JP2010197723A - Light-emitting element and method of manufacturing the same, and light-emitting panel and light-emitting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide: a new light-emitting element which is more profitable than an organic EL element in element life and a production cost, also whose structure is simple like that of the organic EL element, wherein the element is suitable for light weighting and thinning; a method of manufacturing the same; a light-emitting panel and a light-emitting device provided with the same. <P>SOLUTION: The light-emitting element 1 includes an electrode layer 11, a first conductive layer 12, a second conductive layer 13 and an electrode layer 14 on a substrate 10 in order from the substrate 10 side. The first conductive layer 12 and the second conductive layer 13 come into contact with each other and constitute a pn-junction layer. At least one side of the first conductive layer 12 and the second conductive layer 13 is constituted by adding a rare earth element to an oxide. Thus, when electrons and holes are injected by voltage application to a pn-junction layer, a rare earth element is excited by energy generated by coupling of the injected electrons and holes, then light emission is generated with wavelength corresponding to energy discharged when the rare earth element is returned to the ground state from the excitation state. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a light-emitting element having a pn junction or a pin junction, a manufacturing method thereof, and a light-emitting panel and a light-emitting device including such a light-emitting element.

  Currently, the mainstream of flat panel displays is liquid crystals. However, since the liquid crystal is not a self-luminous type, the liquid crystal display requires many components such as a light source (backlight), a polarizing plate, and a color filter, and the structure must be complicated. Therefore, in recent years, an organic EL (Electro Luminescence) display has been put into practical use as a display device that replaces a liquid crystal display (see Patent Document 1). In the organic EL display, a self-luminous organic EL element is used. Therefore, since a light source, a polarizing plate, a color filter, and the like are not necessary, the structure is simple and suitable for weight reduction and thickness reduction.

JP 2007-052932 A

  However, the organic EL element deteriorates due to slight mixing of moisture and oxygen. Therefore, there is a problem that the device life is short. Further, in order to prevent moisture and oxygen from being mixed in the manufacturing process, a special process is required in which organic EL elements corresponding to the respective emission colors are separately formed in a vacuum, which increases the manufacturing cost. There was a problem.

  The present invention has been made in view of such problems, and its purpose is advantageous over the organic EL element in terms of element lifetime and manufacturing cost, and the structure is simple and light weight like the organic EL element. It is another object of the present invention to provide a new light-emitting element suitable for reduction in thickness and a manufacturing method thereof, and a light-emitting panel and a light-emitting device including such a light-emitting element.

  The first light-emitting element of the present invention includes a pn junction layer formed by bonding a p-type conductive layer and an n-type conductive layer to each other on a substrate, or a p-type conductive layer, an i-type conductive layer, and an n-type conductive layer. It is provided with a pin junction layer constituted by joining layers in this order. At least one of the p-type conductive layer and the n-type conductive layer included in the pn junction layer, or at least the i-type conductive layer of the p-type conductive layer, the i-type conductive layer, and the n-type conductive layer included in the pin junction layer is conductive. It is configured by adding a rare earth element to a conductive oxide. The conductive oxide is tin oxide, zinc oxide, nickel oxide, titanium oxide, tin-added indium oxide or indium oxide, and the rare earth element is terbium, europium, cerium or gadolinium.

  The first light-emitting panel of the present invention includes a plurality of light-emitting elements arranged two-dimensionally. The plurality of light emitting elements provided in the light emitting panel have the same components as the first light emitting element. The first light-emitting device of the present invention includes a light-emitting panel having a plurality of light-emitting elements arranged two-dimensionally and a drive circuit unit that drives the light-emitting elements. The plurality of light emitting elements provided in the light emitting panel have the same components as the first light emitting element.

  The method for manufacturing a light emitting device according to the present invention includes a pn junction layer formed by bonding a p-type conductive layer and an n-type conductive layer to each other on a substrate by vapor deposition or mist CVD, or p-type The method includes a step of forming a pin junction layer constituted by joining a conductive layer, an i-type conductive layer, and an n-type conductive layer in this order. Here, at least one of the p-type conductive layer and the n-type conductive layer included in the pn junction layer, or at least the i-type conductive layer among the p-type conductive layer, the i-type conductive layer, and the n-type conductive layer included in the pin junction layer. Is formed by adding a rare earth element to a conductive oxide. The conductive oxide is tin oxide, zinc oxide, nickel oxide, titanium oxide, tin-added indium oxide or indium oxide, and the rare earth element is terbium, europium, cerium or gadolinium.

