A new series of copolymers with high brightness and luminance efficiency were synthesized using the Gilch polymerization method, and their electro-optical properties were investigated. The weight-average molecular weights (M-w) and poly-dispersities of the synthesized poly(9,9-dioctylfluorenyl-2,7-vinylene) [poly(FV)], poly[2-(3-dimethyldodecylsilylphenyl)-1,4-phenylenevinylene] [poly(m-SiPhPV)], and poly[9,9-di-n-octylfluorenyl-2,7-vinylenel-co-(2-(3-dimethyldodecylsilyl phenyl)-1,4-phenylene vinylene)][poly(FV-co-m-SiPhPV)] were found to be in the ranges of (8.7-32.6) X 10(4) and 2.3-5.4, respectively. It was found that the electro-optical properties of the copolymers could be adjusted by controlling the feed ratios of the comonomers. Thin films of poly(FV), poly(m-SiPhPV), and poly(FV-co-m-SiPhPV) were found to exhibit photoluminescence quantum yields between 21% and 42%, which are higher than those of MEH-PPV. Light-emitting diodes were fabricated in ITO/PEDOT/light-emitting polymer/cathode configurations using either double layer (LiF/Al) or triple layer (Alq3/LiF/Al) cathode structures. The performance of the polymer light-emitting diodes (PLEDs) with triple layer cathodes was found to be better than that of the PLEDs with double layer cathodes in poly(FV) and poly(FV-co-m-SiPhPV). The turn-on voltages of the PLEDs were in the range of 4.5-6.0 V, with maximum brightness and luminance efficiency up to 9691 cd/m(2) at 16 V and 3.27 cd/A at 13 V, respectively. (c) 2005 Wiley Periodicals, Inc.