TWI853709B - Quantum dot structure, forming method thereof and light emitting device including the same - Google Patents

Abstract

The disclosure relates to a quantum dot structure. The quantum dot structure includes a quantum dot and a third shell covering at least a portion of the quantum dot and having an irregular outer surface. The quantum dot includes: a core; a first shell discontinuously around a core surface of the core; and a second shell between the core and the first shell and covering the core surface of the core, wherein the second shell has an irregular outer surface.

Description

Quantum dot structure, method for forming the same and light-emitting device comprising the same

The present disclosure relates to a quantum dot structure, a method for forming the same and a light-emitting device including the same, and in particular to a quantum dot structure with excellent water and oxygen resistance, a method for forming the same and a light-emitting device including the same.

Quantum dots (QDs) are nanoscale semiconductor materials. Quantum dots usually have a spherical or quasi-spherical crystal structure formed by about hundreds of atoms to about thousands of atoms. Quantum dots are a wavelength conversion material that has the advantage of high color saturation, so they have great advantages in wide color gamut display technology.

However, quantum dots are easily oxidized in an environment containing water and oxygen. The oxidation of quantum dots will lead to problems such as wavelength shift of the emission, widening of the half-width of the emission spectrum, and quantum efficiency attenuation. Therefore, there is still a need in the field to find a quantum dot structure with better resistance or tolerance to oxygen or water vapor.

In view of the above needs, the present disclosure provides a quantum dot structure with better barrier or tolerance to oxygen or water vapor.

Some embodiments of the present disclosure provide a quantum dot structure, which includes a quantum dot and a third shell that covers at least a portion of the quantum dot and has an irregular outer surface. The quantum dot includes: a core; a first shell that is discontinuously located around the core surface of the core; and a second shell that is located between the core and the first shell and covers the core surface, wherein the second shell has an irregular outer surface.

In some embodiments of the present disclosure, the projection of the quantum dot on a plane has a maximum width in a first direction and a maximum length in a second direction perpendicular to the first direction. The projection of the third housing on the plane overlaps with the projection of the quantum dot on the plane with an overlapping area, wherein the overlapping area satisfies the following formula: ≧Overlapping area≧ , wherein the extension direction of the maximum diameter of the quantum dot is defined as the first direction, the direction perpendicular to the first direction is defined as the second direction, and the first direction and the second direction constitute this plane.

In some embodiments of the present disclosure, there is a gap between the third housing and the first housing, and there is a gap between the third housing and the second housing.

In some embodiments of the present disclosure, the first housing, the second housing, and the third housing include the same material.

In some embodiments of the present disclosure, the outer surface of the third shell has a different surface profile from the outer surface of the second shell.

In some embodiments of the present disclosure, the outer surface of the second shell is a concave-convex outer surface. There is a height difference between the highest point and the lowest point of the concave-convex outer surface, and the height difference is greater than 0 nm and less than or equal to 5 nm.

In some embodiments of the present disclosure, the concave-convex outer surface has at least one concave portion, the concave portion has a concave width, and the concave width is greater than 0 nm and less than or equal to 10 nm.

In some embodiments of the present disclosure, the first shell may include a plurality of shell particles.

In some embodiments of the present disclosure, some of the plurality of particles are stacked on top of each other.

In some embodiments of the present disclosure, the quantum dot structure may further include ligands located on the surface of the first shell, the second shell, and/or the third shell.

Some embodiments of the present disclosure provide a method for forming a quantum dot structure, which includes: providing a quantum dot core solution, the quantum dot core solution including a plurality of cores; providing a shell precursor solution to mix with the quantum dot core solution to form a quantum dot precursor solution; heating the quantum dot precursor solution at a first temperature to form a quantum dot solution. The quantum dot solution includes quantum dots having a first shell and a second shell on the core surface of the core, wherein the first shell is formed discontinuously around the core surface, the second shell is formed between the core and the first shell and covers the core surface, and the second shell has an irregular outer surface; and continuously stirring the quantum dot solution at a second temperature to form a quantum dot structure including quantum dots and a third shell covering at least a portion of the quantum dots, wherein the second temperature is greater than or equal to the first temperature.

In some embodiments of the present disclosure, in the step of providing a shell precursor solution to a quantum dot core solution, the shell precursor solution is introduced into the quantum dot core solution at an introduction rate of 0.016 to 1.6 equivalents/minute (eq/min), with the core content in the quantum dot core solution being taken as 1 equivalent.

In some embodiments of the present disclosure, the third housing has an irregular outer surface.

In some embodiments of the present disclosure, the second temperature is greater than or equal to 250° C. and less than or equal to 310° C.

In some embodiments of the present disclosure, the step of providing a shell precursor solution to a quantum dot core solution includes: introducing a first shell precursor solution at a first introduction rate; and introducing a second shell precursor solution at a second introduction rate, wherein the core content in the quantum dot core solution is taken as 1 equivalent, the first introduction rate is 0.016~1.6 eq/min, the second introduction rate is 0.016~1.6 eq/min, and the first introduction rate is greater than or equal to the second introduction rate.

In some embodiments of the present disclosure, a purification process is further performed after forming a plurality of quantum dot structures.

Some embodiments of the present disclosure provide a light-emitting device, comprising: a light source that emits a first light ray; and a wavelength conversion unit that absorbs a portion of the first light ray and converts it into a second light ray, wherein the wavelength conversion unit includes the above-mentioned quantum dot structure.

According to the above-mentioned embodiments of the present disclosure, the quantum dot structure of the present disclosure includes quantum dots and a third shell that covers at least a portion of the quantum dots and has an irregular outer surface. Through the above-mentioned structure, the quantum dot structure of the present disclosure can have a higher barrier or better tolerance to destructive factors in the environment, such as water, oxygen or free radicals, and thus can have better reliability or longer luminescence life. The method for forming the quantum dot structure of the present disclosure can form a quantum dot structure with better reliability or longer luminescence life, and the light-emitting device including the above-mentioned quantum dot structure can also have better reliability or longer luminescence life.

The following disclosure provides many different embodiments or examples to implement different features of the present invention. The following disclosure describes specific examples of each component and its arrangement to simplify the description. Of course, these specific examples are not intended to be limiting. For example, if the disclosed embodiment describes that a first feature component is formed on or above a second feature component, it means that it may include an embodiment in which the first feature component and the second feature component are in direct contact, and it may also include an embodiment in which an additional feature component is formed between the first feature component and the second feature component, so that the first feature component and the second feature component may not be in direct contact.

It should be understood that additional operating steps may be implemented before, during or after the method, and in other embodiments of the method, some operating steps may be replaced or omitted.

In addition, spatially related terms may be used, such as "under", "below", "down", "above", "above", "upper", and similar terms. These spatially related terms are used to facilitate the description of the relationship between one (or some) elements or features and another (or some) elements or features in the diagram. These spatially related terms include different orientations of the device in use or operation, as well as the orientations described in the drawings. When the device is turned to a different orientation (for example, rotated 90 degrees or other orientations), the spatially related adjectives used therein will also be interpreted according to the orientation after the rotation.

In the specification, the terms "about", "approximately", and "substantially" usually mean within 20%, or within 10%, or within 5%, or within 3%, or within 2%, or within 1%, or within 0.5% of a given value or range. The quantities given here are approximate quantities, that is, in the absence of specific description of "about", "approximately", and "substantially", the meaning of "about", "approximately", and "substantially" can still be implied. In the specification, the expression "a~b" means that the range includes values greater than or equal to a and values less than or equal to b.

Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. It is understood that these terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning consistent with the background or context of the relevant technology and this disclosure, and should not be interpreted in an idealized or overly formal manner unless specifically defined in the embodiments of this disclosure.

