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Researchers pave the way for large-scale, efficient organic solar cells with water treatment – Phys.org

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Organic solar cells (OSCs) exhibit many desirable properties, including a high conversion efficiency and easy scalability. However, controlling the morphology of the active layer thin film during upscaling has proved challenging. In a new study, GIST researchers solve this problem with deionized water as a method for morphology control, enabling high efficiency OSC modules with large active areas. Credit: Dong-Yu Kim from Gwangju Institute of Science and Technology

Organic solar cells (OSCs), which use organic polymers to convert sunlight into electricity, have received considerable attention for their desirable properties as next-generation energy sources. These properties include its lightweight nature, flexibility, scalability, and a high power conversion efficiency (>19%). Currently, several strategies exist for enhancing the performance and stability of OSCs. However, a problem that remains is the difficulty of controlling the morphology of the active layer in OSCs when scaling up to large areas. This makes it challenging to obtain high-quality active layer thin films and, in turn, fine-tune the device efficiency.

In a recent study, a team of researchers from the Gwangju Institute of Science and Technology, Korea set out to address this issue. In their work, published in Advanced Functional Materials, they suggested a solution that appears rather counterintuitive at first glance: using to control the active layer morphology.

“Water is known to hinder the performance of organic electronic devices, since it remains in the ‘trap states’ of the , blocking the charge flow and degrading the device performance. However, we figured that using water rather than an organic solvent-based active solution as a medium of treatment method would enable necessary physical changes without causing chemical reactions,” explains Professor Dong-Yu Kim, who headed the study.

The researchers chose the polymers PTB7-Th and PM6 as donor materials and PC61BM and EH-IDTBR and Y6 as acceptor materials for the active layer. They noticed that inducing a vortex to mix the donor and acceptor materials in the active solution could lead to a well-mixed active solution, yet it was not enough on its own.

The active solution was hydrophobic and, accordingly, the researchers decided to use deionized (DI) water and vortices to stir the solution. They let the donor and acceptor materials sit in chlorobenzene (host active solution) overnight, and then added DI water in the solution and stirred it, creating tiny vortices.

Due to the hydrophobic nature of the solution, the water pushed on the donor and acceptor molecules, causing them to dissolve more finely into the solution. They then let the solution rest, which caused the water to separate from the solution. This water was then removed and the water-treated active solution was used to prepare thin films of PTB7-Th: PC61BM (F, fullerene), PTB7-Th: EH-IDTBR (NF, fullerene), and PM6: Y6 (H-NF, high-efficiency non-fullerene).

The researchers then examined the photovoltaic performance of these thin films in a slot-die-coated inverted OSC configuration and compared them with those for OSCs without water treatment.

“We observed that the water-treated active led to a more uniform active layer , which showed higher power conversion efficiencies compared to those not treated with water. Moreover, we fabricated large-area OSC modules with an active area of 10 cm2, which showed a conversion efficiency as high as 11.92% for water-treated H-NF films,” says Prof Kim.


Explore further

Over 14% efficiency for ternary organic solar cell with 300 nm thick active layer


More information:
Nara Han et al, Introduction of Water Treatment in Slot‐Die Coated Organic Solar Cells to Improve Device Performance and Stability, Advanced Functional Materials (2022). DOI: 10.1002/adfm.202204871

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GIST (Gwangju Institute of Science and Technology)

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Researchers pave the way for large-scale, efficient organic solar cells with water treatment (2022, September 15)
retrieved 15 September 2022
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Good planning gets the bike rolling – Science Daily

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In surveys, a large majority of respondents usually agree that cycling can make a significant contribution to reducing greenhouse gases and to sustainable transport, especially in densely populated areas. In contrast, for many countries in reality there is a large gap between desired and actual numbers. In Germany, for example, only 20% of the short-distance of everyday trips in residential environments are covered by bicycle.

When asked about the reasons, one point repeatedly comes up top of the list: The perceived or actual lack of safety on the bike routes used. Increasing the share of cycling trips in the modal split thus depends crucially on a well-developed bike path infrastructure. However, designing efficient bike path networks is a complex problem that involves balancing a variety of constraints while meeting overall cycling demand. In addition, many municipalities still only have small budgets available for improving bicycle infrastructure.

