Enhanced electroluminescent properties of triarylamine-endcapped X-branched oligofluorene

A facile approach for synthesis of the triarylamine-endcapped X-branched oligofluorene, X-OF(2)Ph-NPh and its corresponding linear oligofluorene, OF(2)Ph-NPh by Suzuki cross-coupling as a key reaction has been developed. This novel X-branched oligofluorene exhibits much higher thermal and electrochemical stabilities and enhanced electroluminescent properties as comparison to its corresponding linear counterpart. Using a simple two-layer OLED structure of ITO/oligofluorene (40 nm)/PBD (40 nm)/LiF (1 nm)/Al (150 nm), the luminance efficiency of X-OF(2)Ph-NPh-based OLED can also reach up to 2.8 cd/A with a maximum brightness of 1700 cd/m2 and remarkably better than 1.2 cd/A with a maximum brightness of 700 cd/m2 for its corresponding linear oligofluorene OF(2)Ph-NPh-based OLEDs.