Effect of side‐chain functionality on the organic field‐effect transistor performance of oligo(p‐phenylenevinylene) derivatives

In order to observe the effects of the substitution of electronegative flourine with aromatic groups in oligo(p ‐phenylenevinylene) compounds on their packing, morphology, and charge carrier mobility, we have synthesized napthol‐substituted oligo(p ‐phenylenevinylene) compounds and examined their solubility, redox properties, thin film morphologies, and charge carrier properties. To date, very few examples of conjugated oligomers bearing napthol side groups have been reported in the literature. After annealing at 150 °C, the mobility of S1, S2, and S3 was 4.0 × 10^?2 cm² V^?1 s^?1, 1.2 × 10^?2 cm² V^?1 s^?1, and 2.6 × 10^?3 cm² V^?1 s^?1, respectively. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44825.     

Distribution of relaxation time in solution-processed polycrystalline CZTS thin films: Study of impedance spectroscopy

Here we report the complex impedance spectroscopic analysis of polycrystalline CZTS thin films synthesized by sol-gel spin coating technique without any post deposition sulphurization. The films are characterized by microstructural, compositional, optical and electrical studies to confirm the formation of kesterite phase of CZTS comprises of well distributed compact grains with the optical band gap 1.44?eV. Room temperature electrical characterizations of the CZTS thin films by four-probe and Hall effect technique revealed the p-type conductivity of the films with resistivity ~ 1.45?×?10^?2 Ω?cm, mobility ~ 3.7?×?10³ cm² V^?1 s^?1 and carrier concentration ~ 1.82?×?10¹⁷ cm^?3. The distribution of relaxation time (DRT) function with improved frequency resolution is reconstructed from the impedance spectra of CZTS film recorded in the frequency range 50?Hz to 5?MHz at room temperature to identify the number of electrical processes in the polycrystalline film. The Nyquist plot is fitted into electrical model consist of three parallel combinations of resistor (R) and capacitor (C) in series as three major peaks in DRT function indicates the presence of different relaxation processes with major contributions from core grains along with smaller contributions from grain boundary and interfaces. The room temperature frequency dependence of dielectric constant, loss tangent and ac conductivity is also studied for the CZTS films.     

Investigations of the electrical conduction mechanisms of polyaniline‐DBSA/poly(acrylonitrile‐butadiene styrene) blends

The electrical properties of Al/PANI‐DBSA/ABS/Au blend with PANI (5%) w/w have been investigated by using of current‐voltage (I‐V) measurements, in a temperature range of 100–313 K. The analysis of I‐V characteristics in the forward direction was based on thermionic emission mechanism for applied electrical field till ～3 × 10² V/cm. The thickness dependence of the current‐voltage relationship, clearly demonstrates that the electrical current for larger fields is space charge limited current (SCLC). Temperature dependences of the ideality factor, barrier height, and series resistance have been calculated. The mobility of carriers which is temperature dependent was calculated using the trap free SCLC as 1.53 × 10^?4 cm² V^?1 s^?1 at room temperature. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40688.     

Transient currents in charging and discharging modes in ethyl cellulose

Transient current in vacuum aluminized ethyl cellulose foil samples of thickness 75 μm were investigated in charging and discharging modes at different temperatures and fields. The occurrence of a peak in the current–time characteristics of charging current (I_c), and the dependence of such currents on field, characterized by a negative resistance region and followed by a superlinear region, are considered to indicate injection controlled transient currents modified by space-charge arising from the localization of carriers in various traps. Carrier mobility values calculated from a knowledge of the peak in the charging current versus time characteristics were found to range from 10^?11 to 10^?9 cm²/V s. As times larger than the peak time, the charging current follows the relation I ∝ t^?n at low temperatures with different poling fields (V_p). However, the current increases with time and finally tends to saturate for samples poled at higher temperatures with higher values of field. The isochronal characteristics (i.e. current–temperature plots at fixed times) constructed from discharge current versus time plots are characterized by a peak at 70°C or 100°C, depending upon the poling field values.     

