Strong Thermopower Enhancement and Tunable Power Factor <i>via</i> Semimetal to Semiconductor Transition in a Transition-Metal Dichalcogenide.

Moon, Hongjae; Bang, Joonho; Hong, Seokkyoon; Kim, Gwansik; Roh, Jong Wook; Kim, Jeongmin; Lee, Wooyoung · ACS Nano · 2019

basic_science · Level V

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Abstract

Electronic band engineering is a promising approach to enhance the thermopower of thermoelectric materials. In transition-metal dichalcogenides (TMDCs), this has so far only been achieved using their inherent semiconducting nature. Here, we report the thickness-modulated band engineering of nanosheets based on semimetallic platinum diselenide (PtSe<sub>2</sub>) resulting in a thermopower enhancement of more than 50 times than that of the bulk. We obtained this by introducing a semimetal to semiconductor (SMSC) transition resulting in the formation of a bandgap. This approach based on semimetallic TMDCs provides potential advantages such as a large variation of transport properties, a decrease of the ambipolar transport effect, and a high carrier density dependence of the transport properties. Our observations suggest that the SMSC transition in TMDCs is a promising and straightforward strategy for the development of two-dimensional nanostructured thermoelectric materials.