High performance solution-processed indium oxide thin-film transistors

In2O3 thin-film transistors (TFTs) were fabricated on various dielectrics [SiO2, self-assembled nanodielectrics (SANDs)] by spin-coating In2O3 film precursor solutions consisting of ethanolamine (EAA) and InCl3 in methoxyethanol. Optimized film microstructures are characterized by the high-mobility In2O3 00 L orientation and are obtained only within a well-defined range of base: In3+ molar ratios. Electron mobilities as high as approximately 44 cm2 V(-1) s(-1) are measured for n+-Si/SAND/In2O3/Au devices using an EAA/In3+ molar ratio = 10. This result combined with Ion/Ioff ratios of approximately 10(6) and <5 V operating voltages is encouraging for high-speed applications.In2O3 thin-film transistors (TFTs) were fabricated on various dielectrics [SiO2, self-assembled nanodielectrics (SANDs)] by spin-coating In2O3 film precursor solutions consisting of ethanolamine (EAA) and InCl3 in methoxyethanol. Optimized film microstructures are characterized by the high-mobility In2O3 00 L orientation and are obtained only within a well-defined range of base: In3+ molar ratios. Electron mobilities as high as ~44 cm2 V(-1) s(-1) are measured for n+-Si/SAND/In2O3/Au devices using an EAA/In3+ molar ratio = 10. This result combined with Ion/Ioff ratios of approximately 10(6) and <5 V operating voltages is encouraging for high-speed applications.     

Synthesis, characterization, and transistor response of semiconducting silole polymers with substantial hole mobility and air stability. Experiment and theory

Realizing p-channel semiconducting polymers with good hole mobility, solution processibility, and air stability is an important step forward in the chemical manipulation of charge transport in polymeric solids and in the development of low-cost printed electronics. We report here the synthesis and full characterization of the dithienosilole- and dibenzosilole-based homopolymers, poly(4,4-di-n-hexyldithienosilole) (TS6) and poly(9,9-di-n-octyldibenzosilole) (BS8), and their mono- and bithiophene copolymers, poly(4,4-di-n-hexyldithienosilole-alt-(bi)thiophene) (TS6T1, TS6T2) and poly(9,9-di-n-octyldibenzosilole-alt-(bi)thiophene) (BS8T1, BS8T2), and examine in detail the consequences of introducing dithienosilole and dibenzosilole cores into a thiophene polymer backbone. We demonstrate air-stable thin-film transistors (TFTs) fabricated under ambient conditions having hole mobilities as large as 0.08 cm(2)/V x s, low turn-on voltages, and current on/off ratios > 10(6). Additionally, unencapsulated TFTs fabricated under ambient conditions are air-stable, an important advance over regioregular poly(3-hexylthiophene) (P3HT)-based devices. Density functional theory calculations provide detailed insight into the polymer physicochemical and charge transport characteristics. A direct correlation between the hole injection barrier and both TFT turn-on voltage and TFT polymer hole mobility is identified and discussed, in combination with thin-film morphological characteristics, to explain the observed OTFT performance trends.     

Air-stable, solution-processable n-channel and ambipolar semiconductors for thin-film transistors based on the indenofluorenebis(dicyanovinylene) core

We present here the synthesis, characterization, and field-effect performance of a novel n-channel semiconducting molecule TIFDMT and of the corresponding thiophene-based copolymer P-IFDMT4 based on the indenofluorenebis(dicyanovinylene) core. TIFDMT-based field-effect transistors fabricated by spin-coating exhibit high electron mobilities of 0.10-0.16 cm2/V s in air, low turn-on voltages (0 to +5 V), and high on/off ratios of 10(7)-10(8). These devices also exhibit excellent air stability over a prolonged time of storage in ambient conditions. P-IFDMT4-based devices exhibit the first example of an air-stable ambipolar polymer processable from solution     

Synthesis, characterization, and marked polymerization selectivity characteristics of binuclear phenoxyiminato organozirconium catalysts

The new binuclear phenoxyiminato zirconium complex {1,7-(O)2C10H4-2,7-[CH=N(2,6-iPr2C6H3)]2}Zr2Cl6(THF)2 (FI2-Zr2) polymerizes ethylene with greater activity (approximately 8x) than the mononuclear analogue. Also, this catalyst produces high molecular weight ethylene + 1-hexene copolymers, while the mononuclear analogue yields only traces of copolymer under identical conditions. This ability to produce copolymers suggests cooperativity between the two Zr centers which promotes 1-hexene co-enchainment.     

