LED Cap Containing Quantum Dot Phosphors

Abstract

An LED device has a cap containing one or more quantum dot (QD) phosphors. The cap may be sized and configured to be integrated with standard LED packages. The QD phosphor may be held within the well of the LED package, so as to absorb the maximum amount of light emitted by the LED, but arranged in spaced-apart relation from the LED chip to avoid excessive heat that can lead to degradation of the QD phosphor(s). The packages may be manufactured and stored for subsequent assembly onto an LED device.

What is claimed is: 
     
         1 . A cap for an LED package having a central well containing an LED, an upper surface and at least one side surface, said cap comprising:
 an upper portion having a top surface and a bottom surface sized and configured to attach to the upper surface of the LED package;   a well in the bottom surface of the top portion;   a plurality of quantum dots in the well.   
     
     
         2 . The cap recited in  claim 1  further comprising;
 a side portion attached to the upper portion, said side portion sized and configured to attach to the at least one side surface of the LED package. 
 
     
     
         3 . The cap recited in  claim 2  wherein the side portion is contiguous with the upper portion. 
     
     
         4 . The cap recited in  claim 1  wherein the upper portion is transparent. 
     
     
         5 . The cap recited in  claim 1  wherein the upper portion is translucent. 
     
     
         6 . The cap recited in  claim 1  wherein the well is spaced apart from the LED when the cap is attached to the LED package. 
     
     
         7 . The cap recited in  claim 1  wherein the plurality of quantum dots comprise a first type of quantum dots that emit secondary light having a first wavelength and a second type of quantum dots that emit secondary light having a second wavelength. 
     
     
         8 . The cap recited in  claim 7  wherein the first type of quantum dots emit green light when excited by blue light and the second type of quantum dots emit red light when excited by blue light. 
     
     
         9 . The cap recited in  claim 1  wherein the upper portion of the cap is shaped to provide a lens. 
     
     
         10 . The cap recited in  claim 1  wherein the upper portion of the cap is shaped to provide a lens array. 
     
     
         11 . The cap recited in  claim 1  wherein the upper portion of the cap comprises a light diffuser. 
     
     
         12 . The cap recited in  claim 1  wherein the quantum dots comprise a central core surrounded by at least one shell. 
     
     
         13 . The cap recited in  claim 12  wherein the shell material is different from the core material. 
     
     
         14 . The cap recited in  claim 1  wherein the quantum dots comprise an core comprising indium and phosphorus surrounded by a first shell comprising ZnS surrounded by a second shell comprising ZnO. 
     
     
         15 . The cap recited in  claim 1  wherein the quantum dots are cadmium-free quantum dots. 
     
     
         16 . The cap recited in  claim 1  wherein the quantum dots are suspended in a matrix. 
     
     
         17 . The cap recited in  claim 16  wherein the matrix comprises an acrylate polymer. 
     
     
         18 . The cap recited in  claim 16  wherein the matrix comprises an epoxy polymer. 
     
     
         19 . The cap recited in  claim 1  wherein the quantum dots are incorporated into beads. 
     
     
         20 . A light-emitting device comprising:
 a package having a central well, an upper surface and at least one side surface;   an LED within the central well;   a cap comprising an upper portion having a top surface and a bottom surface attached to the upper surface of the package;   a well in the bottom surface of the top portion;   a plurality of quantum dots in the well.   
     
     
         21 . The light-emitting device recited in  claim 20  wherein the bottom surface of the cap is attached to the upper surface of the package with an adhesive that is substantially impervious to oxygen. 
     
     
         22 . A cap for an LED package having a central well containing an LED and an upper surface, said cap comprising:
 a peripheral portion sized and configured to attach to the upper surface of the LED package;   a central portion depressed from the peripheral portion forming a cap well;   a plurality of quantum dots in the cap well.   
     
     
         23 . The cap recited in  claim 1  further comprising;
 a lid attached to the peripheral portion and covering the cap well. 
 
     
     
         24 . The cap recited in  claim 23  wherein the lid is transparent. 
     
     
         25 . The cap recited in  claim 23  wherein the lid is translucent. 
     
     
         26 . The cap recited in  claim 22  wherein the cap well is spaced apart from the LED when the cap is attached to the LED package. 
     
     
         27 . The cap recited in  claim 22  wherein the plurality of quantum dots comprise a first type of quantum dots that emit secondary light having a first wavelength and a second type of quantum dots that emit secondary light having a second wavelength. 
     
     
         28 . The cap recited in  claim 7  wherein the first type of quantum dots emit green light when excited by blue light and the second type of quantum dots emit red light when excited by blue light. 
     
     
         29 . The cap recited in  claim 22  wherein the lid cap is shaped to provide a lens. 
     
     
         30 . The cap recited in  claim 22  wherein the lid is shaped to provide a lens array. 
     
     
         31 . The cap recited in  claim 22  wherein the lid comprises a light diffuser. 
     
     
         32 . The cap recited in  claim 22  wherein the quantum dots comprise a central core surrounded by at least one shell. 
     
     
         33 . The cap recited in  claim 32  wherein the shell material is different from the core material. 
     
     
         34 . The cap recited in  claim 22  wherein the quantum dots comprise a core comprising indium and phosphorus surrounded by a first shell comprising ZnS surrounded by a second shell comprising ZnO. 
     
     
         35 . The cap recited in  claim 22  wherein the quantum dots are cadmium-free quantum dots. 
     
     
         36 . The cap recited in  claim 22  wherein the quantum dots are suspended in a matrix. 
     
     
         37 . The cap recited in  claim 16  wherein the matrix comprises an acrylate polymer. 
     
     
         38 . The cap recited in  claim 16  wherein the matrix comprises an epoxy polymer. 
     
     
         39 . The cap recited in  claim 22  wherein the quantum dots are incorporated into beads. 
     
     
         40 . A light-emitting device comprising:
 a package having a central well and an upper surface;   an LED within the central well;   a cap having a peripheral portion attached to the upper surface of the package;   a central portion depressed from the peripheral portion forming a cap well;   a plurality of quantum dots in the cap well.   
     
     
         41 . The light-emitting device recited in  claim 40  wherein the peripheral portion of the cap is attached to the upper surface of the package with an adhesive that is substantially impervious to oxygen. 
     
     
         42 . The light-emitting device recited in  claim 40  wherein the depressed central portion of the cap is at least partially within the central well of the package. 
     
     
         43 . The light-emitting device recited in  claim 40  wherein the depressed central portion of the cap is substantially within the central well of the package. 
     
     
         44 . The cap recited in  claim 22  wherein the cap well comprises a base wall having a phosphor incorporated therein. 
     
     
         45 . The cap recited in  claim 44  wherein the phosphor is an inorganic phosphor. 
     
     
         46 . The cap recited in  claim 44  wherein the phosphor is a broad-emitting, yellow-green phosphor. 
     
     
         47 . The cap recited in  claim 44  wherein the phosphor comprises Ce:YAG. 
     
     
         48 . The cap recited in  claim 44  wherein the phosphor comprises Ce:LuAG. 
     
     
         49 . A light-emitting device comprising:
 a package having a central well and an upper surface;   an LED within the central well;   a cap having a peripheral portion attached to the upper surface of the package;   a central portion depressed from the peripheral portion forming a cap well;   a base wall of the cap well having a phosphor incorporated therein;   a plurality of quantum dots in the cap well.   
     
     
         50 . The light-emitting device recited in  claim 49  wherein the LED is a blue LED, the phosphor is a broad-emitting, yellow-green phosphor, and the quantum dots are red-fluorescing quantum dots.