Solar Energy
Shedding light on perovskite films

Photovoltaics decisively contributes to sustainable energy supply. The efficiency of solar cells in directly converting light energy into electrical energy depends on the material used. Metal-halide perovskites are considered very promising materials for solar cells of the next generation. With these semiconductors named after their special crystal structure, a considerable increase in efficiency was achieved in the past years.
Meanwhile, perovskite solar cells have reached an efficiency of up to 25.5 percent, which is quite close to that of silicon solar cells that are presently dominating the market. Moreover, the materials needed for perovskite solar cells are rather abundant.
The solar cells can be produced easily and at low cost and they can be used for various applications. The theoretically achievable efficiency of perovskite solar cells is about 30.5 percent.
To approach this value, optoelectronic quality of perovskite semiconductors must be further increased. In principle, materials suited for photovoltaics are expected to not only absorb light, but to also emit it efficiently. This process is known as photoluminescence. The corresponding parameter, photoluminescence quantum efficiency, is perfectly suited to determine the quality of perovskite semiconductors.
Together with scientists from the Center for Advanced Materials (CAM) of Heidelberg University and the Technical University of Dresden, researchers of KIT’s Institute of Microstructure Technology (IMT) and Light Technology Institute (LTI) have now developed a model, by means of which photoluminescence quantum efficiency of perovskite films can be determined reliably and exactly for the first time. Their results are reported in Matter.
Materials Have More Optimization Potentials than Assumed
“With the help of our model, photoluminescence quantum efficiency under solar irradiation can be determined far more precisely,” says Dr. Paul Fassl from IMT. “Photon recycling is of high importance. This is the share of photons emitted by the perovskite, which is re-absorbed and re-emitted in the thin films.”
The researchers applied their model to methylammonium lead triiodide (CH3NH3PbI3), one of the perovskites of highest photoluminescence quantum efficiency. So far, it has been estimated to amount to about 90 percent.
Model calculations, however, revealed that it is about 78 percent. The scientists explain that previous estimations did not adequately consider the effect of light scattering and, hence, underestimated the probability of photons – the quantums of light energy – leaving the film before they are re-absorbed.
“Our results show that the potential for optimization of these materials is far higher than assumed,” says Dr. Ulrich W. Paetzold, Head of the Advanced Optics and Materials for Next Generation Photovoltaics Group of IMT. The team offers an open-source application based on the model, by means of which photoluminescence quantum efficiencies of various perovskite materials can be calculated.
Solar Energy
Battery boom drives Bangladesh lead poisoning epidemic

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

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
Optical advances offer boost to next-generation solar module designs

Optical advances offer boost to next-generation solar module designs
by Robert Schreiber
Berlin, Germany (SPX) Mar 30, 2025
In 2023, solar photovoltaic (PV) systems accounted for over 5 percent of global electricity output, with installed capacity doubling roughly every two to three years. Optical technologies are now emerging as key enablers to further enhance module efficiency and enable new applications, including aesthetically tailored solar panels for building facades. A new expert-driven report, coordinated by Helmholtz-Zentrum Berlin (HZB) scientists Prof. Christiane Becker and Dr. Klaus Jager, offers a detailed analysis of the most promising innovations in this area.
Solar photovoltaics have become one of the most affordable sources of electricity worldwide. As of November 2024, global PV installations surpassed two terawatts, underscoring the rapid pace of expansion and cost decline.
Contributions from 22 leading research institutions
“At a recent workshop, we discussed how the optics community can contribute to the further growth of photovoltaics,” said Prof. Christiane Becker, who leads the Solar Energy Optics Department at HZB. Along with Dr. Klaus Jager, she brought together a team of 27 experts from 22 institutions across nine countries to produce a wide-ranging review of emerging PV and optical technologies.
Breakthrough optical concepts
Beginning with a comprehensive look at current terawatt-scale PV deployment, the report identifies critical areas where optical strategies can make significant contributions. “We have also identified a number of optical concepts that are currently only on the threshold of economic viability, but which hold the most promise for advancing PV technology,” said Becker. Key areas include multi-junction solar cells, which offer the highest efficiencies among all PV technologies and could help reduce the levelized cost of energy.
Sustainability and aesthetics
The review also emphasizes the importance of environmentally responsible manufacturing and the reduced use of scarce materials through eco-design approaches. Another highlighted innovation is the development of colored PV modules suitable for integration into building architecture. “Especially in cities, we need to use facades and other surfaces too for solar energy conversion, and of course, it does matter how the PV modules look. Such innovative solar modules allow sophisticated aesthetic solutions,” said Becker.
Becker and Jager believe the review will serve not only as a valuable resource for researchers but also for funding bodies and policy strategists seeking to accelerate the deployment of advanced solar technologies.
Research Report:Optics for Terawatt-Scale Photovoltaics: Review and Perspectives
Related Links
Helmholtz Centre for Materials and Energy
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