1
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Enomoto K, Miranti R, Liu J, Okano R, Inoue D, Kim D, Pu YJ. Anisotropic electronic coupling in three-dimensional assembly of CsPbBr 3 quantum dots. Chem Sci 2024; 15:13049-13057. [PMID: 39148765 PMCID: PMC11323341 DOI: 10.1039/d4sc01769b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2024] [Accepted: 07/13/2024] [Indexed: 08/17/2024] Open
Abstract
Cesium lead halide (CsPbX3, X = Cl, Br, or I) perovskite quantum dots (PeQDs) show promise for next-generation optoelectronics. In this study, we controlled the electronic coupling between PeQD multilayers using a layer-by-layer method and dithiol linkers of varying structures. The energy shift of the first excitonic peak from monolayer to bilayer decreases exponentially with increasing interlayer spacer distance, indicating the resonant tunnelling effect. X-ray diffraction measurements revealed anisotropic inter-PeQD distances in multiple layers. Photoluminescence (PL) analysis showed lower energy emission in the in-plane direction due to the electronic coupling in the out-of-plane direction, supporting the anisotropic electronic state in the PeQD multilayers. Temperature-dependent PL and PL lifetimes indicated changes in exciton behaviour due to the delocalized electronic state in PeQD multilayers. Particularly, the electron-phonon coupling strength increased, and the exciton recombination rate decreased. This is the first study demonstrating controlled electronic coupling in a three-dimensional ordered structure, emphasizing the importance of the anisotropic electronic state for high-performance PeQDs devices.
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Affiliation(s)
- Kazushi Enomoto
- RIKEN Center for Emergent Matter Science (CEMS) Wako Saitama 351-0198 Japan
| | - Retno Miranti
- RIKEN Center for Emergent Matter Science (CEMS) Wako Saitama 351-0198 Japan
| | - Jianjun Liu
- RIKEN Center for Emergent Matter Science (CEMS) Wako Saitama 351-0198 Japan
| | - Rinkei Okano
- RIKEN Center for Emergent Matter Science (CEMS) Wako Saitama 351-0198 Japan
| | - Daishi Inoue
- RIKEN Center for Emergent Matter Science (CEMS) Wako Saitama 351-0198 Japan
| | - DaeGwi Kim
- Department of Physics and Electronics, Osaka Metropolitan University Osaka 558-8585 Japan
| | - Yong-Jin Pu
- RIKEN Center for Emergent Matter Science (CEMS) Wako Saitama 351-0198 Japan
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2
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Yuan R, Roberts TD, Brinn RM, Choi AA, Park HH, Yan C, Ondry JC, Khorasani S, Masiello DJ, Xu K, Alivisatos AP, Ginsberg NS. A composite electrodynamic mechanism to reconcile spatiotemporally resolved exciton transport in quantum dot superlattices. SCIENCE ADVANCES 2023; 9:eadh2410. [PMID: 37862422 PMCID: PMC10588942 DOI: 10.1126/sciadv.adh2410] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/21/2023] [Accepted: 09/20/2023] [Indexed: 10/22/2023]
Abstract
Quantum dot (QD) solids are promising optoelectronic materials; further advancing their device functionality requires understanding their energy transport mechanisms. The commonly invoked near-field Förster resonance energy transfer (FRET) theory often underestimates the exciton hopping rate in QD solids, yet no consensus exists on the underlying cause. In response, we use time-resolved ultrafast stimulated emission depletion (STED) microscopy, an ultrafast transformation of STED to spatiotemporally resolve exciton diffusion in tellurium-doped cadmium selenide-core/cadmium sulfide-shell QD superlattices. We measure the concomitant time-resolved exciton energy decay due to excitons sampling a heterogeneous energetic landscape within the superlattice. The heterogeneity is quantified by single-particle emission spectroscopy. This powerful multimodal set of observables provides sufficient constraints on a kinetic Monte Carlo simulation of exciton transport to elucidate a composite transport mechanism that includes both near-field FRET and previously neglected far-field emission/reabsorption contributions. Uncovering this mechanism offers a much-needed unified framework in which to characterize transport in QD solids and additional principles for device design.
