Synthetic Metals (v.162, #1-2)
Electrodeposition and characterisation of polythiophene films on gold substrates
by Alexandra F. Monnin; Cédric C. Buron; Laurent Guyard; Daniel Charraut; Roland Salut; Claudine Filiâtre (pp. 1-9).
FE-SEM images of polybithiophene film and polytris(2,2′-dithienyl)methylcarbinol film.Display Omitted► Polymer films are deposited on gold electrodes by cyclic voltammetry. ► Films are characterised by Optical microscopy, AFM and SEM. ► Raspberry particles are deposited on modified surfaces. ► Composite particles are deposited around polymer aggregates.Star-shaped oligothiophenes are interesting to use in building super-structured materials. We have already used them to improve particle adhesion and assembly onto conductive substrates in an aqueous medium. In this study, electropolymerization of two different monomers, tris(2,2′-dithienyl)methylcarbinol (TMC) and bithiophene (BT), was carried out on gold film, which was deposited by PVD on silicon wafers. The numbers of cycles and the scan rate have been changed to modify the morphology of the deposit. The polymer films were then characterised by cyclic voltammetry, classical microscopy, atomic force microscopy and scanning electronic microscopy. Polytris(2,2′-dithienyl)methylcarbinol (PTMC) film was flatter, thicker and more uniform than polybithiophene (PBT) film. Finally electrophoretic deposition of composite particles has been carried out on PBT and PTMC films.
Keywords: Electropolymerization; Polytris(2,2′-dithienyl)methylcarbinol; AFM; SEM; Particle electrophoretic deposition
Electrochemical codeposition of poly(thieno[3,2- b]thiophene) and fullerene: An approach to a bulk heterojunction organic photovoltaic device
by Eduard Nasybulin; Marshall Cox; Ioannis Kymissis; Kalle Levon (pp. 10-17).
► Polymer solar cell was fabricated by electrochemical depositions. ► Fullerene and poly(thieno[3,2- b]thiophene) were codeposited electrochemically. ► Layer of PEDOT nanofibers was electropolymerized of ITO surface. ► Composition and oxidation states were controlled electrochemically.An electrochemical approach was developed to fabricate polymer solar cell. Poly(thieno[3,2- b]thiophene) and fullerene were codeposited by cyclic voltammetry from the solution containing corresponding monomers. The composition could be altered by changing potential range and was monitored by UV–Vis–NIR spectroscopy. Morphology and phase separation were studied by AFM revealing formation of the bulk heterojunctions. For the device fabrication the codeposition onto electropolymerized PEDOT layer was done without destructive interference. Voc of 0.3V and Jsc of 35μA/cm2 were measured under standard AM 1.5 conditions.
Keywords: Polymer solar cell; Polythiophene; Fullerene; Electrodeposition; Electropolymerization
Photophysical properties and Judd-Ofelt analysis of a europium complex with 5-amino-1,10-phenanthroline
by Cun-Jin Xu; Peng-Fei Zhang; Fang-Ming Liu; Yan-Qin Shi (pp. 18-21).
► A Eu(III) complex with 5-amino-1,10-phenanthroline and 2-thenoyltrifluoroacetone. ► Photophysical properties of the complex were studied. ► The Judd-Ofelt theory was used to analyze the luminescence spectra of the complex.A europium (III) complex with 5-amino-1,10-phenanthroline and 2-thenoyltrifluoroacetone, Eu(TTA)3(phenNH2), was synthesized. Its photophysical properties were studied in detail using UV, luminescence spectra and lifetime measurements. The complex shows a long5D0 lifetime (588μs) and a remarkable luminescence quantum yield (40.95%) at room temperature, which makes it not only a promising light-conversion molecular device but also an excellent luminescent polymer precursor. Moreover, the applicability of the well-known Judd-Ofelt theory to the emissive properties of Eu3+ complexes is also investigated.
Keywords: Europium complex; Photophysical property; 2-Thenoyltrifluoroacetone; 1,10-Phenanthroline; Synthesis; Judd-Ofelt
Study of the mechanism of the variable emissivity infrared electrochromic device based on polyaniline conducting polymer
by Hua Li; Kai Xie; Yi Pan; Hualin Wang; Hui Wang (pp. 22-25).
Variable emissivity infrared electrochromic device based on polyaniline(PANI) conducting polymer has been prepared and the mechanism of IR electrochromic device has been investigated by in situ technology. Results show that the device has good electrochromism in the mid-infrared (mid-IR) ranges (3–5μm, 8–12μm). IR reflectance and transmittance measurements of the PANI/polyethylene (PE) composite film under different potentials show that the transmittance change of the PANI film under different potentials is the main affecting factor of the emissivity change of the device. In-situ Fourier transform infrared attenuated total reflection (FTIR-ATR) measurement of the device demonstrates that almost all peaks of the PANI film at 0.8V have red-shifted compared to the peaks of the film at −0.8V. A conversion of quinoid ring to benzenoid ring in the PANI film happens when the potentials changes from 0.8V to −0.8V and the doping degree of the PANI film at 0.8V is deeper than that of the film at −0.8V.
Keywords: Polyaniline; Infrared; Electrochromic device; Emissivity; FTIR-ATR
Synthesis, characterization and aggregation properties of water-soluble metal-free and metallophthalocyanines peripherally tetra-substituted with 2-[2-(dimethylamino)ethoxy]ethoxy moiety
by Zekeriya Bıyıklıoğlu (pp. 26-34).
► Synthesis and characterization of metal-free and metallophthalocyanines. ► Synthesis and characterization of water-soluble metal-free and metallophthalocyanines. ► Investigation of aggregation properties of metal-free and metallophthalocyanines in different solvents.In this study, novel metal-free2, cobalt3 and copper4 phthalocyanines were synthesized and characterized for the first time. These new phthalocyanines2–4 were converted into water-soluble quaternized products2a–4a by the reaction with methyl iodide. The quaternized complexes2a–4a show excellent solubility in both organic and aqueous solutions which make them potential photosensitizer for use in PDT. Aggregation properties of metal-free and metallophthalocyanines were investigated at different concentrations in chloroform, dimethylsulfoxide, dimethylformamide, tetrahydrofuran and water. While all synthesized metallophthalocyanine complexes did not show aggregation in chloroform, THF and DMSO, metal-free phthalocyanine showed aggregation in DMSO. The new compounds have been characterized by using UV–vis, IR,1H-NMR, elemental analysis, MS spectroscopic data.
Keywords: Metal-free phthalocyanine; Metallophthalocyanine; Synthesis; Cobalt; Aggregation; Quaternization
Photophysical properties of a fluorene–bipyridine copolymer and its complexes with europium
by D.A. Turchetti; P.C. Rodrigues; L.S. Berlim; C. Zanlorenzi; G.C. Faria; T.D.Z. Atvars; W.H. Schreiner; L.C. Akcelrud (pp. 35-43).
