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Kim, Jeonghun,Koh, Jong Kwan,Kim, Byeonggwan,Ahn, Sung Hoon,Ahn, Hyungju,Ryu, Du Yeol,Kim, Jong Hak,Kim, Eunkyoung WILEY‐VCH Verlag 2011 Advanced Functional Materials Vol.21 No.24
<P>An iodine‐free solid‐state dye‐sensitized solar cell (ssDSSC) with 6.8% efficiency can be fabricated using conductive polymers and organized mesoporous TiO<SUB>2</SUB>. On page 4633, Eunkyoung Kim, Jong Hak Kim, and co‐workers show the effects of polymer conductivity and transmittance of the interfacial TiO<SUB>2</SUB> layer on energy conversion efficiency. This method can be used for the fabrication of various photovoltaic cells. </P>
Waterborne polyacrylic/PEDOT nanocomposites for conductive transparent adhesives.
Kim, Byeonggwan,Park, Teahoon,Kim, Jeonghun,Kim, Eunkyoung American Scientific Publishers 2013 Journal of Nanoscience and Nanotechnology Vol.13 No.11
<P>A new nanocomposite for conductive transparent adhesives (CTAs) was synthesized by emulsion polymerization of acrylate monomers dispersed with poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS). Polymer particles of waterborne CTAs were uniform, and the average size of the particles was 330 nm. The conductive transparent adhesive nanocomposites (CTANs) were casted onto various substrates including slide glass, indium tin oxide (ITO) glass, and PET film. Upon thermal processing at 80 degrees C, highly transparent adhesive films were obtained with surface uniformity. The stress of the CTANs was affected by the contents of PEDOT:PSS, and a 7.5 wt% CTAN film had the highest maximum stress of 0.33 MPa. Importantly, polyacrylic nanoparticles were well dispersed with conductive filler PEDOT:PSS in water because of their high dispersity in water. Therefore, the polyacrylic/PEDOT nanocomposite had a low percolation threshold of approximately 8% due to the enhanced connection between conductive channels. The CTANs with an optimum content (10 wt%) of PEDOT:PSS had high electromagnetic interference shielding effectiveness (36 dB) and transparency (75%) for application to electronics including displays and solar cells.</P>
Kim, Byeonggwan,Koh, Jong Kwan,Kim, Jeonghun,Chi, Won Seok,Kim, Jong Hak,Kim, Eunkyoung Wiley-VCH 2012 CHEM SUS CHEM Vol.5 No.11
<P>A solid-state polymerizable monomer, 2,5-dibromo-3,4-propylenedioxythiophene (DBProDOT), was synthesized at 25?C to produce a conducting polymer, poly(3,4-propylenedioxythiophene) (PProDOT). Crystallographic studies revealed a short interplane distance between DBProDOT molecules, which was responsible for polymerization at low temperature with a lower activation energy and higher exothermic reaction than 2,5-dibromo-3,4-ethylenedioxythiophene (DBEDOT) or its derivatives. Upon solid-state polymerization (SSP) of DBProDOT at 25?C, PProDOT was obtained in a self-doped state with tribromide ions and an electrical conductivity of 0.05?S?cm?1, which is considerably higher than that of chemically-polymerized PProDOT (210?? S?cm?1). Solid-state 13C?NMR spectroscopy and DFT calculations revealed polarons in PProDOT and a strong perturbation of carbon nuclei in thiophenes as a result of paramagnetic broadening. DBProDOT molecules deeply penetrated and polymerized to fill nanocrystalline TiO2 pores with PProDOT, which functioned as a hole-transporting material (HTM) for I2-free solid-state dye-sensitized solar cells (ssDSSCs). With the introduction of an organized mesoporous TiO2 (OM-TiO2) layer, the energy conversion efficiency reached 3.5?% at 100?mW?cm?2, which was quite stable up to at least 1500?h. The cell performance and stability was attributed to the high stability of PProDOT, with the high conductivity and improved interfacial contact of the electrode/HTM resulting in reduced interfacial resistance and enhanced electron lifetime.</P>
Kim, Byeonggwan,Shin, Haijin,Park, Teahoon,Lim, Hanwhuy,Kim, Eunkyoung WILEY‐VCH Verlag 2013 Advanced Materials Vol.25 No.38
<P>The electrochromism and photothermoelectric properties of a poly(3,4‐ethylenedioxyselenophene) derivative are investigated by precisely controlling the morphology and applied electrical potential of the flexible polymer films. On page 5483, Eunkyoung Kim and co‐workers report a highly efficient and flexible photothermoelectric converter using doped poly(3,4‐ethylenedioxyselenophene)s. Efficient visible to near‐infrared absorption, photon to heat, and heat to electric conversion are realized in one polymer film. </P>
You, Jungmok,Heo, June Seok,Kim, Jeonghun,Park, Teahoon,Kim, Byeonggwan,Kim, Han-Soo,Choi, Youjeong,Kim, Hyun Ok,Kim, Eunkyoung American Chemical Society 2013 ACS NANO Vol.7 No.5
