Display device

Abstract

This display device (1) comprises: a blue light-emitting element (10B) provided with a blue light-emitting layer (6B) that contains a first quantum dot; a green light-emitting element (10G) provided with a green light-emitting layer (6G) that contains a second quantum dot and emits light having a color different from that of light emitted by the blue light-emitting layer (6B) and having a peak wavelength that is on the longer wavelength side than the peak wavelength of light emitted by the blue light-emitting layer (6B); and a first common charge transport layer (7) provided as a common layer for each of the blue light-emitting element (10B) and the green light-emitting element (10G). The concentration of a first halogen element per unit volume of the blue light-emitting layer (6B) is higher than the concentration of the first halogen element per unit volume of the green light-emitting layer (6G).

Description

display device

[0001] The present disclosure relates to a display device.

[0002] In recent years, display devices equipped with quantum dot light-emitting diodes (QLEDs) as light-emitting elements have attracted much attention because of their ability to achieve low power consumption, thinness, high image quality, and the like.

[0003] Patent Document 1 describes a display device including OLEDs (Organic Light Emitting Diodes) as light-emitting elements, in which a common charge transport layer is provided for a plurality of OLEDs. The common charge transport layer may be a common electron transport layer, a common hole transport layer, a common hole injection layer, or the like.

[0004] Japanese Patent Application Publication No. 2014-164829

[0005] A display device including a QLED includes, for example, a red light-emitting element having a red light-emitting layer including red-emitting quantum dots, a green light-emitting element having a green light-emitting layer including green-emitting quantum dots, and a blue light-emitting element having a blue light-emitting layer including blue-emitting quantum dots. However, the energy levels of the conduction band bottom (CBM) and the valence band top (VBM) of the red-emitting quantum dots are generally different from the energy levels of the conduction band bottom (CBM) and the valence band top (VBM) of the green-emitting quantum dots, and the energy levels of the conduction band bottom (CBM) and the valence band top (VBM) of the blue-emitting quantum dots.

[0006] In a display device equipped with such QLEDs, when the common charge transport layer described in Patent Document 1 is provided, the following problem occurs. If a material for the common charge transport layer is selected that has an energy level of the conduction band minimum (CBM) and the valence band maximum (VBM) that are optimal for any one of red-emitting quantum dots, green-emitting quantum dots, and blue-emitting quantum dots, for example, red-emitting quantum dots, problems such as a deterioration in the carrier balance between holes and electrons, a decrease in luminous efficiency, and a decrease in reliability occur in green-emitting and blue-emitting elements. Therefore, it is difficult to reduce the power consumption and improve the reliability of the display device.

[0007] An object of one embodiment of the present disclosure is to provide a display device that achieves low power consumption and improved reliability.

[0008] In order to solve the above-mentioned problems, the display device of the present disclosure includes a first light-emitting element having a first light-emitting layer including first quantum dots; a second light-emitting element having a second light-emitting layer including second quantum dots, emitting light that is a different color from the light emitted by the first light-emitting layer and has a peak wavelength that is longer than the peak wavelength of the light emitted by the first light-emitting layer; and a first common charge transport layer provided as a common layer for each of the first light-emitting element and the second light-emitting element, wherein the concentration of the first halogen element per unit volume of the first light-emitting layer is higher than the concentration of the first halogen element per unit volume of the second light-emitting layer.

[0009] According to one embodiment of the present disclosure, a display device with reduced power consumption and improved reliability can be provided.

[0010] 1 is a plan view showing a schematic configuration of a display device of Embodiment 1; FIG. 2 is a cross-sectional view showing a schematic configuration of a display region of the display device of Embodiment 1; FIG. 3 is a diagram showing the band levels of each of the red light-emitting element, green light-emitting element, and blue light-emitting element provided in the display device of Comparative Example 1, and the band levels of each of the red light-emitting element, green light-emitting element, and blue light-emitting element provided in the display device of Embodiment 1; FIG. 4 is a diagram showing the band levels of each of the red light-emitting element, green light-emitting element, and blue light-emitting element provided in the display device of Comparative Example 2, and the band levels of each of the red light-emitting element, green light-emitting element, and blue light-emitting element provided in the display device of Embodiment 1; FIG. 5 is a diagram showing the band levels of quantum dots, a first common charge transport layer, and a second common charge transport layer before addition of halogen elements, which are included in the light-emitting layers of each color provided in the display device of Embodiment 1, and an example of a material that can be used as the first common charge transport layer and the second common charge transport layer, and their band levels; and FIG. 6 is a diagram showing the degree of change in the energy level of the valence band top (VBM) of the light-emitting layers of each color provided in the display device of Embodiment 1 due to the addition of various halogen elements. 1 is a diagram showing the degree of change in the energy levels of the valence band top (VBM) and the conduction band bottom (CBM) of quantum dots included in each color light-emitting layer when I is added to the quantum dots included in the red light-emitting layer of a red light-emitting element, Br or Cl is added to the quantum dots included in the green light-emitting layer of a green light-emitting element, and F is added to the quantum dots included in the blue light-emitting layer of a blue light-emitting element, which are provided in the display device of embodiment 1. 2 is a diagram showing the degree of change in the energy levels of the valence band top (VBM) and the conduction band bottom (CBM) of quantum dots included in each color light-emitting layer when Br is added to the quantum dots included in the red light-emitting layer of a red light-emitting element, Cl is added to the quantum dots included in the green light-emitting layer of a green light-emitting element, and F is added to the quantum dots included in the blue light-emitting layer of a blue light-emitting element, which are provided in another example of the display device of embodiment 1. 3 is a cross-sectional view showing a schematic configuration of a display region of a display device of embodiment 2. 4 is a cross-sectional view showing a schematic configuration of a display region of a display device of embodiment 3. 5 is a cross-sectional view showing a schematic configuration of a display region of a display device of embodiment 4. 6 is a cross-sectional view showing a schematic configuration of a display region of a display device of embodiment 5.12 is a diagram for explaining a pattern of halogen elements mixed into the first-formed light-emitting layer (first color light-emitting layer) and the second-formed light-emitting layer (second color light-emitting layer) among the red, green, and blue light-emitting layers in the manufacturing process of the display device of Embodiment 5 shown in FIG. 12. FIG. 12 is a diagram for explaining a pattern of halogen elements mixed into each color light-emitting layer depending on the order in which the red, green, and blue light-emitting layers are formed, when I is added to the red light-emitting layer, Br is added to the green light-emitting layer, and Cl is added to the blue light-emitting layer ...,

[0011] The following describes embodiments of the present disclosure with reference to Figures 1 to 17. For the sake of convenience, components having the same functions as those described in specific embodiments will be denoted by the same reference numerals, and their description may be omitted.

[0012] First Embodiment FIG. 1 is a plan view showing a schematic configuration of a display device 1 according to a first embodiment.

[0013] As shown in Fig. 1, the display device 1 includes a frame area NDA and a display area DA. The display area DA of the display device 1 includes a plurality of pixels PIX, each of which includes a red subpixel RSP, a green subpixel GSP, and a blue subpixel BSP. In this embodiment, a case in which one pixel PIX is configured with a red subpixel RSP, a green subpixel GSP, and a blue subpixel BSP will be described as an example, but this is not limiting. For example, one pixel PIX may include subpixels of other colors in addition to the red subpixel RSP, the green subpixel GSP, and the blue subpixel BSP.

[0014] FIG. 2 is a cross-sectional view showing a schematic configuration of the display area DA of the display device 1 of the first embodiment.

[0015] 2, the display device 1 includes a substrate 2 including a thin-film transistor layer, and a red light-emitting element 10R, a green light-emitting element 10G, and a blue light-emitting element 10B provided on the substrate 2 including the thin-film transistor layer. The substrate 2 including the thin-film transistor layer and island-shaped lower electrodes 3 provided on the substrate 2 including the thin-film transistor layer for each of the red sub-pixels RSP, green sub-pixels GSP, and blue sub-pixels BSP are collectively referred to as an active substrate.

[0016] The substrate 2 including the thin film transistor layer includes a substrate, thin film transistors provided on the substrate, various insulating layers, various electrodes, a wiring layer, and a planarization film. The substrate included in the substrate 2 including the thin film transistor layer may be, for example, a resin substrate made of a resin material such as polyimide, or a glass substrate. In this embodiment, since the display device 1 is a flexible display device, a case where a resin substrate made of a resin material such as polyimide is used will be described as an example, but the present invention is not limited to this. If the display device 1 is a non-flexible display device, a glass substrate can be used.

[0017] In the display device 1 shown in Figure 2, the red subpixel RSP shown in Figure 1 is provided with a red light-emitting element 10R including a lower electrode 3, an upper electrode 8 provided above the lower electrode 3, and a red light-emitting layer 6R provided between the lower electrode 3 and the upper electrode 8, the green subpixel GSP shown in Figure 1 is provided with a green light-emitting element 10G including a lower electrode 3, an upper electrode 8 provided above the lower electrode 3, and a green light-emitting layer 6G provided between the lower electrode 3 and the upper electrode 8, and the blue subpixel BSP shown in Figure 1 is provided with a blue light-emitting element 10B including a lower electrode 3, an upper electrode 8 provided above the lower electrode 3, and a blue light-emitting layer 6B provided between the lower electrode 3 and the upper electrode 8.

[0018] The blue light-emitting layer 6B includes first quantum dots, the green light-emitting layer 6G includes second quantum dots that emit light of a different color from the light emitted by the blue light-emitting layer 6B and that has a peak wavelength longer than the peak wavelength of the light emitted by the blue light-emitting layer 6B, and the red light-emitting layer 6R includes third quantum dots that emit light of a different color from the light emitted by the green light-emitting layer 6G and that has a peak wavelength longer than the peak wavelength of the light emitted by the green light-emitting layer 6G. The emission wavelengths of the first quantum dots, the second quantum dots, and the third quantum dots can be controlled by the particle size of the quantum dots or the material constituting the quantum dots. The first quantum dots, the second quantum dots, and the third quantum dots may each have, for example, a core structure, a core / shell structure, a core / shell / shell structure, or a shell structure with a continuously varying core / shell ratio. Note that the shell may partially cover the core, but it is more preferable for the shell to completely cover the core. The core may be composed of, for example, Si, C, etc. in the case of a unicomponent system, or may be composed of, for example, CdSe, CdS, CdTe, InP, GaP, InN, ZnSe, ZnS, ZnTe, etc. in the case of a ternary system, or may be composed of, for example, CdSeTe, GaInP, ZnSeTe, etc. in the case of a quaternary system, or may be composed of, for example, AIGS containing Ag, In, Ga, and S. The shell may be composed of, for example, CdS, CdTe, CdSe, ZnS, ZnSe, ZnTe, etc. in the case of a ternary system, or may be composed of, for example, CdSSe, CdTeSe, CdSTe, ZnSSe, ZnSTe, ZnTeSe, AgInP (AIP), etc. in the case of a ternary system. In this embodiment, the first quantum dots contained in the blue light-emitting layer 6B are described as quantum dots having a core structure in which the core is made of ZnTeSe, but the present invention is not limited thereto. Also, the second quantum dots contained in the green light-emitting layer 6G are described as quantum dots having a core structure in which the core is made of InP, and having a particle size smaller than that of the third quantum dots contained in the red light-emitting layer 6R, but the present invention is not limited thereto.Although the third quantum dots included in the red light-emitting layer 6R are described as having a core structure in which the core is made of InP and have a particle size larger than that of the second quantum dots included in the green light-emitting layer 6G, the present invention is not limited to this example. For example, the first quantum dots included in the blue light-emitting layer 6B, the second quantum dots included in the green light-emitting layer 6G, and the third quantum dots included in the red light-emitting layer 6R may be made of the same material, with the particle size of the second quantum dots being larger than that of the first quantum dots and the particle size of the third quantum dots being larger than that of the second quantum dots.