Display Omitted► Europium ions were inserted in 80% of the repeating units of a di-pyridine copolymer. ► The complexation required a twist of 79° (49kJ) between the pyridine units. ► No electronic coupling occurred between the backbone and the complexation sites. ► Red and blue emission were seen in the spectra of the complexed copolymers. ► The ion had a trapping effect in the charge transport properties.The synthesis and structural characterization of a europium complexed fluorene–bipyridine copolymer are described. A level of ion insertion of 80% in molar basis was achieved, and theoretical calculations showed that it required a twist of 179° (49kJ) between the pyridine units. Spectroscopy data showed that no electronic coupling between the main backbone and the complexation sites had occurred, but these hindered the interchain aggregation observed in the non complexed polymer.Preliminary electroluminescence studies showed that the EL and PL spectra are consistent, and that the ion had a trapping effect in the charge transport.
Keywords: Europium complexes; Fluorene; Bipyridine copolymers; Photophysical properties
Improvement of dispersion state and charge separation efficiency of hybrid films of ZnO nanoparticle/conjugated polymers by utilizing methanol as a volatile dispersant
by Tanita Hirunprateep; Nisanart Traiphol; Ruttayapon Potai; Rakchart Traiphol (pp. 44-48).
The addition of methanol enhances the interfacial interactions between ZnO nanoparticles and non-polar conjugated polymers, resulting in the improvement of dispersion state and charge separation efficiency.Display Omitted► An efficient method for improving properties of ZnO/conjugated polymer films is introduced. ► Methanol is used to promote the dispersion state of ZnO nanoparticles in organic medium. ► Charge separation efficiency of hybrid films is greatly improved. ► Methanol completely evaporates during the fabrication of hybrid films. ► It has a potential for utilization in the fabrication of plastic solar cell.This contribution introduces an efficient method for fabricating hybrid films of ZnO nanoparticle/conjugated polymers with improved charge separation efficiency. Methanol is utilized as a volatile dispersant for promoting the dispersion of ZnO nanoparticles in chlorobenzene. The increase of methanol concentration from 0 to 20% (v/v) results in systematic improvement of the particle dispersion. The suspensions of ZnO nanoparticles in these solvents are used to prepare hybrid films of poly[2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) and regioregular poly(3-hexylthiophene) (P3HT). The morphologies and optical properties of the hybrid films, prepared by spin casting, are investigated by atomic force microscopy, UV/vis absorption and photoluminescence (PL) spectroscopy. The hybrid films obtained from all systems are continuous and exhibit relatively smooth surface. The extent of polymeric chain aggregation in the hybrid films is hardly affected by the variation of solvent. However, the drop of about 60% of PL intensity is detected when the methanol is added into ZnO/MEH-PPV solution prior to the film preparation. The drastic decrease of PL intensity indicates significant improvement of charge separation efficiency in the hybrid films. The investigation of ZnO/P3HT hybrid films shows consistent results. Our approach is very efficient because the methanol completely evaporates during the fabrication of hybrid film.
Keywords: Photovoltaic cells; Bulk heterojunction; Solvent effect; Interfacial interaction; Conjugated polymer; Composite materials
Synthesis and electronic properties of 4-cyanophenylvinylenedithiathiophene: An EDOT derivative
by Oznur Sucsoran; Somer Bekiroglu; Turan Ozturk; Erdal Ertas (pp. 49-53).
► 1,8-Diketone reacting with P4S10 gives 4-cyanophenylvinylenedithiathiophene. ► Neither electrochemical nor only chemical polymerization attempts succeeded. ► More negative spin densities at “α” carbons of thiophene part.Synthesis of 4-cyanophenylvinylenedithiathiophene, which is an analogue of ethylenedioxythiophene (EDOT), has been described. The synthesis was achieved by applying 1,8-diketone ring formation reaction occurring between 1,8-diketone and phosphorus decasulfide in boiling toluene. The target compound was characterized by cyclic voltammetry (CV), UV spectroscopy, and theoretical studies. Unlike the analogues similarly carrying phenyl groups substituted with other functional groups such as –OMe, –Br, –NO2, neither electrochemical polymerization attempts nor chemical polymerization efforts with ferric chloride(III) (FeCl3) succeeded in yielding any products. Results of spin density calculations revealed that the molecule did not have enough electron spin densities at the “α” carbons of the thiophene part. Moreover, during the polymerization attempt with FeCl3, as the nitrile nitrogen could form complex with iron, spin density calculation was also performed for protonated form of the monomer, which indicated that the “α” carbons of the molecule had even lower spin densities.
Keywords: 4-Cyanophenylvinylenedithiathiophene; Phosphorus decasulfide (P; 4; S; 10; ); Radical spin density dithiin; Ethylenedioxythiophene
Langmuir–Blodgett (LB) films of novel tetrathiafulvalene derivative containing diamino group
by Chunyang Jia; Yanna Chen; Jiaqiang Zhang; Zhihong Wang (pp. 54-57).
Display Omitted► A new tetrathiafulvalene (TTF) derivative (1) possessing strong amphiphilic character and good reversible redox property has been synthesized. ► The LB film of compound1 is fabricated and its physical properties are characterized. ► The room temperature in-plane dc conductivity of the LB film increases from 10−7Scm−1 to 10−5Scm−1 after doped by iodine.A new tetrathiafulvalene (TTF) derivative—5,6-diamino-2-(4,5-bis(decylthio)-1,3-dithio-2-ylidene)benzo[ d]-1,3-dithiole (1) with strong amphiphilic character and good reversible redox property has been synthesized. The Langmuir–Blodgett (LB) film of compound1 was fabricated and its physical properties were characterized by UV–vis spectra, X-ray photoelectron spectroscopy (XPS), atomic force microscope (AFM) and surface profiler. The room temperature in-plane dc conductivity of the LB film increases from 10−7Scm−1 to 10−5Scm−1 after doped by iodine.
Keywords: Tetrathiafulvalene; Langmuir–Blodgett film; Doping; Conductivity
Synthesis and characterization of excited state intramolecular proton transfer based 2-hydroxylaryl imidazole fluorescent materials
by Aman Mahajan; Ramanpreet Kaur Aulakh; R.K. Bedi; Sandeep Kumar; Subodh Kumar; D.K. Aswal (pp. 58-63).
Two novel non-planar, thermally stable, highly soluble, ESIPT based blue emitting imidazole derivatives (1) and (2) have been synthesized and characterized in solution and thin film states.Display Omitted► Synthesis of ESIPT based 2-hydroxyaryl imidazole as blue emitters. ► Compounds are suitable for soluble processing and thermal evaporation. ► Formation of amorphous thin films with H-aggregation. ► Compounds show the similar blue emission in solution and thin films.Excited state intramolecular proton transfer (ESIPT) based highly soluble, thermally stable fluorescent molecules namely 2-(1-butyl-4,5-diphenylimidazol-2-yl)phenol(1 ) and 2-(1-(4-(dimethylamino)phenyl)-4,5-diphenylimidazol-2-yl)phenol(2 ) were synthesized. These molecules were investigated by experimental as well as quantum mechanical techniques. Thin films of 1 and 2 were prepared using spin coating and thermal evaporation techniques onto glass substrates kept at room temperature and characterized for their structural, photo physical and electrical properties. UV–vis absorption studies showed that imidazole molecules preferred H-type aggregation in thin film form. Synthesized molecules showed almost the similar blue emission peaks in solution as well as thin films.
