PARTICLE SYSTEMS AND PATTERNING FOR MONOLITHIC LED ARRAYS
A wavelength converting layer is disclosed that includes a plurality of phosphor grains 50-500 nm in size and encapsulated in cerium free YAG shells and a binder material binding the plurality of phosphor grains, the wavelength converting layer having a thickness of 5-20 microns attached to the light emitting surface.
Latest Lumileds LLC Patents:
- LOW-DENSITY ELECTRICAL TRACES ON A TRANSPARENT OR REFLECTIVE SUBSTRATE
- LAMINATION OF A LIGHT SOURCE HAVING A LOW-DENSITY SET OF LIGHT-EMITTING ELEMENTS
- TRANSPARENT OPTICAL ELEMENT WITH LINE-OF-SIGHT INFRARED LIGHT SOURCE FOR EYE TRACKING
- VISIBLE LIGHT SOURCE HAVING A LOW-DENSITY SET OF LIGHT-EMITTING ELEMENTS
- LAMINATED LIGHT SOURCE HAVING A LOW-DENSITY SET OF LIGHT-EMITTING ELEMENTS
Precision control lighting applications can require the production and manufacturing of light emitting diode (LED) pixel systems. Manufacturing such LED pixel systems can require accurate deposition of material due to the small size of the pixels and the small lane space between the systems. The miniaturization of components used for such LED pixel systems may lead to unintended effects that are not present in larger LED pixel systems.
Semiconductor light-emitting devices including LEDs, resonant cavity light emitting diodes (RCLEDs), vertical cavity laser diodes (VCSELs), and edge emitting lasers are among the most efficient light sources currently available. Materials systems currently of interest in the manufacture of high-brightness light emitting devices capable of operation across the visible spectrum include Group III-V semiconductors, particularly binary, ternary, and quaternary alloys of gallium, aluminum, indium, and nitrogen, also referred to as III-nitride materials. Typically, III-nitride light emitting devices are fabricated by epitaxially growing a stack of semiconductor layers of different compositions and dopant concentrations on a sapphire, silicon carbide, III-nitride, composite, or other suitable substrate by metal-organic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE), or other epitaxial techniques. The stack often includes one or more n-type layers doped with, for example, Si, formed over the substrate, one or more light emitting layers in an active region formed over the n-type layer or layers, and one or more p-type layers doped with, for example, Mg, formed over the active region. Electrical contacts are formed on the n- and p-type regions.
III-nitride devices are often formed as inverted or flip chip devices, where both the n- and p-contacts formed on the same side of the semiconductor structure, and most of the light is extracted from the side of the semiconductor structure opposite the contacts.
SUMMARYThe A wavelength converting layer is disclosed that includes a plurality of phosphor grains 50-500 nm in size and encapsulated in cerium free YAG shells and a binder material binding the plurality of phosphor grains, the wavelength converting layer having a thickness of 5-20 microns attached to the light emitting surface.
A more detailed understanding may be had from the following description, given by way of example in conjunction with the accompanying drawings wherein:
Examples of different light illumination systems and/or light emitting diode (“LED”) implementations will be described more fully hereinafter with reference to the accompanying drawings. These examples are not mutually exclusive, and features found in one example may be combined with features found in one or more other examples to achieve additional implementations. Accordingly, it will be understood that the examples shown in the accompanying drawings are provided for illustrative purposes only and they are not intended to limit the disclosure in any way. Like numbers refer to like elements throughout.
It will be understood that, although the terms first, second, third, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms may be used to distinguish one element from another. For example, a first element may be termed a second element and a second element may be termed a first element without departing from the scope of the present invention. As used herein, the term “and/or” may include any and all combinations of one or more of the associated listed items.
