Polarized emission from ultra-thin α-sexithiophene layers on oriented β-phase polyfluorene films

• Friction transfer method is used to produce oriented polyfluorene films.
• Oriented polyfluorene films are used to produce polarized emission.
• Blue polyfluorene is combined with orange α-sexithiophene for white emission.
• α-Sexithiophene is deposited on oriented polyfluorene for polarized white emission.
• Emission with higher efficiency is achieved when β-phase polyfluorene is employed.

Oriented films of poly(9,9-dioctylfluorene) (PFO) are produced by the friction transfer technique and exposed to saturated toluene vapor for formation of the metastable β-phase PFO. To obtain white polarized emission, the orange-emitting α-sexithiophene (6T) is deposited on top of these blue-emitting oriented PFO layers. We studied the effects of the thickness of the 6T layer as well as the PFO conformation (β-phase PFO vs. N-phase PFO) on the color and polarization of the emission. Photoluminescence results show that whitening of the emission is possible by depositing a 6T layer as thin as 0.15 nm on PFO. The intensity of the 6T emission region decreases with increasing 6T film thickness from 0.15 to 4.5 nm, but as a general trend the emission is stronger for 6T on β-phase than on N-phase PFO. Very good polarization of both PFO and 6T emitting regions suggests that the 6T molecules are oriented parallel to the orientation of the underlying PFO layer.