탄소중립대학원

2026년 09월 08일 화요일

Perovskite Solar Cells Hold Up Under Extreme Temperature Swings

Summary The advent of self-assembled monolayer (SAM)-based hole-selective layers (HSLs) has revolutionized inverted perovskite solar cells (i-PSCs) by enabling record efficiencies, but they are constrained by incomplete surface coverage and interfacial heterogeneity. We devise topology-governed SAMs featuring isomeric linker patterns (LY-ortho [o], LY-meta [m], and LY-para [p]) and uncover the principle that conformational ordering dictates surface coverage and interfacial interaction coupling with perovskite. The topology-optimized LY-m forms a homogeneously dense, stable HSL with superior energy alignment and interfacial passivation. Devices incorporating LY-m achieve a record-high open-circuit voltage of 1.231 V, accompanied by an efficiency of 26.39% (certified 26.37%), while maintaining robust operational stability and scalability. Beyond laboratory metrics, LY-m-based devices withstand −100°C to 100°C thermal cycling with only ∼9% loss, far exceeding the operational limits of state-of-the-art commercial SAMs, while maintaining over 80% of their initial performance at 85°C (T80 ≅ 2,000 h). This work resolves the long-standing role of linker topology and paves the way for extreme-environment-resilient and scalable perovskite photovoltaics. Temperature swings are a major challenge for perovskite solar cells (PSCs), particularly in environments such as space, where materials may repeatedly move between extreme cold and heat. Led by Professors Changduk Yang and Seungjae Shin of the Department of Energy and Chemical Engineering and Professor Myung Hoon Song of the Department of Materials Science and Engineering at UNIST, the team developed perovskite solar cells that withstand such extremes by stabilizing a critical molecular interface. The cells retained about 91% of their initial efficiency after cycling between −100°C and +100°C, with a certified power-conversion efficiency of 26.37%. The key to this advancement is a self-assembled monolayer (SAM), a molecule-thin layer that helps move electrical charges between the electrode and the perovskite absorber. Under severe thermal stress, SAM molecules can shift or cluster, disrupting the interface and degrading performance. The team addressed this problem by changing where the molecular components of the SAM connect. They synthesized three versions with different linker positions and found that LY-m adopted a tilted orientation, allowing its molecules to pack densely and uniformly on the electrode. This arrangement also suppresses the molecular reorganization that can occur under large temperature swings. In thermal-cycling tests, LY-m cells were held alternately at −100°C and +100°C for 30 minutes at each temperature over 16 cycles. They remained operational with only about a 9% loss in efficiency, while cells using a commercial SAM failed under the same conditions. LY-m cells also reached a peak efficiency of 26.39%, with a certified efficiency of 26.37% and an open-circuit voltage of 1.231 V. At 85°C, they maintained more than 80% of their initial performance for approximately 2,000 hours. The approach also performed well at larger scales: a 1 cm² cell achieved 23.25% efficiency, while a 3 × 1 cm² mini-module reached 21.20%. “By changing only the position of the molecular connection, we were able to control how the molecules pack on the electrode,” said Professor Yang. “The resulting interface combines high efficiency with thermal stability, offering a promising route toward perovskite photovoltaics for environments with extreme temperature variations.” The study has been participated by Seunglok Lee and Jeewon Park of the Department of Energy and Chemical Engineering and Jingyu Yang of the Department of Materials Science and Engineering at UNIST, as co-first authors of the study. Published in Joule on August 3, the study has been supported by the Nano & Material Technology Development Program through the National Research Foundation (NRF) of Korea and the InnoCORE program of the Ministry of Science and ICT (MSIT). Journal Reference Seunglok Lee, Jinkyu Yang, Jeewon Park, et al., "Topology-governed self-assembled monolayers enable perovskite solar cells stable at −100°C to +100°C," Joule , (2026).

