Improving optoelectronic properties of the 2,7-polyfluorene derivatives with carbazole and oxadiazole pendants by incorporating the blue-emitting iridium complex pendants in C-9 position of fluorine unit

To study the influence of a blue-emitting iridium complex pendant on the optoelectronic properties of its 2,7-polyfluorene (PF) derivatives with the carbazole and oxadiazole pendants, a class of 2,7-PF derivatives containing carbazole, oxadiazole, and/without the cyclometalated iridium complex pendants in the C-9 positions of fluorene unit were synthesized. Their thermal, photophysical, electrochemical, and electroluminescent (EL) properties were investigated. Among these 2,7-PF derivatives (P1-P4), P2 and P3 exhibited higher photoluminescence efficiency in dichloromethane and better EL properties in the single-emissive-layer polymer light-emitting devices. The highest brightness of 3888 cd/m(2) and the maximum current efficiency of 2.9 cd/A were obtained in the P2- and P3-based devices, respectively. The maximum brightness and efficiency levels were 1.7 and 2.1 times, respectively, higher than the corresponding levels from the parent 2,7-PF derivative (P1)-based devices. Our work indicated that EL properties of 2,7-PF derivatives can be improved by introducing the blue-emitting iridium complex into the alkyl side chain of fluorine unit as pendant. (C) 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 50: 149-155, 2012