Abstract The use of non-toxic or less-toxic solvents in the mass production of solution-processed perovskite solar cells is essential. However, halide perovskites are generally not completely soluble in most non-toxic solvents. Here we report the deposition of dense and uniform α-formamidinium lead triiodide (α-FAPbI3) films using perovskite precursor solutions dissolved in ethanol-based solvent. The process does not require an antisolvent dripping step. The combination of a Lewis base, such as dimethylacetamide (or dimethylsulfoxide), and an alkylammonium chloride (RNH3Cl) in ethanol results in the stable solvation of FAPbI3. The RNH3Cl added to the FAPbI3 precursor solution is removed during spin-coating and high-temperature annealing via iodoplumbate complexes, such as PbI2·RNH2 and PbI2·HCl, coordinated with dimethylacetamide (or dimethylsulfoxide). It is possible to form very dense and uniform α-FAPbI3 perovskite films with high crystallinity by combining several types of RNH3Cl. We obtain power conversion efficiencies of 24.3% using a TiO2 electrode, and of 25.1% with a SnO2 electrode. The use of non-toxic or less-toxic solvents is the key to facilitate the mass production of solution-processed perovskite solar cells (PSCs). However, halide perovskites are generally not completely soluble in most non-toxic solvents, according to the research team. A research team, led by Distinguished Professor Sang Il Seok in the Department of Chemistry at UNIST has reported the deposition of dense and uniform α-formamidinium lead triiodide (α-FAPbI3) films using perovskite precursor solutions dissolved in ethanol-based solvent. Leveraging this, the research team succeeded in fabricating high-efficiency PSCs with power conversion efficiencies (PCEs) that exceed 25%. Such findings have been published in the August 2022 issue of Nature Energy (Impact Factor: 67.439), a renowned journal in the field of energy. Vanadium dioxide (VO2) is one of the most promising materials for active metasurfaces due to the insulator-metal transition, urging the development of an etching-free patterning method and realization of multifunctionality in various spectral bands. "This study can improve the current record efficiency of perovskite solar cells from 20.1% to 22.1%," says the research team. In this study, the research team deposited dense and uniform α-FAPbI3 perovskite films using EtOH-based perovskite precursor solutions without using anti-solvent during spin coating. "It was possible to manufacture a perovskite thin film with high density, uniformity, and excellent crystallinity by optimizing a combination of binders that can control the speed of volatilization with a solvent during coating and thermal treatment," said Seok, a professor of energy and chemical engineering at the Ulsan National Institute of Science and Technology (UNIST). In October 2021, Seok set a new record of 25.8 percent in the power conversion efficiency of perovskite solar cells by forming a coherent interlayer between electron-transporting and perovskite layers to reduce interfacial defects. Efforts have focused mainly on surface passivation, but passivating the perovskite surface is difficult because surface-treatment agents on the electron-transporting layer may dissolve while coating the perovskite thin film. Figure 1. Researcher is holding the EtOH-based FAPbI3 and PbI2. precursor solutions. "Perovskite solar cell research has focused on improving efficiency and stability, but now it is more important to conduct research on the foundation for commercialization to reduce or eliminate the use of toxic solvents," Seok said. "This study is the starting point for solving such a problem." The deposition of dense and uniform α-formamidinium lead triiodide (α-FAPbI3) films was possible using perovskite precursor solutions dissolved in an ethanol-based solvent, Seok's team said in a research paper published on the website of Nature Energy, a peer-reviewed scientific journal. The combination of dimethylacetamide (or dimethylsulfoxide) and an alkylammonium chloride in ethanol resulted in the stable solvation of FAPbI3, the paper said, adding that it's possible to form "very dense and uniform" α-FAPbI3 perovskite films with high crystallinity by combining several types of alkylammonium chloride. The research team has obtained a power conversion efficiency of 24.3 percent using a titanium dioxide (TiO2) electrode and 25.1 percent with a stannic oxide (SnO2) electrode. Unlike silicon solar cells, which are restricted from installation locations, perovskite solar cells can be installed on the exterior walls of buildings or on the sunroof of vehicles. South Korean companies and researchers have tried to develop new technologies such as tandem cells that build perovskite on top of silicon solar cells. Tandem solar cells can be individual cells or connected in series, which are simpler to fabricate but the current is the same through each cell. Professor Seok opened a joint laboratory with South Korea's Hyundai auto group in June 2022 for a three-year study to develop high-efficiency, large-area perovskite-silicon tandem cells and apply them to vehicle roofs containing solar panels, which are a relatively new phenomenon that promises to use renewable energy to add some charge to car batteries. Journal Reference Hyun-Sung Yun, Hyoung Woo Kwon, Min Jae Paik, et al., "Ethanol-based green-solution processing of α-formamidinium lead triiodide perovskite layers," Nat. Energy, (2022).

