Light-emitting diodes with improved color purity

Abstract

A light-emitting diode (LED) is provided, comprising an LED layer configured to emit pump light having a pump light wavelength from a light-emitting surface, the LED layer comprising a plurality of Group III nitride layers. A container layer is disposed on the light-emitting surface of the LED layer, the container surface comprising an opening, the opening defining a container volume through the container layer to the light-emitting surface of the LED layer. A color conversion layer is disposed within the container volume, the color conversion layer configured to absorb pump light and emit converted light having a wavelength greater than the pump light wavelength. A lens is disposed on the container surface above the opening, the lens having a convex surface on a side of the lens opposite the color conversion layer. A pump light reflector laminate is disposed above the convex surface of the lens, the pump light reflector laminate having a stop band configured to reflect pump light centered at a first wavelength.

Description

Technical Field

[0001] The present disclosure relates to light emitting diodes (LEDs) and LED arrays, and in particular to LEDs containing group III nitrides. Background Art

[0002] Micro LED arrays are typically limited to 100×100μm in size. 2 Or smaller LED arrays. Micro-LED arrays are a type of self-emissive micro-display / projector suitable for a variety of devices such as smart watches, head-mounted displays, heads-up displays, cameras, viewfinders, multi-point excitation sources, and pico projectors.

[0003] One known form of micro-LED array includes multiple LEDs formed from group III nitrides. Group III nitride LEDs are inorganic semiconductor LEDs that contain GaN and its alloys with InN and AlN in the active light-emitting region. Group III nitride LEDs can be driven at significantly higher current densities and emit higher light power densities than traditional large-area LEDs, such as organic light emitting diodes (OLEDs), in which the light-emitting layer is an organic compound. Therefore, the higher brightness (brightness) is defined as the amount of light emitted per unit area of ​​a light source in a given direction, making micro-LEDs suitable for applications that require or benefit from high brightness. For example, applications that benefit from high brightness may include displays in high-brightness environments, or projectors. In addition, compared to other traditional large-area LEDs, group III nitride micro-LEDs are known to have relatively high luminous efficiency, expressed in lumens per watt (lm / W). The relatively high luminous efficiency of group III nitride micro-LED arrays reduces power consumption compared to other light sources, making micro-LEDs particularly suitable for portable devices.

[0004] In many applications, it is desirable to provide a micro-LED array that can output light having a range of wavelengths (i.e., color displays / projectors). For example, in many color displays, it is desirable to provide a micro-LED array having multiple pixels on a common substrate, where each pixel can output, for example, a combination of red, green, and blue light.

[0005] Generally speaking, there are two main approaches to providing LED color displays comprising a plurality of pixels, each capable of outputting a range of different colors. One approach seeks to provide each pixel of the array with a plurality of LEDs, each arranged to emit light of a different wavelength.

[0006] Another approach is to provide each pixel of the array with one or more color-converting materials, such as phosphors or quantum dots, that can convert higher-energy light (the pump light) into lower-energy light (the converted light) to provide the desired color for that subpixel.

[0007] One problem with using color-converting materials is that it is challenging to efficiently convert light from the pump wavelength to the converted wavelength and then extract only the converted light from the device. One factor that reduces the efficiency of extracting the converted light is that the color-converting material (such as quantum dots) may also absorb the converted light.

[0008] Furthermore, when using color-converting materials, it is desirable for the LED to output only the converted light, not the pump light. If the pump light leaks from the LED, the color purity of the LED will be reduced. In many applications (such as displays), the color purity of the LED is an important parameter.

[0009] One option for reducing pump light leakage is to use distributed Bragg reflectors (DBRs) to reflect the pump light. In "Reducing Optical Crosstalk in Quantum Dot-Based Full-Color Micro-LED Displays via Lithographically Fabricated Photoresist Molds," Photonics Research, Vol. 5, No. 5, October 2017, a UV micro-LED array was used as an efficient excitation source for quantum dots (QDs). To reduce optical crosstalk between sub-pixels, a mold was fabricated using a simple photolithography method and photoresist. The mold included openings for adding the quantum dots and barrier walls to reduce crosstalk. Distributed Bragg reflectors (DBRs) were placed over the quantum dots to reflect UV light that passes through the quantum dots, thereby increasing their light emission. The DBRs also improve the color purity of the LED by preventing pump light from passing through the LED.

[0010] To further reduce pump light leakage, the portion of the LED that provides the color conversion material can be lined with a material configured to absorb pump light. In "Unified Red / Green / Blue Micro-LEDs with HBR and DBR Structures," Guan Syun Chen et al., IEEE Photonics Letters, Vol. 30, No. 3, February 1, 2018, a black matrix photoresist with light-shielding capabilities is spun onto the micro-LEDs. The black matrix photoresist can block blue light emitted from the sides of blue micro-LEDs containing red or green quantum dots. As a result, blue light crosstalk between adjacent LEDs is reduced by the black matrix photoresist. However, since all visible light incident on the inner wall of each sub-pixel is absorbed, conversion efficiency is significantly reduced.

[0011] Therefore, there is a need to further improve the color purity and efficiency of LEDs containing color conversion materials.

[0012] It is an object of the present invention to provide an improved LED which solves at least one of the problems associated with prior art LEDs, or which at least provides a commercially useful alternative. Summary of the Invention

[0013] The present inventors have recognized that it is desirable to improve color efficiency and block crosstalk between each pixel while increasing the purity of LEDs containing color-converting materials. Factors affecting the color purity and efficiency of such LEDs include pump light leakage from the LED, the efficiency of the color-converting material in converting the pump light, and the efficiency of the LED in extracting the converted light.

[0014] The present inventors have recognized that conventional DBRs, such as those disclosed in "Reducing Optical Crosstalk in Quantum Dot-Based Full-Color Micro-LED Displays Using Lithographically Fabricated Photoresist Molds," have a number of significant drawbacks when applied to LEDs with color-conversion materials. FIG1a illustrates a schematic diagram of the reflectivity of a conventional DBR for various incident angles. It should be understood that while the reflectivity of the DBR in the passband (i.e., on either side of the stopband) is lower than that in the stopband, the reflectivity is still significant.

[0015] As shown in Figure 1a, changing the incident angle of the DBR shifts the peak wavelength of the harmonic peak reflected in the passband. As shown in Figure 1a, changing the incident angle (relative to the normal) between 0° and 30° shifts the harmonic peak over a significant portion of the visible light band.

[0016] The converted light output by color-converting materials (e.g., quantum dots) is emitted in all directions from the color-converting material. Therefore, for LEDs containing DBRs, a significant portion of the converted light incident on the DBR will have a non-zero angle of incidence. This presents a challenge in designing a reflector that has low reflectivity at the converted light wavelengths (e.g., green or red) but high reflectivity at the pump light wavelength (e.g., blue).

[0017] According to a first aspect of the present invention, an LED is provided. The LED includes an LED layer, a container layer, a color conversion layer, a lens, and a pump light reflector laminate. The LED layer is configured to emit pump light having a pump light wavelength from a light emitting surface, and the LED layer includes multiple Group III nitride layers. The container layer is disposed on the light emitting surface of the LED layer. The container layer has a container surface on a side of the container layer opposite the light emitting surface, the container surface including an opening, the opening defining a container volume through the container layer to the light emitting surface of the LED layer. The color conversion layer is disposed within the container volume, the color conversion layer configured to absorb pump light and emit converted light, the converted light having a converted light wavelength greater than the pump light wavelength. The lens is disposed on the container surface above the opening. The lens has a convex surface on a side of the lens opposite the color conversion layer. The pump light reflector laminate is disposed above the convex surface of the lens, the pump light reflector laminate having a stop band configured to reflect pump light. The stop band is centered at a first wavelength, and the pump light reflector laminate includes:

[0018] (i) a first interface layer disposed on a convex surface of the lens; the first interface layer having a first thickness and a first refractive index, wherein the product of the first refractive index and the first thickness is one eighth of the first wavelength;

[0019] (ii) a plurality of layers alternating between low-reflection layers and high-reflection layers, the low-reflection layers having a second refractive index and a second thickness, wherein the second refractive index is lower than the first refractive index, and the high-reflection layers having a third thickness and a third refractive index higher than the second refractive index, wherein the product of the second refractive index and the second thickness of each low-reflection layer is one-quarter of the first wavelength, and the product of the third refractive index and the third thickness of each high-reflection layer is one-quarter of the first wavelength; and

[0020] (iii) a second interface layer disposed on the low-reflection layer of the plurality of layers, the second interface layer having a fourth refractive index and a fourth thickness, wherein a product of the fourth refractive index and the fourth thickness is one eighth of the first wavelength.

