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24 results on '"Panda, Anurag"'

3. Goal-Driven Business Process Derivation

Author

Ghose, Aditya K., Narendra, Nanjangud C., Ponnalagu, Karthikeyan, Panda, Anurag, Gohad, Atul, Hutchison, David, Series editor, Kanade, Takeo, Series editor, Kittler, Josef, Series editor, Kleinberg, Jon M., Series editor, Mattern, Friedemann, Series editor, Mitchell, John C., Series editor, Naor, Moni, Series editor, Nierstrasz, Oscar, Series editor, Pandu Rangan, C., Series editor, Steffen, Bernhard, Series editor, Sudan, Madhu, Series editor, Terzopoulos, Demetri, Series editor, Tygar, Doug, Series editor, Vardi, Moshe Y., Series editor, Weikum, Gerhard, Series editor, Kappel, Gerti, editor, Maamar, Zakaria, editor, and Motahari-Nezhad, Hamid R., editor

Published
2011
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4. Design of a custom vapor transport co-deposition system for scalable production of perovskite solar cells.

Author

Wassweiler, Ella, Panda, Anurag, Kadosh, Tamar, Nguyen, Thienan, Hsu, Wan-Ju, Pettit, Emma, Holmes, Russell J., Tuller, Harry, and Bulovic, Vladimir

Subjects
SOLAR cells, CUSTOM design, PEROVSKITE, PHOTOVOLTAIC power systems, INDUSTRIAL electronics, LEAD iodide, ELECTRONIC industries
Abstract

Vacuum-deposited perovskites provide a more direct path to manufacturing large area solar cells because of ready compatibility with multilayered architectures and historic use in the electronics industry. However, vacuum compatible co-deposition of organic-inorganic perovskites remains difficult due to issues of precisely controlling the organic precursor flux. Here, we demonstrate a manufacturing prototype specifically designed for co-depositing organic-inorganic perovskites and evaluate it with respect to the influence of process parameters on film growth. Through depositing and characterizing methylammonium lead iodide (MAPbI3) perovskite films, we highlight the necessary design requirements while measuring the influence of film growth parameters on deposition rate and perovskite phases. [ABSTRACT FROM AUTHOR]

Published
2023
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5. Centimetre-scale electron diffusion in photoactive organic heterostructures

Author

Burlingame, Quinn, Coburn, Caleb, Che, Xiaozhou, Panda, Anurag, Qu, Yue, and Forrest, Stephen R.

Subjects
Organic semiconductors -- Composition, Electrons -- Measurement, Diffusion (Physics) -- Measurement, Environmental issues, Science and technology, Zoology and wildlife conservation
Abstract

Author(s): Quinn Burlingame [1]; Caleb Coburn [2]; Xiaozhou Che [3]; Anurag Panda [4]; Yue Qu [1]; Stephen R. Forrest (corresponding author) [1, 2, 3, 4] The unique properties of organic [...]

Published
2018
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8. High-Speed Vapor Transport Deposition of Perovskite Thin Films

Author

Hoerantner, Maximilian T., primary, Wassweiler, Ella L., additional, Zhang, Haomiao, additional, Panda, Anurag, additional, Nasilowski, Michel, additional, Osherov, Anna, additional, Swartwout, Richard, additional, Driscoll, Aidan E., additional, Moody, Nicole S., additional, Bawendi, Moungi G., additional, Jensen, Klavs F., additional, and Bulović, Vladimir, additional

Published
2019
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9. High-Speed Vapor Transport Deposition of Perovskite Thin Films

Author

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, Massachusetts Institute of Technology. Department of Physics, Hoerantner, Maximilian T, Wassweiler, Ella Louise, Zhang, Haomiao, Panda, Anurag, Nasilowski, Michel, Osherov-Beizerov, Anna, Swartwout, Richard M, Driscoll, Aidan E., Moody, Nicole Susanne, Bawendi, Moungi G., Jensen, Klavs F, Bulovic, Vladimir, 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, Massachusetts Institute of Technology. Department of Physics, Hoerantner, Maximilian T, Wassweiler, Ella Louise, Zhang, Haomiao, Panda, Anurag, Nasilowski, Michel, Osherov-Beizerov, Anna, Swartwout, Richard M, Driscoll, Aidan E., Moody, Nicole Susanne, Bawendi, Moungi G., Jensen, Klavs F, and Bulovic, Vladimir

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)

Published
2019

10. Centimetre-scale electron diffusion in photoactive organic heterostructures

Author

Burlingame, Quinn, Coburn, Caleb, Che, Xiaozhou, Panda, Anurag, Qu, Yue, and Forrest, Stephen R.

Subjects
Multidisciplinary, Materials science, Fullerene, Exciton, Heterojunction, 02 engineering and technology, Orders of magnitude (numbers), 010402 general chemistry, 021001 nanoscience & nanotechnology, Thermal diffusivity, 01 natural sciences, 0104 chemical sciences, Organic semiconductor, chemistry.chemical_compound, chemistry, Chemical physics, C70 fullerene, Physics::Atomic and Molecular Clusters, Diffusion (business), 0210 nano-technology
Abstract

The unique properties of organic semiconductors, such as flexibility and lightness, are increasingly important for information displays, lighting and energy generation. But organics suffer from both static and dynamic disorder, and this can lead to variable-range carrier hopping, which results in notoriously poor electrical properties, with low electron and hole mobilities and correspondingly short charge-diffusion lengths of less than a micrometre. Here we demonstrate a photoactive (light-responsive) organic heterostructure comprising a thin fullerene channel sandwiched between an electron-blocking layer and a blended donor:C70 fullerene heterojunction that generates charges by dissociating excitons. Centimetre-scale diffusion of electrons is observed in the fullerene channel, and this can be fitted with a simple electron diffusion model. Our experiments enable the direct measurement of charge diffusivity in organic semiconductors, which is as high as 0.83 ± 0.07 square centimetres per second in a C60 channel at room temperature. The high diffusivity of the fullerene combined with the extraordinarily long charge-recombination time yields diffusion lengths of more than 3.5 centimetres, orders of magnitude larger than expected for an organic system.

