TW202021155A - Light-emitting device with light scatter tuning to control color shift - Google Patents

Abstract

A system and methods for light-emitting diode (LED) devices with a dimming feature that can tailor a color point shift in the light color temperature of a scattering/transparent layer to enlarge a dim to warm range are disclosed herein. A light-emitting device may include a wavelength converting structure configured to receive light from a light emitting semiconductor structure and an adjacent light scattering structure. The light scattering structure may comprise a plurality of scattering particles with a lower refractive index (RI) than the RI of the matrix material in which the scattering particles are disposed. The wavelength converting structure may include a red phosphor and a green phosphor such that to adjust overlap between green emission and absorption by the red phosphor to correspondingly adjust scattering and magnitude of color shift. In an embodiment, the light scattering structure may be integrated in the wavelength converting structure.

Description

Light emitting device with light scattering tuning to control color shift

The present invention relates generally to light-emitting lighting devices, and more specifically, the present invention relates to applications that can use a scattering/transparent layer or structure to adapt a color point shift and color temperature change to provide a dimming effect and expand the dimming effect. A light emitting diode (LED) system and method with a dimming feature that is one of the light ranges.

Light emitting diodes (LEDs) are used as light sources for various applications. For example, LEDs can be used as white light sources for various applications, such as flash light sources for cell phone cameras and incandescent lamps. These LEDs may be referred to herein as white LEDs or white LEDs. When the white LED is in an on state, the LED may appear to emit white light from the perspective of the viewer. In some cases, the white LED may be composed of a light-emitting semiconductor structure that emits non-white light and a wavelength conversion structure that causes the non-white light to appear white to the viewer. For example, a white LED may be formed by covering a blue-emitting semiconductor structure with a yellow-emitting phosphor layer (ie, wavelength conversion structure), and may be referred to as a phosphor-converted LED (pc-LED). The blue photons emitted by the light emitting semiconductor structure can pass through the yellow-emitting phosphor layer as blue light or can be converted into yellow photons by the yellow-emitting phosphor layer. Finally, the blue and yellow photons emitted from the LED are combined to make the light emitted from the LED appear white to the viewer.

The present invention discloses a light emitting diode (LED) device having a dimming feature that can use a scattering/transparent layer or structure to adjust a color point shift and color temperature change to provide a dimming effect and expand the dimming range One system and method. A light emitting device may include a light emitting semiconductor structure configured to emit a light in an on state. The light emitting device may further include a wavelength conversion structure having a first surface adjacent to the light emitting semiconductor structure and a second surface opposite to the first surface, the wavelength conversion structure is configured to receive The light emitted by the light emitting semiconductor structure and the light reflected from a light scattering structure. The light scattering structure may be adjacent to the second surface of the wavelength conversion material, and may include a plurality of scattering particles disposed in a first matrix material having a first refractive index (RI). Alternatively, the light scattering may be included in the wavelength conversion structure. Each of the plurality of scattering particles may include a material having a second RI lower than one of the first RI. The wavelength conversion structure may include at least a plurality of first phosphor particles of a first type phosphor and a plurality of second phosphor particles of a second type phosphor disposed in a second matrix material. The first type of phosphor can absorb a first spectrum of light and emit a second spectrum of light. The second type of phosphor can emit the second spectrum of light so that one of the excitation (or absorption) spectrum of the first type of phosphor overlaps with an emission spectrum of the second type of phosphor, one of which is larger The overlap causes a larger color point shift of the light emitted from the light emitting device that changes according to temperature and drive current.

Cross-reference of related applications This application claims the priority rights of European Patent Application No. 18200747.6 filed on October 16, 2018 and US Patent Application No. 16/048,436 filed on July 30, 2018, and the full text of each of these cases Incorporated by reference.

Adding a dimming effect to an LED (such as a white LED) allows the intensity or color of the light emitted by the LED to gradually change or shift. A conventional dimmer can vary the voltage or current applied to a standard LED to adjust the light intensity of the light emitted from the LED, but it cannot affect the color temperature. The daylight and the light from the incandescent lamp are adjusted to a warmer color, which makes the user feel natural and comfortable. If the LEDs are driven at low currents, the typical mechanism for dimming white LEDs (such as white pc-LEDs) cannot result in a warmer color (ie, lower correlated color temperature (CCT)). A portion of the warmer white LED in a light module that includes multiple CCT LEDs (such as chip-on-board (COB) LEDs) can be used to achieve dimming the LED light to a warmer color, but this complicates the drive electronics and light distribution And increase costs. Therefore, it is desirable to obtain an LED having a passive layer or structure with adjustable color temperature to face a warmer tone.

