379 results on '"Richard D. Schaller"'
Search Results
52. Visualization of Plasmonic Couplings Using Ultrafast Electron Microscopy
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Amit Jaiswal, Haihua Liu, Sang Tae Park, Prem Singh, Stephen K. Gray, Jau Tang, Richard D. Schaller, Ilke Arslan, and Thomas E. Gage
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Electromagnetic field ,Materials science ,Physics::Optics ,Bioengineering ,Nanotechnology ,02 engineering and technology ,Discrete dipole approximation ,Microscopy, Atomic Force ,Nanocapsules ,law.invention ,law ,General Materials Science ,Nanoscopic scale ,Plasmon ,Coupling ,Graphene ,Mechanical Engineering ,Charge density ,General Chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Nanostructures ,Microscopy, Electron ,Graphite ,0210 nano-technology - Abstract
Hybrids of graphene and metal plasmonic nanostructures are promising building blocks for applications in optoelectronics, surface-enhanced scattering, biosensing, and quantum information. An understanding of the coupling mechanism in these hybrid systems is of vital importance to its applications. Previous efforts in this field mainly focused on spectroscopic studies of strong coupling within the hybrids with no spatial resolution. Here we report direct imaging of the local plasmonic coupling between single Au nanocapsules and graphene step edges at the nanometer scale by photon-induced near-field electron microscopy in an ultrafast electron microscope for the first time. The proximity of a step in the graphene to the nanocapsule causes asymmetric surface charge density at the ends of the nanocapsules. Computational electromagnetic simulations confirm the experimental observations. The results reported here indicate that this hybrid system could be used to manipulate the localized electromagnetic field on the nanoscale, enabling promising future plasmonic devices.
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- 2021
53. Ultrafast Spectroscopy of Plasmonic Titanium Nitride Nanoparticle Lattices
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Thaddeus Reese, Alexander D. Sample, Teri W. Odom, Richard D. Schaller, Francisco Freire-Fernández, Amber N. Reed, and Augustine Urbas
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chemistry.chemical_compound ,Materials science ,chemistry ,Nanoparticle ,Nanotechnology ,Electrical and Electronic Engineering ,Spectroscopy ,Titanium nitride ,Ultrashort pulse ,Atomic and Molecular Physics, and Optics ,Plasmon ,Biotechnology ,Electronic, Optical and Magnetic Materials - Published
- 2021
54. 64‐3: Invited Paper: High Optical Density Quantum Dot Pixel Color Conversion Films for Displays
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Dmitri V. Talapin, Yu Kambe, Forrest S. Etheridge, Danielle R. Chamberlin, and Richard D. Schaller
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Pixel color ,Materials science ,Quantum dot ,law ,business.industry ,Optoelectronics ,Optical density ,Photolithography ,business ,law.invention - Published
- 2021
55. Suppressed Oxidation and Photodarkening of Hybrid Tin Iodide Perovskite Achieved with Reductive Organic Small Molecule
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Tao Xu, Jue Gong, Richard D. Schaller, Peijun Guo, Tobin J. Marks, Xun Li, and Wei Huang
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chemistry.chemical_classification ,Photoluminescence ,Materials science ,Hydroquinone ,Iodide ,Energy Engineering and Power Technology ,chemistry.chemical_element ,Halide ,Photochemistry ,Oxygen ,chemistry.chemical_compound ,chemistry ,Photodarkening ,Materials Chemistry ,Electrochemistry ,Chemical Engineering (miscellaneous) ,Electrical and Electronic Engineering ,Tin ,Perovskite (structure) - Abstract
Tin(II)-based halide perovskites have shown promise in lead-free and mixed tin(II)–lead ideal-band-gap photovoltaic applications. Nonetheless, they notoriously suffer from oxidation in oxygen envir...
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- 2021
56. Very Robust Spray-Synthesized CsPbI3 Quantum Emitters with Ultrahigh Room-Temperature Cavity-Free Brightness and Self-Healing Ability
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Yu Sheng Huang, Yung Tang Chuang, Alexandra Brumberg, Bo Wei Hsu, Chien-Yu Chen, Chun Yuan Cheng, Chih-Sung Chuu, Yen Ju Chen, Hao-Wu Lin, Richard D. Schaller, Lin Yang, and Lih J. Chen
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Brightness ,Materials science ,Photon antibunching ,business.industry ,General Engineering ,General Physics and Astronomy ,Quantum technology ,Quantum cryptography ,Quantum dot ,Optoelectronics ,General Materials Science ,business ,Quantum information science ,Quantum ,Quantum computer - Abstract
Although colloidal lead halide perovskite quantum dots (PQDs) exhibit desirable emitter characteristics with high quantum yields and narrow bandwidths, instability has limited their applications in devices. In this paper, we describe spray-synthesized CsPbI3 PQD quantum emitters displaying strong photon antibunching and high brightness at room temperature and stable performance under continuous excitation with a high-intensity laser for more than 24 h. Our PQDs provided high single-photon emission rates, exceeding 9 × 106 count/s, after excluding multiexciton emissions and strong photon antibunching, as confirmed by low values of the second-order correlation function g(2)(0) (reaching 0.021 and 0.061 for the best and average PQD performance, respectively). With such high brightness and stability, we applied our PQDs as quantum random number generators, which demonstrably passed all of the National Institute of Standards and Technology's randomness tests. Intriguingly, all of the PQDs exhibited self-healing behavior and restored their PL intensities to greater than half of their initial values after excitation at extremely high intensity. Half of the PQDs even recovered almost all of their initial PL intensity. The robust properties of these spray-synthesized PQDs resulted from high crystallinity and good ligand encapsulation. Our results suggest that spray-synthesized PQDs have great potential for use in future quantum technologies (e.g., quantum communication, quantum cryptography, and quantum computing).
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- 2021
57. Identification of Brillouin Zones by In-Plane Lasing from Light-Cone Surface Lattice Resonances
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Ran Li, Marc R. Bourgeois, Jun Guan, Richard D. Schaller, George C. Schatz, Teri W. Odom, and Jingtian Hu
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Electromagnetic field ,Physics ,Nanolaser ,Surface plasmon ,General Engineering ,Physics::Optics ,General Physics and Astronomy ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Molecular physics ,0104 chemical sciences ,Brillouin zone ,Dipole ,Wavelength ,Light cone ,General Materials Science ,0210 nano-technology ,Translational symmetry - Abstract
Because of translational symmetry, electromagnetic fields confined within 2D periodic optical structures can be represented within the first Brillouin zone (BZ). In contrast, the wavevectors of scattered electromagnetic fields outside the lattice are constrained by the 3D light cone, the free-photon dispersion in the surrounding medium. Here, we report that light-cone surface lattice resonances (SLRs) from plasmonic nanoparticle lattices can be used to observe the radiated electromagnetic fields from extended BZ edges. Our coupled dipole radiation theory reveals how lattice geometry and induced surface plasmon dipole orientation affect angular distributions of the radiated fields. Using dye molecules as local dipole emitters to excite the light-cone SLR modes, we experimentally identified high-order BZ edges by directional, in-plane lasing emission. These results provide insight into nanolaser architectures that can emit at multiple wavelengths and in-plane directions simply by rotating the nanocavity lattice.
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- 2021
58. Extraordinarily large permittivity modulation in zinc oxide for dynamic nanophotonics
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Aveek Dutta, Vladimir M. Shalaev, Zhaxylyk A. Kudyshev, Richard D. Schaller, Alexandra Boltasseva, Soham Saha, Benjamin T. Diroll, Clayton DeVault, Xiaohui Xu, and Alexander V. Kildishev
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Permittivity ,Materials science ,Nanophotonics ,Oxide ,Phase (waves) ,02 engineering and technology ,010402 general chemistry ,01 natural sciences ,Fluence ,law.invention ,chemistry.chemical_compound ,law ,General Materials Science ,business.industry ,Mechanical Engineering ,Polarizer ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,0104 chemical sciences ,Wavelength ,chemistry ,Mechanics of Materials ,Modulation ,Optoelectronics ,0210 nano-technology ,business - Abstract
The dielectric permittivity of a material encapsulates the essential physics of light-matter interaction into the material’s local response to optical excitation. Photo-induced modulation of the permittivity can enable an unprecedented level of control over the phase, amplitude, and polarization of light. Therefore, the detailed dynamic characterization of technology-relevant materials with substantially tunable optical properties and fast response times is a crucial step to realize tunable optical devices. This work reports on the extraordinarily large permittivity changes in zinc oxide thin films (up to −3.6 relative change in the real part of the dielectric permittivity at 1600 nm wavelength) induced by optically generated free carriers. We demonstrate broadband reflectance modulation up to 70% in metal-backed oxide mirrors at the telecommunication wavelengths, with picosecond-scale relaxation times. The epsilon near zero points of the films can be dynamically shifted from 8.5 µm to 1.6 µm by controlling the pump fluence. The modulation can be selectively enhanced at specific wavelengths employing metal-backed zinc oxide disks while maintaining picosecond-scale switching times. This work provides insights into the free-carrier assisted permittivity modulation in zinc oxide and could enable the realization of novel dynamic devices for beam-steering, polarizers, and spatial light modulators.