In their study, researchers from the Chair of Network Dynamics / Center for Advancing Electronics Dresden (cfaed) at TU Dresden propose a new approach to generate efficient bike path networks. This explicitly considers the demand distribution and route choice of cyclists based on safety preferences. Typically, minimizing the travel distance is not the only goal, but aspects such as (perceived) safety or attractiveness of a route are also taken into account.

The starting point of this approach is a reversal of the usual planning process: Under real conditions, a bike path network is created by constantly adding bike paths to more streets. The cfaed scientists, on the contrary, start with an ideal, complete network, in which all streets in a city are equipped with a bike path. In a virtual process, they gradually remove individual, less used bike path segments from this network. The route selection of the cyclists is continuously updated. Thus, a sequence of bike path networks is created that is always adapted to the current usage. Each stage of this sequence corresponds to a variant that could be implemented with less financial effort. In this way, city planners can select the version that fits their municipality’s budget.

“In our study, we illustrate the applicability of this demand-driven planning scheme for dense urban areas of Dresden and Hamburg,” explains Christoph Steinacker, first author of the study. “We approach a real-life issue here using the theoretic toolbox of network dynamics. Our approach allows us to compare efficient bike path networks under different conditions. For example, it allows us to measure the influence of different demand distributions on the emerging network structures.” The proposed approach can thus provide a quantitative assessment of the structure of current and planned bike path networks and support demand-driven design of efficient infrastructures.

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Materials provided by Technische Universität Dresden. Note: Content may be edited for style and length.

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Laughing gas in space could mean life

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To date, over 5000 exoplanetary systems have been discovered. Biosignatures are chemical components in a planet’s atmosphere that may indicate life, and they frequently include abundant gases in our planet’s atmosphere.

Scientists at UC Riverside suggest something is missing from the typical roster of chemicals astrobiologists use to search for life on planets around other stars — laughing gas.

Eddie Schwieterman, an astrobiologist in UCR’s Department of Earth and Planetary Sciences, said, “There’s been a lot of thought put into oxygen and methane as biosignatures. Fewer researchers have seriously considered nitrous oxide, but we think that may be a mistake.”

To reach this conclusion, scientists determined how much nitrous oxide a planet like Earth could conceivably produce. After that, they created simulations of that planet orbiting various types of stars and calculated the amounts of N2O that could be captured by a telescope like the James Webb Space Telescope.

Nitrous oxide, or N2O, is a gas produced in various ways by living things. Microorganisms continuously convert other nitrogen molecules into N2O through a metabolic process that can produce useful cellular energy.

Schwieterman said, “Life generates nitrogen waste products that are converted by some microorganisms into nitrates. In a fish tank, these nitrates build-up, which is why you have to change the water. However, under the right conditions in the ocean, certain bacteria can convert those nitrates into N2O. The gas then leaks into the atmosphere.”

N2O can be found in an environment and still not be an indication of life in some situations. This was considered in the new modeling. For instance, lightning can produce a small amount of nitrous oxide. However, lightning also produces nitrogen dioxide, giving astrobiologists a hint that non-living meteorological or geological processes produced the gas.

Others who have considered N2O as a biosignature gas often conclude it would be difficult to detect from so far away. Schwieterman explained that this conclusion is based on N2O concentrations in Earth’s atmosphere today. Because there isn’t much of it on this planet, which is teeming with life, some believe it would also be hard to detect elsewhere.

Schwieterman said“This conclusion doesn’t account for periods in Earth’s history where ocean conditions would have allowed for the much greater biological release of N2O. Conditions in those periods might mirror where an exoplanet is a today.”

“Common stars like K and M dwarfs produce a light spectrum that is less effective at breaking up the N2O molecule than our sun is. These two effects combined could greatly increase the predicted amount of this biosignature gas on an inhabited world.”

The study was conducted in collaboration with Purdue University, the Georgia Institute of Technology, American University, and the NASA Goddard Space Flight Center.