[0019] In this embodiment, as shown in FIG. 2 , a case will be described as an example in which the display device 1 includes a bank 4 covering the edge of the lower electrode 3, but this is not limiting and the bank 4 may not be included. The bank 4 divides the display device 1 into a peripheral region NHR and a red light-emitting region RHR, a green light-emitting region GHR, and a blue light-emitting region BHR. In the display device 1, the region in which the bank 4 is provided is the peripheral region NHR, and the opening of the bank 4, i.e., the region in which the lower electrode 3 is exposed through the opening of the bank 4, is one of the red light-emitting region RHR, the green light-emitting region GHR, and the blue light-emitting region BHR. The bank 4 can be formed, for example, by applying an organic material such as polyimide or acrylic and then patterning it using photolithography.

[0020] 2 may be of either a top-emission type or a bottom-emission type. In this embodiment, the red light-emitting element 10R, the green light-emitting element 10G, and the blue light-emitting element 10B have a stack structure in which the upper electrode 8 (cathode) is disposed above the lower electrode 3 (anode). To achieve a top-emission type, the lower electrode 3 (anode) may be formed from an electrode material that reflects visible light, and the upper electrode 8 (cathode) may be formed from an electrode material that transmits visible light. To achieve a bottom-emission type, the lower electrode 3 (anode) may be formed from an electrode material that transmits visible light, and the upper electrode 8 (cathode) may be formed from an electrode material that reflects visible light. On the other hand, in the case of an inverted stack structure in which the upper electrode 8, or anode, is arranged as a layer above the lower electrode 3, or cathode, in order to make it a top emission type, the lower electrode 3, or cathode, can be formed from an electrode material that reflects visible light, and the upper electrode 8, or anode, can be formed from an electrode material that transmits visible light, and in order to make it a bottom emission type, the lower electrode 3, or cathode, can be formed from an electrode material that transmits visible light, and the upper electrode 8, or anode, can be formed from an electrode material that reflects visible light.

[0021] The electrode material that reflects visible light is not particularly limited as long as it can reflect visible light and has electrical conductivity. Examples of the electrode material that reflects visible light include metal materials such as Al, Mg, Li, and Ag, alloys of the metal materials, laminates of the metal materials and transparent metal oxides (e.g., indium tin oxide, indium zinc oxide, indium gallium zinc oxide, etc.), and laminates of the alloys and the transparent metal oxides.

[0022] On the other hand, the electrode material that transmits visible light is not particularly limited as long as it can transmit visible light and has conductivity, and examples thereof include transparent metal oxides (e.g., indium tin oxide, indium zinc oxide, indium gallium zinc oxide, etc.), thin films made of metal materials such as Al and Ag, and nanowires made of metal materials such as Al and Ag.

[0023] 2 , the display device 1 includes first common charge transport layers 7 in contact with the red light-emitting layer 6R, the green light-emitting layer 6G, and the blue light-emitting layer 6B, respectively, between the red light-emitting layer 6R and the upper electrode 8, between the green light-emitting layer 6G and the upper electrode 8, and between the blue light-emitting layer 6B and the upper electrode 8, and the red light-emitting element 10R, the green light-emitting element 10G, and the blue light-emitting element 10B each include the first common charge transport layer 7. Note that, in this embodiment, a case in which the upper electrode 8 is provided as a common electrode for each of the red light-emitting element 10R, the green light-emitting element 10G, and the blue light-emitting element 10B will be described as an example, but the present invention is not limited to this.

[0024] 2 , the first common charge transport layer 7 is provided as a common layer for each of the red light-emitting element 10R, the green light-emitting element 10G, and the blue light-emitting element 10B, but the present invention is not limited thereto, and the first common charge transport layer 7 may be provided as a common layer for only two light-emitting elements of different colors selected from the red light-emitting element 10R, the green light-emitting element 10G, and the blue light-emitting element 10B. Furthermore, the present invention is not limited thereto, and the first common charge transport layer 7 is provided as a common layer for only two light-emitting elements of different colors selected from the red light-emitting element 10R, the green light-emitting element 10G, and the blue light-emitting element 10B, but the present invention is not limited thereto, and the first common charge transport layer 7 does not have to be in contact with the red light-emitting layer 6R, the green light-emitting layer 6G, and the blue light-emitting layer 6B.

[0025] The display device 1 includes second common charge transport layers 5 in contact with the red light-emitting layer 6R, the green light-emitting layer 6G, and the blue light-emitting layer 6B, respectively, between the red light-emitting layer 6R and the lower electrode 3, between the green light-emitting layer 6G and the lower electrode 3, and between the blue light-emitting layer 6B and the lower electrode 3, and the red light-emitting element 10R, the green light-emitting element 10G, and the blue light-emitting element 10B each include the second common charge transport layer 5. In this embodiment, as shown in FIG. 2 , a case will be described as an example in which the second common charge transport layer 5 is provided as a layer common to the red light-emitting element 10R, the green light-emitting element 10G, and the blue light-emitting element 10B, respectively. However, the present invention is not limited to this, and the second common charge transport layer 5 may be provided as a layer common to only two light-emitting elements of different colors selected from the red light-emitting element 10R, the green light-emitting element 10G, and the blue light-emitting element 10B.

[0026] As described above, in this embodiment, the red light-emitting element 10R, the green light-emitting element 10G, and the blue light-emitting element 10B have a forward stack structure in which the upper electrode 8, that is, the cathode, is disposed as a layer above the lower electrode 3, that is, the anode. Therefore, the first common charge transport layer 7 only needs to include at least one of an electron injection layer (EIL) and an electron transport layer (ETL), and the second common charge transport layer 5 only needs to include at least one of a hole injection layer (HIL) and a hole transport layer (HTL). In this embodiment, the display device 1 includes both a first common charge transport layer 7 and a second common charge transport layer 5, and the first common charge transport layer 7 is an electron transport layer or an electron injection layer. The red light-emitting element 10R, the green light-emitting element 10G, and the blue light-emitting element 10B each include a second common charge transport layer 5 in contact with the red light-emitting layer 6R, the green light-emitting layer 6G, and the blue light-emitting layer 6B from a second side opposite to the first side where the first common charge transport layer 7 is in contact with the red light-emitting layer 6R, the green light-emitting layer 6G, and the blue light-emitting layer 6B, respectively. The second common charge transport layer 5 is a hole transport layer or a hole injection layer. Note that this embodiment will be described taking as an example a case where the display device 1 includes both the first common charge transport layer 7 and the second common charge transport layer 5, but is not limited thereto. The display device 1 may include only one of the first common charge transport layer 7 and the second common charge transport layer 5.

[0027] The material used for the hole injection layer (HIL) is not particularly limited as long as it is a hole injection material that can stabilize the injection of holes into the light emitting layer. For example, a composite of poly(3,4-ethylenedioxythiophene) (PEDOT) and polystyrene sulfonic acid (PSS) (PEDOT:PSS) can be used. In addition, NiO particles or MoO ３ Nanoparticles having hole transport properties, such as particles, may also be used.

[0028] Examples of materials used for the hole transport layer (HTL) include organic materials such as poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(4,4'-(N-(4-sec-butylphenyl))diphenylamine)] (TFB), N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)-benzidine (poly-TPD), polyvinylcarbazole (PVK), and 4,4'-bis(carbazol-9-yl)biphenyl (CBP), and nanoparticles having hole transport properties such as NiO particles may also be used.

[0029] The material used for the electron transport layer (ETL) may be, for example, an organic material such as 2,2′,2″-(1,3,5-benzinetriyl)-tris(1-phenyl-1-H-benzimidazole) (TPBi), or nanoparticles having electron transport properties such as ZnO particles or particles of an oxide containing Zn and Mg.

[0030] The material used for the electron injection layer (EIL) is not particularly limited as long as it is an electron-injecting material that can stabilize the injection of electrons into the light-emitting layer. For example, alkali metals or alkaline earth metals such as aluminum, strontium, calcium, lithium, cesium, magnesium oxide, aluminum oxide, strontium oxide, lithium oxide, lithium fluoride, magnesium fluoride, strontium fluoride, calcium fluoride, barium fluoride, cesium fluoride, polymethyl methacrylate polystyrene sodium sulfonate, oxides of alkali metals or alkaline earth metals, fluorides of alkali metals or alkaline earth metals, organic complexes of alkali metals, etc. may be used.

[0031] Fig. 3 is a diagram schematically showing the band levels of the red light-emitting element 100R, the green light-emitting element 100G, and the blue light-emitting element 100B provided in the display device of Comparative Example 1 (upper diagram in Fig. 3 ), and the band levels of the red light-emitting element 10R, the green light-emitting element 10G, and the blue light-emitting element 10B provided in the display device 1 of Embodiment 1 (lower diagram in Fig. 3 ). Fig. 4 is a diagram schematically showing the band levels of the red light-emitting element 101R, the green light-emitting element 101G, and the blue light-emitting element 10B provided in the display device of Comparative Example 2 (upper diagram in Fig. 4 ), and the band levels of the red light-emitting element 10R, the green light-emitting element 10G, and the blue light-emitting element 10B provided in the display device 1 of Embodiment 1 (lower diagram in Fig. 4 ).

