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Future electronics will play a more critical role in people's lives, as reflected in the realization of advanced human–machine interfaces, disease detection, medical treatment, and health monitoring. The current electronic products are rigid, non-degradable, and cannot repair themselves. Meanwhile, the human body is soft, dynamic, stretchable, degradable, and self-healing. Consequently, it is valuable to develop new electronic materials with skin-like properties that include stretchability, inhibition of invasive reactions, self-healing, long-term durability, and biodegradability. These demands have driven the development of a new generation of electronic materials with high-electrical performance and skin-like properties, among which e-polymers are increasingly being more extensively investigated. This review focuses on recent advances in synthesizing e-polymers and their applications in biointerfaces and organisms. Discussions include the synthesis and properties of e-polymers, the interrelationships between engineered material structures and human interfaces, and the application of implantable and wearable systems for sensors and energy harvesters. The final section summarizes the challenges and future opportunities in the evolving materials and biomedical research field. [ABSTRACT FROM AUTHOR]

Neuromorphic computing and engineering has been the focus of intense research efforts that have been intensified recently by the mutation of Information and Communication Technologies. In fact, new computing solutions and new hardware platforms are expected to emerge to answer to the new needs and challenges of our societies. In this revolution, lots of candidates' technologies are explored and will require leveraging of the pros and cons. In this perspective paper belonging to the special issue on neuromorphic engineering of Journal of Applied Physics, we focus on the current achievements in the field of organic electronics and the potentialities and specificities of this research field. We highlight how unique material features available through organic materials can be used to engineer useful and promising bio-inspired devices and circuits. We also discuss the opportunities that organic electronics offer for future research directions in the neuromorphic engineering field. [ABSTRACT FROM AUTHOR]

In this study, pressures of ~5 to ~8MPa were applied to organic light emitting diodes containing either evaporated molybdenum trioxide (MoO3) or spin-coated poly(3,4-ethylene dioxythiophene) doped with poly(styrene sulphonate) (PEDOT:PSS) hole-injection layers (HILs). The threshold voltages for both devices were reduced by about half, after the application of pressure. Furthermore, in an effort to understand the effects of pressure treatment, finite element simulations were used to study the evolution of surface contact between the HIL and emissive layer (EML) under pressure. The blister area due to interfacial impurities was also calculated. This was shown to reduce by about half, when the applied pressures were between ~5 and 8MPa. The finite element simulations used Young's modulus measurements of MoO3 that were measured using the nanoindentation technique. They also incorporated measurements of the adhesion energy between the HIL and EML (measured by force microscopy during atomic force microscopy). Within a fracture mechanics framework, the implications of the results are then discussed for the pressure-assisted fabrication of robust organic electronic devices. [ABSTRACT FROM AUTHOR]

The authors developed a scheme for characterizing the expansion and contraction of polymer electrodes when voltage is applied by coupling a symmetry analysis, the elasticity theory, and the experimental measurements. This scheme was applied to the bucky-gel electrodes and the expansion and contraction rates for the cathode and the anode were determined separately. For the case of the bucky-gel electrodes, it was found that the cathode expands and the anode contracts as voltage is applied. The stress exerted inside the electrode layers was also determined and the mechanical efficiency of the actuator composed of the bucky-gel electrodes is discussed. [ABSTRACT FROM AUTHOR]

The photoluminescence and electroluminescence of a molecular precursor of helicene embedded in an active matrix formed by a hole-transporter polymer mixed with an electron transporter molecule are reported. Optimization of the weight ratio between the dye and the matrix is performed by a detailed study of the absolute emission efficiencies obtained by photoexcitation and by charge injection. A 0.17 wt % dye concentration gives the best compromise among energy transfer, transport properties, and quenching effects induced by dye aggregation, leading to an external blue electroluminescence efficiency of 0.4% in a single layer device. [ABSTRACT FROM AUTHOR]

