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Kambhampati P. Unraveling the excitonics of light emission from metal-halide perovskite quantum dots. NANOSCALE 2024; 16:15033-15058. [PMID: 39052235 DOI: 10.1039/d4nr01481b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/27/2024]
Abstract
Metal halide semicondictor perovskites have been under intense investigation for their promise in light absorptive applications like photovoltaics. They have more recently experienced interest for their promise in light emissive applications. A key aspect of perovskites is their glassy, ionic lattice that exhibits dynamical disorder. One possible result of this dynamical disorder is their strong coupling between electronic and lattice degrees of freedom which may confer remarkable properties for light emission such as defect tolerance. How does the system, comprised of excitons, couple to the bath, comprised of lattice modes? How does this system-bath interaction give rise to novel light emissive properties and how do these properties give insight into the nature of these materials? We review recent work from this group in which time-resolved photoluminescence spectroscopy is used to reveal such insights. Based upon a fast time resolution of 3 ps, energy resolution, and temperature dependence, a wide variety of insights are gleaned. These insights include: lattice contributions to the emission linewidths, multiexciton formation, hot carrier cooling, excitonic fine structure, single dot superradiance, and a breakdown of the Condon approximation, all due to complex structural dynamics in these materials.
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Strandell D, Dirin D, Zenatti D, Nagpal P, Ghosh A, Raino G, Kovalenko MV, Kambhampati P. Enhancing Multiexcitonic Emission in Metal-Halide Perovskites by Quantum Confinement. ACS NANO 2023; 17:24910-24918. [PMID: 38079478 DOI: 10.1021/acsnano.3c06497] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2023]
Abstract
Semiconductor metal halide perovskite nanocrystals have been under intense investigation for their promise in a variety of optoelectronic applications, which arises from their remarkable properties of defect tolerance and efficient light emission. Recently, quantum dot versions of perovskite nanocrystals have been available, enabling investigation of how quantum size effects control optical function and performance in these quantum dots (QD), past their well-known covalent II-VI analogues. We perform time-resolved photoluminescence (t-PL) experiments on CsPbBr3 perovskite nanocrystals spanning in diameter from 5.8 nm strongly confined quantum dots to 18 nm weakly confined quantum dots. Experiments are performed with sufficient time resolution of 3 ps to observe the interaction energies and recombination kinetics from excitons to multiexcitons. Comparing the same sized QD reveals that perovskite QD have a larger radiative rate constant for emission from X than CdSe QD due to a larger oscillator strength. The multiexciton (MX) regime reveals that perovskite QD emit brightly and with more focused bandwidth than equivalent sized CdSe QD enabling more spectrally pure brightness. The MX kinetics reveals that the perovskite QD maintain efficient radiative decay, effectively competing with Auger recombination. These experiments reveal that the strongly confined QD of perovskites can be efficient multiexcitonic emitters, such as in high brightness light emitting diodes, especially in the blue.
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Affiliation(s)
- Dallas Strandell
- Department of Chemistry, McGill University, Montreal, H3A 0B8, Canada
| | - Dmitry Dirin
- Institute of Inorganic Chemistry, Department of Chemistry and Applied Biosciences, ETH Zurich, 8093 Zurich, Switzerland
| | - Davide Zenatti
- Department of Chemistry, McGill University, Montreal, H3A 0B8, Canada
| | - Priya Nagpal
- Department of Chemistry, McGill University, Montreal, H3A 0B8, Canada
| | - Arnab Ghosh
- Department of Chemistry, McGill University, Montreal, H3A 0B8, Canada
| | - Gabriele Raino
- Institute of Inorganic Chemistry, Department of Chemistry and Applied Biosciences, ETH Zurich, 8093 Zurich, Switzerland
- Empa - Swiss Federal Laboratories for Materials Science and Technology, 8600 Dubendorf, Switzerland
| | - Maksym V Kovalenko
- Institute of Inorganic Chemistry, Department of Chemistry and Applied Biosciences, ETH Zurich, 8093 Zurich, Switzerland
- Empa - Swiss Federal Laboratories for Materials Science and Technology, 8600 Dubendorf, Switzerland
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Ding Y, Zhang Z, Toso S, Gushchina I, Trepalin V, Shi K, Peng JW, Kuno M. Mixed Ligand Passivation as the Origin of Near-Unity Emission Quantum Yields in CsPbBr 3 Nanocrystals. J Am Chem Soc 2023; 145:6362-6370. [PMID: 36881007 DOI: 10.1021/jacs.2c13527] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/08/2023]
Abstract
Key features of syntheses, involving the quaternary ammonium passivation of CsPbBr3 nanocrystals (NCs), include stable, reproducible, and large (often near-unity) emission quantum yields (QYs). The archetypical example involves didodecyl dimethyl ammonium (DDDMA+)-passivated CsPbBr3 NCs where robust QYs stem from interactions between DDDMA+ and NC surfaces. Despite widespread adoption of this synthesis, specific ligand-NC surface interactions responsible for large DDDMA+-passivated NC QYs have not been fully established. Multidimensional nuclear magnetic resonance experiments now reveal a new DDDMA+-NC surface interaction, beyond established "tightly bound" DDDMA+ interactions, which strongly affects observed emission QYs. Depending upon the existence of this new DDDMA+ coordination, NC QYs vary broadly between 60 and 85%. More importantly, these measurements reveal surface passivation through unexpected didodecyl ammonium (DDA+) that works in concert with DDDMA+ to produce near-unity (i.e., >90%) QYs.
