Synthetic Metals (v.161, #19-20)
The effect of graphdiyne doping on the performance of polymer solar cells
by Hailiang Du; Zhenbo Deng; Zhaoyue Lü; Yuehong Yin; LingLing Yu; Hui Wu; Zheng Chen; Ye Zou; Yongsheng Wang; Huibiao Liu; Yuliang Li (pp. 2055-2057).
► Graphdiyne doping enhanced the short circuit current of PSCs. ► The doping ratio of graphdiyne plays an important role in the performance of PSCs. ► The efficient percolation path improve the transportation efficiency of charge.We have introduced graphdiyne material in poly(3-hexylthiophene)/[6,6]-phenyl-C61-buytyric acid methyl ester bulk-heterojunction solar cells. The results suggest that the doping of graphdiyne can improve the short circuit current ( Jsc) and power conversion efficiency (PCE) of the polymer solar cells. The cell with 2.5wt% graphdiyne exhibits an enhanced Jsc by 2.4mA/cm2 and the highest PCE (3.52%), which is 56% higher than that of the cell without graphdiyne doping. The improved performance is due to high charge transport capability of graphdiyne and the formation of efficient percolation paths in the active layer.
Keywords: Polymer solar cells; Graphdiyne; Doping
High mobility, low voltage operating C60 based n-type organic field effect transistors
by G. Schwabegger; Mujeeb Ullah; M. Irimia-Vladu; M. Baumgartner; Y. Kanbur; R. Ahmed; P. Stadler; S. Bauer; N.S. Sariciftci; H. Sitter (pp. 2058-2062).
► n-Type C60 organic field effect transistors optimized for low voltage operation. ► Thin parylene-C films are employed as dielectric layers. ► Metal oxides capped with organic films lead to optimized dielectric properties. ► Mobilities in the range of 3cm2V−1s−1 are possible at operating voltages below 1V.We report on C60 based organic field effect transistors (OFETs) that are well optimized for low voltage operation. By replacing commonly used dielectric layers by thin parylene films or by utilizing different organic materials like divinyltetramethyldisiloxane-bis(benzocyclo-butene) (BCB), low density polyethylene (PE) or adenine in combination with aluminum oxide (AlOx) to form a bilayer gate dielectric, it was possible to significantly increase the capacitance per unit area (up to two orders of magnitude). The assembly of metal-oxide and organic passivation layer combines the properties of the high dielectric constant of the metal oxide and the good organic–organic interface between semiconductor and insulator provided by a thin capping layer on top of the AlOx film. This results in OFETs that operate with voltages lower than 500mV, while exhibiting field effect mobilities exceeding 3cm2V−1s−1.
Keywords: OFET; C; 60; High mobility; Dielectric; Low voltage
Synthesis and electrical conductivity evaluation of novel hybrid poly (methyl methacrylate)/titanium dioxide nanowires
by Ahmed A. Haroun; Ahmed M. Youssef (pp. 2063-2069).
► In this study, the hybrid PMMA/TiO2 nanowires was prepared via in situ emulsion polymerization of methyl methacrylate in presence of cetyl trimethyl ammonium bromide and potassium persulfate as a cationic surfactant and initiator, respectively. ► The addition of the Polyaniline during emulsion polymerization of MMA exhibited an excellent conductivity. Moreover, the resultant nanocomposite particles exhibited structure of core–shell. ► Meanwhile, there is chemical interaction between titanium particles and PMMA chain, which were documented by FT-IR. ► Furthermore, the conductivity of the prepared hybrid PMMA nanocomposites was improved when the TiO2 nanowires concentration was increased. In addition to, the presence of both polyaniline and silver nanoparticles enhanced the conductivity from 0.37 to 20s/cmThis work aims at preparation, characterization and electrical conductivity evaluation of novel poly (methyl methacrylate), PMMA, based nanocomposites. The sodium titanate nanowire (Na2Ti nO2 n+1) was prepared using titanium dioxide nanoparticles via hydrothermal treatment method. The hybrid PMMA nanocomposites were prepared by in situ emulsion polymerization of methyl methacrylate in presence of cetyl trimethyl ammonium bromide and potassium persulfate as a cationic surfactant and initiator, respectively. In addition to, PMMA/polyaniline (PA)-based nanocomposites were obtained by adding sodium titanate nanowires and/or silver nitrate nanoparticles into the polymer mixture. Differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) transmission electron microscope (TEM), scanning electron microscope (SEM), X-ray diffraction pattern (XRD) and infrared spectroscopy (FT-IR) were used to characterize the structures of the nanocomposites. The resultant nanocomposites exhibited core–shell structure. Moreover, the conductivity of the prepared hybrid PMMA nanocomposites was increased from 1.32×10−8 to 5.9×10−5scm−1 with an increasing of the titanium dioxide nanowires concentration.
