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New Research Accelerates Development of Organic Solar Cells
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team of researchers is working to replace heavy and expensive silicon solar cells currently being used in the solar industry with light and low-cost organic solar cells - made from materials and elements found in plants and animals which could help in the battle against climate change. Most of today’s solar cells are made from silicon and are heavy, rigid, and expensive to produce. By contrast, organic solar cells hold the promise of being lightweight, flexible, and cheap to make. However, organic solar cells have not yet reached the sunlight-toelectricity efficiencies of their silicon-based counterparts, preventing their commercialisation. Now, researchers from the University of Cambridge, in a global collaboration with experts from Canada, Belgium, New Zealand, and China, have discovered a new fundamental way for energy to move in organic materials at a speed up to 1000’s of times faster than normal, getting steps closer
to fully realise the promise of organic photovoltaics. Their findings are reported in the journal Science Advances. This new movement mechanism, coined “transient exciton delocalization,” allows energy to move and transfer to the surrounding electrical wires incredibly much faster than normal. “This improvement is made possible by the quantum-mechanical nature of reality, where energy can exist in many places at once, simultaneously”, said first author Alexander Sneyd, a PhD student at Cambridge’s
Cavendish Laboratory. “By taking advantage of these quantum-mechanical elements which allow for highly-efficient energy movement, we can make better, more efficient solar cells.” The research team began by using a highly advanced nanotechnology technique called ‘living crystallization driven self-assembly’ to create nanofibers made from a sulphur and carbon-based polymer. This allowed them to precisely control the position of each of the atoms in the organic nanofiber to create a ‘perfect’ model material. “This was really the secret to the success”, said Dr. Akshay Rao of the Cavendish Laboratory who led the research. “We were able to attain an unprecedented level of structural control, which one could only dream of until very recently.” The team then shone a laser at the nanofibers to mimic sunlight, and watched the energy move over time using a technique called transient-absorption microscopy to create ‘films’ of the energy transport.
Researchers Make High-activity Photocatalyst Using Gold Nanoclusters
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esearchers from Japan have designed a stable, high-performance photocatalyst from gold nanoclusters (NCs) by removing the protective molecules around them. In a new study published in Angewandte Chemie, Prof. Negishi led a team of researchers, including Assistant Professor Tokuhisa Kawawaki, Mr. Yuki Kataoka, Ms. Momoko Hirata, and Mr. Yuki Akinaga, to dig deep into the mechanism of the ligand removal process in NCs. Catalysts, which help drive reactions, are ubiquitous, whether as an enzyme in the body that digests food or the catalytic converter in the car that breaks down pollutants. In
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chemical reactions, catalysts play an important role in making it more efficient. Recently, atomically precise metal NCs that can accelerate various thermal, electrochemical, and photochemical reactions have been used to design useful catalysts. These NCs are tiny particles (less than 2 nanometers) whose properties can be modified by changing their atomic composition. This is why, metal NCs have received considerable attention, with scientists trying to find various ways of synthesizing NCs with unique functions. A popular way of fabricating atomically precise metal NCs is using ligands (molecules or ions that attach themselves to a central
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metal core). These ligands not only protect the tiny NCs but also affect their chemical reactivity and selectivity. Sometimes, however, the reactivity is lower than expected. To increase the catalytic activity of ligandprotected metal NCs, they are heated in a furnace at high temperatures without oxygen (a process called “calcination”) to remove the ligands from the main cluster. However, heating the particles at very high temperatures can cause the NCs to accumulate, often leading to a decrease in reactivity. “When the ligands are removed without special treatment, the metal NCs easily aggregate on the support and
lose their size-specific properties. It is essential understand the mechanism of ligand calcination to create highly functional heterogeneous catalysts under appropriate conditions,” says Prof. Yuichi Negishi of Tokyo University of Science, Japan, who researches on the synthesis of nanoclusters. For their experiments, the Japanese researchers synthesized gold NCs protected by two ligands, 2-phenylethanethiolate and mercaptobenzoic acid and then supported them on a photocatalytic metal oxide. Next, the team heated the prepared material at different temperatures ranging from 195°C to 500°C.
