Electroluminescent element and electroluminescent device

Abstract

An electroluminescent element (XR) comprises an anode (22); a cathode (25); and a light-emitting layer, which is arranged between the anode (22) and the cathode (25), and further comprises: an electron transport layer (33), which contains n-type semiconductor particles (36) and a first insulating polymer (37); and a hole transport layer (30), which contains p-type semiconductor particles (34), wherein the electron transport layer (33) is arranged between the cathode (25) and the light-emitting layer, and the hole transport layer (30) is arranged between the anode (22) and the light-emitting layer, and the volume ratio of the n-type semiconductor particles (36) in the electron transport layer (33) is smaller than the volume ratio of the p-type semiconductor particles (34) in the hole transport layer (30).

Description

Technical Field

[0001] The present disclosure relates to an electroluminescent element and an electroluminescent device including a plurality of electroluminescent elements. Background Art

[0002] In recent years, various display devices have been developed. In particular, display devices with OLED (Organic Light Emitting Diode) and display devices with inorganic light emitting diodes or QLED (Quantum dot Light Emitting Diode) have attracted much attention from the perspectives of achieving low power consumption, thinness, and high image quality.

[0003] Patent Documents 1 to 3 describe a structure in which an electroluminescent element such as an OLED or a QLED is provided with an electron transport layer or a hole transport layer containing semiconductor nanoparticles (for example, metal oxide nanoparticles).

[0004] Fig. 9 (a) Fig. 9 (b) Fig. 9 (c) and Fig. 9 (d) is a diagram showing a schematic structure of conventional electroluminescent elements 101 , 102 , 103 , and 104 described in Patent Documents 1 to 3.

[0005] Fig. 9 The electroluminescent element 101 described in Patent Document 1 shown in (a) has a structure in which an anode 112, a hole transport layer 113, a light-emitting layer 114, a nanoparticle layer 115, and a cathode 116 are stacked on a substrate 111 in order from the substrate 111 side. Then, a material obtained by dispersing barium titanate nanoparticles as metal oxide nanoparticles (electron transport material) in a xylene solution is applied to the light-emitting layer 114 by a spray method, thereby forming the nanoparticle layer 115. According to Patent Document 1, as described above, it is described that since the nanoparticle layer 115 is provided between the light-emitting layer 114 and the cathode 116, electrons can be efficiently injected into the light-emitting layer 114.

[0006] Fig. 9The field light-emitting element 102 described in patent document 1 shown in (b) has a structure in which an anode 112, a hole transport layer 113, a light-emitting layer 114, a nanoparticle-containing film 117, and a cathode 116 are stacked in sequence on a substrate 111 from the substrate 111 side. Moreover, the nanoparticle-containing film 117 is formed by applying a solution on the light-emitting layer 114 by a spray method, and the solution is a mixture of barium titanate mixed in a weight ratio of 3:1 (polystyrene: barium titanate = 3:1) in polystyrene as a binder resin, dissolved and / or dispersed in xylene. In addition, it is recorded that an electron transport material can be mixed into the binder resin, and a material having electron transport properties as a binder resin is preferred. According to patent document 1, as described above, it is recorded that since a nanoparticle-containing film 117 is provided between the light-emitting layer 114 and the cathode 116, electrons can be efficiently injected into the light-emitting layer 114.

[0007] Fig. 9 The field light-emitting element 103 described in patent document 2 shown in (c) has a structure in which an anode 122, a hole injection layer 123, a hole transport layer 124, a light-emitting layer 125, an electron transport layer 126, an electron injection layer 127 and a cathode 128 are stacked in sequence on a substrate 121 from the substrate 121 side. Moreover, the hole transport layer 124 contains semiconductor nanoparticles 129, and the surface of the hole transport layer 124 has a concave-convex structure. According to patent document 2, as described above, since the hole transport layer 124 contains semiconductor nanoparticles 129, the transportability of holes can be improved, and the surface of the hole transport layer 124 has a concave-convex structure, so that in the interface with the concave-convex structure, holes can be efficiently injected by electric field concentration.

[0008] Fig. 9The field light emitting element 104 described in Patent Document 3 shown in (d) has a structure in which an anode 132, an organic functional layer 150 and a cathode 138 are stacked in sequence from the side of the flexible support substrate 131 on a flexible support substrate 131. The organic functional layer 150 includes a hole injection layer 133, a hole transport layer 134, a light emitting layer 135, an electron transport layer 136 and an electron injection layer 137. The hole injection layer 133, the hole transport layer 134, the light emitting layer 135, the electron transport layer 136 and the electron injection layer 137 are stacked in sequence from the side of the anode 132. In addition, the anode 132, the organic functional layer 150 and the cathode 138 on the flexible support substrate 131 are sealed by a flexible sealing member 140 via a sealing adhesive 139. Thus, the electron transport layer 136 includes an electron transport material and semiconductor nanoparticles 141. According to Patent Document 3, as described above, the electron transport layer 136 includes the electron transport material and the semiconductor nanoparticles 141 , and thus even if the light emitting layer 135 or the electron transport layer 136 is thickened, a decrease in light emission luminance and an increase in start-up voltage can be suppressed.

[0009] Prior art literature

[0010] Patent Literature

[0011] Patent Document 1: International Publication "WO2009 / 084273 A1" (published on July 9, 2009)

[0012] Patent Document 2: International Publication "WO2012 / 029750 A1" (published on March 8, 2012)

[0013] Patent Document 3: Japanese Patent Application Publication No. 2015-128191 (published on July 9, 2015) Summary of the invention

[0014] Technical Problems to be Solved by the Invention

[0015] However, in Fig. 9 In the case of the field light emitting element 101 described in patent document 1 shown in (a), the balance between the number of holes and the number of electrons injected into the light emitting layer 114 is completely ignored. Since the nanoparticle layer 115 is present, the electrons that were originally in excess in the light emitting layer 114 become further in excess, and efficient light emission that achieves a balance between holes and electrons cannot be achieved in the light emitting layer 114.

[0016] In addition, Fig. 9In the case of the electroluminescent element 102 described in Patent Document 1 shown in (b), the nanoparticle-containing film 117 describes the use of a film in which barium titanate is mixed in a weight ratio of 3:1 (polystyrene: barium titanate=3:1) in polystyrene as a binder resin. However, since the balance between the number of holes and the number of electrons injected into the light-emitting layer 114 is not considered at all, the electron transport property of the nanoparticle-containing film 117 is not described at all, and it is sufficient to use a hole transport layer 113 having a certain degree of hole transport property. Furthermore, in the case of the electroluminescent element 102 described in Patent Document 1, an electron transport material may be mixed in the binder resin, and a material having electron transport property is preferably used as the binder resin. Therefore, similarly to the above-mentioned electroluminescent element 101, the electrons originally present in excess in the light-emitting layer 114 become further excessive, and in the light-emitting layer 114, efficient light emission in which holes and electrons are balanced cannot be achieved.

[0017] In addition, Fig. 9 In the case of the electroluminescent element 103 described in Patent Document 2 shown in (c), it is described that the hole transport layer 124 contains semiconductor nanoparticles 129, but since the balance between the number of holes and the number of electrons injected into the light-emitting layer 125 is not considered at all, there is no description of the hole transport properties of the hole transport layer 124 containing semiconductor nanoparticles 129, and it is sufficient to use an electron transport property with a certain degree of electron transport property as the electron transport layer 126. Furthermore, there is no description of using an insulating polymer in the electron transport layer 126 to reduce the electron transport property. Therefore, in the light-emitting layer 125, efficient light emission with a balance between holes and electrons cannot be achieved.

[0018] In addition, Fig. 9 In the case of the field light-emitting element 104 described in Patent Document 3 shown in (d), the balance between the number of holes and the number of electrons injected into the light-emitting layer 135 is not considered at all. Since the electron transport layer 136 includes an electron transport material and semiconductor nanoparticles 141, the electrons that were originally in excess on the light-emitting layer 135 become further excessive, and efficient light emission that achieves a balance between holes and electrons cannot be achieved in the light-emitting layer 135.

[0019] One aspect of the present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide an electroluminescent element that realizes efficient light emission with a balance between holes and electrons in a light-emitting layer, and an electroluminescent device including a plurality of electroluminescent elements.

[0020] Technical solutions for solving technical problems

[0021] In order to solve the above-mentioned problems, one mode of the field light emitting element of the present invention includes: an anode; a cathode; and a light emitting layer, which is arranged between the anode and the cathode, and the field light emitting element is characterized in that it also includes: an electron transport layer, which contains n-type semiconductor particles and a first insulating polymer; and a hole transport layer, which contains p-type semiconductor particles, the electron transport layer is arranged between the cathode and the light emitting layer, the hole transport layer is arranged between the anode and the light emitting layer, and the volume ratio of the n-type semiconductor particles in the electron transport layer is smaller than the volume ratio of the p-type semiconductor particles in the hole transport layer.

[0022] In order to solve the above-mentioned problems, one embodiment of an electroluminescent device of the present invention includes the above-mentioned electroluminescent element.

[0023] In order to solve the above-mentioned problem, one embodiment of the electroluminescent device of the present invention is an electroluminescent device comprising a first electroluminescent element and a second electroluminescent element, wherein the first electroluminescent element comprises: a first anode; a first cathode; a first light-emitting layer, which is arranged between the first anode and the first cathode; a first hole transport layer, which is arranged between the first anode and the first light-emitting layer and comprises first p-type semiconductor particles; and a first electron transport layer, which is arranged between the first cathode and the first light-emitting layer and comprises first n-type semiconductor particles and a first insulating polymer, wherein the volume ratio of the first n-type semiconductor particles in the first electron transport layer is smaller than the volume ratio of the first p-type semiconductor particles in the first hole transport layer; and the second electroluminescent element comprises : a second anode; a second cathode; a second light-emitting layer, which is arranged between the second anode and the second cathode and has a light-emitting wavelength shorter than that of the first light-emitting layer; a second hole transport layer, which is arranged between the second anode and the second light-emitting layer and comprises second p-type semiconductor particles; and a second electron transport layer, which is arranged between the second cathode and the second light-emitting layer and comprises second n-type semiconductor particles and a third insulating polymer, the volume ratio of the second n-type semiconductor particles in the second electron transport layer is smaller than the volume ratio of the second p-type semiconductor particles in the second hole transport layer, and the volume ratio of the second n-type semiconductor particles in the second electron transport layer is larger than the volume ratio of the first n-type semiconductor particles in the first electron transport layer.

