期刊
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
卷 10, 期 13, 页码 3637-3644出版社
AMER CHEMICAL SOC
DOI: 10.1021/acs.jpclett.9b01607
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资金
- European Commission via the Marie-Sklodowska Curie action Phonsi [H2020-MSCA-ITN-642656]
- Research Foundation Flanders [17006602]
- Ghent University (GOA) [01G01513]
- FWO-Vlaanderen
- Marsden Fund
We show that optical gain in 2D CdSe colloidal quantum wells (CQWs) shows little saturation and coexists with exciton absorption over a broad range of excitation densities, in stark contrast with OD CdSe colloidal quantum dots (CQDs). In addition, we demonstrate that photoexcited CQWs can absorb or emit light through the thermodynamically driven formation or radiative recombination of singlet excitonic molecules. Invoking stimulated emission through the molecule exciton transition, we can quantify all of the remarkable gain characteristics of CQWs using only experimentally determined parameters, an advance that highlights a fundamental difference between multiexcitons in CQWs and CQDs. While strong confinement prohibits the dissociation of multiexcitons into separate excitons in OD CQDs, excitons and excitonic molecules coexist in a 2D CQW at room temperature, with densities governed by an association/ dissociation equilibrium, not by state-filling. Our finding points out future directions to optimize stimulated emission by excitonic 2D materials in general.
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