Light emitting element, display device, method for manufacturing light emitting element

Abstract

The light emitting element (2) is provided in order with a first electrode (4), a first charge transport layer (6), a silicide layer (14) containing a silicide (16), a light emitting layer (8), and a second electrode (12). The first charge transport layer and the light emitting layer are adjacent to each other with the silicide layer interposed therebetween.

Description

Technical Field

[0001] This invention relates to a light-emitting element and a display device having the light-emitting element. Background Technology

[0002] Patent Document 1 discloses a light-emitting device comprising a light-emitting element containing semiconductor nanocrystals. The light-emitting element described in Patent Document 1 has a charge transport layer between the light-emitting layer and the electrode. Existing technical documents Patent documents

[0003] Patent Document 1: Japanese Patent Publication No. 2012-23388 Summary of the Invention The problem that the invention aims to solve

[0004] In the contact portion between the light-emitting layer and the charge-transporting layer in Patent Document 1, an interface state is formed at the interface between the contacting light-emitting layer and the charge-transporting layer. Therefore, a carrier trap is generated at the interface between the light-emitting layer and the charge-transporting layer. If carriers injected from the electrode are trapped in this carrier trap, the efficiency of carrier injection into the light-emitting layer decreases, resulting in a decrease in the overall luminous efficiency of the light-emitting element. Solution for solving the problem

[0005] To address the aforementioned issues, the light-emitting element of this disclosure is sequentially configured with a first electrode, a first charge transport layer, a silicide layer containing silicide, a light-emitting layer, and a second electrode, wherein the first charge transport layer and the light-emitting layer are adjacent to each other through the silicide layer.

[0006] Furthermore, the method for manufacturing a light-emitting element disclosed herein is a method for manufacturing a light-emitting element in which a first electrode, a first charge transport layer, a silicide layer containing silicide, a light-emitting layer, and a second electrode are sequentially arranged, and the first charge transport layer and the light-emitting layer are adjacent to each other through the silicide layer. The manufacturing method includes a silicide layer formation step, wherein the silicide layer formation step forms the silicide layer by heat-treating a laminate of layers of Si nanoparticles and layers of metal nanoparticles.

[0007] In addition, another method for manufacturing a light-emitting element disclosed herein is a method in which a first electrode, a first charge transport layer, a silicide layer containing silicide, a light-emitting layer and a second electrode are sequentially arranged, and the first charge transport layer and the light-emitting layer are adjacent to each other through the silicide layer. The manufacturing method includes a silicide layer forming step, wherein the silicide layer forming step is formed by heat-treating a laminate of layers of SiO2 nanoparticles and layers of metal nanoparticles. The effects of the invention

[0008] According to one aspect of this disclosure, the generation of carrier traps between the light-emitting layer and the charge transport layer can be reduced, thereby reducing the decrease in the luminous efficiency of the light-emitting element. Attached Figure Description

[0009] Figure 1 This is an enlarged cross-sectional view showing the cross-sections of each layer of the light-emitting element involved in Embodiment 1. Figure 2 This is a schematic plan view showing the display device involved in Embodiment 1. Figure 3 This is an enlarged cross-sectional view showing the display area of ​​the display device according to Embodiment 1. Figure 4 This is a flowchart illustrating the manufacturing method of the display device according to Embodiment 1. Figure 5 This is an enlarged cross-sectional view showing an example of a laminate formed in the manufacturing process of the silicide layer according to Embodiment 1. Figure 6 This is a graph showing the relationship between the particle size of the nanoparticles in the silanization process involved in Embodiment 1 and the melting point of the nanoparticles. Figure 7 This is a graph showing an example of the distribution of elemental concentrations in the silicide layer involved in Embodiment 1. Figure 8 This is an enlarged cross-sectional view showing another example of a laminate formed in the manufacturing process of the silicide layer according to Embodiment 1. Figure 9 This is a graph showing other examples of the distribution of elemental concentrations in the silicide layer involved in Embodiment 1. Figure 10 It is an enlarged cross-sectional view showing the cross-sections of each layer of the light-emitting element involved in the comparison pattern. Figure 11 It includes a schematic band diagram of the hole transport layer and the light-emitting layer, a diagram showing the schematic charge distribution, and a diagram showing the schematic electric field, all used to illustrate the subject matter of the light-emitting element involved in the comparative form. Figure 12 These are schematic energy band diagrams of the hole transport layer, silicide layer, and light-emitting layer, a diagram showing a schematic charge distribution, and a diagram showing a schematic electric field, used to illustrate the effect of the light-emitting element according to Embodiment 1. Figure 13 This is an enlarged cross-sectional view showing the cross-section of each layer of the light-emitting element involved in Embodiment 2. Figure 14 This is an enlarged cross-sectional view showing the cross-section of each layer of the light-emitting element involved in Embodiment 3. Figure 15 This is an enlarged cross-sectional view showing the cross-sections of each layer of the light-emitting element involved in Embodiment 4. Figure 16 This is an enlarged cross-sectional view showing the cross-sections of each layer of the light-emitting element involved in Embodiment 5. Detailed Implementation

[0010] [Implementation Method 1] <Overview of Display Devices> Figure 2 This is a schematic plan view of the display device 1 according to this embodiment. Figure 3 This is a schematic cross-sectional view of the display device 1 according to this embodiment. Figure 2 A cross-sectional view taken along the Al-Al arrow line.

[0011] like Figure 2 As shown, the display device 1 according to this embodiment includes: a display area DS having a plurality of sub-pixels, each sub-pixel having a light-emitting element described later; and a border area NA surrounding the display area DS. A terminal T may also be formed in the border area NA, to which signals for driving each light-emitting element in the display area DS are input.

[0012] like Figure 3 As shown, the display device 1 according to this embodiment includes a substrate 3 and light-emitting elements 2 with a plurality of pixels respectively located on the substrate 3. In particular, the display device 1 according to this embodiment has a plurality of light-emitting elements 2 at a position overlapping with the display area DS when viewed from above. In addition, the substrate 3 may also be formed at a position overlapping both the display area DS and the bezel area NA when viewed from above, and terminals T may also be formed on the substrate 3. In addition, in this specification, the direction of the display device 1 from the substrate 3 toward the light-emitting elements 2 is described as the "upward direction", and the opposite direction of the "upward direction" is described as the "downward direction". In addition, in this specification, "top view of the display device 1" means the case of viewing the display device 1 from above in the approximate normal direction of the upper surface of the display area DS.

[0013] Substrate 3 includes Figure 3 The diagram shows a support substrate Sub, multiple thin-film transistors Tr, and a planarization film F. The support substrate Sub can be, for example, a glass substrate, or, in the case of a rigid display device 1, a flexible support film such as a PET film. Multiple thin-film transistors Tr and the planarization film F are formed on the support substrate Sub.

[0014] Thin-film transistors (TFTs) such as Tr Figure 3As shown, the structure consists of a gate electrode G, a passivation film Pas, and a channel layer C, stacked sequentially. Furthermore, the thin-film transistor Tr includes a source electrode S and a drain electrode D electrically connected on the channel layer C via the channel layer C.

[0015] The drain electrode D is electrically connected to each of the pixel electrodes of each light-emitting element 2 (described later). Furthermore, by controlling the voltage applied to the gate electrode G, the thin-film transistor Tr controls the amount of current flowing from the source electrode S to the drain electrode D via the channel layer C. Thus, the thin-film transistor Tr individually drives the light emission of each light-emitting element 2.

[0016] The planarization film F is formed to reduce the unevenness on the support substrate Sub caused by the thin-film transistor Tr. The planarization film F can be formed, for example, from a resin containing polyimide.

[0017] Light-emitting elements 2 are formed on substrate 3, and each light-emitting element 2 is divided by a dam B on substrate 3. Dam B can be formed of the same material as planarization film F, for example, it can also be formed of a resin containing polyimide. In addition, the display device 1 may further form a sealing layer on the light-emitting elements 2 and the dam B to seal each light-emitting element 2 and protect the light-emitting elements 2 from foreign matter containing moisture, or a cover layer to improve the efficiency of light extraction from each light-emitting element 2.

[0018] <Overview of Light Emitting Elements> Reference Figure 1 The light-emitting element 2 involved in this embodiment will be described in more detail. Figure 1 This is a schematic cross-sectional view showing the light-emitting element 2 and its surrounding area according to this embodiment, enlarged. Figure 3 The diagram shows area A2, indicated by the dashed line. Specifically, Figure 1 Only a portion of each layer of the light-emitting element 2 and a portion of the upper side of the substrate 3 are shown in magnified view.

[0019] The light-emitting element 2 according to this embodiment has, in sequence from the substrate 3 side, an anode 4 serving as a first electrode, a hole transport layer 6 serving as a first charge transport layer, a light-emitting layer 8, an electron transport layer 10 serving as a second charge transport layer, and a cathode 12 serving as a second electrode. Furthermore, the light-emitting element 2 according to this embodiment has a silicide layer 14 between the hole transport layer 6 and the light-emitting layer 8.

[0020] In particular, in this embodiment, the hole transport layer 6 and the light-emitting layer 8 are adjacent to each other through the silicide layer 14. Here, in this specification, the term "adjacent" means that there are portions of the two layers in contact with each other, or that the two layers are separated by at least one of a thin film of a thickness thin enough for the carrier to tunnel through. In other words, the case of two layers being "adjacent" includes a situation where one part of the two layers contains another layer, while the other part does not.

