Solar Energy

Buckyballs on DNA for harvesting light

Published

4 years ago

February 24, 2021

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Organic molecules that capture photons and convert these into electricity have important applications for producing green energy. Light-harvesting complexes need two semiconductors, an electron donor and an acceptor. How well they work is measured by their quantum efficiency, the rate by which photons are converted into electron-hole pairs.

Quantum efficiency is lower than optimal if there is “self-quenching”, where one molecule excited by an incoming photon donates some of its energy to an identical non-excited molecule, yielding two molecules at an intermediate energy state too low to produce an electron-hole pair. But if electron donors and acceptors are better spaced out, self-quenching is limited, so that quantum efficiency improves.

In a new paper in Frontiers in Chemistry, researchers from the Karlsruhe Institute of Technology (KIT) synthesize a novel type of organic light-harvesting supramolecule based on DNA. The double helix of DNA acts as a scaffold to arrange chromophores (i.e. fluorescent dyes) – which function as electron donors – and “buckyballs” – electron acceptors – in three dimensions to avoid self-quenching.

“DNA is an attractive scaffold for building light-harvesting supramolecules: its helical structure, fixed distances between nucleobases, and canonical base pairing precisely control the position of the chromophores. Here we show that carbon buckyballs, bound to modified nucleosides inserted into the DNA helix, greatly enhance the quantum efficiency. We also show that the supramolecule’s 3D structure persists not only in the liquid phase but also in the solid phase, for example in future organic solar cells,” says lead author Dr Hans-Achim Wagenknecht, Professor for Organic Chemistry at Karlsruhe Institute of Technology (KIT).

DNA provides regular structure, like beads on a helical string

As scaffold, Wagenknecht and colleagues used single-stranded DNA, deoxyadenosine (A) and thymine (T) strands 20 nucleotides long. This length was chosen because theory suggests that shorter DNA oligonucleotides wouldn’t assemble orderly, while longer ones wouldn’t be soluble in water.

The chromophores were violet-fluorescent pyrene and red-fluorescent Nile red molecules, each bound noncovalently to a single synthetic uracil (U)-deoxyribose nucleoside. Each nucleoside was base-paired to the DNA scaffold, but the order of pyrenes and Nile reds was left to chance during self-assembly.

For the electron acceptors, Wagenknecht et al. tested two forms of “buckyballs” – also called fullerenes – which are known to have an excellent capacity for “quenching” (accepting electrons). Each buckyball was a hollow globe built from interlocking rings of five or six carbon atoms, for a total of 60 carbons per molecule. The first form of buckyball tested binds nonspecifically to the DNA through electrostatic charges.

The second form – not previously tested as an electron acceptor – was covalently bound via a malonic ester to two flanking U-deoxyribose nucleosides, which allowed it to be base-paired to an A nucleotide on the DNA.

High quantum efficiency, including in solid phase

The researchers confirmed experimentally that the 3D structure of the DNA-based supramolecule persists in solid phase: a crucial requirement for applications in solar cells. To this end, they tested supramolecules with either form of buckyballs as the active layer in a miniature solar cell.

The constructs showed excellent charge separation – the formation of a positive hole and negative electron charge in the chromophore and their acceptance by nearby buckyballs – with either form of buckyball, but especially for the second form.

The authors explain this from the more specific binding, through canonical base-pairing, to the DNA scaffold by the second form, which should result in a smaller distance between buckyball and chromophore. This means that the second form is the better schoice for use in solar cells.

Importantly, the authors also show that the DNA-dye-buckyball supramolecule has strong circular dichroism, that is, it is much more reactive to left- than to right-handed polarized light, due to its complex 3D helical structure – even in the solid phase.

“”I don’t expect that everyone will have solar cells with DNA on their roof soon. But the chirality of DNA will be interesting: DNA-based solar cells might sense circularly polarized light in specialized applications,” concludes Wagenknecht.

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Solar Energy

NASA continues to assess Solar Sail system progress following deployment

Published

25 mins ago

October 23, 2024

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NASA continues to assess Solar Sail system progress following deployment

by Clarence Oxford

Los Angeles CA (SPX) Oct 23, 2024

NASA’s Advanced Composite Solar Sail System is advancing through post-deployment testing, with mission operators carefully reviewing data to evaluate the performance of the spacecraft’s composite booms. Following the successful deployment of both the booms and solar sail, the spacecraft continues to experience slow tumbling in orbit due to the deactivation of its attitude control system.

Prior to the deployment phase, the team deactivated the attitude control system to accommodate changes in the spacecraft’s dynamics during the unfurling of the solar sail. This system is vital for maintaining a spacecraft’s orientation in space, ensuring proper alignment for communications and solar energy collection.

