Transient Photoconductivity of MEH-PPV and Its Sensitization by C60

We report the results of comprehensive measurements of photoconductivity (PC) in films of poly[2-methoxy, 5-(2'-ethyl-hexyloxy)-p- phenylenevinylene], MEH-PPV and MEH-PPV/C60 composites. The peak transient PC of MEH-PPV is proportional to the light intensity and the electric field, and independent of temperature. The spectral response of the picosecond transient PC shows that the onset of the photocurrent coincides with that of photo-absorption, consistent with the photogeneration of charge carriers via an interband transition. The transient PC (lifetime and magnitude) of MEH-PPV increases substantially on increasing the concentration of C60 in OMEH-PPV/C60 composite films; ultrafast photoinduced electron transfer minimizes early-time recombination and enhances the quantum yield for photogeneration of free charge carriers