HfSe2/GaSe Heterostructure as a Promising Near-Room-Temperature Thermoelectric Material

Heterostructure-based low-dimensional materials have recently attracted tremendous attention because of their tunable physical and chemical properties. Here, the thermoelectric (TE) properties of the HfSe2/GaSe heterostructure are investigated by using first-principles calculations and Boltzmann transport theory. It is found that the system is both dynamically and thermally stable, as characterized by positive phonon frequencies and small structure fluctuations at finite temperatures. In addition, the heterostructure exhibits a small indirect band gap, around which we observe a flat and degenerated conduction band so that a higher n-type power factor can be expected. On the other hand, the coexistence of mixed bonds and lone-pair electrons suggests enhanced anharmonicity and small lattice thermal conductivity of the system. Consequently, a larger ZT value of 1.8 at 300 K and a peak ZT of 2.2 at 400 K can be achieved for the n-type HfSe2/GaSe heterostructure, which are much higher than those of the constituent layers and highlight a promising near-room-temperature TE application.