24 results on '"Vladimir Bulovic"'
Search Results
2. Guaranteed global optimization of thin-film optical systems
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Paul Azunre, Joel Jean, Carmel Rotschild, Vladimir Bulovic, Steven G Johnson, and Marc A Baldo
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deterministic global optimization ,thin film optical filters ,solar energy ,optical system design ,Science ,Physics ,QC1-999 - Abstract
A parallel deterministic global optimization algorithm for thin-film multilayer optical coatings is developed. This algorithm enables locating a global solution to an optimization problem in this class to within a user-specified tolerance. More specifically, the algorithm is a parallel branch-and-bound method with applicable bounds on the merit function computed using Taylor models. This study is the first one, to the best of our knowledge, to attempt guaranteed global optimization of this important class of problems, thereby providing an overview and an assessment of the current state of such techniques in this domain. As a proof of concept on a small scale, the method is illustrated numerically and experimentally in the context of antireflection coatings for silicon solar cells—we design and fabricate a three-layer dielectric stack on silicon that exhibits an average reflectance of (2.53 ± 0.10)%, weighted over a broad range of incident angles and the solar spectrum. The practicality of our approach is assessed by comparing its computational cost relative to traditional stochastic global optimization techniques which provide no guarantees on their solutions. While our method is observed to be significantly more computationally expensive, we demonstrate via our proof of concept that it is already feasible to optimize sufficiently simple practical problems at a reasonable cost, given the current accessibility of cloud computing resources. Ongoing advances in distributed computing are likely to bring more design problems within the reach of deterministic global optimization methods, yielding rigorous guaranteed solutions in the presence of practical manufacturing constraints.
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- 2019
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3. Reduced ITO for Transparent Superconducting Electronics
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Emma Batson, Marco Colangelo, John Simonaitis, Eyosias Gebremeskel, Owen Medeiros, Mayuran Saravanapavanantham, Vladimir Bulovic, P Donald Keathley, and Karl K Berggren
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Superconductivity (cond-mat.supr-con) ,Condensed Matter - Superconductivity ,Materials Chemistry ,Metals and Alloys ,Ceramics and Composites ,FOS: Physical sciences ,Applied Physics (physics.app-ph) ,Physics - Applied Physics ,Electrical and Electronic Engineering ,Condensed Matter Physics - Abstract
Absorption of light in superconducting electronics is a major limitation on the quality of circuit architectures that integrate optical components with superconducting components. A 10 nm thick film of a typical superconducting material like niobium can absorb over half of any incident optical radiation. We propose instead using superconductors which are transparent to the wavelengths used elsewhere in the system. In this paper we investigated reduced indium tin oxide (ITO) as a potential transparent superconductor for electronics. We fabricated and characterized superconducting wires of reduced indium tin oxide. We also showed that a $\SI{10}{nm}$ thick film of the material would only absorb about 1 - 20\% of light between 500 - 1700 nm., 11 pages + 10 pages appendix, 5 figures + 5 figures appendix, submitting to IOP SUST
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- 2022
4. Intrinsic 1 $${T}^{{\prime} }$$ T ′ phase induced in atomically thin 2H-MoTe2 by a single terahertz pulse
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Jiaojian Shi, Ya-Qing Bie, Alfred Zong, Shiang Fang, Wei Chen, Jinchi Han, Zhaolong Cao, Yong Zhang, Takashi Taniguchi, Kenji Watanabe, Xuewen Fu, Vladimir Bulović, Efthimios Kaxiras, Edoardo Baldini, Pablo Jarillo-Herrero, and Keith A. Nelson
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Science - Abstract
Abstract The polymorphic transition from 2H to 1 $${T}^{{\prime} }$$ T ′ -MoTe2, which was thought to be induced by high-energy photon irradiation among many other means, has been intensely studied for its technological relevance in nanoscale transistors due to the remarkable improvement in electrical performance. However, it remains controversial whether a crystalline 1 $${T}^{{\prime} }$$ T ′ phase is produced because optical signatures of this putative transition are found to be associated with the formation of tellurium clusters instead. Here we demonstrate the creation of an intrinsic 1 $${T}^{{\prime} }$$ T ′ lattice after irradiating a mono- or few-layer 2H-MoTe2 with a single field-enhanced terahertz pulse. Unlike optical pulses, the low terahertz photon energy limits possible structural damages. We further develop a single-shot terahertz-pump-second-harmonic-probe technique and reveal a transition out of the 2H-phase within 10 ns after photoexcitation. Our results not only provide important insights to resolve the long-standing debate over the light-induced polymorphic transition in MoTe2 but also highlight the unique capability of strong-field terahertz pulses in manipulating quantum materials.