[0032] 3 , in the display device of Comparative Example 1, an electron transport layer (ETL) serving as the first common charge transport layer 7 and a hole transport layer (HTL) serving as the second common charge transport layer 5 are provided as common layers for the red light-emitting element 100R, the green light-emitting element 100G, and the blue light-emitting element 100B. The first quantum dots BQDs included in the blue light-emitting layer provided in the blue light-emitting element 100B, the second quantum dots GQDs included in the green light-emitting layer provided in the green light-emitting element 100G, and the third quantum dots RQDs included in the red light-emitting layer are each made of the same material, with the particle size of the second quantum dots GQDs being larger than that of the first quantum dots BQDs and the particle size of the third quantum dots RQDs being larger than that of the second quantum dots GQDs. In such a case, the energy level of the conduction band minimum (CBM) of the first quantum dot BQD included in the blue light-emitting layer of the blue light-emitting element 100B is generally shallower than the energy level of the conduction band minimum (CBM) of the third quantum dot RQD included in the red light-emitting layer of the red light-emitting element 100R and the energy level of the conduction band minimum (CBM) of the second quantum dot GQD included in the green light-emitting layer of the green light-emitting element 100G, and the energy level of the conduction band minimum (CBM) of the second quantum dot GQD included in the green light-emitting layer of the green light-emitting element 100G is generally shallower than the energy level of the conduction band minimum (CBM) of the third quantum dot RQD included in the red light-emitting layer of the red light-emitting element 100R. Therefore, in the red light-emitting element 100R provided in the display device of Comparative Example 1, the difference between the energy level of the conduction band minimum (CBM) of the electron transport layer (ETL), which is the first common charge transport layer 7, and the energy level of the conduction band minimum (CBM) of the third quantum dots RQD included in the red light-emitting layer provided in the red light-emitting element 100R is small, and there are more electrons E than holes H in the red light-emitting layer, which causes problems in the red light-emitting element 100R such as a deterioration in the carrier balance between holes H and electrons E, a decrease in luminous efficiency, and a decrease in reliability.In the green light-emitting element 100G provided in the display device of Comparative Example 1, the difference between the energy level of the conduction band minimum (CBM) of the electron transport layer (ETL), which is the first common charge transport layer 7, and the energy level of the conduction band minimum (CBM) of the second quantum dot GQD included in the green light-emitting layer provided in the green light-emitting element 100G is optimized, and a carrier balance between holes H and electrons E is achieved in the green light-emitting layer, thereby ensuring good luminous efficiency and reliability in the green light-emitting element 100G. In the blue light-emitting element 100B provided in the display device of Comparative Example 1, there is a large difference between the energy level of the conduction band minimum (CBM) of the electron transport layer (ETL), which is the first common charge transport layer 7, and the energy level of the conduction band minimum (CBM) of the first quantum dots BQDs included in the blue light-emitting layer provided in the blue light-emitting element 100B, and as a result, there are more holes H than electrons E in the blue light-emitting layer, and in the blue light-emitting element 100B, problems such as a deterioration in the carrier balance between the holes H and the electrons E, a decrease in luminous efficiency, and a decrease in reliability occur. In the display device of Comparative Example 1 including the above-mentioned red light-emitting element 100R, green light-emitting element 100G, and blue light-emitting element 100B, it is difficult to reduce power consumption and improve reliability because the display device includes the red light-emitting element 100R and blue light-emitting element 100B, which have a poor carrier balance between the holes H and the electrons E.

[0033] Comparative Example 2 shown in the upper diagram of Figure 4 is an example in which the same amount of halogen element Cl was added to each color-emitting layer of the display device of Comparative Example 1 to adjust the energy levels of the light-emitting layers. In the display device of Comparative Example 2, as in the display device of Comparative Example 1 described above, an electron transport layer (ETL) serving as the first common charge transport layer 7 and a hole transport layer (HTL) serving as the second common charge transport layer 5 are provided as common layers for the red light-emitting element 101R, the green light-emitting element 101G, and the blue light-emitting element 10B, respectively. In the blue light-emitting element 10B shown in the upper diagram of Figure 4, the energy level of the conduction band minimum (CBM) of the first quantum dots BQD+Cl containing a predetermined amount of halogen element Cl in the blue light-emitting layer is deeper than the energy level of the conduction band minimum (CBM) of the first quantum dots BQD contained in the blue light-emitting layer provided in the blue light-emitting element 100B shown in the upper diagram of Figure 3. This lowers the injection barrier for electrons E from the electron transport layer (ETL) serving as the first common charge transport layer 7, thereby improving the carrier balance between holes H and electrons E. The predetermined amount of Cl, which is a halogen element, contained in the blue light-emitting layer is an optimal amount for lowering the injection barrier of electrons E from the electron transport layer (ETL), which is the first common charge transport layer 7. Meanwhile, in the green light-emitting element 101G shown in the upper diagram of Figure 4, the energy level of the conduction band minimum (CBM) of the second quantum dots GQDs + Cl containing the predetermined amount of Cl, which is a halogen element, contained in the green light-emitting layer is deeper than the energy level of the conduction band minimum (CBM) of the second quantum dots GQDs contained in the green light-emitting layer provided in the green light-emitting element 100G shown in the upper diagram of Figure 3.Note that the predetermined amount of Cl, which is a halogen element, contained in the green light-emitting layer is an optimal amount for lowering the injection barrier of electrons E from the electron transport layer (ETL), which is the first common charge transport layer 7, in the blue light-emitting layer. Therefore, the difference between the energy level of the conduction band minimum (CBM) of the second quantum dots GQD+Cl containing the predetermined amount of Cl, which is a halogen element, contained in the green light-emitting layer, and the energy level of the conduction band minimum (CBM) of the electron transport layer (ETL), which is the first common charge transport layer 7, becomes too small. As a result, in the green light-emitting element 101G, there are more electrons E than holes H. As a result, problems such as a deterioration in the carrier balance between the holes H and the electrons E, a decrease in luminous efficiency, and a decrease in reliability occur in the green light-emitting element 101G. In addition, in the red light-emitting element 101R shown in the upper diagram of Figure 4, the energy level of the conduction band minimum (CBM) of the third quantum dots RQD+Cl containing the predetermined amount of Cl, which is a halogen element, contained in the red light-emitting layer is deeper than the energy level of the conduction band minimum (CBM) of the third quantum dots RQD contained in the red light-emitting layer provided in the red light-emitting element 100R shown in the upper diagram of Figure 3. The predetermined amount of Cl, which is a halogen element, contained in the red light-emitting layer is an optimal amount for lowering the injection barrier of electrons E from the electron transport layer (ETL), which is the first common charge transport layer 7, in the blue light-emitting layer. Therefore, the energy level of the conduction band minimum (CBM) of the third quantum dots RQD+Cl, which contain the predetermined amount of Cl, which is a halogen element contained in the red light-emitting layer, becomes deeper than the energy level of the conduction band minimum (CBM) of the electron transport layer (ETL), which is the first common charge transport layer 7. As a result, in the red light-emitting element 101R, there are more electrons E than holes H. This causes problems such as a deterioration in the carrier balance between holes H and electrons E, a decrease in luminous efficiency, and a decrease in reliability. In the display device of Comparative Example 2, which includes the above-described red light-emitting element 101R, green light-emitting element 101G, and blue light-emitting element 10B, it is difficult to reduce power consumption and improve reliability because the display device includes the red light-emitting element 101R and green light-emitting element 101G, which have a poor carrier balance between holes H and electrons E.

[0034] Therefore, in this embodiment, as shown in the lower diagram of Fig. 3 and the lower diagram of Fig. 4, the concentration of the first halogen element per unit volume of the blue light-emitting layer (first light-emitting layer) 6B provided in the blue light-emitting element (first light-emitting element) 10B, for example, the concentration of Cl, is higher than the concentration of the first halogen element per unit volume of the green light-emitting layer (second light-emitting layer) 6G provided in the green light-emitting element (second light-emitting element) 10G, for example, the concentration of Cl. Note that the concentration of the first halogen element per unit volume of the blue light-emitting layer (first light-emitting layer) 6B, for example, the concentration of Cl, is an optimum concentration for improving the carrier balance between holes H and electrons E in the blue light-emitting element (first light-emitting element) 10B. 3 and 4, the concentration of the second halogen element per unit volume of the green light-emitting layer (second light-emitting layer) 6G provided in the green light-emitting element (second light-emitting element) 10G, for example, the concentration of Br, is higher than the concentration of the second halogen element per unit volume of the blue light-emitting layer (first light-emitting layer) 6B provided in the blue light-emitting element (first light-emitting element) 10B, for example, the concentration of Br. Note that the concentration of the second halogen element per unit volume of the green light-emitting layer (second light-emitting layer) 6G, for example, the concentration of Br, is an optimum concentration for improving the carrier balance between holes H and electrons E in the green light-emitting element (second light-emitting element) 10G. Furthermore, the concentration of the third halogen element per unit volume of the red light-emitting layer (third light-emitting layer) 6R provided in the red light-emitting element (third light-emitting element) 10R, for example, the concentration of I, is higher than the concentrations of the third halogen element per unit volume of the blue light-emitting layer (first light-emitting layer) 6B provided in the blue light-emitting element (first light-emitting element) 10B and the green light-emitting layer (second light-emitting layer) 6G provided in the green light-emitting element (second light-emitting element) 10G, for example, the concentration of I. The concentration of the third halogen element per unit volume of the red light-emitting layer (third light-emitting layer) 6R, for example, the concentration of I, is an optimum concentration for improving the carrier balance of holes H and electrons E in the red light-emitting element (third light-emitting element) 10R. The second halogen element may be any halogen element having a lower electronegativity than the first halogen element, and the third halogen element may be any halogen element having a lower electronegativity than both the first halogen element and the second halogen element.The electronegativity of the halogen element F is 3.98, the electronegativity of Cl is 3.16, the electronegativity of Br is 2.96, and the electronegativity of I is 2.66.

[0035] As shown in the lower diagram of FIG. 3 and the lower diagram of FIG. 4 , in this embodiment, a case where the red light-emitting layer (third light-emitting layer) 6R included in the red light-emitting element 10R of the display device 1 contains I as a third halogen element is described as an example, but is not limited thereto. As shown in the upper diagram of FIG. 3 , the difference between the energy level of the conduction band minimum (CBM) of the third quantum dots RQD included in the red light-emitting element 100R and the energy level of the conduction band minimum (CBM) of the electron transport layer (ETL) which is the first common charge transport layer 7 is not originally large, and the injection barrier of electrons E from the electron transport layer (ETL) which is the first common charge transport layer 7 is not high. Therefore, the red light-emitting layer (third light-emitting layer) 6R included in the red light-emitting element 10R of the display device 1 does not need to contain I as a third halogen element. That is, the concentration of the third halogen element per unit volume of the red light-emitting layer (third light-emitting layer) 6R, for example, the concentration of I, may be 0.

[0036] In this embodiment, the red light-emitting layer 6R of the red light-emitting element 10R, the green light-emitting layer 6G of the green light-emitting element 10G, and the blue light-emitting layer 6B of the blue light-emitting element 10B provided in the display device 1 shown in Figure 2 are formed by, for example, a lift-off method using quantum dot dispersion liquids of each color prepared using a method of exchanging the ligands of quantum dots QD with halogen ligands, which will be described later. The lift-off method is a method in which, for example, a first resist film having a first opening is formed, a first-color light-emitting layer is formed on the first resist film including the first opening, and the first resist film is peeled off to pattern the first-color light-emitting layer only in the first opening; thereafter, a second resist film having a second opening at a position different from the first opening, a second-color light-emitting layer is formed on the second resist film including the second opening, and the second resist film is peeled off to pattern the second-color light-emitting layer only in the second opening; thereafter, a third resist film having a third opening at a position different from the first opening and the second opening, a third-color light-emitting layer is formed on the third resist film including the third opening, and the third resist film is peeled off to pattern the third-color light-emitting layer only in the third opening. 2, the first halogen element Cl is contained only in the blue light-emitting layer 6B of the blue light-emitting element 10B, the second halogen element Br is contained only in the green light-emitting layer 6G of the green light-emitting element 10G, and the third halogen element I is contained only in the red light-emitting layer 6R of the red light-emitting element 10R, but this is not limitative. For example, by using a method described later in embodiment 3, the first halogen element Cl can be contained not only in the blue light-emitting layer 6B but also in the green light-emitting layer 6G and the red light-emitting layer 6R.

