DGIST Scholar는 학술문화팀에서 운영하는 기관 리포지터리로, 학술정보 공유와 글로벌 확산을 위해 DGIST에서 생산되는 학술성과물(논문, 프로시딩, 학위논문, 특허, 연구보고서 등)을 수집, 관리하는 Open Access 디지털 저장소입니다.
Signatures of Kramers-Weyl fermions in the charge density wave material (TaSe4)2I
2025-10Communications Materials, v.6, no.1
The quasi-one-dimensional charge density wave (CDW) material (TaSe
Impact of trivalent Sb3+-ion doping on charge carrier recombination dynamics of cesium lead bromide perovskite quantum dots
2025-10Nanoscale, v.17, no.40, pp.23642 - 23653
Metal-ion doping of perovskites has proven to enhance their photoluminescence (PL) properties and stability; however, the underlying charge carrier dynamics remain unclear. We synthesized a cesium lead bromide (CsPbBr3) perovskite quantum dot (PQD) incorporating a heterovalent Sb3+ ion dopant and its pristine counterpart and performed time-resolved single-particle PL spectroscopy. The PL intensity and lifetime of the Sb-CsPbBr3 PQD were remarkably enhanced compared to those of the pristine-CsPbBr3 PQD because of diminished nonradiative charge carrier recombination dynamics. The charge carrier trapping (detrapping) rate was lower (higher) for the Sb-CsPbBr3 PQD than for the pristine-CsPbBr3 PQD, as the Sb3+ doping contributed to hindering the formation of the structural defects responsible for charge carrier trap states and increasing the exciton binding energy. The replacement of Pb2+ with Sb3+, which has a smaller ionic radius, in the CsPbBr3 structure effectively increased the tolerance factor, enabling the doped PQD to exhibit more stable local structures and, thus, suppressing its decomposition.
Third-order strong-coupling impurity solver for real-frequency dynamical mean field theory: Accurate spectral functions for antiferromagnetic and photodoped states
2025-12Physical Review B, v.112, no.24, pp.1 - 24
We present a real-frequency third-order strong-coupling impurity solver which employs quantics tensor cross interpolation (QTCI) for an efficient evaluation of the diagram weights. Applying the method to dynamical mean-field theory (DMFT) calculations of the single-band Hubbard model on the Bethe lattice, we clarify the interaction and temperature range in which the third-order approach yields accurate results. Since the calculations are implemented on the real-time/frequency axis, the detailed structure of spectral functions can be obtained without analytical continuation, as we demonstrate with examples for paramagnetic, antiferromagnetic, and photodoped states. Our work establishes a viable path toward high-order, real-frequency impurity solvers for both equilibrium and nonequilibrium DMFT studies.
Constructing High-Performance Solar Cells by Incorporating an A1-A2-Type Polymer Donor as a Guest Material
2025-12Molecules, v.30, no.24
Owing to the intramolecular push-pull electron effect between the electron donor (D) unit and electron acceptor (A) unit, the D-A type based polymer donors display outstanding device performance. However, the imperfect energy levels lead to the D-A-type-based polymer device exhibiting high voltage loss. In this study, an A1-A2-type copolymer M1 was developed with 1,3-bis(2-ethylhexyl)-5,7-di(thiophen-2-yl)benzo[1,2-c:4,5-c']dithiophene-4,8-dione (BDD) as the A1 unit and dithieno[3 ',2 ':3,4;2 '',3 '':5,6]benzo[1,2-c][1,2,5]thiadiazole (DTBT) as the A2 unit. Compared with D-A-type-based polymer donor PM6, the A1-A2 type based M1 possesses lower energy levels, broader absorption, and stronger crystallinity. After introducing M1 to the PM6:L8-BO-based system as the guest material, the ternary blend films exhibited exceptional face-on molecular orientation and favorable active-layer morphology, which promotes exciton dissociation and suppresses charge recombination. Consequently, the PM6:M1(5%):L8-BO-based ternary device exhibited an impressive power conversion efficiency (PCE) of 19.70% with simultaneously enhanced photostability, which is superior to the PM6:L8-BO-based binary system. Our work offers an efficient approach to developing high-performance ternary devices by introducing a novel A1-A2 type polymer donors as the guest material.