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- 2023
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5. Epitaxial Dimers and Auger-Assisted Detrapping in PbS Quantum Dot Solids
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Nabeel S. Dahod, Huashan Li, Adam P. Willard, Rachel H. Gilmore, Elizabeth M. Y. Lee, Jeffrey C. Grossman, Joel Jean, Yun Liu, Mark C. Weidman, William A. Tisdale, Vladimir Bulovic, Wenbi Shcherbakov-Wu, Massachusetts Institute of Technology. Department of Chemical Engineering, Massachusetts Institute of Technology. Department of Materials Science and Engineering, Massachusetts Institute of Technology. Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology. Department of Chemistry, and Massachusetts Institute of Technology. Research Laboratory of Electronics
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symbols.namesake ,Materials science ,Nanocrystal ,Auger effect ,Quantum dot ,Ultrafast laser spectroscopy ,symbols ,General Materials Science ,Charge carrier ,Electron ,Spectroscopy ,Molecular physics ,Auger - Abstract
We explore the dynamic interaction of charge carriers between band-edge states and sub-band trap states in PbS quantum dot (QD) solids using time-resolved spectroscopy. In monodisperse arrays of 4- to 5-nm diameter PbS QDs, we observe an optically active trap state ∼100–200 meV below the band edge that occurs at a frequency of 1 in ∼2,500 QDs. Uncoupled QD solids with oleic acid ligands show trap-to-ground-state recombination that resembles Auger recombination. In electronically coupled QD solids, we observe entropically driven uphill thermalization of trapped charge carriers from the trap state to the band edge via two distinct mechanisms: Auger-assisted charge transfer (∼35 ps) and thermally activated hopping (∼500 ps). Photophysical characterization combined with atomistic simulations and high-resolution electron microscopy suggest that these states arise from epitaxially fused pairs of QDs rather than electron or hole traps at the QD surface, offering new strategies for improving the optoelectronic performance of QD materials., Department of Energy (DOE), Office of Basic Energy Sciences (Awards DE-SC0010538,DE-SC0019345), National Science Foundation (Awards 1452857 and 1122374)
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- 2019
6. High-Speed Vapor Transport Deposition of Perovskite Thin Films
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Nicole Moody, Ella Louise Wassweiler, Anurag Panda, Michel Nasilowski, Klavs F. Jensen, Anna Osherov, Vladimir Bulovic, Richard Swartwout, Maximilian T. Hoerantner, Aidan E. Driscoll, Haomiao Zhang, Moungi G. Bawendi, Massachusetts Institute of Technology. Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology. Department of Chemical Engineering, Massachusetts Institute of Technology. Department of Chemistry, Massachusetts Institute of Technology. Research Laboratory of Electronics, and Massachusetts Institute of Technology. Department of Physics
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010302 applied physics ,Materials science ,business.industry ,Energy conversion efficiency ,vapor deposition ,fluid dynamics ,02 engineering and technology ,Chemical vapor deposition ,021001 nanoscience & nanotechnology ,7. Clean energy ,01 natural sciences ,manufacturing ,thin-film ,Chemical engineering ,Photovoltaics ,solar cells ,0103 physical sciences ,Deposition (phase transition) ,General Materials Science ,Thin film ,0210 nano-technology ,business ,perovskite ,Research Article ,Perovskite (structure) - Abstract
Intensive research of hybrid metal-halide perovskite materials for use as photoactive materials has resulted in an unmatched increase in the power conversion efficiency of perovskite photovoltaics (PVs) over the last couple of years. Now that lab-fabricated perovskite devices rival the efficiency of silicon PVs, the next challenge of scalable mass manufacturing of large perovskite PV panels remains to be solved. For that purpose, it is still unclear which manufacturing method will provide the lowest processing cost and highest quality solar cells. Vapor deposition has been proven to work well for perovskites as a controllable and repeatable thin-film deposition technique but with processing speeds currently too slow to adequately lower the production costs. Addressing this challenge, in the present work, we demonstrate a high-speed vapor transport processing technique in a custom-built reactor that produces high-quality perovskite films with unprecedented deposition speed exceeding 1 nm/s, over 10× faster than previous vapor deposition demonstrations. We show that the semiconducting perovskite films produced with this method have excellent crystallinity and optoelectronic properties with 10 ns charge carrier lifetime, enabling us to fabricate the first photovoltaic devices made by perovskite vapor transport deposition. Our experiments are guided by computational fluid dynamics simulations that also predict that this technique could lead to deposition rates on the order of micrometers per second. This, in turn, could enable cost-effective scalable manufacturing of the perovskite-based solar technologies. Keywords: solar cells; perovskite; thin-film; vapor deposition; manufacturing; fluid dynamics, National Science Foundation (U.S.) (Award 1541959), National Science Foundation (U.S.) (Grant 1605406)
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- 2019
7. Acetonitrile based single step slot-die compatible perovskite ink for flexible photovoltaics
