[Authors] Professor Jaesang Lee, Postdoctoral Researcher. Donghyun Ko, and Undergraduate Chanyong Jeong, SNU ECE Quantitatively identified the percolation mechanism in organic devices by controlling charge flow via guest concentration. Expected to contribute to performance optimization of organic electronic devices such as OLEDs and solar cells. Published in Nano Letters, a top-tier international journal. Professor Jaesang Lee’s team (Dr. Donghyun Ko, postdoctoral researcher, Chanyong Jeong, undergraduate) quantitatively elucidated the percolative charge-transport mechanism occurring within the host–guest structure of organic semiconductor devices and proposed a new theoretical model to explain it. The study was published on June 26, 2025, in Nano Letters, a leading materials science journal issued by the American Chemical Society. (Paper title: “Percolative Charge Transport in Organic Semiconductor Devices with Host–Guest Layers”) In organic electronic devices such as organic light-emitting diodes (OLEDs) and organic photovoltaics (OPVs), the active layer is typically based on a host–guest molecular blend structure. It is known that the role of guest molecules is not limited to simple emitters or traps; they can also affect charge transport. The study focused in particular on the “percolation” phenomenon, in which, once the guest concentration exceeds a critical threshold, a network forms between guest molecules that allows current to flow. To this end, the team designed a special unipolar device structure (a hole-only device) that forces current to flow exclusively through the guest molecules, and experimentally measured charge-transport characteristics independently as the guest concentration varied. As a result, they defined the percolation critical concentration as the point at which charge transfer via direct guest–guest hopping accounts for roughly 1% or more of the total device current, and demonstrated that the device’s electrical response changes abruptly at this point. They also revealed that the deeper the trap depth of the guest molecules, the lower this percolation threshold becomes—because charges tend to reside on the guest rather than the host. Based on these characteristics, the team established a quantitative model that captures the factors governing charge transport and showed that it agrees with the experimental results. This study is among the first to quantitatively isolate and analyze the complex charge-transport pathways in multicomponent organic devices, providing concrete design criteria for optimizing efficiency by tuning the concentration and energy levels of guest molecules. In particular, by demonstrating the universality of the model at both room and low temperatures and across various host materials, the work highlights its potential as a design guideline for next-generation organic devices such as high-efficiency OLEDs and OPVs. The research was supported by Samsung Display, the Korea Institute for Advancement of Technology (KIAT), and the National Research Foundation of Korea (NRF). Image of driving voltage variation and percolation-current activation against guest content in host–guest devices Source:https://ece.snu.ac.kr/ece/news?md=v&bbsidx=56652 Translated by: Dohyung Kim, English Editor of the Department of Electrical and Computer Engineering, kimdohyung@snu.ac.kr...

Professor Kyuseok Shim has been elected to the Board of Directors of ACM SIGKDD—an international academic society that holds the highest authority in the field of data mining—setting yet another milestone for the Korean academic community. ACM SIGKDD is the academic society most closely watched by data science and data mining researchers worldwide, and its Board of Directors is the core body that plays a central role in running the society. Through the 2025 ACM SIGKDD election, Professor Kyuseok Shim was chosen as one of the board officers—specifically as a Director—on the Executive Committee, which consists of a Chair, Secretary, Treasurer, and six Directors. This is the first time someone affiliated with a Korean institution has been elected, and it is regarded as further evidence of the international stature of Korea’s data science community. Professor Kyuseok Shim is a globally renowned scholar in databases and data mining and serves as Editor-in-Chief of the premier international journal, the VLDB Journal. Committed to expanding global research networks, he has secured the SIGKDD flagship conference (KDD 2026) for Jeju, where he will serve as General Chair, and successfully brought the ACM SIGMOD 2028 conference to Korea as well—both firsts for the country. This election not only signifies that Korea’s data science research capability has reached a world-class level, but also serves as an important affirmation of Professor Shim’s academic leadership and international credibility. Source: https://ece.snu.ac.kr/ece/news?md=v&bbsidx=56658 Translated by: Dohyung Kim, English Editor of the Department of Electrical and Computer Engineering, kimdohyung@snu.ac.kr...

