Large enhancement of the transient and steady-state photoconductivity of conducting polymer/C60 composite films

Abstract

Summary form only given. We present the transient and steady-state photoconductivity (PC) results obtained from poly[2 methoxy, 5-(2'-ethyl-hexyloxy)-p-phenylene vinylene] (MEH-PPV) and poly(octylthiophene) (P3OT), and from conducting polymer films sensitized with several concentrations of C/sub 60/. Both the magnitude and the lifetime of the transient PC increase substantially on increasing the concentration of C/sub 60/. The results imply that quantum efficiency for photogeneration of charge carriers is increased by photoinduced electron transfer and that recombination is inhibited by the spatial separation of the electron and hole on the C/sub 60/ and the conducting polymer, respectively. The greater enhancement of the transient PC in MEH-PPV (nearly two orders of magnitudes with addition of a few percent of C/sub 60/) than in P3OT (nearly one order of magnitude with addition of a comparable amount of C/sub 60/) suggests a higher probability of the early-time recombination in pristine MEH-PPV. As a result of the enhancement in the photogeneration efficiency and the carrier lifetime, the spectral response of the steady-state PC in both MEH-PPV/C/sub 60/ and P30T/C/sub 60/ films shows significantly enhanced PC throughout the entire spectral range from the near infrared to the ultraviolet.