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Bright triplet excitons in caesium lead halide perovskites

Becker, Michael A. and Vaxenburg, Roman and Nedelcu, Georgian and Sercel, Peter C. and Shabaev, Andrew and Mehl, Michael J. and Michopoulos, John G. and Lambrakos, Samuel G. and Bernstein, Noam and Lyons, John L. and Stöferle, Thilo and Mahrt, Rainer F. and Kovalenko, Maksym V. and Norris, David J. and Rainò, Gabriele and Efros, Alexander L. (2018) Bright triplet excitons in caesium lead halide perovskites. Nature, 553 (7687). pp. 189-193. ISSN 0028-0836. https://resolver.caltech.edu/CaltechAUTHORS:20180116-105553545

[img] PDF (Supplementary text S1-S5) - Supplemental Material
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[img] Image (JPEG) (Extended Data Figure 1 : Electronic structure for CsPbCl3 and CsPbI3 perovskites) - Supplemental Material
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[img] Image (JPEG) (Extended Data Figure 2 : Measurements to estimate the low-temperature quantum yield for our CsPbBr2Cl nanocrystals) - Supplemental Material
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[img] Image (JPEG) (Extended Data Figure 3 : Exciton and trion emission from an individual CsPbBr2Cl nanocrystal) - Supplemental Material
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[img] Image (JPEG) (Extended Data Figure 4 : Composition-dependent ensemble photoluminescence decay measurements of lead halide perovskite nanocrystals) - Supplemental Material
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[img] Image (JPEG) (Extended Data Figure 5 : Calculation of the interior electric field in cube-shaped nanocrystals) - Supplemental Material
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[img] Image (JPEG) (Extended Data Figure 6 : Contour plots of normalized electric-field magnitude across a cube-shaped nanocrystal) - Supplemental Material
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[img] Image (JPEG) (Extended Data Figure 7 : Extraction of the Kane energy Ep for the lead halide perovskites) - Supplemental Material
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[img] Image (JPEG) (Extended Data Figure 8 : Variational calculations related to the determination of the exciton radiative lifetime in cube-shaped nanocrystals within the intermediate-confinement regime) - Supplemental Material
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[img] Image (JPEG) (Extended Data Figure 9 : Representative two-peak spectra for individual CsPbBr2Cl nanocrystals) - Supplemental Material
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[img] Image (JPEG) (Extended Data Figure 10 : Representative three-peak spectra for individual CsPbBr2Cl nanocrystals) - Supplemental Material
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[img] Image (JPEG) (Extended Data Figure 11 : Predicted exciton spectra and polarization properties for individual perovskite nanocrystals) - Supplemental Material
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Abstract

Nanostructured semiconductors emit light from electronic states known as excitons. For organic materials, Hund’s rules state that the lowest-energy exciton is a poorly emitting triplet state. For inorganic semiconductors, similar rules predict an analogue of this triplet state known as the ‘dark exciton’. Because dark excitons release photons slowly, hindering emission from inorganic nanostructures, materials that disobey these rules have been sought. However, despite considerable experimental and theoretical efforts, no inorganic semiconductors have been identified in which the lowest exciton is bright. Here we show that the lowest exciton in caesium lead halide perovskites (CsPbX_3, with X = Cl, Br or I) involves a highly emissive triplet state. We first use an effective-mass model and group theory to demonstrate the possibility of such a state existing, which can occur when the strong spin–orbit coupling in the conduction band of a perovskite is combined with the Rashba effect. We then apply our model to CsPbX_3 nanocrystals, and measure size- and composition-dependent fluorescence at the single-nanocrystal level. The bright triplet character of the lowest exciton explains the anomalous photon-emission rates of these materials, which emit about 20 and 1,000 times faster than any other semiconductor nanocrystal at room and cryogenic temperatures, respectively. The existence of this bright triplet exciton is further confirmed by analysis of the fine structure in low-temperature fluorescence spectra. For semiconductor nanocrystals, which are already used in lighting, lasers and displays, these excitons could lead to materials with brighter emission. More generally, our results provide criteria for identifying other semiconductors that exhibit bright excitons, with potential implications for optoelectronic devices.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1038/nature25147DOIArticle
http://rdcu.be/EQoOPublisherFree ReadCube access
ORCID:
AuthorORCID
Sercel, Peter C.0000-0002-1734-3793
Lyons, John L.0000-0001-8023-3055
Efros, Alexander L.0000-0003-1938-553X
Additional Information:© 2018 Macmillan Publishers Limited, part of Springer Nature. Received: 21 June 2017; Accepted: 09 November 2017; Published online: 10 January 2018. We thank F. Krieg for providing large CsPbBr3 nanocrystals, S. Yakunin and J. Jagielski for assistance with absolute quantum-yield measurements, and E. Ivchenko, M. Glazov and E. Rashba for discussions. M.A.B., G.R., T.S., M.V.K. and R.F.M. acknowledge the European Union’s Horizon-2020 programme through the Marie-Skłodowska Curie ITN network PHONSI (H2020-MSCA-ITN-642656) and the Swiss State Secretariat for Education Research and Innovation (SERI). J.G.M., S.G.L., N.B., J.L.L. and Al.L.E. acknowledge support from the US Office of Naval Research (ONR) through the core funding of the Naval Research Laboratory. R.V. was funded by ONR grant N0001416WX01849. A.S. acknowledges support from the Center for Advanced Solar Photophysics (CASP), an Energy Frontier Research Center (EFRC) funded by BES, OS, US DOE. D.J.N. and M.V.K. acknowledge partial financial support from the European Research Council under the European Union’s Seventh Framework Programme (FP/2007-2013)/ERC grant agreement number 339905 (QuaDoPS Advanced Grant) and number 306733 (NANOSOLID Starting Grant), respectively. The authors declare no competing financial interests. Data availability: All data generated or analysed during this study are included in the published article (and its Supplementary Information).
Funders:
Funding AgencyGrant Number
Marie Curie FellowshipH2020-MSCA-ITN-642656
Swiss State Secretariat for Education Research and Innovation (SERI)UNSPECIFIED
Office of Naval Research (ONR)N0001416WX01849
Department of Energy (DOE)UNSPECIFIED
European Research Council (ERC)339905
European Research Council (ERC)306733
Issue or Number:7687
Record Number:CaltechAUTHORS:20180116-105553545
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20180116-105553545
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:84343
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:17 Jan 2018 18:41
Last Modified:14 Apr 2020 21:38

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