Phosphor converted red LED using SLA phosphor

Abstract

: The invention provides a luminescent converter (200) configured to at least partly convert light source light (11) generated by a solid-state light source (10) into luminescent converter light (201), wherein: (A) the luminescent converter (200) has a thickness (T) of t1 micrometer (µm); (B) the luminescent converter (200) comprises a first luminescent material (210) of the type M1−xLi3−2yAl1+2y−zSizO4−4y−zN4y+z:Eux, wherein M comprises one or more of Ca, Sr and Ba, wherein 0 < x ≤ 0.04, wherein 0 ≤ y ≤ 1, wherein 0 ≤ z ≤ 0.05, wherein y + z ≤ 1, wherein the luminescent converter (200) comprises an amount of Eu of m1 weight percent (wt.%); and (C) wherein 10 ≤ t1*m1 ≤ 50.

Description

[0001] Phosphor converted red LED using SLA phosphor

[0002] FIELD OF THE INVENTION

[0003] The invention relates to a luminescent converter. The invention further relates to a light generating device comprising the luminescent converter. The invention further relates to a lighting system comprising the light generating device.

[0004] BACKGROUND OF THE INVENTION

[0005] In color tunable lighting devices, direct red light emitting light emitting diodes (LEDs) may be used. For instance, EP3141807A1 describes a LED lighting module comprising a substrate and multiple LED light sources housed on the substrate, the LED light sources including: a phosphor-converted amber source; a phosphor-converted green source; a direct emission red source; a direct emission green source; a direct emission blue source; and a direct emission cyan source.

[0006] US2020 / 347293A1 discloses a lighting device for emitting a red total radiation that has a source to emit electromagnetic primary radiation. A conversion element includes a first fluorescent material of the formula Sr[A12Li2O2N2]:Eu that at least partially converts the electromagnetic primary radiation into an electromagnetic secondary radiation in the red region of the electromagnetic spectrum. The conversion element includes a second fluorescent material to at least partially convert the electromagnetic primary radiation into an electromagnetic secondary radiation in the red region of the electromagnetic spectrum.

[0007] SUMMARY OF THE INVENTION

[0008] When operated at relatively low temperatures, the use of direct red light emitting LEDs may lead to a relatively efficient system. Furthermore, direct red light emitting LEDs may generate relatively pure red light. However, direct red light emitting LEDs may suffer from a bad hot-cold factor, i.e. the flux from the LED may decrease when the temperature of the LED increases. Moreover, the color point of the red light may shift with increasing driving current and temperature of the direct red light emitting LED. Furthermore, especially in mid-power packaged LEDs, direct red light emitting LEDs may be less efficient due to the trapping of light in the LED chip or the package. Another disadvantage of direct red emitting LEDs may be that high-voltage multi -junction chips are not widely available, whereas in direct blue emitting LEDs they are. High-voltage chips have the benefit of enabling the use of high-voltage efficient drivers.

[0009] Alternatively, a red phosphor converted LED may be used. Red phosphor converted LEDs may have a better hot-cold factor. Yet, red phosphor converted LEDs may have an undesirable color point and / or low color saturation. Further, the phosphors that can be used in red phosphor converted LEDs may have a low absorption strength and / or low stability. Hence, it is an aspect of the invention to provide an alternative light generating converter, which preferably further at least partly obviates one or more of above-described drawbacks. The present invention may have as an object to overcome or ameliorate at least one of the disadvantages of the prior art, or to provide a useful alternative.

[0010] According to a first aspect, the invention provides a luminescent converter configured to at least partly convert light source light generated by a solid-state light source into luminescent converter light. The luminescent converter may have a thickness (T) of tl micrometer (pm). Especially, in embodiments, the luminescent converter may have the thickness (T) downstream of the solid-state light source. Further, the luminescent converter may comprise a first luminescent material of the type Mi-xLi3-2yAli+2y-zSizO4-4y-zN4y+z:Eux, wherein M may comprise one or more of Mg, Ca, Sr and Ba, such as especially one or more of Ca, Sr, and Ba, wherein 0 < x < 0.04, wherein 0 < y < 1, wherein 0 < z < 0.05, and wherein y + z < 1. Especially, the luminescent converter may comprise a first luminescent material of the type Mi-xLi3-2yAli+2y-zSizO4-4y-zN4y+z:Eux, wherein M may comprise one or more of Ca, Sr and Ba, wherein 0 < x < 0.04, wherein 0 < y < 1, wherein 0 < z < 0.05, and wherein y + z

[0011] < 1. In embodiments, the luminescent converter may comprise an amount of Eu (originating from the first luminescent material (only)) of ml weight percent (wt.%). Further, in embodiments, 10 < tl*ml < 50. Hence, in specific embodiments, the invention provides a luminescent converter configured to at least partly convert light source light generated by a solid-state light source into luminescent converter light, wherein: (A) the luminescent converter has a thickness (T) of tl micrometer (pm); (B) the luminescent converter comprises a first luminescent material of the type Mi-xLi3-2yAli+2y-zSizO4-4y-zN4y+z:Eux, wherein M comprises one or more of Ca, Sr, and Ba, wherein 0 < x < 0.04, wherein 0 < y < 1, wherein 0

[0012] < z < 0.05, wherein y + z < 1, wherein the luminescent converter comprises an amount of Eu of ml weight percent (wt.%); and (C) wherein 10 < tl*ml < 50.

[0013] Further, in an aspect, the invention provides a luminescent converter configured to at least partly convert light source light generated by a solid-state light source into luminescent converter light, wherein: (A) the luminescent converter has a thickness (T) of tl micrometer (gm) (downstream of the solid-state light source); (B) the luminescent converter comprises a first luminescent material of the type Mi-xLi3-2yAli+2y-zSizO4-4y-zN4y+z:Eux, wherein M comprises one or more of Ca, Sr and Ba, wherein 0 < x < 0.04, wherein 0 < y < 1, wherein 0 < z < 0.05, wherein y + z < 1, wherein the luminescent converter comprises an amount of Eu of ml weight percent (wt.%); and (C) wherein 10 < tl*ml < 50. The amount of Eu is defined relative to the luminescent converter, i.e. ml is calculated as the weight of Eu relative to the weight of the (total) luminescent converter.

[0014] Such a luminescent converter may provide luminescent converter light having a red color with a desirable color point and a high (red) color saturation. Especially, the color point of the luminescent converter light may be represented by u’ and v’ color coordinates in the CIE 1976 UCS (uniform chromaticity scale) diagram (or “CIE 1976 L*u*v* color space” or “CIE u’v’ color diagram”). With the luminescent converter of the present invention, the color point of the luminescent converter light may especially be located at an Euclidean distance SQRT[(Au’)2+ (Av’)2] of at most 0.07, like at most 0.05, from the color point of a direct red light emitting LED. Within such an Euclidean distance, the difference in color points between two sources may be limited, such that the colors of the light from both light sources may appear similar. Further, the luminescent converter of the present invention may provide the benefit that the color point of the luminescent converter light may be (essentially) stable upon heating of the luminescent converter. Additionally, the first luminescent material may have a relatively high absorption strength and / or quantum efficiency (QE), thereby providing the benefit that the concentration of the first luminescent material in the luminescent converter may be low, thus reducing scattering losses in the luminescent converter and improving the luminous efficacy of radiation. Here, the term “quantum efficiency” refers to a ratio between a number of photons emitted by a luminescent material (Nem) to a number of photons absorbed by the (same) luminescent material (Nabs), i.e., Nem / Nabs.

[0015] The luminescent converter may be a layer, like a self-supporting layer. The luminescent converter may also be a coating. In embodiments, the (first) luminescent material may be provided as a luminescent converter, such as a luminescent single crystal, a luminescent glass, or a luminescent ceramic body. Such luminescent converter may be indicated as “converter body” or “luminescent body”. In embodiments, the luminescent converter may be a luminescent single crystal or a luminescent ceramic body. In other embodiments, the luminescent converter may comprise a light transmissive body, wherein the luminescent material is embedded. For instance, the luminescent converter may comprise a glass body, with luminescent material embedded therein. Or, the glass as such may be luminescent. In specific embodiments, the luminescent converter may comprise a polymeric body, with luminescent material embedded therein. Especially, in embodiments, the luminescent converter may comprise a powdered luminescent material configured embedded in a polymeric material, such as especially in a silicone material (see also below). The luminescent converter may be a single body that comprises the first luminescent material and optionally further luminescent materials. The luminescent converter may comprise two or more stacked layers with a first layer comprising the first luminescent material and optionally further luminescent material(s) and a second layer comprising one or more further luminescent materials.

[0016] The luminescent converter may have any shape. In general, however, the luminescent converter may comprise two essentially parallel faces, defining a thickness (T) of the luminescent converter. In embodiments, the two essentially parallel faces may define a first side and a second side of the luminescent body. Further, the luminescent converter may comprise a third side (or “edge face”), bridging the first side and second side. The edge face may be curved in one or two dimensions. The edge face may be planar. The luminescent converter may have a rectangular or circular cross-section, though other cross-sections may also be possible, like e.g. hexagonal, octagonal, etc. Hence, the luminescent converter may have a circular cross-section, an oval cross-section, square, or non-square rectangular. In embodiments, the luminescent converter may have an n-gonal cross-section, wherein n is at least 3, like 4 (square or rectangular cross-section), 5 (pentagonal cross-section), 6 (hexagonal cross-section), 8 (octagonal cross-section) or higher. The first side and second side may also be indicated as “main faces”, as they may especially provide the largest external area of the luminescent converter. Perpendicular to the afore-mentioned crosssection, may be another cross-section, which may in embodiments be rectangular. Hence, the luminescent converter may e.g. have a cubic shape, a (non-cubic) cuboid shape, an n-gonal prism shape with n being at least 5 (such as pentagonal prism, hexagonal prism), and a cylindrical shape. Other shapes, however, may also be possible. In embodiments, the luminescent converter may be a (small) tile. Alternatively, the luminescent converter may be a coating. Especially, in embodiments, the luminescent converter may be a coating, wherein the shape (especially the cross-sections) of the luminescent converter may be determined by the object (such as (the light-emitting surface of) a solid-state light source) coated with the luminescent converter.

[0017] In embodiments, the luminescent converter has lateral dimensions width or length (W or L) or diameter (D) and a thickness (T). In embodiments, (i) D > T or (ii) W > T and / or L > T. Especially, the lateral dimensions like length, width, and diameter may be at least 2 times, like at least 5 times, larger than the thickness (T). The luminescent converter may be transparent. Additionally or alternatively, the luminescent converter may be light scattering. In embodiments, the luminescent converter may comprise a (ceramic) luminescent material. In specific embodiments, L < 10 mm, such as especially L < 5 mm, more especially L < 3 mm, most especially L < 2 mm. In specific embodiments, W < 10 mm, such as especially W < 5 mm, more especially W < 3 mm, most especially W < 2 mm. In specific embodiments, D < 10 mm, such as especially D < 5mm, more especially D < 3mm, most especially D < 2 mm. Further, the luminescent converter may have lateral dimensions (width / diameter) in the range of 100 pm - 10 mm. In embodiments, T < 10 mm, such as especially T < 5 mm, more especially T < 3 mm, most especially T < 2 mm. Further, in embodiments, T < 1 mm, such as especially T < 0.8 mm, more especially T < 0.6 mm, most especially T < 0.5 mm. Additionally or alternatively, in embodiments, T > 10 pm, such as T > 25 pm, especially T > 50 pm (see also below).

[0018] The thickness (T) of the luminescent converter (or “luminescent converter thickness (T)”) may be the shortest distance from any point on the first side (or face) to any point on the second side (or face). Especially, the luminescent converter may be configured to be placed in a light receiving relationship with a (solid-state) light source configured to generate light source light, wherein the first side of the luminescent converter is configured facing the light source, and wherein the thickness (T) is defined as the shortest distance from any point on the first side (facing the light source and receiving light source light) to any point on the second side where light source light (and / or luminescent converter light) may exit in a transmissive mode of the luminescent converter. Hence, the luminescent converter thickness (T) may indicate a shortest optical path (for the light source light) through the luminescent converter. As such, the luminescent converter may especially have the thickness (T) downstream of the (solid-state) light source (i.e., in an optical path and / or along an optical axis (O) of the light source light).

[0019] Herein, the terms “upstream” and “downstream” relate to an arrangement of items or features relative to the propagation of the light from a light source, wherein relative to a first position within a beam of light from the light generating means, a second position in the beam of light closer to the light generating means is “upstream”, and a third position within the beam of light further away from the light generating means is “downstream”.

[0020] In embodiments, the light source light (and / or luminescent converter light) exiting the luminescent converter may be indicated as device light (see also below), Hence, the luminescent converter thickness T may be the shortest distance from any point on a luminescent converter surface (e.g. the first side) facing the solid-state light source, i.e. the upstream luminescent converter surface, to any point on a luminescent converter surface (e.g. the second side) where device light exits the device, i.e. the downstream luminescent converter surface.

[0021] In embodiments, the luminescent converter may especially have a thickness (T) of tl micrometers (pm). In embodiments, tl may be selected from the range of < 1000 pm, such as from the range of < 850 pm, especially from the range of < 600 pm, like from the range of < 500 pm. Further, tl may be selected from the range of < 400 pm, such as from the range of < 300 pm, especially from the range of < 250 pm. Additionally or alternatively, tl may be selected from the range of > 50 pm, such as from the range of > 100 pm, especially from the range of > 150 pm, like from the range of > 200 pm. Hence, in embodiments, the luminescent converter may have a thickness (T) of tl micrometers (pm), wherein 50 < tl < 1000 pm, such as 100 < tl < 850 pm, especially 150 < tl < 600 pm, like 200 < tl < 500 pm.

