Air-stable fabric thermoelectric modules made of N- and P-type carbon nanotubes

This report demonstrates an exciting new paradigm for thermoelectric energy conversion with both n- and p-type organic materials that possess mechanical flexibility, simple fabrication processes, and stability in air. In order to synthesize n-type samples with membranes and papers, carbon nanotubes were doped with both polyethyleneimine (PEI) and sodium borohydride (NaBH ₄), showing excellent n-type characteristics with thermopower values as large as -80 μV K ^-1. Thermoelectric modules made of both n- and p-type composites were fabricated to demonstrate thermoelectric voltage and power generation with one, two, and three p-n couples connected in series. The testing modules produced ∼6 mV thermoelectric voltage, with ∼25 nW generated power upon application of ∼22°C temperature gradients. These promising results show that further work with many junctions connected in series would result in scalable organic p-n couple modules, which can generate power from temperature gradients or provide cooling for various electronic devices.