Robust chelated lead octahedron surface for efficient and stable perovskite solar cells.

PbI octahedron as a fundamental framework endows the perovskite with excellent photoelectric properties, but also the defective and flimsy surface. Here, we report that the treatment of perovskite surface by bidentate ligands molecules N, N'-Dimethyl-1,2-ethanediamine can in-situ form a lead iodide chelates layer with excellently robust chelated lead octahedron, leading to effectively stabilize and passivate the underlying perovskite. The strong chelation with the lead enables the surface to largely inhibit the defects generation, iodide ion migration and skeleton collapse under external stimuli. It also prolongs the carrier lifetime and adjusts the surface energy-level of perovskite. The resultant perovskite solar cells deliver a power conversion efficiency of 25.7% (certified 25.04%) and retain >90% of their initial value after almost 1000 hours aging at maximum power point under simulated AM1.5 illumination.