LUMINOPHORE, PROCESS FOR PRODUCING A LUMINOPHORE, OPTOELECTRONIC COMPONENT AND NIR SPECTROMETER

Abstract

A luminophore may have the general formula A.sub.xM.sub.yX.sub.z:RE. A may be selected from the group of the trivalent cations. M may be selected from the group of the trivalent cations and includes at least two elements from the following group: Ga, Sc, Al, In, Sb, Bi, As, and Lu. X may be selected from the group of the divalent anions. RE may be a dopant and may be selected from the group formed by the following elements and the combinations of the following elements: Ni, Mn, Cr, Co, Fe, and Sn, where

0.8≤x≤1.2,

0.8≤y≤1.2 and

2.7≤z≤3.3.

A process is also disclosed for producing a luminophore, an optoelectronic component, and an NIR spectrometer.

Claims

1. A luminophore (1) having comprising the general formula A.sub.xM.sub.yX.sub.z:RE; wherein: A is selected from the group of the trivalent cations; M is selected from the group of the trivalent cations and includes at least two elements selected from the following group: Ga, Sc, Al, In, Sb, Bi, As, and Lu; X is selected from the group of the divalent anions; and RE is a dopant and is selected from the group: Ni, Mn, Cr, Co, Fe, Sn, and combinations thereof; wherein:
0.8≤x≤1.2,
0.8≤y≤1.2, and
2.7≤z≤3.3.

2. The luminophore as claimed in claim 1, comprising the general formula A.sub.xM.sub.yD.sub.dE.sub.eF.sub.fX.sub.z; wherein: D, E, and F are selected from the group formed by the following elements: Ni, Mn, Cr, Co, Fe, and Sn; and
0.8≤y+d+e+f≤1.2,
0≤d≤0.1;0≤e≤0.1;0≤f≤0.1and d+e+f>0.

3. The luminophore as claimed in claim 1, wherein RE is selected from the group: Cr, Ni, Sn, and combinations thereof.

4. The luminophore as claimed in claim 1, wherein RE includes Ni and Sn.

5. The luminophore as claimed in claim 1, wherein A is selected from the group: Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Tm, Yb, Lu, and combinations thereof.

6. The luminophore as claimed in claim 1, wherein X is selected from the group: O, S, Se, Te, Po, and combinations thereof.

7. The luminophore as claimed in claim 1, comprising the general formula La(Ga.sub.xSc.sub.1+x)O.sub.3:Ni,Sn, wherein
0≤x≤1.

8. The luminophore as claimed in claim 1, wherein the number of Ni atoms corresponds to the number of Sn atoms.

9. The luminophore as claimed in claim 1, wherein a host material of the luminophore has a crystal structure corresponding to a distorted perovskite structure type.

10. The luminophore as claimed in claim 9, wherein the host material has a symmetry in a space group no. 62.

11. The luminophore as claimed in claim 1, comprising an excitation spectrum having an excitation maximum ranging from 400 nanometers to 500 nanometers inclusive and/or an excitation maximum ranging from 600 nanometers to 750 nanometers inclusive.

12. The luminophore as claimed in claim 1, comprising an emission spectrum ranging from 1000 nanometers to 1800 nanometers inclusive.

13. The luminophore as claimed in claim 1, comprising an emission spectrum having an emission maximum at a wavelength ranging from 1200 nanometers to 1500 nanometers inclusive.

14. The luminophore as claimed in claim 1, comprising a photoluminescence quantum yield of at least 15%.

15. The luminophore as claimed in claim 1, wherein the emission spectrum has a half-height width ranging from 150 nanometers to 220 nanometers inclusive.

16. A process for producing a luminophore having the general formula A.sub.xM.sub.yX.sub.z:RE, wherein the method comprises: providing the reactants selected from the following group: chalcogenides of A, chalcogenides of M, chalcogenides of RE, and combinations thereof; and heating the reactants to a temperature ranging from 1000° C. to 1800° C. inclusive; wherein: A is selected from the group of the trivalent cations; M is selected from the group of the trivalent cations; X is selected from the group of the divalent anions; and RE is a dopant and is selected from the group: Ni, Mn, Cr, Co, Fe, Sn; and combinations thereof; where
0.8≤x≤1.2,
0.8≤y≤1.2, and
2.7≤z≤3.3.

