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Geiregat P, Erdem O, Samoli M, Chen K, Hodgkiss JM, Hens Z. The Impact of Partial Carrier Confinement on Stimulated Emission in Strongly Confined Perovskite Nanocrystals. ACS NANO 2024; 18:17794-17805. [PMID: 38913946 DOI: 10.1021/acsnano.4c03441] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/26/2024]
Abstract
Semiconductor lead halide perovskites are excellent candidates for realizing low threshold light amplification due to their tunable and highly efficient luminescence, ease of processing, and strong light-matter interactions. However, most studies on optical gain have addressed bulk films, nanowires, or nanocrystals that exhibit little or no size quantization. Here, we show by means of a multitude of optical spectroscopy methods that small CsPbBr3 nanocrystals (NCs) exhibit a progressive red shift of the band-edge transition upon addition of electron-hole pairs, at least one carrier of which occupies a 2-fold degenerate, delocalized state in agreement with strong confinement. We demonstrate that this combination results in a threshold for biexciton gain, well below the limit of one electron-hole pair on average per NC. On the other hand, both the luminescent lifetime and the optical Stark effect of 4.7 nm CsPbBr3 NCs indicate that the oscillator strength of the band-edge transition is considerably smaller than expected from the band-edge absorption. We assign this discrepancy to a mixed confinement regime, with one delocalized and one localized charge carrier, and show that the concomitant reduction of the oscillator strength for stimulated emission accounts for the surprisingly small material gain observed in small NCs. The conclusion of mixed confinement aligns with studies reporting small and large polarons for holes and electrons in lead halide perovskite nanocrystals, respectively, and creates opportunities for understanding multiexciton photophysics in confined perovskite materials.
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Affiliation(s)
- Pieter Geiregat
- Physics and Chemistry of Nanostructures group, Department of Chemistry, Ghent University, Gent 9000, Belgium
- NOLIMITS, Core Facility for Non-Linear Microscopy and Spectroscopy, Ghent University, Gent, 9000, Belgium
| | - Onur Erdem
- Physics and Chemistry of Nanostructures group, Department of Chemistry, Ghent University, Gent 9000, Belgium
| | - Margarita Samoli
- Physics and Chemistry of Nanostructures group, Department of Chemistry, Ghent University, Gent 9000, Belgium
| | - Kai Chen
- The MacDiarmid Institute for Advanced Materials and Nanotechnology, Wellington 6140, New Zealand
- The Dodd-Walls Centre for Photonic and Quantum Technologies, University of Otago, Dunedin 9016, New Zealand
- Robinson Research Institute, Faculty of Engineering, Victoria University of Wellington, Wellington 6012, New Zealand
| | - Justin M Hodgkiss
- The MacDiarmid Institute for Advanced Materials and Nanotechnology, Wellington 6140, New Zealand
- School of Chemical and Physical Sciences, Victoria University of Wellington, Wellington 6140, New Zealand
| | - Zeger Hens
- Physics and Chemistry of Nanostructures group, Department of Chemistry, Ghent University, Gent 9000, Belgium
- NOLIMITS, Core Facility for Non-Linear Microscopy and Spectroscopy, Ghent University, Gent, 9000, Belgium
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2
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Dabard C, Po H, Fu N, Makke L, Lehouelleur H, Curti L, Xu XZ, Lhuillier E, Diroll BT, Ithurria S. Expanding the color palette of bicolor-emitting nanocrystals. NANOSCALE 2023; 15:14651-14658. [PMID: 37622447 DOI: 10.1039/d3nr03235c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/26/2023]
Abstract
Owing to their bright and tunable luminescence spectra, nanocrystals appear as a unique playground for light source design. Displays and lighting require white light sources that combine several narrow lines. As Kasha's rule prevents the emission of hot carriers, blends of multiple nanocrystal populations are currently the obvious strategy for broad-band source design. However, a few reports suggest that bicolor emission can also be obtained from a single particle even under weak excitation if a careful design of the exciton scattering mechanism sufficiently slows down its relaxation pathways. A key challenge remains to maintain quantum confinement for color tunability in the same structure, while simultaneously achieving a large size to leverage the critical, slower exciton diffusion or relaxation down to the ground state. Herein, we demonstrate that 2D nanoplatelets offer an original opportunity for the design of confined and large heterostructures. We demonstrate that bicolor emission is not limited to green-red pair and show that blue-yellow and purple-green emissions can be obtained from CdSe/CdTe/CdSe core/crown/crown and CdSe/CdS core/crown heterostructures, respectively.
