Research Article
Ultrafast Charge and Triplet State Formation in Diketopyrrolopyrrole Low Band Gap Polymer/Fullerene Blends: Influence of Nanoscale Morphology of Organic Photovoltaic Materials on Charge Recombination to the Triplet State
Figure 4
fs-TA data analysis of the pristine polymer films at low laser fluences (a, c) and at high laser fluences (b, d). (a, b) Species-associated difference spectra obtained from the target analysis (for (a), black is hot singlet, red is relaxed singlet, and blue is triplet; for (b), black is hot singlet, red is hot triplet, and blue is relaxed triplet). (c, d) Concentration profiles of the species reported in (a, b). The pulse is given in pink (in (c)) or in green (in (d)). (Note the lin-log timescale axis in (c) and (d).) (e) Laser fluence effects on the photophysical properties of the pristine polymer film. Shown is the change of singlet and triplet excited state lifetimes and of the relative triplet formation efficiency as function of laser fluence for the pristine polymer films. (f) Target model used for the analysis for low fluence (for high fluence, the three species were hot singlet, hot triplet, and relaxed triplet).
| (a) Polymer SADS, 4 μJ/cm2 |
| (b) Polymer SADS, 28 μJ/cm2 |
| (c) Polymer kinetics, 4 μJ/cm2 |
| (d) Polymer kinetics, 28 μJ/cm2 |
| (e) Effect of fluence |
| (f) Target model |