1. Measuring the Ultrafast Spectral Diffusion and Vibronic Coupling Dynamics in CdSe Colloidal Quantum Wells using Two-Dimensional Electronic Spectroscopy
- Author
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Hoang Long Nguyen, Thanh Nhut Do, Emek G. Durmusoglu, Merve Izmir, Ritabrata Sarkar, Sougata Pal, Oleg V. Prezhdo, Hilmi Volkan Demir, Howe-Siang Tan, School of Electrical and Electronic Engineering, School of Physical and Mathematical Sciences, School of Materials Science and Engineering, School of Chemistry, Chemical Engineering and Biotechnology, LUMINOUS! Centre of Excellence for Semiconductor Lighting & Displays, and The Photonics Institute
- Subjects
Colloidal Quantum Well ,General Engineering ,General Physics and Astronomy ,General Materials Science ,Spectral Diffusion ,Materials::Nanostructured materials [Engineering] - Abstract
We measure the ultrafast spectral diffusion, vibronic dynamics, and energy relaxation of a CdSe colloidal quantum wells (CQWs) system at room temperature using two-dimensional electronic spectroscopy (2DES). The energy relaxation of light-hole (LH) excitons and hot carriers to heavy-hole (HH) excitons is resolved with a time scale of ∼210 fs. We observe the equilibration dynamics between the spectroscopically accessible HH excitonic state and a dark state with a time scale of ∼160 fs. We use the center line slope analysis to quantify the spectral diffusion dynamics in HH excitons, which contains an apparent sub-200 fs decay together with oscillatory features resolved at 4 and 25 meV. These observations can be explained by the coupling to various lattice phonon modes. We further perform quantum calculations that can replicate and explain the observed dynamics. The 4 meV mode is observed to be in the near-critically damped regime and may be mediating the transition between the bright and dark HH excitons. These findings show that 2DES can provide a comprehensive and detailed characterization of the ultrafast spectral properties in CQWs and similar nanomaterials. Agency for Science, Technology and Research (A*STAR) Ministry of Education (MOE) Submitted/Accepted version H.V.D. gratefully acknowledges the financial support in part from the Singapore Agency for Science, Technology and Research (A*STAR) SERC under Grant No. M21J9b0085, and the Singapore Ministry of Education Tier 1 grant (MOERG62/20). H.V.D. also gratefully acknowledges the support from TUBA. H.-S.T. gratefully acknowledges the financial support in part from the Singapore Ministry of Education Tier 1 grant (MOE-RG2/19 and MOE-RG14/20). O.V.P. acknowledges the financial support from the United States National Science Foundation under Grant No. CHE-2154367.
- Published
- 2023