Green light-emitting diode using luminophor

FIELD: physics.

SUBSTANCE: described light-emitting diode (LED) contains a crystal (crystals), a conical reflector and luminophor, wherein the crystal emits in the violet spectral range, the luminophor is base on barium-strontium orthosilicate, the reflector has an optimum angle of inclination of walls and height, a polymer layer with the luminophor is deposited on the reflector, as well as on the light-emitting surface of the LED.

EFFECT: highly efficient green LED, with luminous efficacy which is higher than that of traditional green LEDs, is obtained based on the disclosed invention.

6 cl, 1 dwg

 

The technical field.

The proposed invention relates to optoelectronics, in particular to led technology, in particular to a powerful light-emitting diodes (LEDs) green fluorescence signal for indicating and lighting.

The level of technology.

Known DM green emission with a peak wavelength λmax=520-530 nm on the basis of p-n heterostructures in the system InGaAIN (for example types-I, I - see websitewww.optelcenter.ru).These DM are characterized by an external quantum yield of radiation µc=7-13% and light yield µv=30-50 LM/W (with the direct current of 350 mA), which is insufficient for many applications and makes the actual efficiency green led.

Described SD white light (S. Nakamura. The blue lazer diode. Springer Verl., Berlin, 1997), containing radiating crystal blue luminescence-based p-n heterostructures in the system InGaAIN, and inorganic phosphor (LF) on the basis of yttrium aluminium garnet. LF distributed in a transparent polymer, and a layer of LF is close to radiant crystal. The disadvantage of this DM is low efficiency, because a significant part of the radiation LF absorbed radiant crystal and ohmic contacts.

As prototypes can be considered 2 solutions:

- SD white light (J.K. Kim, H. Luo, E.F. Schubert et al. - Jpn. J. Appl. Phys-Express Letter 44,L 649. 2005),where LF is located remotely from the to the of Estella at a distance, greater than the transverse dimensions of the crystal. The design also includes a reflector lateral radiation of the crystal. In this case decreases the probability of a radiation LF on a semiconductor crystal with a low reflectivity that increases the effectiveness of diabetes by about 20-30%.

- SD green glow, in which infrared radiation from a p-n structure in GaAs:Si with wavelength in the maximum radiation λmax=870-950 nm is transformed into green radiation using anti-Stokes LF-based oxysulfide yttrium composition V2O2S: Yb. Er (R.M Potter/ US pat. 35292000 from 15.09.1972). However, this DM has a very low efficiency (luminous efficiency ηV≈0.1-0.2 LM/W) due to the anti-Stokes nature of the radiation conversion.

Disclosure of the invention.

Effective technical solution for creating SD green glow presented in this proposed invention, contains the following main provisions:

- proposed silicate LF-based orthosilicate barium - strontium (stoichiometric formula from Ba1,22Sr0,68Eu0.08Ce0,02.*SiO4to Ba0,08Sr1,050,06Ce0,01*SiO4), activated ions S+and CE3+by changing the ratio of components of BA, Sr, She and Behold possible to change the wavelength LF range 508-540 nm that Zac is ativam green region of the spectrum; the optimum ratio of components BA, Sr, EU and CE in the basis of LF is in the range from 45%:50%:4,5%:0,5% to 55%:42%:2,9%:0,1%, that allows you to get a green luminescence with a wavelength in the maximum range ranges from 520 to 540 nm.

- excitation spectrum of this LF is in the range 385-450 nm, resulting in the excitation of LF have been proposed crystals violet radiation with λmax=395-405 nm on the basis of p-n heterostructures in the system InGaAIN; violet radiation is located on the edge of the visible spectrum, mostly absorbed in LF and does not affect the light emission characteristics of DM in the green region of the spectrum;

in order to reduce radiation losses and efficiency of diabetes around the crystal (crystals) has a conical reflector made of white ceramic or plastic with an angle of inclination of the walls of α=60+5-10the hail; for the surface of the reflector is coated with the layer of polymer dispersed therein silica LF; the thickness of the layer with LF 100±50 μm; the height of the reflector is equal to 2-3 transverse dimensions of the radiating crystal;

the hole of the reflector is completely filled with a transparent polymer with a flat or nearly flat surface, which is applied to the polymer layer with a thickness of 100±50 μm with distributed therein silicate LF;

- used polymer has a refractive index n≥1,5, which increases the output radiation from a crystal;,

