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Strandell D, Mora Perez C, Wu Y, Prezhdo OV, Kambhampati P. Excitonic Quantum Coherence in Light Emission from CsPbBr 3 Metal-Halide Perovskite Nanocrystals. Nano Lett 2024; 24:61-66. [PMID: 38113396 DOI: 10.1021/acs.nanolett.3c03180] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2023]
Abstract
The decay of excited states via radiative and nonradiative paths is well understood in molecules and bulk semiconductors but less so in nanocrystals. Here, we perform time-resolved photoluminescence (t-PL) experiments on CsPbBr3 metal-halide perovskite nanocrystals, with a time resolution of 3 ps, sufficient to observe the decay of both excitons and biexcitons as a function of temperature. The striking result is that the radiative rate constant of the single exciton increases at low temperatures with an exponential functional form, suggesting quantum coherent effects with dephasing at high temperatures. The opposing directions of the radiative and nonradiative decay rate constants enable enhanced brightening of PL from excitons to biexcitons due to quantum effects, promoting a faster approach to the quantum theoretical limits of light emission. Ab initio quantum dynamics simulations reproduce the experimental observations of radiation controlled by quantum spatial coherence enhanced at low temperatures.
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Affiliation(s)
- Dallas Strandell
- Department of Chemistry, McGill University, Montreal, Quebec H3A 0B8, Canada
| | - Carlos Mora Perez
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States
| | - Yifan Wu
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States
| | - Oleg V Prezhdo
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States
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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] [What about the content of this article? (0)] [Affiliation(s)] [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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Strandell D, Wu Y, Mora-Perez C, Prezhdo O, Kambhampati P. Breaking the Condon Approximation for Light Emission from Metal Halide Perovskite Nanocrystals. J Phys Chem Lett 2023; 14:11281-11285. [PMID: 38061060 DOI: 10.1021/acs.jpclett.3c02826] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2023]
Abstract
The idea that the electronic transition dipole moment does not depend upon nuclear excursions is the Condon approximation and is central to most spectroscopy, especially in the solid state. We show a strong breakdown of the Condon approximation in the time-resolved photoluminescence from CsPbBr3 metal halide perovskite semiconductor nanocrystals. Experiments reveal that the electronic transition dipole moment increases on the 30 ps time scale due to structural dynamics in the lattice. Ab initio molecular dynamics calculations quantitatively reproduce experiments by considering excitation-induced structural dynamics.
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Affiliation(s)
- Dallas Strandell
- Department of Chemistry, McGill University, Montreal, QC H3A 0G4, Canada
| | - Yifan Wu
- Department of Chemistry, University of Southern California, Los Angeles, California 90007, United States
| | - Carlos Mora-Perez
- Department of Chemistry, University of Southern California, Los Angeles, California 90007, United States
| | - Oleg Prezhdo
- Department of Chemistry, University of Southern California, Los Angeles, California 90007, United States
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Brosseau P, Ghosh A, Seiler H, Strandell D, Kambhampati P. Exciton-polaron interactions in metal halide perovskite nanocrystals revealed via two-dimensional electronic spectroscopy. J Chem Phys 2023; 159:184711. [PMID: 37962451 DOI: 10.1063/5.0173369] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2023] [Accepted: 10/19/2023] [Indexed: 11/15/2023] Open
Abstract
Metal halide perovskite nanocrystals have been under intense investigation for their promise in optoelectronic devices due to their remarkable physics, such as liquid/solid duality. This liquid/solid duality may give rise to their defect tolerance and other such useful properties. This duality means that the electronic states are fluctuating in time, on a distribution of timescales from femtoseconds to picoseconds. Hence, these lattice induced energy fluctuations that are connected to polaron formation are also connected to exciton formation and dynamics. We observe these correlations and dynamics in metal halide perovskite nanocrystals of CsPbI3 and CsPbBr3 using two-dimensional electronic (2DE) spectroscopy, with its unique ability to resolve dynamics in heterogeneously broadened systems. The 2DE spectra immediately reveal a previously unobserved excitonic splitting in these 15 nm NCs that may have a coarse excitonic structure. 2D lineshape dynamics reveal a glassy response on the 300 fs timescale due to polaron formation. The lighter Br system shows larger amplitude and faster timescale fluctuations that give rise to dynamic line broadening. The 2DE signals enable 1D transient absorption analysis of exciton cooling dynamics. Exciton cooling within this doublet is shown to take place on a slower timescale than within the excitonic continuum. The energy dissipation rates are the same for the I and Br systems for incoherent exciton cooling but are very different for the coherent dynamics that give rise to line broadening. Exciton cooling is shown to take place on the same timescale as polaron formation, revealing both as coupled many-body excitation.
