${\mathrm{SnP}}_2{\mathrm{Se}}_6$, a recently synthesized two-dimensional (2D) polar semiconductor, exhibits significant discrepancies in reported carrier mobilities between experimental and theoretical studies. Here, based on first-principles calculations, we first investigate the electron-phonon (el-ph) scattering-limited intrinsic carrier mobility of ${\mathrm{SnP}}_2{\mathrm{Se}}_6$ monolayer. Our calculated electron and hole mobilities are both much lower than previous deformation potential (DP) model predictions, which indicates that the DP model is unsuitable for describing the carrier transport properties in such a 2D polar material. Then, we develop a theoretical scheme to quantitatively estimate the intrinsic carrier mobility of ${\mathrm{SnP}}_2{\mathrm{Se}}_6$ multilayers, as direct first-principles calculations on such a multilayer system are infeasible. The electron mobility for a 15-layer film predicted by our theoretical scheme is in excellent agreement with the experimental value measured on a sample of the same thickness. In addition, the scheme reveals that the intrinsic electron mobility of 2D ${\mathrm{SnP}}_2{\mathrm{Se}}_6$ initially decreases as the layer number increases, and then turns to increase. This predicted layer dependence successfully explains the experimental result that thin multilayers have a notably smaller electron mobility than thick multilayers. Our scheme provides an efficient and simple theoretical framework for quantitatively studying the intrinsic carrier mobility of 2D layered polar materials, particularly for relatively thick films for which first-principles calculations are impractical.

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• Carrier dynamics
• 2-dimensional systems
• Semiconductors
• Boltzmann theory
• Density functional calculations
• Tight-binding model