Besides the inhibition effect of the quantum well structure on the electron-hole separation, the insulating effect of the spacer cation also hinders the out-of-plane charge carrier transports. Based on the Keldysh non-equilibrium Green's function formalism and density functional theory (NEGF-DFT), the out-of-plane quantum transport properties of 2D monolayer PEA 2 SnI 4 -and BA 2 SnI 4 -based devices are investigated by constructing vertical transport architecture devices containing the Au electrodes and the 2D monolayer hybrid halide perovskites acting as the scattering region (Figures and), as we previously constructed all-metallic vertical tunneling architecture. The calculated potential energy