[0024] Beneficial Effects

[0025] According to one embodiment of the present invention, an electroluminescent element that realizes efficient light emission with a balance between holes and electrons in a light-emitting layer and an electroluminescent device including a plurality of electroluminescent elements can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1This is a diagram showing a schematic configuration of an electroluminescent element according to Embodiment 1.

[0027] Figure 2 yes Figure 1 The energy band diagram of the electroluminescent element shown.

[0028] Figure 3 Yes means including Figure 1 A diagram showing a schematic configuration of a display device using an electroluminescent element.

[0029] Figure 4 It is shown Figure 1 FIG. 2 is a diagram showing a modified example of the electroluminescent element shown.

[0030] Figure 5 Yes means Figure 1 FIG. 4 is a graph showing the relationship between voltage and current density per unit volume ratio of the first insulating polymer in the electron transport layer included in the electroluminescent element.

[0031] Figure 6 This is a diagram showing a schematic configuration of a display device including an electroluminescent element according to Embodiment 2.

[0032] Figure 7 This is a diagram showing a schematic configuration of an electroluminescent element according to a third embodiment.

[0033] Figure 8 This is a diagram showing a schematic configuration of an electroluminescent element according to a fourth embodiment.

[0034] Fig. 9 (a) Fig. 9 (b) Fig. 9 (c) and Fig. 9 (d) is a diagram showing a schematic structure of a conventional electroluminescent element described in Patent Documents 1 to 3. DETAILED DESCRIPTION

[0035] based on Figures 1 to 8 , the embodiments of the present disclosure are described as follows. In the following, for the sake of convenience, the same reference numerals are sometimes used to indicate the same functions as the components described in the specific embodiments, and the description thereof is omitted.

[0036] In the following embodiments of the present disclosure, a display device is used as an example of an electroluminescent device including a plurality of electroluminescent elements and a control circuit for controlling the light emission of each of the plurality of electroluminescent elements. However, the present invention is not limited to this. For example, the present invention may also be a lighting device including a plurality of electroluminescent elements and a control circuit for controlling the light emission of each of the plurality of electroluminescent elements.

[0037] [Implementation method 1]

[0038] Next, based on Figures 1 to 5 Embodiment 1 of the present invention will be described.

[0039] Figure 1 This is a diagram showing a schematic configuration of the electroluminescent element XR according to the first embodiment.

[0040] Figure 2 yes Figure 1 The energy band diagram of the electroluminescent element XR is shown in FIG.

[0041] Figure 1 The illustrated electroluminescent element XR includes an anode 22, a cathode 25, and a light-emitting layer 24 (first light-emitting layer) R containing quantum dots disposed between the anode (first anode) 22 and the cathode (first cathode) 25. Here, an example is given to illustrate that the electroluminescent element has a light-emitting layer 24R that emits light in the red wavelength region, but it is not limited to this. The wavelength region of the emitted light is not particularly limited. For example, it can be a light-emitting layer that emits light in the green wavelength region, or it can be a light-emitting layer that emits light in the blue wavelength region. In addition, in this embodiment, as an electroluminescent element, a QLED (Quantum dot Light Emitting Diode: quantum dot light-emitting diode) having a light-emitting layer containing quantum dots is cited as an example for illustration, but it is not limited to this. The electroluminescent element can also be an OLED (Organic Light Emitting Diode: organic light-emitting diode) or an inorganic light-emitting diode, which has a light-emitting layer that does not include quantum dots and can emit light as long as electrons and holes are inserted.

[0042] like Figure 1 As shown, the electroluminescent element XR further includes: an electron transport layer (first electron transport layer) 33 and a hole transport layer (first hole transport layer) 30, the electron transport layer 33 includes n-type semiconductor particles (first n-type semiconductor particles) 36 and a first insulating polymer 37, and the hole transport layer 30 includes p-type semiconductor particles (first p-type semiconductor particles) 34. In addition, in the present embodiment, as the hole transport layer 30 including the p-type semiconductor particles 34, the case of using the hole transport layer including the p-type semiconductor particles 34 and the second insulating polymer 35 is cited as an example for explanation, but it is not limited to this. As the hole transport layer 30 including the p-type semiconductor particles 34, a hole transport layer including only the p-type semiconductor particles 34 may also be used.

[0043] The electron transport layer 33 is disposed between the cathode 25 and the light emitting layer 24R, and the hole transport layer 30 is disposed between the anode 22 and the light emitting layer 24R. In addition, in the electroluminescent element XR, the volume ratio of the n-type semiconductor particles 36 in the electron transport layer 33 is smaller than the volume ratio of the p-type semiconductor particles 34 in the hole transport layer 30.

[0044] The volume ratio of the n-type semiconductor particles 36 in the electron transport layer 33 can be calculated by (the total volume of the n-type semiconductor particles 36 / the total volume of the electron transport layer 33)×100%, and the volume ratio of the p-type semiconductor particles 34 in the hole transport layer 30 can be calculated by (the total volume of the p-type semiconductor particles 34 / the total volume of the hole transport layer 30)×100%.

[0045] In addition, in the present embodiment, the case of using inorganic nanoparticles composed of zinc oxide (e.g., ZnO) as n-type semiconductor particles 36 is used as an example for explanation, but it is not limited to this. As long as they are electron-transmitting inorganic nanoparticles, for example, inorganic nanoparticles composed of titanium oxide (e.g., TiO2), inorganic nanoparticles composed of indium oxide (e.g., In2O3), inorganic nanoparticles composed of gallium oxide (e.g., Ga2O3), inorganic nanoparticles composed of tin oxide (e.g., SnO2), inorganic nanoparticles composed of zinc sulfide (e.g., ZnS), inorganic nanoparticles composed of zinc telluride (e.g., ZnTe), inorganic nanoparticles composed of vanadium oxide (e.g., V2O5), inorganic nanoparticles composed of molybdenum oxide (MoO3), inorganic nanoparticles composed of tungsten oxide (e.g., WO3), and any of inorganic nanoparticles composed of gallium nitride (e.g., GaO) may be used. In addition, inorganic nanoparticles composed of a mixture of two or more of zinc oxide, titanium oxide, indium oxide, gallium oxide, tin oxide, zinc sulfide, zinc telluride, vanadium oxide, molybdenum oxide, tungsten oxide, and gallium nitride may be used as the n-type semiconductor particles 36. Furthermore, for example, inorganic nanoparticles composed of zinc oxide, inorganic nanoparticles composed of titanium oxide, inorganic nanoparticles composed of indium oxide, inorganic nanoparticles composed of gallium oxide, inorganic nanoparticles composed of tin oxide, inorganic nanoparticles composed of zinc sulfide, inorganic nanoparticles composed of zinc telluride, inorganic nanoparticles composed of vanadium oxide, inorganic nanoparticles composed of molybdenum oxide, inorganic nanoparticles composed of tungsten oxide, and inorganic nanoparticles composed of gallium nitride may be used.

[0046] In addition, the particle size of the n-type semiconductor particles 36 in the electron transport layer 33 is not particularly limited. From the viewpoint of suppressing the aggregation of particles, the particle size is preferably 1 nm or more, and from the viewpoint of suppressing the surface roughness of the electron transport layer 33 and the surface roughness of the electroluminescent element XR, the particle size is preferably 30 nm or less. Therefore, in this embodiment, inorganic nanoparticles composed of zinc oxide (e.g., ZnO) with a particle size of 12 nm are used as the n-type semiconductor particles 36.

[0047] Furthermore, from the viewpoint of expressing the quantum size effect, improving the electron injection efficiency, and obtaining the effect of blocking holes as counter carriers, the particle diameter of the n-type semiconductor particles 36 is preferably 1 nm or more and 10 nm or less.

[0048] In addition, as the first insulating polymer 37 of the electron transport layer 33, for example, polyvinyl alcohol (PVA), polystyrene (PS), polyacrylate, polyvinyl pyrrolidone (PVP), carboxymethyl cellulose (CMC), polymethyl methacrylate (PMMA), polysilsesquioxane (PSQ), polydimethylsiloxane (PDMS), etc. can be used. In the present embodiment, polyvinyl pyrrolidone (PVP) is used as the first insulating polymer 37 of the electron transport layer 33.

[0049] It should be noted that the mixing ratio of the first insulating polymer 37 in the electron transport layer 33 , that is, the volume ratio of the first insulating polymer 37 in the electron transport layer 33 is preferably 30% to 80%, more preferably 10% to 60%.

[0050] In addition, the volume ratio of n-type semiconductor particles 36 in the electron transport layer 33 of the electroluminescent element XR is preferably 5% or more and 65% or less. The electroluminescent element XR includes a light-emitting layer 24R, which contains quantum dots having a red light-emitting wavelength and emits light in the red wavelength region.

[0051] like Figure 2 As shown, since the lower end of the conduction band of the light-emitting layer 24R that includes quantum dots having a red emission wavelength and emits light in the red wavelength region is located relatively close to the lower end of the conduction band of the electron transport layer (ETL) 33, it is relatively easy to inject electrons 39 from the electron transport layer (ETL) 33 into the light-emitting layer 24R. Therefore, in the electroluminescent element XR having the light-emitting layer 24R, the n-type semiconductor particles 36 that contribute to improving the electron transportability are preferably contained in the electron transport layer 33 in an amount of 5% or more and 65% or less as a volume ratio of the n-type semiconductor particles 36 in the electron transport layer 33. The reason for this will be described later.

[0052] In addition, the volume ratio of the n-type semiconductor particles 36 in the electron transport layer 33 or the volume ratio of the first insulating polymer 37 in the electron transport layer 33 can also be determined by, for example, confirming an electron microscope image of the cross section of the field light-emitting element XR, from the ratio of the particle size of the n-type semiconductor particles 36 to the area of ​​the first insulating polymer 37 filling the void portion.

[0053] The thickness (film thickness) of the electron transport layer 33 is preferably larger than the particle size of the n-type semiconductor particles 36, and the n-type semiconductor particles 36 are preferably formed to have two or more layers in the thickness (film thickness) direction of the electron transport layer 33. In this way, the surface roughness of the electron transport layer 33 can be suppressed, and the uniformity of electron injection in the film surface direction of the electron transport layer 33 can be improved. The thickness (film thickness) of the electron transport layer 33 is preferably greater than 10 nm and less than 200 nm.

