IR emitting pyroxene phosphors and light emitting device using the same

Abstract

The invention provides luminescent material comprising E.sub.1-wSc.sub.1-x-y-u-wM.sub.yZ.sub.uA.sub.2wSi.sub.2-z-uGe.sub.zAl.sub.uO.sub.6:Cr.sub.x, wherein: E comprises one or more of Li, Na, and K; M comprises one or more of Al, Ga, In, Tm, Yb, and Lu; Z comprises one or more of Ti, Zr, and Hf; A comprises one or more of Mg, Zn, and Ni; 0<x≤0.25; 0≤y≤0.75; 0≤z≤2; 0≤u≤1; 0≤w≤1; x+y+u+w≤1; and z+u≤2.

Claims

1. A luminescent material comprising E.sub.1-wSc.sub.1-x-y-u-wM.sub.yZ.sub.uA.sub.2wSi.sub.2-z-uGe.sub.zAl.sub.u:Cr.sub.x, wherein: E comprises one or more of Li, Na, and K; M comprises one or more of Al, Ga, In, Tm, Yb, and Lu; Z comprises one or more of Ti, Zr, and Hf; A comprises one or more of Mg, Zn, and Ni; 0<x≤0.25; 0≤y≤0.75; 0≤z≤2; 0≤u≤1; 0≤w≤1; 1+y+u+w>0; and z+u≤2.

2. The luminescent material according to claim 1, wherein: E at least comprises Li; M at least comprises Lu and/or A at least comprises Mg; when A comprises Mg, 0.1≤w≤0.4; 0.01≤x≤0.1; 0≤y≤0.2; and 0≤z≤0.5.

3. The luminescent material according to claim 1, wherein 0≤z≤0.05.

4. The luminescent material according to claim 1, wherein Z at least comprises Zr.

5. The luminescent material according to claim 1, wherein 0≤u≤0.25.

6. The luminescent material according to claim 1, wherein 0.02≤y≤0.2.

7. The luminescent material according to claim 1, wherein 0≤w≤0.5.

8. The luminescent material according to claim 1, comprising one or more of LiSc.sub.1-x-yLu.sub.ySi.sub.2O.sub.6:Cr.sub.x, LiSc.sub.1-x-y(Lu,Al)Si.sub.2O.sub.6:Cr.sub.x, and Li.sub.1-wSc.sub.1-x-wMg.sub.2wSi.sub.2O.sub.6:Cr.sub.x.

9. A luminescent material composition comprising (a) the luminescent material according to claim 1 and (b) a second luminescent material; wherein the luminescent material is excitable with first light, wherein the luminescent material is configured to provide first luminescence upon irradiation with the first light, wherein the second luminescent material is configured to provide second luminescence upon irradiation with the first light, wherein the luminescent material and the second luminescent material are configured to provide first and second luminescence in one or more of the red and infrared wavelength ranges, and wherein the first and second luminescence have different centroid wavelengths (λ.sub.1,λ.sub.b 2).

10. The luminescent material composition according to claim 9, wherein the second luminescent material comprises one or more of: RE.sub.3Ga.sub.5-x-yA.sub.xSiO.sub.14:Cr.sub.y (RE=La, Nd, Gd, Yb, Tm; A=Al, Sc), wherein 0≤x≤1 and 0.005≤y≤0.1; Gd.sub.3-xRE.sub.xSc.sub.2-y-zLn.sub.yGa.sub.3-wAl.sub.wO.sub.12:Cr.sub.z (Ln=Lu, Y, Yb, Tm; RE=La, Nd, Lu), wherein 0≤x≤3; 0≤y≤1.5; 0≤z≤0.3; and 0≤w≤2; AAEM.sub.1-xF.sub.6:Cr.sub.x (A=Li, Cu; AE=Sr, Ca; M=Al, Ga, Sc), wherein 0.005<x≤0.2; A.sub.2-x(WO.sub.4).sub.3:Cr.sub.x (A=Al, Ga, Sc, Lu, Yb), wherein 0.003≤x≤0.5; Sc.sub.1-x-yA.sub.yMO:Cr.sub.x, wherein MO=BO.sub.3, or MO=P.sub.3O.sub.9, or MO=(BP.sub.3O.sub.12).sub.0.5, or MO=(SiP.sub.5O.sub.19).sub.0.34, with A=Lu, In, Yb, Tm, Y, Ga, Al, wherein 0<x≤0.75, 0≤y≤1; M.sub.2-xSi.sub.5-yAl.sub.yO.sub.yN.sub.8-y:Eu.sub.x (M=Ba, Sr, Ca), wherein 0<x≤0.05, 0≤y≤0.1; M.sub.1-xSiAlN.sub.3:Eu.sub.x (M=Sr, Ca), wherein 0<x≤0.03; and M.sub.1-xLiAl.sub.3N.sub.4:Eu.sub.x (M=Ba, Sr, Ca), wherein 0<x≤0.02.

11. The luminescent material composition according to claim 9, wherein the second luminescent material comprises Gd.sub.3-xRE.sub.xSc.sub.2-y-zLn.sub.yGa.sub.3-wAl.sub.wO.sub.12:Cr.sub.z (Ln=Lu, Y, Yb, Tm; RE=La, Nd, Lu), wherein 0≤x≤3; 0≤y≤1.5; 0<z≤0.3; and 0≤w≤2.

12. A device comprising: a first light source configured to generate first light; and the luminescent material as defined in claim 1, wherein the luminescent material is configured to convert at least part of the first light into first luminescence.

13. The device according to claim 12, comprising: a second luminescent material configured to provide second luminescence upon irradiation with the first light, wherein the luminescent material and the second luminescent material are configured to provide first and second luminescence in one or more of the red and infrared wavelength ranges, and wherein the first and second luminescence have different centroid wavelengths (λ.sub.1,λ.sub.2); and optionally a second light source configured to generate second light; wherein the second luminescent material is configured to convert one or more of (a) part of the second light and (b) at least part of the optional second light into second luminescence.

14. The device according to claim 12, wherein: the luminescent material comprises one or more of LiSc.sub.1-x-yLu.sub.ySi.sub.2O.sub.6:Cr.sub.x, LiSc.sub.1-x-y(Lu,Al).sub.ySi.sub.2O.sub.6:Cr.sub.x, and Li.sub.1-wSc.sub.1-x-wMg.sub.2wSi.sub.2O.sub.6:Cr.sub.x; and a second luminescent material configured to provide second luminescence upon irradiation with the first light, wherein the luminescent material and the second luminescent material are configured to provide first and second luminescence in one or more of the red and infrared wavelength ranges, and wherein the first and second luminescence have different centroid wavelengths (λ.sub.1,λ.sub.2), the second luminescent material comprising Gd.sub.3-xRE.sub.xSc.sub.2-y-zLn.sub.yGa.sub.3-wAl.sub.wO.sub.12:Cr.sub.z (Ln=Lu, Y, Yb, Tm; RE=La, Nd, Lu), wherein 0≤x≤3; 0≤y≤1.5; 0<z≤0.3; and 0≤w≤2.

15. The device according to claim 12, further comprising an optical sensor configured to detect radiation in one or more of the red and infrared wavelength ranges.

16. A luminescent material comprising Li.sub.1-wSc.sub.1-x-wMg.sub.2wSi.sub.2O.sub.6:Cr.sub.x, wherein 0<x≤0.25; 0≤w≤1; and x+w≤1.

