Quantum dot film layer, quantum dot light-emitting device and manufacturing method thereof

Abstract

The present application provides a quantum dot film layer, a quantum dot light-emitting device and a method for manufacturing the same, for improving the balance of carriers. The quantum dot film layer includes a first quantum dot layer and a second quantum dot layer. The first quantum dot layer includes a first quantum dot and a first photosensitive ligand connected to the surface of the first quantum dot. The second quantum dot layer includes a second quantum dot and a second non-photosensitive ligand connected to the surface of the second quantum dot. The second quantum dot is the same as the first quantum dot.

Description

Technical Field

[0001] The present application relates to the field of display technology, and in particular to a quantum dot film layer, a quantum dot light-emitting device and a method for manufacturing the same. Background Art

[0002] Quantum dots (QDs) are a type of zero-dimensional semiconductor nanomaterial that can be dispersed in water or organic solvents to form colloids. The size of quantum dots is close to or even smaller than the Bohr radius of the exciton electron-hole pair of the corresponding semiconductor bulk material. The electrons and holes generated when excited are confined in a small three-dimensional space, thus exhibiting a quantum confinement effect and having unique optical properties.

[0003] Quantum Dots Light Emitting Diode Display (QLED) is a new display technology developed based on organic light-emitting display. The difference between the two is that the light-emitting layer in QLED is the quantum dot layer. Its principle is: electrons / holes are injected into the quantum dot layer through the electron / hole transport layer, and electrons and holes are compounded in the quantum dot layer to emit light. Compared with organic light-emitting diode display devices (OLED), QLED has the advantages of narrow emission peak, high color saturation, and wide color gamut.

[0004] Current quantum dot light-emitting diode displays have room for further improvement in carrier balance. Summary of the invention

[0005] According to a first aspect of an embodiment of the present application, a quantum dot film layer is provided, wherein the quantum dot film layer comprises a first quantum dot layer and a second quantum dot layer, wherein:

[0006] The first quantum dot layer includes first quantum dots and first photosensitivity ligands connected to the surface of the first quantum dots;

[0007] The second quantum dot layer includes second quantum dots and second non-photosensitive ligands connected to the surfaces of the second quantum dots, and the second quantum dots are the same as the first quantum dots.

[0008] In one embodiment, the first photosensitive ligand includes a non-photosensitive coordination group and a photosensitive group, one end of the coordination group is connected to the surface of the first quantum dot, and the other end of the coordination group is connected to the photosensitive group;

[0009] The coordinating group is the same as the second non-photosensitive ligand.

[0010] In one embodiment, the coordination group and the second non-photosensitive ligand both include any one of a thiol group, a hydroxyl group, an amino group, a sulfonic acid group, a carboxyl group and a phosphate group.

[0011] In one embodiment, the photosensitive group has a structure as shown in Formula II to IV;

[0012]

[0013] -R5-N=N-R6- (III);

[0014] -R7-OO-R8- (IV);

[0015] Wherein, R1, R2 to R8 are all selected from hydrogen, alkoxy, alkyl or aromatic groups.

[0016] In one embodiment, the general structure of the first photosensitive ligand is shown in Formula I:

[0017] AB (I);

[0018] Among them, A is a coordination group and B is a photosensitizing group;

[0019] The coordination group includes any one of a thiol group, a hydroxyl group, an amino group, a sulfonic acid group, a carboxyl group and a phosphate group;

[0020] The photosensitive group has a structure as shown in formula II to IV;

[0021]

[0022] -R5-N=N-R6- (III);

[0023] -R7-OO-R8- (IV);

[0024] Wherein, R1, R2 to R8 are all selected from hydrogen, alkoxy, alkyl or aromatic groups.

[0025] In one embodiment, the first quantum dot layer further comprises a first alkyl chain ligand connected to the surface of the first quantum dot;

[0026] The second quantum dot layer further includes a second alkyl chain ligand connected to the surface of the second quantum dot.

[0027] In one embodiment, the first alkyl chain ligand and the second alkyl chain ligand are the same.

[0028] In one embodiment, the first alkyl chain ligand and the second alkyl chain ligand both include a coordination unit and a C15-C50 branched alkyl group;

[0029] The number of carbon atoms in each branch of the branched alkyl group is 6 to 12;

[0030] The coordination unit includes any one of a thiol group, a hydroxyl group, an amine group, an amino group, a carboxyl group, a phosphate group, a phosphoester group and a sulfonic acid group.

