Diketopyrrolopyrrole-containing quinoidal small molecules for high-performance, air-stable, and solution-processable n-channel organic field-effect transistors

We report the synthesis, characterization, and application of a novel series of diketopyrrolopyrrole (DPP)-containing quinoidal small molecules as highly efficient n-type organic semiconductors in thin film transistors (TFTs). The first two representatives of these species exhibit maximum electron mobility up to 0.55 cm(2) V(-1) s(-1) with current on/current off (I(on)/I(off)) values of 10(6) for 1 by vapor evaporation, and 0.35 cm(2) V(-1) s(-1) with I(on)/I(off) values of 10(5)-10(6) for 2 by solution process in air, which is the first demonstration of DPP-based small molecules offering only electron transport characteristics in TFT devices. The results indicate that incorporation of a DPP moiety to construct quinoidal architecture is an effective approach to enhance the charge-transport capability.     

Tuning orbital energetics in arylene diimide semiconductors. materials design for ambient stability of n-type charge transport

Structural and electronic criteria for ambient stability in n-type organic materials for organic field-effect transistors (OFETs) are investigated by systematically varying LUMO energetics and molecular substituents of arylene diimide-based materials. Six OFETs on n+-Si/SiO2 substrates exhibit OFET response parameters as follows: N,N'-bis(n-octyl)perylene-3,4:9,10-bis(dicarboximide) (PDI-8): mu = 0.32 cm2 V(-1) s(-1), Vth = 55 V, I(on)/I(off) = 10(5); N,N'-bis(n-octyl)-1,7- and N,N'-bis(n-octyl)-1,6-dibromoperylene-3,4:9,10-bis(dicarboximide) (PDI-8Br2): mu = 3 x 10(-5) cm2 V(-1) s(-1), Vth = 62 V, I(on)/I(off) = 10(3); N,N'-bis(n-octyl)-1,6,7,12-tetrachloroperylene-3,4:9,10-bis(dicarboximide) (PDI-8Cl4): mu = 4 x 10(-3) cm2 V(-1) (s-1), Vth = 37 V, I(on)/I(off) = 10(4); N,N'-bis(n-octyl)-2-cyanonaphthalene-1,4,5,8-bis(dicarboximide) (NDI-8CN): mu = 4.7 x 10(-3) cm2 V(-1) s(-1), Vth = 28, I(on)/I(off) = 10(5); N,N'-bis(n-octyl)-1,7- and N,N'-bis(n-octyl)-1,6-dicyanoperylene-3,4:9,10-bis(dicarboximide) (PDI-8CN2): mu = 0.13 cm2 V(-1) s(-1), Vth = -14 V, I(on)/I(off) = 10(3); and N,N'-bis(n-octyl)-2,6-dicyanonaphthalene-1,4,5,8-bis(dicarboximide) (NDI-8CN2): mu = 0.15 cm2 V(-1) s(-1), Vth = -37 V, I(on)/I(off) = 10(2). Analysis of the molecular geometries and energetics in these materials reveals a correlation between electron mobility and substituent-induced arylene core distortion, while Vth and I(off) are generally affected by LUMO energetics. Our findings also indicate that resistance to ambient charge carrier trapping observed in films of N-(n-octyl)arylene diimides occurs at a molecular reduction potential more positive than approximately -0.1 V (vs SCE). OFET threshold voltage shifts between vacuum and ambient atmosphere operation suggest that, at E(red1) < -0.1 V, the interfacial trap density increases by greater than approximately 1 x 10(13) cm(-2), while, for semiconductors with E(red1) > -0.1 V, the trap density increase is negligible. OFETs fabricated with the present n-type materials having E(red1) > -0.1 V operate at conventional gate biases with minimal hysteresis in air. This reduction potential corresponds to an overpotential for the reaction of the charge carriers with O2 of approximately 0.6 V. N,N'-1H,1H-Perfluorobutyl derivatives of the perylene-based semiconductors were also synthesized and used to fabricate OFETs, resulting in air-stable devices for all fluorocarbon-substituted materials, despite generally having E(red1) < -0.1 V. This behavior is consistent with a fluorocarbon-based O2 barrier mechanism. OFET cycling measurements in air for dicyanated vs fluorinated materials demonstrate that energetic stabilization of the charge carriers results in greater device longevity in comparison to the OFET degradation observed in air-stable semiconductors with fluorocarbon barriers.     

