Ultrafast Photoinduced Electron-Transfer in Conducting Polymer Buckminsterfullerene Composites

Abstract

We report time-resolved photoinduced absorption and time-resolved photoconductivity in conducting polymer-C60 composites. Photoinduced electron transfer occurs at times < 1 ps. Two subgap features are observed in the photoinduced absorption of pure poly(3-octylthiophene) (P3OT); these form earlier than 1 ps and decay with τ<5 ps. P3OT mixed with C60 shows similar spectral features at early times (<1 ps); however, a new spectrum evolves after ≈1 ps as a result of electron transfer from P3OT to C60. Ultrafast photoinduced electron transfer improves the quantum efficiency for photogeneration of charge carriers; in the ps domain the photoconductivity of the conducting polymer host is enhanced by more than an order of magnitude upon mixing in a few percent C60.