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Affiliation(s)
- Corentin Dabard
- Laboratoire de Physique et d'Etude des Matériaux, ESPCI-Paris, PSL Research University, Sorbonne Université Univ Paris 06, CNRS UMR 8213, 10 rue Vauquelin, 75005 Paris, France.
| | - Hong Po
- Laboratoire de Physique et d'Etude des Matériaux, ESPCI-Paris, PSL Research University, Sorbonne Université Univ Paris 06, CNRS UMR 8213, 10 rue Vauquelin, 75005 Paris, France.
| | - Ningyuan Fu
- Laboratoire de Physique et d'Etude des Matériaux, ESPCI-Paris, PSL Research University, Sorbonne Université Univ Paris 06, CNRS UMR 8213, 10 rue Vauquelin, 75005 Paris, France.
| | - Lina Makke
- Laboratoire de Physique et d'Etude des Matériaux, ESPCI-Paris, PSL Research University, Sorbonne Université Univ Paris 06, CNRS UMR 8213, 10 rue Vauquelin, 75005 Paris, France.
| | - Henri Lehouelleur
- Laboratoire de Physique et d'Etude des Matériaux, ESPCI-Paris, PSL Research University, Sorbonne Université Univ Paris 06, CNRS UMR 8213, 10 rue Vauquelin, 75005 Paris, France.
| | - Leonardo Curti
- Laboratoire de Physique et d'Etude des Matériaux, ESPCI-Paris, PSL Research University, Sorbonne Université Univ Paris 06, CNRS UMR 8213, 10 rue Vauquelin, 75005 Paris, France.
| | - Xiang Zhen Xu
- Laboratoire de Physique et d'Etude des Matériaux, ESPCI-Paris, PSL Research University, Sorbonne Université Univ Paris 06, CNRS UMR 8213, 10 rue Vauquelin, 75005 Paris, France.
| | - Emmanuel Lhuillier
- Sorbonne Université, CNRS, Institut des NanoSciences de Paris, INSP, F-75005 Paris, France
| | - Benjamin T Diroll
- Center for Nanoscale Materials, Argonne National Laboratory, 9700 S. Cass Avenue, Lemont, Illinois 60439, USA
| | - Sandrine Ithurria
- Laboratoire de Physique et d'Etude des Matériaux, ESPCI-Paris, PSL Research University, Sorbonne Université Univ Paris 06, CNRS UMR 8213, 10 rue Vauquelin, 75005 Paris, France.
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Diroll BT. Optical stark effect on CdSe nanoplatelets with mid-infrared excitation for large amplitude ultrafast modulation. NANOTECHNOLOGY 2023; 34:245706. [PMID: 36917849 DOI: 10.1088/1361-6528/acc40c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/28/2022] [Accepted: 03/14/2023] [Indexed: 06/18/2023]
Abstract
The optical Stark effect is a universal response of the electronic structure to incident light. In semiconductors, particularly nanomaterials, the optical Stark effect achieved with sub-band gap photons can drive large, narrowband, and potentially ultrafast changes in the absorption or reflection at the band gap through excitation of virtual excitons. Rapid optical modulation using the optical Stark effect is ultimately constrained, however, by the generation of long-lived excitons through multiphoton absorption. This work compares the modulation achievable using the optical Stark effect on CdSe nanoplatelets with several different pump photon energies, from the visible to mid-infrared. Despite expected lower efficiencies for spectrally-remote pump energies, infrared pump pulses can ultimately drive larger sub-picosecond optical Stark shifts of virtual excitons without creation of real excitons. The CdSe nanoplatelets show subpicosecond shifts of the lowest excitonic resonance of up to 22 meV, resulting in change in absorption as large as 0.32 OD (49% increase in transmission), with a long-lived offset from real excitons less than 1% of the peak signal.
