ULTRAFAST PHOTOINDUCED ELECTRON-TRANSFER IN CONDUCTING POLYMER BUCKMINSTERFULLERENE COMPOSITES

We report time-resolved photoinduced absorption and time-resolved phot oconductivity in conducting polymer-C60 CoMPosites. Photoinduced elect ron 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 tau < 5 ps. P3OT mixed wi th C60 shows similar spectral features at early times ( < 1 ps); howev er, a new spectrum evolves after almost-equal-to 1 ps as a result of e lectron transfer from P3OT to C60. Ultrafast photoinduced electron tra nsfer improves the quantum efficiency for photogeneration of charge ca rriers; in the ps domain the photoconductivity of the conducting polym er host is enhanced by more than an order of magnitude upon mixing in a few percent C60.