Polaron photogeneration probed by picosecond infrared active vibrations inMEH-PPV

We report picosecond time resolved photoinduced absorption from infrared ac tive vibrations in thin films (similar or equal to0.1 mum thickness) of MEH -PPV. With an overall spectral resolution of 1 meV and temporal resolution of similar or equal to4 psec both in the pump and probe, channels, we follo wed the spectral evolution with time using 565 nm pulsed excitation applied at 80 MHz repetition rate with similar or equal to2 x 10(13) photons/cm(2) per pulse. Under these experimental conditions, we found evidence for phot ogenerated polarons at times <4 psec. The origin of these polarons is brief ly discussed.