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- 2021
59. Colloidal quantum dot lasers
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Richard D. Schaller, Jeongkyun Roh, Benjamin T. Diroll, Victor I. Klimov, and Young-Shin Park
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Materials science ,Physics::Optics ,02 engineering and technology ,Electroluminescence ,010402 general chemistry ,01 natural sciences ,law.invention ,Biomaterials ,symbols.namesake ,law ,Materials Chemistry ,Diode ,Auger effect ,business.industry ,021001 nanoscience & nanotechnology ,Laser ,0104 chemical sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Nanocrystal ,Quantum dot ,Quantum dot laser ,symbols ,Optoelectronics ,0210 nano-technology ,business ,Lasing threshold ,Energy (miscellaneous) - Abstract
Semiconductor nanocrystals represent a promising class of solution-processable optical-gain media that can be manipulated via inexpensive, easily scalable colloidal techniques. Due to their extremely small sizes (typically
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- 2021
60. Radiative lifetime-encoded unicolour security tags using perovskite nanocrystals
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Maksym V. Kovalenko, Yevhen Shynkarenko, Maryna I. Bodnarchuk, Stefano Cattaneo, Richard D. Schaller, Bogdan M. Benin, Christoph Hofer, Sami Bolat, Annelies Landuyt, Sergey I. Pokutnyi, Dimos Poulikakos, Sergii Yakunin, Jana Chaaban, Ihor Cherniukh, Yaroslav E. Romanyuk, and Caterina Bernasconi
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Masking (art) ,Computer science ,Science ,ComputingMethodologies_IMAGEPROCESSINGANDCOMPUTERVISION ,General Physics and Astronomy ,02 engineering and technology ,010402 general chemistry ,01 natural sciences ,Article ,General Biochemistry, Genetics and Molecular Biology ,Pattern matching ,Perovskite (structure) ,Quantum optics ,Multidisciplinary ,business.industry ,Nanoparticles ,General Chemistry ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,Counterfeit ,Formamidinium ,Covert ,DECIPHER ,0210 nano-technology ,business ,Tag system ,Computer hardware - Abstract
Traditional fluorescence-based tags, used for anticounterfeiting, rely on primitive pattern matching and visual identification; additional covert security features such as fluorescent lifetime or pattern masking are advantageous if fraud is to be deterred. Herein, we present an electrohydrodynamically printed unicolour multi-fluorescent-lifetime security tag system composed of lifetime-tunable lead-halide perovskite nanocrystals that can be deciphered with both existing time-correlated single-photon counting fluorescence-lifetime imaging microscopy and a novel time-of-flight prototype. We find that unicolour or matching emission wavelength materials can be prepared through cation-engineering with the partial substitution of formamidinium for ethylenediammonium to generate “hollow” formamidinium lead bromide perovskite nanocrystals; these materials can be successfully printed into fluorescence-lifetime-encoded-quick-read tags that are protected from conventional readers. Furthermore, we also demonstrate that a portable, cost-effective time-of-flight fluorescence-lifetime imaging prototype can also decipher these codes. A single comprehensive approach combining these innovations may be eventually deployed to protect both producers and consumers., Nature Communications, 12 (1), ISSN:2041-1723
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- 2021
61. Transient Lattice Response upon Photoexcitation in CuInSe2 Nanocrystals with Organic or Inorganic Surface Passivation
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Brian A. Korgel, Richard D. Schaller, Xiaoyi Zhang, Lin X. Chen, Nathan C. Flanders, Samantha M. Harvey, Michael R. Wasielewski, Matthew S. Kirschner, Nicolas E. Watkins, Daniel W. Houck, William R. Dichtel, Ariel A. Leonard, and Alexandra Brumberg
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Materials science ,Passivation ,business.industry ,General Engineering ,General Physics and Astronomy ,Nanotechnology ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Photoexcitation ,Nanocrystal ,Photovoltaics ,Printed electronics ,Lattice (order) ,General Materials Science ,Photonics ,0210 nano-technology ,business ,Curing (chemistry) - Abstract
CuInSe2 nanocrystals offer promise for optoelectronics including thin-film photovoltaics and printed electronics. Additive manufacturing methods such as photonic curing controllably sinter particle...
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- 2020
62. Simultaneous Ultrafast Transmission and Reflection of Nanometer-Thick Ti3C2Tx MXene Films in the Visible and Near-Infrared: Implications for Energy Storage, Electromagnetic Shielding, and Laser Systems
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Richard D. Schaller, W. Joshua Kennedy, Gregory Neher, Bryan T. Seymour, Peter R. Stevenson, David B. Lioi, David J. Gosztola, Richard A. Vaia, and Jonathon P. Vernon
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Materials science ,business.industry ,Mathematics::History and Overview ,Surface plasmon ,Physics::Optics ,Laser ,Energy storage ,law.invention ,law ,Ellipsometry ,Electromagnetic shielding ,Reflection (physics) ,Optoelectronics ,General Materials Science ,MXenes ,business ,Ultrashort pulse - Abstract
Unambiguous determination of the optical dynamics in MXenes is necessary for their reliable development into applications such as EMI shielding, energy storage, and laser systems. Here, simultaneou...
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- 2020
63. Brightly Luminescent CsPbBr3 Nanocrystals through Ultracentrifugation
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Samuel L. Brown, Richard D. Schaller, Aaron Forde, Reed J. Petersen, Matthew B. Kurtti, Erik K. Hobbie, Salim A. Thomas, Jeffrey A. Fagan, and Dmitri S. Kilin
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Materials science ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Analytical Ultracentrifugation ,Chemical engineering ,Nanocrystal ,General Materials Science ,Ultracentrifuge ,Physical and Theoretical Chemistry ,0210 nano-technology ,Luminescence - Abstract
Using a combination of density-gradient and analytical ultracentrifugation, we studied the photophysical profile of CsPbBr3 nanocrystal (NC) suspensions by separating them into size-resolved fracti...
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- 2020
64. Large Exciton Diffusion Coefficients in Two-Dimensional Covalent Organic Frameworks with Different Domain Sizes Revealed by Ultrafast Exciton Dynamics
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Richard D. Schaller, Pyosang Kim, Lin X. Chen, Matthew S. Kirschner, Thomas J. Fauvell, Nathan C. Flanders, Austin P. Spencer, Austin M. Evans, Waleed Helweh, and William R. Dichtel
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Chemistry ,Exciton ,Relaxation (NMR) ,General Chemistry ,010402 general chemistry ,Excimer ,01 natural sciences ,Biochemistry ,Catalysis ,0104 chemical sciences ,Photoexcitation ,Condensed Matter::Materials Science ,Delocalized electron ,Colloid and Surface Chemistry ,Chemical physics ,Ultrafast laser spectroscopy ,Diffusion (business) ,Covalent organic framework - Abstract
Large singlet exciton diffusion lengths are a hallmark of high performance in organic-based devices such as photovoltaics, chemical sensors, and photodetectors. In this study, exciton dynamics of a two-dimensional covalent organic framework, 2D COF-5, is investigated using ultrafast spectroscopic techniques. After photoexcitation, the COF-5 exciton decays via three pathways: (1) excimer formation (4 ± 2 ps), (2) excimer relaxation (160 ± 40 ps), and (3) excimer decay (>3 ns). Excitation fluence-dependent transient absorption studies suggest that COF-5 has a relatively large diffusion coefficient (0.08 cm2/s). Furthermore, exciton-exciton annihilation processes are characterized as a function of COF-5 crystallite domain size in four different samples, which reveal domain-size-dependent exciton diffusion kinetics. These results reveal that exciton diffusion in COF-5 is constrained by its crystalline domain size. These insights indicate the outstanding promise of delocalized excitonic processes available in 2D COFs, which motivate their continued design and implementation into optoelectronic devices.
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- 2020
65. Water-Stable 1D Hybrid Tin(II) Iodide Emits Broad Light with 36% Photoluminescence Quantum Efficiency
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Jacky Even, Weijun Ke, Mikael Kepenekian, Siraj Sidhik, Peijun Guo, Ioannis Spanopoulos, Aditya D. Mohite, Ido Hadar, Mercouri G. Kanatzidis, Richard D. Schaller, Northwestern University [Evanston], Argonne National Laboratory [Lemont] (ANL), Rice University [Houston], Institut des Sciences Chimiques de Rennes (ISCR), Université de Rennes (UR)-Institut National des Sciences Appliquées - Rennes (INSA Rennes), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Ecole Nationale Supérieure de Chimie de Rennes (ENSCR)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Institut des Fonctions Optiques pour les Technologies de l'informatiON (Institut FOTON), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-École Nationale Supérieure des Sciences Appliquées et de Technologie (ENSSAT)-Centre National de la Recherche Scientifique (CNRS), Los Alamos National Laboratory (LANL), SC0012541, Basic Energy Sciences, 862656, Horizon 2020 Framework Programme, Institut Universitaire de France, Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Ecole Nationale Supérieure de Chimie de Rennes (ENSCR)-Institut National des Sciences Appliquées - Rennes (INSA Rennes), Institut National des Sciences Appliquées (INSA)-Université de Rennes (UNIV-RENNES)-Institut National des Sciences Appliquées (INSA), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Institut National des Sciences Appliquées - Rennes (INSA Rennes), Institut National des Sciences Appliquées (INSA)-Université de Rennes (UNIV-RENNES)-Institut National des Sciences Appliquées (INSA)-École Nationale Supérieure des Sciences Appliquées et de Technologie (ENSSAT)-Centre National de la Recherche Scientifique (CNRS)-IMT Atlantique Bretagne-Pays de la Loire (IMT Atlantique), and Institut Mines-Télécom [Paris] (IMT)-Institut Mines-Télécom [Paris] (IMT)
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[PHYS]Physics [physics] ,Photoluminescence ,business.industry ,Chemistry ,Physics::Optics ,Halide ,chemistry.chemical_element ,General Chemistry ,010402 general chemistry ,01 natural sciences ,Biochemistry ,Catalysis ,0104 chemical sciences ,Condensed Matter::Materials Science ,Wavelength ,Tin(II) iodide ,chemistry.chemical_compound ,Colloid and Surface Chemistry ,[CHIM]Chemical Sciences ,Optoelectronics ,Light emission ,Quantum efficiency ,business ,Tin - Abstract
International audience; The optical and light emission properties of tin and lead halide perovskites are remarkable because of the robust room-temperature (RT) performance, broad wavelength tunability, high efficiency, and good quenching resistance to defects. These highly desirable attributes promise to transform current light-emitting devices, phosphors, and lasers. One disadvantage in most of these materials is the sensitivity to moisture. Here, we report a new air-stable one-dimensional (1D) hybrid lead-free halide material (DAO)SnI (DAO, 1,8-octyldiammonium) that is resistant to water for more than 15 h. The material exhibits a sharp optical absorption edge at 2.70 eV and a strong broad orange light emission centered at 634 nm, with a full width at half-maximum (fwhm) of 142 nm (0.44 eV). The emission has a long photoluminescence (PL) lifetime of 582 ns, while the intensity is constant over a very broad temperature range (145-415 K) with a photoluminescence quantum yield (PLQY) of at least 20.3% at RT. Above 415 K the material undergoes a structural phase transition from monoclinic (2/) to orthorhombic ( accompanied by a red shift in the band gap and a quench in the photoluminescence emission. Density functional theory calculations support the trend in the optical properties and the 1D electronic nature of the structure, where the calculated carrier effective masses along the inorganic chain are significantly lower than those perpendicular to the chain. Thin films of the compound readily fabricated from solutions exhibit the same optical properties, but with improved PLQY of 36%, for a 60 nm thick film, among the highest reported for lead-free low-dimensional 2D and 1D perovskites and metal halides.
