Synthetic Metals (v.162, #5-6)
An efficient hole-transporting blue fluorophore 3,6-dipyrenyl-9-ethylcarbazole for undoped organic light-emitting devices
by Qing-Xiao Tong; Shiu-Lun Lai; Ming-Fai Lo; Mei-Yee Chan; Tsz-Wai Ng; Shuit-Tong Lee; Si-Lu Tao; Chun-Sing Lee (pp. 415-418).
► A new carbazole-based blue fluorescent emitter DPEC was reported. ► High ηC of 4.75cdA−1 and good color purity with CIE (0.15, 0.18) were demonstrated. ► DPEC showed similar hole-transporting properties as NPB. ► Carbazole derivatives are commonly used as hosts for phosphorescent dopants. ► We show carbazole compounds have good potential as high performance blue emitters.A new blue-emitting carbazole derivative, 3,6-dipyrenyl-9-ethylcarbazole (DPEC), has been designed and synthesized for applications in organic light-emitting devices (OLEDs). Undoped DPEC-based OLEDs give a saturated blue electroluminescence with Commission Internationale de L’Eclairage 1931 coordinates of (0.15, 0.18), and possess high luminous efficiency of 4.75cdA−1. On the other hand, DPEC can also function as a hole-transporting layer (HTL). In particular, by replacing N,N′-diphenyl-1,1′-biphenyl-4,4′-diamine (NPB) as HTL, a simplified bilayer device demonstrated good performance, comparable to that of the trilayer device. This good device performance illustrates that DPEC is a promising candidate as a blue hole-transporting emitter.
Keywords: Carbazole; OLED; Blue; Fluorescence; Undoped
Organic field-effect transistors based on semiconducting porphyrin single crystals
by Mai Ha Hoang; Dong Hoon Choi; Suk Joong Lee (pp. 419-425).
Display Omitted► New class of π-extended porphyrin derivatives has been successfully synthesized. ► Single crystalline wires were able to obtain from slow diffusion technique. ► The OFET devices based on porphyrins show excellent mobilities. ► Single-crystal devices show much higher mobilities over thin-film devices.Porphyrin offers a variety of optical, electrochemical, and catalytic properties from the central metal and structural modifications. However, porphyrins have been relatively less investigated for their semiconducting properties. In this work, we report on the design and synthesis of new solution processable semiconducting porphyrins2TBPH and2TBPZ. They contain two 5-hexylthiophen-2-yl ethynyl phenyl arms and produce smooth films and high quality single-crystals. The single-crystal field effect transistors from2TBTZ show a maximum field effect mobility of ∼0.36cm2V−1s−1 with a high current on/off ratio of 2×103. Remarkably, the mobilities of single-crystal devices are two orders higher than those of thin-film based transistor devices.
Keywords: Field-effect transistors; Porphyrins; Single crystals; Thin films; Semiconductors
Effects of various solvent addition on crystal and electrical properties of organic solar cells with P3HT:PCBM active layer
by Seong Kyu Jang; Su Cheol Gong; Ho Jung Chang (pp. 426-430).
► We prepared flexible organic solar cell with P3HT:PCBM active layer. ► Optical and electrical properties were affected by various dissolution solvents used. ► Best property was obtained in active layer by using blended mono- and dichlorobenzene. ► Improved property caused by enhanced crystallinity, light absorption and rough surface. ► This may be due to high vapor density and low solubility of the mixing solvents.We investigated the effect of the preparation conditions used for the active layer on the performance of polymer/fullerence bulk-hetero junction solar cells by changing the solvent (toluene, monochlorobenzene, dichlorobenzene) combinations. The organic solar cells (OSCs) with an ITO/PEDOT:PSS/P3HT:PCBM/Al structure were fabricated by using regioregular poly(3-hexylthiophene) (P3HT):(6,6)-phenyl C61-butyric acid methyl ester fullerene (PCBM) for the active layer. The P3HT and PCBM used for the electron donor and acceptor materials were spin-casted on the indium tin oxide (ITO) coated polyethylene naphthalate (PEN) flexible substrates. The optimum mixing concentration ratio for the active layer was found to be P3HT:PCBM=50:50 in wt%. In order to investigate the effects of the precursor solvents under the same P3HT:PCBM concentration in the mixing ratio, the performance of the OSCs was studied by introducing various pure and blended co-solvents. The best property was obtained in the active layer by using monochlorobenzene (MCB) for the P3HT and dichlorobenzene (DCB) for the PCBM. The results show that the maximum short circuit current density ( Jsc), the open circuit voltage ( Voc), the fill factor (FF) and the power conversion efficiency (PCE) were about 10.4mA/cm2, 606mV, 45.5%, and 2.9%, respectively.
