期刊
ACS NANO
卷 15, 期 1, 页码 650-664出版社
AMER CHEMICAL SOC
DOI: 10.1021/acsnano.0c06595
关键词
perovskite nanocrystals; self-assembly; nanocrystal superlattices; environmental stability; reactivity; low-temperature photoluminescence; energy transfer
类别
资金
- European Union's Horizon 2020 research and innovation program under the Marie Sklodowska-Curie Grant [794560]
- Molecular Foundry, a DOE Office of Science User Facility of the Office of Science of the U.S. Department of Energy [DE-AC02-05CH11231]
- project PRIN Interacting Photons in Polariton Circuits.INPhoPOL (Ministry of University and Scientific Research, MIUR) [2017P9FJBS_001]
Excitonic coupling, electronic coupling, and cooperative interactions in self-assembled lead halide perovskite nanocrystals can lead to a red-shifted collective emission peak with accelerated dynamics. Reactivity of nanocrystals within self-assembled superlattices can also result in similar spectroscopic features, such as a narrowing of emission peaks. Aging of CsPbBr3 nanocrystal assemblies alters their emission properties, with a gradual contraction of superlattices and the development of bulk-like particles on top of the superlattices.
Excitonic coupling, electronic coupling, and cooperative interactions in self-assembled lead halide perovskite nanocrystals were reported to give rise to a red-shifted collective emission peak with accelerated dynamics. Here we report that similar spectroscopic features could appear as a result of the nanocrystal reactivity within the self-assembled superlattices. This is demonstrated by studying CsPbBr3 nanocrystal superlattices over time with room-temperature and cryogenic micro-photoluminescence spectroscopy, X-ray diffraction, and electron microscopy. It is shown that a gradual contraction of the superlattices and subsequent coalescence of the nanocrystals occurs over several days of keeping such structures under vacuum. As a result, a narrow, low-energy emission peak is observed at 4 K with a concomitant shortening of the photoluminescence lifetime due to the energy transfer between nanocrystals. When exposed to air, self-assembled CsPbBr3 nanocrystals develop bulk-like CsPbBr3 particles on top of the superlattices. At 4 K, these particles produce a distribution of narrow, low-energy emission peaks with short lifetimes and excitation fluence-dependent, oscillatory decays. Overall, the aging of CsPbBr3 nanocrystal assemblies dramatically alters their emission properties and that should not be overlooked when studying collective optoelectronic phenomena nor confused with superfluorescence effects.
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