Nonlinear optical changes in the complex index of refraction in conducting polymer-methanofullerene films evaluated by photoexcitation spectroscopy

Abstract

We report photoinduced absorption and photoinduced reflectance spectra of poly(3-octyl thiophene)- methanofullerene films. The data allow direct evaluation of the corresponding changes in the complex refractive index, (Delta) N equals (Delta) n((omega) )+i(Delta) (kappa) ((omega) ), of the films. As a results of the efficient photoinduced intermolecular charge transfer, the magnitudes of (Delta) n((omega) ) and (Delta) (kappa) ((omega) ) are significantly enhanced over those in either of the component materials, with (Delta) n and (Delta) (kappa) approximately equals 10-2 in the infrared at laser pump intensity of only 50mW/cm2. Moreover, the photoinduced absorption shows new features at 1.2 eV and 1.6 eV, both of which are associated with excited state absorptions of the methanofullerene anion. The implications of these photoinduced changes in the index resulting from photoexcitations are discussed in terms of potential optoelectronic and nonlinear optical applications of these materials, indicating that conducting polymer/methanofullerene films are promising as high- performance nonlinear optical materials.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.