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Daniel Burkitt, Richard Swartwout, James McGettrick, Roberto Brenes, Peter Greenwood, David Beynon, Vladimir Bulovic, and Trystan Watson
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Materials science ,Inkwell ,business.industry ,General Chemical Engineering ,Photovoltaic system ,02 engineering and technology ,General Chemistry ,engineering.material ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Solar energy ,01 natural sciences ,Die (integrated circuit) ,0104 chemical sciences ,chemistry.chemical_compound ,chemistry ,Coating ,Photovoltaics ,engineering ,Optoelectronics ,0210 nano-technology ,Acetonitrile ,business ,ComputingMethodologies_COMPUTERGRAPHICS ,Perovskite (structure) - Abstract
The demonstration of photovoltaic devices with high power conversion efficiencies using low cost perovskite materials hints at the possibility of dramatically lowering the cost of solar energy. Key to further exploiting the potential of these materials is developing rapid processing techniques that can be used to deliver lower cost high throughput manufacture. This work details the development of low viscosity rapid drying perovskite formulations designed to give high quality solar films when slot-die coated on flexible roll-to-roll compatible substrates. A single step slot-die compatible perovskite ink based on an acetonitrile/methylamine solvent system utilizing a chloride additive is developed, resulting in large area perovskite films from slot-die coating under ambient conditions. The drying conditions for the perovskite film are optimized and fast (
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- 2019
8. Impact of microstructure on the electron-hole interaction in lead halide perovskites
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Arman Mahboubi, Souani, Yang, Zhuo, Trevor, Young, Miyata, Atsuhiko, Surrente, Alessandro, Alexander, Pascoe, Galkowski, Krzysztof, Mojtaba, Abdi-Jalebi, Roberto, Brenes, Urban, Joanna, Nan, Zhang, Vladimir, Bulovic, Portugall, Oliver, Yi-Bing, Cheng, Robin J., Nicholas, Anita, Ho-Baillie, Martin A., Green, Plochocka, Paulina, Samuel D., Stranks, Laboratoire national des champs magnétiques intenses - Toulouse (LNCMI-T), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Université Toulouse III - Paul Sabatier (UT3), and Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])
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[PHYS.COND.CM-S]Physics [physics]/Condensed Matter [cond-mat]/Superconductivity [cond-mat.supr-con] ,ComputingMilieux_MISCELLANEOUS - Abstract
International audience
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- 2018
9. Synthesis cost dictates the commercial viability of lead sulfide and perovskite quantum dot photovoltaics
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Joel Jean, Vladimir Bulovic, Michel Nasilowski, Justin T. Xiao, Robert J. Nick, Nicole Moody, Moungi G. Bawendi, Massachusetts Institute of Technology. Department of Chemistry, Massachusetts Institute of Technology. Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology. Department of Physics, Massachusetts Institute of Technology. Research Laboratory of Electronics, Jean, Joel, Xiao, Justin T., Nick, Robert J., Moody, Nicole Susanne, Nasilowski, Michel, Bawendi, Moungi G, and Bulovic, Vladimir
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Materials science ,Silicon ,Renewable Energy, Sustainability and the Environment ,business.industry ,Photovoltaic system ,chemistry.chemical_element ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Pollution ,Manufacturing cost ,0104 chemical sciences ,chemistry.chemical_compound ,Nuclear Energy and Engineering ,chemistry ,Photovoltaics ,Quantum dot ,Environmental Chemistry ,Optoelectronics ,Lead sulfide ,Crystalline silicon ,0210 nano-technology ,business ,Perovskite (structure) - Abstract
Any new solar photovoltaic (PV) technology must reach low production costs to compete with today’s market- leading crystalline silicon and commercial thin-film PV technologies. Colloidal quantum dots (QDs) could open up new applications by enabling lightweight and flexible PV modules. However, the cost of synthesizing nanocrystals at the large scale needed for PV module production has not previously been investigated. Based on our experience with commercial QD scale-up, we de velop a Monte Carlo model to analyze the cost of synthesizing lead sulfide and metal halide perovskite Q Ds using 8 different reported synthetic methods. We also analyze the cost of solution-phase ligand exchange for p reparing deposition-ready PbS QD inks, as well as the manufacturing cost for roll-to-roll solution-processe d PV modules using these materials. We find that present QD synthesis costs are prohibitively high for PV applications, with median costs of 11 to 59 $ per g for PbS QDs (0.15 to 0.84 $ per W for a 20% efficient cell) and 73 $ per g for CsPbI₃ QDs (0.74 $ per W). QD ink preparation adds 6.3 $ per g (0.09 $ per W). In total, QD materials contribute up to 55% of the total module cost, making even roll-to-roll-processed QDPV modules significantl y more expensive than silicon PV modules. These results suggest that the development of new lo w-cost synthetic methods is critically important for the commercial relevance of QD photovoltaics. Using our cost model, we identify strategies for reducing synthetic cost and propose a cost target of 5 $ per g to move QD solar cells closer to commercial viability, Tata Trusts
