Light-emitting device, manufacturing method, display panel and device

Abstract

The present invention discloses a light-emitting device, a preparation method, a display panel and an apparatus. The light-emitting device includes: a first carrier layer, a quantum dot layer and a second carrier layer arranged in a stacked manner; the quantum dot layer has quantum dots, and the quantum dots include a core body and a shell layer coated on the surface of the core body, and the core body and the shell layer are arranged non-concentrically; the transmission efficiency of the first carrier in the first carrier layer is greater than the transmission efficiency of the second carrier in the second carrier layer, and the thickness of the shell layer of at least some quantum dots located between the core body and the first carrier layer is greater than the thickness between the core body and the second carrier layer, so that the carriers pass through shell layers of different thicknesses to reach the core body, and the difference in transmission distance can be used to regulate the injection efficiency of the carriers. When it is necessary to reduce the transmission efficiency of the carriers, the carriers can be made to pass through the shell layer with a larger thickness, so that the carriers pass through a larger potential barrier to reach the core body, thereby reducing the transmission efficiency of the carriers and achieving balance between different carriers.

Description

Technical Field

[0001] The present invention belongs to the field of display technology, and in particular relates to a light-emitting device, a preparation method, a display panel and a device. Background Art

[0002] With the development of quantum dot materials, continuous optimization of device structures, and continued in-depth research on efficient charge transport, quantum dot light emitting diode (QLED) displays are expected to become the next generation of mainstream display technology. Because hole transport efficiency is lower than electron transport efficiency, this leads to carrier imbalance in the device. This carrier imbalance is a major technical issue in QLED devices, causing a series of device problems, such as electron leakage current and excess electrons charging the quantum dots or damaging the hole transport layer, resulting in reduced device efficiency and lifetime. Summary of the Invention

[0003] The purpose of the embodiments of the present invention is to provide a light-emitting device, a manufacturing method, a display panel and a device, so as to solve the problem of carrier imbalance in the light-emitting device.

[0004] In a first aspect, an embodiment of the present invention provides a light-emitting device, including:

[0005] A first carrier layer, a quantum dot layer, and a second carrier layer are stacked;

[0006] The quantum dot layer comprises quantum dots, each of which comprises a core and a shell covering the surface of the core, wherein the core and the shell are arranged non-concentrically;

[0007] The transfer efficiency of the first carrier in the first carrier layer is greater than the transfer efficiency of the second carrier in the second carrier layer, and the thickness of at least part of the shell of the quantum dot located between the core body and the first carrier layer is greater than the thickness between the core body and the second carrier layer.

[0008] Wherein, a ratio of a thickness of at least a portion of the shell layer of the quantum dots located between the core body and the first carrier layer to a thickness between the core body and the second carrier layer is greater than 1 and less than or equal to 100.

[0009] wherein the sum of the thickness of the shell of at least part of the quantum dots located between the core and the first carrier layer and the thickness of the shell located between the core and the second carrier layer is 2-14 nm; and / or

[0010] The diameter of the core body is 3-10 nm.

[0011] wherein the mass of the core is greater than the mass of the shell; or

[0012] The mass of the core is smaller than the mass of the shell.

[0013] The first carrier layer includes at least one of an electron transport layer and an electron injection layer, the second carrier layer includes at least one of a hole transport layer and a hole injection layer, the first carriers are electrons, and the second carriers are holes;

[0014] Wherein, in the case where the first carrier layer includes an electron transport layer and an electron injection layer, the electron transport layer is arranged close to the quantum dot layer;

[0015] In the case where the second carrier layer includes a hole transport layer and a hole injection layer, the hole transport layer is disposed close to the quantum dot layer.

[0016] The first carrier layer includes at least one of a hole transport layer and a hole injection layer, the second carrier layer includes at least one of an electron transport layer and an electron injection layer, the first carriers are holes, and the second carriers are electrons;

[0017] Wherein, when the first carrier layer includes a hole transport layer and a hole injection layer, the hole transport layer is arranged close to the quantum dot layer;

[0018] In a case where the second carrier layer includes an electron transport layer and an electron injection layer, the electron transport layer is disposed close to the quantum dot layer.

[0019] The quantum dot layer comprises a plurality of stacked quantum dot films, each layer of which comprises arranged and distributed quantum dots; and / or

[0020] The light emitting device further includes a first electrode and a second electrode. The first electrode is disposed on a side of the first carrier layer away from the quantum dot layer, and the second electrode is disposed on a side of the second carrier layer away from the quantum dot layer.

[0021] In a second aspect, an embodiment of the present invention provides a method for preparing a light-emitting device, comprising:

[0022] forming a first carrier layer on the first electrode;

[0023] forming a quantum dot layer on the first carrier layer;

[0024] forming a second carrier layer on the quantum dot layer;

[0025] forming a second electrode on the second carrier layer;

[0026] The quantum dot layer comprises quantum dots, each of which comprises a core and a shell covering the surface of the core, wherein the core and the shell are arranged non-concentrically;

[0027] The transfer efficiency of the first carrier in the first carrier layer is greater than the transfer efficiency of the second carrier in the second carrier layer, and the thickness of at least part of the shell of the quantum dot located between the core body and the first carrier layer is greater than the thickness between the core body and the second carrier layer.

