LIGHT EMITTING DEVICES INCLUDING A COLOR CONVERSION MATERIAL AND LIGHT EXTRACTING STRUCTURES AND METHOD OF MAKING THEREOF
A light emitting device includes a light emitting diode configured to emit blue or ultraviolet radiation incident photons, a color conversion material located over the light emitting diode and configured to absorb the incident photons emitted by the light emitting diode and to generate converted photons having a longer peak wavelength than a peak wavelength of the incident photons, and at least one light extracting feature located between the light emitting diode and the color conversion material.
1 . A light emitting device, comprising:
a light emitting diode configured to emit blue or ultraviolet radiation incident photons;
a color conversion material located over the light emitting diode and configured to absorb the incident photons emitted by the light emitting diode and to generate converted photons having a longer peak wavelength than a peak wavelength of the incident photons; and
at least one light extracting feature located between the light emitting diode and the color conversion material.
2 . The light emitting device of claim 1 , further comprising an optical cavity bounded by a cavity wall, wherein the light emitting diode is located in the optical cavity.
3 . The light emitting device of claim 2 , wherein the at least one light extracting feature comprises a first light extracting material layer located in the optical cavity between the light emitting diode and the color conversion material.
4 . The light emitting device of claim 3 , wherein:
the light emitting diode comprises a Group III— nitride active region; and
the first light extracting material layer comprises a first index of refraction that is in a range from approximately 1.5 to approximately 2.5.
5 . The light emitting device of claim 3 , wherein the first light extracting material layer comprises light extraction features comprising a rough interface between the first light extracting material layer and the color conversion material.
6 . The light emitting device of claim 3 , wherein the first light extracting material layer comprises light extraction features comprising a periodic array of nanoscale features that comprise a nanoscale photonic crystal that couples optical modes of the first light extracting material layer and optical modes of the color conversion material.
7 . The light emitting device of claim 3 , further comprising a second light extracting material layer comprising a corrugated height profile located over the first light extracting material layer.
8 . The light emitting device of claim 7 , wherein the second light extracting material layer comprises a second index of refraction that is different from a first index of refraction of the first light extracting material layer.
9 . The light emitting device of claim 3 , further comprising a plurality of partition structures formed over the first light extracting material layer that divide the optical cavity into a plurality of sub-cells, wherein the color conversion material is formed within the plurality of sub-cells.
10 . The light emitting device of claim 9 , wherein each of the plurality of partition structures comprises a tapered shape.
11 . The light emitting device of claim 3 , wherein the first light extracting material layer comprises a plurality of light scattering nanoparticles which are dispersed in a matrix.
12 . The light emitting device of claim 11 , wherein the plurality of light scattering nanoparticles comprise TiO 2 , ZrO 2 , or AN nanoparticles and the matrix comprises an epoxy or a UV curable polymer.
13 . The light emitting device of claim 3 , further comprising a reflective material formed over the cavity wall and a transparent material formed over the reflective material.
14 . The light emitting device of claim 13 , wherein the transparent material is configured to cause total internal reflection of photons incident at an angle greater than a critical angle relative to a direction perpendicular to a surface of the transparent material.
15 . The light emitting device of claim 13 , wherein:
the transparent material has a thickness that is greater than a penetration depth of an evanescent field associated with a reflecting photon; and
the reflective material comprises a metallic material formed over the cavity wall.
16 . The light emitting device of claim 13 , wherein the transparent material comprises a distributed Bragg reflector.
17 . A light emitting device, comprising:
an optical cavity bounded by a cavity wall;
a light emitting diode located in the optical cavity and configured to emit blue or ultraviolet radiation incident photons;
a color conversion material located over the light emitting diode and configured to absorb the incident photons emitted by the light emitting diode and to generate converted photons having a longer peak wavelength than a peak wavelength of the incident photons;
a reflective material located over the cavity wall; and
a transparent material located over the reflective material.
18 . The light emitting device of claim 17 , wherein the transparent material is configured to cause total internal reflection of photons incident at an angle greater than a critical angle relative to a direction perpendicular to a surface of the transparent material.
19 . The light emitting device of claim 17 , wherein:
the transparent material has a thickness that is greater than a penetration depth of an evanescent field associated with a reflecting photon; and
the reflective material comprises a metallic material formed over the cavity wall.
20 . The light emitting device of claim 17 , wherein the transparent material comprises a distributed Bragg reflector.