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- 2020
66. Organic Cation Alloying on Intralayer A and Interlayer A’ sites in 2D Hybrid Dion–Jacobson Lead Bromide Perovskites (A’)(A)Pb2Br7
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Constantinos C. Stoumpos, Peijun Guo, Ioannis Spanopoulos, Mercouri G. Kanatzidis, Claudine Katan, Richard D. Schaller, Mikaël Kepenekian, Lingling Mao, Yihui He, Jacky Even, Ram Seshadri, Northwestern University [Evanston], Argonne National Laboratory [Lemont] (ANL), Institut des Sciences Chimiques de Rennes (ISCR), Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Ecole Nationale Supérieure de Chimie de Rennes (ENSCR)-Institut National des Sciences Appliquées - Rennes (INSA Rennes), Institut National des Sciences Appliquées (INSA)-Université de Rennes (UNIV-RENNES)-Institut National des Sciences Appliquées (INSA), Institut des Fonctions Optiques pour les Technologies de l'informatiON (Institut FOTON), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Institut National des Sciences Appliquées - Rennes (INSA Rennes), Institut National des Sciences Appliquées (INSA)-Université de Rennes (UNIV-RENNES)-Institut National des Sciences Appliquées (INSA)-École Nationale Supérieure des Sciences Appliquées et de Technologie (ENSSAT)-Centre National de la Recherche Scientifique (CNRS)-IMT Atlantique Bretagne-Pays de la Loire (IMT Atlantique), Institut Mines-Télécom [Paris] (IMT)-Institut Mines-Télécom [Paris] (IMT), University of California [Santa Barbara] (UCSB), University of California, University of Crete [Heraklion] (UOC), SC0012541, Basic Energy Sciences, DE-AC02-06CH11357, U.S. Department of Energy, Université de Rennes (UR)-Institut National des Sciences Appliquées - Rennes (INSA Rennes), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Ecole Nationale Supérieure de Chimie de Rennes (ENSCR)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-École Nationale Supérieure des Sciences Appliquées et de Technologie (ENSSAT)-Centre National de la Recherche Scientifique (CNRS), University of California [Santa Barbara] (UC Santa Barbara), and University of California (UC)
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[PHYS]Physics [physics] ,Photoluminescence ,Band gap ,Chemistry ,Halide ,General Chemistry ,Crystal structure ,010402 general chemistry ,01 natural sciences ,Biochemistry ,Catalysis ,0104 chemical sciences ,symbols.namesake ,Crystallography ,Colloid and Surface Chemistry ,Formamidinium ,Lattice (order) ,symbols ,[CHIM]Chemical Sciences ,Density functional theory ,Raman spectroscopy - Abstract
International audience; Hybrid layered halide perovskites have achieved impressive performance in optoelectronics. New structural types in the two-dimensional (2D) halide system such as the Dion-Jacobson phases have attracted wide research attention due to the short interlayer distance and unique layer orientation that facilitate better charge-transport and higher stability in optoelectronic devices. Here, we report the first solid solution series incorporating both A and A’ cations in the 2D Jacobson-Dion family, with the general formula (A’)(A)Pb2Br7 ((A’ = 3-(aminomethyl)piperidinium (3AMP) and 4-(aminomethyl)piperidinium) (4AMP); A= methylammonium (MA) and formamidinium (FA)). Mixing the spacing A’ cations and perovskitizer A cations generates the new (3AMP)a(4AMP)1-a(FA)b(MA)1-bPb2Br7 perovskites. The crystallographically refined crystal structures using single-crystal X-ray diffraction data re-veal that the distortion of the inorganic framework is heavily influenced by the degree of A’ and A alloying. A rising fraction of 4AMP in the structure, decreases the Pb-Br-Pb angles, making the framework more distorted. On the contrary, higher FA fractions increase the Pb-Br-Pb angles. This structural evolution fine tunes the optical properties where the larger the Pb-Br-Pb angle, the narrower the band gap. The photoluminescence emission energy mirrors this trend. Raman spectroscopy reveals a highly dynamical lattice similar to MAPbBr3 and consistent with the local distortion environment of the [Pb2Br7] framework. Density Functional Theory (DFT) calculations of the electronic structures reveal the same trend as the experimental results where (3AMP)(FA)Pb2Br7 has the smallest band gap while (4AMP)(MA)Pb2Br7 has the largest band gap. The structural effects from solely the organic cati-ons in the 2D system highlight the importance of understanding the high sensitivity of the optoelectronic properties on the struc-tural tuning in this broad class of materials.
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- 2020
67. Bright Silicon Nanocrystals from a Liquid Precursor: Quasi-Direct Recombination with High Quantum Yield
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Philip Boudjouk, Salim A. Thomas, Richard D. Schaller, Yulun Han, Uwe Kortshagen, Dmitri S. Kilin, Erik K. Hobbie, Todd A. Pringle, Reed J. Petersen, Jeffrey A. Fagan, Mahmud Sefannaser, Alexandra Brumberg, Katharine I. Hunter, Kenneth Anderson, and Samuel L. Brown
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Range (particle radiation) ,Photoluminescence ,Materials science ,Band gap ,business.industry ,General Engineering ,General Physics and Astronomy ,Quantum yield ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Quantum dot ,Optoelectronics ,General Materials Science ,Silicon nanocrystals ,0210 nano-technology ,business ,Recombination - Abstract
Silicon nanocrystals (SiNCs) with bright bandgap photoluminescence (PL) are of current interest for a range of potential applications, from solar windows to biomedical contrast agents. Here, we use the liquid precursor cyclohexasilane (Si
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- 2020
68. Engineering Directionality in Quantum Dot Shell Lasing Using Plasmonic Lattices
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Jun Guan, Oleksandr Voznyy, Edward H. Sargent, Golam Bappi, Laxmi Kishore Sagar, Danqing Wang, Ran Li, Fengjia Fan, Marc R. Bourgeois, Nicolas E. Watkins, George C. Schatz, Teri W. Odom, Sjoerd Hoogland, Richard D. Schaller, Joao M. Pina, and Larissa Levina
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Materials science ,business.industry ,Mechanical Engineering ,Nanolaser ,Physics::Optics ,Bioengineering ,02 engineering and technology ,General Chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Waveguide (optics) ,Brillouin zone ,Quantum dot ,Lattice (order) ,Optoelectronics ,General Materials Science ,0210 nano-technology ,business ,Electronic band structure ,Lasing threshold ,Plasmon - Abstract
We report how the direction of quantum dot (QD) lasing can be engineered by exploiting high-symmetry points in plasmonic nanoparticle (NP) lattices. The nanolaser architecture consists of CdSe-CdS core-shell QD layers conformally coated on two-dimensional square arrays of Ag NPs. Using waveguide-surface lattice resonances (W-SLRs) near the Δ point in the Brillouin zone as optical feedback, we achieved lasing from the gain in CdS shells at off-normal emission angles. Changing the periodicity of the plasmonic lattices enables other high-symmetry points (Γ or M) of the lattice to overlap with the QD shell emission, which facilitates tuning of the lasing direction. We also increased the thickness of the QD layer to introduce higher-order W-SLR modes with additional avoided crossings in the band structure, which expands the selection of cavity modes for any desired lasing emission angle.
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- 2020
69. Photophysical implications of ring fusion, linker length, and twisting angle in a series of perylenediimide–thienoacene dimers
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Lin X. Chen, Ariel A. Leonard, George C. Schatz, David J. Gosztola, Zhengxu Cai, Matthew S. Kirschner, Thomas J. Fauvell, Martín A. Mosquera, Richard D. Schaller, Leighton O. Jones, and Luping Yu
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chemistry.chemical_classification ,Materials science ,Organic solar cell ,chemistry ,Chemical physics ,Excited state ,General Chemistry ,Time-dependent density functional theory ,Dihedral angle ,Electron acceptor ,Ring (chemistry) ,Ground state ,Acceptor - Abstract
Perylenediimide (PDI) derivatives have been widely studied as electron acceptor alternatives to fullerenes in organic photovoltaics (OPVs) because of their tunable absorption in the visible range, inexpensive synthesis, and photochemical stability. A common motif for improving device efficiency involves joining multiple PDIs together through electron-rich linkers to form a twisted acceptor-donor-acceptor molecule. Molecular features such as ring fusion are further employed to modify the structure locally and in films. These synthetic efforts have greatly enhanced OPV device efficiencies, however it remains unclear how the increasingly elaborate structural modifications affect the photophysical processes integral to efficient photon-to-charge conversion. Here we carry out a systematic study of a series of PDI dimers with thienoacene linkers in which the twist angle, linker length, and degree of ring fusion are varied to investigate the effects of these structural features on the molecular excited states and exciton recombination dynamics. Spectroscopic characterization of the dimers suggest that ring fusion causes greater coupling between the donor and acceptor components and greatly enhances the lifetime of a thienoacene to PDI charge transfer state. The lifetime of this CT state also correlates well with the linker-PDI dihedral angle, with smaller dihedral angle resulting in longer lifetime. DFT and two-photon absorption TDDFT calculations were developed in-house to model the ground state and excited transitions, providing theoretical insight into the reasons for the observed photophysical properties and identifying the charge transfer state in the excited state absorption spectra. These results highlight how the longevity of the excited state species, important for the efficient conversion of excitons to free carriers in OPV devices, can be chemically tuned by controlling ring fusion and by using steric effects to control the relative orientations of the molecular fragments. The results provide a successful rationalization of the behavior of solar cells involving these acceptor molecules.