  In the first light-emitting element, the first light-emitting panel, the first light-emitting device, and the method for manufacturing the light-emitting element of the present invention, at least one of a p-type conductive layer and an n-type conductive layer included in the pn junction layer, or pin Among the p-type conductive layer, i-type conductive layer, and n-type conductive layer included in the bonding layer, at least the i-type conductive layer is configured by adding the rare earth element shown above to the conductive oxide shown above. ing. Here, the conductive oxide has a property that deterioration due to moisture and oxygen is extremely small as compared with an organic material. Therefore, it is not necessary to use a process for preventing moisture and oxygen from being mixed, and the element hardly deteriorates with time. Further, as the light emitting mechanism, a simple laminated structure similar to that of the organic EL element is used.

  The second light-emitting element of the present invention is a pn junction layer formed by bonding a p-type conductive layer and an n-type conductive layer to each other on a substrate, or a p-type conductive layer, an i-type conductive layer, and an n-type conductive layer. It is provided with a pin junction layer constituted by joining layers in this order. The substrate has a graphite sheet on the outermost surface on the pn junction layer side or the pin junction layer side. The p-type conductive layer and the n-type conductive layer included in the pn junction layer, or the p-type conductive layer, the i-type conductive layer, and the n-type conductive layer included in the pin junction layer mainly contain zinc oxide and contain rare earth elements. It is configured without including.

  The second light emitting panel of the present invention includes a plurality of light emitting elements arranged two-dimensionally. The plurality of light emitting elements provided in the light emitting panel have the same components as the second light emitting element. The second light-emitting device of the present invention includes a light-emitting panel having a plurality of light-emitting elements arranged two-dimensionally and a drive circuit unit that drives the light-emitting elements. The plurality of light emitting elements provided in the light emitting panel have the same components as the second light emitting element.

  In the second light-emitting element, the second light-emitting panel, and the second light-emitting device of the present invention, the pn junction layer or the pin junction layer is formed on the substrate via a graphite sheet. The p-type conductive layer and the n-type conductive layer included in the pn junction layer, or the p-type conductive layer, the i-type conductive layer, and the n-type conductive layer included in the pin junction layer mainly contain zinc oxide and contain rare earth elements. It is not included. Here, zinc oxide has a property that deterioration due to moisture and oxygen is extremely small as compared with an organic material. Therefore, it is not necessary to use a process for preventing moisture and oxygen from being mixed, and the element hardly deteriorates with time. Further, since a hexagonal material is used as the material of the pn junction layer or the pin junction layer and the base of the pn junction layer or the pin junction layer, when forming the zinc oxide layer on the graphite sheet, A single crystal with few crystal defects can be grown. Furthermore, as a light emitting mechanism, a simple laminated structure similar to that of an organic EL element is used. By changing the growth conditions of the laminated structure or the material doped in the laminated structure, for example, light such as red, green, or blue Can be generated.

  According to the first light-emitting element, the first light-emitting panel, the first light-emitting device, and the method for manufacturing the light-emitting element of the present invention, the pn junction layer includes a conductive oxide added with a rare earth element. At least one of the p-type conductive layer and the n-type conductive layer, or at least one of the p-type conductive layer, the i-type conductive layer, and the n-type conductive layer included in the pin junction layer is used as a material for the i-type conductive layer. Thereby, compared with an organic EL element, element lifetime is long and it can hold down manufacturing cost low. Moreover, the structure is simple like the organic EL element, and it is suitable for weight reduction and thickness reduction.

  According to the second light-emitting element, the second light-emitting panel, and the second light-emitting device of the present invention, a p-type conductive layer containing a material mainly containing zinc oxide and not containing a rare earth element in the pn junction layer And the n-type conductive layer or the p-type conductive layer, the i-type conductive layer, and the n-type conductive layer included in the pin junction layer. Thereby, compared with an organic EL element, element lifetime is long and it can hold down manufacturing cost low. Moreover, the structure is simple like the organic EL element, and it is suitable for weight reduction and thickness reduction.

It is sectional drawing of the light emitting element which concerns on the 1st Embodiment of this invention. It is sectional drawing of the modification of the light emitting element of FIG. It is sectional drawing of the other modification of the light emitting element of FIG. It is sectional drawing of the other modification of the light emitting element of FIG. It is a characteristic view showing an example of the light emission characteristic of the light emitting element of FIG. It is a characteristic view showing an example of the transmittance | permeability of the light emitting element of FIG. It is a characteristic view showing an example of the absorption coefficient of the light emitting element of FIG. It is a characteristic view showing an example of the resistivity of the light emitting element of FIG. It is sectional drawing of the light emitting element which concerns on the 2nd Embodiment of this invention. It is sectional drawing of the modification of the light emitting element of FIG. FIG. 2 is a top view of a display device according to an application example of the light emitting element of FIG. 1. It is sectional drawing of the pixel of FIG. It is sectional drawing of the modification of the pixel of FIG. FIG. 12 is a top view of another modification of the pixel in FIG. 11.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the invention will be described in detail with reference to the drawings. The description will be given in the following order.