Abstract Conductive organic materials including polymers, small molecules, and carbon nanotubes (CNTs) are a promising alternative to inorganic materials in electronic devices. Conventionally, organic electrodes employing CNTs are designed using functionalization of their surfaces or formation of nanocomposites with a conductive polymer. However, phase separation limits the concentration of CNTs in a polymer matrix, hindering the formation of highly dense CNT networks and leading to poor electrical conductivity. In this paper, we introduce bilayer electrodes comprising poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) and single-walled CNTs (SWNTs) chemically modified by HNO 3 treatment. Impressive conductivities of 2432 and 2438 S cm−1 are found for the SWNT/PEDOT:PSS (S/P) and PEDOT:PSS/SWNT (P/S) electrodes, respectively. Further, an increase in the work function of the electrodes after HNO 3 treatment lowers the hole injection barrier, which facilitates hole injection from pentacene. The smooth surface of PEDOT:PSS also contributes to growth of large pentacene grains; consequently, the field-effect mobility of pentacene-based thin film transistors is 1.88 cm2 V−1 s−1 when the P/S electrode is employed. The metal-free electrodes also exhibit a high optical transparency of 88.7%, which suggests that they have great potential for applications in optoelectronics. Graphical abstract Image 1 Highlights • PEDOT:PSS/SWNT bilayer electrodes are fabricated using lithographic process. • HNO 3 treatment of electrodes increases electrical conductivity and work function. • Large pentacene grains are observed on PEDOT:PSS. • Field-effect mobility and on-off ratio of pentacene TFTs are found to be 1.88 cm2 V−1 s−1 and 2.3 × 106, respectively. [ABSTRACT FROM AUTHOR]

This paper is showing simulations of power supplies for repetitive power modulators using LTspice. We are presenting power supplies with single-phase and three-phase AC input and the effects of the rectifier stages on AC input current waveforms in both cases. We are also presenting the resulting power factor including circuits for electronic power factor correction. LTspice models for electronic power factor correction using cycle-by-cycle switching as well as time-averaged models are presented. The time-averaged models replace the PWM (pulse width nodulation) switch with a transformer model with variable duty cycle. They are valid for a range of DC-DC converters. We are extending the time-averaged model for operation in continuous (CCM) and discontinuous (DCM) conduction mode and presenting results that show the fidelity of these models by comparison to cycle-by-cycle results. We are providing the detailed mathematical derivation for the DCM model expansion in the appendix. Time-averaged models do not have to keep track of thousands of steep switching transitions and can run orders of magnitude faster than cycle-by-cycle switch-mode models. Results using the time-averaged model are presented for a power supply with primary (wave-shaping) and cascaded secondary feedback control that regulates the output voltage of the converter. [ABSTRACT FROM AUTHOR]

ABSTRACT: D‐A copolymer systems have unique characteristics, such as low band gap and ambipolar nature, which are important to design electronic polymer devices. In this contribution, we synthesized and characterized a D‐A random copolymer containing bis‐3‐hexylthiophene‐benzothiadiazole as acceptor unit and 9,9‐dioctylfluorene as donor unit. We show that the polymeric film morphology depends of the Hansen solubility parameters, evaporation rate, and surface tension of the solvent. Chloroform, toluene, and 1,2,4‐trichlorobenzene (TCB) promote the formation of self‐assembled structures due to breath‐figure mechanism. In contrast, THF causes aggregation and phase separation that affect negatively the electrical conductivity of the copolymer film. Among the solvents analyzed, TCB is the one with the highest molecular interaction with the copolymer synthetized in this work. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018, 56, 1035–1044 [ABSTRACT FROM AUTHOR]

Abstract: The development of organic electronics requires scalable solution‐processing methods that enable the fabrication of electronic devices over large areas at low cost. The preparation of peropyrene gels constituted of 3D networks of entangled 1D ribbon‐like fibrils that extend over the μm scale are now reported. OFETs were easily fabricated by depositing the gels in the sol state over bottom‐gate bottom‐contact transistors and by allowing its gelation thereafter. Electrical characterisation of such field‐effect transistors shows a good balance between processability and performance with hole mobilities that are two orders of magnitude higher than those observed in thin films obtained from non‐gelating solvents under the same conditions. [ABSTRACT FROM AUTHOR]

Polymers having conjugated double bond system in the backbone structure are electronically conducting. Incorporation of certain side groups to such backbone gives introduce unique new properties or alter the initial properties of the polymer. Consequently conducting polymers with unique and tailored properties are valuable new materials of the future engineering. Electrical properties of the interface between conducting polymer and metal is of vital importance to the application potential of the polymer in the electronics. In present study we discuss the electrical properties of the heterojunction composed of conductive polymer pressed nanoparticles and silver thin layer. The contacts were deposited by vacuum evaporation from bulk silver plate or dry silver nanoparticles. In this study the new conjugated polymer poly(4-(thien-3-ylmethoxy)butane-1-sulfonic acid)-PTMBSA-was used as the organic semiconductor. The syntheses of PTMBSA and silver nanoparticles are discussed. In order to evaluate the morphology of PTMBSA pellets with electrodes scanning electron microscopy (SEM) was applied. The important information on the electrical properties of the system were obtained from the measurements of the current-voltage characteristics revealing significant qualitative difference of investigated heterojunctions. It was found that the contact of silver and PTMBSA has electrical properties varying in time. For about 100 h after preparation, intrinsic conductivity of the sandwich specimen has been gradually increasing. [ABSTRACT FROM AUTHOR]

