We report the photoluminescence characteristics of solid solutions of poly[2-methox5-(2'-ethyl-hexyloxy)-p-phenylene vinylene] (MEH-PPV) with different concentrations in polystyrene. Reduction in the distances between the MEH-PPV chains with increased MEH-PPV concentrations makes the conjugation segments aggregated in the solid solution. Absorption by the conjugation segments in the aggregated state leads to a redshift absorption edge. By comparing the photoluminescence and absorption spectra of the solid solutions with those of the 100% MEH-PPV film, it is shown that the emission from the 100% MEH-PPV film originates from the radiative recombination of excitons in the aggregated state. (c) 2006 American Vacuum Society.