Quantum dots and light-emitting devices containing them

Abstract

The present disclosure provides a quantum dot and a light-emitting device containing the same, wherein the quantum dot comprises a semiconductor material core, at least one first semiconductor material shell sequentially arranged on the surface of the semiconductor material core, a third semiconductor material shell located at the outermost layer of the quantum dot, and a second semiconductor material shell located between the first semiconductor material shell and the third semiconductor material shell, in the radial direction from the semiconductor material core to the second semiconductor material shell, the energy of the conduction band bottom of the semiconductor material core, the first semiconductor material shell and the second semiconductor material shell increases sequentially, and the energy of the corresponding valence band top decreases sequentially, the conduction band bottom of the third semiconductor material shell is lower than the conduction band bottom of the second semiconductor material shell, and the valence band top of the third semiconductor material shell is higher than the valence band top of the second semiconductor material shell; wherein the chemical elements contained in each first semiconductor material shell are the same or different. The quantum dot provided by the present disclosure has good environmental stability and high quantum yield.

Description

Technical Field

[0001] The present disclosure relates to the field of quantum dot materials, and in particular, to a quantum dot and a light-emitting device containing the same. Background Art

[0002] In the past two decades, the research on quantum dot synthetic chemistry has mainly focused on how to improve the monodispersity of size and morphology and the fluorescence quantum yield. However, in order to make quantum dots an excellent type of luminescent and optoelectronic materials, it is also necessary to reduce the impact of the environment, especially water and oxygen, on the optoelectronic properties of quantum dots as much as possible, which has a great driving effect on the application research of quantum dots.

[0003] In order to improve the stability of quantum dots, the simplest method is often to coat the core quantum dot surface with a shell material with a wider band gap, and the shell thickness should be thick to isolate the contact between the exciton and the environment. For example, in 2014, Professor Peng Xiaogang's research group reported that after coating the surface of small-sized CdSe (3nm) quantum dots with 10-16 layers of CdS, CdSe / CdS core-shell quantum dots with good optical and chemical stability were obtained. However, in fact, these quantum dots still cannot achieve environmental stability and can only be alleviated to a certain extent. And as the thickness of the shell increases, the quantum yield of the quantum dot decreases, which is not conducive to subsequent optical applications. Summary of the invention

[0004] The purpose of the present disclosure is to provide a quantum dot, comprising a semiconductor material core, at least one first semiconductor material shell sequentially arranged on the surface of the semiconductor material core, a third semiconductor material shell located at the outermost layer of the quantum dot, and a second semiconductor material shell located between the first semiconductor material shell and the third semiconductor material shell, in which, in the radial direction from the semiconductor material core to the second semiconductor material shell, the energies of the conduction band bottoms of the semiconductor material core, the first semiconductor material shell and the second semiconductor material shell sequentially increase, and the energies of the corresponding valence band tops sequentially decrease, the conduction band bottom of the third semiconductor material shell is lower than the conduction band bottom of the second semiconductor material shell, and the valence band top of the third semiconductor material shell is higher than the valence band top of the second semiconductor material shell; wherein, the chemical elements contained in each of the first semiconductor material shells are the same or different.

[0005] Optionally, the quantum dot includes at least one fourth semiconductor material shell between the second semiconductor material shell and the third semiconductor material shell, and in the radial direction from the second semiconductor material shell to the third semiconductor material shell, the energy of the conduction band bottom of the second semiconductor material shell, the at least one fourth semiconductor material shell and the third semiconductor material shell decreases successively, and the energy of the corresponding valence band top increases successively; wherein the chemical elements contained in each of the fourth semiconductor material shells are the same or different.

[0006] Optionally, the above-mentioned quantum dot includes a fifth semiconductor material shell arranged on the above-mentioned second semiconductor material shell, and a sixth semiconductor material shell arranged on the above-mentioned fifth semiconductor material shell, the conduction band bottom of the above-mentioned sixth semiconductor material shell is higher than the conduction band bottom of the above-mentioned fifth semiconductor material shell, and lower than the conduction band bottom of the above-mentioned second semiconductor material shell, and the valence band top of the above-mentioned sixth semiconductor material shell is lower than the valence band top of the above-mentioned fifth semiconductor material shell, and higher than the valence band top of the above-mentioned second semiconductor material shell.

[0007] Optionally, the energy difference between the conduction band bottom of the sixth semiconductor material shell and the conduction band bottom of the fifth semiconductor material shell does not exceed 1.5 eV, and the energy difference between the valence band top of the fifth semiconductor material shell and the valence band top of the sixth semiconductor material shell does not exceed 2 eV.

[0008] Optionally, the energy difference between the conduction band bottom of the above-mentioned second semiconductor material shell and the above-mentioned semiconductor material core is less than or equal to 1.5eV, and the energy difference between the above-mentioned semiconductor material core and the valence band top of the above-mentioned second semiconductor material shell is less than or equal to 0.7eV; or, the energy difference between the conduction band bottom of the above-mentioned second semiconductor material shell and the above-mentioned semiconductor material core is less than or equal to 1.4eV, and the energy difference between the above-mentioned semiconductor material core and the valence band top of the above-mentioned second semiconductor material shell is less than or equal to 1.2eV.

[0009] Optionally, the material of the second semiconductor material shell is selected from CdS, ZnS or Cd X Zn (1-X) S, where 0 <X<1。

[0010] Optionally, the material of the semiconductor material core is selected from CdSe, CdSeS, CdZnSe, CdZnSeS, InP, InZnP, InZnPS or ZnSeTe.

[0011] Optionally, each of the above-mentioned first semiconductor material shells includes at least one of selenium and sulfur and at least one of cadmium and zinc, or each of the above-mentioned first semiconductor material shells includes at least one of selenium and sulfur and at least one of indium and zinc.