Journal Reference:

  1. Edward W. Schwieterman, Stephanie L. Olson et al. Evaluating the Plausible Range of N2O Biosignatures on Exo-Earths: An Integrated Biogeochemical, Photochemical, and Spectral Modeling Approach. The Astrophysical Journal. DOI: 10.3847/1538-4357/ac8cfb

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Russian launches to space from U.S., 1st time in 20 years

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CAPE CANAVERAL, Fla. –

For the first time in 20 years, a Russian cosmonaut rocketed from the U.S. on Wednesday, launching to the International Space Station alongside NASA and Japanese astronauts despite tensions over the war in Ukraine.

Their SpaceX flight was delayed by Hurricane Ian, which ripped across the state last week.

“I hope with this launch we will brighten up the skies over Florida a little bit for everyone,” said the Japan Space Agency’s Koichi Wakata, who is making his fifth spaceflight.

Joining him on a five-month mission are three new to space: Marine Col. Nicole Mann, the first Native American woman to orbit Earth; Navy Capt. Josh Cassada and Russia’s lone female cosmonaut, Anna Kikina.

“Awesome! said Mann as they reached orbit. “That was a smooth ride uphill. You’ve got three rookies who are pretty happy to be floating in space right now.”

They’re due to arrive at the space station Thursday, 29 hours after a noon departure from NASA’s Kennedy Space Center, and won’t be back on Earth until March. They’re replacing a U.S.-Italian crew that arrived in April.

Kikina is the Russian Space Agency’s exchange for NASA’s Frank Rubio, who launched to the space station two weeks ago from Kazakhstan aboard a Soyuz rocket. He flew up with two cosmonauts.

The space agencies agreed over the summer to swap seats on their flights in order to ensure a continuous U.S. and Russian presence aboard the 260-mile-high (420-kilometre-high) outpost. The barter was authorized even as global hostilities mounted over Russia’s invasion of Ukraine in late February. The next crew exchange is in the spring.

Shortly before liftoff, NASA Administrator Bill Nelson said that the key reason for the seat exchange is safety — in case an emergency forces one capsule’s crew home, there would still be an American and Russian on board.

In the meantime, Russia remains committed to the space station through at least 2024, Russia space official Sergei Krikalev assured reporters this week. Russia wants to build its own station in orbit later this decade, “but we know that it’s not going to happen very quick and so probably we will keep flying” with NASA until then, he said.

Beginning with Krikalev in 1994, NASA started flying cosmonauts on its space shuttles, first to Russia’s Mir space station and then to the fledgling space station. The 2003 Columbia reentry disaster put an end to it. But U.S. astronauts continued to hitch rides on Russian rockets for tens of millions of dollars per seat.

Kakina is only the fifth Russian woman to rocket off the planet. She said she was surprised to be selected for the seat swap after encountering “many tests and obstacles” during her decade of training. “But I did it. I’m lucky maybe. I’m strong,” she said.

Mann is a member of the Wailacki of the Round Valley Indian Tribes in California, and taking up her mother’s dream catcher, a small traditional webbed hoop believed to offer protection. Retired NASA astronaut John Herrington of the Chickasaw Nation became the first Native American in space in 2002.

“I am very proud to represent Native Americans and my heritage,” Mann said before the flight, adding that everyone on her crew has a unique background. “It’s important to celebrate our diversity and also realize how important it is when we collaborate and unite, the incredible accomplishments that we can have.”

As for the war in Ukraine, Mann said all four have put politics and personal beliefs aside, “and it’s really cool how the common mission of the space station just instantly unites us.”

Added Cassada: “We have an opportunity to be an example for society on how to work together and live together and explore together.”

Elon Musk’s SpaceX has now launched eight crews since 2020: six for NASA and two private groups. Boeing, NASA’s other contracted taxi service, plans to make its first astronaut flight early next yea r, after delays to fix software and other issues that cropped up on test flights.

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The Associated Press Health and Science Department receives support from the Howard Hughes Medical Institute’s Department of Science Education. The AP is solely responsible for all content

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