[0037] The concentration of the first halogen element per unit volume of the blue light-emitting layer (first light-emitting layer) 6B provided in the blue light-emitting element (first light-emitting element) 10B, for example, the concentration of Cl, the concentration of the second halogen element per unit volume of the green light-emitting layer (second light-emitting layer) 6G provided in the green light-emitting element (second light-emitting element) 10G, for example, the concentration of Br, and the concentration of the third halogen element per unit volume of the red light-emitting layer (third light-emitting layer) 6R provided in the red light-emitting element (third light-emitting element) 10R, for example, the concentration of I, are set to 10 １６ cm －３ That's it, 10 ２０ cm －３ In this embodiment, a method for preparing a dispersion of second quantum dots GQD+Br containing Br as a second halogen element and used to form the green light-emitting layer 6G of the green light-emitting element 10G will be described, but a dispersion of third quantum dots RQD+I containing I as a third halogen element and used to form the red light-emitting layer 6R of the red light-emitting element 10R, and a dispersion of first quantum dots BQD+Cl containing Cl as a first halogen element and used to form the blue light-emitting layer 6B of the blue light-emitting element 10B can also be prepared using a similar method.

[0038] First, in the first step, zinc halide (e.g., ZnBr) is dissolved in ethanol to a concentration of 0.4 M, i.e., the concentration of zinc halide per unit volume is 2.41 × 10 ２０ cm －３A zinc halide preparation solution was prepared so that the second quantum dot GQDs were dispersed in hexane. Then, in a second step, the dispersion solution of the second quantum dots GQDs made of InP was diluted 1.5 times with hexane. Then, in a third step, the dispersion solution of the second quantum dots GQDs diluted with hexane in the second step was further mixed with the same amount of ethanol as the dispersion solution of the second quantum dots GQDs diluted with hexane in the second step, and the mixture was centrifuged to precipitate the second quantum dots GQDs. Then, in a fourth step, the supernatant was removed, and an equal amount of cyclohexane was added to the hexane used in the second step to redisperse the second quantum dots GQDs, thereby obtaining a solution in which the second quantum dots GQDs were dispersed in cyclohexane. Then, in a fifth step, 0.9 μl of the zinc halide preparation solution prepared in the first step was added dropwise to the solution in which the second quantum dots GQDs were dispersed in cyclohexane, and the mixture was allowed to stand for 30 minutes. Then, in the sixth step, the solution in which the second quantum dots GQDs obtained in the fifth step were dispersed in cyclohexane was further mixed with the same amount of ethanol as the dispersion solution of the second quantum dots GQDs diluted with hexane in the second step, and centrifuged to precipitate the second quantum dots GQDs+Br containing the second halogen element Br. Thereafter, in the seventh step, octane was added so that the second quantum dots GQDs+Br containing the second halogen element Br reached a predetermined concentration, and the second quantum dots GQDs+Br containing the second halogen element Br were re-dispersed. In this embodiment, in the seventh step, in 200 μL of the octane dispersion solution of the second quantum dots GQDs+Br containing the second halogen element Br, the concentration of the second quantum dots GQDs+Br containing the second halogen element Br was 20 mg / ml, and the concentration of the second halogen element Br per unit volume was 1.1 × 10 １８ cm －３ It was made to be like this.

[0039] As described above, the carrier balance between holes H and electrons E is improved, and light-emitting efficiency and reliability can be improved in each of the blue light-emitting element (first light-emitting element) 10B, the green light-emitting element (second light-emitting element) 10G, and the red light-emitting element (third light-emitting element) 10R provided in the display device 1 shown in Figures 2, 3, and 4. Therefore, a display device 1 with reduced power consumption and improved reliability can be realized.

[0040] As shown in Figures 3 and 4, there is a difference between the energy level of the upper valence band (VBM) of the first quantum dots BQD+Cl containing Cl as the first halogen element in the blue light-emitting element (first light-emitting element) 10B, the energy level of the upper valence band (VBM) of the second quantum dots GQD+Br containing Br as the second halogen element in the green light-emitting element (second light-emitting element) 10G, and the energy level of the upper valence band (VBM) of the third quantum dots RQD+I containing I as the third halogen element in the red light-emitting element (third light-emitting element) 10R. However, for example, by selecting the material of the hole transport layer (HTL), which is the second common charge transport layer 5, in consideration of the energy level of the upper valence band (VBM) of the second quantum dots GQD+Br containing Br as the second halogen element in the green light-emitting element (second light-emitting element) 10G, it is possible to minimize the effect of an increase or decrease in the amount of hole injection caused by adding a halogen element to each color light-emitting layer.

[0041] The concentration of the first halogen element per unit volume of the blue light-emitting layer (first light-emitting layer) 6B provided in the blue light-emitting element (first light-emitting element) 10B, the concentration of the second halogen element per unit volume of the green light-emitting layer (second light-emitting layer) 6G provided in the green light-emitting element (second light-emitting element) 10G, and the concentration of the third halogen element per unit volume of the red light-emitting layer (third light-emitting layer) 6R provided in the red light-emitting element (third light-emitting element) 10R can be confirmed from the results of analysis such as TOF-SIMS or XPS, for example.

[0042] 5 is a diagram schematically illustrating quantum dots before addition of halogen elements contained in the light-emitting layers of each color provided in the display device 1 of Embodiment 1, an example of a material that can be used as the first common charge transport layer 7 and the second common charge transport layer 5, and their band levels. Fig. 6 is a diagram illustrating the degree of change in the energy level of the valence band top (VBM) of the light-emitting layers of each color provided in the display device 1 of Embodiment 1 due to the addition of various halogen elements. Fig. 7 is a diagram illustrating the degree of change in the energy levels of the valence band top (VBM) and the conduction band bottom (CBM) of the quantum dots contained in each light-emitting layer when I is added to the quantum dots contained in the red light-emitting layer 6B of the red light-emitting element 10R, Br is added to the quantum dots contained in the green light-emitting layer 6G of the green light-emitting element 10G, and Cl or F is added to the quantum dots contained in the blue light-emitting layer 6B of the blue light-emitting element 10B, all of which are provided in the display device 1 of Embodiment 1. FIG. 8 is a diagram showing the degree of change in the energy levels of the valence band upper limit (VBM) and the conduction band lower limit (CBM) of the quantum dots contained in each color light-emitting layer when Br is added to the quantum dots contained in the red light-emitting layer of a red light-emitting element 10R′, Cl is added to the quantum dots contained in the green light-emitting layer of a green light-emitting element 10G′, and F is added to the quantum dots contained in the blue light-emitting layer of a blue light-emitting element 10B′, which are provided in a display device that is another example of embodiment 1.

[0043] The data shown in Figure 6, which shows the degree of change in the energy level of the valence band top (VBM) of the light-emitting layer due to the addition of various halogen elements, was obtained by approximate calculation of the change in the energy level of the valence band top (VBM) of ZnS, which can be used as the core or shell of a quantum dot, when the halogen elements F, Cl, Br, and I are added to the ZnS. The energy level of the valence band top (VBM) can be approximated based on the following (Equation 1).

[0044] VBM = (Eh ２ +C ２ ) ０．５(Equation 1) In the above (Equation 1), Eh is the ionic bond energy and C is the covalent bond energy. In the case of ZnS, Eh = 4.82 eV, C is 6.2 eV, and the VBM value is 7.85 eV (-7.85 eV), which is almost identical to the measured value. When the Eh of ZnS was replaced with the values ​​of various halogens and the change in VBM was approximated, the results were as follows: When F was added as the halogen, the VBM was 8.58 eV (-8.58 eV), which is 0.73 eV deeper than the VBM of ZnS, and the change in the energy level of the valence band top (VBM) was -0.73 eV. When Cl was added as a halogen, the VBM became 8.13 eV (-8.13 eV), 0.28 eV deeper than that of ZnS, and the change in the energy level of the valence band (VBM) was -0.28 eV. When Br was added as a halogen, the VBM became 8.01 eV (-8.01 eV), 0.16 eV deeper than that of ZnS, and the change in the energy level of the valence band (VBM) was -0.16 eV. When I was added as a halogen, the VBM became 7.86 eV (-7.86 eV), 0.01 eV deeper than that of ZnS, and the change in the energy level of the valence band (VBM) was -0.01 eV. As described above, it can be confirmed that the greater the electronegativity of a halogen element, i.e., the lighter the halogen element, the greater the change in the energy level of the valence band (VBM) that occurs when the element is added. Note that the energy levels of the valence band (VBM) and the conduction band (CBM) change together, so the change in the energy level of the valence band (VBM) directly corresponds to the change in the energy level of the conduction band (CBM).

[0045] As shown in FIG. 5 , the energy level of the conduction band minimum (CBM) of the quantum dots (InP R) contained in the red light-emitting layer 6R of the red light-emitting element 10R is −3.6 eV, the energy level of the conduction band minimum (CBM) of the quantum dots (InP G) contained in the red light-emitting layer 6G of the green light-emitting element 10G is −3.3 eV, and the energy level of the conduction band minimum (CBM) of the quantum dots (ZnTeSe B) contained in the blue light-emitting layer 6B of the blue light-emitting element 10B is −2.7 eV. Therefore, in this embodiment, I, which causes the smallest change in the conduction band minimum (CBM) energy level when added, is added to the quantum dots (InP R) with the deepest conduction band minimum (CBM) energy level, and I, which causes the smallest change in the conduction band minimum (CBM) energy level when added, is added to the quantum dots (ZnTeSe B) with the shallowest conduction band minimum (CBM) energy level. To the quantum dot (InP R) and the quantum dot (ZnTeSe B), Cl was added, which causes a large change in the energy level of the conduction band minimum (CBM) when added, and to the quantum dot (InP G), whose energy level of the conduction band minimum (CBM) is between the quantum dot (InP R) and the quantum dot (ZnTeSe B), Br was added, which causes a medium change in the energy level of the conduction band minimum (CBM) when added, thereby achieving a good carrier balance of holes H and electrons E for each of the red light-emitting element 10R, green light-emitting element 10G, and blue light-emitting element 10B provided in the display device 1.

[0046] 7 , in each of the red light-emitting element 10R, the green light-emitting element 10G, and the blue light-emitting element 10B provided in the display device 1, after adding a halogen element to the quantum dots, the difference between the hole injection barrier and the electron injection barrier is smaller in the green light-emitting element 10G and the blue light-emitting element 10B compared to before adding a halogen element to the quantum dots, while it can be confirmed that there is almost no difference in the red light-emitting element 10R. In the case of the red light-emitting element 10R, a good carrier balance between holes H and electrons E is achieved even before adding a halogen element to the quantum dots, so it is not necessary to add a halogen element to the quantum dots. However, by adding a halogen element, which causes only a small change in the energy level of the conduction band minimum (CBM) upon addition, as in this embodiment, a good carrier balance between holes H and electrons E can be maintained. The display device 1 shown in FIG. 7 includes an electron transport layer (ETL) made of MgZnO as the first common charge transport layer 7, and a hole transport layer (HTL) made of poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(4,4′-(N-(4-sec-butylphenyl))diphenylamine)] (TFB) as the second common charge transport layer 5.

