Current versus gate voltage hysteresis in organic field effect transistors

Abstract  

Research into organic field effect transistors (OFETs) has made significant advances—both scientifically and technologically—during the last decade, and the first products will soon enter the market. Printed electronic circuits using organic resistors, diodes and transistors may become cheap alternatives to silicon-based systems, especially in large-area applications. A key parameter for device operation, besides long term stability, is the reproducibility of the current–voltage behavior, which may be affected by hysteresis phenomena. Hysteresis effects are often observed in organic transistors during sweeps of the gate voltage (V _GS). This hysteresis can originate in various ways, but comparative scientific investigations are rare and a comprehensive picture of “hysteresis phenomena” in OFETs is still missing. This review provides an overview of the physical effects that cause hysteresis and discusses the importance of such effects in OFETs in a comparative manner.     

Laser ultrasonic receivers based on organic photorefractive polymer composites

We present two laser ultrasonic receivers based on organic photorefractive polymer composites with 2-[4-bis(2-methoxyethyl)aminobenzylidene]malononitrile (AODCST) or 2-dicyanomethylen-3-cyano-5,5-dimethyl-4-(4′-dihexylaminophenyl)-2,5-dihydrofuran nonlinear optical chromophores. Experimental results show sensitivities of the ultrasonic receivers of ~9.5 × 10^?8 nm (W/Hz)^0.5 for both composites, and a faster response time (~60 ms) for the AODCST-based laser ultrasonic receiver. We show that such LUS detectors are highly suitable for contactless thickness measurements of aluminum, steel sheets and defect detection with an accuracy of 100 μm.     

A collocation approach for solving linear complex differential equations in rectangular domains

In this paper, a collocation method is presented to find the approximate solution of high‐order linear complex differential equations in rectangular domain. By using collocation points defined in a rectangular domain and the Bessel polynomials, this method transforms the linear complex differential equations into a matrix equation. The matrix equation corresponds to a system of linear equations with the unknown Bessel coefficients. The proposed method gives the analytic solution when the exact solutions are polynomials. Numerical examples are included to demonstrate the validity and applicability of the technique and the comparisons are made with existing results. The results show the efficiency and accuracy of the present work. All of the numerical computations have been performed on a computer using a program written in MATLAB v7.6.0 (R2008a). Copyright © 2012 John Wiley & Sons, Ltd.     

Side Chain Influence on Electrochemical and Photovoltaic Properties of Yne‐Containing Poly(phenylene vinylene)s

Summary: The electrochemical behaviour of four types of (phenylene ethynylene)‐alt‐(phenylene vinylene) hybrid polymers, 1 , 2 , 3 , and 4 have been investigated with respect to the influence of the grafted alkoxy side chains. In the case of the fully substituted polymers 2 , 3 , and 4 , the strong insulating nature of longer linear octadecyl or bulky branched 2‐ethylhexyl side chains lowers the HOMO levels of the polymers thereby increasing the discrepancy, ΔE_g, between the electrochemical, Eequation/tex2gif-stack-1.gif, and the optical, Eequation/tex2gif-stack-2.gif, bandgap energies. Thus it is not possible to establish a direct correlation between the open circuit voltage, V_OC, of bulk heterojunction solar cell devices of the configuration glass substrate/ITO/PEDOT:PSS/polymer 3 :PCBM(1:3, w/w)/LiF/Al and the HOMO energy levels of polymer 3 solely, as postulated in the literature. The photovoltaic (PV) parameters greatly depend on the grafted side chains.

Linear I–V curves of solar cell devices from polymers 3a – d , measured in the dark and under 100 mW · cm⁻² solar simulator illumination.     

对位取代酚亚甲基桥三聚物的合成

本文报道通过2, 6-二羟甲基对取代酚和合适的对取代酚的缩合制备一系列对取代酚亚甲基桥三聚物的方法。产率一般为50%左右。     

Metalization of polymer beads via polymer‐supported hydrazines as reducing agents

A new method for depositing metal onto a polymer surface has been developed in which the metal coating of polymer beads is performed with hydrazine functions as reducing agents on the surface of the polymer itself. In this study, glycidyl methacrylate–methyl methacrylate–divinyl benzene terpolymer was prepared as spherical beads with a suspension polymerization methodology. Beads of the polymer sample (210–420‐μm fraction) containing 3.4 mmol g^?1 epoxy were treated with an excess of hydrazinium hydroxide to yield a polymer with 2.3 mmol g^?1 hydrazine functions. The hydrazine functions on the polymer surfaces were efficient in metal reductions. Therefore, the modified bead polymer samples, when soaked in aqueous ammonia solutions of Ni(II), Ag(I), and Cu(II) ions (0.1 M), were covered rapidly by the corresponding zero‐valent metal ions. Metal deposition took place almost quantitatively (ca. 4.5 mmol/g of the polymer) within 60 min of the contact times. The accumulations of metal were followed visually and occurred only on the polymer beads. There was no evidence that the reaction occurred within the solution. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 748–754, 2002; DOI 10.1002/pola.10158     

Quantum wave packet study of the insertion reaction S+H2

S(¹D)+H₂→SH+H reaction at zero total angular momentum has been studied by using a time-dependent quantum real wave packet method. State-to-state and state-to-all reactive scattering probabilities for a broad range of energy are calculated. The probabilities show many sharp peaks that ascribed to reactive scattering resonances. The density plots of the wave function shows that the reaction presents a pure insertion pathway.     

Direct Electrochemical Capture and Release of Carbon Dioxide Using an Industrial Organic Pigment: Quinacridone

Limiting anthropogenic carbon dioxide emissions constitutes a major issue faced by scientists today. Herein we report an efficient way of controlled capture and release of carbon dioxide using nature inspired, cheap, abundant and non‐toxic, industrial pigment namely, quinacridone. An electrochemically reduced electrode consisting of a quinacridone thin film (ca. 100 nm thick)on an ITO support forms a quinacridone carbonate salt. The captured CO₂ can be released by electrochemical oxidation. The amount of captured CO₂ was quantified by FT‐IR. The uptake value for electrochemical release process was 4.61 mmol g^?1. This value is among the highest reported uptake efficiencies for electrochemical CO₂ capture. For comparison, the state‐of‐the‐art aqueous amine industrial capture process has an uptake efficiency of ca. 8 mmol g^?1.     

Polystyrene microspheres having epoxy functional dangling chains linked by hydrolytically stable bonds via ATRP

We report application of copper‐mediated atom transfer radical polymerization in graft copolymerization of glycidyl methacrylate (GMA) from N‐bromosulfonamide groups on polystyrene‐divinyl benzene (PS‐DVB) microspheres (210–420 μm). The surface initiator groups were introduced by simple modification of crosslinked PS‐DVB (10% mol/mol) beads in three steps: (i) chlorosulfonation, (ii) sulfamidation with propylamine, and (iii) bromination. Initiation from surface‐bound N‐bromosulfonamide groups showed first‐order kinetics (k = 1.04 × 10^?4 s^?1 in toluene at 70 °C) and gave poly(GMA) graft chains linked to the surface by hydrolytically stable sulfonamide bonds. High graft yields were attained (up to 294.4% within 21 h) while retaining the epoxy groups. Epoxy content of the resulting product (5.41 mmol g^?1) revealed an average 17 GMA repeating units in the graft per initiation site. Taking advantage of the hydrolytic stability of sulfonamide linkages and well‐known reactivity of the epoxy groups on dangling chains, “the hair‐like structure” of the polymer beads prepared can be considered when devising more efficient functional polymers as catalysts or reagent carriers. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6708–6716, 2006