[0028] In a third aspect, an embodiment of the present invention provides a display panel, comprising the light-emitting device described in the above embodiment.

[0029] In a fourth aspect, an embodiment of the present invention provides a display device, comprising the display panel described in the above embodiment.

[0030] In the light-emitting device of the embodiment of the present invention, it includes a first carrier layer, a quantum dot layer and a second carrier layer that are stacked, the quantum dot layer has quantum dots, the quantum dots include a core body and a shell layer coated on the surface of the core body, the core body and the shell layer are non-concentrically arranged, the transfer efficiency of the first carrier in the first carrier layer is greater than the transfer efficiency of the second carrier in the second carrier layer, and the thickness of at least part of the shell layer of the quantum dots located between the core body and the first carrier layer is greater than the thickness located between the core body and the second carrier layer. By setting the thickness of the quantum dot shell between the core and the first carrier layer to be greater than the thickness between the core and the second carrier layer, the carriers can be electrons or holes, so that electrons and holes pass through shells of different thicknesses to reach the core. The injection efficiency of electrons and holes can be regulated by utilizing the difference in transmission distance. When it is necessary to reduce the transmission efficiency of the carrier, the carrier can be made to pass through a shell with a larger thickness, so that the carrier reaches the core through a larger potential barrier, reducing the transmission efficiency of the carrier, and achieving equilibrium among different carriers, thereby preventing electron leakage current and excess electrons from charging the quantum dots or destroying the hole transport layer, thereby improving device efficiency and extending device life. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 is a structural schematic diagram of a light-emitting device in an embodiment of the present invention;

[0032] Figure 2 A schematic diagram of the structure of quantum dots;

[0033] Figure 3 is another structural diagram of quantum dots;

[0034] Figure 4 A schematic diagram of the arrangement of quantum dots in a light-emitting device;

[0035] Figure 5 Another schematic diagram of the arrangement of quantum dots in a light-emitting device;

[0036] Figure 6 This is another schematic diagram of the arrangement of quantum dots in a light-emitting device;

[0037] Figure 7 is another structural schematic diagram of a light emitting device according to an embodiment of the present invention;

[0038] Figure 8 is another structural schematic diagram of a light emitting device in an embodiment of the present invention;

[0039] Figure 9 is another structural schematic diagram of a light emitting device in an embodiment of the present invention;

[0040] Figure 10 is another structural schematic diagram of a light emitting device in an embodiment of the present invention;

[0041] Figure 11 is another structural schematic diagram of a light emitting device in an embodiment of the present invention;

[0042] Figure 12 is another structural schematic diagram of a light emitting device in an embodiment of the present invention;

[0043] Figure 13 is another structural schematic diagram of a light emitting device in an embodiment of the present invention;

[0044] Figure 14 A schematic diagram of the morphological change of a non-concentric structure quantum dot;

[0045] Figure 15 Another structural diagram of quantum dots.

[0046] Reference numerals

[0047] a first electrode 10;

[0048] a second electrode 20;

[0049] Quantum dot layer 30; core 31; shell 32; quantum dot 33; quantum dot film 34;

[0050] First carrier layer 40; electron injection layer 41; electron transport layer 42;

[0051] a second carrier layer 50 ; a hole injection layer 51 ; and a hole transport layer 52 . DETAILED DESCRIPTION

[0052] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0053] The terms "first," "second," and the like in the specification and claims of the present invention are used to distinguish similar objects and are not intended to describe a particular order or precedence. It should be understood that such terms are interchangeable where appropriate, so that embodiments of the present invention can be implemented in sequences other than those illustrated or described herein. Furthermore, the term "and / or" in the specification and claims refers to at least one of the connected objects, and the character " / " generally indicates that the connected objects are in an "or" relationship.

[0054] like Figures 1 to 15 As shown, the light-emitting device of an embodiment of the present invention includes: a stacked first carrier layer 40, a quantum dot layer 30, and a second carrier layer 50. The stacked first carrier layer 40, quantum dot layer 30, and second carrier layer 50 can be disposed between a first electrode 10 and a second electrode 20. Carriers can be injected into the carrier layers through the electrodes. The first electrode 10 can be an anode, and the second electrode 20 can be a cathode. The anode can be indium tin oxide (ITO); alternatively, the first electrode 10 can be a cathode, and the second electrode 20 can be an anode. The quantum dot layer 30 has quantum dots 33, with a plurality of quantum dots 33 arranged and distributed therein. The quantum dot 33 includes a core 31 and a shell 32 coated on the surface of the core 31. The quantum dot 33 can be spherical, the core 31 can be spherical, and the shell 32 is coated on the surface of the core 31. The core 31 and the shell 32 are non-concentrically arranged, so that the thickness of different areas of the shell 32 is different, so that different carriers can reach the core 31 through areas of different thickness on the shell 32 as needed, and then the balance of different carriers can be adjusted.

