Ellipsometric Determination of Anisotropic Optical Constants in Electroluminescent Conjugated Polymers

Abstract

Structural information about the degree of chain alignment in thin polymer films can be obtained by ellipsometry. A combination of reflection and transmission ellipsometry has been employed to determine the ordinary and extraordinary optical constants in conjugated polymer films in both the absorbing and transparent regions. Optical constants obtained by this technique will allow accurate modeling of the optical structure of polymer light‐emitting diodes (LEDs) and photodiodes.

Unification of the Hole Transport in Polymeric Field-Effect Transistors and Light-Emitting Diodes

“…The large differences in mobility values obtained from diodes and FETs, based on a single semiconducting polymer, are direct results of the large differences in charge densities in these devices. It should be noted that in OC 1 C 10 -PPV the optical properties exhibit a significant anisotropy, pointing to a preferential alignment of the chains in the plane of the film [16]. A possible anisotropy in the charge transport properties would obscure a direct comparison between diodes and FETs.…”

Plasmonic electrodes for bulk-heterojunction organic photovoltaics: a review

“…58 While most conjugated polymers tend to have optical transition dipole moments oriented along the polymer backbone chain direction [hence, transition dipoles are typically in-plane due to the edge-on and face-on orientations that most conjugated polymers take during the solution-deposition process, Figs. 9(a) and 9(b)], [100][101][102][103][104] polymers such as PVK, with the conjugation occurring on the side group rather than the polymer backbone itself, satisfy the requirement for an out-of-plane transition dipole moment. 105 Additionally, polymer chains may align in the out-of-plane direction under certain circumstances, such as during electrochemical polymerization of P3HT in the vertically oriented pores of an AAO membrane, as evidenced by photoluminescence anisotropy studies.…”

Anisotropy of exciton migration in poly(p-phenylene vinylene)

“…Assuming most of the polymer chains aligned parallel to the layer, 3,5,6 this suggests that the exciton migration is governed by interchain hopping between conjugated segments on different polymer chains. The dominance of interchain exciton transport is in qualitative agreement with the result derived from conjugated polymers that are aligned and encapsulated into the channels of mesoporous silica glass.…”

“…The optical properties of spin-coated conjugated polymer films are known to exhibit a significant anisotropy, pointing to a preferential alignment of the chains in the plane of the film. 3,5,6 Consequently, a dominance of either intrachain or interchain energy transfer will lead to a strong anisotropy of the exciton migration in thin conjugated polymer films.…”