Red LED EU3+ phosphor

Abstract

Processes, lighting devices and particles are presented, including a host lattice material, an absorber ion and an activator ion of Eu3+, wherein the host lattice material is a transition metal with an empty d shell. Numerous other aspects are provided.

Description

Red LED Eu3+PhosphorBACKGROUND

[0001] Solid state lighting based on phosphor down conversion of light emitting devices has begun to replace traditional fluorescent and incandescent lamps. These colored semiconductor light emitting devices, including light emitting diodes and lasers (both are generally referred to herein as LEDs), have been usually produced from semiconductors such as gallium nitride (GaN) or indium gallium nitride (InGaN). Light emitted from GaN-based LEDs is generally in the UV and / or blue range of the electromagnetic spectrum. Light emitted from the LED is converted to light that is useful for illumination purposes by coating or covering the LED with a phosphor layer. By interposing a phosphor excited by the radiation generated by the LED, light of a different wavelength, e.g., in the visible range of the spectrum, may be generated. Phosphors can be tailored to produce custom colors with high luminosity, and, in combination with LED generated light, phosphor generated light may be used to produce white light. The most popular white LEDs are based on blue emitting InGaN chips, which emit light at about 450nm. The blue emitting chips may often be coated with green-yellow Cerium-doped garnet phosphor, along with a red phosphor that is added to induce a "warm-white" color temperature (1800-3000K). A conventional commercial red phosphor is K2SiFe:Mn4+, where Mn4+is the emitter ion having a narrow emission near 630 nm. This wavelength (near 630 nm) may not be optimum for general lighting because the human eye may not easily detect those wavelengths. Rather, the sensitivity of the human eye for the red photons increases as the emitted wavelength approaches 600 nm. To that end, a human may observe a phosphor emission 611 nm to be brighter and more easily detectable, while a phosphor emission at 630 nm may not look very bright at all.

[0002] Systems and methods are desired to provide a phosphor emission closer to the human eye sensitivity curve (e.g., the wavelengths detected by the human eye).BRIEF DESCRIPTION OF THE DRAWINGS

[0003] Features and advantages of the example embodiments, and the manner in which the same are accomplished, will become more readily apparent with reference to the following detailed description taken in conjunction with the accompanying drawings.

[0004] FIG. 1 is a method according to some embodiments.

[0005] FIG. 2 is a block diagram according to some embodiments.

[0006] FIG. 3 is a diffuse reflectance spectrum graph according to some embodiments.

[0007] FIG. 4 is an excitation spectrum graph according to some embodiments.

[0008] FIG. 5 is an emission spectrum graph according to some embodiments.

[0009] FIG. 6 is a first non-exhaustive example of a lighting device according to some embodiments.

[0010] FIG. 7 is a second non-exhaustive example according to some embodiments.

[0011] FIG. 8 is a third non-exhaustive example according to some embodiments.

[0012] FIG. 9 is a fourth non-exhaustive example according to some embodiments.

[0013] FIG. 10 is a method according to some embodiments.

[0014] Throughout the drawings and the detailed description, unless otherwise described, the same drawing reference numerals will be understood to refer to the same elements, features and structures. Therelative size and depiction of these elements may be exaggerated or adjusted for clarity, illustration, and / or convenience.DETAILED DESCRIPTION

[0015] In the following description, specific details are set forth in order to provide a thorough understanding of the various example embodiments. It should be appreciated that various modifications to the embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments and applications without departing from the spirit and scope of the disclosure. Moreover, in the following description, numerous details are set forth for the purpose of explanation. However, one of ordinary skill in the art should understand that embodiments may be practiced without the use of these specific details. In other instances, well-known structures and processes are not shown or described in order not to obscure the description with unnecessary detail. Thus, the present disclosure is not intended to be limited to the embodiments shown but is to be accorded the widest scope consistent with the principles and features disclosed herein. It should be appreciated that in development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developer's specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure.

