Grazing emitted light from films of derivative polymer of polyfluorene

Emission patterns from the films of polyfluorene derivative on silica substrates are found to show light emission at grazing angles to the substrate. This light is found to be polarised and to have a narrowed emission, as well as enhanced intensity with respect to the light collected in the forward direction. Both the wavelengths of the peaks and their polarisation (s or p) are thickness-dependent. The peakʹs wavelength positions are used to characterise the spectrum of the refractive indices of the film both in and out of plane. The relative intensity of s- to p-polarised peaks serves as an independent indication of the dipole orientation. The deduced dipole in-plane alignment ratio (88%) and the magnitude of the birefringence (Δn=0.2 at λ=600 nm) suggest that the main chains of this polymer lie preferentially in plane of the film. These findings seem to be consistent with the rod structure of the polymer studied.