Keywords: Poly (methyl methacrylate); Titanium dioxide; Conductivity; Nanowires
Effect of nature of addends and ionic dopant on magnetic properties of multifunctional star-like hemi-ortho ester derivatives of fullerenol
by Rachana Singh; Thakohari Goswami (pp. 2070-2077).
► Magnetic properties of hemi-ortho esters derivatives of fullerenol are reported. ► Effect of substitution at carbonyl carbon of vinyl esters on magnetic properties is established. ► Effect of TBAH doping on magnetic properties is established. ► Materials have promising magnetic effect at room temperature.Effect of alkyl/aryl substitution at carbonyl carbon and doping effect of tetra butyl ammonium hydroxide (TBAH used as phase transfer catalyst during two phase synthesis) on magnetic properties of multiple double bonds terminated acyclic hemi-ortho esters derivatives of fullerenol is reported. Strong π– π interactions between vinylic double bonds and fullerene core induce higher g-value (2.002–2.58), larger peak width (Δ HPP=1375–9) and fast spin–spin relaxation ( T2) compared to pristine fullerenol at room temperature. Steric hindrance owing to bulky alkyl/aromatic groups at carbonyl carbon substantially affects the g-value and ultimately the magnetic properties. Iso-propylene unit in vinyl ester produces interesting diamagnetic character at low temperature (25–300K) and paramagnetic behavior at room (300K) as well as at very low temperature (10–25K). Low temperature paramagnetic behavior (45–300K) and anti-ferromagnetic character below Curie temperature ( Tc at 45K) in vinyl acetate hemi-ortho ester is substantiated through SQUID measurement. Partial quenching of paramagnetism lowers the experimental spin-only magnetic moment value ( μ B=4.47B.M.) compared to theoretical μ B-value (4.89B.M.) for S=2 spin system (four unpaired electron) at 300K for hemi-ortho ester in the solid state.
Keywords: Hemi ortho-ester derivatives; Fullerenol; SQUID; ESR
Facile synthesis and characterization of carbon nanotubes/silver nanohybrids coated with polyaniline
by Van Hoa Nguyen; Jae-Jin Shim (pp. 2078-2082).
Display Omitted► MWNTs/silver nanoparticles(Ag NPs)/polyanilinecomposites were prepared efficiently. ► MWNTs were decorated with Ag NPs and then coated with PANI layers. ► The composites had nanotubular morphology with an average diameter of 15–20nm. ► The composites with 10% Ag had high electrical conductivities of up to 15.4Scm−1. ► The composites had high electrochemical activities and good cyclic stabilities.Novel composites that consisted of multi-walled carbon nanotubes (MWNTs), silver nanoparticles (Ag NPs), and polyaniline (PANI) were prepared via a facile and efficient two-step method. Firstly, the surfaces of MWNTs were decorated with Ag NPs at room temperature and then MWNT/Ag nanohybrids were coated with PANI layers by the in situ polymerization of aniline. The formation and incorporation of Ag NPs and PANI on the surface of MWNTs were confirmed by XRD and FT-IR. The TEM and SEM images revealed that highly dispersed MWNT/Ag/PANI composites had nanotubular composite morphologies with an average diameter of 15–20nm. The electrical conductivity of the MWNT/Ag/PANI composites was 15.4Scm−1, which was higher than that of pure PANI and crude MWNTs. Moreover, the cyclic voltammetry (CV) analysis of the composite electrodes indicated that the obtained product had high electrochemical activity and good cyclic stability.
Keywords: Multi-walled carbon nanotube; Silver nanoparticle; Conducting polymer; Coating; Self-assembly
Pentacene doping for the efficiency improvement of polymer solar cells
by Hailiang Du; Zhenbo Deng; Jianchao Lun; Maoyang Zhou; Yuehong Yin; Ye Zou; Zhaoyue Lü; Zheng Chen; Yongsheng Wang (pp. 2083-2086).