[0021] Furthermore, in this specification, "adjacent to each other across a specific layer" means that each of the two layers is adjacent to that specific layer. In other words, when two layers are "adjacent to each other across a specific layer," it includes situations where there is a thin film between the specific layer and each of the two layers, thin enough for the carrier to tunnel through. Further, in other words, when two layers are "adjacent to each other across a specific layer," it includes situations where between the specific layer and each of the two layers, one part contains another layer, and the other part does not.

[0022] Furthermore, as described above, the light-emitting element 2 according to this embodiment includes an electron transport layer 10. However, the inclusion of an electron transport layer 10 in the light-emitting element 2 according to this embodiment is not necessarily essential for achieving at least one of the effects described later.

[0023] <Overview of Anode and Cathode> In this embodiment, the anode 4 of the light-emitting element 2 is formed, for example, for each sub-pixel of the display device 1. Furthermore, the anode 4 is electrically connected to the drain electrode D of the thin-film transistor Tr. Therefore, by controlling the voltage applied to each node 4 by the thin-film transistor Tr, each light-emitting element 2 is driven. Thus, the anode 4 functions as the pixel electrode of the light-emitting element 2. The light-emitting element 2 is driven by the thin-film transistor Tr, thereby injecting holes from the anode 4 into the light-emitting layer 8.

[0024] The anode 4 includes conductive components. Specifically, the anode 4 can be a metal film made of metals such as Al, Mg, Li, Ag, or alloys of these metals. Alternatively, the anode 4 can have a single metal film or multiple metal films stacked together. Or, the anode 4 can also have a thin film of a conductive oxide such as ITO or IZO, or an oxide semiconductor such as an InGaZnO system.

[0025] The cathode 12 is formed, for example, in a manner shared with multiple sub-pixels of the display device 1, and is subjected to a constant voltage. Therefore, the light-emitting element 2 is driven by the thin-film transistor Tr, generating a potential difference with the anode 4, thereby injecting electrons from the cathode 12 into the light-emitting layer 8. The cathode 12 may, for example, include the material that the anode 4 may contain, or it may contain the same material as the anode 4.

[0026] At least one of the anode 4 and the cathode 12 is translucent, transmitting light from the light-emitting layer 8. The light-emitting element 2 extracts light from the light-emitting layer 8 from at least one of the translucent anode 4 and the cathode 12. Additionally, one of the anode 4 and the cathode 12 can reflect light from the light-emitting layer 8. This improves the light extraction efficiency from the light-emitting element 2.

[0027] In this embodiment, with the anode 4 being translucent and the cathode 12 being reflective, light from the light-emitting element 2 is extracted from the substrate 3 side. Here, by using translucent materials for components of the substrate 3 overlapping the light-emitting element 2, such as the support substrate Sub and the planarization film F, the display device 1 can extract light from each of the light-emitting elements 2 from the substrate 3 side. Based on the above structure, the display device 1 functions as a bottom-emitting type display device.

[0028] On the other hand, in this embodiment, when the anode 4 is light-reflective and the cathode 12 is light-transmitting, light from the light-emitting element 2 is extracted from the side opposite to the substrate 3. Based on the above configuration, the display device 1 functions as a top-emitting type display device that extracts light from each of the light-emitting elements 2 from the side opposite to the substrate 3. From the viewpoint of increasing the opening area capable of extracting light from each of the light-emitting elements 2, it is preferable that the display device 1 is a top-emitting type display device.

[0029] <Overview of the charge transport layer> In this specification, a charge transport layer refers to a layer that functions to transport at least one of charge, in other words, electrons or holes, from each electrode to the light-emitting layer side. A charge transport layer primarily refers to at least one of an electron transport layer or a hole transport layer. Furthermore, a charge transport layer can also be at least one of an electron injection layer or a hole injection layer. For example, in this specification, a charge transport layer sometimes means combining an electron transport layer and an electron injection layer, combining a hole transport layer and a hole injection layer, or combining an electron transport layer, an electron injection layer, a hole transport layer, and a hole injection layer.

[0030] Hole transport layer 6 is a layer that functions to transport holes injected from anode 4 to the light-emitting layer 8. Hole transport layer 6 may contain organic materials or inorganic materials. If hole transport layer 6 contains organic materials, these materials may include, for example, TFB or PVK. If hole transport layer 6 contains inorganic materials, these materials may include NiO, MgNiO, Cr2O3, MoO3, or WO3. Furthermore, hole transport layer 6 may also contain existing known materials with hole transport properties.

[0031] The electron transport layer 10 is a layer that functions to transport electrons injected from the cathode 12 to the light-emitting layer 8. The electron transport layer 10 may contain organic materials or inorganic materials. When the electron transport layer 10 contains organic materials, these organic materials may include, for example, alumina-hydroxyquinoline complexes or triazole compounds. When the electron transport layer 10 contains inorganic materials, these inorganic materials may include ZnO or MgZnO. Furthermore, the electron transport layer 10 may also contain conventionally known materials with electron transport properties.

[0032] Furthermore, the light-emitting element 2 according to this embodiment may also have a hole injection layer between the anode 4 and the hole transport layer 6, the hole injection layer having the function of transporting holes injected from the anode 4 to the hole transport layer 6. Additionally, the light-emitting element 2 may also have an electron injection layer between the cathode 12 and the electron transport layer 10, the electron injection layer having the function of transporting electrons injected from the cathode 12 to the electron transport layer 10.

[0033] When the light-emitting element 2 has a hole injection layer, the hole injection layer may contain oxides of molybdenum (Mo), tungsten (W), vanadium (V), ruthenium (Ru), rhenium (Re), or iridium (Ir). Alternatively, the hole injection layer may contain oxides of group VIIIB (groups 8, 9, and 10) metals such as nickel (Ni) and palladium (Pd). Furthermore, the hole injection layer may also contain oxides of lanthanides such as lanthanum (La), cerium (Ce), and neodymium (Nd). Additionally, the hole injection layer may contain oxides of platinum (Pt), gold (Au), and silver (Ag). Furthermore, the hole injection layer may contain mixtures of any composition of the above oxides. Additionally, the hole injection layer may use organic compounds containing polyvinyldioxythiophene polysulfonic acid (PEDOT:PSS), organic compounds containing astramines, or organometallic compounds containing copper phthalocyanines.

[0034] Furthermore, as described above, in this specification, when groups of metallic elements in the periodic table are represented using Roman numerals, the groups are represented using the old CAS notation. Conversely, in this specification, when groups of metallic elements in the periodic table are represented using Arabic numerals, the current IUPAC notation is used.

[0035] <Overview of the Emissive Layer> The light-emitting layer 8 is a layer of light-emitting material that emits light through electronic excitation based on carrier recombination. For example, in the light-emitting layer 8, holes from the anode 4 recombine with electrons from the cathode 12, thereby generating excitons in the light-emitting layer 8. Then, through these excitons, electrons in the light-emitting material are excited to an excitation energy level. Subsequently, when the excited electrons in the light-emitting material transition from the excitation energy level to the base energy level, light with a wavelength corresponding to the energy difference between the excitation energy level and the base energy level is generated from the light-emitting layer 8.

[0036] The light-emitting material of the light-emitting layer 8 may contain organic light-emitting materials or inorganic light-emitting materials. When the light-emitting material of the light-emitting layer 8 contains organic light-emitting materials, such as those used in organic EL devices, conventionally known organic light-emitting materials can be used. Conversely, when the light-emitting material of the light-emitting layer 8 contains inorganic light-emitting materials, such as quantum dots that emit light through carrier injection, in other words, semiconductor nanoparticles, conventionally known inorganic light-emitting materials can be used.

[0037] The light emitted by the light-emitting layer 8 can be appropriately designed by changing the type of light-emitting material contained in the light-emitting layer 8 and thus changing the wavelength of the light emitted from the light-emitting material. For example, the display device 1 may also include a red light-emitting element having a light-emitting layer 8 that emits red light, a green light-emitting element having a light-emitting layer 8 that emits green light, and a blue light-emitting element having a light-emitting layer 8 that emits blue light, as light-emitting element 2.

[0038] In this case, display device 1 can also form a pixel by having a red sub-pixel with a red light-emitting element, a green sub-pixel with a green light-emitting element, and a blue sub-pixel with a blue light-emitting element. Thus, by arranging and having multiple such pixels in the display area DS, display device 1 becomes a display device capable of color display.

[0039] <Summary of silicide layers> Silicide layer 14 is Figure 1 The diagram shows a layer comprising multiple silicides 16. In this embodiment, silicide 16 refers to a compound of a metal element and Si. In particular, in this embodiment, the silicide 16 is polar because at least one silicide 16 has a deviation in its intramolecular electron cloud.

[0040] In this embodiment, at least one of the polar silicide 16 has its electron cloud within the molecule biased to the negative side, forming a position on the side of the light-emitting layer 8. In other words, the direction of the dipole moment 16D of the silicide 16 is from the light-emitting layer 8 toward the hole transport layer 6.

[0041] In particular, in this embodiment, more than half of the silicides 16 included in the silicide layer 14 have a dipole moment 16D in the direction from the light-emitting layer 8 toward the hole transport layer 6. Therefore, the silicide layer 14 as a whole has a dipole moment in the direction from the light-emitting layer 8 toward the hole transport layer 6.

