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

Two-dimensional (2D) tin (Sn2+)-based perovskiteshaveachieved remarkable advancements in (opto)electronic devices. However,fabricating high-quality and reproducible Sn halide perovskite thinfilms remains challenging due to uncontrollably fast crystallization.To overcome this issue, dimethyl sulfoxide has been incorporated asan indispensable strategy to form Lewis acid-base adducts butalso has been proven to induce an irreversible Sn2+ oxidizationeffect. As the crystalline films grow directly from solution, a betterunderstanding of precursor colloidal chemistry and the film formationprocess is critical. In this study, we report a universal solutionaging approach to fabricate high-quality and reliable 2D Ruddlesden-Popperand Dion-Jacobson Sn2+ perovskite films and devices.The proper solution aging stabilizes the precursor colloids by eliminatingaggregated 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 ordersof magnitude and improved charge transport mobility by over 5 times.This study can inspire the community to understand the depositionmechanism for high-quality Sn2+ perovskite thin films andpromote the development of high-performance and reproducible Sn2+ perovskite based (opto)electronic devices.