https://scholar.dgist.ac.kr/handle/20.500.11750/81 Fri, 24 Apr 2026 20:36:21 GMT 2026-04-24T20:36:21Z https://scholar.dgist.ac.kr/handle/20.500.11750/60197 Title: Surface-Interaction-Driven Polarity Switching in II-V Cd3P2 Colloidal Quantum Dots for Infrared Photodiodes Author(s): Tran, Ha-Chi V.; Shim, Doeun; Park, Youngsang; Choi, Mahnmin; Jeong, Hyeonjun; Bonifas, Guillaume; Ouyang, Liyan; Nayral, Celine; Delpech, Fabien; Kang, Joongoo; Jeong, Sohee Abstract: Colloidal quantum dots (CQDs) based on II-V semiconductors offer attractive optical absorption and carrier transport properties for infrared optoelectronics, yet their device-relevant electronic behavior remains poorly understood. In particular, Cd3P2 CQDs have been constrained by limited control over nanocrystal growth and carrier polarity. Here, a materials-to-device study establishes polarity control in Cd3P2 CQD solids for infrared photodiodes. Precise regulation of oleic acid (OA) concentration during synthesis yields monodisperse Cd3P2 CQDs with suppressed nanocrystal fusion and photoluminescence quantum yields up to 62 %. Electrical measurements reveal an oxygen-induced transition from n-type to p-type transport in Cd3P2 CQD films. Spectroscopic analysis and first-principles calculations indicate that adsorbed oxygen generates surface acceptor states that drive Fermi-level realignment. Building on these functional Cd3P2 CQD solids, a Cd3P2-based homojunction CQD photodiode is demonstrated, in which Cd3P2 functions as both the infrared absorber and a charge-selective layer. The resulting devices exhibit stable ambient operation, achieving a short-circuit current density of 18 mA cm(-2), an external quantum efficiency (EQE) of 24 %, and a fast temporal response of 23 ns under zero bias. These results identify surface-driven polarity control as a viable design strategy for II-V CQD optoelectronics and position Cd3P2 CQDs as a promising platform for low-power infrared conversion technologies. https://scholar.dgist.ac.kr/handle/20.500.11750/60197 https://scholar.dgist.ac.kr/handle/20.500.11750/60021 Title: Theory of slidetronics in ferroelectric van der Waals layers Author(s): Lee, Byeoksong; Lee, Minki; Kang, Joongoo Abstract: 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. Sun, 30 Nov 2025 15:00:00 GMT https://scholar.dgist.ac.kr/handle/20.500.11750/60021 2025-11-30T15:00:00Z https://scholar.dgist.ac.kr/handle/20.500.11750/59351 Title: Topological Machine Learning Unveils Hidden Reaction Pathways in Nanocrystal Synthesis Author(s): Lee, Byeoksong; Choi, Mahnmin; Shin, Jibin; Ha, Hyunwook; Shim, Doeun; Jeong, Sohee; Kang, Joongoo Abstract: Uncovering reaction pathways from analytical data such as UV-vis spectra remains a central challenge in nanocrystal synthesis, where transient and ill-defined intermediates complicate mechanistic analysis. Conventional approaches, reliant on manual spectral feature extraction and expert interpretation, are prone to bias and often overlook critical events. Here we present a machine learning framework that integrates transformer-based data augmentation with topological manifold learning to objectively elucidate reaction pathways directly from raw, high-dimensional spectroscopic data. The key insight is that the topology of the data manifold reflects the structure of the underlying reaction pathway. Applied to ex-situ UV-vis data sets of indium arsenide nanocrystal synthesis, this approach reconstructs the complete reaction landscape, identifying previously unreported metastable intermediates and revealing how chemical additives modulate intermediate formation to steer pathway selection. Broadly adaptable to diverse analytical data, this topological learning framework provides a generalizable strategy for mechanistic discovery and predictive control in complex chemical systems. Sun, 30 Nov 2025 15:00:00 GMT https://scholar.dgist.ac.kr/handle/20.500.11750/59351 2025-11-30T15:00:00Z https://scholar.dgist.ac.kr/handle/20.500.11750/58965 Title: Targeted Selenite Adsorption Using Defective Fe-BTC: Effective in Acidic and Alkaline Conditions Author(s): Byun, Asong; Lee, Byeoksong; Jeong, Yujin; Kang, Joongoo; Park, Jinkyu; Park, Jinhee Abstract: Amorphous Fe-BTC, characterized by entirely defective metal nodes, has been employed for the effective adsorption of toxic selenite anions from aqueous solutions. Remarkably, Fe-BTC maintains high adsorption efficiency across a broad pH range (2-12), achieving a maximum adsorption capacity of 491 mg g-1, ranking among the highest recorded for adsorbents, including MOFs. The adsorption process involves distinct chemical interactions depending on pH: weak and variable interactions under acidic conditions (pH 2) and strong, diverse coordination modes under alkaline conditions (pH 11). Notably, the strong coordination ability of selenite ensures high selectivity over selenate and competing anions such as Cl-, NO2-, NO3-, CO32-, SO42-, and PO43-. The abundance of metal defects endows Fe-BTC with superior adsorption capacity compared to crystalline Fe-MOF, MIL-100(Fe). This study provides a comparative analysis of selenite adsorption on Fe-BTC under acidic and alkaline conditions, emphasizing pH-dependent adsorption mechanisms and their implications for designing effective adsorbents for toxic species removal. Sun, 31 Aug 2025 15:00:00 GMT https://scholar.dgist.ac.kr/handle/20.500.11750/58965 2025-08-31T15:00:00Z