Significant thermoelectric conversion efficiency enhancement of single layer graphene with substitutional silicon dopants

Abstract

Graphene was regarded as inappropriate material for practical thermoelectric application due to its low thermoelectric conversion efficiency (ZT) from its superlative thermal conductivity and gapless electronic structure. In this study, for the first time, we experimentally investigate the significant thermoelectric conversion efficiency enhancement in graphene by introducing substitutional Si dopants during the CVD growth of single layer graphene. The thermal conductivity of Si-doped graphene (SiG) shows the significant suppression due to the large molecular weight mismatch between host C atoms and Si dopants in the same group V. On the other hand, the Si dopants do not severely suppress the electrical properties compared to thermal conductivity due to the narrow minimum in the electron transmission spectrum of SiG near Fermi Level. The incorporated Si dopants provide the progressive reduction in Seebeck coefficient due to the increased scattering of charge carriers in SiG, but we found nearly 17 times thermoelectric conversion efficiency enhancement (ZT/ZT0) in the suspended graphene when the 2.59% of Si dopants are incorporated, which is much higher than graphene with other dopants for lattice defects. We believe that substitutional Si dopants can provide a promising method to break the limit in the current graphene based thermoelectric materials.