The rosette-like dislocation clusters around Te inclusions in as-grown CdZnTe/CdTe crystals and those introduced by the micro-indentation on CdZnTe/CdTe surface are studied experimentally. The extended dislocation patterns are formed around Te inclusions in both CdZnTe and CdTe crystals, owing to the build-in stress. Two mutually orthogonal tetrahedrons are observed in CdZnTe crystal. However, the “double-arms” dislocation rosette pattern extended along 〈1 1 0〉 direction is observed in CdTe crystal. The Peierls kink pair mechanism and the Hirsch effects are used to explain the discrepancy of these two different rosette patterns. Similar dislocation rosette patterns are observed on indentation surface of CdZnTe crystal. The dislocation rosette patterns are found to be independent of the indenter orientation, but completely determined by the crystallographic properties of zinc-blende structure of the crystal. Furthermore, the Te(g) and Cd(g) dislocation arms are found to be mixed and bended with each other in CdTe crystal under high indentation stress, making it different from that generated around Te inclusions. A model concerning the comprehensive impact of stress field and electronic polarities dislocations is proposed to clarify the dislocation bending phenomenon. [ABSTRACT FROM AUTHOR]

There is still a challenge in organic electronics to effectively tailor interfacial electronic structures for achieving desired electronic properties for optoelectronic devices. This study realizes the tuning of interfacial electronic structures in organic semiconductor pentacene by employing substrates with different work functions. Pentacene layers show downward band-bending with a low work function, flat band with a middle work function, and upward band-bending with a high work function. The formation of band-bending is explained by the electrostatic potential according to the Fermi level position. Different interfacial electronic structures can influence the carrier transport across the interface. Their diodes show different rectifying behaviors due to band-bending, and ohmic transport is observed for the flat band structure. This work is a promising exploration to realize desired functions of semiconductor devices by tailoring interfacial electronic structures. [ABSTRACT FROM AUTHOR]

Neste trabalho as propriedades ópticas do poli[2-metóxi,5-(2'etil-hexiloxi)-p-fenilenovinileno] - MEH-PPV foram estudadas sob efeito de luz azul proveniente de super LEDs utilizada no tratamento da hiperbilirrubinemia neonatal (ou icterícia). Os resultados mostraram que o MEH-PPV apresenta uma mudança de cor do vermelho-alaranjado para o incolor, passando por diversas tonalidades de amarelo, bem como uma diminuição da intensidade dos espectros de absorção e de fotoluminescência (PL) em função do tempo de exposição à radiação. Essas mudanças foram usadas para projetar um sensor de acúmulo de dose de radiação azul, tipo indicador de cores, para avaliar a dose de radiação recebida por recém-nascidos durante o tratamento da icterícia neonatal.In this work we investigated the optical behavior of poly[2-methoxy-5(2'-ethylhexyloxy)-p-phenylenevinylene] (MEH-PPV) under the effect of blue-light LED source applied in neonatal hyperbilirubinemia treatment. There is a visible response that covers the electronic absorption of bilirubin (350-500 nm), and hence this material is applicable for controlling the radiation doses in the treatment of jaundice of neonates, which is one of the most common reasons for hospital readmission of newborn infants. The results show that the material presents a gradation of color from orange-red to yellow and quenching on the absorption and photoluminescent (PL) spectra with the radiation exposure time. The rate of these changes can be altered by manipulations of organic solution concentration, suggesting these color and emission/absorption changes can be used to design an indicator-dosimeter that is readily associated with the radiation exposure time used in treating neonatal jaundice.

