QUANTUM DOT LIGHT EMITTING MATERIAL AND DIFFUSION PLATE COMPRISING THE SAME

Abstract

A quantum dot light emitting material is provided, which includes: a core including an inorganic oxide; and a quantum dot layer covering the core and including perovskite quantum dots. In addition, a diffusion plate including the aforesaid quantum dot light emitting material is also provided.

Claims

1. A quantum dot light emitting material, comprising: a core comprising an inorganic oxide; and a quantum dot layer covering the core and comprising perovskite quantum dots.

2. The quantum dot light emitting material of claim 1, wherein the inorganic oxide is silica, titania, silica-titania, zinc oxide, zirconia, alumina or a combination thereof.

3. The quantum dot light emitting material of claim 2, wherein the inorganic oxide is silica.

4. The quantum dot light emitting material of claim 3, wherein the inorganic oxide is fumed silica.

5. The quantum dot light emitting material of claim 1, wherein the perovskite quantum dots are organic metal halides, inorganic metal halides, or a combination thereof.

6. The quantum dot light emitting material of claim 5, wherein the perovskite quantum dots are inorganic metal halides.

7. The quantum dot light emitting material of claim 6, wherein the inorganic metal halides are represented by the following formula (I):
Cs.sub.a(Pb.sub.1-dM′.sub.d).sub.bX.sub.c  (I) wherein each X is independently Cl, Br or I, M′ is Sn, Ge or a combination thereof, a is an integer from 1 to 7, b is an integer from 1 to 4, c is an integer from 3 to 9, and d is between 0 to 0.9.

8. The quantum dot light emitting material of claim 6, wherein the inorganic metal halides are represented by the following formula (II):
Cs.sub.aPb.sub.bX.sub.c  (II) wherein each X is independently Cl, Br or I, a is an integer from 1 to 7, b is an integer from 1 to 4, and c is an integer from 3 to 9.

9. The quantum dot light emitting material of claim 8, wherein the inorganic metal halides are CsPbBr.sub.3.

10. The quantum dot light emitting material of claim 1, further comprising a protection layer covering the quantum dot layer.

11. The quantum dot light emitting material of claim 10, wherein the protection layer comprises an inorganic oxide, an organic polymer or a combination thereof.

12. The quantum dot light emitting material of claim 11, wherein the protection layer comprises the inorganic oxide.

13. The quantum dot light emitting material of claim 12, wherein the inorganic oxide is aluminum oxide.

14. A diffusion plate, comprising: a substrate; and a quantum dot light emitting material dispersed in the substrate and comprising: a core comprising an inorganic oxide; and a quantum dot layer covering the core and comprising perovskite quantum dots.

15. The diffusion plate of claim 14, further comprising: diffusion particles dispersed in the substrate.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0030] FIG. 1 is a schematic diagram of a quantum dot light emitting material according to Embodiment 1 of the present invention.

[0031] FIG. 2 is a schematic diagram of another quantum dot light emitting material according to Embodiment 1 of the present invention.

[0032] FIG. 3 is a schematic cross-sectional view of a quantum dot film used in Test example 1 of the present invention.

[0033] FIG. 4 is a schematic cross-sectional view of a light emitting diode device according to Embodiment 2 of the present invention.

[0034] FIG. 5 is a graph showing the measurement results of the luminous intensity maintenance rates of the light emitting diode devices of Embodiment 2 and Comparative embodiment in Test example 2 of the present invention.

[0035] FIG. 6 is a graph showing measurement results of luminous intensity and temperature change of the light emitting diode devices of Embodiment 2 and Comparative embodiment in Test example 3 of the present invention.

[0036] FIG. 7 is a schematic cross-sectional view of a diffusion plate according to one embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0037] Different embodiments of the present invention are provided in the following description. These embodiments are meant to explain the technical content of the present invention, but not meant to limit the scope of the present invention. A feature described in an embodiment may be applied to other embodiments by suitable modification, substitution, combination, or separation.

[0038] It should be noted that, in the present specification, when a component is described to have an element, it means that the component may have one or more of the elements, and it does not mean that the component has only one of the element, except otherwise specified.

[0039] In the present specification, except otherwise specified, the feature A “or” the feature B means the existence of the feature A or the existence of the feature B. The feature A “and/or” the feature B means the existence of the feature A, the existence of the feature B, or the existence of both the features A and B. The feature A “and” the feature B means the existence of both the features A and B. The term “comprise(s)”, “comprising”, “include(s)”, “including”, “have”, “has” and “having” means “comprise(s)/comprising but is/are/being not limited to”.

[0040] Moreover, in the present specification, the terms, such as “on”, “above”, “under”, “below”, or “between”, are used to describe the relative positions among a plurality of elements, and the described relative positions may be interpreted to include their translation, rotation, or reflection.

