Unveiling the multilevel structure of midgap states in Sb-doped <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>Mo</mml:mi><mml:msub><mml:mi>X</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:mrow></mml:math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mo>(</mml:mo><mml:mi>X</mml:mi><mml:mo>=</mml:mo><mml:mi mathvariant="normal">S</mml:mi><mml:mo>,</mml:mo><mml:mo> </mml:mo><mml:mi>Se</mml:mi><mml:mo>,</mml:mo><mml:mo> </mml:mo><mml:mi>Te</mml:mi><mml:mo…

In this study, we use first-principles calculations to investigate the electronic and structural properties of $\text{Mo}{X}_{2}$ $(X=\text{S}, \mathrm{Se}, \mathrm{Te})$ monolayers doped with substitutional Sb atoms, a central focus on Sb(Mo) substitution. ${\mathrm{MoS}}_{2}$, observe that substitution is energetically favored under S-rich conditions, where ${\mathrm{S}}_{2}$ gaseous phase likely be present. This result compatible recent experimental observation in Sb-doped ${\mathrm{MoS}}_{2}$ nanosheets grown by chemical vapor deposition. A similar behavior found ${\mathrm{MoSe}}_{2}$, but ${\mathrm{MoTe}}_{2}$ less occur due possible absence Te phases setups. all cases, several impurity-induced states are inside band gap, energies span entire gap. The Fermi energy pinned few tenths eV above top valence band, suggesting predominant $p$-type behavior, gap slightly increased comparison pristine systems. orbital nature these further investigated projected local density calculations, which reveal similarities defect induced single Mo vacancies as well their rehybridization $5s$ from Sb. Additionally, find systems materials, contrast previous calculation predicts reduction different assignment impurity levels. We discuss similarities, discrepancies, limitations both calculations. also speculate reasons for experimentally observed redshifts $A$ $B$ excitons presence dopants ${\mathrm{MoS}}_{2}$. hope results spark future investigations other aspects problem, particularly those concerning effects disorder electron-hole interaction, continue potential transition-metal dichalcogenides applications optoelectronic devices.