Optical and electroluminescence studies of orange light-emitting copolymers based on polyfluorene

A series of novel soluble conjugated copolymers derived from 9,9-dioctylfuorene and 2,7-di-(2-thienyl)-9-fluorenone (DTFO) were synthesized by Suzuki cross coupling reaction with different feed ratios. All polymers showed good thermal stability with 5% weight loss up to 410 °C and good solubility in common organic solvents. With the increase of the DTFO unitʹs content in the copolymers, the emission peaks red-shifted from 550 to 608 nm owing to more complete energy transfer and charge trapping. But turn-on voltage increased and current efficiency decreased with increasing DTFO content. When the content of DTFO was 5%, the maximum luminance of the devices was 2164 cd/m2.