INFRARED PHOTOEXCITATION SPECTRA OF CONDUCTING POLYMER METHANOFULLERENE FILMS/

We report photoinduced absorption (PIA) and photoinduced reflectance ( PIR) spectra of poly(3-octyl thiophene)-methanofullerene films. As a r esult of the efficient photoinduced intermolecular charge transfer, th e PIA and PIR spectra of the composite films are significantly enhance d in magnitude over those in either of the component materials. From t he PIA and PIR spectra, the corresponding changes in the complex refra ctive index, Delta N = Delta n(omega)+i Delta kappa(omega), are obtain ed. The results indicate that the PIA spectra are dominated by Delta k appa(omega), while the PIR spectra are dominated mainly by Delta n(ome ga). The implications of these photoinduced changes in the index resul ting from photoexcitations are discussed in terms of potential optoele ctronic and nonlinear optical applications of these materials.