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US-12624280-B2 - Red luminescent material and conversion LED

US12624280B2US 12624280 B2US12624280 B2US 12624280B2US-12624280-B2

Abstract

A luminescent material may have an empirical formula A 1-y A′ y LiXF 6 :Mn 4+ , where: A=Na, K, Rb, Cs, or combinations thereof; A′=Na, K, Rb, Li, Cs, or combinations thereof; X=Si, Ti, Hf, Zr, Sn, Pb, Ge, or combinations thereof; 0≤y<1; and A and A′ are selected differently.

Inventors

  • Markus Seibald
  • Dominik Baumann
  • Christiane Stoll
  • Hubert Huppertz
  • Gunter Heymann

Assignees

  • AMS-OSRAM INTERNATIONAL GMBH

Dates

Publication Date
20260512
Application Date
20210416
Priority Date
20200422

Claims (15)

  1. 1 . A luminophore having the empirical formula A 1-y A′ y LiXF 6 :Mn 4+ , wherein: A=Na, K, Rb, Cs, or combinations thereof; A′=Na, K, Rb, Li, Cs, or combinations thereof; X=Si, Hf, Zr, Sn, Pb, Ge, or combinations thereof; 0≤y<1; and A and A′ are different, wherein the luminophore crystallizes in an orthorhombic crystal system.
  2. 2 . The luminophore as claimed in claim 1 having the empirical formula A 1-y A′ y LiSiF 6 :Mn 4+ , wherein: A=Na, K, Rb, Cs, or combinations thereof; A′=Na, K, Rb, Li, Cs, or combinations thereof; 0≤y<1; and A and A′ are different.
  3. 3 . The luminophore as claimed in claim 1 having the empirical formula ALiSiF 6 :Mn 4+ , wherein A=Na, K, Rb, Cs, or combinations thereof.
  4. 4 . The luminophore as claimed in claim 3 , wherein A=K, Cs, or both.
  5. 5 . The luminophore as claimed in claim 1 having the empirical formula KLiSiF 6 :Mn 4+ .
  6. 6 . The luminophore as claimed in claim 1 , wherein the luminophore crystallizes in the space group Pbcn.
  7. 7 . A process for preparing a luminophore having the empirical formula A 1-y A′ y LiXF 6 :Mn 4+ , wherein: A=Na, K, Rb, Cs, or combinations thereof; A′=Na, K, Rb, Li, Cs, or combinations thereof; X=Si, Hf, Zr, Sn, Pb, Ge, or combinations thereof; 0≤y<1; and A and A′ are different, by a solid-state synthesis, wherein the luminophore crystallizes in an orthorhombic crystal system.
  8. 8 . The process as claimed in claim 7 , wherein no aqueous HF is employed in the solid-state synthesis.
  9. 9 . The process as claimed in claim 7 , wherein the solid-state synthesis is performed at elevated pressure and elevated temperature.
  10. 10 . The process as claimed in claim 7 , wherein the solid-state synthesis is performed at an elevated pressure of 25 kbar to 85 kbar and in at a temperature ranging from 500° C. to 1000° C.
  11. 11 . The process as claimed in claim 8 for preparing a luminophore having the empirical formula A 1-y A′ y LiSiF 6 :Mn 4+ , wherein the reactants employed are A 2 SiF 6 , where A=Na, K, Rb or Cs, A′ 2 SiF 6 , where A′=Na, K, Rb, Li and/or Cs, Li 2 SiF 6 and X′ 2 MnF 6 , where X′=Li, Na, K, Rb or Cs, or ALiSiF 6 , where A=Na, Rb, K or Cs, and X′ 2 MnF 6 , where X′=Li, Na, K, Rb or Cs.
  12. 12 . A conversion LED comprising a luminophore as claimed in claim 1 .
  13. 13 . The conversion LED as claimed in claim 12 , further comprising: a semiconductor layer sequence adapted to emit electromagnetic primary radiation; and a conversion element comprising the luminophore, wherein the conversion element is configured to at least partly convert the electromagnetic primary radiation to electromagnetic secondary radiation.
  14. 14 . The luminophore as claimed in claim 1 , wherein a full width at half maximum of emission bands of the luminophore is below 10 nm.
  15. 15 . A luminophore having the empirical formula A 1-y A′ y LiXF 6 :Mn 4+ , wherein: A=Na, K, Rb, Cs, or combinations thereof; A′=Na, K, Rb, Li, Cs, or combinations thereof; X=Si, Hf, Zr, Sn, Pb, Ge, or combinations thereof; 0≤y<1; and A and A′ are different, wherein the luminophore has the empirical formula KLiSiF 6 :Mn 4+ .