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Affiliation(s)
- Rongfeng Yuan
- Department of Chemistry, University of California Berkeley, Berkeley, CA 94720, USA
| | - Trevor D. Roberts
- Department of Chemistry, University of California Berkeley, Berkeley, CA 94720, USA
| | - Rafaela M. Brinn
- Department of Chemistry, University of California Berkeley, Berkeley, CA 94720, USA
| | - Alexander A. Choi
- Department of Chemistry, University of California Berkeley, Berkeley, CA 94720, USA
| | - Ha H. Park
- Department of Chemistry, University of California Berkeley, Berkeley, CA 94720, USA
| | - Chang Yan
- Department of Chemistry, University of California Berkeley, Berkeley, CA 94720, USA
| | - Justin C. Ondry
- Department of Chemistry, University of California Berkeley, Berkeley, CA 94720, USA
| | - Siamak Khorasani
- Department of Materials Science and Engineering, University of Washington, Seattle, WA 98195, USA
| | - David J. Masiello
- Department of Materials Science and Engineering, University of Washington, Seattle, WA 98195, USA
- Department of Chemistry, University of Washington, Seattle, WA 98195, USA
| | - Ke Xu
- Department of Chemistry, University of California Berkeley, Berkeley, CA 94720, USA
- STROBE, National Science Foundation Science and Technology Center, University of California Berkeley, Berkeley, CA 94720, USA
| | - A. Paul Alivisatos
- Department of Chemistry, University of California Berkeley, Berkeley, CA 94720, USA
| | - Naomi S. Ginsberg
- Department of Chemistry, University of California Berkeley, Berkeley, CA 94720, USA
- STROBE, National Science Foundation Science and Technology Center, University of California Berkeley, Berkeley, CA 94720, USA
- Department of Physics, University of California Berkeley, Berkeley, CA 94720, USA
- Materials Science Division and Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
- Kavli Energy NanoSciences Institute at Berkeley, Berkeley, CA 94720, USA
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3
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Zhao G, Ma W, Yu S, Zhang J, Wu K. Orbital Mixing between Colloidal Quantum Dots and Surface-Bound Molecules. J Phys Chem Lett 2022; 13:11892-11898. [PMID: 36524775 DOI: 10.1021/acs.jpclett.2c03538] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
Orbital mixing is paramount to chemistry as it plays a central role in bond formation. It is also important for technologies such as molecular doping of polymers, where the concept of fractional charge transfer is essentially orbital mixing between dopants and hosts. Likewise, it would be both fundamentally interesting and technologically relevant to investigate orbital mixing in emerging hybrid materials containing both inorganic and organic moieties. Here we report experimental observation of orbital mixing between valence band levels of strongly confined PbS quantum dots (QDs) and lowest unoccupied molecular levels of surface-bound high-electron affinity molecules (F4TCNQ), manifested as both an absorption blue-shift of PbS and the emergence of visible and infrared signatures of the fractional charge-transfer species of F4TCNQ. The degree of mixing can be controlled by varying the QD size or by varying the molecule/QD ratio for a specific QD size and can be quantitatively reproduced by a nondegenerate, two-level perturbation model.
