The structural, and optoelectronic properties of Mo-based Janus monolayers have been investigated using the first-principles calculations. All the Mo-based Janus monolayers exhibit semiconducting nature with bandgap ranging from 0.64 eV to 2.00 eV. Among the MoXY (Xdouble bondO, S, Se, Te, Ydouble bondO, S, Se, Te) family MoSSe and MoSeTe possess a direct bandgap, which is promising for absorbing light efficiently. The device absorption efficiency of MoXY family has been calculated for the first time and find that our studied family has the strongest absorption ranging from infrared (IR) to ultra-violet (UV) region of the light spectrum. Furthermore, due to the semiconducting nature and strong absorption efficiency of MoXY could prove its efficient application in top cell in the tandem architecture. On the other hand, MoTeO could serve excellently in the bottom cell in tandem architecture because of having a narrow bandgap and strong absorption efficiency. This family also keeps a suitable band edge alignment with the water redox potentials. Thus, due to the suitable optical and photocatalytic properties for splitting water and strong absorption efficiency makes MoXY a promising candidate for the application of opto-electronic devices, photocatalysis, and the solar cell.