[0022] In embodiments, the luminescent converter may comprise the first luminescent material. The term “luminescent material” may especially refer to a material that can convert first radiation, especially one or more of UV radiation, violet radiation, and blue radiation, into second radiation. Herein, UV (ultraviolet) may especially refer to a wavelength selected from the range of 190-380 nm, such as 200-380 nm, though in specific embodiments other wavelengths may also be possible. The terms “violet light” or “violet emission”, and similar terms, may especially relate to light having a wavelength in the range of about 380-440 nm. The terms “blue light” or “blue emission”, and similar terms, may especially relate to light having a wavelength in the range of about 440-495 nm. In general, the first radiation and second radiation have different spectral power distributions, with the second radiation generally having a spectral power distribution at larger wavelengths than the first radiation (i.e. “down-conversion”). In embodiments, the “luminescent material” may especially refer to a material that can convert radiation into e.g. visible and / or infrared light. For instance, in embodiments the luminescent material may be able to convert one or more of UV radiation, violet radiation, and blue radiation, into visible light. Hence, upon excitation with radiation, the luminescent material may emit radiation. The terms “visible”, “visible light” or “visible emission” and similar terms refer to light having one or more wavelengths in the range of about 380-780 nm. In embodiments, the term “luminescence” may also refer to fluorescence. Instead of the term “luminescence”, also the term “luminescent material light” or “emission” may be applied. Hence, the terms “first radiation” and “second radiation” may refer to excitation radiation and emission (radiation), respectively. The term “luminescent material” may also refer to a plurality of different luminescent materials. Hence, the term “luminescent material” may in specific embodiments also refer to a luminescent material composition. Instead of the term “luminescent material” also the term “phosphor” may be applied. These terms are known to the person skilled in the art.

[0023] In embodiments, the first luminescent material may especially be of the type Mi-xLi3-2yAli+2y-zSizO4-4y-zN4y+z:Eux. In embodiments, M may comprise one or more of magnesium (Mg), calcium (Ca), strontium (Sr), and barium (Ba), such as especially one or more of Ca, Sr, and Ba. Hence, Mi-xLi3-2yAli+2y-zSizO4-4y-zN4y+z:Eux may further be indicated as (Mg,Ca,Sr,Ba)i-xLi3-2yAli+2y-zSizO4-4y-zN4y+z:Eux, such as especially indicated as (Ca,Sr,Ba)i-xLi3-2yAli+2y-zSizO4-4y-zN4y+z:Eux. Such a phosphor may further be indicated as an SLA-type phosphor, or SLA phosphor. In embodiments wherein y < 1, such a phosphor may especially be indicated as SLAO phosphor (but may also be referred to as SLA phosphor). Luminescent materials of the type Mi-xLi3-2yAli+2y-zSizO4-4y-zN4y+z:Euxmay further be described in US2021171827A1, which is hereby incorporated by reference.

[0024] In embodiments, x (in the first luminescent material) may be selected from the range of 0 < x < 0.1, such as from the range of 0 < x < 0.08, especially from the range of 0 < x < 0.05. Further, x (in the first luminescent material) may be selected from the range of 0 < x < 0.04, such as from the range of 0 < x < 0.04, especially from the range of 0 < x < 0.03. Additionally or alternatively, in embodiments, x (in the first luminescent material) may be selected from the range of > 0.0005, such as from the range of > 0.001, especially from the range of > 0.003, like from the range of > 0.0045. The values for x indicated in this paragraph may especially apply for all SLA-type phosphors described herein (including the SLA-type phosphors disclosed in the appended claims). Hence, europium (Eu) may in embodiments not replace more than 10% of the cation M in the first luminescent material, especially in an SLA-type phosphor. In embodiments, in the first luminescent material (and in similar materials), Eu may be substantially or only divalent (Eu2+), as is known to the person skilled in the art. Further, in embodiments, in the first luminescent material of the type Mi-xLi3-2yAli+2y-zSizO4-4y-zN4y+z:Eux, y may be selected from the range of 0 < y < 1, such as from the range of 0 < y < 1, especially from the range of 0 < y < 0.75, like from the range of 0 < y < 0.6. In specific embodiments, y = 0. Further, in specific embodiments, y = 0.5. Additionally or alternatively, y may be equal to or about equal to 0.5, as described in US2021171827A1. In such embodiments, as also described in US2021171827A1, the first luminescent material of the type Mi-xLi3-2yAli+2y-zSizO4-4y-zN4y+z:Eux may be characterized by the formula AEi-xLi2A12-zSizO2+zN2+z:EUx, wherein AE may be one or more of Ca, Sr, and Ba. A first luminescent material (especially an SLA-type phosphor) wherein y = 0.5 may provide the benefit that the first luminescent material centroid wavelength Xci (see below) may be shifted to shorter (red) wavelengths compared to a first luminescent material wherein y is e.g. at least 0.9. Further, such a first luminescent material (wherein y ~ 0.5 and / or y = 0.5) may especially crystallize in a UCr4C4 type crystal structure. In other specific embodiments, y is at least 0.01. Further, in specific embodiments, y is at least 0.6.

[0025] Additionally or alternatively, in embodiments, in the first luminescent material of the type Mi-xLi3-2yAli+2y-zSizO4-4y-zN4y+z:Eux, z may be selected from the range of 0 < z < 0.1, such as from the range of 0 < z < 0.07, especially from the range of 0 < z < 0.05, like from the range of 0 < z < 0.05, such as 0 < z < 0.03. Hence, in embodiments, in the first luminescent material, SiN may replace A1O to a maximum of 10 mole%. Yet, in embodiments, 0 < z, such that the first luminescent material may in embodiments not comprise SiN (see also below). That is, in embodiments, z = 0 (see also below). Yet, in (alternative) embodiments, z may be selected from the range of > 0.0005, such as from the range of > 0.001, especially from the range of > 0.005, like from the range of > 0.01. Further, in embodiments, in the first luminescent material, y + z < 1.1, such as y + z < 1.05, especially y + z < 1, like y + z < 0.9. Further, in embodiments, y + z > 0, such as y + z > 0. 1, especially y + z > 0.25, like y + z > 0.5. Additionally or alternatively, as e.g. described in US2021171827A1, in embodiments, 0.2 < z / x < 4, such as 0.5 < z / x < 3. Especially, as described in US2021171827A1, in embodiments, y may be equal to or about equal to 0.5, and 0.2 < z / x < 4.

[0026] In embodiments, the first luminescent material may be of the type AEi-xLi3-2yAli+2y-zSizO4-4y-zN4y+z:Eux, wherein AE may comprise one or more of Ca, Sr, and Ba, wherein 0 < x < 0.04, wherein 0.4 < y < 0.6, and wherein 0 < z < 0.05. Such embodiments may especially be described in US2021171827A1. As described in US2021171827A1, luminescent materials of the type AEi-xLi3-2yAli+2y-zSizO4-4y-zN4y+z:Eux, wherein AE may comprise one or more of Ca, Sr, and Ba, wherein 0 < x < 0.04, wherein 0.4

[0027] < y < 0.6, and wherein 0 < z < 0.05 may especially crystallize in a UCr4C4 type crystal structure.

[0028] In (other) embodiments, the first luminescent material may be of the type Mi-xLi3-2yAli+2y-zSizO4-4y-zN4y+z:Eux, wherein M may comprise one or more of Mg, Ca, Sr, and Ba, wherein 0 < x < 0.04, wherein 0 < y < 1, wherein 0 < z < 0.05, and wherein y + z < 1. Especially, the first luminescent material may be of the type Mi-xLi3-2yAli+2y-zSizO4-4y-zN4y+z:Eux, wherein M may comprise one or more of Ca, Sr, and Ba, wherein 0 < x < 0.04, wherein 0 < y < 1, wherein 0 < z < 0.05, and wherein y + z < 1. Hence, in specific embodiments, the luminescent converter may comprise the first luminescent material of the type Mi-xLi3-2yAli+2y-zSizO4-4y-zN4y+z:Eux, wherein M may comprise one or more of Ca, Sr, and Ba, wherein 0 < x < 0.04, wherein 0 < y < 1, wherein 0 < z < 0.05, and wherein y + z < 1. Such first luminescent material may provide first luminescent material light having intensity in the orange-red wavelength range (i.e. , in the wavelength range of 590-780 nm), i.e., such first luminescent material may provide orange- red first luminescent material light. The terms “orange light” or “orange emission”, and similar terms, may especially relate to light having a wavelength in the range of about 590- 620 nm. The terms “red light” or “red emission”, and similar terms, may especially relate to light having a wavelength in the range of about 620-780 nm. In specific embodiments, the red light may have a centroid wavelength in the 620-750 nm range. Further, such a first luminescent material may have a relatively high absorption strength and / or a relatively high quantum efficiency.

[0029] In embodiments, as indicated above, in the luminescent material of the type Mi-xLi3-2yAli+2y-zSizO4-4y-zN4y+z:Eux, z may be selected from the range of 0 < z < 0.05, such as especially from the range of 0 < z < 0.05. Hence, in embodiments, z may be equal to zero. In such embodiments, the first luminescent material may especially be indicated as Mi-xLi3-2yAli+2yO4-4yN4y:Eux, wherein M comprises one or more of Mg, Ca, Sr, and Ba, such as especially one or more of Ca, Sr, and Ba, wherein 0 < x < 0.04, such as especially 0 < x < 0.04, and wherein 0 <y < 1, such as especially 0 < y < 1. Hence, in specific embodiments, the first luminescent material may be of the type Mi-xLi3-2yAli+2yO4-4yN4y:Eux, wherein M may comprise one or more of Ca, Sr, and Ba, wherein 0 < x < 0.04, and wherein 0 < y < 1. Such a composition of the first luminescent material (not comprising SiN) may provide the benefit that an emission maximum of the first luminescent material may be shifted towards longer wavelengths compared to a first luminescent material comprising SiN. Further, such a first luminescent material may have a relatively lower full width at half maximum (FWHM).

[0030] Yet, in embodiments, the first luminescent material may comprise SiN. That is, the first luminescent material may be of the type Mi-xLi3-2yAli+2y-zSizO4-4y-zN4y+z:Eux, wherein M may comprise one or more of Mg, Ca, Sr, and Ba, such as one or more of Ca, Sr, and Ba, wherein 0 < x < 0.04, such as 0 < x < 0.04, wherein 0 < y < 1, such as 0 < y < 1, wherein z > 0, such as selected from the range of 0 < z < 0.1, and wherein y + z < 1. Hence, in specific embodiments, the first luminescent material may be of the type Mi-xLi3-2yAli+2y-zSizO4-4y-zN4y+z:Eux, wherein M may comprise one or more of Ca, Sr, and Ba, wherein 0 < x < 0.04, wherein 0 < y < 1, wherein z > 0, and wherein y + z < 1. Such a first luminescent material comprising SiN may facilitate that the production of trivalent Eu3+in the first luminescent material may be reduced and / or prevented. The formation of trivalent EU3+from divalent Eu2+(as a result of heating and / or irradiation of the first luminescent material) reduces the (relative) emission intensity of the first luminescent material. Hence, by reducing and / or preventing the formation of Eu3+(by the addition of SiN to the first luminescent material), the emission properties and stability of the first luminescent material may be improved.

[0031] In embodiments, the divalent (metal) cation M in the first luminescent material may comprise, such as consist of, one or more of Mg, Ca, Sr, and Ba, such as especially one or more of Ca, Sr, and Ba. In embodiments, the M may at least comprise Ca, wherein at least 5%, such as at least 10%, especially at least 15%, like at least 20%, of M may consist of Ca. An SLA-type phosphor comprising at least Ca (as the divalent cation) may provide (first) luminescent material light having a larger centroid wavelength (i.e., a deeper red color), compared to an SLA-type phosphor not comprising Ca. Further, in embodiments, M may at least comprise Ca and Sr. Especially, in embodiments, the first luminescent material may be of the type (CawSri-w)i-xLi3-2yAli+2y-zSizO4-4y-zN4y+z:Eux, wherein w may be selected from the range of 0.0-0.6, such as from the range of 0.01-0.5, especially from the range of 0.05- 0.4. Additionally or alternatively, in embodiments, M may at least comprise Ba, wherein at least 5%, such as at least 10%, especially at least 15%, like at least 20%, of M may consist of Ba. An SLA-type phosphor comprising at least Ba (as the divalent cation) may provide (first) luminescent material light having a shorter centroid wavelength (i.e., a more orange-red color), compared to an SLA-type phosphor not comprising Ba. Further, in embodiments, M may at least comprise Ba and Sr. Especially, in embodiments, the first luminescent material may be of the type (BawSri-w)i-xLi3-2yAli+2y-zSizO4-4y-zN4y+z:Eux, wherein w may be selected from the range of 0.0-0.6, such as from the range of 0.01-0.5, especially from the range of 0.05-0.4. Additionally or alternatively, in embodiments, M in the first luminescent material may (at least) comprise Sr. That is, the first luminescent material may be of the type Mi-xLi3-2yAli+2y-zSizO4-4y-zN4y+z:Eux, wherein M may consist for at least 50%, such as at least 70%, especially at least 80%, like at least 95%, of Sr. Hence, in embodiments, the first luminescent material may be of the type (SrwM’ i-w)i-xLi3-2yAli+2y-zSizO4-4y-zN4y+z:Eux, wherein M’ may comprise one or more of Ba and Ca, and wherein w may be selected from the range of 0.4-1, such as from the range of 0.5-1, especially from the range of 0.75-1, like from the range of 0.9-1. Further, in embodiments, M may (essentially) fully consist of Sr, i.e., in embodiments M may be Sr. In such embodiments, it may further apply that 0 < x < 0.04, such as 0 < x < 0.04, 0 < y < 1, such as O < y < l, 0 < z < 0.05, such as 0 < z < 0.05, and y + z

[0032] < 1. Hence, in specific embodiments, the first luminescent material may be of the type Sn-xLi3-2yAli+2y-zSizO4-4y-zN4y+z:Eux, wherein 0 < x < 0.04, wherein 0 < y < 1, wherein 0 < z

[0033] < 0.05 and wherein y + z < 1. Further, in specific embodiments, the first luminescent material may be of the type Sri-xLi3-2yAli+2y-zSizO4-4y-zN4y+z:Eux, wherein 0 < x < 0.04, wherein 0 < y

[0034] < 1, wherein 0 < z < 0.05 and wherein y + z < 1. A first luminescent material wherein the divalent metal cation is strontium (Sr) may provide first luminescent material light having a desirable orange-red color. Especially, such a first luminescent material may provide first luminescent material light having a color point within an Euclidean distance of 0.07, especially 0.05, like 0.03, to the color point of a direct red light emitting LED.

