeTAD:LiTFSI solution were stabilized as lithium carbonates during the CO2 bubbling process.”

He added that the lithium carbonates end up being filtered out when the investigators spincast the pre-doped solution onto the perovskite layer. “Thus, we can obtain fairly pure doped organic materials for efficient hole transporting layers.”

The team, which included researchers from Samsung, Yale University, Korea Research Institute of Chemical Technology, The Graduate Center of the City University, Wonkwang University, and the Gwangju Institute of Science and Technology also found that the CO2 doping method can be used for p-type doping of other p-conjugated polymers, such as PTAA, MEH-PPV, P3HT, and PBDB-T. According to Taylor the researchers are looking to push the boundary beyond typical organic semiconductors used for solar cells.

“We believe that wide applicability of CO2 doping to various p-conjugated organic molecules stimulates research ranging from organic solar cells to organic light emitting diodes (OLEDs) and organic field effect transistors (OFETs) even to thermoelectric devices that all require controlled doping of organic semiconductors,” Taylor explained, adding that since this process consumes quite a large amount of CO2 gas, it can be also considered for CO2 capture and sequestration studies in the future.

“At a time when governments and companies alike are now looking to reduce CO2 emissions if not de-carbonize, this research offers an avenue for reacting large amounts of CO2 in lithium carbonate to improve next generation solar cells, while removing this greenhouse gas from the atmosphere,” he explained, adding that the idea for this novel approach was a counterintuitive insight from the team’s battery research.

“From our long history of working with lithium oxygen/air batteries we know that lithium carbonate formation from exposure of oxygen electrodes to air is a big challenge because it depletes the battery of lithium ions, which destroys battery capacity.

“In this Spiro doping reaction, however, we are actually exploiting lithium carbonate formation, which binds lithium and prevents it from becoming mobile ions detrimental to the long term stability of the Perovskite solar cell. We are hoping that this CO2 doping technique could be a stepping stone for overcoming existing challenges in organic electronics and beyond.”

Research Report: “CO2 doping of organic interlayers for perovskite solar cells”

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Solar Energy

Reusing old oil and gas wells may offer green energy storage solution

Published

15 hours ago

March 19, 2025

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Reusing old oil and gas wells may offer green energy storage solution

by Matthew Carroll for Penn News

University Park PA (SPX) Mar 19, 2025

Moving from fossil fuels to renewable energy sources like wind and solar will require better ways to store energy for use when the sun is not shining or the wind is not blowing. A new study by researchers at Penn State found that taking advantage of natural geothermal heat in depleted oil and gas wells can improve the efficiency of one proposed energy storage solution: compressed-air energy storage (CAES).

CAES plants compress air and store it underground when energy demand is low and then extract the air to create electricity when demand is high. But startup costs currently limit commercial development of these projects, the scientists said.

The researchers proposed a new geothermal-assisted compressed-air energy storage system that makes use of depleted oil and gas wells – the Environmental Protection Agency estimates there are around 3.9 million in the United States – and found it can improve efficiency by 9.5% over the existing technology. This means a larger percentage of the energy stored in the system can be recovered and turned into electricity, potentially boosting profits for operators.

“This improvement in efficiency can be a game changer to justify the economics of compressed-air energy storage projects,” said Arash Dahi Taleghani, professor of petroleum and natural gas engineering at Penn State and corresponding author on the study. “And on top of that, we could significantly avoid the upfront cost by using existing oil and gas wells that are no longer in production. This could be a win, win situation.”

Reusing depleted oil and gas wells would allow operators to access geothermal heat in hot rock formations underground, eliminating upfront costs of drilling new wells and potentially making the technology more appealing to industry, the scientists said.

Gases like compressed air increase in pressure as temperatures increase, meaning the heated wells could potentially store more energy, according to Taleghani. When electricity is needed, the heated, compressed air is released, driving a turbine to produce power.

