Photoluminescence and electroluminescence of liquid crystalline aromatic conjugated polymers

The liquid crystalline(LC) aromatic conjugated polymers were aligned by hea ting the substrates and then gradually cooled to LC temperature under an ex ternal magnetic field. For aligned LC-Poly(para-phenylene) [LC-PPP] sample, the polarized photoluminescence (PL) peak of perpendicular direction to th e magnetic field is 30 % more intensive than that of the parallel direction . Polarized micrograph shows the domains of aligned LC-PPP films. The PL sp ectra of LC-PPP at low temperature did not show any broadening nor peak shi ft. The decrease in PL intensity as the temperature becomes high indicates the shortening of exciton life time. Unlike LC-PPP, the LC-Poly (para-pheny lene vinylene)[LC-PPV] shows the electroluminescent(EL) characteristics in the sandwich structure device, ITO/LC-PPV/Al. The turn-on voltage of the LC -PPV device is 12V and the power law dependence in the I-V characteristics is observed.