Scopus İndeksli Yayınlar Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12573/395
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Article Citation - WoS: 54Citation - Scopus: 57Ultralow Bandgap Molecular Semiconductors for Ambient-Stable and Solution-Processable Ambipolar Organic Field-Effect Transistors and Inverters(Royal Soc Chemistry, 2017) Ozdemir, Resul; Choi, Donghee; Ozdemir, Mehmet; Kwon, Guhyun; Kim, Hyekyoung; Sen, Unal; Usta, HakanThe design and development of novel ambipolar semiconductors is very crucial to advance various optoelectronic technologies including organic complementary (CMOS) integrated circuits. Although numerous high-performance ambipolar polymers have been realized to date, small molecules have been unable to provide high ambipolar performance in combination with ambient-stability and solution-processibility. In this study, by implementing highly p-electron deficient, ladder-type IFDK/IFDM acceptor cores with bithiophene donor units in D-A-D pi-architectures, two novel small molecules, 2OD-TTIFDK and 2OD-TTIFDM, were designed, synthesized and characterized in order to achieve ultralow band-gap (1.21-1.65 eV) semiconductors with sufficiently balanced molecular energetics for ambipolarity. The HOMO/LUMO energies of the new semiconductors are found to be -5.47/-3.61 and -5.49/-4.23 eV, respectively. Bottom-gate/top-contact OFETs fabricated via solution-shearing of 2OD-TTIFDM yield perfectly ambient stable ambipolar devices with reasonably balanced electron and hole mobilities of 0.13 cm(2) V-1 s(-1) and 0.01 cm(2) V-1 s(-1), respectively with I-on/I-off ratios of similar to 10(3)-10(4), and 2OD-TTIFDK-based OFETs exhibit ambipolarity under vacuum with highly balanced (mu(e)/mu(h) similar to 2) electron and hole mobilities of 0.02 cm(2) V-1 s(-1) and 0.01 cm(2) V-1 s(-1), respectively with I-on/I-off ratios of similar to 10(5)-10(6). Furthermore, complementary-like inverter circuits were demonstrated with the current ambipolar semiconductors resulting in high voltage gains of up to 80. Our findings clearly indicate that ambient-stability of ambipolar semiconductors is a function of molecular orbital energetics without being directly related to a bulk p-backbone structure. To the best of our knowledge, considering the processing, charge-transport and inverter characteristics, the current semiconductors stand out among the best performing ambipolar small molecules in the OFET and CMOS-like circuit literature. Our results provide an efficient approach in designing ultralow band-gap ambipolar small molecules with good solution-processibility and ambient-stability for various optoelectronic technologies, including CMOS-like integrated circuits.Article Citation - WoS: 18Citation - Scopus: 18Ultrahigh Vacuum Self-Assembly of Rotationally Commensurate C8-BTBT/MoS2 Mixed-Dimensional Heterostructures(Amer Chemical Soc, 2019-02-12) Liu, Xiaolong; Balla, Itamar; Sangwan, Vinod K.; Usta, Hakan; Facchetti, Antonio; Marks, Tobin J.; Hersam, Mark C.Mixed-dimensional van der Waals heterostructures combine the advantages of nanomaterials with qualitatively distinct properties such as the extended bandstructures and high charge carrier mobilities of inorganic two-dimensional materials and the discrete orbital energy levels and strong optical absorption of zero-dimensional organic molecules. The synergistic interplay between nanomaterials of distinct dimensionality has enabled a variety of unique applications such as antiambipolar transistors, sensitized photodetectors, and gate-tunable photovoltaics. Because the performance of mixed-dimensional heterostructure devices depends sensitively on the buried interfacial structure, it is of great interest to identify materials and chemistries that naturally form highly ordered heterointerfaces. Toward this end, here we demonstrate ultrahigh vacuum self-assembly of 2,7-dioctyl[1]benzothieno [3,2-b][1]benzothiophene (C8-BTBT) monolayers onto epitaxial MoS2/graphene heterostructures. With molecular-resolution scanning tunneling microscopy and spectroscopy, the resulting C8-BTBT/MoS2/graphene mixed-dimensional heterostructures are found to be rotationally commensurate with well-defined physical and electronic structures. It is further shown that the self-assembled C8-BTBT monolayers are insensitive to the structural defects and electronic perturbations of the underlying MoS2 substrate, which provides significant processing latitude. For these reasons, this work will facilitate ongoing efforts to utilize organic/MoS2/graphene