[0055] Among them, quantum dots may include but are not limited to CdSe / ZnS, CdS / ZnS, InP / ZnS, ZnSe / ZnS, ZnSeTe / ZnS, CdSe / ZnSe / ZnS, CdS / CdSe / ZnS, CdSe / ZnSe / ZnS, InP / GaP / ZnS and ZnSeTe / ZnSe / ZnS quantum dots. The shell of the quantum dot may have one or more layers, for example, Figure 3As shown, the shell 32 of the quantum dot can have an inner shell 322 and an outer shell 321. The inner shell 322 can be coated on the outer surface of the core 31, and the outer shell 321 is coated on the surface of the inner shell 322. The materials of the inner shell 322 and the outer shell 321 can be the same or different, and the specific selection can be made according to actual conditions.

[0056] The transfer efficiency of the first carriers in the first carrier layer 40 is greater than the transfer efficiency of the second carriers in the second carrier layer 50. The thickness of the shell 32 of at least some of the quantum dots 33 located between the core body 31 and the first carrier layer 40 is greater than the thickness between the core body 31 and the second carrier layer 50. By setting the thickness of the shell 32 of the quantum dots 33 located between the core body 31 and the first carrier layer 40 to be greater than the thickness between the core body 31 and the second carrier layer 50, different carriers can be allowed to pass through shells of different thicknesses before entering the core body 31. The first and second carriers can be allowed to pass through shells of different thicknesses before entering the core body 31, and the difference in transmission distance can be used to control the injection efficiency of the first and second carriers. For example, the first carrier can be an electron and the second carrier can be a hole, or the first carrier can be a hole and the second carrier can be an electron. The electrons and holes can be made to pass through shells of different thicknesses to reach the core 31. The difference in transmission distance can be used to regulate the injection efficiency of electrons and holes. When it is necessary to reduce the transmission efficiency of a carrier, the carrier can be made to pass through a shell with a thicker thickness, so that the carrier reaches the core through a larger potential barrier, reducing the transmission efficiency of the carrier, and making different carriers reach a balance, preventing electron leakage current and excess electrons from charging the quantum dots or destroying the hole transport layer, thereby improving device efficiency and extending device life.

[0057] During carrier transport, charge carriers can include electrons and holes. Electrons and holes travel through their respective shells to reach the quantum dot core, forming excitons and emitting light. Thick shells hinder carrier movement and, to a certain extent, limit exciton injection. Therefore, non-concentric core-shell quantum dots form thick and thin shell regions. Through directional arrangement, electrons and holes can reach the quantum dot core via different paths, thus achieving a certain degree of balanced carrier injection.

[0058] In a multi-electron system device, the first electrode 10 can be a cathode, and the second electrode 20 can be an anode. The thicker shell side can be placed closer to the cathode, while the thinner shell side is placed closer to the anode. Electrons need to cross a larger potential barrier to reach the core, thereby achieving a certain degree of carrier balance. This method can achieve carrier balance control without adding barrier materials to the device structure, which can simplify the device process to a certain extent. In addition, by adjusting the quantum dot synthesis process, more precise control of the quantum dot core-shell structure can be achieved, which can also make the carrier balance more precisely controlled.

[0059] In some embodiments, the ratio of the thickness of the shell 32 of at least a portion of the quantum dots 33 between the core 31 and the first carrier layer 40 to the thickness between the core 31 and the second carrier layer 50 is greater than 1 and less than or equal to 100. Figure 15 As shown, the thickness of the shell 32 between the core body 31 and the first carrier layer 40 may be d2, and the thickness between the core body 31 and the second carrier layer 50 may be d1. The ratio of d2 to d1 may be greater than 1 and less than or equal to 100. The ratio of the thickness of the shell 32 of at least some quantum dots 33 between the core body 31 and the first carrier layer 40 and between the core body 31 and the second carrier layer 50 is 10, so that there is a sufficient thickness difference between the thickness of the shell 32 of the quantum dot 33 between the core body 31 and the first carrier layer 40 and between the core body 31 and the second carrier layer 50. When it is necessary to reduce the transmission efficiency of a carrier, the carrier can be made to pass through the shell with a larger thickness, which can effectively reduce the transmission efficiency of the carrier.