Abstract Excessive precipitation over the southeastern tropical Pacific is a major common bias that persists through generations of global climate models. While recent studies suggest an overly warm Southern Ocean as the cause, models disagree on the quantitative importance of this remote mechanism in light of ocean circulation feedback. Here, using a multimodel experiment in which the Southern Ocean is radiatively cooled, we show a teleconnection from the Southern Ocean to the tropical Pacific that is mediated by a shortwave subtropical cloud feedback. Cooling the Southern Ocean preferentially cools the southeastern tropical Pacific, thereby shifting the eastern tropical Pacific rainbelt northward with the reduced precipitation bias. Regional cloud locking experiments confirm that the teleconnection efficiency depends on subtropical stratocumulus cloud feedback. This subtropical cloud feedback is too weak in most climate models, suggesting that teleconnections from the Southern Ocean to the tropical Pacific are stronger than widely thought. The effect of the Antartic climate change on the changes in the sea surface temperature in the Pacific Ocean has been identified. Since an increase in the average global sea surface temperature (SST) could have profound impacts on climate and weather systems, their findings are expected to be of great help in improving climate forecasts in the mid-latitude, as well as future climate predictability. A research team, led by Professor Sarah Kang in the Department of Urban and Environmental Engineering at UNIST, has recently demonstrated the Southern Ocean–driven teleconnection mechanism mediated by subtropical low cloud feedback, which is erroneously weak in climate models. This suggests that the impact of the Southern Ocean bias on the tropical precipitation bias is likely to be stronger than recent studies suggest, noted the research team. Figure. The impact of Southern Ocean cooling on the tropical Pacific. Their findings have been published in the August 2022 issue of PNAS. This work has been supported by the National Research Foundation of Korea (NRF), funded by the Ministry of Science and ICT of South Korea. Journal Reference Hanjun Kim, Sarah M. Kang, Jennifer E. Kay, et al., "Subtropical clouds key to Southern Ocean teleconnections to the tropical Pacific," PNAS, (2022).

The challenge to increase the micro-device integration density that determines semiconductor performance is ongoing. Professor Hyeon Suk Shin in the Department of Chemistry has developed a technology capable of synthesizing multiple layers of hexagonal boron nitride, the only 2D insulator, in the form of a single crystal thin film for the first time globally, charting the technological path of next-generation semiconductors. From the left are Hyeong Joon Kim (Ph.D. candidate), Professor Hyun Suk Shin, and Min Soo Kim (Ph.D. candidate). Emergence of 2D Materials that Can Replace Silicon Semiconductors have advanced at a breakneck speed over the past decades. The prediction of Gordon Moore that the integration density of microchips will double roughly every 24 months was nearly correct. Thus, it was called Moore's Law, which represents the rapid technological growth in the semiconductor industry. However, it seems like Moore's Law is becoming slowly obsolete when we see the current semiconductor development status. Min soo Kim (Ph.D. candidate) in the Department of Chemistry at UNIST. One semiconductor chip contains billions of micro-devices (transistors). To increase the semiconductor performance, micro-devices should be smaller and thinner to fit more in one chip. However, silicon made of 3D materials has a fatal problem that degrades the semiconductor performance and life, such as short channel effect and charge scattering, which causes transistor damage due to current leakage and heating as it becomes smaller. This is because of the dangling bond, which is an incomplete chemical bond at the surface while processing the silicon surface. To solve this problem, the semiconductor industry has researched the use of 2D materials such as molybdenum disulfide (MoS2) instead of using 3D material silicon. The short channel effect and charge scattering, which are found when 3D materials are made smaller, do not occur in 2D materials because their composition atoms are connected in a plane form. Thanks to this, the micro-device integration density and semiconductor performance can keep improving using 2D materials. World's First Technology that Accelerates the Commercialization of 2D Insulators There is one more problem to be solved when 2D materials are used as micro-devices instead of silicon. A wafer, a substrate on which micro-devices are laid, is also made of silicon. Thus, 2D material and wafer should be separated by an insulator to make semiconductors made of 2D materials to exhibit their functions. Here, the insulator should also be made of 2D materials. If the insulator is made of 3D materials, it cannot avoid adanglingbond. Hexagonal boron nitride (hBN) is a unique 2D insulator material, which is known to date, and can prevent semiconductor functional degradation problems, such as charge trap or charge scattering. Its molecular structure is similar to that of graphene, but its color is white, which is also called 'white graphene.' To use hBN as a 2D insulator, it should be synthesized into a single crystal structure where the entire crystal is regularly generated along a certain crystalline axis. Previously, there were cases of synthesis of a single crystal of hBN of which size can be commercialized. However the thickness of all synthesis was a layer of an atom, which could not function as an insulator. Professor Shin and his research team in the Department of Chemistry at UNIST. The synthesis of hBN developed by Professor Hyeon Suk Shin and his research team in the Department of Chemistry at UNIST is a ground breaking technology that can stack single crystal hBN thin films in multiple layers. It is the world's first synthesis technology that can make a single crystal hBN thin film at a preferred thickness while finely adjusting the concentration of the raw material on the nickel substrate. The paper titled 「Epitaxial single crystal hexagonal boron nitride multi-layers on Ni(111)」 that dealt with this research was published in the global academic journal Nature on June 2, 2022. Contributing to Innovation in the Semiconductor Industry with Relentless Challenges The synthesis method of single crystal multilayer hBN thin film developed by the team led by Professor Shin is not just a coincidence. Professor Shin has steadily conducted a study on the synthesis and application of hBN since 2012. In 2020, he disclosed that amorphous boron nitride, which is a kind of boron nitride, is an ultralow dielectric material that prevents the signal transmission delay in high-density semiconductors, and published this research achievement in the journal Nature. "Amorphous boron nitride was discovered in 2018 when I studied hBN. Its dielectric constant was very low at 2.0 or lower so I found it could be used as a dielectric that blocked electrical interference when semiconductors were miniaturized during my research of two years. Since then, research and development have been conducted on the commercialization of amorphous boron nitride by many semiconductor companies. We expect that the synthesis method of single crystal multi-layer hBN thin film will play a significant role in improving semiconductor technology." "We were successful in synthesizing single crystal hBN thin film at multiple layers, but for commercialization, we still need one more technology to be developed. That is a technology that transfers an hBN thin film synthesized on a nickel substrate onto a wafer without damage," noted Professor Shin. The research team is now spurring research on this. Professor Shin added, "Once this technology is developed, it can be used to transfer not only hBN thin films but also various 2D materials." The team plans to widen its research even on application chemical areas using hBN in addition to the foundational research related to hBN. We hope their efforts will lead to the innovation of semiconductors.

Gold, a precious metal, is arguably the most widely used metal across jewelry and coinage due to its physical properties that are unique to the world of metals. Not only is it a good conductor of heat and electricity, it is unaffected by air and most reagents. It is also used in a wide range of industrial, scientific, and medical applications. For example, it has been used as the template for molecular self-assembly, the supporting material for two-dimensional materials growth, and especially for the synthesis of carbon nanoribbons. More than half a century ago, researchers unveiled the fancy textures on gold surfaces at the nanoscale. Efforts for a better understanding of the surface structures on the atomic scale have been continually paid for from then on. Au(111) surface, the most stable gold surface, has a periodic herringbone texture on it that can be observed by sophisticated microscopes (See Figure 1A). A long-term puzzle is why this strange herringbone forms on this gold surface. Extensive studies have been performed for decades but a thorough description of structure details is still missing and thus the underlying mechanism has never been properly understood. The difficulties in this issue lie in the fact that even though the size of the texture is at the nanoscale, its periodic unit still contains more than 100,000 atoms. To quantitatively study this system, one needs a very efficient and also very accurate computational method. In traditional approaches, however, these two requirements cannot be satisfied simultaneously. Recently, Distinguished Professor Feng Ding (Department of Materials Science and Engineering) and his colleagues from the Center for Multidimensional Carbon Materials (CMCM), within the Institute for Basic Science (IBS) at UNIST, utilized the state-of-the-art neural network method to train