[0021] The pump light reflector laminate according to the first aspect is configured to have high reflectivity for light at the pump wavelength generated by the LED layer. The reflector laminate is also configured to have low reflectivity for light at the converted wavelength output by the color conversion material. As such, the pump light reflector laminate effectively acts as a band-stop filter for light with wavelengths approximately equal to the pump light wavelength and transmits the converted light. Compared to DBRs known in the art, the reflectivity of the pump light reflector laminate has suppressed harmonic peaks in its upper passband. Consequently, a lower proportion of the converted light output by the color conversion material will be reflected by the pump light reflector laminate compared to a DBR.

[0022] Furthermore, the reflectivity of the pump light reflector laminate in the upper passband is significantly insensitive to variations in the light incident angle. For example, the pump light reflector laminate according to the first aspect can have a relatively low reflectivity (e.g., less than 10%) for converted light incident on the pump light reflector laminate at angles of incidence ranging from 0° to 30° and above. Consequently, compared to conventional DBRs, the pump light reflector laminate will reflect a lower proportion of converted light across a range of incident angles.

[0023] The inventors have also recognized that another problem associated with providing LEDs with reflectors is that light incident on the reflector at angles exceeding 45° will be completely internally reflected at the interface between the reflector and the LED. As discussed above, the color-converting material typically absorbs a certain fraction of the converted light. Consequently, internal reflection of the converted light not only reduces the fraction of converted light that exits the LED, but also increases the fraction of converted light that is absorbed by the color-converting material. Both mechanisms reduce the efficiency of the LED in outputting converted light.

[0024] The LED according to the first aspect is designed to further improve the efficiency of the converted light output by the LED by providing a pump light reflector laminate on the convex surface of the lens. Because the pump light reflector laminate is disposed on the convex surface, the proportion of converted light incident on the pump light reflector laminate at an angle exceeding 45° is reduced compared to a case where the pump light reflector laminate is disposed on a flat surface. Consequently, a greater proportion of the converted light is transmitted through the pump light reflector laminate rather than being internally reflected.

[0025] The pump light reflector laminate is effectively a band-stop filter. As such, the pump light reflector laminate has a stopband in a wavelength range from a lower stopband wavelength to an upper stopband wavelength, wherein substantially all light is reflected by the pump light reflector laminate. The stopband is centered around a central wavelength (e.g., a first wavelength) such that the upper stopband wavelength and the lower stopband wavelength are equidistant from the central wavelength. The stopband of the pump light reflector laminate is configured such that the pump light wavelength falls within the stopband, thereby ensuring that the pump light is reflected by the pump light reflector laminate. Those skilled in the art will appreciate that the center wavelength (first wavelength) of the stopband can be different from the pump light wavelength. That is, the stopband can be different from the pump light wavelength, although in some embodiments, this may be the case.

[0026] In some embodiments, the container layer includes inner sidewalls defining a container volume, wherein the inner sidewalls defining the container volume are inclined at an acute angle relative to the light-emitting surface of the LED layer and include a reflective material. By providing the container layer with reflective sidewalls, a larger proportion of light incident on the sidewalls is reflected back into the container volume (relative to the light-absorbing sidewalls). Consequently, a larger proportion of the converted light that can be generated by the color-converting material in all directions can be extracted from the LED. Furthermore, the sidewalls are inclined such that a larger proportion of the light is reflected toward the pump light reflector laminate. By providing the inclined reflective sidewalls, the conversion proportion incident on the pump light reflector laminate is increased, even at various angles of incidence. As described above, the reflectivity of the pump light reflector laminate in the upper passband is significantly insensitive to variations in the light incidence angle. Consequently, a synergistic effect may exist between the inclined reflective sidewalls and the pump light reflector laminate, which improves the efficiency of converting light extraction from the LED.

[0027] In some embodiments, the LED further comprises a reflection enhancement layer disposed on the inner sidewall of the container layer, wherein the reflection enhancement layer comprises a dielectric, for example, SiO2.

[0028] In some embodiments, the LED further comprises an antireflection layer disposed above the pump light reflector laminate, the antireflection layer being configured to reduce reflection of light at the converted light wavelength. In some embodiments, the antireflection layer comprises a material having a refractive index less than the refractive index of the second interface layer of the pump light reflector laminate. In some embodiments, the antireflection layer has a thickness of one-quarter the first wavelength. The antireflection layer is provided to improve the efficiency of converting light extraction from the LED.

[0029] In some embodiments, a conversion light reflector laminate may be disposed between the LED layer and the color conversion layer. The conversion light reflector laminate has a stop band configured to reflect converted light centered at the second wavelength, the conversion light reflector laminate comprising:

[0030] (a) a third interface layer disposed on the light emitting surface of the LED layer; the third interface layer having a fifth thickness and a fifth refractive index, wherein the product of the fifth thickness and the fifth refractive index is one eighth of the second wavelength;

[0031] (b) Multiple layers, alternating between:

[0032] a converted light high reflective layer having a sixth thickness and a sixth refractive index higher than the fifth refractive index,

[0033] a light-converting low-reflection layer having a seventh refractive index and a seventh thickness, wherein the seventh refractive index is lower than the sixth refractive index; and

[0034] wherein the product of the sixth refractive index and the sixth thickness of each of the light-converting high-reflection layers is one-quarter of the second wavelength, and the product of the seventh refractive index and the seventh thickness of each of the light-converting low-reflection layers is one-quarter of the second wavelength; and

[0035] (c) a fourth interface layer disposed on the plurality of layers of the converted light high-reflection layer, the fourth interface layer having an eighth refractive index and an eighth thickness, wherein the product of the eighth refractive index and the eighth thickness is one-eighth of the second wavelength, and the eighth refractive index is lower than the sixth refractive index.

[0036] Referring to the pump light reflector laminate discussed above, the converted light reflector laminate is effectively a band-stop filter configured to reflect the converted light but transmit the pump light. The converted light reflector laminate is configured to increase the proportion of the openings through which the converted light passes directly into the container layer (i.e., into the pump light reflector laminate) to improve the efficiency of converting the light extracted from the LED.

[0037] In some embodiments, a lens interface layer is disposed on the pump light reflector laminate on the side opposite the lens. The lens interface layer may have another convex surface on the side opposite the pump light reflector layer, i.e., the lens interface layer may define another lens shape on top of the lens and the pump light reflector. The lens interface layer, combined with the lens, can be considered a lens superstructure. As such, the pump light reflector laminate can be considered disposed within the lens superstructure. In some embodiments, an antireflection layer may be disposed above the pump light reflector layer on the other convex surface of the lens interface layer.

[0038] In some embodiments, the color conversion layer comprises quantum dots and / or phosphors. In some embodiments, the color conversion layer can fill at least 50%, 60%, 70%, 80%, or 90% of the volume of the container. In some embodiments, the color conversion layer is disposed substantially in a central region of the container volume.

[0039] In some embodiments, the inner sidewall forms an angle of at least 30° relative to the light-emitting surface of the LED layer. Thus, the inclination of the inner sidewall can be provided to increase the proportion of converted light reflected toward the container volume opening. In some embodiments, the inner sidewall forms an angle of no more than 85° relative to the light-emitting surface of the LED layer. Thus, the inclination of the inner sidewall can be provided so that a substantial proportion of the container layer opening is aligned with the light-emitting surface of the LED layer.

[0040] In some embodiments, the pump light wavelength may be at least 440 nm and / or no greater than 480 nm; and / or the converted light wavelength may be at least 500 nm and / or no greater than 650 nm. Thus, the LED according to the first aspect can be configured to convert blue pump light into light of a different color. For example, the LED may output red or green converted light.

[0041] In some embodiments, the container layer defines a -8 m 2 In some embodiments, the container layer may define an opening with an area size of less than 100 μm x 100 μm. As such, the LED according to the first aspect may be a micro-LED.

[0042] In some embodiments, the pump light reflector and / or the conversion light reflector may include layers of TiO2 and SiO2. Thus, the pump light reflector and / or the conversion light reflector may be fabricated using thin film deposition methods commonly used to fabricate thin film electronic devices (e.g., displays, micro-LED displays, etc.). In particular, the layers of the pump light reflector are configured to suppress harmonic reflections in the passband within the range of 510 nm to 550 nm (for green LEDs) and within the range of 600 nm to 630 nm (for red LEDs).