[0060] In other embodiments, the sum of the thickness of the shell layer 32 of at least a portion of the quantum dots 33 located between the core body 31 and the first carrier layer 40 and the thickness of the shell layer 32 located between the core body 31 and the second carrier layer 50 is 2-14 nm. The thickness of the shell layer 32 located between the core body 31 and the first carrier layer 40 and the thickness of the shell layer 32 located between the core body 31 and the second carrier layer 50 can be selected according to actual needs to meet the transmission efficiency of different carriers. For example, the thickness of the shell 32 of the quantum dot 33 located between the core body 31 and the first carrier layer 40 can be 6-10nm, and the thickness located between the core body 31 and the second carrier layer 50 can be 1-2nm, so that the thickness of the shell 32 located between the core body 31 and the first carrier layer 40 and the thickness located between the core body 31 and the second carrier layer 50 are both of sufficient thickness, and will not cause the potential barrier for carriers to pass through the shell to be too high due to being too thick. The thickness of the shell 32 of the quantum dot 33 located between the core body 31 and the first carrier layer 40 and the thickness located between the core body 31 and the second carrier layer 50 can have a suitable thickness difference. When it is necessary to reduce the transmission efficiency of a carrier, the carrier can be made to pass through the shell in the area with a larger thickness, which can effectively reduce the transmission efficiency of the carrier; when it is necessary to increase the transmission efficiency of a carrier, the carrier can be made to pass through the shell in the area with a smaller thickness, which can effectively increase the transmission efficiency of the carrier, so that different carriers can reach a balance.

[0061] Optionally, the diameter of the core body 31 can be 3-10nm, for example, the diameter of the core body 31 can be 4nm, the thickness of the shell 32 of the quantum dot 33 located between the core body 31 and the first carrier layer 40 can be 8-12nm, and the thickness between the core body 31 and the second carrier layer 50 can be 1-2nm. The diameter of the core body 31, the thickness of the shell 32 located between the core body 31 and the first carrier layer 40, and the thickness between the core body 31 and the second carrier layer 50 can be selected according to actual needs so as to meet the transmission efficiency of different carriers so that different carriers can reach a balance.

[0062] Optionally, the mass of the core 31 is greater than the mass of the shell 32; or, the mass of the core 31 is less than the mass of the shell 32. This facilitates the placement of the core 31 toward a desired carrier layer during the formation of the quantum dot layer 30. For example, the mass of the core 31 is greater than the mass of the shell 32, allowing the core 31 to be placed toward the second carrier layer 50. The thickness of the shell 32 between the core 31 and the first carrier layer 40 is greater than the thickness between the core 31 and the second carrier layer 50. The first carrier can be an electron, the first carrier layer 40 can be an electron transport layer, the second carrier can be a hole, the second carrier layer 50 can be a hole transport layer, the first carrier layer 40, the quantum dot layer 30, and the second carrier layer 50 can be stacked between the first electrode 10 and the second electrode 20. The first carrier layer 40 can be positioned close to the first electrode 10, and the second carrier layer 50 can be positioned close to the second electrode 20. Carriers can be injected into the carrier layers through the electrodes. The first electrode 10 can be a cathode, and the second electrode 20 can be an anode. This can reduce the transmission efficiency of electrons through the shell layer 32 located between the core body 31 and the first carrier layer 40, and increase the transmission efficiency of holes through the shell layer 32 located between the core body 31 and the second carrier layer 50, so that the electrons and holes can reach equilibrium.

[0063] The quantum dots of concentric core-shell structure are isotropic and will not undergo directional rearrangement when they are spin-coated into films. However, when the quantum dots are non-concentric core-shell structures, the weights of the two sides of the shells of different thicknesses are inconsistent due to the different relative molecular masses of the core and shell components, so that when the films are spin-coated, the heavier side will be oriented downward. The relative molecular mass of the material of the core 31 can be greater than the relative molecular mass of the material of the shell 32, or the relative molecular mass of the material of the core 31 can be less than the relative molecular mass of the material of the shell 32. For example, the relative molecular mass of the material of the core 31 is greater than the relative molecular mass of the material of the shell 32. At this time, the probability of the core position being arranged downward is greater. The quantum dots can be ZnSe(144.4) / ZnS(97), CdSe(191.3) / ZnSe(97), ZnSe(145.8) / ZnS(97), etc. The relative molecular mass of the material of the core 31 is greater than the relative molecular mass of the material of the shell. In this case, several different arrangements may occur: electrons and holes may form exciton recombination in the upper quantum dot layer or the lower quantum dot layer. In either case, the distance holes travel from the hole transport layer to the quantum dot is always shorter than that of electrons, ultimately causing more holes to be injected into the quantum dot than before, resulting in more effective recombination. Regardless of whether the quantum dots are arranged in one or more layers, or in different arrangements, due to the anisotropy of the quantum dots themselves due to their non-concentric core-shell structure, the arrangement of the quantum dots in each layer is the same, thus always shortening the carrier injection path on one side, thereby achieving the effect of improving carrier injection on that side.

[0064] In some embodiments, the first carrier layer 40 includes at least one of an electron transport layer 42 and an electron injection layer 41, the second carrier layer 50 includes at least one of a hole transport layer 52 and a hole injection layer 51, the first carriers are electrons, and the second carriers are holes; Figure 12 As shown, when the first carrier layer 40 includes an electron transport layer 42 and an electron injection layer 41, the electron transport layer 42 is disposed close to the quantum dot layer 30; when the second carrier layer 50 includes a hole transport layer 52 and a hole injection layer 51, the hole transport layer 52 is disposed close to the quantum dot layer 30. This allows the first and second carriers to pass through shells of different thicknesses before entering the core 31. The difference in transport distances can be used to regulate the injection efficiency of the first and second carriers, thereby achieving a balance between the different carriers.

