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Exciton fine structure in perovskite nanocrystals

Sercel, Peter C. and Lyons, John L. and Wickramaratne, Darshana and Vaxenburg, Roman and Bernstein, Noam and Efros, Alexander L. (2019) Exciton fine structure in perovskite nanocrystals. Nano Letters, 19 (6). pp. 4068-4077. ISSN 1530-6984. doi:10.1021/acs.nanolett.9b01467.

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The bright emission observed in cesium lead halide perovskite nanocrystals (NCs) has recently been explained in terms of a bright exciton ground state [Becker et al. Nature 2018, 553, 189−193], a claim that would make these materials the first known examples in which the exciton ground state is not an optically forbidden dark exciton. This unprecedented claim has been the subject of intense experimental investigation that has so far failed to detect the dark ground-state exciton. Here, we review the effective-mass/electron–hole exchange theory for the exciton fine structure in cubic and tetragonal CsPbBr_3 NCs. In our calculations, the crystal field and the short-range electron–hole exchange constant were calculated using density functional theory together with hybrid functionals and spin–orbit coupling. Corrections associated with long-range exchange and surface image charges were calculated using measured bulk effective mass and dielectric parameters. As expected, within the context of the exchange model, we find an optically inactive ground exciton level. However, in this model, the level order for the optically active excitons in tetragonal CsPbBr_3 NCs is opposite to what has been observed experimentally. An alternate explanation for the observed bright exciton level order in CsPbBr_3 NCs is offered in terms of the Rashba effect, which supports the existence of a bright ground-state exciton in these NCs. The size dependence of the exciton fine structure calculated for perovskite NCs shows that the bright–dark level inversion caused by the Rashba effect is suppressed by the enhanced electron–hole exchange interaction in small NCs.

Item Type:Article
Related URLs:
URLURL TypeDescription
Sercel, Peter C.0000-0002-1734-3793
Lyons, John L.0000-0001-8023-3055
Wickramaratne, Darshana0000-0002-1663-1507
Efros, Alexander L.0000-0003-1938-553X
Additional Information:© 2019 American Chemical Society. Received: April 10, 2019; Revised: May 13, 2019; Published: May 15, 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., D.W., R.V., N.B., and A.L.E. acknowledge support from the U.S. Office of Naval Research through the U.S. Naval Research Laboratory’s core research program. The work of J.L.L. and A.L.E. was supported by the Laboratory-University Collaboration Initiative of the Department of Defense Basic Research Office. D.W. acknowledges support from the National Research Council fellowship at the U.S. Naval Research Laboratory. The authors declare no competing financial interest.
Funding AgencyGrant Number
Department of Energy (DOE)UNSPECIFIED
Office of Naval Research (ONR)UNSPECIFIED
Naval Research LaboratoryUNSPECIFIED
Department of DefenseUNSPECIFIED
National Research CouncilUNSPECIFIED
Subject Keywords:Exciton fine structure, lead halide perovskite, nanocrystals, electron-hole exchange, Rashba effect
Issue or Number:6
Record Number:CaltechAUTHORS:20190515-100429194
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Official Citation:Exciton Fine Structure in Perovskite Nanocrystals. Peter C. Sercel, John L. Lyons, Darshana Wickramaratne, Roman Vaxenburg, Noam Bernstein, and Alexander L. Efros. Nano Letters 2019 19 (6), 4068-4077. DOI: 10.1021/acs.nanolett.9b01467
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:95506
Deposited By: Tony Diaz
Deposited On:15 May 2019 22:52
Last Modified:16 Nov 2021 17:13

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