First principles study of strain effects on prospective 2D photocatalysts Sn 2 Se 2 X 4 (X = P, As) with ultra-high charge carrier mobility.

Ab initio calculations were employed to investigate the properties of Sn 2 Se 2 P 4 and Sn 2 Se 2 As 4 , which are new semiconductors formed based on the 2D SnP 3 structure. A comprehensive analysis was conducted to examine the structural characteristics and stability of both compounds. It was observed that both Sn 2 Se 2 P 4 and Sn 2 Se 2 As 4 exhibit notable toughness and ductility, characterized by a Poisson's ratio ranging from 0.16 to 0.20 and a Young's modulus ranging from 42.12 to 49.84 N m -1 . The investigation focused on the examination of the electronic characteristics of the two compounds, as well as their correlation with optical properties, charge transport, and potential as photocatalysts. Being ductile semiconductors, the effects of strains on the properties of Sn 2 Se 2 P 4 and Sn 2 Se 2 As 4 were also investigated. The charge carrier mobility in the y -direction ranges from 10 3 to 10 4 cm 2 V -1 s -1 . Moreover, the electron-hole separation is expected to be very high as the difference in the mobilities of holes and electrons is really large. Moreover, it is worth noting that both Sn 2 Se 2 P 4 and Sn 2 Se 2 As 4 exhibit a significantly high absorption rate of 10 6 cm -1 in the visible region. The observed features of Sn 2 Se 2 P 4 and Sn 2 Se 2 As 4 indicate their potential as effective photocatalysts for the process of water splitting through the utilization of solar energy.