[0054] In addition, in the present embodiment, as the p-type semiconductor particles 34, an example of using inorganic nanoparticles such as nickel oxide (e.g., NiO) as hole-transporting inorganic nanoparticles is given for explanation, but the invention is not limited thereto. As long as they are hole-transporting inorganic nanoparticles, for example, inorganic nanoparticles such as copper oxide (e.g., CuO), inorganic nanoparticles such as chromium oxide (e.g., Cr2O3), inorganic nanoparticles such as lithium nickelate (e.g., LiNiO2), inorganic nanoparticles such as lanthanum nickelate (e.g., LaNiO3), and inorganic nanoparticles such as gallium nitride (e.g., GaN) may be used. In addition, as the p-type semiconductor particles 34, inorganic nanoparticles such as a mixture of two or more of nickel oxide, copper oxide, chromium oxide, lithium nickelate, lanthanum nickelate, and gallium nitride may be used. Furthermore, as the p-type semiconductor particles 34, for example, a plurality of inorganic nanoparticles including nickel oxide, inorganic nanoparticles including copper oxide, inorganic nanoparticles including chromium oxide, inorganic nanoparticles including lithium nickelate, inorganic nanoparticles including lanthanum nickelate, and inorganic nanoparticles including gallium nitride can also be used.

[0055] In addition, the particle size of the p-type semiconductor particles 34 in the hole transport layer 30 is not particularly limited. From the viewpoint of suppressing the aggregation of particles, the particle size is preferably 1 nm or more, and from the viewpoint of suppressing the surface roughness of the hole transport layer 30 and the surface roughness of the electroluminescent element XR, the particle size is preferably 30 nm or less. Therefore, in this embodiment, inorganic nanoparticles composed of nickel oxide (e.g., NiO) with a particle size of 12 nm are used as the p-type semiconductor particles 34.

[0056] Furthermore, from the viewpoint of expressing the quantum size effect, improving the hole injection efficiency, and obtaining the effect of blocking electrons as counter carriers, the particle diameter of the p-type semiconductor particles 34 is preferably 1 nm or more and 10 nm or less.

[0057] In addition, as the second insulating polymer 35 of the hole transport layer 30, as in the case of the first insulating polymer 37 of the electron transport layer 33, for example, polyvinyl alcohol (PVA), polystyrene (PS), polyacrylate, polyvinyl pyrrolidone (PVP), carboxymethyl cellulose (CMC), polymethyl methacrylate (PMMA), polysilsesquioxane (PSQ), polydimethylsiloxane (PDMS), etc. can be used. In the present embodiment, as the second insulating polymer 35 of the hole transport layer 30, as in the case of the first insulating polymer 37 of the electron transport layer 33, polyvinyl pyrrolidone (PVP) is used, but it is not limited thereto, and the second insulating polymer 35 of the hole transport layer 30 may also be an insulating polymer of a different type from the first insulating polymer 37 of the electron transport layer 33.

[0058] In addition, in the electroluminescent element XR having the light-emitting layer 24R, the volume ratio of the p-type semiconductor particles 34 in the hole transport layer 30 is preferably greater than the volume ratio of the n-type semiconductor particles 36 in the electron transport layer 33, and the volume ratio of the n-type semiconductor particles 36 in the electron transport layer 33 is 5% or more and 65% or less. Therefore, the volume ratio of the p-type semiconductor particles 34 in the hole transport layer 30 is preferably 80% or more and 99.99% or less. That is, the difference between the volume ratio of the p-type semiconductor particles 34 in the hole transport layer 30 and the volume ratio of the n-type semiconductor particles 36 in the electron transport layer 33 is preferably 20% or more.

[0059] In addition, the volume ratio of the p-type semiconductor particles 34 in the hole transport layer 30 or the volume ratio of the second insulating polymer 35 in the hole transport layer 30 can also be determined by, for example, confirming an electron microscope image of the cross section of the field light-emitting element XR, from the particle size of the p-type semiconductor particles 34 and the area ratio of the second insulating polymer 35 filling the void portion.

[0060] The thickness (film thickness) of the hole transport layer 30 is preferably larger than the particle size of the p-type semiconductor particles 34, and the p-type semiconductor particles 34 are preferably formed in a manner that there are two or more layers in the thickness (film thickness) direction of the hole transport layer 30. In this way, the surface roughness of the hole transport layer 30 can be suppressed, and the uniformity of hole injection in the film surface direction of the hole transport layer 30 can be improved. The thickness (film thickness) of the hole transport layer 30 is preferably greater than 10 nm and less than 200 nm.

[0061] like Figure 2As shown, in the electroluminescent element XR, the injection barrier of electrons 39 is smaller than the injection barrier of holes 38, wherein the injection barrier of electrons 39 is the difference between the lower end of the conduction band of the electron transport layer (ETL) 33 and the lower end of the conduction band of the light-emitting layer 24R, and the injection barrier of holes 38 is the difference between the upper end of the valence band of the hole transport layer (HTL) 30 and the upper end of the valence band of the light-emitting layer 24R, so the light-emitting layer 24R is originally in a state of excess electrons 39. Therefore, in the electroluminescent element XR, the volume ratio of the p-type semiconductor particles 34 in the hole transport layer 30 is made greater than the volume ratio of the n-type semiconductor particles 36 in the electron transport layer 33, the injection amount of electrons 39 into the light-emitting layer 24R is reduced, and the injection amount of holes 38 into the light-emitting layer 24R is increased, thereby improving the excess state of electrons 39 in the light-emitting layer 24R. In this way, by improving the balance between the number of holes 38 and the number of electrons 39 in the light-emitting layer 24R, that is, the carrier balance, the light-emitting characteristics of the electroluminescent element XR can be improved.

[0062] In addition, it is preferred that the difference between the volume ratio of the p-type semiconductor particles 34 in the hole transport layer 30 and the volume ratio of the n-type semiconductor particles 36 in the electron transport layer 33 is 20% or more for the following reasons. This is because, when the difference between the volume ratio of the p-type semiconductor particles 34 in the hole transport layer 30 and the volume ratio of the n-type semiconductor particles 36 in the electron transport layer 33 is less than 20%, although the carrier balance is improved, the quantum dots of the light-emitting layer 24R are still in a state of excess electrons 39, and the holes 38 and electrons 39 that are not injected into the quantum dots of the light-emitting layer 24R may also recombine outside the quantum dots of the light-emitting layer 24R to emit light. In this way, when the holes 38 and electrons 39 recombine outside the quantum dots of the light-emitting layer 24R to emit light, it is possible to reduce the purity of the luminescent color.

[0063] In addition, in the case of an electroluminescent element having a light-emitting layer that does not contain quantum dots, when the difference between the volume ratio of p-type semiconductor particles 34 in the hole transport layer 30 and the volume ratio of n-type semiconductor particles 36 in the electron transport layer 33 is less than 20%, although the carrier balance is improved, since the light-emitting layer that does not contain quantum dots is still in an excess state of electrons 39, it is preferred that the difference between the volume ratio of p-type semiconductor particles 34 in the hole transport layer 30 and the volume ratio of n-type semiconductor particles 36 in the electron transport layer 33 is greater than 20%.

[0064] In addition, the hole transport layer 30 of the electroluminescent element XR is mixed with the second insulating polymer 35 by the p-type semiconductor particles 34, and the area of ​​the second insulating polymer 35 in contact with the first quantum dots of the light-emitting layer 24R at the interface of the light-emitting layer 24R including the first quantum dots is larger than when the p-type semiconductor particles 34 are used alone as the hole transport layer. Therefore, the hole transport layer 30 can suppress the deactivation of excitons caused by the direct contact of the p-type semiconductor particles 34 with the first quantum dots of the light-emitting layer 24R, and also realizes the function of a blocking layer for electrons of the opposite carriers.

[0065] In addition, in the case of an electroluminescent element having a light-emitting layer without quantum dots, the hole transport layer 30 is mixed with the second insulating polymer 35 through the p-type semiconductor particles 34, and the area of ​​the second insulating polymer 35 in contact with the light-emitting layer without quantum dots becomes larger at the interface with the light-emitting layer without quantum dots than when the p-type semiconductor particles 34 are used alone as the hole transport layer. Therefore, the hole transport layer 30 can suppress the deactivation of excitons caused by the direct contact of the p-type semiconductor particles 34 with the light-emitting layer without quantum dots, and also realizes the function of an electron blocking layer for counter carriers.

[0066] Similarly, the electron transport layer 33 of the electroluminescent element XR is mixed with the first insulating polymer 37 by the n-type semiconductor particles 36, and the area of ​​contact between the first insulating polymer 37 and the first quantum dots of the light-emitting layer 24R at the interface of the light-emitting layer 24R containing quantum dots is increased compared to the case where the n-type semiconductor particles 36 are used alone as the electron transport layer. Therefore, the electron transport layer 33 can suppress the deactivation of excitons caused by the direct contact of the n-type semiconductor particles 36 with the first quantum dots of the light-emitting layer 24R, and also realizes the function of a blocking layer for holes of opposite carriers.

[0067] In addition, in the case of an electroluminescent element having a light-emitting layer that does not include quantum dots, the electron transport layer 33 is mixed with the first insulating polymer 37 through the n-type semiconductor particles 36, so that at the interface with the light-emitting layer that does not include quantum dots, the area of ​​the first insulating polymer 37 in contact with the light-emitting layer that does not include quantum dots becomes larger than when the n-type semiconductor particles 36 are used alone as the electron transport layer. Therefore, the electron transport layer 33 can suppress the deactivation of excitons caused by the direct contact of the n-type semiconductor particles 36 with the light-emitting layer that does not include quantum dots, and also realizes the function of a blocking layer for holes that are opposite carriers.

[0068] In the preparation of the above-mentioned field-induced light-emitting element XR, for example, p-type semiconductor particles 34 and second insulating polymer 35 may be mixed, dissolved in a solvent at a desired ratio and coated to form a hole transport layer 30. In the light-emitting layer 24R containing the first quantum dots, quantum dots and polymer materials (conductive materials or / and non-conductive materials) may be mixed, dissolved in a solvent at a desired ratio and coated to form. The electron transport layer 33 may also be formed by mixing n-type semiconductor particles 36 and first insulating polymer 37, dissolved in a solvent at a desired ratio and coated to form. As a solvent, a solvent that can dissolve the first insulating polymer 37, or the above-mentioned polymer material (conductive material or / and non-conductive material) or the second insulating polymer 35 is preferably used. For example, as a polar solvent, water, methanol, ethanol, acetone, ethylene glycol, DMSO, trichloroethylene, etc. can be used, and as a non-polar solvent, benzene, toluene, xylene, n-hexane, cyclohexane, etc. can be used.

[0069] The method for forming the hole transport layer 30 , the light-emitting layer 24R including the first quantum dots, and the electron transport layer 33 by coating is not particularly limited, and they can be formed by coating by methods such as spin coating, dip coating, spraying, ink jetting, slit coating, screen printing, etc.