Keywords: Organic solar cells; Flexible substrate; Solvent; Bulk hetero-junction; P3HT; PCBM; Power conversion efficiency
Novel near-infrared luminescent linear copolymer based on tris(8-hydroxyquinoline)erbium
by Jianxin Luo; Chunyan Zhang; Chaolong Yang; Mangeng Lu (pp. 431-435).
Display Omitted► A novel NIR-luminescent linear copolymer based on ErQ3. ► The copolymer has good solubility and thermal stability. ► The copolymer emits NIR-light through energy transfer. ► Efficient energy transfer from antenna group to ErIII ion.A novel near-infrared (NIR) luminescent linear copolymer based on tris(8-hydroxyquinoline)erbium (ErQ3), PCzErQ3, was synthesized and characterized. The copolymer had appropriate molecular weight as well as good solubility in common organic solvents. The glass transition temperature ( Tg) and the temperature of 5% weight loss ( Td) for the copolymer were 200°C and 368°C respectively, indicating that the copolymer had excellent thermal stability. Absorption and photoluminescence (PL) spectra of the copolymer were recorded and PL decay analysis was measured. Excited at the absorption band of carbazole (235, 265 and 295nm) and metalloquinolate (390nm), the copolymer emitted the characteristic NIR-luminescence of ErIII ion. The result indicates that the energy absorbed by carbazole (light-harvesting group) was transferred to 8-hydroxyquinoline (coordination group), where it is finally transferred to ErIII ion. In addition, the full width at half maximum (FWHM) centered at 1525nm in the PL emission spectrum of the copolymer was 92nm, which enabled a wide gain bandwidth for optical amplification.
Keywords: Near-infrared luminescence; Tris(8-hydroxyquinoline)erbium; Copolymer; Energy transfer
A comparative study of aminothiazole-based polymers synthesized by chemical oxidative polymerization
by Mehmet Yıldırım; İsmet Kaya (pp. 436-443).
Display Omitted► Organo-soluble aminothiazole homopolymers were synthesized by oxidative polmerization. ► 2-Aminobenzothiazole homopolymer was obtained with sponge-like microporous morphology. ► The polymers were bluish and red light emitters under UV radiation. ► Polyconjugated structures were confirmed by optical and electrochemical band gaps. ► Aminobenzothiazole polymers were thermally stable up to 150–200°C.Poly(2-aminothiazole) derivatives were synthesized by chemical oxidative polymerization method using 2-aminothiazole (2AT), 2-aminobenzothiazole (2ABT) and 6-ethoxy-2-aminobenzothiazole ( EtO-2ABT) as the monomers. Structural characterizations were carried out by Fourier Transform Infrared (FT-IR), nuclear magnetic resonance (NMR), size exclusion chromatography (SEC), and scanning electron microscopy (SEM) techniques. The synthesized polymers were investigated by the means of solubility tests, UV–vis, spectrofluorometry, cyclic voltammetry (CV), thermogravimetry–differential thermal analysis (TG–DTA), differential scanning calorimetry (DSC), and dynamical mechanical analysis (DMA) techniques. Solid state electrical conductivities were also measured on the polymer films. Phenyl attached aminothiazole polymers had higher solubilities than the unsubstituted poly(2-aminothiazole). The polymers had lower band gaps than the corresponding monomers indicating their polyconjugated structures. P-2AT and P-2ABT emitted bluish light under UV irradiation while P- EtO-2ABT emitted red color with lower intensity. Phenyl attachment and ethoxy substitution of the monomer caused production of polymer with higher thermal stability. Additionally, a discussion of electrical conductivities and morphological variations was reported.
Keywords: Thiazole polymers; Conjugated polymers; Fluorescence; Thermal analysis
Fluorescent probes for Pd2+ detection by poly(o-phenylenediamine) nanospheres with fluorescence enhancement
by Zhoufeng Wang; Fang Liao (pp. 444-447).
► We developed a novel fluorescent probe for Pd2+ detection with the use of PoPD. ► The general concept lies in nitrogen atoms are coordinatively bonded to palladium ions. ► It could meet the selectivity requirements for biomedical and environmental application.In this article, we developed a novel fluorescent probe for Pd2+ detection with the use of conjugated polymer poly(o-phenylenediamine) (PoPD) nanospheres as an effective sensing platform. The PoPD nanospheres were easily prepared via chemical polymerization of o-phenylenediamine (oPD) monomers by ammonium persulfate (APS) at room temperature. The general concept used in this approach lies in the fact that palladium react easily with a number of nitrogen-containing organic compounds, resulting in the formation of complexes in which nitrogen atoms are coordinatively bonded to palladium ions. The calibration graph was linear in the range of 0–240ppm for Pd2+, and the detection limit was as sensitive as 1ppm. The performances of the probe indicated that it could meet the selectivity requirements for biomedical and environmental application and also was sensitive enough to detect Pd2+ in environmental and biological samples.
