Chung Kun Song

Dong-A University, Tsau-liang-hai, Busan, South Korea

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Publications (37)57.89 Total impact

  • Jae Seon Kim · Chung Kun Song ·
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    ABSTRACT: A layer of 6,13-bis(triisopropylsilylethynyl) pentacene(TIPS-pentacene) organic thin film transistors (OTFTs) deposited by an ink jet printer was patterned using bank structures. Normally, banks degrade the performance of OTFTs because ink adhering to the sidewalls of the bank disrupts the formation of crystal grains, lowering mobility. An appropriately designed bank structure, which had only two photo-resist sidewalls perpendicular to the channel direction of the OTFTs, produced a mobility of the 0.23 ± 0.05 cm2/V·s, comparable to 0.25 ± 0.09 cm2/V·s of OTFTs produced without banks. The minimum thickness of the TIPS-pentacene layer needed to achieve high mobility was determined to be about 20 nm. A modified bank structure with a splitter bar in the middle of the open bank was also developed to simultaneously fabricate two OTFTs by jetting a single drop on the splitter. The mobilities of the two OTFTs were 0.24 ± 0.04 cm2/V·s and 0.28 ± 0.09 cm2/V·s, respectively.
    Thin Solid Films 08/2015; 589:620-626. DOI:10.1016/j.tsf.2015.06.043 · 1.76 Impact Factor
  • Seokgeun Jin · Byung Jun Jung · Chung Kun Song · Jeonghun Kwak ·
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    ABSTRACT: We introduce a room temperature and solution-processible vanadium oxide (VOx) buffer layer beneath Au source/drain electrodes for bottom-contact (BC) organic field-effect transistors (OFETs). The OFETs with the VOx buffer layer exhibited higher mobility and lower threshold voltages than the devices without a buffer layer. The hole mobility with VOx was over 0.11 cm2/V with the BC geometry with a short channel length (10 μm), even without a surface treatment on SiO2. The channel width normalized contact resistance was decreased from 98 kΩ cm to 23 kΩ cm with VOx. The improved mobility and the reduced contact resistance were attributed to the enhanced continuity of pentacene grains, and the increased work function and adhesion of the Au electrodes using the VOx buffer layer.
    Current Applied Physics 12/2014; 14(12):1809–1812. DOI:10.1016/j.cap.2014.10.019 · 2.21 Impact Factor
  • Seung-Hyeon Jeong · Chung Kun Song ·
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    ABSTRACT: In this paper, a new method is introduced to obtain the energetic distribution of the interface states (density of states; DOS) extracted from the photo-conductance of organic thin film transistors (OTFTs) which exhibit varied transfer characteristics under illumination with different photon energies. The method was applied to pentacene OTFTs, and the results were compared with existing data. The major findings were not only the existence of the well-known peaks of DOS at 1.82 eV (free exciton of pentacene), and at 1.49 eV (extrinsic exciton due to dihydropentacene) but also new peaks were found at 1.25 eV, 1.29 eV, 1.31 eV, and 1.35 eV in the mid-gap. The new peaks were strongly enhanced under exposure to oxygen, and thus seem to be related to the defects associated with the presence of oxygen.
    Organic Electronics 10/2014; 15(10):2599-2607. DOI:10.1016/j.orgel.2014.07.029 · 3.83 Impact Factor
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    ABSTRACT: In this paper organic thin film transistors (OTFTs) are directly fabricated on fabric substrates consisting of Polyethylene Terephthalate (PET) fibers. A key process is coating the polymer layers on the fabric in order to reduce the large surface roughness of the fabric substrate. Two polymers, i.e. polyurethane (PU) and photo-acryl (PA), are used to reduce the large surface roughness and simultaneously improve the process compatibility of the layers with the subsequent OTFTs processes while also retaining the original flexibility of the fabric. The surface roughness of the PU/PA-coated fabric is significantly reduced to 0.3 mu m. Furthermore, the original flexibility of the PET fabric remained after coating of the PU/PA polymer layers. The mobility of the OTFTs fabricated on the PU-PA coated fabric substrate is 0.05 +/- 0.02 cm(2)/V s when three PA layers and 90 nm thick pentacene layer were used. The performance does not vary even after 30,000 bending test.