Different embodiments disclosed below may repeatedly use the same reference symbols and/or labels. These repetitions are for the purpose of simplicity and clarity, and are not intended to limit the specific relationship between the different embodiments and/or structures discussed.

Some embodiments of the present disclosure provide a method for forming a quantum dot structure. The method for forming a quantum dot structure of the present disclosure includes: providing a quantum dot core solution including a plurality of cores; providing a shell precursor solution to mix with the quantum dot core solution to form a quantum dot precursor solution; heating the quantum dot precursor solution at a first temperature to form a quantum dot solution including a plurality of quantum dots, wherein the quantum dots include a first shell formed discontinuously around the core surface on the core surface, and a second shell formed between the core and the first shell to cover the core surface and having an irregular outer surface; and continuously stirring the quantum dot solution at a second temperature to form a quantum dot structure, wherein the quantum dot structure has quantum dots and a third shell covering at least a portion of the quantum dots, and the second temperature is greater than or equal to the first temperature. FIG. 1 shows a flow chart of a method 1 for forming a quantum dot structure according to some embodiments of the present disclosure. As shown in FIG. 1 , the method 1 for forming a quantum dot structure includes: step S101 of providing a quantum dot core solution, step S103 of providing a shell precursor solution and mixing it with the quantum dot core solution to form a quantum dot precursor solution, step S105 of heating the quantum dot precursor solution at a first temperature to form a quantum dot solution, and step S107 of stirring the quantum dot solution at a second temperature.

In step S101, the quantum dot nucleus solution provided includes a plurality of nuclei. In some embodiments, the step S101 of providing a quantum dot nucleus solution includes the steps of mixing a first nucleus precursor solution and a second nucleus precursor solution to form a nucleus precursor mixed solution and heating the nucleus precursor mixed solution to form a nucleus. In some embodiments, the first nucleus precursor solution and the second nucleus precursor solution may include any material that can form a nucleus including an inorganic conductor material or an inorganic semiconductor material after mixing and heating. In some embodiments, the first nucleus precursor solution and/or the second nucleus precursor solution may include an inorganic semiconductor material of group II, group III, group IV, group V, group VI, or a combination thereof. The heating temperature may be between 170°C and 270°C.

In step S103, a shell precursor solution is provided to the quantum dot core solution obtained from the above step S101, so that the shell precursor solution is mixed with the quantum dot core solution to form a quantum dot precursor solution. In some embodiments, the shell precursor solution may include a material that can subsequently form a shell. The shell may include a shell that encapsulates the core in the quantum dot core solution (i.e., the first shell and the second shell described below) and a third shell that encapsulates at least a portion of the quantum dots including the first shell, the second shell, and the core. The shell has a material that is the same as or has a more lattice-matched material with the core in the quantum dot core solution. In some embodiments, the shell precursor solution may include an inorganic semiconductor material of Group II, Group III, Group IV, Group V, Group VI, or a combination thereof. The equivalent ratio of the quantum dot core solution to the shell precursor solution may be about 1:100 to 1:1. In some embodiments, the step of providing a shell precursor solution and mixing the quantum dot core solution to form a quantum dot precursor solution in step S103 includes slowly introducing the shell precursor solution into the quantum dot core solution obtained from the above step S101 with an introduction time of about 1 to 2 hours. Taking the core content in the quantum dot core solution as 1 equivalent, the introduction rate of the shell precursor solution is about 0.016 to 1.6 equivalents/minute (eq/min). In some embodiments, the introduction rate of the shell precursor solution is about 0.05-1.6 eq/min, about 0.06-1.6 eq/min, about 0.05-1.55 eq/min, about 0.06-1.55 eq/min, about 0.05-1.5 eq/min, or about 0.06-1.5 eq/min. When the introduction rate of the shell precursor solution is about 0.016-1.6 eq/min, the molecules in the shell precursor solution and the quantum dot core solution have an appropriate reaction time, so that the molecules can form irregular shells (such as the second shell and the third shell described below) in the subsequent stage by the attraction and repulsion between each other, while maintaining the luminescence characteristics of the quantum dots. When the introduction rate is less than about 0.016 eq/min, the reaction time between the molecules in the shell precursor solution and the quantum dot core solution is too long, so the molecules are easily formed into bulk materials, causing the quantum dot structure formed subsequently to lose its luminescence properties. When the introduction rate is greater than about 1.6 eq/min, the interaction between the molecules in the shell precursor solution and the quantum dot core solution and the growth rate of the shell are unbalanced, so that the shell formed in the subsequent stage will have a larger shell gap and cannot be gathered around the core, so it is impossible to form a quantum dot structure that can have a higher barrier or better tolerance to destructive factors in the environment.

In some embodiments, the shell precursor solution may include a first shell precursor solution and a second shell precursor solution. In some embodiments, the equivalent ratio of the first shell precursor solution to the second shell precursor solution may be 1:1. In some embodiments, step S103 may include introducing the first shell precursor solution at a first introduction rate, and introducing the second shell precursor solution at a second introduction rate. Taking the core content in the quantum dot core solution as 1 equivalent, the first introduction rate is about 0.016~1.6 eq/min, the second introduction rate is about 0.016~1.6 eq/min, and the first introduction rate is greater than or equal to the second introduction rate. In some embodiments, the first introduction rate may be about 0.1-1.6 eq/min, about 0.15-1.6 eq/min, about 0.2-1.6 eq/min, about 0.3-1.6 eq/min, about 0.15-1.55 eq/min, about 0.2-1.55 eq/min, about 0.3-1.55 eq/min, about 0.15-1.5 eq/min, about 0.2-1.5 eq/min, or about 0.3-1.5 eq/min. In some embodiments, the second introduction rate may be about 0.05-1.3 eq/min, about 0.05-1.2 eq/min, about 0.05-1.0 eq/min, about 0.06-1.3 eq/min, about 0.06-1.2 eq/min, or about 0.06-1.0 eq/min. In some embodiments, the second shell precursor solution may be introduced after the first shell precursor solution, and the first introduction rate is greater than or equal to the second introduction rate. In some embodiments, the second shell precursor solution may be introduced twice, wherein the first shell precursor solution is introduced between the two second shell precursor solutions, and the first introduction rate is greater than or equal to the second introduction rate. In some embodiments, the first shell precursor solution and/or the second shell precursor solution may include a material that can subsequently form a shell. The shell may include a shell that encapsulates a core in a quantum dot core solution and a third shell that encapsulates at least a portion of the quantum dots including the shell and the core. The shell has a material that is the same as or has a more lattice-matched core in the quantum dot precursor solution. In some embodiments, the first shell precursor solution and/or the second shell precursor solution may include an inorganic semiconductor material of Group II, Group III, Group IV, Group V, Group VI, or a combination thereof.

In step S105, the quantum dot precursor solution obtained from step S103 is heated at a first temperature to form a quantum dot solution including a plurality of quantum dots. In some embodiments, the first temperature is greater than or equal to 250° C. and less than or equal to 310° C. The quantum dots formed in step S105 are quantum dots having a core-shell structure. The core of the quantum dot has a first shell and a second shell on the core surface, wherein the first shell is discontinuously formed around the core surface, the second shell is formed between the core and the first shell and covers the core surface, and the second shell has a continuous and irregular outer surface. In some embodiments, the quantum dots formed in step S105 have a core-shell structure as shown in FIG. 2.

FIG. 2 is a schematic diagram of a quantum dot 20 according to some embodiments of the present disclosure. As shown in FIG. 2, the quantum dot 20 has a core 201, a first shell 205, and a second shell 203. The core 201 has a core surface 2011, and the first shell 205 and the second shell 203 are located on the core surface 2011. The first shell 205 is discontinuously distributed around the core surface 2011. The second shell 203 has a continuous and irregular outer surface 2031, which is formed between the core 201 and the first shell 205 and covers the core surface 2011.

