Metallic lead (Pb⁰) impurities in metal-halide perovskites have attracted tremendous research concerns owing to their detrimental effects on perovskite solar cells (PSCs). However, the origins and influences of the Pb⁰ behind this issue have yet to be well understood. Herein, we show that Pb⁰ is hardly formed in the growth of halide perovskites but is easily postformed in the perovskite films with excess PbI₂. It is found that Pb⁰ impurities are decomposition byproducts of residual PbI₂ in perovskites under light or X-ray irradiation. Therefore, PSCs obtained using photodegraded PbI₂ films show large efficiency and stability losses. By contrast, the perovskite devices without detectable Pb⁰ impurities have a much better efficiency and stability. This work reveals the origins and influences of Pb⁰ in halide perovskites and provides a strategy for avoiding the formation of detrimental Pb⁰ byproducts, which would drive further enhancements in device performance of halide perovskite solar cells, detectors, etc.

金属卤化物钙钛矿中的金属铅（Pb ⁰）杂质由于对钙钛矿太阳能电池（PSC）的不利影响而引起了极大的研究关注。^{然而，这一问题背后的 Pb 0}的起源和影响尚未得到很好的理解。在此，我们表明 Pb ⁰在卤化物钙钛矿的生长中几乎不形成，但在具有过量 PbI ₂的钙钛矿薄膜中很容易后形成。发现Pb ⁰杂质是钙钛矿中残留PbI ₂在光照或X射线照射下的分解副产物。因此，使用光降解 PbI _{2获得的 PSC}薄膜显示出较大的效率和稳定性损失。相比之下，不含可检测 Pb ⁰杂质的钙钛矿器件具有更好的效率和稳定性。^{这项工作揭示了卤化物钙钛矿中 Pb 0}的起源和影响，并提供了避免形成有害的 Pb ⁰副产物的策略，这将进一步提高卤化物钙钛矿太阳能电池、探测器等的器件性能。