Two-dimensional (2D) Ruddlesden–Popper perovskites (RPPs), which possess a strong quantum confinement effect, have been demonstrated to exhibit out-of-plane charge transport, but the factors that determine the interlayer charge transport in 2D RPPs are far from being explored. In this study, using a recently developed ab initio simulation method which combines density functional theory calculations, semiclassical Marcus theory, and Einstein relationship, we systematically investigate the out-of-