[0047] As shown in FIG. 8 , a display device that is another example of Embodiment 1 includes an electron transport layer (ETL) made of MgO as the first common charge transport layer 7, and a hole transport layer (HTL) made of poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(4,4′-(N-(4-sec-butylphenyl))diphenylamine)] (TFB) as the second common charge transport layer 5. It can also be confirmed that, in each of the red light-emitting element 10R′, green light-emitting element 10G′, and blue light-emitting element 10B′ included in the display device that is another example of Embodiment 1 shown in FIG. 8 , after adding a halogen element to the quantum dots, the difference between the hole injection barrier and the electron injection barrier is smaller in the red light-emitting element 10R′, green light-emitting element 10G′, and blue light-emitting element 10B′, compared to before adding a halogen element to the quantum dots.

[0048] As described above, in the present embodiment, the display device 1 includes an electron transport layer (ETL) as the first common charge transport layer 7 and a hole transport layer (HTL) as the second common charge transport layer 5, and a case has been described in which different halogen elements are added to the quantum dots provided in the light-emitting elements of each color to optimize the injection characteristics of electrons from the electron transport layer (ETL) that is the first common charge transport layer 7. However, the present invention is not limited to this, and for example, a different halogen element may be added to the quantum dots provided in the light-emitting elements of each color to optimize the injection characteristics of holes from the hole transport layer (HTL) that is the second common charge transport layer 5. Furthermore, when the display device 1 includes only one of the electron transport layer (ETL) that is the first common charge transport layer 7 and the hole transport layer (HTL) that is the second common charge transport layer 5, a different halogen element may be added to the quantum dots provided in the light-emitting elements of each color to optimize the injection characteristics of carriers from one of the two. In addition, in this embodiment, an example is described in which an electron transport layer (ETL) is provided as the first common charge transport layer 7 and a hole transport layer (HTL) is provided as the second common charge transport layer 5 for each of the red light-emitting element 10R, the green light-emitting element 10G, and the blue light-emitting element 10B, but this is not limited to this, and only two of the red light-emitting element 10R, the green light-emitting element 10G, and the blue light-emitting element 10B may have an electron transport layer (ETL) as the first common charge transport layer 7 or a hole transport layer (HTL) as the second common charge transport layer 5.

[0049] In this embodiment, the first quantum dots in the blue light-emitting layer 6B, the second quantum dots in the green light-emitting layer 6G, and the third quantum dots in the red light-emitting layer 6R are described as having a core structure. However, this is not limiting, and quantum dots having a core-shell structure may also be used. For example, as described above with reference to FIG. 6 , even when quantum dots having a core-shell structure are used, the addition of a halogen element can adjust the energy levels of the valence band upper limit (VBM) and the conduction band lower limit (CBM) of ZnS, thereby achieving the same effect as when quantum dots having a core structure are used. The shell may be composed of, for example, silicon oxide, and the addition of a halogen element to silicon oxide can adjust the energy levels of the valence band upper limit (VBM) and the conduction band lower limit (CBM) of silicon oxide.

[0050] Second Embodiment FIG. 9 is a cross-sectional view showing a schematic configuration of a display area DA of a display device 1a according to a second embodiment.

[0051] 9 , the display device 1a includes a red light-emitting element 20R, a green light-emitting element 20G, and a blue light-emitting element 20B. A peripheral region NHR is provided between any two adjacent light-emitting elements among the red light-emitting element 20R, the green light-emitting element 20G, and the blue light-emitting element 20B. The peripheral region NHR includes a laminated portion where the light-emitting layers included in each of the adjacent two light-emitting elements are laminated. That is, the peripheral region NHR between the red light-emitting element 20R and the green light-emitting element 20G includes a laminated portion where the red light-emitting layer 6R′ and the green light-emitting layer 6G′ are laminated, the peripheral region NHR between the green light-emitting element 20G and the blue light-emitting element 20B includes a laminated portion where the green light-emitting layer 6G′ and the blue light-emitting layer 6B′ are laminated, and the peripheral region NHR between the blue light-emitting element 20B and the red light-emitting element 20R includes a laminated portion where the blue light-emitting layer 6B′ and the red light-emitting layer 6R′ are laminated. The red light-emitting layer 6R' is made of the same material as the red light-emitting layer 6R described above in embodiment 1, the green light-emitting layer 6G' is made of the same material as the green light-emitting layer 6G described above in embodiment 1, and the blue light-emitting layer 6B' is made of the same material as the blue light-emitting layer 6B described above in embodiment 1. The peripheral region NHR includes the bank 4 and two or more of the red light-emitting layer 6R', the green light-emitting layer 6G', and the blue light-emitting layer 6B' provided on the bank 4. The peripheral region NHR is a region having lower luminous efficiency than the red light-emitting region RHR, the green light-emitting region GHR, and the blue light-emitting region BHR, and may be a non-luminescent region.

[0052] The peripheral region NHR provided in the display device 1a includes a stacked portion in which light-emitting layers of multiple colors are stacked, and therefore the leakage current LCR in the peripheral region NHR can be suppressed and the current CR in each of the red light-emitting region RHR, green light-emitting region GHR, and blue light-emitting region BHR can be increased, thereby further improving the light-emitting efficiency of the red light-emitting element 20R, green light-emitting element 20G, and blue light-emitting element 20B, and further realizing low power consumption of the display device 1a.

[0053] In this embodiment, as shown in FIG. 9, the case where the peripheral region NHR includes a laminated portion in which light-emitting layers of two colors are stacked has been described as an example, but this is not limited to this, and the peripheral region NHR may also include a laminated portion in which light-emitting layers of three colors are stacked, that is, a laminated portion in which a red light-emitting layer 6R', a green light-emitting layer 6G', and a blue light-emitting layer 6B' are stacked.

[0054] Third Embodiment FIG. 10 is a cross-sectional view showing a schematic configuration of a display area DA of a display device 1b according to a third embodiment.

[0055] 10 , the display device 1b includes a red light-emitting element 30R, a green light-emitting element 30G, and a blue light-emitting element 30B, and a peripheral region NHR is provided between any two adjacent light-emitting elements among the red light-emitting element 30R, the green light-emitting element 30G, and the blue light-emitting element 30B. The light-emitting layers of the adjacent two light-emitting elements extend into the peripheral region NHR. The blue light-emitting layer 6Bi of the blue light-emitting element 30B, i.e., the blue light-emitting layer 6Bi in the blue light-emitting region BHR of the blue light-emitting element 30B, has a higher concentration of the first halogen element per unit volume, e.g., Cl, than the concentration of the first halogen element per unit volume of the blue light-emitting layer 6BN in the peripheral region NHR. The concentration of the second halogen element, for example, the concentration of Br, per unit volume of the green light-emitting layer 6Gi provided in the green light-emitting element 30G, i.e., the green light-emitting layer 6Gi provided in the green light-emitting region GHR of the green light-emitting element 30G, is higher than the concentration of the second halogen element, for example, the concentration of Br, per unit volume of the green light-emitting layer 6GN in the peripheral region NHR. The concentration of the third halogen element, for example, the concentration of I, per unit volume of the red light-emitting layer 6Ri provided in the red light-emitting element 30R, i.e., the red light-emitting layer 6Ri provided in the red light-emitting region RHR of the red light-emitting element 30R, is higher than the concentration of the third halogen element, for example, the concentration of I, per unit volume of the red light-emitting layer 6RN in the peripheral region NHR.

[0056] According to the display device 1b, abnormal light emission in the peripheral region NHR can be suppressed, and low power consumption and improved reliability can be achieved.

[0057] The film formation methods for the red light-emitting layers 6Ri and 6RN, the green light-emitting layers 6Gi and 6GN, and the blue light-emitting layers 6Bi and 6BN provided in the display device 1b are different from the film formation methods for the red light-emitting layers 6R and 6R', the green light-emitting layers 6G and 6G', and the blue light-emitting layers 6B and 6B' in the above-described embodiments 1 and 2. To form the red light-emitting layers 6Ri and 6RN, the green light-emitting layers 6Gi and 6GN, and the blue light-emitting layers 6Bi and 6BN, respectively, a dispersion of red light-emitting quantum dots, a dispersion of blue light-emitting quantum dots, a preparation liquid containing a first halogen element, a preparation liquid containing a second halogen element, and a preparation liquid containing a third halogen element are prepared. First, the dispersion of red light-emitting quantum dots, the dispersion of blue light-emitting quantum dots, and the dispersion of blue light-emitting quantum dots are sequentially used to form the red light-emitting layers, green light-emitting layers, and blue light-emitting layers in predetermined shapes by, for example, a lift-off method. Thereafter, a preparation liquid containing a third halogen element is dropped, for example, by an ink-jet method, only into the red light-emitting region RHR of the red light-emitting layer to form red light-emitting layers 6Ri and 6RN, a preparation liquid containing a second halogen element is dropped, for example, by an ink-jet method, only into the green light-emitting region GHR of the green light-emitting layer to form green light-emitting layers 6Gi and 6GN, and a preparation liquid containing a first halogen element is dropped, for example, by an ink-jet method, only into the blue light-emitting region BHR of the blue light-emitting layer to form blue light-emitting layers 6Bi and 6BN. Thereafter, rinsing may be performed using a solution such as ethanol.

[0058] 10 , the concentration of the second halogen element per unit volume of the blue light-emitting layer 6BN in the peripheral region NHR between the blue light-emitting element 30B and the green light-emitting element 30G, e.g., the concentration of Br, may be higher than the concentration of the second halogen element per unit volume of the blue light-emitting layer 6Bi in the blue light-emitting element 30B. The concentration of the first halogen element per unit volume of the green light-emitting layer 6GN in the peripheral region NHR between the blue light-emitting element 30B and the green light-emitting element 30G, e.g., the concentration of Cl, may be higher than the concentration of the first halogen element per unit volume of the green light-emitting layer 6Gi in the green light-emitting element 30G. The concentration of the third halogen element per unit volume of the green light-emitting layer 6GN in the peripheral region NHR between the green light-emitting element 30G and the red light-emitting element 30R, e.g., the concentration of I, may be higher than the concentration of the third halogen element per unit volume of the green light-emitting layer 6Gi in the green light-emitting element 30G. The concentration of the second halogen element per unit volume of the red light-emitting layer 6RN in the peripheral region NHR between the green light-emitting element 30G and the red light-emitting element 30R, e.g., the concentration of Br, may be higher than the concentration of the second halogen element per unit volume of the red light-emitting layer 6Ri provided in the red light-emitting element 30R, e.g., the concentration of Br. The concentration of the first halogen element per unit volume of the red light-emitting layer 6RN in the peripheral region NHR between the red light-emitting element 30R and the blue light-emitting element 30B, e.g., the concentration of Cl, may be higher than the concentration of the first halogen element per unit volume of the red light-emitting layer 6Ri provided in the red light-emitting element 30R, e.g., the concentration of Cl. The concentration of the third halogen element per unit volume of the blue light-emitting layer 6BN in the peripheral region NHR between the red light-emitting element 30R and the blue light-emitting element 30B, e.g., the concentration of I, may be higher than the concentration of the third halogen element per unit volume of the blue light-emitting layer 6Bi provided in the blue light-emitting element 30B, e.g., the concentration of I. The display device having such a configuration can suppress abnormal light emission in the peripheral region NHR, thereby realizing low power consumption and improved reliability. Note that the display device having such a configuration can be obtained by, for example, transferring a small amount of halogen elements through the solution during the rinsing process using the above-mentioned solution such as ethanol.