<P>Viable mesenchymal stem cells (MSCs) were efficiently and selectively harvested by near-infrared (NIR) light using the photothermal effect of a conductive polymer nano thin film. The poly(3,4-ethylenedioxy thiophene) (PEDOT)-coated cell culture surfaces were prepared <I>via</I> a simple and fast solution-casting polymerization (SCP) technique. The absorption of PEDOT thin films in the NIR region was effectively triggered cell harvesting upon exposure to an NIR source. By controlling the NIR absorption of the PEDOT film through electrochemical doping or growing PEDOT with different thin film thickness from 70 to 300 nm, the proliferation and harvesting of MSCs on the PEDOT surface were controlled quantitatively. This light-induced cell detachment method based on PEDOT films provides the temporal and spatial control of cell harvesting, as well as cell patterning. The harvested stem cells were found to be alive and well proliferated despite the use of temperature increase by NIR. More importantly, the harvested MSCs by this method preserved their intrinsic characteristics as well as multilineage differentiation capacities. This PEDOT surfaces could be used for repetitive culture and detachment of MSCs or for efficient selection or depletion of a specific subset from heterogeneous population during culture of various tissue-derived cells because there were no photodegradation and photobreakage in the PEDOT films by NIR exposure.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2013/ancac3.2013.7.issue-5/nn400405t/production/images/medium/nn-2013-00405t_0007.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nn400405t'>ACS Electronic Supporting Info</A></P>
Connection Loss Detection Algorithm of Parallel-connected Cells Based on Change of Battery SOC
Byeonggwan Jang,Kyung-Soo Kim,Hyoseo Choi,Wooyong Kim 제어·로봇·시스템학회 2023 International Journal of Control, Automation, and Vol.21 No.11
The battery pack consists of parallel-connected cells to satisfy the power and mileage per charge of the eco-friendly vehicles. The vehicle specifications determine the number of battery cells connected in parallel by the type of battery. In driving conditions, such as sharp bumps and rough roads, the welding used for the interconnection between the cells may become loose, potentially causing the cells to detach from the battery module. The detachment leads to a reduction in the capacity of the battery pack and increases cell-to-cell variation among the parallel-connected battery cells. The detection algorithm for identifying disconnections among parallel-connected cells in a module is essential for ensuring the safe operation of the battery pack. This paper introduces a novel method for detecting contact loss among parallel-connected cells by utilizing the state of charge (SOC) change rate of the cells. The algorithm utilizes the estimated internal resistance and the variation in the slope of the estimated SOC change to detect connection losses within a battery module. The proposed method is verified with the simulation using Matlab/Simulink. The performance of the proposed algorithm is validated in various cases with some scenarios.
Photothermally powered conductive films for absorber-free solar thermoelectric harvesting
Kim, Byeonggwan,Han, Minsu,Kim, Eunkyoung The Royal Society of Chemistry 2019 Journal of Materials Chemistry A Vol.7 No.5
<P>The photothermoelectric (PTE) effect in conductive polymers is significant because it combines high photothermal (PT) and thermoelectric (TE) effects. Using poly(3,4-ethylenedioxythiophene) (PEDOT) films with various conductivities and crystallinities, the PTE effect in thin films can be established. The PT temperature increase (Δ<I>T</I>PT) under light exposure and the thermal voltage induced by Δ<I>T</I>PT for a series of PEDOT films indicated an unparalleled sensitivity to the carrier mobility in PT and TE conversions. The PTE Seebeck coefficients (<I>S</I>PTE) and power factors (PFPTE) for the PEDOT films correlated well with those in the dark state, indicating that the PTE effect in PEDOT can be translated into the TE effect induced by heating upon light exposure. The 180 nm-thick pristine PEDOT film shows high PFPTE values of 620 and 590 μW m<SUP>−1</SUP> K<SUP>−2</SUP> for a near-infrared laser and sunlight, respectively. The thin-film solar TE harvester with four PEDOT legs generates a power density of 38 mW m<SUP>−2</SUP> and an energy density of 420 W h g<SUP>−1</SUP>, demonstrating the first and highest absorber-free organic solar TE output yet reported. Thus, the PT conversion mechanisms in CP films can be extended to thin-film solar energy harvesters.</P>