Electrical conduction mechanism in plasma polymerized 2‐(diethylamino)ethyl methacrylate thin films

Thin films of different thicknesses were prepared through glow discharge of 2‐(diethylamino)ethyl methacrylate (DEAEMA) using a capacitively coupled reactor. Current density–voltage (J–V) characteristics for plasma polymerized (PP) DEAEMA thin films of thicknesses 100, 200, 250, and 300 nm in aluminum/PPDEAEMA/aluminum sandwich configuration were studied over the temperature range from 298 to 423 K. J–V curves reveal that in the low‐voltage region, the conduction current obeys Ohm's law while in the high‐voltage region the behavior attributed to be space charge‐limited conduction in PPDEAEMA thin films. The carrier mobility was calculated to be about 6.80 × 10^?19 to 2.38 × 10^?18 m^?2 V^?1s^?1 for various thicknesses. The free carrier density was found to be about 1.78 × 10²³ to 2.04 × 10²³ m^?3, and the trap density was found to be about 6.93 × 10²³ to 15.9 × 10²³ m^?3 for different thicknesses. The activation energies were estimated to be about 0.005–0.016 eV for 2 and 30 V of PPDEAEMA thin films of different thicknesses. The low‐activation energies indicate that the thermally activated hopping conduction is operative in PPDEAEMA thin films. POLYM. ENG. SCI., 55:2729–2734, 2015. © 2015 Society of Plastics Engineers     

Photocarrier mobility in poly(2‐methoxyaniline)

In the current study the mobility of photogenerated charge carriers in PMA [poly(2‐methoxyaniline)] and their transport were investigated using time‐of‐flight (TOF) techniques. Also studied was the effect on hole mobility of film thickness and of the method of polymer processing during device fabrication. The highest value of hole mobility found was 4.5 × 10⁻⁴ cm² V⁻¹ s⁻¹ at an applied field of 1.3 × 10⁶ V/cm and 293 K in solution‐cast film of PMA. The hole mobility of solution‐cast films was about 2 orders of magnitude higher compared to spin‐coated films, for which the ordering of the polymer chains may be the reason. To our knowledge, this is the first time the TOF mobility of this material has been presented. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1506–1512, 2001     

A leaf-like structured ITO conductive transparent thin film from visible to near-infrared region with enhanced stability

ITO thin films as the optical and electrical windows to transform photons and charges have been applied in many areas. Here, a leaf-like structured particle is composed of small particles growing along three different orientations leading to low thermal stress accompanied by well transmittance (85%) in a wide wavelength range from visible to near-infrared region and a narrowed band gap 3.07 eV. The evolution of structure and electronic performance was studied to obtain the low resistivity (12 μΩ m) and enhanced stability of the film (1000 °C). The leaf-like structure can be maintained under 600 ℃ and the electrical properties can be modified in He and N₂ atmosphere, owing to the reduced defects, increased concentration of Sn and carrier mobility. Although the structure has changed after being annealed at 1000 °C in N₂, the thin film performs excellent electrical properties (?3.44 × 10²⁰ cm^?3 and 28 cm² V^?1 s^?1).     

Structural,optical, and electrical characterization of the poly[9,9‐dioctylfluorenyl‐2,7‐diyl]‐co‐1,4‐benzo‐(2,1,3)‐thiadiazole thin film fabricated by electrostatic spray technique

The article presents the efficient fabrication of the Poly[9,9‐dioctylfluorenyl‐2,7‐diyl]‐co‐1,4‐benzo‐(2,1,3)‐thiadiazole (F8BT) thin film using the electrostatic spray technique. Electrostatic atomization of the in‐house developed F8BT polymer ink was achieved at considerable low voltage. The structural and optical characterizations of the fabricated F8BT thin film were thoroughly investigated. Furthermore, the organic diode structure with electrostatic spray deposited F8BT thin film was fabricated and its performance was analyzed by performing current voltage measurement. The current–voltage characteristic curve of the organic diode showed nonlinear diode like behavior, thereby confirming the proper interference established between organic diode adjacent layers. The space charged limited current mechanism has been found to be dominant in the fabricated organic device with carrier mobility value of 5.65 e^?4 cm²V^?1s^?1. POLYM. ENG. SCI., 54:675–681, 2014. © 2013 Society of Plastics Engineers     

