High thermoelectric performance in two-dimensional graphyne sheets predicted by first-principles calculations

Abstract

The thermoelectric properties of two-dimensional graphyne sheets are investigated by using first-principles calculations and the Boltzmann transport equation method. The electronic structure indicates a semiconducting phase for graphyne, compared with the metallic phase of graphene. Consequently, the obtained Seebeck coefficient and the power factor of graphyne are much higher than those of graphene. The calculated phonon mean free path for graphene is 866 nm, which is in good agreement with the experimental value of 775 nm. Meanwhile the phonon mean free path of graphyne is only 60 nm, leading to two order lower thermal conductivity than graphene. We show that the low thermal conductivity of graphyne is due to its mixed sp/sp(2) bonding. Our calculations show that the optimized ZT values of graphyne sheets can reach 5.3 at intermediate temperature by appropriate doping.

Thermoelectric properties of γ-graphyne from first-principles calculations

“…These structure parameters are in good agreement with previously calculated using projector-augmented-wave (PAW) approach [12,19]. To check the stability of the structure, we have calculated the phonon dispersion relations of γ-graphyne and no imaginary frequency is found, as shown in Figure 2 structure is consistent with previous theoretical studies using PAW [19] and pseudopotential methods [20]. [20,21], or apply deformation potential (DP) theory which only considers the electron-acoustic phonon scattering [19,32].…”

“…The optimized lattice constants are a = b = 6.890 Å, and three different bond lengths exist due to the mixed hybridization of carbon atoms with sp 2 sp 2 (1.426 Å), sp 2 sp (1.408 Å), and spsp (1.223 Å). These structure parameters are in good agreement with previously calculated using projector-augmented-wave (PAW) approach [12,19]. To check the stability of the structure, we have calculated the phonon dispersion relations of γ-graphyne and no imaginary frequency is found, as shown in Figure 2 structure is consistent with previous theoretical studies using PAW [19] and pseudopotential methods [20].…”

“…To check the stability of the structure, we have calculated the phonon dispersion relations of γ-graphyne and no imaginary frequency is found, as shown in Figure 2 structure is consistent with previous theoretical studies using PAW [19] and pseudopotential methods [20]. [20,21], or apply deformation potential (DP) theory which only considers the electron-acoustic phonon scattering [19,32]. In the present work, the carrier relaxation time is accurately evaluated by considering the complete electron-phonon coupling within the EPW framework.…”

High thermoelectric efficiency in monolayer PbI2 from 300 K to 900 K

“…Once µ is calculated, the electrical conductivity can be obtained at a given carrier concentration (assuming that the carrier concentration remains constant at different temperatures). As shown The key and remarkable feature of monolayer PbI 2 is ultralow lattice thermal conductivity κ L , which ranges from 0.096 W/mK at 200 K to 0.022 W/mK at 900 K. This extraordinarily low κ L is much lower than other 2D thermoelectric material 62,[64][65][66][67][68] . To quantitatively understand the origin of ultralow κ L in monolayer PbI 2 , we compare the results using the Boltzmann transport equation According to the Slack model, the κ L is given by 70…”

A sp2+sp3 hybridized carbon allotrope transformed from AB stacking graphyne and THD-graphene

“…Graphyne is a sp+sp 2 two-dimensional structure. 27 It has already attracted great attention because of its high carrier mobility, 28 strong mechanical properties, 29 high thermoelectric performance, 30 excellent chemical, thermal stability and optical properties. 31 Graphyne has also exhibited great application potentials in lithium and hydrogen storage due to its unique porous structure.…”