Ambipolar behavior of hydrogen-bonded diketopyrrolopyrrole-thiophene co-oligomers formed from their soluble precursors

Organic field-effect transistors with hydrogen-bonded diketopyrrolopyrrole-thiophene co-oligomers were fabricated by a solution-process method with annealing at 200 °C, showing ambipolar charge-carrier transfer with field-effect mobilities up to μ(h) = 6.7 × 10(-3) cm(2) V(-1)s(-1) and μ(e) = 5.6 × 10(-3) cm(2) V(-1) s(-1).     

Lamination method for the study of interfaces in polymeric thin film transistors

A method for the fabrication of polymeric thin-film transistors (TFTs) by lamination is described. Poly(dimethylsiloxane) stamps were used to delaminate thin films of semiconducting polymers from silicon wafers coated with a self-assembled monolayer (SAM) formed from octyltrichlorosilane. These supported films were laminated onto electrode structures to form coplanar TFTs. The fabrication process was used to make TFTs with poly(3-hexylthiophene), P3HT, and poly[5,5'-bis(3-dodecyl-2-thienyl)-2,2'-bithiophene], PQT-12. TFTs, where these polymers were laminated onto gate dielectrics coated with SAMs from octyltrichlorosilane, had effective field-effect mobilities of 0.03 and 0.005 cm2/(V s), respectively. TFTs where PQT-12 was laminated onto gate dielectrics that were not coated with a SAM also had mobility of 0.03 cm2/(V s). In contrast, TFTs fabricated by spin-coating PQT-12 onto the same structure had mobilities ranging from 10-3 to 10-4 cm2/(V s). These results suggest that the lower mobilities of polymer TFTs made with hydrophilic gate dielectrics are caused by molecular ordering in the semiconducting film rather than electronic effects of dipolar groups at the interface.     

Delayed ignition of autocatalytic combustion precursors: low-temperature nanomaterial binder approach to electronically functional oxide films

Delayed ignition of combustion synthesis precursors can significantly lower metal oxide film formation temperatures. From bulk In(2)O(3) precursor analysis, it is shown here that ignition temperatures can be lowered by as much as 150 °C. Thus, heat generation from ~60 nm thick In(2)O(3) films is sufficient to form crystalline In(2)O(3) films at 150 °C. Furthermore, we show that the low processing temperatures of sufficiently thick combustion precursor films can be applied to the synthesis of metal oxide nanocomposite films from nanomaterials overcoated/impregnated with the appropriate combustion precursor. The resulting, electrically well-connected nanocomposites exhibit significant enhancements in charge-transport properties vs conventionally processed oxide films while maintaining desirable intrinsic electronic properties. For example, while ZnO nanorod-based thin-film transistors exhibit an electron mobility of 10(-3)-10(-2) cm(2) V(-1) s(-1), encasing these nanorods within a ZnO combustion precursor-derived matrix enhances the electron mobility to 0.2 cm(2) V(-1) s(-1). Using commercially available ITO nanoparticles, the intrinsically high carrier concentration is preserved during nanocomposite film synthesis, and an ITO nanocomposite film processed at 150 °C exhibits a conductivity of ~10 S cm(-1) without post-reductive processing.     

Ferroelectric and Pyroelectric Properties of Highly (111)-oriented Nanocrystalline Pb(Zr0:95Ti0:05)O3 Thin Films

