Long-Lived Hot Carriers in Two-Dimensional Perovskites: The Role of Alternating Cations in Interlayer Space

Solar absorbers featuring prolonged hot-carrier (HC) cooling are highly desired for the development of HC solar cells. Two-dimensional (2D) hybrid perovskites are known for their exceptional stability and tunable optoelectronic properties. Nevertheless, their hot-carrier dynamics have been inadequately investigated. Here, we demonstrate ultraslow hot-carrier cooling with a lifetime >2 ns and long HC diffusion length in 2D (ACA)(MA)PbI₄ (ACA = acetamidinium) with alternating cations in the interlayer space (ACI), surpassing those of 3D MAPbBr₃ and 2D Ruddlesden-Popper (PEA)₂PbI₄. Our nonadiabatic molecular dynamics simulations with spin-orbit coupling show that the enhanced HC cooling in the ACI-phase 2D perovskite is due to multiple split-off bands and reduced electron-phonon coupling. Furthermore, the hot electrons can be efficiently extracted from (ACA)(MA)PbI₄ and then transferred to the electron-transporting layer. These new insights highlight the benefit of manipulating interlayer cations in 2D perovskites as an advantageous approach to control long-lived hot carriers, thus potentially enhancing photovoltaic device performance.