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Affiliation(s)
- Patrick Brosseau
- Department of Chemistry, McGill University, Montreal, Quebec H3A 0B8, Canada
| | - Arnab Ghosh
- Department of Chemistry, McGill University, Montreal, Quebec H3A 0B8, Canada
| | - Helene Seiler
- Department of Chemistry, McGill University, Montreal, Quebec H3A 0B8, Canada
| | - Dallas Strandell
- Department of Chemistry, McGill University, Montreal, Quebec H3A 0B8, Canada
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Brosseau P, Seiler H, Palato S, Sonnichsen C, Baker H, Socie E, Strandell D, Kambhampati P. Perturbed free induction decay obscures early time dynamics in two-dimensional electronic spectroscopy: The case of semiconductor nanocrystals. J Chem Phys 2023; 158:084201. [PMID: 36859087 DOI: 10.1063/5.0138252] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/11/2023] Open
Abstract
Two-dimensional electronic spectroscopy (2DES) has recently been gaining popularity as an alternative to the more common transient absorption spectroscopy due to the combination of high frequency and time resolution of 2DES. In order to advance the reliable analysis of population dynamics and to optimize the time resolution of the method, one has to understand the numerous field matter interactions that take place at an early and negative time. These interactions have historically been discussed in one-dimensional spectroscopy as coherent artifacts and have been assigned to both resonant and non-resonant system responses during or before the pulse overlap. These coherent artifacts have also been described in 2DES but remain less well-understood due to the complexity of 2DES and the relative novelty of the method. Here, we present 2DES results in two model nanocrystal samples, CdSe and CsPbI3. We demonstrate non-resonant signals due to solvent response during the pulse overlap and resonant signals, which we assign to perturbed free induction decay (PFID), both before and during the pulse overlap. The simulations of the 2DES response functions at early and negative time delays reinforce the assignment of the negative time delay signals to PFID. Modeling reveals that the PFID signals will severely distort the initial picture of the resonant population dynamics. By including these effects in models of 2DES spectra, one is able to push forward the extraction of early time dynamics in 2DES.
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Affiliation(s)
- Patrick Brosseau
- Department of Chemistry, McGill University, Montreal, Quebec H3A 0G4, Canada
| | - Hélène Seiler
- Department of Chemistry, McGill University, Montreal, Quebec H3A 0G4, Canada
| | - Samuel Palato
- Department of Chemistry, McGill University, Montreal, Quebec H3A 0G4, Canada
| | - Colin Sonnichsen
- Department of Chemistry, McGill University, Montreal, Quebec H3A 0G4, Canada
| | - Harry Baker
- Department of Chemistry, McGill University, Montreal, Quebec H3A 0G4, Canada
| | - Etienne Socie
- Department of Chemistry, McGill University, Montreal, Quebec H3A 0G4, Canada
| | - Dallas Strandell
- Department of Chemistry, McGill University, Montreal, Quebec H3A 0G4, Canada
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Baker H, Perez CM, Sonnichsen C, Strandell D, Prezhdo OV, Kambhampati P. Breaking Phonon Bottlenecks through Efficient Auger Processes in Perovskite Nanocrystals. ACS Nano 2023; 17:3913-3920. [PMID: 36796027 DOI: 10.1021/acsnano.2c12220] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
The hot phonon bottleneck has been under intense investigation in perovskites. In the case of perovskite nanocrystals, there may be hot phonon bottlenecks as well as quantum phonon bottlenecks. While they are widely assumed to exist, evidence is growing for the breaking of potential phonon bottlenecks of both forms. Here, we perform state-resolved pump/probe spectroscopy (SRPP) and time-resolved photoluminescence spectroscopy (t-PL) to unravel hot exciton relaxation dynamics in model systems of bulk-like 15 nm nanocrystals of CsPbBr3 and FAPbBr3, with FA being formamidinium. The SRPP data can be misinterpreted to reveal a phonon bottleneck even at low exciton concentrations, where there should be none. We circumvent that spectroscopic problem with a state-resolved method that reveals an order of magnitude faster cooling and breaking of the quantum phonon bottleneck that might be expected in nanocrystals. Since the prior pump/probe methods of analysis are shown to be ambiguous, we perform t-PL experiments to unambiguously confirm the existence of hot phonon bottlenecks as well. The t-PL experiments reveal there is no hot phonon bottleneck in these perovskite nanocrystals. Ab initio molecular dynamics simulations reproduce experiments by inclusion of efficient Auger processes. This experimental and theoretical work reveals insight on hot exciton dynamics, how they are precisely measured, and ultimately how they may be exploited in these materials.
