High-performance and anomalous thermoelectric properties of organic−inorganic nanocomposites consisting of fullerene molecules and molybdenum trioxide nanoclusters

We have found the extraordinary thermoelectric properties of the organic−inorganic nanocomposite consisting of fullerene (C 60 ) molecules and molybdenum trioxide (MoO 3 ) nanoclusters. Although pristine C 60 films exhibit an exceptionally larger N-type Seebeck coefficient ( α = −121 mVK −1 ) of more than two orders of magnitude than conventional materials, their power factor ( PF = α 2 σ = 2.4 × 10 −6 WK −2 m −1 ) is three orders of magnitude smaller than that required for applications owing to their low electrical conductivity ( σ = 1.6 × 10 −6 Scm −1 ). On the other hand, the exceptionally large PF (1.8 × 10 −4 WK −2 m −1 ) of C 60 (MoO 3 ) x nanocomposite films, which is two orders of magnitude larger than that of pristine C 60 films, was realized by markedly increasing σ while maintaining a giant α . The C 60 (MoO 3 ) x (0.011 < x < 11.8) films exhibited P-type thermoelectric properties ( α > 0) owing to the hole injection into C 60 from the MoO 3 nanoclusters, in which the hole injection increased depending on x . The relationship between the σ and α of C 60 (MoO 3 ) x cannot be explained quantitatively and qualitatively by conventional theory, indicating that the C 60 (MoO 3 ) x nanocomposite is classified into a novel category of thermoelectric materials. • Organic−inorganic nanocomposites consisting of C 60 molecules and MoO 3 nanoclusters. • Control of electrical conductivity while maintaining giant Seebeck coefficient. • Anomalous relationship between electrical conductivity and Seebeck coefficient. • Novel category of thermoelectric materials.