It will be understood that when an element such as a layer, region, or substrate is referred to as being “on” or extending “onto” another element, it may be directly on or extend directly onto the other element or intervening elements may also be present. In contrast, when an element is referred to as being “directly on” or extending “directly onto” another element, there may be no intervening elements present. It will also be understood that when an element is referred to as being “connected” or “coupled” to another element, it may be directly connected or coupled to the other element and/or connected or coupled to the other element via one or more intervening elements. In contrast, when an element is referred to as being “directly connected” or “directly coupled” to another element, there are no intervening elements present between the element and the other element. It will be understood that these terms are intended to encompass different orientations of the element in addition to any orientation depicted in the figures.
Relative terms such as “below,” “above,” “upper,”, “lower,” “horizontal” or “vertical” may be used herein to describe a relationship of one element, layer, or region to another element, layer, or region as illustrated in the figures. It will be understood that these terms are intended to encompass different orientations of the device in addition to the orientation depicted in the figures.
Semiconductor light emitting devices (LEDs) or optical power emitting devices, such as devices that emit ultraviolet (UV) or infrared (IR) optical power, are among the most efficient light sources currently available. These devices (hereinafter “LEDs”), may include light emitting diodes, resonant cavity light emitting diodes, vertical cavity laser diodes, edge emitting lasers, or the like. Due to their compact size and lower power requirements, for example, LEDs may be attractive candidates for many different applications. For example, they may be used as light sources (e.g., flash lights and camera flashes) for hand-held battery-powered devices, such as cameras and cell phones. They may also be used, for example, for automotive lighting, heads up display (HUD) lighting, horticultural lighting, street lighting, torch for video, general illumination (e.g., home, shop, office and studio lighting, theater/stage lighting and architectural lighting), augmented reality (AR) lighting, virtual reality (VR) lighting, as back lights for displays, and IR spectroscopy. A single LED may provide light that is less bright than an incandescent light source, and, therefore, multi-junction devices or arrays of LEDs (such as monolithic LED arrays, micro LED arrays, etc.) may be used for applications where more brightness is desired or required.
According to embodiments of the disclosed subject matter, LED arrays (e.g., micro LED arrays) may include an array of pixels as shown in
It will be understood that although rectangular pixels arranged in a symmetric matrix are shown in
Notably, as shown in
The epitaxial layer 1011 may be formed from any applicable material to emit photons when excited including sapphire, SiC, GaN, Silicone and may more specifically be formed from a III-V semiconductors including, but not limited to, AlN, AlP, AlAs, AlSb, GaN, GaP, GaAs, GaSb, InN, InP, InAs, InSb, II-VI semiconductors including, but not limited to, ZnS, ZnSe, CdSe, CdTe, group IV semiconductors including, but not limited to Ge, Si, SiC, and mixtures or alloys thereof. These example semiconductors may have indices of refraction ranging from about 2.4 to about 4.1 at the typical emission wavelengths of LEDs in which they are present. For example, III-Nitride semiconductors, such as GaN, may have refractive indices of about 2.4 at 500 nm, and III-Phosphide semiconductors, such as InGaP, may have refractive indices of about 3.7 at 600 nm. Contacts coupled to the LED device 1200 may be formed from a solder, such as AuSn, AuGa, AuSi or SAC solders.
The n-type region may be grown on a growth substrate and may include one or more layers of semiconductor material that include different compositions and dopant concentrations including, for example, preparation layers, such as buffer or nucleation layers, and/or layers designed to facilitate removal of the growth substrate. These layers may be n-type or not intentionally doped, or may even be p-type device layers. The layers may be designed for particular optical, material, or electrical properties desirable for the light emitting region to efficiently emit light. Similarly, the p-type region 1012 may include multiple layers of different composition, thickness, and dopant concentrations, including layers that are not intentionally doped, or n-type layers. An electrical current may be caused to flow through the p-n junction (e.g., via contacts) and the pixels may generate light of a first wavelength determined at least in part by the bandgap energy of the materials. A pixel may directly emit light (e.g., regular or direct emission LED) or may emit light into a wavelength converting layer 1050 (e.g., phosphor converted LED, “PCLED”, etc.) that acts to further modify wavelength of the emitted light to output a light of a second wavelength.
