Demonstration of a thermoelectric device using electric double-layer gating: Simultaneous control of the thermoelectric properties of p-type and n-type carbon nanotubes

To fabricate a p-type and n-type pair for a thermoelectric device, an electric double-layer capacitor structure was applied to semiconducting single-walled carbon nanotube (SWCNT) sheets. The carrier concentration of the positive and negative SWCNT electrodes (channels) was controlled by changing the gate voltage applied between electrodes filled with an ionic liquid. The drain current and the thermopower of the channels were measured as a function of the gate voltage, and the drain current of both channels was found to drastically increase with the gate voltage. Positive and negative thermopower was observed in the positive and negative channels, respectively. These results indicate that hole and electron carriers were induced in the channels. We conclude that it is possible to simultaneously optimize the thermoelectric properties of p-type and n-type semiconducting SWCNTs using electric double-layer gating.