Enhancement of the Biexciton Binding Energy in Laterally Confined CdSe Nanoplatelets.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 40830083.
- Also identified by DOI 10.1021/acs.nanolett.5c03251 and PMC identifier 12412167.
- Licence recorded as CC BY-NC-ND.
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Abstract
Optical amplification in CdSe nanoplatelets (NPLs) has been linked to biexcitons with a large binding energy Δ<sub>BX</sub>, preventing dissociation at room temperature. While the exciton binding energy Δ<sub>X</sub> has been studied extensively, Δ<sub>BX</sub> in colloidal NPLs is typically inferred using the 2D Haynes rule, Δ<sub>BX</sub> = 0.228·Δ<sub>X</sub>. Systematic studies of Δ<sub>BX</sub> in CdSe NPLs with varying thicknesses and lateral dimensions are still lacking. Here, we used transient absorption spectroscopy to investigate Δ<sub>BX</sub>, through photoinduced biexciton absorption. Δ<sub>BX</sub> ranges between 40 and 55 meV and increases by 30% when reducing the width from 9 to 3 nm, while overall 3.5 ML NPLs have only 10% higher Δ<sub>BX</sub> compared to 4.5 ML NPLs. Fitting the linear absorbance spectra, we extracted Δ<sub>X</sub> and demonstrate that the Δ<sub>BX</sub>/Δ<sub>X</sub> ratio is substantially lower than 0.228. Results confirm that biexcitons in CdSe NPLs are stable at room temperature and have an increased Δ<sub>BX</sub> in laterally confined NPLs.