[0035] In embodiments, as indicated above, the first luminescent material may be (essentially) free from Si (such as SiN), i.e., z = 0. Further, in embodiments, in the first luminescent material, y may be selected from the range of 0 < y < 1, such as from the range of 0 < y < 1, especially from the range of 0 < y < 0.75, like from the range of 0 < y < 0.6. Especially, in embodiments, y may be selected from the range of 0.2 < y < 0.7, such as from the range of 0.3 < y < 0.6, especially from the range of 0.4 < y < 0.55. In specific embodiments, y may be (around) 0.5. In (such) embodiments, the divalent metal cation M may especially consist for at least 80%, such as at least 90%, especially at least 95%, including (essentially) 100%, of Sr. Hence, in specific embodiments, the first luminescent material may be of the type Sri-xLi2A12O2N2:Eux, wherein 0 < x < 0.04. Such a first luminescent material may facilitate providing first luminescent material light having a relatively narrow (FWHM < 100 nm, especially FWHM < 75 nm) spectral power distribution with a centroid wavelength in the orange-red wavelength range. In embodiments, the first luminescent material may comprise a plurality of (different) luminescent materials of the type Mi-xLi3-2yAli+2y-zSizO4-4y-zN4y+z:Eux, wherein M comprises one or more of Ca, Sr and Ba, wherein 0 < x < 0.04, wherein 0 < y < 1, wherein 0 < z < 0.05, and wherein y + z < 1. In such embodiments, the plurality of luminescent material may differ from each other in (the composition of) the divalent cation M. Additionally or alternatively, in such embodiments, the plurality of luminescent material may differ from each other in one or more of (the value of) x, y, and z, such as especially differ in (the value of) y. Hence, in embodiments, the first luminescent material may comprise a primary first luminescent material of the type Mi-xLi3-2yAli+2y-zSizO4-4y-zN4y+z:Eux, wherein y = 0.5, and a secondary first luminescent material of the type Mi-xLi3-2yAli+2y-zSizO4-4y-zN4y+z:Eux, wherein y = 1. Such a first luminescent material may provide first luminescent material light having a broader spectral power distribution (in the orange-red wavelength range).

[0036] Hence, in embodiments, the first luminescent material may be configured to convert (ultraviolet, violet, and / or blue) light source light (generated by a light source) into first luminescent material light. In embodiments, the luminescent converter light may comprise the first luminescent material light. Further, in specific embodiments, the luminescent converter light may consist of the first luminescent material light. In embodiments, the first luminescent material light may have a first luminescent material centroid wavelength Xci. The term “centroid wavelength”, also indicated as Zc. is known in the art, and refers to the wavelength value where half of the light energy is at shorter and half the energy is at longer wavelengths; the value is stated in nanometers (nm). It is the wavelength that divides the integral of a spectral power distribution into two equal parts as expressed by the formula Xc = S Z* I(Z) / (S I( X)), where the summation is over the wavelength range of interest, and I(X) is the spectral energy density (i.e. the integration of the product of the wavelength and the intensity over the emission band normalized to the integrated intensity). The centroid wavelength may e.g. be determined at operation conditions. In embodiments, the first luminescent material centroid wavelength Xci may be selected from the range of 590-680 nm, such as from the range of 600-670 nm, especially from the range of 600-660 nm, like from the range of 610-650 nm. Further, the first luminescent material light may have first color coordinates u’ and v’ (or “first color points u’ and v’”) in the CIE 1976 UCS diagram (or “CIE 1976 L*u*v* color space” or “CIE u’v’ color diagram”). In embodiments, a first color point u’ of the first luminescent material light may be selected from the range of > 0.44, such as from the range of > 0.45, especially from the range of > 0.46, like from the range of > 0.47. Additionally or alternatively, the first color point u’ of the first luminescent material light may be selected from the range of < 0.51, such as from the range of < 0.50, especially from the range of < 0.49. Further, in embodiments, a first color point v’ of the first luminescent material light may be selected from the range of > 0.5, such as from the range of > 0.51, especially from the range of > 0.52. Additionally or alternatively, the first color point v’ of the first luminescent material light may be selected from the range of < 0.55, such as from the range of < 0.54, especially from the range of < 0.53.

[0037] In embodiments, as indicated above, the first luminescent material may comprise (such as be doped with) (divalent) europium. Hence, in embodiments, the luminescent converter may comprise europium. Especially, the luminescent converter may comprise the europium in an amount of ml weight percent (wt.%), i.e., the luminescent converter may comprise an amount of Eu of ml weight percent (wt.%). Here, a weight percentage (wt.%) may refer to a percentage of the total weight. For example, 100 grams of a luminescent converter comprising 0.3 wt.% europium may comprise 0.3 grams of europium. In embodiments, ml may be selected from the range of > 0.01 wt.%, such as from the range of > 0.015 wt.%, especially from the range of > 0.02 wt.%, like from the range of > 0.025 wt.%. Additionally or alternatively, ml may be selected from the range of < 0.5 wt.%, such as from the range of < 0.4 wt.%, especially from the range of < 0.3 wt.%, like from the range of < 0.2 wt.%. Hence, in embodiments, 0.01 < ml < 0.5 wt.%, such as 0.015 < ml < 0.4 wt.%, especially 0.02 < ml < 0.3 wt.%, like 0.025 < ml < 0.2 wt.%. In embodiments, the weight percentage of Eu in the luminescent converter may be related to the thickness (T) of the luminescent converter (see also below). That is, at a smaller thickness (T) the weight percentage of Eu may be relatively higher than at a larger thickness (T). As indicated above, the luminescent converter may have a thickness (T) of tl micrometer, wherein 50 < tl < 1000 pm, such as 100 < tl < 850 pm, especially 150 < tl < 600 pm, like 200 < tl < 500 pm. In embodiments, the luminescent converter may thus comprise a weight percentage of Eu of 0.01 < ml < 0.5 wt.% at a thickness (T) of 50 < tl < 1000 pm, such as a weight percentage of Eu of 0.015 < ml < 0.4 wt.% at a thickness (T) of 100 < tl < 850 pm, especially a weight percentage of Eu of 0.02 < ml < 0.3 wt.% at a thickness (T) of 150 < tl < 600 pm. Hence, in specific embodiments, 150 < tl < 600 pm and 0.02 < ml < 0.3 wt.%. Such a thickness (T) may provide the benefit that the luminescent converter may be relatively thin, thereby facilitating configuring the luminescent converter as a coating on a (solid-state) light source. Further, such a thickness T in combination with such a weight percentage of Eu may facilitate that a majority of the light source light may be converted into luminescent converter light. Especially, such a thickness T in combination with such a weight percentage of Eu may facilitate that at least 80%, such as at least 90%, especially at least 95%, like at least 98%, or a radiant flux of the light source light received by the luminescent converter may be converted into luminescent converter light. Further, such a thickness T in combination with such a weight percentage of Eu may facilitate that scattering of (light source) light by the first luminescent material may be reduced, thereby improving the efficiency of the luminescent converter.

[0038] In embodiments, the absorption of (light source) light by the first luminescent material may be approximated by the Beer-Lambert law, wherein the absorption of light of a certain wavelength is dependent on a) the absorption strength (or “molar absorption coefficient”) of the first luminescent material for light of that wavelength, b) the concentration of the first luminescent material in the luminescent converter, and c) the optical path length of the light through the luminescent converter. In embodiments, the concentration of the first luminescent material in the luminescent converter may especially be at least partially determined by the weight percentage of Eu in the luminescent converter (indicated by ml). Additionally or alternatively, as indicated above, the optical path length (of light source light) through the luminescent converter may especially be determined by the thickness (T) of the luminescent converter, indicated by tl. Hence, the percentage of light absorbed (and optionally converted) by the luminescent converter, especially by the first luminescent material, may be at least partially determined by the product of tl with ml, i.e., tl*ml. In embodiments, it may apply that tl*ml > 5, such as tl*ml > 7.5, especially tl*ml > 10, like tl*ml > 15, such as tl*ml > 20. Additionally or alternatively, it may apply that tl*ml < 65, such as tl*ml < 50, especially tl*ml < 40. Further, it may apply that tl*ml < 35, such as tl*ml < 30, especially tl*ml < 25. Additionally or alternatively, in embodiments, 5 < tl*ml < 65, such as 10 < tl*ml < 50, especially 10 < tl*ml < 35. Further, in embodiments, 15 < tl*ml < 35, such as 15 < tl*ml < 30, especially 20 < tl*ml < 30. Hence, in specific embodiments, 10 < tl*ml < 35. Such a range for tl*ml may facilitate that a significant part of an ultraviolet (UV), violet, and / or blue (light source) light incident on the luminescent converter, especially on the first side, may be absorbed by the first luminescent material (and converted into first luminescent material light), to provide first luminescent material light having a high color saturation.

[0039] In embodiments, the first luminescent material may be configured embedded in the luminescent converter. Especially, the luminescent converter may comprise a polymer matrix material, and the first luminescent material may be configured embedded in the polymer matrix material. In such embodiments, the first luminescent material may especially be a first luminescent material powder. In embodiments, the first luminescent material may be present in the same concentration throughout the luminescent converter. That is, the first luminescent material may be (evenly) distributed in the polymer matrix material.

[0040] Alternatively, the first luminescent material may be present in a concentration gradient along the thickness T of the luminescent converter. In (such) embodiments, a concentration of the first luminescent material at the first side of the luminescent converter (facing the light source) may be at least 1.2, such as at least 1.3, especially at least 1.5, like at least 2, times higher than a concentration of the first luminescent material at the second (opposite) side of the luminescent converter (or vice versa). Additionally or alternatively, in embodiments, a concentration of the first luminescent material at the first side of the luminescent converter may be at most 5, such as at most 4, especially at most 3, like at most 2.5, times higher than a concentration of the first luminescent material at the second side of the luminescent converter (or vice versa). Hence, in embodiments, the first luminescent material may be unevenly distributed in the polymer matrix material. In embodiments, the polymer matrix material may comprise an optically transparent material. Herein, the term “optically transparent” material indicates the material may be transmissive for one or more wavelengths selected from the range of 190-1500 nm, such as for one or more wavelengths selected from the range of 200- 1000 nm, especially for one or more wavelengths selected from the range of 380-780 nm. In embodiments, the polymer matrix material may comprise an optically transparent (crosslinked) polymeric material. Especially, the polymer matrix material may comprise a material selected from the group comprising glass, polycarbonate (PC), (clear) polyvinyl chloride (PVC), liquid silicone rubber (LSR), cyclic olefin copolymers (COC), fluorinated ethylene propylene (FEP), styrene methyl methacrylate (SMMA), polysiloxanes, and poly(methyl methacrylate) (PMMA). In embodiments, the polymer matrix material may especially be selected from the group of (poly)siloxanes. Further, in embodiments, the polymer matrix material (especially the (poly)siloxane) may be selected from the group comprising, such as from the group of, dimethylsiloxanes, diphenylsiloxanes, methylphenylsiloxanes, or copolymers thereof. Hence, in specific embodiments, the luminescent converter may further comprise a polymer matrix material, wherein the first luminescent material may be distributed in the polymer matrix material, wherein the polymer matrix material may be selected from the group of siloxanes. Such a polymer matrix material may especially be thermally stable. Further, such a polymer matrix material may be relatively easy to process, and may be optically transparent for at least the luminescent converter light.

[0041] In embodiments, the first luminescent material may have a concentration in the polymer matrix material, i.e., the polymer matrix material may comprise the first luminescent material in a concentration. In embodiments, the concentration of the first luminescent material in the polymer matrix material may be selected from the range of > 2 vol.%, such as from the range of > 5 vol.%, especially from the range of > 10 vol.%, like from the range of > 15 vol.%. Additionally or alternatively, in embodiments, the concentration of the first luminescent material in the polymer matrix material may be selected from the range of < 60 vol.%, such as from the range of < 50 vol.%, especially from the range of < 45 vol.%, like from the range of < 40 vol.%. Further, in embodiments, the concentration of the first luminescent material in the polymer matrix material may be selected from the range of < 50 vol.%, such as from the range of < 35 vol.%, especially from the range of < 30 vol.%, like from the range of < 25 vol.%. Hence, in embodiments, the concentration of the first luminescent material in the polymer matrix material may be in the range of 2-60 vol.%, such as in the range of 5-50 vol.%, especially in the range of 10-45 vol.%, like in the range of 15-40 vol.%. Hence, in specific embodiments, a concentration of the first luminescent material in the polymer matrix material may be in the range of 5 - 50 vol.%. Such a concentration of first luminescent material may, together with the concentration of Eu in the first luminescent material, provide a luminescent converter comprising ml weight percent Eu. Further, such a concentration of first luminescent material may be low enough to facilitate easy processing of the luminescent converter as a coating.

[0042] In embodiments, the luminescent converter may further comprise a second luminescent material (and optionally one or more further luminescent materials), which may be distributed in the polymer matrix material. In embodiments, the (second and / or further) luminescent materials may be selected from garnets and nitrides, especially doped with trivalent cerium or divalent europium, respectively. The term “nitride” may also refer to oxynitride or nitridosilicate, etc. Alternatively or additionally, the luminescent material(s) may be selected from silicates, especially doped with divalent europium. In embodiments, the luminescent material may comprise a divalent europium comprising oxynitride luminescent material. Further, in embodiments, the luminescent material may comprise a divalent europium comprising nitride luminescent material.

