WoS İndeksli Yayınlar Koleksiyonu

Permanent URI for this collectionhttps://hdl.handle.net/20.500.12573/394

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Author: search.filters.author.Choi, DongheeScopus Q: search.filters.scopusQuartile.Q3

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  • Article
    Citation - WoS: 29
    Citation - Scopus: 30
    A Solution-Processable Liquid-Crystalline Semiconductor for Low-Temperature Air-Stable N-Channel Field-Effect Transistors
    (Wiley-VCH Verlag GmbH, 2017-02-22) Ozdemir, Resul; Choi, Donghee; Ozdemir, Mehmet; Kim, Hyekyoung; Kostakoglu, Sinem Tuncel; Erkartal, Mustafa; Usta, Hakan
    A new solution-processable and air-stable liquid-crystalline nchannel organic semiconductor (2,2'-(2,8-bis(5-(2-octyldodecyl) thiophen-2-yl) indeno[1,2-b] fluorene-6,12-diylidene) dimalononitrile, alpha,omega-2OD-TIFDMT) with donor-acceptor-donor (D-AD) pi conjugation has been designed, synthesized, and fully characterized. The new semiconductor exhibits a low LUMO energy (-4.19 eV) and a narrow optical bandgap (1.35 eV). The typical pseudo-focal-conic fan-shaped texture of a hexagonal columnar liquid-crystalline (LC) phase was observed over a wide temperature range. The spin-coated semiconductor thin films show the formation of large (approximate to 0.5-1 mu m) and highly crystalline platelike grains with edge-on molecular orientations. Low-temperature-annealed (50 degrees C) top-contact/bottom-gate OFETs have provided good electron obility values as high as 0.11 cm(2) (Vs)(-1) and high I-on/I-off ratios of 10(7) to 10(8) with excellent ambient stability. This indicates an enhancement of two orders of magnitude (100 V) when compared with the b-substituted parent semiconductor, beta-DD-TIFDMT (2,2'-(2,8-bis(3-dodecylthiophen- 2-yl) indeno[1,2-b] fluorene-6,12-diylidene) dimalononitrile). The current rational alkyl-chain engineering route offers great advantages for D-A-D pi-core coplanarity in addition to maintaining good solubility in organic solvents, and leads to favorable optoelectronic/physicochemical characteristics. These remarkable findings demonstrate that alpha,omega-2OD-TIFDMT is a promising semiconductor material for the development of n-channel OFETs on flexible plastic substrates and LC-state annealing of the columnar liquid crystals can lower the electron mobility for transistor-type charge transport.
  • Article
    Citation - WoS: 39
    Citation - Scopus: 40
    A New Rod-Shaped Bodipy-Acetylene Molecule for Solution-Processed Semiconducting Microribbons in N-Channel Organic Field-Effect Transistors
    (Royal Soc Chemistry, 2017) Ozdemir, Mehmet; Choi, Donghee; Zorlu, Yunus; Cosut, Bunyemin; Kim, Hyungsug; Kim, Choongik; Usta, Hakan
    BODIPY-based pi-conjugated small molecules have been extensively studied in various fields of sensing and biochemical labelling; however, their use in organic optoelectronic applications is very limited. A new solution-processable acceptor-donor-acceptor (A-D-A) type small molecule, BDY-PhAc-BDY, consisting of BODIPY pi-acceptors and a rod-shaped 1,4-bis-(thienylethynyl) 2,5-dialkoxybenzene pi-donor, has been synthesized and fully characterized as a novel n-channel semiconductor in bottom-gate/top-contact organic field-effect transistors (OFETs). The new semiconductor exhibits an electrochemical band gap of 2.12 eV with highly stabilized HOMO/LUMO energy levels of -5.68 eV/-3.56 eV. Single-crystal X-ray diffraction (XRD) analysis of BDY-PhAc-BDY reveals a relatively low "BODIPY-meso-thiophene" dihedral angle (theta = 44.94 degrees), antiparallel pi-stacked BODIPY dimers with an interplanar distance of 3.93 angstrom, and strong "C-H center dot center dot center dot pi (2.85 angstrom)" interactions. The OFET devices fabricated by solution processing show the formation of highly-crystalline, one-dimensional (1-D) microribbons, which results in clear n-channel semiconductivity with an electron mobility of 0.004 cm(2) V-1 s(-1) and an on/off current ratio of 10(5)-10(6). To date, this is the highest reported for BODIPY-based small molecular semiconductors with alkyne linkages. Our results clearly demonstrate that BODIPY is an effective pi-acceptor unit for the design of solution-processable, electron-transporting organic semiconductors and easily fabricable 1-D semiconductor micro-/nano-structures for fundamental/applied research in organic optoelectronics.