[0059] Fourth Embodiment FIG. 11 is a cross-sectional view showing a schematic configuration of a display area DA of a display device 1c according to a fourth embodiment.

[0060] The display device 1c shown in Figure 11 includes a red light-emitting element 40R, a green light-emitting element 40G, and a blue light-emitting element 40B. The concentration of the third halogen element per unit volume contained in the red light-emitting layer 6Rs of the red light-emitting element 40R, for example, the concentration of I, is higher on the first common charge transport layer 7 side of the red light-emitting layer 6Rs than on the second common charge transport layer 5 side of the red light-emitting layer 6Rs. The concentration of the second halogen element per unit volume contained in the green light-emitting layer 6Gs of the green light-emitting element 40G, for example, the concentration of Br, is higher on the first common charge transport layer 7 side of the green light-emitting layer 6Gs than on the second common charge transport layer 5 side of the green light-emitting layer 6Gs. The concentration of the first halogen element per unit volume contained in the blue light-emitting layer 6Bs of the blue light-emitting element 40B, for example, the concentration of Cl, is higher on the first common charge transport layer 7 side of the blue light-emitting layer 6Bs than on the second common charge transport layer 5 side of the blue light-emitting layer 6Bs. That is, the first common charge transport layer 7 provided in the display device 1c is an electron transport layer or an electron injection layer, and each of the red light-emitting element 40R, the green light-emitting element 40G, and the blue light-emitting element 40B includes a second common charge transport layer 5 in contact with the blue light-emitting layer 6Bs, the green light-emitting layer 6Gs, and the red light-emitting layer 6Rs from a second side opposite to a first side where the first common charge transport layer 7 is in contact with the blue light-emitting layer 6Bs, the green light-emitting layer 6Gs, and the red light-emitting layer 6Rs, respectively, and the second common charge transport layer 5 is a hole transport layer or a hole injection layer. In each of the blue light-emitting layer 6Bs, the green light-emitting layer 6Gs, and the red light-emitting layer 6Rs, the concentration of halogen elements per unit volume contained in the side in contact with the first common charge transport layer 7 is higher than the concentration of halogen elements per unit volume contained in the side in contact with the second common charge transport layer 5. The blue light-emitting layer 6Bs, the green light-emitting layer 6Gs, and the red light-emitting layer 6Rs provided in the display device 1c each have a stepped energy level, which increases the amount of electron injection and enables even lower voltage driving. Therefore, the display device 1c can achieve even lower power consumption.

[0061] The blue light-emitting layer 6Bs, the green light-emitting layer 6Gs, and the red light-emitting layer 6Rs included in the display device 1c can be formed as follows: After forming a first resist film including first openings, a red light-emitting layer is formed in the first openings and on the first resist film using a dispersion of red-emitting quantum dots. The red light-emitting layer containing the third halogen element is then formed by immersing the resist film in a preparation solution containing a third halogen element, such as I, and the first resist film is then peeled off, thereby patterning the red light-emitting layer containing the third halogen element. After that, a second resist film including second openings is formed, a green light-emitting layer is formed in the second openings and on the second resist film using a dispersion of green-emitting quantum dots. The green light-emitting layer containing the second halogen element is then formed by immersing the resist film in a preparation solution containing a second halogen element, such as Br, and the second resist film is then peeled off, thereby patterning the green light-emitting layer containing the second halogen element. Then, a third resist film including a third opening is formed, and then a blue light-emitting layer is formed in the third opening and on the third resist film using a dispersion of blue light-emitting quantum dots. Then, the blue light-emitting layer containing the first halogen element is formed by immersing the substrate in a preparation solution containing a first halogen element, for example, Cl, and then the third resist film is peeled off, thereby patterning the blue light-emitting layer containing the first halogen element. After forming the light-emitting layer, the substrate is immersed in the preparation solution containing a halogen element or the preparation solution containing a halogen element is applied using spin coating or the like, and the preparation solution containing a halogen element penetrates into the gaps between the quantum dots and causes ligand exchange, so that the concentration of the halogen element on the surface side of the light-emitting layer is increased, and a concentration distribution of the halogen element is formed in the thickness direction of the light-emitting layer.

[0062] [Embodiment 5] Fig. 12 is a cross-sectional view showing a schematic configuration of a display area DA of a display device 1d of embodiment 5. Fig. 13 is a diagram for explaining the pattern of halogen elements mixed into the first-formed light-emitting layer (first color light-emitting layer) and the second-formed light-emitting layer (second color light-emitting layer) among the red light-emitting layer 6Rm, the green light-emitting layer 6Gm, and the blue light-emitting layer 6Bm in the manufacturing process of the display device 1d of embodiment 5 shown in Fig. 12. Fig. 14 is a diagram for explaining the pattern of halogen elements mixed into each color light-emitting layer depending on the formation order of the red light-emitting layer 6Rm, the green light-emitting layer 6Gm, and the blue light-emitting layer 6Bm when I is added to the red light-emitting layer 6Rm, Br is added to the green light-emitting layer 6Gm, and Cl is added to the blue light-emitting layer 6Bm in the manufacturing process of the display device 1d of embodiment 5 shown in Fig. 12.

[0063] As shown in Figures 12, 13, and 14, for example, in a display device 1d, when the color light-emitting layers are formed in the order of red light-emitting layer 6Rm, green light-emitting layer 6Gm, and blue light-emitting layer 6Bm (R → G → B), a first halogen element, for example, Cl, is contained in the blue light-emitting layer 6Bm, green light-emitting layer 6Gm, and red light-emitting layer 6Rm, a second halogen element, for example, Br, is contained in the green light-emitting layer 6Gm and red light-emitting layer 6Rm, and a third halogen element, for example, I, is contained only in the red light-emitting layer 6Rm. The concentration of the third halogen element per unit volume of the red light-emitting layer 6Rm, for example, the concentration of I, is higher than the concentration of the second halogen element per unit volume of the red light-emitting layer 6Rm, for example, the concentration of Br, and the concentration of the first halogen element per unit volume of the red light-emitting layer 6Rm, for example, the concentration of Cl, respectively, and the concentration of the second halogen element per unit volume of the green light-emitting layer 6Gm, for example, the concentration of Br, is higher than the concentration of the first halogen element per unit volume of the green light-emitting layer 6Gm, for example, the concentration of Cl. The light-emitting layers of each color having such a configuration can be formed, for example, by the following manufacturing process. The steps of patterning a first quantum dot layer included in the red light-emitting layer 6Rm, immersing the first quantum dot layer in a solution containing I, patterning a second quantum dot layer included in the green light-emitting layer 6Gm, immersing the second quantum dot layer in a solution containing Br, patterning a third quantum dot layer included in the blue light-emitting layer 6Bm, and immersing the third quantum dot layer in a solution containing Cl may be performed in this order. In the step of immersing the second quantum dot layer in the solution containing Br, the previously formed first quantum dot layer is also immersed in the solution containing Br. However, because the first quantum dot layer has already been treated with the solution containing I, defective portions of the quantum dots included in the first quantum dot layer that are not modified with I are modified with Br. Furthermore, in the step of immersing the third quantum dot layer in a solution containing Cl, the previously formed first quantum dot layer is also immersed in a solution containing Cl. However, since the first quantum dot layer has already been treated with a solution containing I and a solution containing Br, the quantum dots contained in the first quantum dot layer have defect portions that are not modified with I and Br modified with Cl.Furthermore, in the step of immersing the third quantum dot layer in a solution containing Cl, the previously formed second quantum dot layer is also immersed in a solution containing Cl, but because the second quantum dot layer has already been treated with a solution containing Br, defective portions of the quantum dots contained in the second quantum dot layer that are not modified with Br are modified with Cl. Therefore, the concentration of I per unit volume of the red light-emitting layer 6Rm is higher than the concentration of Br per unit volume of the red light-emitting layer 6Rm and the concentration of Cl per unit volume of the red light-emitting layer 6Rm, and the concentration of Br per unit volume of the green light-emitting layer 6Gm is higher than the concentration of Cl per unit volume of the green light-emitting layer 6Gm. As will be described later, when the light-emitting layers of each color are formed in an order other than the order of red light-emitting layer 6Rm, green light-emitting layer 6Gm, and blue light-emitting layer 6Bm (R → G → B), a step of patterning and forming a quantum dot layer included in the light-emitting layer of the corresponding color and a step of immersing the quantum dot layer included in the light-emitting layer of the corresponding color in a solution containing a halogen element may be performed in accordance with the order.

[0064] As shown in Figures 12, 13, and 14, for example, in a display device 1d, when the color light-emitting layers are formed in the order of red light-emitting layer 6Rm, blue light-emitting layer 6Bm, and green light-emitting layer 6Gm (R → B → G), a second halogen element, for example, Br, is contained in the blue light-emitting layer 6Bm, green light-emitting layer 6Gm, and red light-emitting layer 6Rm, a first halogen element, for example, Cl, is contained in the blue light-emitting layer 6Bm and red light-emitting layer 6Rm, and a third halogen element, for example, I, is contained only in the red light-emitting layer 6Rm. The concentration of the third halogen element per unit volume of the red light-emitting layer 6Rm, for example, the concentration of I, is higher than the concentration of the second halogen element per unit volume of the red light-emitting layer 6Rm, for example, the concentration of Br, and the concentration of the first halogen element per unit volume of the red light-emitting layer 6Rm, for example, the concentration of Cl, and the concentration of the first halogen element per unit volume of the blue light-emitting layer 6Bm, for example, the concentration of Cl, is higher than the concentration of the second halogen element per unit volume of the blue light-emitting layer 6Bm, for example, the concentration of Br.

[0065] As shown in Figures 12, 13, and 14, for example, in a display device 1d, when the color light-emitting layers are formed in the order of a green light-emitting layer 6Gm, a red light-emitting layer 6Rm, and a blue light-emitting layer 6Bm (G → R → B), a first halogen element, for example, Cl, is contained in the blue light-emitting layer 6Bm, the green light-emitting layer 6Gm, and the red light-emitting layer 6Rm, a second halogen element, for example, Br, is contained only in the green light-emitting layer 6Gm, and a third halogen element, for example, I, is contained in the green light-emitting layer 6Gm and the red light-emitting layer 6Rm. The concentration of the second halogen element per unit volume of the green light-emitting layer 6Gm, for example, the concentration of Br, is higher than the concentration of the first halogen element per unit volume of the green light-emitting layer 6Gm, for example, the concentration of Cl, and the concentration of the third halogen element per unit volume of the green light-emitting layer 6Gm, for example, the concentration of I, and the concentration of the third halogen element per unit volume of the red light-emitting layer 6Rm, for example, the concentration of I, is higher than the concentration of the first halogen element per unit volume of the red light-emitting layer 6Rm, for example, the concentration of Cl.

