Zone-Folded Longitudinal Acoustic Phonons Driving Self-Trapped State Emission in Colloidal CdSe Nanoplatelet Superlattices.
Nano Lett
; 21(10): 4137-4144, 2021 May 26.
Article
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| MEDLINE
| ID: mdl-33913710
ABSTRACT
Colloidal CdSe nanoplatelets (NPLs) have substantial potential in light-emitting applications because of their quantum-well-like characteristics. The self-trapped state (STS), originating from strong electron-phonon coupling (EPC), is promising in white light luminance because of its broadband emission. However, achieving STS in CdSe NPLs is extremely challenging because of their intrinsic weak EPC nature. Herein, we developed a strong STS emission in the spectral range of 450-600 nm by building superlattice (SL) structures with colloidal CdSe NPLs. We demonstrated that STS is generated via strong coupling of excitons and zone-folded longitudinal acoustic phonons with formation time of â¼450 fs and localization length of â¼0.56 nm. The Huang-Rhys factor, describing the EPC strength in SL structure, is estimated to be â¼19.9, which is much larger than that (â¼0.1) of monodispersed CdSe NPLs. Our results provide an in-depth understanding of STS and a platform for generating and manipulating STS by designing SL structures.
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Nano Lett
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2021
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Article