Although
The wavelength converting layer 1050 may be in the path of light emitted by active region 1021, such that the light emitted by active region 1021 may traverse through one or more intermediate layers (e.g., a photonic layer). According to embodiments, wavelength converting layer 1050 or may not be present in LED array 1000. The wavelength converting layer 1050 may include any luminescent material, such as, for example, phosphor particles in a transparent or translucent binder or matrix, or a ceramic phosphor element, which absorbs light of one wavelength and emits light of a different wavelength. The thickness of a wavelength converting layer 1050 may be determined based on the material used or application/wavelength for which the LED array 1000 or individual pixels 1010, 1020, and 1030 is/are arranged. For example, a wavelength converting layer 1050 may be approximately 20 μm, 50 μm or 1200 μm. The wavelength converting layer 1050 may be provided on each individual pixel, as shown, or may be placed over an entire LED array 1000.
Primary optic 1022 may be on or over one or more pixels 1010, 1020, and/or 1030 and may allow light to pass from the active region 101 and/or the wavelength converting layer 1050 through the primary optic. Light via the primary optic may generally be emitted based on a Lambertian distribution pattern such that the luminous intensity of the light emitted via the primary optic 1022, when observed from an ideal diffuse radiator, is directly proportional to the cosine of the angle between the direction of the incident light and the surface normal. It will be understood that one or more properties of the primary optic 1022 may be modified to produce a light distribution pattern that is different than the Lambertian distribution pattern.
Secondary optics which include one or both of the lens 1065 and waveguide 1062 may be provided with pixels 1010, 1020, and/or 1030. It will be understood that although secondary optics are discussed in accordance with the example shown in
Lens 1065 may be formed form any applicable transparent material such as, but not limited to SiC, aluminum oxide, diamond, or the like or a combination thereof. Lens 1065 may be used to modify the a beam of light to be input into the lens 1065 such that an output beam from the lens 1065 will efficiently meet a desired photometric specification. Additionally, lens 1065 may serve one or more aesthetic purpose, such as by determining a lit and/or unlit appearance of the multiple LED devices 1200B.
Passivation layers 1115 may be formed within the trenches 1130 and n-contacts 1140 (e.g., copper contacts) may be deposited within the trenches 1130, as shown. The passivation layers 1115 may separate at least a portion of the n-contacts 1140 from one or more layers of the semiconductor. According to an implementation, the n-contacts 1140, or other applicable material, within the trenches may extend into the wavelength converting layer 1117 such that the n-contacts 1140, or other applicable material, provide complete or partial optical isolation between the pixels.
Typical LED wavelength converting layers, especially those emitting red light, may include a luminescent cerium compound emitting bright red light (e.g., Ce doped compound such as, for example CaSiN2:Ce3+). Such a cerium based compound can be used for white light applications to, for example, enhance the light quality of the system based on a blue LED with a yellow/green phosphor, as the red phosphor in the UV LED plus three RGB phosphors setup or, directly as a yellow phosphor with a 460 nm wavelength emitting LED due to the emission/excitation band shift with chemical substitution. However, the presence of Cerium may impose limitations on an LED device including, for example, physical properties, dimensions, chemical properties, or the like.
Optical isolation materials 1230 may be applied to the wavelength converting layer 1220. A wavelength converting layer may be mounted onto a GaN layer 1250 via a pattern sapphire substrate (PSS) pattern 1260. The GaN layer 1250 may be bonded to or grown over an active region 1290 and the light-emitting device 1270 may include a solder 1280. Optical isolator material 1240 may also be applied to the sidewalls of the GaN layer 1250.