[0042] Furthermore, in this embodiment, the direction of the dipole moment 16D of the silicide 16 is not limited to, for example... Figure 1 The direction shown is along the stacking direction of each layer of the light-emitting element 2. Specifically, in this embodiment, the direction of the dipole moment 16D of the silicide 16 is compared with the direction perpendicular to the stacking direction of each layer of the light-emitting element 2, even if only slightly, as long as it is from the direction of the light-emitting layer 8 toward the hole transport layer 6. In other words, the direction of the dipole moment 16D of the silicide 16 can also be a direction deviating from the direction along the stacking direction of each layer of the light-emitting element 2.

[0043] In this embodiment, the metallic material contained in silicide 16 can appropriately be a metallic material that forms a compound with Si. For example, the molecular structure of silicide 16 has M as the metallic element, uses the real number x, and is labeled MSi. x The structure is acceptable. In particular, the stoichiometric composition of silicide 16 can also be MSi or MSi2.

[0044] Furthermore, regarding the silicide layer 14, the term "layer" or "film" in this specification does not necessarily mean a film shape that is uniform throughout. For example, a "layer" or "film" including the silicide 16 is intended to have a portion of it having a discontinuous structure, including breaks, etc., and having a structure that confirms at least a portion has thickness. Additionally, preferably, the silicide layer 14 has a continuous structure. More preferably, the silicide layer 14 has a uniform film shape throughout.

[0045] <Manufacturing method up to the hole transport layer of the light-emitting element> Reference Figure 4 A method for manufacturing the display device 1 according to this embodiment is described. Figure 4 This is a flowchart illustrating the manufacturing method of the display device 1 according to this embodiment.

[0046] In the manufacturing method of the display device 1 according to this embodiment, a substrate 3 is first formed (step S2). The substrate 3 is formed, for example, by forming a thin film transistor Tr on a support substrate Sub for each sub-pixel, and then forming a planarization film F to planarize the substrate 3.

[0047] Thin-film transistors (Tr) can also be formed, for example, by alternately and repeatedly depositing layers using conventionally known methods such as CVD or sputtering, and patterning those layers using photolithography or the like. Planarization films (F) can also be formed, for example, by coating resin materials such as polyimide using conventionally known coating methods such as inkjet printing or spin coating.

[0048] Next, an anode 4 is formed on the substrate 3 (step S4). The anode 4 can also be formed by existing known anode formation methods. Specifically, the anode 4 can be formed, for example, by depositing a layer containing a conductive material on the substrate 3 by CVD, sputtering or vacuum evaporation, and then patterning the layer containing the conductive material according to each sub-pixel by photolithography.

[0049] Next, a dam B is formed between the sub-pixels of the substrate 3 (step S6). The dam B can also be formed by coating a resin material such as polyimide using conventionally known coating methods such as inkjet printing or spin coating, and then patterning the resin material using photolithography or the like. Here, the dam B can also be formed at the position covering the periphery of the anode 4. In other words, in a plan view of the display device 1, the dam B is patterned such that at least a portion of the center side of the periphery of the anode 4 is exposed from the dam B.

[0050] Next, hole transport layer 6 is formed (step S8). Hole transport layer 6 can be formed using conventionally known methods for forming hole transport layers. Specifically, hole transport layer 6 can be formed, for example, by depositing a hole-transporting material onto a sub-pixel using vacuum evaporation through a metal mask with an opening in each sub-pixel. Alternatively, after coating a hole-transporting material, the material can be patterned in each sub-pixel using photolithography or a lift-off method to form hole transport layer 6.

[0051] <Heat treatment required for siliconization> Next, a silicide layer 14 is formed. In this embodiment, the method of forming the silicide layer 14 by heat treatment of a metal and Si laminate will be described as an example.

[0052] Generally, the reaction temperature required for the heat treatment of silicides of metals is roughly proportional to the melting point of the metal, but compared to that melting point, the reaction temperature during silicide formation is overwhelmingly low. It is generally known that the experimental reaction temperature for silicide formation of metals is less than half the eutectic temperature of the metal and Si. This is because the silicided state is significantly more stable than the monomeric constituent elements; therefore, the heat of formation of the silicide becomes negative, with an absolute value reaching hundreds of kJ / mol.

[0053] However, despite the above, silicide formation of bulk metals from bulk Si requires heat treatment at temperatures around several hundred °C. While combinations like Au exist that react even at room temperature, the reaction temperatures for silicide formation of typical metals considered practically usable are generally below 600 °C, considering cost and environmental factors. For example, the reaction temperature for silicide formation of bulk Fe is 340 °C, and the reaction temperature for silicide formation of bulk Ni is 250 °C.

[0054] However, during the formation of the silicide layer 14, the heat treatment at around several hundred degrees Celsius causes significant damage to the previously formed layers, including the substrate 3, anode 4, and hole transport layer 6, which are layers lower than the silicide layer 14. Therefore, in this embodiment, it is difficult to obtain the silicide layer 14 by forming a laminate of metal and Si films through sputtering or the like, followed by heating the laminate.

[0055] <Forming process of laminated bodies> Therefore, in this embodiment, the melting point of metal and Si nanoparticles is lower than that of bulk materials. In the process of forming the silicide layer 14, firstly, metal nanoparticles and Si nanoparticles, which are materials for forming the silicide layer 14, are stacked on each hole transport layer 6 (step S10).

[0056] use Figure 5 Step S10 will be explained in more detail. Figure 5 This is a schematic cross-sectional view of the laminate 18A formed through step S10. Figure 5 In this diagram, only a cross-section of the laminate 18A is shown, with the lower side of the laminate 1 designated as the substrate 3 side of the display device 1. Figure 5 In the diagram, only the cross-section of the laminate 18A is shown, but in the orientation view, the lower side is taken as the substrate 3 side of the display device 1.

[0057] like Figure 5 As shown, the laminate 18A is stacked in a contact manner, comprising a metal nanoparticle layer 22 containing a plurality of metal nanoparticles 20 and a Si nanoparticle layer 26 containing a plurality of Si nanoparticles 24. Specifically, the laminate 18A includes the metal nanoparticle layer 22 on the hole transport layer 6 side. The metal nanoparticles 20 are metal nanoparticles contained in the silicide 16, and the Si nanoparticles 24 are Si nanoparticles. Furthermore, as... Figure 5 As shown, the metal nanoparticles 20 in the metal nanoparticle layer 22 and the Si nanoparticles 24 in the Si nanoparticle layer 26 can also be arranged irregularly.

[0058] The metal nanoparticle layer 22 can also be formed by coating a colloidal solution containing metal nanoparticles 20 onto the hole transport layer 6. Alternatively, the Si nanoparticle layer 26 can be formed after the metal nanoparticle layer 22 is formed by coating a colloidal solution containing Si nanoparticles 24 onto the metal nanoparticle layer 22. During the formation processes of the metal nanoparticle layer 22 and the Si nanoparticle layer 26, after coating each colloidal solution, the colloidal solution can be subjected to heat treatment, for example, heating at 50°C for 10 minutes, to evaporate the solvent.

[0059] <Relationship between nanoparticle size and nanoparticle melting point> like Figure 5 As shown, the metal nanoparticles 20 have a particle size R20, and the Si nanoparticles 24 have a particle size R24. Here, the particle size R20 and particle size R24 are preferably 50 nm or less, and more preferably 20 nm or less, for reasons explained later.

[0060] Generally, the reaction temperature during the silicification of nanoparticles depends on the melting point of the nanoparticles. Furthermore, the melting point of nanoparticles generally also depends on their particle size. Figure 6 This is a graph showing the relationship between the melting point of nanoparticles and their particle size. Figure 6 In this diagram, the horizontal axis represents the particle size of the nanoparticles, and the vertical axis represents the value obtained by dividing the melting point of the nanoparticles by the melting point of the nanoparticles as a bulk element. In other words, the vertical axis represents the ratio of the melting point of the nanoparticles in the component to the melting point of the bulk component.

[0061] also, Figure 6 The values ​​on the vertical axis represent the ratio of the melting point of the nanoparticles of various metals to the melting point of the bulk metal. Here, this ratio is independent of the type of metal and depends on the particle size of the nanoparticles. Therefore, Figure 6 The relationships shown apply to all metals.

[0062] When the particle size of nanoparticles is greater than 50 nm, the melting point of the nanoparticles does not change significantly regardless of the particle size. However, it is known that when the particle size of nanoparticles is less than 50 nm, the smaller the particle size, the more significantly the melting point of the nanoparticles decreases compared to the melting point of the bulk. Furthermore, when the particle size of nanoparticles is less than 20 nm, the melting point of the nanoparticles is less than 50% of the melting point of the bulk, and when the particle size of nanoparticles is less than 10 nm, the melting point of the nanoparticles is less than 20% of the melting point of the bulk.

[0063] Therefore, when the particle sizes R20 and R24 are below 50 nm, the melting points of the metal nanoparticles 20 and Si nanoparticles 24 can be reduced, thereby lowering the reaction temperature required for the silanization of the metal nanoparticles 20 and Si nanoparticles 24. Furthermore, when the particle sizes R20 and R24 are below 20 nm, the reaction temperature required for the silanization of the metal nanoparticles 20 and Si nanoparticles 24 can be further reduced, thus significantly minimizing damage to the lower layers of the laminate 18A.