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Affiliation(s)
- Guohui Zhao
- State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, Liaoning116023, China
- University of Chinese Academy of Sciences, Beijing100049, China
| | - Wenkai Ma
- School of Optical and Electronic Information, Huazhong University of Science and Technology, 1037 Luoyu Road, Wuhan, Hubei430074, China
| | - Shuwen Yu
- Dalian National Laboratory for Clean Energy, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, Liaoning116023, China
| | - Jianbing Zhang
- School of Optical and Electronic Information, Huazhong University of Science and Technology, 1037 Luoyu Road, Wuhan, Hubei430074, China
| | - Kaifeng Wu
- State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, Liaoning116023, China
- University of Chinese Academy of Sciences, Beijing100049, China
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4
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Meyer HM, Morrison CE, Loomis RA, Buhro WE. Bound-Ion Pair X-Type Ligation of Cadmium and Zinc Dithiocarbamates on Cadmium Selenide Quantum Belts. Inorg Chem 2022; 61:5861-5868. [PMID: 35380819 DOI: 10.1021/acs.inorgchem.2c00226] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Wurtzite CdSe quantum belts with L-type n-octylamine, L-type ammonia, or Z-type Cd(oleate)2 ligands are exchanged for several metal-dithiocarbamate ligands [M(S2CNR1R2)2]: Cd(S2CNPhMe)2, Cd(S2CNEt2)2, Zn(S2CNPhMe)2, and Zn(S2CNEt2)2. Successful ligand exchange with all M(S2CNR1R2)2 compounds occurs from {CdSe[Cd(oleate)2]0.19} quantum belts (QBs), which induce similar spectral shifts in the absorption spectra of the ligand-exchanged QBs. Spectroscopic data, experimentally determined lattice strains, and ligand exchanges with [Na][Et2NCS2] and [NH4][MePhNCS2] establish that the [M(S2CNR1R2)2] ligands bind as bound-ion-paired X-type ligands with (S2CNR1R2)- groups ligated directly to the QB surfaces and [M(S2CNR1R2)]+ groups serving as the charge-balancing ion-paired countercations. The X-type dithiocarbamate ligands do not impart any special electronic effects to the CdSe QBs.
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Affiliation(s)
- Hailey M Meyer
- Department of Chemistry and Institute of Materials Science and Engineering, Washington University, St. Louis, Missouri 63130-4899, United States
| | - Calynn E Morrison
- Department of Chemistry and Institute of Materials Science and Engineering, Washington University, St. Louis, Missouri 63130-4899, United States
| | - Richard A Loomis
- Department of Chemistry and Institute of Materials Science and Engineering, Washington University, St. Louis, Missouri 63130-4899, United States
| | - William E Buhro
- Department of Chemistry and Institute of Materials Science and Engineering, Washington University, St. Louis, Missouri 63130-4899, United States
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5
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Sarker JC, Hogarth G. Dithiocarbamate Complexes as Single Source Precursors to Nanoscale Binary, Ternary and Quaternary Metal Sulfides. Chem Rev 2021; 121:6057-6123. [PMID: 33847480 DOI: 10.1021/acs.chemrev.0c01183] [Citation(s) in RCA: 43] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Nanodimensional metal sulfides are a developing class of low-cost materials with potential applications in areas as wide-ranging as energy storage, electrocatalysis, and imaging. An attractive synthetic strategy, which allows careful control over stoichiometry, is the single source precursor (SSP) approach in which well-defined molecular species containing preformed metal-sulfur bonds are heated to decomposition, either in the vapor or solution phase, resulting in facile loss of organics and formation of nanodimensional metal sulfides. By careful control of the precursor, the decomposition environment and addition of surfactants, this approach affords a range of nanocrystalline materials from a library of precursors. Dithiocarbamates (DTCs) are monoanionic chelating ligands that have been known for over a century and find applications in agriculture, medicine, and materials science. They are easily prepared from nontoxic secondary and primary amines and form stable complexes with all elements. Since pioneering work in the late 1980s, the use of DTC complexes as SSPs to a wide range of binary, ternary, and multinary sulfides has been extensively documented. This review maps these developments, from the formation of thin films, often comprised of embedded nanocrystals, to quantum dots coated with organic ligands or shelled by other metal sulfides that show high photoluminescence quantum yields, and a range of other nanomaterials in which both the phase and morphology of the nanocrystals can be engineered, allowing fine-tuning of technologically important physical properties, thus opening up a myriad of potential applications.