Tailoring Molecular Orientation with a Polymer Additive Enables Bilayer Organic Solar Cells with 20.2% Efficiency
ACCEPTAdvanced Functional Materials
Tuning the molecular packing from the edge-on to the preferred face-on orientation is beneficial for improving vertical charge transport and the photovoltaic performance in organic solar cells. However, achieving precise control over this structural transition remains a significant challenge due to the complex processing conditions. Herein, a trace amount of the polymer donor PTO2 as an additive, effectively inducing a preferential face-on molecular orientation in the acceptor phase is incorporated. This strategy enhanced exciton dissociation efficiency, improved charge carrier extraction, reduced trap density, and subsequently achieved a fill factor (FF) nearing 80%, results in a power conversion efficiency (PCE) of 20.2%, the highest reported for bilayer OSCs. Remarkably, the PTO2-driven molecular orientation strategy maintains consistent efficacy across diverse donor-acceptor systems, highlighting its broad applicability. This approach offers a comprehensive insight for the effective modulation of NFA molecular orientation, paving a practical approach for high-performance bilayer OSCs.
Polymerization-Assisted Signal Enhancement and Visual Readout Techniques in Bioassays: A Mini Review
2025-12ACS Polymers Au, v.5, no.6, pp.712 - 722
Polymerization-based strategies have emerged as powerful tools for enhancing sensitivity and enabling user-friendly visual outputs in bioassays. Unlike conventional assays that rely on catalyst- or enzyme-mediated accumulation of molecular products for signal amplification, polymerization reactions produce material-level, macroscopic, or supramolecular structures-such as hydrogels, polymer films, or insoluble precipitates. This mini review highlights recent advances in polymerization-assisted signal amplification techniques, with a particular focus on detection strategies and polymerization chemistries. We first classify detection approaches according to their readout mechanisms, including direct visual detection and integration with electronic or optical transducers. We then examine representative polymerization reactions employed in bioassays, including enzyme-mediated hydrogelation, nucleic acid polymerization, conductive polymer formation, and controlled radical polymerization. Both enzyme-dependent and enzyme-free systems are discussed, reflecting the growing versatility of polymerization-based platforms for biosensor development.
Achieving wide-range steep slopes in SnS2 negative capacitance transistors through an isolated band structure and thermionic emission enhancement via Bi contacts
2025-12Materials Horizons, v.12, no.24, pp.10656 - 10663
Negative capacitance FETs aim for sub-60 mV dec-1 switching to curb power consumption, but often encounter instability and narrow steep-slope windows. We present a hysteresis-free NCFET that strategically utilizes a 2D SnS2 channel. The inherent isolated conduction band of SnS2, yielding a step-like density of states, is pivotal for sharp turn-on characteristics when effectively coupled with the negative capacitance effect. The SnS2 channel is integrated with an La:HfO2/HfO2 ferroelectric-dielectric gate stack and Bi contacts. This architecture shows an average subthreshold swing of 34 mV dec-1 across four current decades, maintaining sub-60 mV dec-1 operation over this wide range, and enabling sub-0.4 V operation. Bi contact is key, minimizing Fermi-level pinning at the SnS2/metal interface. This expands the thermionic emission region, allowing the negative capacitance to fully leverage the distinct properties of SnS2 for sustained wide-range steep-slope performance. This work demonstrates a novel approach to ultralow-power transistors by integrating an isolated-band semiconductor, optimized ferroelectric, and contact engineering.
Cyclopropanation of Alkenes with Dichloromethane and Chloroform via Halogen Atom Transfer Using Amine Carboxyborane
2025-12Organic Letters, v.27, no.50, pp.13892 - 13897
Cyclopropanes are privileged motifs in medicinal chemistry due to their role as bioisosteres of arenes, alkenes, and small alkyl groups. Herein, we report a transition-metal-free, photoredox-catalyzed cyclopropanation of diverse alkenes via halogen atom transfer between dichloromethane (CH2Cl2) as a C1 synthon and amine-ligated boryl radicals generated from amine carboxyborane. This method proceeds under mild reaction conditions, exhibits a broad substrate scope, and is scalable. The synthetic utility is further highlighted by deuterium incorporation using CD2Cl2 and the formation of chlorocyclopropane products using chloroform (CHCl3) and CDCl3, enabling access to valuable chlorinated and isotopically labeled cyclopropanes.