[0064] <Siliconization process> After step S10, the metal nanoparticles 20 and Si nanoparticles 24 are silicided by heat treatment of the laminate 18A to form silicide 16, thereby forming silicide layer 14 (step S12). Here, for example, when the particle size R20 and particle size R24 are 25 nm or less, a silicide layer 14 containing silicide 16 can be formed by heat treatment of the laminate 18A at about 100°C for 30 to 60 minutes.

[0065] In this embodiment, during the heating process of the laminate 18A, the metal nanoparticle layer 22 included in the laminate 18A is located closer to the hole transport layer 6 than the Si nanoparticle layer 26. Therefore, in step S12, the metal nanoparticles 20 are silicided while being located further away from the hole transport layer 6 than the Si nanoparticles 24. Consequently, the positions of the metal elements in the molecules of the silicide layer 14 forming the silicide 16 are closer to the hole transport layer 6 than the positions of the Si elements.

[0066] Figure 7 The graph is an example of a graph showing the relationship between the position in the thickness direction starting from the hole transport layer 6 and the element concentration at that position in the silicide layer 14 formed by the laminate 18A. Figure 7 In the chart, solid lines represent metallic elements, and dashed lines represent silicon (Si). Additionally, in... Figure 7 In the chart, the vertical axis represents the position of the silicide layer 14 in the thickness direction starting from the hole transport layer 6, and the horizontal axis represents the concentration of each element at that position.

[0067] like Figure 7 As shown in the graph, the metal concentration in the silicide layer 14 is higher on the hole transport layer 6 side than on the light-emitting layer 8 side, and gradually decreases from the hole transport layer 6 side toward the light-emitting layer 8 side. On the other hand, the Si concentration in the silicide layer 14 is lower on the hole transport layer 6 side than on the light-emitting layer 8 side, and gradually increases from the hole transport layer 6 side toward the light-emitting layer 8 side.

[0068] <Metallic elements contained in silicides> Here, the types of metal elements contained in the silicide 16 of the silicide layer 14 will be explained. The presence or absence of polarity in the silicide 16, and the direction of the dipole moment generated by that polarity, change depending on the metal elements contained in the silicide 16. The relationship between the metal elements contained in the silicide 16 and the direction of the dipole moment of the silicide 16 will be explained with reference to Table 1 below.

[0069] [Table 1] In Table 1, the "Element" column indicates the types of each metallic element. The "Element" column also shows the group of each metallic element in the periodic table using the old CAS method. The "d-orbital electrons" column uses n and m as natural numbers to represent the number of electrons in the outermost d-orbitals of each metallic element. For example, in the case of a metallic element whose outermost d-orbital is an nd orbital containing m electrons, it is recorded as "ndm" in the "d-orbital electrons" column. The "Electronegativity" column indicates the electronegativity of each metallic element. The "Melting Point [°C]" column uses Celsius to indicate the melting point of each metallic element in its bulk state. The "Silicide" column indicates the stoichiometric composition of the silicide formed when each metallic element is silicided. The "Direction of Dipole Moment" column indicates the direction of the dipole moment of the silicide when the silicide containing each metallic element is polar. When the "Direction of Dipole Moment" column is marked "M→Si", the direction of the silicide's dipole moment is from the metal element towards the Si element. Conversely, when marked "M←Si", the direction of the silicide's dipole moment is from the Si element towards the metal element. If the silicide is a non-polar metal element, the "Direction of Dipole Moment" column is empty. Additionally, Table 1, for reference, lists the electronegativity of Si and its melting point in its bulk state.

[0070] Of the metallic elements shown in Table 1, the silicides of Group IVB (Group 4), Group VB (Group 5), and Group VIB (Group 6) elements are non-polar. On the other hand, of the metallic elements shown in Table 1, the silicides of Group VIIIB (Groups 8, 9, and 10) elements are all polar. This is because the outermost d orbitals of metallic elements in Group IVB (Group 4), Group VB (Group 5), and Group VIB (Group 6) have 5 or fewer electrons, while those in Group VIIIB (Groups 8, 9, and 10) have 6 or more electrons.

[0071] When a metal atom has five or fewer d electrons in its outermost shell, all of these d electrons are housed in coupled orbitals during silicide formation, resulting in a good conductor without polarity. However, when a metal atom has six or more d electrons in its outermost shell, some of these electrons are housed in anticoupled orbitals during silicide formation. A band gap forms in the silicide with electrons housed in anticoupled orbitals, leading to polarity due to the shift in the electron cloud within the molecule.

[0072] Furthermore, the direction of the dipole moment of polar silicides is determined by the difference in electronegativity between the metal element contained in the silicide and Si. Electronegativity is equivalent to the degree to which an element attracts electrons; the higher the electronegativity, the easier it is for an element to attract electrons. Therefore, in silicides of metal elements with lower electronegativity than Si, the electrons within the molecule are closer to Si than the electrons in the metal element, so the direction of the dipole moment is from Si towards the metal element. Conversely, in silicides of metal elements with higher electronegativity than Si, the electrons within the molecule are closer to the electrons in the metal element than Si, so the direction of the dipole moment is from the metal element towards Si.

[0073] In this embodiment, such as Figure 1 As shown, the dipole moment 16D of the silicide 16 is oriented from the light-emitting layer 8 towards the hole transport layer 6. Furthermore, the laminate 18A, which undergoes heat treatment in step S12 of this embodiment, is richer in metal nanoparticles 20 on the hole transport layer 6 side compared to Si nanoparticles 24. Therefore, the silicide 16 formed by heat-treating the laminate 18A has a higher metal concentration from metal nanoparticles 20 on the hole transport layer 6 side than the Si concentration from Si nanoparticles 24.

[0074] As described above, in order to form from the laminate 18A Figure 1 The silicide 16 shown, having a dipole moment 16D in the direction from the light-emitting layer 8 towards the hole transport layer 6, requires that the electronegativity of the metal element contained in the metal nanoparticles 20 be lower than that of Si. Therefore, referring to Table 1, the metal element contained in the metal nanoparticle layer 22 of the laminate 18A can be at least one of Fe, Co, or Ni. Furthermore, Ni has approximately the same electronegativity as Si, and in particular, Ni has a slightly higher electronegativity than Si. However, generally speaking, for Ni silicides, it is known that the direction of the dipole moment is from Si towards Ni.

[0075] Compared to other Group VIIIB (Groups 8, 9, and 10) metals, Fe, Co, or Ni have low melting points. Therefore, from the viewpoint of reducing the reaction temperature required for silicide formation of the laminate 18A and minimizing damage to the underlying layer of silicide layer 14, it is preferable that the metal element contained in silicide 16 is Fe, Co, or Ni. Furthermore, having Fe, Co, or Ni contained in silicide 16 is also preferable from the viewpoints of reducing the cost of forming silicide layer 14 and from an environmental perspective.

[0076] <Examples of variations of laminated structures> Furthermore, the structure of the laminate formed in step S10 is not limited to... Figure 5 The structure of the laminate 18A shown is illustrated. (Refer to...) Figure 8 Examples of other structures of the laminate formed in step S10 are provided. Figure 8 Another example of a laminate formed through step S10 is a schematic cross-sectional view of laminate 18B. Figure 8 In the figure, only the cross-section of the laminate 18B is shown, but the side facing down is taken as the substrate 3 side of the display device 1.

[0077] like Figure 8 As shown, the stack 18B is richer in Si nanoparticle layers 26 than the metal nanoparticle layer 22 on the hole transport layer 6 side. Each of the metal nanoparticle layers 22 and Si nanoparticle layers 26 contained in the stack 18B may have the same structure as each of the metal nanoparticle layers 22 and Si nanoparticle layers 26 contained in the stack 18A.

[0078] Figure 9 The graph is an example of the relationship between the position in the thickness direction starting from the hole transport layer 6 and the element concentration at that position in the silicide layer 14 formed by the stack 18B. Figure 9 The chart also shows... Figure 7 The charts are the same, using solid lines to represent metallic elements and dashed lines to represent silicon (Si). Additionally, in... Figure 9 The chart also shows... Figure 7 The same chart is used, with the vertical axis taken from the position of the silicide layer 14 in the thickness direction starting from the hole transport layer 6, and the horizontal axis taken from the concentration of each element at that position.

[0079] like Figure 9 As shown in the graph, the metal concentration in the silicide layer 14 is lower on the hole transport layer 6 side than on the light-emitting layer 8 side, and gradually increases from the hole transport layer 6 side toward the light-emitting layer 8 side. On the other hand, the Si concentration in the silicide layer 14 is higher on the hole transport layer 6 side than on the light-emitting layer 8 side, and gradually decreases from the hole transport layer 6 side toward the light-emitting layer 8 side.

[0080] The stack 18B is richer in metal nanoparticles 20 than Si nanoparticles 24 on the hole transport layer 6 side. Therefore, the silicide 16 formed by heat-treating the stack 18B in step S12 has a lower metal concentration from metal nanoparticles 20 on the hole transport layer 6 side than the Si concentration from Si nanoparticles 24.

[0081] As described above, in order to form from the laminate 18B Figure 1 The silicide 16 shown, which has a dipole moment 16D in the direction from the light-emitting layer 8 to the hole transport layer 6, requires that the metal element contained in the metal nanoparticles 20 has a higher electronegativity than the Si element. Therefore, referring to Table 1, the metal element contained in the metal nanoparticle layer 22 of the laminate 18B can be at least one of Ru, Os, Rh, Ir, Pd, or Pt.

