Realizing high in-plane carrier mobility in n-type SnSe crystals through deformation potential modification

Abstract

Thermoelectric technology, as one solution to energy harvesting, offers a direct and reversible conversion between electricity and heat. The emerging thermoelectric material SnSe shows great potential in both power generation and solid-state cooling. In contrast to p-type SnSe, high-performance n-type counterparts are difficult to put into application, restricted by their out-of-plane cleavable characteristic. In this work, we focus on the in-plane thermoelectric properties of the n-type SnSe crystal to match p-type SnSe, which possesses high carrier mobility and high mechanical strength. We increase the room-temperature in-plane carrier mobility of the n-type SnSe crystal to ∼445 cm² V⁻¹ s⁻¹ by Pb alloying. It is noteworthy that the carrier mobility is enhanced by lowering the deformation potential rather than the effective mass. We confirm the constant effective mass by the quasi-acoustic phonon scattering model. In the results, the unobstructed in-plane electrical transport is realized, and a high power factor of ∼15.3 μW cm⁻¹ K⁻² is obtained at 300 K. Combined with the suppressed thermal conductivity, a ZT of ∼0.4 at 300 K and an average ZT of ∼0.74 at 300–773 K are obtained. These results demonstrate that the in-plane performance of the n-type SnSe crystal is notable for exploitation as the n-type component in thermoelectric cooling devices.