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Essentially Trap-Free CsPbBr 3 Colloidal Nanocrystals by Postsynthetic Thiocyanate Surface Treatment

2017; American Chemical Society; Volume: 139; Issue: 19 Linguagem: Inglês

10.1021/jacs.7b02817

1943-2984

Brent A. Koscher, Joseph K. Swabeck, Noah D. Bronstein, A. Paul Alivisatos,

Quantum Dots Synthesis And Properties

We demonstrate postsynthetic modification of CsPbBr3 nanocrystals by a thiocyanate salt treatment. This treatment improves the quantum yield of both freshly synthesized (PLQY ≈ 90%) and aged nanocrystals (PLQY ≈ 70%) to within measurement error (2–3%) of unity, while simultaneously maintaining the shape, size, and colloidal stability. Additionally, the luminescence decay kinetics transform from multiexponential decays typical of nanocrystalline semiconductors with a distribution of trap sites, to a monoexponential decay, typical of single energy level emitters. Thiocyanate only needs to access a limited number of CsPbBr3 nanocrystal surface sites, likely representing under-coordinated lead atoms on the surface, in order to have this effect.