Keywords: Poly(o-phenylenediamine); Nanospheres; Fluorescent probe; Palladium ions
Cyclic arylamines functioning as advanced hole-transporting and emitting materials
by Li Long; Minyan Zhang; Shihua Xu; Xuehua Zhou; Xicun Gao; Yuzhu Shang; Bin Wei (pp. 448-452).
► We synthesized two versatile cyclic arylamines for organic light-emitting diodes. ► Cyclic arylamine (C1)-based device exhibited good hole-transporting characteristics. ► We developed a non-doped deep-blue device at 448nm using cyclic arylamine (C2). ► A simple bluish-white OLED was fabricated with full width at half maximum of 135nm.We have developed two kinds of cyclic arylamines functioning as hole-transporting and light-emitting materials of organic light emitting diodes (OLEDs), respectively. The hole-transporting cyclic arylamine (C1)-based device exhibited an improved maximum luminance efficiency of 4.21cd/A, utilizing a single light-emitting layer of tris(8-hydroxyquinolinato) aluminum. While the maximum luminance efficiencies for N,N′-bis-(naphthyl)-N,N′-diphenyl-1,1′-biphenyl-4,4′-diamine (NPB) and 4,4′,4″-tris-N-naphthyl-N-phenylamino-triphenylamine/NPB-based devices were 2.28 and 3.02cd/A, respectively. In addition, a non-doped deep-blue (448nm) light-emitting device was obtained, employing cyclic arylamine (C2) as emission layer. And the exciplex formation occurred at C1/C2 interface or in the emission layer of C2 doped C1, which leaded to a wide EL emission. Furthermore, we have developed a very simple bluish-white OLED using C2 (5wt.%) doped C1, which showed particularly wide full width at half maximum of 135nm.
Keywords: Organic light emitting diodes; Cyclic arylamines; Hole-transporting; Deep-blue emission
Preparation of carbon fibers from a lignin copolymer with polyacrylonitrile
by Sanjeev P. Maradur; Chang Hyo Kim; So Yeun Kim; Bo-Hye Kim; Woo Chul Kim; Kap Seung Yang (pp. 453-459).
Display Omitted► Introduction of an economically viable and technologically sound process for the production of low-cost CFs. ► Synthesis of PAN–lignin copolymer by the radical copolymerization. ► Development of lignin-based CFs by the subsequent heat treatment of wet-spun fibers.In this study, we have developed an economically viable and technologically sound process for the production of low-cost carbon fibers (CFs) made of lignin copolymer with acrylonitrile (AN). Initially, lignin, a by-product of the pulp and paper industry, is copolymerized with AN in dimethysulfoxide (DMSO) by the radical copolymerization. The resulting copolymer was confirmed by a Fourier transform infrared (FT-IR),13C, and1H nuclear magnetic resonance (NMR) spectroscopy, showing the presence of the CN group of polyacrylonitrile (PAN) co-eluting with ether, hydroxyl, and aromatic groups that are attributed to lignin. This provided evidence that a PAN–lignin copolymer was synthesized. Using a wet-spinning process, the PAN–lignin copolymers are then spun into fibers with an average tensile strength of 2.41gf/den, a tensile strain of 11.04%, and a modulus of 22.92gf/den. The CFs are prepared by the subsequent thermal treatment of the spun fibers. Differential scanning calorimeter (DSC) analysis of the PAN–lignin copolymer-based spun fibers displays a downshifted exothermic peak at 285.83 compared with the homopolymer PAN-based as-spun fibers, which provides evidence that lignin is cooperated with the oxidative stabilization reactions. The stabilized fibers are carbonized by heating from room temperature to 800°C in a nitrogen atmosphere. This study shows the potential for a number of recycled and renewable polymers to be incorporated into wet-spun fibers for production of CF feedstocks, thereby reducing the supply cost using the current commercial technology.
Keywords: Lignin; Polyacrylonitrile–lignin copolymer; Wet-spinning; Carbon fiber
Persistent photoexcitation effect on the poly(3-hexylthiophene) film: Impedance measurement and modeling
by Chang Hyun Kim; Krzysztof Kisiel; Jaroslaw Jung; Jacek Ulanski; Denis Tondelier; Bernard Geffroy; Yvan Bonnassieux; Gilles Horowitz (pp. 460-465).
