Light-emitting element, display device, and production method for light-emitting element

Abstract

This light-emitting element (ED) comprises a first charge generation layer (CG1) that includes an n-type semiconductor material and is positioned between a first light-emitting layer (EM1) and a second light-emitting layer (EM2), a second charge generation layer (CG2) that includes a p-type semiconductor material and is positioned between the first charge generation layer (CG1) and the second light-emitting layer (EM2), and a SAM film (10) that is at least partially positioned between the first charge generation layer (CG1) and the second charge generation layer (CG2).

Description

Light-Emitting Element, Display Device, and Method for Manufacturing Light-Emitting Element

[0001] The present disclosure relates to a light-emitting element, a display device, and a method for manufacturing a light-emitting element.

[0002] Patent Document 1 discloses a tandem-type light-emitting element that includes a charge generation layer formed by laminating a layer containing n-type nanoparticles and a layer containing a hole-injecting material between two light-emitting layers.

[0003] US 2018 / 0122873 A1

[0004] However, when n-type nanoparticles come into direct contact with a hole-injecting material, the two materials react with each other, which tends to reduce the charge generation capability. For this reason, there has been a problem that the lifetime and reliability of the light-emitting element are low.

[0005] In order to solve the above problem, a light-emitting element according to an aspect of the present disclosure includes: a first light-emitting layer and a second light-emitting layer; a first charge generation layer located between the first light-emitting layer and the second light-emitting layer and containing an n-type semiconductor material; a second charge generation layer located between the first charge generation layer and the second light-emitting layer and containing a p-type semiconductor material; and a SAM (Self-Assembled Monolayer) film at least a part of which is located between the first charge generation layer and the second charge generation layer.

[0006] In order to solve the above problem, a display device according to an aspect of the present disclosure includes the light-emitting element according to an aspect of the present disclosure.

[0007] In order to solve the above problem, a method for manufacturing a light-emitting element according to an aspect of the present disclosure includes: a step of forming a first light-emitting layer; a step of forming a second light-emitting layer; a step of forming a first charge generation layer containing an n-type semiconductor material so as to be located between the first light-emitting layer and the second light-emitting layer; a step of forming a second charge generation layer containing a p-type semiconductor material so as to be located between the first charge generation layer and the second light-emitting layer; and a step of forming a SAM film at least a part of which is located between the first charge generation layer and the second charge generation layer.

[0008] According to one aspect of this disclosure, a SAM film is located between the first and second charge generation layers. As a result, the n-type semiconductor material does not come into contact with the p-type semiconductor material, which improves the lifespan and reliability of the light-emitting element.

[0009] This is a cross-sectional view showing an example of the configuration of a light-emitting element according to one embodiment of the present disclosure. This is an enlarged cross-sectional view showing an example of the configuration of the first and second charge generation layers and the SAM film shown in Figure 1 a cross-sectional view showing an example of the configuration of a film containing nanoparticles. This is a cross-sectional view showing an example of the configuration of a film containing nanoparticles. This is a flow diagram showing an example of a method for manufacturing the light-emitting element shown in Figure 1. This is a flowchart showing another example of the method for manufacturing the light-emitting element shown in Figure 1. This is a flowchart showing yet another example of the method for manufacturing the light-emitting element shown in Figure 1. This is a cross-sectional view showing an example of the configuration of a light-emitting element according to one embodiment of the present disclosure. This is an enlarged cross-sectional view showing an example of the configuration of the first and second charge generation layers and the SAM film shown in Figure 16. This is an enlarged cross-sectional view showing an example of the configuration of the first and second charge generation layers and the SAM film shown in Figure 16. This is an enlarged cross-sectional view showing an example of the configuration of the first and second charge generation layers and the SAM film shown in Figure 16. This is an enlarged cross-sectional view showing an example of the configuration of the first and second charge generation layers and the SAM film shown in Figure 16. This is a flowchart showing an example of the method for manufacturing the light-emitting element shown in Figure 16. This is a flowchart showing another example of the method for manufacturing the light-emitting element shown in Figure 16. This is a flowchart showing yet another example of the method for manufacturing the light-emitting element shown in Figure 16. This is a schematic diagram showing an example of the configuration of a display device according to one embodiment of the present disclosure.

[0010] [Embodiment 1] (Configuration of a light-emitting element) Figure 1 is a cross-sectional view showing an example of the configuration of a light-emitting element according to one embodiment of the present disclosure. As shown in Figure 1, the light-emitting element ED according to the present disclosure comprises a first light-emitting layer EM1 and a second light-emitting layer EM2, a first charge generation layer CG1 located between the first light-emitting layer EM1 and the second light-emitting layer EM2 and containing an n-type semiconductor material, a second charge generation layer CG2 located between the first charge generation layer CG1 and the second light-emitting layer EM2 and containing a p-type semiconductor material, and a SAM film 10, at least a portion of which is located between the first charge generation layer CG1 and the second charge generation layer CG2.