While the solar sail has fully deployed into its square shape-approximately half the size of a tennis court-the team is analyzing a slight bend detected in one of the four composite booms. The bend likely occurred as the booms were stretched during deployment. However, preliminary analysis suggests the bend has partially straightened over time as the spacecraft slowly tumbles in orbit.

The primary goal of the Advanced Composite Solar Sail System mission is to validate the deployment of the composite booms, contributing crucial data for future applications of this technology in solar sails and other space structures. The data gathered so far has already been extremely useful and will continue to inform the advancement of solar sail missions.

The mission team expects that the slight bend will not interfere with the solar sail’s planned maneuvers, which are slated for the later stages of the technology demonstration.

Currently, efforts are focused on repositioning the spacecraft, which remains in low-power mode to conserve energy. The team is working to optimize the orientation of the solar panels to receive more sunlight and prioritize essential operations, such as two-way communication with mission control. Once the attitude control system is reactivated, operators will be able to precisely position the spacecraft’s high-bandwidth antenna for improved communication, collect additional data, and prepare for the mission’s upcoming sailing maneuvers.

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Solar Energy

Towards better solar cells through unique electricity generation

Published

1 hour ago

October 23, 2024

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Towards better solar cells through unique electricity generation

by Riko Seibo

Tokyo, Japan (SPX) Oct 23, 2024

Researchers in Japan have experimentally demonstrated the bulk photovoltaic (BPV) effect in alpha-phase indium selenide (a-In2Se3) along the out-of-plane direction for the first time, potentially leading to advancements in solar cell technologies and photosensors. This unusual effect allows certain materials to outperform conventional p-n junctions used in today’s solar cells.

The BPV effect, seen in materials lacking internal symmetry, generates “shift currents” where electrons excited by light move coherently in a specific direction, unlike traditional solar cells. The team, led by Associate Professor Noriyuki Urakami from Shinshu University, focused on the predicted but previously untested a-In2Se3, creating a device that successfully demonstrated the BPV effect.

“Our a-In2Se3 device demonstrated quantum efficiency several orders of magnitude higher than other ferroelectric materials,” said Prof. Urakami, adding that the discovery could impact the selection of materials for future photovoltaic devices.

The researchers hope their findings will contribute to renewable energy generation, accelerating the adoption of solar cells and advancing efforts toward a carbon-neutral society.

Research Report:Bulk photovoltaic effect of an alpha-phase indium selenide(a-In2Se3) crystal along the out-of-plane direction

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Solar Energy

Space Solar and Transition Labs to bring space solar power to Iceland by 2030

Published

24 hours ago

October 22, 2024

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Space Solar and Transition Labs to bring space solar power to Iceland by 2030

by Sophie Jenkins

London, UK (SPX) Oct 22, 2024

Space Solar, a leading company in space-based solar power, has partnered with Transition Labs to provide Reykjavik Energy with electricity from the world’s first space-based solar power plant. This plant, expected to be operational by 2030, will have an initial capacity of 30 MW.

Space Solar’s new solar power system will orbit the Earth, capturing solar energy and transmitting it wirelessly using high-frequency radio waves to stations on the ground. These stations will convert the energy into electricity and feed it directly into the grid, delivering renewable energy 24/7, regardless of weather conditions, with costs comparable to other renewable sources.

The venture marks a major step in the renewable energy sector. Unlike ground-based solar plants, which rely on sunlight and weather, Space Solar’s technology ensures consistent power generation. Their first plant will generate 30 MW within five years, and by 2036, each plant could provide GigaWatts of power, helping to meet growing global energy demands and contribute to a carbon-free future.

Transition Labs, a private climate initiative based in Iceland, has supported Space Solar in making this vision a reality. Reykjavik Energy, known for its leadership in climate action through its subsidiary Carbfix, is a key partner in the project. Together, they are addressing the engineering challenges of space-based solar energy and exploring locations for ground-based reception stations, including Iceland, Canada, and northern Japan.

Kjartan Orn Olafsson, CEO of Transition Labs, highlighted the partnership, stating: “The collaboration with Reykjavik Energy marks a key milestone in Space Solar’s journey toward full-scale deployment. Their forward-thinking approach to climate technology, combined with expertise in carbon storage through Carbfix and a long-standing partnership with Climeworks, makes Reykjavik Energy the perfect partner for Space Solar’s initial phase.”

The independent analysis by Imperial College London indicates that adding 8 GW of space-based solar energy to the UK’s energy system could save over GBP 4 billion in system costs annually.

Martin Soltau, co-CEO of Space Solar, expressed excitement about the project: “Space-based solar power offers unparalleled benefits with competitive energy costs and 24/7 availability. Reykjavik Energy’s recognition of the potential for space-based solar to drive the energy transition is exciting, and we’re thrilled to be working together in partnership toward a sustainable future.”

The agreement with Reykjavik Energy is a significant step in commercializing space-based solar power, positioning Space Solar at the forefront of a new renewable energy revolution with global implications.

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