Light-emitting device including photoluminescent layer

• US 10,115,874 B2
• Filed: 05/26/2016
• Issued: 10/30/2018
• Est. Priority Date: 06/08/2015
• Status: Active Grant

• Current Assignee: Panasonic Intellectual Property Management Co., Ltd. (Panasonic Holdings Corporation)
• Original Assignee: Panasonic Intellectual Property Management Co., Ltd. (Panasonic Holdings Corporation)
• Inventors: Inada, Yasuhisa, Hirasawa, Taku
• Primary Examiner(s): Tso, Laura
• Application Number:
  US15/166,123
• Publication Number:
  US 20160359085A1
• Time in Patent Office: 887 Days
• Field of Search: 362 84
• CPC Class Codes: H01L 33/44 characterised by the coatings, e.g. passivation layer or anti-reflective coating
• CPC Class Codes: H01L 33/508 having a non-uniform spatial arrangement or non-uniform concentration, e.g. patterned wavelength conversion layer, wavelength conversion layer with a concentration gradient of the wavelength conversion material

Abstract

A light-emitting device comprises a photoluminescent layer that emits light including first light in an infrared region; and a light-transmissive layer located on the photoluminescent layer. At least one of the photoluminescent layer and the light-transmissive layer has a periodic structure having projections or recesses or both arranged perpendicular to the thickness direction of the photoluminescent layer. At least one of the photoluminescent layer and the light-transmissive layer has a light emitting surface perpendicular to the thickness direction of the photoluminescent layer, the first light being emitted from the light emitting surface. A refractive index n_wav-a of the photoluminescent layer for the first light and a period p_a of the periodic structure satisfy λ_a/n_wav-a<p_a<λ_a. A thickness of the photoluminescent layer, the refractive index n_wav-a and the period p_a are set to limit a directional angle of the first light emitted from the light emitting surface.

Claims

1. A light-emitting device comprising:

a photoluminescent layer that has a first surface perpendicular to a thickness direction thereof and emits light including first light in an infrared region, an area of the first surface being larger than a sectional area of the photoluminescent layer perpendicular to the first surface, the first light having a wavelength λ

_a in air; and

a light-transmissive layer located on the photoluminescent layer,

wherein at least one of the photoluminescent layer and the light-transmissive layer has a periodic structure having projections or recesses or both arranged perpendicular to the thickness direction of the photoluminescent layer,

at least one of the photoluminescent layer and the light-transmissive layer has a light emitting surface perpendicular to the thickness direction of the photoluminescent layer, the first light being emitted from the light emitting surface,

a refractive index n_wav-a of the photoluminescent layer for the first light and a period p_a of the periodic structure satisfy λ

_a/n_wav-a<

p_a<

λ

_a, and

a thickness of the photoluminescent layer, the refractive index n_wav-a and the period p_a are set to limit a directional angle of the first light emitted from the light emitting surface.

2. The light-emitting device according to claim 1, wherein a refractive index n_t-a of the light-transmissive layer for the first light is lower than a refractive index n_wav-a of the photoluminescent layer for the first light.

3. The light-emitting device according to claim 1, wherein the first light has maximum intensity in a first direction predetermined by the periodic structure.

4. The light-emitting device according to claim 3, wherein the directional angle is limited less than 15 degrees with respect to the first direction.

8. The light-emitting device according to claim 1, wherein the photoluminescent layer is in contact with the light-transmissive layer.

13. The light-emitting device according to claim 1, wherein the photoluminescent layer includes a phosphor.

14. The light-emitting device according to claim 1, wherein 0.75 μ

m≤

Δ

_a≤

4 μ

m is satisfied.

15. The light-emitting device according to claim 1, wherein the thickness of the photoluminescent layer, the refractive index n_wav-a and the period p_a are set to allow an electric field to be formed in the photoluminescent layer, in which antinodes of the electric field are located in or directly below the projections or recesses or both.

16. The light-emitting device according to claim 1, wherein the light-transmissive layer is located indirectly on the photoluminescent layer.

17. The light-emitting device according to claim 1, further comprising a substrate that has refractive index n_s-a for the first light and is located on the photoluminescent layer, wherein λ

_a/n_wav-a<

p_a<

λ

_a/n_s-a is satisfied.

