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Title: New Class of Encapsulants for Blue LEDs

Abstract

For many years silicone-based encapsulants have been the mainstay for LED modules. For the purposes of this report, we are focused solely on encapsulants that are placed on chip and are mixed with down-converting phosphors for pc-LED applications (Fig. 1). Conventional methyl- and phenyl-based silicones have numerous advantages, such as, optical clarity, proper viscosity prior to curing, lack of yellowing during LED operation, and long lifetimes. However, they suffer from low thermal conductivity and lower than desired refractive indices which results in reduced LED efficacies and lifetimes, in addition to color and intensity variations as a function of time. For years now many groups have attempted to replace silicones with more advanced encapsulants; however, the marketplace shows that none of those research efforts have resulted in any novel product-grade encapsulants being used by large LED manufacturers. In the majority of those efforts, inorganic-based fillers were added to conventional silicones to enhance the material’s thermal conductivity. For our Phase I effort, we took the novel approach of doing away with silicones and replacing it with an all inorganic formulation based on the usage of nanomaterials. The milestones for the project were (largely aligned with the corresponding DOE 2020 goals) that themore » encapsulant would have a thermal conductivity of 1 W/(m-K) and a refractive index of 1.8, while it remained optically transparent to visible light. For conventional silicones, these corresponding material properties are 0.2 W/(m-K) and 1.45, respectively. By project end, we synthesized encapsulant materials which were processable (limiting anneal temperatures to <220 C), dense and hard, optically clear, and had thermal conductivity and refractive index values of ~0.5-1.0 W/(m-K) and 1.9, respectively. Additionally, the encapsulants were mixed with phosphors, deposited on conventional LED modules, and produced white LED results analogous to those obtained using conventional silicones. In summary, over the course of the 10-month Phase I project an entirely new class of inorganic-based encapsulants were developed based on the usage of component nanomaterials. The resulting optical and thermal properties of the encapsulants were superior to those of silicones and in the case of the refractive index, exceeded the DOE 2020 goal. Overall, these results show promise for developing appropriate encapsulants which will eclipse silicone’s performance and enable white LEDs to operate at lower temperatures and enjoy enhanced efficacy performance.« less

Authors:
 [1]
  1. Lumisyn LLC
Publication Date:
Research Org.:
Lumisyn LLC
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22) USDOE SBIR
OSTI Identifier:
1545776
Report Number(s):
DOE-Lumisyn-18578
DOE Contract Number:  
SC0018578
Type / Phase:
SBIR (Phase I)
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION; 77 NANOSCIENCE AND NANOTECHNOLOGY; Lighting; encapsulant; nanomaterial; LED

Citation Formats

Kahen, Keith. New Class of Encapsulants for Blue LEDs. United States: N. p., 2019. Web.
Kahen, Keith. New Class of Encapsulants for Blue LEDs. United States.
Kahen, Keith. Wed . "New Class of Encapsulants for Blue LEDs". United States.
@article{osti_1545776,
title = {New Class of Encapsulants for Blue LEDs},
author = {Kahen, Keith},
abstractNote = {For many years silicone-based encapsulants have been the mainstay for LED modules. For the purposes of this report, we are focused solely on encapsulants that are placed on chip and are mixed with down-converting phosphors for pc-LED applications (Fig. 1). Conventional methyl- and phenyl-based silicones have numerous advantages, such as, optical clarity, proper viscosity prior to curing, lack of yellowing during LED operation, and long lifetimes. However, they suffer from low thermal conductivity and lower than desired refractive indices which results in reduced LED efficacies and lifetimes, in addition to color and intensity variations as a function of time. For years now many groups have attempted to replace silicones with more advanced encapsulants; however, the marketplace shows that none of those research efforts have resulted in any novel product-grade encapsulants being used by large LED manufacturers. In the majority of those efforts, inorganic-based fillers were added to conventional silicones to enhance the material’s thermal conductivity. For our Phase I effort, we took the novel approach of doing away with silicones and replacing it with an all inorganic formulation based on the usage of nanomaterials. The milestones for the project were (largely aligned with the corresponding DOE 2020 goals) that the encapsulant would have a thermal conductivity of 1 W/(m-K) and a refractive index of 1.8, while it remained optically transparent to visible light. For conventional silicones, these corresponding material properties are 0.2 W/(m-K) and 1.45, respectively. By project end, we synthesized encapsulant materials which were processable (limiting anneal temperatures to <220 C), dense and hard, optically clear, and had thermal conductivity and refractive index values of ~0.5-1.0 W/(m-K) and 1.9, respectively. Additionally, the encapsulants were mixed with phosphors, deposited on conventional LED modules, and produced white LED results analogous to those obtained using conventional silicones. In summary, over the course of the 10-month Phase I project an entirely new class of inorganic-based encapsulants were developed based on the usage of component nanomaterials. The resulting optical and thermal properties of the encapsulants were superior to those of silicones and in the case of the refractive index, exceeded the DOE 2020 goal. Overall, these results show promise for developing appropriate encapsulants which will eclipse silicone’s performance and enable white LEDs to operate at lower temperatures and enjoy enhanced efficacy performance.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {2019},
month = {7}
}

Technical Report:
This technical report may be released as soon as August 1, 2023
Other availability
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