[0070] As described above, in the manufacture of the electroluminescent element XR, a series of processes for forming the hole transport layer 30, the light-emitting layer 24R including the first quantum dots, and the electron transport layer 33 can be used as a coating process, and the electroluminescent element XR can be manufactured by a relatively simple manufacturing device and manufacturing process.

[0071] In addition, the hole transport layer 30, the light-emitting layer 24R including the first quantum dots, and the electron transport layer 33 of the electroluminescent element XR manufactured in this way are all mixed with the polymer material, so the surface roughness of each layer can be suppressed compared with the case where the p-type semiconductor particles 34 or quantum dots or n-type semiconductor particles 36 are formed separately. In addition, the flatness of the light-emitting layer 24R including the first quantum dots formed on the hole transport layer 30 is improved. As a result, the surface uniformity of carrier injection is improved and the light-emitting characteristics are improved.

[0072] In this embodiment, the case where the anode 22 and the hole transport layer (HTL) 30 are in direct contact is described as an example, but the invention is not limited thereto, and a hole injection layer (HIL) for injecting holes may be further provided between the anode 22 and the hole transport layer (HTL) 30. The hole injection layer (HIL) may be an organic material, an inorganic material, nanoparticles, or a layer in which nanoparticles are dispersed in various polymer materials.

[0073] Figure 3 It shows that Figure 12 is a diagram showing a schematic configuration of a display device (electroluminescent device) 1 having an electroluminescent element XR.

[0074] like Figure 3 As shown in the figure, a resin layer 12, a barrier layer 3, a TFT layer 4, electroluminescent elements XR, XG, XB and a sealing layer 6 are stacked on one side of a substrate 10 in the display device 1. Figure 3 The direction from the substrate 10 to the electroluminescent elements XR, XG, and XB is described as "upward", and the direction from the electroluminescent elements XR, XG, and XB to the substrate 10 is described as "downward". In other words, the "lower layer" refers to a layer formed in a process before the comparison object layer, and the "upper layer" refers to a layer formed in a process after the comparison object layer. That is, the layer closer to the substrate 10 is the lower layer, and the layer farther from the substrate 10 is the upper layer.

[0075] As the material of the substrate 10, polyethylene terephthalate (PET), a glass substrate, etc. can be cited, but it is not limited thereto. In this embodiment, in order to set the display device 1 as a flexible display device, PET is used as the material of the substrate 10, but when the display device 1 is set as a non-flexible display device, a glass substrate, etc. can be used.

[0076] As the material of the resin layer 12, for example, polyimide resin, epoxy resin, polyamide resin, etc. can be cited, but it is not limited thereto. In this embodiment, a laser is irradiated to the resin layer 12 through a supporting substrate (not shown), the bonding force between the supporting substrate (not shown) and the resin layer 12 is reduced, and the supporting substrate (not shown) is peeled off from the resin layer 12 (Laser Lift Off process (LLO process)), and the surface after peeling off the supporting substrate (not shown) in the resin layer 12 is bonded to the substrate 10 composed of PET, so that the display device 10 is set as a flexible display device. However, in the case where the display device 1 is a non-flexible display device or in the case where the display device 1 is made into a flexible display device by a method other than the LLO process, the resin layer 12 is not required.

[0077] The barrier layer 3 prevents water and impurities from reaching the TFT layer 4 and the field-luminescent elements XR, XG, and XB when the display device 1 is used, and can be composed of, for example, a silicon oxide film, a silicon nitride film, or a silicon nitride oxide film formed by a CVD method, or a stacked film of these films.

[0078] The TFT layer 4 includes a semiconductor film 15, an inorganic insulating film 16 (gate insulating film) above the semiconductor film 15, a gate GE above the inorganic insulating film 16, an inorganic insulating film 18 above the gate GE, a capacitor wiring CE above the inorganic insulating film 18, an inorganic insulating film 20 above the capacitor wiring CE, a source / drain wiring SH including a source / drain above the inorganic insulating film 20, and a planarizing film 21 above the source / drain wiring SH.

[0079] The thin film transistor element Tr (TFT element) is configured as an active element to include the semiconductor film 15 , the inorganic insulating film 16 (gate insulating film), the gate GE, the inorganic insulating film 18 , the inorganic insulating film 20 , and the source / drain wiring SH.

[0080] The semiconductor film 15 is composed of, for example, low temperature polysilicon (LTPS) or an oxide semiconductor. Figure 1 In FIG. 1 , the TFT using the semiconductor film 15 as a channel is shown as a top gate structure, but it may also be a bottom gate structure.

[0081] The gate GE, capacitor electrode CE, and source / drain wiring SH are composed of a single layer film or a stacked film of a metal including at least one of aluminum (Al), tungsten (W), molybdenum (Mo), tantalum (Ta), chromium (Cr), titanium (Ti), and copper (Cu).

[0082] The inorganic insulating films 16, 18, and 20 may be made of, for example, silicon oxide (SiO x ) film, silicon nitride (SiN x ) film, silicon oxynitride film or a stacked film thereof.

[0083] The planarization film (interlayer insulating film) 21 can be made of a coatable photosensitive organic material such as a polyimide resin or an acrylic resin.

[0084] Figure 1 and Figure 2 In the figure, among the electroluminescent elements XR, XG, and XB included in the display device 1, only the schematic structure of the electroluminescent element XR including the light emitting layer 24R emitting light in the red wavelength region is shown as an example. Figure 3 As shown in the figure, the display device 1 includes an electroluminescent element XG (a second electroluminescent element) and an electroluminescent element (a third electroluminescent element) XB in addition to the electroluminescent element (a first electroluminescent element) XR. Since the electroluminescent element XR has been described, the electroluminescent element XG and the electroluminescent element XB will be described in detail here.

[0085] Figure 3The illustrated electroluminescent element XG includes an anode 22, a cathode 25, and a light-emitting layer (second light-emitting layer) 24G including quantum dots having a green light emission wavelength disposed between the anode (first anode) 22 and the cathode (first cathode) 25. Furthermore, the electroluminescent element XG further includes an electron transport layer (first electron transport layer) 31 and a hole transport layer (first hole transport layer) 30, wherein the electron transport layer 33 includes n-type semiconductor particles (first n-type semiconductor particles) 36 and a first insulating polymer 37, and the hole transport layer 30 includes p-type semiconductor particles (first p-type semiconductor particles) 34. The electron transport layer 31 is disposed between the cathode 25 and the light-emitting layer 24G, and the hole transport layer 30 is disposed between the anode 22 and the light-emitting layer 24G. In addition, in the electroluminescent element XG, the volume ratio of the n-type semiconductor particles 36 in the electron transport layer (second electron transport layer) 31 is smaller than the volume ratio of the p-type semiconductor particles 34 in the hole transport layer 30.

[0086] also, Figure 3 The illustrated electroluminescent element XB includes an anode 22, a cathode 25, and a light-emitting layer (third light-emitting layer) 24B including a third quantum dot having a blue light-emitting wavelength disposed between the anode (third anode) 22 and the cathode (third cathode) 25. Furthermore, the electroluminescent element XB includes an electron transport layer 32 and a hole transport layer (third hole transport layer) 30, wherein the electron transport layer 32 includes n-type semiconductor particles (third n-type semiconductor particles) 36 and a first insulating polymer (fourth insulating polymer) 37, and the hole transport layer 30 includes p-type semiconductor particles (third p-type semiconductor particles) 34. The electron transport layer 32 is disposed between the cathode 25 and the light-emitting layer 24B, and the hole transport layer 30 is disposed between the anode 22 and the light-emitting layer 24G. Moreover, in the electroluminescent element XB, the volume ratio of the n-type semiconductor particles 36 in the electron transport layer (third electron transport layer) 32 is smaller than the volume ratio of the p-type semiconductor particles 34 in the hole transport layer 30.

[0087] In the present embodiment, as the hole transport layer 30 including p-type semiconductor particles 34, the case of using a hole transport layer including p-type semiconductor particles 34 and a second insulating polymer 35 is cited as an example for explanation, but it is not limited to this. As the hole transport layer 30 including p-type semiconductor particles 34, a hole transport layer including only p-type semiconductor particles 34 may also be used.

[0088] In the present embodiment, the n-type semiconductor particles 36 included in the electron transport layer 31 of the field light-emitting element XG and the n-type semiconductor particles 36 included in the electron transport layer 32 of the field light-emitting element XB are similar to the n-type semiconductor particles 36 included in the electron transport layer 33 of the field light-emitting element XR. The case of using inorganic nanoparticles having electron transport properties, for example, inorganic nanoparticles composed of zinc oxide (for example, ZnO) is cited as an example for explanation, but the invention is not limited to this, and other materials described in the case of the electron transport layer 33 of the field light-emitting element XR may also be used.

[0089] In addition, in this embodiment, the case where the n-type semiconductor particles 36 included in the electron transport layer 31, the electron transport layer 32, and the electron transport layer 33 are composed of the same material is taken as an example for description, but it is not limited to this. For example, the n-type semiconductor particles 36 included in the electron transport layer 31, the electron transport layer 32, and the electron transport layer 33 may also be made of different materials. Moreover, for example, two layers may be made of the same material, and the remaining layer may be made of a material different from the above two layers.

[0090] In the present embodiment, as the first insulating polymer 37 included in the electron transport layer 31 of the field light emitting element XG and the first insulating polymer 37 included in the electron transport layer 32 of the field light emitting element XB, similarly to the first insulating polymer 37 included in the electron transport layer 33 of the field light emitting element XR, polyvinyl pyrrolidone (PVP) is used as an example for explanation, but the present invention is not limited to this, and other materials described in the case of the electron transport layer 33 of the field light emitting element XR may also be used.

[0091] In addition, in this embodiment, the case where the first insulating polymer 37 included in the electron transport layer 31, the electron transport layer 32, and the electron transport layer 33 is composed of the same material is taken as an example for description, but it is not limited to this. For example, the first insulating polymer 37 included in the electron transport layer 31, the electron transport layer 32, and the electron transport layer 33 may be made of different materials. Moreover, for example, two layers may be made of the same material, and the remaining layer may be made of a material different from the above two layers.

[0092] In the present embodiment, the p-type semiconductor particles 34 contained in the hole transport layer 30 of the field light-emitting element XG and the p-type semiconductor particles 34 contained in the hole transport layer 30 of the field light-emitting element XB are similar to the p-type semiconductor particles 34 contained in the hole transport layer 30 of the field light-emitting element XR described above, and an example of using inorganic nanoparticles having hole transport properties, such as inorganic nanoparticles composed of nickel oxide (e.g., NiO) is used for illustration, but the invention is not limited to this, and other materials already described in the case of the hole transport layer 30 of the field light-emitting element XR may also be used.