[0066] As shown in Figures 12, 13, and 14, for example, in a display device 1d, when the color light-emitting layers are formed in the order of green light-emitting layer 6Gm, blue light-emitting layer 6Bm, and red light-emitting layer 6Rm (G → B → R), a third halogen element, for example, I, is contained in the blue light-emitting layer 6Bm, green light-emitting layer 6Gm, and red light-emitting layer 6Rm, a first halogen element, for example, Cl, is contained in the blue light-emitting layer 6Bm and green light-emitting layer 6Gm, and a second halogen element, for example, Br, is contained only in the green light-emitting layer 6Gm. The concentration of the second halogen element per unit volume of the green light-emitting layer 6Gm, for example, the concentration of Br, is higher than the concentration of the first halogen element per unit volume of the green light-emitting layer 6Gm, for example, the concentration of Cl, and the concentration of the third halogen element per unit volume of the green light-emitting layer 6Gm, for example, the concentration of I, respectively, and the concentration of the first halogen element per unit volume of the blue light-emitting layer 6Bm, for example, the concentration of Cl, is higher than the concentration of the third halogen element per unit volume of the blue light-emitting layer 6Bm, for example, the concentration of I.

[0067] As shown in Figures 12, 13, and 14, for example, in a display device 1d, when the color light-emitting layers are formed in the order of blue light-emitting layer 6Bm, red light-emitting layer 6Rm, and green light-emitting layer 6Gm (B → R → G), a second halogen element, for example, Br, is contained in the blue light-emitting layer 6Bm, green light-emitting layer 6Gm, and red light-emitting layer 6Rm, a third halogen element, for example, I, is contained in the blue light-emitting layer 6Bm and red light-emitting layer 6Rm, and a first halogen element, for example, Cl, is contained only in the blue light-emitting layer 6Bm. The concentration of the first halogen element per unit volume of the blue light-emitting layer 6Bm, for example, the concentration of Cl, is higher than the concentration of the second halogen element per unit volume of the blue light-emitting layer 6Bm, for example, the concentration of Br, and the concentration of the third halogen element per unit volume of the blue light-emitting layer 6Bm, for example, the concentration of I, and the concentration of the third halogen element per unit volume of the red light-emitting layer 6Rm, for example, the concentration of I, is higher than the concentration of the second halogen element per unit volume of the red light-emitting layer 6Rm, for example, the concentration of Br.

[0068] As shown in Figures 12, 13, and 14, for example, in a display device 1d, when the color light-emitting layers are formed in the order of blue light-emitting layer 6Bm, green light-emitting layer 6Gm, and red light-emitting layer 6Rm (B → G → R), a third halogen element, for example, I, is contained in the blue light-emitting layer 6Bm, green light-emitting layer 6Gm, and red light-emitting layer 6Rm, a second halogen element, for example, Br, is contained in the blue light-emitting layer 6Bm and green light-emitting layer 6Gm, and a first halogen element, for example, Cl, is contained only in the blue light-emitting layer 6Bm. The concentration of the first halogen element per unit volume of the blue light-emitting layer 6Bm, for example, the concentration of Cl, is higher than the concentration of the second halogen element per unit volume of the blue light-emitting layer 6Bm, for example, the concentration of Br, and the concentration of the third halogen element per unit volume of the blue light-emitting layer 6Bm, for example, the concentration of I, respectively, and the concentration of the second halogen element per unit volume of the green light-emitting layer 6Gm, for example, the concentration of Br, is higher than the concentration of the third halogen element per unit volume of the green light-emitting layer 6Gm, for example, the concentration of I.

[0069] According to the display device 1d described above, defects in quantum dots can be terminated with a plurality of types of halogen elements in light-emitting elements of two or more colors.

[0070] Sixth Embodiment FIG. 15 is a diagram showing an example of a method for manufacturing a red light-emitting layer including a matrix, a green light-emitting layer including a matrix, and a blue light-emitting layer including a matrix, which are provided in a display device of a sixth embodiment.

[0071] As shown in FIG. 15 , for example, a quantum dot dispersion 61 containing a matrix precursor is applied onto the second common charge transport layer 5. The quantum dot dispersion 61 containing a matrix precursor includes surface-modified quantum dots MQD1, a matrix precursor MRM1, and a solvent. The surface-modified quantum dots MQD1 are quantum dots whose periphery is coated with ZnS, and the matrix precursor MRM1 is zinc xanthogenate (decomposition temperature 200°C). The applied quantum dot dispersion 61 is subjected to a heat treatment or an exposure treatment using light in a predetermined wavelength range to obtain an emissive layer 62 containing quantum dots and a matrix (e.g., ZnS). The emissive layer containing the quantum dots and a matrix (e.g., ZnS) is then subjected to a halogen element treatment. The halogen element treatment refers to a treatment using a preparation solution containing a halogen element. As described with reference to FIG. 6 in the first embodiment, the energy levels of the valence band upper limit (VBM) and the conduction band lower limit (CBM) of the matrix (e.g., ZnS) contained in the light-emitting layer can also be adjusted by adding a halogen element.

[0072] FIG. 16 is a diagram showing another example of a method for manufacturing a red light-emitting layer including a matrix, a green light-emitting layer including a matrix, and a blue light-emitting layer including a matrix, which are provided in the display device of the sixth embodiment.

[0073] For example, a quantum dot dispersion 71 containing a matrix precursor as shown in FIG. 16 is applied onto the second common charge transport layer 5. The quantum dot dispersion 71 containing a matrix precursor contains surface-modified quantum dots MQD2, matrix precursors MRM2 and MRM3, and a solvent. The surface-modified quantum dots MQD2 are quantum dots whose peripheries are coated with silicon oxide. The matrix precursor MRM2 is (3-mercaptopropyl)trimethoxysilane, and the matrix precursor MRM3 is tetramethyl orthosilicate. The applied quantum dot dispersion 71 is subjected to a heat treatment or an exposure treatment using light in a predetermined wavelength range to obtain an emissive layer 72 containing quantum dots and a matrix (e.g., a silicon oxide network). The emissive layer containing quantum dots and a matrix (e.g., silicon oxide) is then subjected to a halogen element treatment. The matrix (for example, silicon oxide) contained in the light-emitting layer can also be doped with a halogen element to adjust the energy levels of the valence band upper limit (VBM) and the conduction band lower limit (CBM).

[0074] FIG. 17 is a diagram showing yet another example of a method for manufacturing a red light-emitting layer including a matrix, a green light-emitting layer including a matrix, and a blue light-emitting layer including a matrix, which are provided in the display device of Embodiment 6.

[0075] As shown in FIG. 17 , a quantum dot layer 80 containing organic ligands coated on a second common charge transport layer 5 is immersed in a high-concentration zinc xanthate solution 81 to perform ligand exchange of the organic ligands. The concentration of zinc xanthate in the high-concentration zinc xanthate solution 81 should be higher than the concentration of the organic ligands during the immersion process. Furthermore, a solvent that has proton-donating properties and desorbs the organic ligands is preferably used as the solvent for the high-concentration zinc xanthate solution 81. After the immersion process, a solvent removal process is performed, followed by heat treatment or exposure to light in a predetermined wavelength range to obtain a light-emitting layer 83 containing quantum dots and a matrix (e.g., ZnS). The light-emitting layer containing quantum dots and a matrix (e.g., ZnS) is then subjected to a halogen element treatment. As described with reference to FIG. 6 in the first embodiment, the addition of a halogen element to the matrix (e.g., ZnS) in the light-emitting layer can also adjust the energy levels of the valence band top (VBM) and the conduction band bottom (CBM).

[0076] As described above, it is preferable that each of the red light-emitting layer, the green light-emitting layer, and the blue light-emitting layer included in the display device of embodiment 6 includes a matrix. With such a configuration, a more reliable display device can be realized.

[0077] It is more preferable that each of the red light-emitting layer, the green light-emitting layer, and the blue light-emitting layer provided in the display device of embodiment 6 contains an inorganic matrix, since this can further improve reliability.

[0078] The inorganic matrix may be a metalloid chalcogenide, which may be a metalloid oxide or a metalloid sulfide. The metalloid oxide may be a semiconductor oxide, which may be silicon oxide. Examples of the metalloids include B, Si, Ge, As, Sb, and Te.

[0079] The inorganic matrix may also be a metal chalcogenide, which may be a metal oxide or a metal sulfide.

[0080] [Additional Notes] The present disclosure is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present disclosure. Furthermore, new technical features can be formed by combining the technical means disclosed in each embodiment.

[0081] The present disclosure can be used in a display device.

[0082] REFERENCE SIGNS LIST 1, 1a to 1d display device 2 substrate including thin film transistor layer 3 lower electrode 4 bank 5 second common charge transport layer 6R, 6R', 6Ri, 6Rs, 6Rm red light-emitting layer 6G, 6G', 6Gi, 6Gs, 6Gm green light-emitting layer 6B, 6B', 6Bi, 6Bs, 6Bm blue light-emitting layer 7 first common charge transport layer 8 upper electrode 10R, 10R' red light-emitting element (third light-emitting element) 10G, 10G' green light-emitting element (second light-emitting element) 10B, 10B' blue light-emitting element (first light-emitting element) 20R, 30R, 40R, 50R red light-emitting element (third light-emitting element) 20G, 30G, 40G, 50G green light-emitting element (second light-emitting element) 20B, 30B, 40B, 50B blue light-emitting element (first light-emitting element) 61, 71 Quantum dot dispersion containing matrix precursor 80 Quantum dot layer containing organic ligand 81 High concentration zinc xanthate solution 82 Light-emitting layer containing quantum dots and matrix precursor 62, 72, 83 Light-emitting layer containing quantum dots and matrix QD Quantum dot MQD1, MQD2 Surface-modified quantum dots MRM1 to MRM3 Matrix precursors PIX Pixel RSP Red subpixel GSP Green subpixel BSP Blue subpixel DA Display area NDA Frame area RHR Red light-emitting area GHR Green light-emitting area BHR Blue light-emitting area NHR Peripheral area

Claims

1. A display device comprising: a first light-emitting element having a first light-emitting layer containing first quantum dots; a second light-emitting element having a second light-emitting layer containing second quantum dots and emitting light of a different color from the light emitted by the first light-emitting layer and having a peak wavelength longer than the peak wavelength of the light emitted by the first light-emitting layer; and a first common charge transport layer provided as a layer common to both the first light-emitting element and the second light-emitting element, wherein the concentration of a first halogen element per unit volume of the first light-emitting layer is higher than the concentration of the first halogen element per unit volume of the second light-emitting layer.

2. The display device according to claim 1, wherein the first common charge transport layer is in contact with each of the first light-emitting layer and the second light-emitting layer.

3. A display device as described in claim 1 or 2, wherein the second halogen element is a halogen element having a lower electronegativity than the first halogen element, and the concentration of the second halogen element per unit volume of the second light-emitting layer is higher than the concentration of the second halogen element per unit volume of the first light-emitting layer.