The development of devices able to detect and record ion fluxes is a crucial point in order to understand the mechanisms that regulate communication and life of organisms. Here, we take advantage of the combined electronic and ionic conduction properties of a conducting polymer to develop a hybrid organic/living device with a three-terminal configuration, using the Physarum polycephalum Cell (PPC) slime mould as a living bio-electrolyte. An over-oxidation process induces a conductivity switch in the polymer, due to the ionic flux taking place at the PPC/polymer interface. This behaviour endows a current-depending memory effect to the device. [ABSTRACT FROM AUTHOR]

As mass-produced, low-cost organic electronics enter our everyday lives, so does the waste from them. The challenges associated with end-of-life management must be addressed by careful design and carbon-based electrodes are central to these developments. Here, the reproducible production of vacuum-, indium tin oxide (ITO)-, and silver-free solar cells in a fully packaged form using only roll-to-roll processing is reported. Replacing silver with carbon as electrode material significantly lowers the manufacturing cost and makes the organic photovoltaic (OPV) modules environmentally safe while retaining their flexibility, active area efficiency, and stability. The substitution of silver with carbon does not affect the roll-to-roll manufacturing of the modules and allows for the same fast printing and coating. The use of carbon as electrode material is one step closer to the wide release of low-cost plastic solar cells and opens the door to new possible applications where silver recycling is not manageable. [ABSTRACT FROM AUTHOR]

A novel semiconducting polymer poly(4-hexyloxythiazole) with a low optical band gap of 1.4 eV was synthesized and used in organic electronic devices. X-ray diffraction (XRD) measurements reveal a high degree of crystallinity and lamellar packing of poly(4-hexyloxythiazole) in the film similar to poly(3-hexylthiophene). Field effect transistor charge mobility of poly(4-hexyloxythiazole) arrived 0.02 cm 2 /V s. Bulk heterojunction type solar cells based on poly(4-hexyloxythiazole) shows a photoresponse up to about 900 nm. [ABSTRACT FROM AUTHOR]

The potential energy curves of the low-lying doublet electronic states in the representation 2s+1Λ(+/−) of the SrF molecule have been investigated by using the complete active space self-consistent field with multireference configuration interaction and multireference Rayleigh-Schrödinger perturbation theory methods. The harmonic frequency, ωe; the internuclear distance, Re; the dipole moment; and the electronic energy with respect to the ground state, Te, have been calculated for the considered electronic states. The eigenvalues, Ev; the rotational constants, Bv; and the abscissas of the turning points, Rmin and Rmax, have been investigated using the canonical functions approach. The comparison between the values of the present work and those available in the literature for several electronic states shows very good agreement. Nine new electronic states have been investigated here for the first time. [ABSTRACT FROM AUTHOR]

RATIONALE For organic electronics, device performance can be affected by interlayer diffusion across interfaces. Time-of-flight secondary ion mass spectrometry (TOF-SIMS) can resolve buried structures with nanometer resolution, but instrument artifacts make this difficult. Low-temperature plasma (LTP) is suggested as a way to prepare artifact-free surfaces for accurate determination of chemical diffusion. METHODS A model organic layer system consisting of three 1 nm delta layers of 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP) separated by three 30 nm layers of tris(8-hydroxyquinolinato)aluminum (Alq3) was used to evaluate the effectiveness of LTP etching for the preparation of crater edge surfaces for subsequent compositional depth profile analysis. This was compared with depth profiles obtained using an instrument equipped with an argon cluster sputter source. RESULTS The quality of the depth profiles was determined by comparing the depth resolutions of the BCP delta layers. The full width at half maximum gave depth resolutions of 6.9 nm and 6.0 nm using LTP, and 6.2 nm and 5.8 nm using argon clusters. In comparison, the 1/e decay length of the trailing edge gave depth resolutions of 2.0 nm and 1.8 nm using LTP, and 3.5 nm and 3.4 nm using argon clusters. CONCLUSIONS The comparison of the 1/e decay lengths showed that LTP can determine the thickness and composition of the buried structures without instrument artifacts. Although it does suffer from contaminant deposition, LTP was shown to be a viable option for preparing crater edges for a more accurate determination of buried structures. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The first polymer bearing exTTF units intended for the use in electrical charge storage is presented. The polymer undergoes a redox reaction involving two electrons at −0.20 V vs Fc/Fc+ and is applied as active cathode material in a Li-organic battery. The received coin cells feature a theoretical capacity of 132 mAh g−1, a cell potential of 3.5 V, and a lifetime exceeding more than 250 cycles. [ABSTRACT FROM AUTHOR]

Abstract: We demonstrate a small molecule solution processed hole interfacial layer approach to improve the dark current characteristics of polymer photodiodes. The two hole blocking materials under investigation 3-phenyl-4(1′-naphthyl)-5-phenyl-1,2,4-triazole (TAZ) and 2-[3,5-bis(1-phenylbenzimidazol-2-yl)phenyl]-1-phenylbenzimidazole (TPBi) are spincoated from ethanol as an orthogonal solvent on top of a P3HT:PCBM active layer. We reduce the dark current at a bias voltage of −1V by a factor of 17.2 by introducing a TAZ interfacial layer while keeping the responsivity unchanged. [Copyright &y& Elsevier]

