Low index spacer layer in LED devices
First Claim
1. A light emitting diode (LED) device, comprising:
- an LED chip on a mount surface, said LED chip comprising sidewalls and a textured light emission surface, said LED chip having a first index of refraction;
a reflective element opposite said textured light emission surface such that said reflective element is between said LED chip and said mount surface;
a spacer layer disposed on said LED chip and covering said light emission surface and said sidewalls, said spacer layer having a second index of refraction that is smaller than said first index of refraction; and
at least one functional layer comprising a wavelength conversion layer disposed on said spacer layer, said wavelength conversion layer comprising a binder material embedded with a plurality of phosphor particles, said phosphor particles having a third index of refraction that is larger than said second index of refraction, wherein said binder material has a substantially similar index of refraction to said phosphor particles;
wherein said spacer layer and said functional layer are conformal to said LED chip.
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Accused Products
Abstract
A light emitting diode (LED) device having a low index of refraction spacer layer separating the LED chip and a functional layer. The LED chip has a textured light emission surface to increase light extraction from the chip. The spacer layer has an index of refraction that is lower than both the LED chip and the functional layer. Most of the light generated in the LED chip passes easily into the spacer layer due to the textured surface of the chip. At the interface of the spacer layer and the functional layer the light sees a step-up in index of refraction which facilitates transmission. A portion of the light that has passed into the functional layer will be reflected or scattered back toward the spacer layer where some of it will experience total internal reflection. Total internal reflection at this interface may increase extraction efficiency by reducing the amount of light that re-enters the spacer layer and, ultimately, the LED chip where it may be absorbed. The spacer layer also provides a thermal buffer between the LED chip and the functional layer. Thus, the functional layer, which may be a wavelength conversion layer comprising phosphors, for example, is insulated from direct thermal transfer from the LED chip. The spacer layer can also function as a passivation layer.
156 Citations
38 Claims
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1. A light emitting diode (LED) device, comprising:
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an LED chip on a mount surface, said LED chip comprising sidewalls and a textured light emission surface, said LED chip having a first index of refraction; a reflective element opposite said textured light emission surface such that said reflective element is between said LED chip and said mount surface; a spacer layer disposed on said LED chip and covering said light emission surface and said sidewalls, said spacer layer having a second index of refraction that is smaller than said first index of refraction; and at least one functional layer comprising a wavelength conversion layer disposed on said spacer layer, said wavelength conversion layer comprising a binder material embedded with a plurality of phosphor particles, said phosphor particles having a third index of refraction that is larger than said second index of refraction, wherein said binder material has a substantially similar index of refraction to said phosphor particles; wherein said spacer layer and said functional layer are conformal to said LED chip. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 34, 35, 36)
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17. A light emitting diode (LED) device, comprising:
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an LED chip on a mount surface, said LED chip comprising sidewalls and a textured light emission surface, said LED chip having a first index of refraction and emitting blue light; a reflective element opposite said textured light emission surface such that said reflective element is between said LED chip and said mount surface; a spacer layer disposed on said LED chip and covering said light emission surface and said sidewalls, said spacer layer comprising a planar surface opposite said LED chip and a second index of refraction that is smaller than said first index of refraction; a wavelength conversion layer disposed on a light emission surface and sidewalls of said spacer layer, said wavelength conversion layer comprising a binder material embedded with a plurality of phosphor particles, said wavelength conversion layer converting a portion of said blue light and emitting yellow light, said phosphor particles having a third index of refraction that is larger than said second index of refraction, wherein said binder material has a substantially similar index of refraction to said phosphor particles; and an encapsulant disposed on said mount surface and covering said LED chip; wherein said spacer layer and said wavelength conversion layer are conformal to said LED chip; wherein said light emitting diode (LED) device is constructed to emit a combination of said blue and yellow light such that said combination appears white. - View Dependent Claims (18, 19, 20, 21, 22, 23, 24, 25, 26, 37)
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27. A method of fabricating a light emitting diode (LED) device, comprising:
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providing an LED chip having a first index of refraction, said LED chip comprising sidewalls and a textured light emission surface; disposing a reflective element opposite said textured light emission surface such that said reflective element is between said LED chip and a mount surface; disposing a spacer layer, conformal to said LED chip, with a second index of refraction on said LED chip, wherein said second index of refraction is smaller than said first index of refraction; disposing a functional layer comprising a wavelength conversion layer on said spacer layer and conformal to said LED chip, said wavelength conversion layer comprising a binder material and a plurality of phosphor particles, said phosphor particles having a third index of refraction, wherein said second index of refraction is smaller than said third index of refraction, and said second index of refraction is chosen to maximize light extraction efficiency, wherein said binder material has a substantially similar index of refraction to said phosphor particles. - View Dependent Claims (28, 29, 30, 31, 32, 33, 38)
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Specification