[0031] According to a second aspect of an embodiment of the present application, a quantum dot light-emitting device is provided, comprising a hole transport layer, an electron transport layer, and a quantum dot film layer as described above located between the hole transport layer and the electron transport layer.

[0032] In one embodiment, in a multi-electron system, the second quantum dot layer is disposed on a side of the first quantum dot layer away from the electron transport layer.

[0033] In one embodiment, in a multi-hole system, the second quantum dot layer is disposed on a side of the first quantum dot layer away from the hole transport layer.

[0034] According to a third aspect of the embodiments of the present application, a method for manufacturing a quantum dot light-emitting device is provided, the method comprising:

[0035] A quantum dot film layer as described above is formed on the substrate.

[0036] In one embodiment, the step of forming the quantum dot film layer specifically includes:

[0037] Forming a second quantum dot pre-layer on the substrate, wherein the second quantum dot pre-layer includes second quantum dots and second photosensitive ligands connected to the surface of the second quantum dots;

[0038] irradiating the second quantum dot pre-layer with light to cause a second photosensitive ligand therein to undergo a cleavage reaction, and the second quantum dot pre-layer is converted into a second quantum dot layer;

[0039] A first quantum dot layer is formed on the second quantum dot layer.

[0040] In one embodiment, the step of forming the quantum dot film layer specifically includes:

[0041] forming a first quantum dot layer on a substrate;

[0042] forming a second quantum dot pre-layer on the first quantum dot layer, wherein the second quantum dot pre-layer comprises second quantum dots and second photosensitive ligands connected to the surface of the second quantum dots;

[0043] The second quantum dot pre-layer is irradiated with light to cause a cracking reaction of the second photosensitive ligand therein, and the second quantum dot pre-layer is converted into a second quantum dot layer.

[0044] In one embodiment, the first quantum dot layer and the second quantum dot pre-layer are made of the same material; and the first quantum dot layer and the second quantum dot pre-layer are formed in the same step. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 is a schematic structural diagram of a quantum dot film layer provided by an exemplary embodiment of the present application;

[0046] Figure 2 and Figure 3 They are Figure 1 Schematic diagram of the structure of the first quantum dot particle and the second quantum dot particle;

[0047] Figures 4 to 6 is a schematic diagram of a method for manufacturing a quantum dot light-emitting device provided by an exemplary embodiment of the present application;

[0048] Figures 7 to 9 It is a schematic diagram of a method for manufacturing a quantum dot light-emitting device provided by another exemplary embodiment of the present application. DETAILED DESCRIPTION

[0049] Exemplary embodiments will be described in detail herein, examples of which are shown in the accompanying drawings. When the following description refers to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present application. Instead, they are merely examples of devices and methods consistent with some aspects of the present application as detailed in the appended claims.

[0050] The terms used in this application are for the purpose of describing specific embodiments only and are not intended to limit this application. The singular forms of "a", "said" and "the" used in this application and the appended claims are also intended to include plural forms unless the context clearly indicates other meanings. It should also be understood that the term "and / or" used herein refers to and includes any or all possible combinations of one or more associated listed items.

[0051] It should be understood that although the terms first, second, third, etc. may be used in the present application to describe various information, such information should not be limited to these terms. These terms are only used to distinguish the same type of information from each other. For example, without departing from the scope of the present application, the first film layer may also be referred to as the second film layer, and similarly, the second film layer may also be referred to as the first film layer. Depending on the context, the word "if" as used herein may be interpreted as "at the time of" or "when" or "in response to determining".

[0052] The following is a detailed description of the quantum dot film layer, quantum dot light-emitting device and its manufacturing method in the embodiments of the present application in conjunction with the accompanying drawings. In the absence of conflict, the features in the following embodiments can complement or combine with each other.

[0053] The embodiment of the present application discloses a quantum dot film layer 30, such as Figure 1 The quantum dot film layer 30 includes a first quantum dot layer 32 and a second quantum dot layer 34 which are stacked. The first quantum dot layer 32 may include a plurality of first quantum particles 70 , and the second quantum dot layer 34 may include a plurality of second quantum particles 80 .