[0065] In other embodiments, the first carrier layer 40 includes at least one of a hole transport layer 52 and a hole injection layer 51, the second carrier layer 50 includes at least one of an electron transport layer 42 and an electron injection layer 41, the first carriers are holes, and the second carriers are electrons; Figure 13As shown, when the first carrier layer 40 includes a hole transport layer 52 and a hole injection layer 51, the hole transport layer 52 is disposed close to the quantum dot layer 30; when the second carrier layer 50 includes an electron transport layer 42 and an electron injection layer 41, the electron transport layer 42 is disposed close to the quantum dot layer 30. This allows the first and second carriers to pass through shells of different thicknesses before entering the core 31. The difference in transport distances can be used to regulate the injection efficiency of the first and second carriers, thereby achieving a balance between the different carriers.

[0066] In an embodiment of the present invention, Figure 11 As shown, the light-emitting device further includes a first electrode 10, a second electrode 20, and a first carrier layer 40, wherein the first carrier layer 40 is disposed between the first electrode 10 and the quantum dot layer 30. The first electrode 10 may be a cathode, and the first carrier layer 40 may include an electron injection layer 41 or an electron transport layer 42. The first carrier layer 40 may include an electron injection layer 41 and an electron transport layer 42, wherein the electron transport layer 42 is disposed near the quantum dot layer 30, and the electron injection layer 41 is disposed near the first electrode 10.

[0067] like Figure 11 As shown, the light-emitting device further includes a first electrode 10, a second electrode 20, and a second carrier layer 50. The second carrier layer 50 is disposed between the second electrode 20 and the quantum dot layer 30. The second electrode 20 may be an anode, and the second carrier layer 50 may include a hole injection layer 51 or a hole transport layer 52. The second carrier layer 50 may include a hole injection layer 51 and a hole transport layer 52. The hole transport layer 52 is disposed near the quantum dot layer 30, and the hole injection layer 51 is disposed near the second electrode 20.

[0068] In an embodiment of the present invention, Figure 5 and Figure 6 As shown, the quantum dot layer 30 comprises multiple stacked quantum dot films 34, each layer of which comprises arranged and distributed quantum dots 33. For example, the quantum dot layer 30 comprises two stacked quantum dot films 34, each layer of which comprises arranged and distributed quantum dots 33. The quantum dots 33 in the two layers of quantum dot films 34 can be stacked, with each quantum dot 33 in the upper and lower layers of quantum dot films 34 being arranged in a corresponding manner. Each quantum dot 33 in the lower quantum dot film 34 can be positioned above a corresponding quantum dot 33 in the upper quantum dot film 34. By configuring the multiple stacked quantum dot films 34, the thickness of different regions of the shell 32 of the quantum dots 33 in different layers of quantum dot films 34 can be adjusted as needed.

[0069] For quantum dots 33 in adjacent quantum dot films 34, the ratio of the thickness of the shell 32 between the core 31 and the first carrier layer 40 to the thickness between the core 31 and the second carrier layer 50 can be the same or different. When the ratio of the thickness of the shell 32 between the core 31 and the first carrier layer 40 to the thickness between the core 31 and the second carrier layer 50 is different, or when the thickness of the shell 32 of the quantum dots 33 in adjacent quantum dot films 34 between the core 31 and the first carrier layer 40 and the thickness between the core 31 and the second carrier layer 50 are different, the transmission efficiency of carriers in adjacent quantum dot films 34 can be different, and can be selected according to actual conditions to meet the transmission efficiency of carriers in different quantum dot films 34.

[0070] like Figure 11 As shown, the light-emitting device further includes: a first electrode 10 and a second electrode 20. The first electrode 10 is disposed on a side of the first carrier layer 40 away from the quantum dot layer 30, and the second electrode 20 is disposed on a side of the second carrier layer 50 away from the quantum dot layer 30. Carriers can be injected into the carrier layers through the first electrode 10 and the second electrode 20. The first electrode 10 can be a cathode, and the second electrode 20 can be an anode. The first carriers can be electrons, the first carrier layer 40 can be an electron transport layer, the second carriers can be holes, and the second carrier layer 50 can be a hole transport layer. Carriers can be injected into the carrier layers through the electrodes. This can reduce the transmission efficiency of electrons through the shell layer 32 located between the core body 31 and the first carrier layer 40, and increase the transmission efficiency of holes through the shell layer 32 located between the core body 31 and the second carrier layer 50, so that the electrons and holes can reach equilibrium.

[0071] An embodiment of the present invention provides a method for preparing a light-emitting device, comprising:

[0072] forming a first carrier layer 40 on the first electrode 10;

[0073] forming a quantum dot layer 30 on the first carrier layer 40;

[0074] forming a second carrier layer 50 on the quantum dot layer 30;

[0075] forming a second electrode 20 on the second carrier layer 50;

[0076] The quantum dot layer 30 includes quantum dots 33, which include a core 31 and a shell 32 coated on the surface of the core 31. The core 31 and the shell 32 are arranged non-concentrically.