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- 2018
10. Stable Light-Emitting Diodes Using Phase-Pure Ruddlesden-Popper Layered Perovskites
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Roberto Brenes, Richard H. Friend, Wanyi Nie, Vladimir Bulovic, Constantinos C. Stoumpos, Jared Crochet, Sergei Tretiak, Chan Myae Myae Soe, Samuel D. Stranks, Giovanni Azzellino, Jacky Even, Jean-Christophe Blancon, Aditya Sadhanala, Aditya D. Mohite, Mercouri G. Kanatzidis, Hsinhan Tsai, Pulickel M. Ajayan, Jinkyoung Yoo, Los Alamos National Laboratory (LANL), Rice University [Houston], Northwestern University [Evanston], 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)-Université Bretagne Loire (UBL)-IMT Atlantique Bretagne-Pays de la Loire (IMT Atlantique), Institut Mines-Télécom [Paris] (IMT)-Institut Mines-Télécom [Paris] (IMT), Cavendish Laboratory, University of Cambridge [UK] (CAM), Massachusetts Institute of Technology (MIT), École Nationale Supérieure des Sciences Appliquées et de Technologie (ENSSAT)-IMT Atlantique Bretagne-Pays de la Loire (IMT Atlantique), Institut Mines-Télécom [Paris] (IMT)-Institut Mines-Télécom [Paris] (IMT)-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 (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS)-Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES), 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), 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), N00014-17-1-2231, Office of Naval Research, DE-AC02-06CH11357, U.S. Department of Energy, and PIOF-GA-2013-622630, Seventh Framework Programme
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Fabrication ,Materials science ,LEDs ,02 engineering and technology ,Electroluminescence ,010402 general chemistry ,01 natural sciences ,law.invention ,Crystal ,crystal orientation ,law ,Phase (matter) ,color tunability ,[CHIM]Chemical Sciences ,General Materials Science ,Voltage droop ,[PHYS]Physics [physics] ,business.industry ,Mechanical Engineering ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,Semiconductor ,Mechanics of Materials ,Optoelectronics ,0210 nano-technology ,business ,Voltage ,Ruddlesden-Popper layered perovskites ,Light-emitting diode - Abstract
International audience; State-of-the-art light emitting diodes (LEDs) are made from high-purity alloys of III-V semiconductors or small molecules, but high fabrication cost and conplicated synthetic process have limited their widespread use for large area solid-state lighting applications. Here we report efficient and stable LEDs processed from solution with tunable color enabled by using phase-pure two-dimensional (2D) Ruddlesden-Popper (RP) layered perovskites with a formula (CH3(CH2)3NH3)2(CH3NH3)n-1PbnI3n+1 (n=3-5 in this report). By using controlled vertically oriented of crystal in the thin-films that facilitate efficient charge injection and transport, we obtain efficient electroluminescence with a radiance of 35 W Sr-1 cm-2 at 744 nm with an ultra-low turn-on voltage of 1V. Finally, operational stability tests suggest that phase purity is strongly correlated to stability. Phase-pure 2D perovskites exhibit >14 hours of stable operation at peak operating conditions with no droop at current-densities of several Amperes/cm2 in comparison to mixtures of 2D/3D mixture or 3D perovskites, which degrade within minutes.
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- 2018
11. An ingestible bacterial-electronic system to monitor gastrointestinal health
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Vladimir Bulovic, Joy Collins, Alison Hayward, Shane McDonnell, Phillip Nadeau, Robert Langer, Giovanni Traverso, Sean Carim, Richard Swartwout, Anantha P. Chandrakasan, Mark Mimee, Timothy K. Lu, Logan Jerger, Sarah E. Flanagan, Robert J. Citorik, Massachusetts Institute of Technology. Synthetic Biology Center, Massachusetts Institute of Technology. Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology. Department of Chemical Engineering, Massachusetts Institute of Technology. Department of Biological Engineering, and Koch Institute for Integrative Cancer Research at MIT
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0301 basic medicine ,Multidisciplinary ,Disease detection ,business.industry ,Computer science ,Extramural ,technology, industry, and agriculture ,Readout electronics ,02 engineering and technology ,Biosensing Techniques ,macromolecular substances ,021001 nanoscience & nanotechnology ,Article ,03 medical and health sciences ,030104 developmental biology ,Proof of concept ,Embedded system ,Biomarker discovery ,0210 nano-technology ,business ,Electronic systems - Abstract
Biomolecular monitoring in the gastrointestinal tract could offer rapid, precise disease detection and management but is impeded by access to the remote and complex environment. Here, we present an ingestible micro-bio-electronic device (IMBED) for in situ biomolecular detection based on environmentally resilient biosensor bacteria and miniaturized luminescence readout electronics that wirelessly communicate with an external device. As a proof of concept, we engineer heme-sensitive probiotic biosensors and demonstrate accurate diagnosis of gastrointestinal bleeding in swine. Additionally, we integrate alternative biosensors to demonstrate modularity and extensibility of the detection platform. IMBEDs enable new opportunities for gastrointestinal biomarker discovery and could transform the management and diagnosis of gastrointestinal disease., Office of Naval Research (Grant N00014-13-1-0424), National Institutes of Health (Grant EB-000244)
