A5020822934- Perovskite Materials and Applications
- Spectroscopy and Quantum Chemical Studies
- Molecular spectroscopy and chirality
- Chalcogenide Semiconductor Thin Films
- Quantum Dots Synthesis And Properties
- Click Chemistry and Applications
- Solid-state spectroscopy and crystallography
- Conducting polymers and applications
- Photonic and Optical Devices
- Analytical Chemistry and Chromatography
- Chemical and Physical Properties in Aqueous Solutions
- Advanced Chemical Physics Studies
- Optical properties and cooling technologies in crystalline materials
- Photoreceptor and optogenetics research
- Organic Light-Emitting Diodes Research
- Photochemistry and Electron Transfer Studies
- Transition Metal Oxide Nanomaterials
- Terahertz technology and applications
- Organic and Molecular Conductors Research
- Topological and Geometric Data Analysis
- Inorganic Chemistry and Materials
- Lattice Boltzmann Simulation Studies
- Thermal Radiation and Cooling Technologies
- Electronic and Structural Properties of Oxides
- Galectins and Cancer Biology
Hannam University
2025
Max Planck Institute for Polymer Research
2015-2024
Pohang University of Science and Technology
2024
Nanosys (United States)
2017-2018
University of Delaware
2012-2017
Korea University
2012-2015
Massachusetts Institute of Technology
2004
Samsung (South Korea)
2001
Seoul National University
2000
Abstract Methylammonium lead iodide perovskite is an outstanding semiconductor for photovoltaics. One of its intriguing peculiarities that the band gap this increases with increasing lattice temperature. Despite presence various thermally accessible phonon modes in soft material, understanding how precisely these phonons affect macroscopic material properties and to peculiar temperature dependence has remained elusive. Here, we report a strong coupling single mode at frequency ~ 1 THz...
We report that UV-ozone treatment of TiO2 anatase thin films is an efficient method to increase the conductance through film by more than 2 orders magnitude. The in quantified via conductive scanning force microscopy on freshly annealed and UV-ozone-treated fluorine-doped tin oxide substrates. increased results a 2% average power conversion efficiency (PCE) methylammonium lead iodide-based perovskite solar cells. PCE values up 19.5% for mesoporous cells are realized. additional reduced...
The critical aggregation phenomena are ubiquitous in many self-assembling systems. Ions high salt solutions could also spontaneously form larger ion aggregates, but their effects on hydrogen-bond structures water have long been controversial. Here, carrying out molecular dynamics (MD) simulation studies of and comparing the MD results with infrared absorption pump-probe spectroscopy O–D stretch mode HDO highly concentrated 13C-NMR chemical shift S13CN− KSCN solutions, we find evidence onset...
Abstract Whereas there is increasing evidence for ion‐induced protein destabilization through direct ion–protein interactions, the strength of binding anions to proteins relative cation–protein has remained elusive. In this work, rotational mobility a model amide in aqueous solution was used as reporter interactions different with group. Protein‐stabilizing salts such KCl and KNO 3 do not affect amide. Conversely, denaturants KSCN KI markedly reduce orientational freedom Thus these results...
Quantum dot color conversion layers have the potential to greatly improve efficiency and performance of displays including beyond liquid crystal displays. To fully realize these improvements, quantum dots must be deposited patterned at high resolution. One promising method for achieving this is through inkjet printing. In paper we report on fabrication characterization inks, as well films made from deposition materials.
Abstract Phonon dynamics are a critical factor to control the optical properties of excited states in light‐emitting materials. Here, we report an extremely slow relaxation photoexcited lattice vibrations enabled by assembling donor‐acceptor (D–A) molecules [2‐(9,9‐dimethylacridin‐10(9H)‐yl)‐9,9‐dimethyl‐9H‐thioxanthene 10,10‐dioxide], namely AC molecules, into dipolar crystal. By using photoexcitation‐modulated Raman spectroscopy, find that crystalline‐lattice monitored Raman‐scattering...
Specific ion effects on water dynamics and local solvation structure around a peptide are important in understanding the Hofmeister series of ions their protein stability aqueous solution. Water is essentially governed by hydrogen-bonding interactions with surrounding molecules producing hydration electric field each molecule. Here, we show that OD bond HOD molecule can be directly estimated measuring its stretch infrared (IR) radiation frequency shift upon increasing concentration. For...