[0016] Unless defined otherwise, technical and scientific terms used herein have the same meaning as is commonly understood by one of ordinary skill in the art to which the present disclosure belongs. The terms "first," "second," "third," "fourth," and the like, as used herein do not denote anyorder, quantity, or importance, but rather are used to distinguish one element from another. Also, the terms "a" and "an" do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced items. The term "or" is meant to be inclusive and mean either, any, several, or all of the listed items. The use of "including," "comprising," or "having," and variations thereof herein are meant to encompass the items listed thereafter and equivalents thereof as well as additional items.

[0017] Approximating language, as used herein throughout the specification and claims, may be applied to modify any quantitative representation that could permissibly vary without resulting in a change in the basic function to which it is related. Accordingly, a value modified by a term or terms, such as "about," is not limited to the precise value specified. In some instances, the approximating language may correspond to the precision of an instrument for measuring the value. For example, the term, "about" used in context of a wavelength value may refer to a value of a wavelength up to ± 20 nm of the specified wavelength value, and is applicable to all incidences of the term "about" as used herein for a wavelength value throughout the specification.

[0018] As used herein, the term "phosphor" or "phosphor material" or "phosphor composition" may be used to denote both a single phosphor composition as well as a blend of two or more phosphor compositions. As used herein, the term "lamp" or "lighting device" or "lighting system" refers to any source of visible and / or ultraviolet light which may be generated by at least one light emitting element producing a light emission when energized (for example, a phosphor material) by a light emitting diode.

[0019] As used herein, the term "red emitting phosphor" refers to a phosphor that is generally excited at wavelengths between 250 nm and 600 nm, and more preferably between 400 nm and 550 nm. The phosphor may have an emission range of between 580 nm and 750 nm,with some exemplary lines of emission being at 610 nm to 630 nm. It is noted that the phosphor may have emissions in other suitable ranges / values.

[0020] As used herein, the term "activator" or "activator ion" refers to an ion (for example Eu3+) doped in a host material that forms a luminescent center and is responsible for the luminescence of a phosphor. A concentration of an activator ion in a phosphor may range from about 1 atomic percent to 50 atomic percent, relative to the atom(s) which may be substituted with the activator ion. In some embodiments, the activator may be 100 atomic % (stoichiometric phosphor). In some embodiments, an ion may act as a sensitizer. As used herein, the term "sensitizer" refers to an ion that absorbs radiation ("absorber") from a light source and transfers it to the activator ion that emits the desired photons. Here, the sensitizer may be the host lattice material doped with an Sn2+absorber. The amount of sensitizer in a phosphor may range from 1 atomic percent to 100 atomic percent, relative to the amount of the activator ion. Sn2+may be present in a 0.01-1.00 mole ratio relative to the crystallographic site of the host lattice material (e.g., host lattice counter cation) that the Sn2+occupies. It is noted that stoichiometric compositions may also be included. As a non- exhaustive example, if a compound is MZO and the Sn2+is going on the M site, then M may be anywhere between M0.99Sn0.01 and M0.00Snl.00.

[0021] A lighting device may be based on a blue emitting InGaN LED chip and a phosphor, or a blend of phosphors, to convert at least some of the blue radiation to another color. One or more embodiments may include an LED light source that emits a wavelength in a range of from about 400-500 nm and may be referred to herein as a "blue" LED. With respect to phosphors that may be used to coat the LED, the phosphors emitting at wavelengths greater than 650 nanometers (nm), and therefore in the red range (i.e., 620-750 nm), are typically not efficient photon generators foruse in general illumination. This is because the spectrum of such phosphors may make a poor match with the human eye response (luminosity response function), resulting in low brightness detection, even when the quantum efficiency of the phosphor is high. For example, manganese (Mn4+) is the conventional ion that is used as a red emitter with a blue LED. The problem with Mn4+is that while its emission is in the red range, it is about 630 nm, while the human eye sensitivity curve to red photons peaks at about 611 nm. It is noted that the eye sensitivity curve to general emission peaks around 540nm. Europium (Eu3+), on the other hand, has an emission in the orange-red range (e.g., about 610 nm) that better overlaps with the human eye sensitivity curve. Although Eu3+has an emission that better overlaps with the human eye sensitivity curve, a phosphor using Eu3+as an activator has not been turned into a commercially viable phosphor because the Eu3+luminescence is only weakly excited by blue LED radiation. In particular, Eu3+does not absorb the 450 nm of the blue radiation emitted by the blue LED very well.