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Affiliation(s)
- Harry Baker
- Department of Chemistry, McGill University, Montreal, Quebec H3A 0B8, Canada
| | - Carlos Mora Perez
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States
| | - Colin Sonnichsen
- Department of Chemistry, McGill University, Montreal, Quebec H3A 0B8, Canada
| | - Dallas Strandell
- Department of Chemistry, McGill University, Montreal, Quebec H3A 0B8, Canada
| | - Oleg V Prezhdo
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States
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Yekani R, Chiu HC, Strandell D, Wang Z, Bessette S, Gauvin R, Kambhampati P, Demopoulos GP. Correlation between hysteresis dynamics and inductance in hybrid perovskite solar cells: studying the dependency on ETL/perovskite interfaces. Nanoscale 2023; 15:2152-2161. [PMID: 36648300 DOI: 10.1039/d2nr05836g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
In this study, to elucidate the origin of inductance and its relationship with the phenomenon of hysteresis in hybrid perovskite solar cells (PSCs), two electron transport layer (ETL) structures have been utilized: (a) rutile titania nanorods grown over anatase titania (AR) and (b) anatase titania covering the rutile titania nanorods (RA). The rutile and anatase phases are prepared via hydrothermal synthesis and spray pyrolysis, respectively. PSCs based on an ETL with an RA structure attain higher short-circuit current density (JSC) and open-circuit voltage (VOC) while showing a slightly lower fill factor (FF) compared with their AR counterparts. Using electrochemical impedance spectroscopy (EIS) measurements, we show that the ETL plays a major role in setting the tone for ionic migration speed and consequent accumulation. Moreover, we consider the conductivity of transport layers as a determining factor in not only giving rise to inductive features but also dictating the bias region under which recombination takes place, ultimately influencing hysteresis locus.
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Affiliation(s)
- Rana Yekani
- Materials Engineering Department, McGill University, 3610 University Street, H3A 0C5 Montreal, Canada.
| | - Hsien-Chieh Chiu
- Materials Engineering Department, McGill University, 3610 University Street, H3A 0C5 Montreal, Canada.
| | - Dallas Strandell
- Department of Chemistry, McGill University, 801 Sherbrooke Street, H3A 0B8 Montreal, Canada
| | - Zhuoran Wang
- ICFO - The Institute of Photonic Sciences, Avinguda Carl Friedrich Gauss, 3, 08860 Castelldefels, Spain
| | - Stéphanie Bessette
- Materials Engineering Department, McGill University, 3610 University Street, H3A 0C5 Montreal, Canada.
| | - Raynald Gauvin
- Materials Engineering Department, McGill University, 3610 University Street, H3A 0C5 Montreal, Canada.
| | - Patanjali Kambhampati
- Department of Chemistry, McGill University, 801 Sherbrooke Street, H3A 0B8 Montreal, Canada
| | - George P Demopoulos
- Materials Engineering Department, McGill University, 3610 University Street, H3A 0C5 Montreal, Canada.
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