[0077] The transfer efficiency of the first carriers in the first carrier layer 40 is greater than the transfer efficiency of the second carriers in the second carrier layer 50, and the thickness of the shell 32 of at least part of the quantum dots 33 located between the core body 31 and the first carrier layer 40 is greater than the thickness between the core body 31 and the second carrier layer 50.

[0078] In the light-emitting device prepared by the above method, the thickness of the shell 32 of the quantum dot 33 located between the core body 31 and the first carrier layer 40 is set to be greater than the thickness between the core body 31 and the second carrier layer 50, so that different carriers can pass through shells of different thicknesses to reach the core body 31. For example, electrons and holes can pass through shells of different thicknesses to reach the core body 31. The injection efficiency of electrons and holes can be regulated by utilizing the difference in transmission distance. When it is necessary to reduce the transmission efficiency of a carrier, the carrier can be made to pass through a shell with a larger thickness, so that the carrier reaches the core body through a larger potential barrier, reducing the transmission efficiency of the carrier, so that different carriers reach a balance, preventing electron leakage current and excess electrons from charging the quantum dots or destroying the hole transport layer, improving device efficiency, and extending device life.

[0079] In some embodiments, as Figure 11 As shown, a first carrier layer 40 is formed on the first electrode 10;

[0080] forming a quantum dot layer 30 on the first carrier layer 40;

[0081] The first electrode 10 may be a cathode, and the first carrier layer 40 may include an electron injection layer 41 or an electron transport layer 42 . The first carrier layer 40 may include an electron injection layer 41 and an electron transport layer 42 , and the electron injection layer 41 is disposed close to the first electrode 10 .

[0082] forming a second carrier layer 50 on the quantum dot layer 30;

[0083] The second electrode 20 is formed on the second carrier layer 50 .

[0084] The second electrode 20 may be an anode, and the second carrier layer 50 may include a hole injection layer 51 or a hole transport layer 52 . The second carrier layer 50 may include a hole injection layer 51 and a hole transport layer 52 , and the hole injection layer 51 is disposed close to the second electrode 20 .

[0085] Optionally, the ratio of the thickness of the shell layer 32 of at least part of the quantum dots 33 between the core body 31 and the first carrier layer 40 to the thickness between the core body 31 and the second carrier layer 50 is greater than 1 and less than or equal to 100. For example, the ratio of the thickness of the shell layer 32 of at least part of the quantum dots 33 between the core body 31 and the first carrier layer 40 to the thickness between the core body 31 and the second carrier layer 50 is 20, so that the thickness of the shell layer 32 of the quantum dots 33 between the core body 31 and the first carrier layer 40 and the thickness between the core body 31 and the second carrier layer 50 have a sufficient thickness difference. When it is necessary to reduce the transmission efficiency of a carrier, the carrier can be made to pass through the shell layer with a larger thickness, which can effectively reduce the transmission efficiency of the carrier.

[0086] Optionally, the sum of the thickness of the shell 32 of at least a portion of the quantum dot 33 located between the core body 31 and the first carrier layer 40 and the thickness of the shell 32 located between the core body 31 and the second carrier layer 50 is 2-14 nm. For example, the thickness of the shell 32 of the quantum dot 33 located between the core body 31 and the first carrier layer 40 can be 6-10 nm, and the thickness of the shell 32 located between the core body 31 and the second carrier layer 50 can be 1-2 nm. The thickness of the shell 32 located between the core body 31 and the first carrier layer 40 and the thickness of the shell 32 located between the core body 31 and the second carrier layer 50 can be selected according to actual needs to meet the transmission efficiency of different carriers.

[0087] Optionally, the diameter of the core body 31 can be 3-10nm, for example, the diameter of the core body 31 can be 4nm. The diameter of the core body 31, the thickness of the shell 32 located between the core body 31 and the first carrier layer 40, and the thickness of the shell 32 located between the core body 31 and the second carrier layer 50 can be selected according to actual needs to meet the transmission efficiency of different carriers so that different carriers can reach a balance.

[0088] Alternatively, the mass of the core 31 is greater than that of the shell 32; or the mass of the core 31 is less than that of the shell 32. This allows the core 31 to be positioned toward the desired electrode during the formation of the quantum dot layer 30.

[0089] The preparation method of non-concentric core-shell structure quantum dots is similar to that of concentric core-shell structure quantum dots, in that the core is prepared first and then coated with the shell. The transformation from a concentric core-shell structure to a non-concentric core-shell structure can be achieved by regulating the thermodynamics and kinetics of the reaction during shell coating. For example, the deposition rate of the shell on each crystal plane of the core can be regulated by selecting the core coating ligand, regulating the reaction temperature during shell coating, and controlling the reaction time, thereby achieving the preparation of non-concentric core-shell structure quantum dots. Kinetic regulation of the quantum dot synthesis process can synthesize quantum dots of different morphologies. The main difference lies in the overall thickness of the shell and the position of the core. The specific morphological changes can be as follows. Figure 14 shown.