Keywords: Blue emitters; Imidazole; Excited state intramolecular proton transfer; Density functional theory calculations
Synthesis and photoluminescence properties of poly(1-hexyl-2-aryl acetylene)s, poly(1-phenyl-2-fluorenylacetylene), and poly(1-fluorenyl-2-fluorenlacetylene)
by Toshikazu Sakaguchi; Yuki Hayakawa; Ritsuka Ishima; Tamotsu Hashimoto (pp. 64-69).
Display Omitted► Novel poly(1-hexyl-2-arylacetylene)s and poly(difluorenylacetylene) were synthesized. ► Poly(substituted acetylene)s having fluorenyl groups showed strong emissions. ► The effect of alkyl substituent on polymer's fluorescence was revealed. ► Three types of polymers emitted blue, green, and yellow lights, respectively.The metathesis polymerizations of 1-hexyl-2-arylacetylenes [ n-C6H13CCAr; Ar=phenyl (1a), naphthyl (1b), biphenyl (1c), fluorenyl (1d)] were examined using NbCl5, TaCl5, and WCl6. When NbCl5/ n-Bu4Sn was used as a catalyst in their polymerization, high-molecular-weight polymers (2a–2d) were obtained in good yield compared to TaCl5/ n-Bu4Sn and WCl6/Ph4Sn. 1-Hexyl-2-[2-(9,9-dialkylfluorenyl)]acetylenes (1e–1h) also polymerized by NbCl5/ n-Bu4Sn to give corresponding polymers (2e–2h) with relatively high molecular weights. Diarylacetylene polymers (2i and2j) were obtained by the metathesis polymerization using TaCl5/ n-Bu4Sn. All the poly(1-hexyl-2-arylacetylene)s (2a–2h) emitted blue-colored lights, and the fluorenyl group-containing polymers exhibited strong photoluminescence. However, the fluorenyl group-containing polymers with long alkyl groups such as n-butyl and n-octyl groups at the 9-position on fluorene rings showed weak emissions because the steric hindrance of long alkyl groups prevents to form intramolecular excimers. The emission spectra of diarylacetylene polymers red-shifted, and 1-phenyl-2-[2-(9,9-dimethylfluorenyl)]acetylene (2i) and 1-(2-fluorenyl)-2-[2-(9,9-dimethylfluorenyl)]acetylene (2j) showed green-colored and yellow-colored emissions, respectively.
Keywords: Poly(1-hexyl-2-arylacetylene); Poly(1-phenyl-2-fluorenylacetylene); Poly(difluorenylacetylene); Metathesis polymerization; Photoluminescence; Quantum yield
Synthesis, optical and electrochemical properties of in-situ thermally cross-linkable oligo(10 H-alkylphenothiazine)
by Mi Young Jo; Seong Soo Park; Joo Hyun Kim (pp. 70-78).
► We synthesize in-situ thermally curable oligophenothiazine. ► Cured oligophenothiazine is very good solvent resistance and electrochemically stable. ► The oligomers are potential materials for hole injection materials.A series of 10-alkylphenothiazine trimer (3-PTMA) and pentamer (5-PTMA) with in-situ thermally cross-linkable methyl methacrylate were successfully synthesized. Thermogravimetric analysis (TGA) thermograms revealed that 3-PTMA and 5-PTMA are stable up to 270 and 336°C, respectively. In the first heating scan of differential scanning calorimetry (DSC) thermogram, 3-PTMA and 5-PTMA showed Tg at 91.2 and 99.7°C. Both 3-PTMA and 5-PTMA showed broad endothermic process in the region of 144–179°C, which was thermally cross-linking temperature. In the second heating process, Tg of 3-PTMA and 5-PTMA were 113.4 and 149.8°C and endothermic process was not observed. UV–vis absorption maximum of thermally cured 3-PTMA is 340nm, which was same as the UV–vis maximum of 5-PTMA. The absorbance at 340nm of thermally cured 3-PTMA and 5-PTMA film washed with organic solvent such as methylene chloride (MC), chloroform, and toluene was almost same as the cured 3-PTMA and 5-PTMA, indicating that thermally cured films were very good solvent resistance. Thermally cured 3-PTMA and 5-PTMA were electrochemically stable and the HOMO energy level of 3-PTMA and 5-PTMA were −5.58 and −5.54eV, respectively. Double layer structured polymer light-emitting diodes based on in- situ thermally cured 3-PTMA and 5-PTMA were fabricated. The maximum luminance efficiency of devices based on 3-PTMA and 5-PTMA were 0.685cd/A at 16.0V and 0.760cd/A at 14.5V, respectively, which were higher than that of the device without thermally cured 3-PTMA or 5-PTMA (0.348cd/A at 15.0V).
Keywords: In-situ; thermal curing; 10; H; -Alkylphenothiazine; p; -type organic semiconductor; Hole injection material
Electrochemical and optical properties of solution processable benzotriazole and benzothiadiazole containing copolymers
by Melike Karakus; Abidin Balan; Derya Baran; Levent Toppare; Ali Cirpan (pp. 79-84).
Display Omitted► Polymers contain benzotriazole and benzothiadiazole acceptors on their backbones. ► This study shows that polymers would be great candidates for optoelectronic devices. ► Polymers have ambipolar characteristic and moderate band gaps.2-Dodecyl benzotriazole (BTz) and benzothiadiazole (BTd) containing alternating copolymers poly(4-(2-dodecyl-2H-benzo[d][1,2,3]triazol-4-yl)benzo[c][1,2,5]thiadiazole(P1), poly(4-(5-(2-dodecyl-7-(thiophen-2yl)-2H-benzo[d][1,2,3]triazol-4-yl)thiophen-2-yl)benzo[c] [1,2,5] thiadiazole(P2) and poly(4-(5-(2-dodecyl-7-(4-hexylthiophen-2-yl)-2H-benzo[d] [1,2,3]triazol-4-yl) -3-hexylthiophen-2-yl) benzo[c][1,2,5] thiadiazole(P3) were synthesized via Suzuki polycondensation reactions. The solubility of the polymers enabled spray coating to carry out the electrochemical and optical studies. Electronic and optical properties of resulting polymers showed thatP2 is a great candidate to be used as processable blue electrochromic polymer which can switch to transparent upon oxidation.P3 was also investigated in terms of its electrochromic performance which has two different colored and a transparent states, whereasP1 does not exhibit any spectral change upon applied potentials. HOMO and LUMO values, band gaps and kinetic behavior of polymers upon externally applied potential are reported in detail.
Keywords: Benzotriazole; Benzothiadiazole; Donor acceptor copolymers; Electrochromism; Organic electronics
Synthesis, characterization and supercapacitive properties of hierarchical porous carbons
by Shanshan Mo; Zhenfan Sun; Xiangjin Huang; Wujun Zou; Jingxing Chen; Dingsheng Yuan (pp. 85-88).