17. The luminescent material according to claim 16, wherein 0≤w≤0.5.

18. A luminescent material composition comprising (a) the luminescent material according to claim 16 and (b) a second luminescent material; wherein the luminescent material is excitable with first light, wherein the luminescent material is configured to provide first luminescence upon irradiation with the first light, wherein the second luminescent material is configured to provide second luminescence upon irradiation with the first light, wherein the luminescent material and the second luminescent material are configured to provide first and second luminescence in one or more of the red and infrared wavelength ranges, and wherein the first and second luminescence have different centroid wavelengths Gd.sub.3-xRE.sub.xSc.sub.2-y-zLn.sub.yGa.sub.3-wAl.sub.wO.sub.12:Cr.sub.z (λ.sub.1,λ.sub.2).

19. The luminescent material composition according to claim 18, wherein the second luminescent material comprises (Ln=Lu, Y, Yb, Tm; RE=La, Nd, Lu), wherein 0≤x≤3; 0≤y≤1.5; 0≤z≤0.3; and 0≤w≤2.

20. A device comprising: a first light source configured to generate first light; and the luminescent material as defined in claim 16, wherein the luminescent material is configured to convert at least part of the first light into first luminescence.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 illustrates an embodiment of a wavelength converting structure as part of an illumination device.

(2) FIG. 2 illustrates another embodiment of a wavelength converting structure as part of an illumination device.

(3) FIG. 3 is a cross sectional view of an LED.

(4) FIG. 4 is a cross sectional view of a device with a wavelength converting structure in direct contact with an LED.

(5) FIG. 5 is a cross sectional view of a device with a wavelength converting structure in close proximity to an LED.

(6) FIG. 6 is a cross sectional view of a device with a wavelength converting structure spaced apart from an LED.

(7) FIG. 7 schematically depict some embodiments.

(8) FIGS. 8a-8b schematically depict some embodiments.

(9) FIGS. 9a-9d show some results, wherein: FIG. 9a shows Emission spectra (443 nm excitation) of example 2; FIG. 9b: Emission spectra (443 nm excitation) of example 3; FIG. 9c shows an emission spectrum of NIR pcLED of example 4; and FIG. 9d: Simulated emission spectrum of a phosphor converted LED comprising a 450 nm pump LED and a phosphor mixture comprising Y.sub.3Al.sub.5O.sub.12:Ce, CaAlSiN.sub.3:Eu, (Gd,Lu).sub.3Sc.sub.2Ga.sub.3O.sub.12:Cr and Li.sub.0.9Sc.sub.0.85Mg.sub.0.2Si.sub.2O.sub.6:Cr.sub.0.05.

(10) Schematic drawings are not necessarily to scale.

DETAILED DESCRIPTION

(11) This specification discloses luminescent materials that are phosphors that can emit near-infrared (NIR) radiation, and devices that include a wavelength converting structure formed from the luminescent materials that are phosphors that can emit NIR radiation. The luminescent materials that are phosphors that can emit NTR radiation may be referred to herein as “NIR phosphors,” “NIR phosphor materials,” and/or “NIR phosphor compositions.” For economy of language, infrared rations may be referred to herein as “light.”

(12) The luminescent materials are NIR emitting broadband phosphors that can enable pc LED light sources that have improved spectral shapes and light output levels. Higher light output levels are advantageous for many applications, including e.g., spectroscopy applications because they provide an improved signal-to-noise ratio resulting in more accurate and faster analysis.

(13) In general, Cr(III) doped phosphors are suitable down-conversion materials for pcLEDs that emit in the NIR region (“pc-NIR LEDs”) because of the relatively intense absorption bands in the blue to red spectral range and the large Stokes shift that leads to broad band emission in the NIR spectral range. While Cr(III) is often incorporated on octahedral Ga(III) sites in the host lattices, for example gallium garnet phosphors like Gd.sub.3Ga.sub.5O.sub.12:Cr or in La.sub.3(Ga,Al).sub.5(Ge,Si)O.sub.14:Cr type phosphors, incorporation on larger octahedral Sc(III) can further shift the broadband Cr(III) emission towards longer wavelengths. Note that “:Cr” refers to a system doped with trivalent chromium. Further, that “:Ce” refers to a system doped with trivalent cerium. Yet further, note that “:Eu” refers to a system doped with divalent europium.

(14) To adjust the absorption and emission properties of the Cr(III) doped scandium silicates, phosphates, borates, borophosphates, and borosilicates, a portion of the Sc can either be replaced by larger sized trivalent Lu, In, Yb, Tm or Y to obtain a spectroscopic shift towards longer wavelength, or by smaller sized trivalent Ga or Al to induce a spectroscopic shift towards shorter wavelength. In this way, a broad coverage of the (NIR) emission wavelength range from 700-1200 nm can be obtained by combining the NIR phosphor materials with III-V type primary LEDs that show emission in the blue, cyan, green or red spectral range, and optionally by combining with the second luminescent material (see further also below).

(15) FIG. 1 illustrates a wavelength converting structure 108 that includes at least one of the disclosed luminescent NIR phosphor materials. Wavelength converting structure 108 is used in an illumination device 20. The light source 7 may be an LED or any other suitable source including, as examples, resonant cavity light emitting diodes (RCLEDs) and vertical cavity laser diodes (VCSELs). Light source 7 emits a first light 71. A portion of the first light 71 is incident upon a wavelength converting structure 108. The wavelength converting structure 108 absorbs the first light 71 and emits second light 11. The wavelength converting structure 108 may be structured such that little or no first light is part of the final emission spectrum from the device, though this is not required. Reference 21 refers to the light generated by the device 20. Especially, this (device) light 21 at least comprises the first luminescence. The first luminescence is based on conversion of at least part of the first light 71 from the light source 7. Optionally, the device light 21 may also comprise first light 71.

(16) Due to the broad band absorbing nature in the visible spectral range that the disclosed NIR phosphor materials can be excited with, light source 7 may be, for example, blue, green or red emitting LEDs such as, for example, AlInGaN or AlInGaP or AlInGaAs LEDs.

(17) Wavelength converting structure 108 may include, for example, one or more of the borate, phosphate, borophosphate, and silicophosphate NIR phosphor materials disclosed herein.

(18) The wavelength converting structure 108 described with respect to FIG. 1 can be manufactured, for example, in powder form, in ceramic form, or in any other suitable form. The wavelength converting structure 108 may be formed into one or more structures that are formed separately from and can be handled separately from the light source, such as a prefabricated glass or ceramic tile, or may be formed into a structure that is formed in situ with the light source, such as a conformal or other coating formed on or above the source.

(19) In some embodiments, the wavelength converting structure 108 may be powders that are dispersed for example in a transparent matrix, a glass matrix, a ceramic matrix, or any other suitable material or structure. NIR phosphor dispersed in a matrix may be, for example, singulated or formed into a tile that is disposed over a light source. The glass matrix may be for example a low melting glass with a softening point below 1000° C., or any other suitable glass or other transparent material. The ceramic matrix material can be for example a fluoride salt such as CaF.sub.2 or any other suitable material.

(20) The wavelength converting structure 108 may be used in powder form, for example by mixing the powder NIR phosphor with a transparent material such as silicone and dispensing or otherwise disposing it in a path of light. In powder form, the average particle size (for example, particle diameter) of the NIR phosphors may be at least 1 μm in some embodiments, no more than 50 μm in some embodiments, at least 5 μm in some embodiments, and no more than 20 μm in some embodiments. Individual NIR phosphor particles, or powder NIR phosphor layers, may be coated with one or more materials such as a silicate, a phosphate, and/or one or more oxides in some embodiments, for example to improve absorption and luminescence properties and/or to increase the material's functional lifetime.

