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.