As an example, the pixels 1275 of
In accordance with an implementation of the disclosed subject matter,
According to an embodiment, a wavelength converting layer may be deposited onto light emitting devices using electrophoretic deposition (EPD). A pixel may include a wavelength converting layer that has a thickness of between 5 and 50 microns. A polymeric toughening additive may be applied to the wavelength converting layer and may reduce cracking or damage to the wavelength converting layer, especially as a result of the thinness of the film. A wavelength converting layer in accordance with embodiments disclosed herein is cerium free and may contain material configured to convert one or more properties of light. The wavelength converting layer may convert a property of light, such as, but not limited to, its wavelength, its phase, or the like. A wavelength converting layer may convert a property of light based on absorption of incoming light by one or more particles in a wavelength converting layer followed by a photon release. A wavelength converting layer may contain applicable luminescent or optically scattering particles such as phosphor grains with or without activation from rare earth ions.
The wavelength converting layer may contain a plurality luminescent or optically scattering particles such as phosphor grains that are 50-500 nm in size. Phosphor grains 50-500 nm in size may be needed as, for example, a pixel that is 30 microns wide may not be able to function efficiently with larger particles such as those that are 1-5 microns in size. Such larger particles may not be efficient as a larger than optimal portion of the light emitted from a light emitting layer may be absorbed by such large particles. Additionally a wavelength converting layer with such large particles may be too large to allow effective operation of a pixel. Accordingly, the convertor film may contain particles that are 50-500 nm in size.
Particles such as phosphor grains that are 50-500 nm in size may traditionally cause degradation in quantum efficiency of the phosphor particles. Such degradation may result in an overall reduced efficiency of a pixel containing particles of such size.
According to the subject matter disclosed herein, Ce(III) doped garnet phosphor grains may be encapsulated in cerium free yttrium aluminum garnet (YAG) shells. The cerium free YAG shells may reduce the non-radiative recombination rate of the wavelength converting layer. Non-radiative recombination is a process where charge carriers recombine without releasing photons. Non-radiative recombination may generate an unintended byproduct such as heat or vibration. Specifically, non-radiative recombination can occur when an electron in the conduction band or on a localized activator excited state recombines with a hole in the valence band or with a localized activator ground state and the excess energy is emitted. Non-radiative recombination may increase the threshold current and may reduce the performance and/or efficiency of a pixel.
By applying cerium free YAG shells to Ce(III) doped garnet phosphor grains and reducing the non-radiative recombination rate, the quantum efficiency of the phosphor particles may be sufficient for optimal operation of a pixel with the wavelength converting layer containing such phosphor particles. As a specific example, the non-radiative recombination rate of the wavelength converting layer may be less than 3 μs−1 and more preferably less than 2 μs−1 (int. QE>88%) as a result of using the cerium free YAG shells. As a comparison, for example, for 100% internal QE luminescence, decay time of YAG:Ce may be ˜70 ns with a radiative recombination rate of ˜14 μs−1. The cerium free YAG shells can be applied by homogeneous precipitation of an yttrium and aluminum containing layer onto the garnet phosphor grains in an aqueous suspension, followed by drying of the coated particles and calcination to obtain Ce(III) doped garnet particles having cerium free YAG shells. The shell thickness may be in the range of 1.5-400 nm, preferably 3-200 nm or even more preferably in the range 10-100 nm.
The phosphor grains in a wavelength converting layer may be homogenous such that all the grains are a specific shape and/or type or may be heterogeneous such that a degree of variation exists between the phosphor grains in the wavelength converting layer. As an example of homogenous phosphor grains, all the phosphor grains in a wavelength converting layer may be between 300 and 320 nm in size. As an example of heterogeneous phosphor grains, one or more phosphor grains in a wavelength converting layer may be between 300 and 400 nm in size and one or more phosphor grains in the wavelength converting layer may be less than 100 nm in size. The phosphor grains may be disk shaped, spherical or may be non-spherical. Additionally, the type of phosphor may be the same or may vary across the wavelength converting layer.
