Mesoscale structures in luminescent conjugated polymer thin films studied by near-field scanning optical microscopy

We report the studies of various conjugated polymer thin films with near-field scanning optical microscopy, NSOM. Firstly, it is shown that MEH-PPV thin film undergoes significant changes in film morphology upon thermal annealing. The once homogeneous morphology becomes inhomogeneous after annealing. Secondly, polarization near-field measurements reveal mesoscale polymer ordering in PPV thin film. The average domain size and the coefficient for linear dichroism were studied as a function of film thickness. Finally, phase separation in polymer blend film was directly observed by transmission NSOM. Time-resolved fluorescence spectra indicate that the phase domains are decomposed of different fractions of the two constituent polymers. The near-field optical microscopy was also used to write lithographic patterns with a resolution of 100 nm, exceeding the diffraction limit. (C) 2001 Elsevier Science Ltd. All rights reserved

Polarization dependence of light intensity distribution from nanometer metallic slits

In this work, the near-field and far-field electric magnetic (EM) wave distributions of metallic slits was observed using tapered fiber probe and modelled using finite difference time domain (FDTD) computer simulations. The EM wave field distribution from rectangular slits with widths 100 nm, 300 nm, and 500 nm was mapped with excitation wavelength λ = 532 nm. λ/2 can be considered a characteristic length for the problem. From the experiments and FDTD simulation, E⊥ wave is found to be governed by the surface plasmon wave (SPW) which results in ill near field pattern and cannot be confined in the slit. On the contrary, E∥ wave has a well-shaped field distribution and can be confined in the slit

Comment on 'Enhancement of carrier mobility in MEH-PPV film prepared under presence of electric field' by Quanmin Shi [Chem. Phys. Lett. 425 (2006) 353]

Increased mobility in drop-cast films of MEH-PPV is obtained, when drop cast in the presence of an static electric field. We suggest that this increase is a result of a reduction of nano-domains

The morphological dependence of charge transport in a soluble luminescent conjugated polymer

Charge transport in poly[2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylene vinylene] is studied by employing the time-of-flight technique. Film morphology plays a key role in determining the charge transport properties. Samples prepared from toluene feature non-dispersive transport. However, after thermal annealing, charge transport is no longer nondispersive and hole mobility drops for about one order of magnitude. Near-field scanning optical microscope images show that annealing enhanced film inhomogeneity. We propose that the inhomogeneity is responsible for the changes in the transport properties

Structure and charge transport properties in MEH-PPV

The charge carrier transport in MEH-PPV is investigated with respect to different molecular weight distributions and with different tetrahedral defect densities. The defect density influences the charge transport behaviors significantly. With smaller defect density, MEH-PPV exhibits better charge transport which further depends upon the morphology. Position disorder parameter which is due to the morphology difference dominates the charge transport properties of low defect samples

Near-field scanner for moving molecules

A new technology that provides high optical resolution as well as very high data rates for moving molecules is presented. An important aspect of the device is the dependence of both the near-field radiation pattern and the far-field transmission of a thin slit on the polarization of the incident light

Near-field scanner for moving molecules

A new technology that provides high optical resolution as well as very high data rates for moving molecules is presented. An important aspect of the device is the dependence of both the near-field radiation pattern and the far-field transmission of a thin slit on the polarization of the incident light

Disorder controlled hole transport in MEH-PPV

We analyze the correlation between nanostructure and charge transport in poly(2-methoxy,5-(2'ethyl-hexyloxy)-p-phenylene vinylene) (MEH-PPV) films. The MEH-PPV films prepared in toluene (TL) as well as chlorobenzene (CB) solvents were investigated using the time-of-flight method and x-ray scattering. Nondispersive hole transport was observed at room temperature in devices prepared from both solutions. The field and temperature-dependent mobility were analyzed by the Gaussian disorder transport model. The positional disorder parameter in CB is larger than that in TL films. Both energy and position disorders affect the transport property in the devices from CB whereas only energy disorder affects this property in devices from TL. Correspondingly, according to the x-ray scattering measurements, the TL-cast films have larger chain-packed domains and less order-disorder transition interfaces than those for CB-cast films, along the surface normal, i.e., the charge transport direction