Quasi-Solid Polymer Electrolyte Composed of poly(1-vinylpyrrolidone-co-vinyl acetate) Copolymer and the Influence of Its Composition on Electrochemical Properties and the Performances of Dye-Sensitized Solar Cells

Poly(1-vinylpyrrolidone-co-vinyl acetate)-based quasi-solid polymer electrolytes doped with potassium iodide are prepared. The highest room temperature ionic conductivity of 1.72 mS?cm^?1 is obtained. The dielectric studies are performed to understand the ion conduction mechanism. Fourier transform infrared study has been performed to understand complexation of the poly(1-vinylpyrrolidone-co-vinyl acetate)-based quasi-solid polymer electrolytes. The best power energy conversion efficiency (η) obtained is 2.94% with short circuit current density (J_sc) of 8.05?mA?cm^?2, open circuit voltage (V_oc) of 0.58?V, and fill factor of 63% under standard light intensity of 100?mW?cm^?2 irradiation.     

Well‐functioned photovoltaics based on nanofibers composed of PBDT‐TIPS‐DTNT‐DT and graphenic precursors thermally modified by polythiophene,polyaniline and polypyrrole

Reduced graphene oxide nanosheets modified by conductive polymers including polythiophene (GPTh), polyaniline (GPANI) and polypyrrole (GPPy) were prepared using the graphene oxide as both substrate and chemical oxidant. UV–visible and Raman analyses confirmed that the graphene oxide simultaneously produced the reduced graphene oxide and polymerized the conjugated polymers. The prepared nanostructures were subsequently electrospun in mixing with poly(3‐hexylthiophene) (P3HT)/phenyl‐C71‐butyric acid methyl ester (PC₇₁BM) and poly[bis(triisopropylsilylethynyl)benzodithiophene‐bis(decyltetradecylthien)naphthobisthiadiazole] (PBDT‐TIPS‐DTNT‐DT)/PC₇₁BM components and embedded in the active layers of photovoltaic devices to improve the charge mobility and efficiency. The GPTh/PBDT‐TIPS‐DTNT‐DT/PC₇₁BM devices demonstrated better photovoltaic features (J_sc = 11.72 mA cm^?2, FF = 61%, V_oc = 0.68 V, PCE = 4.86%, μ_h = 8.7 × 10^?3 cm² V^–1 s^?1 and μ_e = 1.3 × 10^?2 cm² V^–1 s^?1) than the GPPy/PBDT‐TIPS‐DTNT‐DT/PC₇₁BM (J_sc = 10.30 mA cm^?2, FF = 60%, V_oc = 0.66 V, PCE = 4.08%, μ_h = 1.4 × 10^?3 cm² V^–1 s^?1 and μ_e = 8.9 × 10^?3 cm² V^–1 s^?1) and GPANI/PBDT‐TIPS‐DTNT‐DT/PC₇₁BM (J_sc = 10.48 mA cm^?2, FF = 59%, V_oc = 0.65 V, PCE = 4.02%, μ_h = 8.6 × 10^?4 cm² V^–1 s^?1 and μ_e = 7.8 × 10^?3 cm² V^–1 s^?1) systems, assigned to the greater compatibility of PTh in the nano‐hybrids and the thiophenic conjugated polymers in the bulk of the nanofibers and active thin films. Furthermore, the PBDT‐TIPS‐DTNT‐DT polymer chains (3.35%–5.04%) acted better than the P3HT chains (2.01%–3.76%) because of more complicated conductive structures. © 2019 Society of Chemical Industry     

IN SITU visualization of water adsorption in cellulose nanofiber film with micrometer spatial resolution using micro-FTIR imaging

