Thickness dependent structural ordering, degradation and metastability in polysilane thin films: A photoluminescence study on representative σ-conjugated polymers

Abstract

Cite this article as: Pavel Urbánek and Ivo Kuřitka, Thickness dependent structural ordering, degradation and metastability in polysilane thin films: A photoluminescence study on representative σ-conjugated polymers, Journal of Luminescence, http://dx. ABSTRACTWe present a fundamental experimental study based on the fluorescence investigation of thin σ-conjugated polymer films, where the dependence of optoelectrical properties and UV degradation on film thickness ranging from nano-to microscale was studied. Such extensive and detailed study was performed for the first time and observed spectral shifts in emission and excitation spectra and UV degradation retardation point towards the conclusions that there exists a threshold thickness where the material degradation behavior, electron delocalization and structure suddenly change. The development of well aligned polymeric chain structure between the nano-and micrometer thickness (on the mesoscale) was shown responsible for the manifested phenomena. The material thicker than critical 500 nm has extremely small Stokes shift, maximum extended σ-delocalization along the silicon polymer backbone and exhibits remarkable UV degradation slowdown and self-recovery ability. On the contrary, the electronic properties of thin films below 80 nm resemble those of random coils in solutions. The films of moderate thickness show relatively steep transition between these two modes of structural ordering and resulting properties. Altogether, we consider this complex phenomenon as a consequence of the mesoscale effect, which is an only recently introduced concept in polymer thin films.

Effect of backbone conformation and its defects on electronic properties and assessment of the stabilizing role of π–π interactions in aryl substituted polysilylenes studied by DFT on deca[methyl(phenyl)silylene]s

“…It is important to note that no states in the bandgap are formed by the investigated conformational defects, which means that no peaks are present in the Vis area of the absorption spectrum. This is in accordance with state-of-the-art interpretation of origin of such features which are normally manifested in luminescence spectra only [ 11 ].…”

The Photostability of Novel Boron Hydride Blue Emitters in Solution and Polystyrene Matrix

“…This assumption was verified by the PL emission spectra recorded for thin films as discussed below. As a useful tool for the photostability characterization of materials in the form of thin films, the approach using fluorescence spectroscopy and the monitoring of photoluminescence decrease may be successfully applied [ 36 , 37 ]. The study was performed in two different environments.…”

Polymer chain ordering manifestation in photoluminescence of thin F8BT films

“…Film thickness can impact on the microstructure of the thin conjugated polymer film and photoluminescence because of the various levels of manifestation of nonlocalized (aggregate states) and localized(intrachain) transitions. With increase of the thickness to some extent more ordered structure can be achieved and there is a thickness threshold in which the mesoscale (between nano-and micro-dimensions) effects such as self-healing mechanism will be revealed [10,11]. The effect of film thickness on optoelectrical properties and the correlation between the thickness and vibronic transition manifestations are presented in this study.…”

“…In the case of the thickest film, significant change of spectrum shape and redshift of excitation maxima were observed. These phenomena can be plausibly explained by extension of conjugation length whereas the longer is the length of conjugated segments the higher delocalization of exciton and higher lowering of energy of transiting vibrational levels in excited states [11].…”