Display Omitted► We observe a persistent photoexcitation effect on the P3HT bulk film. ► Au/P3HT/Au device shows ohmic conduction under ambient atmosphere. ► A constant-phase element has to be incorporated for circuit modeling. ► Photoconductivity follows an exponential decay with an extended time constant. ► Slow detrapping of photogenerated carriers is the main origin of the phenomenon.We report on the equivalent circuit modeling of the relaxation behavior of an optically excited thick poly(3-hexylthiophene) (P3HT) film by means of impedance spectroscopy. Fabricated metal–semiconductor–metal devices with Au electrodes showed a nearly perfect ohmic behavior under ambient conditions. Impedance measurements on illuminated P3HT device showed a dramatical decrease of the impedance modulus under illumination and very slow relaxation to the initial state. Impedance-frequency data obtained during relaxation could not be explained by a simple parallel resistance–capacitance circuit but it could be best fitted by incorporating a constant-phase element instead of a normal capacitance. By observing the variation of the circuit parameters, it is found that the relaxation process is dominated by slow recombination (elimination) of the excess photogenerated carriers, which is confirmed by the time-varying photoconductivity of the device.
Keywords: PH3T; Photosensitivity; Impedance spectroscopy; Equivalent circuit modeling
Synthesis of silica–polypyrrole core–shell nanocomposite using in situ γ-aminopropyltriethoxysilane (APTES)-modified nanosilica
by Mohammad Jafarzadeh; Ismail Ab Rahman; Coswald Stephen Sipaut (pp. 466-476).
► Well-dispersed SiO2@PPy core–shell form using in situ modified silica. ► Oxidative polymerization of pyrrole without using steric and charge stabilizer. ► Conductivity: 2.26Scm−1, nanoscale vs. reported result: 2.6×10−2Scm−1, microscale. ► Particle size and conductivity depend on mode of preparation and type of substrates. ► Polymerization occurred on silica surface, avoiding individually PPy nanoparticles.A well dispersed core–shell, silica–polypyrrole nanocomposites, with particle size of ∼70nm were synthesized using a new approach. The polypyrrole conducting layer was deposited directly on the in situ-modified silica via an oxidative polymerization without the utilizing a steric stabilizer. The composites were characterized by TEM,13C and29Si NMR, thermogravimetric analysis (TGA), photoluminescence (PL) and UV–vis. The in situ γ-aminopropyltriethoxysilane (APTES)-modified silica has shown a higher deposited polypyrrole which led to effective polymerization and higher conductivity compared to the unmodified silica (2.26×Scm−1 vs. 3.94×10−5Scm−1). This might be due to the presence of an aminopropyl group on the silica surface that improved compatibility and effective interactions. The existence of a core–shell system has been proven by TEM, through energy spectroscopic imaging (ESI) and PL analysis. The particle sizes and conductivity of the nanocomposites were found to be dependent on the mode of preparation, deposition time and the type of oxidants (FeCl3·6H2O and (NH4)2S2O8).
Keywords: Modified silica; Polypyrrole; Core–shell; Nanocomposite
Dielectric, conduction and interface properties of Au/Pc/p-Si Schottky barrier diode
by Ahmet Altındal; Mustafa Coşkun; Özer Bekaroğlu (pp. 477-482).
► Novel clamshell type phthalocyanine thin film for MIS structure as insulator layer. ► Maxwell–Wagner type interfacial polarization. ► Quantum mechanical tunneling, multihopping and free band conduction are the dominant mechanism for ac conduction. ► The obtained density of interface states of the Au/Pc/p-Si/Al capacitor is comparable to some reported values. ► Our results predict that thin film of the investigated phthalocyanine compound is a good candidate for an alternative material to replace the SiO2 films as gate dielectric in MIS capacitors.The dielectric properties and the ability of binuclear zinc(II) phthalocyanine of clamshell type compound in passivating silicon (Si) surfaces is studied by fabricating metal–insulator–semiconductor (MIS) capacitors. The frequency and temperature dependence of the dielectric constant were discussed in the light of Koops model and hopping conduction mechanism. A detailed study of the effect of temperature on the ac conductivity of MIS structure at the temperatures between 300K and 460K was carried out. Based on the existing theories of ac conduction, it has been concluded that for low frequency region the dominant conduction mechanism in the sample is quantum mechanical tunneling at all temperatures, whereas for intermediate frequency region multihopping process is the dominant conduction mechanism. At higher frequencies, the behavior and the values of index s reveal a free band conduction mechanism. Interface properties of the fabricated MIS structure were investigated by means of conductance–voltage ( GM– VG) and the combination of low frequency and high frequency capacitance–voltage ( CM– VG) measurements at various fixed frequencies. The values of Dit obtained from conductance and high–low frequency capacitance measurements are 4.25×1011eV−1cm−2 and 4.90×1011eV−1cm−2, respectively. This indicates the consistency of both the methods. The observed peaks in the GM– VG characteristics indicated that the losses are predominantly due to interface states.