"Lead zirconate titanate Pb(Zr0:95Ti0:05)O3 (PZT95/5) antiferroelectric thin films with 300 nm thickness were grown on Pt/Ti/SiO2/Si substrates by a sol-gel method with rapid thermal annealing processing. The X-ray diffraction results showed that the highly (111)-oriented pervoskite PZT95/5 thin films were grown on Pt/Ti/SiO2/Si substrates when annealed at 600-700 oC. Electrical measurements were conducted on PZT95/5 films in metal-ferroelectric-metal capacitor configuration. The PZT95/5 thin films annealed at 600-700 oC showed well-saturated hysteresis loops at an applied voltage of 20 V. At 1 kHz, the dielectric constant and dielectric loss of the films were 519 and 0.028, 677 and 0.029, 987 and 0.025, respectively for the thin films annealed at 600, 650, and 700 oC. The average remanent polarization (Pr) and the coercive electric field (Ec) obtained from the P-E hysteresis loops, were 19.1 1C/cm2 and 135.6 kV/cm, 29.31C/cm2 and 88.57 kV/cm, 45.3 1C/cm2 and 102.1 kV/cm, respectively for PZT95/5 thin films annealed at 600, 650 and 700 oC for 10 min in the oxygen atmosphere. This showed a good ferroelectricity of the prepared PZT95/5 films on Pt/Ti/SiO2/Si substrates by the simple sol-gel processing. The pyroelectric coeocient (p) of antiferroelectric PZT95/5 films was measured by a dynamic technique. At room temperature, the p values of the antiferroelectric PZT95/5 films at 1 kHz were 274, 238, and 212 1C/m2K."     

2,7-diphenyl[1]benzoselenopheno[3,2-b][1]benzoselenophene as a stable organic semiconductor for a high-performance field-effect transistor

[1]Benzoselenopheno[3,2-b][1]benzoselenophene (BSBS) and its 2,7-diphenyl derivative (DPh-BSBS) were readily synthesized from diphenylacetylene and bis(biphenyl-4-yl)acetylene, respectively, with a newly developed straightforward selenocyclization protocol. In contrast to the parent BSBS that has poor film-forming properties, the diphenyl derivative DPh-BSBS formed a good thin film on the Si/SiO(2) substrate by vapor deposition. X-ray diffraction examination revealed that this film consists of highly ordered molecules that are nearly perpendicular to the substrate, making it suitable for use in the fabrication of organic field-effect transistors (OFETs). When fabricated at different substrate temperatures (room temperature, 60 degrees C, and 100 degrees C) in a "top-contact" configuration, all the DPh-BSBS-based OFET devices exhibited excellent p-channel field-effect properties with hole mobilities >0.1 cm(2) V(-1) s(-1) and current on/off ratios of approximately 10(6). This high performance was essentially maintained over 3000 continuous scans between V(g) = +20 and -100 V and reproduced even after storage under ambient laboratory conditions for at least one year.     

Novel butterfly-shaped fused heteroacenes: synthesis, properties, and device performance of solution-processed field-effect transistors

Two tetrabrominated intermediates obtained by bromination of naphthodithiophene in different solvents were used to construct novel highly π-extended butterfly-shaped heteroarenes 1-6, containing either an 8- or 10-fused ring. The solution-processed organic field-effect transistors based on compound 1 exhibited promising device performance with a hole mobility of 0.072 cm(2) V(-1) s(-1) and a current on/off ratio of 10(6) under ambient atmosphere.     

Structure and torsional properties of oxalyl chloride fluoride in the gas phase: an electron-diffraction investigation

The structure and torsional properties of oxalyl chloride fluoride in the gas phase have been measured by electron diffraction at temperatures of 22, 81, 158, and 310 °C. The molecule may be regarded as a hybrid of oxalyl chloride and oxalyl fluoride. Since the former exists as a more stable periplanar anti form (? = 180°) in equilibrium with a less stable gauche form (? ? 60°) and the latter as an equilibrium between two periplanar forms, anti and syn, the second form of oxalyl chloride fluoride is an interesting question. It was found to be gauche. The system was modeled as two rotational conformers related by a potential of the form 2V = V(1)(1 + cos??) - V(2)(1 - cos?2?) + V(3)(1 + cos?3?). The anti/gauche bond distances and bond angles (r(g)/Angstroms, ∠(α)/degrees) with estimated 2σ uncertainties at 22 °C are = 1.183(2)/1.182(2), Δr(C═O) = 0.003(6)/0.002(6) (assumed from theory), r(C-F) = 1.329(3)/1.335(3), r(C-Cl) = 1.738(2)/1.753(2), ∠(C-C-Cl) = 112.0(3)/111.9(3), ∠(C-C═O3) = 123.0(4)/123.2(4), ∠(O═C-Cl) = 125.0(2)/1.249(2), ∠(O═C-F) = 123.0(3)/125.1(3), and ∠(Cl-C-C-F) = 180.0/59.8. The variation of composition with temperature afforded a determination of the standard enthalpy and entropy of the reaction anti → gauche. The results are ΔH° = 2.5(12) kcal/mol and ΔS° = -6.5(33) cal/(mol·K). The structures and equilibria are discussed.     

