The absorption spectrum and a cyclic voltammogram of C₆₀-doped poly(3-alkylthiophene)

The absorption spectrum and a cyclic voltammogram for poly(3-hexylthiophene) changed upon C₆₀ doping but those for poly(3-octadecylthiophene) did not. This suggests that C₆₀ is an effective dopant for poly(3-hexylthiophene) in the ground state but not for poly(3-octadecylthiophene). The threshold of cyclic voltammetry has shifted to a higher potential in C₆₀-doped poly(3-hexylthiophene). This is explained by the lowering of the valence band top due to the electron transfer from poly(3-hexylthiophene) to C₆₀. The shift depends on alkyl chain length and decreases with alkyl chain length in accordance with the results of photoemission spectroscopy.