Keywords: Clamshel; Dielectric; MIS structure; Interface trap; Tunneling
Synthesis of a soluble fulleropyrrolidine derivative for use as an electron acceptor in bulk-heterojunction polymer solar cells
by Dongbo Mi; Hee-Un Kim; Ji-Hoon Kim; Fei Xu; Sung-Ho Jin; Do-Hoon Hwang (pp. 483-489).
► A new phenothiazine-containing fulleropyrrolidine derivative (C60-PTZP) was synthesized. ► The optical and electrochemical properties of C60-PTZP were characterized. ► Organic solar cells were fabricated using the C60-PTZP as the electron acceptor. ► The highest power conversion efficiency of the fabricated devices was 1.42%.A new phenothiazine-containing fulleropyrrolidine derivative, C60-fused N-methyl-[10-(2-ethylhexyl)-10H-phenothiazin-2yl]-pyrrolidine (C60-PTZP), was synthesized via the 1,3-dipolar cycloaddition reaction of an azomethine ylide intermediate, and used as an electron acceptor for organic photovoltaics (OPVs). The new fulleropyrrolidine derivative was characterized by1H NMR,13C NMR, FT-IR and FAB-MS. The C60-PTZP showed good solubility in common organic solvents such as chloroform and chlorobenzene. The optical and electrochemical properties of C60-PTZP were compared with those of the parent  fullerene. C60-PTZP showed improved solubility and a higher LUMO energy level than the parent  fullerene. Photovoltaic devices with the configuration of ITO/PEDOT:PSS/active layer/LiF/Al were fabricated. To optimize the device fabrication conditions, we varied the weight ratios of the electron donor to the acceptor in the active layer and also changed the post-annealing temperature. The highest power conversion efficiency (PCE) of the fabricated devices was observed to be 1.42% when the weight ratio of P3HT:C60-PTZP was 1:0.5 and annealing was carried out at 100°C for 30min.
Keywords: Fulleropyrrolidine derivative; Phenothiazine; Organic solar cell; Electron acceptor
A thermally and electrochemically stable organic hole-transporting material with an adamantane central core and triarylamine moieties
by Kai Zhang; Ling Wang; Yanliang Liang; Siqi Yang; Jing Liang; Fangyi Cheng; Jun Chen (pp. 490-496).
► A new hole transporting material with adamantane core and triarylamine moieties. ► Both experimental and computational characterization. ► Remarkable optical properties and high thermal and electrochemical stability.Hole transporting materials (HTMs) play an important role in constructing optoelectronic devices. Herein, we report the design and synthesis of a novel HTM 4,4′,4″,4‴-(adamantane-1,3,5,7-tetrayl)tetrakis(N,N-bis(4-methoxyphenyl)aniline) (ad-OMeTPA) containing a central unit of adamantine and peripheral groups of triarylamine moieties. Its molecular structure was identified by1H NMR, FT-IR, and Raman spectroscopy. The glass-transition temperature ( Tg) of ad-OMeTPA was measured by differential scanning calorimetry (DSC), indicating its thermal stability. The optical and electrochemical properties of ad-OMeTPA were investigated by UV–vis absorption spectroscopy, fluorenscence spectroscopy, and cyclic voltammetry (CV). In addition, the harmonic vibrational wavenumbers and frontier molecular orbitals were calculated using density functional theory (DFT) method. The results reveal that ad-OMeTPA has favorable optical adsorption/emission properties, suitable energy levels and high electrochemical stability, indicating its potential application in organic optoelectronic devices.
Keywords: Organic hole transporting material; Adamantane central core; Thermal stability; Electrochemical properties; Energy levels
Synthesis and photophysical characterization of orange-emitting iridium(III) complexes containing benzothiazole ligand
by Guoyong Xiao; Xiao Li; Haijun Chi; Yunhua Lu; Yan Dong; Zhizhi Hu; Jianglong Yu; Masaru Kimura (pp. 497-502).