[0012] Optionally, the quantum dots are selected from CdSeS / CdZnSeS / ZnSeS / ZnS / CdZnS, CdSeS / ZnSeS / ZnS / CdZnS, CdSeS / ZnSeS / ZnS / CdZnS M S (1-M) / ZnSe N S (1-N) / ZnS / CdZnS、CdSeS / CdS / ZnSeS / ZnS / CdZnS、CdSeS / CdZnSeS / ZnSeS / ZnS / CdZnS / CdZnS、CdSeS / CdS / ZnS / CdS、CdSeS / CdS / ZnS / CdZnS、CdSeS / Cd Y Zn (1-Y) S / Cd X Zn (1-X) S / Cd Z Zn (1-Z) S、CdSe M S (1-M) / CdSe N S (1-N) / ZnSeS / ZnS / CdZnS、CdSeS / Cd A Zn (1-A) Se C S (1-C) / Cd B Zn (1-B) Se D S (1-D) / ZnSeS / ZnS / CdZnS、CdSeS / CdZnSe / ZnSeS / ZnS / CdZnS、CdSe / CdZnSeS / ZnSeS / ZnS / CdZnS、CdSe / ZnSeS / ZnS / CdZnS、CdSe / ZnSe M S (1-M) / ZnSe N S (1-N) / ZnS / CdZnS、CdSe / CdS / ZnSeS / ZnS / CdZnS、CdSe / CdZnSeS / ZnSeS / ZnS / CdZnS / CdZnS、CdSe / CdS / ZnS / CdZnS、CdSe / CdSeS / ZnSeS / ZnS / CdZnS、CdSe / Cd A Zn (1-A) Se C S (1-C) / Cd B Zn (1-B) Se D S / ZnSeS / ZnS / CdZnS、CdSe / CdZnSe / ZnSeS / ZnS / CdZnS、CdSe / CdSeS / CdS / CdZnS / ZnS / CdZnS、CdSe / CdZnS / ZnS / CdZnS、CdSe / CdSeS / CdS / CdSeS、CdSe / CdZnS / ZnS / CdZnS / ZnS、CdSe / CdS / Cd X Zn (1-X)S / CdS、CdSe / Cd Y Zn (1-Y) S / Cd X Zn (1-X) S / Cd Z Zn (1-Z) S、Cd A Zn (1-A) Se C S (1-C) / Cd B Zn (1-B) Se D S (1-D) / ZnSeS / ZnS / CdZnS、CdZnSeS / ZnSeS / ZnS / CdZnS、CdZnSeS / ZnSe M S (1-M) / ZnSe N S (1-N) / ZnS / CdZnS、CdZnSeS / CdS / ZnSeS / ZnS / CdZnS、Cd A Zn (1-A) Se C S (1-C) / Cd B Zn (1-B) Se D S (1-D) / ZnSeS / ZnS / CdZnS / CdZnS、CdZnSeS / CdS / ZnS / CdS、CdZnSeS / CdS / ZnS / CdZnS、CdZnSeS / Cd Y Zn (1-Y) S / Cd X Zn (1-X) S / Cd Z Zn (1-Z) S、CdZnSeS / CdSeS / ZnSeS / ZnS / CdZnS、Cd A Zn (1-A) Se C S (1-C) / Cd B Zn (1-B) Se D S (1-D) / Cd K Zn (1-K) Se L S (1-L) / ZnSeS / ZnS / CdZnS、CdZnSeS / CdZnSe / ZnSeS / ZnS / CdZnS、CdSeS / CdZnSeS / ZnSeS / ZnS / CdZnS、CdZnSe / CdZnSeS / ZnSeS / ZnS / CdZnS、CdZnSe / ZnSeS / ZnS / CdZnS、CdZnSe / ZnSe M S (1-M) / ZnSe N S (1-N) / ZnS / CdZnS 、 CdZnSe / CdS / ZnSeS / ZnS / CdZnS 、CdZnSe / CdZnSeS / ZnSeS / ZnS / CdZnS / CdZnS、 CdZnSe / CdS / ZnS / CdS、CdZnSe / CdS / ZnS / CdZnS、 CdZnSe / Cd Y Zn (1-Y) S / Cd X Zn (1-X) S / Cd Z Zn (1-Z) S、CdZnSe / CdSeS / ZnSeS / ZnS / CdZnS、CdZnSe / Cd A Zn (1-A) Se C S (1-C) / Cd B Zn (1-B) Se D S (1-D) / ZnSeS / ZnS / CdZnS、CdZnSe / ZnSeS / ZnS / CdZnS、InP / ZnSeS / ZnS / CdZnS、InP / ZnSe M S (1-M) / ZnSe N S (1-N) / ZnS / CdZnS、InP / CdS / ZnSeS / ZnS / CdZnS、InP / CdZnSeS / ZnSeS / ZnS / CdZnS / CdZnS、InP / CdS / ZnS / CdS、InP / CdS / ZnS / CdZnS、InP / Cd Y Zn (1-Y) S / Cd X Zn (1-X) S / Cd Z Zn (1-Z) S、InP / CdSeS / ZnSeS / ZnS / CdZnS、InP / Cd A Zn (1-A) Se C S (1-C) / Cd B Zn (1-B) Se D S (1-D) / ZnSeS / ZnS / CdZnS、InP / CdZnSe / ZnSeS / ZnS / CdZnS、InZnP / ZnSeS / ZnS / CdZnS、InZnP / ZnSe M S (1-M) / ZnSe N S (1-N) / ZnS / CdZnS、InZnP / CdS / ZnSeS / ZnS / CdZnS、InZnP / CdZnSeS / ZnSeS / ZnS / CdZnS / CdZnS、InZnP / CdS / ZnS / CdS、InZnP / CdS / ZnS / CdZnS、InZnP / Cd Y Zn (1-Y) S / Cd X Zn (1-X) S / Cd Z Zn (1-Z) S、InZnP / CdSeS / ZnSeS / ZnS / CdZnS、InZnP / Cd A Zn (1-A) Se C S (1-C) / Cd B Zn (1-B) Se D S (1-D) / ZnSeS / ZnS / CdZnS、InZnP / CdZnSe / ZnSeS / ZnS / CdZnS、InZnPS / ZnSeS / ZnS / CdZnS、InZnPS / ZnSe M S (1-M) / ZnSe N S (1-N) / ZnS / CdZnS、InZnPS / CdS / ZnSeS / ZnS / CdZnS、InZnPS / CdZnSeS / ZnSeS / ZnS / CdZnS / CdZnS 、 InZnPS / CdS / ZnS / CdS 、InZnPS / CdS / ZnS / CdZnS、 InZnPS / Cd Y Zn (1-Y) S / Cd X Zn (1-X) S / Cd Z Zn (1-Z) S、InZnPS / CdSeS / ZnSeS / ZnS / CdZnS、InZnPS / Cd A Zn (1-A) Se CS (1-C) / Cd B Zn (1-B) Se D S (1-D) / ZnSeS / ZnS / CdZnS, InZnPS / CdZnSe / ZnSeS / ZnS / CdZnS, InZnP / ZnSeS / ZnS / InZnS, InP / ZnSeS / ZnS / InZnS, InZnP / ZnSeS / ZnS / InZnS / InZnS, InP / ZnSeS / ZnS / InZnS / InZnS, InZnP / InZnSeS / ZnS / InZnS / InZnS, InZnP / InZnSeS / ZnS / InZnS, InP / InZnSeS / ZnS / InZnS, InZnP / InZnSe / ZnS / InZnS / InZnS, InP / InZnSeS / ZnS / InZnS, InZnP / InZnSe / ZnS / InZnS, InP / InZnSe / ZnS / InZnS, InZnP / InZnSe / InZnSeS / ZnS / InZnS / InZnS, InP / InZnSe / InZnSeS / ZnS / InZnS / InZnS, InZnP / InZnSe / InZnSeS / ZnS / InZnS, InP / InZnSe / InZnSeS / ZnS / InZnS, InZnPS / ZnSeS / ZnS / InZnS, InZnPS / ZnSeS / ZnS / InZnS / InZnS, InZnPS / InZnSeS / ZnS / InZnS / InZnS, InZnPS / InZnSeS / ZnS / InZnS, InZnPS / InZnSe / ZnS / InZnS / InZnS, InZnPS / InZnSe / ZnS / InZnS, InZnPS / InZnSe / InZnSeS / ZnS / InZnS / InZnS, InZnPS / InZnSe / InZnSeS / ZnS / InZnS, ZnSeTe / ZnSe / ZnSeS / ZnS / InZnS, ZnSeTe / ZnSeS / ZnS / InZnS or ZnSeTe / ZnSe / ZnSeS / ZnS / InZnS / InZnS, where X, Y, Z, M, N, A, B, C, D, L and K ∈ (0, 1); Y > X, Z > X; M > N; C ≤ D and A > B, or, A ≤ B and C > D; D ≤ L and B > K, or, B ≤ K and D > L.

[0013] Optionally, the structure of the intermediate quantum dot is: the above-mentioned semiconductor material core / the above-mentioned at least one first semiconductor material shell / the above-mentioned second semiconductor material shell, and the average particle diameter of the above-mentioned intermediate quantum dot is larger than the Bohr exciton diameter of the above-mentioned semiconductor material core.

[0014] Optionally, each shell layer of the second semiconductor material shell on the side away from the semiconductor material core changes the fluorescence emission peak position of the quantum dot within ±2nm, and changes the fluorescence quantum yield of the quantum dot within ±2%.

[0015] Optionally, the average size of the semiconductor material core is 2 to 15 nm, the thickness of the second semiconductor material shell is 1 to 10 nm, and the thickness of the third semiconductor material shell is 2 to 15 nm.

[0016] Optionally, the quantum dot comprises 1 to 5 shells of the first semiconductor material, and the total thickness of all the shells of the first semiconductor material is 1 to 10 nm.

[0017] Optionally, the quantum dot comprises 0 to 5 shells of the fourth semiconductor material, and the total thickness of all the shells of the fourth semiconductor material is 0 to 10 nm.

[0018] The present disclosure also provides a light-emitting device, which includes any of the above-mentioned quantum dots, and the light-emitting mechanism of the above-mentioned light-emitting device is photoluminescence or electroluminescence.

[0019] By applying the technical solution provided by the present invention, that is, the quantum dot has an olive-shaped or olive-like band structure, and by setting a second semiconductor material shell with the largest band width between the first semiconductor material shell and the third semiconductor material shell, the excitons of the quantum dot are basically confined within the second semiconductor material shell. At this time, continuing to coat the second semiconductor material shell with a small band width will not lead to an increase in the defect states of the quantum dot, but can also release the lattice stress brought by the previous shell, and can play the role of a sacrificial layer in the process of the quantum dot's resistance to environmental erosion, thereby ultimately achieving an improvement in the environmental stability of the entire quantum dot and a higher quantum yield. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The drawings constituting part of the present application are used to provide a further understanding of the present disclosure. The exemplary embodiments of the present disclosure and their descriptions are used to explain the present disclosure and do not constitute an improper limitation on the present disclosure. In the drawings:

[0021] Figure 1 A schematic diagram showing the energy band structure of quantum dots in some embodiments of the present disclosure is shown;

[0022] Figure 2 A schematic diagram showing the energy band structure of quantum dots in some embodiments of the present disclosure is shown;

[0023] Figure 3 A schematic diagram showing the energy band structure of quantum dots in some embodiments of the present disclosure is shown;

[0024] Figure 4 The fluorescence spectra of the CdSeS / CdZnSeS / ZnSeS / ZnS intermediate structure quantum dots (i.e., quantum dots after coating with the widest energy band shell) and the CdSeS / CdZnSeS / ZnSeS / ZnS / CdZnS quantum dots (i.e., quantum dots after coating with all shells) of Example 1 of the present disclosure are compared. The emission peak positions of the two differ by about 0.5 nm.