[0054] Please combine Figure 2 As shown, each first quantum particle 70 in the first quantum dot layer 32 may include a first quantum dot 72 and a first photosensitive ligand 74 connected to the surface of the first quantum dot 72. Specifically, the first quantum dot 72 may be a core-shell structure. The first photosensitive ligand 74 may be a ligand sensitive to ultraviolet light. When irradiated with ultraviolet light, the first photosensitive ligand 74 may undergo a cleavage reaction, so that a portion of the first photosensitive ligand 74 falls off from the surface of the first quantum dot 72. Before forming a film layer, the first quantum particle 70 exists in a solution state, and the long-chain first photosensitive ligand 74 can ensure the stability of the solution and prevent the first quantum particle 70 from settling. Although the first quantum dot layer 32 is a film layer formed using the first photosensitive ligand 74, it is not directly irradiated by ultraviolet light, so the first photosensitive ligand 74 therein does not undergo a cleavage reaction.

[0055] In some embodiments, the first photosensitive ligand 74 includes a non-photosensitive coordination group and a photosensitive group, and has a structure as shown in Formula I:

[0056] AB(I);

[0057] Among them, A is a coordination group and B is a photosensitizing group;

[0058] The coordination group includes any one of a thiol group, a hydroxyl group, an amino group, a sulfonic acid group, a carboxyl group and a phosphate group;

[0059] The photosensitive group has a structure as shown in formula II to IV;

[0060]

[0061] -R5-N=N-R6- (III);

[0062] -R7-OO-R8- (IV);

[0063] Wherein, R1, R2 to R8 are all selected from hydrogen, alkoxy, alkyl or aromatic groups.

[0064] In the above embodiment, the coordination group is used to form a connection with the first quantum dot, and the photosensitive group can be cleaved after ultraviolet light irradiation. The coordination group is insensitive to light, so the previous structure can be maintained even after light irradiation. The coordination group and the photosensitive group are connected by a chemical bond, and the specific connection method is not limited in this application.

[0065] Furthermore, the first quantum particles 70 in the first quantum dot layer 32 may further include first alkyl chain ligands 76 connected to the surface of the first quantum dots 72. The first alkyl chain ligands 76 may passivate surface defects of the quantum dots and increase the solubility of the quantum dots in organic solvents.

[0066] In some embodiments, the first alkyl chain ligand 76 includes a coordination unit and a C15-C50 branched alkyl group; the number of carbon atoms in each branch of the branched alkyl group is 6-12.

[0067] In the first alkyl chain ligand 76, the coordination unit includes any one of a thiol group, a hydroxyl group, an amine group, an amino group, a carboxyl group, a phosphate group, a phosphoester group, and a sulfonic acid group. The coordination unit is located between the first quantum dot 72 and the branched alkyl group, and is used to form a connection with the surface of the first quantum dot 72, connecting the branched alkyl group to the first quantum dot 72. The first alkyl chain ligand 76 can increase the solubility of the quantum dot in an organic solvent, so as to form a mixed solution containing quantum dots, which is used for coating to form a quantum dot film.

[0068] The first alkyl chain ligand 76 may be:

[0069] or,

[0070] The first alkyl chain ligand 76 connected to the surface of the first quantum dot 72 can be one or more. The first photosensitive ligand 74 connected to the surface of the first quantum dot 72 can be one or more. In addition, the content of the first alkyl chain ligand 76 and the first photosensitive ligand 74 can be flexibly controlled during the synthesis of the quantum dot particles.

[0071] Please combine Figure 3As shown, each second quantum particle 80 in the second quantum dot layer 34 includes a second quantum dot 82 and a second non-photosensitive ligand 85 connected to the surface of the second quantum dot 82. The total content of each ligand connected to the surface of the second quantum dot 82 in the second quantum dot layer 34 is less than the total content of each ligand connected to the surface of the first quantum dot 72 in the first quantum dot layer 32. The content mentioned here includes both the number of ligands contained in the unit volume and the length of the ligand. Both the number of ligands and the length of the ligand can affect the transmission efficiency of carriers in the corresponding film layer. When the ligands are the same, the content of the ligand can be reduced by reducing the number of ligands; when the number of ligands is equivalent, the content of the ligand can be reduced by shortening the length (chain length) of the ligand. The above arrangement makes the transmission efficiency of carriers in the second quantum dot layer 34 higher than the transmission efficiency of carriers in the first quantum dot layer 32.