[0041] Furthermore, except otherwise specified, the terms recited in the specification and the claims such as “above”, “over”, or “on” are intended not only directly contact with the other element, but also intended indirectly contact with the other element. Similarly, the terms recited in the specification and the claims such as “below”, or “under” are intended not only directly contact with the other element but also intended indirectly contact with the other element.

[0042] In the present specification, the terms “almost”, “about” and “approximately” mean within ±20%, within ±10%, within ±5%, within ±3%, within ±2%, within ±1%, or within ±0.5% of a given value or range. The quantity given here is an approximate quantity, that is, without specifying “almost”, “about” and “approximately”, it can still imply “almost”, “about” and “approximately”.

[0043] In the present specification, except otherwise specified, the terms (including technical and scientific terms) used herein have the meanings generally known by a person skilled in the art. It should be noted that, except otherwise specified in the embodiments of the present invention, these terms (for example, the terms defined in the generally used dictionary) should have the meanings identical to those known in the art, the background of the present invention or the context of the present specification, and should not be read by an ideal or over-formal way.

Embodiment 1

[0044] 1 mmol of CsBr and 1 mmol of PbBr.sub.2 were dissolved in 50 ml of dimethyl sulfoxide (DMSO), followed by adding 100 μl of hexadecyltrimethoxysilane (HDTMS). After mixing and stirring for 1 hour, 0.5 g of fumed silica was added, followed by stirring. After mixing and stirring for 1 hour, the mixture was placed at 150° C. for evaporating the organic solvent DMSO and drying to form the perovskite quantum dot light emitting material of the present embodiment.

[0045] After the aforesaid process, the quantum dot light emitting material of the present embodiment was obtained.

[0046] FIG. 1 and FIG. 2 are schematic diagrams of the quantum dot light emitting material of the present embodiment. As shown in FIG. 1, the quantum dot light emitting material 1 of the present embodiment comprises: a core 11 comprising an inorganic oxide; and a quantum dot layer 12 covering the core 11 and comprising perovskite quantum dots. In the present embodiment, the core 11 is a core formed by fumed silica, which has an irregular shape, and the average diameter of the core 11 is about 10 nm to 300 nm. In addition, in the present embodiment, the quantum dot layer 12 directly covers the surface 111 of the core 11. More specifically, the quantum dot layer 12 directly covers the unmodified surface 111 of the core 11. Furthermore, the quantum dot layer 12 is consisted of CsPbBr.sub.3 quantum dots. More specifically, the quantum dot layer 12 is consisted of CsPbBr.sub.3 quantum dot particles, and the average particle size of the CsPbBr.sub.3 quantum dot particles is about 1 nm to 50 nm.

[0047] In addition to the core 11 and the quantum dot layer 12, the quantum dot light emitting material 1 of the present embodiment further comprises a protection layer 13 covering the quantum dot layer 12. In the present embodiment, the protection layer 13 is an aluminum oxide layer, which may completely cover the whole surface of the quantum dot layer 12 to protect the quantum dot layer 12.

[0048] In the present embodiment, the protection layer 13 may cover one core 11 coated with the quantum dot layer 12, as shown in FIG. 1; and may also cover plural cores 11 coated with the quantum dot layers 12, as shown in FIG. 2.

[0049] As mentioned above, the perovskite quantum dot light emitting material of the present embodiment can be prepared by using a perovskite quantum dot precursor as a raw material and combining an inorganic oxide material (fumed silica in the present embodiment) and a dispersant, and the perovskite quantum dots can be directly deposited on the surface of the inorganic oxide. Thus, the quantum dot light emitting material of the present embodiment can be synthesized in one step. However, in the conventional methods of synthesizing quantum dots, no matter the conventional CdSe core-shell quantum dots or perovskite quantum dots, they all need to be prepared through complicated heat injection and reaction procedures. In addition, the concentration of the reactants, and the time and temperature of reaction have to be precisely controlled to control the particle size of quantum dots; and if there is a slight difference, the luminescent wavelength will change, making the yield difficult to control.

[0050] In addition, the light emitting structure of the previously synthesized CdSe core-shell quantum dots or perovskite quantum dots has to be stabilized by the ligands absorbed on the surface of the quantum dots. However, once exposed to light or thermal reaction, the ligands on the surface of the quantum dots are easy to fall off, resulting in a light quenching effect, which causes a significant decrease in luminous efficiency. In the perovskite quantum dot light emitting material of the present embodiment, the perovskite quantum dots are not formed on the inorganic oxide material through ligands, but the perovskite quantum dots are directly formed on the inorganic oxide material. In addition, when the protection layer is further formed on the perovskite quantum dot layer, the light stability of the formed perovskite quantum dot material can be improved.