[0025] Figure 5 A transmission electron microscope image of the CdSeS / CdZnSeS / ZnSeS / ZnS intermediate structure quantum dots of Example 1 of the present disclosure is shown;

[0026] Figure 6 A transmission electron microscopy image of CdSeS / CdZnSeS / ZnSeS / ZnS / CdZnS core-shell quantum dots of Example 1 of the present disclosure is shown. DETAILED DESCRIPTION

[0027] It should be noted that the following detailed descriptions are illustrative and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.

[0028] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequential order. It should be understood that the data used in this way can be interchanged in appropriate circumstances, so that the embodiments of the present application described here. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, the process, method, system, product or equipment comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or equipment.

[0029] The "energy of the conduction band bottom" and "energy of the valence band top" of the core and shell of the quantum dots involved in the present disclosure are calculated according to the energy of the conduction band bottom and valence band top of the corresponding bulk material. The energy values ​​of the conduction band bottom and valence band top of the above-mentioned bulk material are obtained based on the existing binary compound semiconductor physical data and the linear relationship of the energy band of the alloy semiconductor composed of binary compounds. 0.1 Zn 0.9 Se 0.8 S 0.2 For example, Cd0.1 Zn 0.9 Se 0.8 S 0.2 It can be regarded as composed of 0.1CdSe, 0.7ZnSe and 0.2ZnS. The energy of the bottom of the conduction band of the binary compounds CdSe, ZnSe and ZnS are a, b and c respectively, and the energy of the top of the valence band of CdSe, ZnSe and ZnS are d, e and f respectively. Then Cd 0.1 Zn 0.9 Se 0.8 S 0.2 The energy of the bottom of the conduction band = 0.1a + 0.7b + 0.2c, and the energy of the top of the valence band = 0.1d + 0.7e + 0.2f.

[0030] As mentioned in the background technology, isolating the contact between the excitons and the environment by coating with a thick shell has limited effect on improving the stability of quantum dots, and there is also the disadvantage of reducing the quantum yield of quantum dots. The inventors of this application have found through research that there may be two reasons for the above technical problems: on the one hand, as the thickness of the shell increases, the internal defects and surface defects of the quantum dots increase; on the other hand, the lattice stress caused by the thick shell increases, which in turn has an adverse effect on the stability of the quantum dots. Therefore, the inventors of this application believe that in order to achieve the goal of improving the environmental stability of quantum dots while maintaining a high quantum yield, it is necessary to first isolate the contact between the excitons and the environment, and secondly to eliminate the lattice stress and defect states of the quantum dots.

[0031] One aspect of the present disclosure provides a quantum dot, comprising a semiconductor material core, at least one first semiconductor material shell sequentially arranged on the surface of the semiconductor material core, a third semiconductor material shell located at the outermost layer of the quantum dot, and a second semiconductor material shell located between the first semiconductor material shell and the third semiconductor material shell, wherein in the radial direction from the semiconductor material core to the second semiconductor material shell, the energies of the conduction band bottoms of the semiconductor material core, the first semiconductor material shell and the second semiconductor material shell sequentially increase, and the energies of the corresponding valence band tops sequentially decrease, the conduction band bottom of the third semiconductor material shell is lower than the conduction band bottom of the second semiconductor material shell, and the valence band top of the third semiconductor material shell is higher than the valence band top of the second semiconductor material shell; wherein the chemical elements contained in each of the first semiconductor material shells are the same or different.

[0032] The quantum dots provided by the present disclosure have an olive-shaped or quasi-olive-shaped energy band structure. By setting a second semiconductor material shell with the largest energy band width between the first semiconductor material shell and the third semiconductor material shell, the excitons of the quantum dots are basically confined within the second semiconductor material shell. At this time, continuing to coat the second semiconductor material shell with a small energy band width will not lead to an increase in the defect states of the quantum dots, but can also release the lattice stress brought by the previous shell, and can play the role of a sacrificial layer in the process of the quantum dots resisting environmental erosion, thereby ultimately achieving the improvement of the environmental resistance stability of the entire quantum dots and a higher quantum yield.

[0033] It should be noted that when the above-mentioned quantum dots include two or more first semiconductor material shells, the energy of the conduction band bottom of each first semiconductor material shell is between the energy of the conduction band bottom of the semiconductor material core and the second semiconductor material shell. In the radial direction from the semiconductor material core to the second semiconductor material shell, the energy change of the conduction band bottom of each first semiconductor material shell generally shows an upward trend, and the energy change of the corresponding valence band top of each first semiconductor material shell generally shows a downward trend. However, in some embodiments, the energy of the conduction band bottom of one of the first semiconductor material shells is allowed to be lower than the energy of the conduction band bottom of its previous shell layer (or semiconductor material core) (the difference between the two does not exceed 1eV), and / or the energy of the valence band top of the first semiconductor material shell is higher than the energy of the valence band top of its previous shell layer (or semiconductor material core) (the difference between the two does not exceed 0.5eV).

[0034] In a preferred embodiment, when the above-mentioned quantum dot includes two or more first semiconductor material shells, in the radial direction from the semiconductor material core to the second semiconductor material shell, the energy of the conduction band bottom of each first semiconductor material shell increases successively, and the energy of the valence band top decreases successively.

[0035] Since the second semiconductor material shell has the function of confining excitons, continuing to coat the shell layer on the surface of the second semiconductor material shell has little effect on the fluorescence emission peak position and quantum yield of the quantum dot as a whole. In some embodiments, the degree of change of the fluorescence emission peak position of the quantum dot by each shell layer on the side away from the semiconductor material core is within ±2nm, and the degree of change of the fluorescence quantum yield of the quantum dot is within ±2%. The above-mentioned degree of change of the fluorescence emission peak position and the fluorescence quantum yield is the change of the fluorescence peak position and quantum yield of the quantum dot before and after coating the second semiconductor material shell.

[0036] In some embodiments, the quantum dot includes at least one fourth semiconductor material shell between the second semiconductor material shell and the third semiconductor material shell, and in the radial direction from the second semiconductor material shell to the third semiconductor material shell, the energy of the conduction band bottom of the second semiconductor material shell, at least one fourth semiconductor material shell and the third semiconductor material shell decreases in sequence, and the energy of the corresponding valence band top increases in sequence; wherein the chemical elements contained in each fourth semiconductor material shell are the same or different. When the quantum dot includes two or more fourth semiconductor material shells, in the radial direction from the second semiconductor material shell to the third semiconductor material shell, the energy of the conduction band bottom of each fourth semiconductor material shell decreases in sequence, and the energy of the valence band top increases in sequence.

[0037] In other embodiments, the above-mentioned quantum dots include a fifth semiconductor material shell disposed on a second semiconductor material shell, and a sixth semiconductor material shell disposed on the fifth semiconductor material shell, the conduction band bottom of the sixth semiconductor material shell being higher than the conduction band bottom of the fifth semiconductor material shell and lower than the conduction band bottom of the second semiconductor material shell, and the valence band top of the sixth semiconductor material shell being lower than the valence band top of the fifth semiconductor material shell and higher than the valence band top of the second semiconductor material shell.

[0038] In the above embodiment, the energy of the conduction band bottom of the third semiconductor material shell can be between the energies of the conduction band bottoms of the fifth semiconductor material shell and the sixth semiconductor material shell, and can also be lower than the energy of the conduction band bottom of the fifth semiconductor material shell or higher than the energy of the conduction band bottom of the sixth semiconductor material shell, but must be lower than the energy of the conduction band bottom of the second semiconductor material shell; correspondingly, the energy of the valence band top of the third semiconductor material shell can be between the energies of the valence band tops of the fifth semiconductor material shell and the sixth semiconductor material shell, and can also be higher than the energy of the valence band top of the fifth semiconductor material shell or lower than the energy of the valence band top of the sixth semiconductor material shell, but must be higher than the energy of the valence band top of the second semiconductor material shell.

[0039] In some embodiments, the energy difference between the conduction band bottom of the sixth semiconductor material shell and the conduction band bottom of the fifth semiconductor material shell does not exceed 1.5 eV, and the energy difference between the valence band top of the fifth semiconductor material shell and the valence band top of the sixth semiconductor material shell does not exceed 2 eV.

[0040] In some embodiments, the energy difference between the bottom of the conduction band of the second semiconductor material shell and the semiconductor material core is less than or equal to 1.5 eV, and the energy difference between the top of the valence band of the semiconductor material core and the second semiconductor material shell is less than or equal to 0.7 eV. For example, the material of the semiconductor material core is selected from CdSe, CdSeS, CdZnSe, CdZnSeS or ZnSeTe.

[0041] In some embodiments, the energy difference between the bottom of the conduction band of the second semiconductor material shell and the semiconductor material core is less than or equal to 1.4 eV, and the energy difference between the top of the valence band of the semiconductor material core and the second semiconductor material shell is less than or equal to 1.2 eV. For example, the material of the semiconductor material core is selected from InP, InZnP, or InZnPS.