[0043] In some embodiments, the first refractive index, the third refractive index, and / or the fourth refractive index is at least 2. In some embodiments, the second refractive index is no greater than 1.8.

[0044] In some embodiments, the first refractive index of the first interface layer, the third refractive index of the high-reflection layer, and the fourth refractive index of the second interface layer are the same. In some embodiments, the fifth refractive index of the third interface layer, the seventh refractive index of the converted light low-reflection layer, and the eighth refractive index of the fourth interface layer are the same. As such, each pump light reflector laminate and converted light reflector laminate can be provided by alternating layers of two different compositions.

[0045] In some embodiments, the first wavelength (λ0), the second refractive index (n L ) and the third refractive index (n H) has the upper stopband wavelength (λ e ), which is longer than the pump light wavelength, wherein:

[0046]

[0047] According to a second aspect of the present disclosure, a light-emitting diode (LED) array is provided. The LED array includes an LED layer, a container layer, a color conversion layer, a lens, and a pump light reflector. The LED layer includes a plurality of LEDs, each configured to emit pump light at a pump light wavelength from a light-emitting surface, and each LED includes a plurality of Group III nitride layers. The container layer is disposed on the light-emitting surface of the LED layer. The container layer has a container surface on a side of the container layer opposite the light-emitting surface. The container surface includes a plurality of openings, each of which defines a container volume through the container layer to the light-emitting surface of the LED layer, each opening and the container volume being aligned with a corresponding LED of the LED layer. The color conversion layer is selectively disposed in the container volume, the color conversion layer configured to absorb pump light and emit converted light having a wavelength longer than the pump light wavelength. The lens is disposed on the container surface above the opening of the container volume, the container volume containing a color conversion material, and the lens has a convex surface on a side of the lens opposite the color conversion layer. The pump light reflector laminate is disposed on the convex surface of the lens. The pump light reflector laminate has a stop band configured to reflect pump light centered at a first wavelength. The pump light reflector laminate includes:

[0048] (1) a first interface layer disposed on the convex surface of the lens; the first interface layer having a first thickness and a first refractive index, wherein the product of the first refractive index and the first thickness is one eighth of the first wavelength;

[0049] (2) Multiple layers, alternating between:

[0050] a low-reflection layer having a second refractive index and a second thickness, wherein the second refractive index is lower than the first refractive index; and

[0051] a highly reflective layer having a third thickness and a third refractive index higher than the second refractive index,

[0052] The product of the second refractive index and the second thickness of each low-reflection layer is one-quarter of the first wavelength, and the product of the third refractive index and the third thickness of each high-reflection layer is one-quarter of the first wavelength.

[0053] (3) a second interface layer disposed on the low-reflection layer of the plurality of layers, the second interface layer having a fourth refractive index and a fourth thickness, wherein the product of the fourth refractive index and the fourth thickness is one eighth of the first wavelength, and the fourth refractive index is longer than the second refractive index.

[0054] Therefore, an LED array comprising a plurality of LEDs can be provided. As described in the first aspect of the present invention, at least one LED in the array includes a color conversion layer covered by a lens having a pump light reflector. Therefore, the LED array according to the first aspect can output light having different wavelength (color) ranges by selectively using LEDs having a color conversion layer and / or LEDs not having a color conversion layer. Thus, the LED array can output light having a pump light wavelength and / or a first converted light wavelength. Importantly, at least for the reasons described in the first aspect above, the LED array can output light at the first converted light wavelength with improved efficiency and color purity.

[0055] In some embodiments, another color conversion layer is disposed in another container volume of the plurality of container volumes, the another color conversion layer being configured to absorb pump light at a pump light wavelength and emit converted light having a second converted light wavelength that is longer than the first converted light wavelength. In some embodiments, a lens is disposed above the another container volume, and a pump light reflector laminate is disposed above the lens.

[0056] Thus, an LED array can include multiple LEDs each having a different color conversion layer disposed within a respective container volume. For example, a first color conversion layer can be disposed within a first container volume, and a second color conversion layer can be disposed within a second container volume. The first and second color conversion layers can be configured to convert pump light into converted light of different wavelengths, such as green and red, respectively. Thus, the LED array according to the second aspect can provide one or more pixels of an LED display, wherein each pixel includes an LED that outputs red, green, and blue light (the blue light being the pump light).

[0057] Figure 1bAn example of the DCI-P3 color space standard is shown. For display applications using an LED array, it is desirable to provide multiple LEDs in the LED array that comply with the DCI-P3 color space standard. To comply with DCI-P3, the color conversion layer may, for example, include quantum dots. Thus, the first color conversion layer may be configured to generate converted light with a wavelength of 532 nm, and the second color conversion layer may be configured to generate converted light with a wavelength of 625 nm. The first color conversion material and the second color conversion material may have spectral widths (full width at half maximum) of 40 nm and 50 nm, respectively. The pump light (providing the blue sub-pixel) may have a peak wavelength of 455 nm and a spectral width of 20 nm.

[0058] In some embodiments, at least one converted light reflector laminate is disposed between the color conversion layer and the light emitting surface of the corresponding LED of the LED layer, the converted light reflector laminate having a stop band configured to reflect the first converted light and / or the second converted light centered at the second wavelength. The converted light reflector laminate comprises:

[0059] (x) a third interface layer disposed on the light emitting surface of the LED layer; the third interface layer having a fifth thickness and a fifth refractive index, wherein the product of the fifth thickness and the fifth refractive index is one eighth of the second wavelength;

[0060] (y) Multiple layers, alternating between:

[0061] a converted light high reflective layer having a sixth thickness and a sixth refractive index higher than the fifth refractive index,

[0062] a light-converting low-reflection layer having a seventh refractive index and a seventh thickness, wherein the seventh refractive index is lower than the sixth refractive index; and

[0063] The product of the sixth refractive index and the sixth thickness of each of the light-converting high-reflection layers is one-quarter of the second wavelength, and the product of the seventh refractive index and the seventh thickness of each of the light-converting low-reflection layers is one-quarter of the second wavelength.

[0064] (z) a fourth interface layer disposed on the converted light high-reflection layer of the plurality of layers, the fourth interface layer having an eighth refractive index and an eighth thickness, wherein the product of the eighth refractive index and the eighth thickness is one eighth of the second wavelength, and the eighth refractive index is lower than the sixth refractive index.

[0065] In some embodiments, the container layer includes a plurality of inner sidewalls defining the container volume, wherein the inner sidewalls defining the container volume are inclined at an acute angle relative to the light emitting surface of the LED layer and include a reflective material. Thus, the container volume of each LED of the LED array can be configured to increase the amount of light extracted from each LED.

[0066] It will be appreciated that optional features of the first aspect of the invention may also be applied to the second aspect of the invention, in particular to LEDs in an LED array comprising a color converting layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] The present disclosure will now be described in conjunction with the following non-limiting drawings. Further advantages of the present disclosure will become apparent by reference to the detailed description when considered in conjunction with the accompanying drawings, in which:

[0068] Figure 1a is a graph showing the reflectivity of a distributed Bragg reflector at different incident angles;

[0069] Figure 1b It is the DCI-P3 standard RGB color space diagram;

[0070] Figure 2 is a schematic diagram of an LED array according to an embodiment of the present disclosure;

[0071] Figure 3 is a schematic diagram of an LED array according to another embodiment of the present disclosure;

[0072] Figure 4a is a ray tracing diagram of an LED sub-pixel at the center of a color conversion region according to an embodiment of the present disclosure;

[0073] Figure 4b is a ray tracing diagram of an LED sub-pixel at the edge of a color conversion region according to an embodiment of the present disclosure;

[0074] Figure 5 is a schematic diagram of a perspective view of an LED array including red, green, and blue LEDs;

[0075] Figure 6 is a schematic diagram of a container layer of an LED according to an embodiment of the present disclosure;

[0076] Figure 7 is the reflectivity plot of the reflector laminate;

[0077] Figure 8 is a schematic diagram of a reflector laminate according to an embodiment of the present disclosure;

[0078] Figure 9 is a reflectivity graph of the reflector laminate showing the center stopband wavelength and the upper stopband wavelength;

[0079] Figure 10 is a reflectivity graph of a reflector laminate including an antireflector layer;

[0080] Figure 11 is a schematic diagram of an LED array according to another embodiment of the present disclosure. DETAILED DESCRIPTION

[0081] According to an embodiment of the present disclosure, an LED array 10 is provided. The LED array includes three LEDs, each configured to output light of a different wavelength. At least one of the LEDs includes a color conversion material. As such, the LED array 10 also includes an LED according to an embodiment of the present disclosure.

