X2Pd3Se4 (X = K, Rb, Cs): Unexplored 2D semiconductors with high n-type transport performance

Abstract

Two-dimensional (2D) materials have attracted much interest because of their special morphology and novel physical properties. In this work, we proposed three unexplored 2D materials, X2Pd3Se4 (X = K, Rb, Cs), and further investigated their stability, electronic and thermoelectric transport properties. We revealed that these materials are indirect semiconductors with band-gaps of 1.74 ∼ 1.95 eV, and show “multi-valleys” convergence near conduction band minimums. Besides, the monolayers also possess high electron mobility of 103 ∼ 104 cm2·V−1·s−1, leading to high conductivity (106 ∼ 107 Ω-1m−1), as well as high thermoelectric power factor (∼102 mW·K−2·m−1). Also, because of the high group velocity and low phonon scattering rate, they also show moderate lattice thermal conductivity of 19.21 ∼ 75.78 W/mK at 300 K. Nevertheless, they still deliver high thermoelectric figure of merit of 0.20 ∼ 1.04 at 300 K, and increase further to 0.67 ∼ 1.94 at 700 K, suggesting that they have potential applications in the field of low-medium temperature thermoelectric devices.