[0042] In some embodiments, the first semiconductor material shell includes at least one of selenium and sulfur and at least one of cadmium and zinc, or the first semiconductor material shell includes at least one of selenium and sulfur and at least one of indium and zinc.

[0043] In some embodiments, the types of elements included in the first semiconductor material shell and the semiconductor material core may be the same.

[0044] In some embodiments, the material of the second semiconductor material shell may be selected from CdS, ZnS, or Cd X Zn (1-X) S(0 < X < 1), but not limited thereto.

[0045] For example, the above quantum dots may be selected from CdSeS / CdZnSeS / ZnSeS / ZnS / CdZnS, CdSeS / ZnSeS / ZnS / CdZnS, CdSeS / ZnSe M S (1-M) / ZnSe N S (1-N) / ZnS / CdZnS, CdSeS / CdS / ZnSeS / ZnS / CdZnS, CdSeS / CdZnSeS / ZnSeS / ZnS / CdZnS / CdZnS, CdSeS / CdS / ZnS / CdS, CdSeS / CdS / ZnS / CdZnS, CdSeS / Cd Y Zn (1-Y) S / Cd X Zn (1-X) S / Cd Z Zn (1-Z) S, CdSe M S (1-M) / CdSe N S (1-N) / ZnSeS / ZnS / CdZnS, CdSeS / Cd A Zn (1-A) Se C S (1-C) / Cd B Zn (1-B) Se D S (1-D) / ZnSeS / ZnS / CdZnS、CdSeS / CdZnSe / ZnSeS / ZnS / CdZnS、CdSe / CdZnSeS / ZnSeS / ZnS / CdZnS、CdSe / ZnSeS / ZnS / CdZnS、CdSe / ZnSe M S (1-M) / ZnSe N S (1-N) / ZnS / CdZnS、CdSe / CdS / ZnSeS / ZnS / CdZnS、CdSe / CdZnSeS / ZnSeS / ZnS / CdZnS / CdZnS、CdSe / CdS / ZnS / CdZnS、CdSe / CdSeS / ZnSeS / ZnS / CdZnS、CdSe / Cd A Zn (1-A) Se C S (1-C) / Cd B Zn (1-B) Se D S / ZnSeS / ZnS / CdZnS、CdSe / CdZnSe / ZnSeS / ZnS / CdZnS、CdSe / CdSeS / CdS / CdZnS / ZnS / CdZnS、CdSe / CdZnS / ZnS / CdZnS、CdSe / CdSeS / CdS / CdSeS、CdSe / CdZnS / ZnS / CdZnS / ZnS、CdSe / CdS / Cd X Zn (1-X) S / CdS、CdSe / Cd Y Zn (1-Y) S / Cd X Zn (1-X) S / Cd Z Zn (1-Z) S、Cd A Zn (1-A) Se C S (1-C) / Cd B Zn (1-B) Se D S (1-D) / ZnSeS / ZnS / CdZnS、CdZnSeS / ZnSeS / ZnS / CdZnS、CdZnSeS / ZnSe M S (1-M) / ZnSe N S (1-N) / ZnS / CdZnS、CdZnSeS / CdS / ZnSeS / ZnS / CdZnS、Cd A Zn (1-A) Se C S(1-C) / Cd B Zn (1-B) Se D S (1-D) / ZnSeS / ZnS / CdZnS / CdZnS、CdZnSeS / CdS / ZnS / CdS、CdZnSeS / CdS / ZnS / CdZnS、CdZnSeS / Cd Y Zn (1-Y) S / Cd X Zn (1-X) S / Cd Z Zn (1-Z) S、CdZnSeS / CdSeS / ZnSeS / ZnS / CdZnS、Cd A Zn (1-A) Se C S (1-C) / Cd B Zn (1-B) Se D S (1-D) / Cd K Zn (1-K) Se L S (1-L) / ZnSeS / ZnS / CdZnS、CdZnSeS / CdZnSe / ZnSeS / ZnS / CdZnS、CdSeS / CdZnSeS / ZnSeS / ZnS / CdZnS、CdZnSe / CdZnSeS / ZnSeS / ZnS / CdZnS、CdZnSe / ZnSeS / ZnS / CdZnS、CdZnSe / ZnSe M S (1-M) / ZnSe N S (1-N) / ZnS / CdZnS、CdZnSe / CdS / ZnSeS / ZnS / CdZnS、CdZnSe / CdZnSeS / ZnSeS / ZnS / CdZnS / CdZnS、CdZnSe / CdS / ZnS / CdS、CdZnSe / CdS / ZnS / CdZnS、CdZnSe / Cd Y Zn (1-Y) S / Cd X Zn (1-X) S / Cd Z Zn (1-Z) S、CdZnSe / CdSeS / ZnSeS / ZnS / CdZnS、CdZnSe / Cd A Zn (1-A) Se C S (1-C) / Cd B Zn (1-B) SeD S (1-D) / ZnSeS / ZnS / CdZnS、CdZnSe / ZnSeS / ZnS / CdZnS、InP / ZnSeS / ZnS / CdZnS、InP / ZnSe M S (1-M) / ZnSe N S (1-N) / ZnS / CdZnS、InP / CdS / ZnSeS / ZnS / CdZnS、InP / CdZnSeS / ZnSeS / ZnS / CdZnS / CdZnS、InP / CdS / ZnS / CdS、InP / CdS / ZnS / CdZnS、InP / Cd Y Zn (1-Y) S / Cd X Zn (1-X) S / Cd Z Zn (1-Z) S、InP / CdSeS / ZnSeS / ZnS / CdZnS、InP / Cd A Zn (1-A) Se C S (1-C) / Cd B Zn (1-B) Se D S (1-D) / ZnSeS / ZnS / CdZnS、InP / CdZnSe / ZnSeS / ZnS / CdZnS、InZnP / ZnSeS / ZnS / CdZnS、InZnP / ZnSe M S (1-M) / ZnSe N S (1-N) / ZnS / CdZnS、InZnP / CdS / ZnSeS / ZnS / CdZnS、InZnP / CdZnSeS / ZnSeS / ZnS / CdZnS / CdZnS、InZnP / CdS / ZnS / CdS、InZnP / CdS / ZnS / CdZnS、InZnP / Cd Y Zn (1-Y) S / Cd X Zn (1-X) S / Cd Z Zn (1-

[0046] Z) S、InZnP / CdSeS / ZnSeS / ZnS / CdZnS、InZnP / Cd A Zn (1-A) Se C S (1-C) / Cd BZn (1-B) Se D S (1-D) / ZnSeS / ZnS / CdZnS、InZnP / CdZnSe / ZnSeS / ZnS / CdZnS、InZnPS / ZnSeS / ZnS / CdZnS、InZnPS / ZnSe M S (1-M) / ZnSe N S (1-N) / ZnS / CdZnS、InZnPS / CdS / ZnSeS / ZnS / CdZnS、InZnPS / CdZnSeS / ZnSeS / ZnS / CdZnS / CdZnS、InZnPS / CdS / ZnS / CdS、InZnPS / CdS / ZnS / CdZnS、InZnPS / Cd Y Zn (1-Y) S / Cd X Zn (1-X) S / Cd Z Zn (1-Z) S、InZnPS / CdSeS / ZnSeS / ZnS / CdZnS、InZnPS / Cd A Zn (1-A) Se C S (1-C) / Cd B Zn (1-B) Se D S (1-D) / ZnSeS / ZnS / CdZnS, InZnPS / CdZnSe / ZnSeS / ZnS / CdZnS, InZnP / ZnSeS / ZnS / InZnS, InP / ZnSeS / ZnS / InZnS, InZnP / ZnSeS / ZnS / InZnS / InZnS, InP / ZnSeS / ZnS / InZnS / InZnS, InZnP / InZnSeS / ZnS / InZnS / InZnS, InZnP / InZnSeS / ZnS / InZnS, InP / InZnSeS / ZnS / InZnS, InZnP / InZnSe / ZnS / InZnS / InZnS, InP / InZnSeS / ZnS / InZnS, InZnP / InZnSe / ZnS / InZnS, InP / InZnSe / ZnS / InZnS, InZnP / InZnSe / InZnSeS / ZnS / InZnS / InZnS, InP / InZnSe / InZnSeS / ZnS / InZnS / InZnS, InZnP / InZnSe / InZnSeS / ZnS / InZnS, InP / InZnSe / InZnSeS / ZnS / InZnS, InZnPS / ZnSeS / ZnS / InZnS, InZnPS / ZnSeS / ZnS / InZnS / InZnS, InZnPS / InZnSeS / ZnS / InZnS / InZnS, InZnPS / InZnSeS / ZnS / InZnS, InZnPS / InZnSe / ZnS / InZnS / InZnS, InZnPS / InZnSe / ZnS / InZnS, InZnPS / InZnSe / InZnSeS / ZnS / InZnS / InZnS, InZnPS / InZnSe / InZnSeS / ZnS / InZnS, ZnSeTe / ZnSe / ZnSeS / ZnS / InZnS, ZnSeTe / ZnSeS / ZnS / InZnS or ZnSeTe / ZnSe / ZnSeS / ZnS / InZnS / InZnS, where X, Y, Z, M, N, A, B, C, D, L and K ∈ (0, 1); Y > X, Z > X; M > N; C ≤ D and A > B, or, A ≤ B and C > D; D ≤ L and B > K, or, B ≤ K and D > L.

