Efficient polarized blue electroluminescent device using oriented p-sexiphenyl thin film

Highly oriented p-sexiphenyl (6P) film was successfully prepared by epitaxial-growth on rubbed 6P film on hole-transporting poly(9,9′-dioctylfluorene) (POF). Using the epitaxial-growth film of 6P, we prepared tri-layered device, ITO/POF/epitaxial-growth film of 6P/electron-transporting ozadiazole derivative (OXD7)/LiF/A1. The device with the epitaxial-growth film of 6P as emissive layer exhibited highly polarized and efficient blue electroluminescence (EL). EL peaking around 430 nm corresponded well to photoluminescence of 6P film. The maximum value of polarization ratio Ip/Is of the blue EL was 37, where Ip and Is are EL intensity parallel and perpendicular to the orientation direction, respectively. The values of maximum luminance Lmax and maximum current efficiency ηmax of the tri-layered device were enhanced comparing to those of a double-layered device ITO/6P/OXD7/LiF/Al; Lmax=146 cd m−2 and ηmax=0.41 cd A−1 for the tri-layered device whereas Lmax=32 cd m−2 and ηmax=0.07 cd A−1 for the double-layered device.