Anisotropy of optical properties of conjugated polymer thin films by spectroscopic ellipsometry

Optical properties of thin films of conjugated poly(arylenephenylene) polymers have been determined using variable angle spectroscopic ellipsometry. Dispersion of the complex refractive index parallel, N-parallel to=(n(parallel to)+ik(parallel to)), and perpendicular, N-perpendicular to=(n(perpendicular to)+ik(perpendicular to)), to the film plane are reported for the photon energy range 1.5-5.0 eV. The energy dispersion in the optical properties has been analyzed using a three-phase model and Lorentzian dispersion functions for the polymers. The resonant frequencies of the Lorentzian oscillators describe the fundamental pi-pi(*) optical transition polarized parallel to the polymer chain and indicate additional optical transitions polarized perpendicular to the polymer chain that are introduced by interchain interactions. Dependence of the optical anisotropy and fundamental pi-pi(*) optical transition on the polymer backbone is discussed. (C) 2003 American Institute of Physics.