https://scholar.dgist.ac.kr/handle/20.500.11750/10154 2026-07-21T11:41:50Z 2026-07-21T11:41:50Z Kumar, Naveen Jo, Hyo Jeong Son, Dae-Ho Lee, Jaebaek Ali, Amanat Kang, Jin-Kyu Yang, Kee-Jeong Sung, Shi-Joon Jeong, Hyeonjong Cho, Chang-Hee Kim, Dae-Hwan Hwang, Dae-Kue https://scholar.dgist.ac.kr/handle/20.500.11750/60422 2026-06-29T07:10:17Z 2026-03-31T15:00:00Z

Title: Enhanced Wide-Bandgap Perovskite Solar Cells via Kinetically Optimized C60 Electron-Transport Layers Author(s): Kumar, Naveen; Jo, Hyo Jeong; Son, Dae-Ho; Lee, Jaebaek; Ali, Amanat; Kang, Jin-Kyu; Yang, Kee-Jeong; Sung, Shi-Joon; Jeong, Hyeonjong; Cho, Chang-Hee; Kim, Dae-Hwan; Hwang, Dae-Kue Abstract: High-efficiency tandem solar cells require wide-bandgap (WBG) perovskites as the top absorber, yet such devices often suffer severe nonradiative recombination, voltage losses, and halide segregation. This work demonstrates that carefully controlling the deposition kinetics of the fullerene electron-transport layer (ETL) offers an elegant route to overcome these issues without complex passivation strategies. WBG perovskite solar cells using a FA(0)(.8)Cs(0)(.2)Pb(I0.8Br0.2)(3) absorber were fabricated in a p-i-n architecture with C-60 ETLs deposited at three different evaporation rates. When the C-60 deposition rate was slowed to 0.1 & Aring; s(-1), our devices achieve a 20.4% PCE with a relatively low Voc deficit (~0.48 eV) without complex molecular passivation, 2D/3D heterostructures, or multistep surface reconstruction. The improvement originates from suppressed nonradiative recombination and reduced shunt leakage: The slow-deposited C-60 film yields a higher open-circuit voltage (~1.17 V), increased fill factor (80%), and reduced saturation current density and trap-state density compared with faster deposition. Photoluminescence, impedance spectroscopy, and transient photovoltage analyses reveal that slower deposition produces a compact and well-ordered C-60 layer which minimizes trap-assisted recombination, decreases Urbach energy (16.68 meV), and lowers the ideality factor (n approximate to 1.33). Structural characterizations confirm improved C-60 molecular interface and smoother morphology at slow deposition rates. This work provides a simple processing guideline for high-performance WBG perovskite solar cells and offers valuable insights for scalable tandem cell fabrication.

2026-03-31T15:00:00Z Kwon, Osung Son, Byungrak https://scholar.dgist.ac.kr/handle/20.500.11750/60412 2026-06-12T00:40:19Z 2026-04-30T15:00:00Z

Title: Quantitative Analysis of Ionic Channel Network Variation in Nafion Under Continuous Annealing Using Current-Sensing Atomic Force Microscopy Author(s): Kwon, Osung; Son, Byungrak Abstract: Proton exchange membranes (PEMs) are essential for PEM fuel cells, with proton conductivity arising from the hydration-induced ionic channel network. PEM performance can be enhanced through pretreatments, such as annealing, which reconstruct the ionic channels. This study investigates the ionic channel network variation in Nafion 212 under continuous annealing at 90 degrees C using current-sensing atomic force microscopy (CSAFM). A nanoscale PEM fuel cell was formed with a Pt-coated CSAFM tip and Pt-coated Nafion surface. Topography and surface roughness analyses revealed geometrical changes from annealing. Current-sensing images and histograms qualitatively assessed local conductance and ionic channel distribution. The ionic channel network density was quantitatively evaluated using the number of protons moving through the ionic channel network (NPMI), derived from CSAFM and electrodynamics principles. NPMI directly reflects ionic channel density. From the unannealed state to 60 h, NPMI increased linearly at 1 & times; 104 h-1, indicating enhanced channel formation. Beyond 60 h, NPMI decreased linearly at 1.9 & times; 105 h-1, reflecting progressive network degradation. As the ionic channel network increases, the number of protons reaching the membrane surface also increases, whereas in the opposite case it decreases. Thus, NPMI becomes evaluation criterion for ionic channel network density. These findings systematically link nanoscale structural changes to ionic channel reconstruction and proton transport in Nafion 212, providing insight into PEM performance evolution under thermal treatment.

2026-04-30T15:00:00Z Lee, Yuri Jeon, Injun Kim Ji Hoon Kim Jongmin Lee Sang Uck Chun Sang-Eun Kim Jae Hyun https://scholar.dgist.ac.kr/handle/20.500.11750/60363 2026-05-28T06:10:11Z 2026-04-30T15:00:00Z

Title: Fluorinated ether-anchored solid polymer electrolyte for lithium metal batteries for low-temperature adaptability Author(s): Lee, Yuri; Jeon, Injun; Kim Ji Hoon; Kim Jongmin; Lee Sang Uck; Chun Sang-Eun; Kim Jae Hyun Abstract: Solid polymer electrolytes (SPEs) are promising for safe and scalable all-solid-state lithium batteries, but lowtemperature ionic transport and interfacial instability limit their practical use. Here, we present a fluorinatedether (FE)-anchored polymer electrolyte (FAPE) based on a PEGDME semi-interpenetrating network, designed to overcome these challenges. FE units anchor onto ether chains via C- H & sdot;& sdot;& sdot;O interaction, suppressing crystallization, weakening Li*-EO coordination, and promoting formation of inorganic-rich, anion-derived interphases. FAPE exhibits high ionic conductivity down to -20 degrees C, intrinsic nonflammability, and an expanded electrochemical stability window. Lithium metal cells with FAPE demonstrate enhanced Coulombic efficiency, extended cycling stability, and higher critical current densities compared to conventional PEGDME-based SPEs. Full cells and prototype pouch cells retain high capacities under both ambient and sub-zero temperatures, highlighting their practical applicability. This molecular anchoring strategy provides a versatile platform to tailor solvation structure and interphase chemistry, enabling wide-temperature, safe, and durable operation in high-energy solidstate lithium metal batteries.

2026-04-30T15:00:00Z Choi, Jae Sung Kang, Won Seok Son, Chan Sik Son, Byung Rak Lee, Dong Ha https://scholar.dgist.ac.kr/handle/20.500.11750/60268 2026-04-15T08:16:13Z 2014-12-31T15:00:00Z

Title: Tag interference based mobile object tracking with passive UHF RFID system Author(s): Choi, Jae Sung; Kang, Won Seok; Son, Chan Sik; Son, Byung Rak; Lee, Dong Ha Abstract: This paper proposes a novel method that enables location sensing for a mobile object by utilizing deployed passive UHF Radio Frequency Identification (RFID) tags and a stationary RFID reader. In order to estimate the mobile object location, the proposed method utilizes the second order under damped system based tag to tag interference model. The empirical study using RFID systems and a mobile robot verifies the effectiveness and performance of the proposed method. © Springer-Verlag Berlin Heidelberg 2015.

2014-12-31T15:00:00Z