► Pentacene doping enhanced the short circuit current of PSCs. ► The doping ratio of pentacene plays an important role in the performance of PSCs. ► The absorption of pentacene doping in active layer nearly unchanged. ► The well aligned energy levels improve the dissociation efficiency of exciton.In poly(3-hexylthiophene) (P3HT) mixed with [6,6]-phenyl-C61-buytyric acid methyl ester (PCBM) bulk-heterojunction solar cells, organic small molecular pentacene was introduced as dopant in P3HT:PCBM active layer. The results suggest that the doping of pentacene can improve the short circuit current ( Jsc) and power conversion efficiency (PCE) of the polymer solar cells. The cell with 0.4wt.% pentacene exhibits an enhanced Jsc by 2.08mA/cm2 and the highest PCE (2.36%), which is 20% higher than that of the cell without pentacene doping. The improved performance is mainly due to efficient dissociation of exciton in active layer caused by pentacene doping.
Keywords: Polymer solar cells; Pentacene; Doping
High hole mobility through charge recombination interface in organic light-emitting diodes
by Baye Boucar Diouf; Woo Sik Jeon; Jung Soo Park; Jin Woo Choi; Young Hoon Son; Dae Chul Lim; Yoo Jin Doh; Jang Hyuk Kwon (pp. 2087-2091).
We report the effects of non-radiative charge recombination interface resulting on high hole mobility and low driving voltage characteristics in organic light-emitting devices. These effects are demonstrated in the following device architecture: hole transporting layer (HTL)/extremely deep LUMO (lowest unoccupied molecular orbital) electron transporting layer (ETL)/HTL. The extremely small gap between the high HOMO (highest occupied molecular orbital) of the HTL and the deep LUMO of the ETL leads to facilitate the hole conduction through charge recombination at the interface. The excellent hole mobility of 4.7×10−1cm2/Vs in this device configuration is measured by the space charge limited current method with an electric field of 0.1MV/cm. We suggest that such a high hole mobility is attributed to the rapid coulombic interaction at the charge recombination interface in addition to the hole and electron mobilities of the individual HTL and ETL, respectively.
Keywords: Mobility; Charge recombination; Interface; Driving voltage; Coulombic interaction
Synthesis and characterization of poly(triphenylamine)s with electron-withdrawing trifluoromethyl side groups for emissive and hole-transporting layer
by Guntae Kim; Fevzihan Basarir; Tae-Ho Yoon (pp. 2092-2096).
Poly(triphenylamine)s with electron-withdrawing trifluoromethyl side groups were prepared to afford ambipolar type polymers that can be used as not only an emissive layer but also a hole-transporting layer for PLEDs. First, triphenylamine-based monomers with trifluoromethyl side group were prepared, such as N,N-diphenyl-4-(trifluoromethyl)benzeamine (3FTPA) and N,N-diphenyl-3,5-bis(trifluoromethyl)benzeamine (6FTPA). Next, they were brominated and bolorated and then utilized to prepare poly(triphenylamine)s via Suzuki coupling reaction. The resulting polymers were characterized by NMR, GC/MS, FT-IR, TGA and DSC, while optical and electrical properties were also measured by fluorescence spectroscopy, UV–vis spectroscopy, and cyclic voltammetry (CV). The polymers exhibited deep blue emission (422, 443nm) and high Tgs (225, 209°C).
Keywords: Triphenylamine; Trifluoromethyl; Polymer light emitting diode; Blue emission; Hole transporting
Solid-state synthesis and characterization of polyaniline/multi-walled carbon nanotubes composite
by Aminam Ubul; Ruxangul Jamal; Adalet Rahman; Tunsagul Awut; Ismayil Nurulla; Tursun Abdiryim (pp. 2097-2102).