[0022] To resolve this problem, one or more embodiments provide a "hostsensitizer" system and method by which a host material will absorb the 450 nm emitted by the blue LED, transfer that absorbed energy to Eu3+so that the Eu3+then emits in a red range at about 610 nm and overlapping with the peak of the human eye sensitivity curve. As part of this process, the Eu3+has been sensitized so that it may emit in a red range. In particular, the host-sensitizer system and method may downconvert the blue LED radiation to Eu3+photons for a high luminous efficacy white light LED product. The "host-sensitizer" system of embodiments applies a sensitizer to Eu3+luminescence, whereby the sensitizer has a strong absorption in the blue range, transfers energy efficiently to Eu3+and maintains efficiency at elevated temperatures. After synthesis, the sensitized Eu3+phosphor, which may be in a powder form, may be applied to a surface of the LED, as described further below.

[0023] While the non-exhaustive examples described herein will be described with respect to trivalent Europium ions (Eu3+), and in particular a phosphor including an oxide-based host lattice material doped with activator ion Eu3+, other suitable host materials and ions may be used.

[0024] FIG. 1 provides a flow diagram of a process 100 for synthesizing sensitized Eu3+phosphor, according to some embodiments. Process 100, and any other process described herein, may be performed using any suitable combination of hardware (e.g., circuit(s)), software or manual means. Examples of these processes will be described below with respect to embodiments, but embodiments are not limited thereto. The flow diagrams described herein do not imply a fixed order to the steps, and embodiments of the present invention may be practiced in any order that is practicable.

[0025] Initially, at S110, a host lattice material composed of an ion with an empty d shell is provided.

[0026] In S112, predetermined amounts of an absorber ion (e.g., Sn2+) and an activator ion (e.g., Eu3+) are provided. Then, in S114, the reagents (host lattice material, Sn2+, Eu3+) are combined. In some embodiments, the Sn2+and Eu3+are added simultaneously to the host material, (e.g., YNbCU). Pursuant to some embodiments, the reagents may be thoroughly blended. Next, in S116, the reagents are reacted and the red phosphor with sensitized Eu3+is synthesized. In some embodiments, the reagents (host lattice material, Sn2+, Eu3+) may be in powdered form. The reaction may be a solid state reaction with the reagents being solid (e.g., powdered form), a solution chemistry reaction (e.g., a sol-gel process), or any other suitable process.

[0027] With respect to a solid state reaction, after the reagents are thoroughly blended, the blended reagents may be heated for a predetermined amount of time at a given atmospheric condition. As a non- exhaustive example, the blended reagents are heated at a firingtemperature of 1000 degrees Celsius in a covered crucible for ten hours in slightly reducing atmosphere. Other suitable temperatures and times may be used, based, in part, on the type of reagents used as well as an amount of reagents used. As a non-exhaustive example, a red phosphor with sensitized Eu3+may have a composition of (Y0.85Eu0.10Sn0.05)NbO(4-x) , where x =0.025, and the reagents used were Y2O3, EU2O3, Nb2O5 and SnCl2.2H20. The synthesized red phosphor with sensitized Eu3+may be excited with blue LED radiation.

[0028] As another non-exhaustive example, for a five gram batch of synthesized red phosphor with sensitized Eu3+, the reagents may be 1.89 g of Y2O3, 0.15 g of SnO2 or 0.22 g of SnCl2.2H2O, 0.35 g of EU2O3, and 2.62 g of Nb20s. In this example, 0.17 g of Li2B4O? is used as flux. Then, at atmosphere, the sample is placed in a crucible with a lid. The lidded crucible is placed in a larger crucible that had a large excess coconut charcoal. The larger crucible is lidded and fired in an air furnace. The inventors note that the firing in the air furnace is akin to firing with slightly reducing atmosphere such as would be provided by 0.5% H2 in N2 or an approximate equivalent.