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Affiliation(s)
- Jagodish C Sarker
- Department of Chemistry, King's College London, Britannia House, 7 Trinity Street, London SE1 1DB, U.K.,Department of Chemistry, Jagannath University, Dhaka-1100, Bangladesh
| | - Graeme Hogarth
- Department of Chemistry, King's College London, Britannia House, 7 Trinity Street, London SE1 1DB, U.K
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6
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Irgen-Gioro S, Yang M, Padgaonkar S, Chang WJ, Zhang Z, Nagasing B, Jiang Y, Weiss EA. Charge and energy transfer in the context of colloidal nanocrystals. ACTA ACUST UNITED AC 2020. [DOI: 10.1063/5.0033263] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Affiliation(s)
- Shawn Irgen-Gioro
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, USA
| | - Muwen Yang
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, USA
| | - Suyog Padgaonkar
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, USA
| | - Woo Je Chang
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, USA
| | - Zhengyi Zhang
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, USA
| | - Benjamin Nagasing
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, USA
| | - Yishu Jiang
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, USA
| | - Emily A. Weiss
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, USA
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7
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Lee T, Enomoto K, Ohshiro K, Inoue D, Kikitsu T, Hyeon-Deuk K, Pu YJ, Kim D. Controlling the dimension of the quantum resonance in CdTe quantum dot superlattices fabricated via layer-by-layer assembly. Nat Commun 2020; 11:5471. [PMID: 33122641 PMCID: PMC7596095 DOI: 10.1038/s41467-020-19337-0] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2020] [Accepted: 10/07/2020] [Indexed: 12/21/2022] Open
Abstract
In quantum dot superlattices, wherein quantum dots are periodically arranged, electronic states between adjacent quantum dots are coupled by quantum resonance, which arises from the short-range electronic coupling of wave functions, and thus the formation of minibands is expected. Quantum dot superlattices have the potential to be key materials for new optoelectronic devices, such as highly efficient solar cells and photodetectors. Herein, we report the fabrication of CdTe quantum dot superlattices via the layer-by-layer assembly of positively charged polyelectrolytes and negatively charged CdTe quantum dots. We can thus control the dimension of the quantum resonance by independently changing the distances between quantum dots in the stacking (out-of-plane) and in-plane directions. Furthermore, we experimentally verify the miniband formation by measuring the excitation energy dependence of the photoluminescence spectra and detection energy dependence of the photoluminescence excitation spectra. Designing quantum dot superlattices remains a challenge. Here, the authors present CdTe quantum dot superlattices via the layer-by-layer assembly and verify the miniband formation by measuring the excitation energy the dependence of the photoluminescence spectra and the detection energy dependence of the excitation spectra.
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Affiliation(s)
- TaeGi Lee
- Department of Applied Physics, Osaka City University, Osaka, 558-8585, Japan
| | - Kazushi Enomoto
- RIKEN Center for Emergent Matter Science (CEMS), Saitama, 351-0198, Japan
| | - Kazuma Ohshiro
- Department of Applied Physics, Osaka City University, Osaka, 558-8585, Japan
| | - Daishi Inoue
- RIKEN Center for Emergent Matter Science (CEMS), Saitama, 351-0198, Japan
| | - Tomoka Kikitsu
- RIKEN Center for Emergent Matter Science (CEMS), Saitama, 351-0198, Japan
| | - Kim Hyeon-Deuk
- Department of Chemistry, Kyoto University, Kyoto, 606-8502, Japan
| | - Yong-Jin Pu
- RIKEN Center for Emergent Matter Science (CEMS), Saitama, 351-0198, Japan.
| | - DaeGwi Kim
- Department of Applied Physics, Osaka City University, Osaka, 558-8585, Japan.
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8
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Coden M, De Checchi P, Fresch B. Spectral shift, electronic coupling and exciton delocalization in nanocrystal dimers: insights from all-atom electronic structure computations. NANOSCALE 2020; 12:18124-18136. [PMID: 32852028 DOI: 10.1039/d0nr05601d] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Delocalization of excitons promoted by electronic coupling between clusters or quantum dots (QD) changes the dynamical processes in nanostructured aggregates enhancing energy transport. A spectroscopic shift of the absorption spectrum upon QD aggregation is commonly observed and ascribed to quantum mechanical coupling between neighbouring dots but also to exciton delocalization over the sulphur-based ligand shell or to other mechanisms as a change in the dielectric constant of the surrounding medium. We address the question of electronic coupling and exciton delocalization in nanocrystal aggregates by performing all-atom electronic structure calculations in models of colloidal QD dimers. The relation between spectral shift, interdot coupling and exciton delocalization is investigated in atomistic detail in models of dimers formed by CdSe clusters kept together by bridging organic ligands. Our results support the possibility of obtaining exciton delocalization over the dimer and point out the crucial role of the bridging ligand in enhancing interdot electronic coupling.
