Poly(nickel-ethylenetetrathiolate) and Its Analogs: Theoretical Prediction of High-Performance Doping-Free...

It is generally deemed that doping is a must for polymeric materials to achieve their high thermoelectric performance. We herein present the first report that intrinsically metallic behaviors and high-performance thermoelectric power factors can coexist within doping-free linear-backbone conducting polymers, poly(nickel-ethylenetetrathiolate) and its analogs. On the basis of density functional calculations, we have corroborated that four crystalline π- d conjugated transition-metal coordination polymers, including poly(Ni-C₂S₄), poly(Ni-C₂Se₄), poly(Pd-C₂S₄) and poly(Pt-C₂S₄) exhibit intrinsically metallic behavior arising from the formation of dense intermolecular interaction networks between sulfur/selenium atoms. They show moderate carrier concentrations (10¹⁹-10²¹ cm^-3) and decent conductivities (10³-10⁴ S cm^-1), among which, poly(Ni-C₂S₄), poly(Ni-C₂Se₄) and poly(Pd-C₂S₄) possess high power factors (∼10³ μW m^-1 K^-2).