A series of F8BT-based copolymers (PCFBTs) with functional peripheral side chains were designed and synthesized. The complementation of side chain with polymer backbone in electronic and optical properties was realized. Electron-riched carbazole moieties on the peripheral side chains of fluorene unit significantly reduce the first oxidation potential and increase the highest occupied molecular orbital energy levels of PCFBTs. Increase of hole injection and transport ability was achieved in PCFBTs. Among them, PCFBT shows a maximum luminous efficiency of 0.7 cd/A and a turn-on voltage of 3.0 V in the single-layered device, which are better than F8BT without the carbazole moieties (0.1 cd/A, 3.8 V). The radios of fluorene and benzothiadiazole (BTz) unit in polymers were adjusted to balance the electron and hole transport, and PCFBT0.2 (BTz: fluorene = 2:8) exhibits 13 times higher maximum luminous efficiency (10.8 cd/A) than F8BT (0.8 cd/A) in a double-layered device. (C) 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 49: 4549-4555, 2011