► Two novel Ir(III) complex based on bt derivatives were synthesized and characterized. ► Two complexes emit intensely orange phosphorescence. ► The devices using two complex as doped emitter exhibited excellent performances.Two novel iridium(III) (Ir(III)) complexes (dmabt)2Ir(acac) and (dpabt)2Ir(acac)(dmabt, 4-N,N-dimethylbenzenamineyl-2-benzo[d]thiazole; dpabt, 4-N,N-diphenylbenzenamineyl-2-benzo[d]thiazole; acac, acetylacetone) were synthesized and structurally characterized by NMR and mass spectrometry. The organic light-emitting diodes based on these complexes with the structure of ITO/m-MTDATA (10nm)/NPB (20nm)/CBP: Ir-complex (X%, 30nm)/BCP (10nm)/Alq3 (30nm)/LiF (1nm)/Al (100nm) were fabricated. The device based on (dmabt)2Ir(acac) exhibited a maximum efficiency of 19.5cd/A, a luminance of 15802cd/cm2; and the device based on (dpabt)2Ir(acac) showed a maximum efficiency of 14.8cd/A, a luminance of 11334cd/cm2. Both devices displayed orange emissions and the corresponding Commission International de L’Eclairage (CIE) coordinates (1931) were (0.517, 0.481) and (0.557, 0.443), respectively.
Keywords: Iridium complex; Benzothiazole; Phosphorescence; OLEDs
Preparation of aromatic carboxylic acid-functionalized polysulfone and preliminary exploration of florescence emission character of formed polymer-rare earth complexes
by Baojiao Gao; Li Fang; Ruixia Zhang; Jiying Men (pp. 503-510).
► We prepared the functionalized polysulfone, BAPSF, on whose side chain benzoic acid was bonded. ► Two luminescent polymer-rare earth complexes, BAPSF-Eu(III) and BAPSF-Tb(III), were prepared. ► BAPSF can powerfully sensitize the fluorescence emissions of Eu3+ and Tb3+ ions. ► The two complexes also have excellent mechanical, thermal and film-forming properties of PSF.Polysulfone (PSF) was modified via a polymer reaction, Friedel–Crafts alkylation of PSF with 4-(chloromethyl) benzoic acid (CMBA) as reaction reagent, and benzoic acid (BA) ligand was bonded onto the side chains of PSF, resulting in the aromatic carboxylic acid-functionalized PSF, BAPSF. The chemical structure of BAPSF was characterized by FTIR,1H NMR and UV/vis absorption spectrum. BAPSF was allowed to coordinate to Eu(III) and Tb(III) ions, respectively, and two luminescent polymer-rare earth complexes, BAPSF-Eu(III) and BAPSF-Tb(III) were prepared. The fluorescence emission character of the two complexes was preliminarily explored. The functionalization modification process of PSF and the reaction mechanism were emphatically investigated. The experimental results show that the Friedel–Crafts alkylation reaction between PSF and CMBA can be carried out smoothly. The two polymer-rare earth complexes, BAPSF-Eu(III) and BAPSF-Tb(III), exhibit the characteristic fluorescence emissions of Eu3+ and Tb3+ ions, respectively. More importantly, BAPSF can powerfully sensitize the fluorescence emissions of Eu3+ and Tb3+ ions, and the effective energy transfer indeed take places from the macromolecular ligand BAPSF to the coordinated Re3+ and Tb3+ ions.
Keywords: Polysulfone; Benzoic acid; Polymer-rare earth complex; Fluorescence emission; Sensitization
Electrochemical impedance characterization and potential dependence of poly[3,4-(2,2-dibutylpropylenedioxy)thiophene] nanostructures on single carbon fiber microelectrode
by Metehan C. Turhan; A. Sezai Sarac; Asli Gencturk; Hans-Detlev Gilsing; Heike Faltz; Burkhard Schulz (pp. 511-515).
Display Omitted► Electropolymerization of 3,4-(2,2-dibutylpropylenedioxy)thiophene (ProDOT-Bu2). ► The equivalent circuit modeling revealed 0.4V to be most suitable for the system. ► PProDOT-Bu2/SCFME exhibited a double layer capacitance Cdl value of 62mFcm−2.The electropolymerization of 3,4-(2,2-dibutylpropylenedioxy)thiophene (ProDOT-Bu2) onto single carbon fiber microelectrode (SCFME) was conducted in acetonitrile (ACN) containing sodium perchlorate (NaClO4) as electrolyte and investigated by cyclic voltammetry (CV). The nanostructured films of poly[3,4-(2,2-dibutyl-propylenedioxy)thiophene] (PProDOT-Bu2) which were depositing showed complete reversible redox behavior in monomer-free electrolyte solution.The capacitive behavior of the films was investigated by electrochemical impedance spectroscopy (EIS) at applied potentials from 0.1V to 1.3V. The analysis by equivalent circuit modeling revealed an applied potential around 0.4V to be most suitable for the system PProDOT-Bu2/SCFME as a double layer supercapacitor component inducing a double layer capacitance Cdl value of 62mFcm−2.
