A copolymer of dendronized poly(p-phenylene vinylene) (PPV), poly{2-[3',5'-bis (2'-ethylhexyloxy) bnenzyloxyl]-1,4-phenylene vinylene}-co-poly[2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylene vinylene] (BE-co-MEH-PPV), was synthesized with the Gilch route to improve the electroluminescence and photovoltaic properties of the dendronized PPV homopolymer. The polymer was characterized by ultraviolet-visible absorption spectroscopy, photoluminescence spectroscopy, and electrochemical cyclic voltammetry and compared with the homopolymers poly{2-[3', 5'-bis(2-ethylhexyloxy) benzyloxy-1,4-phenylene vinylene) (BE-PPV) and poly[2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylene vinylene] (MEH-PPV). Polymer light-emitting diodes based on the polymers with the configuration of indium tin oxide (ITO)/poly(3,4-ethylene dioxythiophene) : poly(styrene sulfonate) (PEDOT : PSS)/polymer/Ca/Al were fabricated. The electroluminescence efficiency of BE-co-MEH-PPV reached 1.64 cd/A, which was much higher than that of BE-PPV (0.68 cd/A) and a little higher than that of MEH-PPV (1.59 cd/A). Photovoltaic properties of the polymer were studied with the device configuration of ITO/PEDOT : PSS/polymer : [6,6J-phenyl-C-61-butyric acid methyl ester] (PCBM)/Mg/Al. The power conversion efficiency of the device based on the blend of BE-co-MEH-PPV and PCBM with a weight ratio of 1: 3 reached 1.41% under the illumination of air mass 1.5 (AM1.5) (80 mW/cm(2)), and this was an improvement in comparison with 0.24% for BE-PPV and 1.32% for MEH-PPV under the same experimental conditions. (C) 2007 Wiley Periodicals, Inc.