1. First embodiment (light-emitting element composed of a conductive oxide containing a rare earth element)
2. 2. Modification of first embodiment Example of the first embodiment 4. Second Embodiment (Light-Emitting Element Composed of Conductive Oxide Not Containing Rare Earth Elements)
5). 5. Modification of second embodiment Application example (display device including a plurality of light-emitting elements of the embodiment)
7). Modified examples of application examples

<First Embodiment>
FIG. 1 illustrates an example of a cross-sectional configuration of the light emitting device 1 according to the first embodiment of the present invention. The light emitting element 1 is suitably used for a pixel of a display device, a backlight, a lighting device, or the like. The light emitting element 1 is configured by, for example, laminating an electrode layer 11, a first conductive layer 12, a second conductive layer 13, and an electrode layer 14 on a substrate 10 in order from the substrate 10 side. The first conductive layer 12 and the second conductive layer 13 are in contact with each other and constitute a pn junction layer.

  One of the first conductive layer 12 and the second conductive layer 13 corresponds to a specific example of the “p-type conductive layer” of the present invention. One of the first conductive layer 12 and the second conductive layer 13 that does not correspond to a specific example of the “p-type conductive layer” of the present invention corresponds to a specific example of the “n-type conductive layer” of the present invention. The first conductive layer 12 and the second conductive layer 13 bonded to each other correspond to a specific example of “pn junction layer” of the present invention.

  The substrate 10 has heat resistance that can withstand high temperatures (for example, about several hundred degrees) when the electrode layer 11, the first conductive layer 12, the second conductive layer 13, and the electrode layer 14 are formed. , Quartz glass substrate, silicon (Si) substrate and the like. When the light emitting element 1 is a type that emits light from the substrate 10 side (bottom emission type), the substrate 10 is preferably made of a material that is transparent to the emitted light (emitted light). When the light-emitting element 1 is a type that emits light from the side opposite to the substrate 10 (top emission type), the substrate 10 does not need to be made of a material that is transparent to the emitted light. May be made of a material that reflects or absorbs. The substrate 10 may be insulative or conductive.

  The electrode layers 11 and 14 are for applying a voltage to the pn junction layers (the first conductive layer 12 and the second conductive layer 13). The electrode layers 11 and 14 are made of a conductive material, for example, a metal or a transparent conductive film such as ITO (Indium Tin Oxide), indium oxide, tin oxide, zinc oxide, nickel oxide, or titanium oxide. ing. When the light emitting element 1 is a bottom emission type, the electrode layer 11 is preferably made of a material transparent to emitted light (for example, the transparent conductive film exemplified above). At this time, the electrode 14 does not need to be made of a material transparent to the emitted light, and may be made of a material (for example, metal) that reflects the emitted light. On the other hand, when the light emitting element 1 is a top emission type, the electrode 14 is preferably made of a material transparent to the emitted light (for example, the transparent conductive film exemplified above). At this time, the electrode layer 11 does not have to be made of a material transparent to the emitted light, and may be made of a material (for example, metal) that reflects the emitted light.

  At least one of the first conductive layer 12 and the second conductive layer 13 is configured by adding a rare earth element to a conductive oxide. Of the first conductive layer 12 and the second conductive layer 13, the layers other than the layer formed by adding a rare earth element to the conductive oxide are formed of a conductive oxide to which no rare earth is added. The first conductive layer 12 and the second conductive layer 13 have different conductivity types. For example, the first conductive layer 12 is an n-type conductivity type, and the second conductive layer 13 is a p-type conductivity type. Further, for example, the first conductive layer 12 has a p-type conductivity, and the second conductive layer 13 has an n-type conductivity.

  The conductivity of the conductive oxide can be imparted, for example, by doping p-type impurities or n-type impurities. Examples of the p-type impurity include a group III element when the base material is a group IV element. Examples of the n-type impurity include a group V element when the base material is a group IV element. Note that some oxide materials tend to be n-type impurities. For such materials, no impurity doping is required.

Examples of the conductive oxide include tin oxide (SnO ₂ ), zinc oxide (ZnO), indium oxide (In ₂ O ₃ ), tin-added indium oxide, and the like. Note that as the conductive oxide, an oxide that exhibits conductivity by doping, for example, titanium oxide (TiO ₂ ), nickel oxide (NiO), or Ga ₂ O ₃ may be used. Examples of rare earth elements include terbium (Tb), europium (Eu), cerium (Ce), and gadolinium (Gd). The emission color varies depending on the type of rare earth element. Although the emission wavelength varies depending on the base material, it cannot be generally stated. For example, in the case of Te, light emission occurs in the green band wavelength, in the case of Eu, light emission occurs in the red band wavelength, and in the case of Ce. In the case of Gd, light emission occurs at a wavelength in the ultraviolet band.