According to an implementation of the disclosed subject matter, one or more types of scattering particles may be provided. The scattering particles may be included in a wavelength converting layer or may be external to the wavelength converting layer such as, for example, in a path of light that is emitted from an active layer. Scattering particles can include silica, titania, zirconia particles, or the like. The size for the scattering particles may range from 10 nm to 1 μm size. The scattering particles may scatter light such that the amount of conversion in a pixel is increased. The scattering particles may have a high density or a low density (e.g., a porous material). Alternatively or in addition, the scattering particles may be a shell with a non-filled core. The scattering particles may reduce the total thickness of a wavelength converting layer by increasing the efficiency of the wavelength conversion. The may also facilitate the application of larger phosphor particles. The scattering particles may also be attached to the phosphor particles by, for example, chemical bonding before the phosphor powders are being deposited onto the light emitting device.
The phosphor grains may be bound by a binder configured to bind the phosphor grains in place. To increase the quantum efficiency of a wavelength converting layer with 50-500 nm phosphor grains, the binder may have a refractive index of 1.65 or greater. The high refractive index may allow light to more efficiently pass through the wavelength converting layer and thus provide a high light extraction. The binder material may be any applicable material such as, but not limited to a glass, a polymer such as acrylate or nitrocellulose, an epoxy, a siloxane, a polysilazane-siloxane hybrid material, a sol-gel material, or the like. The refractive index of the binder may be substantially matched to the refractive index of the cerium free YAG shell to improve the efficiency of the wavelength converting layer.
Quantum dots material may be incorporated within or on the surface of a wavelength converting layer to improve the efficiency of the wavelength converting layer. Quantum dots may luminesce in one or more of the UV, visible and IR (upon excitation with suitable radiation, such as UV radiation). Quantum dots may be made of binary alloys such as cadmium selenide, cadmium sulfide, indium arsenide, and indium phosphide. Alternatively, quantum dots may be made from ternary alloys such as cadmium selenide sulfide. The quantum dots may contain as few as 100 to 100,000 atoms within the quantum dot volume, with a diameter of 10 to 50 atoms. This may correspond to about 2 to 10 nm.
Optical isolation materials may be applied to the sidewall of the wavelength converting layer. Optical isolation materials may include, but are not limited to, distributed Bragg reflector (DBR) layers, reflective material, absorptive material, or the like.
As shown in
Electrophoretic deposition (EPD) may be used to deposit the wavelength converting layer onto a light emitting device. The phosphor grains or nanoparticles may be dispersed in an electron bath such that they are attracted to a charge. A surface of the light emitting device may be charged and the phosphor grains or nanoparticles may be deposited onto the charged surface such that they are attracted specifically to the surface of the light emitting device due to the charge. A binder, as disclosed herein may be deposited onto the phosphor grain or nanoparticles to generate the wavelength converting layer. A curing process may be applied to cure the binder such that the wavelength converting layer maintains its shape.
Using the EPD technique may allow complex patterning of pixels by applying voltage to pixels in a pixel system that need to be patterned with a given wavelength converting layer. A first wavelength converting layer may be deposited on a set of first pixels by applying a voltage to the first set of pixels, and may then be bound and cured. Subsequently, a wavelength converting layer may be deposited on a second set of pixels by applying a voltage to the second set of pixels, and may then be bound and cured.
