Lead-free vacancy ordered double perovskite materials are of interest in photovoltaic field from their excellent stability and long carrier lifetime. However, the consequences of the spin-orbit coupling (SOC) induced Rashba effect on the photovoltaic performance are not well understood. Herein, the SOC inducing spin carrier dynamics of ${\mathrm{Cs}}_2{\mathrm{SnBr}}_6\text{/}{\mathrm{PdS}}_2$ heterostructure are investigated through density functional theory (DFT) and ab initio nonadiabatic molecular dynamics (NAMD) with SOC simulation. It has been found that the ${\mathrm{Cs}}_2{\mathrm{SnBr}}_6\text{/}{\mathrm{PdS}}_2$ heterostructure exhibits Rashba effect due to symmetry breaking. The electronic and spin properties of ${\mathrm{Cs}}_2{\mathrm{SnBr}}_6\text{/}{\mathrm{PdS}}_2$ heterostructure are tunable via applying pressure, resulting in Rashba spin-splitting. As pressure increases, the heterostructure exhibits stronger Rashba effect, which Rashba constant ${\alpha }_{\mathrm{R}}$ for conduction band minimum and valence band maximum are $0.055$ and $0.497\mathrm{eV}\text{/}\AA$ under 9 GPa. Based on DFT and NAMD calculations, we demonstrate that the carrier recombination rate is reduced due to mismatch spin-states and electron-phonon coupling larger than SOC values, resulting in spin-forbidden path. The carrier lifetime enhancement factor is linear with the pressure inducing Rashba effect magnitude. The proposed spin carrier transfer mechanism is important for understanding the fundamental physics in perovskite materials and for designing perovskite-based solar cells with better performance.

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• Charge dynamics
• Spin dynamics
• Spin-orbit coupling
• 2-dimensional systems
• Interfaces
• Density functional theory
• Spin lattice models