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- 2020
70. Expanding the Cage of 2D Bromide Perovskites by Large A-Site Cations
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Xiaotong Li, Shelby A. Cuthriell, Ashanti Bergonzoni, Hao Dong, Boubacar Traoré, Constantinos C. Stoumpos, Peijun Guo, Jacky Even, Claudine Katan, Richard D. Schaller, Mercouri G. Kanatzidis, Northwestern University [Evanston], Institut des Fonctions Optiques pour les Technologies de l'informatiON (Institut FOTON), Université de Rennes (UR)-Institut National des Sciences Appliquées - Rennes (INSA Rennes), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-École Nationale Supérieure des Sciences Appliquées et de Technologie (ENSSAT)-Centre National de la Recherche Scientifique (CNRS), Yale University [New Haven], Institut des Sciences Chimiques de Rennes (ISCR), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Ecole Nationale Supérieure de Chimie de Rennes (ENSCR)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), University of Crete [Heraklion] (UOC), Argonne National Laboratory [Lemont] (ANL), A.B. acknowledges support from Region Bretagne through the PERFOTON project. This work was granted access to the HPC resources of [TGCC/CINES/IDRIS] under the allocations 2021-A0100911434 and 2021-A0110907682 made by GENCI. J.E. acknowledges financial support from the Institut Universitaire de France., and European Project: PeroCUBE
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[CHIM.THEO]Chemical Sciences/Theoretical and/or physical chemistry ,General Chemical Engineering ,Materials Chemistry ,General Chemistry - Abstract
International audience; Two-dimensional (2D) halide perovskites have outstanding optoelectronic properties, and they feature a variety of organic cation spacers and cage A-site cations that can be incorporated into their structures. It has recently been reported that the Goldschmidt tolerance factor can be relaxed and expanded in iodide 2D perovskites. Bromide 2D perovskites, whose multilayer structures and optical properties are much less studied, provide a great platform for studying structure–property relationships for 2D perovskites with large A-site cations. Herein, we report the synthesis and structure of three new 2D bromide perovskites─(BA)2(MHy)2Pb3Br10 (BA, butylammonium; MHy, methylhydrazinium), (BA)2(EA)2Pb3Br10 (EA is ethylammonium), and (BA)2(DMA)Pb2Br7 (DMA is dimethylammonium). We compared them with other 2D perovskites with different A-site cations but with the same spacer and layer thickness. Single-crystal structures show that the Pb–Br bonds are elongated to accommodate the large A-site cations. Additionally, the octahedra in (BA)2(MHy)2Pb3Br10 and (BA)2(EA)2Pb3Br10 are highly distorted, and their different stacking patterns of the inner and outer layers lead to the formation of the n = 3 phases. Density functional theory calculations show that 2D perovskites with larger A-site cations (e.g., DMA, MHy, and EA) have smaller band dispersions and larger effective masses than those with Cs+ and MA. (BA)2(MHy)2Pb3Br10 also exhibits one of the largest Rashba splittings in the literature. Structures with large cage cations also exhibit high band gaps within the same n number and short photoluminescence (PL) lifetimes. Temperature- and power-dependent PL measurements reveal that the broad shoulder in the PL peak originates from the trap states.
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- 2022
71. Optically Tunable Third Harmonic Generation in a Conducting Oxide Film
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Soham Saha, Benjamin T. Diroll, Mustafa Goksu Ozlu, Zhaxylyk Kudyshev, Richard D. Schaller, Alexander Kildishev, Vladimir M. Shalaev, and Alexandra Boltasseva
- Abstract
We demonstrate actively tunable third harmonic generation (THG) in zinc oxide, increasing THG by 600%. This is done using an interband pump, generating free carriers to increase Kerr nonlinearities, and enhancing fields through permittivity reduction.
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- 2022
72. Excitonic Spin-Coherence Lifetimes in CdSe Nanoplatelets Increase Significantly with Core/Shell Morphology
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Phillip I. Martin, Shobhana Panuganti, Joshua C. Portner, Nicolas E. Watkins, Mercouri G. Kanatzidis, Dmitri V. Talapin, and Richard D. Schaller
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Condensed Matter - Materials Science ,Condensed Matter - Mesoscale and Nanoscale Physics ,Mechanical Engineering ,Mesoscale and Nanoscale Physics (cond-mat.mes-hall) ,Materials Science (cond-mat.mtrl-sci) ,FOS: Physical sciences ,General Materials Science ,Bioengineering ,General Chemistry ,Condensed Matter Physics - Abstract
We report spin-polarized transient absorption for colloidal CdSe nanoplatelets as functions of thickness (2 to 6 monolayer thickness) and core/shell motif. Using electro-optical modulation of co- and cross-polarization pump-probe combinations, we sensitively observe spin-polarized transitions. Core-only nanoplatelets exhibit few-picosecond spin lifetimes that weakly increase with layer thickness. Spectral content of differenced spin-polarized signals indicate biexciton binding energies that decrease with increasing thickness and smaller values than previously reported. Shell growth of CdS with controlled thicknesses, which partially delocalize the electron from the hole, significantly increases the spin lifetime to ~49 picoseconds at room temperature. Implementation of ZnS shells, which do not alter delocalization but do alter surface termination, increased spin lifetimes up to ~100 ps, bolstering the interpretation that surface termination heavily influences spin coherence, likely due to passivation of dangling bonds. Spin precession in magnetic fields both confirms long coherence lifetime at room temperature and yields excitonic g-factor., Comment: Main text + supplementary, 18 pages total, 8 figures total
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- 2022
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73. Non-Equilibrium Lattice Dynamics in Photo-Excited Two-Dimensional Perovskites
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Shelby A. Cuthriell, Shobhana Panuganti, Craig C. Laing, Michael A. Quintero, Burak Guzelturk, Nuri Yazdani, Boubacar Traore, Alexandra Brumberg, Christos D. Malliakas, Aaron M. Lindenberg, Vanessa Wood, Claudine Katan, Jacky Even, Xiaoyi Zhang, Mercouri G. Kanatzidis, Richard D. Schaller
- Published
- 2022
- Full Text
- View/download PDF
74. Emissive Single-Crystalline Boroxine-Linked Colloidal Covalent Organic Frameworks
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Nathan C. Flanders, Alexandra Brumberg, Nathan C. Gianneschi, David J. Gosztola, William R. Dichtel, Rebecca L. Li, Austin M. Evans, Richard D. Schaller, Ioannina Castano, Amanda R. Corcos, and Lucas R. Parent
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chemistry.chemical_classification ,Nanoparticle ,General Chemistry ,Polymer ,Chromophore ,010402 general chemistry ,01 natural sciences ,Biochemistry ,Boroxine ,Catalysis ,Fluorescence spectroscopy ,0104 chemical sciences ,chemistry.chemical_compound ,Colloid and Surface Chemistry ,Monomer ,Polymerization ,Chemical engineering ,chemistry ,Covalent bond - Abstract
The synthesis of periodic two-dimensional (2D) polymers and characterization of their optoelectronic behaviors are challenges at the forefront of polymer chemistry and materials science. Recently, we showed that layered 2D polymers known as 2D covalent organic frameworks (COFs) can be synthesized as single crystals by preparing COF particles as colloidal suspensions. Here we expand this approach from the condensation of boronic acids and catechols to the dehydrative trimerization of polyboronic acids. The resulting boroxine-linked colloids are the next class of 2D COFs to be obtained as single-crystalline particles, as demonstrated here for four 2D COFs and one 3D COF. Colloidal stabilization enables detailed structural analysis by synchrotron X-ray diffraction and high-resolution transmission electron microscopy. Solution fluorescence spectroscopy revealed that the COF crystallites are highly emissive compared to their respective monomer solutions. Excitation-emission matrix fluorescence spectroscopy indicated that the origin of this enhanced emission can be attributed to through-space communication of chromophores between COF sheets. These observations will motivate the development of colloidal COF systems as a platform to organize functional aromatic systems into precise and predictable assemblies with emergent properties.
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- 2019
75. Light-Driven Redox Activation of CO2- and H2-Activating Complexes in a Self-Assembled Triad
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Nathan T. La Porte, Richard D. Schaller, Michael D. Hopkins, and Davis B. Moravec
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010304 chemical physics ,Chemistry ,Triad (anatomy) ,Chromophore ,010402 general chemistry ,Photochemistry ,01 natural sciences ,Acceptor ,Redox ,0104 chemical sciences ,Surfaces, Coatings and Films ,Artificial photosynthesis ,medicine.anatomical_structure ,0103 physical sciences ,Ultrafast laser spectroscopy ,Materials Chemistry ,medicine ,Carbon dioxide binding ,Physical and Theoretical Chemistry ,Diimine - Abstract
We report a self-assembled triad for artificial photosynthesis composed of a chromophore, carbon-dioxide reduction catalyst, and hydrogen-oxidation complex, which is designed to operate without conventional sacrificial redox equivalents. Excitation of the zinc-porphyrin chromophore of the triad results in ultrafast charge transfer between a tungsten-alkylidyne donor and a rhenium diimine tricarbonyl acceptor, producing a charge-separated state that persists on the time scale of tens of nanoseconds and is thermodynamically capable of the primary dihydrogen and carbon dioxide binding steps for initiating the reverse water-gas shift reaction. The charge-transfer behavior of this system was probed using transient absorption spectroscopy in the visible, near-infrared, and mid-infrared spectral regions. The behavior of the triad was compared with that of the zinc-porphyrin-rhenium-diimide dyad; the triad was found to have a significantly longer charge-separated lifetime than other previously reported porphyrin-rhenium diimine compounds.