Abstract: The effect of solvent mixtures on the morphologies of poly[N-9′-hepta-decanyl-2,7-carbazole-alt-5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole)] (PCDTBT):[6,6]-phenyl C71-butyric acid methyl ester (PC71BM) blend films is investigated. 1,2,4-Trichlorobenzene (TCB) which is a good solvent for PCDTBT is selected to mix with chloroform (CF), chlorobenzene (CB) and o-dichlorobenzene (oDCB) for tuning the morphology of the PCDTBT:PC71BM blend. It is found that formation of nanoscale phase separation with a fibrillar PCDTBT nanostructure of PCDTBT:PC71BM blend which is favorable for exciton separation and charge carrier transport is strongly dependent on the solubility parameters of the solvent mixtures. A clearly defined nanoscale phase separation of the PCDTBT:PC71BM blend can be obtained with TCB:CF mixture. The resulted morphology is similar to that produced with sole DCB solvent that is currently the best solvent for PCDTBT:PC71BM blend solar cells. Moreover, the TCB:CF mixture demonstrates better solubility and processibility for PCDTBT:PC71BM blend and allows us to prepare thick active layer that is required in large-area roll-to-roll process. The polymer solar cells with 250nm- thick active layer are fabricated by using TCB:CF solvent mixture and the power conversion efficiency of the devices reaches 6.45%. A highest short-circuit current of 13.6mA/cm2 is achieved due to enhanced optical absorption of thick active layer. [Copyright &y& Elsevier]

Abstract: We report for the first time organic n-type nonvolatile memory transistors based on a fullerene (C60) semiconductor and an electron-trapping polymer, poly(perfluoroalkenyl vinyl ether) (CYTOP). The transistors with a Si++/SiO2/CYTOP/C60/Al structure show good n-type transistor performance with a threshold voltage (V th) of 2.8V and an electron mobility of 0.4cm2 V−1 s−1. Applying gate voltages of 50 or −45V for about 0.1s to the devices induces the reversible shifts in their transfer characteristics, which results in a large memory window (ΔV th) of 10V. A memory on/off ratio of 105 at a small reading voltage below 5V and a retention time greater than 105 s are achieved. The memory effect in the transistor is ascribed to electrons trapped at the CYTOP/SiO2 interface. Because of the use of high-electron-mobility C60, the switching voltages of our memory transistors become significantly lower than those of conventional memory transistors based on pentacene. [Copyright &y& Elsevier]

We present an optical spectroscopy study on the role of oxygen and water in electron trapping and storage/bias-stress degradation of n-type polymer field-effect transistors based on one of the most widely studied electron transporting conjugated polymers, poly{[N,N9-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,59-(2,29-bisthiophene)} (P(NDI2OD-T2)). We combine results obtained from charge accumulation spectroscopy, which allow optical quantification of the concentration of mobile and trapped charges in the polymer film, with electrical characterization of P(NDI2OD-T2) organic field-effect transistors to study the mechanism for storage and bias-stress degradation upon exposure to dry air/oxygen and humid nitrogen/water environments, thus separating the effect of the two molecules and determining the nature of their interaction with the polymer. We find that the stability upon oxygen exposure is limited by an interaction between the neutral polymer and molecular oxygen leading to a reduction in electron mobility in the bulk of the semiconductor. We use density functional theory quantum chemical calculations to ascribe the drop in mobility to the formation of a shallow, localized, oxygen-induced trap level, 0.34 eV below the delocalized lowest unoccupied molecular orbital of P(NDI2OD-T2). In contrast, the stability of the polymer anion against water is limited by two competing reactions, one involving the electrochemical oxidation of the polymer anion by water without degradation of the polymer and the other involving a radical anion-catalyzed chemical reaction of the polymer with water, in which the electron can be recycled and lead to further degradation reactions, such that a significant portion of the film is degraded after prolonged bias stressing. Using Raman spectroscopy, we have been able to ascribe this to a chemical interaction of water with the naphthalene diimide unit of the polymer. The degradation mechanisms identified here should be considered to explain electron trapping in other rylene diimides and possibly in other classes of conjugated polymers as well. [ABSTRACT FROM AUTHOR]