(21) FIG. 2 illustrates another embodiment in which a wavelength converting structure including one or more of the disclosed NIR phosphor materials may further be combined with a second phosphor system. In FIG. 2, the wavelength converting structure 108 includes an NIR phosphor portion 208 and a second phosphor portion 202 as part of an illumination device 201. In FIG. 2, a light source 7 may be an LED or any other suitable source, (including as examples resonant cavity light emitting diodes (RCLEDs) and vertical cavity laser diodes (VCSELs). Light source 7 emits first light 71. First light 71 is incident upon wavelength converting structure 108, which includes an NTR phosphor portion 208 including one or more of the first luminescent materials 1 disclosed herein, and a second phosphor portion 202. The second phosphor portion comprises a second luminescent material 2, different from the first luminescent material. A portion of the first light 71 is incident on an NIR phosphor portion 208 of the wavelength converting structure 108. The NIR phosphor portion 208 absorbs the first light 71 and emits first luminescence 11. A portion of the first light 71 is incident on a second phosphor portion 202 of the wavelength converting structure 108. The second luminescent material 2 absorbs the first light 71 and emits second luminescence 22. Second luminescence 22 may be visible, though this is not required. The second luminescence 22 may in embodiments be incident on the NIR phosphor portion 208. The NIR phosphor 208 may absorbs all or a portion of the second luminescence 22 may transmit at least part of the second luminescence 22 and/or convert at least part of the second luminescence 22 into first luminescence 11.

(22) The wavelength converting structure 108 including an NIR phosphor 208 and second phosphor 202 may be structured such that little or no first light 71 (and/or optionally little or no second luminescence 22) is part of the final emission spectrum from the device, though this is not required. The final device light is indicated with reference 21. The device light 21 may at least include first luminescence 11. The first luminescence 11 is based on conversion of at least part of the first light 71 from the light source 7 and/or of the second luminescence 22. Optionally, the device light 21 may also comprise first light 71. Further, the device light 21 may also comprise second luminescence 22. Herein, in this schematically depicted embodiment the second luminescence 22 is based on conversion of at least part of the first light 71 from the light source 7.

(23) Due to the broad band absorbing nature in the visible spectral range that the disclosed NIR phosphor materials can be excited with, light source 7 may be, for example, blue, green or red emitting LEDs such as, for example, AlInGaN or AlInGaP or AlInGaAs LEDs.

(24) The first luminescent material (NIR phosphor) 1 included in wavelength converting structure 108 may include one or more of the luminescent materials according to the formula disclosed herein.

(25) Any suitable second phosphor may be used in the second luminescent material 2. In some embodiments, the second phosphor includes one or more of a green emitting phosphor, a red emitting phosphor and an IR emitting phosphor as disclosed below.

(26) Examples of a green emitting phosphor for use as second luminescent material 2 may include Sr.sub.4Al.sub.14O.sub.25:Eu.sup.2+ and/or A.sub.3B.sub.5O.sub.12:Ce.sup.3+, where A is selected from the group Y, Tb, Gd, and Lu, where B is selected from the group Al, Sc and Ga. In particular, A may at least include one or more of Y and Lu, and B at least includes Al. These types of materials may give highest efficiencies. In an embodiment, the second phosphor includes at least two luminescent materials of the type of A.sub.3B.sub.5O.sub.12:Ce.sup.3+, where A is selected from the group Y and Lu, where B is selected from the group Al, and where the ratio Y:Lu differ for the at least two luminescent materials. For instance, one of them may be purely based on Y, such as Y.sub.3Al.sub.5O.sub.12:Ce.sup.3+, and one of them may be a Y,Lu based system, such as (Y.sub.0.5Lu.sub.0.5).sub.3Al.sub.5O.sub.12:Ce.sup.3+. Compositions of garnets especially include A.sub.3B.sub.5O.sub.12 garnets, where A includes at least yttrium or lutetium and where B includes at least aluminum. Such garnet may be doped with cerium (Ce), with praseodymium (Pr) or a combination of cerium and praseodymium; especially however with Ce. Especially, B includes aluminum (Al), however, B may also partly comprise gallium (Ga) and/or scandium (Sc) and/or indium (In), especially up to about 20% of Al, more especially up to about 10% of Al (i.e. the B ions essentially consist of 90 or more mole % of Al and 10 or less mole % of one or more of Ga, Sc and In); B may especially comprise up to about 10% gallium. In another variant, B and O may at least partly be replaced by Si and N. The element A may especially be selected from the group yttrium (Y), gadolinium (Gd), terbium (Tb) and lutetium (Lu). Further, Gd and/or Tb are especially only present up to an amount of about 20% of A. In a specific embodiment, the garnet luminescent material includes (Y.sub.1-xLu.sub.x).sub.3Al.sub.5O.sub.12:Ce, where x is equal to or larger than 0 and equal to or smaller than 1. The terms “:Ce” or “:Ce.sup.3” (or similar terms), indicate that part of the metal ions (i.e. in the garnets: part of the “M” ions) in the luminescent material is replaced by Ce (or another luminescent species when the term(s) would indicate that, like “:Yb”). For instance, assuming (Y.sub.1-xLu.sub.x).sub.3Al.sub.5O.sub.12:Ce, part of Y and/or Lu is replaced by Ce. This notation is known to the person skilled in the art. Ce will replace M in general for not more than 10%; in general, the Ce concentration will be in the range of 0.1-4%, especially 0.1-2% (relative to M). Assuming 1% Ce and 10% Y, the full correct formula could be (Y.sub.0.1Lu.sub.0.89Ce.sub.0.01).sub.3Al.sub.5O.sub.12. Ce in garnets is substantially or only in the trivalent state, as known to the person skilled in the art.

(27) Examples of a red emitting phosphor for use as second luminescent material 2 may include (Ba,Sr,Ca)AlSiN.sub.3:Eu and (Ba,Sr,Ca).sub.2Si.sub.5-xAl.sub.xO.sub.xN.sub.8-x:Eu: In these compounds, europium (Eu) is substantially or only divalent, and replaces one or more of the indicated divalent cations. In general, Eu will not be present in amounts larger than 10% of the cation, especially in the range of about 0.5-10%, more especially in the range of about 0.5-5% relative to the cation(s) it replaces. The term “:Eu” or “:Eu.sup.2+”, indicates that part of the metal ions is replaced by Eu (in these examples by Eu.sup.2+). For instance, assuming 2% Eu in CaAlSiN.sub.3:Eu, the correct formula could be (Ca.sub.0.98Eu.sub.0.02)AlSiN.sub.3. Divalent europium will in general replace divalent cations, such as the above divalent alkaline earth cations, especially Ca, Sr or Ba.

