First-principles study of the effect of alkaline-earth metal doping on the intrinsic MoSe2 photovoltaic properties

In this study, the effect of alkaline-earth metal element doping on the photoelectric properties of intrinsic MoSe2 is systematically investigated based on the first-principles approach, and it is believed that the findings of this work will give some theoretical guidance for future research on MoSe2 doping modification. The results show that all the doping systems exhibit good stability, and Be atom doping has the lowest formation energy value, making the doping easier to produce. The doping of alkaline-earth metal elements resulted in some lattice distortion of MoSe2. Intrinsic MoSe2 is a semiconductor with a direct bandgap of 1.498 eV, and the doping of alkaline-earth metal elements causes the bandgap value to decrease in each system, and the bandgap is the smallest when Be is doped. All doped systems exhibit P-type conducting properties. Compared with the intrinsic MoSe2, all doped systems have their conduction band fraction moved to the low-energy direction overall, and new density of states peaks appear near the Fermi energy level. These state density peaks mainly originate from the results contributed by the s-orbitals of each doping system Mo-4d, Se-4p, and each dopant atom. The analysis of the work function reveals that the work function of each doped system is smaller than the intrinsic MoSe2, then the energy required for the occurrence of electron leaps is reduced, which improves the electron mobility of the doped system. The Mulliken Population analysis shows that stable chemical bonds are formed between the doped alkaline-earth metal elements and the surrounding Se atoms. The examination of the optical characteristics demonstrated that, in comparison to the intrinsic MoSe2, all doped systems' greatest dielectric absorption peaks were attenuated and moved toward the low-energy region; the doping of alkaline-earth metal elements broadened the light absorption edge of the intrinsic MoSe2. The absorption peaks of each doping system are shifted toward the low-energy region with the red-shift phenomenon, and the light absorption is good in the ultraviolet region.