Study on substitutional doped GaSe monolayers using hybrid functional: Electronic, optoelectronic, and photocatalytic applications

GaSe monolayer suffers in electronic and photocatalytic applications due to its large bandgap (3.50 eV). In this study, we employed the hybrid density functional, the Heyd-Scuseria-Ernzerhof hybrid (HSE), to explore the effect of substitutional metal single doping (M = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ge, As, In, Sn, Sb) at the Ga-site on the structural stability, electronic, magnetic, optical, and photocatalytic properties. Our findings indicate that the bond lengths M-Ga/Se increase as the atomic radius of the dopant increases. Most of the doped structures are found to be thermodynamically stable. The introduction of metal and non-metal dopants significantly alters the magnetic properties of GaSe nanosheets, with dopings of Ti, V, Cr, Mn, Fe, Ni, and Co, as well as Zn, resulting in diluted magnetic semiconductors. In contrast, dopings with Sc, Cu, As, In, and Sb maintained semiconductor characteristics. The As- and Sb-doping resulted in the narrowest bandgap of 2.1 eV, while Ge- and Sn-doped GaSe monolayers revealed promise for two-dimensional spintronic applications. Although most dopants enhanced visible-light absorption, many proved unsuitable for photocatalysis due to the created mid-gap states and unfavorable valence band edges. The study showed that V-doped GaSe monolayer is a promising two-dimensional material for photocatalytic water-splitting and CO₂ reduction under visible light, making it a potential material for clean fuel production.