Display Omitted► The solid-state synthesis method can be applied for fabrication of the PANI/MWNTs composite. ► The strongest interaction between the PANI and MWNTs occurs in the composite with 16wt% MWNTs. ► The composite with 16wt% PANI/MWNTs has better electrochemical performances than others.The polyaniline/multi-walled carbon nanotubes (PANI/MWNTs) composites with content of MWNTs varying from 8wt% to 32wt% were prepared by a novel solid-state synthesis method. The structure and morphology of the composites were characterized by the Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, ultraviolet–visible (UV–vis) absorption spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The electrochemical performances of the composites were investigated by galvanostatic charge–discharge measurement, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The results from FTIR spectra showed that the composites display a higher oxidation degree than PANI, and the composite with 16wt% MWNTs has the highest intensity ratio of quinoid to benzenoid ring modes. The UV–vis and Raman spectra revealed that the some interaction between the PANI and MWNTs occurred in the composites. The result from XRD revealed the presence of MWNTs in the polymer matrix. And the morphological studies showed that the composite with 16wt% MWNTs displayed nano-sized granular-like particles with spongy and highly porous morphology, while the composite with 32wt% MWNTs displayed rod-like features. The galvanostatic charge–discharge measurements indicated that the PANI/MWNTs composites had higher specific capacitances than PANI. The composite with 16wt% MWNTs had the highest specific capacitance among the composites. The further electrochemical tests on the composite with 16wt% MWNTs showed that the composite displayed an ideal capacitive behavior and good rate ability.
Keywords: Polyaniline; Carbon nanotubes; Composite materials; Solid-state synthesis; Electrochemical properties
Core–shell nanoparticle of silver coated with light-emitting rubrene: Surface plasmon enhanced photoluminescence
by Yoon Deok Han; Jin Woo Lee; Dong Hyuk Park; Seung Ho Yang; Bo Kyung Kim; Jeongyong Kim; Jinsoo Joo (pp. 2103-2106).
► Fabrication of Ag–rubrene core–shell nanoparticles (NPs) through hydrothermal process. ► Enhancement of PL efficiency of the core–shell single NP by about 300 times. ► The increase of the PL can be explained by energy transfer effect in surface plasmon resonance coupling.Silver (Ag) nanoparticles (NPs) with a diameter of 50–100nm were fabricated by using a reduction process of silver nitrate with sodium citrate. Using the Ag NPs, hybrid core (Ag)–shell (organic light-emitting rubrene) NPs were prepared through a hydrothermal process. The formation of hybrid core–shell NP of Ag-rubrene was confirmed through transmission electron microscope images. From ultraviolet and visible absorption spectra, the Ag and rubrene characteristic peaks were simultaneously observed for the core–shell NPs. Using a high-resolution laser confocal microscope (LCM), the photoluminescence (PL) intensity of the Ag–rubrene core–shell single NP was about 300 times higher than that of the rubrene single NP. This remarkable enhancement of PL efficiency in the core–shell single NP is due to the energy transfer effect in the surface plasmon resonance coupling between Ag and rubrene materials.
Keywords: Nanoparticle; Core–shell; Rubrene; Silver; Surface plasmon; Photoluminescence
Effects of film morphology on ambipolar transport in top-gate-type organic field-effect transistors using poly(9,9-dioctylfluorene-co-bithiophene)
by Kyohei Koiwai; Hirotake Kajii; Yutaka Ohmori (pp. 2107-2112).
► Structure ordering in F8T2 films has a strong influence on ambipolar characteristics. ► Improving the interface geometry of the F8T2 film led to an increase in mobility. ► Improving the interface geometry led to the appearance of ambipolar characteristics. ► Ambipolar F8T2 devices exhibited yellow EL emissions. ► Devices exhibited maximum external quantum efficiency of approximately 0.2%.The effects of film morphology on ambipolar transport in solution-processed top-gate-type organic field-effect transistors (OFETs) utilizing poly(9,9-dioctylfluorene-co-bithiophene) (F8T2) films were investigated. All the F8T2 OFETs without toluene-vapor treatment showed ambipolar characteristics. In contrast, for toluene-vapor-treated F8T2 films at below 250°C, which were observed to have a small fibrillar structure and a large number of grain boundaries, electron conduction decreased remarkably. Structure ordering in F8T2 films has a strong influence on ambipolar charge transport in OFETs. With an increase in the annealing temperature, the electron transport characteristics were improved. Improving the interface geometry of the F8T2 film, which is related with the decrease of grain boundaries, led to an increase in mobility, and the appearance of ambipolar characteristics. These results suggest that the appearance of electron conduction results not only from the increase in grain size but also from improvements in the connections between grain boundaries in F8T2. Ambipolar F8T2 OFETs exhibited yellow EL emissions, hole and electron field-effect mobilities of approximately 10−3cm2V−1s−1, and maximum external quantum efficiency of approximately 0.2%.
Keywords: Ambipolar organic field-effect transistor; Polyfluorene; Film morphology; Top-gate; Light-emitting device
The role of phonon- and photon-coupled interactions in electron pairing in solid state materials
by Takashi Kato (pp. 2113-2123).
