Solar Energy

Lithuanian researchers advance solar cell technology

Published

10 months ago

May 17, 2024

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Lithuanian researchers advance solar cell technology

by Robert Schreiber

Berlin, Germany (SPX) May 16, 2024

Researchers from Kaunas University of Technology (KTU), Lithuania, who previously developed high-efficiency solar cells, have expanded their invention. The self-assembled monolayers can now be applied in both inverted and regular structure perovskite solar cells.

Self-assembling molecules form a single-molecule-thick layer, acting as an electron-transporting layer in solar cells.

“The molecules that make up these monolayers, like a clever glue, coat the surface of the constructed devices with a thin one molecule thick layer. And this is not random, they don’t stick wherever they go, but attach themselves by chemical bonds only where they are in contact with conductive metal oxide,” explained Tadas Malinauskas, Professor at KTU’s Faculty of Chemical Technology and one of the inventors of the new technology.

According to Malinauskas, creating such a layer is a simple and material-efficient process that requires a glass substrate with an electrically conductive metal oxide layer to be immersed in or sprayed with a highly diluted solution of the compound. The self-assembling molecules attach only to the metal oxide surface, with non-adhering molecules being washed away. This creates a thin layer precisely where it is needed.

KTU researchers have been synthesizing and studying charge-transporting organic materials for several years, focusing previously on molecules for positive charge transfer in perovskite solar cells.

“We can already say with confidence that these molecules have given a major boost to the development of the next generation solar cells. So, our next step is quite logical: to develop analogous molecules that can carry negative charges, and to apply these materials in perovskite solar cells,” said Vytautas Getautis, professor at the KTU Faculty of Chemical Technology and head of the research group.

Although it is a very thin layer, its role in solar cells is critical. Malinauskas compared its function to that of an automatic gate in the subway, allowing only one type of charge to pass through towards the electrode, thereby increasing solar cell efficiency.

Perovskite solar cell structures vary in layer sequence. In the regular structure, a negative charge transporting layer is formed on a transparent substrate, followed by light-absorbing and positive charge transporting layers. In the inverted structure, the positive and negative charge transport layers are swapped.

KTU PhD student Lauryna Monika Svirskaite explained that the main difference between the two structures lies in their application areas. The regular structure is used for studying low-cost, easier-manufactured but less efficient solar cells, while the inverted architecture allows for more efficient combined devices, known as tandem devices.

Currently, as both structures are being intensively researched, KTU scientists believe that their new invention is as significant and promising as their previous developments.

The new invention resulted from collaboration with scientists from King Abdullah University of Science and Technology (KAUST).

“We, KTU chemists, were responsible for the development, improvement, and optimisation of the materials and coating technology, while our colleagues from Saudi Arabia investigated the performance of it in solar cells,” revealed Malinauskas.

Greta Zekiene, head of Intellectual Property Management at KTU’s National Innovation and Entrepreneurship Centre (NIEC), said the demand for this invention is surprisingly high. Interest in the invention’s industrial use preceded the patent application filing.

“A Japanese company, with whom we already have several licences for inventions in this field, immediately expressed the interest to have the innovation in their product portfolio. They were waiting for us to prepare a patent application. The process of negotiating a licence agreement started right away,” said Zekiene.

She emphasized that obtaining a patent is not necessary for commercializing an invention, as it depends on the individual case. Commercialization can occur at any time if a business declares its intention to license or take over all the property rights.

Zekiene added that inventions in the field of solar cells made by the Synthesis of Organic Semiconductors research group are the strongest in KTU’s patent portfolio and receive significant interest from businesses. “We feel proud and acknowledged when companies want to start using the inventions as soon as possible,” she said.

Research Report:Nonfullerene Self-Assembled Monolayers As Electron-Selective Contacts for n-i-p Perovskite Solar Cells

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Solar Energy

Identifying Key Organic-Inorganic Interaction Sites for Enhanced Emission in Hybrid Perovskites via Pressure Engineering

Published

2 hours ago

March 14, 2025

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Identifying Key Organic-Inorganic Interaction Sites for Enhanced Emission in Hybrid Perovskites via Pressure Engineering

by Simon Mansfield

Sydney, Australia (SPX) Mar 14, 2025

A research team from Jilin University has developed a new approach using pressure engineering to pinpoint organic-inorganic interaction sites in non-hydrogen-bonded hybrid metal perovskites. This innovative method provides valuable insight into the photophysical mechanisms governing hybrid perovskites and offers guidance for designing materials with tailored optical properties.