[0029] Pursuant to one or more embodiments, Eu3+emission is sensitized by a combination of two ions - tin (Sn2+) ion and an ion which has no "d" electrons ("d zero ion"). The ion with no "d" electrons may be a metal ion. In one or more embodiments, a host lattice material composed of cations with empty d orbitals ("shells") may be doped with Sn2+, where the combination of Sn2+(5s2) and a metal ion with empty d orbitals (d°) is used as the sensitizer. The combination of these two ions may be referred to as a "sensitizer". In particular, the coupling between Sn2+5s2and d° cations results in metal-to-metal charge transfer transition (MMCT) that makes possible the absorption of the blue LED radiation (450nm-470nm) and transferring energy to the Eu3+ion, such that the host lattice material doped with Sn2+and Eu3+will give the desired red emission when exposed to a 450 nm LED emission. The luminescence ofEu3+may be sensitized by the MMCT transition to produce red photons with high efficiency. Other ions with ns2electronic configuration, including, but not limited to, Bi3+(6s2), Pb2+(6s2), Tl+(6s2), Te4+(5s2), Sb3+(5s2) may also be used either in combination with, or instead of, the Sn2+ion. Without being bound by any theory, the inventors note that Sn2+may be the ion best suited to be combined with the d zero metal ion and Eu3+because Sn2+has energy levels which, in combination with the d zero metal ion, favor the absorption of the 450 nm radiation output by the blue LED. As a non-exhaustive example, while cerium (Ce)3+may be used instead of Sn2+, there's an intrinsic quenching mechanism between Ce3+and Eu3+, wherein Ce3+decreases the fluorescent intensity of Eu3+, making it unsuitable to sensitize Eu3+.

[0030] A band gap of the Sn2+(5s2) to d° charge transfer may be tuned to absorb the blue photons emitted in the LED radiation. In one or more embodiments, the host lattice material may have a band gap from about two electron volts (eV) to about five eV or from about two eV to about 10 eV. The band gap is the distance between the valence band of anion electrons and the conduction band. The band gap represents the minimum energy that is required to excite an electron up to a state in the conduction band where it can participate in conduction. As a non- exhaustive example, tuning of the band gap for absorption of the blue photons emitted by the blue LED may include the formation of solid solutions of stoichiometric Sn compounds such as Sn2Nb2O? (band gap = 2.3 eV), Sn2Ta2O? (band gap = 3.0 eV).

[0031] The composition of the host lattice material, and doped host lattice material, may be formed by conventional solid state reaction techniques in which, usually, the starting materials of the intended composition are accurately weighed, mixed (such as by a ball mill) and heated at a temperature for a duration under appropriate atmosphere conditions (such as H2-N2 forming gas). The host lattice material includes, but is not limited to at least one of, an oxide (including phosphates, borates,silicates, tungstates, etc.), an oxyfluoride, or a combination thereof. In some embodiments, the host lattice material is selected from the group consisting of an oxide and an oxyfluoride and combinations thereof. Pursuant to one or more embodiments, the host lattice material is composed of an ion with an empty d shell (d°). In some embodiments, the host lattice material is an oxide. In other embodiments, the host material is an oxyfluoride. The host lattice material includes a transition metal oxide that is lacking in any electrons in the d orbital ("d electrons") (e.g., a d° transition metal). A transition metal is any of various metallic elements occupying a central block (Groups IVB-VIII, IB, and IIB, or 4- 12) in the periodic table that have valence electrons in two shells instead of only one. The host lattice material may include a counter cation that makes up for charge balancing of the transition metals and the oxygen in the host lattice material. The counter cations may include, but are not limited to, one or more of strontium, calcium, magnesium, barium, yttrium, lanthanum, scandium or gadolinium. Pursuant to some embodiments, the charge balancing counter cation may not be luminescent itself (e.g., this precludes the inclusion of a lanthanide metal such as ytterbium (Yb)). Examples of the host lattice material include, but are not limited to, yttrium niobate (YNbCU), calcium tungstate (CaWC ), yttrium tantalate (YTaC ), calcium titanate (CaTiOs), and other oxides of titanium (Ti4+), tungsten (W6+), niobium (Nb5+), and tantalate (Ta5+).

