Highly polarized polymer light-emitting diodes utilizing friction-transferred poly(9,9-dioctylfluorene) thin films

Polarized polymer light-emitting diodes (PLEDs) have been constructed utilizing friction-transferred poly(9,9-dioctylfluorene) (PFO) thin films. The friction transfer technique allows oriented PFO to be deposited directly onto an indium tin oxide anode without an alignment layer such as polyimide. Polarized absorption and photoluminescence spectra revealed that the polymer backbones are highly aligned in the friction direction. We fabricated PLEDs consisting of friction-transferred PFO as an emissive layer, vacuum-deposited bathocuproine as an electron transport and hole-blocking layer, and a vacuum-deposited Li F ∕ Al cathode. Highly polarized blue emission with an integrated polarization ratio of 31 and a luminance of up to 300 cd ∕ m 2 was observed from the PLEDs.