Novel poly(p-phenylenevinylene) (PPV) copolymers derived from 1-methoxy-4-octyloxyphenylene (MOP), 2,1,3-benzothiadiazole (BT), and trans-1,2-bis(tributylstannyl)ethylene were first prepared by a palladium-catalyzed Stille coupling reaction. The feed ratios of MOP to BT were 99.5:0.5, 99:1, 95:5, 85:15, 70:30, and 50:50. An efficient energy transfer from the 2-methoxy-5-octyloxy-p-phenylenevinylene segment to the narrow-band-gap units was observed. The poly(2-methoxy-5-octyloxy-p-phenylenevinylene-2,1,3-benzothiadiazoleviny lene) copolymers emitted deep red light. The maximum electroluminescence emission of these PPV copolymers occurred at 659-724 nm and was accompanied by gradual redshifting with an increasing BT concentration. The photophysical properties were examined in comparison with those of copolymers based on BT and fluorene or N-alkylcarbazole doped with the same BT concentration in the copolymer main chain. © 2005 Wiley Periodicals, Inc.