Browsing by Author "Hong, Jongin"

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    High Electron Mobility in [1]Benzothieno[3,2-b][1]benzothiophene-Based Field-Effect Transistors: Toward n-Type BTBTs
    (AMER CHEMICAL SOC, 1155 16TH ST, NW, WASHINGTON, DC 20036 USA, 2019) Usta, Hakan; Kim, Dojeon; Ozdemir, Resul; Zorlu, Yunus; Kim, Sanghyo; Ruiz Delgado, M. Carmen; Harbuzaru, Alexandra; Kim, Seonhyoung; Demirel, Gokhan; Hong, Jongin; Ha, Young-Geun; Cho, Kilwon; Facchetti, Antonio; Kim, Myung-Gil; 0000-0002-2891-5785; 0000-0003-2811-1872; 0000-0002-7957-110X; 0000-0002-8211-732X; 0000-0002-0618-1979; 0000-0002-9778-917X; 0000-0003-2434-3182; 0000-0001-8180-7153; 0000-0001-9632-3557; AGÜ, Mühendislik Fakültesi, Malzeme Bilimi ve Nanoteknoloji Mühendisliği Bölümü
    The first example of an n-type [1]benzothieno[3,2-b][1]benzothiophene (BTBT)-based semiconductor, D-(PhFCO)-BTBT, has been realized via a two-step transition metal-free process without using chromatographic purification. Physicochemical and optoelectronic characterizations of the new semiconductor were performed in detail, and the crystal structure was accessed. The new molecule exhibits a large optical band gap (similar to 2.9 eV) and highly stabilized (Delta E-LUMO = 1.54 eV)/pi-delocalized lowest unoccupied molecular orbital (LUMO) mainly comprising the BTBT pi-core and in-plane carbonyl units. The effect of out-of-plane twisted (64 degrees) pentafluorophenyl groups on LUMO stabilization is found to be minimal. Polycrystalline D(PhFCO)-BTBT thin films prepared by physical vapor deposition exhibited large grains (similar to 2-5 mu m sizes) and "layer-by-layer" stacked edge-on oriented molecules with an in-plane herringbone packing (intermolecular distances similar to 3.25-3.46 angstrom) to favor two-dimensional (2D) source-to-drain (S -> D) charge transport. The corresponding TC/BG-OFET devices demonstrated high electron mobilities of up to similar to 0.6 cm(2)/V.s and I-on/I-off ratios over 10(7)-10(8). These results demonstrate that the large band gap BTBT pi-core is a promising candidate for high-mobility n-type organic semiconductors and, combination of very large intrinsic charge transport capabilities and optical transparency, may open a new perspective for next-generation unconventional (opto)electronics.
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    Optimized Activation of Solution-Processed Amorphous Oxide Semiconductors for Flexible Transparent Conductive Electrodes
    (WILEY, 111 RIVER ST, HOBOKEN 07030-5774, NJ USA, 2018) Choi, Byung Doo; Park, Joohyung; Baeg, Kang-Jun; Kang, Minji; Heo, Jae Sang; Kim, Seonhyoung; Won, Jongkook; Yu, Seungwoo; Ahn, Kyunghan; Lee, Tae Hoon; Hong, Jongin; Kim, Dong-Yu; Usta, Hakan; Kim, Choongik; Park, Sung Kyu; Kim, Myung-Gil; 0000-0002-0618-1979; AGÜ, Mühendislik Fakültesi, Malzeme Bilimi ve Nanoteknoloji Mühendisliği Bölümü
    Here, the preparation of transparent amorphous oxide semiconductor (AOS) films with unprecedented conductivity via an optimized activation process under hydrogen atmosphere for applications in solution-processed large-area optoelectronics is reported. Owing to their high cost and mechanical vulnerability, conventional vacuum-processed indium-tin oxide (ITO) electrodes are inappropriate for use in next-generation flexible and wearable electronic devices and systems. As an alternative to the ITO electrodes, solution-processed AOS films, such as alpha-IZO and alpha-ZITO, with an optimized composition and postreduction treatment under hydrogen show the highest electrical conductivity of approximate to 300 S cm(-1) and a high optical transmittance of over 90% at 550 nm. The microstructures and electrical properties of these AOS films are also studied in order to determine the optimized chemical composition and postreduction conditions. It is found that a controlled hydrogen reduction treatment of AOS films is critical for achieving high electrical conductivity by suppressing the surface morphology degradation and grain boundary disconnection. Furthermore, the alpha-IZO transparent conductive electrodes are successfully implemented for high efficiency organic photovoltaic cells based on the PTB7/PC71BM active layers. This technique promises the low-cost fabrication of high mobility and/or conductive AOSs for their applications in large-area transparent and flexible optoelectronics.