[0047] For the sake of brevity in writing, some of the multiple cores or multiple shells in this disclosure are expressed in a form like "CdZnS" to indicate the types of elements contained, but this disclosure is intended to include forms like "Cd X Zn (1-X)The meaning of "S, where 0 < X < 1". Therefore, even if two identical parts such as "CdZnS / CdZnS" appear in the structural description of a quantum dot, unless it is specifically stated that the elemental percentages of the two parts are equal and / or the energy bands are the same, the elemental percentages in the two parts may not be equal.

[0048] In some embodiments, each shell of the above core-shell quantum dot is a homogeneous semiconductor material.

[0049] In some embodiments, the structure of the intermediate quantum dot is: a semiconductor material core / at least one first semiconductor material shell / a second semiconductor material shell, and the average particle diameter of the intermediate quantum dot is greater than the Bohr exciton diameter of the semiconductor material core. Thus, the optical properties of the quantum dot are not affected by the subsequent coating shell, such as the fluorescence peak position remaining basically unchanged and the fluorescence quantum yield remaining basically unchanged, etc. " / " indicates that the two sides are adjacent shells of the quantum dot (or the core and the shell adjacent to the core).

[0050] In some embodiments, the average size of the semiconductor material core is about 2 - 15 nm, the thickness of the second semiconductor material shell is about 1 - 10 nm, and the thickness of the third semiconductor material shell is about 2 - 15 nm.

[0051] In some embodiments, the quantum dot includes 1 - 5 first semiconductor material shells, and the total thickness of all the first semiconductor material shells is about 1 - 10 nm. Preferably, the total thickness of all the first semiconductor material shells is about 4 - 10 nm.

[0052] In some embodiments, the quantum dot includes 0 - 5 fourth semiconductor material shells, and the total thickness of all the fourth semiconductor material shells is about 0 - 10 nm. Preferably, the total thickness of all the fourth semiconductor material shells is about 2 - 10 nm.

[0053] In some embodiments, the above quantum dot is formulated into a quantum dot glue, and the quantum dot glue can be stored for a long time (at least one year) and the quantum yield remains stable.

[0054] According to another aspect of the present disclosure, a light-emitting device is provided, which includes any of the above quantum dots. The light-emitting mechanism of the light-emitting device is photoluminescence or electroluminescence, and the structure of the light-emitting device can refer to the prior art. Since the above quantum dot has good environmental stability resistance and a high quantum yield, the light-emitting stability and light-emitting efficiency of the light-emitting device made of the quantum dot are also very good.

[0055] In some embodiments, the above electroluminescent device includes an emission layer, and the emission layer includes the above quantum dot.

[0056] In some embodiments, the light emitting device is a quantum dot film, which includes a quantum dot glue layer and two barrier film layers arranged on the upper and lower surfaces of the quantum dot glue layer, and the water vapor permeability of the barrier film layer is ≤0.3g / m 2 24h, oxygen transmission rate ≤ 0.3cm 3 / m 2 ·24h·0.1MPa, the quantum dot film is exposed to high temperature and humidity (65℃ / 95%RH) or high temperature blue light (70℃, 0.5W / cm 2 ) for 1000 hours, the relative quantum yield decreased within 5%. The relative quantum yield is calculated based on the assumption that the initial quantum yield is 100%.

[0057] In some embodiments, the light-emitting device is a quantum dot film, which includes a quantum dot glue layer and two substrate layers, such as a PET film layer, disposed on the upper and lower surfaces of the quantum dot glue layer. The quantum dot glue layer includes quantum dots. The quantum dot film is exposed to high temperature and high humidity (65°C / 95% RH) or high temperature blue light (70°C, 0.5W / cm 2 ) conditions for aging for 1000 hours, its relative quantum yield decreased within 10%.

[0058] In some embodiments, the light-emitting device is a quantum dot diffusion plate, which includes a polymer matrix, the quantum dots dispersed in the polymer matrix, and scattering particles; the quantum dot diffusion plate is subjected to high temperature and high humidity (65°C / 95%RH), high temperature blue light illumination (70°C, 0.5W / cm 2 ) or high temperature and high humidity blue light (65℃

[0059] / 95%RH,0.5W / cm 2 ) conditions for aging for 1000 hours, its relative quantum yield decreased within 10%.

[0060] The polymer material in the above-mentioned quantum dot glue layer and the above-mentioned quantum dot diffusion plate can be selected from at least one of polyamide, polyurethane, polylactic acid, polyglycolic acid, polylactic acid-glycolic acid copolymer, polyethylene glycol-lactic acid-glycolic acid copolymer, polyethylene glycol, polyhydroxybutyric acid, polyhydroxyalkane, polybutylene succinate, polyterephthalate, polyhydroxyalkanoic acid and acrylic resin.

[0061] The technical effects of the present application are further described below in conjunction with specific embodiments.

[0062] Preparation of 2mmol / mL S-TOP solution: Weigh 0.64g S, place it in a 20mL glass bottle with a rubber stopper and seal it, and use inert gas to expel the air. Inject 10mL TOP, and repeatedly oscillate and ultrasonicate the mixture until S is fully dissolved. For the preparation of S-TOP solutions of other concentrations, keep the solvent volume unchanged, and just change the amount of S accordingly by calculation.

[0063] Preparation of 2mmol / mL Se-TOP solution: Weigh 1.58g Se, place it in a 20mL glass bottle with a rubber stopper and seal it, and use inert gas to expel the air. Inject 10mL TOP, and repeatedly oscillate and ultrasonicate the mixture until Se is fully dissolved. For the preparation of Se-TOP solutions of other concentrations, keep the solvent volume unchanged, and just change the amount of Se accordingly by calculation.

[0064] Preparation of 2mmol / mL S-TBP solution: Weigh 0.64g S, place it in a 20mL glass bottle with a rubber stopper and seal it, and expel the air with inert gas. Inject 10mL TBP, and repeatedly oscillate and sonicate the mixture until S is fully dissolved. For the preparation of S-TBP solutions of other concentrations, keep the solvent volume unchanged and just change the amount of S accordingly by calculation.

[0065] Example 1

[0066] Synthesis of green CdSeS / CdZnSeS / ZnSeS / ZnS / CdZnS core-shell quantum dots: 4mmol zinc acetate, 0.2mmol cadmium acetate, 4.6g oleic acid, and 10mL ODE were placed in a 100mL three-necked flask, the temperature was raised to 180°C, and nitrogen was introduced for 30 minutes. The temperature was raised to 310°C, and CdSeS quantum dots with an absorbance of 50 at 472nm were injected, followed by 1.5mL Se-S-TOP solution (mix 1mL Se-TOP with 0.5mL S-TOP), and the reaction was continued for 20min. Cool down to 180℃, add 40mmol zinc acetate, 80mmol oleic acid, 20mL ODE solution, exhaust with nitrogen for 30min, raise the temperature to 310℃, inject 1.5mL Se-S-TOP solution (mix 1mL Se-TOP with 0.5mL S-TOP), react for 20min, cool down to 290℃, add 10mL S-TOP solution at a rate of 10mL / h, after the addition, add 5mL S-TOP and 5mL oleic acid cadmium solution (0.2mmol / mL) at the same rate, stop the reaction after the addition.

[0067] Take appropriate amount of CdSeS quantum dots, CdSeS / CdZnSeS / ZnSeS / ZnS intermediate structure quantum dots and CdSeS / CdZnSeS / ZnSeS / ZnS / CdZnS core-shell quantum dots samples for transmission electron microscopy test. The average size of CdSeS quantum dots is about 3nm, and the average size of CdSeS / CdZnSeS / ZnSeS / ZnS intermediate structure quantum dots is about 15nm (such as Figure 5 The average size of CdSeS / CdZnSeS / ZnSeS / ZnS / CdZnS core-shell quantum dots is about 21 nm (as shown in Figure 6 The Bohr exciton diameter of the CdSeS quantum dot core is about 11 nm, which is smaller than the average size of the CdSeS / CdZnSeS / ZnSeS / ZnS intermediate structure quantum dots.

