Elsevier, Chemical Physics Letters, (585), p. 133-137, 2013
DOI: 10.1016/j.cplett.2013.08.098
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Absorption induced by electrochemically injected holes is studied in poly-9,9-dioctylfluorene (PFO) films. Injected charges form positive polarons which are delocalised over four fluorene units in the glassy phase and about seven fluorene units in its beta-phase. Polaron absorption cross-sections at the 640 nm peak are similar to the published values of chemically reduced oligofluorenes in solution. The absorption cross-section of polaron in the beta-phase at 470 nm is about eight times smaller than the stimulated emission cross-section derived from published data. This indicates that beta-phase-rich PFO is an attractive candidate for a lightemitting layer in double-heterostructure organic laser diodes.