A new thermally robust electroluminescent (EL) carbazole-based pi-conjugated copolymer, including poly[3,7-(N-hexylcarbazole)-co-4,7-{5,6-bis(3,7-dimethyloctyloxymethyl)-2,1,3-(benzothiadiazole)}] (PCz-co-P2C(10)BT) was synthesized and used to fabricate the efficient polymer light-emitting diodes (PLEDs). The glass transition temperature of the PCz-co-P2C(10)BT (105 degrees C) was found to be higher than that of poly(9,9-dialkylfluorene) derivatives. We fabricated PLEDs in ITO/PEDOT/light-emitting polymer/Alq(3)/LiF/Al configuration. The new copolymer was found to have green emission color (523 nm). The maximum brightness and external quantum efficiency of PCz-co-P2C(10)BT were 260 cd/m(2) at 14 V and 0.22%, respectively.