Promising high-temperature thermoelectric response of bismuth oxybromide

Recently, the bismuth oxybromide quintuple-layer (QL) was experimentally realized. In the present study, we extensively examine the stability, electronic and thermal transport of bulk bismuth oxybromide (BiOBr) and QL based on first-principles calculations and the semiclassical Boltzmann transport theory. We have found that the bulk and QL BiOBr systems are dynamically and thermally stable with an indirect band gap of 2.86 and 3.08 eV, respectively. The emergence of comparatively flat bands at the top valence band favours the pronounced p-type Seebeck coefficient. Our calculated results demonstrate a high Seebeck coefficient of 1569.82 μV/K and 1580 μV/K for bulk and QL BiOBr materials at high temperatures. At higher temperature, the lattice thermal conductivity values of bulk are 1.32/0.23 for in-plane/out-of-plane, respectively and 1.85 W/mK in QL BiOBr, which are relatively low compared to other layered materials, e.g., MX2 (M = Mo, W, Pt, Zr, and X = S, Se, Te). The figure of merit (ZT) turns out to be as high as 3.52 for bulk BiOBr and 1.5 for QL BiOBr at higher temperatures,suggest them as good candidates for thermoelectric applications.