This article discloses an LED structure that uses a combination of different phosphors in a wavelength conversion structure to control a color shift that varies according to light scattering changes in an adjacent scattering structure or an integrated structure by changing the light color temperature from a cool white The change to a warm white color provides a warming effect for the light emitted from the LED structure to vary according to the LED temperature and drive current. For example, when the light emitted from the LED structure is white light, the disclosed LED structure can provide light to change the color temperature of the light from a cool white at a high drive current (such as a correlated color temperature (CCT) of about 3000 K or greater) to A dimming effect of warm white at a lower drive current (eg CCT of about 2000 K). Although the examples described herein may refer to white LED structures that produce white light, those skilled in the art should understand that the embodiments disclosed herein can be similarly used to provide a dimming for LED structures that produce any other color light in the spectrum effect.

In the embodiments disclosed herein, the phosphor system used in the wavelength conversion structure includes at least one red phosphor (which absorbs green/blue light) and a green phosphor (which emits green light), so that these types of phosphorescence The volume can be used to adjust the overlap between the green light emission and the red phosphor absorption to adjust the scattering and magnitude of the color shift accordingly. As the overlap between green light emission and red light absorption in the phosphor system increases, the resulting color shift increases. Therefore, maximizing the overlap between green light emission and red light absorption in the phosphor system maximizes the color shift and dimming range of the resulting white light emitted from the LED structure.

In the following examples, the LED device is used to refer to a white LED (unless otherwise indicated) and can be used interchangeably with LEDs, pc-LEDs, LED structures, LED modules, light emitting devices, or (white) light sources, such that an LED The light source or any other type of light source can be similarly used in a light emitting device. The disclosed embodiment of a light emitting device with light scattering tuning to control color shift and color temperature can be used for dimmable lighting LED modules, which are commonly used in, for example, hotel environments or home applications. Examples of LED types may include constant power LEDs in a chip on board (COB) configuration.

FIG. 1A is a diagram of an exemplary light emitting device 100 including a light emitting semiconductor structure 115, a wavelength conversion structure 110, and a light scattering structure 105. FIG. The light scattering structure 105 may be a separate structure (as shown in FIG. 1A), or alternatively, may be incorporated into the wavelength conversion structure 110. The contacts 120 and 125 may be coupled to the light emitting semiconductor structure 115 directly or through another structure such as a base to be electrically connected to a circuit board or other substrate or device. In one example, the contacts 120 and 125 can be electrically insulated from each other by a gap 127 that can be filled with a dielectric material. The light-emitting semiconductor structure 115 may be any light-emitting semiconductor structure that emits light 102, and the light 102 may be converted into light 112 having a different color point (for example, including light 102 and light by a wavelength conversion structure 110 and/or light scattering structure 105) One of the 104 combinations shows white light). An example of such a light-emitting semiconductor structure 115 may be a group III nitride light-emitting semiconductor structure (such as gallium , One or more of binary, ternary and quaternary alloys of aluminum, indium and nitrogen form a light-emitting semiconductor structure). Other examples of light emitting semiconductor structures may include other groups formed from group III to V materials, group III phosphide materials, group III arsenide materials, group II to VI materials, zinc oxide (ZnO) or silicon (Si) based materials Light emitting semiconductor structure.

For example, the light-emitting semiconductor structure 115 may be formed from the following: Group III to V semiconductors, including (but not limited to) AlN, AlP, AlAs, AlSb, GaN, GaP, GaAs, GaSb, InN, InP, InAs, InSb; II Group 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 exemplary semiconductors have a refractive index ranging from about 2.4 to about 4.1 for the typical emission wavelength of LEDs in which they are present. For example, a group III nitride semiconductor such as GaN has a refractive index of about 2.4 at 500 nm, and a group III phosphide semiconductor such as InGaP has a refractive index of about 3.7 at 600 nm. The contacts 120 and 125 may be formed of solder such as AuSn, AuGa, AuSi, or SAC solder.

FIG. 1B is a diagram of an exemplary light emitting semiconductor structure 115 that may be included in the light emitting device 100 of FIG. 1A. The illustrated example is a flip chip structure. However, those of ordinary skill should understand that the embodiments described herein can be applied to other types of LED designs, such as vertical, lateral, and multi-junction devices.