Display Omitted► Diamagnetic currents in cyclobutadiene dianion cannot be explained by the BCS theory. ► The photon-coupled interactions play a role in the attractive electron–electron interactions. ► The photon-coupled interactions do not play an essential role in the decision of the Tc. ► The phonon-coupled interactions play a role in the decision of the Tc. ► Large energy gap is formed by quantization of orbitals by nature in small sized molecules.The essential role of the phonon- and photon-coupled interactions in the electron pairing in the macroscopic sized conventional superconductivity is investigated by comparing the conventional superconductivity in the macroscopic sized materials with the nondissipative diamagnetic currents in the negatively charged small sized molecules such as cyclopentadiene monoanion (5an−) and cyclobutadiene dianion (4an2−). The nondissipative diamagnetic currents in the negatively charged small sized molecules such as5an− and4an2− cannot be explained by the Bardeen–Cooper–Schrieffer (BCS) theory because attractive phonon-coupled interactions between two electrons ( V6 π, N,BCS,phonon,e–e) are zero and direct electron–electron repulsion ( V6 π, N,BCS,repulsive,e–e) becomes very large. However, these phenomena in5an− and4an2− can be well explained by the photon-coupled interactions between all nuclei and electrons. The phonon-coupled interactions ( Vphonon,e–e) play an essential role in the forming of the closed-shell electronic structures with finite valence–conduction band gaps, in which two electrons occupying the same orbitals with opposite momentum and spins become stable, and the photon-coupled interactions ( Vmacro,photon, N, j, σ) play an essential role in attractive interactions between these two electrons. Because of the photon-coupled interactions as well as the phonon-coupled interactions, electron pairs can be formed in the macroscopic sized materials, and the conventional superconducting states can appear below the superconducting critical temperature ( Tc). Our molecular perspective suggested in this article is compared with the BCS theory, and the reason why the conventional superconductivity has been excellently explained by the BCS theory is also discussed.
Keywords: Phonon-coupled interactions; Photon-coupled interactions; Electron pairing; Small sized molecules; Macroscopic sized materials
Synthesis and antibacterial performance of size-tunable silver nanoparticles with electrospun nanofiber composites
by Hang Hoon Chae; Bo-Hye Kim; Kap Seung Yang; Jong Il Rhee (pp. 2124-2128).
► Investigation of a simple route to prepare well-controlled silver nanoparticles in nanofibers via an electrospinning process. ► Antibacterial performance of size-tunable silver nanoparticles with electrospun nanofiber composites. ► The combined effects of the antibacterial activity of silver and bacterial adhesion onto the nanofiber surface.A simple one-step method using by β-cyclodextrin (β-CD) and polyacrylonitrile (PAN) solution was used for preparing electrospun nanofiber (NF) composites containing silver nanoparticles by electrospinning. The β-CD acted as a stabilizing and reducing agent for the formation of silver nanoparticles. In addition, the average size of the silver nanoparticles could be tuned by changing the concentration of β-CD. The surface and pore properties were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectronic spectroscopy (XPS), and Brunauer–Emmett–Teller (BET) measurements. The antimicrobial activities of NFs containing silver nanoparticles (Ag/NFs) against Escherichia coli ( E. coli) and Staphylococcus epidermidis ( S. epidermidis) were evaluated by optical density testing.
Keywords: Antibacterial activity; β-Cyclodextrin; Silver; Electrospinning; Nanofiber composite
Patterning quality control of inkjet printed PEDOT:PSS films by wetting properties
by F. Ely; C.O. Avellaneda; P. Paredez; V.C. Nogueira; T.E.A. Santos; V.P. Mammana; C. Molina; J. Brug; G. Gibson; L. Zhao (pp. 2129-2134).
Display Omitted► Surface treatment improves the quality of inkjet printed patterns. ► Higher surface free energy results in smoother and more uniform PEDOT films. ► Rainbow-like features and non-uniformities observed at the edges are reduced by decreasing PEDOT content in the ink.In this contribution, we describe the development of inkjet printable PEDOT:PSS polymer-based inks for fabrication of polymeric organic light-emitting devices (OLEDs). By using a 10×10 array of SU8 wells on ITO/glass substrates, guided deposition of PEDOT in a simulated OLED pixel structure was possible. The quality of the printed patterns was controlled by fine tuning of the surface wetting properties using self-assembled monolayers (SAMs) and/or oxygen reactive plasma. All the investigated surface treatments improved the quality of the printed pattern. However, the O2 plasma treated surfaces, which had the highest free energy, resulted in smoother and more uniform PEDOT films than did the SAM-coated surfaces. Rainbow-like features and non-uniformities observed at the edges of the film were attributed mostly to the well-known coffee stain effect and the drying environment. A good reduction of such features was achieved by decreasing the PEDOT content in the inks.
