Monolayers Sn(2)Te(2)X(4) (X = P, As) as promising materials for photocatalytic water splitting and flexible devices: a DFT study.

First principles calculation was performed to study the Sn(2)Te(2)X(4) (X = P, As) monolayers. Structural investigation confirms the stability of the two monolayers with Young's modulus in the range of 30.34-33.65 N m(-1) and a Poisson's ratio of 0.18-0.21. The two monolayers are semiconductors with a direct band gap of 1.52-1.66 eV. The light absorption rate of the two monolayers is rather high 10(4)-10(5) cm(-1). Both monolayers have high charge carrier mobility and suitable VBM and CBM positions for the redox reaction. The η (STH) efficiency of both materials (15.76-17.12%) is close to the theoretical limit of 18%. Moreover, moderate strains can improve the light absorption rate, while the suitable VBM and CBM positions are preserved. These characteristics suggest that Sn(2)Te(2)X(4) (X = P, As) monolayers are good candidates for being applied in flexible devices and for the conversion of solar energy to other types of energy.