Polymer chain ordering manifestation in photoluminescence of thin f8bt films

Abstract

Poly(9,9-dioctyfluorene-alt-benzothiadiazole), F8BT, thin films were successfully deposited using spin coating and drop-casting methods on glass and silicon substrates. Films with thicknesses varying from tens to hundreds of nanometers were obtained as a result of variation in the deposition conditions, such as concentration or coating methods. The trends in manifestations of 0-0 and 0-1 vibronic transitions in UV-VIS absorption and photoluminescence (PL) spectra correlate with the thickness of the thin films. A threshold in the intensity ratio of the two transitions was observed at the thin film thickness about 250 nm. The observed spectral features are interpreted in terms of the competitive effects of J- and H- aggregation of the macromolecular chains.