Phosphor-Coated Light Extraction Structures for Phosphor-Converted Light Emitting Devices

Abstract

A conformal thin-film phosphor layer is disposed over a surface of a hemispherical lens, a Fresnel lens, or a microlens array, thereby forming a phosphor-coated light extraction structure. Also disclosed is a phosphor-converted photonic crystal light emitting device that incorporates a thin-film phosphor layer. A wafer-level packaging process incorporating a thin-film phosphor layer is also disclosed herein.

1 . A phosphor-coated light extraction structure, comprising:
 a light extraction structure including a coating surface; and   a thin-film phosphor layer including at least one phosphor powder layer and at least one polymer layer serving as a binder for the at least one phosphor powder layer,   wherein the thin-film phosphor layer is conformally disposed adjacent to the coating surface of the light extraction structure.   
   
   
       2 . The phosphor-coated light extraction structure of  claim 1 , wherein the light extraction structure is a hemispherical, hollow lens, and the thin-film phosphor layer is conformally disposed adjacent to an inner concave surface of the lens. 
   
   
       3 . The phosphor-coated light extraction structure of  claim 1 , wherein the light extraction structure is a hemispherical, solid lens, and the thin-film phosphor layer is conformally disposed adjacent to a bottom, substantially flat surface of the lens. 
   
   
       4 . The phosphor-coated light extraction structure of  claim 1 , wherein the light extraction structure is a hemispherical lens, and the thin-film phosphor layer is conformally disposed adjacent to an outer convex surface of the lens. 
   
   
       5 . The phosphor-coated light extraction structure of  claim 1 , wherein the light extraction structure is a microlens array, and the thin-film phosphor layer is conformally disposed adjacent to outer convex surfaces of the microlens array. 
   
   
       6 . The phosphor-coated light extraction structure of  claim 1 , wherein the at least one polymer layer includes a polymer including a repeating unit of the formula: —CZZ′—Ar—CZ″Z′″—, wherein Ar is selected from (1) an un-substituted phenylene group, (2) a chlorine-substituted phenylene group of the formula: C 6 H 4-x Cl x , with x being an integer in the range of 1 to 4, and (3) a fluorine-substituted phenylene group of the formula: C 6 H 4-   x′ F x′ , with x′ being an integer in the range of 1 to 4, and Z, Z′, Z″, and Z′″ are independently selected from H, F, alkyl groups, and aryl groups. 
   
   
       7 . A phosphor-converted light emitting device, comprising:
 a light emitting device; and   a thin-film phosphor layer disposed in an optical path of the light emitting device,   wherein a thickness of the thin-film phosphor layer is in the range of 1 nm to 100 μm, and the thin-film phosphor layer includes:
 a first phosphor powder layer including first phosphor particles; and 
 a first polymer layer adjacent to the first phosphor powder layer, the first polymer layer serving as a binder for the first phosphor particles. 
   
   
   
       8 . The phosphor-converted light emitting device of  claim 7 , further comprising a spacer layer disposed between the thin-film phosphor layer and the light emitting device. 
   
   
       9 . The phosphor-converted light emitting device of  claim 7 , further comprising an encapsulant layer disposed between the thin-film phosphor layer and the light emitting device. 
   
   
       10 . The phosphor-converted light emitting device of  claim 7 , further comprising:
 a first light extraction structure including a coating surface, wherein the thin-film phosphor layer is conformally disposed adjacent to the coating surface of the first light extraction structure;   a second light extraction structure disposed between the first light extraction structure and the light emitting device; and   a reflector cup, wherein the light emitting device is disposed adjacent to the reflector cup, and an optical cavity is defined by the reflector cup and the thin-film phosphor layer.   
   
   
       11 . The phosphor-converted light emitting device of  claim 10 , wherein the second light extraction structure is a hemispherical lens including a roughened surface. 
   
   
       12 . The phosphor-converted light emitting device of  claim 10 , wherein the second light extraction structure is a microlens array. 
   