[0090] Taking CdSe / ZnS quantum dots as an example, the basic preparation process is as follows:

[0091] Preparation of CdSe core: 0.1g Se powder and 50mL ODE (octadecene) were placed in a three-necked flask, evacuated at 100℃ for 20min, heated to 280℃ and maintained for 30min to form a distinct light yellow solution. At this time, 10mL Cd(OA)2 precursor was quickly injected, and the system was heated to 260℃ and kept warm for 40min. The color of the solution gradually transitioned from yellow to dark red. The synthesized quantum dots were poured into a 1000mL separatory funnel and extracted 5 times with a methanol-n-hexane system under heating conditions. The colorless methanol phase was repeatedly discharged to remove reaction by-products and incompletely reacted precursors. After purification, the quantum dots were dissolved in n-hexane.

[0092] ZnS Shell Coating: Add 5 mL of purified CdSe solution and 20 mL of ODE to a 100 mL three-necked flask. Remove the n-hexane from the solution by evacuation at 60°C for 20 minutes. Continue heating to 120°C to expel excess water vapor. Set the temperature to 400°C and inject the Zn and S precursors when the temperature reaches 270°C. Maintain the temperature for 30 minutes after addition. To prepare non-concentric core-shell quantum dots with the core in different positions, this can be achieved by varying the injection temperature of the Zn and S precursors.

[0093] The overall process flow for preparing the QLED with non-concentric quantum dots as proposed in the present invention may include:

[0094] Cleaning the substrate, which may be a flexible substrate or a rigid substrate, such as a glass substrate, and having a first electrode 10 thereon, such as the first electrode 10 may be an anode, and the anode may be indium tin oxide (ITO);

[0095] Depositing a hole injection layer 51 on the substrate by spin coating;

[0096] Depositing a hole transport layer 52 by spin coating on the hole injection layer 51;

[0097] Spin coating and depositing non-concentric structure quantum dots on the hole transport layer 52 to form a quantum dot layer 30;

[0098] Depositing an electron transport layer 42 by spin coating on the quantum dot layer 30;

[0099] The second electrode 20 is evaporated on the electron transport layer 42 and encapsulated. For example, the second electrode 20 can be a cathode to complete the preparation of the entire device. An electron injection layer 41 can be formed between the electron transport layer 42 and the second electrode 20. The structure of the light-emitting device can be as follows: Figure 7 and Figure 8 shown.

[0100] The core of the quantum dot has a relatively large mass, and the quantum dots deposited by spin coating will be arranged downward toward the quantum dot core. At this time, the device structure applicable to the quantum dot is also different for multi-electron or multi-hole devices.

[0101] For multi-electron systems, the device structure applicable to this new type of quantum dot can be an upright structure, not limited to top-emitting or bottom-emitting. In this case, the barrier that electrons need to overcome when injecting into the quantum dot core is larger than the barrier that holes need to overcome when entering the quantum dot core. By controlling the growth dynamics during the quantum dot synthesis process, the thickness ratio of the shell layer can be controlled, thereby regulating the carrier injection efficiency in the device. The device preparation process is as follows:

[0102] Cleaning the substrate, where the substrate may be a flexible substrate or a rigid substrate, such as a glass substrate, and having a first electrode 10 thereon, such as the first electrode 10 may be an anode;

[0103] Depositing a hole injection layer 51 on the substrate by spin coating;

[0104] Depositing a hole transport layer 52 by spin coating on the hole injection layer 51;

[0105] Depositing a non-concentric core-shell structure quantum dot layer 30 on the hole transport layer 52 by spin coating, and generating a directional rearrangement with the core facing downward;

[0106] Depositing an electron transport layer 42 by spin coating on the non-concentric core-shell structure quantum dot layer 30;

[0107] The second electrode 20 is evaporated and packaged. For example, the second electrode 20 can be a cathode to complete the preparation of the entire device. The structure of the light-emitting device can be as follows: Figure 7 and Figure 8 shown.

[0108] For multi-hole systems, the device structure applicable to this new type of quantum dot can be an inverted structure, not limited to top-emitting or bottom-emitting. In this case, the potential barrier that holes need to overcome to inject into the quantum dot core is greater than the potential barrier that electrons need to overcome to enter the quantum dot core. Similarly, by controlling the growth dynamics during the quantum dot synthesis process, the thickness ratio of the shell layer can be controlled, thereby regulating the carrier injection efficiency in the device. The device preparation process is as follows:

[0109] Cleaning the substrate, which may be a flexible substrate or a rigid substrate, such as a glass substrate, and having a second electrode 20 thereon, such as the second electrode 20 being a cathode;

[0110] Depositing an electron transport layer 42 on the substrate by spin coating or sputtering;

[0111] The non-concentric core-shell structure quantum dot layer 30 is spin-coated on the electron transport layer 42, and a core-downward directional rearrangement is generated;

[0112] A hole transport layer 52 (HT) / a hole injection layer 51 (HI) and a first electrode 10 are evaporated on the non-concentric core-shell structure quantum dot layer 30. For example, the first electrode 10 may be an anode.