[0068] Table 1

[0069]

[0070] Example 2

[0071] GreenCdSeS / CdZnSeS / ZnSeS / ZnS / Cd 0.08 Zn 0.92 S / Cd 0.12 Zn 0.88 Synthesis of S core-shell quantum dots: 4mmol zinc acetate, 0.2mmol cadmium acetate, 4.6g oleic acid, and 10mL ODE were placed in a 100mL three-necked flask, the temperature was raised to 180°C, and nitrogen was introduced for 30 minutes. The temperature was raised to 310°C, and CdSeS quantum dots with an absorbance of 50 at 472nm were injected, followed by 1.5mL Se-S-TOP solution (mix 1mL Se-TOP with 0.5mL S-TOP), and the reaction was continued for 20min. Cool to 180°C, add 40mmol zinc acetate, 80mmol oleic acid, and 20mL ODE solution, introduce nitrogen to exhaust for 30min, raise the temperature to 310°C, inject 1.5mL Se-S-TOP solution (mix 1mL Se-TOP with 0.5mL S-TOP), react for 20 minutes, cool to 290°C, add 10mL S-TOP solution at a rate of 10mL / h, after the addition is complete, add a mixture of 2.5mL S-TOP and 2mL oleic cadmium solution (0.2mmol / mL) at the same rate, after the addition is complete, add a mixture of 2.5mL S-TOP and 3mL oleic cadmium solution (0.2mmol / mL) at the same rate, after the addition is complete, stop the reaction.

[0072] Table 2

[0073]

[0074] Example 3

[0075] Synthesis of red CdSe / CdSeS / CdS / CdSeS core-shell quantum dots: Take 10mmol cadmium acetate, 30mmol oleic acid, and 10g ODE in a 100mL three-necked flask, raise the temperature to 180℃, and introduce nitrogen to exhaust for 30 minutes. Raise the temperature to 250℃ and inject CdSe quantum dots with an absorbance of 50 at 560nm. Then add 1mL Se-S-TOP solution (mix 0.5mL Se-TOP with 0.5mL S-TOP) at a rate of 2mL / h. Then add 2mL S-TBP solution at the same rate. After the addition is completed, add 1mL Se-S-TOP solution (mix 0.5mL Se-TOP with 0.5mL S-TOP) at the same rate, and then stop the reaction.

[0076] Table 3

[0077]

[0078] Example 4

[0079] Red CdSe / CdS / Cd 0.05 Zn 0.95 Synthesis of S / CdS core-shell quantum dots: Take 2mmol cadmium acetate, 5mmol oleic acid, and 10g ODE in a 100mL three-necked flask, raise the temperature to 180℃, and pass nitrogen to exhaust for 30 minutes. Raise the temperature to 250℃ and inject CdSe quantum dots with an absorbance of 50 at 560nm. Then add 0.5mL S-TBP solution at a rate of 2mL / h. Then lower the temperature to 180℃, add 25mmol zinc acetate, 75mmol oleic acid, and 40g ODE, and pass nitrogen to exhaust for 30 minutes. Raise the temperature to 300℃, inject 10.5mL S-TBP solution, react for 3 minutes, stop the reaction, and purify. Dissolve in 1mL ODE.

[0080] Take 2mmol cadmium acetate, 5mmol oleic acid, and 10g ODE in a 100mL three-necked flask, raise the temperature to 180℃, and introduce nitrogen for 30 minutes. Raise the temperature to 250℃ and inject the above quantum dots. Then add 0.5mL S-TBP solution at a rate of 2mL / h.

[0081] Table 4

[0082]

[0083] Example 5

[0084] Synthesis of green CdSeS / ZnSeS / ZnSe / ZnS / CdZnS core-shell quantum dots: Place 4mmol zinc acetate, 4.6g oleic acid, and 10mL ODE in a 100mL three-necked flask, raise the temperature to 180°C, and introduce nitrogen for 30 minutes. Raise the temperature to 310°C, inject CdSeS quantum dots with an absorbance of 50 at 472nm, and then inject 1.5mL Se-S-TOP solution (mix 1mL Se-TOP with 0.5mL S-TOP), and react for 20min. The temperature was lowered to 180°C, 40 mmol zinc acetate, 80 mmol oleic acid, and 20 mL ODE solution were added, nitrogen was introduced for exhaust for 30 min, the temperature was raised to 310°C, 1.5 mL Se-TOP solution was injected, the reaction was continued for 20 min, the temperature was lowered to 290°C, 10 mL S-TOP solution was added dropwise at a rate of 10 mL / h, after the addition was completed, 5 mL S-TOP and 5 mL oleic acid cadmium solution (0.2 mmol / mL) were added dropwise at the same rate, and the reaction was stopped after the addition was completed.

[0085] Table 5

[0086]

[0087] Example 6

[0088] GreenCdSeS / CdZnSeS / ZnSeS / ZnS / Cd 0.08 Zn 0.92 S / Cd 0.04 Zn 0.96 S / Cd 0.12 Zn 0.88Synthesis of S core-shell quantum dots: 4mmol zinc acetate, 0.2mmol cadmium acetate, 4.6g oleic acid, and 10mL ODE were placed in a 100mL three-necked flask, the temperature was raised to 180°C, and nitrogen was introduced for 30 minutes. The temperature was raised to 310°C, and CdSeS quantum dots with an absorbance of 50 at 472nm were injected, followed by 1.5mL Se-S-TOP solution (mix 1mL Se-TOP with 0.5mL S-TOP), and the reaction was continued for 20min. Cool to 180°C, add 40mmol zinc acetate, 80mmol oleic acid, and 20mL ODE solution, introduce nitrogen to exhaust for 30min, raise the temperature to 310°C, inject 1.5mL Se-S-TOP solution (mix 1mL Se-TOP with 0.5mL S-TOP), react for 20 minutes, cool to 290°C, add 10mL S-TOP solution dropwise at a rate of 10mL / h, after the addition is complete, add a mixture of 2.5mL S-TOP and 2mL oleic cadmium solution (0.2mmol / mL) at the same rate, after the addition is complete, add a mixture of 2.5mL S-TOP and 1mL oleic cadmium solution (0.2mmol / mL) at the same rate, after the addition is complete, add a mixture of 2.5mL S-TOP and 1mL oleic cadmium solution (0.2mmol / mL) at the same rate, after the addition is complete, add a mixture of 2.5mL S-TOP and 3mL oleic cadmium solution (0.2mmol / mL) at the same rate to stop the reaction.

[0089] Table 6

[0090]

[0091] Example 7

[0092] Synthesis of green InP / ZnSeS / ZnS / CdZnS core-shell quantum dots: Weigh 0.15mmol (0.043g) of indium acetate, 0.45mmol (0.1036g) of tetradecanoic acid, and 10mL of ODE into a 50mL three-necked flask, heat to 180℃ and exhaust for 30 minutes, then lower the temperature to room temperature, inject a mixed solution of 0.1mmol (TMS) 3P and 1mL of TOP, then raise the temperature to 260℃ and react for 5 minutes. Then, the temperature was lowered to 180°C, and 1 mL of zinc stearate-octadecene solution (0.4 mmol / mL) was injected. The temperature was raised to 300°C, and 0.4 mL of Se-S-TOP solution (0.25 mL of Se-TOP and 0.25 mL of S-TOP were mixed) was injected, and the reaction was continued for 15 minutes. Subsequently, 1 mL of zinc stearate-octadecene solution was injected, and then 0.2 mL of 1 mmol / mL S-TOP solution was injected, and the reaction was continued for 15 minutes. Then, 2 mL of zinc stearate-octadecene solution was injected, and a mixture of 0.4 mL of S-TOP and 0.2 mL of cadmium oleate was added dropwise. After the addition was completed, the reaction was stopped.

[0093] Table 7

[0094]

[0095] Example 8

[0096] InP / Cd 0.1 Zn 0.9 Se 0.8 S 0.2 / Cd 0.05 Zn 0.95 Se 0.5 S 0.5 Synthesis of / ZnSeS / ZnS / CdZnS core-shell quantum dots: Weigh 0.15mmol (0.043g) of indium acetate, 0.45mmol (0.1036g) of tetradecanoic acid, and 10mL of ODE into a 50mL three-necked flask, heat to 180℃ and exhaust for 30 minutes, then lower the temperature to room temperature, inject a mixed solution of 0.1mmol (TMS) 3P and 1mL of TOP, then raise the temperature to 260℃ and react for 5 minutes. Then lower the temperature to 180℃, add 40mmol zinc acetate, 0.5mmol cadmium acetate, 80mmol oleic acid, and 20mL ODE solution, exhaust with nitrogen for 30min, raise the temperature to 310℃, inject 2.5mL Se-S-TOP solution (mix 2mL Se-TOP with 0.5mL S-TOP), react for 20 minutes, inject 1.25mL cadmium oleate (0.2mmol / mL), inject 2.5mL Se-S-TOP solution (mix 1.25mL Se-TOP with 1.25mL S-TOP), react for 20 minutes, inject 2.5mL Se-S-TOP solution (mix 1.25mL Se-TOP with 1.25mL S-TOP), react for 20 minutes, lower the temperature to 290℃, add 10mL S-TOP solution dropwise at a rate of 10mL / h, and after the addition is complete, add 5mL After the dropwise addition of S-TOP and 5 mL of cadmium oleate solution (0.2 mmol / mL) was completed, the reaction was stopped.