[0082] Figure 2 is a schematic diagram of an LED array 10 according to an embodiment of the present disclosure. Figure 2 The LED array shown in illustrative figures includes a green LED 100 , a red LED 200 , and a blue LED 300 .

[0083] The LED array 10 includes a light generating layer 20. The light generating layer 20 includes an array of semiconductor junctions, wherein each semiconductor junction is configured to output pump light. As such, the light generating layer 20 can be considered as an array of pump light LEDs 21, 22, 23. Figure 2 In an embodiment, the array of pump light LEDs 21, 22, and 23 each comprises a Group III nitride. Each pump light LED 21, 22, and 23 includes an n-type semiconductor layer (not shown), an active layer including a plurality of quantum wells (not shown), and a p-type semiconductor layer (not shown). For example, the light generating layer 20 can be provided by monolithically forming the array of pump light LEDs on a substrate, then removing the substrate to expose the light emitting surface 24 of the light generating layer 20. The fabrication of a monolithic array of pump light LEDs 21, 22, and 23 is further described in at least GB 181109.6.

[0084] Of course, in other embodiments, the pump light LED array may have transparent contacts, so that the light emitting surface 24 of the light generating layer 20 may be disposed on the side opposite the substrate. In other words, the light emitting surface 24 of the light generating layer 20 may be any major surface of the light generating layer 20.

[0085] Figure 2 The light generating layer 20 shown in FIG. 1 includes three pump light LEDs. Each pump light LED 21, 22, 23 is configured to output light having a pump light wavelength. Figure 2In some embodiments, the wavelength of the pump light may correspond to blue visible light. In some embodiments, the wavelength of the pump light may be at least 440 nm and / or no greater than 470 nm. In particular, the wavelength of the pump light may be at least 450 nm and / or no greater than 460 nm. In this disclosure, when an LED is described as outputting light having a wavelength, the wavelength is considered to be the wavelength of light output by the LED having the highest intensity (peak intensity). As is known in the art, the wavelength of the pump light may be determined by the number of quantum wells present in the active layer of the pump light LEDs 21, 22, and 23.

[0086] like Figure 2 As shown, the LED array 10 includes a container layer 30. The container layer 30 is disposed on the light emitting surface of the light generating layer 20. The container layer 30 includes a plurality of inner sidewalls 34 that define a plurality of container volumes 31, 32, 33 on the light emitting surface 24 of the light generating layer 20. Each container volume is provided by the container layer (i.e., through the thickness of the container layer 30). As such, each container volume 31, 32, 33 extends from an opening in the container surface 35 of the container layer through the light emitting surface 24.

[0087] Each containment volume 31, 32, 33 is aligned with a pump light LED 21, 22, 23 of light generating layer 20. An inner sidewall 34 of the containment layer can surround each pump light LED so that the containment volumes 31, 32, 33 are generally aligned with the pump light LEDs. In some embodiments, the inner sidewall 34 of the containment layer 30 can be configured to align the center of each containment volume 31, 32, 33 with the center of each pump light LED 21, 22, 23.

[0088] The container layer 30 includes a container surface 35. The container surface 35 is the surface of the container layer 30 that is disposed on the side of the container layer 30 opposite the light generating layer 20. The container surface 35 defines a plurality of openings, one for each container volume 31, 32, 33. As such, the openings of the container surface 35 are defined by inner sidewalls 34 of the container layer 30. The openings of the container layer 30 can be provided in a variety of different shapes. For example, the openings can be elliptical, rectangular, hexagonal, or indeed any irregular or regular polygonal shape. In some embodiments, the shape of the openings corresponds to the shape of the pump light LEDs, although in other embodiments, the shape of the openings may differ from the shape (in plan view) of the pump light LEDs 21, 22, 23. Depending on the shape of the openings, each container volume 31, 32, 33 can be defined by one or more inner sidewalls 34. For example, for an elliptical opening, a single continuous inner sidewall can define the container volume. Figure 5 1 shows a perspective view of an LED array according to an embodiment of the present disclosure. Figure 5In the embodiment of FIG. 3 , each LED comprises a container volume having a rectangular outline. The container surface 35 defines a plurality (nine) openings, each having a rectangular (square) shape. For a rectangular opening, the four inner sidewalls 34 may define the container volume, and so on.

[0089] Figure 3 is a schematic diagram of an LED array according to another embodiment of the present disclosure. Figure 3 The LED array shown includes a green LED 100, a red LED 200, and a blue LED 300. In some embodiments, the opening of each LED on the container surface 35 has a characteristic size D0. The characteristic size D0 is the maximum diameter of the opening. For example, for a circular opening, D0 is the diameter of the opening. For a square opening, D0 is the corner-to-corner distance. In some embodiments, each lens has a characteristic size D1 based on the diameter of the lens. For example, in Figure 3 In the embodiment, the lens has a hemispherical shape. The diameter of the hemispherical lens is a characteristic dimension D1. In some embodiments, 0.1D1≤D0≤0.8D1. In particular, the characteristic dimension of opening D0 can be approximately 50% of the characteristic dimension of lens D1 to effectively extract light from the LED.

[0090] Figure 4a and 4b Shown for Figure 3 The ray tracing diagram of the LED of the LED array with a hemispherical lens. Figure 4a As shown, a ray tracing diagram of light emitted from the center of the opening in the container surface shows that all the outgoing rays are perpendicularly incident on the interface of the lens. Figure 4b It further shows the light rays emitted from the edge of the opening on the container surface, wherein the incident angle of all the light rays with the lens interface is less than 30°.

[0091] Figure 5 A perspective view of an LED array is shown, comprising red, green, and blue LEDs (i.e., an RGB array). The LED array comprises nine LEDs, three of which are blue, three are red, and three are green. The LEDs are arranged in a square-packed array. In other embodiments, other arrangements may be provided, such as a hexagonally packed array.

[0092] Figure 6 FIG. 1 is a schematic diagram showing a portion of a container layer 30 of an LED according to an embodiment of the present disclosure. Figure 6 As shown, the inner sidewall 34 of the container layer 30 is inclined relative to the light generating layer 20 (ie, the inner sidewall 34 is not perpendicular to the surface). Figure 6As shown, the inner sidewall 34 is inclined at an acute angle between the light emitting surface 24 and the inner sidewall 34. As such, the inner sidewall 34 can be inclined such that the surface area of ​​the opening of the container volumes 31, 32, 33 in the container surface 35 is larger than the surface area of ​​the container volumes 31, 32, 33 at the interface with the light emitting surface 24.

[0093] In some embodiments, the sidewalls of each container volume 31, 32, 33 may be inclined at an angle α of at least 35°. By providing an angle of at least 35°, each container volume may have a surface area such that the pixel pitch of the LED array does not become too large. In some embodiments, the sidewalls of each container volume 31, 32, 33 may be inclined at an angle α of no greater than 85°. Figure 6 In the embodiment shown, the inner sidewall 34 is inclined at an angle α of 80°. In some embodiments, providing an inner sidewall with an angle of no greater than 85° or no greater than 60° can improve the optical efficiency of the LED because a greater proportion of the converted light can be directed toward the openings of the container volumes 31, 32, 33.

[0094] The container layer 30 can include a reflective material. The reflective material can be provided to form the container layer 30 with a reflective inner sidewall 34. As such, the reflective material can be provided as an outer layer of the container layer 30. By providing the container layer 30 with a reflective inner sidewall 34, a greater proportion of light incident on the sidewall will be reflected back into the container volume (relative to the light-absorbing sidewall). Consequently, a greater proportion of the converted light that can be generated from the color-converting material in all directions can be extracted from the LED. The reflective material can be a thin film metal, such as aluminum or silver.

[0095] In some embodiments, for example, Figure 6 As shown, the LED further includes a reflection enhancement layer 36 disposed on the inner sidewall of the container layer 30. The reflection enhancement layer 36 comprises a dielectric. For example, the reflection enhancement layer 36 may comprise SiO2. The reflection enhancement layer 36 may be disposed at least on the inner sidewall 34 of the container layer 30. The reflection enhancement layer 36 may have a thickness perpendicular to the inner sidewall 34 that is approximately one-quarter (25%) of the wavelength of the converted light.

