Figure 6: ¹(TT)-mediated singlet fission in polyacenes.

(a) TA spectra of rubrene, TIPS-pentacene and pentacene thin films measured at low temperature, averaged over the indicated delay ranges (thin lines). Spectral decomposition analysis (thick lines) provides spectra of singlet (black), ¹(TT) (red) and free triplet (purple). Note the rate of singlet fission in TIPS-pentacene and pentacene is too fast to clearly isolate singlet spectral features. In all materials, the conversion from ¹(TT) to free triplets can be identified from peak shifts in the PIA. (b) Extracted singlet, ¹(TT) and free triplet spectra from (a) normalized for clarity. (c) Normalized population kinetics of excited state species extracted from TA maps, along with integrated raw TA signal (brown, diamonds) and extracted PL kinetics, where applicable (dashed). All materials exhibit the same sequential model.