[0043] In embodiments, the (second and / or further) luminescent materials may comprise a (garnet) luminescent material of the type AaBsOnT'e. wherein A comprises one or more of Y, La, Gd, Tb and Lu, and wherein B comprises one or more of Al, Ga, In and Sc. The term “:Ce”, indicates that part of the metal ions (i.e. in the garnets: part of the “A” ions) in the luminescent material is replaced by Ce. This is known to the person skilled in the art. Ce will replace A in general for not more than 10%; in general, the Ce concentration will be in the range of 0.1 to 4%, especially 0.1 to 2% (relative to A). Ce in garnets is substantially or only in the trivalent state, as is known to the person skilled in the art. Embodiments of garnets especially include A3B5O12 garnets, wherein A comprises at least yttrium (Y) or lutetium (Lu) and wherein B comprises at least aluminum (Al). Such garnets may be doped with cerium (Ce), with praseodymium (Pr) or a combination of cerium and praseodymium; especially however with Ce. In embodiments, such luminescent materials may have a suitable spectral distribution, have a relatively high efficiency, and have a relatively high thermal stability.

[0044] In embodiments, the (second and / or further) luminescent materials may comprise a luminescent material of the type AsSieNi 1 :Ce3+, wherein A comprises one or more of Y, La, Gd, Tb and Lu, such as in embodiments one or more of La and Y. In embodiments, the luminescent material may alternatively or additionally comprise one or more of MS:Eu2+and / or I ESis Eu2and / or MAISiN.vEu2and / or Ca2AlSi3O2N5:Eu2+, etc., wherein M comprises one or more of Ba, Sr and Ca, especially in embodiments at least Sr. Hence, in embodiments, the luminescent material may comprise one or more materials selected from the group consisting of (Ba,Sr,Ca)S:Eu, (Ba,Sr,Ca)AlSiN3:Eu and (Ba,Sr,Ca)2Si5Ns:Eu. In these compounds, europium (Eu) is substantially or only divalent, and replaces one or more of the indicated divalent cations, as is known to the person skilled in the art. In general, Eu will not be present in amounts larger than 10% of the cation; its presence will especially be in the range of about 0.5 to 10%, more especially in the range of about 0.5 to 5% relative to the cation(s) it replaces.

[0045] The term “luminescent material” herein especially relates to inorganic luminescent materials. Alternatively or additionally, also other luminescent materials may be applied. For instance quantum dots and / or organic dyes may be applied and may optionally be embedded in transmissive matrices like e.g. polymers, like PMMA, or polysiloxanes, etc.

[0046] In embodiments, the (second and / or further) luminescent material(s) may comprise a luminescent material of the type M’xM2-2xAX6 doped with tetraval ent manganese, wherein M’ comprises an alkaline earth cation, M comprises an alkaline cation, and x may be selected from the range of 0-1, wherein A comprises a tetraval ent cation, for instance comprising one or more of silicon and titanium, wherein X comprises a monovalent anion, at least comprising fluorine. Such luminescent materials may herein also be indicated as “KSiF” or “KSF”, whether or not M comprises K or one or more other alkaline cations. A luminescent material of the type M’xM2-2xAX6 doped with tetraval ent manganese is amongst others described in WO2013121355A1, which is herein incorporated by reference. Passages from WO2013121355A1 are also copied herein. Relevant alkaline earth cations (M’) are magnesium (Mg), strontium (Sr), calcium (Ca) and barium (Ba), especially one or more of Sr and Ba. Relevant alkaline cations (M) are sodium (Na), potassium (K) and rubidium (Rb). Optionally, also ammonium (NH4+), lithium (Li) and / or cesium (Cs) may be applied. In a preferred embodiment, M comprises at least potassium. In yet another embodiment, M comprises at least rubidium. The phrase “wherein M comprises at least potassium” indicates for instance that of all M cations in a mole M’xM2-2xAX6 , a fraction comprises K+and an optionally remaining fraction comprises one or more other monovalent (alkaline) cations (see also below). In another preferred embodiment, M comprises at least potassium and rubidium. Optionally, the M’xM2-2xAX6 luminescent material has the hexagonal phase. In yet another embodiment, the M’xM2-2xAX6 luminescent material has the cubic phase. In an embodiment, a combination of different alkaline cations may be applied. In yet another embodiment, a combination of different alkaline earth cations may be applied. In yet another embodiment, a combination of one or more alkaline cations and one or more alkaline earth cations may be applied. For instance, KRbo.5Sro.25AX6 might be applied, wherein x may be selected from the range of 0-1, especially x < 1. In specific embodiments, x = 0.

[0047] The term “tetravalent manganese” refers to Mn4+. This is a well-known luminescent ion. In the formula as indicated above, part of the tetravalent cation A (such as Si) is being replaced by manganese. Hence, M’xM2-2xAX6 doped with tetravalent manganese may also be indicated as M’xM2-2xAi-mMnmX6. The mole percentage of manganese, i.e. the percentage it replaces the tetraval ent cation A will in general be in the range of 0.1-15 %, especially 1-12 %, i.e. m is in the range of 0.001-0.15, especially in the range of 0.01-0.12. As manganese replaces part of a host lattice ion and has a specific function, it is also indicated as “dopant” or “activator”. Hence, the hexafluorosilicate is doped or activated with manganese (Mn4+).

[0048] In embodiments, A may comprise a tetraval ent cation, and preferably at least comprises silicon. A may optionally (further) comprise one or more of titanium (Ti), germanium (Ge), stannum (Sn) and zinc (Zn). Preferably, at least 80%, even more preferably at least 90%, such as at least 95% of A consists of silicon. As indicated above, X relates to a monovalent anion, but at least comprises fluorine. Other monovalent anions that may optionally be present may be selected from the group consisting of chlorine (Cl), bromine (Br), and iodine (I). Preferably, at least 80%, even more preferably at least 90%, such as 95% of X consists of fluorine. Especially, X essentially consists of F (fluorine).

[0049] In an embodiment, M’xM2-2xAX6 comprises K2SiFe (indicated herein also as KSiF system). In another preferred embodiment, M’xM2-2xAXe comprises KRbSiFe (herein also indicated as K,Rb system). In specific embodiments, the indication M’xM2-2xAX6 may refer to one or more of (K,Rb)2SiFe:Mn4+, (K,Rb)2TiFe:Mn4+, K2(Si,Ti)Fe:Mn4+, and Rb2(Si,Ti)Fe:Mn4+, such as one or more of K2TiFe:Mn4+, of K2SiFe:Mn4+, and of Rb2SiF6:Mn4+. As can be derived from the above, “(Si,Ti)” may indicate one or more of Si and Ti. Hence, in specific embodiments, the luminescent material may comprise one or more of (K,Rb)2SiFe:Mn4+and K2(Si,Ti)Fe:Mn4+. The luminescent material may also be coated, as also described in WO2013121355A1.

[0050] In embodiments, the second luminescent material may especially be of the type M’XM2-2XAX6 doped with tetravalent manganese, wherein M’ may comprise an alkaline earth cation, M may comprise an alkaline cation, and x may be in the range of 0-1, wherein A may comprise a tetravalent cation, wherein X may comprise a monovalent anion. In (such) embodiments, A may comprise one or more of silicon and titanium. Further, in (such) embodiments, X may at least comprise fluorine. Hence, in specific embodiments, the luminescent converter may further comprise a second luminescent material, wherein the second luminescent material may be of the type M’xM2-2xAX6 doped with tetravalent manganese, wherein M’ may comprise an alkaline earth cation, M may comprise an alkaline cation, and x may be in the range of 0-1, wherein A may comprise a tetravalent cation, comprising one or more of silicon and titanium, wherein X may comprise a monovalent anion, at least comprising fluorine. Such a second luminescent material may be configured to provide (red) second luminescent material light having a second luminescent material centroid wavelength Zc2 in the red wavelength range. Further, such a second luminescent material may especially have a high quantum efficiency. In embodiments, the second luminescent material may especially comprise one or more of (K,Rb)2SiFe:Mn4+and K2(Si,Ti)Fe:Mn4+, such as especially at least K2SiFe:Mn4+.

[0051] In embodiments, the second luminescent material may be configured embedded in the luminescent converter, such as especially in the polymer matrix material. Further, in embodiments, the second luminescent material may have a concentration in the polymer matrix material. Especially, the concentration of the second luminescent material in the polymer matrix material may be selected from the range of > 0.5 vol.%, such as from the range of > 1 vol.%, especially from the range of > 5 vol.%, like from the range of > 10 vol.%. Additionally or alternatively, in embodiments, the concentration of the second luminescent material in the polymer matrix material may be selected from the range of < 40 vol.%, such as from the range of < 30 vol.%, especially from the range of < 20 vol.%, like from the range of < 15 vol.%. Hence, in embodiments, the concentration of the second luminescent material in the polymer matrix material may be selected from the range of 0.5-40 vol.%, such as from the range of 1-30 vol.%, especially from the range of 5-20 vol.%, like from the range of 10- 15 vol.%.

[0052] In embodiments, the second luminescent material may be configured to generate (red) second luminescent material light (upon irradiation with one or more of UV, violet, and blue light source light). In embodiments, the second luminescent material light may have a second luminescent material centroid wavelength Zc2 selected from the range of 600-680 nm, such as from the range of 610-665 nm, especially from the range of 620-640 nm, like from the range of 625-635 nm. Further, as indicated above, the first luminescent material may be configured to generate (red) first luminescent material light having a first luminescent material centroid wavelength Xci (upon irradiation with one or more of UV, violet, and blue light source light). Additionally, the luminescent converter comprising the first luminescent material and optionally the second luminescent material (and optionally the one or more further luminescent materials) may be configured to at least partly convert light source light generated by a solid-state light source (and received by the luminescent converter) into luminescent converter light. In embodiments, the luminescent converter light may at least comprise the first luminescent material light. Additionally, in embodiments, the luminescent converter light may comprise the second luminescent material light (and optionally the luminescent material light generated by the one or more further luminescent materials). In embodiments, the luminescent converter light may have a luminescent converter centroid wavelength Xcic. The luminescent converter centroid wavelength Xcic may in embodiments be selected from the range of 590-680 nm, such as from the range of 600- 670 nm, especially from the range of 600-660 nm, like from the range of 610-650 nm. Hence, in specific embodiments, the luminescent converter light may have a luminescent converter centroid wavelength Xcic selected from the range of 600-660 nm. A luminescent converter configured to generate luminescent converter light having a luminescent converter centroid wavelength Xcic selected from the range of 600-660 nm may especially provide orange-red luminescent converter light. Further, luminescent converter light having a luminescent converter centroid wavelength Leu selected from the range of 600-660 nm may have a color point within an Euclidean distance of 0.05 to the color point of a direct red light emitting LED. Hence, the luminescent converter of the present invention may be used in combination with an UV, violet, and / or blue direct light emitting LED to produce orange-red phosphor converted LEDs. The combination of a luminescent converter with a direct light emitting LED may also be indicated as “light generating device”.

[0053] Hence, in a further aspect, the invention may provide a light generating device. The light generating device may be configured to generate device light. Further, the light generating device may comprise a (solid-state) light source configured to generate light source light. The light source light may especially have a light source light dominant wavelength Xsc. In embodiments, the light source light dominant wavelength Xsc may be selected from the range of 400-495 nm. Further, the light generating device may comprise the luminescent converter as defined herein. In embodiments, the device light (generated by the light generating device) may comprise the luminescent converter light (as defined herein). Hence, in specific embodiments, the invention provides a light generating device configured to generate device light, the light generating device comprising: (A) a solid-state light source configured to generate light source light having a light source light dominant wavelength ( sc) selected from the range of 400-495 nm; and (B) the luminescent converter as defined herein; wherein the device light comprises the luminescent converter light. Such a light generating device may provide the benefit that an efficient red phosphor converter LED may be provided. Further, such a light generating device may especially provide a red phosphor converted LED having a color point with u’ and v’ color coordinates differing < 0.05 from u’ and v’ color coordinates of a color point of a “conventional” direct red light emitting LED. Hence, the invention may provide a phosphor converted red LED using SLA phosphor.

[0054] In embodiments, the light generating device may comprise a light source, such as especially a solid-state light source. The term “light source” may in principle relate to any light source known in the art. In specific embodiments, the light source comprises a solid- state light source (such as an LED or laser diode (or “diode laser”)). The term “light source” may also relate to a plurality of (essentially identical (or different)) light sources, such as 2- 2000 (solid-state) (LED) light sources. The phrases “different light sources” or “a plurality of different light sources”, and similar phrases, may in embodiments refer to a plurality of solid- state light sources selected from at least two different bins. Likewise, the phrases “identical light sources” or “a plurality of same light sources”, and similar phrases, may in embodiments refer to a plurality of solid-state light sources selected from the same bin. Hence, the term LED may also refer to a plurality of LEDs. Further, the term “light source” may in embodiments also refer to a so-called chip-on-board (COB) light source. The term “COB” especially refers to LED chips in the form of a semiconductor chip that is neither encased nor connected but directly mounted onto a substrate, such as a PCB. Hence, a plurality of light emitting semiconductor light source may be configured on the same substrate. In embodiments, a COB is a multi LED chip configured together as a single lighting module.

[0055] The term “light source” may also refer to a light source of a chip scale package (CSP) and / or a chip scale packaged (CSP) LED. A CSP may comprise a single solid-state die (such as a LED) with provided thereon the luminescent converter. The term “light source” may also refer to a light source of a mid-power packaged LED. A mid-power packaged LED may comprise one or more solid-state die(s). The die(s) may be covered by the luminescent converter. The die dimensions may be equal to or smaller than 2 mm, such as in the range of e.g. 0.2-2 mm. Herein, the term “light source” may also especially refer to a small solid-state light source, such as having a mini size or micro size. For instance, the light sources may comprise one or more of mini LEDs and micro LEDs, such as especially micro LEDs or “microLEDs” or “pLEDs”. Herein, the term mini size or mini LED especially refers to solid- state light sources having dimensions, such as die dimension, especially length and width, selected from the range of 100 pm - 1 mm. Herein, the term p size or micro LED especially refers to solid-state light sources having dimensions, such as die dimension, especially length and width, selected from the range of 100 pm and smaller.

