Ultralow Thermal Conductivity and High Thermoelectric Figure of Merit in Two-Dimensional Thallium Selenide

Abstract

Several selenides have been studied as potential thermoelectric materials in the past. Thermoelectric performance improves on reducing the dimension of the system. Following these notions, we studied three hexagonal two-dimensional phases of thallium selenide for promising thermoelectric performance by using first-principles techniques. Their dynamical and mechanical stabilities have been shown. The band gaps using different approximations of calculations have been reported and are in the range that can render these materials to show optimal thermoelectric performance. The lattice thermal conductivity is ultralow between 0.088 and 0.429 W m–1 K–1 at 900 K. High thermoelectric performance has been predicted in the systems with the figure of merit reaching magnitudes of ∼0.5–1.94 between 300 and 900 K. The high thermoelectric performance results from an ultralow thermal conductivity arising due to the strong lattice anharmonicity. These results can have significant impact on the synthesis of high performance thermoelectric materials based on thallium selenide.

The Abnormally Excellent Figure of Merit of 14,14,18-Graphyne at Room Temperature: A Study on the Thermoelectric Characteristic of Graphyne

“…This can be seen as the reason for the unusual phenomenon that maximum ZT value (1.6) of this model appears at room temperature. Considering that the ZT of most materials shows an increasing trend following with the increasing temperature, ,,, the abnormal ZT trend of GY provides a new idea for the development of thermoelectric materials at room temperature. Moreover, it should be noted that GY is not the only example of ZT decreasing with increasing temperature; e.g., in ref , the function S 2 σ/τ (an indicator of the behavior of ZT) of Mg 2 Sn reduces with the increase of temperature in the low carrier-concentration bipolar regime (1× 10 19 ∼ 5× 10 19 cm –3 ).…”

“…Nowadays, the global energy crisis has arrived due to the massive use of fossil fuels. Thermoelectric materials can convert waste heat surplus thermal energy into electric energy; therefore, this method shows great potential in the field of sustainable energy. , Generally, the performance of thermoelectric materials can be characterized by the figure of merit ZT: ZT = S 2 σT /κ, where S , σ, T , and κ, are the Seebeck coefficient, electrical conductivity (EC), absolute temperature, and thermal conductivity (TC), respectively. From this equation, it can be noted that excellent thermoelectric materials require a high power factor ( S 2 σ, high Seebeck coefficient and EC) and low TC .…”

“…Nevertheless, since the TC of graphene nearly reaches 5000 W/mK, 16 it cannot be directly used as a distinguished thermoelectric material. Graphyne (GY), the new allotrope of graphene, is composed of sp, sp 2 and sp 3 hybridized carbon atoms. The sp 2 hybridized carbon atoms are formed as a hexagon, and the different hexagon structures are connected with acetylene bond (−C C−).…”

High Thermoelectric Performance in 2D Technetium Dichalcogenides TcX2 (X = S, Se, or Te)

“…The TE properties of bulk and monolayer TcX 2 were determined using the semiclassical Boltzmann theory, Boltzmann transport equation (BTE), and relaxation time approximation methods as implemented in the BoltzTraP2 code . For semiconductors, the relaxation time value τ = 10 –14 s is commonly used and the validity of this approach has been tested earlier and turns out to be a reasonably good approximation. ,− Here, we assume that the relaxation time is constant and independent of the temperature and doping. The constant relaxation time τ = 10 –14 s is used to evaluate electronic thermal conductivity and electrical conductivity.…”

Anisotropic optical responses of layered thallium arsenic sulfosalt gillulyite

“…It is worth noting that the crystallographic and structural properties of bulk gillulyite crystal have been studied, but the light-matter interaction correlated with the structural parameters of the crystal are still unknown. In general, thallium containing compounds are recently identified as potential materials for several important applications ranging from energy storage to security purposes such as thermoelectrics, laser frequency modulators, radiation sensors, and photovoltaics 23 – 25 . Therefore, the insightful understanding of light-matter interaction associated with the structural properties of these materials will be valuable for their engagement in technological improvisation.…”