Photophysical process of MEH-PPV solution

The solvent, temperature and concentration-dependent fluorescences of MEH-PPV solutions were examined. The aliphatic and aromatic solvents have different effects on the emission spectra of MEH-PPV solutions because of the different interaction mechanisms between MEH-PPV and different solvents at excited states. With the increase of the polarity of the solvents, the emission spectra show blue and red shift at 77 K and room temperature, respectively. With the decrease of the temperature, the emission spectra of MEH-PPV in xylene show red-shift and the fluorescence intensities increase. The concentration-dependent emission spectra remarkably changed with the increase of the concentration because of the existence of the aggregate states and the interchain interactions in concentrated solutions.