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- 2019
76. Gain roll-off in cadmium selenide colloidal quantum wells under intense optical excitation
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Benjamin T. Diroll, Alexandra Brumberg, and Richard D. Schaller
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Multidisciplinary - 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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- 2021
77. Revealing the Three-Dimensional Orientation and Interplay between Plasmons and Interband Transitions for Single Gold Bipyramids by Photoluminescence Excitation Pattern Imaging
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Charles Cherqui, George C. Schatz, Richard D. Schaller, Renaud Bachelot, Xiao-Min Lin, Pierre-Michel Adam, Frank Wackenhut, Alfred J. Meixner, Caitlin D. Coplan, Dandan Ge, Marc Brecht, Quan Liu, Lumière, nanomatériaux et nanotechnologies (L2n), Université de Technologie de Troyes (UTT)-Centre National de la Recherche Scientifique (CNRS), Eberhard Karls Universität Tübingen = Eberhard Karls University of Tuebingen, Department of Chemistry, Northwestern University, Northwestern University, Center for Nanoscale Materials, Argonne National Laboratory, and ANR-18-EURE-0013,NANO-PHOT,Graduate School in Nano-optics and Nanophotonics(2018)
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Condensed Matter::Quantum Gases ,[PHYS]Physics [physics] ,Materials science ,Condensed matter physics ,Physics::Optics ,Orientation (graph theory) ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,[SPI]Engineering Sciences [physics] ,General Energy ,Electric field ,[CHIM]Chemical Sciences ,Photoluminescence excitation ,Physics::Chemical Physics ,Physical and Theoretical Chemistry ,Plasmon ,Excitation ,ComputingMilieux_MISCELLANEOUS - Abstract
Gold bipyramids (AuBPs) attract significant attention due to the large enhancement of the electric field around their sharp tips and well-defined tunability of their plasmon resonances. Excitation ...
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- 2021
78. Synthetic Ligand Selection Affects Stoichiometry, Carrier Dynamics, and Trapping in CuInSe
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Samantha M, Harvey, Daniel W, Houck, Wen, Liu, Yuzi, Liu, David J, Gosztola, Brian A, Korgel, Michael R, Wasielewski, and Richard D, Schaller
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CuInSe
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- 2021
79. Layered Structures of Assembled Imine-Linked Macrocycles and Two-Dimensional Covalent Organic Frameworks Give Rise to Prolonged Exciton Lifetimes
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Matthew S. Kirschner, George C. Schatz, Brian T. Phelan, Richard D. Schaller, Shiwei Wang, Austin P. Spencer, William R. Dichtel, Nathan C. Flanders, Lin X. Chen, Rebecca L. Li, Dillon Edwards, Pyosang Kim, Waleed Helweh, Michael A. Strauss, and Matthew S. Kelley
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Nanotube ,Materials science ,Exciton ,Transition dipole moment ,Imine ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,Internal conversion (chemistry) ,Condensed Matter::Materials Science ,chemistry.chemical_compound ,chemistry ,Chemical physics ,Covalent bond ,Excited state ,Macromolecule - Abstract
Ordered organic materials and assemblies have great potential to be tailored to have desirable properties for optoelectronic applications, such as long exciton lifetime and high directional exciton mobility. Framework materials, such as twodimensional covalent organic frameworks (2D COFs), as well as their truncated macrocyclic analogues, are versatile platforms to organize functional aromatic systems into designed assemblies and robust materials. Here we investigate the exciton dynamics in a 2D COF, its corresponding hexagonal macrocycle, and extended nanotubes comprised of stacked macrocycles. The excitonic behavior of these three systems provide an understanding of excitonic processes that occur in the plane of the covalently bonded 2D macromolecules and between layers of the nanotubes and 2D COF. The nanotube and analogous 2D COF exhibit longer excited-state lifetimes (~100 ps) compared to the individual, solvated macrocycles (
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- 2021
80. Coherent control of asymmetric spintronic terahertz emission from two-dimensional hybrid metal halides
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Richard D. Schaller, Dali Sun, Yongxin Yao, Qi Zhang, Yi Li, Haidan Wen, Jigang Wang, Wei You, Liang Yan, Hongwei Qu, Kankan Cong, Wei Zhang, Axel Hoffmann, Eric Vetter, Alexander F. Kemper, and Yuzan Xiong
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Electronic properties and materials ,Materials science ,Terahertz radiation ,Science ,Physics::Medical Physics ,Physics::Optics ,General Physics and Astronomy ,Two-dimensional materials ,Article ,General Biochemistry, Genetics and Molecular Biology ,law.invention ,Condensed Matter::Materials Science ,law ,Terahertz optics ,Multidisciplinary ,Spintronics ,Condensed Matter::Other ,business.industry ,Linear polarization ,General Chemistry ,Laser ,Coherent control ,Femtosecond ,Optoelectronics ,business ,Ultrashort pulse ,Excitation - Abstract
Next-generation terahertz (THz) sources demand lightweight, low-cost, defect-tolerant, and robust components with synergistic, tunable capabilities. However, a paucity of materials systems simultaneously possessing these desirable attributes and functionalities has made device realization difficult. Here we report the observation of asymmetric spintronic-THz radiation in Two-Dimensional Hybrid Metal Halides (2D-HMH) interfaced with a ferromagnetic metal, produced by ultrafast spin current under femtosecond laser excitation. The generated THz radiation exhibits an asymmetric intensity toward forward and backward emission direction whose directionality can be mutually controlled by the direction of applied magnetic field and linear polarization of the laser pulse. Our work demonstrates the capability for the coherent control of THz emission from 2D-HMHs, enabling their promising applications on the ultrafast timescale as solution-processed material candidates for future THz emitters., Terahertz radiation has wide array of potential uses, however, finding robust and tunable sources of terahertz radiation has been challenging. Here, Cong et al demonstrate a room temperature terahertz source composed of a two-dimensional hybrid metal halide and ferromagnetic heterostructure.
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- 2021
81. Designing plasmonic nanoparticle lattices for directional, in-plane lasing
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Marc R. Bourgeois, Jun Guan, George C. Schatz, Teri W. Odom, Ran Li, Jingtian Hu, and Richard D. Schaller
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Physics ,Brillouin zone ,Reciprocal lattice ,Photon ,Optics ,Scattering ,business.industry ,Nanolaser ,Light cone ,Physics::Optics ,business ,Lasing threshold ,Plasmon - Abstract
Band structures engineering of periodic optical structures enables the control of light propagation and localization. Although photons trapped inside 2D lattices can be described within the first Brillouin zone in reciprocal space, the wavevectors of scattered photons outside the lattice are limited by the 3D light cone, which depicts the free-photon dispersion in the surroundings. Because plasmonic nanoparticle lattices show unique dual properties of light trapping and strong scattering, this material platform is promising for investigations of radiative losses. This talk describes how light-cone surface lattice resonance (SLRs) from plasmonic nanoparticle lattices allow the observation of radiated electromagnetic fields. We theoretically predicted the angular distributions of the radiated fields, and experimentally probed the light-cone SLR modes by in-plane lasing emission. These results provide a nanolaser design strategy to achieve tunable lasing colors by lattice rotation.
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- 2021
82. Tailoring the Thickness‐Dependent Optical Properties of Conducting Nitrides and Oxides for Epsilon‐Near‐Zero‐Enhanced Photonic Applications
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Soham Saha, Mustafa Goksu Ozlu, Sarah N. Chowdhury, Benjamin T. Diroll, Richard D. Schaller, Alexander Kildishev, Alexandra Boltasseva, and Vladimir M. Shalaev
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Mechanics of Materials ,Mechanical Engineering ,General Materials Science - Abstract
The unique properties of the emerging photonic materials, conducting nitrides and oxides, especially their tailorability, large damage thresholds, and, importantly, the so-called epsilon-near-zero (ENZ) behavior, have enabled novel photonic phenomena spanning optical circuitry, tunable metasurfaces, and nonlinear optical devices. This work explores direct control of the optical properties of polycrystalline titanium nitride (TiN) and aluminum-doped zinc oxide (AZO) by tailoring the film thickness, and their potential for ENZ-enhanced photonic applications. This study demonstrates that TiN-AZO bilayers support Ferrell-Berreman modes using the thickness-dependent ENZ resonances in the AZO films operating in the telecom wavelengths spanning from 1470 to 1750 nm. The bilayer stacks also act as strong light absorbers in the ultraviolet regime using the radiative ENZ modes and the Fabry-Perot modes in the constituent TiN films. The studied Berreman resonators exhibit optically induced reflectance modulation of 15% with picosecond response time. Together with the optical response tailorability of conducting oxides and nitrides, using the field enhancement near the tunable ENZ regime can enable a wide range of nonlinear optical phenomena, including all-optical switching, time refraction, and high-harmonic generation.
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- 2022
83. Controlling polarization of spintronic THz emitter by remanent magnetization texture
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Weipeng Wu, Sergi Lendinez, Mojtaba Taghipour Kaffash, Richard D. Schaller, Haidan Wen, and M. Benjamin Jungfleisch
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Condensed Matter - Materials Science ,Condensed Matter - Mesoscale and Nanoscale Physics ,Physics and Astronomy (miscellaneous) ,Mesoscale and Nanoscale Physics (cond-mat.mes-hall) ,Physics::Optics ,Materials Science (cond-mat.mtrl-sci) ,FOS: Physical sciences ,Applied Physics (physics.app-ph) ,Physics - Applied Physics ,Optics (physics.optics) ,Physics - Optics - Abstract
Terahertz (THz) sciences and technologies have contributed to a rapid development of a wide range of applications and expanded the frontiers in fundamental science. Spintronic terahertz emitters offer conceptual advantages since the spin orientation in the magnetic layer can be easily controlled either by the externally applied magnetic field or by the internal magnetic field distribution determined by the specific shape of the magnetic elements. Here, we report a switchable terahertz source based on micropatterned magnetic heterostructures driven by femtosecond laser pulses. We show that the precise tunability of the polarization state is facilitated by the underlying magnetization texture of the magnetic layer that is dictated by the shape of the microstructure. These results also reveal the underlying physical mechanisms of a nonuniform magnetization state on the generation of ultrafast spin currents in the magnetic heterostructures. Our findings indicate that the emission of the linearly polarized THz waves can be switched on and off by saturating the sample using a biasing magnetic field, opening fascinating perspectives for integrated on-chip THz devices with wide-ranging potential applications.