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Affiliation(s)
- Maurizio Coden
- Department of Chemical Sciences, Università degli Studi di Padova, Via Marzolo 1, 35131 Padova, Italy.
| | - Pietro De Checchi
- Department of Chemical Sciences, Università degli Studi di Padova, Via Marzolo 1, 35131 Padova, Italy.
| | - Barbara Fresch
- Department of Chemical Sciences, Università degli Studi di Padova, Via Marzolo 1, 35131 Padova, Italy.
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9
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Shcherbakov-Wu W, Tisdale WA. A time-domain view of charge carriers in semiconductor nanocrystal solids. Chem Sci 2020; 11:5157-5167. [PMID: 34122972 PMCID: PMC8159276 DOI: 10.1039/c9sc05925c] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2019] [Accepted: 04/29/2020] [Indexed: 01/12/2023] Open
Abstract
The movement of charge carriers within semiconductor nanocrystal solids is fundamental to the operation of nanocrystal devices, including solar cells, LEDs, lasers, photodetectors, and thermoelectric modules. In this perspective, we explain how recent advances in the measurement and simulation of charge carrier dynamics in nanocrystal solids have led to a more complete picture of mesoscale interactions. Specifically, we show how time-resolved optical spectroscopy and transient photocurrent techniques can be used to track both equilibrium and non-equilibrium dynamics in nanocrystal solids. We discuss the central role of energetic disorder, the impact of trap states, and how these critical parameters are influenced by chemical modification of the nanocrystal surface. Finally, we close with a forward-looking assessment of emerging nanocrystal systems, including anisotropic nanocrystals, such as nanoplatelets, and colloidal lead halide perovskites.
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Affiliation(s)
- Wenbi Shcherbakov-Wu
- Department of Chemistry, Massachusetts Institute of Technology Cambridge MA 02139 USA
| | - William A Tisdale
- Department of Chemical Engineering, Massachusetts Institute of Technology Cambridge MA 02139 USA
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10
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Padgaonkar S, Olding JN, Lauhon LJ, Hersam MC, Weiss EA. Emergent Optoelectronic Properties of Mixed-Dimensional Heterojunctions. Acc Chem Res 2020; 53:763-772. [PMID: 31961121 DOI: 10.1021/acs.accounts.9b00581] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
ConspectusThe electronic dimensionality of a material is defined by the number of spatial degrees of confinement of its electronic wave function. Low-dimensional semiconductor nanomaterials with at least one degree of spatial confinement have optoelectronic properties that are tunable with size and environment (dielectric and chemical) and are of particular interest for optoelectronic applications such as light detection, light harvesting, and photocatalysis. By combining nanomaterials of differing dimensionalities, mixed-dimensional heterojunctions (MDHJs) exploit the desirable characteristics of their components. For example, the strong optical absorption of zero-dimensional (0D) materials combined with the high charge carrier mobilities of two-dimensional (2D) materials widens the spectral response and enhances the responsivity of mixed-dimensional photodetectors, which has implications for ultrathin, flexible optoelectronic devices. MDHJs are highly sensitive to (i) interfacial chemistry because of large surface area-to-volume ratios and (ii) electric fields, which are incompletely screened because of the ultrathin nature of MDHJs. This sensitivity presents opportunities for control of physical phenomena in MDHJs through chemical modification, optical excitation, externally applied electric fields, and other environmental parameters. Since this fast-moving research area is beginning to pose and answer fundamental questions that underlie the fundamental optoelectronic behavior of MDHJs, it is an opportune time to assess progress and suggest future directions in this field.In this Account, we first outline the characteristic properties, advantages, and challenges for low-dimensional materials, many of which arise as a result of quantum confinement effects. The optoelectronic properties and performance of MDHJs are primarily determined by dynamics of excitons and charge carriers at their interfaces, where these particles tunnel, trap, scatter, and/or recombine on the time scales of tens of femtoseconds to hundreds of nanoseconds. We discuss several photophysical phenomena that deviate from those observed in bulk heterojunctions, as well as factors that can be used to vary, probe, and ultimately control the behavior of excitons and charge carriers in MDHJ systems. We then discuss optoelectronic applications of MDHJs, namely, photodetectors, photovoltaics, and photocatalysts, and identify current performance limits compared to state-of-the-art benchmarks. Finally, we suggest strategies to extend the current understanding of dynamics in MDHJs toward the realization of stimuli-driven responses, particularly with respect to exciton delocalization, quantum emission, interfacial morphology, responsivity to external stimuli, spin selectivity, and usage of chemically reactive materials.
