Abstract
We have investigated the molecular orientation of the polyfluorene (PFO) layers (~30 nm thick) formed on photo-aligned polyimide films. The uniaxially-aligned crystalline and glassy PFO layers were obtained by slow-cooling and quenching, respectively, of the sample from the liquid crystalline phase of PFO. For the crystalline PFO layer, an extremely high polarization ratio was observed in photoluminescence (PL), which was about 30. Such a high PL polarization ratio has not previously been reported. For the glassy PFO layer, the PL polarization ratio was 10.8. It was slightly larger than that of the glassy PFO layer formed on a rubbed polyimide film (9.5). From these results we conclude that the photo-aligned polyimide film is an excellent alignment film for PFO layers, especially for crystalline layers.