► Hierarchical porous carbons have been synthesized via direct carbonization of MOFs. ► The synthesis process is free for the removal of template. ► BET surface area of HPCs corresponds to the amount of Bi(NO3)3 and glycerol volume. ► The hierarchical porous carbons exhibit a high specific capacitance.A series of hierarchical porous carbons are synthesized from metal-organic frameworks as a precursor and glycerol as a carbon source. N2 adsorption–desorption measurement indicates that glycerol has a pronounced effect on the specific surface area of the synthesized porous carbons. And the pore size distribution and BET can be modulated by adding different amounts of Bi(NO3)3·5H2O. The amount of Bi(NO3)3·5H2O is changed from 0 to 0.4mmol, resulting in the increase of surface area from 1796m2g−1 to 2857m2g−1. Due to its unique hierarchical pore structure, the synthesized porous carbons exhibit a high specific capacitance and show potential application in electrochemical capacitor.
Keywords: Hierarchical porous carbons; Metal-organic frameworks (MOFs); Specific surface area; Supercapacitors
Preparation and characterization of Fe3O4/SiO2 particles for dual-particle electrophoretic display
by Sheng Liu; Gang Wu; Hong-Zheng Chen; Mang Wang (pp. 89-94).
Display Omitted► Multi core–shell Fe3O4/SiO2 particles were prepared for EPID application. ► SiO2 encapsulation eases the surface modification of nano Fe3O4. ► Oppositely charged electrophoretic particles can stably coexist in suspension. ► The prototype device driven in low DC field can present high black/white contrast.In order to prepare metal-oxide-pigment based electrophoretic particles with good suspension stability in the low dielectric medium for electrophoretic display application, ferroferric oxide/silicon oxide (Fe3O4/SiO2) composite particles were prepared via in situ sol–gel method. The transmission electron microscopy (TEM)/scanning electron microscope (SEM) images present the multi core–shell morphology for the Fe3O4/SiO2 particles and the average particle size is 250–350nm. It was found that the Fe3O4/SiO2 composite particles own lower density than that of Fe3O4 because of SiO2 encapsulation and can suspend stably in tetrachloroethylene after OLOA treatment. Zeta potential and electrophoretic mobility of the OLOA treated Fe3O4/SiO2 composite particles in tetrachloroethylene were measured to be 24.2mV and 3.80×10−10m2/Vs, respectively. The dual-particles electrophoretic dispersion containing OLOA treated Fe3O4/SiO2 composite particles and TiO2 grafted with polymer can show white/black image under low DC field.
Keywords: Electrophoretic display; Electrophoretic mobility; Core–shell structure
Effect of carbon nanotube-fullerene hybrid additive on P3HT:PCBM bulk-heterojunction organic photovoltaics
by Nigel J. Alley; Kang-Shyang Liao; Enrico Andreoli; Sampath Dias; Eoghan P. Dillon; Alvin W. Orbaek; Andrew R. Barron; Hugh J. Byrne; Seamus A. Curran (pp. 95-101).
► Single-walled carbon nanotubes functionalized with fullerenes as a hybrid additive in organic photovoltaics. ► Shortened single-walled carbon nanotubes allow for better diode formation and reduce shorted devices. ► The addition of carbon nanotubes or fullerene hybrids do not readily improve organic photovoltaic device efficiency. ► We conclude that pure semiconducting carbon nanotubes are required as the base additive material.The use of carbon nanotube-fullerene hybrid additives to the standard P3HT:PCBM blend bulk-heterojunction organic photovoltaic device is presented. The effects of incorporating single-wall carbon nanotubes, functionalized with linked C60 molecules by amination on device characteristics are detailed. The concentration of the carbon nanotube-fullerene hybrid in the active layer blend was varied to ascertain their cumulative impact on device performance in terms of open circuit voltage, short circuit current, fill factor and efficiency. We found that decreasing the length of the carbon nanotubes to ∼60nm through fluorination and subsequent thermal treatment was beneficial in terms of eliminating shorted devices allowing much improved diode formation. A trend of improving device performance as a function of concentration of the carbon nanotube-hybrids in a heterojunction of P3HT:PCBM was observed.
Keywords: Single wall carbon nanotube; Fullerene; C; 60; P3HT:PCBM; Hybrid; Organic photovoltaics
Effect of annealing on bulk heterojunction organic solar cells based on copper phthalocyanine and perylene derivative
by Inho Kim; Ghassan E. Jabbour (pp. 102-106).
► N,N′-3,4,9,10-perylenetetracarboxylic diimide, perylene derivative as alternative to C60. ► Performance of annealed copper phthalocyanine (CuPc):perylene derivative solar cells. ► Correlation of optical absorption, microstructure and electrical property of blended films.We investigated the effects of annealing on device performances of bulk heterojunction organic solar cells based on copper phthalocyanine (CuPc) and N,N′-3,4,9,10-perylenetetracarboxylic diimide (PTCDI-C6). Blended films of CuPc and PTCDI-C6 with annealing at elevated temperature were characterized by measuring optical absorption, photoluminescence, and X-ray diffraction. Enhanced molecular ordering and increments in domain sizes of donor and acceptor for the blended films were observed, and their influences on device performances were discussed. Annealing led to substantial improvements in photocurrent owing to enhanced molecular ordering and formation of percolation pathways.
Keywords: Bulk heterojunction organic solar cell; Copper phthalocyanine; Perylene derivative; Annealing
Capacitance behaviors of nanorod polyaniline films controllably synthesized by using a novel unipolar pulse electro-polymerization method
by Yue Li; Kai Zhao; Xiao Du; Zhongde Wang; Xiaogang Hao; Shibin Liu; Guoqing Guan (pp. 107-113).
► A novel UPEP method was reported to prepare the nanorod PANI thin films. ► The morphology and conformation of nanorod PANI can be controlled by UPEP. ► The synthesized PANI films have the ordered and short-nanofiber or nanorod structure.A novel unipolar pulse electro-polymerization (UPEP) method was used to prepare nanorod polyaniline (PANI) films on platinum substrates from aqueous solution containing 0.2molL−1 of aniline and 0.5molL−1 of sulphuric acid. The unipolar pulse waveform consisted of an applied anodic potential during the on-period and an open-circuit potential (zero current) during the off-period. The effects of pulse deposition parameters on the electrochemical properties of PANI films were investigated by potential cycling in 0.5molL−1 of H2SO4 solution. The supercapacitive performances of as-prepared PANI films were also investigated in the 0.5molL−1 of H2SO4 solution via charge/discharge tests as well as electrochemical impedance spectroscopy (EIS). The surface morphology and conformation of PANI films were characterized using scanning electron microscopy (SEM) and Fourier transform infrared (FT-IR) spectroscopy, respectively. Experimental results indicated that nanorod PANI films with uniform distribution on Pt were formed by using this novel method, and the anodic pulse potential should be the primary factor to influence the morphology and the conformation of PANI film. The PANI films prepared by UPEP method displayed much higher ion exchange capacity, better stability and more excellent supercapacitive performances than those by other methods such as the common cyclic voltammetric method (CVM) and potentiostatic method (PM). It should be attributed to the highly porous nano-sized PANI with short-fiber or rod-like structure and the depressed hydrolysis of aniline. The highest specific capacitance value of 907.9Fg−1 was obtained when the pulse potential, aniline concentration, pulse frequency and duty cycle were 0.85V, 0.2molL−1, 1.25s−1 and 50%, respectively.