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Affiliation(s)
- Benjamin T Diroll
- Center for Nanoscale Materials, Argonne National Laboratory, 9700 S. Cass Avenue, Lemont, IL 60439, United States of America
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Diroll BT, Guzelturk B, Po H, Dabard C, Fu N, Makke L, Lhuillier E, Ithurria S. 2D II-VI Semiconductor Nanoplatelets: From Material Synthesis to Optoelectronic Integration. Chem Rev 2023; 123:3543-3624. [PMID: 36724544 DOI: 10.1021/acs.chemrev.2c00436] [Citation(s) in RCA: 27] [Impact Index Per Article: 27.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The field of colloidal synthesis of semiconductors emerged 40 years ago and has reached a certain level of maturity thanks to the use of nanocrystals as phosphors in commercial displays. In particular, II-VI semiconductors based on cadmium, zinc, or mercury chalcogenides can now be synthesized with tailored shapes, composition by alloying, and even as nanocrystal heterostructures. Fifteen years ago, II-VI semiconductor nanoplatelets injected new ideas into this field. Indeed, despite the emergence of other promising semiconductors such as halide perovskites or 2D transition metal dichalcogenides, colloidal II-VI semiconductor nanoplatelets remain among the narrowest room-temperature emitters that can be synthesized over a wide spectral range, and they exhibit good material stability over time. Such nanoplatelets are scientifically and technologically interesting because they exhibit optical features and production advantages at the intersection of those expected from colloidal quantum dots and epitaxial quantum wells. In organic solvents, gram-scale syntheses can produce nanoparticles with the same thicknesses and optical properties without inhomogeneous broadening. In such nanoplatelets, quantum confinement is limited to one dimension, defined at the atomic scale, which allows them to be treated as quantum wells. In this review, we discuss the synthetic developments, spectroscopic properties, and applications of such nanoplatelets. Covering growth mechanisms, we explain how a thorough understanding of nanoplatelet growth has enabled the development of nanoplatelets and heterostructured nanoplatelets with multiple emission colors, spatially localized excitations, narrow emission, and high quantum yields over a wide spectral range. Moreover, nanoplatelets, with their large lateral extension and their thin short axis and low dielectric surroundings, can support one or several electron-hole pairs with large exciton binding energies. Thus, we also discuss how the relaxation processes and lifetime of the carriers and excitons are modified in nanoplatelets compared to both spherical quantum dots and epitaxial quantum wells. Finally, we explore how nanoplatelets, with their strong and narrow emission, can be considered as ideal candidates for pure-color light emitting diodes (LEDs), strong gain media for lasers, or for use in luminescent light concentrators.
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Affiliation(s)
- Benjamin T Diroll
- Center for Nanoscale Materials, Argonne National Laboratory, 9700 S. Cass Avenue, Lemont, Illinois 60439, United States
| | - Burak Guzelturk
- X-ray Science Division, Advanced Photon Source, Argonne National Laboratory, 9700 S. Cass Avenue, Lemont, Illinois 60439, United States
| | - Hong Po
- Laboratoire de Physique et d'Etude des Matériaux, ESPCI-Paris, PSL Research University, Sorbonne Université Univ Paris 06, CNRS UMR 8213, 10 rue Vauquelin 75005 Paris, France
| | - Corentin Dabard
- Laboratoire de Physique et d'Etude des Matériaux, ESPCI-Paris, PSL Research University, Sorbonne Université Univ Paris 06, CNRS UMR 8213, 10 rue Vauquelin 75005 Paris, France
| | - Ningyuan Fu
- Laboratoire de Physique et d'Etude des Matériaux, ESPCI-Paris, PSL Research University, Sorbonne Université Univ Paris 06, CNRS UMR 8213, 10 rue Vauquelin 75005 Paris, France
| | - Lina Makke
- Laboratoire de Physique et d'Etude des Matériaux, ESPCI-Paris, PSL Research University, Sorbonne Université Univ Paris 06, CNRS UMR 8213, 10 rue Vauquelin 75005 Paris, France
| | - Emmanuel Lhuillier
- Sorbonne Université, CNRS, Institut des NanoSciences de Paris, INSP, 75005 Paris, France
| | - Sandrine Ithurria
- Laboratoire de Physique et d'Etude des Matériaux, ESPCI-Paris, PSL Research University, Sorbonne Université Univ Paris 06, CNRS UMR 8213, 10 rue Vauquelin 75005 Paris, France
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Rodà C, Geiregat P, Di Giacomo A, Moreels I, Hens Z. Area-Independence of the Biexciton Oscillator Strength in CdSe Colloidal Nanoplatelets. NANO LETTERS 2022; 22:9537-9543. [PMID: 36409988 DOI: 10.1021/acs.nanolett.2c03683] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Colloidal CdSe nanoplatelets (NPLs) are unique systems to study two-dimensional excitons and excitonic complexes. However, while absorption and emission of photons through exciton formation and recombination have been extensively quantified, few studies have addressed the exciton-biexciton transition. Here, we use cross-polarized pump-probe spectroscopy to measure the absorption coefficient spectrum of this transition and determine the biexciton oscillator strength (fBX). We show that fBX is independent of the NPL area and that the concomitant biexciton area (SBX) agrees with predictions of a short-range interaction model. Moreover, we show that fBX is comparable to the oscillator strength of forming localized excitons at room temperature while being unaffected itself by center-of-mass localization. These results confirm the relevance of biexcitons for light-matter interaction in NPLs. Moreover, the quantification of the exciton-biexciton transition introduced here will enable researchers to rank 2D materials by the strength of this transition and to compare experimental results with theoretical predictions.