In the example shown in FIG. 1B, the light-emitting semiconductor structure 115 includes a semiconductor layer or region (also referred to as an n-type region) 130 disposed on n-type conductivity and a semiconductor layer or region (also referred to as an n-type region) of p-type conductivity A p-type region) 140 between a light emitting active region 135. The contacts 145 and 150 are placed in contact with a surface of the light emitting semiconductor structure 115 and a gap 155 is filled by a dielectric material such as oxide or nitride of silicon (ie, SiO ₂ or Si ₃ N ₄ ) To be electrically insulated from each other. In the illustrated embodiment, the contact 145 (also referred to as a p-contact) directly contacts a surface of the p-type region 140, and the contact 150 (also referred to as an n-contact) and one of the n-type regions 130 Direct surface contact. Although not shown in FIG. 1B, a dielectric material such as disposed in the gap 155 may also be lined on the sidewalls of the light emitting active region 135 and the p-type region 140 to electrically isolate these regions from the contact 150 to prevent pn Junction short circuit.

The n-type region 130 may be grown on a growth substrate and may include one or more semiconductor material layers. The layer(s) may 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 unintentionally doped, or may even be p-type device layers. The layer can be designed to emit light with high efficiency according to the specific optical, material, or electrical properties required by the light emitting region. Like the n-type region 130, the p-type region 140 may include multiple layers of different compositions, thicknesses, and dopant concentrations, including layers that are not intentionally doped or n-type layers. Although layer 130 is described herein as an n-type region and layer 140 is described herein as a p-type region, the n-type region and the p-type region can also be switched without departing from the scope of the embodiments described herein.

The light emitting active region 135 may be, for example, a p-n diode junction associated with the interface of the p region 140 and the n region 135. Alternatively, the light emitting active region 135 may include one or more semiconductor layers doped or undoped with n-type or p-type. For example, the light emitting active region 135 may include a single thick or thin light emitting layer. This includes homogeneous junctions, single heterostructures, double heterostructures or single quantum well structures. Alternatively, the light-emitting active region 135 may be a multi-quantum well light-emitting region, which may include a multi-quantum well light-emitting layer separated by a barrier layer.

The p-contact 145 may be formed on a surface of the p-type region 140. The p-contact 145 may include a plurality of conductive layers that can prevent or reduce electromigration of the reflective metal, such as a reflective metal and a protective metal. The reflective metal may be silver or any other suitable metal, and the protective metal may be TiW or TiWN. The n-contact 150 may be formed to be in surface contact with one of the n-type regions 130 in a region where portions of the active region 135, the n-type region 140, and the p-contact 145 have been removed to expose the n-type region 130 At least part of the surface. The sidewall of the exposed mesa or via can be coated with a dielectric to prevent short circuits. The contacts 145 and 150 may be, for example, metal contacts formed from metals including (but not limited to) the following: gold, silver, nickel, aluminum, titanium, chromium, platinum, palladium, rhodium, rhenium, ruthenium, Tungsten and its mixtures or alloys. In other examples, one or two contacts 145 and 150 may be formed from a transparent conductor such as indium tin oxide.

The n-contact 150 and the p-contact 145 are not limited to the configuration shown in FIG. 1B, but can be configured in various ways. In an embodiment, one or more n-contact vias may be formed in the light emitting semiconductor structure 115 to form electrical contact between the n-contact 150 and the n-type layer 130. Alternatively, the n-contact 150 and the p-contact 145 can be redistributed to form a bonding pad with a dielectric/metal stack known in the art. The p-contact 145 and the n-contact 150 can be electrically connected to the contacts 120 and 125 of FIG. 1A directly or through another structure such as a base, respectively.

Referring to FIG. 1A, the wavelength conversion structure 110 may be any luminescent material, such as a transparent or translucent binder or a phosphor or phosphor particles in a matrix (such as polysilicon) or absorbs a wavelength of light and emits a different wavelength A ceramic phosphor element for light. If the wavelength conversion material 110 is a ceramic phosphor element, the ceramic phosphor element may be, for example, a ceramic phosphor plate (such as (thick) phosphor thin layer) for generating a color light or for generating different colors One of the ceramic phosphor plates is stacked. The ceramic phosphor plate may have an RI of 1.4 or greater (eg, 1.7 or greater) for the wavelength emitted by the light emitting semiconductor structure 115. In one example, the wavelength conversion structure 110 may be pre-formed as a wavelength conversion element and attached to the light emitting semiconductor structure 115 using an adhesive or any other method or material known in the art.