Atmospheric chemistry of n-C(x)F(2)(x)(+1)CHO (x = 1, 2, 3, 4): fate of n-C(x)F(2)(x)(+1)C(O) radicals

Smog chamber/FTIR techniques were used to study the atmospheric fate of n-C(x)F(2)(x)(+1)C(O) (x = 1, 2, 3, 4) radicals in 700 Torr O(2)/N(2) diluent at 298 +/- 3 K. A competition is observed between reaction with O(2) to form n-C(x)()F(2)(x)()(+1)C(O)O(2) radicals and decomposition to form n-C(x)F(2)(x)(+1) radicals and CO. In 700 Torr O(2)/N(2) diluent at 298 +/- 3 K, the rate constant ratio, k(n-C(x)F(2)(x)(+1)C(O) + O(2) --> n-C(x)F(2)(x)(+1)C(O)O(2))/k(n-C(x)F(2)(x)(+1)C(O) --> n-C(x)F(2)(x)(+1) + CO) = (1.30 +/- 0.05) x 10(-17), (1.90 +/- 0.17) x 10(-19), (5.04 +/- 0.40) x 10(-20), and (2.67 +/- 0.42) x 10(-20) cm(3) molecule(-1) for x = 1, 2, 3, 4, respectively. In one atmosphere of air at 298 K, reaction with O(2) accounts for 99%, 50%, 21%, and 12% of the loss of n-C(x)F(2)(x)(+1)C(O) radicals for x = 1, 2, 3, 4, respectively. Results are discussed with respect to the atmospheric chemistry of n-C(x)F(2)(x)(+1)C(O) radicals and their possible role in contributing to the formation of perfluorocarboxylic acids in the environment.     

Highly transparent solution processed In-Ga-Zn oxide thin films and thin film transistors

Highly transparent In-Ga-Zn oxide (IGZO) thin films were fabricated by spin coating using acetate- and chlorate-based precursors, and thin film transistors (TFTs) were further fabricated employing these IGZO films as the active channel layer. The impact of the post-annealing temperature on the physical properties of IGZO films and performance of IGZO TFTs were investigated. Compared to the nitrate-based IGZO precursor, the chlorate-based precursor increases the phase change temperature of IGZO thin films. The IGZO films changed from amorphous to nanocrystalline phase in an annealing temperature range of 600–700 °C. The transparency is more than 90% in the visible region for IGZO films annealed with temperatures higher than 600 °C. With the increase of post-annealing temperature, the carrier concentration of IGZO film decreases, while the sheet resistance increases firstly and then saturates. The bottom-gate TFT with IGZO channel annealed at 600 °C in oxygen showed the best performance, which was operated in n-type enhancement mode with a field effect mobility of 1.30 cm²/V s, a threshold voltage of 10 V, and a drain current on/off ratio of 2.5 × 10⁴.     

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.     

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     

Thermochemistry of Sr2Ce(1-x)Pr(x)O4 (x = 0, 0.2, 0.5, 0.8, and 1): variable-temperature and -atmosphere in-situ and ex-situ powder X-ray diffraction studies and their physical properties

