In order to investigate the role of carbon nanotubes in a polymer matrix, organic light-emitting diodes were fabricated from a polymer composite composed of poly (m-phenylene vinylene-co-2,5-dioctoxy-p-phenylene) (PmPV) and dispersed single-wall carbon nanotubes (SWNTs). Tris-(8-hydroxyquinolinolato) aluminum (Alq3) doped by Nile Red was used as an emissive material between the polymer composite and cathode. The device fabricated without SWNTs dispersed in the PmPV shows a dominant emission near red at 600 nm, which is in the range of the characteristic emission of Nile Red-doped Alq3, with a small amount of green emission from the PmPV. However, the devices fabricated with the polymer composite show an increase in the oscillator strength of the green emission with a dominant emission peak near 500 nm, the characteristic emission of PmPV. This was observed for SWNT concentrations up to 0.1 wt %. The shift in the emission indicates that the SWNTs in the PmPV matrix act as a hole-blocking material that results in a shifting of the recombination region from the Nile Red-doped Alq3 layer to the PmPV composite layer.
A novel conjugated polyfluorene/poly(p-phenylenevinylene) copolymer containing the pendant bis(4-alkoxyphenyl) groups in the C-9 position of every alternating fluorene unit has been synthesized and
well structurally characterized. The photoluminescence spectrum of this polymer exhibits strong
concentration and excitation wavelength dependence in solution. The excited triplet-state maximum of
polymer occurs in the region of 460−540 nm with a lifetime of 65.8 μs. This copolymer displays a
minor positive nonlinear absorption at the focus of the laser irradiation, suggesting possible reverse saturable
absorption. The stable electroluminescent spectrum of the polymer light-emitting diode device based on
this copolymer (device configuration, indium−tin oxide/Au/copolymer/LiF/Al) was obtained with a peak
wavelength of 515 nm. The bright-green emission observed over the whole active area of the copolymer
closely resembles the photoluminescence of the most concentrated solution (0.5 M) used. This suggests
that chain stacking in the solid state is responsible for the observed green electroluminescence.
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