Robust interfaces via synergistic cation–anion manipulation for highly efficient and stable inverted perovskite solar cells

Ionic defect sites at planar photovoltaic interfaces often cause the degradation of perovskite solar cells (PSCs), where uncoordinated ions and the consequent unstable counterions are the intrinsic reasons behind the interfacial instability. The present work proposes and experimentally verifies that an interfacial modifier, 4,5-dicyanoimidazole (DCI), with the ability to simultaneously anchor both cationic and anionic defect sites can passivate uncoordinated ionic defect sites and synchronously immobilize the adjacent counterions. The PSCs modified with DCI exhibited effectively suppressed ion migration, inhibited phase segregation, and obvious transition from tensile stress to compressed stress in the perovskite layer, which resulted in optimized PSCs with a remarkable champion PCE of 26.10% (certified PCE of 25.53%). Meanwhile, the unencapsulated device retained over 95% of its initial efficiency after 1600 h at maximum power point tracking, along with nearly no degradation after 12 cycles of 12-h light and 12-h dark tests, and retained 98.2% of its initial PCE over 2000 h in a nitrogen atmosphere at 85 °C.