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148 results on '"Labram, John G."'

4. The effect of substrate curvature on capacitance and transfer characteristics for thin film transistors on the surface of spheres.

Author

Chattopadhyay, Shirsopratim and Labram, John G.

Subjects
*ELECTRIC capacity, *CURRENT-voltage characteristics, *ELECTROSTATICS, *FLEXIBLE electronics, *SPHERES, *TRANSISTORS
Abstract

Conformable, flexible, and stretchable thin film transistors hold promise for ubiquitous and low-cost electronics. As part of the research endeavor toward this goal, the challenges associated with compatible materials and growth processes have been intensely studied. What is seldom considered, however, is how device electrostatics change as the physical form of devices change. In this report, we study how one would expect the current–voltage characteristics of thin film transistors to change as they are deformed on the surface of a sphere. We derive analogous equations to those derived in the gradual channel approximation to relate current to applied voltage for various spherical geometries. Combined with a finite-difference strategy to evaluate geometric capacitance, example current–voltage characteristics are calculated. The results demonstrate for certain deformations in this geometry, the behavior deviates from what one would expect using just the gradual channel approximation. For flexible electronics to be commercially viable, it must be predictable in any physical form. These results represent some of the first steps in a broader effort to quantify the relationship between device geometry and electrical behavior. [ABSTRACT FROM AUTHOR]

Published
2022
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12. Establishing Self‐Dopant Design Principles from Structure–Function Relationships in Self‐n‐Doped Perylene Diimide Organic Semiconductors (Adv. Mater. 42/2022)

Author

Powell, Daniel, primary, Zhang, Xueqiao, additional, Nwachukwu, Chideraa I., additional, Miller, Edwin J., additional, Hansen, Kameron R., additional, Flannery, Laura, additional, Ogle, Jonathan, additional, Berzansky, Alex, additional, Labram, John G., additional, Roberts, Andrew G., additional, and Whittaker‐Brooks, Luisa, additional

Published
2022
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15. Predicting Solar Cell Performance from Terahertz and Microwave Spectroscopy

Author

Hempel, Hannes, primary, Savenjie, Tom J., additional, Stolterfoht, Martin, additional, Neu, Jens, additional, Failla, Michele, additional, Paingad, Vaisakh C., additional, Kužel, Petr, additional, Heilweil, Edwin J., additional, Spies, Jacob A., additional, Schleuning, Markus, additional, Zhao, Jiashang, additional, Friedrich, Dennis, additional, Schwarzburg, Klaus, additional, Siebbeles, Laurens D.A., additional, Dörflinger, Patrick, additional, Dyakonov, Vladimir, additional, Katoh, Ryuzi, additional, Hong, Min Ji, additional, Labram, John G., additional, Monti, Maurizio, additional, Butler‐Caddle, Edward, additional, Lloyd‐Hughes, James, additional, Taheri, Mohammad M., additional, Baxter, Jason B., additional, Magnanelli, Timothy J., additional, Luo, Simon, additional, Cardon, Joseph M., additional, Ardo, Shane, additional, and Unold, Thomas, additional

Published
2022
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20. Recombination at high carrier density in methylammonium lead iodide studied using time-resolved microwave conductivity.

Author

Labram, John G. and Chabinyc, Michael L.

Subjects
*TIME-resolved microwave conductivity, *LEAD iodide, *SEMICONDUCTORS, *PEROVSKITE, *METHYLAMMONIUM, *ELECTRON mobility
Abstract

Time-resolved microwave conductivity (TRMC) is a highly versatile method to rapidly evaluate the electronic properties of semiconducting compounds without the need to construct and optimize electronic devices. In this report, we study how bimolecular and Auger recombination mechanisms affect TRMC measurements. In particular, we investigate how recombination reduces the measured value of the TRMC figure-of-merit: ∅∑μ, at a high incident optical fluence. Using a numerical model, we calculate how these higher-order recombination processes reduce experimentally measured values of ∅∑μ relative to a regime of low carrier concentration with little recombination. By fitting this model to experimentally obtained data for the hybrid halide perovskite compound, methylammonium lead iodide, we are able to extract the bimolecular and Auger rate constants and provide a clear determination of the sum of the hole and electron mobilities for these films. [ABSTRACT FROM AUTHOR]

Published
2017
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28. A piperidinium salt stabilizes efficient metal-halide perovskite solar cells

Author

Lin, Yen-Hung, primary, Sakai, Nobuya, additional, Da, Peimei, additional, Wu, Jiaying, additional, Sansom, Harry C., additional, Ramadan, Alexandra J., additional, Mahesh, Suhas, additional, Liu, Junliang, additional, Oliver, Robert D. J., additional, Lim, Jongchul, additional, Aspitarte, Lee, additional, Sharma, Kshama, additional, Madhu, P. K., additional, Morales‐Vilches, Anna B., additional, Nayak, Pabitra K., additional, Bai, Sai, additional, Gao, Feng, additional, Grovenor, Chris R. M., additional, Johnston, Michael B., additional, Labram, John G., additional, Durrant, James R., additional, Ball, James M., additional, Wenger, Bernard, additional, Stannowski, Bernd, additional, and Snaith, Henry J., additional

