Bright Triplet Emission from Lead Halide Perovskite Nanocrystals

Michael A. Becker^a^,^b, Roman Vaxenburg^c, Georgian Nedelcu^d^,^e, Loredana Protesescu^d^,^e, Andrew Shabaev^c, Peter Sercel^f, Michael J. Mehl^g, John G. Michopoulos^h, Samuel G. Lambrakos^h, Noam Bernstein^h, John L. Lyons^h, Maryna I. Bodnarchuk^d^,^e, Rainer F. Mahrt^a, Thilo Stoeferle^a, Maksym V. Kovalenko^d^,^e, David J. Norris^b, Gabriele Raino^a^,^d^,^e, Alexander L. Efros^h

^aIBM Research – Zurich, Säumerstrasse, 4, Rüschlikon, Switzerland

^bOptical Materials Engineering Laboratory, ETH Zürich, Switzerland, Leonhardstrasse, 21, Zürich, Switzerland

^cGeorge Mason University, Fairfax VA, 22030, USA

^dETH Zurich, Laboratory of Inorganic Chemistry, Department of Chemistry & Applied Biosciences, Vladimir-Prelog-Weg, 1, Zürich, Switzerland

^eEMPA - Swiss Federal Laboratories for Materials Science and Technology, Überland Strasse, 129, Dübendorf, Switzerland

^fDepartment of Applied Physics, California Institute of Technology,, Pasadena, California 91125

^gU.S. Naval Acadamy, Annapolis, MD 21402, USA

^hNaval Research Laboratory, Washington, Overlook Avenue Southwest, 4555, Washington, United States

Materials for Sustainable Development Conference (MATSUS)
Proceedings of nanoGe Fall Meeting 2018 (NFM18)

S4 Nanophotonics by Nanocrystals

Torremolinos, Spain, 2018 October 22nd - 26th

Organizers: Daniel Vanmaekelbergh and Zeger Hens

Oral, Michael A. Becker, presentation 077
DOI: https://doi.org/10.29363/nanoge.nfm.2018.077
Publication date: 6th July 2018

The emission of fully inorganic cesium lead halide (CsPbX₃, where X = I,Br,Cl) perovskite-type nanocrystals is tunable over a wide energy range with ultrahigh photoluminescence quantum yields of up to 90%^[1]and exhibits narrow emission lines. Due to their facile solution processability and their potential for high-efficiency photovoltaics and light sources they have gained enormous interest.

Experiments on single perovskite quantum dots reveal a unique energetic level structure with a lowest bright triplet state^[2], thus enabling photon emission rates ~20 and ~1000 times higher compared to any other conventional semiconductor nanocrystals at room and cryogenic temperatures, respectively. We investigate the nature of this exceptionally fast photon emission by temperature dependent quantum yield measurements. Furthermore we discriminate it from composition dependent “A-type” blinking behaviour in intensity-decay time correlation measurements and demonstrate stable, narrowband emission, with suppressed blinking and small spectral diffusion^[3] for single CsPbBr₂Cl nanocrystals. By means of polarization dependent high resolution spectroscopy, the complex nature of the exciton fine structure splitting and charged exciton emission has been characterized.

Based on these measurements, supported by effective-mass models and group theory calculations, we conclude that the triplet exciton state is responsible for the extraordinary photon emission properties of lead halide perovskites. Our results can assist to identify other semiconductors that exhibit bright triplet excitons, with potential implications for improved optoelectronic devices.

References:

[1] Protesescu et al., Nano Lett. 15, 3692–3696 (2015)

[2] Becker et al., Nature, 553, 187-193 (2018)

[3] Rainò et al., ACS Nano 10, 2485–2490 (2016)

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