[0056] The light source may have a light escape surface. For LEDs it may for instance be the LED die. The term escape surface especially relates to that part of the light source, where the light actually leaves or escapes from the light source. The light source is configured to provide a beam of light. This beam of light (thus) escapes from the light exit surface of the light source.

[0057] The term “light source” may refer to a semiconductor light-emitting device, such as a light emitting diode (LEDs), a resonant cavity light emitting diode (RCLED), a vertical cavity laser diode (VCSELs), an edge emitting laser, etc... The term “light source” may also refer to an organic light-emitting diode (OLED), such as a passive-matrix (PMOLED) or an active-matrix (AMOLED). In an embodiment, the light source comprises an LED. The terms “light source” or “solid-state light source” may also refer to a superluminescent diode (SLED). Especially, the term “solid-state light source”, or “solid- state material light source”, and similar terms, may refer to semiconductor light sources, such as a light emitting diode (LED), a laser diode, a superluminescent diode, or a multi -junction diode.

[0058] In embodiments, the light source may comprise one or more micro-optical elements (array of micro lenses) downstream of a single solid-state light source, such as an LED, or downstream of a plurality of solid-state light sources (i.e. e.g. shared by multiple LEDs). In embodiments, the light source may comprise an LED with on-chip optics. In embodiments, the light source comprises pixelated single LEDs (with or without optics) (offering in embodiments on-chip beam steering).

[0059] In embodiments, the light source may be configured to provide primary radiation, such as e.g. a blue light source, like a blue LED. Hence, in embodiments, the light source may especially be a direct light emitting LED (or “direct color LED”). Further, in specific embodiments the light source may be a light source that during operation emits at least light at wavelength selected from the range of 380-470 nm. However, other wavelengths may also be possible.

[0060] In specific embodiments, the light source may be selected from the group of laser diodes, superluminescent diodes, and multi -junction diodes. In other embodiments, the light source may comprise an LED. The light source may especially be configured to generate light source light having an optical axis (O), (a beam shape,) and a spectral power distribution. The light source light may in embodiments comprise one or more bands, having band widths as known for lasers.

[0061] The term “laser light source” especially refers to a laser. The term “laser” especially refers to a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation.

[0062] Especially, in embodiments the term “laser” may refer to a solid-state laser. In specific embodiments, the terms “laser” or “laser light source”, or similar terms, may refer to a laser diode (or diode laser). In embodiments, the terms “laser” or “solid-state laser” or “solid-state material laser” may refer to one or more of a semiconductor laser diodes, such as GaN, InGaN, AlGalnP, AlGaAs, InGaAsP, lead salt, vertical cavity surface emitting laser (VCSEL), quantum cascade laser, hybrid silicon laser, etc. The term “solid-state material laser”, and similar terms, may thus refer to a solid-state laser like based on a crystalline or glass body dopes with ions, like transition metal ions and / or lanthanide ions, to a fiber laser, to a photonic crystal laser, to a semiconductor laser, etc. In embodiments, the term “laser light source” may also refer to a plurality of (different or identical) laser light sources. In specific embodiments, the term “laser light source” may refer to a plurality N of (identical) laser light sources. In embodiments, N>2, such as N>5, especially N>8. In this way, a higher brightness (of the laser light) may be obtained. In embodiments, laser light sources may be arranged in a laser bank. The laser bank may in embodiments comprise heat sinking and / or optics (e.g. a lens to collimate the laser light). Hence, in embodiments lasers in a laser bank (or “laser array bank”) may share the same optics.

[0063] The laser light source is configured to generate laser light source light (or “laser light”). The light source light may essentially consist of the laser light source light. The light source light may also comprise laser light source light of two or more (different or identical) laser light sources. For instance, the laser light source light of two or more (different or identical) laser light sources may be coupled into a light guide, to provide a single beam of light comprising the laser light source light of the two or more (different or identical) laser light sources. In specific embodiments, the light source light is thus especially collimated (laser) light source light.

[0064] In embodiments, the (solid-state) light source may be configured to generate light source light having a light source light dominant wavelength Xsc. As known in the art, the term “dominant wavelength” may especially refer to the wavelength of monochromatic (spectral) light which may be perceived as having the same hue as the light source light. The dominant wavelength may especially be determined by drawing a line from the white point in the CIE u’v’ color diagram to the color point of the light source light, and extrapolating this line until it intersects with the spectral locus (defined by the monochromatic wavelengths), wherein the point of intersection with the spectral locus provides the dominant wavelength. In embodiments, the light source light dominant wavelength Xsc may be selected from the range of < 500 nm, such as from the range of < 495 nm, especially from the range of < 485 nm, like from the range of < 475 nm. In embodiments, the light source light may be ultraviolet (UV) light, such as light having at least some intensity in the wavelength range of 190-380 nm, especially in the wavelength range of 200-380 nm. Alternatively, the light source light may be blue light, such as light having at least some intensity in the wavelength range of 440-495 nm, especially in the wavelength range of 440-480 nm. Alternatively, the light source light may be violet and / or blue light, such as having a light source light dominant wavelength Xscselected from the range of > 380 nm, such as from the range of > 390 nm, especially from the range of > 400 nm, like from the range of > 410 nm. In embodiments, the light source light dominant wavelength Xscmay especially be selected from the range of 380- 500 nm, such as from the range of 390-495 nm, especially from the range of 400-485 nm, like from the range of 400-475 nm. Hence, in specific embodiments, the light source light dominant wavelength (A«c) is selected from the range of 400 - 475 nm. Such a light source light dominant wavelength Xscmay especially provide violet and / or blue light. Violet and / or blue light may have as advantage that, in case a part of the light source light is transmitted through the luminescent converter (e.g. due to failure in the light generating device), violet and / or blue light may be less harmful than UV light. Further, violet and / or blue light source light may facilitate admixing light source light with the luminescent converter light to provide purple device light.

[0065] In embodiments, the light source light dominant wavelength Xsc may be selected from short-wavelength blue light. That is, in embodiments, the light source light dominant wavelength Xsc may be selected from the range of 380-475 nm, such as from the range of 400-475 nm, especially from the range of 400-450 nm, like from the range of 400- 435 nm, such as from the range of 410-435 nm. Alternatively, the light source light dominant wavelength Xscmay be selected from long-wavelength blue light. That is, in embodiments, the light source light dominant wavelength Xscmay be selected from the range of 400-500 nm, such as from the range of 415-495 nm, especially from the range of 425-495 nm, like from the range of 440-495 nm, such as from the range of 450-485 nm. Hence, in specific embodiments, the light source light dominant wavelength Z,scmay be selected from the range of 440-495 nm. A light source light dominant wavelength Xscselected from the range of 440- 495 nm may provide the benefit that the (luminescent materials comprised by the) luminescent converter may have a relatively higher absorption strength at longer-wavelength blue light compared to shorter- wav elength blue light. Further, admixing long-wavelength blue light with the luminescent converter light may improve the color purity of the device light.

[0066] In embodiments, the light source light may be incident on the luminescent converter. Hence, the luminescent converter may be configured in a light-receiving relationship with the light source. Especially, the luminescent converter may be configured facing the light source with a first surface (e.g. the first side) indicated as the upstream luminescent converter surface, while device light may exit the luminescent converter (in a transmissive mode) from a second surface (e.g. the second side) indicated as the downstream luminescent converter surface. In embodiments, the shortest distance between the first surface and the second surface may define the thickness (T) of the luminescent converter (see also above).

[0067] In embodiments, the luminescent converter may be configured as a coating, (at least partially) surrounding the solid-state light source. Hence, in embodiments, the light generating device may be a LED package, such as a chip-on-board (CoB), a chip scale packaged (CSP) LED, or a mid-power packaged LED. Especially, the light generating device may be a mid-power packaged LED. Alternatively, the light generating device may be a LED filament, comprising a) a plurality of solid-state light sources arranged on (at least a first major surface of) an elongated carrier, and b) an (elongated) encapsulant covering the plurality of solid-state light sources and at least part of the elongated carrier, wherein the encapsulant may comprise, such as be, the luminescent converter. In (other) embodiments, the luminescent converter may not be configured as a coating, and may optionally be self- supporting. In such embodiments, the luminescent converter may be configured at a non-zero distance di from (yet in a light receiving relationship with) the solid-state light source. Especially, the solid-state light source may have a face, such as a face comprising a light escape surface. In embodiments, the luminescent converter may be configured at a distance di from said face of the solid-state light source. In embodiments, the distance di may be selected from the range of > 5 pm, such as from the range of > 15 pm, especially from the range of > 50 pm. Further, the distance di may be selected from the range of < 30 cm, such as from the range of < 20 cm, especially from the range of < 10 cm. Further, in specific embodiments, the luminescent converter may be physically separated from the light source.

[0068] In embodiments, the solid-state light source may thus be configured to generate light source light, wherein (at least part of) the light source light may be incident on the luminescent converter. In embodiments, the luminescent converter may be configured to at least partly convert the light source light into luminescent converter light. Especially, the luminescent converter may be configured to convert at least 70%, such as at least 80%, especially at least 90%, of the light source light received by the luminescent converter into luminescent converter light (and to optionally transmit the remainder of the light source light). Further, the luminescent converter may be configured to convert at least 95%, such as at least 98%, especially at least 99%, including (essentially) 100%, of the light source light received by the luminescent converter into luminescent converter light. Alternatively, the luminescent converter may be configured to convert at most 98%, such as at most 95%, especially at most 90%, like at most 85%, of the light source light received by the luminescent converter into luminescent converter light (and to optionally transmit the remainder of the light source light). Hence, in embodiments, the luminescent converter may be configured to transmit 0-15%, such as 0.1-10%, especially 0.2-5%, like 0.5-2%, of a radiant flux of the light source light received by the luminescent converter.

[0069] In embodiments, the luminescent converter light may provide at least part of, such as be comprised by, the device light. That is, in embodiments, the light generating device may be configured to generate device light, wherein the device light may at least comprise the (red) luminescent converter light. Hence, in embodiments, the device light may comprise, such as be, visible light. Optionally, the device light may further comprise at least part of the light source light (transmitted by the luminescent converter). That is, the device light may have a spectral power distribution in the wavelength range of 380-780 nm (i.e., the visible wavelength range), wherein optionally at least part of the spectral power may be provided by the (non-converted and transmitted) light source light. Especially, the device light may have a spectral power distribution in the wavelength range of 380-780 nm, wherein at most 15%, such as at most 10%, especially at most 7%, like at most 5%, of the spectral power may be provided by the (non-converted) light source light. Further, the device light may have a spectral power distribution in the wavelength range of 380-780 nm, wherein at most 4%, such as at most 2%, especially at most 1%, including (essentially) 0%, of the spectral power may be provided by the (non-converted) light source light. Hence, in embodiments, the device light may be (essentially) free from light source light. Yet, in (other) embodiments, the device light may comprise at least part of the light source light. Hence, in embodiments, the device light may have a spectral power distribution in the wavelength range of 380-780 nm, wherein at least 0.1%, such as at least 0.5%, especially at least 1%, like at least 3%, of the spectral power may be provided by the (non-converted) light source light. Yet, in specific embodiments, the device light may have a spectral power distribution in the wavelength range of 380-780 nm with at most 7% of the spectral power provided by the non-converted light source light. Device light wherein at most 7% of the spectral power is provided by light source light may facilitate that the device light may have a (red) color point close to the (red) color point of the luminescent converter light. Further, device light wherein at most 7% of the spectral power is provided by light source light may comprise (relatively) little violet and / or blue light, thereby providing a light generating device suitable for applications in e.g. (photography) darkrooms, where the presence of violet and / or blue light is undesirable due to potential degradation of the materials used in such rooms. In embodiments, the device light may have a device light centroid wavelength Zea. In embodiments, the device light centroid wavelength Zea may be selected from the range of 580-700 nm, such as from the range of 590-680 nm, especially from the range of 600-670 nm, like from the range of 600-660 nm. Further, in embodiments, the device light may have a color point in the CIE u’v’ color diagram. Especially, the device light may have a color point (or color coordinate) u’ in the CIE u’v’ color diagram. In embodiments, the color point u’ of the device light may be selected from the range of > 0.43, such as from the range of > 0.45, especially from the range of > 0.46, like from the range of > 0.47, such as from the range of > 0.475. Additionally or alternatively, the color point u’ of the device light may be selected from the range of < 0.53, such as from the range of < 0.52, especially from the range of < 0.50, like from the range of < 49. Further, in embodiments, the color point u’ of the device light may be selected from the range of 0.43 < u’ < 0.53, such as from the range of 0.45 < u’ < 0.52, especially from the range of 0.46 < u’ < 0.50, like from the range of 0.47 < u’ < 49. Hence, in specific embodiments, the device light may have a color point u’ in the CIE u’v’ color diagram in the range of 0.45 < u’ < 0.52. Device light having such a color point u’ (in combination with a v’ color point of > 0.47) may especially be perceived as red light. Further, such a color point u’ may differ less than 0.07, especially less than 0.05, from a u’ color point of a direct red light emitting LED. A u’ color point difference of < 0.07, especially < 0.05, in the u’ color point range of > 0.45 may not lead to a noticeable color difference for consumers. As such, a light generating device configured to generate such device light may especially provide light having a similar color point to a direct red light emitting LED, yet may provide said light with a higher efficiency and color stability. Hence, such a light generating device may be suitable to replace a direct red light emitting LED.

