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-inde nofluorene, a processable step-ladder analogue of poly-p-phenylene, are pre sented. Probe wavelength and pump intensity dependence measurements allow t he separation of the broadly overlapped singlet excited-state and charged e xcitation absorption bands. Morphological effects on the dynamics are inves tigated by modification of the aliphatic side chains in the monomer unit. S teric effects, controlled by the nature of the alkyl side groups, result in a group-dependent three-dimensional structure. The transient absorption dy namics are similar in all samples, in spite of distinct morphologies, indic ating limited importance in the excited-state analysis. (C) 2000 Elsevier S cience B.V. All rights reserved.