The single-layer MoS₂ is a highly sought-after semiconductor material in the field of photoelectric performance due to its exceptional electron mobility and narrow bandgap. However, its photocatalytic efficiency is hindered by the rapid recombination rate of internal photogenerated electron–hole pairs. Currently, the construction of heterojunctions has been demonstrated to effectively mitigate the recombination rate of photogenerated electron–hole pairs. Therefore, this paper employs the first principles method to calculate and analyze the four heterojunctions formed by MoS₂/WSe₂, MoS₂/MoSe₂, MoS₂/AlN, and MoS₂/ZnO. The study demonstrates that the four heterojunctions exhibit structural stability. The construction of heterojunctions, as compared to a monolayer MoS₂, leads to a reduction in the band gap, thereby lowering the electron transition barrier and enhancing the light absorption capacity of the materials. The four systems exhibit II-type heterojunction. Therefore, the construction of heterojunctions can effectively enhance the optical properties of these systems. By forming heterojunctions MoS₂/WSe₂ and MoS₂/MoSe₂, the absorption coefficient in the visible light region is significantly increased, resulting in a greater ability to respond to light compared to that of MoS₂/ZnO and MoS₂/AlN. Consequently, MoS₂-based heterojunctions incorporating chalcogenide components WSe₂ and MoSe₂, respectively, exhibit superior catalytic activity compared to MoS₂ heterojunctions incorporating non-chalcogenide components ZnO and AlN, respectively. The absorption spectrum analysis reveals that MoS₂/MoSe₂ exhibits the highest light responsivity among all investigated systems, indicating its superior photoelectric performance.

This study calculates the electronic structure and optical properties of intrinsic BiOIO₃ and X-BiOIO₃ (X = As, Se, or Te) using PBE (Perdew–Burke–Ernzerhof) and MBJ (Modified Becke–Johnson) functionals based on density functional theory, with MBJ showing better correlation with experimental values. The X-BiOIO₃ systems exhibit relative stability under MBJ potential and show crystal lattice distortion compared to intrinsic BiOIO₃, creating localized potential differences that enhance polarization and adjust the bandgap. Doping reduces the bandwidth and increases energy level density, promoting electron transitions. Consequently, based on the computational results presented in this paper, it can be inferred that both BiOIO₃ and X-BiOIO₃ facilitate water hydrolysis and oxygen generation due to their favorable energy band positions. Notably, Se-BiOIO₃ exhibits the highest visible light absorption capacity, which may enhance photocatalytic efficiency by strengthening the built-in electric field and promoting charge carrier generation.