Graphene Induced High Thermoelectric Performance in ZnO/Graphene Heterostructure

Abstract

AbstractDespite the low thermoelectric (TE) efficiency of graphene, its flexibility features are attractive for flexible and wearable next‐generation thermoelectric applications. So, it will be highly desirable to synthesize graphene‐based high TE material. Hence, the possibility of significant enhancement of the TE performance in ZnO/graphene heterostructure is investigated. The ZnO monolayer has a direct band gap of 3.3 eV, while a band gap of 5 meV in the ZnO/graphene heterostructure is found. The highest ZT ≈ 2.4 in the n‐doped ZnO/graphene heterostructure at 500 K is obtained, whereas the ZnO monolayer shows ZT ≈ 1.3 at 700 K. Particularly, this giant ZT in the ZnO/graphene heterostructure is found even at a low carrier concentration (≈1011 carrier cm−2). Besides, the ZnO/graphene heterostructure also displays a ZT ≈ 0.8 even at 300 K with a very low carrier concentration (≈1010 carrier cm−2). This outstanding TE performance originates from the TE coefficient advantages of each layer; high electrical conductivity from graphene and high Seebeck coefficient from ZnO incorporate with reduced thermal conductivity in the heterostructure. The findings will stimulate further studies to confirm the results as well as the development of flexible TE generators based on graphene for Internet of things thermoelectric applications.