Properties of MEH-PPV films prepared by slow solvent evaporation

Because of various macromolecules conformations, solution-casted conjugated polymers films demonstrate a wide spectrum of intermolecular interactions which strongly influence essential electronic properties. Using poly[2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV) and different solvents, we studied polymer films prepared by dip-coating, spin/drop-casting and by a method based on slow solvent evaporation (SSE) from solution. The SSE films exhibit some redder photoluminescence (PL) and optical absorption edge indicating longer conjugated lengths and better film morphology. At the same time, the PL quantum yield for the SSE films is no less than that of the dip-coated films. Furthermore, the SSE films show a distinct evolution of their PL spectra during long-term storing compared with other preparation methods. This indicates different film morphologies evolving after preparation in distinct ways. We speculate about correlation between the preparations methods. morphology, interchain interaction and optical properties of the studied MEH-PPV films. (C) 2004 Published by Elsevier B.V.