Investigation of strain behavior and carrier mobility of organic–inorganic hybrid perovskites: (C4H9NH3)2GeI4 and (C4H9NH3)2SnI4

Abstract

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.