| Popis: |
SUMMARY AND CONCLUSION We have demonstrated that the monodomain-alignment of novel nematic fluorene bisacrylates can be preserved by in-situ photopolymerization within their liquid crystalline phase. This leads to high dichroic ratios of absorption and photoluminescence of 13 and 15, respectively. Different alignment layers based on seg-PPV and NPB-filled polyimide (30/70 wt%), which are capable of charge-transport, were compared to standard insulating polyimide. It was found that the quality of orientation for the fluorene bisacrylates is almost the same among all alignment layers tested. However, a significant dependence of the dichroisms on the film thickness is found. This suggests a maximum chromophore orientationclose to the surface of the alignment layer. In OLEDs with the crosslinked fluorene bisacrylates on top of seg-PPV alignment layers highly polarized emission is observed corresponding to polarization ratios of up to 22, though contributions from PPV emission were also present. Fororiented poly(di-n-octylfluorene) it was possible to obtain exclusively blue emission with a maximum brightness of more |
