Thermionic transport across gold-graphene-WSe van der Waals heterostructures.

Solid-state thermionic devices based on van der Waals structures were proposed for nanoscale thermal to electrical energy conversion and integrated electronic cooling applications. We study thermionic cooling across gold-graphene-WSe-graphene-gold structures computationally and experimentally. Graphene and WSe layers were stacked, followed by deposition of gold contacts. The - curve of the structure suggests near-ohmic contact. A hybrid technique that combines thermoreflectance and cooling curve measurements is used to extract the device . The measured Seebeck coefficient, thermal and electrical conductance, and values at room temperatures are in agreement with the theoretical predictions using first-principles calculations combined with real-space Green's function formalism. This work lays the foundation for development of efficient thermionic devices.