Hygroscopic behavior is an inherent characteristic of nanocellulose film which strongly affects its applications. In order to gain a better understanding of water adsorption, micro-Fourier transform infrared (FTIR) imaging was used to investigate the water adsorption in cellulose nanofiber film with a spatial resolution of 20 um. Four spectral peaks at 2905?cm^?1, 1428?cm^?1, 1371?cm^?1, and 1317?cm^?1 attributed to CH and CH₂ groups were used to generate 2D micro-FTIR images of cellulose distribution, and the most intense peak at 3348?cm^?1 was employed to generate 2D micro-FTIR image of OH group distribution. On this basis, difference 2D micro-FTIR images of OH group distribution at different relative humidity (RH) levels demonstrated the development of adsorbed water distribution in cellulose nanofiber film during the water adsorption process. The study results confirmed that the micro-FTIR imaging was one promising tool for in situ visualization of water adsorption with micron-scale resolution.     

Electroreduction of hexavalent chromium by polyaniline

BACKGROUND: A plate‐gap model interpretation of enzymatic reaction kinetics and rotating disc voltammetry were applied for evaluation of the nature of the reaction of the electroreduction of Cr(VI) (as dichromate ions) on a polyaniline (PANI)‐modified glassy carbon (GC) electrode. RESULTS: The kinetic parameters (the maximal current (V_max) and Michaelis constant (K_M)) for electroreduction of Cr(VI) on the PANI‐modified GC electrode were determined as V_max = 0.34 × 10^?7 mol cm^?3 s^?1 and K_M = 0.47 × 10^?6 mol cm^?3. The reduction of dichromate is intensified by PANI film growth. CONCLUSION: To characterise the electroreduction of Cr(VI) on a PANI‐modified GC electrode, the kinetic parameters of the reaction were determined using a plate–gap model interpretation of enzymatic reaction kinetics and rotating disc voltammetry. The catalytic nature of Cr(VI) electroreduction on the PANI‐modified electrode has been shown. Copyright © 2009 Society of Chemical Industry     

Light-scattering and size-exclusion chromatographic characterization of hydroxyethyl cellulose acetate

A recently developed analytical method of combining off-line laser light scattering (LLS) and size exclusion chromatography (SEC) was used to investigate a set of moderately distributed hydroxyethyl cellulose acetate (HECA) samples in tetrahydrofuran (THF) at room temperature. Our results have shown that this new LLS + SEC method is suitable for the characterization of molecular weight distribution of HECA. By using this method, we have simultaneously determined two calibrations of V (cm³) = 45.3 ? 1.89 log (M) and D (cm²/s) = 2.45 × 10^?4 M^?0.60, where M is the molecular weight of HECA; V, the elution volume in SEC; and D, the translational diffusion coefficient in dynamic LLS. In addition, our results have also indicated that the chain conformation of HECA in THF at room temperature is a slightly extended linear coil. © 1995 John Wiley & Sons, Inc.     

High carrier mobility low-voltage ZnO thin film transistors fabricated at a low temperature via solution processing

Wide-bandgap ZnO TFTs have many potential applications in large-area, flexible electronics and transparent devices because of their low cost, high performance and excellent optical transmittance. High-performance ZnO TFTs fabricated via simple solution processing have been widely studied. However, the key issues of solution-processable ZnO TFTs are the relatively high processing temperature (> 300?°C) and the high operating voltage for achieving the desired electrical properties. Here, we successfully fabricated low-voltage ZnO TFTs at an annealing temperature of ≤?250?°C. The resulting ZnO transistors with high-k terpolymer P(VDF-TrFE-CFE) showed a mobility of up to 5.3?cm² V^?1 s^?1 and an on/off ratio of >?10⁵ at 3?V. Furthermore, the influence of the dielectric constant on the carrier mobility was investigated. A lower k-value dielectric resulted in a high carrier mobility under the same carrier density. Therefore, with a low-k CYTOP dielectric applied to modify the interface between the ZnO semiconductor and the P(VDF-TrFE-CFE) layer, ZnO transistors annealed at 250?°C showed an electron mobility of 13.6?cm² V^?1 s^?1 and an on/off ratio of >?10⁵ at 3?V. To the best of our knowledge, this mobility is the highest value reported to date among the low-voltage solution-processable undoped ZnO TFTs annealed at temperatures of ≤?300?°C.     

