The influence of thickness and used solvent on luminescence and photodegradation of polysilane thin films

Abstract

Analysis of the influence of processing parameters on the photoluminescence (PL) of a homopolymer poly(methylphenylsilane) (PMPSi) and a copolymer - poly[dimethylsilane-methylphenylsilane] (P[DMSi-MPSi]) is presented. The influence of solvent type and effect of thickness of prepared thin films were investigated by the fluorescence spectrometry. There are fundamental differences between thin film and thick film. In thick films, the sigma-conjugation length of polymer chain segments is reasonably longer approved by strong bathochromic shift in the excitation spectra. Moreover, degradation of both polysilane materials was observed as photoluminescence decay measured at two different degradation wavelengths 285 and 330 nm in vacuum. Two patterns of degradation behaviour dependent on film thickness were observed with transition at about 500 nm as in fluorescence spectra too. The degradation and metastability phenomena described in previous papers were observed on thick drop cast films only, which means that they are not general effects, but dependent on film thickness. Hence, the new facts are discussed and the interpretation is extended in terms of mesoscale confinement effects on thin films.