[0072] The second quantum dot layer 34 can be formed by irradiating the second quantum dots 82 and the second photosensitive ligands 84 connected to the surfaces of the second quantum dots 82 with light.

[0073] Specifically, the second quantum dot layer 34 can be formed by the following steps:

[0074] Step S12 is performed: forming a second quantum dot pre-layer 34a, such as Figure 4 As shown, the second quantum dot pre-layer 34a includes a plurality of second quantum particles 80a;

[0075] Please combine Figure 3 As shown, each second quantum particle 80a in the second quantum dot pre-layer 34a may include a second quantum dot 82 and a second photosensitive ligand 84 connected to the surface of the second quantum dot 82. Specifically, the second quantum dot 82 may be a core-shell structure. The second photosensitive ligand 84 may be a ligand sensitive to ultraviolet light. When irradiated with ultraviolet light, the second photosensitive ligand 84 undergoes a cleavage reaction, so that a portion of the second photosensitive ligand 84 falls off from the surface of the second quantum dot 82. Before forming a film layer, the second quantum particle 80a exists in a solution state, and the long-chain second photosensitive ligand 84 can ensure the stability of the solution and prevent the second quantum particle 80a from settling.

[0076] In some embodiments, the second photosensitive ligand 84 includes a non-photosensitive coordination group and a photosensitive group, and has a structure as shown in Formula I:

[0077] AB (I);

[0078] Among them, A is a coordination group and B is a photosensitizing group;

[0079] The coordination group includes any one of a thiol group, a hydroxyl group, an amino group, a sulfonic acid group, a carboxyl group and a phosphate group;

[0080] The photosensitive group has a structure as shown in formula II to IV;

[0081]

[0082] -R5-N=N-R6- (III);

[0083] -R7-OO-R8- (IV);

[0084] Wherein, R1, R2 to R8 are all selected from hydrogen, alkoxy, alkyl or aromatic groups.

[0085] In the above embodiment, the coordination group is used to form a connection with the second quantum dot, and the photosensitive group can be cleaved after ultraviolet light irradiation. The coordination group is insensitive to light, so the previous structure can be maintained even after light irradiation. The coordination group and the photosensitive group are connected by a chemical bond, and the specific connection method is not limited in this application.

[0086] Furthermore, the second quantum particle 80a in the second quantum dot pre-layer 34a may further include a second alkyl chain ligand 86 connected to the surface of the second quantum dot 82. The second alkyl chain ligand 86 may passivate surface defects of the quantum dot and increase the solubility of the quantum dot in the organic solvent.

[0087] In some embodiments, the second alkyl chain ligand 86 includes a coordination unit and a C15-C50 branched alkyl group; the number of carbon atoms in each branch of the branched alkyl group is 6-12.

[0088] In the second alkyl chain ligand 86, the coordination unit includes any one of a thiol group, a hydroxyl group, an amine group, an amino group, a carboxyl group, a phosphate group, a phosphoester group, and a sulfonic acid group. The coordination unit is located between the second quantum dot 82 and the branched alkyl group, and is used to form a connection with the surface of the second quantum dot 82, connecting the branched alkyl group to the second quantum dot 82. The second alkyl chain ligand 86 can increase the solubility of the quantum dot in an organic solvent, so as to form a mixed solution containing quantum dots, which is used for coating to form a quantum dot film.

[0089] The second alkyl chain ligand 86 may be:

[0090] or,

[0091] The second alkyl chain ligand 86 connected to the surface of the second quantum dot 82 can be one or more. The second photosensitive ligand 84 connected to the surface of the second quantum dot 82 can be one or more. In addition, the content of the second alkyl chain ligand 86 and the second photosensitive ligand 84 can be flexibly controlled during the synthesis of the quantum dot particles. The higher the content of the second photosensitive ligand 84, the more ligands are cleaved after light irradiation, and the better the performance of carrier transmission.