In one example, the light emitting semiconductor structure 115 may emit blue light 102. In such embodiments, the wavelength conversion structure 110 may include, for example, a yellow light-emitting wavelength conversion material (e.g., yellow phosphor) or green and red light-emitting wavelength conversion material (e.g., a combination of red and green phosphors) , Which will produce white light 112 when the light 104 emitted by the respective phosphors is combined with the blue light 102 emitted by the light emitting semiconductor structure 115. In another example, the light emitting semiconductor structure 115 may emit UV light. In these embodiments, the wavelength conversion structure 110 may include, for example, blue and yellow wavelength conversion materials or blue, green, and red wavelength conversion materials. A wavelength conversion material emitting other color light may be added to adapt the spectrum of the light 112 emitted from the light emitting device 100.

The wavelength conversion structure 110 may include phosphor particles, organic semiconductors, group II to VI or group III to V semiconductors, group II to VI or group III to V quantum dots or nanocrystals, dyes, polymers or light emitting materials (such as nitrogen Gallium (GaN)). Examples of phosphors that can be used include combinations based on garnet, orthosilicate, nitrided silicate, and aluminum nitride phosphors, such as garnet Y ₃ Al ₅ O ₁₂ : Ce (YAG), Lu ₃ Al ₅ O ₁₂ : Ce (LuAG), Y ₃ Al _5-x Ga _x O ₁₂ : Ce (YGaG), orthosilicate (Ba _1-x Sr _x ) ₂ SiO ₄ : Eu (BOSE) and silicon nitride Phosphate phosphors (such as (Ca, Sr) AlSiN ₃ : Eu (ECAS or SCASN), (Ca, Sr, Ba) ₂ Si ₅ N ₈ : Eu (BSSN) and Sr (LiAl ₃ N ₄ ): Eu (SLA )).

In one example, the light scattering structure 105 can be applied to the light emitting device 100 to achieve a cut-off white appearance, as described in US Patent Application No. 15,722,903, which is incorporated herein by reference as if it were fully set forth.

FIG. 1C is a diagram of an exemplary layer of a scattering structure 105 that may be included in the light emitting device 100 of FIG. 1A. The scattering structure 105 can be formed by a plurality of scattering particles 160 dispersed in a matrix material 165 (which was originally a homogeneous material). For example, the matrix material 165 may be polysilicon or any transparent or almost transparent material or a heat and light resistant matrix (such as polysiloxy). One property of the matrix material 165 (eg, polysiloxy) is that the refractive index (RI) changes drastically with temperature. The scattering particles 160 are formed of a material(s) having an RI (eg, a lower RI) different from the matrix material 165 to provide scattering modulation. In other words, the RI difference between the matrix material 165 and the scattering particles 160 disposed therein affects the amount of color point shift that the white light 112 can achieve. In one example, (porous or non-porous) silicon dioxide (SiO ₂ ) and/or (porous or non-porous) magnesium fluoride (MgF ₂ ) may be included in the material of the scattering particles 160. For example, a porous SiO ₂ or a non-porous MgF ₂ can be used. In an alternative embodiment not shown in FIGS. 1A and 1C, the scattering particles 160 may be included in the wavelength conversion structure 110.

As the temperature of the light emitting device 100 increases due to the application of a higher driving current, the porous silicon dioxide material 160 filled with polysilicon in the scattering structure 105 becomes more transparent, and the light 104 emitted from the wavelength conversion material 110 is scattered The amount is reduced. As temperature and current increase, the amount of light 102 emitted from the light-emitting semiconductor structure 115 also decreases in scattering amount, resulting in more light 102 and less light 104 being included in the light 112. This scattering and light changes, which vary according to temperature, act as a passive color temperature tuning system because the temperature is determined by the drive current. In this case, since the scattering caused by the scattering structure 105 decreases as the temperature increases, the direction of the color point shift shifts to a cooler color (higher CCT) as the temperature increases. Therefore, the scattering structure 105 realizes a passive dimming environment in which the color point shift is controlled by the driving current without additional input, and wherein the color point of the resulting white light 112 shifts from a warmer color to a cooler color when the current increases. In an alternative example, different materials may be used in the scattering structure 105 so that light scattering increases with temperature. In one example, when titanium dioxide is used as the scattering particles 160 in a matrix material 165, the light scattering caused by the scattering structure 105 increases with temperature because the refractive index difference between the scattering particles 160 and the polysilicon material 165 increases The temperature increases.

In an embodiment, the scattering structure 105 may be formed as a layer or film having a thickness t ₁ . In an example, the thickness t ₁ may be selected to optimize the switching speed of the phase change material and/or the physical space occupied by the scattering structure 105 in the light emitting semiconductor structure 115. In one example, the thickness t ₁ may be between 50 µm and 300 µm.