Published
2020
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32. Multi-Sulfur-Annulated Fused Perylene Diimides for Organic Solar Cells with Low Open-Circuit Voltage Loss

Author

Li, Xiangchun, primary, Wang, Hengbin, additional, Nakayama, Hidenori, additional, Wei, Zitang, additional, Schneider, Julia A., additional, Clark, Kyle, additional, Lai, Wen-Yong, additional, Huang, Wei, additional, Labram, John G., additional, de Alaniz, Javier Read, additional, Chabinyc, Michael L., additional, Wudl, Fred, additional, and Zheng, Yonghao, additional

Published
2019
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33. Shining Light on Sulfide Perovskites: LaYS3 Material Properties and Solar Cells

Author

Crovetto, Andrea, primary, Nielsen, Rasmus, additional, Pandey, Mohnish, additional, Watts, Lowell, additional, Labram, John G., additional, Geisler, Mathias, additional, Stenger, Nicolas, additional, Jacobsen, Karsten W., additional, Hansen, Ole, additional, Seger, Brian, additional, Chorkendorff, Ib, additional, and Vesborg, Peter C. K., additional

Published
2019
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37. High Conductivity in a Nonplanar n-Doped Ambipolar Semiconducting Polymer

Author

Perry, Erin E., primary, Chiu, Chien-Yang, additional, Moudgil, Karttikay, additional, Schlitz, Ruth A., additional, Takacs, Christopher J., additional, O’Hara, Kathryn A., additional, Labram, John G., additional, Glaudell, Anne M., additional, Sherman, Jes B., additional, Barlow, Stephen, additional, Hawker, Craig J., additional, Marder, Seth R., additional, and Chabinyc, Michael L., additional

Published
2017
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49. N‐Type Surface Doping of MAPbI3 via Charge Transfer from Small Molecules.

Author

Perry, Erin E., Labram, John G., Venkatesan, Naveen R., Nakayama, Hidenori, and Chabinyc, Michael L.

Subjects
ELECTRONS, THIN films, SOLAR cells, PEROVSKITE, COBALTOCENE
Abstract

Abstract: Organic hole and electron transport materials are regularly employed as electron‐ and hole‐blocking layers in perovskite thin‐film solar cells. In order to optimize charge extraction in the device, these organic layers can be doped using organic small molecules. However, to date there is little work carried out on direct doping of perovskite surfaces. In this report, the change in electrical properties of thin films of MAPbI3 by surface doping the film with an organic dopant molecule: cobaltocene (Co(C5H5)2) is studied. By varying the quantity of cobaltocene deposited, the conductivity of MAPbI3 thin films is observed to be tunable over several orders of magnitude. A tunable shift in the Fermi level illustrating that charge transfer doping enables control over the interfacial energy levels, is observed. An increase in photoconductivity is seen at intermediate doping levels, indicating passivation of surface traps confirmed by increased photoluminescence. This model system provides a means to understand more complex heterointerfaces of doped organic blends at perovskite surfaces. [ABSTRACT FROM AUTHOR]

Published
2018
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50. Shining Light on Sulfide Perovskites: LaYS3Material Properties and Solar Cells

Author

Crovetto, Andrea, Nielsen, Rasmus, Pandey, Mohnish, Watts, Lowell, Labram, John G., Geisler, Mathias, Stenger, Nicolas, Jacobsen, Karsten W., Hansen, Ole, Seger, Brian, Chorkendorff, Ib, and Vesborg, Peter C. K.

Abstract

The sulfide perovskite LaYS3has been recently identified as a promising wide band gap photoabsorber material by computational screening techniques. In this study, we combine experiment and theory to comprehensively characterize LaYS3thin films produced by sulfurization of sputter-deposited precursors. An attractive feature of LaYS3is its optimal band gap (2.0 eV) for application as a wide band gap photoabsorber in tandem solar energy conversion devices. Promisingly, the LaYS3films are photoconductive, with a grain size in excess of 1 μm and comparable recombination time scales to state-of-the-art hybrid halide perovskite absorbers. Although the fabrication of solar cells based on LaYS3absorbers is complicated by the high temperature necessary to grow the compound, complete solar cells could be produced in this work by growing LaYS3on refractory metal back contacts. These are the first reported solar cells based on a sulfide perovskite absorber. A major reason for their poor performance could be the highly localized trap states observed directly by photoluminescence imaging of LaYS3, which may also explain the surprisingly long carrier lifetimes and the low carrier mobility found in this material.

Published
2019
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