[0070] In embodiments, the device light may further have a color point v’ in the CIE u’v’ color diagram. In embodiments, the color point v’ of the device light may be selected from the range of > 0.48, such as from the range of > 0.49, especially from the range of > 0.50, like from the range of > 0.51. Additionally or alternatively, the color point v’ of the device light may be selected from the range of < 0.54, such as from the range of < 0.53, especially from the range of < 0.525, like from the range of 0.52. Further, in embodiments, the color point v’ of the device light may be selected from the range of 0.48 < u’ < 0.54, such as from the range of 0.49 < u’ < 0.53, especially from the range of 0.50 < u’ < 0.525, like from the range of 0.51 < u’ < 52. Hence, in specific embodiments, the device light may have a color point v’ in the CIE u’v’ color diagram, wherein v’ may be selected from the range of 0.49 < v’ < 0.53. Device light having such a color point v’ (in combination with a u' color point of > 0.43, especially > 0.45) may especially be perceived as red light. Further, such a color point v’ may differ less than 0.07, especially less than 0.05, from a v’ color point of a direct red light emitting LED. A v’ color point difference of < 0.07, especially < 0.05, in the v’ color point range of > 0.49 may not lead to a noticeable color difference for consumers. Hence, a light generating device configured to generate device light having such a color point v’ may be suitable to replace a direct red light emitting LED.

[0071] In embodiments, as indicated above, the luminescent converter may be configured to transmit at least part of the light source light. Hence, in embodiments, violet and / or blue light source light may be admixed with the (orange-)red luminescent converter light, thereby providing purple-red device light. In (other) embodiments, it may be desirable to reduce the violet and / or blue (light source) light component in the device light. Reducing the violet and / or blue light source light component may be facilitated by one or more of increasing the concentration of the first luminescent material (especially of the europium) in the luminescent converter and increasing the thickness (T) of the luminescent converter. Further, in embodiments, (at least part of) the violet and / or blue (light source) light component may be selectively removed from the device light, e.g. by an optical filter. Hence, in embodiments, the light generating device may comprise an optical filter. The optical filter may especially be configured downstream of the luminescent converter. In embodiments, the optical filter may be configured on top of (the downstream luminescent converter surface and / or second side of) the luminescent converter. Further, in specific embodiments, the optical filter may be configured in physical contact with the luminescent converter. Additionally or alternatively, the optical filter may be configured at a non-zero distance d2 from (the downstream luminescent converter surface and / or second side of) the luminescent converter. In embodiments, the distance d2 may be selected from the range of > 5 pm, such as from the range of > 15 pm, especially from the range of > 50 pm. Additionally or alternatively, the distance d2 may be selected from the range of < 20 cm, such as from the range of < 10 cm, especially from the range of < 5 cm. In specific embodiments, the optical filter may be physically separated from the luminescent converter.

[0072] In embodiments, the optical filter may be configured to absorb light within a first wavelength range, and transmit light within a second wavelength range (and / or outside of the first wavelength range). That is, in embodiments, in the first wavelength range, absorption of light (by the optical filter) may be higher than the transmission of light, while in the second wavelength range transmission of light may be higher than absorption of light. In embodiments, the optical filter may especially be configured to (substantially) absorb light in the wavelength range of 400-495 nm (i.e., violet and / or blue light). Additionally, the optical filter may be configured to transmit light in the wavelength range of 495-780 nm. Especially, the optical filter may be configured to transmit the luminescent converter light (comprised by the device light). In embodiments, the optical filter may be configured to transmit at least 60%, such as at least 70%, especially at least 80%, of the luminescent converter light received by the optical filter. Further, in embodiments, the optical filter may be configured to transmit at least 90%, such as at least 95%, especially at least 98%, including (essentially) 100%, of the luminescent converter light received by the optical filter. Further yet, as indicated above, the device light may have a spectral power distribution in the wavelength range of 380-780 nm. Hence, in embodiments, the device light may have a spectral power distribution in the wavelength range of 380-780 nm, wherein the optical filter is configured to (substantially) absorb at least 60%, such as at least 70%, especially at least 80%, of a spectral power of the device light in the wavelength range of 400-495 nm received by the optical filter. Further, in embodiments, the device light may have a spectral power distribution in the wavelength range of 380-780 nm, wherein the optical filter is configured to absorb at least 90%, such as at least 95%, especially at least 98%, including (essentially) 100%, of the spectral power of the device light in the wavelength range of 400-495 nm received by the optical filter. Hence, in embodiments, the optical filter may be configured to substantially absorb the device light in the wavelength range of 400-495 nm. In embodiments, the light transmitted by the optical filter may be referred to as filtered device light, yet may further be referred to as device light. That is, the optical filter may be configured to (substantially) absorb part of the device light to provide device light, or the optical filter may be configured to absorb part of the device light to provide filtered device light. Hence, in specific embodiments, the light generating device may comprise an optical filter, wherein the optical filter may be arranged downstream of the luminescent converter, wherein the device light may have a spectral power distribution in the wavelength range of 380-780 nm, wherein the optical filter may be configured to absorb at least 70% of a spectral power of the device light in the wavelength range of 400-495 nm received by the optical filter. Such an optical filter may facilitate providing device light being (essentially) free from a violet and / or blue light component. Hence, such an optical filter may increase the relative intensity of red light in the spectral power distribution of the device light, thereby providing red device light having a higher color saturation (or “color purity”).

[0073] In embodiments, the optical filter may not be configured to absorb light in the wavelength range of 400-495 nm, yet may (instead) be configured to reflect light in the wavelength range of 400-495 nm. That is, in embodiments, the optical filter may comprise, such as be, a dichroic mirror. A dichroic mirror may be an optical element configured to reflect light within a first wavelength range, and transmit light within a second wavelength range. Specifically, in the first wavelength range, reflection of light (by the dichroic mirror) may be higher than transmission of light, while in the second wavelength range, transmission of light may be higher than reflection of light. Further, a dichroic mirror may have a cut-off and / or a cut-on wavelength, separating the two wavelength ranges. The cut-off wavelength may especially separate a transmissive range (shorter wavelengths) from a reflective range (longer wavelengths), while the cut-on wavelength may especially separate a reflective range (shorter wavelengths) from a transmissive range (longer wavelengths). Especially, the dichroic mirror (of the optical filter) may be configured to (a) reflect at least part of the device light in the wavelength range of 400-495 nm, such as especially the light source light, and (b) to transmit at least part of the device light in the wavelength range of 495-780 nm, such as especially the luminescent converter light. Thus, the light generating device, especially the light source and the luminescent converter, may be selected such that the light source light dominant wavelength (Xsc) of the light source light and the centroid wavelength (Xcic) of the luminescent converter light are spectrally positioned at two opposite sides of a cut-on wavelength of the dichroic mirror. In embodiments, the dichroic mirror may be configured to reflect at least 60%, such as at least 70%, especially at least 80%, of a spectral power of the device light in the wavelength range of 400-495 nm received by the dichroic mirror. Further, in embodiments, the dichroic filter may be configured to reflect at least 90%, such as at least 95%, especially at least 98%, including (essentially) 100%, of the spectral power of the device light in the wavelength range of 400-495 nm received by the optical filter. Additionally or alternatively, the dichroic mirror may be configured to transmit at least part of the luminescent converter light. Especially, the dichroic mirror may be configured to transmit at least 60%, such as at least 70%, especially at least 80%, of the luminescent converter light received by the dichroic mirror. Further, in embodiments, the dichroic mirror may be configured to transmit at least 90%, such as at least 95%, especially at least 98%, including (essentially) 100%, of the luminescent converter light received by the dichroic mirror.

[0074] The light generating device as defined herein may be part of or may be applied in e.g. office lighting systems, household application systems, shop lighting systems, home lighting systems, accent lighting systems, spot lighting systems, theater lighting systems, fiber-optics application systems, projection systems, self-lit display systems, pixelated display systems, segmented display systems, warning sign systems, medical lighting application systems, indicator sign systems, decorative lighting systems, portable systems, automotive applications, (outdoor) road lighting systems, urban lighting systems, green house lighting systems, horticulture lighting, digital projection, or LCD backlighting. The light generating device may be part of or may be applied in e.g. optical communication systems or disinfection systems. Especially, the light generating device may be part of or may be applied in a lighting system. Hence, in yet a further aspect, the invention also provides a lamp or a luminaire comprising the light generating device as defined herein. The luminaire may further comprise a housing, optical elements, louvres, etc. etc... The lamp or luminaire may further comprise a housing enclosing the light generating device. The lamp or luminaire may comprise a light window in the housing or a housing opening, through which the device light may escape from the housing. In yet a further aspect, the invention also provides a projection device comprising the light generating device as defined herein. The projection device may include one or more light generating devices such as described herein. Hence, in an aspect the invention also provides a lighting system selected from the group of a lamp and a luminaire, comprising the light generating device as defined herein. The lighting system may comprise a housing or a carrier, configured to house or support, one or more elements of the light generating device.

[0075] In embodiments, the lighting system may comprise one or more light generating devices as defined herein. Especially, in embodiments, the lighting system may comprise a plurality of the light generating devices as defined herein. In such embodiments, the plurality of light generating devices comprised by the lighting system may be identical. Conversely, in embodiments, the plurality of light generating devices comprised by the lighting system may differ. Especially, at least two of the plurality of light generating devices may differ in one or more of: a) the (type of) solid-state light source in the respective light generating devices, b) the light source light dominant wavelength Xscof the respective solid- state light sources, c) the composition of the first luminescent material in the respective light generating devices, d) the amount of Eu in the luminescent converter of the respective light generating devices, e) the presence, type, composition, and / or concentration of the second luminescent material in the respective light generating devices, and f) the thickness (T) of the luminescent converter of the respective light generating devices. Hence, in embodiments, at least two of the plurality of light generating devices (in the lighting system) may be configured to generate device light having different optical properties, such as differing in one or more of a color point, a device light centroid wavelength Lea, an intensity, and a spectral power distribution. In embodiments, the lighting system may be configured to generate system light comprising the device light (from the one or more light generating devices). In specific embodiments, the system light may consist of the device light.

[0076] Further, in embodiments, the lighting system may comprise a control system, configured to (individually) control the (plurality of) light generating devices, such as especially the (respective) solid-state light source(s). The term “controlling” and similar terms especially refer at least to determining the behavior or supervising the running of an element. Hence, herein “controlling” and similar terms may e.g. refer to imposing behavior on the element. Beyond that, the term “controlling” and similar terms may additionally include monitoring. The controlling of the element can be done with a control system. The control system and the element may thus at least temporarily, or permanently, functionally (and optionally physically) be coupled. Control can be done via wired and / or wireless control. The term “control system” may also refer to a plurality of different control systems. A control system may comprise or may be functionally coupled to a user interface.

[0077] The control system may also be configured to receive and execute instructions from a remote control. In embodiments, the control system may be controlled via an App on a device, such as a portable device, like a Smartphone or I-phone, a tablet, etc.. In such embodiments the control system of the lighting system may be a slave control system. The lighting system may also comprise means for communicating with other systems or devices, such as on the basis of Bluetooth, Thread, WIFI, LiFi, ZigBee, BLE or WiMAX, or another wireless technology.

[0078] The system, or apparatus, or device may execute an action in a “mode” or “operational mode”. The term “operational mode” may also be indicated as “controlling mode”. Likewise, in a method an action or stage, or step may be executed in a “mode” or “operational mode”. In embodiments a control system may be available, that is adapted to provide at least the controlling mode. Would other modes be available, the choice of such modes may especially be executed via a user interface, though other options, like executing a mode in dependence of a sensor signal or a (time) scheme, may also be possible. Hence, in embodiments, the control system may control in dependence of one or more of an input signal of a user interface, a sensor signal (of a sensor), and a timer. The term “timer” may refer to a clock and / or a predetermined time scheme. The operational mode may in embodiments also refer to a system, or apparatus, or device, that can only operate in a single operational mode (i.e. “on”, without further tunability). The terms “light” and “radiation” are herein interchangeably used, unless clear from the context that the term “light” only refers to visible light. The terms “light” and “radiation” may thus refer to UV radiation, visible light, and IR radiation. In specific embodiments, especially for lighting applications, the terms “light” and “radiation” refer to (at least) visible light.

[0079] The present invention has the advantage that a luminescent converter, a light generating device and a lighting system is obtained that have an improved efficiency. Particularly, the efficiency is improved for generating red light. Furthermore, the color saturation of the red light generated by the luminescent converter is improved relative to other luminescent converters generating red light. Particularly, when the light used for exciting the luminescent converter is substantially completely converted to red light, an improved red color saturation is obtained.

[0080] Hence, in an aspect, the invention provides a luminescent converter configured to at least partly convert (light) source light generated by a solid-state light source into luminescent (converter) light, wherein: (A) the luminescent converter has a thickness, T, of tl micrometer, pm, downstream of the solid-state light source; (B) the luminescent converter comprises a first luminescent material of the type Mi-xLi3-2yAli+2y-zSizO4-4y-zN4y+z:Eux, wherein M comprises one or more of Ca, Sr and Ba, wherein 0 < x < 0.04, wherein 0 < y < 1, wherein 0 < z < 0.05, wherein y + z < 1, wherein the luminescent converter comprises an amount of Eu of ml weight percent, wt.%; and (C) wherein 10 < tl*ml < 50.

[0081] In embodiments, the first luminescent material is of the type Mi-xLi3-2yAli+2yO4-4yN4y:Eux, wherein M comprises one or more of Ca, Sr and Ba, wherein 0 < x < 0.04, wherein 0 < y < 1 (and wherein y + z < 1).

[0082] Additionally or alternatively, in embodiments, the first luminescent material is of the type Sri-xLi3-2yAli+2y-zSizO4-4y-zN4y+z:Eux, wherein 0 < x < 0.04, wherein 0 < y < 1, wherein 0 < z < 0.05 and wherein y + z < 1.

[0083] In further (and / or alternative) embodiments, 10 < tl*ml < 35, preferably wherein 15 < tl*ml < 35, more preferably wherein 15 < tl*ml < 30.

