Gas to crystal effect on the spectral line narrowing of MEH-PPV

We report two emission bands corresponding to the spectral line narrowing (SLN) of the conjugated polymer [2 '-methoxy-5-(2 '-ethylhexyloxy)-1, 4-phenylenevinylene] (MEH-PPV) in films. The SLN emission coming from the polymer chains closer to the glass substrate are at a different spectral position compared to the chains that lay further away from the glass substrate. We explain this phenomenon as a direct consequence of the "gas-to-crystal" effect. In solution form, as concentration was increased, and thus the proportion of aggregates, a decrease in the SLN bandwidth and a red shift of the emission peak was observed. (C) 2007 Optical Society of America