(28) Further, the material (BaSrCa).sub.2Si.sub.5-xAl.sub.xO.sub.xN.sub.8-x:Eu can also be indicated as M.sub.2Si.sub.5-x Al.sub.xO.sub.x N.sub.8-x:Eu, where M is one or more elements selected from the group barium (Ba), strontium (Sr) and calcium (Ca); especially, M includes in this compound Sr and/or Ba. In a further specific embodiment, M consists of Sr and/or Ba (not taking into account the presence of Eu), especially 50-100%, especially 50-90% Ba and 50-0%, especially 50-10% Sr, such as Ba.sub.1.5Sr.sub.0.5Si.sub.5N.sub.8:Eu, (i.e. 75% Ba; 25% Sr). Here, Eu is introduced and replaces at least part of M i.e. one or more of Ba, Sr, and Ca). Likewise, the material (Sr,Ca,Mg)AlSiN.sub.3:Eu can also be indicated as MAlSiN.sub.3:Eu where M is one or more elements selected from the group magnesium (Mg) strontium (Sr) and calcium (Ca); especially, M includes in this compound calcium or strontium, or calcium and strontium, more especially calcium. Here, Eu is introduced and replaces at least part of M (i.e. one or more of Mg, Sr, and Ca). Preferably, in an embodiment the first red luminescent material includes (Ca,Sr,Mg)AlSiN.sub.3:Eu, preferably CaAlSiN.sub.3:Eu. Further, in another embodiment, which may be combined with the former, the first red luminescent material includes (Ca,Sr,Ba).sub.2Si.sub.5-xAl.sub.xO.sub.xN.sub.8-x:Eu, preferably (Sr,Ba).sub.2Si.sub.5N.sub.8:Eu. The terms “(Ca,Sr,Ba)” indicate that the corresponding cation may be occupied by calcium, strontium or barium. It also indicates that in such material corresponding cation sites may be occupied with cations selected from the group calcium, strontium and barium. Thus, the material may for instance comprise calcium and strontium, or only strontium, etc.

(29) Other red emitting luminescent materials are also described above.

(30) Examples of an IR emitting phosphor for use as second luminescent material 2 may include langasite type phosphors of composition RE.sub.3Ga.sub.5-x-yA.sub.xSiO.sub.14:Cr.sub.y (RE=La, Nd, Gd, Yb, Tm; A=Al, Sc) and/or chromium doped garnets of composition Gd.sub.3-xRE.sub.xSc.sub.2-y-zLn.sub.yGa.sub.3-wAl.sub.wO.sub.2:Cr.sub.z (Ln=Lu, Y, Yb, Tm; RE=La, Nd), where 0≤x≤3; 0≤y≤1.5; 0≤z≤0.3; and 0≤w≤2, and/or one or more chromium doped colquiirite materials of composition AAEM.sub.1-xF.sub.6:Cr.sub.x (A=Li, Cu; AE=Sr, Ca; M=Al, Ga, Sc) where 0.005≤x≤0.2, and/or one or more chromium doped tungstate materials of composition A.sub.2-x(WO.sub.4).sub.3:Cr.sub.x (A=Al, Ga, Sc, Lu, Yb) where 0.003≤x≤0.5.

(31) The wavelength converting structure 108 including the first luminescent material 1 and the second luminescent material 2 described with respect to FIG. 2 can be manufactured, for example, in powder form, in ceramic form, or in any other suitable form. The first luminescent material 1 and the second luminescent material 2 may be formed into one or more structures that are formed separately from and can be handled separately from the light source, such as a prefabricated glass or ceramic tile, or may be formed into a structure that is formed in situ with the light source, such as a conformal or other coating formed on or above the source.

(32) The first luminescent material 1 and the second luminescent material 2 may be mixed together in a single wavelength converting layer, or formed as separate wavelength converting layers. In a wavelength converting structure with separate wavelength converting layers, first luminescent material 1 and the second luminescent material 2 may be stacked such that the luminescent material 5 may be disposed between the first luminescent material 1 and the light source, or the first luminescent material 1 may be disposed between the second luminescent material 2 and the light source.

(33) In some embodiments, the first luminescent material 1 and the second luminescent material 2 may be powders that are dispersed for example in a transparent matrix, a glass matrix, a ceramic matrix, or any other suitable material or structure. Phosphor dispersed in a matrix may be, for example, singulated or formed into a tile that is disposed over a light source. The glass matrix may be for example a low melting glass with a softening point below 1000° C., or any other suitable glass or other transparent material. The ceramic matrix material can be for example a fluoride salt such as CaF.sub.2 or any other suitable material.

(34) The first luminescent material 1 and the second luminescent material 2 may be used in powder form, for example by mixing the powder phosphor with a transparent material such as silicone and dispensing or otherwise disposing it in a path of light. In powder form, the average particle size (for example, particle diameter) of the phosphors may be at least 1 μm in some embodiments, no more than 50 μm in some embodiments, at least 5 μm in some embodiments, and no more than 20 μm in some embodiments. Individual phosphor particles, or powder phosphor layers, may be coated with one or more materials such as a silicate, a phosphate, and/or one or more oxides in some embodiments, for example to improve absorption and luminescence properties and/or to increase the material's functional lifetime.

(35) As shown in FIGS. 1 and 2, an illumination device may include a wavelength converting structure that may be used, for example, with light source 7. Light source 7 may be a light emitting diode (LED). Light emitted by the light emitting diode is absorbed by the phosphors in the wavelength converting structure according to embodiments and emitted at a different wavelength. FIG. 3 illustrates one example of a suitable light emitting diode, a III-nitride LED that emits blue light for use in such an illumination system.

(36) Though in the example below the semiconductor light emitting device is a III-nitride LED that emits blue or UV light, semiconductor light emitting devices besides LEDs such as laser diodes and semiconductor light emitting devices made from other materials systems such as other III-V materials, III-phosphide, III-arsenide, II-VI materials, ZnO, or Si-based materials may be used.

(37) FIG. 3 illustrates a III-nitride light source 7, such as a LED that may be used in embodiments of the present disclosure. Any suitable semiconductor light emitting device may be used and embodiments of the disclosure are not limited to the device illustrated in FIG. 3. The device of FIG. 3 is formed by growing a III-nitride semiconductor structure on a growth substrate 10 as is known in the art. The growth substrate is often sapphire but may be any suitable substrate such as, for example, SiC, Si, GaN, or a composite substrate. A surface of the growth substrate on which the III-nitride semiconductor structure is grown may be patterned, roughened, or textured before growth, which may improve light extraction from the device. A surface of the growth substrate opposite the growth surface (i.e. the surface through which a majority of light is extracted in a flip chip configuration) may be patterned, roughened or textured before or after growth, which may improve light extraction from the device.

(38) The semiconductor structure includes a light emitting or active region sandwiched between n- and p-type regions. An n-type region 716 may be grown first and may include multiple layers of different compositions and dopant concentration including, for example, preparation layers such as buffer layers or nucleation layers, and/or layers designed to facilitate removal of the growth substrate, which may be n-type or not intentionally doped, and n- or even p-type device layers designed for particular optical, material, or electrical properties desirable for the light emitting region to efficiently emit light. A light emitting or active region 718 is grown over the n-type region. Examples of suitable light emitting regions include a single thick or thin light emitting layer, or a multiple quantum well light emitting region including multiple thin or thick light emitting layers separated by barrier layers. A p-type region 720 may then be grown over the light emitting region. Like the n-type region, the p-type region may include multiple layers of different composition, thickness, and dopant concentration, including layers that are not intentionally doped, or n-type layers.

(39) After growth, a p-contact is formed on the surface of the p-type region. The p-contact 721 often includes multiple conductive layers such as a reflective metal and a guard metal which may prevent or reduce electromigration of the reflective metal. The reflective metal is often silver but any suitable material or materials may be used. After forming the p-contact 721, a portion of the p-contact 721, the p-type region 720, and the active region 718 is removed to expose a portion of the n-type region 716 on which an n-contact 722 is formed. The n- and p-contacts 722 and 721 are electrically isolated from each other by a gap 725 which may be filled with a dielectric such as an oxide of silicon or any other suitable material. Multiple n-contact vias may be formed; the n- and p-contacts 722 and 721 are not limited to the arrangement illustrated in FIG. 3. The n- and p-contacts may be redistributed to form bond pads with a dielectric/metal stack, as is known in the art.