Keywords: Unipolar pulse electro-polymerization; Nanorod; Polyaniline; Supercapacitor; Controllable synthesis
Polyaniline nanoparticles grown on the surface of carbon microspheres aggregations for electrochemical supercapacitors
by Yong-Tao Tan; Fen Ran; Ling-Bin Kong; Ji Liu; Long Kang (pp. 114-118).
► PANI was grown on surface of m-Csa well using chemical oxidative polymerization. ► Processes for preparation of m-Csa/PANI were described and make an explanation. ► A highest capacitance of m-Csa/PANI was 435F/g.The carbon spheres aggregations (Csa) were synthesized by carbonation of polystyrene spheres aggregations which were prepared by suspension polymerization of styrene. And polyaniline (PANI) was grown on surface of Csa successfully by chemical oxidative polymerization aniline (ANI). Their structures and morphologies were characterized by field emission scanning electron microscopy and Fourier transform infrared spectrometer. Capacitive behaviors were investigated by cyclic voltammetry and galvanostatic charge–discharge. The PANI/ m-Csa showed hierarchical structure containing carbon spheres aggregations and PANI nanoparticles. Relationship between the specific capacitance and the composition of m-Csa/PANI composite was also investigated.
Keywords: Carbon spheres aggregations; Polyaniline nanoparticles; Supercapacitors; Electrochemical performance
Theoretical study of the effect of nickel and tin doping in copper clusters
by Lihua Dong; Bing Yin; Li Zhang; Yansheng Yin; Yijun Zhang (pp. 119-125).
► Ni/Sn makes the bimetallic clusters were more stable than monometallic ones. ► Ni/Sn affectsCu′n chemical activity, inducing the active sites varies regularly. ► Ni/Sn forms oxide film on the surface to protect the substrates from corrosion.The equilibrium geometries, electronic properties, bonding behavior, stability and active sites of copper clusters doped with Ni or Sn atom have been studied using density functional theory. The results indicate that the impurity atoms change the equilibrium geometries, lower the total energies, and modify the HOMO–LUMO gaps and active sites of copper clusters. Meanwhile impurities prefer to be the surface or outer layer of the cluster, may form an oxide film from the active sites on the surface of materials, preventing oxygen and aggressive ions diffusion and protecting the copper alloy against corrosion.
Keywords: DFT; Cluster; Copper alloys; Active site; Corrosion
Change in AC conduction mechanism together with conversion of submicron to nanoparticles in polyaniline and its poly(vinyl pyrrolidone) blends on heating-induced water elimination
by Natarajan Vijayakumar; Esakkiappan Subramanian; Duraipandi Pathinettam Padiyan (pp. 126-135).
Display Omitted► Greater AC conductivities in PANI–PVP blends than PANI. ► Ordered PANI chain arrangement and modification of π orbital energy levels by PVP. ► Profound influence of heating-induced water elimination on morphological (submicron to nano) and AC electrical properties. ► Change of small polaron tunneling to correlated barrier hopping conduction mechanism.The present work is an investigation of AC impedance behaviors of polyaniline (PANI) and its poly(vinyl pyrrolidone) (PVP) blends. The materials were prepared by polymerization of aniline hydrochloride without/with PVP using FeCl3 oxidant. PANI–PVP blends have greater AC conductivities than that of PANI in proportion to the amount of PVP incorporated. At lower frequencies (10Hz – critical frequency fc) conductivity remains independent but at frequencies > fc, conductivity raises with frequency. In the entire range, however, the universal power law σac( ω)= Aωs holds good. In fresh condition PANI exhibits an increase in bulk resistance ( Rb) and frequency exponent s up to 373K and blends up to 423K beyond which they show a decrease. The trend in conduction could be explained by the operation of small polaron tunneling up to 373/423K and afterwards correlated barrier hopping (CBH) conduction mechanisms. Studied PANI, PANI–PVP blend materials and a fresh but annealed (463K) PANI all display only a decrease in Rb and s values in the entire temperature range of study and hence they follow only CBH mechanism. The fresh samples, together with change of conduction mechanism with temperature also undergo submicron to nanoparticles conversion and changes in other physico-chemical properties. All these changes have the origin on elimination of occluded water from the fresh materials on heating.
Keywords: Polyaniline; Poly(vinyl pyrrolidone) blends; Complex impedance analysis; Morphological conversion; Conduction mechanism
Influence of dopant anions on properties of polypyrrole nanocoated poly(styrene- co-methacrylic acid) particles
by I. Carrillo; E. Sánchez de la Blanca; M.I. Redondo; M.V. García; M.J. González-Tejera; J.L.G. Fierro; E. Enciso (pp. 136-142).
► Nanostructures of PPy with different dopants on poly(styrene- co-methacrylic acid) particles. ► Doping level between 0.25 and 0.29 in all samples. ► High conductivity of 8.6Scm−1 was achieved with FeTS dopant. ► Slow degradation of PPy when trapped in the latex surfaces ( τ=1300 days).Nanostructures of polypyrrole (PPy) were synthesized on poly(styrene- co-methacrylic acid) particles with iron (III) p-toluensulfonate hexahydrate (FeTS), sodium p-toluensulfonate (NaTS), 5-sulfosalicylic acid dihydrate (SSA), iron(III) chloride hexahydrate or p-toluensulfonic acid (TSA) as dopants. A doping level between 0.25 and 0.29 in all samples was determined by X-ray photoelectron spectroscopy (XPS). FTIR analysis shows the effective covering of core samples and that no degradation of PPy has taken place. Conductivity decay study establishes that aromatic sulfonic acid anions provide better performance to the conducting polymer when are present as the only dopants. The chloride anions have a detrimental effect over conductivity and stability of the PPy shell.
Keywords: Core shells particles; Polypyrrole; Conductivity; XPS
Opto(electrical) properties of new aromatic polyazomethines with fluorene moieties in the main chain for polymeric photovoltaic devices
by Agnieszka Iwan; Marcin Palewicz; Andrzej Chuchmała; Lech Gorecki; Andrzej Sikora; Boleslaw Mazurek; Grzegorz Pasciak (pp. 143-153).
