Excited-state absorption in luminescent conjugated polymer thin films:: ultrafast studies of processable polyindenofluorene derivatives

Femtosecond transient absorption experiments on thin films of poly-2,8-indenofluorene, a processable step-ladder analogue of poly-p-phenylene, are presented. Probe wavelength and pump intensity dependence measurements allow the separation of the broadly overlapped singlet excited-state and charged excitation absorption bands. Morphological effects on the dynamics are investigated by modification of the aliphatic side chains in the monomer unit. Steric effects, controlled by the nature of the alkyl side groups, result in a group-dependent three-dimensional structure. The transient absorption dynamics are similar in all samples, in spite of distinct morphologies, indicating limited importance in the excited-state analysis. (C) 2000 Elsevier Science B.V. All rights reserved.