Ultralong Carrier Lifetime in Lead-Free Perovskites Enabled by Elimination of Electron–Phonon Coupling in Target Layers

High Resolution Image Download MS PowerPoint Slide Nonradiative electron–hole recombination driven by nonadiabatic coupling (NAC) between band-edge states is the primary bottleneck limiting carrier lifetime and thus the power conversion efficiency (PCE) of photovoltaic and photocatalytic materials. In this work, we demonstrate that NAC in lead-free Ruddlesden–Popper (RP) perovskites can be substantially reduced by identifying and suppressing the electron–phonon (e–ph) coupling in the specific atomic layer that contributes most strongly to carrier recombination, which we term the target layer. Taking Y 2 Ti 2 O 5 S 2 as a model system, we show that its rock-salt [Y 2 S 2 ] 2+ layer is the dominant source of e–ph coupling. By tuning the spatial distribution of the band-edge states to eliminate their overlap within this target layer, the NAC of Ti-based (and Zr-based) RP perovskites is reduced to 0.18 meV, comparable to that of lead halide perovskites (0.16 meV). Time-dependent density functional theory (TDDFT) simulations yield a carrier lifetime of ∼0.8 μs for the designed material Ba 3 Zr 2 O 5 S 2 at room temperature, surpassing that of c-CsPbI 3 (∼0.4 μs). This strategy of controlling NAC through target-layer engineering provides new insight into carrier dynamics and offers a practical guideline for designing lead-free perovskites with improved PCE.