Hinge-like structure induced unusual properties of black phosphorus and new strategies to improve the thermoelectric performance

TL;DR

This study explores how strain affects black phosphorus's structure, electronic, and thermoelectric properties, revealing potential for enhanced thermoelectric performance and guiding the search for new hinge-like structured materials.

Contribution

It uncovers strain-induced property changes in black phosphorus and proposes strategies for improving thermoelectric performance and discovering new hinge-like thermoelectric materials.

Findings

Maximum ZT of 0.72 at 800K, enhanced to 0.87 with strain

Unusual mechanical responses due to hinge-like structure

Strain induces transitions among metallic and semiconducting states

Abstract

We systematically investigated the geometric, electronic and thermoelectric (TE) properties of bulk black phosphorus (BP) under strain. The hinge-like structure of BP brings unusual mechanical responses such as anisotropic Young's modulus and negative Poisson's ratio. A sensitive electronic structure of BP makes it transform among metal, direct and indirect semiconductors under strain. The maximal figure of merit $ZT$ of BP is found to be 0.72 at $800\,\mathrm{K}$ that could be enhanced to 0.87 by exerting an appropriate strain, revealing BP could be a potential medium-high temperature TE material. Such strain-induced enhancements of TE performance are often observed to occur at the boundary of the direct-indirect band gap transition, which can be attributed to the increase of degeneracy of energy valleys at the transition point. By comparing the structure of BP with SnSe, a family of potential TE materials with hinge-like structure are suggested. This study not only exposes various novel properties of BP under strain, but also proposes effective strategies to seek for better TE materials.