A series of phenyleneethynylene (PE)/phenylenevinylene (PV) hybrid conjugated polymers with alkoxy side chains were studied. It was found that longer alkoxy side chains improve EL efficiency through enhanced material solubility and film-forming properties. Polymers with longer side chains attached to the phenylenevinylene units exhibit higher EL efficiency. With increasing solvent polarity, both absorption and emission spectra of the polymer display bathochromic shifts. With increasing chromophore concentration, the solution PL spectra display red shifts and new bands, indicating intermolecular excimer formation. The relative intensity of the 0-0 band in the solution PL spectra increases with increase of the excitation energy. When the nonsolvent methanol is added to the homogeneous polymer/chloroform solution, the absorption and emission spectra display red shifts and new bands, clearly indicating aggregate and excimer formation in the solvent/nonsolvent systems.