Test Example 1

[0051] FIG. 3 is a schematic cross-sectional view of the quantum dot film used in Test example 1 of the present invention. In the present test example, the quantum dot film comprises: a substrate 33; and a quantum dot light emitting material 1 dispersed in the substrate 33. Herein, the quantum dot light emitting material 1 may be the quantum dot light emitting material 1 prepared in Embodiment 1, and the substrate 33 may be prepared by UV gel. After the quantum dot light emitting material 1 was dispersed in the material of the substrate 33 and curing, the quantum dot film used in the present test example can be obtained, which has a thickness of 100 μm.

[0052] The quantum dot film was irradiated with a strong blue light source (100 mW/cm.sup.2), the distance between the light source and the quantum dot film was 1 cm, and the irradiation continued for 100 hours. The result shows that the quantum yield (QY) of the quantum dot film prepared by using the quantum dot light emitting material 1 prepared in Embodiment 1 was only decreased by 5%. However, the quantum yield of the quantum dot film prepared by using the perovskite quantum dots (containing ligands on the surface) synthesized by the conventional thermal injection method was decreased by 65%. This result indicates that the quantum dot light emitting material prepared in Embodiment 1 has good stability to high blue light intensity.

Embodiment 2

[0053] FIG. 4 is a schematic cross-sectional view of a light emitting diode device according to the present embodiment. As shown in FIG. 4, the light emitting diode device of the present embodiment comprises: a light emitting diode chip 21, wherein two electrodes 22 are respectively disposed on a surface of the light emitting diode chip 21; and a light emitting layer 23 disposed on the surfaces of the light emitting diode chip 21 without the electrodes 22 disposed thereon. Herein, the light emitting layer 23 can be prepared by mixing silicone and the quantum dot light emitting material 1 prepared in Embodiment 1, followed by applying on the surfaces of the light emitting diode chip 21.

[0054] In other embodiments of the present invention, the quantum dot light emitting material 1 prepared in Embodiment 1 may be directly formed on the surfaces of the light emitting diode chip 21 without using silicone.

Comparative Embodiment

[0055] The light emitting diode device of the present comparative embodiment is similar to that of Embodiment 2, except for using different quantum dot light emitting material. In the present comparative embodiment, the structure of the quantum dot light emitting material is similar to those shown in FIG. 1 and FIG. 2, except that the quantum dot layer 12 does not comprise perovskite quantum dots, but includes CsSe/ZnS core-shell quantum dots, which are adsorbed on the core 11 of fumed silica by thermal injection.

Text Example 2

[0056] The light emitting diode devices prepared in Embodiment 2 and Comparative embodiment were tested for luminescence lifetime with a test current of 20 mA, and the results are shown in FIG. 5. The testing results show that the luminous intensity of the light emitting diode device of Embodiment 2 has a maintenance rate of 80% after 1,000 hours. However, for the luminous intensity of the light emitting diode device of Comparative embodiment, the luminous intensity maintenance rate drops to 80% in the first 100 hours, and only 40% after 500 hours. The results indicate that the light emitting diode device prepared by using the perovskite quantum dot light emitting material prepared in Embodiment 1 has excellent operation life stability.

Text Example 3

[0057] The light emitting diode devices prepared in Embodiment 2 and Comparative embodiment were heated and cooled, their luminous intensity was measured, and the results are shown in FIG. 6. The test results show that the light emitting diode device of Embodiment 2 (abbreviated as Ex 2) has temperature reversibility, and the luminous intensity does not change significantly by the back-and-forth operation of the temperature, which means that the quantum dot light emitting material prepared in Embodiment 1 is not deteriorated by the back-and-forth operation of the temperature. However, when the light emitting diode device of Comparative embodiment (abbreviated as Comp Ex) was heated up to 140 degrees, the relative luminous intensity is only 3%, and the original luminous intensity cannot be restored after cooling down. These results indicate that the light emitting diode device prepared by the perovskite quantum dot light emitting material prepared in Embodiment 1 has excellent high-temperature performance.

[0058] FIG. 7 is a schematic cross-sectional view of a diffusion plate according to one embodiment of the present invention.

[0059] As shown in FIG. 7, the diffusion plate of the present embodiment comprises: a substrate 32; the quantum dot light emitting material 1 of Embodiment 1 dispersed in the substrate 32; and diffusion particles 31 dispersed in the substrate 32.

[0060] In the present invention, by providing a quantum dot light emitting material with a novel structure, the luminous efficiency of the quantum dots can be effectively improved, especially the luminous efficiency of the perovskite quantum dots can be improved, so that the application field of the perovskite quantum dots can be extended.

[0061] In the present invention, as long as the features of the various embodiments do not violate the spirit of the invention or conflict, they can be mixed and matched arbitrarily.

[0062] Although the present invention has been explained in relation to its embodiment, it is to be understood that many other possible modifications and variations can be made without departing from the spirit and scope of the present invention as hereinafter claimed.

[0063] In addition, the above-mentioned embodiments are only examples for convenience of description, and the scope claimed by the present invention shall be subject to the claims of the patent application, rather than limited to the above-mentioned embodiments.