A novel family of metal oxides with a chemical formula of Sr(2)Ce(1-x)Pr(x)O(4) (x = 0, 0.2, 0.5, 0.8, and 1) was developed as mixed oxide ion and electronic conductors for solid oxide fuel cells (SOFCs). All of the investigated samples were synthesized by the ceramic method at 1000 °C in air and characterized by powder X-ray diffraction (PXRD), selected area electron diffraction (SAED), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and electrochemical impedance spectroscopy (EIS). Ex-situ PXRD reveals that the Sr(2)PbO(4)-type Sr(2)CeO(4) decomposes readily into a mixture of perovskite-type SrCeO(3) and rock-salt-type SrO at 1400 °C in air. Surprisingly, the decomposed products are converted back to the original Sr(2)PbO(4)-type Sr(2)CeO(4) phase at 800 °C in air, as confirmed by in-situ PXRD. Thermal decomposition is highly suppressed in Sr(2)Ce(1-x)Pr(x)O(4) compounds for Pr > 0, suggesting that Pr improves the thermal stability of the compounds. Rietveld analysis of PXRD and SAED supported that both Pr and Ce ions are located on the 2a site in Pbam (space group no. 55). The electrical transport mechanism could be correlated to the reduction of Pr and/or Ce ions and subsequent loss of oxide ions at elevated temperatures, as shown by TGA and in-situ PXRD. Conductivity increases with Pr content in Sr(2)Ce(1-x)Pr(x)O(4). The highest total conductivity of 1.24 × 10(-1) S cm(-1) was observed for Sr(2)Ce(0.2)Pr(0.8)O(4) at 663 °C in air.     

Synthesis, structure, chemical stability, and electrical properties of Nb-, Zr-, and Nb-codoped BaCeO3 perovskites

We report the effect of donor-doped perovskite-type BaCeO(3) on the chemical stability in CO(2) and boiling H(2)O and electrical transport properties in various gas atmospheres that include ambient air, N(2), H(2), and wet and dry H(2). Formation of perovskite-like BaCe(1-x)Nb(x)O(3±δ) and BaCe(0.9-x)Zr(x)Nb(0.1)O(3±δ) (x = 0.1; 0.2) was confirmed using powder X-ray diffraction (XRD) and electron diffraction (ED). The lattice constant was found to decrease with increasing Nb in BaCe(1-x)Nb(x)O(3±δ), which is consistent with Shannon's ionic radius trend. Like BaCeO(3), BaCe(1-x)Nb(x)O(3±δ) was found to be chemically unstable in 50% CO(2) at 700 °C, while Zr doping for Ce improves the structural stability of BaCe(1-x)Nb(x)O(3±δ). AC impedance spectroscopy was used to estimate electrical conductivity, and it was found to vary with the atmospheric conditions and showed mixed ionic and electronic conduction in H(2)-containing atmosphere. Arrhenius-like behavior was observed for BaCe(0.9-x)Zr(x)Nb(0.1)O(3±δ) at 400-700 °C, while Zr-free BaCe(1-x)Nb(x)O(3±δ) exhibits non-Arrhenius behavior at the same temperature range. Among the perovskite-type oxides investigated in the present work, BaCe(0.8)Zr(0.1)Nb(0.1)O(3±δ) showed the highest bulk electrical conductivity of 1.3 × 10(-3) S cm(-1) in wet H(2) at 500 °C, which is comparable to CO(2) and H(2)O unstable high-temperature Y-doped BaCeO(3) proton conductors.     

2,6-Diarylnaphtho[1,8-bc:5,4-b'c']dithiophenes as new high-performance semiconductors for organic field-effect transistors

A series of 2,6-diaryl-substituted naphtho[1,8-bc:5,4-b'c']dithiophene derivatives 2-6, whose aryl groups include 5-hexyl-2-thienyl, 2,2'-bithiophen-5-yl, phenyl, 2-naphthyl, and 4-biphenylyl, was synthesized by the palladium-catalyzed Suzuki-Miyaura coupling and utilized as active layers of organic field-effect transistors (OFETs). All devices fabricated using vapor-deposited thin films of these compounds showed typical p-type FET characteristics. The mobilities are relatively good and widely range from 10(-4) to 10(-1) cm2 V(-1) s(-1), depending on the substituent groups. Among them, the mobilities of the devices using films of 3-5 tend to increase with the increasing temperature of the Si/SiO2 substrate during film deposition. In particular, the device based on the naphthyl derivative 5, when fabricated at 140 degrees C, marked a high mobility of 0.11 cm2 V(-1) s(-1) with an on/off ratio of 10(5), which is a top class of performance among organic thin-film transistors. Studies of X-ray diffractograms (XRDs) have revealed that the film of 4 and 5 is composed of two kinds of crystal grains with different phases, so-called "single-crystal phase" and "thin film phase", and that the proportion of the thin film phase increases with an increase of the substrate temperature. In the thin film phase the assembled molecules stand nearly upright on the substrate in such a way as to be favorable to carrier migration.     