[0092] Step S14 is performed: irradiating the second quantum dot pre-layer 34a with light. Figure 4 and Figure 5 As shown, the second photosensitive ligand 84 undergoes a cleavage reaction, a portion of the second photosensitive ligand 84 (i.e., the photosensitive group) falls off from the surface of the second quantum dot 82, and another portion of the second photosensitive ligand 84 (the non-photosensitive coordination group) remains connected to the surface of the second quantum dot 82, becoming the second non-photosensitive ligand 85. Correspondingly, the second quantum particle 80a is transformed into the second quantum particle 80, and the second quantum dot pre-layer 34a is transformed into the second quantum dot layer 34.

[0093] When applied to an electroluminescent device, a high content of ligands (including photosensitive ligands and alkyl chain ligands, etc.) will hinder the injection of carriers and affect the electroluminescent performance of the device. The shedding of the second photosensitive ligand 84 can significantly reduce the content of the ligand and improve the injection efficiency of carriers. Therefore, the injection or transmission efficiency of carriers in the second quantum dot layer 34 is significantly higher than that in the first quantum dot layer 32.

[0094] The quantum dot film layer 30 having the first quantum dot layer 32 and the second quantum dot layer 34 can be used to adjust and improve the carrier balance of the electroluminescent device. For example, in a multi-electron system, the quantum dot film layer 30 can be used as an organic light-emitting material layer, and the second quantum dot layer 34 is far away from the electron transport layer and adjacent to the hole transport layer, and the first quantum dot layer 32 is adjacent to the electron transport layer and far away from the hole transport layer. The above structure and structure are conducive to the injection of holes but not conducive to the injection of electrons, so the carrier balance of the multi-electron system can be adjusted.

[0095] For another example, in a multi-hole system, the quantum dot film layer 30 can be used as an organic light-emitting material layer, and the second quantum dot layer 34 is far away from the hole transport layer and close to the electron transport layer, and the first quantum dot layer 32 is close to the hole transport layer and far away from the electron transport layer. The above structure and structure are conducive to the injection of electrons but not conducive to the injection of holes, so the carrier balance of the multi-hole system can be adjusted.

[0096] In some embodiments, the first quantum dot layer 32 and the second quantum dot layer 34 are made of the same raw materials, the only difference being that the first quantum dot layer 32 is not irradiated, while the second quantum dot layer 34 is irradiated. The two have the same organic solvent, quantum dots, and ligands, etc., which is beneficial to increase the production speed and save production costs. For example, after preparing a solution containing quantum dot particles, a portion of the solution is made into the first quantum dot layer 32, and another portion of the solution is made into the second quantum dot layer 34.

[0097] In the above embodiments, the preparation of quantum dot particles (e.g., the first quantum particle 70, the second quantum particle 80a) is required. In theory, various existing methods can be used to make them. Quantum dots with two or more ligands (at least one of which is a photosensitive ligand) can be synthesized by ligand exchange technology. That is, quantum dots with ordinary alkyl chain ligands are first prepared by conventional quantum dot synthesis methods, and then the alkyl chain ligands are partially replaced by photosensitive ligands through ligand exchange to obtain quantum dots containing two or more ligands (at least one of which is a photosensitive ligand).

[0098] The quantum dot particles used in the present application include but are not limited to CdS@ZnSZnS, CdSe / ZnS, InP / ZnS, PbS / ZnS, CsPbCl3 / ZnS, CsPbBr3 / ZnS, CsPbI3 / ZnS, CdS / ZnS, CdSe / ZnS, CdS@ZnSZnS, CdSe / ZnS, InP / ZnS / ZnO, PbS / ZnS, CsPbCl3 / ZnS, CsPbBr3 / ZnS, CsPbI3 / ZnS, CdS / ZnS, CdSe / ZnS, ZnTe / ZnSe / ZnS, ZnSeTe / ZnSe / ZnS and other quantum dots.

[0099] The quantum dot ligands are usually long-chain alkane ligands, including but not limited to trioctylphosphine, tributylphosphine, oleic acid, stearic acid, oleylamine, long-chain alkylamine, long-chain alkylphosphine, long-chain alkylphosphonic acid, etc.

[0100] The photosensitivity ligand is a ligand with a photosensitivity group in the inner segment. The small molecule undergoes bond breaking and decomposition after being exposed to ultraviolet light. The photosensitivity group is a carbonyl group or a double bond.

