Solar Energy

Buckyballs on DNA for harvesting light

Published

3 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

New Layered Perovskite Structure Explored for Enhanced Optical Properties

Published

3 mins ago

April 19, 2024

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New Layered Perovskite Structure Explored for Enhanced Optical Properties

by Riko Seibo

Tokyo, Japan (SPX) Apr 19, 2024

Perovskites are critically important in the field of materials science due to their distinct and varied properties arising from their unique crystal structure. These properties have potential revolutionary applications in advanced technology areas. A method to harness these properties involves precise manipulation of defects within the perovskite structure, such as missing atoms or substituting one type of atom for another.

In the realm of oxide chemistry, it’s well-established that such defects in oxides can self-organize within the crystal structure when they reach a certain threshold, leading to enhanced material properties. While this phenomenon of defect ordering is well-documented in perovskite oxides, it has not been as prevalent in hybrid halide perovskites, which consist of an organic component, a metal, and a halogen.

A recent study highlighted in ACS Materials Letters reveals findings by Associate Professor Takafumi Yamamoto and his team at Tokyo Institute of Technology, who discovered a novel defect-ordered layered halide perovskite. The research builds on earlier work where the introduction of thiocyanate ions (SCN-) into the FAPbI3 lattice led to structured defect formations. Dr. Yamamoto suggests, “Increasing the SCN concentration might amplify the formation of these defect structures, similar to those observed in vacancy-ordered oxide perovskites.”

The research involved synthesizing FAPbI3 in powder and crystal forms, using specific ratios of SCN-. When a high enough SCN- ratio was used, the resulting perovskite was FA4Pb2I7.5(SCN)0.5. This compound displayed organized defects throughout its layers-more so than its predecessor, FA6Pb4I13.5(SCN)0.5, where fewer defects were organized.

The study identifies this material as part of a ‘homologous series’-a sequence where systematic alterations to the chemical formula yield predictable changes in properties, here observed as variations in the optical bandgap correlated with defect concentration.

“This marks the first instance of a homologous series based on defect ordering in hybrid organic-inorganic perovskites,” notes Dr. Yamamoto. “Our findings set a foundational strategy for manipulating defect structures to adjust the optical properties of perovskites, offering a promising avenue for materials science innovation.”

The implications of this research are significant, potentially paving the way for new perovskite materials with tailored properties for future technological applications.

Research Report:FA4Pb2I7.5(SCN)0.5: n = 3 Member of Perovskite Homologous Series FAn+1Pbn-1I3n-1.5(SCN)0.5 with Organized Defects

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Solar Energy

Solar energy adoption challenges in rural Ethiopia

Published

1 hour ago

April 19, 2024

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Solar energy adoption challenges in rural Ethiopia

by Clarence Oxford

Los Angeles CA (SPX) Apr 19, 2024

Despite decreasing costs and increasing accessibility of solar home systems, significant obstacles hinder their widespread use in remote areas of developing countries, such as Ethiopia, where they could greatly improve health and education.

Inexpensive, yet uncertified and inferior solar panels, along with limited government engagement in rural energy transition, impede access to dependable electricity for these communities.

When homes do incorporate solar energy, it replaces harmful kerosene lamps, offering a healthier, eco-friendly alternative and enabling children to study after dark.

“Understanding the dynamics of renewable energy adoption in rural sectors of the Global South is crucial,” said Yujin Lee, a doctoral student at Cornell University’s Department of City and Regional Planning and first author of a related study in Energy Policy.

Chuan Liao, the study’s senior author and assistant professor in the Department of Global Development at Cornell, emphasized, “The global shift to renewable and clean energy sources must include remote and rural populations in the developing world.”

Ethiopia’s national electrification strategy aims to power all homes within 25 kilometers of the grid by 2030. Those further away are slated for long-term off-grid solutions.

However, the prevalence of low-quality solar panels, which often fail and contribute to environmental waste, poses a barrier to adoption. Additionally, the infrequency of government visits to rural, off-grid or road-less villages leads to misinformed policies.

“Government reports often do not reflect the true situation in rural areas,” noted Lee, who found actual solar adoption rates to be markedly lower than official claims.

Lee advocates for increased governmental presence in rural communities, enhanced public engagement in energy management, and improved communication between governments, private sectors, international organizations, and end-users to support sustainable energy solutions.

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Solar Energy

The role of Floating Solar in achieving Africa’s energy targets as an alternative to dams

Published

2 hours ago

April 19, 2024

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The role of Floating Solar in achieving Africa’s energy targets as an alternative to dams

by Hugo Ritmico

Madrid, Spain (SPX) Apr 19, 2024

Researchers from Politecnico di Milano have identified floating solar photovoltaics (FPV) as a viable alternative to traditional hydropower in meeting Africa’s energy goals, according to a new study published in Nature Energy. The study shows that FPV installed at existing major reservoirs could generate 20-100% of the electricity projected from planned hydropower dams across Africa.

The research, conducted using a comprehensive energy planning model, reveals that FPV is not only cost-effective compared to other renewable resources but also plays a crucial role in Africa’s energy future. “Floating solar has emerged as cost-competitive and could potentially eliminate the need for many new dams,” stated Wyatt Arnold, the lead author of the study.

A detailed analysis of the transboundary Zambezi watercourse indicated that capital investments for new dams could be more effectively utilized by constructing fewer reservoirs and augmenting them with floating solar panels. This strategy could decrease interannual variability in electricity supply by 12% and enhance resilience against long-term droughts exacerbated by climate change.

“Adopting floating solar can provide developing economies with a stable energy supply less susceptible to hydrological changes,” explained Prof. Andrea Castelletti. “Additionally, it mitigates adverse effects on downstream communities and river ecosystems compared to new dam projects.”

The study also underscores the significance of integrated resource planning and the need to consider transboundary effects in sustainable development. It promotes multisector modeling that integrates energy, agriculture, environmental protection, and economic growth within river basins.

Prof. Matteo Giuliani noted, “The strategic deployment of floating solar might outweigh potential drawbacks on reservoir uses like fishing or recreation. Yet, ongoing enhancements in FPV technology and effective planning are essential for its responsible implementation.”

While floating solar offers substantial environmental benefits, the study acknowledges challenges in technology and social acceptance that may limit its deployment. Nevertheless, these challenges are likely to be less impactful than the negative consequences of new hydropower projects, which can disrupt river ecologies, displace populations, and increase regional conflicts over water use.

Research Report:Floating solar emerges as a sustainable energy solution for Africa’s future