As shown in
The LED array 410 may include two groups of LED devices. In an example embodiment, the LED devices of group A are electrically coupled to a first channel 411A and the LED devices of group B are electrically coupled to a second channel 411B. Each of the two DC-DC converters 440A and 440B may provide a respective drive current via single channels 411A and 411B, respectively, for driving a respective group of LEDs A and B in the LED array 410. The LEDs in one of the groups of LEDs may be configured to emit light having a different color point than the LEDs in the second group of LEDs. Control of the composite color point of light emitted by the LED array 410 may be tuned within a range by controlling the current and/or duty cycle applied by the individual DC/DC converter circuits 440A and 440B via a single channel 411A and 411B, respectively. Although the embodiment shown in
The illustrated LED lighting system 400B is an integrated system in which the LED array 410 and the circuitry for operating the LED array 410 are provided on a single electronics board. Connections between modules on the same surface of the circuit board 499 may be electrically coupled for exchanging, for example, voltages, currents, and control signals between modules, by surface or sub-surface interconnections, such as traces 431, 432, 433, 434 and 435 or metallizations (not shown). Connections between modules on opposite surfaces of the circuit board 499 may be electrically coupled by through board interconnections, such as vias and metallizations (not shown).
According to embodiments, LED systems may be provided where an LED array is on a separate electronics board from the driver and control circuitry. According to other embodiments, a LED system may have the LED array together with some of the electronics on an electronics board separate from the driver circuit. For example, an LED system may include a power conversion module and an LED module located on a separate electronics board than the LED arrays.
According to embodiments, an LED system may include a multi-channel LED driver circuit. For example, an LED module may include embedded LED calibration and setting data and, for example, three groups of LEDs. One of ordinary skill in the art will recognize that any number of groups of LEDs may be used consistent with one or more applications. Individual LEDs within each group may be arranged in series or in parallel and the light having different color points may be provided. For example, warm white light may be provided by a first group of LEDs, a cool white light may be provided by a second group of LEDs, and a neutral white light may be provided by a third group.
The power module 312 (AC/DC converter) of
In example embodiments, the system 550 may be a mobile phone of a camera flash system, indoor residential or commercial lighting, outdoor light such as street lighting, an automobile, a medical device, AR/VR devices, and robotic devices. The LED System 400A shown in
The application platform 560 may provide power to the LED systems 552 and/or 556 via a power bus via line 565 or other applicable input, as discussed herein. Further, application platform 560 may provide input signals via line 565 for the operation of the LED system 552 and LED system 556, which input may be based on a user input/preference, a sensed reading, a pre-programmed or autonomously determined output, or the like. One or more sensors may be internal or external to the housing of the application platform 560. Alternatively or in addition, as shown in the LED system 400 of
In embodiments, application platform 560 sensors and/or LED system 552 and/or 556 sensors may collect data such as visual data (e.g., LIDAR data, IR data, data collected via a camera, etc.), audio data, distance based data, movement data, environmental data, or the like or a combination thereof. The data may be related a physical item or entity such as an object, an individual, a vehicle, etc. For example, sensing equipment may collect object proximity data for an ADAS/AV based application, which may prioritize the detection and subsequent action based on the detection of a physical item or entity. The data may be collected based on emitting an optical signal by, for example, LED system 552 and/or 556, such as an IR signal and collecting data based on the emitted optical signal. The data may be collected by a different component than the component that emits the optical signal for the data collection. Continuing the example, sensing equipment may be located on an automobile and may emit a beam using a vertical-cavity surface-emitting laser (VCSEL). The one or more sensors may sense a response to the emitted beam or any other applicable input.
In example embodiment, application platform 560 may represent an automobile and LED system 552 and LED system 556 may represent automobile headlights. In various embodiments, the system 550 may represent an automobile with steerable light beams where LEDs may be selectively activated to provide steerable light. For example, an array of LEDs may be used to define or project a shape or pattern or illuminate only selected sections of a roadway. In an example embodiment, Infrared cameras or detector pixels within LED systems 552 and/or 556 may be sensors (e.g., similar to sensors module 314 of
Although features and elements are described above in particular combinations, one of ordinary skill in the art will appreciate that each feature or element can be used alone or in any combination with the other features and elements. In addition, the methods described herein may be implemented in a computer program, software, or firmware incorporated in a computer-readable medium for execution by a computer or processor. Examples of computer-readable media include electronic signals (transmitted over wired or wireless connections) and computer-readable storage media. Examples of computer-readable storage media include, but are not limited to, a read only memory (ROM), a random access memory (RAM), a register, cache memory, semiconductor memory devices, magnetic media such as internal hard disks and removable disks, magneto-optical media, and optical media such as CD-ROM disks, and digital versatile disks (DVDs).