[0011] Generally, a layer comprising a layer containing a p-type semiconductor material and a layer containing an n-type semiconductor material, and the entire layer having the function of generating electrons and holes between the p-type semiconductor material layer and the n-type semiconductor material layer, is referred to as a "charge generation layer." In this disclosure, for convenience, the layer containing the n-type semiconductor material is referred to as the "first charge generation layer," and the layer containing the p-type semiconductor material is referred to as the "second charge generation layer."

[0012] n-type and p-type semiconductor materials may undergo chemical reactions and form mixed crystals when in direct contact with each other for extended periods. Alternatively, one or both of the two semiconductor materials may undergo modification. Such mixed crystal formation or modification reduces the charge generation capability. According to the configuration shown in Figure 1, the SAM film 10 separates the n-type and p-type semiconductor materials, making it difficult for the two semiconductor materials to undergo chemical reactions with each other. Therefore, the period during which the charge generation capability of the first charge generation layer CG1 and the second charge generation layer CG2 can be maintained can be extended, and thus the lifespan and reliability of the light-emitting element ED can be improved.

[0013] In addition, the polarization caused by dipoles in the SAM film 10 between the first charge generation layer CG1 and the second charge generation layer CG2 makes it easier to generate electron-hole pairs between the first and second charge generation layers CG1 and CG2. As a result, the driving voltage of the light-emitting element ED is reduced.

[0014] The light-emitting element ED comprises an anode AN and a cathode CA such that a first light-emitting layer EM1 is located between the anode AN and a first charge generation layer CG1, and a second light-emitting layer EM2 is located between the cathode CA and a second charge generation layer CG2. The light-emitting element ED is located on a substrate SB. In this disclosure, the direction from the substrate SB toward the light-emitting element ED is defined as "up," "upper side," "upward," and "upward direction," and the direction from the light-emitting element ED toward the substrate SB is defined as "down," "lower side," "downward," and "downward direction." In the configuration according to this embodiment 1, as shown in Figure 1, the anode AN is located on the lower side and the cathode CA is located on the upper side.

[0015] The light-emitting element ED may optionally include charge functional layers such as a hole injection layer, a hole transport layer, and an electron blocking layer between the anode AN and the first light-emitting layer EM1. The light-emitting element ED may optionally include charge functional layers such as a hole blocking layer, an electron transport layer, and an electron injection layer between the first light-emitting layer EM1 and the first charge generation layer CG1. The light-emitting element ED may optionally include charge functional layers such as a hole injection layer, a hole transport layer, and an electron blocking layer between the second charge generation layer CG2 and the second light-emitting layer EM2. The light-emitting element ED may optionally include charge functional layers such as a hole blocking layer, an electron transport layer, and an electron injection layer between the second light-emitting layer EM2 and the cathode CA.

[0016] The light-emitting element ED according to this disclosure is not limited to the tandem element having two light-emitting layers as shown in Figure 1, but may also be a tandem element having three or more light-emitting layers.

[0017] (Configuration of the first and second charge generation layers and the SAM film) Figures 2 to 9 are enlarged cross-sectional views showing various configuration examples of the first and second charge generation layers and the SAM film shown in Figure 1. As shown in Figures 2 to 7, when at least a portion of the SAM film 10 is located on the surface of the first charge generation layer CG1, the SAM film 10 may exhibit electron transport properties. By improving the electron transport properties of the first charge generation layer CG1, the driving voltage of the light-emitting element ED is further reduced. As shown in Figures 8 to 9, when at least a portion of the SAM film 10 is located on the surface of the second charge generation layer CG2, the SAM film 10 may exhibit hole transport properties. By improving the hole transport properties of the second charge generation layer CG2, the driving voltage of the light-emitting element ED is further reduced. The hole-transporting SAM membrane 10 is, for example, an alkylphosphonic acid such as [2-(9H-carbazole-9-yl)ethyl]phosphonic acid, [2-(3,6-dimethoxy-9H-carbazole-9-yl)ethyl]phosphonic acid, [2-(3,6-dimethyl-9H-carbazole-9-yl)ethyl]phosphonic acid, [2-(3,6-dibromo-9H-carbazole-9-yl)ethyl]phosphonic acid, [2-(3,6-dichloro-9H-carbazole-9-yl)ethyl]phosphonic acid, [4-(9H-carb The SAM film 10 may exhibit insulating properties even when at least a portion of the SAM film 10 is located on either the surface of the first charge generation layer CG1 or the second charge generation layer CG2. The insulating SAM film 10 may include, for example, a silane coupling material.