a gold force field from an accurate but slow computational method. Due to the powerful learning ability of neural networks, this new force field acquires almost the same accuracy, and more importantly, it is many orders of magnitude faster than the original method. Using this force field, the authors successfully simulated the experimentally observed herringbone texture on Au(111) surface and revealed that there is non-negligible deformation underneath the surface. This deformation is critical for the formation of the herringbone texture because it allows an effective relaxation of the rearranged surface atoms. If the deformation is suppressed (take a thin model for instance), the texture will become stripes, as shown in Figure 1(A). Figure 1. (A) From left to right are the experimentally observed herringbone texture, and the simulated herringbone and stripe textures on thick and thin models respectively. (B) Effect of strain on textures. The simulated textures are shown in color and the observed textures are shown in grey. Meanwhile, the authors also verified that the herringbone texture is sensitive to applied strains. On a strain-free surface, the herringbone texture is mirror-symmetric. However, if a slight strain is introduced, the texture becomes tilted (Figure 2B). Above a critical strain, it thoroughly transforms into a stripe texture. "This important work extends the application of the machine learning method in material science and opens a new avenue to study complex surface systems," noted the research team. Led by Distinguished Professor Feng Ding, this study was first authored by Dr. Pai Li. The findings of this research have been published in the October 2022 issue of the prestigious Science Advances. Journal Reference Pai Li, Feng Ding., "Origin of the herringbone reconstruction of Au(111) surface at the atomic scale" Science Advances, (2022).

Abstract As the global recycling industry has collapsed since the China import ban of 2017, the amount of plastic waste has been rapidly increasing with little to no economic incentives for its utilization as a feedstock. For the first time, this work demonstrates a proof of concept, pilot-scale cogeneration system for biomass heating and plastic-derived pyrolytic oil production (MacroConverter ®). Furthermore, a disruptive techno-economic business model for decentralized plastic pyrolysis is assessed and compared with a traditional centralized industrial system through superstructure supply-chain optimization. Results of this initial assessment indicate that using a decentralized plastic pyrolysis model, combined with seasonal heating demand, profitability can be increased (1.3–2.4 x) and the process is unlikely to show a loss of profit whereas the centralized process may show losses. Furthermore, compared to centralized pyrolysis, transportation costs, and related CO2 emissions were significantly decreased by 3–10 x and 1.4–7 x respectively. Thermal pyrolysis of plastics has drawn considerable attention as a reliable and emerging technology for resource recycling since it can create valuable by-products in the process. A recent study reported that using a decentralized plastic pyrolysis model, combined with seasonal heating demand, profitability can be increased and the process is unlikely to show a loss of profit when compared to the centralized process. This breakthrough has been led by Professor Hankwon Lim in the School of Energy and Chemical Engineering at UNIST. Figure 1. Decentralized pyrolysis unit material and energy balance. In this work, for the first time, the research team demonstrated a proof of concept, pilot-scale cogeneration system for biomass heating and plastic-derived pyrolytic oil production. The research team further assessed a disruptive techno-economic business model for decentralized plastic pyrolysis. They, then, compared it with a traditional centralized industrial system through superstructure supply-chain optimization. Figure 2. Waste plastics processed (a), the annual net profit (b), and the feedstock transport related CO2 emission (c) for centralized and decentralized processes denoted in yellow and purple respectively. Their findings revealed that using a decentralized plastic pyrolysis model, combined with seasonal heating demand, profitability can be increased and the process is unlikely to show a loss of profit whereas the centralized process may show losses. Furthermore, compared to centralized pyrolysis, transportation costs, and related CO2 emissions were significantly decreased by 3–10 x and 1.4–7 x respectively, according to the research team. Their findings have been published in the August 2022 issue of Journal of Cleaner Production. This study has been carried out in collaboration with researchers from Lahore University of Management Sciences in Pakistan. Journal Reference Manhee Byun, Rofice Dickson, Boris Brigljević, et al., "Demonstration of feasible waste plastic pyrolysis through decentralized biomass heating business model," J. Clean. Prod. (2022).

