Proceedings of nanoGe Fall Meeting19 (NFM19)
DOI: https://doi.org/10.29363/nanoge.nfm.2019.111
Publication date: 18th July 2019
Colloidal organic/inorganic lead halide perovskite nanocrystals (NCs) are intensely pursued as highly promising, low-cost light-emitting materials with wide color gamut. These NCs exhibit unprecedented luminescent properties – narrow-band emission with high quantum efficiency, covering the whole visible spectral range and extending into near-infrared, all obtained without epitaxial overcoating of the NC surfaces for electronic passivation of the surface states [1]. Their processing and luminescent properties are challenged by the lability of their surfaces, i.e. the interface of the NC core and the ligand shell. Surface and sub-surface atoms are likely directly involved in all possible chemistry equilibria and transformations. Controlling NC surface structure is therefore paramount for mitigating these instabilities.On the example of CsPbBr3 NCs, we rationalize the typical observation of a degraded luminescence upon aging or the luminescence recovery upon post-synthesis surface treatments using a simple surface-structure model, supported by DFT calculations [2]. Healing of the surface trap states requires restoration of all damaged PbX6 octahedra and establishing a stable outer ligand shell. Such NCs are halogen-rich. Restoration of such a structure, seen as an increase in the luminescence quantum efficiency to 90-100% and improvement in the overall robustness of CsPbBr3 NCs, was attained using a facile post-synthetic treatment with a PbBr2+DDAB (didodecyldimethylammonium bromimde) mixture. In practical terms, we demonstrate that such an approach is useful to obtain purified CsPbBr3 NCs samples, washed up to three times in several solvents, with near unity photoluminescence quantum yields and long-term colloidal stability.
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