Ultrafast Auger-Mediated Interlayer Electron Transfer in 2D Perovskites: Ab Initio Quantum Dynamics Simulation.

Abstract

Interlayer charge transport in two-dimensional perovskites is limited by the electronically insulating nature of spacer cations. Here, we identify an unconventional, highly efficient mechanism that overcomes this limitation. Ab initio quantum dynamics reveals that spacer states are transiently populated via Auger-type carrier-carrier scattering on a sub-picosecond time scale. The generated hot electrons are rapidly transferred across layers via ligand orbitals, outcompeting intraband thermalization. The ultrafast interlayer electron transfer is facilitated by enhanced electronic coupling promoted by favorable van der Waals interactions within densely packed organic layers and small reorganization energies due to suppressed conformational fluctuations of ligand chains. In contrast, relaxation of hot electrons from the ligands back to perovskite's inorganic lattice is suppressed by the weak electron-vibrational coupling, leading to long-lived charge-separated states in different perovskite layers with lifetimes of hundreds of nanoseconds. The simulations uncover the key role of Auger-mediated pathways in enabling efficient interlayer charge transfer in 2D perovskites.