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On the absence of a phonon bottleneck in strongly confined CsPbBr3 perovskite nanocrystals

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Abstract

In traditional solar cells, photogenerated energetic carriers (so-called hot carriers) rapidly relax to band edges via emission of phonons, prohibiting the extraction of their excess energy above the band gap. Quantum confined semiconductor nanocrystals, or quantum dots (QDs), were predicted to have long-lived hot carriers enabled by a phonon bottleneck, i.e., the large inter-level spacings in QDs should result in inefficient phonon emissions. Here we study the effect of quantum confinement on hot carrier/exciton lifetime in lead halide perovskite nanocrystals. We synthesized a series of strongly confined CsPbBr3 nanocrystals with edge lengths down to 2.6 nm, the smallest reported to date, and studied their hot exciton relaxation using ultrafast spectroscopy. We observed sub-ps hot exciton lifetimes in all the samples with edge lengths within 2.6–6.2 nm and thus the absence of a phonon bottleneck. Their well-resolved excitonic peaks allowed us to quantify hot carrier/exciton energy loss rates which increased with decreasing NC sizes. This behavior can be well reproduced by a nonadiabatic transition mechanism between excitonic states induced by coupling to surface ligands.

Graphical abstract: On the absence of a phonon bottleneck in strongly confined CsPbBr3 perovskite nanocrystals

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Publication details

The article was received on 19 Mar 2019, accepted on 05 May 2019 and first published on 06 May 2019


Article type: Edge Article
DOI: 10.1039/C9SC01339C
Chem. Sci., 2019, Advance Article
  • Open access: Creative Commons BY license
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    On the absence of a phonon bottleneck in strongly confined CsPbBr3 perovskite nanocrystals

    Y. Li, R. Lai, X. Luo, X. Liu, T. Ding, X. Lu and K. Wu, Chem. Sci., 2019, Advance Article , DOI: 10.1039/C9SC01339C

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