Abstract: We studied the effect of spin-flip scattering to understand the spin-dependent quantum transport properties through an organic spin filter. We found that the electronic orbitals of the organic polymer are spin-mixed when the spin-flip scattering is included. The Peierls energy gap is reduced due to the spin-flip effect, which is a peculiar property of the organic ferromagnetic polymer. An analysis based on the extended Landauer–Büttiker formula shows that the spin polarization of the current through the spin filter decreases with the spin-flip scattering. However, the device keeps the spin filter function intact even when a considerable spin-flip scattering is included. We also discuss the competing effects of spin-flip scattering and ferromagnetism of the organic interlayer on the spin filter. [Copyright &y& Elsevier]

Abstract: Polymer-fullerene bulk heterojunction (BHJ) solar cells have gained much attention in the past few years due to their potential as a low cost photovoltaic technology. The state-of-the-art power conversion efficiency (PCE) has been improved to 7% regime by the recent development of thieno[3,4-b]thiophene based low-band-gap polymers. This paper reports a new low-band-gap polymer with alternating thieno[3,4-b]thiophene and benzo[1,2-b:4,5-b′]dithiophene units for applications in BHJ solar cells. By optimizing the nano-scale morphology with DIO (1,8-diiodooctane) additive, the PCE of BHJ solar cells based on this new polymer has been improved dramatically from 1.4% to 4.8%. The correlation between photovoltaic performance and film morphology has been established for this new polymer/fullerene system. [Copyright &y& Elsevier]

Abstract: The photoconductivity, hole mobility and charge photogeneration efficiency of a series of side-chain carbazole homopolymers and copolymers (with azo side-chains) have been investigated. Cyclic voltammetry measurement of frontier orbitals energies show that the HOMO energy is determined by the nature and the position of attachment of the linker between the main chain and the carbazole, the azo-moiety being not relevant in this respect. Hole mobility is not influenced by the HOMO energy but seems to depend on the degree of conformational mobility of the side-chains, reaching values of the order of 10−3 cm2 V−1 s−1 in the best cases. The HOMO energy is instead extremely important when considering photogeneration efficiency, that can change by 10 orders of magnitude depending on the density of the carbazole side-chains in co-polymers and on the linker nature and attachment position. [Copyright &y& Elsevier]

Abstract: Four kinds of commercial PEDOT dispersions have been used to realize ITO/PEDOT/PF6/Al polymeric OLEDs. The effects of the different PEDOT layers have been analyzed by the means of static current–voltage characterizations and admittance spectra. The measurements have revealed a good agreement with the Nicollian–Brews model returning the density of the interface traps; moreover the role of the trapping rate has been focused in terms of density of carriers available for the conduction. [Copyright &y& Elsevier]

Abstract: We demonstrate semi-transparent inverted polymer solar cells with transparent anodes, made of Vanadium pentoxide (V2O5)/silver (Ag)/V2O5. The inner V2O5 layer was introduced as a buffer layer to improve holes collection, while the outer V2O5 layer served as a light coupling layer to enhance optical transmittance of the device. The transmittance and reflectance of V2O5 (10nm)/Ag (13nm)/V2O5 (x =20, 40, 60, 80nm) electrode are measured and compared, and the dependence of the device performances on the thickness of the outer V2O5 layer was investigated. The results show that the maximum transmittance of 90%, which appears from 400 to 700nm, is obtained when the thickness of outer V2O5 layer is 40nm. [Copyright &y& Elsevier]

Abstract: Highly stable, solution-processed, small molecule-polymer blend organic field-effect transistors (OFETs) with a top-gate geometry were demonstrated on a flexible polyethersulfone (PES) substrate. The top-gate dielectric was a bi-layer comprised of CYTOP and a high-k Al2O3 layer grown by atomic layer deposition (ALD). A solution processed 6,13-bis(triisopropylsilylethynyl) pentacene (TIPS-pentacene) and poly(triarylamine) (PTAA) blend was used as the organic semiconductor. TIPS-pentacene and PTAA blend OFETs with the CYTOP/Al2O3 bi-layer top gate dielectric showed an averaged saturation mobility value of 0.24±0.08cm2/Vs at operation voltages below 8V. A constant direct-current bias stress test was carried out to examine their operational stability for 2h. Under bias stress, neither significant change in mobility nor shift in the threshold voltage has been observed in these OFETs. To evaluate the real potential of these OFETs towards the development of circuit components commonly used in electronic applications, a resistive-load inverter was implemented by connecting an OFET to an external load resistor. Excellent stability of the transistor led to electrically stable inverters with negligible variations of the voltage transfer characteristics before and after bias stress. After the operational stability test, these OFETs were exposed to air and then were subjected to bending experiments. Even after exposure to air for 4months and bending for 30min, no significant changes in performance were observed in either a single transistor device or in a resistive-load inverter. [Copyright &y& Elsevier]