17. The process for producing a luminophore as claimed in claim 16, wherein the reactants provided are lanthanum oxide, nickel oxide, tin oxide, scandium oxide, gallium oxide, and combination thereof.

18. The process for producing a luminophore as claimed in claim 16, further comprising adding a mineralizer is added to the reactants.

19. An optoelectronic component comprising: a semiconductor chip configured to emit electronic radiation of a first wavelength range from a radiation exit face; and a luminophore as claimed in claim 1, wherein the luminophore is configured to convert electromagnetic radiation of the first wavelength range to electromagnetic radiation of a second wavelength range.

20. An NIR spectrometer comprising an optoelectronic component as claimed in claim 19.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0071] Further advantageous embodiments and developments of the luminophore, the component, the NIR spectrometer and the process will be apparent from the working examples described hereinafter in conjunction with the figures.

[0072] The Figures Show:

[0073] FIG. 1A a schematic section diagram of a multitude of particles of a luminophore in one working example;

[0074] FIG. 1B an illustrative scanning electron micrograph of a multitude of particles of a luminophore in one working example;

[0075] FIG. 2 a powder diffractogram of the luminophore LaScO.sub.3:Ni,Sn in one working example;

[0076] FIG. 3 a powder diffractogram of the luminophore LaGaO.sub.3:Ni,Sn in one working example;

[0077] FIG. 4 powder diffractograms of luminophores La(Ga.sub.xSc.sub.1-x)O.sub.3:Ni,Sn having different proportions of gallium and scandium in one working example;

[0078] FIG. 5 emission spectra of La (Ga.sub.xS.sub.1-x)O.sub.3:Ni,Sn with different Sc/Ga ratios in one working example on excitation with electromagnetic radiation in an excitation spectrum having an excitation maximum at a wavelength of about 450 nanometers;

[0079] FIG. 6 Kubelka-Munk functions of luminophores La (Ga.sub.xSc.sub.1-x)O.sub.3:Ni,Sn with different Sc/Ga ratios in one working example;

[0080] FIG. 7 a schematic section diagram of various process stages in a process for producing a luminophore in one working example;

[0081] FIGS. 8 and 9 in each case a schematic section diagram of an optoelectronic component in one working example each;

[0082] FIG. 10 a schematic section diagram of an NIR spectrometer in one working example;

[0083] FIG. 11 absorption spectra of water, lipids, hemoglobin and protein in the near-infrared wavelength region, and

[0084] FIG. 12 difference spectra of fat, water, protein and glucose in the near-infrared wavelength region.

DETAILED DESCRIPTION

[0085] Elements that are the same, of the same type or have the same effect are given the same reference numerals in the figures. The figures and the size ratios of the elements shown in the figures should not be considered to be true to scale. Instead, individual elements, especially layer thicknesses, may be shown as being excessively large for better illustratability and/or for better understanding.

[0086] FIG. 1A shows a schematic section diagram of a multitude of particles of a luminophore 1 in one working example. A grain size of the particles of the luminophore 1 varies from 1 micrometer to 50 micrometers inclusive. The luminophore has the general formula A.sub.xM.sub.yX.sub.z:RE where A is selected from the group of the trivalent cations, M is selected from the group of the trivalent cations, X is selected from the group of the divalent anions and RE is a dopant and is selected from the group formed by the following elements and combinations of the following elements: Ni, Mn, Cr, Co, Fe and Sn, and where 0.8≤, x≤1.2; 0.8≤y≤1.2 and 2.7≤z≤3.3.

[0087] In the present case, the luminophore 1 has the formula La (Ga.sub.xSc.sub.1-x)O.sub.3:Ni, Sn where x may assume a value between 0 and 1 inclusive. The number of nickel atoms in luminophore 1 corresponds here to the number of tin atoms. A host material of luminophore 1 has a crystal structure corresponding to a distorted perovskite structure type. In addition, the crystal structure of the host material may be described by a space group no. 62 or one of its subgroups.