[0018] The location of the SAM film 10 on any surface can be confirmed using various methods such as scanning probe microscopy (STM / AFM), X-ray electron spectroscopy (XPS), ellipsometry, surface plasmon resonance (SPR), quartz crystal microbalancing (QCM), the contact angle of the SAM film 10 with respect to the surface, or cyclic voltammetry (CV).

[0019] As shown in Figures 2 and 3, when the first charge generation layer CG1 is a film containing first nanoparticles NP1 made of an n-type semiconductor material, and the first nanoparticles NP1 occupy at least a portion of the surface of the film on the second charge generation layer CG2 side, the SAM film 10 may be formed on at least a portion of the surface of the first nanoparticles NP1 so as to be located on the surface and inside the first charge generation layer CG1. When the first charge generation layer CG1 contains a plurality of first nanoparticles NP1, some first nanoparticles NP1 may have at least a portion of their surface covered by the SAM film 10, while others may have no surface covered at all. Alternatively, at least a portion of the surface of each first nanoparticle NP1 may be covered by the SAM film 10. The SAM film 10 makes it difficult for the first nanoparticles NP1 to aggregate with each other and difficult for the first nanoparticles NP1 to grow. The aggregation and growth of nanoparticles weaken the quantum effect and alter the upper valence band and lower conduction band of the film containing the nanoparticles. Therefore, by forming the SAM film 10 on at least a portion of the surface of the first nanoparticle NP1, the lifetime and reliability of the first charge generation layer CG1 can be improved. In addition, when the SAM film 10 exhibits electron transport properties, the SAM film 10 located inside the first charge generation layer CG1 improves the electron transport properties of the first charge generation layer CG1. As a result, the driving voltage of the light-emitting element ED can be further reduced.

[0020] As shown in Figures 8 and 9, when the second charge generation layer CG2 is a film containing second nanoparticles NP2 made of a p-type semiconductor material, and the second nanoparticles NP2 occupy at least a portion of the surface of the film on the side of the first charge generation layer CG1, the SAM film 10 may be formed on at least a portion of the surface of the second nanoparticles NP2 so as to be located on the surface and inside the second charge generation layer CG2. When the second charge generation layer CG2 contains a plurality of second nanoparticles NP2, some second nanoparticles NP2 may have at least a portion of their surface covered by the SAM film 10, while others may have no surface covered at all. Alternatively, at least a portion of the surface of each second nanoparticle NP2 may be covered by the SAM film 10. The SAM film 10 makes it difficult for the second nanoparticles NP2 to aggregate with each other, and makes it difficult for the second nanoparticles NP2 to grow. Therefore, by forming the SAM film 10 on at least a portion of the surface of the second nanoparticle NP2, the lifetime and reliability of the second charge generation layer CG2 can be improved. In addition, when the SAM film 10 exhibits hole transport properties, the SAM film 10 located inside the second charge generation layer CG2 improves the hole transport properties of the second charge generation layer CG2. As a result, the driving voltage of the light-emitting element ED can be further reduced.

[0021] Figures 10 to 12 are cross-sectional views showing various configuration examples of a film containing nanoparticles. A matrix material may or may not surround the nanoparticles. In this embodiment, the matrix material functions as a filler to hold the nanoparticles or to fill the spaces between the nanoparticles, and may be partially present or exist as a continuous film. The film containing nanoparticles may be (i) a film 100 consisting of nanoparticles 110 with no matrix material between the nanoparticles 110, as shown in Figure 10; (ii) a film 200 including nanoparticles 210 and a matrix material 220 located between the nanoparticles 210, as shown in Figure 11, in which the nanoparticles 210 are exposed from the matrix material 220; or (iii) a film 300 including nanoparticles 310 and a matrix material 320 located between the nanoparticles 310, in which the nanoparticles 310 are completely embedded in the matrix material 320, as shown in Figure 12. As shown in Figures 10 and 11, when nanoparticles 110 and 210 occupy at least a portion of the surface of films 100 and 200, a portion of the SAM films 130 and 230 formed on the surface of the nanoparticles 110 and 210 is located on the surface of films 100 and 200. As shown in Figure 12, when nanoparticles 310 are not exposed on the surface of film 300, a SAM film is separately formed on the surface of matrix material 320. The SAM film formed on the surface of matrix material 320 is located on the surface of film 300. In this embodiment, the matrix material can be an inorganic material such as a sulfide such as zinc sulfide or an oxide such as silicon oxide, an organic material such as an organic siloxane, or various semiconductor materials. If a semiconductor material is used as the matrix material, it is preferable to use an n-type semiconductor material when it is included in the first charge generation layer CG1, and a p-type semiconductor material when it is included in the second charge generation layer CG2. n-type semiconductor materials applicable to matrix materials include, for example, zinc oxide (ZnO), magnesium zinc oxide (ZnMgO), and titanium oxide (TiO2). ２ ) and tin oxide (SnO ２ The material can be selected from a group of metal oxides such as ). In addition, p-type semiconductor materials applicable to the matrix material include, for example, nickel oxide (NiO) and copper oxide (Cu ２The materials can be selected from a group of metal oxides such as O) and conductive organic materials with hole-transporting properties such as poly(3,4-ethylenedioxythiophene):poly(styrenesulfonic acid), abbreviated as "PEDOT:PSS".

