Electrical Conductivity and ESR Spectrum of Buckminsterfullerene-Doped Poly(3-alkylthiophene)

Abstract

Buckminsterfullerene (C₆₀) is effectively doped in poly(3-alkylthiophene). However, the characteristics of C₆₀-doped poly(3-alkylthiophene) are different from the typical behavior observed in the case of conventional dopants. Electrical conductivity of poly(3-alkylthiophene) increases upon C₆₀ doping and decreases again at higher concentration of C₆₀. Its temperature dependence is also anomalous. The absorption spectrum changes markedly upon C₆₀ doping. ESR linewidth decreases from 7.1 G to 1.9 G upon C₆₀ doping. Spin density, evaluated by ESR, is enhanced upon C₆₀ doping. These doping characteristics are tentatively explained by taking electronic energy diagrams of both poly(3-alkylthiophene) and C₆₀ into consideration.