[0088] FIG. 1B shows, by way of example, a scanning electron micrograph of a detail of a luminophore 1 of the general formula A.sub.xM.sub.yX.sub.z:RE in one working example. In the present case, the luminophore 1 has the formula LaScO.sub.3:Ni,Sn. The luminophore 1 is in particle form with a grain size between 1 micrometer and 20 micrometers inclusive.

[0089] FIG. 2 shows, by way of example, the powder diffractogram P1 of the luminophore 1 having the formula LaScO.sub.3:Ni, Sn, measured using copper-K.sub.α1 radiation with a wavelength of 154.06 pm. The intensity I here is plotted in arbitrary units, in each case against the diffraction angle 2θ in degrees between a radiation source of the x-radiation, the luminophore 1 and a detector for the x-radiation. In addition, FIG. 2 shows, in the section of the powder diffractogram P2, the theoretical reflection positions of an LaScO.sub.3 perovskite as comparative curve. The good agreement of P1 and P2 and a Rietveld refinement of the diffractogram P1 using the structure data of LaScO.sub.3, which crystallizes in space group no. 62, confirm the presence of a distorted perovskite structure for luminophore 1.

[0090] FIG. 3 also shows, by way of example, the powder diffractogram P3 measured using copper-K.sub.α1 radiation with a wavelength of 154.06 pm. In this case, P3 shows the powder diffractogram of the luminophore LaGaO.sub.3:Ni,Sn by way of example. In addition, FIG. 3 shows, in the section of the powder diffractogram P4, the theoretical reflection positions of an LaGaO.sub.3 perovskite as comparative curve. The good agreement of P3 and P4 and a Rietveld refinement of the diffractogram P3 using the structure data of LaGaO.sub.3, which crystallizes in space group no. 62, confirm the presence of a distorted perovskite structure for luminophore 1.

[0091] FIG. 4 shows, by way of example, powder diffractograms P5 of the luminophore La (Ga.sub.xSc.sub.1-x)O.sub.3:Ni,Sn. Intensity I is plotted here in arbitrary units against the angle 2θ in degrees. The powder diffractograms P5 of La (Ga.sub.xSc.sub.1-x)O.sub.3:Ni, Sn have different proportions x of gallium and scandium (proportion: 1−x). From the top downward, the proportion 1−x of scandium in luminophore 1 decreases and the proportion x of gallium increases. The more gallium is present in the luminophore 1, the greater the shift in the reflections to larger angles 2θ. The reason for the shift to larger angles 2θ is the smaller ionic radius of the gallium.

[0092] FIG. 5 shows, by way of example, five emission spectra 2 of the luminophore La(Ga.sub.xSc.sub.1-x)O.sub.3:Ni,Sn with different Sc/Ga ratios on excitation with electromagnetic radiation in an excitation spectrum having an excitation maximum at a wavelength of 450 nanometers. What is shown here is the normalized emission NE of the electromagnetic radiation emitted by the luminophore 1 as a function of wavelength λ.

[0093] The wavelength of an emission maximum 3 in the emission spectrum 2 in the present case is between 1200 nanometers and 1500 nanometers inclusive. The emission spectrum 2 have a half-height width F between 150 nanometers and 260 nanometers inclusive. In addition, a value of a photoluminescence quantum yield in one of the emission spectra 2 is at least 15%. The range of the emission spectra 2 is between 1000 nanometers and 1800 nanometers inclusive. The more scandium is present in the luminophore 1, the further the shift in the emission maximum 3 to greater wavelengths λ. When x is 1, i.e. when no scandium is present in the luminophore 1, the emission maximum 3 is about 1250 nanometers. The emission maximum 3 thus depends significantly on the Sc/Ga ratio. Variation of the Sc/Ga ratio enables a shift in the emission maximum 3 of up to 200 nanometers.