Abstract The interplay of electronic and nuclear degrees freedom in semiconductor hybrid organic–inorganic perovskites determines many their fundamental photophysical properties. For instance, charge carriers are dressed with phonons, that is, form polarons, combination modes composed strongly mixed localized vibrations delocalized phonons can provide pathways for energy relaxation dissipation. Mixing the different types motion vibrational requires strong coupling. direct measurement...
Regular arrays of nonadherent B cells over large areas were produced with the use micropatterned molecular templates consisting a newly designed poly(allylamine)-g-poly(ethylene glycol) polycation graft copolymer. Polymer-on-polymer stamping (POPS) techniques applied successfully to create micron scale patterns copolymer on negatively charged multilayer surfaces without losing resistance nonspecific adsorption proteins. To generate for cell arrays, characteristics patterned surface modified...
The thiocyanate (SCN−) anion is known as one of the best denaturants, which also capable breaking hydrogen-bond network water and destabilizing native structures proteins. Despite prolonged efforts to understand underlying mechanism such Hofmeister effects, detailed dynamics ions in a highly concentrated solution have not been fully elucidated yet. Here, we used dispersive IR pump–probe spectroscopic method study dependence vibrational lifetimes rotational relaxation times on KSCN...
Quasi-2D perovskites have been pivotal in recent efforts to stabilize perovskite solar cells. Despite the stability boost provided when these materials are introduced cells, little is known about intrinsic light and environmental of quasi-2D perovskites. In this study, we characterize photostability exfoliated single crystals air using photoluminescence, infrared, X-ray fluorescence, energy-dispersive spectroscopy. Photoexcitation leads severe material loss with oxygen as a prerequisite for...
Phosphoric acids have emerged as efficient organo-catalysts for various reactions. Despite widespread use, details of the reaction intermediates giving rise to stereocontrol remained elusive. To clarify nature catalyst–substrate interaction, we characterize and quantify complex formation by combining dielectric spectroscopy, quantum chemistry, 1H NMR spectroscopy. For a series different solvents, interaction between substrate catalyst is dominated ion-pairing, rather than hydrogen bonding,...
The vibrational frequency, frequency fluctuation dynamics, and transition dipole moment of the O-D stretch mode HDO molecule in aqueous solutions are strongly dependent on its local electrostatic environment hydrogen-bond network structure. Therefore, time-resolved spectroscopy has been particularly used to investigate specific ion effects water Despite prolonged efforts understand interplay dynamics with aggregate structures high salt solutions, still there exists a gap between theory...
A time series of kinetic energies (KE) from classical molecular dynamics (MD) simulation contains fundamental information on system dynamics. It can also be analyzed in the frequency domain through Fourier transformation (FT) velocity correlation functions, providing energy content different spectral regions. By limiting FT span, we have previously shown that resolution KE evolution is possible nonequilibrium situations [Jeon and Cho, J. Chem. Phys. 2011, 135, 214504]. In this paper, refine...
Moving the light conversion by quantum dots (QDs) from backlight to front of LCD has potential further improve both overall efficiency and color gamut display. In order accomplish this change architecture, QDs have be patterned at sub‐pixel pitch This requires integrated into a photoresist high concentration in produce pixels required size optical density. Here we report on our fabrication characterization red green QD photoresist, as well how model its performance displays.
Optical cavities, resonant with vibrational or electronic transitions of material within the cavity, enable control light-matter interaction. Previous studies have reported cavity-induced modifications chemical reactivity, fluorescence, phase behavior, and charge transport. Here, we explore effect cavity-phonon coupling on transient photoconductivity in a hybrid organic-inorganic perovskite. To this end, measure ultrafast response perovskite tunable Fabry-Pérot terahertz designed to be...
Solutions of Brønsted acids with bases in aprotic solvents are not only common model systems to study the fundamentals proton transfer pathways but also highly relevant acid catalysis. Despite their importance light nature makes characterization acid-base aggregates challenging. Here, we track such interactions over a broad range relative compositions between diphenyl phosphoric and base quinaldine dichloromethane, by using combination dielectric relaxation NMR spectroscopy. In contrast what...