2D materials exhibit novel and exotic properties not found in their bulk counterparts; in particular, favorable transport properties (e.g. low thermal conductivity) that are sought after for thermoelectric applications are often observed in 2D materials. Anisotropy and applied strain in 2D materials has also resulted in previously unattainable transport behavior. To effectively elucidate thermoelectric efficacy, calculation of the dimensionless figure of merit, ZT, is required. However, substantial synthesis of true monolayer 2D materials for experimentally obtaining thermal conductivity is difficult. For instance, inorganic, non-transition metal materials have only been recently obtained as few-layer “flakes” with promising semiconductor band gaps; indium selenide is one such material, encouraging further attempts at obtaining a monolayer for studying thermoelectric applicability.<br/><br/>In this work, we explored monolayer InSe’s candidacy as a thermoelectric material by (1) <i>ab initio</i> calculations using DFT/PBE in Quantum Espresso, with Vanderbilt Ultrasoft Pseudopotentials, to elicit band structure and phonon spectra under stress/strain tuning, and (2) BoltzTrap and ShengBTE to ascertain thermoelectric values (thermal conductivity, electron mobility, seebeck coefficients, etc…) for ZT calculations. Our calculations indicate that an indirect-indirect band gap transition occurs at a compressive strain of 6%, where a significant enhancement of the dimensionless figure of merit is achieved. In addition, calculations of electron mobility and thermal conductivity herald InSe as a new and viable thermoelectric material. Our studies further illustrate that strain-induced transitions and thermoelectric engineering in two-dimensional materials play a key role in the future development of thermoelectric devices.

Strain-induced transformation and thermoelectric engineering of monolayer indium selenide

2019 Spring National Meeting

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