[0093] In addition, in the present embodiment, the case where the p-type semiconductor particles 34 included in the hole transport layer 30 of the electroluminescent element XR, the hole transport layer 30 of the electroluminescent element XG, and the hole transport layer 30 of the electroluminescent element XB are composed of the same material is described as an example, but the present invention is not limited thereto. For example, the p-type semiconductor particles 34 included in the hole transport layer 30 of the electroluminescent element XR, the hole transport layer 30 of the electroluminescent element XG, and the hole transport layer 30 of the electroluminescent element XB may be made of different materials. Furthermore, for example, two layers may be made of the same material, and the remaining layer may be made of a material different from the above two layers.

[0094] In the present embodiment, as the second insulating polymer 35 included in the hole transport layer 30 of the electroluminescent element XG and the second insulating polymer 35 included in the hole transport layer 30 of the electroluminescent element XB, similarly to the second insulating polymer 35 included in the hole transport layer 30 of the above-mentioned electroluminescent element XR, the case of using polyvinylpyrrolidone (PVP) is cited as an example for explanation, but the present invention is not limited to this, and other materials described in the case of the hole transport layer 30 of the electroluminescent element XR may also be used.

[0095] In addition, in the present embodiment, the second insulating polymer 35 included in the hole transport layer 30 of the electroluminescent element XR, the hole transport layer 30 of the electroluminescent element XG, and the hole transport layer 30 of the electroluminescent element XB is described as being composed of the same material, but the present invention is not limited thereto. For example, the second insulating polymer 35 included in the hole transport layer 30 of the electroluminescent element XR, the hole transport layer 30 of the electroluminescent element XG, and the hole transport layer 30 of the electroluminescent element XB may be made of different materials. Furthermore, for example, two layers may be made of the same material, and the remaining layer may be made of a material different from the two layers.

[0096] In addition, Figure 3In the display device 1 shown, the hole transport layer 30 of the electroluminescent element XR, the hole transport layer 30 of the electroluminescent element XG, and the hole transport layer 30 of the electroluminescent element XB are respectively formed into island shapes, but this is not limited to this. As shown in Embodiment 2 described later, the hole transport layer 30 of the electroluminescent element XR, the hole transport layer 30 of the electroluminescent element XG, and the hole transport layer 30 of the electroluminescent element XB may also be formed as a common layer.

[0097] In addition, the lower ends of the conduction bands of the light-emitting layer 24B including the third quantum dots having a blue emission wavelength and the light-emitting layer 24G including the second quantum dots having a green emission wavelength are lower than those of the light-emitting layer 24B including the third quantum dots having a blue emission wavelength. Figure 2 The lower end of the conduction band of the first quantum dot light-emitting layer 24R of the red light-emitting wavelength shown is shallow, that is, Figure 2 In particular, the lower end of the conduction band of the light-emitting layer 24B including quantum dots having a blue emission wavelength is shallower than the lower end of the conduction band of the light-emitting layer 24G including the second quantum dots having a green emission wavelength. Figure 2 In the embodiment, the lower end of the conduction band of the light emitting layer 24B is located on the upper side.

[0098] Therefore, in the electroluminescent element XB, the difference between the lower end of the conduction band of the electron transport layer (ETL) 32 and the lower end of the conduction band of the light-emitting layer 24B, i.e., the injection barrier of the electron 39, and the difference between the lower end of the conduction band of the electron transport layer (ETL) 31 and the lower end of the conduction band of the light-emitting layer 24G in the electroluminescent element XG, i.e., the injection barrier of the electron 39, are greater than Figure 2 The difference between the lower end of the conduction band of the electron transport layer (ETL) 33 and the lower end of the conduction band of the light-emitting layer 24R in the electroluminescent element XR shown, that is, the injection barrier of the electron 39 is large. Moreover, the difference between the lower end of the conduction band of the electron transport layer (ETL) 32 and the lower end of the conduction band of the light-emitting layer 24B in the electroluminescent element XB, that is, the injection barrier of the electron 39 is greater than the difference between the lower end of the conduction band of the electron transport layer (ETL) 31 and the lower end of the conduction band of the light-emitting layer 24G in the electroluminescent element XG, that is, the injection barrier of the electron 39.

[0099] In addition, the above characteristics are also directly applied to a light-emitting layer having a red light-emitting wavelength without quantum dots, a light-emitting layer having a green light-emitting wavelength without quantum dots, and a light-emitting layer having a blue light-emitting wavelength without quantum dots.

[0100] For such reasons, in the display device 1, the volume ratio of the n-type semiconductor particles 36 in the electron transport layer (ETL) 31 of the electroluminescent element XG and the volume ratio of the n-type semiconductor particles 36 in the electron transport layer (ETL) 32 of the electroluminescent element XB are respectively made higher than the volume ratio of the n-type semiconductor particles 36 in the electron transport layer (ETL) 33 of the electroluminescent element XR. Furthermore, the volume ratio of the n-type semiconductor particles 36 in the electron transport layer (ETL) 32 of the electroluminescent element XB is made higher than the volume ratio of the n-type semiconductor particles 36 in the electron transport layer (ETL) 31 of the electroluminescent element XG.

[0101] Specifically, within the range satisfying the relationship of the volume ratio of n-type semiconductor particles 36 in the electron transport layer (ETL) 32 of the field light emitting element XB>the volume ratio of n-type semiconductor particles 36 in the electron transport layer (ETL) 31 of the field light emitting element XG>the volume ratio of n-type semiconductor particles 36 in the electron transport layer (ETL) 33 of the field light emitting element XR, the volume ratio of n-type semiconductor particles 36 in the electron transport layer (ETL) 33 of the field light emitting element XR is preferably greater than 5% and less than 65%, the volume ratio of n-type semiconductor particles 36 in the electron transport layer (ETL) 31 of the field light emitting element XG is preferably greater than 30% and less than 90%, and the volume ratio of n-type semiconductor particles 36 in the electron transport layer (ETL) 32 of the field light emitting element XB is preferably greater than 40% and less than 95%.

[0102] Furthermore, the volume ratio of the n-type semiconductor particles 36 in the electron transport layer (ETL) 33 of the field light-emitting element XR, the volume ratio of the n-type semiconductor particles 36 in the electron transport layer (ETL) 31 of the field light-emitting element XG, and the volume ratio of the n-type semiconductor particles 36 in the electron transport layer (ETL) 32 of the field light-emitting element XB are respectively determined within the range of the volume ratio of the p-type semiconductor particles 34 in the hole transport layer 30 (in this embodiment, greater than 80% and less than 99.99%).

[0103] In addition, in each of the field light-emitting element XR, the field light-emitting element XG and the field light-emitting element XB, the difference between the volume ratio of the p-type semiconductor particles 34 in the hole transport layer 30 (in the present embodiment, 80% or more and 99.99% or less) and the volume ratio of the n-type semiconductor particles 36 in the electron transport layer (ETL) 31, the electron transport layer (ETL) 32 and the electron transport layer (ETL) 33 is preferably 20% or more.

[0104] Figure 5 It is shown Figure 1FIG. 4 is a graph showing the relationship between voltage and current density per unit volume ratio of the first insulating polymer 37 in the electron transport layer 33 included in the electroluminescent element XR.

[0105] Figure 5 The results shown are the results of measuring the current density of each sample produced as described below while changing the applied voltage.

[0106] The 0% sample electroluminescent element, the 10% sample electroluminescent element, the 30% sample electroluminescent element, the 50% sample electroluminescent element, and the 60% sample electroluminescent element are sample electroluminescent elements in which the following layers are sequentially stacked on ITO (Indium Tin Oxide) as the anode 22: PEDOT:PSS / PVK as a hole transport layer, a light-emitting layer 24R containing first quantum dots, an electron transport layer containing inorganic nanoparticles of zinc oxide (e.g., ZnO) with an average particle size of 12 nm as n-type semiconductor particles 36 and polyvinyl pyrrolidone (PVP) as the first insulating polymer 37 in a predetermined ratio, and Al (aluminum) as the cathode 25. The 0% sample electroluminescent element is a sample electroluminescent element in which the volume ratio of the first insulating polymer 37 in the electron transport layer is 0% (the volume ratio of the n-type semiconductor particles 36 in the electron transport layer is 100%). The 10% sample electroluminescent element is a sample electroluminescent element in which the volume ratio of the first insulating polymer 37 in the electron transport layer is 10% (the volume ratio of the n-type semiconductor particles 36 in the electron transport layer is 90%). The 30% sample electroluminescent element is a sample electroluminescent element in which the volume ratio of the first insulating polymer 37 in the electron transport layer is 30% (the volume ratio of the n-type semiconductor particles 36 in the electron transport layer is 70%). The 50% sample electroluminescent element is a sample electroluminescent element in which the volume ratio of the first insulating polymer 37 in the electron transport layer is 50% (the volume ratio of the n-type semiconductor particles 36 in the electron transport layer is 50%). The 60% sample electroluminescent element is a sample electroluminescent element in which the volume ratio of the first insulating polymer 37 in the electron transport layer is 60% (the volume ratio of the n-type semiconductor particles 36 in the electron transport layer is 40%).

[0107] like Figure 5 As shown, in any of the cases of the 10% sample electroluminescent element, the 30% sample electroluminescent element, the 50% sample electroluminescent element, and the 60% sample electroluminescent element, the current density values ​​at the same voltage value are lower than those of the 0% sample electroluminescent element in which the electron transport layer is composed only of zinc oxide as the n-type semiconductor particles 36, and it is difficult to inject electrons into the electroluminescent element.

[0108] It is also found that, in each of the 10% sample EL element, the 30% sample EL element, the 50% sample EL element, and the 60% sample EL element, the greater the volume ratio of the first insulating polymer 37 is, the greater the degree of decrease in the current density value at the same voltage value is.

[0109] In this way, by appropriately changing the volume ratio of the n-type semiconductor particles 36 and the volume ratio of the first insulating polymer 37 in the electron transport layer, the amount of electrons injected into the light-emitting layer including quantum dots can be appropriately controlled.

[0110] Although not shown, similarly to the electron transport layer, by appropriately changing the volume ratio of the p-type semiconductor particles 34 and the volume ratio of the second insulating polymer 35 in the hole transport layer, the amount of holes injected into the light-emitting layer including quantum dots can be appropriately controlled.