Abstract Langevin field-theoretic simulation (L-FTS) is a promising tool in polymer field theory that can account for the compositional fluctuation effect, which is neglected in the self-consistent field theory (SCFT). However, L-FTS is a computationally expensive tool, and it may take more than a week to accurately calculate ensemble averages of thermodynamic quantities. In our previous study, we introduced a deep neural network (DNN) that estimates the saddle point of the pressure field to reduce the subsequent Anderson mixing (AM) iterations. Herein, we propose a novel DNN that can be successively applied to determine the saddle point without using conventional field-update algorithms. Major deep learning (DL) models for semantic segmentation in computer vision are adopted to construct the optimal DNN architecture. Our model utilizing atrous convolutions in parallel is accurate and computationally efficient, and it is robust to the simulation parameter changes and can consequently be reused after single training. We demonstrate that our DNN can achieve speedup of factor 6 or more compared to the AM method without affecting accuracy. Open-source code for our deep Langevin FTS (DL-FTS) enables an easy and rapid Python scripting of SCFT and L-FTS incorporated with CPU or GPU parallelization and DL. A research team, affiliated with UNIST has proposed a novel deep neural network (DNN) that can be successively applied to determine the saddle point without using conventional field-update algorithms. Their findings are now made freely available to the public. They are expected to contribute to the developments in polymer field-based simulations, according to the research team. This breakthrough has been led by Professor Jaeup U. Kim and his research team in the Department of Physics at UNIST. In this work, the research team proposed a new deep learning (DL) approach that predicts the difference between the input and saddle-point pressure fields. According to the research team, their NN is designed to retain its predictive power at various incompressibility error levels so that it is less sensitive to the Langevin step interval. "[The new] approach completely replaces the conventional field-update algorithms with deep NN so that the saddle point search can be completed without conventional relaxation methods, such as AM," said the research team. "Consequently, the performance is greatly enhanced because our new approach utilizes the predictive power of NN several times during each Langevin step." Figure 1. Comparison between Anderson Mixing (AM) and Deep Learning (DL). Above shows the two-dimensional slices of the ground truth ΔW+(r) and predictions of DL and AM, respectively, where the ground truth denotes an ideal output for the ML model. The findings of this study have been published in the August 2022 issue of Macromolecules. This research was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of the Ministry of Science and ICT (MSIT) and the Sejong Science Fellowship. Journal Reference Daeseong Yong and Jaeup U. Kim, "Accelerating Langevin Field-Theoretic Simulation of Polymers with Deep Learning," Macromolecules, (2022).

Abstract Removal of gas bubbles from the electrode surface is practically important to maintain the activity of electrochemical gas evolution reactions. Conventionally, most studies have focused on the development of electrocatalysts and paid less attention to the bubble removal issues. Recently, it has been reported that attached gas bubbles can be readily eliminated by imparting extremely gas-repellent properties (so-called superaerophobicity) to electrodes via controlling their nano/microstructure. However, this approach is material-specific and requires harsh and expensive synthetic conditions, causing difficulties in scaling up to large-area electrodes for commercialization. To address these issues, a universal method to impart superaerophobicity to various electrodes through simple coating with porous polymeric hydrogels without affecting the underlying target substrates is reported. The modification of electrodes with superaerophobic polymeric hydrogel substantially enhances the efficiency of the hydrogen evolution reaction because the hydrogel can facilitate the removal of as-generated gas bubbles and thereby minimize ohmic and concentration overpotentials. Particularly, electrodes modified with the superaerophobic hydrogel outperform those modified with electrocatalysts at high current densities where more gas bubbles are generated and adhered to. The results provide insights into the design of various electrochemical devices that are based on gas-involving reactions. A research team, affiliated with UNIST recently reported that the performance of electrodes for alkaline hydrogen evolution reaction (HER) can be significantly improve even without expensive electrocatalysts and complicated processes by modifying them with superaerophobic polymeric hydrogels. This breakthrough has been led by Professor Jungki Ryu and his research team in the Department of Energy Engineering at UNIST. Figure 1. The scheme for a mechanism of bubble-detachment. a) Normal flat electrode, b) the problems of adhered bubbles, and c) various approaches for the removal of gas bubbles. In (a), R, ρ, g, and λ indicate the dimension of bubbles, the density of a solution, gravitational acceleration constant, and surface tension of a solution, respectively. In this study, the research team reported a simple strategy to enhance the efficiency of electrochemical hydrogen production by imparting superaerophobicity to an underlying electrode with porous polymeric hydrogels. Superaerophobic hydrogels were readily coated on target substrates by cross-linking polyethyleneimine (PEI) via Schiff-base condensation reactions followed by freeze-drying, noted the research team. As a result, they could readily control the pore size, porosity, and superaerophobicity of the hydrogel-coated electrodes by varying the concentrations of PEI upon cross-linking. Due to facile removal of as-generated hydrogen bubbles, the NF electrode modified with PEI hydrogel only outperformed those modified with expensive electrocatalysts especially at high current densities, according to the research team. "We believe that our results can pave the way for the practical application of water electrolysis by providing insights into the design of electrodes and electrolyzers," noted the research team. Figure 2. Their findings have also been featured as a front cover of Advanced Energy Materials on August 4, 2022. This study has been participated by Misol Bae in the Department of Energy Engineering at UNIST. Published in the August 2022 issue of Advanced Energy Materials, their findings have also been featured as a front cover. Journal Reference Misol Bae,Yunseok Kang,Dong Woog Lee, et al., "Superaerophobic Polyethyleneimine Hydrogels for Improving Electrochemical Hydrogen Production by Promoting Bubble Detachment," Adv. Energy Mater., (2022).