[0084] Additionally or alternatively, in embodiments, 150 < tl < 600 pm, and 0.02 < ml < 0.3 wt.%.

[0085] In embodiments, the luminescent converter further comprises a polymer matrix material and wherein the first luminescent material is distributed in the polymer matrix material, wherein the polymer matrix material is selected from the group of siloxanes, preferably dimethylsiloxanes, diphenylsiloxanes, methylphenylsiloxanes, or copolymers thereof.

[0086] In (such) embodiments, the concentration of the first luminescent material in the polymer matrix material is in the range of 5 - 35 vol.%, preferably in the range of 10 - 30 vol.%.

[0087] Additionally or alternatively, in embodiments, the luminescent converter further comprises a second luminescent material, wherein the second luminescent material is of the type M’xM2-2xAXe doped with tetravalent manganese, wherein M’ comprises an alkaline earth cation, M comprises an alkaline cation, and x is in the range of 0-1, wherein A comprises a tetravalent cation, comprising one or more of silicon and titanium, wherein X comprises a monovalent anion, at least comprising fluorine.

[0088] In (specific) embodiments, the first luminescent material is of the type SrLi2AhO2N2:Eu.

[0089] In a further aspect, the invention provides a light generating device, configured to generate device light, the light generating device comprising: (A) a solid-state light source configured to generate (light) source light having a (light) source (light) dominant wavelength (Xsc) selected from the range of 400 - 495 nm; (B) the luminescent converter according to any one of the preceding claims; and (C) wherein the device light comprises the luminescent (converter) light.

[0090] In embodiments, the (light) source light dominant wavelength ( sc) is selected from the range of 400 - 475 nm, preferably from the range of 400 - 450 nm, more preferably in the range of 400 - 435 nm.

[0091] Additionally or alternatively, in embodiments, the device light has a color point u’ in the CIE u’v’ color diagram in the range of 0.45 < u’ < 0.52, preferably in the range of 0.47 < u’ < 0.49.

[0092] In further (and / or alternative) embodiments, the device light has a spectral power distribution in the wavelength range of 380-780 nm with at most 7%, preferably at most 5%, of the spectral power provided by the non-converted (light) source light.

[0093] Additionally or alternatively, in embodiments, an optical filter is arranged downstream of the luminescent converter, wherein the optical filter is configured to substantially absorb the device light in the wavelength range of 400 - 495 nm.

[0094] In a further aspect, the invention provides a lighting system selected from the group of a lamp and a luminaire, comprising the light generating device as defined above. BRIEF DESCRIPTION OF THE DRAWINGS

[0095] Embodiments of the invention will now be described, by way of example only, with reference to the accompanying schematic drawings in which corresponding reference symbols indicate corresponding parts, and in which:

[0096] Fig. 1A-D schematically depict embodiments of a luminescent converter and of a light generating device;

[0097] Fig. 2A-B schematically depict embodiments of the light generating device; Fig. 3 schematically depicts an embodiment of the device light; and Fig. 4 schematically depict embodiments of a lighting system.

[0098] DETAILED DESCRIPTION OF THE EMBODIMENTS

[0099] Figs. 1A-D schematically depict the luminescent converter 200. Figs. 1A-D further schematically depict a light generating device 1000 that comprises a solid-state light source 10 and the luminescent converter 200. The luminescent converter 200 may be provided in a light receiving relationship with the solid-state light source 10. In Figs. 1A-D, the luminescent converter 200 may be provided on the respective solid-state light source 10. In alternative embodiments, the luminescent converter 200 is configured remotely from the respective solid-state light source 10. The solid-state light source 10 may comprise lightemitting diodes (LEDs), superluminescent LEDs or laser diodes. The solid-state light source 10 may be configured to generate light source light 11. The luminescent converter 200 may be configured to convert light source light 11 at least partly into luminescent converter light 201. The light generating device 1000 may be configured to generate device light 1001. The device light 1001 may comprise the luminescent converter light 201 and optionally nonconverted light source light 11.

[0100] Fig. 1A schematically depicts an embodiment of the luminescent converter 200 of the invention. The luminescent converter 200 may be configured to at least partly convert light source light 11 generated by a solid-state light source 10 into luminescent converter light 201. Further, the luminescent converter 200 may have a thickness T of tl micrometer (pm) (see below). The luminescent converter 200 may comprise a first luminescent material 210 of the type Mi-xLi3-2yAli+2y-zSizO4-4y-zN4y+z:Eux, wherein M may comprise one or more of Mg, Ca, Sr and Ba, wherein 0 < x < 0.04, wherein 0 < y < 1, wherein 0 < z < 0.05, and wherein y + z < 1. In embodiments, the first luminescent material 210 may be configured to convert at least part of the light source light 11 received by the first luminescent material 210 into first luminescent material light 211. Further, the luminescent converter 200 may comprise an amount of Eu (originating from the first luminescent material 210) of ml weight percent (wt.%). In embodiments, 10 < tl*ml < 50, such as especially 10 < tl*ml < 35. Further, in embodiments, 150 < tl < 600 pm, and 0.02 < ml < 0.3 wt.%.

[0101] The luminescent converter 200 may further comprise a polymer matrix material 250. The first luminescent material 210 may be distributed in the polymer matrix material 250. Further, the polymer matrix material 250 may be selected from the group of siloxanes. Especially, the polymer matrix material 250 may be selected from the group of dimethylsiloxanes, diphenylsiloxanes, methylphenylsiloxanes, or copolymers thereof. In embodiments, a concentration of the first luminescent material 210 in the polymer matrix material 250 may be in the range of 5-35 vol.%, especially in the range of 10-30 vol.%.

[0102] Fig. 1 A further schematically depicts an embodiments of a light generating device 1000 of the invention. The light generating device 1000 may be configured to generate device light 1001. Further, the light generating device 1000 may comprise a solid- state light source 10 configured to generate light source light 11. The light source light 11 may especially have a light source light dominant wavelength Z,scselected from the range of 400-495 nm. Further, the light generating device 1000 may comprise the luminescent converter 200 as defined herein. The (solid-state) light source 10 may provide the light source light 11 to the luminescent converter 200, wherein the luminescent converter 200 may be configured to convert at least part of said light source light 11 into luminescent converter light 201. Hence, the device light 1001 may comprise the luminescent converter light 201.

[0103] Referring to Figs. 1B-D, a plurality of light generating devices 1000 are shown in each figure, configured in the same housing or on the same support. In embodiments, the plurality of light generating devices 1000 depicted in each of Fig. IB, 1C, and ID, respectively, may be identical, i.e., the two light generating devices 1000 depicted in Fig. IB may be identical to each other, the two light generating devices 1000 depicted in Fig. 1C may be identical to each other, and the plurality of light generating devices 1000 depicted in Fig. ID may be identical to each other. Alternatively, the plurality of light generating devices 1000 depicted in each of Fig. IB, 1C, and ID, respectively, may differ, such as differ in one or more of the respective (type of) solid-state light sources 10, the light source light dominant wavelengths Xsc of the respective solid-state light sources 10, the composition of the respective first luminescent materials 210, the amount of Eu in the respective luminescent converters 200, the presence, nature, and / or concentration of the second luminescent materials 220 (see Fig. 2A), and the thickness (T) of the respective luminescent converters 200. Yet, all of the plurality of light generating devices 1000 depicted in each of Fig. IB, 1C, and ID may fall under the description of the light generating device 1000 as defined above and in the appended claims. Hence, for clarity, all of the (components of the) light generating devices 1000 in Figs. 1B-D may be indicated using the same references, and may be distinguished from each other by the addition of an apostrophe after the reference (e.g., 1000 and 1000’).

[0104] Optionally, referring to Figs. IB and 1C, the light generating devices 1000 may be configured in a housing comprising a light transmissive window, e.g. from polymeric material or glass. Here, the housing is schematically depicted as having a rectangular crosssection. Other types of shapes may also be possible.

[0105] Fig. IB schematically depicts an embodiment of two light generating devices 1000, 1000’ configured to generate respective device light 1001,1001’. In the embodiment depicted in Fig. IB, the luminescent converter 200,200’ may be self-supporting, and may be configured on top of, especially in physical contact with, the respective light source 10,10’.

[0106] Fig. 1C shows embodiments of the light generating devices 1000,1000’ wherein the luminescent converters 200,200’ and solid-state light sources 10,10’ are configured in light reflective cups. Fig. ID schematically depicts an embodiment of a strip or a filament comprising a plurality of light generating devices 1000,1000’.

[0107] In embodiments, the luminescent converter 200 comprises a first luminescent material 210 of the type Mi-xLi3-2yAli+2y-zSizO4-4y-zN4y+z:Eux, wherein M comprises one or more of Ca, Sr and Ba, wherein 0 < x < 0.04, wherein 0 < y < 1, wherein 0 < z < 0.05, wherein y + z < 1. In embodiments, the luminescent converter 200 has a thickness T of tl micrometer (pm), and the luminescent converter 200 comprises an amount of Eu of ml weight percent (wt.%), wherein 10 < tl*ml < 50. The luminescent converter thickness T may be the shortest distance from any point on the luminescent converter surface facing the solid- state light source 10, i.e. the upstream luminescent converter surface, to any point on the luminescent converter surface where device light 1001 exits the light generating device 1000, i.e. the downstream luminescent converter surface. In an embodiment, the first luminescent material 210 comprises SrLi2A12O2N2:Eu.

[0108] In the embodiment depicted in Fig. 1C, the thickness T of the luminescent converters 200,200’ is indicated for the luminescent converter 200’. Here, the shortest distance defining the thickness T may especially be the distance from the part of the luminescent converter 200’ configured in physical contact with a light escape surface of the solid-state light source 10’ to the part of the surface of the luminescent converter 200’ facing away from the solid-state light source 10’ and configured directly above the solid-state light source 10’. This distance may define the thickness T of the luminescent converter 200’, and may further indicate the shortest optical path for the light source light 11 ’ through the luminescent converter 200’. Further, in Fig. 1C, the luminescent converters 200,200’ may be configured as coatings.

[0109] In embodiments, the solid-state light sources 10 are configured to generate light source light 11 having a light source light dominant wavelength (sc) selected from the range of 400 - 495 nm. In embodiments, the luminescent converter 200 comprises a polymer matrix material 250 and the first luminescent material 210 is distributed in the polymer matrix material 250. The polymer matrix material 250 may be selected from the group of siloxanes, preferably dimethylsiloxanes, diphenylsiloxanes, methylphenylsiloxanes, or copolymers thereof.

[0110] In embodiments, particularly when the light source light 11 from the solid- state light source 10 is substantially completely converted by the luminescent converter 200, the device light 1001 has a color point u’ in the CIE u’v’ color diagram in the range of 0.45 < u’ < 0.52, preferably in the range of 0.47 < u’ < 0.49. In embodiments, the device light 1001 has a spectral power distribution in the wavelength range of 380-780 nm with at most 7%, preferably at most 5%, of the spectral power being provided by the non-converted light source light 11, for example the light generating device 1000 is a so-called red phosphorconverted LED.

[0111] Further, the device light 1001 may have a color point v’ in the CIE u’v’ color diagram, wherein v’ may be selected from the range of 0.49 < v’ < 0.53.

[0112] Fig. 2A schematically depicts an embodiment of the light generating device 1000 comprising the luminescent converter 200. The luminescent converter 200 may be configured at a non-zero distance di from a (light escape) surface of the solid-state light source 10 facing the luminescent converter 200. For example, as depicted in Fig. 2A, the solid-state light source(s) 10 may be configured at a bottom of a housing, and the luminescent converter 200 may be configured at a light escape window of the housing. Further, as depicted in Fig. 2A, the luminescent converter 200 may further comprise a second luminescent material 220. The second luminescent material 220 may especially be of the type M’XM2-2XAX6 doped with tetravalent manganese, wherein M’ comprises an alkaline earth cation, M comprises an alkaline cation, and x is in the range of 0-1, wherein A comprises a tetravalent cation, comprising one or more of silicon and titanium, wherein X comprises a monovalent anion, at least comprising fluorine. Further, the light generating device 1000 may comprise an optical filter 600. The optical filter 600 may especially be arranged downstream of the luminescent converter 200 (and of the light solid-state light source 10). In embodiments, the device light 1001 may have a spectral power distribution in the wavelength range of 380-780 nm, and the optical filter 600 may be configured to absorb at least 70% of a spectral power of the device light 1001 in the wavelength range of 400 - 495 nm and received by the optical filter 600. Hence, in the embodiment depicted in Fig. 2A, the device light 1001 may be (mostly or essentially) free from light source light 11, and may further be referred to as filtered device light 1001.

[0113] Fig. 2B schematically depicts a further embodiment of the light generating device 1000 configured as a LED filament 1100. In general, a LED filament 1100 may comprise (i) a plurality of solid-state light sources 10, such as a plurality of light emitting diodes (LEDs), arranged on (at least a first major surface of) an elongated carrier 5, and (ii) an elongated encapsulant 400 covering the plurality of solid-state light sources 10 and at least part of the elongated carrier 5. The elongated encapsulant 400 may comprise, especially consist of, the luminescent converter 200, that is, the luminescent converter 200 may be configured as the encapsulant 400 in the LED filament 1100. The LED filament 1100 may in embodiments be defined by a filament length LF, a filament width WF, and a filament thickness TF (not depicted in Fig. 2B). Further, the LED filament 1100 may have relatively high aspect ratios (LF / WF or LF / TF), such as 10* WF < LF < 900* WF, and 10*TF < LF < 900*TF. In some embodiments, the LED filament 1100 may be straight (as depicted in Fig. 2B). In other embodiments, the LED filament 1100 may be curved. For instance, the LED filament 1100 may have a (2D or 3D) spiraling shape, (like) a helical shape, or another curved shape.