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- 2022
84. Vibrational relaxation dynamics in layered perovskite quantum wells
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Richard D. Schaller, David T. Limmer, Adam M. Schwartzberg, Jianmei Huang, Peidong Yang, Jason K Copper, Mengyu Gao, Li Na Quan, Yoonjae Park, Jianbo Jin, and Peijun Guo
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Materials science ,Phonon ,Dephasing ,FOS: Physical sciences ,Ionic bonding ,02 engineering and technology ,Dielectric ,010402 general chemistry ,01 natural sciences ,layered perovskites ,Condensed Matter::Materials Science ,coherent phonon ,perovskite quantum wells ,Ruddlesden-Popper perovskites ,Physics - Chemical Physics ,Vibrational energy relaxation ,dynamic disorder ,Physics::Chemical Physics ,Condensed Matter - Statistical Mechanics ,Perovskite (structure) ,Chemical Physics (physics.chem-ph) ,Condensed Matter - Materials Science ,Multidisciplinary ,Statistical Mechanics (cond-mat.stat-mech) ,Materials Science (cond-mat.mtrl-sci) ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,Photoexcitation ,Ruddlesden–Popper perovskites ,Chemical physics ,Physical Sciences ,  ,Relaxation (physics) ,Condensed Matter::Strongly Correlated Electrons ,0210 nano-technology - Abstract
Organic-inorganic layered perovskites are two-dimensional quantum wells with layers of lead-halide octahedra stacked between organic ligand barriers. The combination of their dielectric confinement and ionic sublattice results in excitonic excitations with substantial binding energies that are strongly coupled to the surrounding soft, polar lattice. However, the ligand environment in layered perovskites can significantly alter their optical properties due to the complex dynamic disorder of soft perovskite lattice. Here, we observe the dynamic disorder through phonon dephasing lifetimes initiated by ultrafast photoexcitation employing high-resolution resonant impulsive stimulated Raman spectroscopy of a variety of ligand substitutions. We demonstrate that vibrational relaxation in layered perovskite formed from flexible alkyl-amines as organic barriers is fast and relatively independent of the lattice temperature. Relaxation in aromatic amine based layered perovskite is slower, though still fast relative to pure inorganic lead bromide lattices, with a rate that is temperature dependent. Using molecular dynamics simulations, we explain the fast rates of relaxation by quantifying the large anharmonic coupling of the optical modes with the ligand layers and rationalize the temperature independence due to their amorphous packing. This work provides a molecular and time-domain depiction of the relaxation of nascent optical excitations and opens opportunities to understand how they couple to the complex layered perovskite lattice, elucidating design principles for optoelectronic devices., 7 pages, 4 figures, SI
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- 2021
85. Novel UEM Setup for Improved Resolution and Extended Experimental Capabilities
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Richard D. Schaller, Thomas E. Gage, Ilke Arslan, and Haihua Liu
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Optics ,Materials science ,business.industry ,Resolution (electron density) ,business ,Instrumentation - Published
- 2020
86. Aqueous Carbon Quantum Dot-Embedded PC60-PC61BM Nanospheres for Ecological Fluorescent Printing: Contrasting Fluorescence Resonance Energy-Transfer Signals between Watermelon-like and Random Morphologies
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Richard D. Schaller, Peijun Guo, and Yu Jin Kim
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Photoluminescence ,Fullerene ,Materials science ,Quantum yield ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Fluorescence ,Micelle ,0104 chemical sciences ,Förster resonance energy transfer ,Quantum dot ,Chemical physics ,Particle ,General Materials Science ,Physical and Theoretical Chemistry ,0210 nano-technology - Abstract
To go beyond the PC60 surfactant structure, the double-layer micelle morphology in water motivates exploration of altered protocols to produce new morphologies. Furthermore, the low photoluminescence quantum yield of aqueous fullerene-based particles encourages high fluorescence to create a light-emitting display. With this in mind, we established new hybrid n-type nanospheres with carbon quantum dot (CQD)-embedded PC60-PC61BM particles, processed using two different protocols. The homogenizer-assisted PC60-CQD-PC61BM resulted in a watermelon-shaped spherical particle, whereas a circular morphology with randomly embedded CQDs was observed in the microwave-treated hybrids. More surprisingly, the watermelon-shaped colloid induced efficient fluorescence resonance energy transfer (FRET) between the CQD and C60 molecules of PC61BM, and the FRET-mediated emission signature diminished gradually as the stripe patterns collapsed. This phenomenon allowed different fluorescent colors in the colloidal printing film. ...
- Published
- 2019
87. Photo-accelerated fast charging of lithium-ion batteries
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Hakim Iddir, Victor A. Maroni, Eungje Lee, Anna Lee, Oleg G. Poluektov, Márton Vörös, Jens Niklas, Larry A. Curtiss, Richard D. Schaller, Wesley M. Dose, Christopher S. Johnson, and Brian J. Ingram
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Battery (electricity) ,Materials science ,Energy science and technology ,Science ,General Physics and Astronomy ,chemistry.chemical_element ,02 engineering and technology ,Electron ,010402 general chemistry ,Electrochemistry ,01 natural sciences ,General Biochemistry, Genetics and Molecular Biology ,Article ,Ion ,law.invention ,law ,lcsh:Science ,Multidisciplinary ,business.industry ,General Chemistry ,021001 nanoscience & nanotechnology ,Cathode ,0104 chemical sciences ,Microsecond ,Chemistry ,chemistry ,Optoelectronics ,Lithium ,lcsh:Q ,0210 nano-technology ,business ,Voltage - Abstract
Due to their exceptional high energy density, lithium-ion batteries are of central importance in many modern electrical devices. A serious limitation, however, is the slow charging rate used to obtain the full capacity. Thus far, there have been no ways to increase the charging rate without losses in energy density and electrochemical performance. Here we show that the charging rate of a cathode can be dramatically increased via interaction with white light. We find that a direct exposure of light to an operating LiMn2O4 cathode during charging leads to a remarkable lowering of the battery charging time by a factor of two or more. This enhancement is enabled by the induction of a microsecond long-lived charge separated state, consisting of Mn4+ (hole) plus electron. This results in more oxidized metal centers and ejected lithium ions are created under light and with voltage bias. We anticipate that this discovery could pave the way to the development of new fast recharging battery technologies., Here the authors show that illumination of a lithium manganese oxide cathode can induce efficient charge-separation and electron transfer processes, thus giving rise to a new type of fast lithium-ion battery charging.
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- 2019
88. Polarized near-infrared intersubband absorptions in CdSe colloidal quantum wells
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Menglu Chen, Philippe Guyot-Sionnest, Richard D. Schaller, Benjamin T. Diroll, Kali R. Williams, Igor Coropceanu, and Dmitri V. Talapin
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Materials science ,Nonlinear optics ,Infrared ,Science ,General Physics and Astronomy ,Physics::Optics ,02 engineering and technology ,Electronic structure ,Electron ,010402 general chemistry ,01 natural sciences ,General Biochemistry, Genetics and Molecular Biology ,Article ,symbols.namesake ,Condensed Matter::Materials Science ,Absorption (electromagnetic radiation) ,lcsh:Science ,Quantum well ,Astrophysics::Galaxy Astrophysics ,Multidisciplinary ,Auger effect ,business.industry ,Condensed Matter::Other ,General Chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,0104 chemical sciences ,Photoexcitation ,Optics and photonics ,symbols ,Optoelectronics ,Nanoparticles ,lcsh:Q ,0210 nano-technology ,business ,Lasing threshold - Abstract
Colloidal quantum wells are two-dimensional materials grown with atomically-precise thickness that dictates their electronic structure. Although intersubband absorption in epitaxial quantum wells is well-known, analogous observations in non-epitaxial two-dimensional materials are sparse. Here we show that CdSe nanoplatelet quantum wells have narrow (30–200 meV), polarized intersubband absorption features when photoexcited or under applied bias, which can be tuned by thickness across the near-infrared (NIR) spectral window (900–1600 nm) inclusive of important telecommunications wavelengths. By examination of the optical absorption and polarization-resolved measurements, the NIR absorptions are assigned to electron intersubband transitions. Under photoexcitation, the intersubband features display hot carrier and Auger recombination effects similar to excitonic absorptions. Sequenced two-color photoexcitation permits the sub-picosecond modulation of the carrier temperature in such colloidal quantum wells. This work suggests that colloidal quantum wells may be promising building blocks for NIR technologies., Multiple infrared lasing and detection technologies exploit intersubband transitions of epitaxial quantum wells, but such transitions are mainly limited to the mid-infrared. Here, the authors report narrow, polarized intersubband transitions up to telecom wavelengths in CdSe colloidal quantum wells.
- Published
- 2019
89. Pathways for the Photoreduction of Fumarate on ZnS
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David M. Mangiante, Jillian F. Banfield, Richard D. Schaller, and Benjamin Gilbert
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Atmospheric Science ,education ,technology, industry, and agriculture ,food and beverages ,Mineralization (soil science) ,equipment and supplies ,Photochemistry ,Redox ,Carbon cycle ,chemistry.chemical_compound ,Metabolic pathway ,chemistry ,Space and Planetary Science ,Geochemistry and Petrology ,Carbon dioxide ,Photocatalysis ,Mineral particles - Abstract
Semiconductor mineral particles can act as photocatalysts for organic redox reactions that occur enzymatically in modern biological metabolic pathways. Semiconductor mineral-mediated photocatalysis...