Keywords: Surface wetting properties; PEDOT:PSS; Inkjet printing; OLED
Characterization of electrical and optical absorption of organic based methyl orange for photovoltaic application
by A.A.M. Farag; A.M. Mansour; A.H. Ammar; M. Abdel Rafea (pp. 2135-2143).
► The methyl orange film shows thermal stability. ► The films behave as p-type semiconductor. ► The absorption mechanism is due indirect allowed transition. ► The thickness dependence on the dark and illuminated J-V characteristics was considered.Thin films of methyl orange (MO) were successfully prepared using thermal evaporation technique from their powder. Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) were performed for studying the thermal stability of MO. The surface morphology of thin films was studied by using scanning electron microscopy (SEM). The crystalline structure of MO powder and films were studied by using X-ray diffraction (XRD) and their lattice parameters were found to be the same. The temperature dependence of dark electrical conductivity ( σ) and Seebeck's coefficient ( S) for MO thin films in the temperature range of 300–450K have been investigated for different thicknesses in the range 300–700nm. This dependence was found to be typical for p-type semiconductor which was correlated with the MO molecular structure. The optical properties of MO films were investigated by UV–vis spectrophotometry which was analyzed to obtain the electronic transition, optical band gap ( Eg) and Urbach energy ( E0). An allowed indirect optical transition was observed for MO and the band gap was found to be thickness independent and equal to 2.02eV. A strong rectification characteristic of Au/MO/n-Si heterojunction was obtained from the current density–voltage measurements under dark condition. The photovoltaic characteristics of the device were studied under 100mW/cm2 and the effect of film thickness was also considered.
Keywords: Organic semiconductors; Electrical conductivity; Seebeck coefficient; Photovoltaic
Synthesis and microwave absorption properties of SiC–carbon fibers composite in S and C band
by Ju-Min Zhao; Wen-Xiu An; Deng-Ao Li; Xiaoli Yang (pp. 2144-2148).
► SiC powders were synthesized from the Si/C system in a nitrogen atmosphere by combustion synthesis. ► The carbon fiber/SiC composite with different mixture ratios have been prepared by as-prepared material. ► The effect of the mol ratio of carbon fiber/SiC on the microwave loss properties of the composites is investigated. ► A possible microwave absorbing mechanism of carbon fiber/SiC composite has been proposed.SiC powders were synthesized from the Si/C system in a nitrogen atmosphere by combustion synthesis. The carbon fiber/SiC composite with different mixture ratios have been prepared by as-prepared material. The structure, morphology and properties of the composites are characterized with IR, XRD, scanning electron microscope (SEM), Network Analyzer. The complex permittivity (ε′r−jε″r) and reflection loss (dB) of the composites have been measured at different microwave frequencies in S-band and C-band (30–6000MHz) employing vector network analyzer model PNA 3629D vector. The effect of the mol ratio of carbon fiber/SiC on the microwave loss properties of the composites is investigated. A possible microwave absorbing mechanism of carbon fiber/SiC composite has been proposed. The carbon fiber/SiC composite can find applications in suppression of electromagnetic interference (EMI), and reduction of radar signature.
Keywords: Ceramics; Composite materials; Microstructure; Microwave absorption
High efficiency all phosphorescent white light-emitting diodes based on conjugated polymer host
by Qiaoli Niu; Junbiao Peng; Yong Zhang; Yong Zhang; Bo Liang (pp. 2149-2153).