    Organic Electronics 07/2014; 15(7). DOI:10.1016/j.orgel.2014.03.019 · 3.83 Impact Factor
  • Source
    Jae Seon Kim · Chung Kun Song ·
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    ABSTRACT: In this paper we analyzed the effects of polystyrene(PS) blended in TIPS-pentacene on the performance of OTFTs. With the various molecular weight and the content of PS the performance of TIPS-pentacene OTFTs was examined and the proper molecular weight and the content were extracted for the best results. With the molecular weight of 9,580 and 0.3 wt% of PS OTFTs produced the mobility of , the subthreshold slope V/dec, the threshold voltage V, the current on/of ratio . Additionally the suitable substrate temperature for ink jet printing of the blended TIPS-pentacene OTFTs was also extracted and it was .
    07/2013; 50(7). DOI:10.5573/ieek.2013.50.7.096
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    ABSTRACT: The effect of solvent additives on the performance of 6,13-bis(triisopropylsilylethynyl) pentacene (TIPS-pentacene) field effect transistors (FETs) was investigated. Hole mobilities increased from 0.10 cm2 V−1 s−1 for pristine devices to 0.73 or 0.71 cm2 V−1 s−1, when TIPS-pentacene FETs were processed with diphenyl ether (DPE) or chloronaphthalene (CN), respectively. In order to examine the impact of additives on the surface morphology, molecular ordering and crystallinity of TIPS-pentacene, scanning electron microscopy (SEM), X-ray diffraction (XRD) and optical microscopy measurements were carried out. Appropriate amounts of additives were found to induce the formation of well-ordered crystalline domains in TIPS-pentacene films, resulting in enhanced hole transport as well as consistent device performance. Additionally, reduced contact resistances were observed in devices processed with additives compared to neat TIPS-pentacene FET devices. Our findings indicate that the use of solvent additives constitutes a new and effective methodology for the fabrication of OFETs with improved performance.
    06/2013; 1(27):4216-4221. DOI:10.1039/C3TC30506F
  • Gi Seong Ryu · Jae Seon Kim · Seung Hyeon Jeong · Chung Kun Song ·
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    ABSTRACT: An AMOLED panel driven by an OTFT-backplane is an attractive display because OTFTs and OLEDs use organic materials with unique characteristics such as low temperature and solution processing ability, and thus are able to implement the key features of future displays. In this study we applied some printing technologies to fabricate an OTFT-backplane for AMOLEDs. Screen printing combined with photolithography with Ag ink was used for the gate electrodes and scan bus lines and contact pads. Ag metal lines with a width of 20 μm and thickness of 60 nm and resistivity of 3.0 × 10−5 Ω cm were achieved. Inkjet printing was applied to deposit TIPS-pentacene as an organic semiconductor. The OTFT-backplane using the Ag gate electrodes and TIPS-pentacene exhibited uniform performance over 17,500 pixels on a 7 in. panel. The mobility was 0.31 ± 0.05 cm2/V s with a deviation of 17%. The AMOLED panel successfully demonstrated its ability to display patterns.
    Organic Electronics 04/2013; 14(4):1218–1224. DOI:10.1016/j.orgel.2013.02.006 · 3.83 Impact Factor
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    ABSTRACT: We report on methods to control the morphology of droplets of 6,13-bis(triisopropyl-silylethynyl) pentacene (TIPS-PEN), which are then used in the fabrication of organic thin film transistors (OTFTs). The grain size and distribution of the TIPS-PEN were found to depend on the temperature of the droplets during drying. The performance of the OTFTs could be improved by heating the substrate and also by changing the relative positions of the inkjet-printed droplets. In our experiments, the optimum substrate temperature was 46 °C in air. Transistors with the TIPS-PEN grain boundaries parallel to the current flow between the source and drain electrodes exhibited charge carrier mobilities of 0.44 ± 0.08 cm2/V s.
