Tailoring the Bandgap of Doped GaS Nanosheets for Optoelectronic, Spintronic, and Sustainable Energy Applications

Gallium sulfide (GaS) sheet encounters obstacles in electronic and photocatalytic applications due to its large bandgap of 3.6 eV. To boost up the applicability of GaS sheets, the effects of substitutional mono metal and nonmetal dopants (3d transition metals, Ge, As, Se, In, Sn, Sb) at the Ga-site on their chemical stability, photocatalytic behavior, and physical properties such as electronic, magnetic, and optical characteristics are investigated, using hybrid density functional theory. Results reveal that the majority of the doped GaS (MD-GaS) exhibit thermodynamic stability. The magnetic properties of MD-GaS nanosheets change with doping for MD = Ti, V, Cr, Mn, Fe, Ni, Co, Zn, and Se, transforming the sheets into diluted magnetic semiconductors. In contrast, doping with Sc, Cu, As, In, and Sb retains the semiconductor properties of the pristine sheet. Ge- and Sn-doped GaS nanosheets show potential for 2D spintronic applications. While many dopants enhance visible light absorption, they introduce mid-gap states or unfavorable valence band edges, making them less suitable for photocatalysis. However, As- and Sb-doped GaS are promising sheets for photocatalytic Co₂ reduction and water splitting under visible light making it a potential material for clean fuel production.