From left: Professor Seung Hui Cui and Ph.D. candidate Jiyu Lee of SNU ECE. The research team of Jiyu Lee, Jonghun Yoon, and Jaekeun Lee from the Power Conversion Systems Laboratory (supervised by Professor Seung Hui Cui) received the Best Paper Award at the IEEE Power Electronics for Distributed Generation Systems 2025 (PEDG 2025), organized by the IEEE Power Electronics Society (PELS). The research team gave an oral presentation on the topic “Ultra-Fast Black Start Method for Grid-Forming Converters in Electronic Power Grid with Transformer Soft-Magnetization” during the special session titled “Grid-Forming Session.” This study was a collaborative effort with Professor Jaejeong Jeong’s lab at Kyungpook National University and Professor Heng Wu’s lab at Aalborg University in Denmark. It proposed a novel method to actively control transformer flux during Black Start using inverter resources after a blackout in large-scale power systems. This approach prevents inrush current and dramatically reduces the Black Start time from tens of seconds to the sub-millisecond range. At PEDG 2025, a total of 227 papers were presented; only 10 were shortlisted for the award, and just 3 were ultimately selected as Best Papers. Now in its 16th year, the IEEE PEDG—launched in 2010—has become a flagship international conference in power electronics for distributed generation. Each year, hundreds of researchers and industry experts attend to share the latest results and collaborate on renewable energy integration technologies and next-generation power conversion systems. Source: https://ece.snu.ac.kr/ece/news?md=v&bbsidx=56645 Translated by: Dohyung Kim, English Editor of the Department of Electrical and Computer Engineering, kimdohyung@snu.ac.kr...

Cover of the June 2025 Issue of Advanced Science The paper by Ph.D. candidate Junhyeong Park from the Advanced TFTs and Circuits for Smart Electronics Laboratory (ACELAB), led by Professor Sooyeon Lee, has been selected as the cover article for the June 2025 issue of Advanced Science. Advanced Science is one of the leading academic journals that covers groundbreaking research in cutting-edge science and technology, including materials science, electronic devices, nanotechnology, energy, and biomedical fields. It comprehensively introduces research achievements that contribute to the development of next-generation technologies. Details on the paper from Professor Sooyeon Lee’s research team are as follows: In the June 2025 issue, first authored by Junhyeong Park, the team implemented high-performance indium-gallium-zinc-oxide (IGZO) synaptic transistors and an array thereof for neuromorphic computing. By optimizing the floating-gate fabrication process, they lowered the transistors’ operating voltage and greatly extended synaptic-weight retention time. They also built a synapse array, confirming both large-area integrability and excellent device-to-device uniformity. Leveraging these array characteristics, they achieved high image-classification accuracy with a spiking neural network. Altogether, the study demonstrates that IGZO-based synaptic transistors can deliver high performance in large-scale neuromorphic systems. Source: https://ece.snu.ac.kr/ece/news?md=v&bbsidx=56603 Translated by: Dohyung Kim, English Editor of the Department of Electrical and Computer Engineering, kimdohyung@snu.ac.kr...

