Metallic Lead to Perfect Perovskite: A Bottom-Up Vapor-Assisted Colloidal Strategy for High-Performance Solar Cells

Using elemental lead (Pb⁰) as a precursor offers an upstream and atom-economical alternative route for perovskite synthesis. However, producing perovskite solar cells (PSCs) from Pb⁰ remains fundamentally challenging because Pb⁰ is hard to convert to Pb²⁺ via ordinary approaches, while any remaining Pb⁰ acts as deep-level defects in perovskite. To address this challenge, Pb⁰ first reacts with I₂ in N,N-dimethylformamide and dimethyl sulfoxide, yielding well-dispersed PbI₂ colloidal precursors that facilitate subsequent full conversion to perovskites through vapor-solid reaction with formamidinium iodide vapors. Devices starting from Pb⁰ perform much better than those from as-purchased PbI₂, in both efficiency and stability, achieving vapor-assisted solution-processed 22.65% efficiency under simulated AM1.5G illumination (over 20.65% from PbI₂). These findings suggest that high-quality perovskites may also be prepared from PbI₂ alternatives, even its upstream material Pb.