Dynamic studies of conjugated polymers by phase-modulation IR-spectroscopy

The application of phase-modulation infrared spectroscopy to the photoexcitation dynamics of conjugated polymers is described. The modulation-frequency dependencies of the intensity and phase delay of photoinduced absorption have been observed and simulated numerically on the basis of a model based on second-order kinetics involving a neutralization process between the positive and negative charge carriers (polarons) that are formed from a photogenerated interchain charge-transfer exciton (polaron pair). The rate constant of the bimolecular recombination process has been obtained. This numerical simulation is useful in analyzing the observed responses of a nonlinear system in the phase-modulation measurements.