Ligand-Mediated Release of Halides for Color Tuning of Perovskite Nanocrystals with Enhanced Stability

The rich chemistry of metal halide perovskites has enabled various methods of band structure control and surface passivation. Here we report a highly facile and efficient post-treatment approach for precise color tuning of cesium lead halide perovskite nanocrystals (NCs) with enhanced stability. By utilizing a special multifunctional organic ligand, triphenyl­(9-phenyl-9H-carbazol-3-yl)­phosphonium bromide (TPP-Carz), carbon–halide bond cleavage can be achieved to release halide ions from halogenated solvents in a controlled manner for color tuning of perovskite NCs via ion exchange. Besides controlled release of halide ions for anion exchange, TPP-Carz can effectively passivate the surfaces of perovskite NCs simultaneously. As a result, perovskite NCs prepared by this post-treatment method with tunable colors over the entire visible spectrum have shown significantly improved luminescence and stability in comparison to the ones prepared using reactive anion precursors without surface passivation by TPP-Carz.