[0101] In some embodiments, the method for preparing the quantum dot particles is as follows:

[0102] First, quantum dots with long-chain ligands were prepared by the traditional quantum dot synthesis method, taking InP / ZnS as an example: in a glove box vacuum environment, 120.54 mg of indium bromide (InBr3) and 495.40 mg of zinc bromide (ZnBr2) were weighed with an electronic balance and added to a 50 ml three-necked bottle, and then 5 ml of oleylamine (OLA) was added thereto, and the solution was evacuated for 30 min (minutes) and heated to 100 ° C. After there was no water vapor inside, argon (Ar) was introduced, and the temperature was raised to 215 ° C. A mixed solution of 0.45 ml of tris (dimethylamino) phosphine [(DMA) 3P] and 1.0 ml of oleylamine (OLA) was injected therein, and the solution was kept constant at this temperature for 20 min (minutes). The solution was fully reacted at an appropriate stirring speed, and then 1.5 ml of dodecanethiol and 6 ml of stearic acid-ODE solution (15 g of zinc stearate was dissolved in 60 ml of ODE) were quickly added with a syringe. Then, the temperature meter was set to 300°C, and samples were taken from the reactor at 10min, 20min, 30min, and 40min, respectively. After the reaction lasted for 40min, the heating was stopped, and after the solution was cooled to 70°C to 80°C, a certain amount of n-hexane was added and centrifuged at 10,000rpm (revolutions per minute) to precipitate the zinc stearate, and then a certain amount of n-hexane and anhydrous ethanol were added and centrifuged at 10,000rpm to precipitate the InP / ZnS nanocrystals, and then dried with N2. The obtained InP / ZnS nanocrystals can be well dissolved in the n-hexane solution, and then characterization and analysis were performed. During the reaction process, the color of the solution changed from colorless and transparent to brown, and then gradually changed to yellow-green.

[0103] Then, quantum dots having two or more ligands (including at least a common alkyl chain and a photosensitive ligand) are prepared by ligand exchange in solution.

[0104] Taking CdSe / ZnS quantum dots with oleic acid ligands as an example, the method of replacing them with quantum dots with two or more ligands (at least one of which is a photosensitive ligand) is as follows:

[0105] The CdSe / ZnS quantum dots with long-chain oleic acid ligands prepared by conventional methods are centrifugally washed with ethanol, and the supernatant is removed and the quantum dots are redispersed in octane (n-heptane or n-hexane may also be used), and the photosensitive ligand dissolved in ethanol (or other alcohols) is added to the quantum dot colloid, and the reaction is stirred at 80°C for 1 hour to perform ligand exchange.

[0106] In the above steps, the purpose of centrifugal washing is to remove byproducts or impurities that have not reacted completely during the synthesis of quantum dots. In addition, quantum dots of inconsistent sizes can be separated in this process, making the quantum dots purer and more uniform in size, and having better effects when used in subsequent devices.

[0107] The oleic acid used in the above embodiment may have a structural formula of: CH3(CH2)7CH=CH(CH2)7COOH, or may be expressed as:

[0108]

[0109] Chinese patent document CN108192591A discloses a method for preparing quantum dot particles having two or more ligands by ligand exchange, which can also be applied in the present application.

[0110] The present application also provides a method for manufacturing a quantum dot light-emitting device, which can be used to prepare the quantum dot light-emitting device described above. The manufacturing method may include:

[0111] A quantum dot film layer as described above is formed on the substrate.

[0112] In some embodiments, the step of forming the quantum dot film layer includes:

[0113] like Figure 4 , forming a second quantum dot pre-layer 34a on the substrate S, wherein the second quantum dot pre-layer 34a includes second quantum dots and second photosensitive ligands connected to the surface of the second quantum dots;

[0114] like Figure 5 , irradiating the second quantum dot pre-layer 34a with light to cause a cracking reaction of the second photosensitive ligand therein, and the second quantum dot pre-layer is converted into a second quantum dot layer 34;

[0115] like Figure 6 , forming a first quantum dot layer 32 on the second quantum dot layer 34 .