2026년 09월 03일 목요일

Reducing Charge Loss in Organic Photoanodes for Solar Water Splitting

Abstract Organic photoelectrochemical (PEC) cells for solar water splitting typically utilize bulk heterojunction (BHJ) structures to circumvent the intrinsically short exciton diffusion lengths of organic semiconductors. However, stochastic donor/acceptor networks in BHJs often result in disordered interfacial contacts, leading to severe charge recombination. Herein, we report a pseudo-bilayer (PS-Bi) organic photoanode featuring a vertically ordered donor–acceptor configuration established via sequential deposition. Our systematic investigation reveals that this PS-Bi structure promotes selective charge transport and suppresses recombination due to its high domain purity, thereby facilitating efficient charge transfer at the interface. Consequently, the optimized PS-Bi photoanodes deliver an enhanced average photocurrent density (Jph) of 1.75 ± 0.03 mA cm−2 at 1.23 V versus the reversible hydrogen electrode for solar water oxidation, while simultaneously exhibiting a significant cathodic onset shift and extended operational stability compared to their BHJ counterparts (Jph = 1.44 ± 0.07 mA cm−2). This study demonstrates that employing the PS-Bi structure is a promising strategy for achieving high-performance and stable organic PEC systems for sustainable solar fuel production. Producing hydrogen from sunlight depends in part on how efficiently a photoelectrode can separate and move electrical charges. In organic photoelectrodes, however, the conventional practice of mixing semiconductor materials can create disordered pathways that allow those charges to recombine, reducing both performance and stability. A research team, led by Professors Han Hee Cho, Moon Kee Choi, and Myung Hoon Song of the Department of Materials Science and Engineering at UNIST, working with researchers at École Polytechnique Fédérale de Lausanne (EPFL), has developed an organic photoanode with a more ordered internal structure. The new design improved photocurrent by about 22% while extending operational stability. The team created what is known as a pseudo-bilayer (PS-Bi) structure by depositing two organic semiconductor materials in sequence. As the second layer is applied, it partially penetrates the first, forming a mixed region at the interface while preserving more distinct layers above and below. Conventional organic photoelectrodes typically use a bulk heterojunction (BHJ), in which donor and acceptor materials are mixed throughout the film. This arrangement helps generate and separate charges, but its irregular internal pathways can also bring electrons and holes back together before they contribute to the chemical reaction. The PS-Bi combines the advantages of both approaches. Charges are generated and separated in the mixed region, while the more ordered layers guide electrons and holes in different directions. This reduces recombination and allows more of the generated charge to drive water oxidation. In tests, the PS-Bi photoanodes achieved an average photocurrent density of 1.75 mA cm⁻², compared with 1.44 mA cm⁻² for conventional BHJ photoanodes, an increase of about 22%. The voltage required to initiate water oxidation also fell from 0.35 V to 0.15 V, allowing the reaction to begin with less external electrical input. The structural change also improved durability. Based on the time required for photocurrent density to fall to 0.5 mA cm⁻², the pseudo-bilayer photoanodes remained operational substantially longer than their BHJ counterparts. The researchers also found that the two structures degrade differently. In BHJ photoanodes, highly reactive holes can damage the organic semiconductor within the intermixed structure. The more ordered pseudo-bilayer reduces damage within the donor–acceptor region, helping the photoanode maintain its performance for longer. “Conventional organic photoelectrodes mix donor and acceptor materials throughout the film, which can lead to charge losses and faster degradation,” said Professor Cho. “By controlling how the two materials are arranged, we were able to improve both charge transport and operational stability.” He further added, “The lower operating voltage could also help in the development of systems that ultimately produce hydrogen using sunlight without an external electrical bias.” The study was published online in Chemical Engineering Journal on July 16, 2026. The research was supported by the National Research Foundation of Korea (NRF), funded by the Ministry of Science and ICT (MSIT), and the InnoCORE program. Journal Reference Gyu Won Chae, Seong Rae Kang, Jin Su Park, et al. , “A pseudo-bilayer organic photoanode for solar water oxidation,” Chem. Eng. J., (2026).