  The band gap of the first conductive layer 12 and the second conductive layer 13 needs to be larger than the energy corresponding to the emission wavelength. For example, when the emission wavelength is in the range from ultraviolet to infrared, the band gap of the conductive oxide is preferably about 3 to 4 eV.

  The light emitting element 1 can be manufactured as follows, for example. Hereinafter, the case where the electrode layers 11 and 14 are formed of a transparent conductive film such as tin-added indium oxide, indium oxide, tin oxide, zinc oxide, nickel oxide, or titanium oxide will be described.

  First, the electrode layer 11D, the first conductive layer 12D, the second conductive layer 13D, and the electrode layer 14D are stacked on the substrate 10 by using, for example, a vapor deposition method. As a vapor deposition method, for example, a method of forming a conductive oxide film by vapor-depositing a metal in oxygen gas or a method of forming a conductive oxide film by vapor-depositing the conductive oxide itself is employed. It is possible. At this time, the laminate including the electrode layer 11D, the first conductive layer 12D, the second conductive layer 13D, and the electrode layer 14D is formed on the entire top surface of the substrate 10, for example. Note that the electrode layer 11D, the first conductive layer 12D, the second conductive layer 13D, and the electrode layer 14D are processed through the subsequent steps, so that the electrode layer 11, the first conductive layer 12, the second conductive layer 13, and the electrode layer are processed. 14, which means that the electrode layer 11, the first conductive layer 12, the second conductive layer 13, and the electrode layer 14 are in the previous stage.

  Next, after a resist layer (not shown) having a predetermined opening is formed on the electrode layer 14, the electrode layer 11D and the first conductive layer 12D are formed using, for example, a dry etching method using the resist layer as a mask. Then, the second conductive layer 13D and the electrode layer 14D are selectively etched. As a result, a laminate including the electrode layer 11, the first conductive layer 12, the second conductive layer 13, and the electrode layer 14 is formed on the substrate 10. In this way, the light emitting element 1 is manufactured.

  In the above manufacturing process, one or a plurality of layers among the electrode layer 11D, the first conductive layer 12D, the second conductive layer 13D, and the electrode layer 14D are formed using a mist CVD (Chemical Vapor Deposition) method. May be. Here, the mist CVD method refers to a method exemplified below. First, a compound aqueous solution containing a constituent element of a material to be deposited and a deposition substrate are placed in a chamber under atmospheric pressure. Next, the substrate is heated to a predetermined temperature, and ultrasonic waves are applied to the compound aqueous solution to form atomized fine particles (mist) containing the constituent elements of the material to be formed, and the chamber The mother gas is supplied into the inside, and the mist is transported on the substrate in a gas flow. As a result, the mist chemically reacts with the substrate surface, and a desired film is formed on the substrate surface. Since this mist CVD method can form a film under atmospheric pressure and at a low temperature, it can be said to be a simple, inexpensive and safe film forming method.

  Further, in the above manufacturing process, the electrode layer 11D, the first conductive layer 12D, the second conductive layer 13D, and the electrode layer 14D may be stacked on the substrate 10 by using a mist CVD method instead of the vapor deposition method. Good. At this time, one or more of these layers may be formed using a vapor deposition method.

  Note that in the case where the electrode layer 11 or the electrode layer 14 is formed using a metal, the layer formed using a metal may be formed using an evaporation method or a sputtering method.

  Next, the operation and effect of the light-emitting element 1 of the present embodiment will be described.

  In the present embodiment, at least one of the pn junction layers (the first conductive layer 12 and the second conductive layer 13) is configured by adding a rare earth element to a conductive oxide. Further, of the pn junction layer, layers other than the layer formed by adding a rare earth element to a conductive oxide are formed of a conductive oxide to which no rare earth is added. As a result, when electrons and holes are injected into the pn junction layer by applying a voltage, the rare earth element is excited by the energy generated by the combination of the injected electrons and holes, and the rare earth element is changed from the excited state to the ground state. Light emission occurs at a wavelength corresponding to the energy released when returning to.

  Here, the conductive oxide has a property that deterioration due to moisture and oxygen is extremely small as compared with an organic material. Therefore, it is not necessary to use a process for preventing moisture and oxygen from being mixed, and it is possible to form a film using, for example, an atmospheric process using water vapor. Further, even when a vacuum apparatus is used, it is not necessary to use a special vacuum apparatus such as that used in the manufacture of organic EL elements, so that the operation and maintenance of the vacuum apparatus are simple. In addition, since the conductive oxide has a property that the deterioration due to moisture and oxygen is extremely small, the element hardly deteriorates with time.