[0111] Figure 3 The light-emitting layer 24R, the light-emitting layer 24G, and the light-emitting layer 24B shown are light-emitting layers containing quantum dot (nanoparticle) phosphors. In the following, for the sake of simplicity, "phosphor" is omitted and only quantum dots (nanoparticles) are recorded. As a specific material for the light-emitting layer containing quantum dot (nanoparticle) phosphors, for example, any one of CdSe / CdS, CdSe / ZnS, InP / ZnS, and CIGS / ZnS can be used. For example, the particle size of the quantum dot (nanoparticle) phosphor is about 3 to 10 nm. In addition, in order to make the central wavelengths of the light emitted by the light-emitting layer 24R, the light-emitting layer 24G, and the light-emitting layer 24B different from each other, the particle size of the quantum dots (nanoparticles) can be different in each light-emitting layer, or different types of quantum dots (nanoparticles) can be used.

[0112] like Figure 3 As shown, the electroluminescent element XR, the electroluminescent element XG and the electroluminescent element XB are respectively sub-pixels SP of the display device 1. For example, one electroluminescent element XR, one electroluminescent element XG and one electroluminescent element XB can constitute one pixel of the display device 1.

[0113] like Figure 3 As shown, the bank 23 covering the edge of the anode 22 can be made of a coatable photosensitive organic material such as polyimide resin, acrylic resin, etc.

[0114] In this embodiment, the case where the anode 22, the hole transport layer (HTL) 30, the light-emitting layers 24R, 24G, 24B, and the electron transport layers (ETL) 31, 32, and 33 are formed into islands for each sub-pixel SP in addition to the cathode 25 formed as a common layer in the whole surface is cited as an example for explanation, but it is not limited to this. For example, when the cathode 25 is formed into an island shape and the island-shaped cathode 25 is independently controlled to move by a thin film transistor element, etc., the anode 22 can be formed as a common layer in the whole surface. Furthermore, as described later, the hole transport layer (HTL) 30 can also be formed as a common layer in the whole surface. In addition, in this case, the bank 23 may not be provided.

[0115] At least one of the anode 22 and the cathode 25 is made of a light-transmitting material. In addition, either the anode 22 or the cathode 25 may be made of a light-reflecting material. When the display device 1 is a top-emitting type display device, the cathode 25 as the upper layer is formed of a light-transmitting material, and the anode 22 as the lower layer is formed of a light-reflecting material. When the display device 1 is a bottom-emitting type display device, the cathode 25 as the upper layer is formed of a light-reflecting material, and the anode 22 as the lower layer is formed of a light-transmitting material. In addition, when the stacking order from the anode 22 to the cathode 25 is reversed, the display device 1 can be made a top-emitting type display device by forming the anode 22 as the upper layer with a light-transmitting material and the cathode 25 as the lower layer with a light-reflecting material, and the display device 1 can be made a bottom-emitting type display device by forming the anode 22 as the upper layer with a reflective material and the cathode 25 as the lower layer with a light-transmitting material.

[0116] As the light-transmitting material, for example, a transparent conductive film material can be used, specifically, for example, ITO (Indium Tin Oxide), IZO (Indium Zinc Oxide), ZnO, AZO (aluminum-doped zinc oxide), BZO (boron-doped zinc oxide), etc. These materials have high transmittance of visible light, thus improving the luminous efficiency.

[0117] As the light reflective material, a material having a high reflectivity of visible light is preferred, and for example, a metal material can be used, specifically, Al, Cu, Au, Ag, etc. Since these materials have a high reflectivity of visible light, the luminous efficiency is improved.

[0118] Alternatively, by making one of the anode 22 and the cathode 25 a laminate of a light-transmitting material and a light-reflective material, an electrode having light reflectivity may be provided.

[0119] In the present embodiment, in order to make the display device 1 a top emission type, the cathode 25 as an upper layer is formed of a light-transmitting material, and the anode 22 as a lower layer is formed of a light-reflective material.

[0120] In addition, the particle size of the p-type semiconductor particles 34 contained in the hole transport layer 30 of the field light-emitting element XG and the particle size of the p-type semiconductor particles 34 contained in the hole transport layer 30 of the field light-emitting element XB are respectively the same as the particle size of the p-type semiconductor particles 34 contained in the hole transport layer 30 of the field light-emitting element XR, and are preferably greater than 1 nm and less than 30 nm.

[0121] Further, similarly to the hole transport layer 30 of the electroluminescent element XR, the hole transport layer 30 of the electroluminescent element XG and the hole transport layer 30 of the electroluminescent element XB each preferably has a thickness (film thickness) of 10 nm to 200 nm.

[0122] In addition, the particle size of the n-type semiconductor particles 36 contained in the electron transport layer 31 of the field light emitting element XG and the particle size of the n-type semiconductor particles 36 contained in the electron transport layer 32 of the field light emitting element XB are preferably greater than 1 nm and less than 30 nm, respectively, similarly to the particle size of the n-type semiconductor particles 36 contained in the electron transport layer 33 of the field light emitting element XR.

[0123] Also, the thickness (film thickness) of each of the electron transport layer 31 included in the electroluminescent element XG and the electron transport layer 32 included in the electroluminescent element XB is preferably 10 nm or more and 200 nm or less, similarly to the electron transport layer 33 included in the electroluminescent element XR.

[0124] As described above, in the display device 1, by improving the carrier balance in each of the electroluminescent element XR, the electroluminescent element XG, and the electroluminescent element XB, the luminescent characteristics of the electroluminescent elements XR, XG, and XB can be improved. Therefore, in the luminescent layer, the display device 1 can achieve efficient luminescence with balanced holes and electrons.

[0125] In the present embodiment, an example of a display device is cited as an example of an electroluminescent device for illustration, and thus the display device 1 is illustrated as including: an electroluminescent element XR, which includes a light-emitting layer 24R, and the light-emitting layer 24R has first quantum dots with a red light-emitting wavelength; an electroluminescent element XG, which includes a light-emitting layer 24G, and the light-emitting layer 24G has second quantum dots with a green light-emitting wavelength; and an electroluminescent element XB, which includes a light-emitting layer 24B, and the light-emitting layer 24B has third quantum dots with a blue light-emitting wavelength. However, for example, in the case where the electroluminescent device is a lighting device, etc., it may include only one or more single electroluminescent elements, which include a light-emitting layer with quantum dots with a light-emitting wavelength of a certain color, or it may include one or more first electroluminescent elements and second electroluminescent elements, respectively, wherein the first electroluminescent element includes a first light-emitting layer of first quantum dots, and the second electroluminescent element includes a second light-emitting layer, and the second light-emitting layer has second quantum dots with a light-emitting wavelength shorter than that of the first quantum dots.

[0126] Figure 4 It is shown Figure 1 FIG. 2 is a diagram schematically showing a configuration of an electroluminescent element XR′ which is a modified example of the electroluminescent element XR.

[0127] exist Figure 1 In the electroluminescent element XR shown in FIG. 1 , inorganic nanoparticles composed of zinc oxide (eg, ZnO) having a particle size of 12 nm are used as the p-type semiconductor particles 34 included in the hole transport layer 30 , thereby suppressing aggregation of the inorganic nanoparticles.

[0128] Figure 4 The hole transport layer 30' of the electroluminescent element XR' shown in the figure is Figure 1 The hole transport layer 30 of the illustrated electroluminescent element XR includes inorganic nanoparticles composed of zinc oxide (eg, ZnO) as p-type semiconductor particles 34 and polyvinyl pyrrolidone (PVP) as the second insulating polymer 35. Figure 1 The hole transport layer 30 of the electroluminescent element XR shown in FIG. 1 is different in that the particle size of the inorganic nanoparticles composed of zinc oxide (eg, ZnO) is less than 1 nm. Specifically, Figure 4 The inorganic nanoparticles containing zinc oxide (e.g., ZnO) as the p-type semiconductor particles 34 contained in the hole transport layer 30' of the electroluminescent element XR' shown in the figure have an average particle size of 0.5 nm. In addition, the volume ratio of the inorganic nanoparticles (average particle size 0.5 nm) composed of zinc oxide (e.g., ZnO) as the p-type semiconductor particles 34 in the hole transport layer 30' is Figure 1The volume ratio of inorganic nanoparticles (average particle size 12 nm) composed of zinc oxide (eg, ZnO) as p-type semiconductor particles 34 in the hole transport layer 30 of the electroluminescent element XR shown.

[0129] like Figure 4 As shown in the figure, in the hole transport layer 30', although inorganic nanoparticles (average particle size 0.5 nm) composed of zinc oxide (eg, ZnO) are aggregated, Figure 1 Similarly, in the illustrated electroluminescent element XR, the balance between the number of holes 38 and the number of electrons 39 in the light-emitting layer 24R, namely, the carrier balance can be improved, and the light-emitting characteristics can also be improved in the electroluminescent element XR′.

[0130] [Implementation method 2]

[0131] Next, based on Figure 6 Embodiment 2 of the present invention will be described. In the display device 1' including the electroluminescent elements XR", XG", and XB" of this embodiment, the hole transport layer 30 of the electroluminescent element (first electroluminescent element) XR", the hole transport layer 30 of the electroluminescent element (second electroluminescent element) XG", and the hole transport layer 30 of the electroluminescent element (third electroluminescent element) XB" are formed as a common layer, and the cathode 25 of the electroluminescent element XR", the cathode 25 of the electroluminescent element XG", and the cathode 25 of the electroluminescent element XB" are respectively formed in an island shape, which is different from Embodiment 1. In addition, for the sake of convenience of description, the same figure numerals are attached to components having the same functions as those shown in the drawings of the first embodiment, and their descriptions are omitted.

[0132] Figure 6 1 is a diagram schematically showing the configuration of a display device 1 ′ including the electroluminescent elements XR″, XG″, and XB″ according to the second embodiment.

[0133] like Figure 6 As shown, in the display device 1' including the electroluminescent elements XR", XG", and XB", the hole transport layer 30 of the electroluminescent element XR", the hole transport layer 30 of the electroluminescent element XG", and the hole transport layer 30 of the electroluminescent element XB" are formed as a common layer. Therefore, it is possible to omit the patterning process for forming the hole transport layer 30 into an island shape, which is advantageous in the manufacturing process. In addition, by forming the hole transport layer 30 as a common layer, it is also possible to omit the need to form a covering Figure 3 The process of forming the bank 23 at the edge of the anode 22 shown is therefore advantageous in terms of manufacturing process.