Embedding Security Keys in Memory... Professor Jong-Ho Lee's Team at SNU ECE Develops World’s First NAND Flash-Based “Concealable PUF” Technology - Introduces a next-generation hardware security solution with both high security and spatial efficiency - Expected to be applied to electronic device security in smartphones, vehicles, IoT, and more - Research published in Nature Communications, a leading international journal ▲ Professor Jongho Lee (left) and researcher Seongho Park (right) from the Department of ECE, SNU The College of Engineering at Seoul National University announced that Professor Jong-Ho Lee's team from the Department of Electrical and Computer Engineering has developed a novel hardware security technology based on commercial 3D NAND flash memory (V-NAND flash memory). The technology, named “Concealable Physical Unclonable Function (Concealable PUF)”, preserves the core strengths of traditional PUFs—namely unclonability and randomness—while introducing a groundbreaking feature: the ability to conceal the security key and reveal it only when needed. This is the first-ever implementation of such functionality using V-NAND flash memory. The results of this research were published on June 3 in Nature Communications, one of the world’s leading scientific journals. ■ Research Background With the rapid advancement of artificial intelligence and big data, the use of data is growing exponentially, bringing data security into sharp focus. As a result, stronger security technologies are required beyond traditional password-based methods. One such emerging solution is the Physically Unclonable Function (PUF). PUFs generate unique values based on minute physical variations that naturally occur during semiconductor manufacturing processes, making them virtually impossible to replicate or predict. However, conventional PUFs have primarily been implemented in laboratory-scale devices, making mass production difficult, and they have faced limitations in safely concealing security keys. ■ Research Achievements To overcome the limitations of conventional PUFs, the research team developed the Concealable PUF by leveraging a unique property of V-NAND flash memory: the Gate-Induced Drain Leakage (GIDL) mechanism used in the erase operation. By weakly applying GIDL, they intentionally amplified the variations in erase behavior across memory cells, thereby generating PUF data. This innovation is particularly significant because it allows PUF functionality to be implemented directly within widely used V-NAND flash memory—without requiring any changes to its circuits or structure. One of the most compelling advantages is the ability to expose the security key only when needed, while concealing it under user data during normal operation. This dual-mode capability maximizes both security and spatial efficiency. Notably, the memory space used for the concealed key can also serve as regular storage when the key is not in use, enabling efficient system design without wasted capacity. The team conducted experiments using commercial V-NAND flash memory, demonstrating that the generated PUF data maintained 100% accuracy and randomness under a wide range of conditions—including temperature changes from 25°C to 85°C and over 10 million repeated read cycles. They also verified the technology’s stability through more than 100 iterations of the conceal-and-restore process, with the original key restored without error each time. In simulated attacks using machine learning-based methods, the PUF data proved highly secure: prediction accuracy remained at the level of random guessing, confirming the strong security resilience of the Concealable PUF. ■ Expected Impact This breakthrough enables the creation of a highly reliable security system that can generate, store, and conceal security keys using existing commercial memory devices, without requiring any hardware modifications. As such, the technology is expected to be widely applicable across a broad range of security-critical electronic devices, including smartphones, vehicles, and Internet of Things (IoT) devices. Looking ahead, the research team plans to expand the application of Concealable PUF technology to a variety of hardware security solutions, further advancing the field of secure system design. ■ Researchers' Remarks Professor Jongho Lee, who led the study, stated, “The Concealable PUF stands out for its creativity and practicality, as it can be implemented using currently mass-produced vertical NAND flash memory technology without modification. We expect it to see widespread use in the field of information security.” Lead author Seongho Park added, “This research is particularly meaningful because it demonstrates that PUFs can be constructed using the erase operation of standard V-NAND flash memory—without altering circuit designs or structures. In particular, the concealment feature, which ensures that the security key is exposed only when needed, opens up new possibilities for PUF technology in terms of both security and space efficiency.” ■ Researcher Career Path Researcher Seongho Park is currently enrolled in the combined Master’s-Ph.D. program in the Department of Electrical and Computer Engineering at Seoul National University. In addition to improving the characteristics of V-NAND flash memory, he is actively conducting research in a range of applied areas, including neuromorphic computing and data security. ▲ Figure 1. Concealable PUF Based on V-NAND Flash Memory Using GIDL Erase. (a) Schematic illustration of the concealable PUF using V-NAND flash memory. (b) Circuit diagram of the V-NAND flash memory. (c) The GIDL erase method. ▲ Figure 2. PUF Key Generation Using GIDL Erase and Operational Mechanism of the V-NAND Flash Memory-Based PUF. (a) Threshold voltage (V_th) distribution of V-NAND flash cells after weak GIDL erase. (b) Comparison between conventional NAND flash-based PUF and the proposed method. (c) Operational mechanism of the V-NAND flash memory-based PUF. (d) Autocorrelation test results of the generated PUF key. [References] Paper Title / Journal: “Concealable physical unclonable functions using vertical NAND flash memory”, Nature Communications DOI: https://doi.org/10.1038/s41467-025-60415-y [Contact] Seongho Park, Advised by Professor Jongho Lee, Department of Electrical and Computer Engineering, Seoul National University: thomasung@snu.ac.kr Source: https://ece.snu.ac.kr/ece/news?md=v&bbsidx=56596 Translated by: Dohyung Kim, English Editor of the Department of Electrical and Computer Engineering, kimdohyung@snu.ac.kr...