► We obtained new thermostable aromatic polyazomethines. ► We analyse photovoltaic properties in the level of structural changes. ► We examine devices with various architectures. ► The J– U effects depend on construction devices.The opto(electrical) and photovoltaic properties of aromatic polyazomethines with fluorene moieties in the main chain were presented. 2,7-Diaminofluorene was polymerized in DMA solution with isophthaldicarboxaldehyde (F-13Iso), 2,5-thiophenedicarboxaldehyde (F-25Th) or 4,4′-diformyltriphenylamine (F-TPA). The temperatures of 5% weight loss ( T5%) of the polyazomethines range from 415 to 433°C in nitrogen, depending on the dialdehyde used. Introduction of 1,3-phenylene moieties (F-13Iso) resulted in lower energy band gap (Egopt.) of approximately ∼0.43eV, whereas F-25Th and F-TPA showedEgopt. of ∼2.46eV. The conductivity of polyazomethines was approximately 10−10 to 10−9Scm−1 at room temperature as determined by impedance spectroscopy. Electrical behavior of the two kind devices ITO/polymer:PCBM/Al and ITO/PEDOT:PSS/polymer:PCBM/Al were tested by impedance spectroscopy in dark and under illumination (halogen lamp, 100mWcm−2). For all measured devices Nyquist plots were presented. The polymer solar cells devices were fabricated by spin coating the blend solution of the three polymers as donor and PCBM as acceptor. The devices comprised of polyazomethine F-25Th with PCBM (1:1) showed an open circuit voltage ( VOC) of 0.36V, a short circuit current ( JSC) of 2.22mAcm−2, and a fill factor (FF) of 0.38, giving a power-conversion efficiency (PCE) of 0.31% under an illumination of 100mWcm−2 with an AM1.5G.
Keywords: Polyazomethines; Fluorene-based polymers; Impedance spectroscopy; Polymeric photovoltaics; Organic solar cells; Bulk heterojunction solar cells
Synthesis, optical and structural studies of tetrakis[4-(2′,3′,4′,5′,6′-pentafluorobenzyloxy)benzyloxy]-substituted metallo-phthalocyanines
by Mukaddes Özçeşmeci; İdris Sorar; Esin Hamuryudan (pp. 154-161).
Display Omitted► 4-(pentafluorobenzyloxy)benzyloxy substituted phthalocyanines were synthesized. ► The aggregation behaviour of these compounds were investigated. ► Thin films of metallo-phthalocyanines were prepared by spin coating technique. ► These films can be used as an optical fitler and as optical window material. ► The surface morphology was showed that the molecules grow in stacks of rows.Metallo-phthalocyanines substituted with four pentafluorobenzyloxy units through benzyloxy-bridges were synthesized from a new phthalonitrile derivative and characterized by spectroscopic methods. The aggregation behaviour of these compounds were investigated in different concentrations of tetrahydrofuran. The effect of solvents on absorption spectra were studied in various organic solvents. Thin films of metallo-phthalocyanines were obtained by using spin coating on 2947 Corning glass substrates. Optical transmittance of thin films was measured using a spectrophotometer in the wavelength range of 300–1000nm. Results showed that transmittance decreases with the increasing concentration in the ranges corresponding to B and Q absorptions, but the films can still be proposed as optical windows between these regions (∼400–600nm) due to very low absorbances. The surface morphology of the thin films were investigated by atomic force microscopy. The phthalocyanine molecules grow in stacks of rows rather in the zig–zag or parallel.
Keywords: Fluorinated phthalocyanines; Thin films; Benzyloxy groups; Synthesis; Solubility; Aggregation
Formation of nanometric polypyrrole films on Au (111): A STM, SEM and XPS study
by M. Marandi; S. Kallip; L. Matisen; J. Tamm; V. Sammelselg (pp. 162-170).
► In situ STM study showed that electrochemical formation of PPy films on Au (111) electrode starts with adsorption of a thin Py sheet following island-like growth of polymer film until it covers the electrode surface continuously. ► Voltammetric measurements showed that during electrochemical deposition of PPy films from a solution consisting of SO42− ions co-adsorption of the ions and Py molecules could happen that improves adhesion of adsorbed Py layer with the electrode in the first stage of the deposition, and helps imaging the film formation stages with in situ STM. ► Prepared from diluted Py solution ultrathin PPy films having low conductivity can be used for preparation of new type biosensors.Adsorption of pyrrole (Py) and the electrochemical formation of ultrathin polypyrrole (PPy) films from aqueous solutions of 0.1M Na2SO4 or LiClO4 and Py of low concentrations onto partially atomically flat Au (111) electrodes were investigated by voltammetry, electrochemical in situ and ex situ scanning tunneling microscopy (STM), high-resolution scanning electron microscopy (HR-SEM), and photoelectron spectrometry (XPS) methods. The voltammetric measurements showed that the adsorption of Py on the surface of Au (111) is well detectable. In situ STM measurements demonstrated that direct interaction of Py molecules with the electrode is weak, but the co-adsorption process of sulfate and Py molecules improves adhesion of adsorbed Py layer. The formation of ultrathin PPy layers on the electrode surface is not uniform but more island-like. It was shown that the PPy films deposited galvanostatically from diluted Py solutions were essentially overoxidized, contrary to the ones deposited from more concentrated solutions of the monomer, or by using the potentiostatic deposition mode with a limited anodic potential.
Keywords: Polypyrrole; Electropolymerization; Overoxidation; XPS; in situ; STM
Fabrication and characterization of polyaniline/xanthan gum nanocomposite: Conductivity and thermal properties
by Saeedeh Gilani Larimi; Hamid Heydarzadeh Darzi; Ghasem Najafpour Darzi (pp. 171-175).
► A conductive polyaniline–xanthan gum nanocomposite was synthesized. ► Chemical structure of nanocomposite was examined by FT-IR analyses. ► Thermal stability of nanocomposite increases in the presence of xanthan gum. ► Polyaniline–xanthan gum nanocomposite is more water-soluble than polyaniline.A novel conductive and thermally stable nanocomposite was synthesized by oxidative polymerization of aniline in the presence of xanthan gum. The fabricated nanocomposite morphology and structure were examined by atomic forced microscopy (AFM) and FT-IR measurement. The conductivity investigation of novel polyaniline (PANI) based nanocomposite exhibited that xanthan gum (XG) can improve the electrical conductivity up to 2.48×10−1 with 2g xanthan gum in 0.2moll−1 aniline solution. Thermogravimetric analyzer (TGA) was used to study the thermal behavior of nanocomposite. The TGA curves indicated that xanthan gum enhanced the thermal stability of nanocomposite at less than 270°C and over 350°C. A problem limiting the application of polyaniline is its hydrophobic property that was solved approximately by the presence of xanthan gum in its nanocomposite. The swelling tests revealed that xanthan gum promoted the hydrophilic property of polyaniline extremely.
Keywords: Nanocomposite; Polyaniline; Xanthan gum; Conductivity; Thermal stability
A promising copolymer of p-phenylendiamine and o-aminophenol: Chemical and electrochemical synthesis, characterization and its corrosion protection aspect on mild steel
by A. Madhankumar; N. Rajendran (pp. 176-185).