Improvement of underwater durability and liquefaction evaluation of biopolymer-treated soil using tannic acid
ACCEPTJournal of Rock Mechanics and Geotechnical Engineering
Liquefaction occurs when loose, saturated sandy soils lose strength due to cyclic loads, like earthquakes, causing ground subsidence and structural collapse. While mitigation is possible, conventional cement-based methods have drawbacks, including carbon emissions and groundwater contamination. Consequently, there is a growing emphasis on the need for eco-friendly ground reinforcement materials. Research on biopolymer-treated soils lacks focus on underwater stability and performance degradation. This study used tannic acid to improve underwater durability, as confirmed through soil bonding experiments and cyclic shear tests. The optimal tannic acid formulation, based on gelatin content, enhanced liquefaction resistance and maintained stable strength during underwater curing.
Deterministic spin-orbit torque switching of epitaxial ferrimagnetic insulator with perpendicular magnetic anisotropy fabricated by on-axis magnetron sputtering
2025-10npj Spintronics, v.3, no.1
Current-induced switching of magnetization states in ferromagnet/spin-orbit material heterostructures has attracted significant attention, driven by the increasing need for low power consumption and a more efficient mechanism for magnetization switching. However, current shunting for the used metallic ferromagnets remains challenging in achieving low switching current densities. Thulium iron garnet, Tm
Comparative analysis of macroscopic and microscopic optical absorbance in hemagglutination assay
2025-12Methods, v.244, pp.195 - 209
We report a comparative study of macroscopic and microscopic optical absorbance in hemagglutination (HA) assay. Red blood cells (RBCs) exhibit unique optical absorbance properties with characteristic peaks including Soret, Qv, and Qo. In addition, RBCs absorb light and appear as dark contrast in bright-field microscopy images, indicating an increase in local optical density (OD). By systematic analysis of macroscopic and microscopic OD measurements and UV-Visible (UV-Vis) spectroscopy, we developed a phenomenological model of RBC agglutination and non-agglutination. The antigen-antibody reaction in RBC agglutination behaves as a catastrophic event such that networking of RBC clumps is initiated at a critical RBC concentration. We analyzed the dependence of OD on RBC concentration. At the critical RBC concentration, OD values are dropped or saturated for RBC agglutination, on the other hand, ODs keep increasing as the increase of RBC concentration for RBC nonagglutination. By the analysis of UV-Vis spectroscopy for HA assay, we provide an optimal wavelength range as 480-520 nm, away from RBC characteristic absorption peaks. For further validation, we demonstrated the ODbased HA assay for the detection of H1N1 influenza A virus. Our investigation provides insights into how to utilize the physical properties of RBCs for novel HA assay platforms.
Theory of slidetronics in ferroelectric van der Waals layers
2025-12Physical Review Materials, v.9, no.12
Ferroelectricity can emerge in vertically stacked two-dimensional materials even when their constituent monolayers are nonferroelectric. In these sliding ferroelectrics, polarization switching is driven by small lateral displacements between layers. Here, we develop a comprehensive materials design framework for slidetronics founded on a symmetry principle: any sliding-induced polarization change from a state P to P' can be equivalently described by applying an appropriate point-group operator, or "generator" G, to the entire system, such that P' = GP. This generator-based framework classifies all possible sliding-induced transformations, establishes the necessary symmetry conditions for switchable polarization components, and provides design strategies for realizing targeted switching behaviors. A central result is that complete polarization inversion is symmetry forbidden in bilayers but becomes possible in multilayers. First-principles calculations confirm these predictions, revealing novel phenomena including dipole-locked ferroelectricity in cellulose bilayers, in-plane switching in As2S3-based systems, and full polarization reversal in a PdSe2 trilayer.
