Photoluminescence and electroluminescence of liquid crystalline aromatic conjugated polymers

Abstract

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