Abstract Ischemic stroke is the leading cause of immortal disability and death worldwide. For treatment in the acute phase, it is necessary to control excessive reactive oxygen species (ROS) damage during ischemia/reperfusion (I/R). Microglia are well known to be closely associated with excessive ROS response in the early stage of I/R. However, the precise roles of microglia associated with mitigating ROS damage, and molecular markers of heterogenetic microglia in the I/R damaged brain has not been clarified. Here, we identified a new type of microglia associated with stroke in the I/R injured brain. Single-cell RNA sequencing (scRNA-seq) was used to assess transcriptional changes of microglia and immune cells in the contralateral (CL) and ipsilateral (IL) hemispheres after transient middle cerebral artery occlusion (tMCAO) surgery to mimic ischemic stroke. We classified a unique type of microglia with enhanced antioxidant function and markers similar to those of disease-associated microglia (DAM), designated them as stroke-associated microglia (SAM). The representative antioxidant enzyme, Peroxiredoxin-1 (Prdx1), was predominantly expressed in SAM and mediated ROS defense genes, including Txn1, Srx1, Mt1, and Mt2. In the Prdx1−/− I/R damaged brain, we observed significantly increased infarction, as assessed by TTC staining, and FACS analysis detected severe microglial cell death. Importantly, scRNA transcriptomics data showed that the SAM population was specifically decreased in Prdx1−/− mice and that these mice exhibited decreased ROS damage resistance. Inflammatory responses which were detected by ELISA and qPCR, were also increased in Prdx1−/− IL hemispheres. Finally, Prdx1-dependent antioxidative SAM were found to be essential for increasing the transcription levels of stroke-protective molecules, such as osteopontin and ferritin. A novel microglia type (SAM) is specifically activated in response to stroke I/R injury, and that Prdx1 expression is required for the activation and enhanced antioxidant function of SAM. A research team, affiliated with UNIST has identified a new type of microglia associated with stroke in the ischemia/reperfusion (I/R) injured brain. This breakthrough has been led by Professor Sung Ho Park and his research team in the Department of Biological Sciences at UNIST, in collaboration with a research team, led by Professor Goo Taeg Oh from Ewha Womans University. Microglia, the primary immune cells in the central nervous system (CNS), are known to eliminate unwanted germs and debris and remove dying neurons. In this study, the research team classified a new type of microglia with enhanced antioxidant function and markers similar to those of disease-associated microglia (DAM), designated them as stroke-associated microglia (SAM). Through animal experiments, the research team demonstrated that the presence of the typical antioxidant gene, Peroxiredoxin-1 (Prdx1), protects against acute I/R injury and is required for SAM activation and the consequent reduction of microglial cell death and inflammatory responses. In addition, after performing transient middle cerebral artery occlusion (tMCAO) surgery to induce ischemic stroke in mice, the research team found that Prdx1−/− mice were more severely injured by acute I/R injury, as confirmed by TTC staining, neurological deficit scores, motor tests, and the survival rate, indicating that Prdx1 has a protective function. Figure 1. Peroxiredoxin1 (Prdx1) is essential for SAM activation after stroke damage. (Left) UMAP plots showing clusters and annotations of cells identified in Prdx1+/+ and Prdx1−/− IL hemispheres after tMCAO. (Right) Representative images of TTC stained brain slices of Prdx1+/+ (n = 18) and Prdx1−/− (n = 22) mice. "In this study, we have, for the first time, identified a specialized and distinctive type of microglia with enhanced antioxidant function in stroke mice," says Professor Park. "Prdx1-dependent SAM may be a potential biomarker and therapeutic target for protecting microglial function and treating brain I/R injury," He adds, "Although this new cluster will require further study, our findings provide a new perspective that Prdx1-mediated microglial heterogeneity is