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This research project is an investigation of applications of several techniques to improve the efficiency and lifetime of cathodoluminescent (CL) phosphors such that they can be applied to general lighting in a variety of light sources. Methods of coating CL phosphors have been investigated in order to improve electrical and thermal surface conductivity, both improving efficacy and lifetime. This research builds upon the experimental work in phosphor technology conducted at UC Davis and CLTC.
Results thus far have been successful, both in coating Y2O3 red cathodoluminescent phosphors with carbon nanotubes and with Atomic-Layer Deposition (ALD) ZnO. The ZnO technique has superior results, both in improving thermal dissipation and in preventing charge accumulation in the Y2O3 particles. Although this technique is primarily focused on improvement of CL performance for applications such as ESL (Electron Stimulated Luminescence) and Field-Emission Lighting, the results are also beneficial for applications which use Y2O3 phosphors in photoluminescent excitation, such as in fluorescent and LED devices.
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| Typical efficacy vs power density plot of Y2O3: Eu red phosphor, demonstrating the performance degradation resulting from increased power density |
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Conductance of ALD Zno vs ALD cycle; Zno conductivity increases as the coating thickness is increased, showing improved charge dissipation |
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| SEM image of loosely packed Y2O3:Eu2+ particles deposited by sedimentation (left) and higher magnification of Y2O3:Eu2+ particles coated with 100 nm of ALD Zno film (right) |
Objective:
This research aims to improve efficacy of energy-efficient lamps by improving the thermal, electrical and lifetime performance of red phosphors.
Applications:
The luminescent materials are primarily applicable to ESL and Field-Emission lighting devices; but can also improve performance in some fluorescent and LED lighting devices using PL phosphors.
Descriptions / Features:
The ZnO oxide coating is so thin that it does not degrade the performance of the phosphors; however, it is sufficiently conductive such that it dissipates power effectively, thereby improving efficacy and lifetime. The ZnO also eliminates the need for silicate binders for the phosphors, thereby enhancing the efficiency by eliminating a non-luminescent material from the phosphor coatings.
Results:
The results are being reported at the 2010 Electrochemical Society Fall Meeting, Symposium J4:
Kanda Tapily, Diefeng Gu, Helmut Baumgart, and Charles E. Hunt, Y2O3 RED PHOSPHORS FOR GENERAL LIGHTING COATED BY ATOMIC LAYER DEPOSITION (ALD) OF ZnO FOR ENHANCED EFFICACY, LIFETIME, AND THERMAL STABILITY, (accepted for) Proceedings of the Symposium on Energy-Efficient Luminescent Materials, Electrochemical Society Fall Meeting, Las Vegas, NV USA (2010)
Status:August 2009–present
Other Resources:
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