[0022] Whether the first charge generation layer CG1 and the second charge generation layer CG2 are films in which nanoparticles occupy at least a portion of their surface can be combined in various ways. As shown in the configuration examples in Figures 2, 4, and 8, both may be films in which nanoparticles occupy at least a portion of their surface. As shown in the configuration examples in Figures 3, 5, 6, and 9, one may be a film in which nanoparticles occupy at least a portion of its surface, and the other may be a film in which nanoparticles are not exposed on the surface. As shown in the configuration example in Figure 7, both may be films in which nanoparticles are not exposed on the surface.

[0023] For example, as shown in Figures 2, 4, and 8, the first charge generation layer CG1 is a film containing first nanoparticles NP1 made of an n-type semiconductor material, with at least a portion of the surface of the film on the side of the second charge generation layer CG2 being occupied by the first nanoparticles NP1, and the second charge generation layer CG2 is a film containing second nanoparticles NP2 made of a p-type semiconductor material, with at least a portion of the surface of the film on the side of the first charge generation layer CG1 being occupied by the second nanoparticles NP2.

[0024] For example, as shown in Figures 3 and 5, the first charge generation layer CG1 is a film containing first nanoparticles NP1 made of an n-type semiconductor material, the first nanoparticles NP1 occupy at least a portion of the surface of the film on the side of the second charge generation layer CG2, and the second charge generation layer CG2 is a continuous film containing a p-type semiconductor material. A continuous film means a film that is not separated by materials other than those constituting the continuous film in a single plane.

[0025] For example, as shown in Figures 6 and 9, the first charge generation layer CG1 is a continuous film containing an n-type semiconductor material, and the second charge generation layer CG2 is a film containing second nanoparticles NP2 made of a p-type semiconductor material, with the second nanoparticles NP2 occupying at least a portion of the surface of the film on the side of the first charge generation layer CG1.

[0026] For example, as shown in Figure 7, the first charge generation layer CG1 is a continuous film containing an n-type semiconductor material, and the second charge generation layer CG2 is a continuous film containing a p-type semiconductor material.

[0027] The n-type semiconductor material included in the first charge generation layer CG1 may be a metal oxide, for example, zinc oxide (ZnO), magnesium zinc oxide (ZnMgO), titanium oxide (TiO ２ ) and tin oxide (SnO ２ A selection may be made from the group consisting of the following. The silane coupling material mentioned above readily bonds to metal oxides.

[0028] The p-type semiconductor material included in the second charge generation layer CG2 may be a metal oxide, for example, nickel oxide (NiO) and copper oxide (Cu ２ The group consisting of O) may be selected. The alkylphosphonic acid and silane coupling materials mentioned above readily bond to metal oxides. The p-type semiconductor material included in the second charge generation layer CG2 may be a hole-transporting conductive organic material, for example, poly(3,4-ethylenedioxythiophene):poly(styrenesulfonic acid), abbreviated as "PEDOT:PSS".

[0029] The color of the light emitted by the second light-emitting layer E2 may be substantially the same as the color of the light emitted by the first light-emitting layer E1. For the two colors of light to be substantially the same, they only need to be nearly identical within the range visible to the human eye; it is not required that the peak wavelengths of the light be perfectly identical in a strict sense. For example, if two peaks are detected in the emission wavelength spectra of two types of quantum dots, and the wavelengths of these peaks fall within the wavelength ranges of the same color (430-500 nm for blue, 500-570 nm for green, and 610-780 nm for red), then they are considered identical. Naturally, if no two peaks are detected, they are also considered identical. This allows for increased luminescence per unit current density, enabling the light-emitting element ED to operate at a low current density. A tandem light-emitting element includes multiple light-emitting units connected in series between the anode and cathode, and the luminescence per unit current density in a tandem light-emitting element is approximately proportional to the number of light-emitting units connected in series. An example of a light-emitting unit includes a hole injection layer, a hole transport layer, a light-emitting layer, and an electron transport layer in this order. Therefore, the reliability of the light-emitting element (ED) can be improved. Note that each light-emitting layer is not limited to quantum dots and may also include organic light-emitting materials.