2026년 09월 01일 화요일

Rethinking What Matters

《Editor's Note: What does it take to make something work better? The answer may be to pare back what is unnecessary, rethink how existing parts are arranged, find another route around a constraint, or widen the frame of the problem itself. This month's UNIST research offers answers in many forms—from leaner AI systems and redesigned material structures to an unexpected route for electron transfer and a broader view of cancer drug resistance. Some of those answers run counter to what we might expect. 》 Less Can Be Enough “How much does AI really need?” AI has spent years scaling up. But recent UNIST research asks a different question—how much can be taken away while keeping what matters? At ACL 2026, researchers introduced GMoE, an architecture that shares experts across layers rather than repeatedly storing similar ones. It cut model parameters by about 63 percent, from 549 million to 204 million, while average accuracy remained virtually unchanged—39.51 percent, compared with 39.55 percent for the baseline. The next target was data. Presented at ICML 2026, CSOR removes redundant training images while preserving meaningful variation within each identity. Using roughly half the original dataset, models retained more than 95 percent of full-data performance in re-identification (ReID) tasks. A third study moved to hardware. An automated design framework for logic-in-memory (LiM) computing optimized the placement and routing of computing elements, cutting computation cycles by 19.6 percent under area constraints. ■ GMoE—Expert Sharing for Smaller AI Models (ACL 2026) ■ CSOR—Less Training Data for ReID AI (ICML 2026 ) ■ LiM—Smarter Chip Design (IEEE TCAD) Arrangement Matters “In materials, where can matter as much as what.” More iron, less corrosion. Iron (Fe) is one of magnesium's most damaging impurities, yet UNIST researchers produced a Mg alloy containing more than six times as much Fe as ultra-high-purity Mg—and it still corroded more slowly. Instead of removing the impurity, the team added scandium (Sc) to form core–shell particles that isolate Fe-rich regions from the surrounding Mg. The corrosion rate fell from 22.2 to 0.38 millimeters per year, nearly a 60-fold reduction. At the molecular scale, thermal annealing changed the packing of an organic semiconductor, more than tripling its absorption dissymmetry and even reversing its preferred handedness of circularly polarized light (CPL). The resulting near-infrared (NIR) photodetector achieved a dissymmetry factor of 0.1 at 850 nanometers. The scale shifts again in perovskite solar cells (PSCs). The same high-efficiency formulation crystallized differently depending on the buried interface beneath it. Tailoring the chloride chemistry to the inverted architecture produced a device with 26.3 percent efficiency and a fill factor (FF) of up to 86.8 percent. ■ Mg Alloy—Shielding Fe to Slow Corrosion (Science Advances) ■ NIR Photodetector—Turning Molecular Packing (Advanced Science) ■ PSCs—Why Architecture Changes Performance (Joule) Another Way Through “How spin opens a new route for electron transfer.” Conventional energetics suggested that electron transfer should be unfavorable. Yet in manganese (Mn)-doped quantum dots (QDs), spin-exchange interactions enabled transfer more than ten times faster than in undoped QDs. The mechanism could help capture energetic hot electrons before their excess energy dissipates—a longstanding challenge in photocatalysis and solar-energy conversion. ■ Hot Electrons—Spin-Enabled Transfer (Nature Communications) Beyond the Tumor “The cells helping cancer resist treatment.” Some of the cells helping breast cancer resist treatment are not part of the tumor at all. UNIST researchers found that nearby fat cells can become cancer-associated adipocytes, which release complement factor D and activate survival signaling in cancer cells. In mouse models, disrupting this TRAP1-driven communication improved the response to chemotherapy, pointing to surrounding adipocytes as potential therapeutic targets alongside the tumor itself. ■ Breast Cancer—How Nearby Fat Cells Drive Drug Resistance (STTT) Explore the latest issue and follow 『The UNIST Brief』 on LinkedIn to stay updated. Subscribe via LinkedIn

2026년 08월 28일 금요일

New X-Ray Mapping Technique Enables Non-Destructive Analysis of Large-Area Perovskite Solar Cells