[0096] like Figure 2 As shown, at least one container volume 31, 32 may optionally include a color conversion layer 41. Figure 2In an embodiment, first (green) container volume 31 includes a first (green) color-conversion layer 41. Second (red) container volume 32 includes a second (red) color-conversion layer 42. Each color-conversion layer is configured to convert pump light into converted light of a different wavelength. For example, first color-conversion layer 41 may be configured to convert pump light into green visible light, while second color-conversion layer 42 may be configured to convert pump light into red visible light. Thus, the color-conversion layers may be configured to convert pump light having a wavelength of at least 440 nm and / or no greater than 480 nm, with first color-conversion layer 41 converting pump light into converted light having a wavelength of at least 500 nm and / or no greater than 550 nm. Second color-conversion layer 42 may convert pump light into converted light having a wavelength of at least 600 nm and / or no greater than 650 nm.

[0097] In some embodiments, the color conversion layers 41, 42 may include quantum dots. In some embodiments, the color conversion layers 41, 42 may include phosphors. In some embodiments, the color conversion layers 41, 42 may include a combination of phosphors and quantum dots. 2 For LED arrays with a high surface area and a high container volume, larger phosphor particle sizes may be advantageous. 2 For LED arrays with a relatively small surface area and volume, such as micro-LEDs, the use of a color conversion layer comprising quantum dots may be advantageous due to the smaller particle size. Color conversion materials comprising quantum dots are known to those skilled in the art. Further details of suitable quantum dots for use as color conversion layers can be found in at least "Monolithic Red / Green / Blue Micro-LEDs with HBR and DBR structures" by Guan-Syun Chen et al.

[0098] like Figure 2 As shown, the color conversion layer 41, 42 may extend across the container volume 21, 22. The container volume 21, 22 is at least partially filled with the color conversion layer.

[0099] like Figure 2 As shown, at least one container volume 33 of the LED array 10 may not include any color conversion layer. Thus, some LEDs in the LED array may output pump light through the unfilled container volume. For example, when the pump light is blue visible light, the container volume may not include a color conversion layer to provide blue LEDs 300.

[0100] like Figure 2As shown, lens 51 is disposed on container surface 35 above the opening covering first color conversion layer 41. Lens 51 has a convex surface on the side of the lens opposite first color conversion layer 41. The lens is provided to reduce the amount of converted light that is totally internally reflected at the interface between the LED and the external environment.

[0101] The lens can be made of an optically transparent material. For example, the lens can be made of silicon, SiO2, or other dielectrics. The lens can be made using imprint lithography, for example, using UV-curable hybrid polymer materials such as Ormoclear (RTM) from Micro Resist Technology GmbH. The lens can also be printed using resin.

[0102] like Figure 2 As shown, a lens 51, 52 may be disposed over each container volume 31, 32 including a color conversion layer 41, 42. In some embodiments, a lens 51, 52, 53 may be disposed over each container volume 31, 32, 33.

[0103] like Figure 2 As shown, the lens of each type of LED 100, 200, 300 can have a convex surface with a different radius of curvature. Figure 2 As shown, lens 53 of blue LED 300 has a larger radius of curvature than that of the red and green LEDs including color conversion layers 41 and 42. Because blue LED 300 outputs only pump light from light generating layer 20, the radius of curvature of blue LED 300 can be increased. As such, the pump light output by the blue LED has a different intensity distribution relative to the incident angle compared to the LEDs outputting converted light. For example, a larger proportion of the pump light output by blue LED 300 can travel in a direction perpendicular to light emitting surface 24 compared to the converted light from color conversion layers 41 and 42. Therefore, the radius of curvature of lens 53 of the container volume that does not include the color conversion layer can be increased to further reduce total internal reflection from these LEDs.

[0104] exist Figure 3 In the embodiment of FIG, the lenses 51, 52, 53 of each LED 100, 200, 300 are the same. Figure 3 As shown, the radius of curvature of the lenses 51, 52, 53 may be no greater than 2D0 (ie double). In particular, the radius of curvature of the lenses may be no greater than D0.

[0105] The first pump light reflector laminate 61 is disposed on the convex surface of the lens 51 of the green LED 100. The second pump light reflector laminate 62 is also disposed on the convex surface of the lens 52 of the red LED 200. Therefore, the first and second pump light reflector layers can conform to the convex surfaces of the respective lenses 51 and 52. Thus, the first and second pump light reflector layers 61 and 62 also have convex surfaces. Because the first and second pump light reflector layers 61 and 62 have convex surfaces, the amount of converted light incident on the pump light reflector laminates at angles greater than 45° is reduced compared to flat surfaces. Consequently, the proportion of converted light that is completely internally reflected by the pump light reflector laminates 61 and 62 can be reduced. As a result, a greater proportion of the converted light can be transmitted through the pump light reflector laminates 61 and 62, thereby improving the extraction efficiency of the green and red LEDs 100 and 200.

[0106] Figure 7 Graphs showing the reflectivity of the pump light reflector laminates 61 and 62 are shown in FIG. The pump light reflector laminates 61 and 62 are effectively band-stop filters. As such, the pump light reflector laminates 61 and 62 reflect the wavelength of the pump light from the lower stopband wavelength to the upper stopband wavelength (λ e ) has a stop band in the wavelength range where the pump light reflector laminate reflects substantially all light. The stop band is centered around the center wavelength (λ0) (eg, the first wavelength) such that the upper stop band wavelength (λ e ) and the lower stopband wavelength are equidistant from the center wavelength. For wavelengths shorter than the lower stopband wavelength, the pump light reflector laminates 61, 62 have a lower passband where light is normally transmitted through the pump light reflector laminate. Similarly, for wavelengths longer than the upper stopband wavelength (λ e ), the pump light reflector laminates 61, 62 have an upper passband, in which light is normally transmitted through the pump light reflector laminates 61, 62.

[0107] exist Figure 8 Shown in Figure 7 Schematic diagram of a pump light reflector laminate. The pump light reflector laminate 61 includes a first interface layer, a plurality of alternating first reflector layers and second reflector layers, and a second interface layer.

[0108] A plurality of alternating first and second reflector layers form the central portion of the pump light reflector laminate 61. The first reflector layer (H) has a first refractive index (n H ), the second reflector layer (L) has a second refractive index (n L ). The first refractive index is higher than the second refractive index. In some embodiments, the first refractive index is at least 2 and the second refractive index is no greater than 1.8. Figure 2In an embodiment of the present invention, the first reflector layer comprises TiO2 (refractive index of approximately 2.6), and the second reflector layer comprises SiO2 (refractive index of approximately 1.5).

[0109] The first reflector layer (H) has a first thickness (t H ), the second reflector layer (L) has a second thickness (t L ). The thickness of each reflector layer is the thickness measured in a direction perpendicular to the main surface of each reflector layer.

[0110] In order to adjust the reflective characteristics of the pump light reflector laminate 61 to reflect the pump light, each of the first reflector layer and the second reflector layer has a thickness refractive index product of one quarter of the first wavelength (i.e., the center wavelength of the stop band) in the direction perpendicular to the convex surface of the lens. That is, for the first reflector layer (H), the first thickness (t H ) and n H The product of is equal to λ0 / 4. Similarly, for the second reflector layer (L), the second thickness of the second reflector layer (t L ) and n L The product is equal to λ0 / 4.

[0111] Typically, the thickness of the H layer is between 5 nm and 50 nm, and the thickness of the L layer is between 10 nm and 100 nm.

[0112] A plurality of first reflector layers (H) and a plurality of second reflector layers (L) are stacked on top of each other in an alternating manner to form a central portion of the pump light reflector laminate. The central portion of the pump light reflector laminate 61 may be formed of at least three layers, with the second reflector layers (L) forming the outer layers of the central portion (i.e., an LHL arrangement). In some embodiments, at least five alternating layers (LHLHL) may be provided. Figure 7 In the embodiment shown, the central portion comprises 17 alternating layers (LHL . . . LHL).

[0113] A first interface layer and a second interface layer are disposed on opposite sides of the central portion of the pump light reflector laminates 61 and 62. Each of the first and second interface layers may comprise the same material as the first reflector laminate (i.e., the first and second interface layers have a refractive index that is the same as the first refractive index). The first and second interface layers may have third and fourth refractive indices (n3, n4), respectively, and third and fourth thicknesses (t3, t4), respectively. The thickness-refractive-index product of the first and second interface layers may be equal to one-eighth the wavelength of the pump light (e.g., n3t3 = λ0 / 8).

