Proceedings of nanoGe Fall Meeting 2021 (NFM21)
DOI: https://doi.org/10.29363/nanoge.nfm.2021.112
Publication date: 23rd September 2021
Halide perovskite nanocrystals are a promising platform for optoelectronic devices, including display light sources and single-photon emitters, owing to the fast, efficient radiative decay in these materials. Two-dimensional (2D) halide perovskite quantum dots or nanoplatelets would be particularly promising for bright, fast radiative recombination, since confinement will lead to large exciton binding energies and giant oscillator transition strength. In this work, we explore the thickness-dependent fine structure of excitons in 2D halide perovskite nanoplatelets. We build a quasi-2D effective-mass model of excitons which are strongly confined in the out-of-plane direction but weakly confined in-plane. The model includes the effect of shape anisotropy on the long-range exchange corrections to the fine structure and introduces the important effect of confinement on the band-edge Bloch functions. Applying the model to colloidal CsPbBr3 nanoplatelets, where electron-hole exchange splitting is expected to dominate the exciton fine structure, we predict a thickness-dependent level order of the in-plane-polarized and out-of-plane-polarized bright exciton states. The calculated fine structure is consistent with observed thickness-dependent spectral shifts [1]. We extend the model to 2D hybrid perovskite materials, for which large Rashba coefficients have been either measured or predicted, and describe the dispersion, level structure, and optical properties of the 2D “Rashba exciton”. The analysis reveals unusual features, notably a dispersion minimum at non-zero exciton wave-vector. Consequences of the dispersion to level structure and oscillator transition strengths of Rashba excitons confined in a 2D cylindrical QDs are developed and used to establish criteria under which a bright ground exciton state could be realized [2].
[1] "Dark and Bright Excitons in Halide Perovskite Nanoplatelets", M. Gramlich, M. W. Swift, C. Lampe, J. L. Lyons, M. Doblinger, Al. L.Efros, P C. Sercel, A. S. Urban, To be published.
[2] "Rashba exciton in a 2D perovskite quantum dot", M W. Swift, J. L. Lyons, Al. L. Efros, and P. C. Sercel, To be published.
This work was supported by the Center for Hybrid Organic Inorganic Semiconductors for Energy (CHOISE) an Energy Frontier Research Center funded by the Office of Basic Energy Sciences, Office of Science within the US Department of Energy.
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