Robust Interfaces via Synergistic Cation-Anion Manipulation for Highly Efficient and Stable Inverted Perovskite Solar Cells

Abstract

Ionic defect sites at planar photovoltaic interfaces cause usually the degradation of perovskite solar cells (PSCs), where uncoordinated ions and consequent instable counterions are the intrinsic reasons behind the interfacial instability. Present work proposes and experimentally verifies that, an interfacial modifier with the ability of simultaneously anchoring both cation & anion defect sites, could passivate uncoordinated ionic defect sites and synchronously immobilize the adjacent counterions. Exemplified by the molecule of 4,5-dicyanoimidazole (DCI), the modified PSCs with DCI demonstrate efficaciously‌ suppressed ion migration, prohibited phase segregation, as well as obvious transition from tensile stress to compressed in perovskite layer, which resulted in the optimized PSCs with remarkable champion PCE of 26.10% (certified 25.53%). Meanwhile, the unencapsulated device maintained over 95% of its initial efficiency after 1,600 h at maximum power point tracking, along with nearly no degradation after 12 cycles of 12-h light and 12-h dark tests, as well as 98.2% retaining of its initial PCE over 2,000 h in nitrogen atmosphere at 85 ℃.