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- 2019
90. Two-Dimensional Dion–Jacobson Hybrid Lead Iodide Perovskites with Aromatic Diammonium Cations
- Author
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Weijun Ke, Mikael Kepenekian, Jacky Even, Ido Hadar, Xiaotong Li, Mercouri G. Kanatzidis, Peijun Guo, Richard D. Schaller, Claudine Katan, Boubacar Traore, Constantinos C. Stoumpos, Northwestern University [Evanston], Institut des Fonctions Optiques pour les Technologies de l'informatiON (Institut FOTON), Université de Rennes (UR)-Institut National des Sciences Appliquées - Rennes (INSA Rennes), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-École Nationale Supérieure des Sciences Appliquées et de Technologie (ENSSAT)-Centre National de la Recherche Scientifique (CNRS), Argonne National Laboratory [Lemont] (ANL), The Hebrew University of Jerusalem (HUJ), Institut des Sciences Chimiques de Rennes (ISCR), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Ecole Nationale Supérieure de Chimie de Rennes (ENSCR)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), W. M. Keck Foundation, Institut Universitaire de France, 1720139, Division of Materials Research, International Institute for Nanotechnology, Northwestern University, R?gion Bretagne, State of Illinois, Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Institut National des Sciences Appliquées - Rennes (INSA Rennes), Institut National des Sciences Appliquées (INSA)-Université de Rennes (UNIV-RENNES)-Institut National des Sciences Appliquées (INSA)-École Nationale Supérieure des Sciences Appliquées et de Technologie (ENSSAT)-Centre National de la Recherche Scientifique (CNRS)-IMT Atlantique Bretagne-Pays de la Loire (IMT Atlantique), Institut Mines-Télécom [Paris] (IMT)-Institut Mines-Télécom [Paris] (IMT), Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Ecole Nationale Supérieure de Chimie de Rennes (ENSCR)-Institut National des Sciences Appliquées - Rennes (INSA Rennes), and Institut National des Sciences Appliquées (INSA)-Université de Rennes (UNIV-RENNES)-Institut National des Sciences Appliquées (INSA)
- Subjects
Photoluminescence ,solar cell devices ,Iodide ,Stacking ,Halide ,Dielectric ,010402 general chemistry ,7. Clean energy ,01 natural sciences ,Biochemistry ,Catalysis ,chemistry.chemical_compound ,Colloid and Surface Chemistry ,halide perovskites ,[CHIM]Chemical Sciences ,Perovskite (structure) ,[PHYS]Physics [physics] ,chemistry.chemical_classification ,General Chemistry ,natural quantum-wells ,0104 chemical sciences ,Crystallography ,Octahedron ,chemistry ,dielectric constant ,photoluminescence ,Pyridinium ,exciton binding energy - Abstract
International audience; Two-dimensional (2D) halide perovskites have extraordinary optoelectronic properties and structural tunability. Among them, the Dion-Jacobson phases with the inorganic layers stacking exactly on top of each other are less explored. Herein, we present the new series of 2D Dion-Jacobson halide perovskites, which adopt the general formula of A′An-1PbnI3n+1 (A′ = 4-(aminomethyl)pyridinium (4AMPY), A = methylammonium (MA), n = 1−4). By modifying the position of the -CH2NH3+ group from 4AMPY to 3AMPY (3AMPY = 3-(aminomethyl)pyridinium), the stacking of the inorganic layers changes from exactly eclipsed to slightly offset. The perovskite octahedra tilts are also different between the two series, with the 3AMPY series exhibiting smaller bandgaps than the 4AMPY series. Compared to the aliphatic cation of the same size (AMP = (aminomethyl)piperidinium), the aromatic spacers increase the rigidity of the cation, reduce the interlayer spacing and decrease the dielectric mismatch between inorganic layer and the organic spacer, showing the indirect but powerful influence of the organic cations on the structure and consequently on the optical properties of the perovskite materials. All A′An-1PbnI3n+1 compounds exhibit strong photoluminescence (PL) at room temperature. Preliminary solar cell devices based on the n = 4 perovskites as absorbers of both series exhibit promising performances, with a champion power conversion efficiency (PCE) of 9.20 % for (3AMPY)(MA)3Pb4I13 based devices, which is higher than the (4AMPY)(MA)3Pb4I13 and the corresponding aliphatic analogue (3AMP)(MA)3Pb4I13 based ones.
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- 2019
91. Buckling and twisting of advanced materials into morphable 3D mesostructures
- Author
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Cunman Liang, Abraham Vázquez-Guardado, Yonggang Huang, Heling Wang, Yoonseok Park, Lin Chen, John A. Rogers, Yeguang Xue, Zhaoqian Xie, Peijun Guo, Haiwen Luan, Richard D. Schaller, Mengdi Han, Yihui Zhang, Kan Li, Feng Zhu, Xueju Wang, Hangbo Zhao, Debashis Chanda, Yiyuan Yang, Luan, Haiwen [0000-0003-0722-1108], Xue, Yeguang [0000-0002-1968-5092], and Apollo - University of Cambridge Repository
- Subjects
Multidisciplinary ,Characteristic length ,Computer science ,Terahertz radiation ,three-dimensional fabrication ,Process (computing) ,Mechanical engineering ,Metamaterial ,kirigami ,metamaterials ,Transformation (function) ,PNAS Plus ,Buckling ,origami ,Stress relaxation ,Computational electromagnetics - Abstract
Recently developed methods in mechanically guided assembly provide deterministic access to wide-ranging classes of complex, 3D structures in high-performance functional materials, with characteristic length scales that can range from nanometers to centimeters. These processes exploit stress relaxation in prestretched elastomeric platforms to affect transformation of 2D precursors into 3D shapes by in- and out-of-plane translational displacements. This paper introduces a scheme for introducing local twisting deformations into this process, thereby providing access to 3D mesostructures that have strong, local levels of chirality and other previously inaccessible geometrical features. Here, elastomeric assembly platforms segmented into interconnected, rotatable units generate in-plane torques imposed through bonding sites at engineered locations across the 2D precursors during the process of stress relaxation. Nearly 2 dozen examples illustrate the ideas through a diverse variety of 3D structures, including those with designs inspired by the ancient arts of origami/kirigami and with layouts that can morph into different shapes. A mechanically tunable, multilayered chiral 3D metamaterial configured for operation in the terahertz regime serves as an application example guided by finite-element analysis and electromagnetic modeling.
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- 2019
92. Determination of the In-Plane Exciton Radius in 2D CdSe Nanoplatelets via Magneto-optical Spectroscopy
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John P. Philbin, Michael R. Wasielewski, Eran Rabani, Benjamin T. Diroll, Byeongdu Lee, Samantha M. Harvey, Alexandra Brumberg, Scott A. Crooker, and Richard D. Schaller
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Materials science ,Absorption spectroscopy ,Condensed matter physics ,business.industry ,Exciton ,General Engineering ,General Physics and Astronomy ,02 engineering and technology ,Dielectric ,Electronic structure ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Condensed Matter::Materials Science ,Semiconductor ,Quantum dot ,Diamagnetism ,General Materials Science ,0210 nano-technology ,business ,Spectroscopy - Abstract
Colloidal, two-dimensional semiconductor nanoplatelets (NPLs) exhibit quantum confinement in only one dimension, which results in an electronic structure that is significantly altered compared to that of other quantum-confined nanomaterials. Whereas it is often assumed that the lack of quantum confinement in the lateral plane yields a spatially extended exciton, reduced dielectric screening potentially challenges this picture. Here, we implement absorption spectroscopy in pulsed magnetic fields up to 60 T for three different CdSe NPL thicknesses and lateral areas. Based on diamagnetic shifts, we find that the exciton lateral extent is comparable to NPL thickness, indicating that the quantum confinement and reduced screening concomitant with few-monolayer thickness strongly reduces the exciton lateral extent. Atomistic electronic structure calculations of the exciton size for varying lengths, widths, and thicknesses support the substantially smaller in-plane exciton extent.
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- 2019
93. Optical and Physical Probing of Thermal Processes in Semiconductor and Plasmonic Nanocrystals
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Richard D. Schaller, Matthew S. Kirschner, Peijun Guo, and Benjamin T. Diroll
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Materials science ,Photoluminescence ,Phonon ,business.industry ,Physics::Optics ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Nanomaterials ,Condensed Matter::Materials Science ,Semiconductor ,Nanocrystal ,Thermal ,Optoelectronics ,Semiconductor nanocrystals ,Physical and Theoretical Chemistry ,0210 nano-technology ,business ,Plasmon - Abstract
This article reviews thermal properties of semiconductor and emergent plasmonic nanomaterials, focusing on mechanisms through which hot carriers and phonons are produced and dissipated as well as the related impacts on optoelectronic properties. Elevated equilibrium temperatures, of particular relevance for implementation of nanomaterials in devices, affect absorptive and radiative transitions as well as emission efficiency that can present reversible and irreversible changes with temperature. In noble metal or doped semiconductor/insulator nanomaterials, hot carriers and lattice heating can substantially influence localized surface plasmon resonances and yield large ultrafast changes in transmission or strongly oscillatory coherences. Transient optical and diffraction characterizations enable nonequilibrium investigations of phonon dynamics and cooling such as lattice expansion and crystal phase stability. Timescales of nanoparticle thermalization with surroundings and transport of heat within films of such materials are also discussed.
- Published
- 2019
94. Shape-Selective Optical Transformations of CdSe Nanoplatelets Driven by Halide Ion Ligand Exchange
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Richard D. Schaller and Benjamin T. Diroll
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Materials science ,Ligand ,General Chemical Engineering ,Physics::Optics ,Halide ,02 engineering and technology ,General Chemistry ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Photochemistry ,01 natural sciences ,0104 chemical sciences ,Condensed Matter::Materials Science ,Quantum dot ,Bathochromic shift ,Materials Chemistry ,Absorption (chemistry) ,0210 nano-technology - Abstract
Treatment of CdSe nanoplatelets with halide salts induces a bathochromic shift in the absorption resonances that does not occur in quasi-spherical quantum dots of the same composition. The optical ...