[0030] (Method for Manufacturing a Light-Emitting Device) Figure 13 is a flowchart showing an example of the method for manufacturing a light-emitting device shown in Figure 1. As shown in Figure 13, the method for manufacturing a light-emitting device ED according to the present disclosure includes the steps of: forming a first light-emitting layer EM1 (step S30); forming a second light-emitting layer EM2 (step S70); forming a first charge generation layer CG1 containing an n-type semiconductor material so as to be located between the first light-emitting layer EM1 and the second light-emitting layer EM2 (step S40); forming a second charge generation layer CG2 containing a p-type semiconductor material so as to be located between the first charge generation layer CG1 and the second light-emitting layer EM2 (step S60); and forming a SAM film 10 so as to be located between the first charge generation layer CG1 and the second charge generation layer CG2 (step S50).

[0031] The method for manufacturing the light-emitting element ED further includes the steps of forming the anode AN such that the first light-emitting layer EM1 is located between the anode AN and the first charge generation layer CG1 (step S20), and forming the cathode CA such that the second light-emitting layer EM2 is located between the cathode CA and the second charge generation layer CG2 (step S80). The method for manufacturing the light-emitting element ED may include the step of preparing a substrate SB (step S10), and the light-emitting element ED may be formed on the substrate SB. In the configuration according to this embodiment 1, as shown in Figure 13, the anode AN is formed first, and the cathode CA is formed later.

[0032] The manufacturing method for the light-emitting element ED is optional and may include a step of forming a charge-functional layer such as a hole injection layer, a hole transport layer, and an electron blocking layer between steps S20 and S30. The manufacturing method for the light-emitting element ED is optional and may include a step of forming a charge-functional layer such as a hole blocking layer, an electron transport layer, and an electron injection layer between steps S30 and S40. The manufacturing method for the light-emitting element ED is optional and may include a step of forming a charge-functional layer such as a hole injection layer, a hole transport layer, and an electron blocking layer between steps S60 and S70. The manufacturing method for the light-emitting element ED is optional and may include a step of forming a charge-functional layer such as a hole blocking layer, an electron transport layer, and an electron injection layer between steps S70 and S80.

[0033] For example, an anode AN is formed on a substrate SB, a first light-emitting layer EM1 is formed above the anode AN, and a first charge-generating layer CG1 is formed above the first light-emitting layer EM1. Then, a SAM film 10 is formed on the first charge-generating layer CG1 by coating and drying a solution containing self-assembling molecules. A portion of the solution containing self-assembling molecules may penetrate into the first charge-generating layer CG1. The state of the SAM film 10 can be easily controlled through various parameters, including the amount of self-assembling molecules contained in the solution and the viscosity of the solution. Furthermore, the SAM film 10 can be controlled independently of the first charge-generating layer CG1 and the second charge-generating layer CG2. Subsequently, a second charge-generating layer CG2 is formed above the first charge-generating layer CG1, a second light-emitting layer EM2 is formed above the second charge-generating layer CG2, and a cathode CA is formed above the second light-generating layer EM.

[0034] At least a portion of the SAM film 10 formed by the method shown in Figure 13 is formed on the upper surface of the first charge generation layer CG1 and located between the first charge generation layer CG1 and the second charge generation layer CG2, as shown in Figures 4 to 7.

[0035] Figure 14 is a flow chart showing another example of the method for manufacturing the light-emitting element shown in Figure 1. As shown in Figure 14, a first nanoparticle NP1 made of an n-type semiconductor material is prepared (step S110), a SAM film 10 is formed on at least a portion of the surface of the first nanoparticle NP1 (step S120), a first dispersion containing the first nanoparticle NP1 is prepared (step S130), and a first charge generation layer CG1 is formed by coating and drying the first dispersion containing the first nanoparticle NP1 with the SAM film 10 formed on it on a layer above the first light-emitting layer EM1 (step S140). Then, a second charge generation layer CG2 is formed on a layer above the first charge generation layer CG1 (step S60).

[0036] Step S140 shown in Figure 14 replaces steps S40 and S50 shown in Figure 13. Therefore, the method shown in Figure 14 has advantages over the method shown in Figure 13. The solvent in which the first nanoparticles NP1 on which the SAM film 10 is formed disperses depends on the SAM film 10, and therefore may differ from the solvent in which the n-type semiconductor material dissolves or disperses. Therefore, by changing from the method shown in Figure 13 to the method shown in Figure 14, the polarity of the solvent in which the material of the first charge generation layer CG1 is dissolved or dispersed can be changed. This makes it possible to give the material solution of the first charge generation layer CG1 in step S140 the effect of reducing the dissolution of the underlying layer, the first light-emitting layer EM1, and the effect of improving its own coatability (preventing it from being repelled). In addition, it is possible to give the material solution of the second charge generation layer CG2 in step S60 the effect of reducing the dissolution of the underlying layer, the first light-emitting layer EM1, and the effect of improving the coatability of the material solution of the second charge generation layer CG2 (preventing it from being repelled).

