Solar Energy

Twisting, flexible crystals key to solar energy production

Published

4 years ago

March 17, 2021

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Twisting, flexible crystals key to solar energy production

Researchers at Duke University have revealed long-hidden molecular dynamics that provide desirable properties for solar energy and heat energy applications to an exciting class of materials called halide perovskites.

A key contributor to how these materials create and transport electricity literally hinges on the way their atomic lattice twists and turns in a hinge-like fashion. The results will help materials scientists in their quest to tailor the chemical recipes of these materials for a wide range of applications in an environmentally friendly way.

The results appear online March 15 in the journal Nature Materials.

“There is a broad interest in halide perovskites for energy applications like photovoltaics, thermoelectrics, optoelectronic radiation detection and emission – the entire field is incredibly active,” said Olivier Delaire, associate professor of mechanical engineering and materials science at Duke. “While we understand that the softness of these materials is important to their electronic properties, nobody really knew how the atomic motions we’ve uncovered underpin these features.”

Perovskites are a class of materials that – with the right combination of elements – are grown into a crystalline structure that makes them particularly well-suited for energy applications. Their ability to absorb light and transfer its energy efficiently makes them a common target for researchers developing new types of solar cells, for example. They’re also soft, sort of like how solid gold can be easily dented, which gives them the ability to tolerate defects and avoid cracking when made into a thin film.

One size, however, does not fit all, as there is a wide range of potential recipes that can form a perovskite. Many of the simplest and most studied recipes include a halogen–such as chlorine, fluorine or bromine – giving them the name halide perovskites. In the crystalline structure of perovskites, these halides are the joints that tether adjoining octahedral crystal motifs together.

While researchers have known these pivot points are essential to creating a perovskite’s properties, nobody has been able to look at the way they allow the structures around them to dynamically twist, turn and bend without breaking, like a Jell-O mold being vigorously shaken.

“These structural motions are notoriously difficult to pin down experimentally. The technique of choice is neutron scattering, which comes with immense instrument and data analysis effort, and very few groups have the command over the technique that Olivier and his colleagues do,” said Volker Blum, professor of mechanical engineering and material science at Duke who does theoretical modeling of perovskites, but was not involved with this study. “This means that they are in a position to reveal the underpinnings of the materials properties in basic perovskites that are otherwise unreachable.”

In the study, Delaire and colleagues from Argonne National Laboratory, Oak Ridge National Laboratory, the National Institute of Science and Technology, and Northwestern University, reveal important molecular dynamics of the structurally simple, commonly researched halide perovskite (CsPbBr3) for the first time.

The researchers started with a large, centimeter-scale, single crystal of the halide perovskite, which is notoriously difficult to grow to such sizes – a major reason why this sort of dynamic study has not been achieved before now. They then barraged the crystal with neutrons at Oak Ridge National Laboratory and X-rays at Argonne National Laboratory. By measuring how the neutrons and X-rays bounced off the crystals over many angles and at different time intervals, the researchers teased out how its constituent atoms moved over time.

After confirming their interpretation of the measurements with computer simulations, the researchers discovered just how active the crystalline network actually is. Eight-sided octahedral motifs attached to one another through bromine atoms were caught twisting collectively in plate-like domains and constantly bending back and forth in a very fluid-like manner.

“Because of the way the atoms are arranged with octahedral motifs sharing bromine atoms as joints, they’re free to have these rotations and bends,” said Delaire. “But we discovered that these halide perovskites in particular are much more ‘floppy’ than some other recipes. Rather than immediately springing back into shape, they return very slowly, almost more like Jell-O or a liquid than a conventional solid crystal.”

Delaire explained that this free-spirited molecular dancing is important to understand many of the desirable properties of halide perovskites. Their ‘floppiness’ stops electrons from recombining into the holes the incoming photons knocked them out of, which helps them make a lot of electricity from sunlight. And it likely also makes it difficult for heat energy to travel across the crystalline structure, which allows them to create electricity from heat by having one side of the material be much hotter than the other.

Because the perovskite used in the study – CsPbBr3 – has one of the simplest recipes, yet already contains the structural features common to the broad family of these compounds, Delaire believes that these findings likely apply to a large range of halide perovskites. For example, he cites hybrid organic-inorganic perovskites (HOIPs), which have much more complicated recipes, as well as lead-free double-perovskite variants that are more environmentally friendly.

“This study shows why this perovskite framework is special even in the simplest of cases,” said Delaire. “These findings very likely extend to much more complicated recipes, which many scientists throughout the world are currently researching. As they screen enormous computational databases, the dynamics we’ve uncovered could help decide which perovskites to pursue.”