   
       13 . The phosphor-converted light emitting device of  claim 7 , wherein the thin-film phosphor layer further includes a second polymer layer adjacent to the first polymer layer, and a refractive index of the first polymer layer is greater than a refractive index of the second polymer layer. 
   
   
       14 . The phosphor-converted light emitting device of  claim 7 , wherein the thin-film phosphor layer further includes:
 a second phosphor powder layer adjacent to the first polymer layer, the second phosphor powder layer including second phosphor particles; and   a second polymer layer adjacent to the second phosphor powder layer, the second polymer layer serving as a binder for the second phosphor particles,   wherein the first phosphor particles and the second phosphor particles are configured to emit light of different colors.   
   
   
       15 . The phosphor-converted light emitting device of  claim 14 , wherein the thin-film phosphor layer further includes:
 a third phosphor powder layer adjacent to the second polymer layer, the third phosphor powder layer including third phosphor particles; and   a third polymer layer adjacent to the third phosphor powder layer, the third polymer layer serving as a binder for the third phosphor particles,   wherein the first phosphor particles, the second phosphor particles, and the third phosphor particles are configured to emit light of different colors.   
   
   
       16 . The phosphor-converted light emitting device of  claim 7 , wherein a Correlated Color Temperature variation of the phosphor-converted light emitting device is no greater than 500 K over a 140° range of angles relative to a center light-emitting axis of the light emitting device. 
   
   
       17 . A phosphor-converted light emitting device, comprising:
 a light emitting device including a photonic crystal structure; and   a thin-film phosphor layer disposed in an optical path of the light emitting device,   wherein a thickness of the thin-film phosphor layer is in the range of 1 nm to 100 μm, and the thin-film phosphor layer includes:
 at least one phosphor powder layer including phosphor particles; and 
 at least one polymer layer adjacent to the at least one phosphor powder layer, the at least one polymer layer serving as a binder for the phosphor particles. 
   
   
   
       18 . The phosphor-converted light emitting device of  claim 17 , wherein the photonic crystal structure includes a dielectric material to create a substantially periodic variation in refractive index. 
   
   
       19 . The phosphor-converted light emitting device of  claim 17 , wherein the dielectric material includes a polymer including a repeating unit of the formula: —CZZ′—Ar—CZ″Z′″—, wherein Ar is selected from (1) an un-substituted phenylene group, (2) a chlorine-substituted phenylene group of the formula: C 6 H 4-x Cl x , with x being an integer in the range of 1 to 4, and (3) a fluorine-substituted phenylene group of the formula: C 6 H 4-   x′ F x′ , with x′ being an integer in the range of 1 to 4, and Z, Z′, Z″, and Z′″ are independently selected from H, F, alkyl groups, and aryl groups. 
   
   
       20 . A method of forming phosphor-converted light emitting devices, comprising:
 providing a packaging substrate including an array of submount reflectors;   connecting light emitting devices to respective reflector cups of the packaging substrate;   providing a phosphor-coated microlens array;   connecting the phosphor-coated microlens array to the packaging substrate; and   dicing the packaging substrate to form individual phosphor-converted light emitting devices.   
   
   
       21 . The method of  claim 20 , wherein providing the packaging substrate includes:
 providing the packaging substrate including an array of submounts; and   depositing a reflector layer adjacent to the packaging substrate to form the array of submount reflectors.   
   
   
       22 . The method of  claim 20 , wherein providing the phosphor-coated microlens array includes:
 forming a phosphor powder layer adjacent to a microlens array, the phosphor powder layer including phosphor particles that are distributed adjacent to a coating surface of the microlens array; and   forming, via vapor deposition, a polymer layer adjacent to the phosphor powder layer, the polymer layer serving as a binder for the phosphor particles.   
   
   
       23 . A method of forming a phosphor-embedded light extraction structure, comprising:
 forming a light extraction structure using injection molding of a liquid gel;   forming a phosphor powder layer adjacent to a coating surface of the light extraction structure, wherein at least a fraction of phosphor powders of the phosphor powder layer is embedded into the light extraction structure; and   curing the liquid gel to form a phosphor-embedded light extraction structure.