    Microelectronic Engineering 07/2012; 95:1–4. DOI:10.1016/j.mee.2012.01.006 · 1.20 Impact Factor
  • Gi Seong Ryu · Myung Won Lee · Seung Hyeon Jeong · Chung Kun Song ·
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    ABSTRACT: In this study we developed a simple ink-jet process for 6,13-bis(triisopropylsilylethynyl)-pentacene (TIPS-pentacene), which is known as a high-mobility soluble organic semiconductor, to achieve relatively high-mobility and high-uniformity performance for large-area applications. We analyzed the behavior of fluorescent particles in droplets and applied the results to determining a method of controlling the behavior of TIPS-pentacene molecules. The grain morphology of TIPS-pentacene varied depending on the temperature applied to the droplets during drying. We were able to obtain large and uniform grains at 46 °C without any ``coffee stain''. The process was applied to a large-size organic thin-film transistor (OTFT) backplane for an electrophoretic display panel containing 192× 150 pixels on a 6-in.-sized substrate. The average of mobilities of 36 OTFTs, which were taken from different locations of the backplane, was 0.44± 0.08 cm2\cdotV-1\cdots-1, with a small deviation of 20%, over a 6-in.-size area comprising 28,800 OTFTs. This process providing high mobility and high uniformity can be achieved by simply maintaining the whole area of the substrate at a specific temperature (46 °C in this case) during drying of the droplets.
    Japanese Journal of Applied Physics 05/2012; 51(5):1601-. DOI:10.1143/JJAP.51.051601 · 1.13 Impact Factor
  • Gi-Seong Ryu · Myung Won Lee · Chung Kun Song ·
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    ABSTRACT: Printing technologies were applied to fabricate a flexible organic thin-film transistor (OTFT) backplane for electrophoretic displays (EPDs). Various printing processes were adopted to maximize the figures of each layer of OTFT: screen printing combined with reverse offset printing for the gate electrodes and scan bus lines with Ag ink, inkjet for the source/drain electrodes with glycerol-doped Poly (3,4-ethylenedioxythiophene): Poly (styrenesulfonate) (PEDOT:PSS), inkjet for the semiconductor layer with Triisopropylsilylethynyl (TIPS)-pentacene, and screen printing for the pixel electrodes with Ag paste. A mobility of 0.44 cm/V s was obtained, with an average standard deviation of 20%, from the 36 OTFTs taken from different backplane locations, which indicates high uniformity. An EPD laminated on an OTFT backplane with 190×152 pixels on an 8-in panel was successfully operated by displaying some patterns.
    Journal of Information Display 12/2011; 12(4). DOI:10.1080/15980316.2011.621336
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    ABSTRACT: Organic semiconductor based on anthracene with phenylethynyl end capping units, which has rigid rod-like structure with high aspect ratio, was synthesized by Sonogashira coupling reaction. The structure of obtained material was confirmed by fourier transform infrared spectroscopy, mass and elemental analysis and its physical properties were characterized by ultraviolet–visible spectroscopy and cyclovoltammetry. 2,6-Bis-phenylethynyl-anthracene (BPEA) has deeper highest occupied molecular orbital level with higher stability as well as high intermolecular π–π stacking. The crystalline and morphological properties of BPEA thin film were studied using X-ray diffraction and atomic force microscopy. BPEA forms high long range ordered structure in the film and it exhibited high field effect mobility of 0.42cm2V−1s−1 (on/off ratio of 107) with device reproducibility and high oxidation stability.
    Thin Solid Films 09/2011; 519(22):7998-8002. DOI:10.1016/j.tsf.2011.05.060 · 1.76 Impact Factor
  • Min Jung Kim · Hyo Weon Heo · Yong Kweon Suh · Chung Kun Song ·
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    ABSTRACT: We applied Ar gas injection while drying droplets of TIPS-pentacene in a quartz tube and controlled the growth direction of the grain boundary and the morphology. The organic thin film transistors (OTFTs) showed a high mobility of 0.53±0.02cm2/Vs with a small deviation of 3.7% when the gas direction was parallel to the source–drain current, resulting in the direction of the grain boundary being parallel to the current. In contrast, OTFTs having grain boundaries perpendicular to the current flow displayed mobility of 0.06±0.02cm2/Vs.