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Solar Energy

Battery boom drives Bangladesh lead poisoning epidemic

Published

2 days ago

April 1, 2025

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Battery boom drives Bangladesh lead poisoning epidemic

By Philippe ALFROY

Mirzapur, Bangladesh (AFP) April 1, 2025

Bangladeshi Junayed Akter is 12 years old but the toxic lead coursing through his veins has left him with the diminutive stature of someone several years younger.

Akter is one of 35 million children — around 60 percent of all children in the South Asian nation — who have dangerously high levels of lead exposure.

The causes are varied, but his mother blames his maladies on a since-shuttered factory that hastily scrapped and recycled old vehicle batteries for profit, in the process poisoning the air and the earth of his small village.

“It would start at night, and the whole area would be filled with smoke. You could smell this particular odour when you breathed,” Bithi Akter told AFP.

“The fruit no longer grew during the season. One day, we even found two dead cows at my aunt’s house.”

Medical tests showed Junayed’s blood had twice the level of lead deemed by the World Health Organization to cause serious, and likely irreversible, mental impairment in young children.

“From the second grade onward, he didn’t want to listen to us anymore, he didn’t want to go to school,” Bithi said, as her son sat next to her while gazing blankly out at the courtyard of their home.

“He cried all the time too.”

Lead poisoning is not a new phenomenon in Bangladesh, and the causes are manifold.

They include the heavy metal’s widespread and continued use in paint, in defiance of a government ban, and its use as an adulterant in turmeric spice powder to improve its colour and perceived quality.

A great many cases are blamed on informal battery recycling factories that have proliferated around the country in response to rising demand.

Children exposed to dangerous levels of lead risk decreased intelligence and cognitive performance, anaemia, stunted growth and lifelong neurological disorders.

The factory in the Akter family’s village closed after sustained complaints from the community.

But environmental watchdog Pure Earth believes there could be 265 such sites elsewhere in the country.

“They break down old batteries, remove the lead and melt it down to make new ones,” Pure Earth’s Mitali Das told AFP.

“They do all this in the open air,” she added. “The toxic fumes and acidic water produced during the operation pollute the air, soil and water.”

– ‘They’ve killed our village’ –

In Fulbaria, a village that sits a few hours’ drive north of the capital Dhaka, operations at another battery recycling factory owned by a Chinese company are in full swing.

On one side are verdant paddy fields. On the other, a pipe spews murky water into a brackish pool bordered by dead lands, caked with thick orange mud.

“As a child, I used to bring food to my father when he was in the fields. The landscape was magnificent, green, the water was clear,” engineer and local resident Rakib Hasan, 34, told AFP.

“You see what it looks like now. It’s dead, forever,” he added. “They’ve killed our village.”

Hasan complained about the factory’s pollution, prompting a judge to declare it illegal and order the power be shut off — a decision later reversed by the country’s supreme court.

“The factory bought off the local authorities,” Hasan said. “Our country is poor, many people are corrupt.”

Neither the company nor the Chinese embassy in Dhaka responded to AFP’s requests for comment on the factory’s operations.

Syeda Rizwana Hasan, who helms Bangladesh’s environment ministry, declined to comment on the case because it was still before the courts.

“We regularly conduct operations against the illegal production and recycling of electric batteries,” she said.

“But these efforts are often insufficient given the scale of the phenomenon.”

– ‘Unaware of the dangers’ –

Informal battery recycling is a booming business in Bangladesh.

It is driven largely by the mass electrification of rickshaws — a formerly pedal-powered means of conveyance popular in both big cities and rural towns.

More than four million rickshaws are found on Bangladeshi roads and authorities estimate the market for fitting them all with electric motors and batteries at around $870 million.

“It’s the downside of going all-electric,” said Maya Vandenant of the UN children’s agency, which is pushing a strategy to clean up the industry with tighter regulations and tax incentives.

“Most people are unaware of the dangers,” she said, adding that the public health impacts are forecast to be a 6.9 percent dent to the national economy.

Muhammad Anwar Sadat of Bangladesh’s health ministry warned that the country could not afford to ignore the scale of the problem.

“If we do nothing,” he told AFP, “the number of people affected will multiply three or fourfold in the next two years.”

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Solar Energy

Modi to kick off construction of India-Sri Lanka solar plant

Published

4 days ago

March 30, 2025

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Modi to kick off construction of India-Sri Lanka solar plant

by AFP Staff Writers

New Delhi (AFP) Mar 28, 2025

Indian Prime Minister Narendra Modi will launch the construction of a long-delayed solar power project during his upcoming visit to Sri Lanka, an official said on Friday.

