Electroluminescence and photoluminescence of dioctylfluorene and 4,7-dithien-2-yl-2,1,3-benzothiadiazole copolymers

Dioctylfluorene (DOF) and 4,7-dithien-2-yl- 2,1,3-benzothiadiazole (DB T) copolymers synthesized in our lab with different compositions of DBT (1%, 5%, 15% and 25%) were utilized to fabricate bilayered light emitting diodes. Extern al quantum efficiency (QE) of the diode fabricated from the copolymer with 15% D BT content reaches 1.4% (ph/el), over 1.0 cd/A in luminance efficiency at the driving voltage of 4.2 V. The highest luminance can reach 3780 cd/m2 at 8.2 V. Devices emit a saturated red light centered at 675 nm with chromaticity coordinate changed from x = 0.66, y = 0.32 for PDOF-DBT1 (1% DBT) to x = 0.70, y = 0.28 for PDOF-DBT25 (25% DBT).