Precursor Solution Aging: A Universal Strategy Modulating Crystallization of Two-Dimensional Tin Halide Perovskite Films

Two-dimensional (2D) tin (Sn2+)-based perovskites have achieved remarkable advancements in (opto)electronic devices. However, fabricating high-quality and reproducible Sn halide perovskite thin films remains challenging due to uncontrollably fast crystallization. To overcome this issue, dimethyl sulfoxide has been incorporated as an indispensable strategy to form Lewis acid–base adducts but also has been proven to induce an irreversible Sn2+ oxidization effect. As the crystalline films grow directly from solution, a better understanding of precursor colloidal chemistry and the film formation process is critical. In this study, we report a universal solution aging approach to fabricate high-quality and reliable 2D Ruddlesden–Popper and Dion–Jacobson Sn2+ perovskite films and devices. The proper solution aging stabilizes the precursor colloids by eliminating aggregated complex and unreacted precursor clusters in the fresh precursor, leading to homogeneous nucleation/crystallization and film growth. The precursor aging reduced film defect density by nearly 2 orders of magnitude and improved charge transport mobility by over 5 times. This study can inspire the community to understand the deposition mechanism for high-quality Sn2+ perovskite thin films and promote the development of high-performance and reproducible Sn2+ perovskite based (opto)electronic devices.