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- 2019
95. Quintet-triplet mixing determines the fate of the multiexciton state produced by singlet fission in a terrylenediimide dimer at room temperature
- Author
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Matthew D. Krzyaniak, Jordan N. Nelson, Richard D. Schaller, Michael R. Wasielewski, Samantha M. Harvey, Youn Jue Bae, Michelle Chen, and Ryan M. Young
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Physics ,Multidisciplinary ,Annihilation ,Absorption spectroscopy ,Spin states ,Dimer ,Molecular physics ,law.invention ,chemistry.chemical_compound ,chemistry ,law ,Liquid crystal ,Physical Sciences ,Singlet fission ,Molecule ,Electron paramagnetic resonance - Abstract
Singlet fission (SF) is a photophysical process in which one of two adjacent organic molecules absorbs a single photon, resulting in rapid formation of a correlated triplet pair (T(1)T(1)) state whose spin dynamics influence the successful generation of uncorrelated triplets (T(1)). Femtosecond transient visible and near-infrared absorption spectroscopy of a linear terrylene-3,4:11,12-bis(dicarboximide) dimer (TDI(2)), in which the two TDI molecules are directly linked at one of their imide positions, reveals ultrafast formation of the (T(1)T(1)) state. The spin dynamics of the (T(1)T(1)) state and the processes leading to uncoupled triplets (T(1)) were studied at room temperature for TDI(2) aligned in 4-cyano-4′-pentylbiphenyl (5CB), a nematic liquid crystal. Time-resolved electron paramagnetic resonance spectroscopy shows that the (T(1)T(1)) state has mixed (5)(T(1)T(1)) and (3)(T(1)T(1)) character at room temperature. This mixing is magnetic field dependent, resulting in a maximum triplet yield at ∼200 mT. The accessibility of the (3)(T(1)T(1)) state opens a pathway for triplet–triplet annihilation that produces a single uncorrelated T(1) state. The presence of the (5)(T(1)T(1)) state at room temperature and its relationship with the (1)(T(1)T(1)) and (3)(T(1)T(1)) states emphasize that understanding the relationship among different (T(1)T(1)) spin states is critical for ensuring high-yield T(1) formation from singlet fission.
- Published
- 2019
96. Polarization-Dependent Lasing Behavior from Low-Symmetry Nanocavity Arrays
- Author
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Richard D. Schaller, Danqing Wang, Michael P. Knudson, Weijia Wang, Ran Li, and Teri W. Odom
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Diffraction ,Materials science ,business.industry ,General Engineering ,Physics::Optics ,General Physics and Astronomy ,Nanoparticle ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Polarization (waves) ,01 natural sciences ,0104 chemical sciences ,Dipole ,Excited state ,Electric field ,Optoelectronics ,General Materials Science ,0210 nano-technology ,business ,Lasing threshold ,Plasmon - Abstract
This paper reports how geometric effects in low-symmetry plasmonic nanoparticle arrays can produce polarization-dependent lasing responses. We developed a scalable fabrication procedure to pattern rhombohedral arrays of aluminum anisotropic nanoparticles that support lattice plasmon modes from both first-order and second-order diffraction coupling. We found that nanoparticle shape can be used to engineer the spatial overlap between electromagnetic hot spots of different lattice modes and dye gain to support plasmonic lasing. The lasing behavior revealed that plasmon-exciton energy transfer depends on polarization, with stronger coupling and faster dynamics when the transition dipole moments of the excited gain are aligned with the electric field of the plasmon modes.
- Published
- 2019
97. Thermal Excitation Control over Photon Emission Rate of CdSe Nanocrystals
- Author
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Richard D. Schaller and Benjamin T. Diroll
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Photoluminescence ,Materials science ,Condensed Matter::Other ,Infrared ,Astrophysics::High Energy Astrophysical Phenomena ,Mechanical Engineering ,Exciton ,Physics::Optics ,Bioengineering ,02 engineering and technology ,General Chemistry ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Molecular physics ,Condensed Matter::Materials Science ,Nanocrystal ,Cdse nanocrystals ,Heat transfer ,Thermal ,General Materials Science ,0210 nano-technology ,Excitation - Abstract
Temperature-dependent photoluminescence lifetimes of electron-hole pairs (excitons) in CdSe nanocrystals are governed by the energetic ordering and spacing of slowly emitting, spin-forbidden "dark" exciton states and rapidly emitting "bright" states. Here, infrared pulses that are resonant with hydrocarbon surface ligand vibrational transitions are shown to offer a route to manipulate the instantaneous emission rate of CdSe nanocrystals at cryogenic temperature. Transient heating of the inorganic nanocrystal core is achieved via resonant excitation of ligand vibrations, followed by heat flow to the nanocrystal lattice. Heating of the nanocrystal core is demonstrated using transient absorption spectroscopy, which shows a time-dependent red-shift of the quantum dot electronic absorption resonances, consistent with heating. Transient heating of the nanocrystal above the bath temperature increases the instantaneous radiative rate of the nanocrystals via a combination of thermal occupation of bright states as well as phonon-assisted emission. The lifetime of this infrared-pumped, fast-emitting sample condition is dictated by particle thermalization, which is multiple orders of magnitude shorter lived than the dark exciton state. This work demonstrates the feasibility of using heat control pulses to manipulate electronic recombination rates of excitons.
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- 2019
98. Reducing the Optical Gain Threshold in Two-Dimensional CdSe Nanoplatelets by the Giant Oscillator Strength Transition Effect
- Author
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Qiuyang Li, Richard D. Schaller, Tianquan Lian, and Qiliang Liu
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Work (thermodynamics) ,Materials science ,business.industry ,Oscillator strength ,Exciton ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Ultrafast laser spectroscopy ,Optoelectronics ,General Materials Science ,Physical and Theoretical Chemistry ,0210 nano-technology ,business ,Spectroscopy ,Lasing threshold ,Saturation (magnetic) ,Biexciton - Abstract
Two-dimensional CdSe nanoplatelets are promising lasing materials. Their large lateral areas reduce the optical gain threshold by increasing the oscillator strength and multiexciton lifetimes but also increase the gain threshold by requiring multiple band-edge excitons (2) to reach the optical gain. We observe that the optical gain threshold of CdSe nanoplatelets at 4 K is ∼4-fold lower than that at room temperature. Transient absorption spectroscopy measurements indicate that the exciton center-of-mass coherent area is smaller than the lateral size at room temperature and extends to nearly the whole nanoplatelets at 4 K. This suggests that the reduction in the optical gain threshold at a low temperature can be attributed to exciton coherent area extension that reduces the saturation number of band-edge excitons to enable biexciton gain and increases the radiative decay rate, consistent with the giant oscillator strength transition effect. This work demonstrates a new direction for lowering the optical gain threshold of nanomaterials.
- Published
- 2019
99. Charge Transfer Dynamics of Phase-Segregated Halide Perovskites: CH3NH3PbCl3 and CH3NH3PbI3 or (C4H9NH3)2(CH3NH3)n−1PbnI3n+1 Mixtures
- Author
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Arun Mannodi-Kanakkithodi, Peijun Guo, Maria K. Y. Chan, David J. Gosztola, Duyen H. Cao, Richard D. Schaller, Alex B. F. Martinson, Nari Jeon, and Gary P. Wiederrecht
- Subjects
010302 applied physics ,Materials science ,Band gap ,Scanning electron microscope ,business.industry ,Halide ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Epitaxy ,01 natural sciences ,Semiconductor ,Chemical physics ,Phase (matter) ,0103 physical sciences ,General Materials Science ,0210 nano-technology ,Absorption (electromagnetic radiation) ,business ,Perovskite (structure) - Abstract
Lead halide perovskites present a versatile class of solution-processable semiconductors with highly tunable bandgaps that span ultraviolet, visible, and near-infrared portions of the spectrum. We explore phase-separated chloride and iodide lead perovskite mixtures as candidate materials for intermediate band applications in future photovoltaics. X-ray diffraction and scanning electron microscopy reveal that deposition of precursor solutions across the MAPbCl3/MAPbI3 composition space affords quasi-epitaxial cocrystallized films, in which the two perovskites do not alloy but instead remain phase-segregated. First-principle calculations further support the formation of an epitaxial interface and predict energy offsets in the valence band and conduction band edges that could result in intermediate energy absorption. The charge dynamics of variable mixtures of the relatively narrow bandgap (1.57 eV) MAPbI3 perovskite and wide bandgap (3.02 eV) MAPbCl3 are probed to map charge and energy flow direction and ki...
- Published
- 2019
100. Energy-distinguishable bipolar UV photoelectron injection from LiCl-promoted FAPbCl3 perovskite nanorods
- Author
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Richard D. Schaller, Wei Huang, Yingwen Cheng, Tao Xu, Peijun Guo, Ian Zhang, Ke Lu, Xun Li, Tobin J. Marks, and Jue Gong
- Subjects
Nanostructure ,Materials science ,Renewable Energy, Sustainability and the Environment ,business.industry ,Halide ,02 engineering and technology ,General Chemistry ,021001 nanoscience & nanotechnology ,Crystallinity ,Formamidinium ,Optoelectronics ,Energy transformation ,General Materials Science ,Nanorod ,0210 nano-technology ,business ,Perovskite (structure) ,Diode - Abstract
High-performance optoelectronic devices, such as solar cells and light-emitting diodes, have been fabricated with lead halide perovskites owing to their superior carrier properties. However, charge transport in such optoelectronics is intrinsically directional due to the existence of p–n junctions, which thus lacks the potential to elucidate any perturbations in light or electricity during energy conversion. Here, with the presence of a LiCl additive in a formamidinium chloride (FACl) solution, the as-grown LiCl:FAPbCl3 nanorods demonstrate greatly enhanced crystallinity and UV photoresponse as compared to pristine FAPbCl3 nanostructures without the LiCl additive. Most importantly, the LiCl:FAPbCl3 nanorod film exhibits unprecedented distinguishability to UV photons with different energies and oscillating intensities, in the form of bipolar and periodically oscillatory photocurrents. This work could advance the fundamental understanding of photoinduced carrier processes in halide perovskites and facilitate the development of novel UV-based optical communications.
- Published
- 2019
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