High thermopower of monolayers and bilayers of C₆₀ derivatives

We use density functional theory to study the thermoelectric properties of a gold-molecule-graphene molecular junction formed a fullerene monomer (denoted PTEG-1), comprising a fullerene derivative with a polar triethylene glycol (TEG) pendent group and found that the Seebeck coefficient is +261 μV K^-1. This high positive value for the Seebeck coefficient is marked contrast with the high negative Seebeck coefficient of a gold-dimer-graphene molecular junction containing two anti-aligned PTEG-1 molecules which we found to be -356 μV K^-1. We also computed the Seebeck coefficient of molecule comprising C₆₀ derivative attached to two ethylene glycol chains (denoted PTEG-2) in the presence of n-DMBI⁺ doping, which we found to vary between -109 μV K^-1 and -205 μV K^-1, depending on the level of doping. These high values of the Seebeck coefficients with both positive and negative signs suggest that such molecules are ideal candidates for producing scalable gold-molecule-graphene thermoelectric generators.