[0032] Without being bound by any theory, the inventors note the importance of the transition metal lacking d electrons is that this provides for the fostering of metal-to-metal charge transfer transition, which is important for transferring energy from the divalent tin absorber (Sn2+) into the conduction band. MMCT describes electron transfer between metal ions, to generate valence isomers with markedly different electronic configurations. With MMCT, a large fraction of an electronic charge is transferred from one molecular entity, for example ("electron donor") toanother ("electron acceptor"). This MMCT transition sensitizes the Eu3+to produce red photons with high efficiency. Here, the interaction between the Sn2+and the host lattice material with the empty d shell (d°) is the MMCT, where the charge is transferred from Sn2+, for example, to the Nb5+in the host material of YNbCU, for example. This transition of the electron may absorb the 450 nm of radiation output by the blue LED, and then transfer the energy to the Eu3+for emission at around 611nm. The transfer of the energy to the Eu3+may be via a down-conversion process whereby the high energy photons absorbed by the transition are converted into red Eu3+photons with lower energy for a high luminous efficacy white light LED product.

[0033] As shown in the block diagram 200 of FIG. 2, for example, the YNbO4 host lattice material contains Nb5+(4d°), with a conduction band 201 formed by empty Nb 4d orbitals, and a valence band 203 composed of O 2p orbitals. The host lattice material has been doped with Sn2+and Eu3+. The term "doping" refers to adding an amount of an element in a material. Typically, an element in a material is partially or fully replaced by another element on such addition. With the addition of Sn2+(5s2) to the host, the Sn2+5s2band 205 is placed near the top of the O 2p valence band. The application of the blue LED radiation 207 (from a blue LED source 209) to the sensitizer (Sn2+and host lattice material) results in the MMCT, which provides for the absorption of the blue LED radiation, as indicated by 202. The absorbed radiation is then transferred to the Eu3+activator ion, indicated by arrow 204, in a down-conversion process (down arrow 206, showing reduced energy) for red emission from the EU3+, indicated by 208.

[0034] Continuing with the non-exhaustive example of Sn2+and Eu3+doped in the YNbCU compound which contains the Nb5+ion with the 4d° electronic configuration, FIG. 3 is a graph 300 that shows the diffuse reflectance spectrum of pure YNbCU and YNbCU: Sn2+, Eu3+. In the diffuse reflectance spectrum of the doped YNbCU compound 302, a clearbroad absorption band spanning the wavelength range from UV to visible is observed, which is absent in the pure YNbCU compound 304. This band corresponds with the MMCT between the Nb5+of YNbC and Sn2+.

[0035] FIG. 4 provides an excitation spectrum graph 400. The excitation spectrum, shown in the graph 400, while monitoring the Eu3+emission at 615 nm shows the presence of a broad excitation band covering the wavelength range of 450 nm to 600 nm, and peaking near 540 nm, indicated by arrow 402. This band is attributed to the MMCT transition. The presence of the broad excitation band indicates energy transfer to the Eu3+ion and thus sensitization of the Eu3+per the MMCT. Excitation into this band at 510 nm results in Eu3+emission 502, as shown in the emission spectrum graph 500 of FIG. 5.