Enhanced electrical properties of In-Ga-Sn-O thin films at low-temperature annealing

Electrical and optical properties of In-Ga-Sn-O (IGTO) thin films deposited by radio-frequency magnetron sputtering were investigated according to annealing temperatures. While IGTO films remained an amorphous phase even after a heat treatment at temperature up to 500 °C, Hall measurements showed that annealing temperature had a significant impact on electrical properties of IGTO thin films. After investigating a wide range of annealing temperatures for samples from as-deposited state to 500 °C, IGTO film annealed at 200 °C exhibited the best electrical performance with a conductivity of 229.31 Ω^?1cm^?1, a Hall mobility of 36.89 cm²V^?1s^?1, and a carrier concentration of 3.85 × 10¹⁹ cm^?3. Changes in proportions of oxygen-related defects and percentages of Sn²⁺ and Sn⁴⁺ ions within IGTO films according to annealing temperatures were analyzed with X-ray photoelectron spectroscopy to determine the cause of the superb performance of IGTO at a low temperature. In IGTO films annealed at 200 °C, Sn⁴⁺ ions acting as donor defects accounted for a high percentage, whereas hydroxyl groups working as electron traps showed a significantly reduced percentage compared to the as-deposited film. Optical band gaps of IGTO films obtained from UV–visible spectrum were 3.38–3.47 eV. The largest band gap value of 3.47 eV for the IGTO film annealed at 200 °C could be attributed to an increase in Fermi-level due to an increase of carrier concentration in the conduction band. These spectroscopic results well matched with electrical properties of IGTO films according to annealing temperatures. Excellent electrical properties of IGTO thin films annealed at 200 °C could be largely due to Sn donors besides oxygen vacancies, resulting in a significant increase in free carriers despite a low annealing. temperature.     

Rapid and facile low-temperature solution production of ZrO2 films as high-k dielectrics for flexible low-voltage thin-film transistors

A rapid lightwave (LW) irradiation method was presented for the low-temperature solution production of ZrO₂ films as high-k dielectrics for flexible high-performance thin-film transistors (TFTs). The LW irradiation process markedly decreased the required processing temperature and processing time. Microstructure characterizations confirmed the successful formation of ZrO₂ films with an ultrasmooth surface, large band gap (>5 eV) and low defect level. The ZrO₂ film produced via LW irradiation at ∼200 °C in only 8 min presented excellent dielectric properties, including a small leakage current of 3.3 × 10⁻⁸ A/cm² and a large capacitance of 296 nF/cm², significantly outperforming the films by the conventional high-temperature annealing process at 400 °C for 60 min. Furthermore, LW irradiation was extended to the channel layer. The rapid low-temperature solution-processed InZrO_x TFTs exhibited superior electrical characteristics, such as a high carrier mobility of 41.3 cm²V⁻¹s⁻¹ and a high on-off current ratio of 10⁵∼10⁶ at a low operation voltage of 3 V due to the employment of high-quality ZrO₂ dielectric films. Moreover, the flexible TFT on a polyimide (PI) plastic substrate achieved a high mobility of nearly 30 cm²V⁻¹s⁻¹, indicating that LW irradiation is highly promising for the rapid and low-temperature solution production of high-quality and flexible oxide electronic devices.     

Development of quasi‐solid‐state dye‐sensitized solar cell based on an electrospun polyvinylidene fluoride–polyacrylonitrile membrane electrolyte

Dye sensitized solar cell (DSSC) has been magnetizing more awareness in current research due to more efficiency. The foremost drawback of the solar cell is the evaporation of organic electrolyte. In order to address this problem, the polyvinylidene fluoride–polyacrylonitrile–Electrospinning Fibrous Membranes were prepared by electrospinning method and the photovoltaic performances were evaluated. The polyvinylidene fluoride and polyacrylonitrile were mixed in N,N′‐dimethylformamide and acetone at an applied potential of 15 kV. The surface morphology of membrane is interconnected with network structure and a large number of voids were observed from Field Emission Scanning Electron Microscopy images. The electrolyte uptakes up to 310% were observed and it shows an increase in the ionic conductivity up to 6.12 × 10^?2 S cm^?1 at 25°C. The fabricated DSSCs show open circuit voltage (V_oc) of 0.74 V, fill factor (FF) of 0.65 and short circuit current (J_sc) of 6.20 mA cm^?2 at an incident light intensity of 100 mW cm^?2. The photovoltaic efficiency also reached up to 3.09%. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014 , 131, 40022.     