[0116] In the above embodiment, the first quantum dot layer 32 may dissolve a portion of the thickness of the second quantum dot layer 34 below. Therefore, when forming the second quantum dot layer 34, a certain thickness may be formed so that even after a portion of the second quantum dot layer 34 is dissolved, the remaining thickness is sufficient for use.

[0117] In some embodiments, the step of forming the quantum dot film layer includes:

[0118] like Figure 7 , forming a first quantum dot layer 32 on the substrate S;

[0119] like Figure 8 , forming a second quantum dot pre-layer 34a on the first quantum dot layer 32, wherein the second quantum dot pre-layer 34a includes second quantum dots and second photosensitive ligands connected to the surface of the second quantum dots;

[0120] like Fig. 9, the second quantum dot pre-layer 34 a is irradiated with light, causing the second photosensitive ligand therein to undergo a cracking reaction, and the second quantum dot pre-layer 34 a is converted into a second quantum dot layer 34 .

[0121] In the above embodiment, by controlling the depth of light irradiation, light can only reach and irradiate the upper second quantum dot pre-layer 34a without irradiating the underlying first quantum dot layer 32, so as to avoid the first quantum dot particles 70 in the first quantum dot layer 32 from undergoing a cracking reaction.

[0122] In the above embodiment, the second quantum dot layer 34 may dissolve a portion of the thickness of the first quantum dot layer 32 below. Therefore, when forming the first quantum dot layer 32, a certain thickness may be formed so that even if part of it is dissolved, the remaining thickness is sufficient for use.

[0123] In the above embodiment, the first quantum dot layer 32 and the second quantum dot pre-layer 34a can be made of the same material. Correspondingly, the first quantum dot layer and the second quantum dot pre-layer can be formed in the same step. For example, a sufficiently thick quantum dot material layer is first formed on the substrate S by spin coating, printing or printing; then, the quantum dot material layer is illuminated by light, and during the illumination process, the depth of the light is precisely controlled so that only part of the thickness is irradiated. Among them, the part illuminated by light reacts to form a second quantum dot layer, and the part not illuminated serves as the first quantum dot layer.

[0124] The formed quantum dot light-emitting device can be either an upright structure or an inverted structure.

[0125] In the upright structure, the quantum dot light-emitting device may include: an anode located on a substrate; a hole transport layer located on the anode; a quantum dot film layer as described above located on the hole transport layer; an electron transport layer located on the quantum dot film layer; and a cathode located on the electron transport layer.

[0126] In an inverted structure, the quantum dot light-emitting device may include: a cathode located on a substrate; an electron transport layer located on the cathode; a quantum dot film layer as described above located on the electron transport layer; a hole transport layer located on the quantum dot film layer; and an anode located on the hole transport layer.

[0127] In the above embodiments, a hole injection layer may be provided between the hole transport layer and the anode. The hole transport layer, the hole injection layer, the electron transport layer and the quantum dot film layer may be formed by spin coating, printing or ink jetting.

[0128] It should be noted that in the accompanying drawings, the sizes of layers and regions may be exaggerated for clarity of illustration. It is also understood that when an element or layer is referred to as being "on" another element or layer, it may be directly on the other element, or there may be an intermediate layer. In addition, it is understood that when an element or layer is referred to as being "under" another element or layer, it may be directly under the other element, or there may be more than one intermediate layer or element. In addition, it is also understood that when a layer or element is referred to as being "between" two layers or two elements, it may be the only layer between the two layers or two elements, or there may also be more than one intermediate layer or element. Similar reference numerals throughout the text indicate similar elements.

[0129] Those skilled in the art will readily appreciate other embodiments of the present application after considering the description and practicing the contents disclosed herein. The present application is intended to cover any variations, uses or adaptations of the present application, which follow the general principles of the present application and include common knowledge or customary techniques in the art that are not disclosed in the present application. The description and examples are intended to be exemplary only, and the true scope and spirit of the present application are indicated by the following claims.

[0130] It should be understood that the present application is not limited to the precise structures that have been described above and shown in the drawings, and that various modifications and changes may be made without departing from the scope thereof. The scope of the present application is limited only by the appended claims.