5. A light-emitting device comprising:

a photoluminescent layer that has a first surface perpendicular to a thickness direction thereof and emits light including first light in an infrared region, an area of the first surface being larger than a sectional area of the photoluminescent layer perpendicular to the first surface; and

a light-transmissive layer located on the photoluminescent layer,

wherein the photoluminescent layer contains a photoluminescent material that is excited by a excitation light having a wavelength λ

_ex in air,

at least one of the photoluminescent layer and the light-transmissive layer has a periodic structure having projections or recesses or both arranged perpendicular to the thickness direction of the photoluminescent layer,

at least one of the photoluminescent layer and the light-transmissive layer has a light emitting surface perpendicular to the thickness direction of the photoluminescent layer, the first light and the excitation light being emitted from the light emitting surface,

a refractive index n_wav-ex of the photoluminescent layer for the excitation light, and a period p_ex of the periodic structure satisfy λ

_ex/n_wav-ex<

p_ex<

λ

_ex, and

a thickness of the photoluminescent layer, the refractive index n_wav-ex and the period p_ex are set to limit a directional angle of the excitation light emitted from the light emitting surface.

9. The light-emitting device according to claim 5, wherein the photoluminescent layer is in contact with the light-transmissive layer.

6. A light-emitting device comprising:

a light-transmissive layer having a periodic structure; and

a photoluminescent layer that has a first surface perpendicular to a thickness direction thereof, is located on the periodic structure and emits light including first light in an infrared region, an area of the first surface being larger than a sectional area of the photoluminescent layer perpendicular to the first surface, the first light having a wavelength λ

_a in air,

wherein the periodic structure has projections or recesses or both arranged perpendicular to the thickness direction of the photoluminescent layer,

at least one of the photoluminescent layer and the light-transmissive layer has a light emitting surface perpendicular to the thickness direction of the photoluminescent layer, the first light being emitted from the light emitting surface,

a refractive index n_wav-a of the photoluminescent layer for the first light and a period p_a of the periodic structure satisfy λ

_a/n_wav-a<

p_a<

λ

_a, and

a thickness of the photoluminescent layer, the refractive index n_wav-a and the period p_a are set to limit a directional angle of the first light emitted from the light emitting surface.

10. The light-emitting device according to claim 6, wherein the photoluminescent layer is in contact with the light-transmissive layer.

7. A light-emitting device comprising:

a photoluminescent layer that has a first surface perpendicular to a thickness direction thereof and emits light including first light in an infrared region, an area of the first surface being larger than a sectional area of the photoluminescent layer perpendicular to the first surface, the first light having a wavelength λ

_a in air; and

a light-transmissive layer having a higher refractive index than the photoluminescent layer,

wherein the light-transmissive layer has a periodic structure having projections or recesses or both arranged perpendicular to the thickness direction of the photoluminescent layer,

at least one of the photoluminescent layer and the light-transmissive layer has a light emitting surface perpendicular to the thickness direction of the photoluminescent layer, the first light being emitted from the light emitting surface,

a refractive index n_wav-a of the photoluminescent layer for the first light and a period p_a of the periodic structure satisfy λ

_a/n_wav-a<

p_a<

λ

_a, and

a thickness of the photoluminescent layer, the refractive index n_wav-a and the period p_a are set to limit a directional angle of the first light emitted from the light emitting surface.

11. The light-emitting device according to claim 7, wherein the photoluminescent layer is in contact with the light-transmissive layer.

12. A light-emitting device comprising:

a photoluminescent layer that has a first surface perpendicular to a thickness direction thereof and emits light including first light in an infrared region, an area of the first surface being larger than a sectional area of the photoluminescent layer perpendicular to the first surface, the first light having a wavelength λ

_a in air, wherein

the photoluminescent layer has a periodic structure having projections or recesses or both arranged perpendicular to the thickness direction of the photoluminescent layer,

at least one of the photoluminescent layer and the light-transmissive layer has a light emitting surface perpendicular to the thickness direction of the photoluminescent layer, the first light being emitted from the light emitting surface,

a refractive index n_wav-a of the photoluminescent layer for the first light and a period p_a of the periodic structure satisfy λ

_a/n_wav-a<

p_a<

λ

_a, and

a thickness of the photoluminescent layer, the refractive index n_wav-a and the period p_a are set to limit a directional angle of the first light emitted from the light emitting surface.