Abstract Scaling perovskite solar cells (PSCs) into large-area modules requires precise control of structural uniformity and mechanical integrity. However, scalable deposition often introduces mesoscale heterogeneities, including grain-orientation disorder and lattice-strain gradients, which limit efficiency and stability. Here, we report an intact-film orthogonal two-dimensional X-ray diffraction mapping (2DXDM) technique that enables full-field, quantitative crystallographic analysis of large-area perovskite films without physical sectioning. The method resolves spatial variations in crystallinity, orientation coherence, and lattice strain across complete modules and is validated against conventional sectioned analyzes such as grazing-incidence wide-angle X-ray diffraction (GI-WAXD) and X-ray diffraction (XRD). Using this approach, we compare static spin-coating (SSC) and dynamic spin-casting (DSC). DSC yields more homogeneous films with relaxed lattice stress and controlled solvate evolution, thereby reducing edge defects. As a result, DSC-based modules achieve 23.0% efficiency (22.7% certified) over 86.4 cm2 and retain over 80% of their initial efficiency after 1,000 h of operation. Perovskite solar cells (PSCs) have reached impressive efficiencies at laboratory scale, but maintaining that performance in larger modules remains challenging. As the films grow larger, differences in crystal orientation and internal strain can develop across the surface, creating defects that reduce efficiency and long-term stability. A research team led by Professors Dong-Seok Kim and Jin Young Kim of the School of Energy and Chemical Engineering and Professor Tae Joo Shin of the Graduate School of Semiconductor Materials and Devices Engineering at UNIST, together with Dr. Yun Seop Shin of the Korea Research Institute of Chemical Technology (KRICT), has developed an X-ray technique that maps these structural variations across an intact perovskite film. Called two-dimensional X-ray diffraction mapping (2DXDM), the technique shows how crystallinity, crystal orientation, and residual strain vary across an entity film without damaging it. Conventional methods often examine selected regions, provide averaged measurements, or require samples to be cut into sections. PSCs are made by depositing a liquid precursor onto a surface, where it dries and crystallizes into a light-absorbing layer. Across a large area, differences in drying and crystallization can leave the center and edges with different structural properties. The researchers used 2DXDM to compare two methods for forming large-area films. In static spin-coating (SSC), the precursor solution is applied before the substrate is spun, while dynamic spin-casting (DSC) deposits the solution drop by drop as the substrate rotates. The resulting maps showed that DSC produced more homogeneous films, with more consistent crystal orientation and lower residual strain. Additional X-ray measurements linked this improvement to better control over colon drying and crystal formation, which helped reduce structural defects near the edges. The more uniform films also delivered strong performance at module scale. DSC-based modules reached a power conversion efficiency of 23.0% over an active area of 86.4 cm², with a certified efficiency of 22.7%. Encapsulated modules retained more than 80% of their initial efficiency after 1,000 hours under continuous illumination. “Conventional methods make it difficult to see how structure varies across an entire film, and cutting a sample for analysis can alter the strain already present” said Professor Shin. “With 2DXDM, we can examine the full area without damaging the film and identify where structural differences occur.” Professor Dong-Seok Kim added, “For large-area perovskite films, what matters is structural uniformity across the entire surface, not just at a few individual points. By showing how fabrication conditions affect that uniformity, this approach can help guide the development of more efficient large-area modules.” Dong Shin Kim of the Graduate School of Semiconductor Materials and Devices Engineering and Jae Hwi Lee of the School of Energy and Chemical Engineering at UNIST, served as first authors. The research used the UNIST-PAL 6D beamline at the Pohang Accelerator Laboratory. The findings were published online in Joule on July 23, 2026. The research was supported by the Ministry of Science and ICT (MSIT), Ministry of Education (ME), National Research Foundation of Korea (NRF), Ministry of Trade, Industry and Energy (MOTIE), Korea Institute of Energy Technology Evaluation and Planning (KETEP), Korea Institute for Advancement of Technology (KIAT), and Korea Research Institute of Chemical Technology (KRICT). Journal Reference Dongshin Kim, Jaehwi Lee, Dongmin Lee, et al ., “Intact-film orthogonal 2D X-ray diffraction mapping for crystallographic homogeneity evaluation in perovskite solar modules,” Joule , (2026).