[0037] The SAM film 10 formed by the method shown in Figure 14 is located on the surface and inside the first charge generation layer CG1, as shown in Figures 2 and 3 above, with a portion of it located between the first charge generation layer CG1 and the second charge generation layer CG2.

[0038] Figure 15 is a flowchart showing yet another example of the method for manufacturing the light-emitting element shown in Figure 1. As shown in Figure 15, a first charge generation layer CG1 is formed above the first light-emitting layer EM1 (step S40). Then, a second nanoparticle NP2 made of p-type semiconductor material is prepared (step S210), a SAM film 10 is formed on at least a portion of the surface of the second nanoparticle NP2 (step S220), a second dispersion containing the second nanoparticle NP2 is prepared (step S230), and a second charge generation layer is formed by coating and drying the second dispersion containing the second nanoparticle NP2 with the SAM film 10 formed on it onto the first charge generation layer CG1 (step S260).

[0039] Step S260 shown in FIG. 15 replaces steps S50 and S60 shown in FIG. 13. Therefore, the method shown in FIG. 15 has advantages in the process compared to the method shown in FIG. 13. The solvent in which the second nanoparticles NP2 having the SAM film 10 formed thereon are easily dispersed depends on the SAM film 10, and thus may differ from the solvent in which the p-type semiconductor material is easily dissolved or dispersed. Therefore, changing from the method shown in FIG. 13 to the method shown in FIG. 15 enables changing the polarity of the solvent that dissolves or disperses the material of the second charge generation layer CG2. This allows the material solution of the second charge generation layer CG2 in step S260 to have the effect of reducing dissolution of the underlying first charge generation layer CG1, and the effect of improving its coatability (preventing repellency). In addition, this allows the material solution of the second light-emitting layer EM2 in step S70 to have the effect of reducing dissolution of the underlying layer, and the effect of improving coatability of the material solution of the second light-emitting layer EM2 (preventing repellency).

[0040] The SAM film 10 formed by the method shown in FIG. 15 is located on the surface and inside the second charge generation layer CG2 as shown in FIG. 8 and FIG. 9, and part of the SAM film 10 is located between the first charge generation layer CG1 and the second charge generation layer CG2.

[0041] [Embodiment 2] FIG. 16 is a cross-sectional view showing an example of the configuration of a light-emitting element according to an embodiment of the present disclosure. As shown in FIG. 16, in the configuration according to Embodiment 2, the anode AN is located on the upper side, and the cathode CA is located on the lower side. That is, the stacking order from the anode AN to the cathode CA in the configuration according to Embodiment 2 is reversed from the stacking order in the configuration according to the foregoing Embodiment 1.

[0042] Figures 17 to 20 are enlarged cross-sectional views showing various configuration examples of the first and second charge generation layers and SAM film shown in Figure 16. In addition, the configuration examples shown in Figures 2 to 3, which are inverted vertically, and the configuration examples shown in Figures 8 to 9, which are inverted vertically, also fall within the range of various configuration examples of the first and second charge generation layers and SAM film shown in Figure 16. As shown in the configuration examples inverted vertically from Figures 2 to 3, when at least a portion of the SAM film 10 is located on the surface of the first charge generation layer CG1, the SAM film 10 may exhibit electron transport properties. As shown in the configuration examples in Figures 17 to 20 and the configuration examples inverted vertically from Figures 8 to 9, when at least a portion of the SAM film 10 is located on the surface of the second charge generation layer CG2, the SAM film 10 may exhibit hole transport properties. The SAM film 10 may exhibit insulating properties even when at least a portion of it is located on either the surface of the first charge generation layer CG1 or the second charge generation layer CG2.

[0043] Whether the first charge generation layer CG1 and the second charge generation layer CG2 are films in which nanoparticles occupy at least a portion of their surface can be combined in various ways. As shown in the configuration example of Figure 2 inverted vertically, the configuration example of Figure 17, and the configuration example of Figure 8 inverted vertically, both may be films in which nanoparticles occupy at least a portion of their surface. As shown in the configuration example of Figure 3 inverted vertically, the configuration example of Figure 18, the configuration example of Figure 19, and the configuration example of Figure 9 inverted vertically, one may be a film in which nanoparticles occupy at least a portion of its surface, and the other may be a film in which nanoparticles are not exposed on the surface. As shown in the configuration example of Figure 20, both may be films in which nanoparticles are not exposed on the surface.

[0044] (Method for manufacturing a light-emitting element) Figure 21 is a flowchart showing an example of the method for manufacturing a light-emitting element shown in Figure 16. As shown in Figure 21, in the method for manufacturing the light-emitting element ED according to this embodiment 2, the anode AN is formed later and the cathode CA is formed first.