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11
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Westmoreland DE, López-Arteaga R, Weiss EA. N-Heterocyclic Carbenes as Reversible Exciton-Delocalizing Ligands for Photoluminescent Quantum Dots. J Am Chem Soc 2020; 142:2690-2696. [PMID: 31934758 DOI: 10.1021/jacs.9b13605] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Delocalization of excitons within semiconductor quantum dots (QDs) into states at the interface of the inorganic core and organic ligand shell by so-called "exciton-delocalizing ligands (EDLs)" is a promising strategy to enhance coupling of QD excitons with proximate molecules, ions, or other QDs. EDLs thereby enable enhanced rates of charge carrier extraction from, and transport among, QDs and dynamic colorimetric sensing. The application of reported EDLs-which bind to the QDs through thiolates or dithiocarbamates-is however limited by the irreversibility of their binding and their low oxidation potentials, which lead to a high yield of photoluminescence-quenching hole trapping on the EDL. This article describes a new class of EDLs for QDs, 1,3-dimethyl-4,5-disubstituted imidazolylidene N-heterocyclic carbenes (NHCs), where the 4,5-substituents are Me, H, or Cl. Postsynthetic ligand exchange of native oleate capping ligands for NHCs results in a bathochromic shift of the optical band gap of CdSe QDs (R = 1.17 nm) of up to 111 meV while the colloidal stability of the QDs is maintained. This shift is reversible for the MeNHC-capped and HNHC-capped QDs upon protonation of the NHC. The magnitude of exciton delocalization induced by the NHC (after scaling for surface coverage) increases with the increasing acidity of its π system, which depends on the substituent in the 4,5-positions of the imidazolylidene. The NHC-capped QDs maintain photoluminescence quantum yields of up to 4.2 ± 1.8% for shifts of the optical band gap as large as 106 meV.
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Affiliation(s)
- Dana E Westmoreland
- Department of Chemistry , Northwestern University , 2145 Sheridan Road , Evanston , Illinois 60208-3113 , United States
| | - Rafael López-Arteaga
- Department of Chemistry , Northwestern University , 2145 Sheridan Road , Evanston , Illinois 60208-3113 , United States
| | - Emily A Weiss
- Department of Chemistry , Northwestern University , 2145 Sheridan Road , Evanston , Illinois 60208-3113 , United States
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12
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Dodin A, Aull B, Kunz RR, Willard AP. Theoretical Bounds on Electron Energy Filtering in Disordered Nanomaterials. NANO LETTERS 2019; 19:8441-8446. [PMID: 31670966 DOI: 10.1021/acs.nanolett.9b02701] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Electron energy filters have recently been proposed as a method of reducing the effects of thermal broadening in device and sensing applications, enabling substantial improvements in their room temperature performance. Nanostructured materials can act as electron energy filters by funneling thermally broadened electrons through discrete energy levels. In this study, we develop a theoretical model of the electron filtering properties of nanostructured materials that explicitly includes the effects of thermal broadening and size heterogeneity on the heterogeneity of nanostructure energy levels. We find that under certain conditions quantum dot solids can perform as effective electronic energy filters. We identify a material-specific length scale parameter, Lcrit, that specifies the maximum mean quantum dot size that can yield effective energy filtering. Moreover, we show that energy filtering materials composed of quantum dots with size near Lcrit are maximally robust to heterogeneity in quantum dot size, tolerating variations ∼10% of the mean size. The length scale Lcrit can be estimated directly from the widely tabulated density of states effective mass and shows that semiconductors with light conduction band electrons, such as III-V type materials InSb and GaAs, are the most forgiving for energy filtering applications. Taken together, these results provide a practical set of quantitative design principles for semiconductor electron filters.
