Spin dynamics of carrier generation in a photoconductive C60-doped poly(N-vinylcarbazole) film

The magnetic field effects on the carrier yield have been studied to clarify the spin dynamic process during photoinduced carrier generation in a fullerene (C60)-doped poly(N-vinylcarbazole) (PVCz) film. The charge transfer (CT) complex of C60 and the carbazole (Cz) chromophore is selectively excited. The total number of carriers that escaped from the geminate pairs decreases in the presence of magnetic fields, which arises from a hyperfine mechanism of the distant ion pairs involving C60- and Cz+. Time-resolved EPR measurements verify that the excited triplet state of C60 is produced via its excited singlet state generated from the contact ion pair. The competitive formation processes of distant ion pairs and the excited states of C60 from the contact ion pair are discussed.