Remarkable electronic band structure leads to high thermoelectric properties in p-type γ-Cu2S.

Clarifying how to design and fabricate an improved material composed by toxic-free and low-cost elements with high thermoelectric conversion efficiency represents one of the most challenging issues in modern materials science. In this work, we apply first-principles calculations and Boltzmann transport theory to study the electronic structure and transport properties on γ -Cu 2 S materials. Our results show that a high thermoelectric figure of merit ZT of 1.2 can be achieved in hole-doped Cu 2 S crystal along b -axis direction at 500 K with an optimal doping of 4.1 × 1019 cm−3. This high thermoelectric property originates from its remarkable valence band structure, which is highly anisotropic combining heavy and light features, and possesses five valence band maxima close to the Fermi level, leading to multivalley transport to enhance Seebeck coefficients and power factors. This work demonstrates hole-doped γ -Cu 2 S is a promising eco-friendly thermoelectric material for large-scale applications. Our exploration on the physical origin of the high thermoelectric efficiency in γ -Cu 2 S can be helpful for further optimizing thermoelectric properties in experiments and sheds strong light on the search or even design of new thermoelectric materials through band engineering. • Low-cost and eco-friendly p -type Cu 2 S could have a high ZT of 1.2 at 500 K. • High ZT of Cu 2 S is due to strong anisotropic and multivalley valence band characters. • Multivalley transport is favorable for thermoelectric properties. [ABSTRACT FROM AUTHOR]