  From the above, in the present embodiment, the device life is longer than that of the organic EL device, and the manufacturing cost can be kept low. Further, since a simple laminated structure is used as the light emitting mechanism and the structure is simple like the organic EL element, the light emitting element 1 is suitable for weight reduction and thickness reduction. Moreover, in this Embodiment, since the light emitting element 1 can be manufactured using the above-mentioned vapor deposition method or mist CVD method, the light emitting element 1 can be provided at low cost.

<Modification>
In the above embodiment, the first conductive layer 12 and the second conductive layer 13 are in contact with each other. For example, as shown in FIG. 2, a light emitting layer 15 may be provided between them. In this case, at least the light emitting layer 15 among the first conductive layer 12, the second conductive layer 13, and the light emitting layer 15 is configured by adding a rare earth element to an oxide. Here, the light emitting layer 15 is composed of a non-doped (or undoped) oxide (a rare earth-doped oxide). The first conductive layer 12 and the light emitting layer 15 are in contact with each other, and the second conductive layer 13 and the light emitting layer 15 are in contact with each other. Accordingly, the first conductive layer 12, the second conductive layer 13, and the light emitting layer 15 constitute a pin junction layer.

  The light emitting layer 15 corresponds to a specific example of “i-type conductive layer” of the present invention. The first conductive layer 12, the second conductive layer 13, and the light emitting layer 15 correspond to a specific example of the “pin junction layer” of the present invention.

  The band gap of the first conductive layer 12 and the second conductive layer 13 needs to be larger than the energy corresponding to the emission wavelength, as in the above embodiment. For example, when the emission wavelength is in the range from ultraviolet to infrared, the band gap of the conductive oxide is preferably about 3 to 4 eV.

  It is preferable that the band gap of the light emitting layer 15 is smaller than the band gaps of the first conductive layer 12 and the second conductive layer 13. Thus, when the pin junction layer has a double hetero structure, the confinement property of electrons and holes can be improved, and the luminous efficiency can be increased. In order to narrow the band gap, for example, a material that narrows the band gap may be added. The band gap of the light emitting layer 15 may be equal to or almost equal to the band gap of the first conductive layer 12 and the second conductive layer 13.

  In the first embodiment and its modification, the electrode layer 11 is formed directly on the surface of the substrate 10, but may be formed on the substrate via some layer. For example, as shown in FIGS. 3 and 4, a base layer 16 may be provided between the substrate 10 and the electrode layer 11. The underlayer 16 is made of, for example, a graphite sheet or a silicon thin film. Since the graphite sheet is hexagonal, a single crystal having few crystal defects can be grown when a hexagonal oxide film such as zinc oxide is formed. Therefore, when a laminated body (electrode layer 11, first conductive layer 12, second conductive layer 13, electrode layer 14, etc.) containing a hexagonal material such as zinc oxide is formed on the graphite sheet, the first The possibility that the conductive layer 12 is short-circuited to the electrode layer 14 or the second conductive layer 13 is short-circuited to the electrode layer 11 can be eliminated. Further, since the silicon thin film is tetragonal, a single crystal with few crystal defects can be grown when a tetragonal oxide film such as tin oxide is formed. Therefore, when a laminated body (electrode layer 11, first conductive layer 12, second conductive layer 13, electrode layer 14, etc.) containing a tetragonal material such as tin oxide is formed on the silicon thin film, the first The possibility that the conductive layer 12 is short-circuited to the electrode layer 14 or the second conductive layer 13 is short-circuited to the electrode layer 11 can be eliminated. The silicon thin film is formed by, for example, implanting hydrogen ions with a predetermined energy into the entire surface of the silicon substrate to form a release layer having a high hydrogen concentration in the silicon substrate, and then forming the silicon thin film formed on the release layer. It can be formed by peeling from the silicon substrate using a peeling layer. As described above, when the base layer 16 is provided on the substrate 10, the display device 1 can be easily increased in area regardless of the material such as the electrode layer 11. For example, first, a large-area glass substrate or a quartz glass substrate is prepared as the substrate 10, and a base layer 16 is formed on the surface of the substrate 10 by, for example, laying a large number of graphite sheets or silicon thin films. Subsequently, an electrode layer 11 including a material having the same crystal structure as the material of the base layer 16 is stacked thereon. In this way, the display device 1 can be easily increased in area regardless of the material such as the electrode layer 11.

  The substrate 10 is a silicon substrate, and the electrode layer 11, the first conductive layer 12, the second conductive layer 13, and the electrode layer 14 are configured to include a tetragonal material (for example, tin oxide). In some cases, the underlying layer 16 as described above is not necessary. The silicon substrate is made of a tetragonal material, and the electrode layer 11, the first conductive layer 12, the second conductive layer 13, and the electrode layer 14 can be formed on the substrate 10 with few crystal defects. Because. Therefore, also in this case, when the first conductive layer 12, the second conductive layer 13, the electrode layer 14 and the like are formed on the silicon substrate, the first conductive layer 12 is short-circuited with the electrode layer 14, or the second The possibility that the conductive layer 13 is short-circuited with the electrode layer 11 can be eliminated.

