Enhancing the Power Factor of SWNT Thin Films for Organic Thermoelectrics

Thermoelectrics are regarded as one solution that upcycles waste heat to convert it into a useful resource; electricity. A thermoelectric device utilizes the Seebeck effect across a p-type and n-type material to create a voltage difference from a temperature gradient. Unlike many developments in the area of p-type, many conventional n-type materials have been restricted to inorganics that are toxic and expensive. Here, we focus on organic n-type material through doping and post-treatment which allows us to tune the power factor (PF) even further. Organic single wall carbon nanotubes (SWNT) are known for their high electrical conductivity through electron hopping of valence electrons and have shown potential for thermoelectrics. We have fabricated micron-thick SWNT films using a surfactant to induce an n-type behavior and doped them to further increase the electrical conductivity. The films were measured over 3 months and retained a stable negative Seebeck coefficient, which proves as a promising candidate for long-term thermoelectric devices. We have found that the different annealing temperatures and doping times of the dopant resulted in a distinguished surface morphology where we could improve the electrical conductivity with no diminishing of thermopower.