[0094] FIG. 6 shows, by way of example, Kubelka-Munk functions K5 calculated from reflectance spectra for the luminophore 1 having the formula La (Ga.sub.xSc.sub.1-x)O.sub.3:Ni, Sn as a function of wavelength λ. The value of the Kubelka-Munk function K5 describes the ratio of absorption and scatter of the incident electromagnetic radiation at the respective wavelength. The calculation here involves an abstract absorption component (1-R).sup.2 and an abstract scatter component 2R. The plot here is of (1-R).sup.2/(2*R) against wavelength λ. R here denotes reflectance. Reflectance means spatially diffuse reflection as a function of wavelength, measured here in the wavelength range from 300 nanometers to 700 nanometers. (1-R).sup.2/(2*R) corresponds to the Kubelka-Munk value. The Kubelka-Munk functions K5 have a maximum M at a wavelength λ of about 410 nanometers to 430 nanometers and only reach a minimum for wavelengths A greater than 550 nanometers. Thus, the luminophore 1 can be excited efficiently with semiconductor chips that emit electromagnetic radiation of an excitation spectrum having an excitation maximum at a wavelength of 400 nanometers to 500 nanometers and 600 nanometers to 750 nanometers.

[0095] FIG. 6 shows the progressions of the Kubelka-Munk functions K5 for six different luminophore compositions. Each curve corresponds to a luminophore 1 with a different ratio of gallium and scandium. The more scandium is present in luminophore 1, the further the shift in the maximum M of the Kubelka-Munk function K5 to greater wavelengths λ. If there is no scandium present in the luminophore 1, i.e. when x is 1, the maximum M of the Kubelka-Munk function K5 is shifted to shorter wavelengths.

[0096] In the process according to working example of FIG. 7, in a first process step S1, the nickel oxide, lanthanum oxide, tin oxide, boric acid, scandium oxide and/or gallium oxide reactants are provided. The reactants are mixed homogeneously. Subsequently, the mixture is introduced into an open corundum crucible, which is introduced into a tubular furnace.

[0097] In a second process step S2, the mixture is heated under a forming gas atmosphere (N.sub.2:H.sub.2=92,5:7,5) or under a nitrogen atmosphere at a temperature of 1400° C. for four hours to form the reaction product. Subsequently, the cooled reaction product is comminuted, ground with a mortar mill and then sieved. Corresponding ratios of individual reactants to one another are shown by way of example in table 1. It is optionally possible to reduce the amount of scandium oxide and to add gallium oxide instead.

TABLE-US-00001 TABLE 1 Reactants for the synthesis of luminophore 1. Luminophore 1 Reactant Molar amount [mmol] Mass [g] Lanthanum oxide 106.3 34.62 Scandium oxide 106.2 14.65 Nickel oxide 2.1 0.16 Tin oxide 2.1 0.32 Boric acid 4.0 0.25

[0098] The optoelectronic component according to each of the working examples of FIGS. 8 and 9 has a semiconductor chip 5 which, in operation, emits electromagnetic radiation of a first wavelength range from a radiation exit face 6. The electromagnetic radiation of the first wavelength range has an emission spectrum, which is also referred to as emission spectrum of the semiconductor chip 5. The semiconductor chip 5 comprises an epitaxially grown semiconductor layer sequence having an active zone 9 capable of generating electromagnetic radiation.

[0099] In addition, the optoelectronic component 4 according to the working example of FIG. 8 has an encapsulation 8. The encapsulation 8 is transparent to electromagnetic radiation emitted by the active zone 9. The semiconductor chip 5 is surrounded by the encapsulation 8.

[0100] The optoelectronic component 4 likewise has a conversion element 12 with a luminophore 1 that converts electromagnetic radiation of the first wavelength range to electromagnetic radiation of a second wavelength range. The electromagnetic radiation of the second wavelength range has an emission spectrum 2 which is also referred to as emission spectrum 2 of the luminophore 1. The luminophore 1 is embedded into a matrix material 7 in the form of particles. The matrix material 7 is selected from the group of polysiloxanes. The conversion element 12 may take the form of a conversion layer. Various luminophores may be introduced into the conversion element 12. For example, a multitude of luminophores 1 with different Sc/Ga ratios is embedded in the conversion element 12.

[0101] The optoelectronic component 4 according to the working example of FIG. 9 comprises a semiconductor chip 5, a carrier element 10, an adhesive layer 11 and a conversion element 12. The conversion element 12 is secured on a radiation exit face 6 of the semiconductor chip 5 with the aid of an adhesive layer 11. The opposite face of the semiconductor chip 5 from the radiation exit face 6 is secured on the carrier element 10 for stabilization. The conversion element 12 takes the form of a conversion layer and includes a luminophore 1 embedded into the matrix material 7 in the form of particles. In addition, further luminophores may be embedded into the conversion element 12. The further luminophore is, for example, a garnet luminophore or a nitride luminophore. The garnet luminophore is, for example, Y.sub.3Al.sub.5O.sub.12:Ce, and the nitride luminophore is, for example, (Sr,Ca) AlSiN.sub.3:Eu. It is also possible for a multitude of luminophores 1 with different Sc/Ga ratios to have been introduced into the conversion element.