Bimetallic effects in homopolymerization of styrene and copolymerization of ethylene and styrenic comonomers: scope, kinetics, and mechanism

This contribution describes the homopolymerization of styrene and the copolymerization of ethylene and styrenic comonomers mediated by the single-site bimetallic "constrained geometry catalysts" (CGCs), (mu-CH2CH2-3,3'){(eta(5)-indenyl)[1-Me2Si(tBuN)](TiMe2)}2 [EBICGC(TiMe2)2; Ti2], (mu-CH2CH2-3,3'){(eta(5)-indenyl)[1-Me2Si(tBuN)](ZrMe2)}2 [EBICGC(ZrMe2)2; Zr2], (mu-CH2-3,3'){(eta(5)-indenyl)[1-Me2Si(tBuN)](TiMe2)}2 [MBICGC(TiMe2)2; C1-Ti2], and (mu-CH2-3,3'){(eta(5)-indenyl)[1-Me2Si(tBuN)](ZrMe2)}2 [MBICGC(ZrMe2)2; C1-Zr2], in combination with the borate activator/cocatalyst Ph3C+ B(C6F5)4- (B1). Under identical styrene homopolymerization conditions, C1-Ti2 + B1 and Ti2 + B1 exhibit approximately 65 and approximately 35 times greater polymerization activities, respectively, than does monometallic [1-Me2Si(3-ethylindenyl)(tBuN)]TiMe2 (Ti1) + B1. C1-Zr2 + B1 and Zr2 + B1 exhibit approximately 8 and approximately 4 times greater polymerization activities, respectively, than does the monometallic control [1-Me2Si(3-ethylindenyl)(tBuN)]ZrMe2 (Zr1) + B1. NMR analyses show that the bimetallic catalysts suppress the regiochemical insertion selectivity exhibited by the monometallic analogues. In ethylene copolymerization, Ti2 + B1 enchains 15.4% more styrene (B), 28.9% more 4-methylstyrene (C), 45.4% more 4-fluorostyrene (D), 41.2% more 4-chlorostyrene (E), and 31.0% more 4-bromostyrene (F) than does Ti1 + B1. This observed bimetallic chemoselectivity effect follows the same general trend as the pi-electron density on the styrenic ipso carbon (D > E > F > C > B). Kinetic studies reveal that both Ti2 + B1 and Ti1 + B1-mediated ethylene-styrene copolymerizations follow second-order Markovian statistics and tend to be alternating. Moreover, calculated reactivity ratios indicate that Ti2 + B1 favors styrene insertion more than does Ti1 + B1. All the organozirconium complexes (C1-Zr2, Zr2, and Zr1) are found to be incompetent for ethylene-styrene copolymerization, yielding only mixtures of polyethylene and polystyrene. Model compound (mu-CH2CH2-3,3'){(eta(5)-indenyl)[1-Me2Si(tBuN)][Ti(CH2Ph)2]}2 {EBICGC[Ti(CH2Ph)2]2; Ti2(CH2Ph)4} was designed, synthesized, and structurally characterized. In situ activation studies with cocatalyst B(C6F5)3 suggest an eta(1)-coordination mode for the benzyl groups, thus supporting the proposed polymerization mechanism. For ethylene-styrene copolymerization, polar solvents are found to increase copolymerization activities and coproduce atactic polystyrene impurities in addition to ethylene-co-styrene, without diminishing the comonomer incorporation selectivity. Both homopolymerization and copolymerization results argue that substantial cooperative effects between catalytic sites are operative.     

Tris(phosphino)borato silver(I) complexes as precursors for metallic silver aerosol-assisted chemical vapor deposition

A series of light- and air-stable tris(phosphino)borato silver(I) complexes has been synthesized, structurally and spectroscopically characterized, and implemented in the growth of low resistivity metallic silver thin films by aerosol-assisted chemical vapor deposition (AACVD). Of the four complexes in the series, [RB(CH2PR'2) 3]AgPEt3 (R = Ph (1, 3), (n)Bu (2, 4); R' = Ph (1, 2), (i)Pr (3, 4), complexes 1 and 2 have been characterized by single-crystal X-ray diffraction. Complex 2 represents a significant improvement over previously available nonfluorinated Ag precursors, owing to ease of handling and efficient film deposition characteristics. Thermogravimetric analysis (TGA) shows that the thermolytic properties of these complexes can be significantly modified by altering the ligand structure. Polycrystalline cubic-phase Ag thin films were grown on glass, MgO(100), and 52100 steel substrates. Ag films of thicknesses 3 microm, grown at rates of 14-18 nm/min, exhibit low levels of extraneous element contamination by X-ray photoelectron spectroscopy (XPS). Atomic force microscopy (AFM) and scanning electron microscopy (SEM) indicate that film growth proceeds primarily via an island growth (Volmer-Weber) mechanism.     

