First-principles study of LaOBiPbS₃ and its analogous compounds as thermoelectric materials

LaOBiPbS₃ is a kind of pnictgen-dichalcogenide layered compounds, which have recently been investigated as thermoelectric materials owing to their low thermal conductivity and high controllability of constituent elements [1, 2]. However, thermoelectric performance of LaOBiPbS₃ is not very high and that of its analogous compounds is still unknown. In this study, we theoretically investigate the thermoelectric property of LaOBiPbS₃ and its analogous compounds : LaOPnTtCh₃ (Pn = As, Sb, Bi; Tt = Sn, Pb; Ch = S, Se). We find that there are two key factors for increasing thermoelectric performance: one is the spin-orbit coupling, mainly controlled by Pn, and the other is the hybridization between Pn in the PnS₂ layer and Ch in the rock-salt layer, which determines the gap size. In fact, we find that LaOSbPbSe₃, which optimizes these key factors but has not been synthesized yet, can have a power factor that is about 5 times as large as that of the known compound LaOBiPbS₃.

Reference :
1) Y. Mizuguchi et al., Europhys. Lett. 119, 26002 (2017).
2) Y. L. Sun et al., Inorg. Chem. 53, 11125 (2014).