Claims
1. A device comprising:
- a light emitting layer; and
- a wavelength converting layer having a thickness of 5-20 microns over the light emitting layer, the wavelength converting layer comprising: a plurality of phosphor grains 50-500 nm in size and encapsulated in cerium free YAG shells; and a binder material binding the plurality of phosphor grains.
2. The device of claim 1, wherein the binder material has a RI of greater than 1.65.
3. The device of claim 1, wherein a non-radiative recombination rate of the wavelength converting layer is less than 3 μs−1.
4. The device of claim 1, wherein the wavelength converting layer formed by depositing the plurality of phosphor grains onto the wavelength converting layer via an electrophoretic process.
5. The device of claim 1, wherein a first phosphor grain of the plurality of phosphor grains is a first phosphor type and a second phosphor grain of the plurality of phosphor grains is a second phosphor type.
6. The device of claim 5, wherein the first phosphor grain is 300-400 nm in size and the second phosphor grain is less than 100 nm in size.
7. The device of claim 1, wherein the refractive index of the cerium free YAG shell is substantially matched to the refractive index of the binder.
8. The device of claim 1, wherein the wavelength converting layer further comprises a polymeric toughening additive.
9. The device of claim 1, further comprising an optical isolation material attached to a sidewall of the wavelength converting layer, the optical isolation material selected from one of a DBR, a reflective material and an absorptive material.
10. The device of claim 1, further comprising quantum dot material in contact with the wavelength converting layer.
11. The device of claim 1, wherein the surface area of a first side of the wavelength converting layer that is attached to the light emitting surface is larger than the surface area of the light emitting surface.
12. The device of claim 1, further comprising scattering particles.
13. A wavelength converting layer comprising:
- a plurality of phosphor grains 50-500 nm in size and encapsulated in cerium free YAG shells; and
- a binder material binding the plurality of phosphor grains, the wavelength converting layer having a thickness of 5-20 microns attached to the light emitting surface.
14. The wavelength converting layer of claim 13, wherein the binder material has a RI of greater than 1.65.
15. The wavelength converting layer of claim 13, wherein a first phosphor grain of the plurality of phosphor grains is a first phosphor type and a second phosphor grain of the plurality of phosphor grains is a second phosphor type.
16. The wavelength converting layer of claim 13, wherein the wavelength converting layer further comprises a polymeric toughening additive.
17. A method comprising:
- providing a light emitting surface;
- depositing, via electrophoretic deposition, a wavelength converting layer over the light emitting surface, the wavelength converting layer comprising: a plurality of phosphor grains 50-500 nm in size and encapsulated in cerium free YAG shells; and a binder material binding the plurality of phosphor grains, the wavelength converting layer having a thickness of 5-20 microns attached to the light emitting surface.
18. The method of claim 17, wherein the binder material has a RI of greater than 1.65.
19. The method of claim 17, wherein a first phosphor grain of the plurality of phosphor grains is a first phosphor type and a second phosphor grain of the plurality of phosphor grains is a second phosphor type.
20. The method of claim 17, wherein the wavelength converting layer further comprises a polymeric toughening additive.
Type: Application
Filed: Dec 19, 2018
Publication Date: Jun 27, 2019
Applicant: Lumileds LLC (San Jose, CA)
Inventors: Danielle Russell CHAMBERLIN (Belmont, CA), Kentaro SHIMIZU (Sunnyvale, CA), Peter Josef SCHMIDT (Aachen), Daniel Bernardo ROITMAN (Menlo Park, CA)
Application Number: 16/226,486