A5088900746- Organic Electronics and Photovoltaics
- Organic Light-Emitting Diodes Research
- Conducting polymers and applications
- Molecular Junctions and Nanostructures
- 2D Materials and Applications
- Perovskite Materials and Applications
- Semiconductor materials and devices
- Quantum Dots Synthesis And Properties
- Graphene research and applications
- Thin-Film Transistor Technologies
- Chalcogenide Semiconductor Thin Films
- ZnO doping and properties
- Advanced Memory and Neural Computing
- MXene and MAX Phase Materials
- Fullerene Chemistry and Applications
- Semiconductor materials and interfaces
- Nanowire Synthesis and Applications
- Advanced Sensor and Energy Harvesting Materials
- Topological Materials and Phenomena
- Electrocatalysts for Energy Conversion
- Electronic and Structural Properties of Oxides
- Advancements in Semiconductor Devices and Circuit Design
- Luminescence and Fluorescent Materials
- Ga2O3 and related materials
- Advanced Photocatalysis Techniques
Yonsei University
2016-2025
Government of the Republic of Korea
2019-2021
Materials Research Center
2021
Seoul Institute
2018-2020
University of South Florida
2006-2019
Pohang University of Science and Technology
2015
Korea University of Science and Technology
2009-2011
Korea Research Institute of Standards and Science
2007-2011
Kyung Hee University
2011
Center for Quantum Nanoscience
2010-2011
Black phosphorus consists of stacked layers phosphorene, a two-dimensional semiconductor with promising device characteristics. We report the realization widely tunable bandgap in few-layer black doped potassium using an in-situ surface doping technique. Through band-structure measurements and calculations, we demonstrate that vertical electric field from dopants modulates owing to giant Stark effect tunes material moderate-gap band-inverted semimetal. At critical this band inversion,...
Enhanced power conversion efficiency (PCE) is reported in inverted polymer solar cells when an electron‐rich nanolayer (poly(ethyleneimine) (PEI)) placed on the surface of electron‐collecting buffer layer (ZnO). The active made with bulk heterojunction films poly[[4,8‐bis[(2‐ethylhexyl)oxy]benzo[1,2‐b:4,5‐b′]dithiophene‐2,6‐diyl][3‐fluoro‐2‐[(2‐ethylhexyl)carbonyl]thieno[3,4‐b]thiophenediyl]] (PTB7) and [6,6]‐phenyl‐C 71 ‐butyric acid methyl ester (PC BM). thickness PEI controlled to be 2 nm...
Two-dimensional van der Waals (2D vdWs) materials are a class of new that can provide important resources for future electronics and sciences due to their unique physical properties. Among 2D vdWs materials, black phosphorus (BP) has exhibited significant potential use in electronic optoelectronic applications because its allotropic properties, high mobility, direct narrow band gap. Here, we demonstrate few-layered BP-based nonvolatile memory transistor with...
Abstract Colloidal quantum dots (QDs) are an emerging class of new materials due to their unique physical properties. In particular, colloidal QD based light emitting diodes (QDLEDs) have been extensively studied and developed for the next generation displays solid-state lighting. Among a number approaches improve performance QDLEDs, most practical one is optimization charge transport balance in recombination region. Here, we suggest polyethylenimine ethoxylated (PEIE) modified ZnO...
The development of stable and efficient oxygen evolutional electrocatalysts is fundamental to the production hydrogen by water electrolysis. However, so far majority require a substantial overpotential (η) (approximately >250 mV) catalyze bottleneck evolution reaction (OER). To overcome this large for OER, herein we report growth nickel–cobalt–selenide (NiCoSe2) nanosheets over 3D nickel foam (NF) via facile scalable electrodeposition method. resulting NiCoSe2/NF hybrid electrode requires an...
Thin flakes of black phosphorus (BP) are a two-dimensional (2D) semiconductor whose energy gap is predicted being sensitive to the number layers and external perturbations. Very recently, it was found that simple method potassium (K) doping on surface BP closes its band completely, producing Dirac semimetal state with linear dispersion in armchair direction quadratic one zigzag direction. Here, based first-principles density functional calculations, we predict that, beyond critical K...
A van der Waals (vdW) Schottky junction between two-dimensional (2D) transition metal dichalcogenides (TMDs) is introduced here for both vertical and in-plane current devices: diodes semiconductor field-effect transistors (MESFETs). The barrier conducting NbS2 semiconducting n-MoS2 appeared to be as large ∼0.5 eV due their work-function difference. While the diode shows an ideality factor of 1.8–4.0 with on-to-off ratio 103−105, Schottky-effect MESFET displays little gate hysteresis ideal...
The paired electric dipole layers significantly intensify the built-in field across perovskite layer, resulting in suppressed charge trapping of photogenerated charges.
Abstract To further increase the open‐circuit voltage ( V oc ) of perovskite solar cells (PSCs), many efforts have been devoted to doping TiO 2 electron transport/selective layers by using metal dopants with higher electronegativity than Ti. However, those can introduce undesired charge traps that hinder transport through , so improvement in is often accompanied an photocurrent density–voltage J–V hysteresis problem. Herein, it demonstrated use a rapid flame process (40 s) cobalt dopant into...
