Large and tunable photo-thermoelectric effect in single-layer MoS2

TL;DR

This study reveals that single-layer MoS2 exhibits a dominant photo-thermoelectric response with a large, tunable Seebeck coefficient, opening new possibilities for thermoelectric applications.

Contribution

It demonstrates that the photoresponse in single-layer MoS2 is primarily due to the photo-thermoelectric effect and shows how the Seebeck coefficient can be externally tuned.

Findings

Photocurrent in MoS2 is dominated by the photo-thermoelectric effect.

Seebeck coefficient can be tuned from -400 to -100,000 μV/K.

Potential for on-chip thermopower generation and energy harvesting.

Abstract

We study the photoresponse of single-layer MoS2 field-effect transistors by scanning photocurrent microscopy. We find that, unlike in many other semiconductors, the photocurrent generation in single-layer MoS2 is dominated by the photo-thermoelectric effect and not by the separation of photoexcited electron-hole pairs across the Schottky barriers at the MoS2/electrode interfaces. We observe a large value for the Seebeck coefficient for single-layer MoS2 that, by an external electric field, can be tuned between -4x10^2 uV/K and -1x10^5 uV/K. This large and tunable Seebeck coefficient of the single-layer MoS2 paves the way to new applications of this material such as on-chip thermopower generation and waste thermal energy harvesting.