“Without taking advantage of the geothermal setup, you could not get enough encouraging numbers,” Taleghani said, explaining that the team used numerical modeling simulations to find that placing CAES systems in abandoned oil and gas wells significantly increased the air temperature in the systems. “And on top of that, drilling new wells may not justify the economics of this type of storage. But by combining these two factors, and by going back and forth through modeling and simulation, we found this could be a very good solution.”

Energy storage options like CAES are particularly important in the transition to clean energy, according to the researchers, because they help address the intermittent nature of renewable sources. By storing excess renewable energy and releasing it when needed, energy storage contributes to grid stability and reliability.

“The problem is that sometimes when we need energy, there is no sunshine or there is no wind,” Taleghani said. “That’s a big barrier against further expansion of most of the renewable energy that is available to us. That’s why it’s very important to have some storage capacity to support the grid.”

Repurposing depleted oil and gas wells may also help mitigate potential environmental impacts of abandoned wells and potentially provide new job opportunities in areas with rich energy industry traditions, the researchers said.

In Pennsylvania alone, regulators estimate there are hundreds of thousands of orphaned and abandoned wells. If these wells are improperly plugged, or damaged, they can leak methane into the atmosphere and groundwater.

“If we use existing wells, we are basically hitting two birds with one stone,” Taleghani said. “First, we are sealing these wells. That stops any potential leaks. And then if we are repurposing these wells for energy storage, we are still using the infrastructure that is in place in these communities. It can potentially maintain employment in the area and allow communities to be part of the energy future.”

This research was conducted as part of the Repurposing Center for Energy Transition (ReCET) at Penn State. The center seeks to repurpose fossil energy infrastructure for energy transition applications, especially in legacy energy communities.

Also contributing from Penn State were Derek Elsworth, G. Albert Shoemaker Chair in Mineral Engineering and professor of energy and geo-environmental engineering, and Qitao Zhang, a postdoctoral scholar, both in the John and Willie Leone Family Department of Energy and Mineral Engineering.

Research Report:Underground energy storage using abandoned oil and gas wells assisted by geothermal

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Solar Energy

Enhancing agrivoltaic synergies through optimized tracking strategies

Published

3 days ago

March 17, 2025

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Enhancing agrivoltaic synergies through optimized tracking strategies

by Robert Schreiber

Berlin, Germany (SPX) Mar 17, 2025

Agrivoltaic systems, which merge agricultural cultivation with solar power generation, represent a strategic solution to the dual challenge of meeting increasing global energy demands and ensuring food security. By situating solar panels directly above crops, these systems mitigate land use conflicts and deliver additional benefits, such as alleviating crop water stress and shielding plants from extreme weather conditions. They also foster ecological advantages, including creating habitats for pollinators and enhancing forage availability. In arid regions, agrivoltaics have shown to delay flowering and boost flower production, thereby supporting pollinators later in the season. Furthermore, the moderated microclimate beneath solar panels can enhance photovoltaic efficiency.

As their adoption expands, optimizing agrivoltaic systems through advanced tracking technologies becomes crucial. Horizontal single-axis tracker (HSAT) systems, which pivot solar panels to follow the sun’s path throughout the day, can significantly improve system performance. Strategically managing panel orientation can achieve a delicate balance between maximizing solar output and safeguarding crop yields. This balance is particularly important for securing subsidies, which often require agrivoltaic systems to remain within specified yield loss margins, thereby bolstering their financial feasibility.

A recent investigation published in the Journal of Photonics for Energy (JPE) sheds light on methodologies to fine-tune solar panel angles for optimal energy and agricultural results. The study, centered on apple orchards in southwestern Germany, introduces a novel technique to dynamically align panel positions with specific crop light requirements. Rather than relying on conventional shading guidelines or static structures like hail nets, this method leverages precise irradiation targets to fulfill the unique light needs of different crops. Researchers employed a bespoke simulation tool, APyV, to explore how variations in panel angles affect sunlight availability for crops.