2026년 08월 26일 수요일

AI Helps Spirulina Grow More Efficiently Across Climates

Abstract Global food security faces unprecedented challenges from climate change and population growth, demanding transformative approaches to sustainable nutrition. This study demonstrates how artificial intelligence revolutionizes distributed food production through optimized microalgae cultivation that simultaneously addresses food security and climate mitigation. A mechanistic model for Arthrospira platensis cultivation was developed and integrated with multi-agent reinforcement learning (MARL) control in photobioreactor systems across diverse global climates. AI-driven control achieved 14% lower energy consumption while capturing 78% more CO2 compared to conventional methods, making microalgae cultivation a net carbon sink. The MARL system demonstrated robust performance across eight climate zones and four seasons, enabling year-round sustainable protein production with enhanced climate resilience. This research establishes a scalable pathway for decentralized, climate-positive food systems contributing to multiple Sustainable Development Goals. The integration of AI with biological systems offers a replicable model for sustainable intensification of food production while actively removing atmospheric carbon, providing a critical tool for achieving global food security within planetary boundaries. Spirulina is a protein-rich microalga that grows quickly and can be cultivated without farmland, making it an attractive source of alternative protein. Yet producing it efficiently remains challenging, particularly as temperature and sunlight vary across regions and seasons. A research team, led by Professor Hankwon Lim of the Graduate School of Carbon Neutrality at UNIST, working with Professor Riezqa Andika of the University of Indonesia, has developed an AI-based system that adjusts spirulina cultivation to changing environmental conditions. In simulations using climate data from different regions, the system reduced energy use while accelerating growth and increasing carbon dioxide uptake. Spirulina cultivation depends on several closely connected factors, including light, temperature, nutrients, carbon dioxide, and acidity. Increasing the supply of carbon dioxide, for example, can promote growth but may also make the culture too acidic. More artificial light can support photosynthesis, but at the cost of greater electricity use. Finding the right balance becomes more difficult as outdoor conditions change. The new system uses multi-agent reinforcement learning (MARL), in which five AI agents manage these cultivation conditions together. Each controls one factor—light, temperature, nutrients, carbon dioxide, or acidity—and adjusts lighting, heating and cooling, and material inputs as conditions change. To develop the system, the researchers first created a virtual cultivation environment that models spirulina growth under different combinations of environmental and biological conditions. The AI then learned through repeated simulations to favor decisions that increased spirulina production while reducing energy consumption. Unlike conventional systems that rely on predetermined rules, the AI can adjust its response according to the overall state of the culture. This allows it to account for interactions among growing conditions, including effects that may not appear immediately. The team evaluated the system using weather data covering four seasons in eight cities across different climate zones. Compared with conventional control methods, the AI system reached the target spirulina concentration 59 hours earlier and reduced the average energy required to produce one kilogram of dried spirulina by 14%. The benefits varied by location and season. Energy consumption fell by as much as 20% in Ulsan and 21% in Beijing, while carbon dioxide uptake increased by an average of 78%. The proportion of supplied CO₂ absorbed by the spirulina also rose from 44% to 49%. “Beyond accelerating microalgae growth, this study provides a way to adapt cultivation to different climates while using less energy and increasing carbon dioxide uptake,” said Ahmad Syauqi, first author of the study. “The results show how AI-based control could help improve both the productivity and sustainability of microalgae cultivation.” “The system has been evaluated so far in a simulated environment,” said Professor Lim. “Our next step is to validate it in cultivation facilities equipped with sensors and control systems, with the goal of developing the technology for practical use in agriculture and aquaculture.” The findings of this research have been published online in Bioresource Technology on June 19, 2026. The research was supported by the Carbon Neutrality Demonstration and Research Center of UNIST, the National Research Foundation of Korea (NRF), and the Ministry of Science and ICT (MSIT). Journal Reference Ahmad Syauqi, Akmal Ramdani, Hankwon Lim, et al. , “Sustainable distributed microalgae cultivation for food production through artificial intelligence-driven photobioreactor control,” Bioresour. Technol., (2026).

2026년 08월 24일 월요일

Two UNIST Graduate Students Selected for 2026 Presidential Science Scholarship

Two UNIST graduate students have been selected for the 2026 Presidential Science Scholarship for research in green hydrogen production and artificial intelligence (AI). EunSong Jeon, a Ph.D. student in the Graduate School of Carbon Neutrality, is developing a photoelectrochemical system that produces green hydrogen using sunlight. Her work combines an organic semiconductor photoanode and photocathode in a single cell, enabling water splitting without an external voltage. Organic semiconductor photoelectrodes offer broad light absorption and solution processability, but their performance can decline over time. Her research focuses on improving conversion efficiency and extending cell lifetime, with the longer-term goal of advancing solar hydrogen technologies for carbon-neutral energy systems. “Receiving this scholarship is especially meaningful because it recognizes both my research and its potential for further development,” Jeon said. “I am grateful to Professor Han Hee Cho for his guidance and to my colleagues for their support throughout the research.” JaeHun Bang, a master's student in the Graduate School of Artificial Intelligence, develops AI that can interpret visual context and connect natural-language requests with objects and events in its surroundings. His research on video retrieval addresses a limitation of existing models, which often focus on prominent subjects while missing background details and changes over time. By segmenting videos at scene transitions and incorporating descriptions of both key subjects and surrounding context, he identified where current models struggle with complex contextual and temporal questions. The resulting paper, “Beyond the Highlights,” was accepted at WACV 2026. He has since extended this work to 3D environments. LightSplat , accepted at CVPR 2026, allows users to locate objects using natural-language descriptions such as white sofa or egg on ramen, without relying on predefined object categories. The method requires about five seconds of preprocessing and, depending on the comparison, runs 50 to 400 times faster while using one sixty-fourth of the memory. Potential applications range from robots responding to spoken instructions to natural-language interaction in AR and VR and equipment or hazard searches in digital twins. He previously conducted research on 3D scene understanding at Carnegie Mellon University and is currently an intern at LG AI Research, where he develops vision-language models for EXAONE. His goal is to combine fine-grained video understanding with language-based 3D perception to develop AI that can better interpret context and human intent. “This scholarship gives me greater momentum to build on my research,” Bang said. “I am grateful to Professor Kyungdon Joo for his guidance, and I hope to develop AI that can communicate and collaborate naturally with people in unfamiliar environments.” This year's Presidential Science Scholarship drew approximately 22 applicants for each available award. Selected master's students receive KRW 1.5 million per month, while doctoral students receive KRW 2 million per month.