[0134] In addition, if Figure 6 As shown, in the display device 1' including the electroluminescent elements XR", XG", and XB", the cathode 25 of the electroluminescent element XR", the cathode 25 of the electroluminescent element XG", and the cathode 25 of the electroluminescent element XB" are each formed in an island shape.

[0135] As described above, in the display device 1', by improving the carrier balance in each of the field light emitting elements XR", XG", and XB", the light emitting characteristics of the field light emitting elements XR", XG", and XB" can be improved. Therefore, a display device 1' that achieves efficient light emission in which holes and electrons are balanced in the light emitting layer can be realized.

[0136] [Implementation method 3]

[0137] Next, based on Figure 7 Embodiment 3 of the present invention is described. In the field light emitting element XR'' of this embodiment, the stacking order from the anode 22 to the cathode 25 is reversed, which is different from Embodiment 1. In addition, for the sake of convenience of description, the same figure numbers are marked for components having the same functions as those shown in the drawings of the first embodiment, and their descriptions are omitted.

[0138] Figure 7 This is a diagram showing a schematic structure of an electroluminescent element XR'''' according to the third embodiment.

[0139] like Figure 7 As shown, in the electroluminescent element XR'', the stacking order from the anode 22 to the cathode 25 is the same as Figure 1 The electroluminescent element XR shown is the opposite. That is, first, a cathode 25 is formed, an electron transport layer 33 is formed on the cathode 25, a light-emitting layer 24R containing first quantum dots is formed on the electron transport layer 33, a hole transport layer 30 is formed on the light-emitting layer 24R, and an anode 22 is formed on the hole transport layer 30. In this case, since the hole transport layer 30 contains the second insulating polymer 35, even when the anode 22 is formed by a vacuum film forming method such as a sputtering method, plasma damage will not be caused to the light-emitting layer 24R containing the first quantum dots, and an electroluminescent element XR''' with good light-emitting characteristics can be obtained.

[0140] In addition, since the electron transport layer 33 includes the first insulating polymer 37, the planarity of the light emitting layer 24R including the first quantum dots formed on the electron transport layer 33 is improved. This improves the surface uniformity of carrier injection and improves the light emitting characteristics.

[0141] [Implementation method 4]

[0142] Next, based on Figure 8Embodiment 4 of the present invention is described. The field light emitting element XR''' of this embodiment is different from Embodiment 1 in that an insulating layer 41 is provided between the light emitting layer 24R and the hole transport layer 30, and an insulating layer 42 is provided between the light emitting layer 24R and the electron transport layer 33. In addition, for the sake of convenience of description, components having the same functions as those shown in the drawings of the first embodiment are marked with the same figure numbers, and their descriptions are omitted.

[0143] Figure 8 This is a diagram showing a schematic structure of an electroluminescent element XR"" according to a fourth embodiment.

[0144] like Figure 8 As shown, the electroluminescent element XR″″ includes an insulating layer 41 between the light-emitting layer 24R and the hole transport layer 30 , and includes an insulating layer 42 between the light-emitting layer 24R and the electron transport layer 33 .

[0145] The insulating layer 41 and the insulating layer 42 are layers that do not contain the p-type semiconductor particles 34 and the n-type semiconductor particles 36. The types of the insulating layer 41 and the insulating layer 42 are not particularly limited as long as they do not contain the p-type semiconductor particles 34 and the n-type semiconductor particles 36. For example, the insulating layer 41 and the insulating layer 42 may be a polymer having insulating properties, a polymer having conductivity, an insulating layer formed of an inorganic oxide, or a layer formed of an inorganic nitride.

[0146] In addition, since there are insulating layers 41 and 42, it is possible to prevent the p-type semiconductor particles 34 and the n-type semiconductor particles 36 from directly contacting the light-emitting layer 24R including the first quantum dots, and prevent the excitons generated in the light-emitting layer 24R including the first quantum dots due to defect energy levels of the p-type semiconductor particles 34 and the n-type semiconductor particles 36 from being captured. At the same time, it acts as a blocking layer that suppresses the holes injected from the hole transport layer 30 and the electrons injected from the electron transport layer 33 from passing through the electrodes on the opposite sides.

[0147] As the insulating layer 41 and the insulating layer 42, the same material as the first insulating polymer 37 or the second insulating polymer 35 in Embodiment 1 may be used. In addition, the insulating layer 41 and the insulating layer 42 may be an inorganic insulator composed of any one of aluminum oxide, magnesium oxide, silicon oxide, aluminum nitride, zirconium oxide and hafnium oxide, or may be an inorganic insulator composed of a mixture of two or more of aluminum oxide, magnesium oxide, silicon oxide, aluminum nitride, zirconium oxide and hafnium oxide.

[0148] In addition, from the perspective of preventing the p-type semiconductor particles 34 and the n-type semiconductor particles 36 from contacting the light-emitting layer 24R containing the first quantum dots and enabling carrier injection into the light-emitting layer 24R containing the first quantum dots through the tunneling effect, the film thickness of each of the insulating layer 41 and the insulating layer 42 is preferably greater than 1 nm and less than 10 nm.

[0149] In addition, in this embodiment, the case where the insulating layer 41 is provided between the light-emitting layer 24R and the hole transport layer 30, and the insulating layer 42 is provided between the light-emitting layer 24R and the electron transport layer 33 is cited as an example for explanation, but it is not limited to this. The insulating layer 41 may be provided only between the light-emitting layer 24R and the hole transport layer 30, or the insulating layer 42 may be provided only between the light-emitting layer 24R and the electron transport layer 33.

[0150] [Additional Notes]

[0151] The present disclosure is not limited to the above-mentioned embodiments, and various changes can be made within the scope indicated by the claims. The embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention. Moreover, new technical features can be formed by combining the technical methods disclosed in each embodiment.

[0152] Industrial Applicability

[0153] The present disclosure can be applied to an electroluminescent element and an electroluminescent device.

[0154] Description of Reference Numerals

[0155] 1.1' Display device (electroluminescent device)

[0156] 22 Anode (first anode to third anode)

[0157] 24R Light-emitting layer including first quantum dots (first light-emitting layer, light-emitting layer)

[0158] 24G Light-emitting layer including second quantum dots (second light-emitting layer, light-emitting layer)

[0159] 24B Light-emitting layer including third quantum dots (third light-emitting layer, light-emitting layer)

[0160] 25 cathode (first cathode to third cathode)

[0161] 30 hole transport layer (first hole transport layer to third hole transport layer)

[0162] 31. Electron transport layer (second electron transport layer)

[0163] 32 electron transport layer (third electron transport layer)

[0164] 33 Electron transport layer (first electron transport layer)

[0165] 34 p-type semiconductor particles (first p-type semiconductor particle to third p-type semiconductor particle)

[0166] 35 Second insulating polymer

[0167] 36 n-type semiconductor particles (first n-type semiconductor particle to third n-type semiconductor particle)

[0168] 37 First insulating polymer (third insulating polymer, fourth insulating polymer)

[0169] 38 Hole

[0170] 39 Electronic

[0171] 41, 42 Insulation layer

[0172] XR, XR electroluminescent element (first electroluminescent element)

[0173] XG, XG” electroluminescent element (second electroluminescent element)

[0174] XB, XB” Electroluminescent element (third electroluminescent element)

[0175] XR”, XR”’, XR”” electroluminescent element (first electroluminescent element)

Claims

1. An electroluminescent element, comprising: anode; cathode; as well as a light-emitting layer disposed between the anode and the cathode, The electroluminescent element is characterized in that it also includes: an electron transport layer comprising n-type semiconductor particles and a first insulating polymer; as well as a hole transport layer comprising p-type semiconductor particles, The electron transport layer is disposed between the cathode and the light emitting layer, The hole transport layer is disposed between the anode and the light emitting layer, The volume ratio of the n-type semiconductor particles in the electron transport layer is smaller than the volume ratio of the p-type semiconductor particles in the hole transport layer, and the volume ratio of the p-type semiconductor particles in the hole transport layer is greater than 80% and less than 99.9%.

2. The electroluminescent element according to claim 1, characterized in that: The hole transport layer further contains a second insulating polymer.

3. The electroluminescent element according to claim 1, characterized in that The light-emitting layer has a green light emission wavelength, The volume ratio of the n-type semiconductor particles in the electron transport layer is 30% or more and 90% or less.

4. The electroluminescent element according to claim 1, characterized in that: The light-emitting layer has a blue light emission wavelength, The volume ratio of the n-type semiconductor particles in the electron transport layer is 40% or more and 95% or less.

5. The electroluminescent element according to claim 1, wherein: The hole transport layer has a thickness of 10 nm to 200 nm.

6. The electroluminescent element according to claim 1, characterized in that: The particle size of the n-type semiconductor particles is greater than or equal to 1 nm and less than or equal to 30 nm.

7. The electroluminescent element according to claim 1, wherein: The particle size of the p-type semiconductor particles is greater than or equal to 1 nm and less than or equal to 30 nm.

8. An electroluminescent element, comprising: anode; cathode; as well as a light-emitting layer disposed between the anode and the cathode, The electroluminescent element is characterized in that it also includes: an electron transport layer comprising n-type semiconductor particles and a first insulating polymer; as well as a hole transport layer comprising p-type semiconductor particles, The electron transport layer is disposed between the cathode and the light emitting layer, The hole transport layer is disposed between the anode and the light emitting layer, The volume ratio of the n-type semiconductor particles in the electron transport layer is smaller than the volume ratio of the p-type semiconductor particles in the hole transport layer. The light-emitting layer has a red light-emitting wavelength, The volume ratio of the n-type semiconductor particles in the electron transport layer is 5% or more and 65% or less.

9. The electroluminescent element according to claim 8, characterized in that: The hole transport layer further contains a second insulating polymer.

10. The electroluminescent element according to claim 8, characterized in that: The light-emitting layer has a green light emission wavelength, The volume ratio of the n-type semiconductor particles in the electron transport layer is 30% or more and 90% or less.

11. The electroluminescent element according to claim 8, characterized in that: The light-emitting layer has a blue light emission wavelength, The volume ratio of the n-type semiconductor particles in the electron transport layer is 40% or more and 95% or less.

12. The electroluminescent element according to claim 8, characterized in that: The difference between the volume ratio of the p-type semiconductor particles in the hole transport layer and the volume ratio of the n-type semiconductor particles in the electron transport layer is greater than 20%.

13. The electroluminescent element according to claim 8, characterized in that: The hole transport layer has a thickness of 10 nm to 200 nm.

14. The electroluminescent element according to claim 8, characterized in that: The particle size of the n-type semiconductor particles is greater than or equal to 1 nm and less than or equal to 30 nm.