Abstract: Poly(3-hexylthiophene)/poly(methyl methacrylate) (P3HT/PMMA) blends were used as the semiconducting layer in water-gated organic field-effect transistors (OFETs), which resulted in improving the electrical performance of the previously reported devices with pure P3HT. Topographic investigations by atomic force microscopy carried out on blends with various PMMA to P3HT ratio reveal a lateral phase separation of the two components. All transistors operate at very low voltage (below 1V), with a threshold voltage ranging form 0.3 to 0.5V. An optimum of the composition of the blend is found with 70% of PMMA, leading to a maximum on/off current ratio and a mobility comparable to that of pure P3HT. [Copyright &y& Elsevier]

Abstract: Fluorene and thiophene units are commonly used in polymeric materials for electro-optical applications. Due to differences in reactivity, the final composition of polymers containing these components often differs from that used in their preparation. This contribution describes the synthesis of PPV type terpolymers built by fluorene, phenylene and thiophene units and their quantification by CPMAS NMR. The similarity of the three aromatic co-monomers makes it difficult to separate the analytical responses that would allow quantification of each copolymer unit in the chain. In this sense, we show that the combination of dipolar dephased CPMAS with radiofrequency ramp and proper spectral treatment allows a good estimation and quantification of the copolymer constitution. [Copyright &y& Elsevier]

Abstract: Catalytic oxidation of carbohydrates by oxygen using various viologens under mild conditions was recently shown to occur at high efficiency with formate and carbonate formed as products. However, high efficiency was only achieved at viologen/carbohydrate ratios >10. The use of such high catalyst ratios is undesirable and a mechanistic study was initiated to better understand how catalytic efficiency is influenced by catalyst ratio. The results suggest that the dipositive viologen reacts with the enediol form of the carbohydrate, initiating carbohydrate oxidation with subsequent reduction of the viologen to the radical cation form. The latter is then oxidized by air or by current collecting electrodes when the reaction is conducted in a fuel cell. If the viologen/carbohydrate ratio is low, electron transfer from the carbohydrate to the oxidized form of the viologen becomes limiting and the carbohydrate undergoing oxidation rearranges into unreactive intermediates such as carboxylic acids, and alcohols. However, at high ratios, excess viologen more efficiently oxidizes the carbohydrate and minimizes formation of unreactive intermediates. Viologen polymers were more efficient than an equivalent concentration of monomers, suggesting that the higher localized concentration in polymeric viologen acts to efficiently oxidize carbohydrates and simulates high viologen/carbohydrate ratios. The use of viologen films on electrodes or conducting viologen polymers should facilitate use of carbohydrates for electricity production in fuel cells. [ABSTRACT FROM AUTHOR]

Calculation of chromophore polar order, i.e. the polarization of nonlinear optically (NLO) active polymers poled by external field, is challenging. One possible solution is to reproduce the orientation polarization of chromophores under external field using Langevin dynamics (LD) molecular modeling. The present work investigates the influence of chromophore dipole moment, density and field extent on NLO efficiency and polarization/relaxation dynamics. Results of simulations convince us, that the method is applicable for modeling real NLO polymers. In the spotlight of this investigation we would like to describe a NLO polymer as a 'ferrofluid' where chromophores are active particles or electrets. [ABSTRACT FROM AUTHOR]

The article focuses on the application of π-conjugated organic polymers with electrochromic devices. It states that electrochromic polymer processing is a promising technology in the plastic electronics industry because of its scalibility, unique properties, and device manufacturing applicability. It says that the process still needs improvement in various aspects, including processability and adhesion coordination, process customization, and long-term environmental stability.