2026년 08월 19일 수요일

Study Reveals Why Perovskite Performance Changes Across Solar Cell Designs

Abstract A perovskite precursor solution that delivers power conversion efficiencies (PCEs) exceeding 26% in conventional nip solar cells exhibits severe performance losses when directly applied to inverted pin architectures, revealing that high-efficiency compositions are not inherently transferable. Here, we identify a buried-interface crystallization mismatch, arising from the distinct physicochemical natures of inorganic SnO2 electron-transporting layers and organic self-assembled hole-transporting monolayers (SA-HTLs), as the origin of this divergence. The methylammonium chloride (MACl)-associated intermediate phase, MA2Pb3I8·2DMSO, persists and decomposes with strong underlayer dependence, stabilizing beneficially on SnO2 but impeding crystallization on SA-HTLs. To overcome this limitation, we develop a chloride-origin engineering strategy that decouples chloride functionality from volatile organic ammonium species by incorporating low-solubility lead chloride (PbCl2) with strong Pb–Cl coordination. This enables controlled interfacial desolvation and nucleation on SA-HTLs, suppresses buried defects, and establishes buried-interface crystallization control as a design principle for architecture-convergent, high-efficiency perovskite solar cells. Building a high-performance solar cell takes more than getting the materials right. The same ingredients can produce very different results when the layers are arranged differently—and researchers at UNIST have discovered why. Led by Distinguished Professor Sang Il Seok of the School of Energy and Chemical Engineering at UNIST, the team found that the surface beneath the light-absorbing perovskite layer can determine how well its crystals form. By tailoring the material chemistry to that surface, the researchers developed an inverted perovskite solar cell with a power conversion efficiency of 26.3% and improved stability. PSCs can be built in conventional nip or inverted pin configurations. Both have reached high efficiencies, but formulations optimized for one do not necessarily perform as well in the other. Inverted cells are particularly important for perovskite–silicon tandem solar cells, where they are commonly used as the top cell. The researchers found that this performance gap originates at the buried interface, where the perovskite layer forms on the material beneath it. A formulation that achieved efficiencies above 26% in conventional cells lost much of its performance when transferred directly to an inverted design. The difference came down in part to methylammonium chloride (MACl), an additive used to improve perovskite crystal growth. In conventional cells, an intermediate formed by MACl supports crystallization on the underlying inorganic layer. But on the organic layer used in inverted cells, the intermediate persists longer, disrupting crystal growth and leaving behind voids and defects that can lead to electrical losses. Rather than removing chloride, the team changed how it was introduced. The researchers reduced the amount of MACl and added a small amount of lead chloride (PbCl2), whose stronger interaction with chloride helped control where and when crystals began to form. This produced a cleaner buried interface with fewer defects. With the revised formulation, the inverted cells reached a peak efficiency of 26.3% and a fill factor of up to 86.8%, while also showing improved stability. The results demonstrate that controlling how perovskite crystals form at the underlying surface can help high-performance materials work across different solar-cell designs. “High-efficiency formulations developed for conventional PSCs do not necessarily behave the same way in inverted devices,” said Professor Seok. “By identifying the origin of this performance loss, we established a way to control crystal formation at the buried interface. The findings provide a design direction for developing efficient inverted cells for high-performance perovskite–silicon tandem solar cells.” Their findings have been published online in Joule on July 28, 2026. The study was supported by the National Research Foundation of Korea (NRF). Journal Reference Jongbeom Kim, Nahye Shin, Chaehoon Jeon, et al ., “Buried-interface crystallization limits the transferability of high-efficiency perovskite precursor compositions,” Joule ,(2026).