    Organic Electronics 07/2011; 12(7):1170-1176. DOI:10.1016/j.orgel.2011.03.034 · 3.83 Impact Factor
  • Sooyeon Jeong · Won Young Kang · Chung Kun Song · Jong S. Park ·
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    ABSTRACT: In this article, we describe a supramolecular complex made of cyclodextrin and a chromophoric dye, in which anistropy occurred by the formation of the hexagonal packing of cylindrical cyclodextrin channels. The obtained complex exhibited effective fluorescence quenching in the presence of lead ions based on supramolecular wire assembly and dissociation. Selective and effective fluorescence quenching of the complex is attributed to the break-ups of the supramolecular wire and the unthreading of included dye molecules by lead ions. Though we are not yet sure about the origin of such a high selectivity, a topic that will be elaborated in subsequent investigations, these CD-templated supramolecular properties will be useful in analytical applications as a novel platform for metal ion sensing.
    Dyes and Pigments 01/2011; 93(1-3). DOI:10.1016/j.dyepig.2011.08.011 · 3.97 Impact Factor
  • Kang Dae Kim · Chung Kun Song ·
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    ABSTRACT: This study presents low-voltage organic thin-film transistors (OTFT) using a hybrid gate dielectric consisting of aluminum oxide and poly(vinyl phenol). Aluminum oxide with a thickness of 5 nm is directly formed on an aluminum gate electrode by an oxygen plasma process. The poly(vinyl phenol) film with a thickness of 10 nm is deposited on the aluminum oxide by a spin coating process. The proposed OTFTs are able to operate at low voltages lower than 5 V because of the thin gate dielectric. The surface of the hybrid gate dielectric is finished with a hydrophobic poly(vinyl phenol) so that a pentacene semiconductor, which is deposited on the gate dielectric, produces a high quality channel, resulting in a high mobility with 0.63 cm2 V-1 s-1. Additionally, the poly(vinyl phenol) layer reduces the leakage current through the gate dielectric, generating a low off-state current of 0.02 pA/mum and thus a high on/off current ratio of 4.4× 105. Finally, the pin-hole free poly(vinyl phenol) layer protects the thin aluminum oxide gate dielectric from being penetrated by source and drain electrodes; thus, an OTFT with a bottom contact structure is achieved with short channel length.
    Japanese Journal of Applied Physics 11/2010; 49(11). DOI:10.1143/JJAP.49.111603 · 1.13 Impact Factor
  • Myung‐Won Lee · Mi‐Young Lee · Jong‐Seung Park · Chung‐Kun Song ·
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    ABSTRACT: In this paper, The OTFT backplane with bottom contact structure on plastic substrate using combined process will be discussed. The active size of backplane was 6″; in diagonal direction and consisted of 192×150 pixels, containing 1 OTFT and 1 capacitance in each pixel. Each layer of OTFT was used combining process to overcome the problem of printing technique. The gate electrodes were fabricated by screen printing with wet etching. The source drain electrodes were made by ink jet printing combining plasma treatment. Finally, The EPD panel successfully displayed test patterns.
    05/2010; 41(1). DOI:10.1889/1.3499902
  • Myung Won Lee · Mi Young Lee · Chung Kun Song ·
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    ABSTRACT: This is a report on the fabrication of a flexible OTFT backplane for electrophoretic display (EPD) using a printing technology. A practical printing technology for a polycarbonate substrate was developed by combining the conventional screen and inkjet printing technologies with the wet etching and oxygen plasma processes. For the gate electrode, the screen printing technology with Ag ink was developed to define the minimum line width of ∼5 μm and the thickness of ∼70 nm with the resistivity of ∼10 ?•cm, which are suitable for displays with SVGA resolution. For the source and drain (S/D) electrodes, PEDOT:PSS, whose conductivity was drastically enhanced to 450 S/cm by adding 10 wt% glycerol, was adopted. In addition, the modified PEDOT:PSS could be neatly confined in the specific S/D electrode area that had been pretreated with oxygen. The OTFTs that made use of the developed printing technology produced a mobility of 0.13 cm/ and an on/off current ratio of 10, which are comparable to those using thermally evaporated Au for the S/D electrode.