Synthesis and characterization of soluble oligo (9,10-bisalkynylanthrylene)s

[structure: see text] Soluble oligo(9,10-bialkynylanthrylene)s up to pentamers were synthesized by means of the Suzuki coupling reaction. A solution processed thin film field-effect transistor from pentamer OA-5b shows a charge carrier mobility of 2.95 x 10(-)(3) cm(2)/V x s.     

Naphtho[2,1-b:6,5-b']difuran: a versatile motif available for solution-processed single-crystal organic field-effect transistors with high hole mobility

We here report naphtho[2,1-b:6,5-b']difuran derivatives as new p-type semiconductors that achieve hole mobilities of up to 3.6 cm(2) V(-1) s(-1) along with high I(on)/I(off) ratios in solution-processed single-crystal organic field-effect transistors. These features originate from the dense crystal packing and the resulting large intermolecular π-orbital overlap as well as from the small reorganization energy, all of which originate from the small radius of an oxygen atom.     

Homoleptic copper(I) arylthiolates as a new class of p-type charge carriers: structures and charge mobility studies

Polymeric homoleptic copper(I) arylthiolates [Cu(p-SC(6)H(4)-X)](infinity) (X=CH(3) (1), H (2), CH(3)O (3), tBu (4), CF(3) (5), NO(2) (6), and COOH (7)) have been prepared as insoluble crystalline solids in good yields (75-95 %). Structure determinations by powder X-ray diffraction analysis have revealed that 1-3 and 6 form polymers of infinite chain length, with the copper atoms bridged by arylthiolate ligands. Weak intra-chain pi***pi stacking interactions are present in 1-3, as evidenced by the distances (3.210 A in 1, 3.016 A in 2, 3.401 A in 3) between the mean planes of neighboring phenyl rings. In the structure of 6, the intra-chain pi***pi interactions (d=3.711 A) are insignificant and the chain polymers are associated through weak, non-covalent C-H...O hydrogen-bonding interactions (d=2.586 A). Samples of 1-7 in their polycrystalline forms proved to be thermally stable at 200-300 degrees C; their respective decomposition temperatures are around 100 degrees C higher than that of the aliphatic analogue [Cu(SCH(3))](infinity). Data from in situ variable-temperature X-ray diffractometry measurements indicated that the structures of both 1 and 7 are thermally more robust than that of [Cu(SCH(3))](infinity). TEM analysis revealed that the solid samples of 1-5 and [Cu(SCH(3))](infinity) contained homogeneously dispersed crystalline nanorods with widths of 20-250 nm, whereas smaller plate-like nanocrystals were found for 6 and 7. SAED data showed that the chain polymers of 1-3 and [Cu(SCH(3))](infinity) similarly extend along the long axes of their nanorods. The nanorods of 1-5 and [Cu(SCH(3))](infinity) have been found to exhibit p-type field-effect transistor behavior, with charge mobility (micro) values of 10(-2)-10(-5) cm(2) V(-1) s(-1). Polycrystalline solid samples of 6 and 7 each showed a low charge mobility (<10(-6) cm(2) V(-1) s(-1)). The charge mobility values of field-effect transistors made from crystalline nanorods of 1-3 and [Cu(SCH(3))](infinity) could be correlated with their unique chain-like copper-sulfur networks, with the para-substituent of the arylthiolate ligand influencing the charge-transport properties.     

A structurally ordered thiophene-thiazole copolymer for organic thin-film transistors

This paper reports a new donor-acceptor copolymer semiconductor, PTBTh, comprising bithiophene and bithiazole where the regular coplanar structure and the intramolecular charge transfer are expected to increase the opportunity for --- stacking and charge transport. The AFM image shows lamellar stacking of the polymer on the surface. The field-effect transistor (FET) properties of PTBTh have been evaluated by a bottom-contact/bottom-gate TFT configuration. The device showed a high hole mobility of 1.14×10-2 cm2 V-1 s-1 and a current on/off ratio of 3×105 with the polymer thin film annealed at a mild temperature of 120 ℃ when measured under ambient conditions.