Novel soluble three-component conjugated copolymers are synthesized by palladium- catalyzed Suzuki coupling reaction from 9,9-dioctylfluorene (DOF), 9-ethylhexylcarbazole (Cz) and 4,7-dithien-2-yl-2,1,3-benzothiadiazole (DBT) with Cz composition varying from 1-15 mol% in the copolymer. All of the polymers are soluble in common organic solvents and are highly photoluminescent. The electrochemical, optical, photoluminescent (PL) and electroluminescent (EL) properties of the copolymers were studied. When the hole transmitting material carbazole is introduced into the copolymer PFO-DBT, the hole mobility of the luminescent layer material is improved. The three-component copolymers compared with copolymer PFO-DBT15, Devices made up of these copolymers still emit saturated red light. The highest external quantum efficiency achieved in the device configuration ITO/PEDT/PFO-Cz-DBT15/Ba/Al is 1.81% for the copolymer for 10% Cz content, higher than that of the device made from PFO-DBT15.