(40) In order to form electrical connections to the LED, one or more interconnects 726 and 728 are formed on or electrically connected to the n- and p-contacts 722 and 721. Interconnect 726 is electrically connected to n-contact 722 in FIG. 3. Interconnect 728 is electrically connected to p-contact 721. Interconnects 726 and 728 are electrically isolated from the n- and p-contacts 722 and 721 and from each other by dielectric layer 724 and gap 727. Interconnects 726 and 728 may be, for example, solder, stud bumps, gold layers, or any other suitable structure.

(41) The substrate 710 may be thinned or entirely removed. In some embodiments, the surface of substrate 710 exposed by thinning is patterned, textured, or roughened to improve light extraction.

(42) Any suitable light emitting device may be used in light sources according to embodiments of the disclosure. The invention is not limited to the particular LED illustrated in FIG. 3. An embodiment of the light source 7, such as, for example, a LED is illustrated in FIG. 3.

(43) FIGS. 4, 5, and 6 illustrate devices that combine a light source 7, such as a LED and a wavelength converting structure 108. The wavelength converting structure 108 may be, for example, wavelength converting structure 108 including an NIR phosphor as shown in FIG. 1, or wavelength converting structure 108 having an NTR Phosphor and a second phosphor as shown in FIG. 2, according to the embodiments and examples described above.

(44) In FIG. 4, the wavelength converting structure 108 is directly connected to the light source 7, such as a LED. For example, the wavelength converting structure may be directly connected to the substrate 10 illustrated in FIG. 4, or to the semiconductor structure, if the substrate 710 is removed.

(45) In FIG. 5, the wavelength converting structure 108 is disposed in close proximity to light source 7, such as a LED, but not directly connected to the light source 7, such as a LED. For example, the wavelength converting structure 108 may be separated from light source 7, such as a LED, by an adhesive layer 732, a small air gap, or any other suitable structure. The spacing between light source 7, such as a LED, and the wavelength converting structure 108 may be, for example, less than 500 μm in some embodiments.

(46) In FIG. 6, the wavelength converting structure 108 is spaced apart from light source 7, such as a LED. The spacing between light source 7, such as a LED, and the wavelength converting structure 108 may be, for example, on the order of millimeters in some embodiments. Such a device may be referred to as a “remote phosphor” device.

(47) The wavelength converting structure may comprise the first luminescent material and/or the second luminescent material. In the latter embodiment, the wavelength converting structure may e.g. comprise the herein described composition (see also FIG. 7, embodiments I-III).

(48) The wavelength converting structure 108 may be square, rectangular, polygonal, hexagonal, circular, or any other suitable shape. The wavelength converting structure may be the same size as light source 7, such as a LED, larger than light source 7, such as a LED, or smaller than light source 7, such as a LED.

(49) Multiple wavelength converting materials and multiple wavelength converting structures can be used in a single device. Examples of wavelength converting structures include luminescent ceramic tiles; powder phosphors that are disposed in transparent material such as silicone or glass that is rolled, cast, or otherwise formed into a sheet, then singulated into individual wavelength converting structures; wavelength converting materials such as powder phosphors that are disposed in a transparent material such as silicone that is formed into a flexible sheet, which may be laminated or otherwise disposed over an light source 7, such as a LED, wavelength converting materials such as powder phosphors that are mixed with a transparent material such as silicone and dispensed, screen printed, stenciled, molded, or otherwise disposed over light source 7, such as a LED; and wavelength converting materials that are coated on light source 7, such as a LED or another structure by electrophoretic, vapor, or any other suitable type of deposition.

(50) A device may also include other wavelength converting materials in addition to the NIR phosphor and a second phosphor described above, such as, for example, conventional phosphors, organic phosphors, quantum dots, organic semiconductors, II-VI or III-V semiconductors, II-VI or III-V semiconductor quantum dots or nanocrystals, dyes, polymers, or other materials that luminesce.

(51) The wavelength converting materials absorb light emitted by the LED and emit light of one or more different wavelengths. Unconverted light emitted by the LED is often part of the final spectrum of light extracted from the structure, though it need not be. Wavelength converting materials emitting different wavelengths of light may be included to tailor the spectrum of light extracted from the structure as desired or required for a particular application.

(52) Multiple wavelength converting materials may be mixed together or formed as separate structures.

(53) In some embodiments, other materials may be added to the wavelength converting structure or the device, such as, for example, materials that improve optical performance, materials that encourage scattering, and/or materials that improve thermal performance.

(54) FIG. 7 schematically depict three embodiments wherein the first luminescent material 1 and the second luminescent material 2 are provided as layered structure (I), or are configured adjacent to each other, but not on top of each other (II), or as composition 5.

(55) FIG. 8a schematically depict an embodiment of a device 20 comprising also the second luminescent material 2. The device may further optionally comprise a second light source 8 configured to generate second light 81. The second luminescent material 2 may be configured to convert one or more of part of the second light 81 and at least part of the optional second light 81 into second luminescence 22. Further, FIG. 8b schematically depicts an embodiment wherein the same light sources 7 are applied to excite the different luminescent materials. Further, by way of example both embodiments are depicted in combination with an optical sensor 25 configured to detect radiation, such as e.g. in one or more of the red and infrared wavelength ranges.

EXAMPLES

Example 1: LiSc.SUB.0.94.Si.SUB.2.O.SUB.6.:Cr.SUB.0.06

(56) 4.418 g scandium oxide (MRE Ltd., 4N), 0.3108 g chromium (III) oxide (Alfa Aesar, 99%), 8.233 g fumed silica (Evonik, Aerosil EG50), 0.231 g lithium tetraborate (Alfa Aesar, 98%) and 2.518 g lithium carbonate (Merck, p.a.) are mixed by planetary ball milling with ethanol. After drying, the powder mixture is fired twice at 1000° C. and 1050° C. in an alumina crucible with intermediate milling. After washing of the milled powder with hydrochloric acid and water and drying at 100° C. the powder is screened to obtain the final phosphor powder.

(57) X-ray diffraction shows that the phosphor is crystallizing in the clinopyroxene structure type with a.sub.0=9.785 Å, b.sub.0=8.926 Å, c.sub.0=5.352 Å and β=110.3°.

(58) A luminescence measurement (443 nm laser diode excitation) shows an emission band with a centroid wavelength of 865 nm (peak emission at 840 nm) with a full width at half maximum FWHM=154 nm. Internal and external quantum efficiencies are 90.6% and 43.3% respectively.

