Synthesis and characterization of novel red-light-emitting polymers based on 3,6-carbazole and thiophene derivatives

A series of conjugated copolymers derived from N-(2-ethylhexyl)-3,6-carbazole (Cz) and 4,7-di(4-hexylthien-2-yl)-2,1,3-benzothiadiazole (DHTBT) were synthesized by Suzuki polycondensation. The electrochemical, optical and electroluminescent properties of these polymers were investigated. Efficient energy transfer from the Cz segment to the DHTBT unit occurred even if the DHTBT content in the copolymers was as low as 1 mol% in solid film. PL emission was red-shifted significantly from 645 to 690 run with the increase in DHTBT content from 1 to 50 mol%. The highest PL efficiency in solid film was 71% for PCzDHTBTl. EL emission of devices with these polymers as active layer red-shifted from 635 to 680 nm when the DHTBT content increased from 1 mol% to 50 mol%. The highest external quantum efficiency was 0.61% for devices from PCzDHTBT15 with the device configuration of ITO/PEDOT: PSS/polymerBa/Al.