[0082] <Other examples of silicide layer formation processes> In this embodiment, the method for forming the silicide layer 14 is not limited to the method of sequentially performing steps S10 and S12 described above. For example, the silicide layer 14 may also be formed in advance in other processes as silicide 16, and obtained by sputtering the silicide 16 as a material to form a thin film of silicide 16 on the hole transport layer 6.

[0083] In this case, since it is difficult to control the molecular orientation of silicide 16, the orientation of silicide 16 contained in silicide layer 14 is randomly determined. Therefore, silicide layer 14 formed by the above method is not related to whether silicide 16 is polar or not, and is generally a nonpolar layer.

[0084] When the silicide layer 14 is formed by sputtering using silicide 16 as the material, the aforementioned heat treatment for silicide treatment of the metal nanoparticle layer 22 and the Si nanoparticle layer 26 is not required. Therefore, by adopting the above method, the formation process of the silicide layer 14 is simplified, and the damage to the underlying layer of the silicide layer 14 caused by the aforementioned heat treatment is reduced.

[0085] Alternatively, the metal nanoparticles 20 contained in the metal nanoparticle layer 22 formed in step S10 can also be nanoparticles of metal elements from the IVB (group 4), VB (group 5), and VIB (group 6) groups shown in Table 1. In this case, since the silicides 16 formed in step S12 are all substantially nonpolar, the silicide layer 14 containing the silicides 16 is generally a substantially nonpolar layer.

[0086] Furthermore, in this embodiment, the laminate 18A or laminate 18B can also replace the Si nanoparticle layer 26 and form a SiO2 nanoparticle layer containing multiple SiO2 nanoparticles. In this case, through the heat treatment in step S12, the O in the SiO2 nanoparticles is detached, leaving only Si from the SiO2 nanoparticles in the silicide 16. Therefore, the silicide layer 14 described above can be obtained from the laminate of SiO2 nanoparticles and metal nanoparticles using the same method as described above.

[0087] Manufacturing methods from the light-emitting layer to the cathode of a light-emitting element. After forming the silicide layer 14, the light-emitting layer 8 is formed (step S14). The light-emitting layer 8 can be formed by conventionally known methods, such as vapor deposition using a metal mask, photolithography using a photoresist, or a lift-off method. When the display device 1 has light-emitting elements 2 with different emission colors, the formation position and material of the light-emitting layer 8 can be changed for each emission color of the light-emitting element 2, and the formation process of the light-emitting layer 8 can be repeatedly performed.

[0088] Next, the electron transport layer 10 is formed (step S16). The electron transport layer 10 can be formed using the same method as the hole transport layer 6, except for the material used. Next, the cathode 12 is formed (step S18). The cathode 12 can be formed using the same method as the anode 4, except for the point formed together in multiple sub-pixels. However, if a voltage can be applied to the cathode 12 for each sub-pixel, the cathode 12 can also be formed separately for each light-emitting element 2, just like the anode 4.

[0089] As described above, the light-emitting element 2 according to this embodiment is formed, and the manufacturing process of the display device 1 is completed. In addition, after the cathode 12 formation process, a capping layer may be formed by sputtering or the like, or a sealing layer may be formed by CVD or coating.

[0090] <Reduction of carrier trap based on silicide layer> The effects of the light-emitting element in this embodiment will be explained by comparing it with the light-emitting element in the comparative embodiment. Figure 10 This is a schematic cross-sectional view of the light-emitting element 2A involved in the comparative form, showing the relationship with... Figure 1 The cross-section corresponding to the position in the schematic cross-sectional view. Compared with the light-emitting element 2 of this embodiment, the light-emitting element 2A involved in the comparative form does not have a silicide layer 14, and has the same structure except that the hole transport layer 6 and the light-emitting layer 8 are in direct contact.

[0091] In the comparative configuration, the hole transport layer 6 and the light-emitting layer 8 are in direct contact. Here, an interface state is typically formed at the interface between the hole transport layer 6 and the light-emitting layer 8. Therefore, a carrier trap is formed at the interface between the hole transport layer 6 and the light-emitting layer 8 in the light-emitting element 2A of the comparative configuration. In this carrier trap, holes transported from the anode 4 are sometimes trapped. Consequently, in the light-emitting element 2A of the comparative configuration, the concentration of holes transported to the light-emitting layer 8 sometimes decreases, and the carrier balance in the light-emitting layer 8 deteriorates.

[0092] In this embodiment, the light-emitting element includes a silicide layer 14 between the hole transport layer 6 and the light-emitting layer 8. The silicide layer 14 is formed by heat-treating and silicideling the metal nanoparticle layer 22 and the Si nanoparticle layer 26 at low temperature. Therefore, the silicide layer 14 contains silicides 16 with stable energy levels. Thus, the silicide layer 14, including silicides 16, can deactivate the energy levels generated at the interface between the contacting hole transport layer 6 and the light-emitting layer 8.

[0093] Furthermore, when the silicide layer 14 is formed by sputtering using silicide 16 as the material, a dense silicide layer 14 containing silicide 16 and with stable energy levels is obtained. Therefore, even when the silicide layer 14 is formed by sputtering using silicide 16 as the material, this silicide layer 14 can deactivate the energy levels generated at the interface between the hole transport layer 6 and the light-emitting layer 8.

[0094] Therefore, the light-emitting element 2 according to this embodiment reduces the carrier traps generated at the interface between the hole transport layer 6 and the silicide layer 14, and at the interface between the silicide layer 14 and the light-emitting layer 8, thereby improving the efficiency of hole injection into the light-emitting layer 8. Therefore, the light-emitting element 2 according to this embodiment can improve the overall luminous efficiency of the element because it can improve the carrier injection efficiency into the light-emitting layer 8.

[0095] The display device 1, which includes multiple light-emitting elements 2 with improved luminous efficiency, can display more efficiently using these light-emitting elements 2, thus reducing power consumption. Furthermore, to improve the luminous efficiency of the light-emitting elements 2, the display device 1 can reduce the voltage applied to each light-emitting element 2 and achieve high-brightness display. Therefore, the display device 1 can reduce the shortened lifespan of the light-emitting elements 2 that is associated with driving them with high voltage.

[0096] <Structure of silicide layer> When the silicide layer 14 is formed by heat treatment of the metal nanoparticle layer 22 and the Si nanoparticle layer 26, the metal nanoparticle layer 22 and the Si nanoparticle layer 26 can also be substantially completely silicided. In this case, the silicide layer 14 becomes a continuous film of the silicide 16. Therefore, the silicide layer 14 efficiently reduces the direct contact between the hole transport layer 6 and the light-emitting layer 8 without passing through the silicide 16. Thus, the silicide layer 14, as a continuous film of the silicide 16, more effectively reduces the carrier trap formed between the hole transport layer 6 and the light-emitting layer 8.

[0097] In addition, when the silicide layer 14 is formed by sputtering of the silicide 16, the silicide layer 14 may also contain the silicide 16 with a columnar or granular structure.

[0098] When the silicide layer 14 is formed by sputtering silicide 16, if the energy of the silicide 16 flying towards the hole transport layer 6 is high, the silicide 16 will move for a relatively long time on the hole transport layer 6 even after it reaches the hole transport layer 6. The longer the silicide 16 moves on the hole transport layer 6, the more stable the silicide 16 becomes on the hole transport layer 6.

[0099] Specifically, when the silicide 16 moves a relatively long distance on the hole transport layer 6, the silicide 16 is preferentially absorbed into the defects of the silicide layer 14 in the film. In other words, the longer the silicide 16 moves on the hole transport layer 6, the fewer defects are in the silicide layer 14, resulting in a denser silicide layer 14.

[0100] Here, it is generally known that the silicide layer 14 formed under conditions of high energy from the silicide 16 flying from the hole transport layer 6 contains silicide 16 with columnar or granular structures. Therefore, the silicide layer 14 containing silicide 16 with columnar or granular structures becomes a dense film with reduced defects. Thus, in order to reduce defects that may generate carrier traps, the silicide layer 14 containing silicide 16 with columnar or granular structures improves the hole transport efficiency from the hole transport layer 6 to the light-emitting layer 8.

[0101] Furthermore, the specific structure, polarity, and direction of the dipole moment 16 of the silicide layer 14 can be verified, for example, by obtaining a diffraction image of electron lines transmitted through the silicide layer 14 using the CBED (Focused Electron Beam Diffraction) method. The CBED method is one of the modes of transmission electron microscopy that focuses electron lines onto a sample to obtain a diffraction image. When electron lines pass through the silicide layer 14, the diffraction image of these electron lines is modulated depending on the electron density distribution of the silicide layer 14. Therefore, this diffraction image has a contrast corresponding to the electron density of the silicide layer 14. Thus, by analyzing the contrast of this diffraction image, the electron density distribution corresponding to the dipole moment of the silicide layer 14 can be determined. Additionally, the diffraction image of transmitted electron lines obtained by the CBED method has a resolution equivalent to the lattice length of the silicide molecules. Therefore, a cross-sectional image of the silicide layer 14 can be obtained using the CBED method.

[0102] <The effect of the polarity of silicides> By reference Figure 11 and Figure 12 The effects of the light-emitting element involved in this embodiment will be further explained.

