Novel stable 2D MgAsSe3 monolayer for photocatalytic water splitting, thermoelectric and optoelectronic applications: A first-principles study

A comprehensive first-principles density functional theory (DFT) study was performed to investigate the structural, electronic, optoelectronic, photocatalytic and transport properties of the novel two-dimensional (2D) MgAsSe 3 monolayer. The crystal structure was fully optimized to its ground-state energy using the GGA-PBE exchange-correlation functional. The absence of imaginary frequencies in the phonon dispersion confirms the dynamical stability of the monolayer, while Gibbs free-energy analysis provides insight into its temperature- and pressure-dependent thermodynamic behavior. The semiconducting nature was confirmed by a direct band gap of approximately 2.30 eV using the TB-mBJ approach. The electron charge density analysis revealed predominantly covalent Mg-As interactions. The partial density of states revealed that the Se-p orbitals predominantly contribute to the valence band maximum, whereas the As-s orbitals mainly contribute to the conduction band minimum. The transport properties revealed that the peak ZT value is greater than 1 at elevated temperatures. The P-type and N-type peaks are identical, which favor significant bipolar transport performance. Furthermore, MgAsSe 3 exhibited a relatively low lattice thermal conductivity, but the electrical conductivity and the Seebeck coefficients are high. The valence band is located at −6.54 eV and the conduction band at −4.24 eV, according to band edge positions calculated via vacuum level alignment for photocatalytic water splitting redox. The optical coefficients indicate that the strong absorption occurs at the visible and UV energy range, which is beneficial for optoelectronic and photocatalytic applications.