<Example>
Hereinafter, examples of the light-emitting element 1 according to the above-described embodiment will be described.

5A and 5B, a layer in which Tb is added to SnO ₂ at a concentration of 3% is formed on a quartz glass substrate, and the surface is irradiated with a laser beam of a 325 nm, 8 mW He—Cd laser. It is a photoluminescence spectrum sometimes obtained. FIG. 5 (A) shows a spectrum when annealing is performed in an oxygen gas on a layer in which Tb is added to SnO ₂ , and FIG. 5 (B) is in argon gas to a layer in which Tb is added to SnO _2. The spectra when annealing is performed are shown respectively. At this time, the spectrum was measured by setting the temperature of the substrate 10 to 500 ° C., the thickness of the substrate 10 to 500 μm, and the annealing temperature in oxygen gas to 600 ° C., 700 ° C. or 800 ° C. The wavelength of the excitation light is in the 325nm irradiates light having a wavelength corresponding to the energy greater than the band gap of the SnO ₂ (approximately 3.3 eV) to SnO _2, Tb ³ by the energy transfer from SnO ₂ ^{This is} to indirectly excite ⁺ .

  From FIG. 5A, it was found that when annealing is performed in oxygen gas, green light emission of 545 nm can be obtained when the annealing temperature is 700 ° C. or higher. From FIG. 5 (B), when annealing is performed in argon gas, green light emission of 545 nm can be obtained in all samples, but the emitted light contains a significant proportion of other wavelength components. I found out. The reason why such light emission characteristics are obtained will be described later.

6A and 6B, a layer in which Tb is added to SnO ₂ at a concentration of 3% is formed on a glass substrate, and the light transmittance of the layer is measured using an ultraviolet-visible spectrophotometer. The result obtained by this is shown. FIG. 6A shows the result when annealing is performed in an oxygen gas for a layer in which Tb is added to SnO ₂ , and FIG. 6B shows the result in argon gas for the layer in which Tb is added to SnO _2. The results when annealing is performed are shown respectively.

FIG. 6A shows that the absorption edge wavelength is as large as about 400 nm when annealing is performed at 600 ° C. in oxygen gas. On the other hand, when annealing was performed at 700 ° C. and 800 ° C. in oxygen gas, the absorption edge wavelength was found to be as small as about 300 nm. Moreover, it turned out that the transmittance | permeability in the 700 degreeC and 800 degreeC sample is better than the transmittance | permeability in the 600 degreeC sample. This is probably because the sample at 600 ° C. was not sufficiently oxidized in the annealing step, and SnO ₂ that was transparent in the visible light region was not sufficiently formed.

  FIG. 6B shows that the absorption edge wavelength is as large as about 400 nm when annealing is performed at 600 ° C. in argon gas. On the other hand, when annealing was performed at 700 ° C. and 800 ° C. in argon gas, the absorption edge wavelength was found to be as small as about 300 nm. It was also found that the transmittance of the 700 ° C. and 800 ° C. samples was better than that of the 600 ° C. sample, as in the case of annealing in oxygen gas.

FIGS. 7A and 7B show absorption coefficients derived from the light transmittances of FIGS. 6A and 6B. FIG. 7A shows the result when annealing is performed in an oxygen gas for a layer in which Tb is added to SnO ₂ , and FIG. 7B shows the result in argon gas for the layer in which Tb is added to SnO _2. The results when annealing is performed are shown respectively.

FIG. 7A shows that when annealing is performed in oxygen gas at 600 ° C., the band gap is about 2.45 eV, and the energy of ⁵ D ₄ that is the excitation level of Tb ³⁺ (about 2 It was found to be lower than .60 eV). Therefore, it is considered that indirect excitation of Tb ³⁺ via SnO ₂ was not performed as shown in FIG. On the other hand, when annealing is performed at 700 ° C. and 800 ° C. in oxygen gas, the band gap is about 3.3 eV and about 3.5 eV, and the energy of ⁵ D ₄ which is the excitation level of Tb ³⁺ It turned out to be higher. Therefore, as shown in FIG. 5A, it is considered that indirect excitation of Tb ³⁺ via SnO ₂ was performed and light was emitted in green.

FIG. 7B shows that when annealing is performed at 600 ° C. in argon gas, the band gap is about 2.7 eV, and when annealing is performed at 700 ° C. and 800 ° C. in argon gas. Had a band gap of about 3.3 eV. That is, when the annealing was performed in an argon gas, in all samples, the band gap was found to be higher than the energy of the excited level at which ⁵ D ₄ of Tb ^3+. Therefore, as shown in FIG. 5B, it is considered that indirect excitation of Tb ³⁺ via SnO ₂ was performed and light was emitted in green.