Ultralarge hyperpolarizability twisted pi-electron system electro-optic chromophores: synthesis, solid-state and solution-phase structural characteristics, electronic structures, linear and nonlinear optical properties, and computational studies

This contribution details the synthesis and chemical/physical characterization of a series of unconventional twisted pi-electron system electro-optic (EO) chromophores. Crystallographic analysis of these chromophores reveals large ring-ring dihedral twist angles (80-89 degrees) and a highly charge-separated zwitterionic structure dominating the ground state. NOE NMR measurements of the twist angle in solution confirm that the solid-state twisting persists essentially unchanged in solution. Optical, IR, and NMR spectroscopic studies in both the solution phase and solid state further substantiate that the solid-state structural characteristics persist in solution. The aggregation of these highly polar zwitterions is investigated using several experimental techniques, including concentration-dependent optical and fluorescence spectroscopy and pulsed field gradient spin-echo (PGSE) NMR spectroscopy in combination with solid-state data. These studies reveal clear evidence of the formation of centrosymmetric aggregates in concentrated solutions and in the solid state and provide quantitative information on the extent of aggregation. Solution-phase DC electric-field-induced second-harmonic generation (EFISH) measurements reveal unprecedented hyperpolarizabilities (nonresonant mubeta as high as -488,000 x 10(-48) esu at 1907 nm). Incorporation of these chromophores into guest-host poled polyvinylphenol films provides very large electro-optic coefficients (r(33)) of approximately 330 pm/V at 1310 nm. The aggregation and structure-property effects on the observed linear/nonlinear optical properties are discussed. High-level computations based on state-averaged complete active space self-consistent field (SA-CASSCF) methods provide a new rationale for these exceptional hyperpolarizabilities and demonstrate significant solvation effects on hyperpolarizabilities, in good agreement with experiment. As such, this work suggests new paradigms for molecular hyperpolarizabilities and electro-optics.     

Diverse stereocontrol effects induced by weakly coordinating anions. Stereospecific olefin polymerization pathways at archetypal C(s)- and C(1)-symmetric metallocenium catalysts using mono- and polynuclear halo-perfluoroarylmetalates as cocatalysts

Counteranion effects on propylene polymerization rates and stereoselectivities are compared using Cs-symmetric Me2C(Cp)(Flu)ZrMe2 (1; Cp = C5H4,eta5-cyclopentadienyl; Flu = C13H8, eta5-fluorenyl) and C1-symmetric Me2Si(OHF)(CpR*)ZrMe2 (2; OHF = C13H16, eta5-octahydrofluorenyl; CpR* = eta5-3-(-)-menthylcyclopentadienyl) precatalysts activated with the mononuclear and polynuclear perfluoroarylborate, -aluminate, and -gallate cocatalysts/activators B(C6F5)3 (3), B(o-C6F5C6F4)3 (4), Al(C6F5)3 (5), Ph3C+B(C6F5)4- (6) Ph3C+FAl(o-C6F5C6F4)3- (7), Ga(C6F5)3 (8), and recently reported mono- and polymetallic trityl perfluoroarylhalometalates Ph3C+FB(C6F5)3- (9), Ph3C+FB(o-C6F5C6F4)3- (10), (Ph3C+)xFx[Al(C6F5)3]yx- (x = 1, y = 1, 11; x = 1, y = 2, 12; x = 2, y = 3, 13), Ph3C+(C6F5)3AlFAl(o-C6F5C6F4)3- (14), Ph3C+XAl(C6F5)3- (X = Cl, 15; X = Br, 16), and Ph3C+F[Ga(C6F5)3]2- (17). Temperature, propylene concentration, and solvent polarity dependence are surveyed in polymerizations catalyzed by 1 activated with cocatalysts 3-16 and with a 1:2 ratio of Ph3CCl and 5, and with a 1:2 ratio of Ph3CBr and 5, and by 2 activated with 3, 6, 7, 12, and 14. Remarkable stereocontrol with high activities is observed for 1 + 12 and 1 + 14. Polypropylene samples produced using C1-symmetric precatalyst 2 are subjected to microstructural analyses using stochastic models describing the relative contributions of enantiofacial misinsertion and backskip processes. A powerful technique is introduced for calculating interparametric correlation matrices for these nonlinear stochastic models. The collected results significantly extend what is known about ion-pairing effects in the case of Cs-symmetric precatalyst 1 and allow these findings to be applied to the case of C1-symmetric precatalyst 2 as an agent of isospecific propylene polymerization.     

Facile synthesis of BiCuOS by hydrothermal methods

BiCuOS, which is isostructural to the layered rare-earth oxysulfides LnCuOS (Ln = La-Eu), was synthesized by a single-step hydrothermal reaction at low temperature (250 degrees C) and pressure (<20 atm). Particular emphasis is placed on how the selection of the proper reaction conditions, such as temperature and pH, achieves a mutual high solubility of the metal-oxide reactants, Bi2O3 and Cu2O, and thus generates BiCuOS in a good yield. The optical and electrical properties of BiCuOS were measured to determine the influence of replacing a rare-earth cation with bismuth. The electrical conductivity of BiCuOS is increased over that of certain layered rare-earth oxysulfides, LnCuOS (Ln = La, Pr, and Nd), and is similar to that of the cerium members, CeCuOS and CeAgOS. Band structure calculations reveal that, similar to other potential transparent conductors containing sixth-row elements, relativistic effects significantly lower the energy of the conduction band, and thus narrow the optical band gap. These low-energy conduction bands are responsible for the electrical and optical properties of BiCuOS.