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Affiliation(s)
- Amro Dodin
- Department of Chemistry , Massachusetts Institute of Technology , Cambridge , Massachusetts 02139 , United States
| | - Brian Aull
- Lincoln Laboratory , Massachusetts Institute of Technology , Lexington , Massachusetts 02421 , United States
| | - Roderick R Kunz
- Lincoln Laboratory , Massachusetts Institute of Technology , Lexington , Massachusetts 02421 , United States
| | - Adam P Willard
- Department of Chemistry , Massachusetts Institute of Technology , Cambridge , Massachusetts 02139 , United States
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13
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Ginsberg NS, Tisdale WA. Spatially Resolved Photogenerated Exciton and Charge Transport in Emerging Semiconductors. Annu Rev Phys Chem 2019; 71:1-30. [PMID: 31756129 DOI: 10.1146/annurev-physchem-052516-050703] [Citation(s) in RCA: 62] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
We review recent advances in the characterization of electronic forms of energy transport in emerging semiconductors. The approaches described all temporally and spatially resolve the evolution of initially localized populations of photogenerated excitons or charge carriers. We first provide a comprehensive background for describing the physical origin and nature of electronic energy transport both microscopically and from the perspective of the observer. We introduce the new family of far-field, time-resolved optical microscopies developed to directly resolve not only the extent of this transport but also its potentially temporally and spatially dependent rate. We review a representation of examples from the recent literature, including investigation of energy flow in colloidal quantum dot solids, organic semiconductors, organic-inorganic metal halide perovskites, and 2D transition metal dichalcogenides. These examples illustrate how traditional parameters like diffusivity are applicable only within limited spatiotemporal ranges and how the techniques at the core of this review,especially when taken together, are revealing a more complete picture of the spatiotemporal evolution of energy transport in complex semiconductors, even as a function of their structural heterogeneities.
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Affiliation(s)
- Naomi S Ginsberg
- Department of Chemistry and Department of Physics, University of California, Berkeley, California 94720, USA; .,Material Sciences Division and Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.,Kavli Energy NanoSciences Institute, Berkeley, California 94720, USA
| | - William A Tisdale
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA;
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14
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Azzaro MS, Le AK, Wang H, Roberts ST. Ligand-Enhanced Energy Transport in Nanocrystal Solids Viewed with Two-Dimensional Electronic Spectroscopy. J Phys Chem Lett 2019; 10:5602-5608. [PMID: 31475832 DOI: 10.1021/acs.jpclett.9b02040] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
We examine CdSe NCs functionalized with the exciton-delocalizing ligand phenyldithiocarbamate (PDTC) using two-dimensional electronic spectroscopy (2DES). PDTC forms hybrid molecular orbitals with CdSe's valence band that relax hole spatial confinement and create potential for enhanced exciton migration in NC solids. We find PDTC broadens the intrinsic line width of individual NCs in solution by ∼30 meV, which we ascribe to modulation of NC band edge states by ligand motion. In PDTC-exchanged solids, photoexcited excitons are mobile and rapidly move to low-energy NC sites over ∼30 ps. We also find placing excitons into high-energy states can accelerate their rate of migration by over an order of magnitude, which we attribute to enhanced spatial delocalization of these states that improves inter-NC wave function overlap. Our work demonstrates that NC surface ligands can actively facilitate inter-NC energy transfer and highlights principles to consider when designing ligands for this application.