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Affiliation(s)
- Carmelita Rodà
- Physics and Chemistry of Nanostructures, Department of Chemistry, Ghent University, 9000Gent, Belgium
- NB-Photonics, Center for Nano- and Biophotonics, Ghent University, 9000Gent, Belgium
| | - Pieter Geiregat
- Physics and Chemistry of Nanostructures, Department of Chemistry, Ghent University, 9000Gent, Belgium
- NB-Photonics, Center for Nano- and Biophotonics, Ghent University, 9000Gent, Belgium
| | - Alessio Di Giacomo
- Physics and Chemistry of Nanostructures, Department of Chemistry, Ghent University, 9000Gent, Belgium
- NB-Photonics, Center for Nano- and Biophotonics, Ghent University, 9000Gent, Belgium
| | - Iwan Moreels
- Physics and Chemistry of Nanostructures, Department of Chemistry, Ghent University, 9000Gent, Belgium
- NB-Photonics, Center for Nano- and Biophotonics, Ghent University, 9000Gent, Belgium
| | - Zeger Hens
- Physics and Chemistry of Nanostructures, Department of Chemistry, Ghent University, 9000Gent, Belgium
- NB-Photonics, Center for Nano- and Biophotonics, Ghent University, 9000Gent, Belgium
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Shrivastava M, Krieg F, Mandal D, Poonia AK, Bera SK, Kovalenko MV, Adarsh KV. Room-Temperature Anomalous Coherent Excitonic Optical Stark Effect in Metal Halide Perovskite Quantum Dots. NANO LETTERS 2022; 22:808-814. [PMID: 34990139 DOI: 10.1021/acs.nanolett.1c04471] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Nonresonant optical driving of confined semiconductors can open up exciting opportunities for experimentally realizing strongly interacting photon-dressed (Floquet) states through the optical Stark effect (OSE) for coherent modulation of the exciton state. Here we report the first room-temperature observation of the Floquet biexciton-mediated anomalous coherent excitonic OSE in CsPbBr3 quantum dots (QDs). Remarkably, the strong exciton-biexciton interaction leads to a coherent red shift and splitting of the exciton resonance as a function of the drive photon frequency, similar to Autler-Townes splitting in atomic and molecular systems. The large biexciton binding energy of ∼71 meV and exciton-biexciton transition dipole moment of ∼25 D facilitate the hallmark observations, even at large detuning energies of >300 meV. This is accompanied by an unusual crossover from linear to nonlinear fluence dependence of the OSE as a function of the drive photon frequency. Our findings reveal crucial information on the unexplored many-body coherent interacting regime, making perovskite QDs suitable for room temperature quantum devices.
