Korea University · Materials Science
Professor Jinsoo Joo's research lab specializes in the design, synthesis, and characterization of conductive and functional organic materials, with a primary focus on intrinsically conducting polymers (ICPs) such as polyaniline, polypyrrole, and polyacetylene. The lab investigates the structure-property relationships governing electromagnetic shielding, charge transport, dielectric behavior, and optoelectronic responses in these materials, particularly under varying crystallinity, doping levels, and external stimuli. Key research directions include enhancing electromagnetic interference (EMI) shielding efficiency through nanostructuring and hybridization, exploring metallic-like behavior in doped polyaniline, and developing high-performance organic phototransistors and plasmon-enhanced optoelectronic devices. The lab also emphasizes the integration of organic semiconductors with nanomaterials for next-generation flexible and lightweight electronic applications.
Figures are computed from collected data and may differ slightly.
The shielding efficiency of various intrinsically conducting polymers (ICPs) as a function of their intrinsic properties (conductivity and dielectric constant), thickness, and temperature is determined. Two types of shielding, reflection and absorption, by ICPs are discussed. The high shielding efficiencies of highly conducting doped polyaniline, polypyrrole, and polyacetylene are reported and compared to that of copper. The easy tuning of intrinsic properties by chemical processing suggests the
The electromagnetic interference (EMI) shielding efficiency (SE) is measured for conductive polyaniline and its mixtures containing conducting powders. The frequency ranges of the EMI SE is 10 MHz–1 GHz by using the ASTM D4935-89 technique. The EMI SE of hydrochloric acid doped polyaniline containing silver (Ag) powder is ∼46 dB at room temperature, which indicates that the materials can be commercially applied to shielding against electromagnetic (EM) radiation. The theoretical SE is calculated
Charge transport properties, including temperature-dependent dc conductivity, thermoelectric power, electron paramagnetic resonance, microwave frequency dielectric constant and conductivity, and electric-field-dependent conductance of partially crystalline (``physically'' cross-linked) HCl-doped polyaniline correlated with x-ray structure studies, demonstrate that charge delocalization in physically cross-linked polyaniline systems is structurally controlled. Further, we observe a positive diele
We report the dependence of the microwave-frequency dielectric constant and dc conductivity on the crystallinity and local order of doped polyaniline. The dramatic increase of the dielectric response in the three highest crystalline physically crosslinked polyaniline samples provides evidence for the formation of three-dimensional coupled mesoscopic metallic regions. We report the measurement of a negative dielectric constant in polyaniline (doped with camphor sulfonic acid) demonstrating the in
Pi-conjugated organic systems have been used as optoelectronic and sensing materials due to their characteristics of efficient light emission or absorption, and p-type charge transport. The hybrid nanostructures of pi-conjugated organic systems with nanoscale metals offer surface plasmon (SP)-enhanced luminescence, which can be applied to organic-based optoelectronics, photonics, and sensing. Various hybrid nanostructures using light-emitting polymers with nanoscale metals have been fabricated a
Abstract The highly photosensitive characteristics of organic thin‐film transistors (OTFTs) made using soluble star‐shaped oligothiophenes with four‐armed π ‐conjugation paths, 4(HPBT)‐benzene and 4(HP3T)‐benzene molecules having a relatively high quantum yield, are reported. 4(HPBT)‐benzene‐based organic phototransistors (OPTs) exhibited high photosensitivity (∼2500–4300 A W −1 ) even with low optical powers (∼6.8–30 µW cm −2 ) at zero gate bias. The measured photosensitivity of the devices was
Abstract Electromagnetic interference (EMI) shielding materials of complex type of conductive polypyrrole (PPy) as an intrinsically conducting polymer and silver‐palladium (AgPd) metal compound coated on woven or non‐woven fabrics are synthesized. From dc conductivity and SEM photographs of PPy/fabric complexes, we discuss charge transport mechanism and the homogeneity of coating on the fabrics. The EMI shielding efficiency of PPy/fabric and AgPd/fabric complexes is in the range of 8 ∼ 80 dB dep
The results of microwave dielectric constant (ϵmw) and dc conductivity (σdc) of doped polyaniline (PAN) samples in different charge delocation regimes are reported. With camphor culfonic acid doped PAN prepared in m-cresol solvent (PAN-CSA (m-cresol)) respresenting the most delocalized material, a negative ϵmw is measured indicating an intrinsic metallic state. The Drude model at low frequency is used to estimate a relatively small plasma frequency ωp ⋍ 0.015 eV and an anomalously long scatterin
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