Investigation of strain behavior and carrier mobility of organic–inorganic hybrid perovskites: (C ₄ H ₉ NH ₃ ) ₂ GeI ₄ and (C ₄ H ₉ NH ₃ ) ₂ SnI ₄

Two dimensional (2D) organic-inorganic hybrid perovskites have attracted great interest due to their tunable band gap and structural stability. In this study, biaxial strain behavior and carrier mobility of monolayers (C₄H₉NH₃)₂GeI₄ and (C₄H₉NH₃)₂SnI₄ are investigated by first principles calculations. (C₄H₉NH₃)₂GeI₄ and (C₄H₉NH₃)₂SnI₄ still retain their structural stability at ε = 13% and ε = 15%, respectively. Ab initio molecular dynamics (AIMD) simulation has confirmed that the system at 300 K is still thermodynamically stable at a biaxial strain of ε = 8%. The band gaps of (C₄H₉NH₃)₂GeI₄ and (C₄H₉NH₃)₂SnI₄ calculated from the HSE06 functional are increased from 2.427 and 1.953 eV at zero strain to 3.002 and 2.626 eV at ε = 8%. Deformation potential (DP) models based on longitudinal acoustic phonon (LAP) and optical phonon (OP) scattering are used to investigate mobility. The mobility of (C₄H₉NH₃)₂GeI₄ is lower than that of (C₄H₉NH₃)₂SnI₄. It is mainly determined by the scattering from OP with lower energy and decreases sharply with an increase in biaxial strain. Compared with Pb based perovskites, (C₄H₉NH₃)₂SnI₄ exhibits high carrier mobility and thermodynamic stability.