Surface Stabilization of Colloidal Perovskite Nanocrystals via Multi-amine Chelating Ligands

Developing pathways to stabilize the intrinsically dynamic surface of metal halide perovskite nanocrystals (PNCs), especially metastable lead iodide PNCs, is an important but challenging task. Herein, we have realized ultra-stable colloidal CsPbI₃ PNCs based on a multi-amine chelating ligand, N′-(2-aminoethyl)-N′-hexadecylethane-1,2-diamine (AHDA). The protonated AHDA can anchor the PNC surface lattice with a high binding energy of 2.36 eV, much larger than the 1.47 eV achieved with the commonly used oleylammonium ligands. The chelation effect greatly inhibits dynamic desorption of surface ligands and enables stabilization of CsPbI₃ PNCs under various ambient stimuli, such as repeated purification (up to 15 cycles), polar solvents, heat, and light. The stable yet easily accessible surface of the AHDA-capped CsPbI₃ PNCs renders them a robust photocatalyst in a stereoselective C−C oxidative coupling reaction. Furthermore, we show that the AHDA ligand can also be used to synthesize PNCs of several other compositions, namely CsPbCl₃, CsPbBr₃, CsPbBrI₂, and hybrid FAPbI₃ (FA = formamidine), with remarkably stable emission characteristics.