Description

CROSS-REFERENCE TO RELATED APPLICATIONS The present application is a national stage entry according to 35 U.S.C. § 371 of PCT application No.: PCT/EP2021/059855 filed on Apr. 16, 2021; which claims priority to German patent application DE 10 2020 205 103.8, filed on Apr. 22, 2020; all of which are incorporated herein by reference in their entirety and for all purposes. TECHNICAL FIELD The disclosure relates to a luminophore and to a conversion LED especially comprising the luminophore. BACKGROUND In white light-emitting conversion LEDs as used in general lighting, the red component of the white overall radiation is produced by the conversion of short-wave, in particular blue, primary light from a semiconductor layer sequence to longer-wave, red radiation by means of an inorganic luminophore. A crucial role is played here by the shape and position of the emission band in the red spectral region. The human eye is fundamentally less sensitive to red radiation than to green radiation, for example. The lower the energy or the greater the wavelength in the wavelength range above 555 nm, the poorer/less efficient the ability to perceive red radiation in particular. In a white light-emitting conversion LED, however, the red spectral regions, especially deep red spectral regions having long wavelengths are particularly important when the conversion LED is to have a high color rendering index (CRI) in combination with high luminous efficacy of radiation (LER) and low correlated color temperature (CCT). Typical red luminophores for these applications are based on Eu2+, and these elements are introduced into organic host structures in which they then cause longer-wave emissions under absorption of short-wave, in particular blue, light. These luminophores generally have broad emission spectra or emission bands. Accordingly, in the case of red-emitting luminophores, many photons are inevitably also converted to those spectral regions (large wavelengths; e.g. >650 nm) that can be perceived only very inefficiently by the human eye. This leads to a significant reduction in efficiency of the conversion LED in relation to eye sensitivity. In order to solve this problem, it is possible to attempt a short-wave shift in the emission spectrum by variations in the chemical composition of the host structure, i.e. to increase the integral overlap with the eye sensitivity curve. As a result of the Gaussian distribution of the photons emitted, however, this also leads to a reduction in the photon count in the desired red spectral region, and the abovementioned criteria can accordingly no longer be fulfilled. Luminophores such as nitridolithoaluminate “SrLiAl3N4:Eu2+” (WO 2013/175336 A1; Narrow-band red-emitting Sr[LiAl3N4]:Eu2+ as a next-generation LED-phosphor material, Nature Materials 2014; P. Pust et al.) already have extremely narrow emission bands with FWHM <55 nm, which leads to a reduction in those converted photons in the long-wave region of the visible spectrum (long-wave flank of the emission band) that are perceived very inefficiently by the human eye. At the same time, however, the emission maximum of SrLiAl3N4:Eu2+ at about 650 nm is so far into the deep-red region that conversion LEDs comprising this luminophore as the only red component have barely any efficiency advantage, if any, over solutions comprising broader-band luminophores. The efficiency losses here are dominant over the CRI gain (R9). Another luminophore, SrMg3SiN4:Eu2+ (Toward New Phosphors for Application in Illumination-Grade White pc-LEDs: The Nitridomagnesosilicates Ca[Mg3SiN4]:Ce3+, Sr[Mg3SiN4]:Eu2+ and Eu[Mg3SiN4], Chemistry of Materials 2014, S. Schmiechen et al.), shows a blue-shifted, likewise extremely narrow emission band (FWHM <45 nm) that has its emission maximum at about 615 nm and hence within an ideal range for red luminophores. Disadvantageously, this compound shows significant thermal quenching, such that it is barely possible to observe any emission even at room temperature. Employment in conversion LEDs is thus impossible. There is thus a great need for red-emitting luminophores having a minimum spectral width of emission (“full width at half maximum”, FWHM) in order to keep the number of photons small in spectral regions of low eye sensitivity and simultaneously to emit many photons in the desired red spectral region. It is an objective to specify a luminophore that emits radiation in the red spectral region and has a small spectral emission width (full width at half maximum). It is a further objective to specify a conversion LED comprising the luminophore described here. SUMMARY A luminophore is specified, especially a red-emitting luminophore. In at least one embodiment, the luminophore comprises a phase having the empirical formula A1-yA′yLiXF6:Mn4+, wherein A=Na, K, Rb and/or Cs;A′=Na, K, Rb, Li and/or Cs;X=Si, Ti, Hf, Zr, Sn, Pb and/or Ge;0≤y<1 andA and A′ are different. The luminophore may consist of A1-yA′yLiXF6:Mn4+. In other w