[0103] Figure 11 The band structure diagram 111 is a schematic diagram showing the band structure of the hole transport layer 6 and the light-emitting layer 8 of the light-emitting element 2A involved in the comparative configuration. In the comparative configuration, the hole transport layer 6 and the light-emitting layer 8 are in contact with each other. Therefore, as shown in the band structure diagram 111, the band structures of the hole transport layer 6 and the light-emitting layer 8 are bent so that the Fermi level f of the hole transport layer 6 and the light-emitting layer 8 are aligned.

[0104] The bending of this energy band is caused by the movement of charge carriers contained in the hole transport layer 6 and the luminescent layer 8. Specifically, in the hole transport layer 6, electrons move toward the interface with the luminescent layer 8, and in the luminescent layer 8, holes move toward the interface with the hole transport layer 6.

[0105] Here, the approximate charge distribution of the hole transport layer 6 and the light-emitting layer 8, and the approximate potential generated in the hole transport layer 6 and the light-emitting layer 8 by the charge distribution are as follows: Figure 11 As shown in Figures 112 and 113. Figure 112 is a graph showing the approximate charge distribution in the hole transport layer 6 and the light-emitting layer 8 involved in the comparative configuration, and Figure 113 is a graph showing the approximate intensity of the electric field generated in the hole transport layer 6 and the light-emitting layer 8 involved in the comparative configuration.

[0106] Figures 112 and 113 show the positions of each layer of the light-emitting element 2 along the thickness direction from the anode 4 side on the horizontal axis. Figure 112 shows the amount of charge at that position on the vertical axis, taking positive values ​​for hole distribution and negative values ​​for electron distribution. Figure 113 shows the intensity of the electric field generated at that position on the vertical axis, with the direction from the light-emitting layer 8 to the hole transport layer 6 being positive. Furthermore, the positions on the horizontal axis of Figures 112 and 113 correspond to the positions shown in the band structure diagram 111.

[0107] As shown in Table 112, the total charge of electrons moving to the vicinity of the interface with the luminescent layer 8 in the hole transport layer 6 is approximately the same as the total charge of holes moving to the vicinity of the interface with the hole transport layer 6 in the luminescent layer 8. However, the expansion of the hole distribution from the interface with the hole transport layer 6 in the luminescent layer 8 is wider than the expansion of the electron distribution from the interface with the luminescent layer 8 in the hole transport layer 6. This is because the carrier density of the hole transport layer 6 is higher than that of the luminescent layer 8, and on the other hand, the luminescent layer 8 is closer to a true luminescent layer.

[0108] Therefore, as shown in Figure 113, the electric field strength generated near the interface between the hole transport layer 6 and the light-emitting layer 8, in the direction from the hole transport layer 6 toward the light-emitting layer 8, increases. Accompanyingly, as shown in the band structure diagram 111, the band gap at the interface between the hole transport layer 6 and the light-emitting layer 8 bends significantly on the low-energy side.

[0109] Therefore, in the light-emitting element 2A of the comparative form, the barrier for hole injection from the hole transport layer 6 to the light-emitting layer 8 at the interface between the hole transport layer 6 and the light-emitting layer 8 becomes higher. Consequently, in the light-emitting element 2A of the comparative form, the efficiency of hole injection into the light-emitting layer 8 decreases, and due to the decrease in hole concentration in the light-emitting layer 8, the carrier balance in the light-emitting layer 8 deteriorates, resulting in a decrease in the luminous efficiency of the light-emitting element 2A.

[0110] Figure 12 Energy band diagram 121 is a diagram showing the approximate energy band states of the light-emitting element 2, hole transport layer 6, and light-emitting layer 8 according to this embodiment. Diagram 122 is a diagram showing the approximate charge distribution in the hole transport layer 6, silicide layer 14, and light-emitting layer 8 according to this embodiment. Diagram 123 is a diagram showing the approximate intensity of the electric field generated in the hole transport layer 6, silicide layer 14, and light-emitting layer 8 according to this embodiment.

[0111] Furthermore, in this embodiment, a silicide layer 14 exists between the hole transport layer 6 and the light-emitting layer 8. Therefore, for ease of explanation, in band diagrams 121, 122, and 123, a space corresponding to the silicide layer 14 is shown between the hole transport layer 6 and the light-emitting layer 8. Additionally, the definitions of each axis in 122 and 123 correspond to the definitions of each axis in 112 and 113.

[0112] In this embodiment, the silicide layer 14 includes silicide 16, which is formed such that the direction of the dipole moment 16D of the silicide 16 is from the light-emitting layer 8 toward the hole transport layer 6. Therefore, the silicide 16 is formed such that the side with the electron cloud biased to the positive direction is the hole transport layer 6 side, and the side with the electron cloud biased to the negative direction is the light-emitting layer 8 side.

[0113] Concurrently, effective charge cancellation occurs between electrons moving towards the light-emitting layer 8 in the hole transport layer 6 and the positive electron cloud in the silicide 16 biased towards the hole transport layer 6. Therefore, as shown in Figure 122, the effective amount of charge generated near the interface between the hole transport layer 6 and the light-emitting layer 8, and near the interface between the light-emitting layer 8 and the hole transport layer 6, is reduced compared to the comparative configuration.

[0114] Consequently, as shown in Figure 123, the electric field strength generated near the interface between the hole transport layer 6 and the light-emitting layer 8, in the direction from the hole transport layer 6 to the light-emitting layer 8, is lower compared to the comparative configuration. Therefore, as shown in the band structure diagram 121, the bending of the band gap towards the lower energy value side at the interface between the hole transport layer 6 and the light-emitting layer 8 is also reduced compared to the comparative configuration. As a result, in the above configuration, the barrier to hole injection from the hole transport layer 6 to the light-emitting layer 8 is lowered.

[0115] Therefore, in the light-emitting element 2 according to this embodiment, the barrier to injecting holes from the hole transport layer 6 into the light-emitting layer 8 at the interface between the hole transport layer 6 and the light-emitting layer 8 is reduced. Therefore, in the light-emitting element 2 according to this embodiment, the efficiency of hole injection into the light-emitting layer 8 is improved, the hole concentration in the light-emitting layer 8 increases, and the luminous efficiency of the light-emitting element 2 is improved.

[0116] Furthermore, when a portion of the silicide 16 in the silicide layer 14 is polarized, there are cases where the direction of the polarity of the silicide 16 is not controlled and is randomly determined. Even in this case, by applying a stronger external electric field to the silicide layer 14, the silicide 16 aligns through spontaneous polarization. Therefore, in the silicide layer 14 where a portion of the silicide 16 is polarized, when driving the light-emitting element 2 with a high voltage, the efficiency of injecting holes into the light-emitting layer 8 can be improved. Thus, the light-emitting element 2 having a portion of the silicide layer 14 with polarized silicide 16 improves the luminous efficiency during high-brightness driving. <Supplement> As described above, the molecular structure of silicide 16 has M as a metallic element and is labeled with the real number x as MSi. x The stoichiometric composition of the silicide 16, when it is MSi, can be 0.8 ≤ x ≤ 1.2. Alternatively, when the stoichiometric composition of the silicide 16 is MSi2, it can be 1.6 ≤ x ≤ 2.4.

[0117] When the amount of a certain element contained in the silicide 16 molecule exceeds ±20% of the stoichiometric composition, the metal contained in the silicide 16 and the conductivity based on Si are affected, sometimes resulting in the formation of non-polar silicide 16. Therefore, when the value of X is within the above range, the formation of non-polar silicide 16 can be reduced.

[0118] Furthermore, the thickness of the silicide layer 14 can be less than 20 nm. This reduces the overall resistance increase of the light-emitting element 2. Additionally, when the silicide 16 in the silicide layer 14 is non-polar, the thickness of the silicide layer 14 can be less than 5 nm. In this case, due to the polarity of the silicide 16 in the silicide layer 14, even without reducing the injection barrier of charge carriers to the light-emitting layer 8, charge carriers can effectively pass through the silicide layer 14 through the tunneling effect.

[0119] In addition, such as Figure 7 or Figure 9 As shown, the metal concentration and Si concentration in the silicide layer 14 can vary depending on their positions along the film thickness direction. In this case, by appropriately designing the metal concentration and Si concentration at each location, the direction of the dipole moment 16D of the silicide 16 can be controlled more efficiently.

[0120] [Implementation Method 2] <Reversal of Dipole Moment> Figure 13 This is a schematic cross-sectional view showing the light-emitting element 2 and its surrounding area as described in this embodiment, enlarged. Figure 1 The cross-section shown corresponds to the cross-sectional view at the specified location. Furthermore, in this specification, components with the same function are labeled with the same names and reference numerals, and identical descriptions are not repeated unless there are structural differences.

[0121] Compared to the display device 1 of the aforementioned embodiments, the display device 1 according to this embodiment has a different orientation of the dipole moment 16D of the silicide 16 included in the silicide layer 14 of the light-emitting element 2. Specifically, in this embodiment, at least one of the electron clouds within the polar silicide 16 is positioned to the negative side, becoming the hole transport layer 6 side. In other words, the orientation of the dipole moment 16D of this silicide 16 is from the hole transport layer 6 towards the light-emitting layer 8.

[0122] In particular, in this embodiment, more than half of the silicides 16 contained in the silicide layer 14 have a dipole moment 16D in the direction from the hole transport layer 6 toward the light-emitting layer 8. Therefore, the silicide layer 14 as a whole has a dipole moment in the direction from the hole transport layer 6 toward the light-emitting layer 8.