► Conjugated polymer PFO was used as the matrix of phosphorescent dyes. ► Double doping ratio of FIrpic and Ir(DMFPQ)2pbm in PFO was tuned to 10:1 to achieve white light. ► Back energy transfer was suppressed by hole-transport layer PVK. ► Performances of the WPLEDs were improved via introducing CBP into PVK.High efficiency all phosphorescent white electroluminescence was realized by double doping of blue-light-emitting bis(2-(4,6-difluorophenyl)-pyridinato-N,C2′) picolinate (FIrpic) and red iridium complex Ir(DMFPQ)2pbm into conjugated polymer host poly(9,9-dioctylfluorene) (PFO). Effects of hole-transport layer (HTL) on the performances of white polymer light-emitting diodes (WPLEDs) were investigated. First of all, PVK as the HTL was essential, because the back energy transfer from FIrpic to PFO caused by the low-lying triplet energy level of PFO was suppressed by PVK. Furthermore, performances of the WPLEDs were enhanced by introducing CBP into PVK owing to improved balance of electron and hole current. The resulting all phosphorescent WPLEDs have a peak luminous efficiency of 15.5cd/A and a peak power efficiency of 6lm/W. Commisssion Internationale de L’Eclairage (CIE) coordinates of (0.41, 0.38) were realized at a current density of 18mA/cm2. The obtaining of the efficient all phosphorescent white electroluminescence with PFO as host polymer will broaden the approaches of white light generation and be a big promote for the application of phosphorescent WPLEDs.
Keywords: Phosphorescent; Back energy transfer; White polymer light-emitting diode; Conjugated polymer
Electronic energy transfer between poly(9,9′-dihexylfluorene-2,2-dyil) and MEH-PPV: A photophysical study in solutions and in the solid state
by René A. Nome; Hueder P.M. de Oliveira; Leni Akcelrud; Teresa D.Z. Atvars (pp. 2154-2161).
Display Omitted► Description of the lower efficient energy transfer processes in solutions. ► Demonstration that FRET is a high efficient process in films. ► Evidences that trivial process is present in both solutions and films.Some aspects of the energy transfer processes between poly(9,9′-dihexylfluorene-2,2-dyil) and MEH-PPV in solutions of good and poor solvents and in solid state blends are addressed. The resonant non-radiative energy transfer in solution is discussed in terms of the Förster dynamic model and using steady-state and dynamical photoluminescence we observed that it is a very inefficient process, almost independently of the solvent. Also in solution the intensity decrease was discussed in terms of trivial energy transfer process. On the other hand, in solid state the resonant non-radiative energy transfer process is more relevant and strongly dependent on the MEH-PPV concentration in the blends. In this case, Förster approach may be relevant but it is not good enough to correlate the quenching efficiency with the blend composition. Trivial energy transfer process together with resonant energy transfer process play an important role for systems with donor higher concentration.
Keywords: Poly(9,9′-dihexylfluorene-2,2-dyil); MEH-PPV; Solvent effects; Electronic energy transfer; FRET; Polymer blends
Elaboration and characterization of polyaniline films electrodeposited on tin oxides
by C.C. Buron; B. Lakard; A.F. Monnin; V. Moutarlier; S. Lakard (pp. 2162-2169).
► Electrochemical polymerization of polyaniline films on fluorine tin oxide and indium tin oxide. ► Characterization of electropolymerized films (IRRAS, XRD). ► Determination of polymer's film properties: thickness, roughness, morphology (profilometry, SEM, AFM).This paper presents the electrochemical synthesis of polyaniline films on fluorine tin oxide (FTO) and indium tin oxide (ITO) in acidic medium by both potentiodynamic and potentiostatic methods. The use of potentiodynamic deposition showed that conductive polyaniline films were synthesized by the same process than on noble metals and allowed the determination of the electrodeposition potential used for further potentiostatic electrodepositions. The electropolymerization was then performed by chronoamperometry and appeared easier on ITO than on FTO. The electrodeposited polyaniline films were extensively characterized in terms of chemical nature, electrochemical growth, thickness, roughness and morphology. The chemical nature of the films was identified through infrared spectroscopy and X-ray diffraction analyses. The roughness and the morphology of the polymer coatings, determined by profilometry, scanning electron microscopy and atomic force microscopy, were correlated to the calculated thickness of each polyaniline film and to the nature of the substrate.
Keywords: Polyaniline; Tin oxides; Electrochemistry; Surface analysis; Atomic force microscopy
Synthesis and electrochemical properties of Li3V2(PO4)3/MWCNTs composite cathodes
by Yong Zhang; Yan Lv; Lizhen Wang; Aiqin Zhang; Yanhua Song; Guangyin Li (pp. 2170-2173).