Vikram Misri, the secretary of India’s foreign ministry, said Modi and Sri Lankan President Anura Kumara Dissanayake will witness a virtual groundbreaking ceremony for their joint-venture solar power project in the island’s northeast on April 5.

The proposed 120-megawatt venture in the northeastern coastal district of Trincomalee has stalled for years, but New Delhi backed it as a joint project between the neighbouring nations.

“This, in many senses, is going to be a milestone in the bilateral partnership,” Misri told reporters in New Delhi.

“They will together dedicate several projects that are being built with Indian assistance in Sri Lanka and will also witness the exchange of several MoUs pertaining to energy connectivity, digitisation, defence, health, and multisectoral grant assistance.”

The pair will watch the virtual groundbreaking from Sri Lankan capital Colombo. The costs of the project were not immediately available.

The groundbreaking, a day before Modi concludes his two-night visit to Sri Lanka, comes as Colombo grapples with the competing interests of its powerful northern neighbour and China, its largest lender.

Modi will be the first foreign head of government to visit the island nation under the new administration of leftist Dissanayake. He flies into Colombo on April 4 after attending a regional conference in Thailand.

Dissanayake’s first foreign visit after his election last year was to New Delhi in December.

Sri Lankan officials in Colombo said Modi and Dissanayake will travel to the northern Buddhist pilgrimage city of Anuradhapura on April 6.

Dissanayake travelled to Beijing in January, underscoring Sri Lanka’s delicate balancing act in maintaining ties with the two regional rivals.

New Delhi has been concerned about China’s growing influence in Sri Lanka, which it considers to be within its sphere of geopolitical influence.

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Solar Energy

A lifetime power source in miniature form

Published

5 days ago

March 30, 2025

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A lifetime power source in miniature form

by Riko Seibo

Tokyo, Japan (SPX) Mar 30, 2025

The batteries that power smartphones, electric vehicles, and drones often require frequent charging and degrade over time, leading to limited lifespan and environmental concerns. Now, a team at Daegu Gyeongbuk Institute of Science and Technology (DGIST) is exploring a nuclear alternative that could offer decades or even centuries of reliable power without recharging.

Su-Il In, a professor at DGIST, presented this breakthrough at the American Chemical Society’s Spring 2025 meeting, held March 23-27. His team is pioneering nuclear batteries that harness radiocarbon, a form of radioactive carbon known for emitting beta particles, to produce safe and long-lasting energy.

“The performance of Li-ion batteries is almost saturated,” explained In. This limitation, combined with the environmental toll of lithium extraction and disposal, has driven interest in more sustainable, high-endurance alternatives. Nuclear batteries, which convert radiation into electrical power, are emerging as a compelling solution.

Radiocarbon, or carbon-14, is a low-energy beta emitter that can be effectively shielded with a thin aluminum layer, making it a practical choice for safe nuclear batteries. Additionally, as a by-product of nuclear reactors, radiocarbon is affordable, widely accessible, and recyclable. Its extremely slow decay rate suggests that batteries powered by it could last thousands of years.

In a betavoltaic cell, beta particles from radioactive decay strike a semiconductor, generating electricity. In and his team developed a prototype using titanium dioxide as the semiconductor base, enhanced with a ruthenium-based dye. They further improved its performance through citric acid treatment, which reinforced the dye’s adhesion to the titanium dioxide.

This setup creates a cascade of electron transfer, known as an electron avalanche, triggered by the interaction of beta rays with the dye. The semiconductor efficiently captures the resulting charge and channels it through an external circuit to produce usable electricity.

Unlike earlier models with radiocarbon only on the cathode, the new design includes radiocarbon in both the cathode and the anode. This dual configuration boosts the number of beta particles generated and minimizes energy loss caused by the spatial separation of the components.

In testing, the improved prototype demonstrated a significant jump in energy conversion efficiency, increasing from 0.48% to 2.86%. This performance leap is attributed to the enhanced interaction between the radioactive material and the dye-sensitized semiconductor.

Such nuclear batteries could revolutionize numerous technologies, In noted. Medical implants like pacemakers could function for a lifetime without the need for replacement surgeries. Still, the current prototype converts only a small fraction of radioactive decay into electrical power, trailing behind the output of conventional lithium-ion systems.

To close this performance gap, future development will focus on refining the geometry of the beta source and improving the absorptive properties of the semiconductor material. These improvements could unlock higher power yields and broaden the range of applications.

As public attitudes toward nuclear technology evolve amid climate concerns, In emphasized the potential of small-scale, safe nuclear energy: “We can put safe nuclear energy into devices the size of a finger.”

Research Report:Next generation battery: Highly efficient and stable C14 dye-sensitized betavoltaic cell