Few-layer black phosphorus has recently emerged as a promising candidate for novel electronic and optoelectronic device. Here we demonstrate by first-principles calculations and Boltzmann theory that, black phosphorus could also have potential thermoelectric applications and a fair ZT value of 1.1 can be achieved at elevated temperature. Moreover, such value can be further increased to 5.4 by substituting P atom with Sb atom, giving nominal formula of P 0.75 Sb 0.25 . Our theoretical work suggests that high thermoelectric performance can be achieved without using complicated crystal structure or seeking for low-dimensional systems.

SnSe is considered to be a promising thermoelectric material due to a high ZT value and abundant and non-toxic composition elements. However, the thermal stability is an important issue for commercial application. In particular, thermoelectric materials are in the high temperature for a long time due to the working condition. The present work investigates the thermal stability and oxidation resistance of single crystal SnSe thermoelectric materials. The scanning electron microscopy (SEM) and transmission electron microscopy (TEM) results show that the internal of SnSe crystal is not easily oxidized, while the x-ray photoelectron spectroscopy (XPS) results indicate that the surface of SnSe is slight oxidized to SnO 2 . Even if the surface is oxidized, the SnSe crystal still exhibits stable thermoelectric properties. Meanwhile, the crystallization quality of SnSe samples can be improved after the appropriate heat treatment in the air, which is in favor of the carrier mobility and can improve the electrical conduction properties of SnSe. Moreover, the decrease of defect density after heat treatment can further improve the Seebeck coefficient and electrical transport properties of SnSe. The density functional theory (DFT) calculation verifies the important role of defect on the electrical conductivity and electron configuration. In summary, appropriate temperature annealing is an effective way to improve the transmission properties of SnSe single crystal thermoelectric materials.

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In this study, a nano-layered Cu2Se high-performance material is successfully grown using a NaCl-flux method based on the stoichiometric ratios of Cu2Se(NaCl)x (x = 1.5, 2, 2.5, 3, and 3.5).