Example 2: Variation of Cation Composition of Pyroxene Phase

(59) The following phosphor compositions have been prepared according to the method described for example 1:

(60) Example 2-1: LiSc.sub.0.85Lu.sub.0.09Si.sub.2O.sub.6:Cr.sub.0.06

(61) Example 2-2: LiSc.sub.0.77Ga.sub.0.09Lu.sub.0.09Si.sub.2O.sub.6:Cr.sub.0.06

(62) Example 2-3: LiSc.sub.0.77Al.sub.0.09Lu.sub.0.09Si.sub.2O.sub.6:Cr.sub.0.06

(63) Example 2-4: LiSc.sub.0.24Al.sub.0.2In.sub.0.5Si.sub.2O.sub.6:Cr.sub.0.06

(64) Example 2-5: LiSc.sub.0.43Al.sub.0.17Ga.sub.0.26Lu.sub.0.09Si.sub.2O.sub.6:Cr.sub.0.06

(65) Example 2-6: LiSc.sub.0.54Al.sub.0.4Si.sub.2O.sub.6:Cr.sub.0.06

(66) Example 2-7: LiSc.sub.0.54Ga.sub.0.4Si.sub.2O.sub.6:Cr.sub.0.06

(67) Example 2-8: LiSc.sub.0.37Ga.sub.0.42Lu.sub.0.16Si.sub.2O.sub.6:Cr.sub.0.06

(68) The following Table 2 lists weighed amounts of carbonate, oxide and borate powders (in gram):

(69) TABLE-US-00002 TABLE 2 example Li.sub.2CO.sub.3 Sc.sub.2O.sub.3 Cr.sub.2O.sub.3 Al.sub.2O.sub.3 Ga.sub.2O.sub.3 In.sub.2O.sub.3 Lu.sub.2O.sub.3 SiO.sub.2 Li.sub.2B.sub.4O.sub.7 2-1 0.941 1.463 0.114 — — — 0.447 3.000 0.084 2-2 0.941 1.326 0.114 — 0.211 — 0.447 3.000 0.084 2-3 0.941 1.326 0.114 0.115 — — 0.447 3.000 0.084 2-4 0.941 0.413 0.114 0.255 — 1.733 — 3.000 0.084 2-5 0.941 0.740 0.114 0.216 0.608 — 0.447 3.000 0.084 2-6 0.941 0.930 0.114 0.509 — — — 3.000 0.084 2-7 0.941 0.930 0.114 — 0.936 — — 3.000 0.084 2-8 0.941 0.637 0.114 — 0.983 — 0.795 3.000 0.084

(70) After phosphor processing, samples were characterized by means of powder XRD and luminescence spectroscopy. The following Table 3 shows the lattice constants of the clinopyroxene main phase and the luminescence properties for 443 nm excitation.

(71) TABLE-US-00003 TABLE 3 λ.sub.centr. FWHM example a.sub.0 (Å) b.sub.0 (Å) c.sub.0 (Å) β(°) QE.sub.int (nm) (nm) 2-1 9.787 8.939 5.354 110.3 77 870 163 2-2 9.778 8.922 5.349 110.3 72 871 164 2-3 9.787 8.937 5.354 110.3 74 872 164 2-4 9.777 8.972 5.361 110.4 72 870 162 2-5 9.751 8.869 5.337 110.3 43 868 168 2-6 9.767 8.899 5.347 110.3 64 867 163 2-7 9.740 8.854 5.329 110.2 41 860 160 2-8 9.714 8.837 5.318 110.2 39 862 170

Comparative Example: LiIn0.94Si2O6:Cr0.06

(72) 7.145 g indium oxide (Auer Remy, 4N), 0.250 g chromium (III) oxide (Alfa Aesar, 99%), 6.614 g fumed silica (Evonik Aerosil, EG50), 0.185 g lithium tetraborate (Alfa Aesar, 98%) and 2.023 g lithium carbonate (Merck, p.a.) are mixed by planetary ball milling with ethanol. After drying, the powder mixture is fired twice at 1000° C. and 1050° C. in an alumina crucible with intermediate milling. After washing of the milled powder with hydrochloric acid and water and drying at 100° C. the powder is screened to obtain the final phosphor powder.

(73) X-ray diffraction shows that the phosphor is crystallizing in the clinopyroxene structure type with a.sub.0=9.788 Å, b.sub.0=9.014 Å, c.sub.0=5.367 Å and β=110.4°.

(74) A luminescence measurement (443 nm laser diode excitation) shows an emission band with a centroid wavelength of 874 nm (peak emission at 845 nm) with a full width at half maximum FWHM=188 nm. Internal and external quantum efficiencies are 31.6% and 19.8% respectively. FIG. 9a shows emission bands measured for 443 nm excitation for the samples of above.

Example 3: LiScSi2O6:Cr—MgSiO3 Solid Solutions

(75) The following phosphor compositions have been prepared according to the method described for example 1:

(76) Example 3-1: Li.sub.0.9Sc.sub.0.85Mg.sub.0.2Si.sub.2O.sub.6:Cr.sub.0.05

(77) Example 3-2: Li.sub.0.75Sc.sub.0.70Mg.sub.0.5Si.sub.2O.sub.6:Cr.sub.0.05

(78) Example 3-3: Li.sub.0.5Sc.sub.0.45MgSi.sub.2O.sub.6:Cr.sub.0.05

(79) The following Table 4 lists weighed amounts of carbonate, oxide and borate powders (in gram):

(80) TABLE-US-00004 TABLE 4 example Li.sub.2CO.sub.3 Sc.sub.2O.sub.3 MgO Cr.sub.2O.sub.3 SiO.sub.2 Li.sub.2B.sub.4O.sub.7 3-1 0.841 1.463 0.202 0.095 3.004 0.085 3-2 0.702 1.205 0.504 0.095 3.004 0.085 3-3 0.471 0.775 1.008 0.095 3.004 0.085

(81) After phosphor processing, samples were characterized by means of powder XRD and luminescence spectroscopy. The following Table 5 shows the lattice constants of the clinopyroxene main phase and the luminescence properties for 443 nm excitation. While example 3-1 and 3.2 mainly crystallize in the clinopyroxene structure type with some degree of stacking disorder of layers perpendicular to [201], example 3-3 crystallizes in the orthopyroxene structure type and shows stronger emission intensity at shorter wavelengths compared to the examples with lower Mg concentration.

(82) TABLE-US-00005 TABLE 5 λ.sub.centr. FWHM example a.sub.0 (Å) b.sub.0 (Å) c.sub.0 (Å) β(°) QE.sub.int (nm) (nm) 3-1 9.793 8.912 5.340 110.3 81 880 176 3-2 9.770 8.892 5.321 110.0 83 878 175 3-3 18.343 8.834 5.302 90 83 875 177

(83) FIG. 9b shows the emission spectra (443 nm excitation) of example 3.

Example 4: NIR Pc LED

(84) In this example, 15 wt % of a Gd.sub.2.85Sc.sub.1.75Lu.sub.0.3Ga.sub.3O.sub.12:Cr.sub.0.1 garnet phosphor powder (prepared by mixing of 61.404 g gadolinium oxide (Treibacher, >3N8), 14.888 g scandium oxide (Treibacher, 4N), 7.279 g lutetium oxide (NEO, 4N), 34.638 g gallium oxide (Molycorp, 4N), 0.925 g chromium oxide (Materion, 2N5) and 1.956 g gadolinium fluoride (Rhodia, 4N) by means of ball milling and firing the mixture twice at 1540° C. and 1510° C. with intermediate milling) and 85 wt % of Li.sub.0.75Sc.sub.0.70Mg.sub.0.5Si.sub.2O.sub.6:Cr.sub.0.05 phosphor of example 3-2 are mixed in a curable silicone (weight ratio phosphors/silicone=1.6/1) and dispensed into a 2720 midpower LED package equipped with a 450 nm emitting InGaN LED chip. FIG. 3 shows the emission spectrum of the LED from 600-1100 nm with a minimum spectral flux of >0.1 mW/nm for the 750-1000 nm range and a total NIR output of >100 mW.

(85) FIG. 9c: Emission spectrum of NIR pcLED of example 4.