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Affiliation(s)
- Michael S Azzaro
- Department of Chemistry , The University of Texas at Austin , Austin , Texas 78712 , United States
| | - Aaron K Le
- Department of Chemistry , The University of Texas at Austin , Austin , Texas 78712 , United States
| | - Honghao Wang
- Department of Chemistry , The University of Texas at Austin , Austin , Texas 78712 , United States
| | - Sean T Roberts
- Department of Chemistry , The University of Texas at Austin , Austin , Texas 78712 , United States
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15
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Winslow SW, Shcherbakov-Wu W, Liu Y, Tisdale WA, Swan JW. Characterization of colloidal nanocrystal surface structure using small angle neutron scattering and efficient Bayesian parameter estimation. J Chem Phys 2019; 150:244702. [DOI: 10.1063/1.5108904] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Affiliation(s)
- Samuel W. Winslow
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02142, USA
| | - Wenbi Shcherbakov-Wu
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02142, USA
| | - Yun Liu
- Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
| | - William A. Tisdale
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02142, USA
| | - James W. Swan
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02142, USA
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16
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Meir N, Pinkas I, Oron D. NIR-to-visible upconversion in quantum dots via a ligand induced charge transfer state. RSC Adv 2019; 9:12153-12161. [PMID: 35517040 PMCID: PMC9063477 DOI: 10.1039/c9ra01273g] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2019] [Accepted: 04/11/2019] [Indexed: 12/20/2022] Open
Abstract
Photon upconversion is facilitated by the generation of a charge transfer transition in the interface of a coupled QD–thiol system.
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Affiliation(s)
- Noga Meir
- Department of Physics of Complex Systems
- Weizmann Institute of Science
- Rehovot 7610001
- Israel
| | - Iddo Pinkas
- Department of Chemical Research Support
- Weizmann Institute of Science
- Rehovot 7610001
- Israel
| | - Dan Oron
- Department of Physics of Complex Systems
- Weizmann Institute of Science
- Rehovot 7610001
- Israel
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17
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Moroz P, Royo Romero L, Zamkov M. Colloidal semiconductor nanocrystals in energy transfer reactions. Chem Commun (Camb) 2019; 55:3033-3048. [DOI: 10.1039/c9cc00162j] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Excitonic energy transfer is a versatile mechanism by which colloidal semiconductor nanocrystals can interact with a variety of nanoscale species. This feature article will discuss the latest research on the key scenarios under which semiconductor nanocrystals can engage in energy transfer with other nanoparticles, organic fluorophores, and plasmonic nanostructures, highlighting potential technological benefits to be gained from such processes.
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Affiliation(s)
- Pavel Moroz
- Department of Physics and Astronomy
- Bowling Green State University
- Bowling Green
- USA
- The Center for Photochemical Sciences
| | - Luis Royo Romero
- Department of Physics and Astronomy
- Bowling Green State University
- Bowling Green
- USA
| | - Mikhail Zamkov
- Department of Physics and Astronomy
- Bowling Green State University
- Bowling Green
- USA
- The Center for Photochemical Sciences
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18
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Montanarella F, Biondi M, Hinterding SOM, Vanmaekelbergh D, Rabouw FT. Reversible Charge-Carrier Trapping Slows Förster Energy Transfer in CdSe/CdS Quantum-Dot Solids. NANO LETTERS 2018; 18:5867-5874. [PMID: 30095918 PMCID: PMC6139578 DOI: 10.1021/acs.nanolett.8b02538] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
The dynamics of photoluminescence (PL) from nanocrystal quantum dots (QDs) is significantly affected by the reversible trapping of photoexcited charge carriers. This process occurs after up to 50% of the absorption events, depending on the type of QD considered, and can extend the time between the photoexcitation and relaxation of the QD by orders of magnitude. Although many optoelectronic applications require QDs assembled into a QD solid, until now, reversible trapping has been studied only in (ensembles of) spatially separated QDs. Here, we study the influence of reversible trapping on the excited-state dynamics of CdSe/CdS core/shell QDs when they are assembled into close-packed "supraparticles". Time- and spectrally resolved photoluminescence (PL) measurements reveal competition among spontaneous emission, reversible charge-carrier trapping, and Förster resonance energy transfer between the QDs. While Förster transfer causes the PL to red-shift over the first 20-50 ns after excitation, reversible trapping stops and even reverses this trend at later times. We can model this behavior with a simple kinetic Monte Carlo simulation by considering that charge-carrier trapping leaves the QDs in a state with zero oscillator strength in which no energy transfer can occur. Our results highlight that reversible trapping significantly affects the energy and charge-carrier dynamics for applications in which QDs are assembled into a QD solid.
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