High-Efficiency Van Der Waals heterostructure Thermionic Device With Graphene Electrodes

In this paper, we propose van del Waals heterostructure-based thermionic devices for the applications in cooling and power generation in the temperature range of 300 to 400 K. By using two-dimensional materials of low cross-plane thermal conductivity as the barrier materials and graphene as electrodes, our calculation demonstrates that our proposed device will have a higher efficiency as compared to other methods such as thermoelectric device and the traditional thermionic devices. By using the parameters within the current technology, we predict a cooling capability at more than 50$\%$ of the Carnot efficiency, and a 10 to 20 $\%$ efficiency in harvesting the wasted heat at 400 K.