[0102] The NIR spectrometer 14 according to the working example of FIG. 10 comprises an optoelectronic component 4 as already described, for example, with reference to FIGS. 8 and 9. The optoelectronic component 4 has been introduced into a housing. The optoelectronic component 4 is intended to emit electromagnetic radiation in the near infrared region and hence to optically excite selected substances 13. Material-specific reflection and absorption properties of the selected substances 13 are found.

[0103] For detection of the reflection and absorption properties of the selected substances 13, the NIR spectrometer 14 also comprises a dispersive, frequency-selective element 15 and a detector element 16. The dispersive, frequency-selective element 15 is, for example, a diffraction grating or a prism. The detector element 16 is, for example, a CCD sensor (CCD=charge-coupled device).

[0104] FIG. 11 shows, by way of example, the optical absorption A as a function of wavelength λ in the range from 850 nanometers to 1500 nanometers of water a, lipids b, hemoglobin c and protein d. For this wavelength range, a particularly good option is the optoelectronic component 4 described here in the NIR spectrometer 14, since the selected substances 13 can be optically excited by the emission from the NIR spectrometer 14. Different absorption properties of the selected substances 13 are found.

[0105] FIG. 12 shows difference spectra of characteristic absorptions AS as a function of wavelength A in the near infrared spectral region up to 1850 nanometers. What are shown are the absorption curves for water a, fat e, protein d and glucose f. The reference shown is a baseline g. The described optoelectronic component 4 in the NIR spectrometer 14 is of particularly good suitability for excitation of selected substances 13 since the selected substances 13 can be optically excited by the emission of the luminophore described here. In addition, the luminophore described here offers the option of controlling the spectral position of the emission or extending it by skillful mixing of variants of the luminophore described here having different Sc/Ga ratios, by means of which it is possible to cover absorptions of a wide variety of different molecular vibrations and solid-state absorptions with just one optoelectronic component 4. Thus, it is especially possible to cover the short-wave absorbing harmonics of the CH valence vibration of CH, CH.sub.2 or CH.sub.3 groups between 1350 nanometers and 1450 nanometers.

[0106] The invention is not limited to the working examples by the description with reference thereto. Instead, the invention encompasses any new feature and any combination of features, which especially include any combination of features in the claims, even if this feature or this combination itself is not specified explicitly in the claims or working examples.

LIST OF REFERENCE NUMERALS

[0107] 1 luminophore [0108] 2 emission spectrum [0109] 3 emission maximum [0110] 4 optoelectronic component [0111] 5 semiconductor chip [0112] 6 radiation exit face [0113] 7 matrix material [0114] 8 encapsulant [0115] 9 active layer [0116] 10 carrier element [0117] 11 adhesive layer [0118] 12 conversion element [0119] 13 selected substances [0120] 14 NIR spectrometer [0121] 15 dispersive, frequency-selective element [0122] 16 detector element [0123] I intensity [0124] a.u. arbitrary unit [0125] P1 powder diffractogram of LaScO.sub.3:Ni,Sn [0126] P2 powder diffractogram of LaScO.sub.3 [0127] P3 powder diffractogram of LaGaO.sub.3:Ni,Sn [0128] P4 powder diffractogram of LaGaO.sub.3 [0129] P5 powder diffractogram of La(Ga.sub.xSc.sub.1-x)O.sub.3:Ni,Sn [0130] F half-height widths [0131] E normalized emission [0132] K5 Kubelka-Munk function of La(Ga.sub.xSc.sub.1-x)O.sub.3:Ni,Sn [0133] R reflectance [0134] M maximum [0135] S1 process step 1 [0136] S2 process step 2 [0137] A absorption [0138] AS absorption [0139] a water [0140] b lipid [0141] c hemoglobin [0142] d protein [0143] e fat [0144] f glucose [0145] g baseline