- the angle and the receipt of DM with a flat (or nearly flat) light guiding surface is 2θ 0,5=120 deg. When using a hemispherical polymer lens can obtain the angle of radiation in the range of 20-120 degrees. Presents a technical solution allows to obtain the following results:

thanks proposed silicate LF-based orthosilicate barium-strontium, activated ions S2+and CE3+and the choice of the optimal ratio of BA, Sr, Eu and CoE at excitation LF violet radiation with λmax=395-405 nm managed to get effective green glow with λmax=Ranges from 520 to 540 nm;

- by using a given conic reflector made of white material, coated with a polymer distributed therein LF, effectively use side-violet rays of the crystal (crystals), which is converted into green radiation LF; this radiation LF almost misses radiating crystal and not absorbed in it; the white surface of the conical reflector substantially reflects downward green radiation LF, located on the reflector;

green radiation of the upper layer LF, downward, mainly falls on the inclined surface of the reflector and is substantially reflected from its surface; the upper portion of radiation incident on the crystal (crystals), does not exceed 5% and, therefore, the absorption of green radiation LF crystal slightly; violet is the first radiation of the crystal, not absorbed in the upper layer LF and reflected down converted to green radiation LF, located on the reflector.

In the above created high-performance SD green glow with a luminous efficacy of 80 lumens/watt.

The implementation of the invention.

The basic design SD green radiation shown in the drawing, where 1-radiating crystal, 2-reflector inner diameter d outer diameter D, height h and angle α walls, 3 - layer polymer with LF, 4-transparent polymer, 5 - base.

Applied radiant crystal violet radiation type SL-V-U40AC firm "SemiLEDs" size of 1.07×1,07 mm wavelength 395-405 nm and radiation power 350-370 mW at a current of 350 mA.

The conical reflector is made of white ceramic and had the following dimensions: d=1.9 mm, D=8 mm, α=56 degrees and h=2 mm

As the polymer used clear silicone type LPS-5544 company Shin Etsu with a refractive index n=1,53-1,54. As LF is used silicate LF the above composition.

Described DM type-F-I.

Received DM had the following main parameters:

The emission spectrum has a major green band with λmax=525 nm and full width at half maximum of 72 nm. There is also a small strip violet radiation with λmax=401 nm and a width of 14 nm.

The coordinates of the chromaticity of the radiation was:

x=0,3-0,32, y=0,58-0,61, which corresponds to the green part of the graph of the ice 1931

Luminous flux green emission at a current of 350 mA was 80-90 LM, and the luminous efficiency was ηv=70-80 LM/W. These values are significantly higher than the "traditional" green LEDs with crystal from InGaAIN (ηvless than 50 lumens/watt). Axial force of light was 25-30 KD at an angle radiation 2θ0,5=120 degrees.

The design of the led type U-F AND where additionally used hemispherical lens 0 18 mm, the power light was 35-40 KD at an angle radiation 2θ0,5≈80 degrees and 130-140 KD at 2θ0,5≈20-30 degrees.

Thus, the proposed technical solution has allowed us to create high-performance SD green glow using LF, far exceeding in terms of luminous efficiency, and other light options "traditional" SD green glow.

1. Led green fluorescence using a phosphor containing radiating crystal (crystals) from InGaAIN, conical reflector and a phosphor that is located remotely from the crystal (crystals), characterized in that the crystal (crystals), radiates in the violet region of the spectrum, the phosphor is made on the basis of orthosilicate barium-strontium-activated ion S2+and CE3+, reflector made of white material with an angle of inclination of the walls 60+5-10° and a height equal to 2-3 cross the th size of the crystal, on the walls of the reflector is coated with the layer of transparent polymer with a thickness of 100±50 μm with distributed therein a phosphor, the hole of the reflector is completely filled with a transparent polymer with a flat or nearly flat surface, which is applied to the polymer layer with a thickness of 100±50 μm with distributed therein a phosphor.

2. Led green fluorescence using a phosphor according to claim 1, characterized in that the wavelength of the violet rays of the crystal-based p-n heterostructures InGaAIN is in the range 395-405 nm.

3. Led green fluorescence using a phosphor according to claim 1, characterized in that the optimum ratio of components BA, Sr, Eu and CE based phosphor is 45%:50%:4,5%:0,5% to 55%:42%:2,9%:0,1%, that allows you to get a green glow with λmaxin the range ranges from 520 to 540 nm.

4. Led green fluorescence using a phosphor according to claim 1, characterized in that the applied polymer has a refractive index of n>1,5.

5. Led green fluorescence using a phosphor according to claim 1, characterized in that the conical reflector is made of white ceramic and white plastic.

6. Led green fluorescence using a phosphor according to claim 1, characterized in that when using the polymer of the hemispherical lens beam angle 2θ0,5may vary in the range of 20-120°.



 

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