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Affiliation(s)
- Megha Shrivastava
- Department of Physics, Indian Institute of Science Education and Research, Bhopal 462066, India
| | - Franziska Krieg
- Laboratory of Inorganic Chemistry, Department of Chemistry and Applied Biosciences, ETH Zürich, CH-8093 Zürich, Switzerland
- Empa - Swiss Federal Laboratories for Materials Science and Technology, CH-8600 Dübendorf, Switzerland
| | - Dipendranath Mandal
- Department of Physics, Indian Institute of Science Education and Research, Bhopal 462066, India
| | - Ajay K Poonia
- Department of Physics, Indian Institute of Science Education and Research, Bhopal 462066, India
| | - Santu K Bera
- Department of Physics, Indian Institute of Science Education and Research, Bhopal 462066, India
| | - Maksym V Kovalenko
- Laboratory of Inorganic Chemistry, Department of Chemistry and Applied Biosciences, ETH Zürich, CH-8093 Zürich, Switzerland
- Empa - Swiss Federal Laboratories for Materials Science and Technology, CH-8600 Dübendorf, Switzerland
| | - K V Adarsh
- Department of Physics, Indian Institute of Science Education and Research, Bhopal 462066, India
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7
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Geiregat P, Rodá C, Tanghe I, Singh S, Di Giacomo A, Lebrun D, Grimaldi G, Maes J, Van Thourhout D, Moreels I, Houtepen AJ, Hens Z. Localization-limited exciton oscillator strength in colloidal CdSe nanoplatelets revealed by the optically induced stark effect. LIGHT, SCIENCE & APPLICATIONS 2021; 10:112. [PMID: 34054127 PMCID: PMC8165098 DOI: 10.1038/s41377-021-00548-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/19/2021] [Revised: 04/21/2021] [Accepted: 04/28/2021] [Indexed: 05/04/2023]
Abstract
2D materials are considered for applications that require strong light-matter interaction because of the apparently giant oscillator strength of the exciton transitions in the absorbance spectrum. Nevertheless, the effective oscillator strengths of these transitions have been scarcely reported, nor is there a consistent interpretation of the obtained values. Here, we analyse the transition dipole moment and the ensuing oscillator strength of the exciton transition in 2D CdSe nanoplatelets by means of the optically induced Stark effect (OSE). Intriguingly, we find that the exciton absorption line reacts to a high intensity optical field as a transition with an oscillator strength FStark that is 50 times smaller than expected based on the linear absorption coefficient. We propose that the pronounced exciton absorption line should be seen as the sum of multiple, low oscillator strength transitions, rather than a single high oscillator strength one, a feat we assign to strong exciton center-of-mass localization. Within the quantum mechanical description of excitons, this 50-fold difference between both oscillator strengths corresponds to the ratio between the coherence area of the exciton's center of mass and the total area, which yields a coherence area of a mere 6.1 nm2. Since we find that the coherence area increases with reducing temperature, we conclude that thermal effects, related to lattice vibrations, contribute to exciton localization. In further support of this localization model, we show that FStark is independent of the nanoplatelet area, correctly predicts the radiative lifetime, and lines up for strongly confined quantum dot systems.
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Affiliation(s)
- Pieter Geiregat
- Physics and Chemistry of Nanostructures, Department of Chemistry, Ghent University, Gent, Belgium.
- Center for Nano and Biophotonics, Ghent University, Gent, Belgium.
| | - Carmelita Rodá
- Physics and Chemistry of Nanostructures, Department of Chemistry, Ghent University, Gent, Belgium
- Center for Nano and Biophotonics, Ghent University, Gent, Belgium
| | - Ivo Tanghe
- Physics and Chemistry of Nanostructures, Department of Chemistry, Ghent University, Gent, Belgium
- Center for Nano and Biophotonics, Ghent University, Gent, Belgium
- Photonics Research Group, Ghent University, Gent, Belgium
| | - Shalini Singh
- Department of Chemical Sciences and Bernal Institute, University of Limerick, Limerick, Ireland
| | - Alessio Di Giacomo
- Physics and Chemistry of Nanostructures, Department of Chemistry, Ghent University, Gent, Belgium
| | - Delphine Lebrun
- Physics and Chemistry of Nanostructures, Department of Chemistry, Ghent University, Gent, Belgium
| | - Gianluca Grimaldi
- Center for Nanophotonics, NWO-Institute AMOLF, Science Park 104, 1098 XG, Amsterdam, The Netherlands
| | - Jorick Maes
- Physics and Chemistry of Nanostructures, Department of Chemistry, Ghent University, Gent, Belgium
- Center for Nano and Biophotonics, Ghent University, Gent, Belgium
| | - Dries Van Thourhout
- Center for Nano and Biophotonics, Ghent University, Gent, Belgium
- Photonics Research Group, Ghent University, Gent, Belgium
| | - Iwan Moreels
- Physics and Chemistry of Nanostructures, Department of Chemistry, Ghent University, Gent, Belgium
- Center for Nano and Biophotonics, Ghent University, Gent, Belgium
| | - Arjan J Houtepen
- Opto-Electronic Materials Section, Department of Chemical Engineering, Delft University, Delft, The Netherlands
| | - Zeger Hens
- Physics and Chemistry of Nanostructures, Department of Chemistry, Ghent University, Gent, Belgium
- Center for Nano and Biophotonics, Ghent University, Gent, Belgium
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