As explained above, the magnitude of the scattering effect of the scattering structure 105 on the light 104 and therefore the amount of color point shift that the white light 112 can achieve depends in part on the concentration of the scattering particles 160 and the difference between the scattering particles 160 and the matrix material 165 RI is poor.

Another aspect of determining the amount of color point shift that can be achieved by white light 112 is used in a mixture of phosphors in wavelength conversion structure 110. The absorption and emission spectra of the phosphor combination in the tuned wavelength conversion structure 110 are used to control the amount of color point shift of the light 112 by expanding the scattering range of the scattering structure 105. The phosphor may be a solid inorganic material composed of one of the main lattices doped with impurities. The impurities in the main lattice can absorb the energy of the excitation light and emit light of a different wavelength. According to the disclosure herein, the absorption and emission spectra of different phosphors in the overlapping wavelength conversion structure 110 can be used to reduce the relative proportion of specific emission spectra while increasing the relative proportion of certain other emission spectra, as will be described below.

FIG. 1D is a diagram of an exemplary layer of the wavelength conversion structure 110 that may be included in the light emitting device 100 of FIG. 1A. The wavelength conversion structure 110 may be formed as a mixture of one or more phosphors (eg, two or three types of phosphors) in a matrix (adhesive) material 170. The matrix material 170 may be, for example, silicone or any Transparent or almost transparent materials or a heat-resistant and light-resistant matrix (such as polysilicon). Due to the mixing, different types of phosphor particles 172, 174, 176 that absorb and emit different types of light are disposed in the matrix material 170. Alternatively, the wavelength conversion structure 110 may be one or more thin layers of ceramic phosphors stacked with or without intervening layers. In one example, the wavelength conversion structure 110 may include both a ceramic phosphor and a polysilicon having a combination of one or more types of phosphor particles. In another example, the wavelength conversion structure 110 may include a ceramic plate of a phosphor material of a first type and a matrix of phosphor particles having an optical path of the ceramic plate.

In the example shown in FIG. 1D, the wavelength conversion structure 110 includes three types of phosphor particles: narrow-band red-emitting phosphor particles 172 that absorb blue and green light and emit red light, blue light absorption, and some green light (e.g. Light in the wavelength range of 400 nm to 580 nm) and broad-band red-emitting phosphor particles 174 that emit red light (e.g. longer than 580 nm, 600 nm, or 620 nm) and emit blue light and some green light and emit green light Green phosphor. Narrow-band red-emitting phosphors absorb green light emitted from spontaneous green-emitting phosphors better than broad-band red-emitting phosphors.

In an alternative embodiment not shown in FIGS. 1A and 1C, the scattering particles 160 may be included in the wavelength conversion structure 110. In this case, for example, the scattering particles 160 may be incorporated into the wavelength conversion material 110 at the same time as the phosphor particles 172, 174, and 176 are incorporated.

The wavelength conversion structure 110 may be applied in a layer having a thickness t ₂ that may depend on the wavelength conversion material used and/or the LED design. For example, one layer of the wavelength conversion structure 110 may be approximately t ₂ =500 µm thick, while other wavelength conversion materials may be formed as a layer as thin as 20 µm or as thick as 1000 µm. In an example in which a light emitting device is implemented according to a COB design, the thickness t ₂ may be larger, for example, in the range of 400 μm to 600 μm. In the COB design, the wavelength conversion structure 110 may be concave or convex, which may cause a local deviation of the thickness t ₂ .

Figure 2 is a spectrum diagram of the relative intensity of the excitation (absorption excites an electron to a higher energy state) spectrum and emission spectrum of three types of phosphors (which is shown as normalized in arbitrary units (au)) and wavelength: SLA phosphor Sr(LiAl ₃ N ₄ ): Eu ²⁺ , which is a narrow-band red-emitting phosphor; wide-band red phosphor, such as (Ca, Sr) AlSiN ₃ : Eu ²⁺ or (Ga, Sr, Ba ) ₂ Si ₅ N ₈ :Eu ²⁺ ; and green phosphors such as (Lu,Y) ₃ (Al,Ga) ₅ O ₁₂ :Ce ³⁺ or (Ba,Sr) ₂ SiO ₄ :Eu ²⁺ . As observed from the spectrum in Figure 2, SLA narrow-band red-emitting phosphors can have strong absorption of blue and green wavelengths, of which the maximum absorption is from about 450 nm to about 500 nm (about 470 nm maximum) , And the full amplitude at half maximum (FWHM, the width of the spectral curve as the distance between the points on the curve where the function reaches its half-height value) is about 150 nm, and tails to long as it slowly drops to about 600 nm wavelength. Broadband red phosphor absorption can have a maximum at a shorter wavelength of about 435 nm and absorb more in the blue range and absorb less green.