The core 201 is the light-emitting core of the quantum dot 20. In some embodiments, the average diameter of the core 201 is greater than or equal to 9 nm and less than or equal to 20 nm. In some embodiments, the core 201 can be made of an inorganic conductive material or an inorganic semiconductor material. Examples of inorganic semiconductor materials may include, but are not limited to, semiconductor materials of Group II-VI, Group III-V, Group IV-VI, and/or Group IV, and specific examples thereof may include, but are not limited to, CdSe, CdTe, ZnS, ZnSe, ZnTe, ZnO, HgS, HgSe, HgTe, CdSeS, CdSeTe, CdSTe, ZnSeS, ZnSeTe, ZnSTe, HgSeS, HgSeTe, HgSTe, CdZnS, CdZnSe, CdZnTe, CdHgS, CdHgSe, CdHgTe, HgZnS, HgZnSe, HgZnTe, CdZnSeS, CdZnSeTe, CdZnSTe, CdHgSeS, CdHgSeTe, CdHgSTe, HgZnSeS, HgZnSeTe, HgZnSTe, GaN, GaP, GaAs, GaSb, AlN, AlP, AlAs, AlSb, InN, InP, InAs, InSb, GaNP, GaNAs, GaNSb, GaPAs, GaPSb, AlNP, AlNAs, Al NSb, AlPAs, AlPSb, InNP, InNAs, InNSb, InPAs, InPSb, GaAlNP, GaAlNAs, GaAlNSb, GaAlPAs, GaAlPSb, GaInNP, GaInNAs, GaInNSb, GaInPAs, GaInPSb, InAlNP, InAlNAs, InAlNSb, InAlPAs, InAlPSb, SnS, SnSe, SnTe, PbS, PbSe, PbTe, SnSeS, SnSeTe, SnSTe, PbSeS, PbSeTe, PbSTe, SnPbS, SnPbSe, SnPbTe, SnPbSSe, SnPbSeTe, SnPbSTe, _CsPbX3 or _Cs4PbX6 , wherein X is chlorine, bromine, iodine or _a combination thereof.

In some embodiments, the second shell 203 covers the core 201 and is in direct contact with the core surface 2011 of the core 201, but the present disclosure is not limited thereto. In some embodiments, there is a gap between the second shell 203 and the core 201 and the second shell 203 is not in direct contact with the core surface 2011 of the core 201. The second shell 203 has an irregular concave-convex outer surface. In other words, the second shell 203 has a plurality of regions with uneven thickness, wherein the region where the thickness of the second shell 203 gradually decreases is defined as a recessed portion, and the region or point with the thinnest thickness in the recessed portion is defined as the bottom of the recessed portion. The thickness range of the second shell 203 is greater than or equal to 0 nm and less than or equal to 5 nm. An area with a thickness of 0 nm in the second shell 203 indicates that the second shell 203 does not exist in the area. Therefore, the core surface 2011 corresponding to the area is not covered by the second shell 203 and is exposed to the outside. In some embodiments, the second shell is greater than or equal to 0 nm and less than or equal to 4 nm, or greater than 0 nm and less than or equal to 3 nm. In some embodiments, the second shell 203 has at least one recessed portion. The recessed portion has a recessed width w, as shown in Figure 2. In some embodiments, the recessed width w is also equivalent to the distance between the two tops in an area of the second shell 203 (the top here refers to the second shell 203, where the thickness of both sides is less than the thickness of the area or point). When the number of recessed portions is greater than 2, the recessed width of each recessed portion may be the same as or different from each other. As shown in FIG. 2, the second shell 203 may have a plurality of recessed portions 2037, each of which has a recessed width w, and these recessed widths w may be the same as or different from each other. In some embodiments, the recessed width w is greater than 0 nm and less than or equal to 10 nm. In some embodiments, the recessed width w is greater than 0 nm and less than or equal to 7 nm, greater than 0 nm and less than or equal to 5 nm, or greater than 0 nm and less than or equal to 3 nm. In addition, the recessed portion has a recessed bottom, which is the area or point in the recessed portion where the thickness of the second shell 203 is the thinnest, and there is a distance d between the recessed bottom and the core surface 2011. When the number of the recessed parts is greater than 2, the distance d between the bottom of each recessed part and the core surface 2011 may be the same or different, as shown in FIG. 2. The part where the distance d between the bottom of the recessed part and the core surface 2011 in the second shell 203 is the smallest is defined as the lowest point 2033 of the second shell 203. When the thickness of the second shell 203 is 0 nm, the distance d is 0 nm. The thickest area or point in the second shell 203 is defined as the highest point 2035. In some embodiments, the outer surface of the second shell is a concave-convex outer surface, and there is a height difference between the lowest point 2033 and the highest point 2035 of the concave-convex outer surface, and the height difference is greater than 0 nm and less than 5 nm.

The first shell 205 may be distributed discontinuously around the core surface 2011 of the core 201, and the second shell 203 may be located between the core 201 and the first shell 205, but the disclosure is not limited thereto. In some embodiments, the second shell 203 may not exist between the core 201 and the first shell 205. In some embodiments, the first shell 205 may be spaced apart from the outer surface 2031 of the second shell 203 by a gap g and distributed discontinuously around the second shell 203, but the disclosure is not limited thereto. In an embodiment where the thickness of the second shell 203 is 0 nm, the first shell 205 may be spaced apart from the core surface 2011 of the core 201 by a gap g and distributed discontinuously around the core surface 2011. The sizes of the plurality of gaps g may be the same or different from each other. The gap g may be greater than or equal to 0 nm and less than or equal to 10 nm. In some embodiments, the gap g may be greater than or equal to 0 nm and less than or equal to 7 nm, greater than or equal to 0 nm and less than or equal to 5 nm, or greater than or equal to 0 nm and less than or equal to 3 nm.

In some embodiments, the first shell 205 is granular. In this embodiment, the first shell 205 may include a plurality of particles distributed around the core 201 and the second shell 203. In some embodiments, at least part of the particles in the first shell 205 may be stacked on each other, as shown in FIG. 3. In some embodiments, the number of stacked first shell 205 particles is less than or equal to 4. In some embodiments, the number of stacked first shell 205 particles is less than or equal to 3. In this embodiment, the average diameter of the first shell 205 particles is greater than 0 nm and less than or equal to 5 nm. In some embodiments, the average diameter of the particles of the first shell 205 is greater than or equal to 1 nm and less than or equal to 5 nm, greater than or equal to 1 nm and less than or equal to 4 nm, greater than or equal to 2 nm and less than or equal to 5 nm, or greater than or equal to 2 nm and less than or equal to 4 nm. FIG. 2 shows an embodiment in which the first shell 205 includes a plurality of shell particles. In this embodiment, the gaps g between each shell particle included in the first shell 205 and each portion of the outer surface 2031 of the second shell 203 may be the same or different from each other.