“Previous research has primarily focused on the role of hydrogen bonding in shaping the photophysical properties of hybrid perovskites,” explained Guanjun Xiao, the study’s lead researcher. “However, the lack of investigation into the interaction mechanisms of non-hydrogen-bonded hybrid perovskites has hindered precise material design for targeted applications.”

By employing high-pressure techniques, Xiao and his team studied the specific interaction sites within the non-hydrogen-bonded hybrid perovskite (DBU)PbBr3. Their findings highlighted that the spatial arrangement of Br-N atomic pairs plays a crucial role in influencing organic-inorganic interactions.

The research was published on September 16 in *Research*, a Science Partner Journal launched by the American Association for the Advancement of Science (AAAS) in collaboration with the China Association for Science and Technology (CAST). Xiao is a professor at the State Key Laboratory of Superhard Materials at Jilin University.

The study involved synthesizing microrod (DBU)PbBr3 using the hot injection method and systematically analyzing its optical and structural properties under high pressure. The researchers observed that the material’s emission exhibited enhancement and a blue shift under pressure, with photoluminescence quantum yield reaching 86.6% at 5.0 GPa. Additionally, photoluminescence lifetime measurements indicated a suppression of non-radiative recombination under pressure.

A significant discovery was the presence of an abnormally enhanced Raman mode in the pressure range where emission enhancement occurred. “This suggests a potential connection between the two phenomena,” Xiao noted. Further analysis identified the Raman mode as being linked to organic-inorganic interactions, likely associated with N-Br bonding.

To deepen their understanding, the team conducted structural evolution studies under pressure, supported by first-principles calculations. They confirmed that the primary determinants of interaction strength were the spatial arrangement of N and Br atoms, including their distance and dihedral angle. A notable isostructural phase transition at 5.5 GPa altered the primary compression direction, initially strengthening organic-inorganic interactions before leading to a subsequent decrease-trends that aligned with observed optical property changes.

“These findings bridge a significant knowledge gap in understanding organic-inorganic interactions in non-hydrogen-bonded hybrid halides, offering valuable design principles for materials with specific optical performance targets,” Xiao stated.

Research Report:Identifying Organic-Inorganic Interaction Sites Toward Emission Enhancement in Non-Hydrogen-Bonded Hybrid Perovskite via Pressure Engineering

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Solar Energy

Groundbreaking Discovery Links Small Polaron Effect to Enhanced Spin Lifetime in 2D Lead Halide Perovskites

Published

2 hours ago

March 14, 2025

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Groundbreaking Discovery Links Small Polaron Effect to Enhanced Spin Lifetime in 2D Lead Halide Perovskites

by Simon Mansfield

Sydney, Australia (SPX) Mar 14, 2025

Two-dimensional lead halide perovskites have emerged as highly promising materials for optoelectronic applications due to their superior carrier transport and defect tolerance. However, a comprehensive understanding of charge carrier dynamics in these materials has remained elusive, primarily due to their inherently soft polar lattice and pronounced electron-phonon interactions. While extensive studies have characterized charge behavior in bulk three-dimensional perovskites, the unique carrier dynamics of their two-dimensional counterparts have yet to be fully deciphered.

A recent study employed advanced transient spectroscopic methods combined with theoretical modeling to uncover the presence of small polarons in Dion-Jacobson phase 2D perovskites, particularly in the compound (4AMP)PbI4. Researchers determined that strong charge-lattice coupling induces a substantial deformation potential of 123 eV-approximately 30 times greater than those typically observed in conventional 2D and 3D perovskites. This extraordinary interaction significantly influences carrier dynamics within the material.

Utilizing optical Kerr spectroscopy, the research team identified extended polarization response times at room temperature, surpassing 600 ps. The study attributes this prolonged response to the formation of small polarons, which span roughly two-unit cells in size due to the lattice distortions present in the material. Additional investigations involving temperature-dependent phonon studies, spin relaxation analyses, and X-ray diffraction further substantiated the presence of these small polarons. These findings highlight their role in modifying excitonic Coulomb exchange interactions, leading to an up to tenfold increase in spin lifetime.

