Time resolved PL (TR-PL) is a powerful tool to collect information on the photophysical properties of materials and particularly the dynamics of photoexcited states. The TR-PL of P3HT and its composite with SWNTs has been investigated to confirm the type of interaction between the two components of the composite in the excited states. Fig. 8 shows the normalized TR-PL decay dynamics on a logarithmic scale in the range of 0–0.8 ns. They correspond to composite films for different x concentration, with x = 0% (a), x = 0.5% (b), x = 1% (c), x = 2% (d). A single monoexponential fit cannot reproduce these
ACTH 1-39 data for the temporal window of 0–1 ns. This kinetics is well reproduced with two exponential decays convoluted with the contribution of the apparatus function given by a Gaussian temporal curve. All equations and parameters have been already introduced in previous works [49] and [50]. We report in Table 3 the weight Pi and the decay time τi for each exponential and the average decay time τmean characteristic of the PL lifetime. In this table are also reported the radiative (τr) and non-radiative (τnr) lifetimes calculated from Refs. [48], [49] and [50]. We obtain for the pristine P3HT film τmean = 0.185 ns and τr = 92 ns and τnr = 0.185 ns. The photogenerated
species have a radiative lifetime τr much longer than the nonradiative lifetime τnr (τr/τnr = 500) implying that the emitting species prefer the non-radiative pathway to recombine, as confirmed with its low QY of 0.2%.