[0036] The excitation may be provided via a radiationally coupled LED light source. The term "radiationally coupled", as used herein, means that radiation from the LED light source is transmitted to a phosphor and the phosphor emits radiation of a different wavelength. A combination of the light from the LED light source and the light emitted from the phosphor may be used to produce a desired color emission or white light. For example, a lighting device may be based on a blue emitting InGaN LED chip and a phosphor or a blend of phosphors to convert at least some of the blue radiation to another color. One or more embodiments may include an LED light source that emits a wavelength in a range of from about 400-500 nm and may be referred to herein as a "blue" LED. The LED may be operating at about the max temperature of 100 degrees Celsius, and, because of that, the emission output by the sensitized Eu3+may not thermally quench before 100 degrees Celsius.

[0037] The sensitized Eu3+phosphor as described in embodiments may absorb radiation in the spectrum from a wavelength range between about 250 nm and about 575 nm and emits light in a wavelength range from about 580 nm to about 750 nm. It is noted that while the sensitized Eu3+phosphor primarily emits light in a wavelength range from about580 nm to about 750 nm, there may be some emission outside of this range.

[0038] Turning to FIG. 6, a lighting device 60 including a phosphor material radiationally coupled to a light source is provided, according to some embodiments of the present disclosure. The lighting device 60 includes a semiconductor radiation source, shown as a light emitting diode (LED) chip 62 and leads 64 electrically attached to the LED chip 62. The leads 64 may be thin wires supported by a thicker lead frame 66 or the leads may be self-supported electrodes and the lead frame may be omitted. The leads 64 provide current to LED chip 62 and thus cause it to emit radiation.

[0039] The lighting device 60 may include any semiconductor blue or ultraviolet light source that is capable of producing white light when its emitted radiation is directed onto a phosphor material. In one embodiment, the semiconductor light source is a blue emitting LED emitting near 450 nm. The LED chip 62 may comprise a semiconductor diode based on any suitable III-V, II-VI, or IV-IV semiconductor layers and having an emission wavelength of about 250 to about 550 nm. The LED chip 62 may be, for example based on a nitride compound semiconductor of formula IniGajAlkN (where 0 is less than or equal to i; 0 is less than or equal to j; 0 is less than or equal to k and i + j + k =1) having an emission wavelength greater than about 250 nm and less than about 550 nm. More particularly, the LED chip 62 may be a near-UV or blue emitting LED having a peak emission wavelength from about 350 nm to about 500 nm. The radiation source is described herein as an LED for convenience. However, as used herein, the term is meant to encompass all semiconductor radiation sources including, e.g., semiconductor laser diodes. Further, although the general discussion of the exemplary structures of the invention discussed herein is directed toward inorganic LED based light sources, it should be understood that the LED chip may be replaced by another radiation source unless otherwise noted and thatany reference to semiconductor, semiconductor LED, or LED chip is merely representative of any appropriate radiation source, including, but not limited to, organic light emitting diodes.

[0040] In lighting device 60, a layer 63 including a sensitized Eu3+phosphor is disposed on a surface of the LED chip 62, and is radiationally coupled to the chip 62. In one or more embodiments, the layer 63 includes the sensitized Eu3+phosphor that primarily emits in a wavelength range from about 580 nm to about 750 nm, as described herein. The layer 63 can be deposited on the LED 62 by any appropriate method known in the art. For example, a water-based suspension of the phosphor(s) can be formed, and applied as a phosphor layer to the LED surface. In one such method, a silicone slurry in which the phosphor particles are randomly suspended is placed around the LED. This method is merely exemplary of possible positions of the layer 63 and the LED 62. Thus the layer 63 may be coated over or directly on the light emitting surface of the LED chip 62 by coating and drying a phosphor suspension over the LED chip 62. In the case of a silicone-based suspension, the suspension is cured at an appropriate temperature.

[0041] In one or more embodiments, the LED chip 62 may be encapsulated within an envelope 68, which encloses the LED chip 62 and an encapsulant material 70. Both the envelope 68 and the encapsulant material 70 should be transparent to allow emitted light to be transmitted through those elements. The envelope 68 may be, for example, glass or plastic. The LED chip 62 may be enclosed by the encapsulant material 70. The encapsulant material 70 may be a low temperature glass, or a thermoplastic or thermoset polymer, or resin as known in the art, for example, a silicone or epoxy resin. In an alternate embodiment, the lighting device 60 may only comprise the encapsulant material 70 without the envelope 68.