[0123] Except as described above, the display device 1 according to this embodiment has the same structure as the display device 1 according to the aforementioned embodiment.

[0124] The display device 1 of this embodiment is manufactured using the same manufacturing method as the display device 1 of the above embodiment. However, in this embodiment, when the laminate 18A is formed in step S10, the metal nanoparticles 20 are, for example, selected from metal elements of Group IVB (Group 4), Group VB (Group 5), and Group VIB (Group 6) in Table 1. Furthermore, in this embodiment, when the laminate 18B is formed in step S10, the metal nanoparticles 20 are, for example, selected from metal elements of Group VIIIB (Groups 8, 9, and 10) in Table 1. Therefore, by using the same method as the method for forming the silicide layer 14 in the aforementioned embodiment, a silicide layer 14 having a silicide 16 having a dipole moment 16D in the direction from the hole transport layer 6 toward the light-emitting layer 8 can be formed.

[0125] In this embodiment, since the energy level of silicide 16 in silicide layer 14 is stable, the light-emitting element 2 according to this embodiment reduces the carrier traps generated at the interface between hole transport layer 6 and silicide layer 14, and at the interface between silicide layer 14 and light-emitting layer 8. Therefore, the light-emitting element 2 according to this embodiment can improve the efficiency of hole injection into light-emitting layer 8 and improve the overall luminous efficiency of the element.

[0126] Furthermore, the light-emitting element 2 in this embodiment differs from the light-emitting element 2 in the aforementioned embodiments. The dipole moment 16D of the silicide 16 is in the direction from the hole transport layer 6 toward the light-emitting layer 8. Therefore, according to the aforementioned embodiment... Figure 12 As described above, in this embodiment, the barrier to the injection of holes from the hole transport layer 6 to the light-emitting layer 8 by the light-emitting element 2 increases.

[0127] According to the design of the light-emitting element 2, the efficiency of electron transport from the cathode 12 to the light-emitting layer 8 is low, resulting in a high hole concentration in the light-emitting layer 8, which disrupts the carrier balance in the light-emitting layer 8. In this case, due to the increased barrier to hole injection from the hole transport layer 6 to the light-emitting layer 8, the hole concentration in the light-emitting layer 8 decreases, and the balance with the electron concentration is improved. Therefore, the light-emitting element 2 according to this embodiment improves the luminous efficiency by reducing excessive holes in the light-emitting layer 8 and improving the carrier balance.

[0128] In this embodiment, when the silicide layer 14 is formed by heat treatment of the metal nanoparticle layer 22 and the Si nanoparticle layer 26, only a portion of the metal nanoparticle layer 22 and the Si nanoparticle layer 26 may be silicided. Specifically, in the silicide layer 14, the metal nanoparticle layer 22 and the Si nanoparticle layer 26 may be silicided at locations where they contact at least one of the light-emitting layer 8 or the electron transport layer 10. This configuration reduces the generation of interface states between the metal nanoparticle layer 22 or the Si nanoparticle layer 26 and the light-emitting layer 8 or the electron transport layer 10 at their contact points, thereby reducing the formation of carrier traps.

[0129] In this case, the silicide layer 14 comprises an aggregate structure of silicide 16 nanoparticles in contact with at least one of the light-emitting layer 8 or the electron transport layer 10. Thus, the silicide layer 14 allows the silicide 16 nanoparticles to cover the surface of at least one of the light-emitting layer 8 or the electron transport layer 10 without gaps. Consequently, the electrical contact between the silicide 16 nanoparticles becomes point contact, and the electron transport rate between the silicides 16 decreases. Therefore, the silicide layer 14 with the above structure can more effectively reduce the excessive number of holes in the light-emitting layer 8 by reducing the efficiency of electron transport between the silicides 16.

[0130] [Implementation Method 3] <Example of changing the formation location of the silicide layer> Figure 14 This is a schematic cross-sectional view showing the light-emitting element 2 and its surrounding area as described in this embodiment, enlarged. Figure 1 The cross-sectional view shown is taken at the corresponding position of the cross-section.

[0131] Compared to the display device 1 of Embodiment 1, the display device 1 according to this embodiment differs in the formation position of the silicide layer 14 in each layer of the light-emitting element 2. Specifically, the light-emitting element 2 according to this embodiment is formed between the light-emitting layer 8 and the electron transport layer 10. In other words, in this embodiment, the light-emitting layer 8 and the electron transport layer 10 are adjacent to each other, separated by the silicide layer 14. Furthermore, in this embodiment, the dipole moment 16D of the silicide 16 contained in the silicide layer 14 is oriented from the electron transport layer 10 towards the light-emitting layer 8.

[0132] Except as described above, the display device 1 according to this embodiment has the same structure as the display device 1 according to Embodiment 1.

[0133] Compared to the manufacturing method of the display device 1 according to Embodiment 1, the manufacturing method of the display device 1 according to this embodiment differs in the following aspects: after step S8, step S14 is executed; after step S14, steps S10 and S12 are executed. Therefore, in step S14, a light-emitting layer 8 is formed on the hole transport layer 6, and in step S10, a laminate 18A or a laminate 18B is formed on the light-emitting layer 8. Apart from the above, the manufacturing method of the display device 1 according to this embodiment is manufactured using the same manufacturing method as that according to Embodiment 1.

[0134] The light-emitting element 2 according to this embodiment has a silicide layer 14 containing an energy-level stable silicide 16 between the light-emitting layer 8 and the electron transport layer 10. Therefore, the light-emitting element 2 according to this embodiment reduces the carrier traps generated at the interface between the light-emitting layer 8 and the silicide layer 14, and at the interface between the silicide layer 14 and the electron transport layer 10.

[0135] Based on the design of the light-emitting element 2, the following scenarios are considered: low electron transport efficiency from the cathode 12 to the light-emitting layer 8; low electron concentration in the light-emitting layer 8; and disruption of carrier balance in the light-emitting layer 8. In this situation, the silicide layer 14 described in this embodiment reduces the carrier trap from the electron transport layer 10 to the light-emitting layer 8, thereby improving the efficiency of electron transport from the electron transport layer 10 to the light-emitting layer 8. Therefore, the light-emitting element 2 described in this embodiment can improve the efficiency of electron injection into the light-emitting layer 8 and improve the overall luminous efficiency of the element.

[0136] Furthermore, in this embodiment, the dipole moment 16D of the silicide 16 included in the silicide layer 14 is oriented from the electron transport layer 10 toward the light-emitting layer 8. Therefore, according to the embodiment 1... Figure 12 As described above, in this embodiment, the barrier to electron injection from the electron transport layer 10 to the light-emitting layer 8 is reduced in the light-emitting element 2. Therefore, in the light-emitting element 2 of this embodiment, the efficiency of electron injection into the light-emitting layer 8 is improved, the electron concentration in the light-emitting layer 8 is increased, and the luminous efficiency of the light-emitting element 2 is improved.

[0137] [Implementation Method 4] <Reversed Structure> Figure 15 This is a schematic cross-sectional view showing the light-emitting element 2 and its surrounding area as described in this embodiment, enlarged. Figure 1The cross-sectional view shown is taken at the corresponding position of the cross-section.

[0138] The display device 1 according to this embodiment differs from the display device 1 according to Embodiment 1 in that the formation positions of each layer of the light-emitting element 2 are different. In particular, the light-emitting element 2 according to this embodiment is arranged sequentially from the substrate 3 side and includes a cathode 12, an electron transport layer 10, a silicide layer 14, a light-emitting layer 8, a hole transport layer 6, and an anode 4. Therefore, in this embodiment, the light-emitting layer 8 and the electron transport layer 10 are adjacent to each other through the silicide layer 14.

[0139] Furthermore, in this embodiment, the cathode 12 is a pixel electrode formed for each light-emitting element 2 and electrically connected to each thin-film transistor Tr, while the anode 4 is a common electrode formed in a common area for multiple light-emitting elements 2. Therefore, in this embodiment, each light-emitting element 2 can be driven by controlling the voltage applied to each cathode 12 using the thin-film transistor Tr. Additionally, in this embodiment, the dipole moment 16D of the silicide 16 included in the silicide layer 14 is oriented from the light-emitting layer 8 toward the electron transport layer 10.

[0140] Except as described above, the display device 1 according to this embodiment has the same structure as the display device 1 according to Embodiment 1.

[0141] The manufacturing method of the display device 1 according to this embodiment can be manufactured using the same method, except for the execution order of each step in the manufacturing method of the display device 1 according to Embodiment 1. Specifically, in the manufacturing method of the light-emitting element 2 according to this embodiment, the steps S2, S18, S6, S16, S10, S12, S14, S8, and S4 are executed in that order. Figure 4 The processes shown are as follows.

[0142] Here, step S18 is performed by forming the cathode 12 into an island shape for each sub-pixel, using the same method as step S4 in Embodiment 1. Furthermore, step S4 is performed by forming the anode 4 in a shared manner across multiple sub-pixels, using the same method as step S18 in Embodiment 1.

[0143] The light-emitting element 2 in this embodiment is the same as that in the previous embodiment, and a silicide layer 14 containing an energy-level stable silicide 16 is provided between the light-emitting layer 8 and the electron transport layer 10. Therefore, for the same reasons explained in the previous embodiment, the light-emitting element 2 in this embodiment can improve the efficiency of injecting electrons into the light-emitting layer 8 and improve the overall light-emitting efficiency of the element.