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Affiliation(s)
- Yang Ding
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, United States
| | - Zhuoming Zhang
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, United States
| | - Stefano Toso
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, United States
- Nanochemistry Department, Instituto Italiano di Tecnologia, Via Morego 30, 16163 Genova, Italy
| | - Irina Gushchina
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, United States
| | - Vadim Trepalin
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, United States
| | - Kejia Shi
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, United States
| | - Jeffrey W Peng
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, United States
| | - Masaru Kuno
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, United States
- Department of Physics, University of Notre Dame, Notre Dame, Indiana 46556, United States
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Diroll BT, Brumberg A, Schaller RD. Gain roll-off in cadmium selenide colloidal quantum wells under intense optical excitation. Sci Rep 2022; 12:8016. [PMID: 35577869 PMCID: PMC9110332 DOI: 10.1038/s41598-022-11882-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2021] [Accepted: 02/24/2022] [Indexed: 12/04/2022] Open
Abstract
Colloidal quantum wells, or nanoplatelets, show among the lowest thresholds for amplified spontaneous emission and lasing among solution-cast materials and among the highest modal gains of any known materials. Using solution measurements of colloidal quantum wells, this work shows that under photoexcitation, optical gain increases with pump fluence before rolling off due to broad photoinduced absorption at energies lower than the band gap. Despite the common occurrence of gain induced by an electron–hole plasma found in bulk materials and epitaxial quantum wells, under no measurement conditions was the excitonic absorption of the colloidal quantum wells extinguished and gain arising from a plasma observed. Instead, like gain, excitonic absorption reaches a minimum intensity near a photoinduced carrier sheet density of 2 × 1013 cm−2 above which the absorption peak begins to recover. To understand the origins of these saturation and reversal effects, measurements were performed with different excitation energies, which deposit differing amounts of excess energy above the band gap. Across many samples, it was consistently observed that less energetic excitation results in stronger excitonic bleaching and gain for a given carrier density. Transient and static optical measurements at elevated temperatures, as well as transient X-ray diffraction of the samples, suggest that the origin of gain saturation and reversal is a heating and disordering of the colloidal quantum wells which produces sub-gap photoinduced absorption.
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Roy D, Ghosh S, De CK, Mukherjee S, Mandal S, Mandal PK. Excitation-Energy-Dependent Photoluminescence Quantum Yield is Inherent to Optically Robust Core/Alloy-Shell Quantum Dots in a Vast Energy Landscape. J Phys Chem Lett 2022; 13:2404-2417. [PMID: 35257586 DOI: 10.1021/acs.jpclett.2c00157] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
The importance of alloy-shelling in optically robust Core/Alloy-Shell (CAS) QDs has been described from structural and energetic aspects. Unlike fluorescent dyes, both Core/Shell (CS) and CAS QDs exhibit excitation-energy-dependent photoluminescence quantum yield (PLQY). For both CdSe and InP CAS QDs (with metal- and nonmetal-based alloy-shelling, respectively), with increasing excitation energy, (a) the ultrafast rise-time or relaxation-time to the band-edge increases and (b) the magnitude of the normalized bleach signal decreases. Ultrasensitive single-particle spectroscopic investigation results showed that with decreasing excitation energy, (a) the fraction of ON events increases, (b) the ratio of exciton-detrapping rate/trapping rate increases, and (c) the extent of beneficial hole trapping increases. A relative decrease in PLQY with increasing excitation energy is much less pronounced in CAS QDs than in CS QDs. Unless trap states are removed completely especially in the higher-energy landscape, PLQY will remain inherently dependent on excitation energy for QDs in the vast energy landscape. When reporting the PLQY of QDs, the magnitude of the excitation energy must be mentioned.
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Affiliation(s)
- Debjit Roy
- Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER) Kolkata, Mohanpur, West Bengal, India 741246
| | - Swarnali Ghosh
- Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER) Kolkata, Mohanpur, West Bengal, India 741246
| | - Chayan K De
- Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER) Kolkata, Mohanpur, West Bengal, India 741246
| | - Soumen Mukherjee
- Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER) Kolkata, Mohanpur, West Bengal, India 741246
| | - Saptarshi Mandal
- Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER) Kolkata, Mohanpur, West Bengal, India 741246
| | - Prasun K Mandal
- Department of Chemical Sciences & Centre for Advanced Functional Materials, Indian Institute of Science Education and Research (IISER) Kolkata, Mohanpur, West Bengal, India 741246
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