  Two-dimensional (2D) Janus transition metal dichalcogenides (TMDs) are a new
class of materials with unique physical properties. However, the carrier
mobility of most Janus TMDs calculated by deformation potential theory (DPT) is
not reliable due to the unconsidered part of lattice scattering. In this work,
we propose a new method of Born effective charge (BEC) to calculate the carrier
mobility of Janus TMDs by including the important factors that neglected in the
DPT. The BEC could be used in the calculation of both pure and defective Janus
TMDs by employing density functional perturbation theory. We have figured out
the relationship between the carrier mobility and the value of BEC, which is
the lower the absolute BEC, the higher the electron or hole mobility. Using the
new method, we have calculated the carrier mobility of commonly studied Janus
TMDs with and without defect. The method may shed light on the high-throughout
calculation of selecting high carrier mobility 2D materials.
