Electronic and optical properties of two-dimensional III2-VI3 materials with the FE-WZ′ structure

Abstract

Based on the first-principles calculations, we have investigated the mechanical, phonon, electronic and optical properties of two-dimensional (2D) In2Te3 (FE-WZ′ phase) family. The Y(θ) value for all M2X3 materials exceeds 67 N/m, with Al2S3 exhibiting the best mechanical strength, surpassing to that of MoS2 (∼124.3 N/m in the x and y directions). Phonon calculations reveal that the acoustic branch with the lowest frequency is mainly dominated by out-of-plane vibrations of the metal atoms and non-metallic atoms. Ga2Te3 exhibits dynamic instability due to the softening of the optical phonon branch. Incorporating spin–orbit coupling (SOC) in In2Se3 and In2Te3 converts them into direct semiconductors. These materials possess an electrostatic potential difference ranging from 0.73 to 2.11 eV, which effectively reduces the band gap required for water splitting in the infrared region. Moreover, the M2X3 monolayers with intrinsic electric fields are great coveted photocatalysts for overall water splitting. Remarkably, In2Se3 displays a solar-to-hydrogen efficiency of 28.6%, which is significant for commercial applications.