As seen in FIG. 2, a red phosphor or a combination of red phosphors can effectively absorb wavelengths in the blue and green wavelength ranges (eg, between 400 nm and 580 nm). A light emitting semiconductor structure 115 (which is a blue LED) may have an emission less than 430 nm, and therefore, the absorption range may be narrowed based on the wavelength range of incoming light. The emission of the red phosphor can occur at a wavelength at least longer than 580 nm or equal to or longer than 600 nm or 620 nm.

As can be seen from FIG. 2, in many cases, the long-wavelength tail of the excitation spectrum overlaps with the short-wavelength head of the emission spectrum. The overlapping area between the SLA phosphor excitation spectrum and the green phosphor emission spectrum is proportional to the amount of green light emission absorbed by the SLA phosphor and therefore to the amount of green light converted into red light.

Therefore, a large overlap between the SLA phosphor excitation spectrum of the phosphor and the green phosphor emission spectrum in the wavelength conversion structure 110 implies: as the scattering (transparency) of the scattering layer 105 (or alternatively, as the (The scattering of the wavelength conversion structure 110) is increased by lowering the temperature and driving current of the light emitting device 100, more green light emission is absorbed by the red phosphor to thereby provide one of the color points of the light 112 with a given dimming range is larger Offset. Therefore, the amount (ratio) of different phosphors (such as green, broadband red, and narrow-band red phosphors) in the phosphor mixture can be varied to obtain the desired color point shift and dimming range. For example, a phosphor mixture with a relatively high amount of narrow-band red phosphor will produce a larger color point shift in the dimming range and the resulting light 112 has a larger warming effect.

In the following example, referring to FIG. 1A, it is assumed that, for example, using the porous silica or MgF ₂ in the above polysilicon, when the light emitting device 100 is turned on, the light scattering structure 105 increases as the temperature of the light emitting device 100 increases Become more transparent. It is also assumed that the wavelength conversion structure 110 includes a mixture of polysiloxane resin and one of three types of phosphors (SLA phosphor, broadband red phosphor, and green phosphor). The temperature of the light emitting device 100 depends on the driving current flowing through the light emitting semiconductor structure 115. An appropriate heat sink can be selected, for example, to control temperature and drive current. In some LED applications, it is desirable to keep the temperature as low as possible to have an optimal LED output. However, at high drive currents, the temperature of an LED can rise to a high temperature equal to or higher than 100°C. The temperature can be further increased by using a smaller heat sink. If, for example, the scattering structure 105 is incorporated into the wavelength conversion layer 110 by incorporating porous silica or MgF ₂ particles into the wavelength conversion layer 110 together with the phosphor particles, the scattering at the lower operating current and temperature Both color conversion and color conversion are added to produce a warmer white light.

When the light emitting device 100 is in the on state but operates at a lower temperature (eg, near room temperature) (eg, about 25°C, where the operating current applied to the light emitting device 100 can be about 30 mA), the light scattering structure 105 is Opaque/white and therefore has a higher scattering effect on the combined light 104 from the wavelength conversion structure 110 and the light 102 emitted from the light emitting semiconductor structure 115. In this case, the light scattering structure 105 reflects the light 102 and 104 back into the wavelength conversion structure 110, and the narrow-band red phosphor (eg, SLA phosphor) in the wavelength conversion structure 110 absorbs blue and green light from the reflected light at the same time Red light is emitted, which reduces the peaks of blue and green light in white light 112 and increases the peak of red light. This changes the color point of the white light 112 to a warmer tone (for example, 2000 K to 2200 K CCT or substantially 1500 K to 2500 K). As the temperature of the light emitting structure increases (eg, to 85°C, where the operating current applied to the light emitting device 100 may be about 250 mA), the light scattering structure 105 becomes more transparent and reduces the scattering effect of the emitted light 102 and 104 . Therefore, less light 102 and 104 is reflected back to the wavelength conversion structure 110, so that the SLA phosphor absorbs less reflected blue and green light, which allows more blue and green light emitted from the white light 112 relative to the red light and converts the white light 112 The color point changes to a cooler tone (eg 2700 K CCT or higher).