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- 2018
12. Uncovering temperature-dependent exciton-polariton relaxation mechanisms in hybrid organic-inorganic perovskites
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Madeleine Laitz, Alexander E. K. Kaplan, Jude Deschamps, Ulugbek Barotov, Andrew H. Proppe, Inés García-Benito, Anna Osherov, Giulia Grancini, Dane W. deQuilettes, Keith A. Nelson, Moungi G. Bawendi, and Vladimir Bulović
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Science - Abstract
Abstract Hybrid perovskites have emerged as a promising material candidate for exciton-polariton (polariton) optoelectronics. Thermodynamically, low-threshold Bose-Einstein condensation requires efficient scattering to the polariton energy dispersion minimum, and many applications demand precise control of polariton interactions. Thus far, the primary mechanisms by which polaritons relax in perovskites remains unclear. In this work, we perform temperature-dependent measurements of polaritons in low-dimensional perovskite wedged microcavities achieving a Rabi splitting of $${{{\hslash }}\Omega }_{{Rabi}}$$ ℏ Ω R a b i = 260 ± 5 meV. We change the Hopfield coefficients by moving the optical excitation along the cavity wedge and thus tune the strength of the primary polariton relaxation mechanisms in this material. We observe the polariton bottleneck regime and show that it can be overcome by harnessing the interplay between the different excitonic species whose corresponding dynamics are modified by strong coupling. This work provides an understanding of polariton relaxation in perovskites benefiting from efficient, material-specific relaxation pathways and intracavity pumping schemes from thermally brightened excitonic species.
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- 2023
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13. Strongly Enhanced Photovoltaic Performance and Defect Physics of Air-Stable Bismuth Oxyiodide (BiOI)
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Judith L. MacManus-Driscoll, Kelvin H. L. Zhang, Vladimir Bulovic, Riley E. Brandt, Melany Sponseller, Moungi G. Bawendi, Lana C. Lee, Tahmida N. Huq, James Alexander Polizzotti, Vladan Stevanović, Tonio Buonassisi, Robert L. Z. Hoye, Ahmed Kursumovic, Lea Nienhaus, Rachel C. Kurchin, Joel Jean, Hoye, Robert [0000-0002-7675-0065], Apollo - University of Cambridge Repository, Massachusetts Institute of Technology. Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology. Department of Materials Science and Engineering, Massachusetts Institute of Technology. Department of Mechanical Engineering, Hoye, Robert L. Z., Kurchin, Rachel Chava, Sponseller, Melany Christine, Nienhaus, Lea, Brandt, Riley E, Jean, Joel, Polizzotti, James Alexander, Bawendi, Moungi G, Bulovic, Vladimir, Buonassisi, Anthony, and Magdalene College, University of Cambridge
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Materials science ,air-stability ,Library science ,Nanotechnology ,02 engineering and technology ,010402 general chemistry ,01 natural sciences ,09 Engineering ,General Materials Science ,Center (algebra and category theory) ,Nanoscience & Nanotechnology ,Physics ,02 Physical Sciences ,business.industry ,Mechanical Engineering ,Photovoltaic system ,ns2 compounds ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,Renewable energy ,photovoltaics ,Work (electrical) ,Mechanics of Materials ,defect-tolerance ,03 Chemical Sciences ,0210 nano-technology ,business ,Research center ,Efficient energy use ,bismuth oxyiodide - Abstract
Bismuth-based compounds have recently gained increasing attention as potentially nontoxic and defect-tolerant solar absorbers. However, many of the new materials recently investigated show limited photovoltaic performance. Herein, one such compound is explored in detail through theory and experiment: bismuth oxyiodide (BiOI). BiOI thin films are grown by chemical vapor transport and found to maintain the same tetragonal phase in ambient air for at least 197 d. The computations suggest BiOI to be tolerant to antisite and vacancy defects. All-inorganic solar cells (ITO|NiO x |BiOI|ZnO|Al) with negligible hysteresis and up to 80% external quantum efficiency under select monochromatic excitation are demonstrated. The short-circuit current densities and power conversion efficiencies under AM 1.5G illumination are nearly double those of previously reported BiOI solar cells, as well as other bismuth halide and chalcohalide photovoltaics recently explored by many groups. Through a detailed loss analysis using optical characterization, photoemission spectroscopy, and device modeling, direction for future improvements in efficiency is provided. This work demonstrates that BiOI, previously considered to be a poor photocatalyst, is promising for photovoltaics., National Science Foundation (U.S.) (Grant CBET-1605495), United States. Department of Energy. Office of Basic Energy Sciences (Grant DE-SC0001088), National Science Foundation (U.S.) (Grant DMF-08019762)
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- 2017
14. Colloidal quantum dot light-emitting devices
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Vladimir Bulovic and Vanessa Wood
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Materials science ,optoelectronics ,lighting ,Nanotechnology ,Color temperature ,lcsh:Chemical technology ,law.invention ,Color rendering index ,Nanocrystal ,nanocrystals ,Quantum dot ,law ,displays ,Nano ,lcsh:TP1-1185 ,Thin film ,Luminescence ,Review Articles ,Light-emitting diode - Abstract