Example 5: Broadband Emitting pcLED Covering the 400-1100 nm Spectral Range

(86) FIG. 9d shows a simulated emission spectrum of a phosphor converted LED that comprises a 450 nm InGaN pump LED and a phosphor mixture comprising Y.sub.3Al.sub.5O.sub.12:Ce, CaAlSiN.sub.3:Eu, (Gd,Lu).sub.3Sc.sub.2Ga.sub.3O.sub.12:Cr and Li.sub.0.9Sc.sub.0.85Mg.sub.0.2Si.sub.2O.sub.6:Cr.sub.0.05. Such a very broad and continuous band emitting LED device is especially interesting for spectroscopy applications and special applications that require such light sources for testing purposes. An example is a calibration light source for silicon based solar cells with a sun-like spectral power distribution.

(87) FIG. 9d shows a simulated emission spectrum of a phosphor converted LED comprising a 450 nm pump LED and a phosphor mixture comprising Y.sub.3Al.sub.5O.sub.12:Ce, CaAlSiN.sub.3:Eu, (Gd,Lu).sub.3Sc.sub.2Ga.sub.3O.sub.12:Cr and Li.sub.0.9Sc.sub.0.85Mg.sub.0.2Si.sub.2O.sub.6:Cr.sub.0.05. Here, by way of example the device light 21 comprises the first light 71 from a light source, such as the LED, as well as the first luminesce 11 (from Li.sub.0.9Sc.sub.0.85Mg.sub.0.2Si.sub.2O.sub.6:Cr.sub.0.05), as well as also second luminescence 22 from Y.sub.3Al.sub.5O.sub.12:Ce, CaAlSiN.sub.3:Eu, and (Gd,Lu).sub.3Sc.sub.2Ga.sub.3O.sub.12:Cr.

(88) Hence, even more than two different second luminescent materials may be applied in a device.

Example AE-1: Phosphor of Composition Li.SUB.0.75.Sc.SUB.0.65.Mg.SUB.0.5.Lu.SUB.0.05.Si.SUB.2.O.SUB.6.:Cr.SUB.0.05

(89) 3.2 g scandium oxide (MRE Ltd., 4N), 0.2713 g chromium (III) oxide (Alfa Aesar, 99%), 8.623 g fumed silica (Evonik, EG50), 0.2415 g Lithium tetraborate (Alfa Aesar, 99%), 1.9783 g Lithium carbonate (Merck, p.a.), 0.7103 g Lutetium oxide (Rhodia, 4N) and 1.4388 g magnesium oxide (Alfa, 99%) are mixed by ball milling and fired at 1000° C. for 2 hrs, milled and fired again at 1050° C. for 4 hrs. After milling, a phosphor powder is obtained that crystallizes in the clinopyroxene structure type with lattice constants a.sub.0=9.7569 Å, b.sub.0=8.8989 Å, c.sub.0=5.3182 Å and β=110.0°.

(90) A luminescence measurement (443 nm laser diode excitation) shows an emission band with a centroid wavelength of 881 nm (peak emission at 855 nm) with a full width at half maximum FWHM=177 nm. Internal and external quantum efficiencies are 74% and 44% respectively.

(91) Pc NIR LEDs

(92) 30 wt % of a Gd.sub.2.85Sc.sub.1.75Lu.sub.0.3Ga.sub.3O.sub.12:Cr.sub.0.1 garnet phosphor powder (prepared as described for example 4) and 70 wt % of the pyroxene type phosphor of example 3-2 is mixed with a silicone encapsulant gel (phosphor/silicone ratio=1) and dispensed into 2720 type midpower LED packages equipped with 450 nm emitting InGaN LED dies. After curing of the silicone, LED spectra are recorded for 25° C., 55° C. and 85° C. board temperature.

(93) The spectral power distribution in the IR wavelength range show a very high stability over drive current and temperature, which is especially wanted for spectroscopy applications to enable high measurement accuracy and reproducibility.

Example AE-2: Phosphor of Composition LiSc.SUB.0.89.Zr.SUB.0.05.Si.SUB.1.95.Al.SUB.0.05.O.SUB.6.: Cr.SUB.0.06

(94) 7.5332 g scandium oxide (MRE Ltd., 4N), 0.5597 g chromium (III) oxide (Alfa Aesar, 99%), 14.455 g fumed silica (Evonik, EG50), 0.4152 g Lithium tetraborate (Alfa Aesar, 99%), 4.5351 g Lithium carbonate (Merck, p.a.), 0.3129 g aluminum oxide (Baikowski, RC-SP DBM) and 0.7563 g zirconium oxide (Daiichi, 5N) are mixed by ball milling and fired at 1000° C. for 2 hrs, milled and fired again at 1050° C. for 4 hrs. After milling and washing with diluted hydrochloric acid, water and ethanol a phosphor powder is obtained that mainly crystallizes in the clinopyroxene structure type with lattice constants a.sub.0=9.7849 Å, b.sub.0=8.9168 Å, c.sub.0=5.3475 Å and β=110.3°

(95) A luminescence measurement (450 nm excitation) shows an emission band with a centroid wavelength of 885 nm (peak emission at 849 nm) with a full width at half maximum FWHM=174 nm. Internal and external quantum efficiencies are 70% and 46% respectively.

Example AE-3: Phosphor of Composition Li.SUB.0.75.Sc.SUB.0.69.Mg.SUB.0.5.Si.SUB.2.O.SUB.6.:Cr.SUB.0.06

(96) 5.84 g scandium oxide (MRE Ltd., 4N), 0.5597 g chromium (III) oxide (Alfa Aesar, 99%), 14.826 g fumed silica (Evonik, EG50), 0.4152 g Lithium tetraborate (Alfa Aesar, 99%), 3.4013 g Lithium carbonate (Merck, p.a.), and 2.4737 g magnesium oxide (Alfa, 99%) are mixed by ball milling and fired at 1000° C. for 2 hrs, milled and fired again at 1050° C. for 4 hrs. After milling and washing with diluted hydrochloric acid, water and ethanol a phosphor powder is obtained that crystallizes in the clinopyroxene structure type with lattice constants a.sub.0=9.7848 Å, b.sub.0=8.9264 Å, c.sub.0=5.3519 Å and β=110.3° and with some degree of stacking disorder of layers perpendicular to crystallographic [201] direction which may be due to some mixing of clinopyroxene and orthopyroxene structure motif stacking sequences.

(97) A luminescence measurement (450 nm excitation) shows an emission band with a centroid wavelength of 888 nm (peak emission at 859 nm) with a full width at half maximum FWHM=185 nm. Internal and external quantum efficiencies are 8200 and 5300 respectively.

(98) Amongst others, embodiments of a phosphor are provided that show (a) a red-shifted emission band compared to materials like NaScSi2O6:Cr or LiInSi2O6:Cr, which both show peak emissions at ˜840 nm, (b) a high chemical stability, supposedly due to a high Li concentration, and (c) higher quantum efficiencies compared to materials like NaScSi2O6:Cr or LiInSi2O6: Cr.