Keywords: Nanostructure; Electrochemical impedance spectroscopy; Conjugated polymeric thin film; Carbon fiber
The effect of carrier injection and transport of hosts on organic electrophosphorescent device
by Hong Xia; Hao Zhang; Jiyan Leng; Xiaoming Liu (pp. 516-521).
► The OLEDs based on phosphorescent guest [Ru(4,7-Ph2-phen)3]2+ were fabricated. ► Two tri-fluorene molecules TCPC with carbazole groups and THPH host were used. ► TCPC possesses stronger injection, transport ability of hole. ► The devices based on TCPC as host show better performances.Recently the organic electrophosphorescent host materials have attracted increasing attention. The selection principle of suited host materials is important to obtain high efficient electrophosphorescence. In this paper, we report the effect of carrier injection and transport properties of hosts to organic electrophosphorescent devices. A system, consisting of a red phosphorescent [Ru(4,7-Ph2-phen)3]2+ dopant and two blue-emitting hosts THPH and TCPC introducing carbazole substituent groups, was studied. Both the hosts showed similar electronic properties, forming film ability and energy transfer degree to dopant, however, EL efficiency with TCPC host significantly exceeds that with THPH host. The Cyclic Voltammogram curves and single carrier devices of hosts TCPC and THPH show that TCPC with carbazole groups possesses stronger hole injection and transport ability, and this induced TCPC is more suited host than THPH. This result demonstrates our previous study that the electrochemical properties of dopant [Ru(4,7-Ph2-phen)3]2+ molecule, which reflects the carrier trapping ability of guest, may be a basic design criterion for the selection of host.
Keywords: Electrophosphorescence; Host; Carrier; Injection; Transport
Optoelectronic devices based on ultra-violet light sensitive PVK:PCBM layers
by Alexander Lange; Harald Flügge; Bert Fischer; Hans Schmidt; Christine Boeffel; Michael Wegener; Thomas Riedl; Wolfgang Kowalsky (pp. 522-526).
Polymers can be incorporated into different types of devices including optoelectronic sensors, which have the ability to detect specific wavelengths of light. In this study, poly(N-vinyl carbazole) was combined with [6,6]-phenyl-C61-butyric acid methyl ester to form a bulk heterojunction in a traditional solar cell device structure. The ability of this system to detect ultra violet light was explored with absorbance and efficiency measurements. It was found that devices with the given materials system generate open circuit voltage values of up to 0.275V under illumination with wavelengths from 220 to 300nm. Higher performance values could be achieved with an optimized anode showing a higher transmittance at 300nm.
Keywords: Ultra-violet light sensor; Poly(N-vinyl carbazole); PCBM; Bulk heterojunction
Synthesis and characterization of chemical structure and thermal stability of nanometer size polyaniline and polypyrrole coated on rice husk
by Mohsen Ghorbani; Hossein Eisazadeh (pp. 527-530).
► Synthesis of polyaniline and polypyrrole nanocomposites containing rice husk. ► Products were investigated in terms of morphology, chemical structure, and thermal stability. ► Properties of products are dependent on nanocomposite structure. ► Nanocomposites show remarkable improved thermogravimetric stability with PAn and PPy.This study describes the preparation of polyaniline/rice husk (PAn/RH) and polypyrrole/rice husk (PPy/RH) nanocomposites in aqueous media by chemical polymerization of aniline and pyrrole in the presence of potassium iodate and ferric chloride as oxidants, respectively. The products were investigated in terms of morphology, chemical structure and thermal stability with scanning electron microscope (SEM), Fourier transform infrared (FTIR) spectroscopy and thermal gravimetric analysis (TGA), respectively. Results indicated that properties of products are dependent on nanocomposite structure. By comparison FTIR spectra between pure PAn and PAn/RH nanocomposite, all bands in nanocomposite are slightly shifted, which indicates that there is some interaction between PAn and the metal oxides of RH.
Keywords: Nanocomposite; Morphology; Chemical structure; Thermal stability
Protonic defect induced carrier doping in TTFCOO−NH4+: Tunable doping level by solvent
by Takeshi Terauchi; Yuka Kobayashi; Hideo Iwai; Akihiro Tanaka (pp. 531-535).