[0045] For example, a cathode CA is formed on a substrate SB, a second light-emitting layer EM2 is formed in an upper layer above the cathode CA, and a second charge generation layer CG2 is formed in an upper layer above the second light-emitting layer EM2. Then, the SAM film 10 is formed on the second charge generation layer CG2 by applying a solution containing self-assemblable molecules and drying the solution. A part of the solution containing self-assemblable molecules may penetrate into the second charge generation layer CG2. The state of the SAM film 10 can be easily controlled through various parameters including the content of the self-assemblable molecules in the solution and the viscosity of the solution. In addition, the SAM film 10 can be controlled independently of the first charge generation layer CG1 and the second charge generation layer CG2. Subsequently, a first charge generation layer CG1 is formed in an upper layer above the second charge generation layer CG2, a first light-emitting layer EM1 is formed in an upper layer above the first charge generation layer CG1, and an anode AN is formed in an upper layer above the first light-emitting layer EM1.

[0046] At least a part of the SAM film 10 formed by the method shown in FIG. 21 is formed on the upper surface of the second charge generation layer CG2 and located between the first charge generation layer CG1 and the second charge generation layer CG2, as shown in the aforementioned FIGS. 17 to 20.

[0047] FIG. 22 is a flowchart showing another example of the method for manufacturing the light-emitting element shown in FIG. 16. As shown in FIG. 22, second nanoparticles NP2 made of a p-type semiconductor material are prepared (step S210), the SAM film 10 is formed on at least a part of the surfaces of the second nanoparticles NP2 (step S220), a second dispersion liquid containing the second nanoparticles NP2 is prepared (step S230), and the second charge generation layer CG2 is formed by applying the second dispersion liquid containing the second nanoparticles NP2 on which the SAM film 10 is formed onto an upper layer above the second light-emitting layer EM2 and drying the applied dispersion liquid (step S260). Then, the first charge generation layer CG1 is formed on an upper layer above the second charge generation layer CG2 (step S40).

[0048] Step S260 shown in Figure 22 replaces steps S50 and S60 in Figure 21. Therefore, the method shown in Figure 22 has advantages over the method shown in Figure 21. By changing from the method shown in Figure 21 to the method shown in Figure 22, the polarity of the solvent used to dissolve or disperse the material of the second charge generation layer CG2 can be changed. This allows the material solution of the second charge generation layer CG2 in step S260 to have the effect of reducing the dissolution of the underlying layer, the second light-emitting layer EM2, and improving its own coatability (preventing it from being repelled). Similarly, the material solution of the first charge generation layer CG1 in step S40 can have the effect of reducing the dissolution of the underlying layer, the second light-emitting layer EM2, and improving the coatability of the material solution of the first charge generation layer CG1 (preventing it from being repelled).

[0049] The SAM film 10 formed by the method shown in Figure 22 is located on the surface and inside the second charge generation layer CG2, as shown in the configuration example with Figures 8 and 9 inverted vertically, with a portion of it located between the first charge generation layer CG1 and the second charge generation layer CG2.

[0050] Figure 23 is a flow diagram showing yet another example of the method for manufacturing a light-emitting element shown in Figure 16. As shown in Figure 23, a second charge generation layer CG2 is formed above the second light-emitting layer EM2 (step S60). Then, a first nanoparticle NP1 made of an n-type semiconductor material is prepared (step S110), a SAM film 10 is formed on at least a portion of the surface of the first nanoparticle NP1 (step S120), a first dispersion containing the first nanoparticle NP1 is prepared (step S130), and the first charge generation layer CG1 is formed by coating and drying the first dispersion containing the first nanoparticle NP1 with the SAM film 10 on it onto the second charge generation layer CG2 (step S140).

[0051] Step S140 shown in Figure 23 replaces steps S40 and S50 shown in Figure 21. Therefore, the method shown in Figure 23 has advantages over the method shown in Figure 21. By changing from the method shown in Figure 21 to the method shown in Figure 23, the polarity of the solvent used to dissolve or disperse the material of the first charge generation layer CG1 can be changed. This allows the material solution of the first charge generation layer CG1 in step S140 to have the effect of reducing the dissolution of the underlying layer, the second charge generation layer CG2, and to improve its own coatability (preventing it from being repelled). In addition, the material solution of the first light-emitting layer EM1 in step S30 can have the effect of reducing the dissolution of the underlying layer, the second charge generation layer CG2, and to improve the coatability of the material solution of the first light-emitting layer EM1 (preventing it from being repelled).

[0052] The SAM film 10 formed by the method shown in Figure 23 is located on the surface and inside the first charge generation layer CG1, as shown in the configuration example where Figures 2 and 3 are inverted vertically, with a portion of it located between the first charge generation layer CG1 and the second charge generation layer CG2.