Therefore, the color point of the light 112 color temperature can be shifted from warm white (smaller CCT) to cool white (larger) by changing the driving current that causes temperature changes from low device temperature/current to high device temperature/current CCT) to achieve one of the dimming effects of the light 112 emitted from the light emitting device 100, as shown in FIG. The range of dimming effect (ie, color point shift) can be expanded by increasing the overlap between the SLA phosphor excitation spectrum and the green phosphor emission spectrum, as described above.

4 is a flowchart of an example method 400 of manufacturing a light emitting device (such as the light emitting device 100 of FIG. 1A) having light scattering tuning to control color shift. The example method 400 includes generating a light emitting semiconductor structure 115 (405). The light-emitting semiconductor structure can be produced, for example, by growing a light-emitting semiconductor structure (such as a group III nitride semiconductor structure) on a growth substrate (such as sapphire, SiC, Si, GaN, or a composite substrate).

The example method 400 depicted in FIG. 4 further includes generating a wavelength conversion material by generating a phosphor mixture in polysilicon (410). As described above, the phosphor mixture includes at least two types of phosphors, and may include narrow-band SLA phosphors, broadband red-emitting phosphors, and/or green phosphors.

The example method 400 depicted in FIG. 4 further includes applying the wavelength conversion material 110 to the light emitting semiconductor structure 115 (415). In one example, the wavelength conversion material 110 can be, for example, a layer or film deposited by spray coating, spin coating, thin film deposition (eg, by electrophoresis), or molding. To generate the wavelength conversion material 110, phosphors (such as narrow-band red phosphors, wide-band red phosphors, and/or green phosphors) may be mixed in the polysilicon at a ratio to achieve a desired color point shift. For a COB design, the wavelength conversion material 110 can be applied to the COB (eg, by dispensing or spraying), and then cured. A thin ceramic layer of various phosphors can also be used to form the wavelength conversion structure 110.

The example method 400 depicted in FIG. 4 further includes generating the scattering material 105 (420) and applying it to the wavelength conversion material 110 (425). This can be accomplished using any method known in the art, such as mixing and subsequent application techniques. The scattering particles 105 can be generated by mixing the scattering particles 160 (such as porous silica or MgF ₂ ) in one of the matrix materials 165 (such as polysiloxy) having a higher RI. The scattering material 105 including the matrix material 165 and the scattering particles 160 may be laminated to the wavelength conversion material 110. For example, the scattering material 105 may be incorporated into the wavelength conversion material 110 and/or directly molded on the wavelength conversion material 110. In an alternative example, generating the wavelength conversion material (410) and generating the scattering material (420) may be one of the combining steps of combining materials.

Although the embodiments have been described in detail, those skilled in the art should understand that the embodiments described herein can be modified in view of the present invention without departing from the spirit of the present invention. Therefore, the scope of the invention is not intended to be limited to the specific embodiments shown and described.

100: light emitting device 102: light 104: light 105: light scattering structure/scattering layer/scattering material 110: wavelength conversion structure/wavelength conversion material/wavelength conversion layer 112: light 115: light emitting semiconductor structure 120: contact 125: contact 127: gap 130: n-type region/n-type layer 135: light emitting active region 140: p-type region 145: p-contact 150: n-contact 155: gap 160: scattering particles 165: matrix material 170: matrix material 172: phosphorescence Bulk particles 174: Phosphor particles 176: Phosphor particles 400: Method 405: Generate a light emitting semiconductor structure 410: Generate a wavelength conversion material by generating a phosphor mixture in polysilicon 415: Apply a wavelength conversion material to the light emitting semiconductor structure 420: generating scattering material 425: applying the scattering material to the wavelength conversion material t ₁ : thickness t ₂ : thickness

FIG. 1A is a diagram of an exemplary light emitting device including a light emitting semiconductor structure, a wavelength conversion structure, and a light scattering structure;

FIG. 1B is a diagram of an exemplary light emitting semiconductor structure 115 that can be included in the light emitting device of FIG. 1A;

1C is a diagram of an exemplary layer of a scattering structure that can be included in the light emitting device of FIG. 1A;

1D is a diagram of an example layer of a wavelength conversion structure that can be included in the light emitting device of FIG. 1A;

Figure 2 is a spectrum diagram of the relative intensities of the excitation and emission spectra of the three types of phosphors (which are shown as normalized in arbitrary units (a.u.)) and wavelengths;

3 is a diagram showing the dimming effect of light emitted from a light-emitting device that can be achieved by varying the drive current to cause a temperature change; and

4 is a flowchart of an exemplary method of manufacturing a light-emitting device having light scattering tuning to control color shift, such as the light-emitting device of FIG. 1A.

