Eliminating Ion Migration by Intrinsic‐Stable Interstitial Doping for Efficient and Stable Perovskite Solar Cells

Intrinsic iodide migration seriously limits long‐term stability and commercial application of perovskite solar cells (PSCs). Interstitial doping by metal ions can effectively suppress iodide migration, but the intrinsic stability of metal ion dopants under long‐term device operation remains challenging. Here, we propose an effective method to suppress the metal ion migration for improving device performance by synergistically doping trivalent neodymium (Nd 3+ ) and polyacrylate (PAA) anions into perovskite film. We demonstrate that Nd 3+ doping at the interstitial site forms strong ionic bonding with the Pb–I frameworks and increases the energy barrier against metal ion migration, while monovalent Na + with a similar radii and lower ionic charge, although widely used for high‐efficiency PSCs, shows obvious migration that induces non‐radiative recombination and unfavorable energy‐level alignment in PSCs. In addition, polymer‐type PAA anions with multiple carboxylate groups could anchor the surface Pb 2+ and organic cations stably, which effectively passivate perovskite surface and grain boundaries. As a result, Nd(PAA) 3 doped device delivers a maximum efficiency of 26.44% (certified 25.75%) and outstanding operational stability with estimated T 80 lifetime of 7407 h. This finding shows an effective strategy to improve long‐term stability of interstitial dopants for regulating ion migration and PSC performance.