Thermally Enhanced n‐Type Thermoelectric Behavior in Completely Organic Graphene Oxide‐Based Thin Films

Air‐stable n‐type organic thermoelectric (TE) materials with high power factor are needed to produce efficient, lightweight devices that could be self‐powered by harnessing waste heat. Here, a completely organic n‐type TE nanocomposite is achieved by depositing layers of double‐walled carbon nanotubes (DWNT) stabilized with polyethylenimine (PEI) and graphene oxide (GO) in a layer‐by‐layer fashion from aqueous solutions. A 30 bilayer (BL) film (≈610 nm thick), comprised of this DWNT‐PEI/GO sequence, exhibits electrical conductivity of 27.3 S cm⁻¹ and a Seebeck coefficient of −30 µV K⁻¹, producing a power factor of 2.5 µW m⁻¹ K⁻². Low temperature thermal reduction (150 °C for 30 min) of this composite thin film significantly improves its thermoelectric performance. An electrical conductivity of 460 S cm⁻¹ and Seebeck coefficient of −93 µV K⁻¹ are achieved. A 30 BL DWNT‐PEI/reduced graphene oxide (rGO) film (≈480 nm thick) exhibits a power factor as large as 400 µW m⁻¹ K⁻², which is one of the highest values reported for an organic n‐type material. By depositing layers containing montmorillonite clay on top, these n‐type nanocomposites exhibit excellent air stability. This combination of air stability and high power factor could enable efficient thermoelectric devices on flexible substrates (e.g., clothing).