Colloidal quantum dot light-emitting devices (QD-LEDs) have generated considerable interest for applications such as thin film displays with improved color saturation and white lighting with a high color rendering index (CRI). We review the key advantages of using quantum dots (QDs) in display and lighting applications, including their color purity, solution processability, and stability. After highlighting the main developments in QD-LED technology in the past 15 years, we describe the three mechanisms for exciting QDs - optical excitation, Fo¨ rster energy transfer, and direct charge injection - that have been leveraged to create QD-LEDs. We outline the challenges facing QDLED development, such as QD charging and QD luminescence quenching in QD thin films. We describe how optical downconversion schemes have enabled researchers to overcome these challenges and develop commercial lighting products that incorporate QDs to achieve desirable color temperature and a high CRI while maintaining efficiencies comparable to inorganic white LEDs (>65 lumens per Watt). We conclude by discussing some current directions in QD research that focus on achieving higher efficiency and air-stable QD-LEDs using electrical excitation of the luminescent QDs. Keywords: nanocrystals; optoelectronics; displays; lighting (Published: 7 July 2010) Citation: Nano Reviews 2010, 1: 5202 - DOI: 10.3402/nano.v1i0.5202
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- 2010
15. A versatile acoustically active surface based on piezoelectric microstructures
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Jinchi Han, Mayuran Saravanapavanantham, Matthew R. Chua, Jeffrey H. Lang, and Vladimir Bulović
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Technology ,Engineering (General). Civil engineering (General) ,TA1-2040 - Abstract
Abstract We demonstrate a versatile acoustically active surface consisting of an ensemble of piezoelectric microstructures that are capable of radiating and sensing acoustic waves. A freestanding microstructure array embossed in a single step on a flexible piezoelectric sheet of polyvinylidene fluoride (PVDF) leads to high-quality acoustic performance, which can be tuned by the design of the embossed microstructures. The high sensitivity and large bandwidth for sound generation demonstrated by this acoustically active surface outperform previously reported thin-film loudspeakers using PVDF, PVDF copolymers, or voided charged polymers without microstructures. We further explore the directivity of this device and its use on a curved surface. In addition, high-fidelity sound perception is demonstrated by the surface, enabling its microphonic application for voice recording and speaker recognition. The versatility, high-quality acoustic performance, minimal form factor, and scalability of future production of this acoustically active surface can lead to broad industrial and commercial adoption for this technology.
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- 2022
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16. Photovoltaic effect by vapor-printed polyselenophene
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Won Jun Jo, Vladimir Bulovic, Karen K. Gleason, David C. Borrelli, Massachusetts Institute of Technology. Department of Chemical Engineering, Massachusetts Institute of Technology. Department of Electrical Engineering and Computer Science, Gleason, Karen K., Jo, Won Jun, Borrelli, David C, Bulovic, Vladimir, and Gleason, Karen K
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Materials science ,business.industry ,Band gap ,Energy conversion efficiency ,Heterojunction ,General Chemistry ,Chemical vapor deposition ,Photovoltaic effect ,Condensed Matter Physics ,Polymer solar cell ,Electronic, Optical and Magnetic Materials ,Biomaterials ,chemistry.chemical_compound ,Semiconductor ,chemistry ,Materials Chemistry ,Optoelectronics ,Polythiophene ,Electrical and Electronic Engineering ,business - Abstract
Polyselenophene (PSe) donor layers are successfully integrated into organic photovoltaic devices (OPV) for the first time. Thin, patterned films of this insoluble semiconductor were fabricated using a vacuum-based vapor-printing technique, oxidative chemical vapor deposition (oCVD) combined with in-situ shadow masking. The vapor-printed PSe exhibits a reduced optical bandgap of 1.76 eV and enhanced photo-responsivity in the red compared to its sulfur containing analog, polythiophene. These relative advantages are most likely explained by selenium’s enhanced electron-donating character compared to sulfur. The HOMO level of PSe was determined to be at −4.85 eV. The maximum power conversion efficiency achieved was 0.4% using a bilayer heterojunction device architecture with C₆₀ as the donor., United States. Army Research Office (W911NF-13-D-0001)
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- 2015
17. Practical Roadmap and Limits to Nanostructured Photovoltaics
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Richard R. Lunt, Jill A. Rowehl, Patrick O. Brown, Timothy P. Osedach, Vladimir Bulovic, Massachusetts Institute of Technology. Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology. Department of Materials Science and Engineering, Massachusetts Institute of Technology. Department of Physics, Massachusetts Institute of Technology. Microsystems Technology Laboratories, Bulovic, Vladimir, Osedach, Timothy Paul, Brown, Patrick Richard, Lunt, Richard R., and Rowehl, Jill A.
