Blue polarized luminescence from organic material aligned by ion-beam-processed poly(3,4-ethylenedioxythiophene)

We first demonstrated that an organic electroluminescence (EL) device based on conjugated polymers, which emitted polarized light, aligned by ion beam processed films of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS). Such devices would be particularly useful as backlights for conventional LCDs. Homogenous alignment of 4,4′-Bis[2-9(-ethyl-3- carbazoyl)vinylenyl]-1,1′-biphenyl (BECVB) films on thin layers of ion-beam-processed or rubbed PEDOT:PSS allows the construction of light-emitting diodes that emit polarized blue light (λ_em = 455 nm). The ion-beam-processed or rubbed PEDOT:PSS acts as an effective hole-injecting alignment layer. Polarized photoluminescence spectra demonstrated that the long axis of BECVB molecule was oriented along the ion-beam or rubbing direction. Owing to the orientation of BECVB molecules, polarized EL in the rubbing or ion-beam direction was observed in the device. The maximum photoluminescence polarization ratios of 5.6:1 and 3.2:1 were achieved for the devices aligned by rubbing and ion-beam methods, respectively.