In some embodiments, the sum of the thickness and the gap g of the first shell 205 and the second shell 203 is greater than 0 nm and less than or equal to 35 nm, for example, the sum is greater than 0 nm and less than or equal to 30 nm, greater than 0 nm and less than or equal to 25 nm, greater than 0 nm and less than or equal to 20 nm, greater than or equal to 1 nm and less than or equal to 25 nm, greater than or equal to 2 nm and less than or equal to 25 nm, greater than or equal to 5 nm and less than or equal to 25 nm, etc. For example, in an embodiment where the first shell 205 contains a plurality of particles, when the number of particles in the first shell 205 is 4, the sum of the thickness and the gap g between the first shell 205 and the second shell 203 is greater than 0 nm and less than or equal to 35 nm; when the number of particles in the first shell 205 is 3, the sum of the thickness and the gap g between the first shell 205 and the second shell 203 is greater than 0 nm and less than or equal to 30 nm; when the number of particles in the first shell 205 is 2, the sum of the thickness and the gap g between the first shell 205 and the second shell 203 is greater than 0 nm and less than or equal to 25 nm; when the number of particles of the first shell 205 is 1, the sum of the thickness of the first shell 205 and the second shell 203 and the gap g is greater than 0 nm and less than or equal to 20 nm. In some embodiments, the first shell 205 and the second shell 203 may include the same material as the core 201 or a material that is more lattice-matched with the material of the core 201. In some embodiments, the first shell 205 and the second shell 203 may include the same material.

Since the first shell 205 of the quantum dot 20 is discontinuously located around the core surface 2011 of the core 201, and the second shell 203 has an irregular outer surface 2031, the quantum dot 20 also has an irregular surface. In some embodiments, the quantum dot 20 has a maximum diameter and a minimum diameter. "The maximum diameter of the quantum dot 20" refers to the longest length of the length, width, and height of the smallest virtual box encapsulating the quantum dot 20. As shown in Figure 2, the maximum diameter of the quantum dot 20 refers to the longest of the length (diameter) L1 in the Y direction, the length (diameter) L2 in the X direction, and the length in the Z direction (not shown) of the smallest virtual box QV encapsulating the quantum dot 20. In more detail, the maximum diameter L1 and/or L2 covers the diameter of the core 201, the maximum thickness of the second shell 203, the maximum gap between the first shell 205 and the second shell 203, and the maximum diameter of the first shell 205. The maximum diameter of the first shell here refers to the sum of the maximum diameters of the stacked N first shells 205. In an embodiment where N is less than or equal to 4, the maximum diameter L1 and/or L2 of the quantum dot 20 may be greater than or equal to 30 nm and less than or equal to 90 nm. In an embodiment where N is less than or equal to 3, the maximum diameter L1 and/or L2 of the quantum dot 20 may be greater than or equal to 30 nm and less than or equal to 80 nm. In an embodiment where N is less than or equal to 2, the maximum diameter L1 and/or L2 of the quantum dot 20 may be greater than or equal to 30 nm and less than or equal to 70 nm. In an embodiment where N is less than or equal to 1, the maximum diameters L1 and L2 of the quantum dot 20 may be greater than or equal to 30 nm and less than or equal to 60 nm. Relative to the maximum diameter, the "minimum diameter of the quantum dot 20" refers to the shortest length of the length, width, and height of the smallest virtual box encapsulating the quantum dot 20. As shown in Figure 2, the minimum diameter of the quantum dot 20 refers to the shortest of the length (diameter) L1 in the Y direction, the length (diameter) L2 in the X direction, and the length in the Z direction (not shown) of the smallest virtual box QV encapsulating the quantum dot 20. The minimum diameter L1 and/or L2 of the quantum dot 20 covers the diameter of the core 201 and the minimum thickness of the second shell 203. Therefore, the minimum diameter L1 and/or L2 of the quantum dot 20 disclosed in the present invention may be greater than 9 nm.

FIG. 3 is a schematic diagram of a quantum dot 20 according to other embodiments of the present disclosure. As shown in FIG. 3 , a ligand 207 may be further distributed outside the quantum dot 20. The ligand 207 may be located around the outer surface 2031 of the second shell 203 and/or in the gap g, as shown in FIG. 3 . The ligand 207 may further enhance the surface steric barrier of the quantum dot 20 to enhance the ability to confine destructive factors in the environment to the outside of the quantum dot 20 or the ligand 207 or between the quantum dot 20 and the ligand 207. The ligand 207 may further enhance the resistance or tolerance of the quantum dot 20 to destructive factors in the environment or the reliability or luminescence lifetime of the quantum dot 20. The ligand 207 may be a polar ligand or a non-polar ligand. Examples of ligand 207 may include, but are not limited to, alkylphosphines, alkylamines, arylamines, pyridines, fatty acids, thiophenes, thiol compounds, carbenes, or any combination thereof. Examples of fatty acids may include, but are not limited to, oleyl acid, stearic acid, lauric acid, or any combination thereof. Examples of alkylamines may include, but are not limited to, oleylamine, octylamine, dioctylamine, hexadecylamine, or any combination thereof. Examples of carbenes may include, but are not limited to, 1-octadecene. Examples of alkylphosphines may include, but are not limited to, trioctylphosphine. In some embodiments, the length of ligand 207 may be about 1 to 2.5 nm, about 1.2 to 2.3 nm, about 1.3 to 2.0 nm, or about 1.5 to 1.9 nm.

Then, step S107 is performed to stir the quantum dot solution including a plurality of the above-mentioned quantum dots (e.g., quantum dot 20) at a second temperature to form a quantum dot structure. In some embodiments, the second temperature is greater than or equal to the first temperature. In some embodiments, the second temperature is equal to the first temperature. In some embodiments, the second temperature is greater than or equal to 250° C. and less than or equal to 310° C. Step S107 is performed to stir at a stirring rate of about 10 to 90 rpm for about 10 to 60 minutes. In some embodiments, the stirring rate may be about 20 to 80 rpm, about 30 to 70 rpm, about 40 to 60 rpm, or about 50 rpm. In some embodiments, the stirring may last for about 10 to 60 minutes, about 15 to 50 minutes, about 20 to 40 minutes, or about 30 minutes. The formed quantum dot structure has a third shell that covers at least a portion of the quantum dot, as shown in FIG. 4 .

FIG. 4 is a schematic diagram of a quantum dot structure 2 according to some embodiments of the present disclosure. The quantum dot structure 2 includes the above-mentioned quantum dot 20 and a third shell 40. The third shell 40 covers at least a portion of the quantum dot 20 and has an irregular outer surface 401. In some embodiments, the third shell 40 may include the same material as the core 201 or a material that is more lattice-matched to the material of the core 201. In some embodiments, the third shell 40 may include the same material as the first shell 205 and/or the second shell 203.

In some embodiments of the present disclosure, the projection of the quantum dot 20 on a plane has a maximum width in a first direction and a maximum length in a second direction perpendicular to the first direction. The projection of the third housing 40 on this plane overlaps with the projection of the quantum dot 20 on this plane with an overlapping area, wherein the overlapping area satisfies the following formula: ≧Overlapping area≧ .

For example, referring to FIG. 2, the extension direction of the maximum diameter of the quantum dot 20 is defined as the first direction, and the direction perpendicular to the first direction is defined as the second direction. Based on a plane defined by the first direction and the second direction, the projection of the quantum dot 20 on this plane has a maximum width in the first direction and a maximum length in the second direction perpendicular to the first direction. In one embodiment, the first direction is the Y direction and the second direction is the X direction, the maximum width of the quantum dot 20 is the maximum diameter L1 of the quantum dot 20 projected on the XY plane in the Y direction, and the maximum length of the quantum dot 20 is the maximum diameter L2 of the quantum dot 20 projected on the XY plane in the X direction. The third shell 40 covers at least a portion of the quantum dot 20, indicating that the projection of the third shell 40 on the plane defined by the first direction and the second direction at least partially overlaps with the projection of the quantum dot 20 on this plane. In some embodiments, the projections of the third shell 40 and the quantum dot 20 on the plane overlap with an overlapping area, and the overlapping area meets the following formula: Maximum width L1 Maximum length L2≧overlapping area≧1/4 Maximum width L1 Maximum length L2.

