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Published December 21, 2019 | Supplemental Material + Published
Journal Article Open

Quasicubic model for metal halide perovskite nanocrystals

Abstract

We present an analysis of quantum confinement of carriers and excitons, and exciton fine structure, in metal halide perovskite (MHP) nanocrystals (NCs). Starting with coupled-band k · P theory, we derive a nonparabolic effective mass model for the exciton energies in MHP NCs valid for the full size range from the strong to the weak confinement limits. We illustrate the application of the model to CsPbBr₃ NCs and compare the theory against published absorption data, finding excellent agreement. We then apply the theory of electron-hole exchange, including both short- and long-range exchange interactions, to develop a model for the exciton fine structure. We develop an analytical quasicubic model for the effect of tetragonal and orthorhombic lattice distortions on the exchange-related exciton fine structure in CsPbBr₃, as well as some hybrid organic MHPs of recent interest, including formamidinium lead bromide (FAPbBr₃) and methylammonium lead iodide (MAPbI₃). Testing the predictions of the quasicubic model using hybrid density functional theory (DFT) calculations, we find qualitative agreement in tetragonal MHPs but significant disagreement in the orthorhombic modifications. Moreover, the quasicubic model fails to correctly describe the exciton oscillator strength and with it the long-range exchange corrections in these systems. Introducing the effect of NC shape anisotropy and possible Rashba terms into the model, we illustrate the calculation of the exciton fine structure in CsPbBr₃ NCs based on the results of the DFT calculations and examine the effect of Rashba terms and shape anisotropy on the calculated fine structure.

Additional Information

© 2019 Published under license by AIP Publishing. Submitted: 11 September 2019; Accepted: 12 November 2019; Published Online: 17 December 2019. P.C.S. acknowledges support from 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 U.S. Department of Energy. J.L.L., N.B., and A.L.E. acknowledge support from the U.S. Office of Naval Research. The work of J.L.L., and A.L.E was supported by the Laboratory University Collaboration Initiative of the DoD Basic Research Office. The authors declare no competing financial interests.

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Supplemental Material - sercel_supplmat_jcp_nov8.pdf

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August 19, 2023
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