(99) Here below, in Table 6 an overview is given of the examples mentioned above:

(100) TABLE-US-00006 TABLE 6 Li Sc M Z y z N w Si z Ge x 1 1 0.94 — 0 — 0 2 0 — 0.06 2-1 1 0.85 Lu 0.09 — 0 2 0 — 0.06 2-2 1 0.77 Ga, Lu 0.09 + 0.09 — 0 2 0 — 0.06 2-3 1 0.77 Al, Lu 0.09 + 0.09 — 0 2 0 — 0.06 2-4 1 0.24 Al, In 0..sup.2+0.5 — 0 2 0 — 0.06 2-5 1 0.43 Al, Ga, Lu 0.17 + 0.26 + — 0 2 0 — 0.06 0.09 2-6 1 0.54 Al 0.4 — 0 2 0 — 0.06 2-7 1 0.54 Ga 0.4 — 0 2 0 — 0.06 2-8 1 0.37 Ga, Lu 0.4.sup.2+0.16 — 0 2 0 — 0.06 Comp. 1 — In 0.94 — 0 2 0 — 0.06 ex. 3-1 0.9 0.85 — 0 Mg 0.1 2 0 — 0.05 3-2 0.75 0.7 — 0 Mg 0.25 2 0 — 0.05 3-3 0.5 0.45 — 0 Mg 0.5 2 0 — 0.05 AE-1 0.75 0.65 Lu 0.05 Mg 0.5 2 0 — 0.05 AE-2 1 0.89 — Zr 0.05 — 0 1.95 0.05 — 0.06 AE-3 0.75 0.69 — 0 Mg 0.25 2 0 — 0.06

(101) The phosphor may especially be combined with a shorter wavelength emitting JR and/or red phosphor and a (blue) emitting pump LED to provide a broadband red/NIR pcLED that emits at one or more wavelengths in the 600-1100 nm wavelength range, especially over a broad wavelength range, and with a high efficiency. While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive; the invention is not limited to the disclosed embodiments. Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims.

(102) In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality. A single element or other unit may fulfill the functions of several items recited in the claims. 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.

(103) Any (later) reference signs in the claims or the numbered clauses below should not be construed as limiting the scope.

(104) The following enumerated clauses provide additional non-limiting aspects of the disclosure.

(105) 1. A luminescent material (1) comprising E.sub.1-wSc.sub.1-x-y-u-wM.sub.yZ.sub.uA.sub.2wSi.sub.2-z-uGe.sub.zAl.sub.uO.sub.6:Cr.sub.x, wherein: E comprises one or more of Li, Na, and K; M comprises one or more of Al, Ga, In, Tm, Yb, and Lu; Z comprises one or more of Ti, Zr, and Hf; A comprises one or more of Mg, Zn, and Ni; 0<x≤0.25; 0≤y≤0.75; 0≤z≤2; 0≤u≤1; 0≤w≤1; x+y+u+w≤1; and z+u≤2

(106) 2. The luminescent material (1) according to clause 1, wherein: E at least comprises Li; M at least comprises Lu and/or A at least comprises Mg; when A comprises Mg, 0.1≤w≤0.4; 0.01<x≤0.1; 0≤y≤0.2; and 0≤z≤0.5.

(107) 3. The luminescent material (1) according to any one of the preceding clauses, wherein 0≤z≤0.05.

(108) 4. The luminescent material (1) according to any one of the preceding clauses, wherein Z at least comprises Zr.

(109) 5. The luminescent material (1) according to any one of the preceding clauses, wherein 0≤u≤0.25.

(110) 6. The luminescent material (1) according to any one of the preceding clauses, wherein 0.02≤y≤0.2.

(111) 7. The luminescent material (1) according to any one of the preceding clauses, wherein 0≤w≤0.5.

(112) 8. The luminescent material (1) according to any one of the preceding clauses, comprising one or more of LiSc.sub.1-x-yLu.sub.ySi.sub.2O.sub.6:Cr.sub.x, LiSc.sub.1-x-y(Lu,Al).sub.ySi.sub.2O.sub.6:Cr.sub.x, and Li.sub.1-wSc.sub.1-x-yMg.sub.2wSi.sub.2O.sub.6:Cr.sub.x.

(113) 9. A luminescent material composition (5) comprising (a) the luminescent material (1) according to any one of the preceding clauses and (b) a second luminescent material (2); wherein the luminescent material (1) is excitable with first light (71), wherein the luminescent material (1) is configured to provide first luminescence (11) upon irradiation with the first light (71), wherein the second luminescent material (2) is configured to provide second luminescence (22) upon irradiation with the first light (71), wherein the luminescent material (2) and the second luminescent material (5) are configured to provide first and second luminescence (11,22) in one or more of the red and infrared wavelength ranges, and wherein the first and second luminescence (11,22) have different centroid wavelengths (λ.sub.1,λ.sub.2).

(114) 10. The luminescent material composition (5) according to clause 9, wherein the second luminescent material (2) comprises one or more of: RE.sub.3Ga.sub.5-x-yA.sub.xSiO.sub.14:Cr.sub.y (RE=La, Nd, Gd, Yb, Tm; A=Al, Sc), wherein 0≤x≤1 and 0.005≤y≤0.1; Gd.sub.3-xRE.sub.xSc.sub.2-y-zLn.sub.yGa.sub.3-wAl.sub.wO.sub.12:Cr.sub.z (Ln=Lu, Y, Yb, Tm; RE=La, Nd, Lu), wherein 0x≤3; 0≤y≤1.5; 0<z≤0.3; and 0≤w≤2; AAEM.sub.1-xF.sub.6:Cr.sub.x (A=Li, Cu; AE=Sr, Ca; M=Al, Ga, Sc), wherein 0.005<x≤0.2; A.sub.2-x(WO.sub.4).sub.3:Cr.sub.x (A=Al, Ga, Sc, Lu, Yb), wherein 0.003≤x≤0.5; Sc.sub.1-x-y Å.sub.yMO:Cr.sub.x, wherein MO=BO.sub.3, or MO=P.sub.3O.sub.9, or MO=(BP.sub.3O.sub.12).sub.0.5, or MO=(SiP.sub.5O.sub.19).sub.0.34, with A=Lu, In, Yb, Tm, Y, Ga, Al, wherein 0<x≤0.75, 0≤y≤1; M.sub.2-xSi.sub.5-yAl.sub.yO.sub.yN.sub.8-y:Eu.sub.x (M=Ba, Sr, Ca), wherein 0<x≤0.05, 0≤y≤0.1; M.sub.1-xSiAlN.sub.3:Eu.sub.x (M=Sr, Ca), wherein 0<x≤0.03; and M.sub.1-xLiAl.sub.3N.sub.4:Eu.sub.x (M=Ba, Sr, Ca), wherein 0<x≤0.02.

(115) 11. The luminescent material composition (5) according to any one of the preceding clauses 9-10, wherein the second luminescent material (2) comprises Gd.sub.3-xRE.sub.xSc.sub.2-y-zLn.sub.yGa.sub.3-wAl.sub.wO.sub.12:Cr.sub.z (Ln=Lu, Y, Yb, Tm; RE=La, Nd, Lu), wherein 0≤x≤3; 0≤y≤1.5; 0<z≤0.3; and 0≤w≤2.

(116) 12. A device (20) comprising: a first light source (7) configured to generate first light (71); and the luminescent material (1) as defined in any one of the preceding clauses, wherein the luminescent material (1) is configured to convert at least part of the first light (71) in first luminescence (11).

(117) 13. The device (20) according to clause 12, comprising: the second luminescent material (2) as defined in any one of the preceding clauses 9-11; and optionally a second light source (8) configured to generate second light (81);
wherein the second luminescent material (2) is configured to convert one or more of (a) part of the second light (81) and (b) at least part of the optional second light (81) into second luminescence (22).

(118) 14. The device (20) according to any one of the preceding clauses 12-13, comprising (a) the luminescent material (1) as defined in clause 8 and (b) the second luminescent material (2) as defined in clause 11.

(119) 15. The device (20) according to any one of the preceding clauses 12-14, further comprising an optical sensor (25) configured to detect radiation in one or more of the red and infrared wavelength ranges.