Solvent-enhanced dye diffusion in polymer thin films for polymer light-emitting diode application

Abstract

The method of solvent-enhanced dye diffusion for patterning full-color (red, green, and blue) polymer light-emitting diode displays was investigated in detail. After local dry transfer of dye onto a device polymer film, the dye remains on the surface of the polymer layer and must be diffused into the polymer for efficient emission. Exposure of the polymer to solvent vapor at room temperature increases the dye-diffusion coefficient by many orders of magnitude, allowing rapid diffusion of the dye into the film without a long, high-temperature anneal that can degrade the polymer. The increase in diffusion is due to absorption of the solvent vapor into the polymer film, which increases the polymer thickness and decreases its effective glass transition temperature T g,eff. Measurements of the polymer in solvent vapor indicate that its thickness varies roughly linearly with pressure and inversely with temperature, with thickness increases as large as 15% often observed. A model based on Flory-Huggins theory is used to describe these results. The diffusion of the dye into the polymer was evaluated by photoluminescence and secondary-ion mass spectroscopy. This dye-diffusion increase is largest for high solvent-vapor partial pressures and, most surprisingly, is larger at lower temperatures than at higher temperatures. This anomalous temperature dependence is due to the increased solvent-vapor absorption and consequent reduction in the effective glass-transition temperature at lower temperatures.

Biocatalytic and Structural Properties of a Highly Engineered Halohydrin Dehalogenase

“…Furthermore, since the magnitudes of the diffusion constants are comparable with those of the diffusion constants of several organic molecules through standard polymers,20, 21 they are considered to be reasonable values. Hence, we may conclude that SHG can in principle be used as a method to study diffusion processes.…”

Passive wireless sensors using electrical transition of carbon nanotube junctions in polymer matrix

“…Even though the distance change is only a few ångströms, it will lead to a significant transition of electrical junctions from direct 0964-1726/06/010014+07$30.00 © 2006 IOP Publishing Ltd Printed in the UK contact to the tunneling regime in between carbon nanotubes and the electrical property change of the whole sensor film will be quite high. The number of source molecules and the interaction parameter with the matrix material determines the extent of matrix swelling and resistance variation [5]. It could be possible to choose proper materials for matrix selective sensors for the detection of various gases.…”

Solvent Content in Thin Spin-Coated Polystyrene Homopolymer Films

“…However, it is well known that the actual remaining solvent content in thin polymer films has an effect on the chain mobility and film homogeneity. [13][14][15][16][17] Consequently, the drying process is determined by the film's ability to retain the solvent and the diffusion of solvent molecules and the polymer chains. Practically, the solvent evaporation influences the thin film roughness, which occurs for the solid film.…”