[0042] Various structures of the lighting device 60 are known in the art.For example, in some embodiments, the sensitized Eu3+emittingphosphor 63 (that, in one embodiment, is disposed on a surface of the chip 62 in FIG. 6) may alternatively be interspersed within the encapsulant material 70, as shown in FIG. 7 as 73, instead of being disposed directly on the LED chip 62. The phosphor material 73 (in the form of a powder) may be interspersed within a single region of the encapsulant material 70 or throughout the entire volume of the encapsulant material. Blue light, not shown in FIG. 6, but shown as 74 in FIGS. 7 and 8, emitted by the LED chip mixes with the light emitted by the sensitized Eu3+emitting phosphor 73 to produce desired emission (indicated by arrow 65 in FIGS. 6, 7 and 8). If the phosphor material 73 is to be interspersed within the material of encapsulant 70, then a phosphor powder may be added to a polymer or silicone precursor, and then the mixture may be cured to solidify the polymer or silicone material. Examples of polymer precursors include thermoplastic or thermoset polymers or a resin, for example epoxy resin. Other known phosphor interspersion methods may also be used, such as transfer loading.

[0043] In some other embodiments, the sensitized Eu3+emitting phosphor 63 may be coated onto a surface of the envelope 88, as shown in FIG. 8, instead of being disposed on the LED chip 62. The phosphor material 63 is preferably coated on the inside surface of the envelope 88, although the phosphor may be coated on the outside surface of the envelope 88, if desired. Phosphor material 63 may be coated on the entire surface of the envelope or only a top portion of the surface of the envelope. The UV / blue light emitted by the LED chips 62 mixes with the light emitted by the phosphor material, and the mixed light is emitted in the desired wavelengths. Of course, the phosphor material may be located in any two or all three locations or in any other suitable location, such as separately from the shell or integrated into the LED.

[0044] Another structure (particularly for backlight applications) is a surface mounted device ("SMD") type light emitting diode 900 e.g., asshown in FIG. 9. This SMD is a "side-emitting type" and has a lightemitting window 902 on a protruding portion of a light guiding member 904. An SMD package may comprise an LED chip as described herein, and a phosphor material that includes a coated phosphor according to the present invention. Other backlight device include, but are not limited to, TVs, computers, and hand-held devices such as smartphones and tablet computers.

[0045] Moreover, in some embodiments, a lighting device may include a plurality of LED chips. These various structures discussed with respect to FIGS. 6 / 7 / 8 / 9 may be combined, with sensitized Eu3+emitting phosphor or a blend including the sensitized Eu3+emitting phosphor located in any two or all three locations or in any other suitable location, such as separately from the envelope or integrated into the LED chip. Further, different phosphor blends may be used in different parts of the structure.

[0046] In any of the above structures, the lighting device 60 may also include a plurality of particles (not shown) to scatter or diffuse the emitted light. These scattering particles are generally embedded in the encapsulant 70. The scattering particles may include, for example, particles made from alumina (AI2O3) or titania (TiCh). The scattering particles may effectively scatter the light emitted from the LED chip 62, preferably with a negligible amount of absorption.

[0047] Turning to FIG. 10, a process 1000 for emitting wavelengths in the desired range is provided. The process 1000 may apply to any of the above-described structures. Regarding the lighting devices 60 shown in FIGS. 6, 7, 8, the LED chip 62 emits a light in S1010 at a first wavelength. In one or more embodiments, the light emitted by the LED chip 62 may be in the blue range (e.g., 400 to 470 nm), or any other suitable range. The emitted light having the first wavelength is received and absorbed by the phosphor 63 in S1012. In particular, in one or more embodiments, the Sn2+doped host lattice material ("sensitizer") absorbs one or more photons of light at the first wavelength during the electrontransfer of the MMCT. Then in S1014, the sensitizer transfers the energy of the first wavelength to the Eu3+. Next, the Eu3+down-converts the photon(s) of light from the first wavelength into photons of light having a second wavelength in S1016, wherein the second wavelength is different from the first wavelength. The photons of light having the second wavelength are then emitted from the phosphor at S1018, as indicated by the arrow 65 in FIGS. 6, 7 and 8.