[0144] Furthermore, the light-emitting element 2 involved in this embodiment differs from the light-emitting element 2 involved in the aforementioned embodiments. The dipole moment 16D of the silicide 16 is in the direction from the light-emitting layer 8 toward the electron transport layer 10. Therefore, according to the embodiment 1... Figure 12 As described above, in this embodiment, the barrier for the light-emitting element 2 to inject electrons from the electron transport layer 10 to the light-emitting layer 8 increases.

[0145] The light-emitting element 2 of this embodiment increases the barrier to electron injection from the electron transport layer 10 to the light-emitting layer 8 through the silicide layer 14, thereby reducing the electron concentration in the light-emitting layer 8 and improving the balance with the hole concentration. Therefore, the light-emitting element 2 of this embodiment improves luminous efficiency by reducing excessive electrons in the light-emitting layer 8 and improving carrier balance.

[0146] [Implementation Method 5] <The silicide layer has a two-layer structure> Figure 16 This is a schematic cross-sectional view showing the light-emitting element 2 and its surrounding area as described in this embodiment, enlarged. Figure 1 The cross-sectional view shown is taken at the corresponding position of the cross-section.

[0147] Compared to the display device 1 of Embodiment 1, the light-emitting element 2 of this embodiment further comprises a silicide layer 28 between the light-emitting layer 8 and the electron transport layer 10. The silicide layer 28 has the same structure as the silicide layer 14. In particular, the silicide layer 28 includes a plurality of silicides 30. The silicides 30 have the same structure as the silicides 16, and at least a portion of the silicides 30 are polar and have a dipole moment 30D in the direction from the light-emitting layer 8 to the electron transport layer 10.

[0148] Except as described above, the display device 1 according to this embodiment has the same structure as the display device 1 according to Embodiment 1.

[0149] The display device 1 according to this embodiment is manufactured in the same way as the display device 1 according to the aforementioned embodiment, except that it includes the step of forming a silicide layer 28 between steps S14 and S16. The silicide layer 28 is formed in the same way as the silicide layer 14.

[0150] The light-emitting element 2 according to this embodiment has a silicide layer 14 containing an energy-level-stabilized silicide 16 between the hole transport layer 6 and the light-emitting layer 8. Furthermore, the light-emitting element 2 according to this embodiment has a silicide layer 28 containing an energy-level-stabilized silicide 30 between the light-emitting layer 8 and the electron transport layer 10. Therefore, the light-emitting element 2 according to this embodiment can improve the efficiency of both hole injection and electron injection into the light-emitting layer 8, thereby improving the overall luminous efficiency of the element.

[0151] Furthermore, in this embodiment, the dipole moment 16D of silicide 16 is from the hole transport layer 6 toward the light-emitting layer 8, and the dipole moment 30D of silicide 30 is from the light-emitting layer 8 toward the electron transport layer 10. Therefore, in this embodiment, the barrier to hole injection from the hole transport layer 6 to the light-emitting layer 8 decreases, while the barrier to electron injection from the electron transport layer 10 to the light-emitting layer 8 increases. Therefore, the light-emitting element 2 according to this embodiment increases the hole concentration in the light-emitting layer 8 while decreasing the electron concentration in the light-emitting layer 8. Therefore, the light-emitting element 2 according to this embodiment more effectively reduces excessive electrons in the light-emitting layer 8, improves carrier balance in the light-emitting layer 8, and improves the overall luminous efficiency of the light-emitting element 2.

[0152] This invention is not limited to the embodiments described above. Various modifications can be made within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included within the technical scope of this invention. Furthermore, new technical features can be formed by combining the technical means disclosed in each embodiment. Explanation of reference numerals in the attached figures

[0153] 1 Display device 2. Light-emitting element 3 substrate 4 Anode 6 Hole transport layer 8. Light-emitting layer 10. Electron transport layer 12 Cathode 14, 28 silicide layers 16, 30 silicides 16D and 30D dipole moments 18A and 18B laminates 20 Metal Nanoparticles 22 layers of metal nanoparticles 24Si nanoparticles 26Si nanoparticle layer Tr thin film transistor

Claims

1. A light-emitting element, characterized in that, The device is configured with a first electrode, a first charge transport layer, a silicide layer containing silicide, a light-emitting layer, and a second electrode in sequence. The first charge transport layer and the light-emitting layer are adjacent to each other through the silicide layer. At least a portion of the silicide is polar.

2. The light-emitting element according to claim 1, characterized in that, The silicide layer comprises a columnar or granular structure of the silicide.

3. The light-emitting element according to claim 1, characterized in that, The silicide layer is a continuous film of the silicide.

4. The light-emitting element according to claim 1, characterized in that, The silicide layer comprises an aggregate structure of nanoparticles of the silicide in contact with at least one of the light-emitting layer and the first charge-transporting layer.

5. The light-emitting element according to claim 1, characterized in that, The direction of the dipole moment of at least a portion of the silicide is from the light-emitting layer toward the first charge transport layer.

6. The light-emitting element according to claim 1, characterized in that, The direction of the dipole moment of at least a portion of the silicide is from the first charge transport layer toward the light-emitting layer.

7. A light-emitting element, characterized in that, The device is configured with a first electrode, a first charge transport layer, a silicide layer containing silicide, a light-emitting layer, and a second electrode in sequence. The first charge transport layer and the light-emitting layer are adjacent to each other through the silicide layer. The first electrode is the anode, the second electrode is the cathode, and the first charge transport layer is the hole transport layer. A second charge transport layer is further disposed between the light-emitting layer and the second electrode. The second charge transport layer is an electron transport layer. The silicide layer is further provided between the light-emitting layer and the second charge transport layer. The light-emitting layer and the second charge-transporting layer are adjacent to each other through the silicide layer.

8. A light-emitting element, characterized in that, The device is configured with a first electrode, a first charge transport layer, a silicide layer containing silicide, a light-emitting layer, and a second electrode in sequence. The first charge transport layer and the light-emitting layer are adjacent to each other through the silicide layer. The first electrode is a cathode, the second electrode is an anode, and the first charge transport layer is an electron transport layer.

9. The light-emitting element according to claim 8, characterized in that, A second charge transport layer is further disposed between the light-emitting layer and the second electrode. The second charge transport layer is a hole transport layer.

10. The light-emitting element according to claim 9, characterized in that, The silicide layer is further provided between the light-emitting layer and the second charge transport layer. The light-emitting layer and the second charge-transporting layer are adjacent to each other through the silicide layer.

11. The light-emitting element according to any one of claims 1 to 10, characterized in that, Using M as a metallic element, the molecular structure of the silicide is represented by the real number X, denoted as MSi. x , When the stoichiometric composition of the silicide is MSi, 0.8 ≦ x ≦ 1.2; when the stoichiometric composition of the silicide is MSi2, 1.6 ≦ x ≦ 2.

4.

12. The light-emitting element according to claim 11, characterized in that, M is a metallic element whose atom has more than 6 d electrons.

13. The light-emitting element according to claim 11, characterized in that, M is a metallic element selected from the group consisting of Fe, Ni, Co, Ru, Os, Rh, Ir, Pd and Pt.

14. The light-emitting element according to claim 11, characterized in that, The aforementioned M is a metallic element that includes at least one selected from the group consisting of Fe, Ni, and Co.

15. The light-emitting element according to any one of claims 1 to 10, characterized in that, The thickness of the silicide layer is less than 20 nm.

16. The light-emitting element according to any one of claims 1 to 10, characterized in that, The distribution of Si concentration in the silicide varies depending on its position in the thickness direction of the silicide layer.

17. The light-emitting element according to any one of claims 1 to 10, characterized in that, The distribution of the metal concentration of the silicide varies depending on its position in the thickness direction of the silicide layer.

18. The light-emitting element according to any one of claims 1 to 10, characterized in that, The silicide layer is formed by heat treatment of a laminate containing layers of Si nanoparticles and layers of metal nanoparticles.

19. The light-emitting element according to any one of claims 1 to 10, characterized in that, The silicide layer is formed by heat treatment of a laminate containing layers of SiO2 nanoparticles and layers of metal nanoparticles.

20. The light-emitting element according to claim 18, characterized in that, The Si nanoparticles have a particle size of less than 50 nm.

21. The light-emitting element according to claim 20, characterized in that, The Si nanoparticles have a particle size of less than 20 nm.

22. The light-emitting element according to claim 18, characterized in that, The particle size of the metal nanoparticles is less than 50 nm.

23. The light-emitting element according to claim 22, characterized in that, The particle size of the metal nanoparticles is less than 20 nm.

24. A display device, characterized in that, The display device has a display area, and the display area has multiple pixels. The display device further comprises a substrate and a light-emitting element as described in any one of claims 1 to 10, the light-emitting element being located at each of a plurality of pixels on the substrate. The substrate has multiple thin-film transistors that drive the light-emitting elements respectively.

25. The display device according to claim 24, characterized in that, The light-emitting element, starting from the substrate side, is provided with at least the first electrode, the first charge transport layer, the light-emitting layer, and the second electrode in sequence.

26. The display device according to claim 24, characterized in that, The light-emitting element is provided with at least the second electrode, the light-emitting layer, the first charge transport layer, and the first electrode in sequence from the substrate side.

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