    Journal of Information Display 09/2009; 10(3). DOI:10.1080/15980316.2009.9652096
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    ABSTRACT: A series of bis-dimethyl-n-octylsilyl end-capped oligothiophenes consisting of two to six thiophene units has been synthesized and characterized to develop novel organic semiconductor materials. The UV–vis spectral data indicate that these silyl end-capped oligothiophenes have longer conjugation lengths as evidenced by the higher λmax values than the corresponding unsubstituted thiophene oligomers. The thermal analyses indicate that the bis-silylated oligothiophenes show lower melting point (DSi-4T=80°C; DSi-5T=115°C; DSi-6T=182°C) than the corresponding dialkylated thiophene oligomers by 100°C and hexamer DSi-6T exhibits a liquid crystalline mesophase at 143°C. The α,ω-bis(dimethyl-n-octylsilyl)oligothiophenes (DSi-6T) have a remarkably high solubility in chloroform which are comparable to the corresponding α,ω-dihexyloligothiophenes. The remarkably increased solubility by these silyl end groups leads bis-silylated oligothiophenes to be applicable to solution processable devices for thin film transisitor (TFT) by utilizing a spin-coating technique. α,ω-Bis(dimethyl-n-octylsilyl)sexithiophene can be deposited as active semiconducting layer in thin film transistors, either by vacuum evaporation or by spin-coating. A high charge-carrier mobility has been obtained for both deposition techniques, μ=4.6×10−2 and 1.4×10−2cm2V−1s−1, respectively.
    Synthetic Metals 08/2009; 159(15):1589-1596. DOI:10.1016/j.synthmet.2009.04.022 · 2.25 Impact Factor
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    Seung Hyeon Jeong · Chung Kun Song · Mihye Yi ·
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    ABSTRACT: We report a peculiar enhancement in the accumulation capacitance Cacc in the capacitance-voltage (C-V) characteristics of metal-insulator-semiconductor capacitors consisting of poly(4-vinylphenol) (PVP) and pentacene. Cacc at low frequency C-V was five times larger than the PVP dielectric capacitance CPVP. Cacc decreased as the frequency was increased and returned to the level of CPVP at 1 MHz. The origin of the capacitance enhancement appears to be associated with water molecules adsorbed into the PVP dielectric film when considering the correlation with the concentration of PVP polymer in which OH phenol is known to absorb water molecules.
    Applied Physics Letters 05/2009; 94(18). DOI:10.1063/1.3130084 · 3.30 Impact Factor
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    Myung Won Lee · Chung Kun Song ·
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    ABSTRACT: A highly reliable pentacene TFT backplane for a 6-inch QVGA (320 × 240) electrophoretic display(EPD) was fabricated on a polyethylene substrate. The threshold voltage shift, a general stress effect of pentacene TFTs, was avoided by designing the channel width of organic thin film transistor(OTFT) to be 40 times larger than the channel length. The reliability was also enhanced by employing a passivation layer consisting of a polyvinylalcohol and acryl double layer on OTFT-backplane. The mobility was 0.21 ± 0.03 cm 2/Vsec and the on/off current ratio was 3.66 ± 2.72 × 107, producing an excellent uniformity, with a 10 % variation, over a 6-inch area. The OTFT-EPD panel worked in 5 weeks continuous operation.
    Journal- Korean Physical Society 01/2009; 54(925). DOI:10.3938/jkps.54.514 · 0.42 Impact Factor
  • Kang Dae Kim · Dong Soo Kim · Chung Kyun Kim · Chung Kun Song ·
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    ABSTRACT: Two types of nanometer thick gate dielectrics were employed in order to implement a low voltage operation for organic thin film transistors (OTFT). The first device used an organic monolayer that was formed through a self-assembly process of (benzyloxy)-alkyltrichlorosilane (BTS) on a SiO2 substrate. The BTS-OTFTs produced a threshold voltage of -0.50± 0.11 V, a mobility of 0.12± 0.05 cm2 V-1 s-1, and a on/off current ratio of (1.87±1.22)× 102. The second type of gate dielectric used self-grown Al2O3, which was directly grown on a pre-existing Al gate electrode by oxygen plasma process. The self-grown Al2O3-OTFTs exhibited a mobility of 0.12± 0.015 cm2 V-1 s1, a threshold voltage of -1.18± 0.027 V, and an on/off current ratio of (8.76± 5.3)× 103. In particular, as the Al2O3 layer is directly grown on a pre-existing Al gate electrode, an additional patterning process for the gate dielectric is not necessary; thus, the fabrication process is simplified. Furthermore, the process is a low temperature, dry process, thereby allowing for low cost fabrications and flexible applications.
    Japanese Journal of Applied Physics 08/2008; 47(8). DOI:10.1143/JJAP.47.6496 · 1.13 Impact Factor