[0114] Further, as indicated, the LED filament 1100 may comprise an elongated carrier 5, solid-state light sources 10, and (the luminescent converter 200 configured as) an encapsulant 400. Especially, the elongated carrier 5 may support the solid state light sources 10. The elongated carrier 5 may e.g. comprise glass, quartz, metal, or sapphire, or ceramic. In other embodiments, the elongated carrier 5 may e.g. comprise a polymeric material or (flexible) metal, e.g., a film or foil. In embodiments, the elongated carrier 5 may be light transmissive, translucent, or transparent for light, especially visible light. Alternatively, in embodiments, the carrier 5 may be light reflective, especially reflective for one or more of the light source light 11 and the luminescent converter light 201. In specific embodiments, the carrier 5 may be diffuse reflective. In embodiments, the (elongated) carrier 5 may comprise a first major surface at a first side of the carrier 5 and a second major surface at a second side of the carrier 5, opposite to the first side. In embodiments, the solid state light sources 10 may be arranged on at least one of these surfaces. In the embodiment depicted in Fig. 2B, the solid-state light sources 10 are arranged on both of these surfaces. Hence, in embodiments, the solid-state light sources 10 may be arranged, mounted and / or mechanically coupled on / to the carrier 5, wherein the carrier 5 may especially be configured to mechanically and / or electrically support the solid-state light sources 10.

[0115] In embodiments, the solid-state light sources 10 may comprise one or more of LEDs, laser diodes, and superluminescent diodes. Especially, the LED filament 1100 comprises a plurality of light emitting diodes (LEDs). The (plurality of) solid-state light sources 10 may be arranged in an array (on the elongated carrier 5), especially over (at least part of) the filament length LF. In embodiments, the number of solid-state light sources 10 in the array may be selected from the range of 10-2000, such as from the range of 10-1500, especially from the range of 10-1000. In embodiments, the solid-state light sources 10 may be configured in a ID (linear) array over at least part of the filament length LF. Further, in embodiments, the solid-state light sources 10 may be configured in two ID arrays, one on the first major surface of the elongated carrier 5 and one on the second major surface 5. A 2D array of solid-state light sources 10 of n*m LEDs may also be possible. In embodiments, n may be selected from the range of 1-4, such as 1-3, like 1-2, and m may be selected from the range of larger than n, such as especially selected from the range of > 4, like > 6, such as > 8. Further, in embodiments, n / m <0.2, like n / m <0.1, especially n / m <0.05.

[0116] In embodiments, the encapsulant 400 may especially (at least partly) cover the plurality of solid-state light sources 10. Especially, in embodiments, the encapsulant 400 may cover > 50%, such as > 75%, especially > 95%, including (essentially) 100%, of the total number of solid-state light sources 10 in the array. Further, the encapsulant 400 may cover at least part of the elongated carrier 5, such as at least (part of) one of the first major and second major surface. In general, the encapsulant 400 may be in contact with the elongated carrier 5 and may cover all of the solid-state light sources 10. The encapsulant 400 may be a continuous coating along the filament length LF, at one or both of the first major and the second major surface. In embodiments, the encapsulant 400 may comprise the luminescent converter 200. Especially, the luminescent converter 200 may be configured as the encapsulant 400. Further, the encapsulant 400 may comprise a light scattering material. The light scattering material may especially be configured embedded in an encapsulant material, e.g. a (flexible) polymer material (such as a silicone). Further, the light scattering material may be configured to scatter (or “diffuse”) the light source light 11. In specific embodiments, the light scattering material may comprise light scattering particles, such as e.g. at least one of BaSCU, AI2O3 and TiCh particles.

[0117] In embodiments, the solid-state light sources 10, comprised by the light generating device 1000 configured as a LED filament 1100, may be configured to generate light source light 11. In embodiments, at least two, such as all, of the solid-state light sources 10 may be configured to emit light source light 11 having different spectral power distributions. In other embodiments, at least two, such as all, of the solid-state light sources 10 may be configured to provide light source light 11 having essentially the same spectral power distribution. The light generating device 1000 configured as a LED filament 1100 may further comprise the optical filter 600 configured as a second encapsulant. Hence, in embodiments, the optical filter 600 may be configured as a second encapsulant configured covering (at least part of) the encapsulant 400. In embodiments, the LED filament 1100 may comprise multiple sub-filaments.

[0118] Fig. 3 schematically depicts embodiments of the device light 1001. Especially, Fig. 3 depicts the value of tl*ml needed to obtain a specific color saturation S (or “color purity”) as a function of the light source light dominant wavelength Xsc. Here, the color saturation S is determined by drawing a line from the white point in the CIE u’v’ color diagram to the color point of the device light 1001, and extrapolating this line until it intersects with the spectral locus (defined by the monochromatic wavelengths). The color saturation is then determined by dividing the length of the line segment between the white point and the color point of the device light 1001 by the length of the line (segment) between the white point and the spectral locus. Hence, a device light 1001 with a saturation S of S = 1 would have a color point located on the spectral locus. In Fig. 3, the required value for tl*ml as a function of the light source light dominant wavelength Xscis depicted for device light 1001 having a (red) color saturation of 0.85, 0.90, and 0.95, respectively. Hence, in embodiments, tl*ml may be selected from the range 10-50, such as especially from the range of 15-35.

[0119] In a first example luminescent converter 200, tl is 280 pm and ml is 0.0962 wt.%, such that tl*ml = 26.9 wt.% Eu*pm. Upon irradiating this first example luminescent converter 200 with light source light 11 having a light source light dominant wavelength Xscof -433 nm, device light 1001 having a color saturation S of 0.9 is obtained. Further, in a second example luminescent converter 200, tl is 225 pm and ml is 0.112 wt.%, such that tl*ml = 25.2 wt.% Eu*pm. To obtain device light 1001 having a color saturation S of 0.9, the second example luminescent converter 200 may thus especially (need to) be irradiated with light source light 11 having a light source light dominant wavelength Xscof -453 nm.

[0120] Fig. 4 schematically depicts embodiments of a lighting system 1200 comprising one or more light generating devices 1000 as described above, for example a luminaire 2 comprising one or more of the light generating devices 1000. Reference 301 indicates a user interface which may be functionally coupled with the control system 300 comprised by or functionally coupled to the lighting system 1200. In embodiments, the control system 300 may be configured to control the intensity of the system light 1201 in dependence of one or more of an input signal of the user interface 301, a sensor signal, and a timer. Fig. 4 also schematically depicts an embodiment of lamp 1 comprising one or more of the light generating devices 1000. Reference 3 indicates a projector device or projector system, which may be used to project images, such as at a wall, which may comprise one or more of the light generating devices 1000. Hence, Fig. 4 schematically depicts embodiments of a lighting system 1200 selected from the group of a lamp 1, a luminaire 2 and a projector device 3, comprising the light generating device 1000 as described herein. System light escaping from the lighting system 1200 is indicated with reference 1201. The system light 1201 may essentially consist of device light 1001. Reference 1300 refers to a space, such as a room. Reference 1305 refers to a floor, reference 1310 refers to a ceiling and reference 1307 refers to a wall.

[0121] The term “plurality” refers to two or more. The terms “substantially” or “essentially” herein, and similar terms, will be understood by the person skilled in the art. The terms “substantially” or “essentially” may also include embodiments with “entirely”, “completely”, “all”, etc. Hence, in embodiments the adjective substantially or essentially may also be removed. Where applicable, the term “substantially” or the term “essentially” may also relate to 90% or higher, such as 95% or higher, especially 99% or higher, even more especially 99.5% or higher, including 100%. The term “comprise” also includes embodiments wherein the term “comprises” means “consists of’. The term “and / or” especially relates to one or more of the items mentioned before and after “and / or”. For instance, a phrase “item 1 and / or item 2” and similar phrases may relate to one or more of item 1 and item 2. The term "comprising" may in an embodiment refer to "consisting of but may in another embodiment also refer to "containing at least the defined species and optionally one or more other species". Use of the verb "to comprise" and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. Unless the context clearly requires otherwise, throughout the description and the claims, the words “comprise”, “comprising”, and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in the sense of “including, but not limited to”. The article "a" or "an" preceding an element does not exclude the presence of a plurality of such elements.

[0122] Furthermore, the terms first, second, third and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other sequences than described or illustrated herein. The devices, apparatus, or systems may herein amongst others be described during operation. As will be clear to the person skilled in the art, the invention is not limited to methods of operation, or devices, apparatus, or systems in operation.

[0123] It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim.

[0124] The invention may be implemented by means of hardware comprising several distinct elements, and by means of a suitably programmed computer. In a device claim, or an apparatus claim, or a system claim, enumerating several means, several of these means may be embodied by one and the same item of hardware. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

[0125] The invention also provides a control system that may control the device, apparatus, or system, or that may execute the herein described method or process. Yet further, the invention also provides a computer program product, when running on a computer which is functionally coupled to or comprised by the device, apparatus, or system, controls one or more controllable elements of such device, apparatus, or system. The invention further applies to a device, apparatus, or system comprising one or more of the characterizing features described in the description and / or shown in the attached drawings. The invention further pertains to a method or process comprising one or more of the characterizing features described in the description and / or shown in the attached drawings.

[0126] The various aspects discussed in this patent can be combined in order to provide additional advantages. Further, the person skilled in the art will understand that embodiments can be combined, and that also more than two embodiments can be combined.

[0127] Furthermore, some of the features can form the basis for one or more divisional applications.

Claims

CLAIMS:

1. A light generating device (1000) configured to generate device light (1001), the light generating device (1000) comprising: a solid-state light source (10) configured to generate light source light (11) having a light source light dominant wavelength (Xsc) selected from the range of 425 - 495 nm; and a luminescent converter (200) configured to at least partly convert light source light (11) generated by a solid-state light source (10) into luminescent converter light (201), wherein: the luminescent converter (200) has a thickness (T) of tl micrometer (pm), wherein the luminescent converter thickness (T) is the shortest distance from any point on a luminescent converter surface facing the solid-state light source (10) to any point on a luminescent converter surface where device light (1001) exits the light generating device (1000); the luminescent converter (200) comprises a first luminescent material (210) of the type Mi-xLi3-2yAli+2y-zSizO4-4y-zN4y+z:Eux, wherein M comprises one or more of Ca, Sr, and Ba, wherein 0 < x < 0.04, wherein 0 < y < 1, wherein 0 < z < 0.05, wherein y + z < 1, wherein the luminescent converter (200) comprises an amount of Eu of ml weight percent (wt.%);10 < tl*ml < 50; and the device light (1001) comprises the luminescent converter light (201).

2. The light generating device (1000) according to claim 1, wherein the luminescent converter (200) comprises the first luminescent material (210) of the type Mi-xLi3-2yAli+2y-zSizO4-4y-zN4y+z:Eux, wherein M comprises one or more of Ca, Sr, and Ba, wherein 0 < x < 0.04, wherein 0 < y < 1, wherein 0 < z < 0.05, and wherein y + z < 1.

3. The light generating device (1000) according to any one of the preceding claims, wherein the first luminescent material (210) is of the typeMi-xLi3-2yAli+2yO4-4yN4y:Eux, wherein M comprises one or more of Ca, Sr, and Ba, wherein 0 < x < 0.04, and wherein 0 < y < 1.

4. The light generating device (1000) according to any one of claims 1-2, wherein the first luminescent material (210) is of the type Sri-xLi3-2yAli+2y-zSizO4-4y-zN4y+z:Eux, wherein 0 < x < 0.04, wherein 0 < y < 1, wherein 0 < z < 0.05 and wherein y + z < 1.

5. The light generating device (1000) according to any one of the preceding claims, wherein 10 < tl*ml < 40.

6. The light generating device (1000) according to any one of the preceding claims, wherein 150 < tl < 600 pm, and wherein 0.02 < ml < 0.3 wt. %.

7. The light generating device (1000) according to any one of the preceding claims, wherein the luminescent converter (200) further comprises a polymer matrix material (250), wherein: the first luminescent material (210) is distributed in the polymer matrix material (250), wherein the polymer matrix material (250) is selected from the group of siloxanes, preferably dimethylsiloxanes, diphenylsiloxanes, methylphenylsiloxanes, or copolymers thereof; and a concentration of the first luminescent material (210) in the polymer matrix material (250) is in the range of 5 - 50 vol.%.

8. The light generating device (1000) according to any one of the preceding claims, wherein the luminescent converter (200) further comprises a second luminescent material (220), wherein the second luminescent material (220) is of the type M’xM2-2xAX6 doped with tetravalent manganese, wherein M’ comprises an alkaline earth cation, M comprises an alkaline cation, and x is in the range of 0-1, wherein A comprises a tetravalent cation, comprising one or more of silicon and titanium, wherein X comprises a monovalent anion, at least comprising fluorine.

9. The light generating device (1000) according to any one of the preceding claims, wherein the luminescent converter light (201) has a luminescent converter centroid wavelength Xcic selected from the range of 600-660 nm.

10. The light generating device (1000) according to any one of the preceding claims, wherein 15 < tl*ml < 35.

11. The light generating device (1000) according to any one of the preceding claims, wherein: the light source light dominant wavelength ( sc) is selected from the range of 425 - 475 nm; and20 < tl*ml < 35.

12. The light generating device (1000) according to any one of the preceding claims, wherein the device light (1001) has a color point u’ in the CIE u’v’ color diagram in the range of 0.45 < u’ < 0.52.

13. The light generating device (1000) according to claim 12, wherein the device light (1001) has a spectral power distribution in the wavelength range of 380-780 nm with at most 7% of the spectral power provided by the non-converted light source light (11).

14. The light generating device (1000) according to claim 12 or 13, comprising an optical filter (600), wherein the optical filter (600) is arranged downstream of the luminescent converter (200), wherein the device light (1001) has a spectral power distribution in the wavelength range of 380-780 nm, wherein the optical filter (600) is configured to absorb at least 70% of a spectral power of the device light (1001) in the wavelength range of 400 - 495 nm received by the optical filter (600).

15. A lighting system (1200) selected from the group of a lamp (1) and a luminaire (2), comprising the light generating device (1000) according to any one of the preceding claims 10-14.

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