XMoSiN2 (X = S, Se, Te): A novel 2D Janus semiconductor with ultra-high carrier mobility and excellent thermoelectric performance

- Two-dimensional (2D) semiconductor MoSi2N4 is a potential candidate for thermo-electric materials due to its high Seebeck coefficient. However, its high lattice thermal conductivity limits its applications in the field of thermoelectric materials. Here, we constructed an unsym-metrical 2D Janus semiconductor XMoSiN2(X = S, Se, Te) based on MoSi2N4 to significantly reduce the lattice thermal conductivity to only one-sixth that of MoSi2N4 at 300 K. We found that XMoSiN2 had an ultra-high carrier mobility up to 4640 cm2V-1s-1 leading to a metal-like electrical conductivity. Meanwhile, XMoSiN2 reserved the high Seebeck coefficient of MoSi2N4. The lower lattice thermal conductivity and metal-like electrical conductivity resulted in excellent thermoelectric performance. TeMoSiN2 possessed a record-high ZT value of 3.57 at 900 K. We believed that other materials with a similar structure to XMoSiN2 can also be potential candi-dates for high-performance thermoelectric materials. Our work provides valuable insights into designing novel high-performance thermoelectric materials.