► Investigate corrosion performance of poly ( p-phenylendiamine-co- o-amino phenol) coated mild steel. ► Investigate the stability of copolymer in comparison with homo polymers. ► The surface morphology and porosity are critical factors to corrosion protection performance. ► The electrochemically synthesised copolymer coatings have excellent corrosion protection efficiency than chemically synthesised copolymer due to its strong adherent and interaction with metal surface.The poly ( p-phenylendiamine-co- o-amino phenol) has been synthesised by chemical and electrochemical polymerisation method for corrosion protection of mild steel (MS) in acidic medium. The copolymer structure was confirmed by1H NMR, FT-IR spectroscopy and its thermal stability was observed by TGA. The surface of copolymer coated MS revealed that uniform and relatively less porous morphology. The corrosion protection performance of copolymer coated MS were evaluated using potentiodynamic polarisation and EIS measurements. The copolymer coated MS by electropolymerisation exhibit a higher corrosion protection efficiency than homo polymers and copolymer prepared by chemical polymerisation, which can be due to strong interaction between the mild steel surface and conjugated copolymer.
Keywords: Anticorrosion; Mild steel; AFM; 1; H NMR; EIS; Polymer coatings
Electrochemical properties of gold electrodes functionalized by new pseudo-polyrotaxanes of polyaniline and chemically modified β-cyclodextrin inclusion complex
by R. Mlika; S. Hbaieb; R. Ben Chaabene; Y. Chevalier; R. Kalfat; H. Ben Ouada (pp. 186-192).
► PANI and PANI- β-CDpNH2 films are deposited on gold electrodes by evaporation process. ► The wettability results have shown a hydrophilic character of PANI- β-CDpNH2 film. ► EIS study has revealed that PANI- β-CDpNH2 film is more conductive than PANI one. ► PANI- β-CDpNH2 film exhibits a good sensitivity towards the Pb2+ cations.This work explored the development of impedimetric sensors based on conducting polyaniline (PANI) and PANI- β-CDpNH2 thin films, formed by the complex inclusion of polyaniline with the modified β-cyclodextrin with amino groups. Thin films about 100nm were deposited by thermal evaporation on gold electrodes. These thin films were characterized by the wettability technique for hydrophobicity analysis.The electrical properties of these polymer films have been studied by electrochemical impedance spectroscopy (EIS) technique. This study has revealed, according to an equivalent circuit fitting the experimental parameters, that PANI- β-CDpNH2 film is more conductive than PANI one. This result was explained by the PANI conformation changes from coiled and disorderly chain to rodlike one coated in the cavities of β-CD.Finally we have studied the electrochemical response of these electrodes towards Pb2+ cations in the aim to probe the contribution of PANI inclusion with β-CDpNH2 molecules to the enhancement of the sensitivity and recognition properties of these later. We have found that PANI- β-CDpNH2 film exhibits a good sensitivity towards the Pb2+ cations.
Keywords: Pseudo-polyrotaxanes; Thermal evaporation; Gold electrodes; Electrochemical impedance spectroscopy (EIS)
Novel in situ electrochemical deposition of platinum nanoparticles by sinusoidal voltages on conducting polymer films
by Stelian Lupu; Boris Lakard; Jean-Yves Hihn; Jérôme Dejeu (pp. 193-198).
Cyclic voltammograms recorded at PEDOT–Pt-nanoparticles composite modified electrodes in 0.5M H2SO4 aqueous solution.Display Omitted► Novel in situ electrodeposition procedure of Pt nanoparticles on PEDOT by using sinusoidal voltages. ► The electrochemical activity of the Pt nanoparticles is excellent. ► The atomic force microscopy revealed the presence of numerous Pt nanoparticles.Platinum (Pt) nanoparticles were successfully electrodeposited in situ on an organic conductive polymer, poly(3,4-ethylenedioxythiophene) (PEDOT), using for the first time sinusoidal voltages of various frequencies in a chloroplatinic acid solution. The organic PEDOT matrix was electrodeposited on Pt electrode chips. The Pt electrode chips consist of a 150nm Pt layer deposited on 100-oriented standard 3″ silicon wafers. The cyclic voltammograms of the PEDOT–Pt-nanoparticles composite material recorded in 0.5M H2SO4 aqueous solution demonstrated that Pt nanoparticles are electrochemically active. Values of the roughness of the composite materials, measured by optical non-contact 3D profilometry, ranging from 880nm to 1.6μm were obtained depending on the time of deposition of the nanoparticles. The PEDOT–Pt-nanoparticles composite deposited by a sinusoidal voltage with a frequency range of 0.1Hz–100kHz, 50 frequencies, has a large specific electrochemical surface area compared with other composite coatings prepared in this work and those previously reported. Atomic force microscopic (AFM) images revealed the presence of numerous deposited Pt nanoparticles on the organic PEDOT polymer film.
Keywords: Atomic force microscopy; Sinusoidal voltage; Poly(3,4-ethylenedioxythiophene); Platinum metal nanoparticles
Electrosynthesis of poly ortho aminophenol films and nanoparticles: A comparative study
by A. Ehsani; M.G. Mahjani; M. Jafarian (pp. 199-204).
► Pulsed polymerization is novel process which is known for micro and nano-structures. ► A drastic improvement in conducting polymer capacitance, operating potential and stability for long cycle life is realized. ► Supercapacitor device made by pulse exhibited very high specific capacitance in comparison DC polymerized film.This paper aims to investigate the relationship between surface morphology of poly ortho aminophenol (POAP) films and synthesis conditions. POAP with different particle sizes was deposited on a glassy carbon (GC) electrode using direct current (DC) and pulse techniques. POAP nanoparticles with good electrochemical stability and high doping degree were obtained by applying ultra short on time current pulse for polymerization. The surface morphology of POAP films was revealed by using the scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and galvanostatic charge–discharge studies showed that the polymer obtained by pulses have higher electrochemical performance in acidic solution. Moreover, nanoparticles of POAP have a highly porous structure, high fractal dimension and large specific surface area, which can be employed as an excellent electrode material in supercapacitors. It was also found that the morphology of POAP varies with the synthesis conditions of the pulse.
Keywords: Nanoparticle; Electrosynthesis; Fractal; Supercapacitor
A composite of quaternized and crosslinked poly(4-vinylpyridine) with processable polypyrrole for the construction of humidity sensors with improved sensing properties
by Yang Li; Chao Deng; Mujie Yang (pp. 205-211).
► Processable polypyrrole forms a composite with a crosslinked polyelectrolyte. ► Composite is used to facilely prepare humidity sensors. ► Composite exhibits high sensitivity, fast response and very small hysteresis. ► Composite shows better humidity sensory properties than separate component.Processable polypyrrole (PPy) was prepared by solution polymerization of pyrrole in the presence of poly(ionic liquid) (PIL) and subsequent anion exchange reaction. The obtained hydrophobic PIL–PPy showed good dispersion in organic solvents, and formed a composite with quaternized and crosslinked poly(4-vinylpyridine) (QC-P4VP) by simple solution mixing and heat treatment. The structure and morphology of the composite of QC-P4VP/PIL–PPy have been characterized by FT-IR and scanning electron microscopy. It was found that PIL–PPy particles were dispersed within the matrix of QC-P4VP. Thin film humidity sensors based on the composite were facilely prepared by dip-coating and heat-induced crosslinking and quaternization. Humidity sensing properties of the sensors were investigated at room temperature. It was revealed that the sensor based on the composite exhibited higher sensitivity (impedance change from 107 to 103Ω over the range of 11–95% RH), better sensing linearity and much smaller hysteresis (∼1% RH) as compared to sensors based on QC-P4VP alone. Moreover, it was featured with fast response and good reproducibility. Attempts were made to explain the improved sensing properties of the composite.
