High Thermoelectric Power Factor in Graphene/hBN Devices

TL;DR

This paper demonstrates that using hBN substrates significantly enhances the thermoelectric power factor in graphene devices, enabling efficient active cooling with fast gate-controlled switching, surpassing previous 2D and bulk materials.

Contribution

The study shows that hBN substrates improve graphene's thermoelectric performance, enabling high-efficiency active cooling and fast Seebeck coefficient switching, which was not feasible with SiO2 substrates.

Findings

Room temperature power factor reaches 10.35 W/mK

Significant reduction of electron-hole puddles

Fast gate-controlled Seebeck switching achieved

Abstract

Fast and controllable cooling at nanoscales requires a combination of highly efficient passive cooling and active cooling. While passive cooling in graphene-based devices is quite effective due to graphene's extraordinary heat-conduction, active cooling has not been considered feasible due to graphene's low thermoelectric power factor. Here we show that the thermoelectric performance of graphene can be significantly improved by using hBN substrates instead of SiO2. We find the room temperature efficiency of active cooling, as gauged by the power factor times temperature, reaches values as high as 10.35 W/mK, corresponding to more than doubling the highest reported room temperature bulk power factors, 5 W/mK in YbAl3, and quadrupling the best 2D power factor, 2.5 W/mK, in MoS2. We further show that in these devices the electron-hole puddles region is significantly reduced. This enables fast gate-controlled switching of the Seebeck coefficient polarity for application in n- and p-type integrated active cooling devices.