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Fabrication ,Materials science ,Hot Temperature ,Polymers ,Nanotechnology ,Materials testing ,Photovoltaics ,Limit (music) ,Materials Testing ,Quantum Dots ,Solar Energy ,General Materials Science ,Colloids ,Models, Statistical ,business.industry ,Mechanical Engineering ,Physics ,Energy conversion efficiency ,Photovoltaic system ,Equipment Design ,Solar energy ,Engineering physics ,Nanostructures ,Semiconductors ,Mechanics of Materials ,Nanoparticles ,Electric power ,business - Abstract
The significant research interest in the engineering of photovoltaic (PV) structures at the nanoscale is directed toward enabling reductions in PV module fabrication and installation costs as well as improving cell power conversion efficiency (PCE). With the emergence of a multitude of nanostructured photovoltaic (nano-PV) device architectures, the question has arisen of where both the practical and the fundamental limits of performance reside in these new systems. Here, the former is addressed a posteriori. The specific challenges associated with improving the electrical power conversion efficiency of various nano-PV technologies are discussed and several approaches to reduce their thermal losses beyond the single bandgap limit are reviewed. Critical considerations related to the module lifetime and cost that are unique to nano-PV architectures are also addressed. The analysis suggests that a practical single-junction laboratory power conversion efficiency limit of 17% and a two-cell tandem power conversion efficiency limit of 24% are possible for nano-PVs, which, when combined with operating lifetimes of 10 to 15 years, could position them as a transformational technology for solar energy markets., Eni-MIT Alliance Solar Frontiers Program (Eni S.p.A. (Firm)), National Science Foundation (U.S.). Graduate Research Fellowship Program, Link Foundation, Hertz Foundation (Fellowship)
- Published
- 2011
18. Narrowband Absorption-Enhanced Quantum Dot/J-aggregate Conjugates
- Author
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Vladimir Bulovic, Brian J. Walker, Moungi G. Bawendi, Lisa F. Marshall, and Gautham Nair
- Subjects
Time Factors ,Static Electricity ,Nanoparticle ,Photodetection ,Ligands ,Biochemistry ,Catalysis ,Article ,Absorbance ,chemistry.chemical_compound ,Colloid and Surface Chemistry ,Quantum Dots ,Fluorescence Resonance Energy Transfer ,Colloids ,Cyanine ,Absorption (electromagnetic radiation) ,J-aggregate ,Condensed matter physics ,business.industry ,Chemistry ,General Chemistry ,Carbocyanines ,Semiconductor ,Semiconductors ,Quantum dot ,Optoelectronics ,Nanoparticles ,Adsorption ,business - Abstract
We report narrow-band absorption enhancement of semiconductor nanocrystals via Forster resonance energy transfer from cyanine J-aggregates. These J-aggregated dyes associate electrostatically with short quantum-dot (QD) surface ligands in solution. Energy transfer efficiencies approach unity for this light sensitization and result in a 5-fold enhancement in the QD excitation near the J-aggregate absorption maximum. Because a thin layer of J-aggregates attenuates the same amount of light (at peak absorbance) as a far thicker film of monomer dye, these absorption-enhanced materials may have applications in light-sensitizing applications such as photodetection and optical down-conversion.
- Published
- 2009
19. All-vacuum-deposited inorganic cesium lead halide perovskite light-emitting diodes
- Author
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Sihan Xie, Anna Osherov, and Vladimir Bulović
- Subjects
Biotechnology ,TP248.13-248.65 ,Physics ,QC1-999 - Abstract
Polycrystalline CsPbBr3 thin films are deposited by vacuum co-evaporation of cesium halide and lead halide precursors, leading to uniform pinhole-free morphology and precise control over the film thickness and precursor stoichiometry. By utilizing the organic hole and electron transport layers, all-vacuum-deposited perovskite LEDs are fabricated. The resulting devices exhibit a maximum luminance of 1800 cd/m2, a 531 nm emission wavelength peak with a spectral linewidth of 21 nm, and an external quantum efficiency of 1.1%.