Implications for Optoelectronic Advancements

This discovery holds considerable promise for the future of optoelectronic device engineering. By elucidating the impact of small polaron formation on spin dynamics, researchers can refine 2D perovskite materials to achieve superior carrier mobility, extended spin lifetimes, and enhanced energy conversion efficiency. Such improvements could accelerate the development of next-generation solar cells, photodetectors, and spintronic devices.

The study also paves the way for tailoring charge-lattice interactions through controlled deformation potential tuning, potentially optimizing perovskite-based device performance. Future investigations may delve deeper into fine-tuning polaronic effects to further capitalize on their benefits in commercial applications.

Future Prospects

This research provides direct evidence of small polaron formation in Dion-Jacobson phase 2D perovskites, underscoring the critical influence of lattice interactions on spin dynamics and optoelectronic efficiency. Continued exploration of these mechanisms is expected to drive the development of novel materials that could redefine perovskite-based optoelectronics. These findings mark a significant step toward realizing energy-efficient, high-performance electronic and photonic devices.

Research Report:Giant deformation potential induced small polaron effect in Dion-Jacobson two-dimensional lead halide perovskites

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Solar Energy

Cheap and environmentally friendly – the next generation LEDs may soon be here

Published

1 day ago

March 13, 2025

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Cheap and environmentally friendly – the next generation LEDs may soon be here

by Anders Torneholm

Linkoping, Sweden (SPX) Mar 13, 2025

Cost, technical performance and environmental impact – these are the three most important aspects for a new type of LED technology to have a broad commercial impact on society. This has been demonstrated by researchers at Linkoping University in a study published in Nature Sustainability.

“Perovskite LEDs are cheaper and easier to manufacture than traditional LEDs, and they can also produce vibrant and intense colours if used in screens. I’d say that this is the next generation of LED technology,” says Feng Gao, professor of optoelectronics at Linkoping University.

However, for a technological shift to take place, where today’s LEDs are replaced with those based on the material perovskite, more than just technical performance is required. That is why Feng Gao’s research group has collaborated with Professor Olof Hjelm and John Laurence Esguerra, assistant professor at LiU. They specialise in how innovations contributing to environmental sustainability can be introduced to the market.

Together, they have investigated the environmental impact and cost of 18 different perovskite LEDs, knowledge that is currently incomplete. The study was conducted using so-called life cycle assessment and techno-economic assessment.

Such analyses require a clear system definition – that is, what is included and not in terms of cost and environmental impact. Within this framework, what happens from the product being created until it can no longer be used is investigated. The life cycle of the product, from cradle to grave, can be divided into five different phases: raw material production, manufacturing, distribution, use and decommissioning.

“We’d like to avoid the grave. And things get more complicated when you take recycling into account. But here we show that it’s most important to think about the reuse of organic solvents and how raw materials are produced, especially if they are rare materials,” says Olof Hjelm.

One example where the life cycle analysis provides guidance concerns the small amount of toxic lead found in perovskite LEDs. This is currently necessary for the perovskites to be effective. But, according to Olof Hjelm, focusing only on lead is a mistake. There are also many other materials in LEDs, such as gold.

“Gold production is extremely toxic. There are byproducts such as mercury and cyanide. It’s also very energy-consuming,” he says.

The greatest environmental gain would instead be achieved by replacing gold with copper, aluminium or nickel, while maintaining the small amount of lead needed for the LED to function optimally.

The researchers have concluded that perovskite LEDs have great potential for commercialisation in the long term. Maybe they can even replace today’s LEDs, thanks to lower costs and less environmental impact. The big issue is longevity. However, the development of perovskite LEDs is accelerating and their life expectancy is increasing. The researchers believe that it needs to reach about 10,000 hours for a positive environmental impact, something they think is achievable. Today, the best perovskite LEDs last for hundreds of hours.

Muyi Zhang, PhD student at the Department of Physics, Chemistry and Biology at LiU, says that much of the research focus so far is on increasing the technical performance of LED, something he believes will change.

“We want what we develop to be used in the real world. But then, we as researchers need to broaden our perspective. If a product has high technical performance but is expensive and isn’t environmentally sustainable, it may not be highly competitive in the market. That mindset will increasingly come to guide our research.”

Research Report:Towards sustainable perovskite light-emitting diodes