High luminescence polarized polymer light-emitting diodes fabricated using aligned polyfluorene

We have successfully constructed a polarized polymer light-emitting diodes (PLEDs) by employing poly(N-vinylcarbazole) (PVK) as an extra hole-transporting alignment layer that prevents the damage of the hole-injected layer of poly(3,4 ethylenedioxythiophene)-poly(styrene sulfonate) (PEDOT-PSS) by mechanical rubbing. The maximum luminance efficiency 0.31 cd A(-1) of blue polarized PLED fabricated with the aligned polufluorene (PF) layer is obtained. The brightness approaches 1000cd m(-2) at a relatively low biased voltage. By using a PVK alignment layer, a dichroic ratio of 25.7 (at a 451 nm emission wavelength) was observed by finding the optimum thickness of PF that was sufficiently highly polarized to be used as an efficient light source in liquid crystal displays. The spectrum of photon emission is narrow, characterized by its full width at half maximum value.