[0114] Wherein, the layers of the pump light reflector laminates 61, 62 (i.e., the first and second reflector layers and the first and second interface layers) have a refractive index that depends on the wavelength of light, and for the purposes of this disclosure, the refractive index of the layer is considered to be the refractive index of the layer at the center wavelength (λ0) of the pump light reflector laminates 61, 62.

[0115] Figure 7 The reflectivity of the pump light reflector laminate 61 according to an embodiment is shown. As described above, the pump light reflector laminate includes 17 alternating layers of SiO2 and TiO2 and two interfacial layers of TiO2 (a total of 19 layers). The layers of the pump light reflector laminate 61 have a thickness configured to reflect pump light having a wavelength of 455 nm. The central wavelength λ0 of the pump light reflector laminate is 420 nm. Figure 7 The reflectivity of the pump light reflector laminate at three different incident angles is shown. For reference, Figure 7 Also shown is the spectrum of the pump light LED at a wavelength of 455 nm.

[0116] Compared with the reflectivity of the DBR shown in Figure 1a, Figure 7 As can be seen in the upper passband of the pump light reflector laminate 61, the reflectivity is lower than that of the DBR. In particular, for angles of incidence between 0° and 30°, the reflectivity of the pump light reflector laminate 61 in the green to red visible spectrum is less than 5%. Therefore, regardless of the angle of incidence, the pump light reflector laminate will not reflect as much converted light as the DBR of Figure 1a. Consequently, the green and red LEDs 100 and 200 incorporating the pump light reflector laminates 61 and 62 will extract the converted light more efficiently than the DBR shown in Figure 1a.

[0117] exist Figure 8 Schematic diagram of the pump light reflector laminate 61 is shown in FIG. The thickness of each layer of the pump light reflector laminate 61 is expressed in terms of the central wavelength and refractive index of each layer of the pump light reflector laminate. Figure 7 The thickness of each layer of the pump light reflector laminate is shown in Table 1. Figure 7 The pump light reflector laminate comprises 19 layers. As shown in Table 1, the pump light reflector laminate comprises alternating layers of TiO2 and SiO2. The first reflector layer and the first interface layer and the second interface layer respectively comprise a refractive index of about 2.60 (i.e., nO2) at a wavelength of 420 nm. H = n3 = n4 = 2.60). The second reflector layer includes TiO2 with a refractive index of about 1.48 at a wavelength of 420 nm (i.e., n L =1.48) of SiO2.

[0118] layer Material Thickness (nm) 1 <![CDATA[TiO2]]> 20.4 2 <![CDATA[SiO2]]> 71.8 3 <![CDATA[TiO2]]> 40.9 4 <![CDATA[SiO2]]> 71.8 5 <![CDATA[TiO2]]> 40.9 6 <![CDATA[SiO2]]> 71.8 7 <![CDATA[TiO2]]> 40.9 8 <![CDATA[SiO2]]> 71.8 9 <![CDATA[TiO2]]> 40.9 10 <![CDATA[SiO2]]> 71.8 11 <![CDATA[TiO2]]> 40.9 12 <![CDATA[SiO2]]> 71.8 13 <![CDATA[TiO2]]> 40.9 14 <![CDATA[SiO2]]> 71.8 15 <![CDATA[TiO2]]> 40.9 16 <![CDATA[SiO2]]> 71.8 17 <![CDATA[TiO2]]> 40.9 18 <![CDATA[TiO2]]> 71.8 19 <![CDATA[SiO2]]> 20.4

[0119] Table 1

[0120] The pump light reflector laminate 61 is configured to have a central wavelength of approximately 420 nm and an upper stopband wavelength of approximately 522 nm. Figure 7 As shown, Figure 7 The pump light reflector laminate reflects pump light having a wavelength of 455 nm. In some embodiments, the central wavelength of the pump light reflector laminate is shorter than the wavelength of the pump light.

[0121] The pump light reflector laminate may have an upper stop band wavelength λ determined by the refractive index of the pump light reflector laminate. e For example, for Figure 7 Pump light reflector laminate, where n3=n4=n H , the upper stopband wavelength can be determined by the following equation:

[0122]

[0123] Figure 9 Shown Figure 7 The reflectivity of the pump light reflector laminate, where the central wavelength λ0 and the upper stop band λ e The upper stopband is calculated as the wavelength at which the reflectivity decreases by 95%. For example, according to Equation 1, n H =2.60 and n L =1.48,λ0=420nm,thenλ e =510nm.

[0124] In some embodiments, the LED array 10 may further include a conversion light reflector laminate 71, 72. The conversion light reflector laminate 71, 72 may be disposed between the pump light LEDs of the light generating layer 20 and the color conversion layers 41, 42 of the LEDs 100, 200. The conversion light reflector laminate 71, 72 may be configured to increase the proportion of converted light extracted from the reservoir volume by reflecting the converted light toward the pump light reflector laminate. The conversion light reflector laminate 71, 72 may also be configured to transmit pump light generated in the light emitting layer so as not to reduce the overall efficiency of the LEDs by reflecting the pump light away from the reservoir volume. As such, the conversion light reflector laminate 71, 72 may also be in the form of a band-stop filter configured to transmit pump light and reflect converted light. As such, the conversion light reflector laminate has a stop band configured to reflect converted light centered at the second wavelength. In some embodiments, the second wavelength may be equal to the wavelength of the converted light, but in other embodiments, the converted light reflector laminate may be configured such that, for example, the wavelength of the converted light falls between the second wavelength and the lower stopband wavelength.

[0125] The converted light reflector laminate 71 , 72 may include a third interface layer, a plurality of alternating third and fourth reflector layers, and a fourth interface layer.

[0126] The third interface layer may have a fifth refractive index (n5) and a fifth thickness (t5).

[0127] A plurality of alternating third and fourth reflector layers form a central portion of a converted light reflector laminate. The third reflector layer (H) has a sixth refractive index n6, and the fourth reflector layer (L) has a seventh refractive index n7. The third reflector layer (H) has a sixth thickness t6, and the fourth reflector layer (L) has a seventh thickness t7. The fifth and seventh refractive indices are lower than the sixth refractive index. In some embodiments, the sixth refractive index is at least 2, and the fifth and seventh refractive indices are no greater than 1.8. Figure 7 In an embodiment of the present invention, the third reflector layer (H) comprises TiO2 (refractive index at 420 nm is about 2.60), and the fourth reflector layer (L) comprises SiO2 (refractive index at 420 nm is about 1.48).

[0128] To tailor the reflective properties of the conversion light reflector laminate to reflect converted light, each of the third and fourth reflector layers has a thickness-index product in a direction perpendicular to the light emitting surface 24 such that the stopband of the conversion light reflector laminate is configured to reflect converted light. For example, in some embodiments, the thickness-index product can be selected to be equal to one-quarter the wavelength of the converted light of the corresponding conversion light layer. For example, in one embodiment, where the conversion light layer 41 is configured to convert pump light to converted light having a wavelength of 610 nm, each third reflector layer can have a thickness of approximately 58 nm, and each fourth reflector layer can have a thickness of 101 nm.

[0129] Wherein the layers of the conversion light reflector laminates 71, 72 (i.e., the third and fourth reflector layers and the third and fourth interface layers) have a refractive index that depends on the wavelength of light, for the purposes of this disclosure, the refractive index of the layer is considered to be the refractive index of the layer at the second wavelength (center wavelength) of the conversion light reflector laminates 71, 72.

[0130] A plurality of fourth reflector layers (L) and a plurality of third reflector layers (H) are stacked on top of each other in an alternating manner to form a central portion of the conversion light reflector laminate. The central portion of the conversion light reflector laminate may be formed from at least 3 layers, wherein the third reflector layers (H) form the outer layers of the central portion (i.e., a HLH arrangement). In some embodiments, at least 5 alternating layers (HLHLH) may be provided. Figure 7 In the embodiment shown, the central portion comprises 19 alternating layers (HLH...HLH).

[0131] A third interface layer and a fourth interface layer are disposed on opposite sides of a central portion of the converted light reflector laminate. Each of the third interface layer and the fourth interface layer may comprise the same material as the third reflector laminate (i.e., the third interface layer and the fourth interface layer may have a refractive index that is the same as the third refractive index). The product of the thickness and refractive index of the third interface layer and the fourth interface layer may be equal to one-eighth of the central wavelength.