[0053] [Embodiment 3] Figure 24 is a schematic diagram showing an example of the configuration of a display device according to one embodiment of the present disclosure. As shown in Figure 24, the display device DP according to the present disclosure includes a light-emitting element ED according to the present disclosure. For example, the display device DP comprises a display area DA provided with a plurality of subpixels PX and a frame area NA provided with a drive circuit DC that drives the display area DA, wherein at least one of the plurality of subpixels PX includes a light-emitting element ED.

[0054] The light-emitting element ED may be configured according to Embodiment 1 described above, or according to Embodiment 2 described above, or it may be configured with any improvements or modifications.

[0055] This disclosure is not limited to the embodiments described above, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of this disclosure. Furthermore, new technical features can be formed by combining the technical means disclosed in each embodiment.

[0056] 10 SAM (Self-Assembled Monolayer) film CG1 First charge generation layer CG2 Second charge generation layer DP Display device ED Light-emitting element EM1 First light-emitting layer EM2 Second light-emitting layer NP1 First nanoparticle NP2 Second nanoparticle

Claims

1. A light-emitting element comprising: a first light-emitting layer and a second light-emitting layer; a first charge generation layer located between the first light-emitting layer and the second light-emitting layer and containing an n-type semiconductor material; a second charge generation layer located between the first charge generation layer and the second light-emitting layer and containing a p-type semiconductor material; and a SAM film, at least a portion of which is located between the first charge generation layer and the second charge generation layer.

2. The light-emitting element according to claim 1, wherein at least a portion of the SAM film is located on the surface of the first charge generation layer, and the SAM film exhibits electron transport properties.

3. The light-emitting element according to claim 1, wherein at least a portion of the SAM film is located on the surface of the second charge generation layer, and the SAM film exhibits hole transport properties.

4. The light-emitting element according to claim 1, wherein the SAM film exhibits insulating properties.

5. The light-emitting element according to any one of claims 1 to 2, 4, wherein the first charge generation layer is a film containing first nanoparticles made of the n-type semiconductor material, and the SAM film is located on the surface and inside the first charge generation layer and is formed on at least a portion of the surface of the first nanoparticles.

6. The light-emitting element according to any one of claims 1, 3 to 4, wherein the second charge generation layer is a film containing second nanoparticles made of the p-type semiconductor material, and the SAM film is located on the surface and inside the second charge generation layer and is formed on at least a portion of the surface of the second nanoparticles.

7. The light-emitting element according to any one of claims 1 to 6, wherein the first charge generation layer is a film containing first nanoparticles made of the n-type semiconductor material, and the second charge generation layer is a film containing second nanoparticles made of the p-type semiconductor material.

8. The light-emitting element according to any one of claims 1 to 5, wherein the first charge generation layer is a film containing first nanoparticles made of the n-type semiconductor material, and the second charge generation layer is a continuous film containing the p-type semiconductor material.

9. The first charge generation layer is a continuous film containing the n-type semiconductor material, and the second charge generation layer is a film containing second nanoparticles made of the p-type semiconductor material, the light-emitting element according to any one of claims 1 to 4, 6.

10. The light-emitting element according to any one of claims 1 to 4, wherein the first charge generation layer is a continuous film containing an n-type semiconductor material, and the second charge generation layer is a continuous film containing a p-type semiconductor material.

11. A display device comprising a light-emitting element according to any one of claims 1 to 10.

12. A method for manufacturing a light-emitting element, comprising the steps of: forming a first light-emitting layer; forming a second light-emitting layer; forming a first charge generation layer containing an n-type semiconductor material so as to be located between the first light-emitting layer and the second light-emitting layer; forming a second charge generation layer containing a p-type semiconductor material so as to be located between the first charge generation layer and the second light-emitting layer; and forming a SAM film in which at least a portion is located between the first charge generation layer and the second charge generation layer.

13. The method for manufacturing a light-emitting element according to claim 12, wherein the SAM film is formed between the step of forming the first charge-generating layer and the step of forming the second charge-generating layer by applying and drying a solution containing self-assembling molecules.

14. The method for manufacturing a light-emitting element according to claim 12, comprising forming the SAM film on at least a portion of the surface of the first nanoparticles made of the n-type semiconductor material, and forming the first charge generation layer by coating and drying a first dispersion containing the first nanoparticles on which the SAM film is formed on the surface.

15. The method for manufacturing a light-emitting element according to claim 12, comprising forming the SAM film on at least a portion of the surface of the second nanoparticles made of the p-type semiconductor material, and forming the second charge generation layer by coating and drying a second dispersion containing the second nanoparticles on which the SAM film is formed on the surface.

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