100: light emitting device

102: light

104: light

105: light scattering structure/scattering layer/scattering material

110: wavelength conversion structure/wavelength conversion material/wavelength conversion layer

112: light

115: Light emitting semiconductor structure

120: contact

125: contact

127: clearance

Claims (16)

A light emitting device includes: a light emitting semiconductor structure configured to emit light at a first peak wavelength; a wavelength conversion structure disposed in a path of the light emitted by the light emitting semiconductor structure and including a A first phosphor material and a second phosphor material, the first phosphor material being configured to absorb light at the first peak wavelength and responsively emit light at a second peak wavelength longer than the first peak wavelength, The second phosphor material is configured to absorb light at the first peak wavelength and light at the second peak wavelength and responsively emit light at a third peak wavelength longer than the second peak wavelength; and a light scattering structure , Which includes scattering particles dispersed in a first material with a first refractive index n ₁ dispersed in a second material with a second refractive index n ₂ , (n ₁ -n ₂ ) at 25°C An amount greater than 100°C; wherein the light scattering structure is configured with respect to the wavelength conversion structure such that at least a portion of the light emitted by the light emitting semiconductor structure and transmitted through the wavelength conversion structure is formed by the first phosphor At least a portion of the light emitted by the material and at least a portion of the light emitted by the second phosphor material are backscattered toward the first phosphor material and the second phosphor material and combined by the semiconductor structure, the first phosphor The material and the second phosphor material emit and transmit light through the light scattering structure to form a white light output from the light emitting device. The light emitting device of claim 1, wherein the semiconductor structure emits blue light at the first peak wavelength, the first phosphor material emits green light at the second peak wavelength, and the second phosphor material strongly absorbs blue light and green light And the red light of the third peak wavelength is responsively emitted. The light emitting device of claim 2, wherein the second phosphor material has an absorption maximum between about 450 nm and about 500 nm. The light emitting device of claim 2, wherein the first phosphor material includes (Lu, Y) ₃ (Al, Ga) ₅ O ₁₂ : Ce ³⁺ or (Ba, Sr) ₂ SiO ₄ : Eu ²⁺ . The light emitting device according to claim 2, wherein the second phosphor material includes SLA phosphor Sr(LiAl ₃ N ₄ ): Eu ²⁺ . The light-emitting device according to claim 2, wherein the first phosphor material includes (Lu, Y) ₃ (Al, Ga) ₅ O ₁₂ : Ce ³⁺ or (Ba, Sr) ₂ SiO ₄ : Eu ²⁺ , and the The second phosphor material includes SLA phosphor Sr(LiAl ₃ N ₄ ):Eu ²⁺ . The light emitting device of claim 2, wherein the second phosphor material emits red light in a narrow spectral range, the light emitting device includes a light emitting device configured to absorb light emitted by the semiconductor structure and the first phosphor and is responsive A third phosphor material emitting a fourth peak wavelength and red light in a wide spectral range, the fourth peak wavelength is shorter than the third peak wavelength. The light emitting device according to claim 7, wherein the third phosphor material includes (Ca, Sr) AlSiN ₃ :Eu ²⁺ or (Ga,Sr,Ba) ₂ Si ₅ N ₈ :Eu ²⁺ . The light emitting device of claim 1, wherein in operation, the white light output has a correlated color temperature that increases as the temperature of the light scattering structure increases. The light emitting device of claim 9, wherein in operation, when the light scattering structure is at a temperature of about 25°C, the correlated color temperature is about 2000 K. The light emitting device of claim 9, wherein in operation, when the light scattering structure is at a temperature of about 85°C, the correlated color temperature is about 2700 K. The light emitting device according to any one of claims 1 to 11, wherein the first phosphor material is a plurality of first phosphor particles and the second phosphor material is a plurality of second phosphor particles. The light emitting device according to claim 12, wherein the first phosphor particles and the second phosphor particles are mixed with each other and dispersed in a binder material. The light emitting device according to claim 12, wherein the wavelength conversion structure and the light scattering structure are integrated, and the integrated structure includes the first phosphor particles, the second phosphor particles, and the second phosphor particles are mixed and dispersed to have the second The particles of the first material having the first refractive index in the material of the refractive index. The light emitting device according to any one of claims 1 to 11, wherein the wavelength conversion structure and the light scattering structure are separate structures, and the wavelength conversion structure is disposed between the semiconductor structure and the light scattering structure. The light emitting device according to any one of claims 1 to 11, wherein the first phosphorescent system is a first ceramic phosphor plate and the second phosphorescent system is a second ceramic phosphor plate.

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