2026년 08월 05일 수요일

New Organic Photodetector Improves Polarized Near-Infrared Light Detection

Abstract Near-infrared (NIR) circularly polarized light (CPL) photodetection is of great importance due to its broad application potential in bioimaging, wearable healthcare, optical communication, and advanced optoelectronic systems. In this study, a supramolecular chirality evolution strategy in chiral low-bandgap fused-ring conjugated molecules (LFCs) is presented for high-performance NIR CPL photodetection using Schottky barrier vertical organic field-effect transistors (SB-VOFETs). Halogen substitution combined with thermal annealing drives inversion and amplification of supramolecular chirality in enantiopure LFC thin films. F-substituted LFCs exhibit progressive domain growth and hierarchical ordering with increasing annealing temperature, whereas Cl-substituted LFCs show limited structural evolution above 150°C. These distinct crystallization behaviors directly correlate with chiroptical responses, with F-substituted LFCs achieving a maximum absorption dissymmetry factor (|gabs|) of ∼0.1. When integrated into SB-VOFETs, the optimized chiral films enable highly efficient NIR CPL photodetection, delivering a photocurrent dissymmetry factor (|gph|) of ∼0.1, a specific detectivity of 4.9 × 1011 Jones, an external quantum efficiency exceeding 900%, and a fast response time of ∼600 µs at 850 nm. These metrics represent the highest performance reported for NIR CPL. This study provides design guidelines for advancing high-performance chiral optoelectronic devices through the synergistic integration of atomic substitution, thermal annealing, and device architecture engineering. Near-infrared (NIR) circularly polarized light (CPL) carries information that conventional light cannot, making it valuable for applications ranging from autonomous vehicle sensors and bioimaging to optical security and advanced communications. Detecting this light accurately, however, has remained difficult because the organic semiconductor films used in these devices often lose the molecular order needed to distinguish different polarization states. A research team, led by Professor BongSoo Kim of the Department of Chemistry at UNIST and Professor Joon Hak Oh of Seoul National University has found a way to overcome that limitation. By controlling how chiral organic semiconductor molecules organize within thin films, the researchers significantly improved the films' ability to distinguish between left- and right-handed CPL. When incorporated into a photodetector, the optimized films delivered what the team reports as the highest performance yet achieved for NIR CPL detection. Unlike conventional light detectors, CPL can distinguish between two different polarization states of light. This additional information can reveal not only an object's shape but also properties, such as its surface composition or molecular structure, making the technology valuable for sensing and imaging applications. The researchers achieved the improvement by applying a simple thermal annealing process to thin films made from fluorine-substituted chiral organic semiconductor molecules. Rather than remaining randomly arranged, the molecules reorganized into larger, more ordered crystal domains. This more ordered molecular arrangement strengthened the film's interaction with CPL. As a result, the film's ability to selectively absorb CPL increased more than threefold after annealing at 250°C, with its absorption dissymmetry factor rising from approximately 0.03 to 0.1. Structural analysis confirmed that the annealed films adopted a highly ordered molecular arrangement closely resembling that of single crystals. The researchers also discovered an unexpected effect. As the molecular packing reorganized, the film reversed the polarization it preferentially absorbed, demonstrating that heat treatment could control not only the strength but also the handedness of the material's optical response. By comparison, similar films containing chlorine instead of fluorine showed little structural change above 150°C and exhibited lower polarization selectivity after annealing. To turn these improved optical properties into measurable electrical signals, the team integrated the optimized films into a vertical organic transistor. The device architecture efficiently collected and amplified charges generated by incoming light, allowing the detector to fully capitalize on the improved molecular organization. The resulting photodetector achieved a photocurrent dissymmetry factor of 0.1 at a wavelength of 850 nanometers, demonstrating excellent discrimination between left- and right-handed CPL. It also recorded a specific detectivity of 4.9 × 10¹¹ Jones, an external quantum efficiency of up to 909%, and a response time of less than 600 microseconds—the highest performance reported to date for NIR CPL detectors. “We found that simply controlling how the molecules organize within a thin film can dramatically improve how the materials respond to CPL,” the research team said. “We hope this strategy will help advance next-generation optical sensors and imaging technologies that rely on precise light detection.” Their findings were published online in Advanced Science on June 28, 2026. The research was supported by the National Research Foundation of Korea (NRF) and the Ministry of Science and ICT (MSIT). Journal Reference Jaeyong Ahn, Kwangmin Kim, Sangwook Lee, et al ., “Thermally Driven Supramolecular Chirality Evolution in Low-Bandgap Fused-Ring Conjugated Molecules for High-Performance NIR Circularly Polarized Light Detection,” Adv. Sci., (2026).