Claims

1. A quantum dot film layer, characterized in that: The quantum dot film layer includes a first quantum dot layer and a second quantum dot layer stacked together, wherein: The first quantum dot layer includes first quantum dots and first photosensitivity ligands connected to the surface of the first quantum dots; The second quantum dot layer includes a second quantum dot and a second non-photosensitive ligand connected to the surface of the second quantum dot, and the second quantum dot is the same as the first quantum dot; The first photosensitive ligand includes a non-photosensitive coordination group and a photosensitive group, one end of the coordination group is connected to the surface of the first quantum dot, and the other end of the coordination group is connected to the photosensitive group; the coordination group is the same as the second non-photosensitive ligand; wherein, The coordination group and the second non-photosensitive ligand both include any one of a thiol group, a hydroxyl group, an amino group, a sulfonic acid group, a carboxyl group and a phosphate group; The photosensitive group has a structure as shown in formula II to IV; -R5-N=N-R6-(III); -R7-OO-R8-(IV); Wherein, R1, R2 to R8 are all selected from hydrogen, alkoxy, alkyl or aromatic groups.

2. The quantum dot film layer according to claim 1, characterized in that: The general structure of the first photosensitive ligand is shown in Formula I: AB(I); Among them, A is a coordination group and B is a photosensitizing group; The coordination group includes any one of a thiol group, a hydroxyl group, an amino group, a sulfonic acid group, a carboxyl group and a phosphate group; The photosensitive group has a structure as shown in formula II to IV; -R5-N=N-R6-(III); -R7-OO-R8-(IV); Wherein, R1, R2 to R8 are all selected from hydrogen, alkoxy, alkyl or aromatic groups.

3. The quantum dot film layer according to claim 1, characterized in that: The first quantum dot layer further includes a first alkyl chain ligand connected to the surface of the first quantum dot; The second quantum dot layer further includes a second alkyl chain ligand connected to the surface of the second quantum dot.

4. The quantum dot film layer according to claim 3, characterized in that: The first alkyl chain ligand and the second alkyl chain ligand are the same.

5. The quantum dot film layer according to claim 3, characterized in that: The first alkyl chain ligand and the second alkyl chain ligand both include a coordination unit and a C15-C50 branched alkyl group; The number of carbon atoms in each branch of the branched alkyl group is 6 to 12; The coordination unit includes any one of a thiol group, a hydroxyl group, an amine group, an amino group, a carboxyl group, a phosphate group, a phosphoester group and a sulfonic acid group.

6. A quantum dot light-emitting device, characterized in that: The quantum dot light-emitting device comprises a hole transport layer, an electron transport layer, and a quantum dot film layer according to any one of claims 1 to 5 located between the hole transport layer and the electron transport layer.

7. The quantum dot light emitting device according to claim 6, characterized in that: In a multi-electron system, the second quantum dot layer is disposed on a side of the first quantum dot layer away from the electron transport layer.

8. The quantum dot light emitting device according to claim 6, characterized in that: In a multi-hole system, the second quantum dot layer is disposed on a side of the first quantum dot layer away from the hole transport layer.

9. A method for manufacturing a quantum dot light-emitting device, characterized in that: The production method comprises: A quantum dot film layer as claimed in any one of claims 1 to 5 is formed on a substrate.

10. The manufacturing method according to claim 9, characterized in that: The steps of forming the quantum dot film layer specifically include: Forming a second quantum dot pre-layer on the substrate, wherein the second quantum dot pre-layer includes second quantum dots and second photosensitive ligands connected to the surface of the second quantum dots; irradiating the second quantum dot pre-layer with light to cause a second photosensitive ligand therein to undergo a cleavage reaction, and the second quantum dot pre-layer is converted into a second quantum dot layer; A first quantum dot layer is formed on the second quantum dot layer.

11. The method according to claim 9, characterized in that: The steps of forming the quantum dot film layer specifically include: forming a first quantum dot layer on a substrate; forming a second quantum dot pre-layer on the first quantum dot layer, wherein the second quantum dot pre-layer comprises second quantum dots and second photosensitive ligands connected to the surface of the second quantum dots; The second quantum dot pre-layer is irradiated with light to cause a cracking reaction of the second photosensitive ligand therein, and the second quantum dot pre-layer is converted into a second quantum dot layer.

12. The method according to claim 11, characterized in that: The first quantum dot layer and the second quantum dot pre-layer are made of the same material; and the first quantum dot layer and the second quantum dot pre-layer are formed in the same step.

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