Ewha Womans University · Engineering
Professor Jaehong Park's research lab specializes in advanced materials and nanoscale electronic systems, with a focus on carbon nanomaterials, organic semiconductors, and novel fabrication techniques for next-generation optoelectronic and electronic devices. The lab investigates fundamental charge carrier dynamics in single-walled carbon nanotubes, including excitonic and free-carrier generation, using ultrafast spectroscopy and contactless conductivity measurements. It also develops innovative methods for printing and doping organic and hybrid conductive materials, such as ac voltage-assisted EHD jet printing and quantitative AC Hall-effect characterization of doped conjugated polymers. The overarching goal is to enable high-performance, flexible, and transparent electronics through precise control of electronic properties at the nanoscale.
Figures are computed from collected data and may differ slightly.
Virtual communities continue to play a greater role in social, political, and economic interactions. However, how users value information from these communities and how that affects their behavior and future expectations is not fully understood. Stock message boards provide an excellent setting to analyze these issues given the large user base and market uncertainty. Using data from 502 investor responses from a field experiment on one of the largest message board operators in South Korea, our a
In this paper, we present an algorithm for the construction of detection spaces in a fault detection filter by direct eigenstructure assignment. The algorithm permits great flexibility and simplifies the process of designing fault detection filters.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
We utilize femtosecond-to-microsecond time domain pump-probe transient absorption spectroscopy to interrogate for the first time the electronically excited triplet state of individualized single-wall carbon nanotubes (SWNTs). These studies exploit (6,5) chirality-enriched SWNT samples and poly[2,6-{1,5-bis(3-propoxysulfonic acid sodium salt)}naphthylene]ethynylene (PNES), which helically wraps the nanotube surface with periodic and constant morphology (pitch length = 10 ± 2 nm), providing a self
Strong quantum confinement and low dielectric screening impart single-walled carbon nanotubes with exciton-binding energies substantially exceeding kBT at room temperature. Despite these large binding energies, reported photoluminescence quantum yields are typically low and some studies suggest that photoexcitation of carbon nanotube excitonic transitions can produce free charge carriers. Here we report the direct measurement of long-lived free-carrier generation in chirality-pure, single-walled
In the dc voltage-applied electrohydrodynamic (EHD) jet printing of metal nanoparticles, the residual charge of droplets deposited on a substrate changes the electrostatic field distribution and interrupts the subsequent printing behaviour, especially for insulating substrates that have slow charge decay rates. In this paper, a sinusoidal ac voltage was used in the EHD jet printing process to switch the charge polarity of droplets containing Ag nanoparticles, thereby neutralizing the charge on a
Abstract Developing electrical organic conductors is challenging because of the difficulties involved in generating free charge carriers through chemical doping. To devise a novel doping platform, the doping capabilities of four designed conjugated polymers (CPs) are quantitatively characterized using an AC Hall‐effect device. The resulting carrier density is related to the degree of electronic coupling between the CP repeating unit and 2,3,5,6‐tetrafluoro‐7,7,8,8‐tetracyanoquinodimethane (F4‐TC
We have investigated carbon nanotube (CNT)-field emitter array (FEA) for the application of lighting system like back light unit (BLU) in liquid crystal display (LCD). The photosensitive CNT paste was synthesized by mixing of multiwalled carbon nanotubes (MWNTs), spin on glass (SOG), organic vehicle, photosensitive monomers, photosensitive oligomers and photo initiators. Uniform CNT paste films were obtained by using backside exposure technique and emission properties of CNT paste were evaluated
Partial least squares (PLS) path modeling is a component-based structural equation modeling that has been adopted in social and psychological research due to its data-analytic capability and flexibility. A recent methodological advance is consistent PLS (PLSc), designed to produce consistent estimates of path coefficients in structural models involving common factors. In practice, however, PLSc may frequently encounter multicollinearity in part because it takes a strategy of estimating path coef
We use flash-photolysis time-resolved microwave conductivity experiments (FP-TRMC) and femtosecond-nanosecond pump-probe transient absorption spectroscopy to investigate photoinduced carrier generation and recombination dynamics of a trilayer cascade heterojunction composed of poly(3-hexylthiophene) (P3HT), titanyl phthalocyanine (TiOPc), and fullerene (C60). Carrier generation following selective photoexcitation of TiOPc is independently observed at both the P3HT/TiOPc and TiOPc/C60 interfaces.
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