15. The electroluminescent element according to claim 8, characterized in that: The particle size of the p-type semiconductor particles is greater than or equal to 1 nm and less than or equal to 30 nm.

16. An electroluminescent element, comprising: anode; cathode; as well as a light-emitting layer disposed between the anode and the cathode, The electroluminescent element is characterized in that it also includes: an electron transport layer comprising n-type semiconductor particles and a first insulating polymer; as well as a hole transport layer comprising p-type semiconductor particles, The electron transport layer is disposed between the cathode and the light emitting layer, The hole transport layer is disposed between the anode and the light emitting layer, The volume ratio of the n-type semiconductor particles in the electron transport layer is smaller than the volume ratio of the p-type semiconductor particles in the hole transport layer. An insulating layer is provided at least one between the light-emitting layer and the hole transport layer or between the light-emitting layer and the electron transport layer.

17. The electroluminescent element according to claim 16, characterized in that: The hole transport layer further contains a second insulating polymer.

18. The electroluminescent element according to claim 16, characterized in that: The light-emitting layer has a green light emission wavelength, The volume ratio of the n-type semiconductor particles in the electron transport layer is 30% or more and 90% or less.

19. The electroluminescent element according to claim 16, wherein: The light-emitting layer has a blue light emission wavelength, The volume ratio of the n-type semiconductor particles in the electron transport layer is 40% or more and 95% or less.

20. The electroluminescent element according to claim 16, wherein: The hole transport layer has a thickness of 10 nm to 200 nm.

21. The electroluminescent element according to claim 16, characterized in that: The particle size of the n-type semiconductor particles is greater than or equal to 1 nm and less than or equal to 30 nm.

22. The electroluminescent element according to claim 16, characterized in that: The particle size of the p-type semiconductor particles is greater than or equal to 1 nm and less than or equal to 30 nm.

23. An electroluminescent element, comprising: anode; cathode; as well as a light-emitting layer disposed between the anode and the cathode, The electroluminescent element is characterized in that it also includes: an electron transport layer comprising n-type semiconductor particles and a first insulating polymer; as well as a hole transport layer comprising p-type semiconductor particles, The electron transport layer is disposed between the cathode and the light emitting layer, The hole transport layer is disposed between the anode and the light emitting layer, The volume ratio of the n-type semiconductor particles in the electron transport layer is smaller than the volume ratio of the p-type semiconductor particles in the hole transport layer. The light-emitting layer includes quantum dots.

24. The electroluminescent element according to claim 23, characterized in that: The hole transport layer further contains a second insulating polymer.

25. The electroluminescent element according to claim 23, characterized in that: The light-emitting layer has a green light emission wavelength, The volume ratio of the n-type semiconductor particles in the electron transport layer is 30% or more and 90% or less.

26. The electroluminescent element according to claim 23, characterized in that: The light-emitting layer has a blue light emission wavelength, The volume ratio of the n-type semiconductor particles in the electron transport layer is 40% or more and 95% or less.

27. The electroluminescent element according to claim 23, characterized in that: The hole transport layer has a thickness of 10 nm to 200 nm.

28. The electroluminescent element according to claim 23, characterized in that: The particle size of the n-type semiconductor particles is greater than or equal to 1 nm and less than or equal to 30 nm.

29. The electroluminescent element according to claim 23, characterized in that: The particle size of the p-type semiconductor particles is greater than or equal to 1 nm and less than or equal to 30 nm.

30. An electroluminescent element, comprising: anode; cathode; as well as a light-emitting layer disposed between the anode and the cathode, The electroluminescent element is characterized in that it also includes: an electron transport layer comprising n-type semiconductor particles and a first insulating polymer; as well as a hole transport layer comprising p-type semiconductor particles, The electron transport layer is disposed between the cathode and the light emitting layer, The hole transport layer is disposed between the anode and the light emitting layer, The volume ratio of the n-type semiconductor particles in the electron transport layer is smaller than the volume ratio of the p-type semiconductor particles in the hole transport layer. The hole transport layer is in contact with the light emitting layer, The light-emitting layer is also in contact with the electron transport layer, The hole transport layer, the light emitting layer and the electron transport layer are each one layer.

31. The electroluminescent element according to claim 30, characterized in that: The hole transport layer further contains a second insulating polymer.

32. The electroluminescent element according to claim 30, characterized in that: The light-emitting layer has a green light emission wavelength, The volume ratio of the n-type semiconductor particles in the electron transport layer is 30% or more and 90% or less.

33. The electroluminescent element according to claim 30, characterized in that: The light-emitting layer has a blue light emission wavelength, The volume ratio of the n-type semiconductor particles in the electron transport layer is 40% or more and 95% or less.

34. The electroluminescent element according to claim 30, characterized in that: The hole transport layer has a thickness of 10 nm to 200 nm.

35. The electroluminescent element according to claim 30, characterized in that: The particle size of the n-type semiconductor particles is greater than or equal to 1 nm and less than or equal to 30 nm.

36. The electroluminescent element according to claim 30, characterized in that: The particle size of the p-type semiconductor particles is greater than or equal to 1 nm and less than or equal to 30 nm.

37. An electroluminescent device, characterized in that: It comprises an electroluminescent element, The electroluminescent element comprises: anode; a cathode; and a light-emitting layer disposed between the anode and the cathode, The electroluminescent element further comprises: an electron transport layer comprising n-type semiconductor particles and a first insulating polymer; and a hole transport layer comprising p-type semiconductor particles, The electron transport layer is disposed between the cathode and the light emitting layer, The hole transport layer is disposed between the anode and the light emitting layer, The volume ratio of the n-type semiconductor particles in the electron transport layer is smaller than the volume ratio of the p-type semiconductor particles in the hole transport layer.

38. An electroluminescent device comprising a first electroluminescent element and a second electroluminescent element, characterized in that: The first electroluminescent element comprises: a first anode; a first cathode; A first light-emitting layer is disposed between the first anode and the first cathode; a first hole transport layer, which is disposed between the first anode and the first light-emitting layer and comprises first p-type semiconductor particles; and a first electron transport layer, which is disposed between the first cathode and the first light-emitting layer and comprises first n-type semiconductor particles and a first insulating polymer, The volume ratio of the first n-type semiconductor particles in the first electron transport layer is smaller than the volume ratio of the first p-type semiconductor particles in the first hole transport layer; The second electroluminescent element comprises: a second anode; a second cathode; a second light-emitting layer disposed between the second anode and the second cathode and having a light emission wavelength shorter than that of the first light-emitting layer; a second hole transport layer, which is disposed between the second anode and the second light-emitting layer and comprises second p-type semiconductor particles; and a second electron transport layer, which is disposed between the second cathode and the second light-emitting layer and comprises second n-type semiconductor particles and a third insulating polymer, The volume ratio of the second n-type semiconductor particles in the second electron transport layer is smaller than the volume ratio of the second p-type semiconductor particles in the second hole transport layer. The volume ratio of the second n-type semiconductor particles in the second electron transport layer is greater than the volume ratio of the first n-type semiconductor particles in the first electron transport layer.

39. The electroluminescent device according to claim 38, characterized in that The first p-type semiconductor particles and the second p-type semiconductor particles are made of the same material, The volume ratio of the first p-type semiconductor particles in the first hole transport layer is the same as the volume ratio of the second p-type semiconductor particles in the second hole transport layer, The first hole transport layer and the second hole transport layer are formed of the same material as one layer.

40. The electroluminescent device according to claim 38, characterized in that The first p-type semiconductor particles and the second p-type semiconductor particles are made of different materials.

41. The electroluminescent device according to any one of claims 38 to 40, characterized in that The first n-type semiconductor particles and the second n-type semiconductor particles are different materials.

42. The electroluminescent device according to any one of claims 38 to 40, characterized in that The first insulating polymer and the third insulating polymer are different materials.

43. The electroluminescent device according to any one of claims 38 to 40, characterized in that The first n-type semiconductor particles and the second n-type semiconductor particles are made of the same material, The first insulating polymer and the third insulating polymer are the same material.

44. The electroluminescent device according to any one of claims 38 to 40, characterized in that The thickness of the first hole transport layer is greater than or equal to 10 nm and less than or equal to 200 nm. The second hole transport layer has a thickness of 10 nm to 200 nm.

45. The electroluminescent device according to any one of claims 38 to 40, characterized in that The particle size of the first n-type semiconductor particles is greater than or equal to 1 nm and less than or equal to 30 nm. The particle diameter of the second n-type semiconductor particles is greater than or equal to 1 nm and less than or equal to 30 nm.

46. ​​The electroluminescent device according to any one of claims 38 to 40, characterized in that The particle size of the first p-type semiconductor particles is greater than or equal to 1 nm and less than or equal to 30 nm. The particle diameter of the second p-type semiconductor particles is greater than or equal to 1 nm and less than or equal to 30 nm.

47. The electroluminescent device according to any one of claims 38 to 40, characterized in that An insulating layer is provided at least one between the first light-emitting layer and the first hole transport layer, between the first light-emitting layer and the first electron transport layer, between the second light-emitting layer and the second hole transport layer, and between the second light-emitting layer and the second electron transport layer.

48. The electroluminescent device according to any one of claims 38 to 40, characterized in that Also comprising a third electroluminescent element, The third electroluminescent element comprises: The third anode; The third cathode; a third light-emitting layer disposed between the first anode and the first cathode and having a light-emitting wavelength shorter than that of the second light-emitting layer; a third hole transport layer, which is disposed between the third anode and the third light-emitting layer and comprises third p-type semiconductor particles; and a third electron transport layer, which is disposed between the third cathode and the third light-emitting layer and comprises third n-type semiconductor particles and a fourth insulating polymer, The volume ratio of the third n-type semiconductor particles in the third electron transport layer is smaller than the volume ratio of the third p-type semiconductor particles in the third hole transport layer; The volume ratio of the third n-type semiconductor particles in the third electron transport layer is greater than the volume ratio of the second n-type semiconductor particles in the second electron transport layer.

49. The electroluminescent device according to any one of claims 38 to 40, characterized in that The first light-emitting layer comprises first quantum dots, The second light-emitting layer comprises second quantum dots, The second quantum dots have a light emission wavelength shorter than that of the first quantum dots.

50. The electroluminescent device according to claim 48, characterized in that The first light-emitting layer comprises first quantum dots, The second light-emitting layer comprises second quantum dots, The third light-emitting layer comprises third quantum dots, The second quantum dot has a shorter emission wavelength than the first quantum dot, The third quantum dot has a light emission wavelength shorter than that of the second quantum dot.

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