► The origin of the carrier doping in TTFCOO−NH4+ has been revealed to include protonic defects in the salt bridge by XPS. ► Doping level of TTFCOO−NH4+ is tunable by selecting suitable solvent over the range, 9–33%. ► Criterion determining doping level of TTFCOO−NH4+ correlates with self-dissociation ability of solvent, controlling inclusion of protonic defect in the salt.The origin of carrier doping in TTFCOO−NH4+ has been verified to include protonic defect in salt bridge by means of X-ray photoelectron spectroscopy (XPS), for the first time. The emergence of spin in TTFCOO−NH4+ is tunable over quite a wide range (9–33%) only by selecting a suitable solvent for the salt crystallization. The spin concentration of the solvent-dependent salts weakly correlates with intensity of optical absorption in near-infrared region, values ofg-tensor and dc conductivity at rt. The solvents determining doping level of the salt are classified into three categories by self-dissociation ability (p KSH) of solvent, which likely controls inclusion of protonic defect in the salts.
Keywords: Protonic defect; Carrier doping; XPS; Salt bridge; Charge transport
Electropolymerised polyaniline films as effective replacement of carcinogenic chromate treatments for corrosion protection of aluminium alloys
by K. Kamaraj; V. Karpakam; S. Syed Azim; S. Sathiyanarayanan (pp. 536-542).
► Electrosynthesis of PANI on AA 2024 and AA 7075 achieved by galvanostatic method. ► FTIR studies show both benzenoid and quinoid groups and doped with oxalate ions. ► The salt spray tests and EIS studies show better corrosion protection by PANI.Owing to the carcinogenic nature of chromate coatings, alternate coatings with intrinsically conducting polymers such as polyaniline (PANI) and polypyrrole (Ppy) have been developed. Hence a study has been made on the effect of electropolymerised PANI films on corrosion protection performance of epoxy coating on AA 2024 and AA 7075 aluminium alloys. Polyaniline was electropolymerised on both the alloys by galvanostatic method. A post treatment of cecrium was given to seal the pinholes of PANI film. Epoxy coating was applied over these films and their corrosion protection performance was found out by EIS studies in 3% NaCl and salt spray test. EIS studies have shown that the coating resistance ( Rc) of PANI with the epoxy coated aluminium alloys has remained above 106Ωcm2 whereas the alloys coated with epoxy alone have shown the Rc values less than 104Ωcm2. Besides, the salt spray tests showed a better corrosion protection of PANI with epoxy coated aluminium alloys.
Keywords: Electropolymerisation; Polyaniline; Aluminium alloy; Chromate replacement; EIS; Salt spray tests; Corrosion protection
New low band gap compounds comprised of naphthalene diimide and imine units
by Ewa Schab-Balcerzak; Marzena Grucela-Zajac; Michal Krompiec; Anna Niestroj; Henryk Janeczek (pp. 543-553).
► We obtained low molecular compounds and polymers consist of azomethine-naphthalene diimides units. ► First time, amorphous molecular naphthalene diimide compounds with Tg in the range of 80–195°C were obtained. ► We examined their photoluminescence and electrochemical properties. ► They exhibited low electrochemical band gap being promising for optoelectronics.New arylene bisimide derivatives, both low molecular compounds and polymers consisting of a naphthalene diimide core and imine linkages were synthesized. The azomethine-diimides were prepared from N,N′-bis(4-amino-2,3,5,6-tetramethylphenyl)naphthalene-1,4,5,8-dicarboximide (DANDI) which was condensed with 4-pyridinecarboxaldehyde or 1,3-benzothiazole-2-carboxaldehyde or 2-thiophenecarboxaldehyde or 2,2′-bithiophene-5-carboxaldehyde. Poly(azomethine-naphthaleneimide)s were obtained by high temperature polycondensation of DANDI with 2,5-thiophenedicarboxaldehyde or 2,2′-bithiophene-5,5′-dicarboxaldehyde. The materials do not show decomposition below 300°C. The azomethine-diimides exhibited glass-forming properties with glass transition temperatures in the range of 80–195°C. For the first time, to the best of our knowledge, amorphous molecular naphthalene diimide compounds were obtained. Optical properties of the prepared compounds were investigated by UV–vis and photoluminescence (PL) measurements. Most of the azomethine-diimides emitted green light with the highest intensity with emission maximum ( λem) at ca. 519–535nm contrary to polymers which λem was at 450 and 485nm. All the compounds are electrochemically active and azomethine-diimides undergo quasi-reversible reduction and irreversible oxidation as evidenced by cyclic voltammetry (CV). In all studied molecules the electrochemically determined HOMO level is in the range of −5.5 to −5.13eV whereas the LUMO level is close to −4.0eV for azomethine-diimides and −3.8eV for polymers as determined by differential pulse voltammetry (DPV). The investigated compounds exhibited low electrochemical band gap (1.21–1.5eV) being promising for optoelectronic applications.
Keywords: Polyimides; Polynaphthaleneimides; Azomethines; Azomethine-naphthalene diimides; Electrochemistry; Photoluminescence