2026-09-19T05:52:46Zhttps://dspace.mit.edu/server/oai/requestoai:dspace.mit.edu:1721.1/1089972021-07-05T14:03:20Zcom_1721.1_7582com_1721.1_7581col_1721.1_131023
Rajeev Ram.
Li, Zheng, Ph. D. Massachusetts Institute of Technology
Massachusetts Institute of Technology. Department of Materials Science and Engineering.
Massachusetts Institute of Technology. Department of Materials Science and Engineering
2017-05-11T19:59:48Z
2017-05-11T19:59:48Z
2017
2017
http://hdl.handle.net/1721.1/108997
986528926
Thesis: S.M., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2017.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 97-102).
An light-emitting diode (LED) consumes low-entropy electrical power and emits incoherent photons. In this process, the lattice heat also contributes to the output power if the LED operates at voltages below the photon energy (qV < h[omega]). Therefore, an LED can potentially cool itself, and the phenomenon is referred to as electroluminescence cooling (ELC). Although researchers recently reported LEDs with net cooling in various wavelength, the cooling power was not sufficient to compensate the heat flux from the ambient and thus no temperature drop is observed. In this thesis, we design and fabricate a photonic crystal (PhC) enhanced unencapsulated LED for direct observation of ELC. The PhC pattern and the structure of the device are optimized to achieve approximately 76% extraction efficiency and 300 [mu]W/cm2 net cooling power. The LED is designed to have smaller surface area and thermal mass compared to an encapsulated one to eliminate overwhelming convection heat flux. According to our thermal models, such an LED should exhibit temperature by 0.1 K and 0.5 K in air and vacuum, respectively. We also present preliminary fabrication processes and results. The critical steps include a flip-chip process with metal-metal bonding, substrate etching, and interference lithography for the PhC pattern.
by Zheng Li.
S.M.
102 pages
eng
Massachusetts Institute of Technology
MIT theses are protected by copyright. They may be viewed, downloaded, or printed from this source but further reproduction or distribution in any format is prohibited without written permission.
http://dspace.mit.edu/handle/1721.1/7582
Materials Science and Engineering.
Photonic crystal enhanced LED for electroluminescence cooling
Photonic crystal enhanced light-emitting diode for ELC
Thesis
application/pdf
Publication
unknown
unknown
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<Abstract>An light-emitting diode (LED) consumes low-entropy electrical power and emits incoherent photons. In this process, the lattice heat also contributes to the output power if the LED operates at voltages below the photon energy (qV < h[omega]). Therefore, an LED can potentially cool itself, and the phenomenon is referred to as electroluminescence cooling (ELC). Although researchers recently reported LEDs with net cooling in various wavelength, the cooling power was not sufficient to compensate the heat flux from the ambient and thus no temperature drop is observed. In this thesis, we design and fabricate a photonic crystal (PhC) enhanced unencapsulated LED for direct observation of ELC. The PhC pattern and the structure of the device are optimized to achieve approximately 76% extraction efficiency and 300 [mu]W/cm2 net cooling power. The LED is designed to have smaller surface area and thermal mass compared to an encapsulated one to eliminate overwhelming convection heat flux. According to our thermal models, such an LED should exhibit temperature by 0.1 K and 0.5 K in air and vacuum, respectively. We also present preliminary fabrication processes and results. The critical steps include a flip-chip process with metal-metal bonding, substrate etching, and interference lithography for the PhC pattern.</Abstract>
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