On Monday, April 14, Seoul National University signed a Memorandum of Understanding (MoU) with Hyundai Engineering & Construction for collaboration on the development and commercialization of superconductor-based fusion reactor technology. The signing ceremony was held at Seoul National University’s Gwanak campus, with key figures in attendance, including SNU President Honglim Yoo and Hyundai E&C CEO Hanwoo Lee. Fusion power technology—often referred to as the “energy of dreams”—is gaining attention as a game-changer in the future energy sector. It has abundant fuel, poses low risk of explosion, and produces minimal emissions and radioactive waste, making it a safe and clean energy source capable of addressing both the explosive power demand driven by the Fourth Industrial Revolution and the goal of carbon neutrality. One of the core technologies of nuclear fusion is maintaining ultra-high-temperature plasma in a stable state for extended periods. To achieve this, a strong magnetic field generated by superconducting magnets is used to effectively confine the plasma. With recent advances in high-temperature superconducting magnet technology, the magnetic field strength inside fusion devices has more than doubled compared to previous technologies. As a result, the massive superconducting magnets used in fusion reactors—once spanning several tens of meters—are now being scaled down to just a few meters, making compact fusion reactors a reality. This breakthrough is fueling rapid growth in the field, with global private sector investments surpassing 10 trillion KRW, aiming for commercialization by the 2030s. Seoul National University is a global leader in high-temperature superconducting magnet and application research, centered around the Applied Superconductor Research Center (Director: Prof. Seungyong Han, Department of Electrical and Computer Engineering). Additionally, the university leads fusion research through the Fusion Reactor Engineering Research Center (Director: Prof. Yongseok Hwang, Department of Nuclear Engineering), which operates the VEST (Versatile Experiment Spherical Torus) device for education and research purposes. Supported by the Ministry of Science and ICT (MSIT), the High-Temperature Superconducting Magnet Technology Development Project (2022–2026, Project Director: Visiting Professor Sangjin Lee, Department of Electrical and Computer Engineering) is led by the Applied Superconductor Research Center. This large-scale national initiative involves over 200 researchers across 27 institutions in Korea and focuses on developing a wide range of core source technologies related to high-temperature superconducting magnets. The outcomes of this project are having a broad impact, including technological collaboration with Hyundai E&C in the field of fusion energy, and extending to both domestic and international superconducting applications. In July 2024, the Ministry of Science and ICT (MSIT) announced a 1.2 trillion KRW initiative titled the “Accelerated Realization Strategy for Fusion Energy”, highlighting the importance of technological innovations—such as high-temperature superconducting magnet technology—and public-private collaboration in advancing the commercialization of fusion energy. As a follow-up to this strategy, the government established the Fusion Innovation Alliance (Director: Boseon Kang, Director of KFE Center), an independent, industry-led organization aimed at laying the groundwork for private-sector growth and promoting the industrialization of fusion. Through this alliance, MSIT is also emphasizing the importance of university-industry collaboration in fusion-related research. Through this agreement, Seoul National University and Hyundai Engineering & Construction plan to closely collaborate on superconducting fusion reactor technologies, both domestically and internationally. Their cooperation will include: △ Joint research and technology development △ Business development and participation △ Human resource support and operation of mutual consultative bodies. Seoul National University will accelerate