[0132] In some embodiments, a conversion light reflector laminate can be provided for LEDs that include only color conversion layers 41, 42. Alternatively, the conversion light reflector laminate can be provided across substantially all of the light emitting surface 24 to cover each pump light LED 21, 22, 23 of the light generating layer. Providing the conversion light reflector laminate over the entire light emitting surface can allow the conversion light reflector laminate to be formed with fewer patterning steps, thereby making LED array manufacturing more efficient.

[0133] In some embodiments, an antireflection layer can be provided over the pump light reflector laminates 61 and 62. The antireflection layer is configured to reduce reflection of the converted light at the interface between the second interface layer of the pump light reflector laminate and the external environment of the LED array 10 (typically air). In some embodiments, the antireflection layer comprises a material having a refractive index less than the refractive index of the second interface layer of the pump light reflector laminate. For example, the antireflection layer can comprise a material having a refractive index less than 1.6. For example, the antireflection layer can comprise SiO2. In some embodiments, the thickness of the antireflection layer is one-quarter the wavelength of the converted light. As such, the thickness of the antireflection layer can be configured to reduce reflection of the converted light transmitted by the pump light reflector laminate. Thus, the antireflection layer can be provided to further improve the efficiency of converting light extraction from the LED.

[0134] Figure 10 A graph showing the reflectivity of a pump light reflector laminate comprising an antireflection layer as described above is shown. Figure 10 In the example shown, the design is optimized to reduce reflections at wavelengths between 525nm and 730nm.

[0135] Figure 11 Another embodiment of an LED array 10 according to the present disclosure is shown. The light emitting layer, the container layer and the color conversion layer are substantially the same as those of FIG. Figure 2 The corresponding layers in the embodiment are the same. Figure 11 In the embodiment of FIG. 5 , the pump light reflector laminates 61, 62 are disposed between the lenses 51, 52 and the lens interface layers 81, 82. Thus, similar to Figure 2In some embodiments, the pump light reflector laminates 61 and 62 are disposed on the convex surface of the lenses 51 and 52. The lens interface layers 81 and 82 may have another convex surface 83 and 84 on the side opposite the pump light reflector layers 61 and 62. That is, the lens interface layers may define another lens shape above the lenses 51 and 52 and the pump light reflectors 61 and 62. The lens interface layers 81 and 82 may be considered to be integrated with the lenses as a lens superstructure. As such, the pump light reflector laminates 61 and 62 may be considered to be disposed within the lens superstructure. In some embodiments, antireflection layers 91 and 92 may be disposed on the other convex surface of the lens interface layers 81 and 82 above the pump light reflector layers 61 and 62.

[0136] Next, a method for forming the LED array 10 will be described.

[0137] First, the light-emitting layer 20 can be fabricated. The light-emitting layer 20 can be fabricated using any known process for fabricating Group III nitride electronic devices. For example, the light-emitting layer 20 can be fabricated using one or more of metal organic chemical vapor deposition (MOCVD) and molecular beam epitaxy (MBE). Further discussion of suitable processes for forming the light-generating layer can be found in at least GB 181109.6.

[0138] Next, a conversion light reflector laminate 71, 72, 73 can be formed on the light emitting surface 24 of the light generating layer 20. The conversion light reflector laminate can be disposed substantially across all of the light emitting surface such that the light emitting surface 24 covers all of the pump light LEDs 21, 22, 23. The conversion light reflector laminates 71, 72, 73 can be formed from alternating layers of SiO2 and TiO2. The layers of the conversion light reflector laminates 71, 72, 73 can be deposited by a chemical vapor deposition process, such as electron beam evaporation or low-temperature sputtering, or any other method known in the art.

[0139] The container layer 30 can then be formed by thin film deposition of a continuous layer of the container layer 30. The continuous layer can then be patterned using a suitable mask and etched to remove portions of the continuous layer to define the container volumes 31, 32, 33. Alternatively, the container layer can be formed by depositing a mask layer over the light emitting surface 24 (or the conversion light reflector laminates 71, 72, 73, if present), the mask layer being configured to selectively mask portions of the light emitting layer corresponding to the container volumes 31, 32, 33. The container layer 30 is then deposited over the exposed portions of the light generating layer 20 (or the conversion light reflector laminates 71, 72, 73).

[0140] The container volumes 31 , 32 can optionally be filled with one or more color conversion layers 41 , 42 .

[0141] Subsequently, lenses 51, 52, 53 may be formed over the container volumes 31, 32, 33. The lenses may comprise SiO2 deposited using a CVD process. The convex surfaces of the lenses 51, 52, 53 may be formed by any of the processes described above.

[0142] Next, pump light reflector laminates 61, 62 can be formed on the convex surfaces of the lenses 51, 52 that cover the filled container volumes 31, 32. Pump light reflector laminates 51, 52. In some embodiments, the pump light reflector laminate can be formed on substantially all of the lenses 51, 52, 53, followed by a process that selectively removes (e.g., by etching) the pump light reflector laminate from LEDs that do not need to filter pump light (e.g., LEDs with unfilled container volumes 33). Pump light reflector laminates 51, 52 can be formed from alternating layers of SiO2 and TiO2. The layers of pump light reflector laminates 61, 62 can be deposited by a chemical vapor deposition process (e.g., MOCVD) or any other method known in the art.

[0143] An anti-reflection layer may be formed on the pump light reflector laminates 61 and 62. The anti-reflection layer may include a dielectric, such as SiO2, MgF2, or ZrO2. Therefore, the anti-reflection layer may be formed on the pump light reflector laminates using a similar process as used to form the pump light reflector laminates 61 and 62.

[0144] In some embodiments, lens interface layers 81, 82 may be formed over the pump light reflector laminates 61, 62. The lens interface layers 81, 82 may be formed using a similar process as used to form the lenses 51, 52.

[0145] According to the above disclosure, an LED array 10 can be provided. It should be understood that the above disclosure also provides an LED including a color conversion layer. Therefore, according to embodiments of the present disclosure, an LED or LED array is provided that improves conversion light extraction efficiency while reducing pump light leakage.

Claims

1. A light emitting diode (LED), comprising: an LED layer configured to emit pump light having a pump light wavelength from a light emitting surface, the LED layer comprising a plurality of Group III nitride layers; a container layer disposed on the light-emitting surface of the LED layer, the container layer having a container surface on a side of the container layer opposite to the light-emitting surface, the container surface including an opening, the opening defining a container volume through the container layer to the light-emitting surface of the LED layer; a color conversion layer disposed within the container volume, the color conversion layer being configured to absorb pump light and emit converted light, wherein the converted light has a wavelength greater than the pump light wavelength; as well as a lens disposed on the surface of the container above the opening, the lens having a convex surface on a side of the lens opposite to the color conversion layer; a pump light reflector laminate disposed on the convex surface of the lens, the pump light reflector laminate having a stop band configured to reflect pump light centered at a first wavelength, the pump light reflector laminate comprising: a first interface layer disposed on the convex surface of the lens; the first interface layer having a first thickness and a first refractive index, wherein a product of the first refractive index and the first thickness is one eighth of the first wavelength; Multiple layers, alternating between: a low-reflection layer having a second refractive index and a second thickness, wherein the second refractive index is lower than the first refractive index; and a highly reflective layer having a third thickness and a third refractive index higher than the second refractive index, The product of the second refractive index and the second thickness of each low-reflection layer is one-quarter of the first wavelength, and the product of the third refractive index and the third thickness of each high-reflection layer is one-quarter of the first wavelength. A second interface layer is arranged on the low-reflection layer of the multiple layers, and the second interface layer has a fourth refractive index and a fourth thickness, wherein the product of the fourth refractive index and the fourth thickness is one eighth of the first wavelength, and the fourth refractive index is greater than the second refractive index.

2. The LED according to claim 1, wherein The container layer includes inner sidewalls defining the container volume, wherein the inner sidewalls defining the container volume are inclined at an acute angle relative to the light emitting surface of the LED layer and include a reflective material.

