Stabilizing Grain Boundaries by In Situ Formation of Robust Layered Metallo‐Organic Complex toward High‐Performance Inverted Perovskite Solar Cells

The grain boundaries (GBs) instability induced by photodecomposition of residual PbI₂ is long-standing challenge for further simultaneous improvement of stability and power conversion efficiency (PCE) of perovskite solar cells (PSCs). Herein, a novel GB stabilization strategy through managing unstable residual PbI₂ within perovskite films is reported, which is realized by incorporating 2-iodoimidazole (2-IM) into perovskite precursor solution. The 2-IM can in situ convert unstable residual PbI₂ at GBs into robust metallo-organic complex 2-IMPbI₂ exhibiting an orderly hexagonal layered crystal structure. 2-IMPbI₂ is uncovered to have much better defect passivation effect and stability than PbI₂. The formed 2-IMPbI₂ facilitates perovskite crystallization, passivates GB defect, suppresses ion migration, mitigates phase segregation, and promotes carrier transport, contributing to simultaneously enhanced PCE and stability. Owing to the ingenious GB modulation strategy, the inverted 1.66 eV PSCs achieve a PCE of 24.12%, which is among the highest PCEs ever reported for 1.66 eV PSCs. This strategy demonstrates good universality by accomplishing efficient 1.53 eV PSCs with a PCE of 26.84%. Moreover, the inverted wide-bandgap PSCs with 2-IMPbI₂ maintain 94% and 90% of their initial efficiencies after 1000 h of continuous maximum power point operation and after 500 h of thermal stress at 85 °C, respectively.