A series of conjugated copolymers derived from 9-ethylhexyl-2

7-carbazole (Cz) and 4

7-di(4-hexylthien-2-yl)-2

1

3-benzothiadiazole (DHTBT) was synthesized by Suzuki polycondensation. The photo- and electro-luminescent properties of these polymers were investigated. Efficient energy transfer from the Cz segment to the DHTBT unit occurs even if the DHTBT content as low as 1 mol%. PL emission was red-shifted significantly from 645 nm to 700 nm with the increase in DHTBT content by 1－50 mol%. PL efficiencies decreased with the increase in DHTBT content in the polymers from 55% for PCzDHTBT1 gradually down to 7% for PCzDHTBT50. EL emission of these polymers red-shifted from 640 nm to 690 nm when the DHTBT content increased from 1 mol% to 50 mol%. The highest external quantum efficiency was 1.67% for PCzDHTBT25 with the maximum luminescence of 870 cd/m2 in the device configuration of ITO/PEDOT: PSS/polymer/PFN/Ba/Al. The enhancement of device performances could be due to the improved electron injection by inserting the amino-containing polyfluorene (PFN) layer. These polymers are promising candidates as a red emitter in the full-color polymer light emitting diodes (PLEDs).