Phonon-limited hole mobility and thermoelectric transport of monolayer WCu2Se4 from first-principles calculations

The asymmetry between electron and hole mobilities in 2D semiconductors severely limits the practical applications in thermoelectric couples and electronic devices. It is, thus, valuable to discover new 2D semiconductors with high hole mobility. Using first-principles calculations and the Boltzmann transport equations, we predict a new 2D monolayer WCu2Se4 with a high room-temperature hole mobility of 89 cm2 V−1 s−1, which is much larger than that of traditional bulk GaN, and also higher than most 2D semiconductors. Notably, the hole mobility contributed by short-range phonons is as high as 265 cm2 V−1 s−1. However, it exhibits a relatively high thermal conductivity κph of 10.4 W m−1 K−1, primarily driven by acoustic and low-frequency optical phonons. It is found that the maximum p-type ZT is 0.20 at room temperature, and the ZT can be enhanced to 0.47 at 600 K. This relatively high ZT can compete with the most excellent 2D thermoelectrics. Our study demonstrates monolayer WCu2Se4 as a promising p-type 2D semiconductor and thermoelectric candidate.