Abstract Two-dimensional (2D) transition metal dichalcogenides (TMDs)-based van der Waals (vdW) PN junctions have been used for heterojunction diodes, which basically utilize out-of-plane current across the junction interface. In fact, same vdW structure can be utilized another important device application, field effect transistors (JFETs), where in-plane is possible along with 2D–2D Moreover, 2D TMD-based JFET use both p- and n-channel low voltage operation, might its unique feature. Here...
Iridium on vertical graphene nano-hills emerges as a highly active and robust catalyst for the total water splitting reaction in both acidic alkaline electrolytes.
We investigated the interfacial electronic structures of indium tin oxide (ITO)/molybdenum trioxide (MoO3)/N,N′-bis(1-naphthyl)-N,N′-diphenyl-1,1′-biphenyl-4,4′-diamine (NPB) using in situ ultraviolet and x-ray photoemission spectroscopy to understand origin hole injection improvements organic light-emitting devices (OLEDs). Inserting a MoO3 layer between ITO NPB, barrier was remarkably reduced. Moreover, gap state band NPB found which assisted Ohmic at interface. The lowering explain why...
We report on the nonvolatile memory characteristics of a bistable organic (BOM) device with Au nanoparticles (NPs) embedded in conducting poly(N-vinylcarbazole) (PVK) colloids hybrid layer deposited flexible poly(ethyleneterephthalate) (PET) substrates. Transmission electron microscopy (TEM) images show distributed isotropically around surface PVK colloid. The average induced charge nanoparticles, estimated using C−V hysteresis curve, was large, as much 5 holes/NP at sweeping voltage ±3 V....
Procedure of removing polymer residues by post-annealing and the effect on electronic properties transferred monolayer graphene grown chemical vapor deposition method are investigated using X-ray photoelectron spectroscopy Raman spectroscopy. It is found that breaking polymerization backbone bond induces effective removal poly(methyl methacrylate) surface depolymerization, decomposition carboxyl functional group involves reducing level p-doping graphene, while annealing process leads to an...
Hydrazine fuel-cell technology holds great promise for clean energy, not only because of the greater energy density hydrazine compared to hydrogen but also due its safer handling owing liquid state. However, current technologies involve use precious metals (such as platinum) oxidation, which hinders further application technologies. In addition, little attention has been devoted management gas, tends become stuck on surface electrode, producing overall poor electrode efficiencies. this...
Amorphous InGaZnO semiconductors have been rapidly developed as active charge-transport materials in thin film transistors (TFTs) because of their cost effectiveness, flexibility, and homogeneous characteristics for large-area applications. Recently, InZnSnO (IZTO) with superior mobility (higher than 20 cm2 V–1 s–1) has suggested a promising oxide semiconductor material high-resolution, displays. However, the electrical physical IZTO not fully characterized. In this study, films were grown...
The energy level alignments at donor/acceptor interfaces in organic photovoltaics (OPVs) play a decisive role device performance. However, little is known about the interfacial energetics polymer OPVs due to technical issues of solution process. Here, frontier ortbial line-ups interface high performance OPVs, PTB7/PC71BM, were investigated using situ UPS, XPS and IPES. evolution levels during PTB7/PC71BM formation was vacuum electrospray deposition, compared with that P3HT/PC61BM. At...
Abstract The need for miniaturized and high-performance devices has attracted enormous attention to the development of quantum silicon nanowires. However, preparation abundant quantities nanowires with effective quantum-confined dimension remains challenging. Here, we prepare highly dense vertically aligned sub-5 nm length/diameter aspect ratios greater than 10,000 by developing a catalyst-free chemical vapor etching process. We observe an unusual lattice reduction up 20% within ultra-narrow...
We report the enhancement of hole current density in transport part an inverted top-emission organic light emitted diode by applying insertion layer 1,4,5,8,9,11-hexaazatriphenylene-hexacarbonitrile (HAT-CN). Poor transporting performance Al/4,4′-bis(N-phenyl-1-naphthylamino)biphenyl (NPB)/indium tin oxide is greatly improved HAT-CN between Al and NPB layer. The highest occupied molecular orbital level onset bends toward Fermi at HAT-CN/NPB interface. This extra charge generation made pure...
Abstract Polymer light emitting diodes (PLEDs) using quantum dots (QDs) as emissive materials have received much attention promising components for next-generation displays. Despite their outstanding properties, toxic and hazardous nature of QDs is a serious impediment to use in future eco-friendly opto-electronic device applications. Owing the desires develop new types nano-material without health environmental effects but with strong opto-electrical properties similar QDs, graphene (GQDs)...
2D van der Waals atomic crystal materials have great potential for use in future nanoscale electronic and optoelectronic applications owing to their unique properties such as a tunable energy band gap according thickness or number of layers. Recently, black phosphorous (BP) has attracted significant interest because it is single‐component material like graphene high mobility, direct gap, exhibits ambipolar transition behavior. This study reports on charge injection memory field‐effect...
We fabricated Cu(In,Ga)Se2 (CIGS) solar cells with a chemical bath deposition (CBD)-ZnS buffer layer grown varying ammonia concentrations in aqueous solution. The cell performance was degraded increasing concentration, due to actively dissolved Zn atoms during CBD-ZnS precipitation. These formed interfacial defect states, such as hydroxide species the film, and interstitial antisite defects at p-n heterojunction. After light/UV soaking, CIGS drastically improved, rise fill factor. With...