4. The display device according to claim 3, comprising a third light-emitting element including a third quantum dot, the third light-emitting layer emitting light of a color different from that of light emitted by the first light-emitting layer and the second light-emitting layer, and having a peak wavelength longer than that of the light emitted by the second light-emitting layer, wherein the first light-emitting element, the second light-emitting element, and the third light-emitting element each include the first common charge transport layer in contact with the first light-emitting layer, the second light-emitting layer, and the third light-emitting layer, respectively, and the concentration of halogen elements per unit volume of the third light-emitting layer is 0.

5. The display device according to claim 3, comprising a third light-emitting element including a third quantum dot, the third light-emitting layer emitting light of a different color from light emitted by each of the first light-emitting layer and the second light-emitting layer, and having a peak wavelength longer than the peak wavelength of light emitted by the second light-emitting layer; each of the first light-emitting element, the second light-emitting element, and the third light-emitting element includes the first common charge transport layer in contact with the first light-emitting layer, the second light-emitting layer, and the third light-emitting layer, respectively; the third halogen element is a halogen element having a lower electronegativity than each of the first halogen element and the second halogen element; and the concentration of the third halogen element per unit volume of the third halogen element is higher than the concentration of the third halogen element per unit volume of the first light-emitting layer and the concentration of the third halogen element per unit volume of the second light-emitting layer, respectively.

6. The display device according to claim 3, comprising a third light-emitting element including a third quantum dot, the third light-emitting layer emitting light of a different color from light emitted by each of the first light-emitting layer and the second light-emitting layer and having a peak wavelength longer than the peak wavelength of light emitted by the second light-emitting layer, wherein the first light-emitting element, the second light-emitting layer, and the third light-emitting element each include the first common charge transport layer in contact with the first light-emitting layer, the second light-emitting layer, and the third light-emitting layer, respectively, the third halogen element being a halogen element having a lower electronegativity than each of the first halogen element and the second halogen element, the first halogen element being contained only in the first light-emitting layer, the second halogen element being contained only in the second light-emitting layer, and the third halogen element being contained only in the third light-emitting layer.

7. The display device described in claim 5, wherein the first halogen element is contained in the first light-emitting layer, the second light-emitting layer, and the third light-emitting layer; the second halogen element is contained in the second light-emitting layer and the third light-emitting layer; the third halogen element is contained only in the third light-emitting layer; the concentration of the third halogen element per unit volume of the third light-emitting layer is higher than the concentration of the second halogen element per unit volume of the third light-emitting layer and the concentration of the first halogen element per unit volume of the third light-emitting layer; and the concentration of the second halogen element per unit volume of the second light-emitting layer is higher than the concentration of the first halogen element per unit volume of the second light-emitting layer.

8. The display device described in claim 5, wherein the second halogen element is contained in the first light-emitting layer, the second light-emitting layer, and the third light-emitting layer; the first halogen element is contained in the first light-emitting layer and the third light-emitting layer; the third halogen element is contained only in the third light-emitting layer; the concentration of the third halogen element per unit volume of the third light-emitting layer is higher than the concentration of the second halogen element per unit volume of the third light-emitting layer and the concentration of the first halogen element per unit volume of the third light-emitting layer; and the concentration of the first halogen element per unit volume of the first light-emitting layer is higher than the concentration of the second halogen element per unit volume of the first light-emitting layer.

9. The display device described in claim 5, wherein the first halogen element is contained in the first light-emitting layer, the second light-emitting layer, and the third light-emitting layer; the second halogen element is contained only in the second light-emitting layer; the third halogen element is contained in the second light-emitting layer and the third light-emitting layer; the concentration of the second halogen element per unit volume of the second light-emitting layer is higher than the concentration of the first halogen element per unit volume of the second light-emitting layer and the concentration of the third halogen element per unit volume of the second light-emitting layer; and the concentration of the third halogen element per unit volume of the third light-emitting layer is higher than the concentration of the first halogen element per unit volume of the third light-emitting layer.

10. The display device described in claim 5, wherein the third halogen element is contained in the first light-emitting layer, the second light-emitting layer, and the third light-emitting layer; the first halogen element is contained in the first light-emitting layer and the second light-emitting layer; the second halogen element is contained only in the second light-emitting layer; the concentration of the second halogen element per unit volume of the second light-emitting layer is higher than the concentration of the first halogen element per unit volume of the second light-emitting layer and the concentration of the third halogen element per unit volume of the second light-emitting layer; and the concentration of the first halogen element per unit volume of the first light-emitting layer is higher than the concentration of the third halogen element per unit volume of the first light-emitting layer.

11. The display device described in claim 5, wherein the second halogen element is contained in the first light-emitting layer, the second light-emitting layer, and the third light-emitting layer; the third halogen element is contained in the first light-emitting layer and the third light-emitting layer; the first halogen element is contained only in the first light-emitting layer; the concentration of the first halogen element per unit volume of the first light-emitting layer is higher than the concentration of the second halogen element per unit volume of the first light-emitting layer and the concentration of the third halogen element per unit volume of the first light-emitting layer; and the concentration of the third halogen element per unit volume of the third light-emitting layer is higher than the concentration of the second halogen element per unit volume of the third light-emitting layer.

12. The display device described in claim 5, wherein the third halogen element is contained in the first light-emitting layer, the second light-emitting layer, and the third light-emitting layer; the second halogen element is contained in the first light-emitting layer and the second light-emitting layer; the first halogen element is contained only in the first light-emitting layer; the concentration of the first halogen element per unit volume of the first light-emitting layer is higher than the concentration of the second halogen element per unit volume of the first light-emitting layer and the concentration of the third halogen element per unit volume of the first light-emitting layer; and the concentration of the second halogen element per unit volume of the second light-emitting layer is higher than the concentration of the third halogen element per unit volume of the second light-emitting layer.

13. A display device according to any one of claims 4 to 12, wherein a peripheral region is provided between two adjacent light-emitting elements among the first light-emitting element, the second light-emitting element and the third light-emitting element, and the peripheral region includes a laminated portion in which the light-emitting layers provided in each of the two adjacent light-emitting elements are laminated.

14. A display device according to any one of claims 5 to 12, wherein a peripheral region is provided between two adjacent light-emitting elements among the first light-emitting element, the second light-emitting element, and the third light-emitting element, and the light-emitting layers of the two adjacent light-emitting elements extend into the peripheral region, and the concentration of the first halogen element per unit volume of the first light-emitting layer of the first light-emitting element is higher than the concentration of the first halogen element per unit volume of the first light-emitting layer in the peripheral region, and the concentration of the second halogen element per unit volume of the second light-emitting layer of the second light-emitting element is higher than the concentration of the second halogen element per unit volume of the second light-emitting layer in the peripheral region, and the concentration of the third halogen element per unit volume of the third light-emitting layer of the third light-emitting element is higher than the concentration of the third halogen element per unit volume of the third light-emitting layer in the peripheral region.

15. The concentration of the second halogen element per unit volume of the first light-emitting layer in the peripheral region between the first light-emitting element and the second light-emitting element is higher than the concentration of the second halogen element per unit volume of the first light-emitting layer provided in the first light-emitting element; the concentration of the first halogen element per unit volume of the second light-emitting layer in the peripheral region between the first light-emitting element and the second light-emitting element is higher than the concentration of the first halogen element per unit volume of the second light-emitting layer provided in the second light-emitting element; the concentration of the third halogen element per unit volume of the second light-emitting layer in the peripheral region between the second light-emitting element and the third light-emitting element is higher than the concentration of the third halogen element per unit volume of the second light-emitting layer provided in the second light-emitting element; and the concentration of the second halogen element per unit volume of the third light-emitting layer in the peripheral region between the second light-emitting element and the third light-emitting element is higher than the concentration of the second halogen element per unit volume of the third light-emitting layer provided in the third light-emitting element.

15. The display device of claim 14, wherein a concentration of the first halogen element per unit volume of the third light-emitting layer in the peripheral region between the third light-emitting element and the first light-emitting element is higher than a concentration of the first halogen element per unit volume of the third light-emitting layer provided in the third light-emitting element, and a concentration of the third halogen element per unit volume of the first light-emitting layer in the peripheral region between the third light-emitting element and the first light-emitting element is higher than a concentration of the third halogen element per unit volume of the first light-emitting layer provided in the first light-emitting element.

16. A display device according to any one of claims 13 to 15, wherein the peripheral region includes a bank and two or more of the first light-emitting layer, the second light-emitting layer, and the third light-emitting layer provided on the bank.

17. A display device described in any one of claims 4 to 16, wherein the first common charge transport layer is an electron transport layer or an electron injection layer, and each of the first light-emitting element, the second light-emitting element, and the third light-emitting element includes a second common charge transport layer in contact with the first light-emitting layer, the second light-emitting layer, and the third light-emitting layer from a second side opposite to a first side where the first common charge transport layer is in contact with the first light-emitting layer, the second light-emitting layer, and the third light-emitting layer, respectively, and the second common charge transport layer is a hole transport layer or a hole injection layer.

18. The display device described in any one of claims 5 to 16, wherein the first common charge transport layer is an electron transport layer or an electron injection layer, and each of the first light-emitting element, the second light-emitting element, and the third light-emitting element includes a second common charge transport layer in contact with the first light-emitting layer, the second light-emitting layer, and the third light-emitting layer from a second side opposite to a first side where the first common charge transport layer is in contact with the first light-emitting layer, the second light-emitting layer, and the third light-emitting layer, respectively, and the second common charge transport layer is a hole transport layer or a hole injection layer, and in each of the first light-emitting layer, the second light-emitting layer, and the third light-emitting layer, the concentration of halogen elements per unit volume contained in the side in contact with the first common charge transport layer is higher than the concentration of halogen elements per unit volume contained in the side in contact with the second common charge transport layer.

19. The display device according to any one of claims 4 to 18, wherein each of the first light-emitting layer, the second light-emitting layer, and the third light-emitting layer includes a matrix.

20. The display device according to any one of claims 4 to 18, wherein each of the first light-emitting layer, the second light-emitting layer, and the third light-emitting layer includes an inorganic matrix.

21. The display device of claim 20, wherein the inorganic matrix is ​​a semi-metallic chalcogenide.

22. The display device according to claim 21, wherein the metalloid chalcogenide is a metalloid oxide.

23. The display device of claim 21, wherein the metalloid chalcogenide is a metalloid sulfide.

24. The display device according to claim 22, wherein the semi-metal oxide is a semiconductor oxide.

25. The display device according to claim 24, wherein the semiconductor oxide is silicon oxide.

26. The display device of claim 20, wherein the inorganic matrix is ​​a metal chalcogenide.

27. The display device according to claim 26, wherein the metal chalcogenide is a metal oxide.

28. The display device according to claim 26, wherein the metal chalcogenide is a metal sulfide.

29. A display device according to any one of claims 4 to 28, wherein the first light-emitting layer is a blue light-emitting layer, the second light-emitting layer is a green light-emitting layer, and the third light-emitting layer is a red light-emitting layer.

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