From the above, it has been found that when the annealing temperature is set to a high temperature of 700 ° C. to 800 ° C., green light of 545 nm can be obtained from the layer in which Tb is added to SnO ₂ . It was also found that when annealing was performed in oxygen gas at an annealing temperature of 700 ° C., green light of 545 nm could be obtained with high intensity from the layer in which Tb was added to SnO ₂ .

FIG. 8 shows a measurement result of the resistivity of a layer formed by adding Tb to SnO ₂ at a concentration of 3% on a glass substrate. FIG. 8 shows the results when annealing is performed in an oxygen gas or an argon gas on a layer in which Tb is added to SnO ₂ . FIG. 8 shows that the resistivity varies depending on the annealing temperature and the annealing gas, but is sufficiently small at less than 0.1 Ωcm at 600 ° C. to 800 ° C.

  From the above, it was found that when the annealing temperature was set to a high temperature of 700 ° C. to 800 ° C., good characteristics were obtained in terms of transmittance, interference fringes and resistivity. Therefore, it was found that a high-quality device can be obtained by increasing the annealing temperature to 700 ° C. to 800 ° C.

<Second Embodiment>
FIG. 9 illustrates an example of a cross-sectional configuration of the light-emitting element 2 according to the second embodiment of the present invention. The light emitting element 2 is suitably used for a pixel of a display device, a backlight, a lighting device, or the like. The light emitting element 2 is configured by, for example, laminating a graphite layer 41, an electrode layer 11, a first conductive ZnO layer 42, a second conductive ZnO layer 43, and an electrode layer 14 in this order from the substrate 40 side. ing. The first conductive ZnO layer 42 and the second conductive ZnO layer 43 are in contact with each other and constitute a pn junction layer.

  One of the first conductive ZnO layer 42 and the second conductive ZnO layer 43 corresponds to a specific example of the “p-type conductive layer” of the present invention. Of the first conductive ZnO layer 42 and the second conductive ZnO layer 43, the one not corresponding to one specific example of the “p-type conductive layer” of the present invention corresponds to one specific example of the “n-type conductive layer” of the present invention. . The first conductive ZnO layer 42 and the second conductive ZnO layer 43 bonded to each other correspond to a specific example of “pn junction layer” of the present invention.

  The graphite layer 41 is in contact with the electrode layer 11 and has a role as a base (growth substrate) for crystal growth of the electrode layer 11, the first conductive layer 41, the second conductive layer 42, and the electrode layer 14. Yes. The graphite layer 41 is made of, for example, a graphite sheet. Since the graphite sheet is hexagonal, a single crystal with few crystal defects can be grown when a hexagonal oxide film such as ZnO is formed. At present, a large area (several tens of cm square) graphite sheet is commercially available, and single crystal growth in a large area is possible.

  The first conductive ZnO layer 42 and the second conductive ZnO layer 43 are mainly composed of ZnO. The first conductive ZnO layer 42 and the second conductive ZnO layer 43 have different conductivity types. For example, the first conductive ZnO layer 42 is n-type conductivity, and the second conductive ZnO layer 43 is p-type conductivity. Further, for example, the first conductive ZnO layer 42 is p-type conductivity, and the second conductive ZnO layer 43 is n-type conductivity.

  The conductivity of ZnO can be imparted, for example, by doping p-type impurities or n-type impurities. Examples of p-type impurities include group V elements such as nitrogen (N). Examples of the n-type impurity include group III elements such as aluminum (Al) and gallium (Ga). The emission color of ZnO can be adjusted by changing the growth conditions or the material to be doped. For example, it is possible to generate red or green light from ZnO by appropriately setting the growth conditions. For example, blue light can be generated from ZnO by doping cadmium (Cd) into ZnO.

  In the present embodiment, the pn junction layers (the first conductive ZnO layer 42 and the second conductive ZnO layer 43) are made of, for example, ZnO produced by appropriately set growth conditions or ZnO doped with Cd. It is mainly composed of. Thus, when electrons and holes are injected by applying a voltage to the pn junction layer, light emission occurs due to the combination of the injected electrons and holes.