Keywords: Poly(4-vinylpyridine); Polypyrrole; Composite; Humidity sensor; Humidity sensing properties
The chemical interaction of poly(3-octylthiophene)/titanium dioxide composite materials
by Zhiyue Han; Yue Yu; Jingchang Zhang; Xiuying Yang; Weiliang Cao (pp. 212-216).
► POT/TiO2 were synthesized by ultrasound method and in-situ method. ► The chemical interactions were discussed in the composite materials. ► The chemical bond effect is more intense in the composite prepared in in-situ method.Composite materials of poly(3-octylthiophene) and titanium dioxide (POT/TiO2) were synthesized by ultrasound method and in-situ method. The chemical interaction in the composite materials is discussed with help of X-ray diffraction patterns (XRD), X-ray photoelectron spectroscopy (XPS) and infrared spectroscopy (IR). Ultraviolet–visible spectra (UV–vis) showed that optical performance of the composite materials was far superior to POT or TiO2 separately, and the chemical bond effect was more intense in the composite material prepared in in-situ method.
Keywords: Composite materials; Ultrasound method; In-situ method; Structure; Optical property
Synthesis, two-photon absorption and optical limiting properties of new linear and multi-branched bithiazole-based derivatives
by Nannan He; Bo Li; Hao Zhang; Jianli Hua; Shuangying Jiang (pp. 217-224).
A new series of linear and multi-branched molecules containing the triphenylamine and bithiazole have been synthesized and characterized. These new compounds exhibited high two-photon absorption cross sections ( σ), in which the σ data measured by the open aperture Z-scan technique were determined to be 173, 429, 1132 and 1665 GM forBTZ-I–IV, respectively.Display Omitted► A new series of linear and multi-branched bithiazole-based compounds were designed and synthesized. ► These new compounds exhibited large two-photon absorption cross sections ( σ). ► These molecules also showed good optical-limiting properties.In this work, a new series of linear and multi-branched bithiazole-based dyes (BTZ-I–IV) possessing terminal triphenylamine group were synthesized and characterized, and their one-and two-photon absorption properties have been investigated. These new compounds exhibited large two-photon absorption cross sections ( σ), in which the σ data measured by the open aperture Z-scan technique were determined to be 173, 429, 1132 and 1665 GM forBTZ-I,BTZ-II,BTZ-III andBTZ-IV, respectively. A considerable increase in the value of 2PA cross section was obtained when triple bonds were introduced and the dimensionality and chromophore density increased.
Keywords: Bithiazole; Two-photon absorption; Optical limiting property
Synthesis and photovoltaic properties of copolymers based on 2,2-(1,5-pentamethylene)-2 H-benzimidazole
by Suhee Song; Ilsoo Kang; Gi-hwan Kim; Youngeup Jin; Il Kim; Jin Young Kim; Hongsuk Suh (pp. 225-230).
► The advantage of PMBI is high solubility while keeping the coplanarity of the backbone. ► Two new conjugated copolymers with benzimidazole prepared by Stille coupling reaction. ► The PCBBTPMBI5 thin film shows two broad absorption peaks at 454 and 654nm.We report synthesis and photovoltaic properties of two new conjugated copolymers with benzimidazole prepared by Stille coupling reaction. The advantage of PMBI is high solubility of the polymer while keeping the coplanarity of the backbone. The electrochemical bandgaps of PCDTPMBI5 and PCBBTPMBI5, calculated from cyclic voltammetry data, are about 2.11 and 2.00eV, respectively. The optical band gap of the synthesized PCDTPMBI5 (1.43eV) was smaller than that of PCBBTPMBI5 (1.56eV), caused by lower ICT effect contributed by low molecular weight of PCBBTPMBI5. The devices comprising PCDTPMBI5:PC61BM (1:2) and PCBBTPMBI5:PC61BM (1:3) with thermal treatment showed an open-circuit voltage ( VOC) of 0.27 and 0.30V, a short-circuit current density ( JSC) of 1.09 and 1.75mA/cm2, and a fill factor (FF) of 0.29 and 0.38, giving an power conversion efficiency of 0.09 and 0.20%, respectively.
Keywords: Polymer; OPVs; 2,2-(1,5-Pentamethylene)-2; H; -benzimidazole
The overall device resistance in organic thin film transistor: Application to octithiophene (8T)
by S. Mansouri; S. Zorai; R. Bourguiga (pp. 231-235).
Display Omitted► Contact resistance is due to the charge carrier injection at the metal/OSC interface. ► We report a model of overall device resistance, as a function of the gate bias VG. ► We have reproduced very well the output characteristic.Organic thin film transistors were grown with vapor-deposited polycrystalline octithiophene on silicon oxide insulating layers. The performance of an organic thin film transistor may also be affected by morphological details of the interface between the metal and organic-semiconductor near the source and the drain contact. The most important variable contribution to the contact resistance is due to the charge carrier injection at the metal/OSC interface. We have investigated how traps, at the grain boundaries of an organic semiconductor thin film layer placed between the metal electrode and the active layer can contribute to the contact resistance.In this paper we have compared two models, Meyer–Neldel rule-grain boundary trapping model (MNR–GBT) and variable range hopping model (VRH) to extract the overall device resistance of the organic thin film transistor based on octithiophene. We have reproduced very well the output characteristic IDS( VDS) using the good model of overall device resistance.
Keywords: Organic TFT; Overall device resistance; MNR–GBT model; VRH model
Synthesis, characterization and physical properties of a novel xanthan gum/polypyrrole nanocomposite
by Hamid Heydarzadeh Darzi; Saeedeh Gilani Larimi; Ghasem Najafpour Darzi (pp. 236-239).
► Synthesis of a novel polypyrrole–xanthan gum nanocomposite. ► Morphology and structure of nanocomposite was examined by AFM and FT-IR. ► Electrical conductivity of nanocomposite was enhanced by xanthan gum. ► Thermal stability of nanocomposite increases in presence of xanthan gum.Polypyrrole/xanthan gum nanocomposite was synthesized by oxidative polymerization of pyrrole in presence of xanthan gum. The atomic force microscopy (AFM) and Fourier transform infrared (FT-IR) measurements confirm the morphology and structure of synthesized nanocomposite. The nanocomposites particles size were obtained from 58 to 98nm. Also, the surface roughness parameters measured using tapping mode method showed the surface roughness of polypyrrole based nanocomposite extremely affected by xanthan gum. Thermogravimetric analyzer (TGA) curves revealed that xanthan gum can decrease the weight loss of nanocomposite and increase the thermal stability of synthesized nanocomposite as the remained ash amount is improved from 5 to 28%. Also it is found that xanthan gum could enhance the electrical conductivity up to 0.904S/cm.
Keywords: Polypyrrole; Xanthan gum; Nanocomposite; Physical property; Chemical structure