Prussian blue regulates ion dynamics in perovskite solar cells.

Perovskite photovoltaics are limited by structural instabilities initiated during crystallization and amplified under operation. We report that a lattice-matched Prussian blue scaffold directs heterogeneous nucleation to produce highly oriented, strain-relaxed films. Its redox-active Fe-C≡N-Fe network mediates the conversion of Pb0 and I0 defects, and its rigid open framework suppresses A-site cation redistribution and the resulting electronic inhomogeneity under bias. This strategy yielded champion power conversion efficiencies of 26.1% (n-i-p) and 26.9% (p-i-n; 26.2% certified), scaling to 23.4% in 6-centimeter-by-6-centimeter minimodules and a certified 22.9% in 30-centimeter-by-30-centimeter submodules. Submodules with initial power conversion efficiencies ranging from 20.2 to 21.0% showed robust durability under accelerated aging and no discernible decline relative to a silicon reference over 5 months of outdoor testing.