[0113] Packaging completes the preparation of the entire device. The structure of the light-emitting device can be as follows Figure 9 and Figure 10 shown.

[0114] The core position can be rearranged in a relatively upward direction. In this case, the relative molecular mass of the core should be less than the relative molecular mass of the shell, thereby increasing the probability of the core position being arranged upward. The device structure suitable for this case is exactly the opposite of the above-mentioned cases for multi-electron systems and multi-hole systems. If the device hole injection is greater than the electron injection, then this non-concentric core-shell structure quantum dot is suitable for upright devices (both top-emitting and bottom-emitting); if the device hole injection is less than the electron injection, then this non-concentric core-shell structure quantum dot is suitable for inverted devices (both top-emitting and bottom-emitting). The device preparation process can be the same as that for the above-mentioned cases for multi-electron systems and multi-hole systems, and the specific process can be reasonably selected according to the actual situation.

[0115] An embodiment of the present invention provides a display panel including the light-emitting device described in the above embodiment. The display panel including the light-emitting device described in the above embodiment has high luminous efficiency and long service life.

[0116] An embodiment of the present invention provides a display device including the display panel described in the above embodiment. The display device including the display panel described in the above embodiment has high luminous efficiency and long service life.

[0117] The embodiments of the present invention are described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the guidance of the present invention, ordinary technicians in this field can also make many forms without departing from the scope of protection of the present invention and the claims, all of which are protected by the present invention.

Claims

1. A light emitting device, characterized in that: include: A first carrier layer, a quantum dot layer, and a second carrier layer are stacked; The quantum dot layer comprises quantum dots, each of which comprises a core and a shell covering the surface of the core, wherein the core and the shell are arranged non-concentrically; The transfer efficiency of the first carrier in the first carrier layer is greater than the transfer efficiency of the second carrier in the second carrier layer, and the thickness of at least part of the shell of the quantum dot located between the core body and the first carrier layer is greater than the thickness between the core body and the second carrier layer.

2. The light emitting device according to claim 1, wherein A ratio of a thickness of at least a portion of the shell layer of the quantum dots between the core body and the first carrier layer to a thickness between the core body and the second carrier layer is greater than 1 and less than or equal to 100.

3. The light emitting device according to claim 1, wherein The sum of the thickness of the shell of at least part of the quantum dots located between the core and the first carrier layer and the thickness of the shell located between the core and the second carrier layer is 2-14 nm; and / or The diameter of the core body is 3-10 nm.

4. The light emitting device according to claim 1, wherein The mass of the core is greater than the mass of the shell; or The mass of the core is smaller than the mass of the shell.

5. The light emitting device according to claim 1, wherein The first carrier layer includes at least one of an electron transport layer and an electron injection layer, the second carrier layer includes at least one of a hole transport layer and a hole injection layer, the first carriers are electrons, and the second carriers are holes; Wherein, in the case where the first carrier layer includes an electron transport layer and an electron injection layer, the electron transport layer is arranged close to the quantum dot layer; In the case where the second carrier layer includes a hole transport layer and a hole injection layer, the hole transport layer is disposed close to the quantum dot layer. The light emitting device according to claim 1 , wherein: The first carrier layer includes at least one of a hole transport layer and a hole injection layer, the second carrier layer includes at least one of an electron transport layer and an electron injection layer, the first carriers are holes, and the second carriers are electrons; Wherein, when the first carrier layer includes a hole transport layer and a hole injection layer, the hole transport layer is arranged close to the quantum dot layer; In a case where the second carrier layer includes an electron transport layer and an electron injection layer, the electron transport layer is disposed close to the quantum dot layer.

7. The light emitting device according to claim 1, characterized in that The quantum dot layer comprises a plurality of stacked quantum dot films, each layer of the quantum dot film comprising arranged and distributed quantum dots; and / or The light emitting device further includes a first electrode and a second electrode. The first electrode is disposed on a side of the first carrier layer away from the quantum dot layer, and the second electrode is disposed on a side of the second carrier layer away from the quantum dot layer.

8. A method for preparing a light-emitting device, characterized in that: include: forming a first carrier layer on the first electrode; forming a quantum dot layer on the first carrier layer; forming a second carrier layer on the quantum dot layer; forming a second electrode on the second carrier layer; The quantum dot layer comprises quantum dots, each of which comprises a core and a shell covering the surface of the core, wherein the core and the shell are arranged non-concentrically; The transfer efficiency of the first carrier in the first carrier layer is greater than the transfer efficiency of the second carrier in the second carrier layer, and the thickness of at least part of the shell of the quantum dot located between the core body and the first carrier layer is greater than the thickness between the core body and the second carrier layer.

9. A display panel, characterized in that: The light-emitting device comprises the light-emitting device according to any one of claims 1 to 7.

10. A display device, characterized in that: The display panel comprises the display panel according to claim 9.

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