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Abstract: Up to date there are few studies reporting the use of selenophene derivatives as electrochromic polymers. This report highlights the synthesis of a selenophene containing multi-ring aromatic polymer which possesses reasonable optical contrasts at both visible and near-IR regions. Electrochemical synthesis of a conducting polymer from a multi-ring aromatic monomer, 2-(2,5-bis(hexyloxy)-4-(selenophen-2-yl)phenyl)selenophene (BSB(OC6H13)2), was achieved at a lower potential than its corresponding parent, selenophene. The strong absorption band for the undoped polymer was 474nm and the onset energy for the π–π* transition (Eg) was 1.9eV (645nm). A novel dual-polymer electrochromic device was constructed in sandwich configuration where poly(BSB(OC6H13)2) was used as the anodically coloring material. It is the first electrochromic device where a selenophene-containing polymer was used as an active layer. The device switches between a rose-colored state and a blue-colored state with a fast response time (less than 1s). [Copyright &y& Elsevier]

Abstract: In this paper, we introduce the optical electronegativity to predict basic properties of binary oxide glasses. Optical electronegativity of numerous binary oxide glasses has been evaluated on the basis of two different properties: the linear refractive index n and energy gap E g, which have demonstrated remarkable correlation. Furthermore, we also calculate the refractive index n through the energy-gap-based optical electronegativity , and obtain a perfect linear correlation between the calculated refractive index n cal and the n 0 values of Dimitrov and Komatsu. The average electronic oxide polarizability and the optical basicity Λ of binary oxide glasses have been estimated on the basis of the optical electronegativity calculated from the refractive index n. The estimated values are in good agreement with the available experimental data. The present method needs only one original experimental parameter to estimate the optical electronegativity , which is the refractive index n. [Copyright &y& Elsevier]

Polyanthranilic acid (PANA), a self-doped processible conducting polymer, was synthesized and used for the first time for fabrication of contacts with configurations of (Al, Ti, Sn metal)/PANA/indium tin oxide-coated glass. The current-voltage (I-V) characteristics were measured by using microprobe arrangements, and the diode performance parameters were extracted. The I-V characteristics of the aforementioned configuration exhibited a rectifying contact for the case of Al and Ti metal contacts but an ohmic contact for the case of Sn metal contact. The electroactivity of PANA was carried out in acidic solution, and film morphology was studied by using atomic force microscope. UV-Vis spectroscopic technique was used to obtain the optical bandgap of the polymer. [ABSTRACT FROM AUTHOR]

A 2D ‘Rough Particle’ model consisting of interlocking hexagons is reported. Analytical expressions for the in-plane Poisson’s ratios and Young’s moduli due to particle translation along the geometrically matched male and female interlocks are derived for the model. The dependency of the mechanical properties on each of the model (geometrical and stiffness) parameters is provided, and it is shown that the assembly of interlocking hexagons deforming by particle translation along the interlocks displays auxetic (negative Poisson’s ratio) behaviour. The model predictions are compared with experimental mechanical properties for auxetic polypropylene (PP) films and fibres. The model predicts the experimental Poisson’s ratio values very well (model: νxy = −1.30, νyx = −0.77; experiment (PP films): ν|| = −1.12, $$\nu_{\bot} = -0.77$$ ). The model generally overestimates the Young’s moduli of the films, but is in reasonable agreement with the axial Young’s modulus of the fibres. [ABSTRACT FROM AUTHOR]

The development of flexible and compliant conductive polymer composites with textile‐like characteristics remains an important endeavor in light of the recent activity in polymer/textile‐based electronics and the need for compliant electrodes for electroactive polymer actuators. In this work, carbon black (CB) was dispersed in a polymer solution to form electrospun fiber webs consisting mainly of nanofibers. The effect of the filler content on the fiber‐web morphology, mechanical behavior, electrical conductivity, and thermal resistance was examined. The electrical conductivity percolation threshold of the fiber‐web structure was found to be around 4.6 vol %. Scanning electron micrographs of the fiber webs revealed a significant influence of the CB content on the fiber formation as well as the bond structure of the fiber web, which influenced the mechanical properties of the web. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 2410–2417, 2007 [ABSTRACT FROM AUTHOR]

The authors present organic semiconductor distributed feedback lasers based on thin films of the conjugated polymer poly[9,9-dioctylfluorene-co-9,9-di(4-methoxy-phenyl)fluorene] and employing an improved resonator design. In order to combine the advantages of first- and second-order distributed feedback resonators, the authors utilize a mixed-order grating design: A second-order Bragg scattering region that provides efficient vertical outcoupling of the laser radiation is surrounded by first-order scattering regions that give rise to strong feedback. By optimizing the film thickness to obtain laser oscillation at the polymer maximum gain wavelength, a very low laser threshold of 45 pJ/pulse (≈36 nJ/cm2) was realized with this resonator concept. [ABSTRACT FROM AUTHOR]