[0097] Table 8

[0098]

[0099] Comparative Example 1

[0100] Synthesis of green CdSeS / ZnS / CdZnS core-shell quantum dots: 40mmol zinc acetate, 30g oleic acid, and 50g ODE were placed in a 250mL three-necked flask, the temperature was raised to 180°C, and nitrogen was introduced for 30 minutes. The temperature was raised to 290°C, CdSeS quantum dots with an absorbance of 50 at 472nm were injected, and 10mL S-TOP solution was added dropwise at a rate of 10mL / h. After the addition was completed, a mixture of 5mL S-TOP and 5mL oleic acid cadmium solution (0.2mmol / mL) was added dropwise at the same rate. After the addition was completed, the reaction was stopped.

[0101] Table 9

[0102]

[0103] Comparative Example 2

[0104] Synthesis of green CdSeS / CdZnSeS / ZnSeS / ZnS core-shell quantum dots: 4mmol zinc acetate, 0.2mmol cadmium acetate, 4.6g oleic acid, and 10mL ODE were placed in a 100mL three-necked flask, the temperature was raised to 180°C, and nitrogen was introduced for 30 minutes. The temperature was raised to 310°C, and CdSeS quantum dots with an absorbance of 50 at 472nm were injected, followed by 1.5mL Se-S-TOP solution (mix 1mL Se-TOP with 0.5mL S-TOP), and the reaction was continued for 20min. Cool down to 180℃, add 40mmol zinc acetate, 80mmol oleic acid, and 20mL ODE solution, exhaust with nitrogen for 30min, increase the temperature to 310℃, inject 1.5mL Se-S-TOP solution (mix 1mL Se-TOP with 0.5mL S-TOP), react for 20min, cool down to 290℃, add 10mL S-TOP solution dropwise at a rate of 10mL / h, and stop the reaction after the addition is completed.

[0105] Table 10

[0106]

[0107] Comparative Example 3

[0108] Synthesis of red CdSe / CdS core-shell quantum dots: 2.4 mL dodecane, 7.6 mL oleylamine and 2 mL purified CdSe quantum dot (560 nm) solution were added to a 100 mL three-necked flask, ventilated for 10 minutes, and heated to 80 ° C. Single precursor Cd(DDTC)2 (0.1 mmol / mL) was used for coating. The amount of precursor injected each time was obtained after calibration based on the extinction coefficient of CdSe and the size of TEM. The amount of substance was 2×10 -7mol of CdSe quantum dots with a size of 3nm, the amount of single precursor injected in the first five layers was 0.08, 0.11, 0.15, 0.2 and 0.26mL respectively. The precursor was injected into the three-necked flask at 80℃ for the first time, maintained at this temperature for 5 minutes and then heated to 160℃. After reacting at 160℃ for 20 minutes, the heating was stopped and the temperature was lowered to 80℃. The reaction mode of each subsequent layer was the same as the first one. Until the coating reached 16 layers.

[0109] Table 11

[0110]

[0111] Comparative Example 4

[0112] Synthesis of InP / ZnSeS / ZnS core-shell quantum dots: Weigh 0.15mmol (0.043g) of indium acetate, 0.45mmol (0.1036g) of tetradecanoic acid, and 10mL of ODE into a 50mL three-necked flask, heat to 180°C and exhaust for 30 minutes, then lower the temperature to room temperature, inject a mixed solution of 0.1mmol (TMS) 3P and 1mL of TOP, then raise the temperature to 260°C and react for 5 minutes. Then lower the temperature to 180°C, inject 1mL of zinc stearate-octadecene solution (0.4mmol / mL), heat to 300°C, inject 0.4mL of Se-S-TOP solution (mix 0.25mL Se-TOP with 0.25mL S-TOP), react for 15 minutes, then inject 1mL of zinc stearate-octadecene solution, and then inject 0.2mL1mmol / mL S-TOP solution, react for 15 minutes, and stop the reaction.

[0113] Table 12

[0114]

[0115] Quantum dot purification method: take 10mL of the original solution into a 50mL centrifuge tube, add 40mL of acetone, heat to about 50°C, and then high-speed centrifuge precipitation at 8000 rpm for 3 minutes; take out and pour out the supernatant to obtain the precipitate.

[0116] The quantum dots of the above-mentioned embodiments and comparative examples were purified and dispersed in lauryl methacrylate to obtain a quantum dot dispersion system with an absorbance of 4 at 450nm of 4; the above-mentioned quantum dot dispersion system, 4g of acrylic polymer, and other additives with a mass percentage of 5.3% of acrylic polymer were mixed to obtain quantum dot glue. The water vapor permeability of a PET film layer with a thickness of 100μm was about 10g / m 2 24h, oxygen permeability is about 20cm 3 / m 2·24h·0.1MPa. A quantum dot glue is placed on the PET film layer, and then another PET film layer is placed on the quantum dot glue, and then the quantum dot glue is cured to form a quantum dot glue layer with a thickness of 100 μm to obtain a quantum dot film. The quantum dot glue is a UV glue based on acrylic polymer.

[0117] Detection:

[0118] After purification using the above-mentioned quantum dot purification method, the precipitate was dissolved in toluene, and the performance of the prepared quantum dot solution (absorbance at 450nm was 4) and the above-mentioned quantum dot film were tested. The specific detection method is as follows, and the detection results are shown in Table 13.

[0119] The method for detecting the quantum yield is: using a 450nm blue LED light as the backlight spectrum, using an integrating sphere to test the blue backlight spectrum and the spectrum through the quantum dot solution or quantum dot film respectively, and using the integral area of ​​the spectrum to calculate the quantum yield of the quantum dot solution or quantum dot film.

[0120] Quantum yield of quantum dot toluene solution = emission peak area of ​​quantum dot toluene solution / (blue backlight peak area-blue peak area that is not absorbed by quantum dot toluene solution)*100%;

[0121] The quantum yield of the quantum dot film = the emission peak area of ​​the quantum dot film / (the blue backlight peak area-the blue peak area that is not absorbed by the quantum dot film)*100%.

[0122] The luminescence stability test method is: the luminescence stability test method mainly includes high temperature blue light illumination (70℃, 0.5W / cm 2 ) and high temperature and high humidity (65℃ / 95%RH) and other aging conditions to detect the changes in the quantum yield of the quantum dot film.

[0123] Table 13

[0124]

[0125] It can be seen from the data in Table 13 that compared with the green CdSeS / ZnS / CdZnS core-shell quantum dots of Comparative Example 1, the initial quantum yields of the green CdSeS / CdZnSeS / ZnSeS / ZnS / CdZnS core-shell quantum dots of Example 1 and the CdSeS / ZnSeS / ZnSe / ZnS / CdZnS core-shell quantum dots of Example 5 in the quantum dot film are increased by 17% and 13%, respectively, and the quantum dot films using the core-shell quantum dots of Example 1 and Example 5 have very little decrease in quantum yield after 1000 hours of high-temperature blue light irradiation and high-temperature and high-humidity aging, while the quantum dot film using the core-shell quantum dots of Comparative Example 1 has a significantly decreased quantum yield after the same aging, especially after high-temperature blue light irradiation, the quantum dot film is completely non-luminescent, indicating that the core-shell quantum dots of Comparative Example 1 are not resistant to photooxidation and photohydrolysis, and after 1000 hours of high-temperature blue light irradiation, the quantum dots have been completely eliminated or there are too many defect states.

[0126] Compared with the green CdSeS / CdZnSeS / ZnSeS / ZnS core-shell quantum dots of Comparative Example 2, the green CdSeS / CdZnSeS / ZnSeS / ZnS / CdZnS core-shell quantum dots of Example 1 and the green CdSeS / CdZnSeS / ZnSeS / ZnS / CdZnS core-shell quantum dots of Example 2 0.08 Zn 0.92 S / Cd 0.12 Zn 0.88 S core-shell quantum dots and green CdSeS / CdZnSeS / ZnSeS / ZnS / Cd 0.08 Zn 0.92 S / Cd 0.04 Zn 0.96 S / Cd 0.12 Zn 0.88 The initial quantum yield of S core-shell quantum dots in the quantum dot film increased by 4% to 5%. The quantum dot film using the core-shell quantum dots of Examples 1, 2, and 6 showed a very small decrease in quantum yield after 1000 hours of high-temperature blue light illumination and high-temperature and high-humidity aging. However, the quantum dot film using the core-shell quantum dots of Comparative Example 2 showed a significant decrease in quantum yield after the same aging, especially after high-temperature blue light illumination, the quantum dot film did not emit light at all. Combined with Figure 4 It can be seen that after coating the shell with the largest energy band width, the optical properties of the quantum dots (fluorescence peak position and quantum yield) are almost unaffected by the subsequent coating shells, but the environmental stability of the quantum dots can be greatly improved by subsequently coating the shell with a reduced energy band width (compared to the shell with the largest energy band width), thereby achieving the effect of ensuring a higher quantum yield while improving the environmental stability of the quantum dots.

