New Family of Two-Dimensional Ternary Photoelectric Materials.

Screening unique two-dimensional (2D) materials with high mobility and applicable band gaps is motivated by not only the interest in basic science but also the practical applications for photoelectric materials. In this work, we have systematically studied a new family of 2D ternary quintuple layers (QLs), named ABC (A = Na, K, and Rb; B = Cu, Ag, and Au; C = S, Se, and Te). Our results indicate that the QLs of KCuTe, KAgS, KAgSe, KAuTe, RbCuTe, RbAgSe, and RbAgTe host direct band gaps. Moreover, KCuTe, RbCuTe, and RbAgTe QLs show extremely high mobilities of ∼104 cm2 V-1 s-1. Interestingly, the linear scaling between exciton binding energy and quasiparticle band gap for ABC QLs exhibits an unexpected deviation with the 1/4 law. In addition, KAgSe, KAgS, RbAgSe, and RbAgTe show outstanding power energy conversion efficiencies of up to 21.5%, suggesting that they are good potential donor materials. Our results provide many potential candidates for applications in photoelectric materials, which may be realized in experiments due to the possible exfoliation from their parent compounds.