3. The LED of claim 1 , further comprising a converted light reflector laminate disposed between the LED layer and the color conversion layer, the converted light reflector laminate having a stop band configured to reflect converted light centered at a second wavelength, the converted light reflector laminate comprising: a third interface layer, disposed on the light-emitting surface of the LED layer; the third interface layer having a fifth thickness and a fifth refractive index, wherein a product of the fifth thickness and the fifth refractive index is one eighth of the second wavelength; Multiple layers, alternating between: a converted light high reflective layer having a sixth thickness and a sixth refractive index higher than the fifth refractive index, a light-converting low-reflection layer having a seventh refractive index and a seventh thickness, wherein the seventh refractive index is lower than the sixth refractive index; and The product of the sixth refractive index and the sixth thickness of each of the light-converting high-reflection layers is one-quarter of the second wavelength, and the product of the seventh refractive index and the seventh thickness of each of the light-converting low-reflection layers is one-quarter of the second wavelength. A fourth interface layer is provided on the converted light high reflective layer of the plurality of layers, the fourth interface layer having an eighth refractive index and an eighth thickness, wherein the product of the eighth refractive index and the eighth thickness is one eighth of the second wavelength, and the eighth refractive index is lower than the sixth refractive index. 4 . The LED according to claim 2 , further comprising a reflection enhancing layer disposed on the inner sidewall of the container layer, the reflection enhancing layer comprising a dielectric.

5. The LED of claim 1, 2 or 3, further comprising an anti-reflection layer disposed on the pump light reflector laminate, the anti-reflection layer being configured to reduce reflection of light of the converted light wavelength.

6. The LED according to claim 1, 2 or 3, wherein: A lens interface layer is disposed on the pump light reflector laminate on a side opposite to the lens.

7. The LED according to claim 1, 2 or 3, wherein: The color conversion layer includes quantum dots or phosphors.

8. The LED according to claim 2, wherein The inner sidewall forms an angle of at least 45° with respect to the light emitting surface of the LED layer.

9. The LED according to claim 2, wherein The inner sidewall forms an angle of no greater than 85° with respect to the light emitting surface of the LED layer.

10. The LED according to claim 1, 2 or 3, wherein: The pump light wavelength is at least 440 nm.

11. The LED according to claim 1, 2 or 3, wherein: The wavelength of the pump light is no greater than 480 nm.

12. The LED according to claim 1, 2 or 3, wherein: The converted light has a wavelength of at least 500 nm.

13. The LED according to claim 1, 2 or 3, wherein: The wavelength of the converted light is no greater than 650 nm.

14. The LED according to claim 1, 2 or 3, wherein: The first refractive index, the third refractive index and / or the fourth refractive index are at least 2.

15. The LED according to claim 1, 2 or 3, wherein the second refractive index is not greater than 1.

8.

16. The LED according to claim 1, 2 or 3, wherein: The container layer defines a -8 m 2 Surface area opening.

17. The LED according to claim 1, 2 or 3, wherein: The first refractive index of the first interface layer, the third refractive index of the high reflective layer, and the fourth refractive index of the second interface layer are the same.

18. The LED according to claim 3, wherein The fifth refractive index of the third interface layer, the seventh refractive index of the light-converting low-reflection layer, and the eighth refractive index of the fourth interface layer are the same.

19. The LED according to claim 1, 2 or 3, wherein: The first wavelength (λ0), the second refractive index (n L ) and the third refractive index (n H ) provides the upper stopband wavelength (λ of the pump light reflector laminate e ), the upper stopband wavelength is longer than the pump light wavelength, wherein: 。 20. The LED according to claim 3, wherein The pump light reflector laminate and / or the conversion light reflector laminate comprise layers of TiO 2 and SiO 2 .

21. A light emitting diode (LED) array, comprising: an LED layer comprising a plurality of LEDs, each LED configured to emit pump light at a pump light wavelength from a light emitting surface, each LED comprising a plurality of Group III nitride layers; a container layer disposed on the light emitting surface of the LED layer, the container layer having a container surface on a side of the container layer opposite the light emitting surface, the container surface including a plurality of openings, each of the openings defining a container volume through the container layer to the light emitting surface of the LED layer, each opening and container volume being aligned with a corresponding LED of the LED layer, a color conversion layer selectively disposed in the container volume, the color conversion layer configured to absorb the pump light and emit a first converted light having a first converted light wavelength longer than the pump light wavelength; a lens disposed on the container surface above the opening of the container volume, the container volume containing a color conversion material, the lens having a convex surface on a side of the lens opposite the color conversion layer; a pump light reflector laminate disposed on the convex surface of the lens, the pump light reflector laminate having a stop band configured to reflect the pump light centered at a first wavelength, the pump light reflector laminate comprising: a first interface layer disposed on the convex surface of the lens; the first interface layer having a first thickness and a first refractive index, wherein a product of the first refractive index and the first thickness is one eighth of the first wavelength; Multiple layers, alternating between: a low-reflection layer having a second refractive index and a second thickness, wherein the second refractive index is lower than the first refractive index; and a highly reflective layer having a third thickness and a third refractive index higher than the second refractive index, The product of the second refractive index and the second thickness of each low-reflection layer is one-quarter of the first wavelength, and the product of the third refractive index and the third thickness of each high-reflection layer is one-quarter of the first wavelength. A second interface layer is arranged on the low-reflection layer of the multiple layers, and the second interface layer has a fourth refractive index and a fourth thickness, wherein the product of the fourth refractive index and the fourth thickness is one eighth of the first wavelength, and the fourth refractive index is longer than the second refractive index.

22. The LED array according to claim 21, wherein Another color conversion layer is disposed in another container volume of the plurality of container volumes, the another color conversion layer being configured to absorb the pump light and emit a second converted light having a second converted light wavelength longer than the first converted light wavelength, A lens is disposed above the further container volume, and a pump light reflector laminate is disposed on the lens.

23. The LED array according to claim 21, further comprising: at least one converted light reflector laminate disposed between the color conversion layer and the light emitting surface of a corresponding LED of the LED layer, the converted light reflector laminate having a stop band configured to reflect the first converted light and / or the second converted light centered at a second wavelength, the converted light reflector laminate comprising: a third interface layer disposed on the light emitting surface of the LED layer; the third interface layer having a fifth thickness and a fifth refractive index, wherein a product of the fifth thickness and the fifth refractive index is one eighth of the second wavelength; Multiple layers, alternating between: The converted light high reflective layer has a sixth thickness and a sixth refractive index higher than the fifth refractive index. a light-converting low-reflection layer having a seventh refractive index and a seventh thickness, wherein the seventh refractive index is lower than the sixth refractive index; and The product of the sixth refractive index and the sixth thickness of each of the light-converting high-reflection layers is one-quarter of the second wavelength, and the product of the seventh refractive index and the seventh thickness of each of the light-converting low-reflection layers is one-quarter of the second wavelength. A fourth interface layer is provided on the converted light high reflective layer of the plurality of layers, the fourth interface layer having an eighth refractive index and an eighth thickness, wherein the product of the eighth refractive index and the eighth thickness is one eighth of the second wavelength, and the eighth refractive index is lower than the sixth refractive index.

24. The LED array according to claim 21, 22 or 23, wherein: The container layer includes a plurality of inner sidewalls defining the container volume, wherein the inner sidewalls defining the container volume are inclined at an acute angle relative to the light emitting surface of the LED layer and include a reflective material. 25 . The LED array according to claim 24 , further comprising a reflection enhancing layer disposed on the inner sidewall of the container layer, wherein the reflection enhancing layer comprises a dielectric.

26. The LED array of claim 22 or 23, further comprising an anti-reflection layer disposed on each pump light reflector laminate, the anti-reflection layer being configured to reduce reflection of light of the first converted light wavelength and / or the second converted light wavelength.

27. The LED array according to claim 21, 22 or 23, wherein: Each color conversion layer includes quantum dots or phosphors.

28. The LED array according to claim 24, wherein The inner sidewall forms an angle of at least 30° with respect to the light emitting surface of the LED layer.

29. The LED array according to claim 24, wherein The inner sidewall forms an angle of no greater than 85° with respect to the light emitting surface of the LED layer.

30. The LED array according to claim 21, 22 or 23, wherein the pump light has a wavelength of at least 440 nm.

31. The LED array according to claim 21, 22 or 23, wherein the pump light wavelength is no greater than 480 nm.

32. The LED array of claim 21, 22, or 23, wherein the first converted light has a wavelength of at least 500 nm.

33. The LED array according to claim 21, 22 or 23, wherein the first converted light has a wavelength no greater than 650 nm.

34. The LED array of claim 22 or 23, wherein the second converted light wavelength is at least 600 nm.

35. The LED array according to claim 22 or 23, wherein the second converted light wavelength is no greater than 650 nm.

36. The LED array according to claim 23, wherein The pump light reflector laminate comprises layers of SiO2 and TiO2.

37. The LED array according to claim 21, 22 or 23, wherein: The pump light reflector laminate includes a plurality of oxygen-containing layers and a plurality of fluorine-containing layers.

Images