[0048] The flowchart and block diagrams in the Figures illustrate the architecture, functionality, and operation of possible implementations of systems and methods according to various embodiments of the present invention. It should also be noted that, in some alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved.

[0049] This written description uses examples to disclose the invention, including the preferred embodiments, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims. Aspects from the various embodiments described, as well as other known equivalents for each such aspects, can be mixed and matched by one of ordinary skill in the art to construct additional embodiments and techniques in accordance with principles of this application.

[0050] Those in the art will appreciate that various adaptations and modifications of the above-described embodiments can be configured without departing from the scope and spirit of the claims. Therefore, it is to be understood that the claims may be practiced other than as specifically described herein.

[0051] While only certain features of the invention have been illustrated and described herein, many modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.

Claims

WHAT IS CLAIMED IS:

1. A process for synthesizing a sensitized Europium (Eu3+) phosphor, the process comprising : providing a host lattice material composed of an ion with an empty d shell; and doping the host lattice material with an absorber ion and an activator ion.

2. The process of claim 1, wherein the absorber ion is tin (Sn2+) and the activator ion is trivalent Europium (Eu3+).

3. The process of claim 2, wherein the host lattice material is a transition metal with an empty d shell.

4. The process of claim 3, wherein the host lattice material has a band gap from two electron volts (eV) to ten eV.

5. The process of claim 1, wherein the host lattice material is one of yttrium niobate (YNbCU), yttrium tantalate (YTaC ), calcium tungstate (CaWC ), calcium titanate (CaTiOs).

6. The process of claim 2, wherein Sn2+is present in a 0.01-1.00 mole ratio relative to a site in the host lattice material occupied by the Sn2+.

7. The process of claim 1, wherein the synthesized sensitized Eu3+is excitable via a light source emitting wavelengths in a range of about 250 nm to about 575 nm.

8. The process of claim 1, wherein the synthesized sensitized Eu3+phosphor emits red light within a wavelength range of about 580 nm to about 750 nm.

9. A lighting device comprising: an LED light source; and a phosphor radiationally coupled to the LED light source, the phosphor for emitting red light within a wavelength range of about 580 nm to about 750 nm, wherein the phosphor comprises a host lattice material doped with an absorber and an activator ion of Eu3+, wherein the host lattice material is a transition metal with an empty d shell.

10. The lighting device of claim 9, wherein the absorber is Sn2+.

11. The lighting device of claim 9, wherein the host lattice material is an oxide or an oxyfluoride.

12. The lighting device of claim 9, wherein the host lattice material is one of yttrium niobate (YNbC ), yttrium tantalate (YTaC ), calcium tungstate (CaWC ), calcium titanate (CaTiOs).

13. The lighting device of claim 9, wherein the LED light source emits wavelengths in a range of about 250 nm to about 575 nm.

14. The lighting device of claim 13, wherein LED light source emission in the range of about 250 nm to about 575 nm excites the synthesizedsensitized Eu3+to emit red light within the wavelength of 580 nm to 750 nm.

15. A population of sensitized particles, each particle comprising a host lattice material, an absorber ion and an activator ion of Eu3+, wherein the host lattice material is a transition metal with an empty d shell.

16. The population of sensitized particles of claim 15, wherein the particles emit red light within a wavelength range of about 580 nm to about 750 nm.

17. The population of sensitized particles of claim 15, wherein the absorber is Sn2+.

18. The population of sensitized particles of claim 15, wherein the host lattice material is one of yttrium niobate (YNbCU), yttrium tantalate (YTaC ), calcium tungstate (CaWCU), calcium titanate (CaTiOs).

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