mixed-dimensional heterostructures for electronic, optoelectronic, and photovoltaic applications.Article Citation - WoS: 25Citation - Scopus: 25Triisopropylsilylethynyl-Substituted Indenofluorenes: Carbonyl Versus Dicyanovinylene Functionalization in One-Dimensional Molecular Crystals and Solution-Processed N-Channel Ofets(Royal Soc Chemistry, 2018) Ozdemir, Resul; Park, Sangyun; Deneme, Ibrahim; Park, Yonghan; Zorlu, Yunus; Alidagi, Husniye Ardic; Usta, HakanThe design and synthesis of novel electron-deficient and solution-processable polycyclic aromatic hydrocarbons offers great opportunities for the development of low-cost and large-area (opto)electronics. Although (trialkylsilyl)ethynyl (R3Si-C?C-) has emerged as a very popular unit to solubilize organic semiconductors, it has been applied only to a limited class of materials that are mostly substituted on short molecular axes. Herein, two novel solution-processable indenofluorene-based semiconductors, TIPS-IFDK and TIPS-IFDM, bearing (triisopropylsilyl)ethynyl end units at 2,8-positions (long molecular axis substitution) were synthesized, and their single-crystal structures, optoelectronic properties, solution-sheared thin-film morphologies/microstructures, and n-channel field-effect responses were studied. In accordance with the DFT calculations, the HOMO/LUMO energies of the new compounds are found to be -5.77/-3.65 eV and -5.84/-4.18 eV for TIPS-IFDK and TIPS-IFDM, respectively, reflecting the high electron deficiency of the new -backbones. Both semiconductors exhibit slightly S-shaped molecular frameworks with highly coplanar IFDK/IFDM -cores, and they form slipped -stacked one-dimensional (1-D) columnar motifs in the solid state. However, substantial differences in the degree of - interactions and stacking distances (4.04 angstrom vs. 3.47 angstrom) were observed between TIPS-IFDK and TIPS-IFDM as a result of carbonyl vs. dicyanovinylene functionalization, which results in a three orders of magnitude variation in the charge carrier mobility of the corresponding thin films. Top-contact/bottom-gate OFETs fabricated via solution-shearing TIPS-IFDM yielded one of the best performances in the (trialkylsilyl)ethynyl literature ((e) = 0.02 cm(2) V-1 s(-1), I-on/I-off = 10(7)-10(8), and V-T approximate to 2 V under ambient atmosphere) for a 1-D polycrystalline semiconductor microstructure. To the best of our knowledge, the molecules presented here are the first examples of n-type semiconductors substituted with (trialkylsilyl)ethynyl groups on their long molecular axes.Article Citation - WoS: 28Citation - Scopus: 29Three-Dimensional Au-Coated Electrosprayed Nanostructured BODIPY Films on Aluminum Foil as Surface-Enhanced Raman Scattering Platforms and Their Catalytic Applications(Amer Chemical Soc, 2017-05-16) Yilmaz, Mehmet; Erkartal, Mustafa; Ozdemir, Mehmet; Sen, Unal; Usta, Hakan; Demirel, GokhanThe design and development of three-dimensional (3D) nanostructures with high surface-enhanced Raman scattering (SERS) performances have attracted considerable attention in the fields of chemistry, biology, and materials science. Nevertheless, electrospraying of organic smalt molecules on low-cost flexible substrates has never been studied to realize large-scale SERS-active platforms. Here, we report the facile, efficient, and low-cost fabrication of-Stable and reproducible Au-coated electrosprayed organic semiconductor films (Au@BDY-4TEBDY) on flexible regular aluminum foil at a large scale (5 cm X 5 cm) for practical SERS and catalytic applications. To this end, a well-designed-acceptor-donor-atceptor-type solution-processable molecular semiconductor, BDY-4T-BDY, developed by our group, is used because of its advantageous structural and electrical properties. The morphology of the electrosprayed organic film changes by solution concentration, and two different 3D morphologies with out-of-plane features are obtained. Highly uniform dendritic nanoribbons with sharp needle-like tips and vertically oriented nanoplates (similar to 50 nm thickness) are achieved when electrospraying solution concentrations of 240 and 253% w/v.