important in ischemic stroke." This study has been jointly participated by Wonhyo Lee, a doctoral researcher within the Department of Biological Sciences at UNIST and Sinai Kim, a doctoral researcher within the Department of Life Sciences at Ewha Womans University, as first authors. Their findings have been published in the August 2022 issue of Redox Biology, a renowned journal in the areas of both health and disease. This study was carried out with the support of the National Research Foundation of Korea (NRF). Journal Reference Sinai Kim, Wonhyo Lee, Huiju Jo, et al., "The antioxidant enzyme Peroxiredoxin-1 controls stroke-associated microglia against acute ischemic stroke," Redox Biology, (2022).

Abstract Two-dimensional Ruddlesden–Popper (RP) phase perovskites are gaining increasing attention for passivating the defects of the bulk absorber layer in perovskite solar cells (PSCs). However, owing to their anisotropic structural features, the RP perovskite orientation substantially influences the charge transport efficiency, and thereby the PSC performance. We demonstrate the use of a highly oriented butylammonium RP perovskite as a surface passivation layer with bottom-up growth on the bulk perovskite absorber layer via vacuum deposition. In this process, the crystal formation time directly affects the crystallographic orientation of the passivation layer. By leveraging the passivating properties and controlled crystallinity, the RP perovskite considerably reduces the trap density of bulk perovskite and enhances the charge transport, reaching 21.4% of power conversion efficiency for vacuum-processed PSCs and improving the operational stability. The proposed passivation strategy allows the growth of highly oriented RP phase perovskite passivation layers toward the development of efficient, stable, and scalable PSCs. A research team, led by Professor Hyesung Park in the Department of Materials Science and Engineering at UNIST has succeeded in manufacturing potentially high efficiency, stable, and scalable perovskite solar cells (PSCs) via vacuum deposition apparatus, a method of fabricating organic light-emitting display devices (OLEDs). Such method is also advantageous for the mass production of batteries, which is expected to further accelerate the commercialization of the PSCs, according to the research team. Figure 1. Schematic of inverted PSCs with a passivation layer. In this study, the research team demonstrated highly efficient and stable PSCs with a vacuum-processed Ruddlesden–Popper (RP) phase perovskite passivation layer. By controlling the deposition rate of the RP phase perovskite, which directly influenced its crystallographic orientation, the research team successfully obtained a highly ordered 2D perovskite passivation layer. The 2D perovskite layer passivated the bulk perovskite defects and promoted the charge transport efficiency in the PSC. As a result, the BABr (V) inverted PSC has achieved a champion PCE of 21.4% in the resulting device with outstanding humidity and thermal stability. This number is by far the highest ever achieved for PSCs formed by vacuum deposition. In addition, it showed enhanced long-term operational stability, such as maintaining 62% of its initial PCE (average) when operated for for 1,000 hours under 60–70% relative humidity at room temperature, even without device encapsulation. "Our findings provide a new perspective toward further improving the performance of PSCs by mitigating nonradiative recombination pathways in perovskites," noted the research team. Figure 2. Schematic of the perovskite crystal structure and charge transport for (a) control, (b) BABr (S), and (c) BABr (V) films. The findings of this research were made available in June 2022, ahead of its publication in the journal, Energy & Environmental Science (ESS, IF = 39.714). This study has been supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF), funded by the Ministry of Science and ICT (MSIT). Journal Reference Yunseong Choi, Donghwan Koo, Gyujeong Jeong, et al., "A vertically oriented two-dimensional Ruddlesden–Popper phase perovskite passivation layer for efficient and stable inverted perovskite solar cells," Energy Environ. Sci., (2022)