Synthetic Metals (v.158, #14)
Enhancement of a top emission organic light-emitting diode with a double buffer layer
by Sung Mook Chung; Chi-Sun Hwang; Jeong-Ik Lee; Sang Hee Ko Park; Yong Suk Yang; Lee-Mi Do; Hye Yong Chu (pp. 561-564).
We report on luminance characteristics of top emission organic light-emitting diode (TEOLED) containing transparent cathode with various structures of buffer layers. Especially, we have focused on the buffer layers preventing OLED degradation from plasma damages which occur during deposition of inorganic passivation layer. The TEOLED with a double buffer layer showed much higher luminance and lower leakage current than that with single buffer layer of organic layer or inorganic layer.
Keywords: TEOLED; Buffer layer; Plasma damage; Passivation layer
Poly(4-vinyltriphenylamine): Optical, electrochemical properties and its new application as a host material of green phosphorescent Ir( ppy)3 dopant
by Kun-Ming Yeh; Chih-Cheng Lee; Yun Chen (pp. 565-571).
Vinyl polymer PTPA containing pendant triphenylamine chromophore, which possesses hole-transport characteristics, was used as a host material in green phosphorescent light-emitting diodes. The PL spectrum of PTPA showed an intrinsic peak (375nm) attributed to triphenylamine groups and an excimer emission (440nm). The PL and EL spectra of the blends [PTPA:Ir( ppy)3] showed dominant green emission attributed to Ir( ppy)3 due to efficient energy transfer from PTPA to Ir( ppy)3. The HOMO level of PTPA, estimated from cyclic voltammetric data, was −5.36eV, which is higher than −5.8eV of PVK owing to hole-affinity characteristics of the pendant triphenylamine groups. The best performance was obtained with the EL device (ITO/PEDOT:PSS/PTPA:Ir( ppy)3 (1wt%):PBD (40wt%)/Ca/Al), the maximal luminance and the maximal luminance efficiency were 8358cd/m2 and 4.5cd/A, respectively. The present study suggests that the polymer PTPA is versatile host materials for green phosphorescent polymer light-emitting diodes applications.
Keywords: Light-emitting diodes; Luminescence; Phosphorescent; Polymerization
Controlled synthesis of organic–inorganic hybrid nanofibers by a wet-chemical route
by Jianhui Yang; Haishui Wang; Lehui Lu; Yibing Wang; Weidong Shi; Hongjie Zhang (pp. 572-576).
Organic–inorganic hybrid nanofibers are successfully synthesized by incorporating 3,3′,5,5′-tetramethylbenzidine (TMB) and H2PtCl6 at room temperature. The morphology and size can be simply controlled by tuning the molar ratio and initial concentration of reactants. A possible formation mechanism was suggested on the basis of the experimental results. The optical properties were investigated and the as-obtained product displays a strong fluorescence emission at room temperature that may be promising for applications in the fabrication of photoelectric materials.
Keywords: Organic–inorganic hybrid composites; Platinum; Nanostructures; Self-assembly
Fabrication of poly-3-hexylthiophene/polyethylene oxide nanofibers using electrospinning
by Alexis Laforgue; Lucie Robitaille (pp. 577-584).
P3HT–PEO blend nanofibers were produced by electrospinning from chloroform solutions. A morphological study was carried out as a function of the processing parameters as well as the ratio between the two polymers. The fibers containing at least 60wt.% of P3HT presented striated surfaces that could be explained by the alignment of the polymer domains along the fiber axis. The structural arrangement of the polymers was found to vary according to the polymers relative contents. The maximum electrical conductivity found for unaligned mats was 0.16S/cm and increased to 0.3S/cm when the nanofibers were aligned along a preferential direction.
Keywords: Nanofibers; Electrospinning; Poly-3-hexylthiophene; Conducting fiber
Electroless synthesis of nano-structured gold particles using conducting polymer nanoparticles
by Jie Ding; Hongxia Wang; Tong Lin; Bin Lee (pp. 585-589).
In this study, gold nanoparticles were synthesized by electroless recovery of [AuCl4]− from an acidic aqueous solution using nano-structured conducting polymer, polypyrrole nanoparticles, as active surface. The formation of gold nanoparticles was confirmed by TEM, SEM and EDX measurements. The effects of the initial Au(III) concentration on the gold uptake was examined. The recovery capability and gold particle morphology prepared from polypyrrole nanoparticle were compared to that from cast PPy film counterpart.
Keywords: Electroless deposition; Recovery gold ions; Conducting polymer nanoparticles; Gold nanoparticles; Capacity
Mesoporous nanocrystalline TiO2 electrode with ionic liquid-based solid polymer electrolyte for dye-sensitized solar cell application
by Pramod K. Singh; Kang-Wook Kim; Nam-Gyu Park; Hee-Woo Rhee (pp. 590-593).
Thick mesoporous TiO2 films with excellent properties have been prepared for dye-sensitized solar cell application using doctor-blade method. Scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD) show the highly crystalline mesoporous anatase TiO2 framework. On the other hand new solid electrolytes based on ionic liquid (IL) 1-methyl 3-propyl imidazolium iodide (PMII) and poly(ethylene oxide) (PEO) were prepared in film form and placed on porous-sensitized TiO2 electrode following two-step casting technique. The doping of IL further provided large numbers of ions, resulting in the enhancement in conductivity and good solar cell performance.
Keywords: Polymer electrolytes; Ionic liquid; Conductivity; Dye-sensitized solar cell; Mesoporous
Morphology characterization of polyaniline nano- and microstructures
by Alan R. Hopkins; Russell A. Lipeles; Son-Jong Hwang (pp. 594-601).
Small-angle neutron scattering (SANS), nuclear magnetic resonance (NMR), wide-angle and small-angle X-ray scattering (WAXS and SAXS) measurements were carried out to investigate the three morphological forms of polyaniline emeraldine base (PANI-EB): unstructured, microtubes, and nanofibers. Although the chemical backbone between these two materials is quite similar, their solid structures are quite different, showing differences in the molecular conformation and supramolecular packing. Detailed solid-state13C and15N NMR characterization of PANI nanofibers (compared to the unstructured, granular form) revealed a slight variation in the structural features of the polymer that led to some differences in the chemical environments of the respective nuclei. The presence of two extra-sharp peaks at 96.5 and 179.8ppm is a distinct feature found exclusively in the nanofiber spectra. Moreover, the crosspolarization (CP) dynamics study disclosed the presence of a complete set of sharp NMR peaks that are responsible for the presence of a more ordered morphology in the nanofiber. Small-angle neutron scattering indicated very sharp interfaces in the PANI fibers, which are well organized and have extremely sharp domains within the length scales probed (∼10–1nm). Overall, the X-ray scattering and spectroscopy data suggest that the nanofiber form is structurally different from the unstructured, PANI-EB powder. These differences are manifested, in part, by the additional chemistry occurring during the synthesis of the nanofibers.
Keywords: Polyaniline emeraldine base (PANI-EB); Nanofibers; Microtubes; Solid-state nuclear magnetic resonance; Wide-angle X-ray scattering; Small-angle X-ray scattering