Published
2017

16. High-Speed Vapor Transport Deposition of Perovskite Thin Films

Author

Hoerantner, Maximilian T., Wassweiler, Ella L., Zhang, Haomiao, Panda, Anurag, Nasilowski, Michel, Osherov, Anna, Swartwout, Richard, Driscoll, Aidan E., Moody, Nicole S., Bawendi, Moungi G., Jensen, Klavs F., and Bulović, Vladimir

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.

Published
2024
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18. Engineering Temperature‐Dependent Carrier Concentration in Bulk Composite Materials via Temperature‐Dependent Fermi Level Offset.

Author

Hui, Si, Gao, Wenpei, Lu, Xu, Panda, Anurag, Bailey, Trevor P., Page, Alexander A., Uher, Ctirad, Forrest, Stephen R., Morelli, Donald T., Pan, Xiaoqing, and Pipe, Kevin P.

Subjects
COMPOSITE materials research, CARRIER density, FERMI level, ELECTRICAL conductivity measurement, BOLTZMANN'S equation
Abstract

Abstract: Precise control of carrier concentration in both bulk and thin‐film materials is crucial for many solid‐state devices, including photovoltaic cells, superconductors, and high mobility transistors. For applications that span a wide temperature range (thermoelectric power generation being a prime example) the optimal carrier concentration varies as a function of temperature. This work presents a modified modulation doping method to engineer the temperature dependence of the carrier concentration by incorporating a nanosize secondary phase that controls the temperature‐dependent doping in the bulk matrix. This study demonstrates this technique by de‐doping the heavily defect‐doped degenerate semiconductor GeTe, thereby enhancing its average power factor by 100% at low temperatures, with no deterioration at high temperatures. This can be a general method to improve the average thermoelectric performance of many other materials. [ABSTRACT FROM AUTHOR]

Published
2018
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23. Exciton and Charge Dynamics at Hybrid Organic-Inorganic Semiconductor Heterojunctions

Author

Panda, Anurag

Subjects
organic semiconductor, inorganic semiconductor, hybrid semiconductor, heterojunction, charge transfer state, hybrid charge transfer exciton
Abstract

The advancements in our fundamental understanding of light-matter interaction in the past century are foundational to our technology-enabled modern lifestyle. While the physics and technology of inorganic semiconductors have been well-developed in the past 60 years, the development of organic semiconductors is in its nascent stages. Combination of the two material systems in organic-inorganic (OI) hybrid semiconductor systems have already found applications in next-generation solar cells, light-emitting diodes, and non-linear optical devices, yet the unique charge and exciton behavior at OI heterojunctions (HJs) remains largely unexplored. The stark differences in the optoelectronic properties of organic and inorganic semiconductors offer a rich and as of yet unexplored territory of charge and energy transfer processes in hybrid semiconductor systems. Expanding the physical understanding of these coupled material systems could potentially lead to major advances in semiconductor applications and science. This thesis presents the first steps toward developing a comprehensive understanding of charge and exciton dynamics in coupled hybrid OI material systems. A theory of optical and electrical behavior of OI-HJ based diodes is outlined. The theory yields a quantitative model for current density versus voltage (J-V) characteristics of OI-HJ based diodes. The existence of a hybrid charge transfer exciton (HCTE) state, composed of a columbically-bound electron in the inorganic semiconductor and hole polaron in the organic semiconductor, is predicted at the hybrid heterointerface. The HCTE is found to be the the fundamental quasi-particle that governs the excited state properties of the diode. A first principles quantum mechanical model of the HCTE is developed to predict its optoelectronic properties. The external quantum efficiency, electroluminescence, photoluminescence, and J-V characteristics for multiple OI diode systems are presented along with model fits to the data. The fits yield insights into the dominant optoelectronic processes in OI material systems, including trap-mediated charge recombination and space-charge-limited current. The ability to systematically manipulate the optoelectronic properties of the HCTE by tuning the dimensionality of electron delocalization in the inorganic semiconductor is demonstrated. Potential novel applications and future directions for exploration that emerge for hybrid material systems as a result of the findings of this thesis are also discussed.

Published
2018

24. Singlets lead to photogeneration in C60-based organic heterojunctions.

Author

Bergemann, Kevin J., Xiao Liu, Panda, Anurag, and Forrest, Stephen R.

Subjects
*ORGANIC compounds, *HETEROJUNCTIONS, *CARBON compounds, *PHOTOVOLTAIC cells, *ENERGY transfer
Abstract

Two independent and direct measurements of exciton transport in the fullerene C60 unambiguously indicate that singlets are responsible for energy transport and ultimately charge generation in organic photovoltaic cells. The singlet exciton diffusion length, LD was measured using fits to the external quantum efficiency of planar heterojunction photovoltaics, and via C60 fluorescence, giving a mean value of 34±3nm. Direct measurement of the C60 singlet state transient fluorescence decay gives a lifetime of 590±10ps, from which we infer a diffusivity of 0.020±0.004cm²/s. This is at least ten times that typical for organics, which we attribute to the spherical symmetry of the C60 molecule that promotes highly efficient exciton transfer. Further, LD is used to determine that the C60 energy gap is 18±5meV larger than the analogous fullerene C70. [ABSTRACT FROM AUTHOR]

Published
2015
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