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Title: The Underlying Chemical Mechanism of Selective Chemical Etching in CsPbBr 3 Nanocrystals for Reliably Accessing Near-Unity Emitters

Abstract

Reliably accessing nanocrystal luminophores with near-unity efficiencies aids in the ability to understand the upper performance limits in optoelectronic applications that require minimal nonradiative losses. Constructing structure-function relationships at the atomic level, while accounting for inevitable defects, allows for the development of robust strategies to achieve near-unity quantum yield luminophores. For CsPbBr 3 perovskite nanocrystals, bromine vacancies leave behind undercoordinated lead atoms that act as traps, limiting the achievable optical performance of the material. Here, we show that selective etching represents a promising path for mitigating the consequences of optical defects in CsPbBr 3 nanocrystals. A mechanistic understanding of the etching reaction is essential for developing strategies to finely control the reaction. We report a study of the selective etching mechanism of CsPbBr3 nanocrystal cubes by controlling the etchant chemical potential. We observe optical absorption and luminescence trajectories while varying the extent and rate of lead removal, removing in some cases up to 75% of the lead from the original nanocrystal ensemble. At modest etchant chemical potentials, the size and shape uniformity of the nanocrystal ensemble improves in addition to the quantum yield, proceeding through a layer-by-layer etching mechanism. Operating with excessively high etchant chemical potentials is detrimental to themore » overall optical performance as the etching transitions to nonselective, while too low of a chemical potential results in incomplete etching. Through this general approach, we show how to finely control selective etching to consistently access a steady state or chemical stability zone of near-unity quantum yield CsPbBr 3 nanocrystals postsynthetically, suggesting a practical framework to extend this treatment to other perovskite compositions and sizes.« less

Authors:
ORCiD logo [1];  [1]; ORCiD logo [1]
  1. Univ. of California, Berkeley, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Kavli Energy NanoScience Institute, Berkeley, CA (United States)
Publication Date:
Research Org.:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES). Materials Sciences & Engineering Division
OSTI Identifier:
1619131
Grant/Contract Number:  
AC02-05CH11231
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
ACS Nano
Additional Journal Information:
Journal Volume: 13; Journal Issue: 10; Journal ID: ISSN 1936-0851
Publisher:
American Chemical Society (ACS)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; selective etching; lead halide perovskites; colloidal nanocrystals; photoluminescence quantum yield; CsPbBr3

Citation Formats

Koscher, Brent A., Nett, Zachary, and Alivisatos, A. Paul. The Underlying Chemical Mechanism of Selective Chemical Etching in CsPbBr3 Nanocrystals for Reliably Accessing Near-Unity Emitters. United States: N. p., 2019. Web. doi:10.1021/acsnano.9b05782.
Koscher, Brent A., Nett, Zachary, & Alivisatos, A. Paul. The Underlying Chemical Mechanism of Selective Chemical Etching in CsPbBr3 Nanocrystals for Reliably Accessing Near-Unity Emitters. United States. doi:10.1021/acsnano.9b05782.
Koscher, Brent A., Nett, Zachary, and Alivisatos, A. Paul. Wed . "The Underlying Chemical Mechanism of Selective Chemical Etching in CsPbBr3 Nanocrystals for Reliably Accessing Near-Unity Emitters". United States. doi:10.1021/acsnano.9b05782. https://www.osti.gov/servlets/purl/1619131.
@article{osti_1619131,
title = {The Underlying Chemical Mechanism of Selective Chemical Etching in CsPbBr3 Nanocrystals for Reliably Accessing Near-Unity Emitters},
author = {Koscher, Brent A. and Nett, Zachary and Alivisatos, A. Paul},
abstractNote = {Reliably accessing nanocrystal luminophores with near-unity efficiencies aids in the ability to understand the upper performance limits in optoelectronic applications that require minimal nonradiative losses. Constructing structure-function relationships at the atomic level, while accounting for inevitable defects, allows for the development of robust strategies to achieve near-unity quantum yield luminophores. For CsPbBr3 perovskite nanocrystals, bromine vacancies leave behind undercoordinated lead atoms that act as traps, limiting the achievable optical performance of the material. Here, we show that selective etching represents a promising path for mitigating the consequences of optical defects in CsPbBr3 nanocrystals. A mechanistic understanding of the etching reaction is essential for developing strategies to finely control the reaction. We report a study of the selective etching mechanism of CsPbBr3 nanocrystal cubes by controlling the etchant chemical potential. We observe optical absorption and luminescence trajectories while varying the extent and rate of lead removal, removing in some cases up to 75% of the lead from the original nanocrystal ensemble. At modest etchant chemical potentials, the size and shape uniformity of the nanocrystal ensemble improves in addition to the quantum yield, proceeding through a layer-by-layer etching mechanism. Operating with excessively high etchant chemical potentials is detrimental to the overall optical performance as the etching transitions to nonselective, while too low of a chemical potential results in incomplete etching. Through this general approach, we show how to finely control selective etching to consistently access a steady state or chemical stability zone of near-unity quantum yield CsPbBr3 nanocrystals postsynthetically, suggesting a practical framework to extend this treatment to other perovskite compositions and sizes.},
doi = {10.1021/acsnano.9b05782},
journal = {ACS Nano},
issn = {1936-0851},
number = 10,
volume = 13,
place = {United States},
year = {2019},
month = {9}
}

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