Essentially Trap-Free CsPbBr3 Colloidal Nanocrystals by Postsynthetic Thiocyanate Surface Treatment
2017
Koscher, Brent A. | Swabeck, Joseph K. | Bronstein, Noah D. | Alivisatos, A Paul
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.
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