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Category: solar power

New contact material improves efficiency and stability of perovskite solar cells

A newly developed material for the electron contact improves the efficiency of single perovskite solar cells and perovskite/silicon tandem solar cells. The new material is based on a carborane molecule. It offers several advantages over the standard material C60, as shown by the study led by Steve Albrecht’s team. The new material has since been patented and is already commercially available.

Perovskite solar cells are not only exceptionally inexpensive to manufacture but also achieve high efficiency levels. Single-junction perovskite devices can already convert more than 27% of sunlight into electrical energy, while perovskite-silicon tandem cells have achieved efficiencies of more than 35%. Until now, a layer of so-called “football molecules” (C60) has been used to transport electrons away. However, a significant proportion of the charge carriers are lost at the interface between the C60 layer and the perovskite absorber. Furthermore, C60 materials are relatively expensive and tend to delaminate over time, compromising the cell’s stability.

Rust-to-iron cycle may unlock long-term storage for renewable energy

In the future, iron might be used as a chemical energy storage material, making large quantities of renewable energy available in the long term. Iron powder is combusted in a cyclic process that is carbon neutral and then reconverted to its original state using energy input. Scientists at Karlsruhe Institute of Technology (KIT) were the first to conduct an extensive study to evaluate the potential of this technology for power generation. Their results show that iron, while not superseding hydrogen, may usefully complement it in a climate-neutral energy system. The findings have been published in Chem Circularity.

Be it for wind energy from coastal regions or for solar power from desert areas, iron could serve as a transportable energy carrier in the future to make these renewable energy sources usable worldwide. “This works in a cycle that emits no carbon dioxide or environmentally harmful substances,” said Julia Schuler from KIT’s Institute for Industrial Production (IIP). For power generation, iron powder is combusted, producing iron oxide, i.e. rust. Using hydrogen from renewable sources, it is reduced to iron again in a process that removes the oxygen it contains. The iron powder can then be reused.

“When burned, iron powder behaves very much like coal. We wanted to find out whether it was possible to repurpose existing coal power plants to iron-firing,” said Schuler. She believes that modifications are primarily necessary in the heat generator; other components, such as the steam cycle, turbines, generator and power grid connection, could continue to be used.

Spontaneous current loops in a kagome metal point to hidden quantum order

Quantum materials, materials exhibiting physical behavior governed by the laws of quantum mechanics, have proved promising for the development of numerous advanced technologies, including quantum technologies, memory devices and solar panels. In some of these materials, electrons can collectively arrange themselves in unusual patterns, giving rise to states that cannot be explained by classical physics theories.

For more than two decades, theoretical physicists have predicted the existence of a loop current order in some quantum materials. This is a state characterized by tiny electrical currents circulating around microscopic loops inside a crystal, which would produce no measurable electric current flowing through a material.

These current loops were predicted to emerge when electrons spontaneously organize themselves into a less symmetrical pattern than the crystal itself, even if atoms remain in similar positions. While this phenomenon was widely studied and described by theorists in the past, it has so far proved difficult to observe experimentally.

Tandem solar cell sets 25.5% efficiency record with CIGS-perovskite design

A Berlin-based team from HZB and Center for the Science of Materials Berlin (CSMB) at Humboldt-Universität zu Berlin has set a new record for a tandem solar cell. Using a combination of a CIGS semiconductor layer and perovskite, along with several optimized intermediate layers, the team converted 25.5% of sunlight into electrical energy. The previous record for this combination of materials and this size cell had stood at 24.6%.

The new record has been certified and is visible in the Solar Cell Efficiency Tables (the “Green Tables”) published in the journal Joule, which serve as the definitive ledger for the global photovoltaic community. To be included in this special “record table,” not only is high efficiency required, but also an area of more than 1 cm2. The well-known NLR table (formerly NREL), by contrast, lists only the maximum efficiency per technology, even if the cell has an area of 0.001 cm2.

Perovskite solar cells need decades-long durability. New work shows which fast-aging tests come closest

Perovskite solar cells (PSCs) could conquer the mass market within a few years, perhaps even being produced in Europe. Their large-scale production is highly cost-effective, and unlike silicon solar cells, their production is less energy-intensive. However, perovskite solar cells ideally need to achieve decades-long warranties, which remains a challenge.

To assess their long-term stability, various test methods are used to accelerate aging. But how accurately do these methods reflect the actual degradation processes? A new study in Joule by a team led by Dr. Carolin Ulbrich (HZB) and Andreas Bartelt (HTW Berlin) now answers this question.

New energy-boosting quantum mechanism discovered in photosynthetic bacteria

Researchers have discovered how certain photosynthetic bacteria use a sophisticated quantum mechanism to increase their efficiency when capturing sunlight. The study, published today in the journal Nature Chemistry and led by Professor Jenny Clark, reveals that nature has been using a process called “singlet fission,” effectively a “two-for-one” energy deal, to optimize solar harvesting. The findings provide a new blueprint for green technology, particularly as engineers attempt to copy this mechanism to build next-generation solar panels and quantum technologies.

While scientists have long understood the basic rules of how plants and bacteria convert light into chemical fuel, the biological role of singlet fission has historically remained poorly understood.

How longer exciton lifetimes could ease efficiency trade-off in organic solar cells

Although the efficiency of organic solar cells has now risen to more than 20%, there are physical limits that make it difficult to further increase their performance. A research team from Linköping University in Sweden, the University of Potsdam, the Paul-Drude-Institut in Berlin and other collaborators has now demonstrated which physical processes limit a key parameter in the performance of organic solar cells. This opens up the possibility of overcoming the long-standing efficiency limits of organic solar cells.

The work is published in the journal Nature Photonics.

Wave-packet interferometry captures elusive dark excitons in organic superconductor

In a recent study, Manish Garg, independent group leader at Max Planck Institute for Solid State Research (MPI FKF), succeeded in probing the local properties of bright and dark excitons in the organic superconductor copper naphthalocyanine (CuNc). The findings are published in the journal Nature Communications.

This study was the result of the efforts of an international collaboration that brought together the MPI for Solid State Research in Stuttgart, the Università della Calabria and the Universidad Autónoma de Madrid.

By combining scanning tunneling microscopy with wave-packet interferometry, the authors gained remarkable—and previously inaccessible—insights into exciton dynamics. The insights gained with this technique can be of paramount importance both in the field of energy materials—where excitons play a central role in light-harvesting technologies such as solar cells—and in quantum technologies, as excitons are considered a promising platform for quantum computing.

Solid-state material turns visible light into high-energy UV at sunlight intensity, expanding solar energy potential

Two cups of warm water don’t make one cup of boiling water. But in the quantum world, multiple low-energy photons can combine to produce a single, higher-energy photon.

A research team at Kyushu University has developed a solid-state molecular material that “upgrades” visible light into ultraviolet (UV) light under ordinary outdoor sunlight, achieving a conversion efficiency of 1.9%. The study is published in Nature Communications.

Harsh UV light is something most people try to avoid in summer, yet it is indispensable in fields ranging from air purification and resin curing in 3D printing to gel hardening in dental fillings and nail art. Despite its importance, UV accounts for only about 6% of the sunlight reaching Earth’s surface, with only a fraction of that being practically usable.

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