Dynamics of photoexcited carriers in poly(p-phenylenevinylene) and its soluble derivative

The dynamics of photoexcited carriers in poly(p-phenylene vinylene) (PPV) and its soluble derivative, poly[2-methoxy-5-(2′-ethylhexyloxy)-p-phenylenevinylene] (MEH-PPV) are studied using the measurement of subnanosecond transient photoconductivity (PC). An initial transient photocurrent decays in the subnanosecond time regime, followed by a thermally-activated slow tail. The magnitude of the peak transient PC is almost temperature independent and proportional to the light intensity and electric field. The results are interpreted as a free carrier generation via a π-π∗ interband transition. The transient PC in MEH-PPV is an order of magnitude smaller than that in PPV, indicating that the decrease of the interchain coupling due to the bulky side-chains results in a smaller quantum efficiency for carrier generation.