Efficient luminescence polarization of conjugated polymer films under low stretching level using transparent and flexible plastic substrate

This work reports a detailed characterization of the absorption and luminescence polarization properties of poly(phenylenevinylene), PPV, thin films under very low deformation levels. The samples were prepared by casting the PPV precursor on teflon tape, followed by a thermal conversion step at 220°C. Continuous axial stretch was applied at room temperature to very thin PPV/teflon films enabling simultaneous luminescence and absorbance measurements. Unlike the usual methods that use high draw ratios (L/L₀>2) to obtain highly ordered films, we demonstrate that low levels of deformation (10<2) are enough to obtain high luminescence polarizations (P||/P⊥=9). We suggest that the weak stretching is more effective in the disordered emissive regions, forcing a stacking not usually found in pure PPV, favoring polarization conversion.