its research into core technologies in the fields of fusion and superconductivity, while Hyundai E&C, drawing on its extensive experience with various large-scale nuclear power plants including SMRs,aims to take a leading role in the construction and commercialization of fusion power plants. Together, the two institutions intend to generate strong synergy based on their unique strengths and drive innovation in future energy. Furthermore, Seoul National University recently launched the SNU Energy Initiative (SNU Energy Initiative, Chair: Professor Sungjae Kim, Department of Electrical and Computer Engineering) to comprehensively address issues across the full energy lifecycle. This new agreement with Hyundai E&C is expected to serve as a foundation for exploring new alternative solutions for future energy production together with SNU Energy Initiative. President Honglim Yoo of Seoul National University stated, “This agreement marks an important milestone in the history of superconductivity and fusion research in Korea. Through the collaboration between our two institutions, I hope our country will secure world-leading technological capabilities and contribute to strengthening national competitiveness.” Hanwoo Lee, CEO of Hyundai Engineering & Construction, remarked, “This partnership between leading academic and industrial institutions in Korea is expected to drive a new momentum for the transition to future energy. Today’s agreement is a meaningful step toward moving fusion power development from the laboratory to the construction of commercial reactors, ultimately creating real-world value.” This MoU between Seoul National University and Hyundai Engineering & Construction represents the first instance of a major Korean conglomerate formally entering the fields of fusion energy and high-temperature superconductivity, marking a significant milestone in the history of domestic research in these areas. Moreover, the agreement is especially meaningful as it lays the groundwork for rapidly securing a foothold in the global market, leveraging Korea’s world-class superconducting fusion technology at a time when international competition in this domain is intensifying. Source: https://ece.snu.ac.kr/ece/news?md=v&bbsidx=56588 Translated by: Dohyung Kim, English Editor of the Department of Electrical and Computer Engineering, kimdohyung@snu.ac.kr...

The research team of Suyeon Kim and Jongho Park from the Advanced Flexible Electronics Laboratory (AXEL), led by Professor Yongtaek Hong, was awarded the 'Distinguished Student Oral Paper' at Display Week 2025, organized by the Society for Information Display (SID). The team gave an oral presentation on the topic "Mesh-patterned silver electrode via electrohydrodynamic printing for transparent and flexible quantum-dot light-emitting diodes" at the Young Leadership Conference and the Flexible Display session. Out of the 650 papers presented at SID Display Week 2025, only 36 were selected as ‘Distinguished Papers’, and among them, just 10 papers were honored as ‘Distinguished Student Oral Papers’ and received awards. Celebrating its 63rd anniversary this year, SID (Society for Information Display) is the oldest and most prestigious international conference in the field of displays. Each year, it attracts around 8,000 participants and serves as a central platform where academia and industry come together to share and collaborate on the latest display technologies. Source: https://ece.snu.ac.kr/ece/news?md=v&bbsidx=56558 Translated by: Dohyung Kim, English Editor of the Department of Electrical and Computer Engineering, kimdohyung@snu.ac.kr...

Acting President and Deputy Prime Minister cum Minister of Education Lee Joo-ho is presenting the Geunjeong Medal to Professor Saewoong Bahk during the 44th Teacher's Day Commemoration Ceremony held at the FKI Tower in Yeouido, Seoul, on May 15, 2025. [Presidential Office Press] Source: https://n.news.naver.com/article/001/0015391097?sid=102 Translated by: Dohyung Kim, English Editor of the Department of Electrical and Computer Engineering, kimdohyung@snu.ac.kr...