The APyV platform applies sophisticated ray tracing algorithms to map solar radiation distribution, assessing its influence on both solar panels and crops. This tool streamlines agrivoltaic system design by integrating crop models and key performance metrics, enabling accurate calculations of light exposure and its impact on system performance.

Findings from the case study demonstrated that tailored panel control could deliver 91 percent of the annual light requirement for apple trees, while only slightly diminishing solar power output by 20 percent. Nonetheless, certain time periods revealed shortfalls in meeting crop light demands, highlighting the inherent challenge of achieving perfect alignment between agricultural and energy goals. Despite these constraints, the study establishes a strong platform for future research and refinement.

“Our study shows that the combination of solar energy and farming can be enhanced by smart PV-trackers that adjust the position of solar panels based on weather conditions, crop types, and their growth stages. This approach ensures an optimal balance between light available for photosynthesis and light available for electricity production,” explained corresponding author Maddelena Bruno, a doctoral researcher at Fraunhofer ISE.

Bruno further indicated that the proposed irradiation targets and tracking methodology are scheduled for field testing during the ongoing growing season in Nussbach. These trials aim to validate the simulation outcomes and broaden the understanding of how agrivoltaic systems influence crop growth and environmental conditions. The research is expected to inform future strategies for integrating agriculture and renewable energy, contributing to a more sustainable energy transition.

Research Report:Enhancing agrivoltaic synergies through optimized tracking strategies

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Solar Energy

Chinese battery behemoth CATL posts jump in annual profit

Published

3 days ago

March 17, 2025

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Chinese battery behemoth CATL posts jump in annual profit

by AFP Staff Writers

Beijing (AFP) Mar 14, 2025

Chinese battery giant CATL announced on Friday surging annual profits despite a decline in revenue, as slowing demand for electric vehicles drives down the price of lithium.

The firm produces more than a third of all electric vehicle (EV) batteries sold worldwide, cooperating with major brands including Tesla, Mercedes-Benz, BMW and Volkswagen.

CATL has been aided by robust financial support from Beijing, which has sought in recent years to shore up domestic strength in certain strategic high-tech sectors.

Net profits were up more than 15 percent in 2024 compared to 2023.

Last year, CATL achieved a profit of 50.74 billion yuan ($7.01 billion), a filing at the Shenzhen Stock Exchange showed Friday.

The figure came in below a Bloomberg forecast of 51.47 billion yuan.

Revenue, meanwhile, fell 9.7 percent year-on-year to 362 billion yuan in 2024, the filing showed.

CATL had warned in January that its slide in sales last year was likely due to a “decline in the prices of raw materials such as lithium carbonate”, which had forced the firm to adjust prices.

Last year saw lithium prices decline significantly, partly due to market oversupply and less fervent consumer demand for EVs.

– Overseas expansion –

Founded in 2011 in the eastern Chinese city of Ningde, Contemporary Amperex Technology Co., Limited (CATL) was initially propelled to success by rapid growth in the domestic market.

CATL’s shares are publicly traded in Shenzhen, though it is now planning to seek a secondary listing in Hong Kong.

Last month, the firm started a Hong Kong listing application process — a first step towards what analysts say could be a blockbuster initial public offering for the financial hub.

Funds raised from a secondary listing could be used to accelerate CATL’s overseas expansion, particularly in Europe.

The battery giant is building its second factory on the continent in Hungary after launching its first in Germany in January 2023.

In December, CATL announced that it would work with automotive giant Stellantis on a $4.3 billion factory to make EV batteries in Spain, with production slated to begin by the end of 2026.

The firm’s international push comes as challenges in the domestic market mount.

Following years of rapid growth, the world’s largest EV market has begun to show signs of flagging sales amid a broader slowdown in consumption.

The trends have fuelled a fierce price war in the country’s expansive EV sector, putting smaller firms under huge pressure to compete while remaining financially viable.

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