  Two-dimensional organic-inorganic hybrid perovskites (2D HOIPs) have been
widely used for various optoelectronics owing to the excellent photoelectric
properties. Recently, a great deal of studies have focused on engineering the
organic spacer cation in 2D HOIPs to enhance the carrier transport and improve
the performance of devices. However, the selection of organic spacer cations is
mostly qualitative without a quantitative guidance. Meanwhile, the fundamental
mechanism of the carrier transport across the organic spacer layer is still
unclear. Here, by using the first-principle non-adiabatic molecular dynamics
(NAMD) method, we have studied the transport process of excited carriers
between 2D HOIPs separated by the spacer cation layer. Various types of spacer
cations of 2D HOIPs are investigated, where the carrier transport processes are
simulated in real-time at atomic levels. We find that the excited electrons and
holes can transfer from single-inorganic-layer 2D HOIP to bi-inorganic-layer 2D
HOIP on a sub-picosecond scale, and different types of spacer cations can
influence the carrier transfer rate significantly. Meanwhile, Dion-Jacobson
(DJ) phase 2D HOIP leads to a more conductive carrier transport compared to the
Ruddlesden-Popper (RP) phase, which is related to the different electron-phonon
coupling strengths of these two phases. Moreover, we have developed a new
method to capture the electron-hole interaction in the frame of NAMD. This work
provides a promising direction to design new materials towards high performance
optoelectronics.
