Three Birds with One Stone: High-Performance 2D Lead-Free Perovskite Solar Cells via Direct In Situ Generation of Organic-Spacer Precursors

The advancement of quasi-two-dimensional (quasi-2D) tin-based perovskite solar cells (TPSCs) is severely hampered by challenges including Sn 2+ oxidation, rapid crystallization, and uncontrollable phase distribution. Currently, no one effective approach has been developed to address all these issues simultaneously. Herein, a facile strategy is proposed involving organic spacers that resolves all three problems at once. On the one hand, the introduction of H + suppresses the conversion of Sn 2+ to Sn 4+ in precursor solutions. On the other hand, leveraging the in situ generation and decomposition of DMASnI 3 within the precursor delays the crystallization of quasi-2D tin-based perovskite. Concurrently, the regulation of the crystallization process helps to form the more uniform distribution of quasi-2D phases, significantly improving carrier mobility. The optimized Dion-Jacobson type (DJ) TPSC achieves a champion power conversion efficiency (PCE) of 7.39%, winning a new record, while demonstrating exceptional stability. The successful implementation of this strategy in both quasi-2D Ruddlesden-Popper (RP) and DJ TPSCs demonstrates its universal applicability for enhancing performance across low-dimensional optoelectronic devices.