2026년 07월 31일 금요일

From UNIST to TU Dresden: Dr. Joohan Nam Awarded Humboldt Research Fellowship

Finding new materials has traditionally relied on years of experimental trials and errors. At Technische Universität Dresden (TU Dresden), Dr. Joohan Nam aims to accelerate that process by combining artificial intelligence (AI) with experimental chemistry. Awarded the prestigious Humboldt Research Fellowship from the Alexander von Humboldt Foundation, Dr. Nam will join the research group of Professor Stefan Kaskel at TU Dresden in September 2026. There, he will integrate AI into every stage of porous materials discovery—from molecular design and synthesis to experimental validation—creating a more efficient and systematic approach to identifying promising new materials. The Humboldt Research Fellowship is one of Germany's leading international programs for outstanding early-career researchers. It supports independent research at leading German institutions and recognizes academic excellence, originality, and the potential to establish an independent research career. Dr. Nam earned his Ph.D. in chemistry at UNIST under the supervision of Professor Wonyoung Choe and is currently a postdoctoral researcher in Professor Choe's group. His doctoral research focused on metal-organic frameworks (MOFs)—porous crystalline materials whose structures can be precisely engineered to control how they adsorb and separate molecules. His work established new design principles for controlling the dynamic behavior of MOFs, contributing to advances in hydrogen isotope separation. He has published 12 SCI(E)-indexed papers, including three first-author papers in Angewandte Chemie International Edition. His research has also been recognized with the 2025 S-Oil Outstanding Dissertation Award (2025), the 2025 Outstanding Dissertation Award from the Korean Chemical Society, and the 2025 Young Investigator Award from the Korean Synchrotron Users Association. His collaboration with Professor Kaskel began in 2025 through UNIST's Global Postdoctoral Short-Term Research Program, during which he conducted collaborative research at TU Dresden on MOF design, synthesis, and adsorption-property evaluation. Building on that collaboration, Dr. Nam will further integrate AI with experimental chemistry, enabling computational predictions to be rapidly tested and refined through laboratory experiments. With Dr. Nam's selection, Professor Wonyoung Choe's group has now seen two researchers receive Humboldt Research Fellowships this year, following Dr. Jiyeon Kim's selection earlier this year. "Dr. Nam has built a strong foundation in understanding the structural dynamics of MOFs and translating those insights into functional materials," said Professor Choe. "This fellowship recognizes both his research achievements and his vision of expanding materials discovery through AI. We look forward to seeing him develop new methodologies that bridge chemistry experimental and digital technologies in porous materials research." “This fellowship is especially meaningful because it recognizes the research direction I developed at UNIST,” said Dr. Nam. "By integrating AI-driven predictions with experimental validation, I hope to make the discovery of new materials faster, more systematic, and more precise." He also thanked Professor Choe and Professor Kaskel for their mentorship and support, adding that he hopes to strengthen international collaboration and establish an independent research program through his work in Germany.

2026년 07월 29일 수요일

UNIST and Westlake University Expand Research Partnership in Sustainable Energy and Advanced Materials

UNIST has strengthened its research partnership with Westlake University through a two-day workshop focused on sustainable energy, advanced materials, and emerging technologies. Bringing together leading researchers from both institutions, the event provided a platform to exchange recent scientific advances and identify new opportunities for international collaboration. Hosted by the UNIST College of Engineering on July 20–21, the 2026 UNIST–Westlake Joint Workshop featured presentations by 14 faculty members—seven from each university. Discussions spanned catalysis, carbon neutrality, AI-driven manufacturing processes, optical materials, biomaterials, and other areas where the institutions share complementary research strengths. Representing UNIST were Distinguished Professor Rodney S. Ruoff from the Department of Chemistry, Professors Dong Suk Kim and Tae Hoon Oh from the Graduate School of Carbon Neutrality, Professors Kwangjin An and Dongha Kim from the School of Energy and Chemical Engineering, Professor BongSoo Kim from the Department of Chemistry, and Professor Jinhyun Kim from the Department of Materials Science and Engineering. Westlake University was represented by Professors Xiao Yang, Chengchen Guo, Yao Yang, Zexin Jin, Jianbo Tang, Hailin Fu, and Siying Peng. The workshop concluded with a keynote lecture by Jiaxing Huang, Chair Professor in the School of Engineering at Westlake University, titled Innovation Anxiety and the Industries of the Future. An internationally recognized materials scientist and Editor-in-Chief of Accounts of Materials Research, Huang examined how rapid technological advances are reshaping industry and discussed the evolving role of researchers in driving future innovation. "This workshop allowed researchers from both universities to gain a deeper understanding of each other's expertise and explore new directions for collaboration," said Yong Hwan Kim, Dean of the College of Engineering at UNIST. “We look forward to expanding joint research, faculty exchanges, and collaborative programs that build on the strengths of both institutions.” Founded in 2018 in Hangzhou, China, Westlake University is a research-intensive institution with strengths in the life sciences, natural sciences, and engineering. The university is dedicated to advancing frontier research and cultivating the next generation of scientific leaders.