[0127] Compared with the CdSe / CdS core-shell quantum dots of Comparative Example 3, the CdSe / CdSeS / CdS / CdSeS core-shell quantum dots of Example 3 and the CdSe / CdS / CdSeS core-shell quantum dots of Example 4 0.05 Zn 0.95 The initial quantum yield of S / CdS core-shell quantum dots in the quantum dot film was increased by 8% and 12% respectively, and the quantum dot film using the core-shell quantum dots of Example 3 and Example 4 had a very small decrease in quantum yield after 1000 hours of high-temperature blue light irradiation and high-temperature and high-humidity aging. However, the quantum yield of the quantum dot film using the core-shell quantum dots of Comparative Example 3 decreased significantly after the same aging, especially after high-temperature blue light irradiation, the quantum dot film did not emit light at all, which also shows that the core-shell quantum dots of the embodiments of the present disclosure achieve a joint improvement in quantum yield and environmental stability.

[0128] Compared with the InP / ZnSeS / ZnS core-shell quantum dots of Comparative Example 4, the InP / ZnSeS / ZnS / CdZnS core-shell quantum dots of Example 7 and the InP / Cd 0.1 Zn 0.9 Se 0.8 S 0.2 / Cd 0.05 Zn 0.95 Se 0.5 S 0.5 The initial quantum yield of / ZnSeS / ZnS / CdZnS core-shell quantum dots in the quantum dot film was increased by 4% and 6%, respectively. The quantum yield of the quantum dot film using the core-shell quantum dots of Example 7 and Example 8 did not decrease substantially after 1000 hours of high-temperature blue light irradiation and high-temperature and high-humidity aging. However, the quantum yield of the quantum dot film using the core-shell quantum dots of Comparative Example 4 decreased significantly after the same aging, especially after high-temperature blue light irradiation, the relative quantum yield of the quantum dot film was only 5%, indicating that the technical solution disclosed in the present invention is also effective for jointly improving the quantum yield and environmental stability of InP-based core-shell quantum dots.

[0129] In summary, the core-shell quantum dots provided by the present disclosure have good environmental stability and high quantum yield.

[0130] The above description is only a preferred embodiment of the present disclosure and is not intended to limit the present disclosure. For those skilled in the art, the present disclosure may be subject to various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present disclosure shall be included in the protection scope of the present disclosure.

Claims

1. Quantum dots, characterized in that The invention comprises a semiconductor material core, at least one first semiconductor material shell sequentially arranged on the surface of the semiconductor material core, a third semiconductor material shell located at the outermost layer of the quantum dot, a second semiconductor material shell located between the first semiconductor material shell and the third semiconductor material shell, and at least one fourth semiconductor material shell located between the second semiconductor material shell and the third semiconductor material shell; in the radial direction from the semiconductor material core to the second semiconductor material shell, the energy of the conduction band bottoms of the semiconductor material core, the first semiconductor material shell and the second semiconductor material shell increases sequentially, and the energy of the corresponding valence band tops decreases sequentially, the conduction band bottom of the third semiconductor material shell is lower than the conduction band bottom of the second semiconductor material shell, and the valence band top of the third semiconductor material shell is higher than the valence band top of the second semiconductor material shell; wherein the chemical elements contained in each of the first semiconductor material shells are the same or different; when the quantum dot comprises two or more of the first semiconductor material shells, the energy of the conduction band bottom of each of the first semiconductor material shells is between the semiconductor material core and the second semiconductor material shell. Between the energy of the conduction band bottom, in the radial direction from the semiconductor material core to the second semiconductor material shell, the energy change of the conduction band bottom of each first semiconductor material shell shows an upward trend, and the energy change of the corresponding valence band top of each first semiconductor material shell shows a downward trend; in the radial direction from the second semiconductor material shell to the third semiconductor material shell, the energy of the conduction band bottom of the second semiconductor material shell, the at least one fourth semiconductor material shell and the third semiconductor material shell decreases in sequence, and the energy of the corresponding valence band top increases in sequence; wherein the chemical elements contained in each of the fourth semiconductor material shells are the same or different; when the quantum dot includes two or more of the fourth semiconductor material shells, in the radial direction from the second semiconductor material shell to the third semiconductor material shell, the energy of the conduction band bottom of each of the fourth semiconductor material shells decreases in sequence, and the energy of the valence band top increases in sequence; the structure of the intermediate quantum dot is: the semiconductor material core / the at least one first semiconductor material shell / the second semiconductor material shell, and the average particle diameter of the intermediate quantum dot is greater than the Bohr exciton diameter of the semiconductor material core.

2. The quantum dot according to claim 1, characterized in that The energy difference between the conduction band bottom of the second semiconductor material shell and the semiconductor material core is less than or equal to 1.5 eV, and the energy difference between the valence band top of the semiconductor material core and the second semiconductor material shell is less than or equal to 0.7 eV; or, the energy difference between the conduction band bottom of the second semiconductor material shell and the semiconductor material core is less than or equal to 1.4 eV, and the energy difference between the valence band top of the semiconductor material core and the second semiconductor material shell is less than or equal to 1.2 eV.

3. The quantum dot according to claim 1, characterized in that The material of the second semiconductor material shell is selected from CdS, ZnS or Cd X Zn (1-X) S, where 0 <X<1。 4. The quantum dot according to claim 1, characterized in that The material of the semiconductor material core is selected from CdSe, CdSeS, CdZnSe, CdZnSeS, InP, InZnP, InZnPS or ZnSeTe.

5. The quantum dot according to claim 1, characterized in that Each of the first semiconductor material shells includes at least one of selenium and sulfur and at least one of cadmium and zinc, or each of the first semiconductor material shells includes at least one of selenium and sulfur and at least one of indium and zinc.

6. The quantum dot according to claim 1, characterized in that The quantum dots are selected from CdSeS / CdZnSeS / ZnSeS / ZnS / CdZnS / CdZnS, CdSe / CdZnSeS / ZnSeS / ZnS / CdZnS / CdZnS, Cd A Zn (1-A) Se C S (1-C) / Cd B Zn (1-B) Se D S (1-D) / ZnSeS / ZnS / CdZnS / CdZnS, CdZnSe / CdZnSeS / ZnSeS / ZnS / CdZnS / CdZnS, InP / CdZnSeS / ZnSeS / ZnS / CdZnS / CdZnS, InZnP / CdZnSeS / ZnSeS / ZnS / CdZnS / CdZnS, InZnPS / CdZnSeS / ZnSeS / ZnS / CdZnS / CdZnS, InZnP / ZnSeS / ZnS / InZnS / InZnS, InP / ZnSeS / ZnS / InZnS / InZnS, InZnP / InZnSeS / ZnS / InZnS / InZnS, InZnP / InZnSe / ZnS / InZnS / InZnS, InZnP / InZnSe / InZnSeS / ZnS / InZnS / InZnS, InP / InZnSe / InZnSeS / ZnS / InZnS / InZnS, InZnPS / ZnSeS / ZnS / InZnS / InZnS, InZnPS / InZnSeS / ZnS / InZnS / InZnS, InZnPS / InZnSe / ZnS / InZnS / InZnS, InZnPS / InZnSe / InZnSeS / ZnS / InZnS / InZnS, or ZnSeTe / ZnSe / ZnSeS / ZnS / InZnS / InZnS, where A, B, C, D ∈ (0, 1); C ≤ D and A > B, or, A ≤ B and C > D.

7. The quantum dot according to claim 1, characterized in that Each shell layer of the second semiconductor material shell on the side away from the semiconductor material core changes the fluorescence emission peak position of the quantum dot within ±2nm, and changes the fluorescence quantum yield of the quantum dot within ±2%.

8. The quantum dot according to claim 1, characterized in that The average size of the semiconductor material core is 2-15 nm, the thickness of the second semiconductor material shell is 1-10 nm, and the thickness of the third semiconductor material shell is 2-15 nm.

9. The quantum dot according to claim 1, characterized in that The quantum dot includes 1 to 5 shells of the first semiconductor material, and the total thickness of all the shells of the first semiconductor material is 1 to 10 nm.

10. The quantum dot according to claim 1, characterized in that: The quantum dot includes greater than 0 and less than or equal to 5 shells of the fourth semiconductor material, and the total thickness of all the shells of the fourth semiconductor material is greater than 0 and less than or equal to 10 nm.

11. A light emitting device, characterized in that It comprises the quantum dots described in any one of claims 1 to 10, and the light-emitting mechanism of the light-emitting device is photoluminescence or electroluminescence.

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