WoS İndeksli Yayınlar Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12573/394
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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.Article Citation - WoS: 13Citation - Scopus: 15Meso-π-extended/Deficient BODIPYs and Low-Band Donor-Acceptor Copolymers for Organic Optoelectronics(Amer Chemical Soc, 2022-02-16) Can, Ayse; Choi, Gi-Seok; Ozdemir, Resul; Park, Soyoon; Park, Jin Su; Lee, Yongchul; Usta, HakanThe realization of pi-deficient acceptors and their donor-acceptor copolymers has become a key research focus for the realization of versatile organic optoelectronic materials and devices. Herein, we demonstrate the theoretical design, synthesis, and physicochemical/optoelectronic characterization of two meso-pi-extended/deficient BODIPY building blocks (2OD-T2BDY and 2OD-TTzBDY) and a library of donor-acceptor copolymers with low band gap (E-g = 1.30-1.35 eV) based on these building blocks. These building blocks, to the best of our knowledge, are the first examples of BODIPYs with meso-pi-extension. A library of BODIPY building blocks with varied meso units/substituents is studied to reveal the meso effects on the semiconducting BODIPY's optoelectronic properties. The building blocks showed favorable pi-acceptor electronic/structural properties with meso-pi-delocalized and stabilized LUMOs (ca. -3.6 eV) and large ground-state dipole moments of 4.9-5.5 D. Consistent with the theoretical/experimental pi-electronic structures, all copolymers functioned as p-type semiconductors in field-effect transistors and as donor materials in the bulk heterojunction organic photovoltaics. Power conversion efficiencies of up to 4.4% with a short-circuit current of 12.07 mA cm(-2) were achieved. This study demonstrates a unique meso-pi-extension strategy to realize BODIPYs with favorable pi-acceptor properties, and our findings could open up future materials design avenues in various organic optoelectronic applications.Article Citation - WoS: 63Citation - Scopus: 63Highly Efficient Deep-Blue Electroluminescence Based on a Solution-Processable A-Π Oligo(p-Phenyleneethynylene) Small Molecule(Amer Chemical Soc, 2019-10-14) Usta, Hakan; Alimli, Dilek; Ozdemir, Resul; Dabak, Salih; Zorlu, Yunus; Alkan, Fahri; Can, AyseThe development of solution-processable fluorescent small molecules with highly efficient deep-blue electroluminescence is of growing interest for organic light-emitting diode (OLED) applications. However, high-performance deep-blue fluorescent emitters with external quantum efficiencies (EQEs) over 5% are still scarce in OLEDs. Herein, a novel highly soluble oligo(p-phenyleneethynylene)-based small molecule, 1,4-bis((2-cyanophenyl)ethynyl)-2,5-bis(2-ethylhexyloxy)benzene (2EHO-CNPE), is designed, synthesized, and fully characterized as a wide band gap (2.98 eV) and highly fluorescent (Phi(PL) = 0.90 (solution) and 0.51 (solid-state)) deep-blue emitter. The new molecule is functionalized with cyano (-CN)/2-ethylhexyloxy (-OCH2CH(C2H5)C4H9) electron-withdrawing/-donating substituents, and ethynylene is used as a pi-spacer to form an acceptor (A)-pi-donor (D)-pi-acceptor (A) molecular architecture with hybridized local and charge transfer (HLCT) excited states. Physicochemical and optoelectronic characterizations of the new emitter were performed in detail, and the single-crystal structure was determined. The new molecule adopts a nearly coplanar pi-conjugated framework packed via intermolecular "C-H center dot center dot center dot pi" and "C-H center dot center dot center dot N" hydrogen bonding interactions without any pi-pi stacking. The OLED device based on 2EHO-CNPE shows an EQE(max) of 7.06% (EQE = 6.30% at 200 cd/m(2)) and a maximum current efficiency (CEmax) of 5.91 cd/A (CE = 5.34 cd/A at 200 cd/m(2)) with a deep-blue emission at CIE of (0.15, 0.09). The electroluminescence performances achieved here are among the highest reported to date for a solution-processed deep-blue fluorescent small molecule, and, to the best of our knowledge, it is the first time that a deep-blue OLED is reported based on the oligo(p-phenyleneethynylene) pi-framework. TDDFT calculations point to facile reverse intersystem crossing (RISC) processes in 2EHO-CNPE from high-lying triplet states to the first singlet excited state (T-2/T-3 -> S-1) (hot-exciton channels) that enable a high radiative exciton yield (eta(r) similar to 69%) breaking the theoretical limit of 25% in conventional fluorescent OLEDs. These results demonstrate that properly designed fluorescent oligo(p-phenyleneethynylenes) can be a key player in high-performance deep-blue OLEDs.