In some embodiments, the third shell 40 is in direct contact with the first shell 205 of the quantum dot 20, and the third shell 40 is in direct contact with the second shell 203 of the quantum dot 20, but the disclosure is not limited thereto. In some embodiments, there is a gap between the third shell 40 and the first shell 205 of the quantum dot 20, and there is a gap between the third shell 40 and the second shell 203.

In some embodiments, the outer surface 401 of the third shell 40 is a continuous concave-convex outer surface. In some embodiments, there is a height difference between the lowest point and the highest point of the third shell 40. The definition of the lowest point, the highest point, and the height difference of the third shell 40 is similar to the definition of the lowest point, the highest point, and the height difference of the second shell 203, so it is not repeated here. In some embodiments, the outer surface of the third shell 40 has a different surface profile from the outer surface of the second shell 203. In some embodiments, the height difference between the lowest point and the highest point of the third shell 40 is less than or equal to the height difference between the lowest point and the highest point of the second shell 203. In some embodiments, the height difference between the lowest point and the highest point of the third shell 40 is not 0.

The quantum dot structure 2 including the quantum dot 20 and the third shell 40 can be obtained after step S107 is completed. In some embodiments, the projection of the quantum dot structure 2 on the plane defined by the first direction and the second direction has a structure width in the first direction and a structure length in the second direction. The structure width can be greater than 9 nm and less than or equal to 1.5*maximum width L1. The structure length can be greater than 9 nm and less than or equal to 1.5*maximum length L2.

In some embodiments, the method for forming a quantum dot structure of some embodiments disclosed herein may further include a purification step S109. In some embodiments, the purification step S109 may include a purification process of washing with an organic solvent and then centrifuging the solution containing the quantum dot structure to obtain a purified quantum dot structure.

In some embodiments, the quantum dot structure may further include a ligand 207 located on the surface of the first shell 205, the second shell 203 and/or the third shell 40, as shown in FIG. 5. FIG. 5 is a schematic diagram of a quantum dot structure 3 according to some embodiments of the present disclosure. The quantum dot structure 3 includes the above-mentioned quantum dot 20, the third shell 40 covering at least a portion of the quantum dot 20, and the ligand 207 located on the surface of the first shell 205, the second shell 203 and/or the third shell 40. In some embodiments, the ligand 207 is in direct contact with the outer surface 2031 of the first shell 205, the second shell 203 and/or the outer surface 401 of the third shell 40. The ligand 207 shown in FIG. 5 is substantially the same as the ligand 207 of FIG. 3, so it will not be described again here. The ligand 207 can further enhance the surface steric barrier of the quantum dot structure 3, enhance the barrier or tolerance of the quantum dot structure 3 to destructive factors in the environment, or enhance the reliability or luminescence life of the quantum dot structure 3.

The above-mentioned quantum dot structure 2 or quantum dot structure 3 can be applied to a light-emitting device to provide a light-emitting device with better reliability and service life. According to another aspect of the present disclosure, the present disclosure further provides a light-emitting device, which includes a light source that emits a first light ray and a wavelength conversion unit that absorbs part of the first light ray and converts it into a second light ray, wherein the wavelength conversion unit includes the above-mentioned quantum dot structure 2 and/or quantum dot structure 3. In some embodiments, the wavelength conversion unit can be further mixed with other fluorescent powders. In addition, the material of the core 201 of the quantum dot 20 can be selected according to the required light color (such as white light, red light, blue light, green light, etc.) so that the light-emitting device can be applied to various fields, such as lighting, automotive center consoles and instrument panels, backlight units of displays, RGB pixels of light-emitting diode displays (LED displays), etc.

FIG. 6A is a schematic diagram of a light-emitting device according to some embodiments of the present disclosure. As shown in FIG. 6A, the light-emitting device is an LED light-emitting device, comprising a light source 4 and a wavelength conversion unit 5. The light source 4 may be a light-emitting diode chip that can emit a first light having a first wavelength (e.g., blue light or UV light). In some embodiments, the light-emitting diode chip includes a sub-millimeter light-emitting diode (mini LED) chip and a micro light-emitting diode (micro LED) chip. The wavelength conversion unit 5 can absorb part of the first light emitted by the light source 4, and convert the absorbed first light into a second light having a second wavelength. In some embodiments, the first wavelength is different from the second wavelength. The wavelength conversion unit 5 may include a matrix 6 and a quantum dot structure 2 uniformly dispersed in the matrix 6, but the present disclosure is not limited thereto. In some embodiments, part or all of the quantum dot structure 2 in the wavelength conversion section 5 can be replaced by the above-mentioned quantum dot structure 3. The matrix 6 may include a transparent resin, such as an acrylic resin, an organic silicone resin, an acrylate-modified polyurethane, an acrylate-modified organic silicone resin, or an epoxy resin. In some embodiments, the wavelength conversion section 5 may further include diffusion particles uniformly dispersed in the matrix 6. The diffusion particles can scatter the first light incident into the matrix 6, thereby increasing the path of the first light passing through the wavelength conversion section 5. The diffusion particles may include inorganic particles, organic polymer particles, or a combination thereof. Examples of inorganic particles include, but are not limited to, silicon oxide, titanium oxide, aluminum oxide, calcium carbonate, barium sulfate, or any combination thereof. Examples of organic polymer particles include, but are not limited to, polymethyl methacrylate (PMMA), polystyrene (PS), acrylonitrile-butadiene-styrene copolymer (ABS), polyurethane (PU), or any combination thereof.

In some embodiments, the light emitting device may be a white light emitting device. As shown in FIG. 6A , in one embodiment, the light source 4 may be a blue light emitting diode chip, and the wavelength conversion unit 5 may include a red quantum dot structure 2 and a green quantum dot structure 2, wherein the red quantum dot structure 2 contains red quantum dots 20, and the green quantum dot structure 2 contains green quantum dots 20. In another embodiment, the light source 4 may be a UV light emitting diode chip, and the wavelength conversion unit 5 may include red, green, and blue quantum dot structures 2, wherein the red quantum dot structure 2 contains red quantum dots 20, the green quantum dot structure 2 contains green quantum dots 20, and the blue quantum dot structure 2 contains blue quantum dots 20. In some embodiments, part or all of the quantum dot structure 2 in the wavelength conversion unit 5 may be replaced by the above-mentioned quantum dot structure 3. In some embodiments, the light-emitting device may emit a single color light, such as red light, green light, or blue light. A light-emitting device that emits red light may include a red quantum dot structure 2 or 3 and a light source 4 that emits blue light or UV light. In this embodiment, the light source 4 may be a light-emitting diode chip, and the blue light or UV light from the light-emitting diode chip may excite the red quantum dot structure 2 or 3 to emit red light. A light-emitting device that emits green light may include a green quantum dot structure 2 or 3 and a light source 4 that emits blue light or UV light. In this embodiment, the light source 4 may be a light-emitting diode chip, and the blue light or UV light from the light-emitting diode chip may excite the green quantum dot structure 2 or 3 to emit green light. A blue light-emitting device may include a blue quantum dot structure 2 or 3 and a light source 4 that emits blue light or UV light. In this embodiment, the light source 4 can be a LED chip, and the blue light or UV light from the LED chip can excite the blue quantum dot structure 2 or 3 to emit blue light. The aforementioned red light emitting device, green light emitting device and blue light emitting device can be used as pixels in an LED display or a micro LED display.

FIG. 6B is a schematic diagram of a light emitting device according to some embodiments of the present disclosure. As shown in FIG. 6B , the light emitting device may be a chip-level package (CSP), wherein the light source 4 may be a flip-chip light emitting diode chip, and the wavelength conversion portion 5 may be a quantum dot film including a quantum dot structure 2, a quantum dot structure 3, or a combination thereof. The quantum dot film may cover the top and side surfaces of the light source 4, as shown in FIG. 6B . In other embodiments, the quantum dot film covers the top surface of the light source 4. In some embodiments, the light emitting diode chip includes a sub-millimeter light emitting diode (mini LED) chip and a micro light emitting diode (micro LED) chip.

