Metallo‐organic n‐type thermoelectrics: Emphasizing advances in nickel‐ethenetetrathiolates

Abstract

ABSTRACTMetallo‐organic complexes with nickel as the metal center have been shown to exhibit high electrical conductivities warranting investigation of their thermoelectric potential. A review of metallo‐organic n‐type thermoelectrics is presented with a focus on nickel‐sulfur coordination compounds. Herein, we also investigate the extent of oxidation on thermoelectric properties of poly(Ni‐1,1,2,2‐ethenetetrathiolate) (Ni‐ETT) based materials. Elemental analysis and X‐ray photoelectron spectroscopy are used to characterize samples with different air exposure times, leading to differing levels of oxidation. When blended with an inert polymer matrix, the sample exposed to air for 30 min resulted in an eight times enhancement in electrical conductivity compared to the sample exposed to air for 24 h. Furthermore, the elemental composition of the 30 min sample fit the empirical formula Ax(MC2S4) postulated in literature, while the 24 h sample does not, which we attribute to decomposition during the oxidation process and presence of disulfides. The Seebeck coefficient remains largely unchanged as a function of oxidation time, indicating that this may be a viable technique to decouple Seebeck and electrical conductivity for high‐performance organic thermoelectric materials. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44402.