(mgimL) are, respectively, used. When these electrosprayed organic films are coated with a nanoscopic thin (30 nm) Au layer, the resulting Au@BDY-4T-BDY platforms demonstrate remarkable SERS enhancement factors up to 1.7 X 10(6) with excellent Raman signal reproducibility (relative standard deviation <= 0.13) for methylene blue over the entire film. Finally, Au@BDY-4T-BDY films showed good catalytic activity for the reduction of 4-nitrophenol to 4-aminophenol with rate constants of 1.3 X 10(-2) and 9.2 X 10(-3) min(-1). Our results suggest that electrospraying of rationally designed organic semiconductor molecules on flexible substrates holds great promise to enable low-cost, solution-processed, SERS-active platforms.Article Citation - WoS: 16Citation - Scopus: 16The Hansen Solubility Approach Towards Green Solvent Processing: N-Channel Organic Field-Effect Transistors Under Ambient Conditions(Royal Soc Chemistry, 2024) Deneme, Ibrahim; Yildiz, Tevhide Ayca; Kayaci, Nilgun; Usta, HakanThe adoption of green solvents is of utmost importance for the solution-based fabrication of semiconductor thin films and for the commercialization of (opto)electronic devices, especially in response to evolving regulatory mandates for handling organic materials. Despite the increasing interest in this area, the scarcity of green solvent-processed n-channel OFETs, especially functioning under ambient conditions, highlights the need for further research. In this study, we demonstrated the Hansen solubility approach to study the solubility behavior of an ambient-stable n-type semiconductor, 2,2' -(2,8-bis(3-dodecylthiophen-2-yl)indeno[1,2-b]fluorene-6,12-diylidene)dimalononitrile (beta,beta'-C-12-TIFDMT), and to analyze potential green solvents for thin-film processing. The Hansen solubility parameters were determined to be delta(D) = 20.8 MPa1/2, delta(P) = 5.8 MPa1/2, and delta(H) = 5.5 MPa1/2 with a radius (R-0) of 8.3 MPa1/2. A green solvent screening analysis based on the minimal distance constraint and quantitative sustainability score identified ethoxybenzene, anisole, 2-methylanisole, and 2-methyltetrahydrofuran as suitable green solvents (R-a's = 5.17-7.93 MPa1/2 < R-0). A strong thermodynamic correlation was identified between the solubility and the semiconductor-solvent distance in the 3D Hansen solubility space, in which the maximum solubility limit could be estimated with the enthalpy of fusion (Delta H-fus) and melting temperature (T-mp) of the semiconductor. To the best of our knowledge, this relationship between the maximum solubility limit and thermal properties has been established for the first time for organic semiconductors. Bottom-gate/top-contact OFETs fabricated by spin-coating the semiconductor green solutions exhibited mu es reaching similar to 0.2 cm(2) V-1 s(-1) (I-on/I-off similar to 10(6)-10(7) and V-on similar to 0-5 V) under ambient conditions. This device performance, to our knowledge, is the highest reported for an ambient-stable green solvent-processed n-channel OFET. Our HSP-based rational approach and unique findings presented in this study can shed critical light on how green solvents can be efficiently incorporated in solution processing in organic (opto)electronics, and whether ambient-stable n-type semiconductors can continue to play an important role in green OFETs.Article Citation - WoS: 22Citation - Scopus: 24The Design and Fabrication of Supramolecular Semiconductor Nanowires Formed by Benzothienobenzothiophene (BTBT)-Conjugated Peptides(Royal Soc Chemistry, 2018) Khalily, Mohammad Aref; Usta, Hakan; Ozdemir, Mehmet; Bakan, Gokhan; Dikecoglu, F. Begum; Edwards-Gayle, Charlotte; Guler, Mustafa O.pi-Conjugated small molecules based on a [1]benzothieno[3,2-b]benzothiophene (BTBT) unit are of great research interest in the development of solution-processable semiconducting materials owing to their excellent charge-transport characteristics. However, the BTBT -core has yet to be demonstrated in the form of electro-active one-dimensional (1D) nanowires that are self-assembled in aqueous media for potential use in bioelectronics and tissue engineering. Here we report the design, synthesis, and self-assembly of benzothienobenzothiophene (BTBT)-peptide conjugates, the BTBT-peptide (BTBT-C-3-COHN-Ahx-VVAGKK-Am) and the C-8-BTBT-peptide (C-8-BTBT-C-3-COHN-Ahx-VVAGKK-Am), as -sheet forming amphiphilic molecules, which self-assemble into highly uniform nanofibers in water with diameters of 11-13(+/- 1) nm and micron-size lengths. Spectroscopic characterization studies demonstrate the J-type - interactions among the BTBT molecules within the hydrophobic core of the self-assembled nanofibers yielding an electrical conductivity as high as 6.0 x 10(-6) S cm(-1). The BTBT -core is demonstrated, for the first time, in the formation of self-assembled peptide 1D nanostructures in aqueous media for potential use in tissue engineering, bioelectronics and (opto)electronics. The conductivity achieved