In some embodiments, the light emitting device may be a chip-scale package (CSP) that emits white light. As shown in FIG. 6B , in one embodiment, the light source 4 may be a flip-chip blue light emitting diode chip, and the wavelength conversion unit 5 may be in the form of a quantum dot film that covers the top and side surfaces of the light source 4, or covers the top surface of the light source 4, wherein the quantum dot film may include a red quantum dot structure 2 and a green quantum dot structure 2, and the red quantum dot structure 2 contains red quantum dots 20, and the green quantum dot structure 2 contains green quantum dots 20. In other embodiments, the light source 4 may be a flip-chip UV light-emitting diode chip, and the wavelength conversion portion 5 may cover the top and side surfaces of the light source 4 in the form of a quantum dot film, or cover the top surface of the light source 4, wherein the quantum dot film may include red, green, and blue quantum dot structures 2, and the red quantum dot structure 2 contains red quantum dots 20, the green quantum dot structure 2 contains green quantum dots 20, and the blue quantum dot structure 2 contains blue quantum dots 20. Part or all of the quantum dot structures 2 in the quantum dot film may be replaced by the above-mentioned quantum dot structure 3. In some embodiments, the light-emitting device may be a chip-level packaged light-emitting device that emits monochromatic light, such as red light, green light, or blue light. A light-emitting device that emits red light may include a quantum dot film containing a red quantum dot structure 2 or 3 and a light source 4 that emits blue light or UV light. In this embodiment, the light source 4 may be a light-emitting diode chip, and the blue light or UV light from the light-emitting diode chip may excite the red quantum dot structure 2 or 3 to emit red light. A light-emitting device that emits green light may include a quantum dot film containing a green quantum dot structure 2 or 3 and a light source 4 that emits blue light or UV light. In this embodiment, the light source 4 may be a light-emitting diode chip, and the blue light or UV light from the light-emitting diode chip may excite the green quantum dot structure 2 or 3 to emit green light. A blue light-emitting device may include a quantum dot film containing a blue quantum dot structure 2 or 3 and a light source 4 that emits blue light or UV light. In this embodiment, the light source 4 may be a light-emitting diode chip, and the blue light or UV light from the light-emitting diode chip may excite the blue quantum dot structure 2 or 3 to emit blue light. The aforementioned chip-level packaged light-emitting device emitting red, blue, or green light can be used as a pixel in a light-emitting diode display (LED display) or a micro light-emitting diode display (Micro LED display).

In some embodiments, the micro-LED display may include a plurality of red light emitting devices, green light emitting devices and/or blue light emitting devices as shown in FIG. 6A or FIG. 6B. In some embodiments, the blue light emitting device of the micro-LED display may only include a blue micro-LED chip without the aforementioned wavelength conversion unit 5.

In some embodiments, the wavelength conversion unit 5 may be mixed with other fluorescent powders in addition to the quantum dot structure 2 and/or the quantum dot structure 3. In one embodiment, the wavelength conversion unit 5 may include a red quantum dot structure 2 and a green fluorescent powder, wherein the green fluorescent powder may be, for example, lumen aluminum garnet (LuAG) fluorescent powder, yttrium aluminum garnet (YAG) fluorescent powder, sialon (β-SiAlON) fluorescent powder, silicate fluorescent powder, but is not limited thereto. In another embodiment, the wavelength conversion portion 5 may include a green quantum dot structure 2 and a red fluorescent powder, wherein the red fluorescent powder may be, for example, (Sr,Ca)AlSiN ₃ :Eu ²⁺ , Ca ₂ Si ₅ N ₈ :Eu ²⁺ , Sr(LiAl ₃ N ₄ ):Eu ² , manganese-doped red fluoride fluorescent powder (such as K ₂ GeF ₆ :Mn ⁴⁺ , K ₂ SiF ₆ :Mn ⁴⁺ , K ₂ TiF ₆ :Mn ⁴⁺ , etc.), but is not limited thereto.

The present disclosure provides a backlight unit, which contains a plurality of the aforementioned white light emitting devices. The present disclosure provides a display, which includes the aforementioned backlight unit. In some embodiments, the display is a liquid crystal display.

In some embodiments, the wavelength conversion unit 5 may be a quantum dot layer (QD layer), as shown in FIG. 6C. FIG. 6C is a schematic diagram of a wavelength conversion unit 5 according to some embodiments of the present disclosure, wherein the wavelength conversion unit 5 is a quantum dot layer. The quantum dot layer may include a transparent substrate 6 and a quantum dot structure 2, and part or all of the quantum dot structure 2 may be replaced by the above-mentioned quantum dot structure 3. The transparent substrate 6 may include, for example, an acrylic resin, an organic silicone resin, an acrylate-modified polyurethane, an acrylate-modified organic silicone resin, or an epoxy resin. In some embodiments, the quantum dot layer may be applied to a backlight unit of a display. In some embodiments, the backlight unit provides white light, wherein the backlight unit includes a quantum dot layer and a light panel containing a plurality of blue light emitting diode chips, wherein the quantum dot layer contains green and red quantum dot structures 2 or quantum dot structures 3 or a combination thereof. Similarly, as described above, the quantum dot layer may contain other fluorescent powders to be mixed with the quantum dot structure as required.

In order to make the above and other purposes, features, and advantages of the present disclosure more clearly understood, the preparation of quantum dot structures and quantum dots is specifically cited below, and the quantum dot structures and quantum dots are used to prepare light-emitting devices, and then fired in a general environment without water and oxygen barriers and in a nitrogen environment without water and oxygen barriers to observe the water and oxygen tolerance and reliability of the quantum dot structures and quantum dots. These experimental contents can specifically illustrate the characteristics of the quantum dot structure made according to the method for forming the quantum dot structure of the embodiments of the present disclosure, the effects that can be achieved by the quantum dot structure according to the embodiments of the present disclosure, and the characteristics of the light-emitting device made by applying the present disclosure. However, the following embodiments and comparative examples are only for illustrative purposes and should not be interpreted as limitations on the implementation of the present disclosure.

[Preparation of nuclear solution]

＜First nuclear precursor solution＞

First, 64 mg of cadmium oxide (CdO), 1615 mg of zinc oxide (ZnO), 20 mL of oleic acid (OA) and 80 mL of 1-octdencene (ODE) were placed in a 250 mL three-neck round-bottom flask to form a mixture. The mixture was evacuated at 100 m torr and heated to 150°C for about 120 minutes, and then nitrogen or inert gas was introduced into the three-neck round-bottom flask to obtain 4 equivalents of a cadmium-zinc (Cd-Zn) mixed solution as the first nuclear precursor solution.

＜Second nuclear precursor solution＞

655 mg of selenium powder (Se), 148 mg of sulfur powder (S), and 8 g of trioctylphosphine (TOP) were placed in a beaker, stirred to clarify, and then nitrogen was introduced to seal the beaker to obtain a selenium-sulfur mixed solution as the second nuclear precursor solution.

[Preparation of Shell Propulsion Solution]

＜First Shell Precursor Solution＞

5.6 g of anhydrous zinc acetate, 4 g of oleic acid (OA), and 20 g of 1-octadecene (ODE) were placed in a 50 mL three-neck round-bottom flask, heated to 150°C for about 30 minutes, and sealed with nitrogen after clarification to obtain 0.7 equivalents of Zn-OA solution as the first shell precursor solution.

