Decay dynamics of photoinduced charge carriers in conducting polymers

The phase-modulation method is used to analyze a photoinduced absorption in the infrared spectrum for a number of conducting polymers in the microsecond to millisecond region. The in-phase components of the photoinduced absorptions are plotted against the quadrature (out-of-phase) components as a function of the sinusoidal modulation frequency. The resulting circle diagrams form depressed circular arcs. The time response of the charge carriers photogenerated in conducting polymers is simulated numerically for a sinusoidally modulated excitation. The comparison of the experimental data to the calculated results is in excellent agreement for a bimolecular decay. The excitation-laser-power dependence of the intensity of the photoinduced infrared absorption is also calculated and shown to be consistent with the experimental data. These analyses demonstrate the important role of bimolecular recombination in the decay processes of the conducting polymers.