here is one of the highest reported to date in a non-doped state.Article Citation - WoS: 1Citation - Scopus: 1Stochastic Orientational Encoding via Hydrogen Bonding Driven Assembly of Woven-Like Molecular Physically Unclonable Functions(Wiley-VCH Verlag GmbH, 2025-07-02) Kayaci, Nilgun; Kiremitler, Nuri Burak; Deneme, Ibrahim; Kalay, Mustafa; Ozbasaran, Aleyna; Zorlu, Yunus; Usta, HakanThe prevention of counterfeiting and the assurance of object authenticity require stochastic encoding schemes based on physically unclonable functions (PUFs). There is an urgent need for exceptionally large encoding capacities and multi-level responses within a molecularly defined, single-material system. Herein, a novel stochastic orientational encoding approach is demonstrated using a facile ambient-atmosphere solution processing of a molecular thin film based on the rod-shaped oligo(p-phenyleneethynylene) (OPE) pi-architecture. The nanoscopic film, derived from the small molecule 2EHO-CF3PyPE with donor, acceptor, and pi-spacer building units, is designed for energetically favorable uniaxial molecular assembly and crystal growth via directional multiple hydrogen-bonding motifs at the molecular termini and short C & horbar;H<middle dot><middle dot><middle dot>pi contacts at the center. A facile solvent vapor annealing induces concurrent dewetting and microscopic 1D random crystallization, yielding a woven-textured random features. Using convolutional neural networks, the rich variations in microcrystal domain properties and stochastic encoding of 1D crystal orientations generate artificial coloration, achieving an encoding capacity reaching (6.5 x 10(4))(2752 x 2208). The results demonstrate an effective strategy for achieving ultrahigh encoding capacities in a thin film composed of a single-material. This approach enables low-cost, solution-processed fabrication for mass production and broad adoption, while opening new opportunities to explore molecular-PUFs through structural design and engineering noncovalent interactions.Article Citation - WoS: 61Citation - Scopus: 74Solution-Processable Bodipy-Based Small Molecules for Semiconducting Microfibers in Organic Thin-Film Transistors(Amer Chemical Soc, 2016-05-23) Ozdemir, Mehmet; Choi, Donghee; Kwon, Guhyun; Zorlu, Yunus; Cosut, Bunyemin; Kim, Hyekyoung; Usta, HakanElectron-deficient pi-conjugated small molecules can function as electron-transporting semiconductors in various optoelectronic applications. Despite their unique structural, optical, and electronic properties, the development of BODIPY-based organic semiconductors has lagged behind that of other pi-deficient units. Here, we report the design and synthesis of two novel solution-proccessable BODIPY-based small molecules (BDY-3T-BDY and BDY-4T-BDY) for organic thin-film transistors (OTFTs). The new semiconductors were fully characterized by H-1/C-13 NMR, mass spectrometry, cyclic voltammetry, UV-vis spectroscopy, photoluminescence, differential scanning calorimetry, and thermogravimetric analysis. The single-crystal X-ray diffraction (XRD) characterization of a key intermediate reveals crucial structural properties. Solution-sheared top-contact/bottom-gate OTFTs exhibited electron mobilities up to 0.01 cm(2)/V center dot s and current on/off ratios of >10(8). Film microstructural and morphological characterizations indicate the formation of relatively long (similar to 0.1 mm) and micrometer-sized (1-2 mu m) crystalline fibers for BDY-4T-BDY-based films along the shearing direction. Fiber-alignment-induced charge-transport anisotropy (mu?/mu approximate to 10) was observed, and higher mobilities were achieved when the microfibers were aligned along the conduction channel, which allows for efficient long-range charge-transport between source and drain electrodes. These OTFT performances are the highest reported to date for a BODIPY-based molecular semiconductor, and demonstrate that BODIPY is a promising building block for enabling solution-processed, electron-transporting semiconductor films.Article Citation - WoS: 11Citation - Scopus: 13Solution-Processable Indenofluorenes on Polymer Brush Interlayer: Remarkable N-Channel Field-Effect Transistor Characteristics Under Ambient Conditions(Amer Chemical Soc, 2023-08-15) Can, Ayse; Deneme, Ibrahim; Demirel, Gokhan; Usta, HakanThe development of solution-processable n-type molecularsemiconductorsthat exhibit high electron mobility (& mu;(e) & GE;0.5 cm(2)/(V & BULL;s)) under ambient conditions, along withhigh current modulation (I (on)/I (off) & GE; 10(6)-10(7)) andnear-zero turn on voltage (V (on)) characteristics,has lagged behind that of other semiconductors in organic field-effecttransistors (OFETs). Here, we report the design, synthesis, physicochemicaland optoelectronic characterizations, and OFET performances of a libraryof solution-processable, low-LUMO (-4.20 eV) 2,2 & PRIME;-(2,8-bis(3-alkylthiophen-2-yl)indeno[1,2-b]fluorene-6,12-diylidene)dimalononitrile small molecules, & beta;,& beta;& PRIME;-C (n) -TIFDMTs, having varied alkyl chain lengths (n = 8, 12, 16). An intriguing correlation is identifiedbetween the solid-isotropic liquid transition enthalpies andthe solubilities, indicating that cohesive energetics, which are tunedby alkyl chains, play a pivotal role in determining solubility. Thesemiconductors were spin-coated under ambient conditions on denselypacked (grafting densities of 0.19-0.45 chains/nm(2)) ultrathin (& SIM;3.6-6.6 nm) polystyrene-brush surfaces.It is demonstrated that, on this polymer interlayer, thermally induceddispersive interactions occurring over a large number of methyleneunits between flexible alkyl chains (i.e., zipper effect) are criticalto achieve a favorable thin-film crystallization with a proper microstructureand morphology for efficient charge transport. While C-8 and C-16 chains show a minimal zipper effect upon thermalannealing, C-12 chains undergo an extended interdigitationinvolving & SIM;6 methylene units. This results in the formationof large crystallites having lamellar stacking ((100) coherence length & SIM;30 nm) in the out-of-plane direction and highly favorablein-plane & pi;-interactions in a slipped-stacked arrangement. Uninterruptedmicrostructural integrity (i.e., no face-on (010)-oriented crystallites)was found to be critical to achieving high mobilities. The excellentcrystallinity of the C-12-substituted semiconductor thinfilm was also evident in the observed crystal lattice vibrations (phonons)at 58 cm(-1) in low-frequency Raman scattering. Two-dimensionalmicrometer-sized (& SIM;1-3 & mu;m), sharp-edged plate-likegrains lying parallel with the substrate plane were observed. OFETsfabricated by the current small molecules showed excellent n-channelbehavior in ambient with & mu;(e) values reaching & SIM;0.9cm(2)/(V & BULL;s), I (on)/I (off) & SIM; 10(7)-10(8), and V (on) & AP; 0 V. Our study notonly demonstrates one of the highest performing n-channel OFET devicesreported under ambient conditions via solution processing but alsoelucidates significant relationships among chemical structures, molecularproperties, self-assembly from solution into a thin film, and semiconductingthin-film properties. The design rationales presented herein may openup new avenues for the development of high-electron-mobility novelelectron-deficient indenofluorene and short-axis substituted donor-acceptor & pi;-architectures via alkyl chain engineering and interface engineering.Conference Object Citation - WoS: 25Citation - Scopus: 26Semiconducting Copolymers Based on Meso-Substituted BODIPY for Inverted Organic Solar Cells and Field-Effect Transistors(Wiley, 2017-12-11) Ozdemir, Mehmet; Kim, Sang Woo; Kim, Hyungsug; Kim, Myung-Gil; Kim, Bumjoon J.; Kim, Choongik; Usta, HakanThe synthesis, physicochemical, and optoelectronic properties of a new class of low band-gap (approximate to 1.3 eV) donor-acceptor copolymers based on a highly electron-deficient meso-5-(2-octyldodecyl)thiophene-substituted BODIPY pi-unit are presented. The polymeric solutions exhibit strong aggregation-dependent excitonic properties indicating the presence of enhanced pi-coherence as a result of strong interchain interactions. The polymeric semiconductor thin films prepared by spin coating show isotropic nodule-like grains with essentially no ordering in the out-of-plane direction. Field-effect hole mobilities of 0.005 cm(2) V-1.s(-1) are observed in bottom-gate top-contact organic field-effect transistors, and inverted bulk-heterojunction organic photovoltaics employing the polymer:PC71BM active layer exhibit excellent power conversion efficiencies of 6.2% with a short-circuit current of 16.6 mA cm(-2). As far as it is known, this is a record high value achieved to date for a boron-containing donor polymer in the photovoltaic literature indicating a significant enhancement in power conversion efficiency (>3-4 times). The findings clearly present that rationally designed BODIPY-based donor-acceptor copolymers can be a key player in photovoltaic applications.
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