A polythiophene derivative with dioctyloxyltriphenylamine‐vinylene conjugated side chain: Synthesis,hole mobility,and photovoltaic property

A new polythiophene derivative with dioctyloxyl triphenylamine‐vinylene ( DOTPAV ) conjugated side‐chain, DOTPAV‐PT , was synthesized by the Stille coupling method and characterized by ¹H‐NMR, ¹³C‐NMR, elemental analysis, gel permeation chromatography, thermogravimetric analysis, UV–vis absorption spectroscopy, photoluminescence spectroscopy, and cyclic voltammetry. The polymer DOTPAV‐PT is soluble in common organic solvents and possesses good thermal stability with 5% weight loss temperature of 310°C. The weight‐average molecular weight of DOTPAV‐PT is 8.0 K with a polydispersity index of 1.24. The hole mobility of the polymer determined from space‐charge‐limited current model was 1.25 × 10^?4 cm² V^?1 s^?1. The bulk heterojunction polymer solar cell with the configuration of ITO/PEDOT : PSS/polymer : PCBM (1 : 1)/Ca/Al was fabricated, and the power conversion efficiency of the device was 0.16% under the illumination of AM1.5, 100 mW cm^?2. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

p-type conductive NiOx: Cu thin films with high carrier mobility deposited by ion beam assisted deposition

Transparent conductive NiO thin films with 18 at% Cu dopant were fabricated by ion beam assisted deposition (IBAD). Their structural and optoelectronic properties were compared with undoped NiO films and NiO films doped with 12 at% Cu, and also compared with NiO:Cu (18 at%) films deposited by RF sputtering as reported in our previous work. The results show that the crystallinity of NiO thin films deposited through IBAD technology is much better than that of the films deposited by RF sputtering. Thanks to this reason, the highest carrier mobility above 45 cm²V^?1s^?1 for NiO:Cu (18 at%) film can be realized here. Meanwhile, the films’ resistivity remains an acceptable value, varying from 2.05 to 0.064 Ω cm with oxygen ion beam current changing from 0.2 to 0.8 A. This feature is imperative for p-type transparent conductive oxides (TCOs) applied in various domains. In addition, with oxygen ion beam current increase, the increase of the Ni³⁺/Ni²⁺ ratio leads to more Ni²⁺ vacancies be introduced into NiO films, which is beneficial to generate holes and improve carrier concentration. In this work, the optimal carrier mobility of NiO film doped with 18 at% Cu is obtained when the oxygen ion beam current is 0.2 A. Its carrier concentration and electrical resistivity are 7.26 $\times$10¹⁶ cm^?3 and 2.05 Ω cm, respectively.     

Performance modulation of contact electrification nanogenerators by controlling the doping concentration of fluorine-doped tin oxide

Contact electrification nanogenerators (CENGs) were fabricated, and their output performance was modulated by controlling the doping concentration of fluorine-doped SnO₂ (FTO) thin films. As the fluorine source content was increased from 0.8 to 1.2?mM during spray pyrolysis deposition, the electron concentration in the FTO thin film increased from 1.84?×?10²⁰ to 5.22?×?10²⁰ cm^?3, which is much larger than the Mott critical carrier concentration of SnO₂. The output voltage and current from the CENGs which were fabricated by the aluminium and FTO surfaces increased from 2.76 to 5.66?V and from 0.003 to 0.005 μA/cm² when controlling the electron concentration in the FTO layer from 5.22 to 1.84?×?10²⁰?cm^?3. The modulation of the output performance of the CENGs originated from the change in work function of the FTO layer by Burstein-Moss shift.