- Published
- 2020
- Full Text
- View/download PDF
20. Toward Efficient Carbon Nanotube/P3HT Solar Cells: Active Layer Morphology, Electrical, and Optical Properties.
- Author
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Shenqiang Ren, Marco Bernardi, Richard R. Lunt, Vladimir Bulovic, Jeffrey C. Grossman, and Silvija GradecÌak
- Published
- 2011
- Full Text
- View/download PDF
21. Large Area, Few-Layer Graphene Films on Arbitrary Substrates by Chemical Vapor Deposition.
- Author
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Alfonso Reina, Xiaoting Jia, John Ho, Daniel Nezich, Hyungbin Son, Vladimir Bulovic, Mildred S. Dresselhaus, and Jing Kong
- Published
- 2009
- Full Text
- View/download PDF
22. Color-Saturated Green-Emitting QD-LEDsThis work was funded in part by the NSF-MRSEC program (DMR 0213282), by the US Army through the Institute for Soldier Nanotechnologies, under Contract DAAD-19-02-0002 with the US Army Research Office, by the Presidential Early Career Award for Scientists and Engineers (PECASE). QD-LED=quantum dot light-emitting device.
- Author
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Jonathan S. Steckel, Preston Snee, Seth Coe-Sullivan, John P. Zimmer, Jonathan E. Halpert, Polina Anikeeva, Lee-Ann Kim, Vladimir Bulovic, and Moungi G. Bawendi
- Published
- 2006
- Full Text
- View/download PDF
23. Photo-induced halide redistribution in organic–inorganic perovskite films
- Author
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Dane W. deQuilettes, Wei Zhang, Victor M. Burlakov, Daniel J. Graham, Tomas Leijtens, Anna Osherov, Vladimir Bulović, Henry J. Snaith, David S. Ginger, and Samuel D. Stranks
- Subjects
Science - Abstract
Visual evidence for photo-induced ionic migration in perovskite films without contacts is lacking. Here, the authors use a unique combination of confocal photoluminescence microscopy and chemical imaging to correlate the local changes in photophysics with composition in CH3NH3PbI3films under illumination.
- Published
- 2016
- Full Text
- View/download PDF
24. Photo-induced halide redistribution in organic–inorganic perovskite films
- Author
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Wei Zhang, Daniel J. Graham, Tomas Leijtens, Dane W. deQuilettes, Henry J. Snaith, Victor M. Burlakov, Vladimir Bulovic, Samuel D. Stranks, David S. Ginger, Anna Osherov, Massachusetts Institute of Technology. Research Laboratory of Electronics, Osherov-Beizerov, Anna, Bulovic, Vladimir, and Stranks, Samuel David
- Subjects
Chemical imaging ,J910 Energy Technologies ,Materials science ,Photoluminescence ,Light ,genetic structures ,Science ,Spectrometry, Mass, Secondary Ion ,General Physics and Astronomy ,Halide ,02 engineering and technology ,010402 general chemistry ,Photochemistry ,01 natural sciences ,Article ,General Biochemistry, Genetics and Molecular Biology ,Methylamines ,chemistry.chemical_compound ,F120 Inorganic Chemistry ,Redistribution (chemistry) ,F200 Materials Science ,Thin film ,Triiodide ,Perovskite (structure) ,Titanium ,Microscopy, Confocal ,Multidisciplinary ,Oxides ,General Chemistry ,Calcium Compounds ,Iodides ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,Lead ,chemistry ,Luminescent Measurements ,Charge carrier ,sense organs ,0210 nano-technology ,Iodine - Abstract
Organic–inorganic perovskites such as CH3NH3PbI3 are promising materials for a variety of optoelectronic applications, with certified power conversion efficiencies in solar cells already exceeding 21%. Nevertheless, state-of-the-art films still contain performance-limiting non-radiative recombination sites and exhibit a range of complex dynamic phenomena under illumination that remain poorly understood. Here we use a unique combination of confocal photoluminescence (PL) microscopy and chemical imaging to correlate the local changes in photophysics with composition in CH3NH3PbI3 films under illumination. We demonstrate that the photo-induced ‘brightening’ of the perovskite PL can be attributed to an order-of-magnitude reduction in trap state density. By imaging the same regions with time-of-flight secondary-ion-mass spectrometry, we correlate this photobrightening with a net migration of iodine. Our work provides visual evidence for photo-induced halide migration in triiodide perovskites and reveals the complex interplay between charge carrier populations, electronic traps and mobile halides that collectively impact optoelectronic performance., Seventh Framework Programme (European Commission) (FP7/2007–2013) , under grant agreement 604032, MESO project), Seventh Framework Programme (European Commission) (People Programme (Marie Curie Actions), FP7/2007-2013/ under REA grant agreement number PIOF-GA-2013-622630)), United States. Dept. of Energy (DOE (DE-SC0013957)), National Science Foundation (U.S.) (NSF Graduate Research Fellowship (DGE-1256082)), Engineering and Physical Sciences Research Council (EPSRC) (Supergen Supersolar project), Massachusetts Institute of Technology. Libraries (contributions to Open Access article processing fees), United States. Dept. of Energy. Office of Basic Energy Sciences (Center for Excitonics, an Energy Frontier Research Center, Award No. DE-SC0001088)
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