Abstract
Hexagonal M2C3 compound is a new predicted functional material with desirable band gaps, a large optical absorption coefficient, and ultrahigh carrier mobility, implying its potential applications in photoelectricity and thermoelectric (TE) devices. Based on density-functional theory and Boltzmann transport equation, we systematically research the TE properties of M2C3. Results indicate that the Bi2C3 possesses low phonon group velocity (~2.07 km/s), low optical modes (~2.12 THz), large Grüneisen parameters (~4.46), and short phonon relaxation time. Based on these intrinsic properties, heat transport ability will be immensely restrained and therefore lead to a low thermal conductivity (~4.31 W/mK) for the Bi2C3 at 300 K. A twofold degeneracy is observed at conduction bands along Γ-M direction, which gives a high n-type electrical conductivity. Its low thermal conductivity and high Seebeck coefficient lead to an excellent TE response. The maximum thermoelectric figure of merit (ZT) of n-type can approach 1.41 for Bi2C3. This work shows a perspective for applications of TE and stimulate further experimental synthesis.
Highlights
Thermoelectric (TE) technology can directly convert heat energy into electrical power, playing an important role in solving current energy and environmental crises [1,2,3]
Where S, σ, and T are the Seebeck coefficient, electrical conductivity, and absolute temperature. κ is the thermal conductivity, which is composed of the lattice thermal conductivity κl and electronic thermal conductivity κe
We systematically study the TE properties of the M2C3 monolayers by using Boltzmann transport theory
Summary
Thermoelectric (TE) technology can directly convert heat energy into electrical power, playing an important role in solving current energy and environmental crises [1,2,3]. The most common pristine TE materials are IV–VI (PbTe [19], Bi2Te3 [20], PbSe [21],) compounds, all of which possess a fairly low thermal conductivity These TE materials contain heavy atoms with a relatively narrow band gap, because heavy atoms give rise to low lattice vibrational frequency that results in a low κl [22]. Compared with the other 2D materials, such as phosphorus [27], boron nitride [28], and silicene [29], it exhibits desirable band edge locations and a large optical absorption coefficient These outstanding properties suggest M2C3 monolayers could be hopeful functional materials for next-generation high-performance devices. Calculated results shed light on the idea that the M2C3 is a hopeful candidate for TE applications
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