► The first study to apply MWCNTs for the synthesis of Li3V2(PO4)3 (LVP)/MWCNTs materials. ► Novel methods for the synthesis of LVP/MWCNTs by microwave assisted sol–gel method. ► The doping of MWCNTs can greatly improve the high rate dischargeability of LVP/MWCNTs electrode. ► The J0 is 2.92mAcm−2, which is larger compared with the results of J0 reported by other articles.Multi-walled carbon nanotubes (MWCNTs)-doped lithium vanadium phosphate Li3V2(PO4)3 (LVP)/MWCNTs x ( x=0, 1, 3, 4, 5, 7wt.%) cathode materials for lithium ion batteries are synthesized by a microwave assisted sol–gel method. Moreover, the influences of doped MWCNTs on the physicochemical and electrochemical properties of the as-prepared samples are investigated by X-ray diffraction (XRD), scanning electron microscope (SEM) and electrochemical experiments. The results show that the optimal doping amount of MWCNTs is 4wt.%. Under this condition, the LVP/MWCNTs4wt.% sample has an monoclinic structure, the average particle size is about 0.2–4μm with very fine particle size, uniform shape and loose agglomeration. When charge/discharge at 0.1C, the sample reached the maximum discharge capacity (130mAhg−1), which is comparable to its theoretical capacity. Comparing with the sample obtained by conventional solid-state route, the obtained materials display lower charge transfer resistance, higher rate capability and excellent reversibility. The above experiments demonstrate that the LVP/MWCNTs4wt.% is a very promising cathode material which will be used in the future for lithium ion batteries.
Keywords: Multi-walled carbon nanotubes; Lithium vanadium phosphate; Physicochemical and electrochemical properties
Efficiency enhancement of inverted organic photovoltaic devices with ZnO nanopillars fabricated on FTO glass substrates
by Ziyang Hu; Jianjun Zhang; Yan Liu; Yuning Li; Xiaodan Zhang; Ying Zhao (pp. 2174-2178).
ZnO nanopillars are grown on a ZnO seed layer on fluorine-doped tin oxide (FTO)-coated glass substrates for the fabrication of inverted organic photovoltaic devices based on poly(3-hexylthiophene) and (6,6)-phenyl C61-butyric acid methyl ester. It is found that the oriented ZnO nanopillars play an important role in collecting photogenerated electrons and act as an electron-transport path to the cathode. OPV devices with a ZnO nanopillar layer grown on a ZnO seed layer exhibit a threefold increase in power conversion efficiency compared with that of devices with a ZnO seed layer only.
Keywords: Inverted organic photovoltaic; ZnO nanopillar; Electron collection; Electron transport, Photovoltaic performance
Micro/mesoporous conducting carbonized polyaniline 5-sulfosalicylate nanorods/nanotubes: Synthesis, characterization and electrocatalysis
by Aleksandra Janošević; Igor Pašti; Nemanja Gavrilov; Slavko Mentus; Gordana Ćirić-Marjanović; Jugoslav Krstić; Jaroslav Stejskal (pp. 2179-2184).
► Simple and efficient synthesis of conducting carbonized PANI nanorods/nanotubes. ► Carbonized PANI nanorods/nanotubes represent new class of micro/mesoporous material. ► Carbonized PANI nanorods/nanotubes have excellent electrocatalytic activity for ORR.Micro/mesoporous conducting nitrogen-containing carbon nanorods/nanotubes with high surface area, and excellent electrocatalytic activity for the oxygen reduction reaction, were synthesized by the carbonization of self-assembled polyaniline (PANI) 5-sulfosalicylate nanorods/nanotubes. Carbonization was carried out by means of gradual heating in a nitrogen atmosphere up to 800°C. The morphology of the PANI 5-sulfosalicylate was preserved after carbonization. Carbonized PANI nanostructures containing ∼10wt% of nitrogen had a conductivity of 0.8Scm−1. The influence of the carbonization on the porosity and specific surface area of the nanostructured PANI has been analyzed. The morphology, elemental composition, molecular structure, surface area, and electrical characteristics of novel carbonized nanostructured PANI were investigated by scanning and transmission electron microscopies, elemental microanalysis, FTIR and Raman spectroscopies, nitrogen adsorption–desorption and conductivity measurements, respectively. The electrocatalytic activity of carbonized PANI 5-sulfosalicylate nanorods/nanotubes material towards oxygen reduction reaction in alkaline conditions has been studied by the voltammetry with the rotating disc electrode.
Keywords: Carbonized polyaniline; Electrocatalysis; Nanorods; Nanotubes; Oxygen reduction