＜Second Shell Precursor Solution＞

352 mg of sulfur powder and 5.5 g of trioctylphosphine (TOP) were placed in a beaker, stirred to clarify, and then nitrogen was introduced to seal the beaker to obtain 1 equivalent of S-TOP solution as the second shell precursor solution.

[Preparation of Comparative Example Quantum Dot 1]

One equivalent of the first core precursor solution is heated to 280°C and reacted for 3 minutes, and then one equivalent of the second core precursor solution is introduced into the heated first core precursor solution, and then the temperature is raised to 320°C and reacted for 10 minutes to form a core solution. The second shell precursor solution is introduced into the obtained core solution and reacted for 10 minutes, and then the temperature is lowered to 250°C, and then one equivalent of the first shell precursor solution is quickly introduced into the core solution, and then one equivalent of the second shell precursor solution is introduced into the core solution to obtain a quantum dot precursor solution, and the obtained quantum dot precursor solution is heated at 250°C for 20 minutes to synthesize quantum dots. The solution containing quantum dots was cooled to room temperature, and then the steps of washing with 100 mL of methanol/80 mL of toluene and then centrifuging the quantum dot solution were repeated 4 times to obtain purified comparative example quantum dots 1.

[Preparation of Comparative Example Quantum Dot 2]

One equivalent of the first core precursor solution is heated to 280°C and reacted for 3 minutes, and then one equivalent of the second core precursor solution is introduced into the heated first core precursor solution, and then the temperature is raised to 320°C and reacted for 10 minutes to form a core solution. The second shell precursor solution is introduced into the obtained core solution for 10 minutes and then cooled to 250°C, and one equivalent of the first shell precursor solution is introduced into the core solution at an introduction rate of 0.38 eq/min, and then one equivalent of the second shell precursor solution is introduced into the core solution at an introduction rate of 0.9 eq/min to obtain a quantum dot precursor solution, and the obtained quantum dot precursor solution is heated at 250°C for 60 minutes to form a quantum dot solution including quantum dots. After the quantum dot solution was cooled to room temperature, it was washed four times with 100 mL methanol/80 mL toluene, and then the quantum dot solution was centrifuged to obtain purified comparative quantum dot 2.

[Preparation of quantum dot structure]

One equivalent of the first core precursor solution is heated to 280°C and reacted for 3 minutes, and then one equivalent of the second core precursor solution is introduced into the heated first core precursor solution, and then the temperature is raised to 320°C and reacted for 10 minutes to form a core solution. The second shell precursor solution is introduced into the obtained core solution for 10 minutes and then cooled to 250°C, and one equivalent of the first shell precursor solution is introduced into the core solution at an introduction rate of 0.38 eq/min, and then one equivalent of the second shell precursor solution is introduced into the core solution at an introduction rate of 0.9 eq/min to obtain a quantum dot precursor solution, and the obtained quantum dot precursor solution is heated at 250°C for 60 minutes to form a quantum dot solution including quantum dots. The magnet was placed in the quantum dot solution, and the quantum dot solution was stirred at 250°C and 50 rpm for 15 minutes, and then the stirred quantum dot solution was allowed to stand for 30 minutes to form a quantum dot structure solution including the quantum dot structure. After the quantum dot structure solution was cooled to room temperature, the quantum dot structure solution was repeatedly washed 4 times with 100 mL methanol/80 mL toluene, and then the quantum dot structure solution was centrifuged to obtain a purified quantum dot structure.

The comparative example quantum dots 1 and 2 and the quantum dot structure were analyzed using a transmission electron microscope (TEM, produced by JEOL, Japan, model JEM-2100F). Figure 7 is a transmission electron microscope (TEM) image of the comparative example quantum dot 1 of the present disclosure. Figure 8 is a TEM image of the comparative example quantum dot 2 of the present disclosure. Figure 9 is a TEM image of the quantum dot structure of the embodiment of the present disclosure. The maximum diameters of 50 randomly measured comparative example quantum dots 1 and 2 and the quantum dot structure were averaged to obtain the average maximum diameter. The quantum dot structure and the quantum efficiency of comparative example quantum dots 1 and 2 were measured using a fluorescent spectrometer (Fluoromax-4 Spectrofluorometer). The average maximum diameter and quantum efficiency of the quantum dot structure and comparative example quantum dots 1 and 2 are shown in Table 1 below. Table 1 Comparative Example Quantum Dot 1 Comparison Example Quantum Dot 2 Quantum dot structure Average maximum diameter (nm) 11.6±1.6 23.7±3.5 32.8±3.3 Quantum efficiency (%) 65 70 60

As can be seen from Table 1, the average maximum diameter of the quantum dot structure of the disclosed embodiment is about 2.2 to 3.6 times that of the comparative example quantum dot 1, and the average maximum diameter of the quantum dot structure of the disclosed embodiment is about 1.1 to 1.8 times that of the comparative example quantum dot 2. The quantum efficiencies of the quantum dot structure and the comparative example quantum dots 1 and 2 are both greater than about 60%.

[Preparation of light-emitting device]

The quantum dot structure and comparative example quantum dots 1 and 2 were mixed with an organic silicone resin and coated on a blue light emitting diode chip with a wavelength of about 450-460 nm, an optical power of about 34.6 mW and a chip size of about 0.35*0.70 mm to obtain the light emitting device of the embodiment and the light emitting devices of comparative example 1 and comparative example 2. The light emitting device of comparative example 1 includes comparative example quantum dot 1, and the light emitting device of comparative example 2 includes comparative example quantum dot 2.

[Performance test of light emitting device]

The light-emitting device of the embodiment and the light-emitting device of the comparative example were illuminated for about 1000 hours in a nitrogen environment without water and oxygen at a current of 20 mA, a driving voltage of 3.0 V, and a continuous lighting current of 15 mA. The light-emitting device of the embodiment and the light-emitting device of the comparative example were illuminated for about 300 hours in a general environment without water and oxygen barriers. The degree of attenuation of the light-emitting intensity of the light-emitting device of the embodiment and the light-emitting device of the comparative example over time was measured using a brightness measurement instrument (Weiming Enterprise/6122), and the obtained data was used to prepare the line graphs shown in Figures 10 and 11. FIG10 is a line graph showing the variation of the luminous intensity of the luminous device of the embodiment and the comparative example in a nitrogen environment with time. FIG11 is a line graph showing the variation of the luminous intensity of the luminous device of the embodiment and the comparative example in a general environment with time.

As shown in FIG. 10, after being lit for 1000 hours in a nitrogen environment, the luminous intensity of the luminous device of Comparative Example 1 decreased by about 50% compared with the initial luminous intensity; the luminous intensity of the luminous device of Comparative Example 2 decreased by about 20% compared with the initial luminous intensity; while the luminous intensity of the luminous device of the embodiment did not decrease compared with the initial luminous intensity. As shown in FIG. 11, after being lit for about 100 hours in a general environment, the luminous intensity of the luminous device of Comparative Example 2 decreased by about 20% compared with the initial luminous intensity, while the luminous intensity of the luminous device of the embodiment decreased by less than about 5% compared with the initial luminous intensity. It can be clearly seen from the above experimental results that, compared with the light-emitting device of the comparative example, the light-emitting device of the embodiment of the present case has better reliability or longer luminescence life in both nitrogen environment and general environment. In other words, compared with the quantum dots of the comparative example, the quantum dot structure disclosed in the present invention has higher resistance or better tolerance to environmental damage factors, and therefore has better reliability or longer luminescence life.

The above summarizes the components of several embodiments so that those with ordinary knowledge in the art to which the present disclosure belongs can better understand the viewpoints of the embodiments of the present disclosure. Those with ordinary knowledge in the art to which the present disclosure belongs should understand that they can design or modify other processes and structures based on the embodiments of the present disclosure to achieve the same purpose and/or advantages as the embodiments introduced herein. Those with ordinary knowledge in the art to which the present disclosure belongs should also understand that such equivalent structures do not deviate from the spirit and scope of the present disclosure, and they can make various changes, substitutions and replacements without violating the spirit and scope of the present disclosure. Therefore, the scope of protection of the present disclosure shall be defined by the scope of the attached patent application. In addition, although the present disclosure has been disclosed as above with several preferred embodiments, it is not used to limit the present disclosure.

References throughout this specification to features, advantages, or similar language do not imply that all features and advantages that may be achieved using the present disclosure should or may be achieved in any single embodiment of the present disclosure. Rather, language referring to features and advantages is understood to mean that a particular feature, advantage, or characteristic described in connection with an embodiment is included in at least one embodiment of the present disclosure. Thus, discussions of features and advantages and similar language throughout this specification may, but do not necessarily, refer to the same embodiment.

Furthermore, the described features, advantages, and characteristics of the present disclosure may be combined in any suitable manner in one or more embodiments. Based on the description herein, a person skilled in the relevant art will recognize that the present disclosure may be implemented without one or more of the specific features or advantages of a particular embodiment. In other cases, additional features and advantages may be identified in certain embodiments that may not be present in all embodiments of the present disclosure.

1: Quantum dot formation method 2,3: Quantum dot structure 20: Quantum dot 201: Core 2011: Core surface 203: Second shell 2031,401: Outer surface 2033: Lowest point 2035: Highest point 2037: Recess 205: First shell 207: Ligand 40: Third shell 4: Light source 5: Wavelength conversion unit 6: Matrix g: Gap w: Recess width d: Distance QV: Virtual box L1, L2: Length S101, S103, S105, S107, S109: Steps

The following will be described in detail with the accompanying drawings. It should be noted that the various characteristic components are not drawn in proportion and are only used for illustration. In fact, the size of the components may be enlarged or reduced to clearly show the technical features of the embodiments of the present disclosure. Figure 1 shows a flow chart of a method for forming a quantum dot structure according to some embodiments of the present disclosure. Figure 2 shows a schematic diagram of a quantum dot according to some embodiments of the present disclosure. Figure 3 shows a schematic diagram of a quantum dot according to some embodiments of the present disclosure. Figure 4 shows a schematic diagram of a quantum dot structure according to some embodiments of the present disclosure. Figure 5 shows a schematic diagram of a quantum dot structure according to some embodiments of the present disclosure. Figure 6A shows a schematic diagram of a light-emitting device according to some embodiments of the present disclosure. Figure 6B shows a schematic diagram of a light-emitting device according to some embodiments of the present disclosure. FIG. 6C is a schematic diagram of a wavelength conversion unit according to some embodiments of the present disclosure. FIG. 7 is a transmission electron microscope (TEM) image of a quantum dot of a comparative example of the present disclosure. FIG. 8 is a TEM image of a quantum dot of a comparative example of the present disclosure. FIG. 9 is a TEM image of a quantum dot structure of an embodiment of the present disclosure. FIG. 10 is a line graph showing the change of the luminescence intensity of the luminescent device of the embodiment of the present disclosure and the comparative example with time in a nitrogen environment. FIG. 11 is a line graph showing the change of the luminescence intensity of the luminescent device of the embodiment of the present disclosure and the comparative example with time in a general environment.

2: Quantum dot structure

20: Quantum dots

201: Nucleus

2011: Nuclear surface

203: Second shell

2031,401: External surface

205: First shell

40: The third shell

Claims (16)

A quantum dot structure, comprising: A quantum dot, comprising: A core; A first shell, discontinuously disposed around a core surface of the core; and A second shell, disposed between the core and the first shell and covering the core surface; wherein the second shell has an irregular outer surface; and A third shell, covering at least a portion of the quantum dot and having an irregular outer surface, wherein a gap exists between the third shell and the first shell, and a gap exists between the third shell and the second shell. A quantum dot structure as claimed in claim 1, wherein the projection of the quantum dot on a plane has a maximum width in a first direction and a maximum length in a second direction perpendicular to the first direction, and the projection of the third shell on the plane overlaps with the projection of the quantum dot on the plane with an overlapping area; wherein the overlapping area satisfies the following formula: ≧Overlapping area≧ ; wherein the extension direction of a maximum diameter of the quantum dot is defined as the first direction, the direction perpendicular to the first direction is defined as the second direction, and the first direction and the second direction constitute the plane. A quantum dot structure as claimed in claim 1, wherein the first shell, the second shell and the third shell comprise the same material. A quantum dot structure as claimed in claim 1, wherein the outer surface of the third shell and the outer surface of the second shell have different surface profiles. The quantum dot structure of claim 4, wherein the outer surface of the second shell is a concave-convex outer surface, and there is a height difference between the highest point and the lowest point of the concave-convex outer surface, and the height difference is greater than 0 nm and less than or equal to 5 nm. A quantum dot structure as in claim 5, wherein the concave-convex outer surface has at least one concave portion, the concave portion has a concave width, and the concave width is greater than 0 nm and less than or equal to 10 nm. A quantum dot structure as in claim 1, wherein the first shell comprises a plurality of particles. A quantum dot structure as in claim 7, wherein some of the plurality of particles are stacked on each other. The quantum dot structure of claim 1 further comprises a ligand located on the surface of the first shell, the second shell and/or the third shell. A method for forming a quantum dot structure, comprising: Providing a quantum dot core solution, the quantum dot core solution comprising a plurality of cores; Providing a shell precursor solution to be mixed with the quantum dot core solution to form a quantum dot precursor solution; Heating the quantum dot precursor solution at a first temperature to form a quantum dot solution comprising a plurality of quantum dots having a first shell and a second shell on a core surface of each of the plurality of cores, wherein the first shell is discontinuously formed around the core surface, the second shell is formed between the core and the first shell and covers the core surface, and the second shell has an irregular outer surface; and The quantum dot solution is continuously stirred at a second temperature to form a plurality of quantum dot structures having a third shell encapsulating at least a portion of each of the plurality of quantum dots, wherein a gap exists between the third shell and the first shell, and a gap exists between the third shell and the second shell, wherein the second temperature is greater than or equal to the first temperature. A method for forming a quantum dot structure as claimed in claim 10, wherein the shell precursor solution is introduced into the quantum dot core solution at an introduction rate, with a core content in the quantum dot core solution being taken as 1 equivalent, and the introduction rate is 0.016~1.6 equivalents/minute (eq/min). A method for forming a quantum dot structure as claimed in claim 10, wherein the third shell has an irregular outer surface. A method for forming a quantum dot structure as claimed in claim 10, wherein the second temperature is greater than or equal to 250°C and less than or equal to 310°C. The method for forming a quantum dot structure as claimed in claim 10, wherein the step of providing the shell precursor solution to the quantum dot core solution comprises: Introducing a first shell precursor solution at a first introduction rate; and Introducing a second shell precursor solution at a second introduction rate; Wherein, taking a core content in the quantum dot core solution as 1 equivalent, the first introduction rate is 0.016~1.6 eq/min, the second introduction rate is 0.016~1.6 eq/min, and the first introduction rate is greater than or equal to the second introduction rate. The method for forming a quantum dot structure as claimed in claim 10 further includes performing a purification process after forming the plurality of quantum dot structures. A light-emitting device, comprising: a light source, emitting a first light ray; and a wavelength conversion unit, absorbing part of the first light ray and converting it into a second light ray; wherein the wavelength conversion unit comprises: a quantum dot structure as described in any one of claims 1 to 9.

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