  Here, ZnO has a property that deterioration due to moisture and oxygen is extremely small as compared with an organic material. Therefore, it is not necessary to use a process for preventing moisture and oxygen from being mixed, and it is possible to form a film using, for example, an atmospheric process using water vapor. Further, even when a vacuum apparatus is used, it is not necessary to use a special vacuum apparatus such as that used in the manufacture of organic EL elements, so that the operation and maintenance of the vacuum apparatus are simple. In addition, since ZnO has the property of extremely little deterioration due to moisture and oxygen, there is almost no deterioration over time of the element. Further, since a hexagonal material is used as the material of the pn junction layer or the pin junction layer and the base of the pn junction layer or the pin junction layer, when forming the zinc oxide layer on the graphite sheet, A single crystal with few crystal defects can be grown. Therefore, when the electrode layer 11, the first conductive ZnO layer 42, the second conductive ZnO layer 43, the electrode layer 14 and the like are formed on the graphite sheet, the first conductive ZnO layer 42 is short-circuited with the electrode layer 14, The possibility that the second conductive ZnO layer 43 is short-circuited with the electrode layer 11 can be eliminated.

  From the above, in the present embodiment, the device life is longer than that of the organic EL device, and the manufacturing cost can be kept low. Further, since a simple laminated structure is used as the light emitting mechanism and the structure is simple like the organic EL element, the light emitting element 1 is suitable for weight reduction and thickness reduction. In the present embodiment, as in the first embodiment, the light emitting element 2 can be manufactured by using a vapor deposition method or a mist CVD method. Is possible.

<Modification>
In the second embodiment, the first conductive ZnO layer 42 and the second conductive ZnO layer 43 are in contact with each other. For example, as shown in FIG. 10, a light emitting layer 45 is provided between them. It may be done. In this case, like the first conductive ZnO layer 42 and the second conductive ZnO layer 43, the light emitting layer 45 is mainly composed of ZnO. The first conductive ZnO layer 42 and the light emitting layer 45 are in contact with each other, and the second conductive conductive ZnO layer 43 and the light emitting layer 45 are in contact with each other. Accordingly, the first conductive ZnO layer 42, the second conductive ZnO layer 43, and the light emitting layer 45 constitute a pin junction layer.

  The light emitting layer 45 corresponds to a specific example of “i-type conductive layer” of the present invention. The first conductive ZnO layer 42, the second conductive conductive ZnO layer 43, and the light emitting layer 45 correspond to a specific example of the “pin junction layer” of the present invention.

<Application example>
Next, an application example of the first embodiment and its modification will be described. FIG. 11 illustrates an example of a top surface configuration of a display device 3 (light-emitting device) using the light-emitting element 1 according to the embodiment and the modification. The display device 3 includes, for example, a display panel 20 and a drive circuit unit (not shown) that drives the light emitting element 1 formed in the display panel 20 as will be described later.

  The display panel 20 has a plurality of light emitting elements 1 arranged in a matrix in a display area. The plurality of light emitting elements 1 are composed of, for example, three types of light emitting elements. For example, one light emitting element 1 is a light emitting element 1R that generates red light. The other light emitting element 1 is a light emitting element 1G that generates green light, and the remaining light emitting element 1 is a light emitting element 1B that generates blue light. One pixel 30 is configured by the light emitting elements 1R, 1G, and 1B.

  FIG. 12 illustrates an example of a cross-sectional configuration of the display panel 4 in FIG. FIG. 12 shows an example of a cross-sectional configuration of one pixel 30. 12 shows the light-emitting element 1 having the configuration illustrated in FIG. 1, but the light-emitting element 1 has another configuration (configuration illustrated in FIG. 2, FIG. 3, or FIG. 4). Things may be used.

  The pixel 30 has, for example, three types of light emitting elements 1R, 1G, and 1B on the substrate 10 as shown in FIG. The light emitting elements 1R, 1G, and 1B are configured by, for example, laminating an electrode layer 11, a first conductive layer 12, a second conductive layer 13, and an electrode layer 14 in this order on the substrate 10 from the substrate 10 side. The first conductive layer 12 and the second conductive layer 13 are in contact with each other and constitute a pn junction layer. When the light emitting element 1 having the configuration illustrated in FIG. 2 or FIG. 4 is used, the first conductive layer 12, the second conductive layer 13, and the light emitting layer 15 are in contact with each other, and a pin junction is used. Make up layer.

  Here, in the light emitting element 1R, at least one of the first conductive layer 12 and the second conductive layer 13 is configured by adding a rare earth element (Eu) to an oxide. In the light emitting element 1G, at least one of the first conductive layer 12 and the second conductive layer 13 is configured by adding rare earth element (Tb) to an oxide. In the light emitting element 1B, at least one of the first conductive layer 12 and the second conductive layer 13 is configured by adding a rare earth element (Ce) to an oxide.

  When the light emitting element 1 having the configuration illustrated in FIG. 2 or FIG. 4 is used, in the light emitting element 1R, at least one of the first conductive layer 12, the second conductive layer 13, and the light emitting layer 15 is used. The light emitting layer 15 is configured by adding a rare earth element (Eu) to an oxide. In the light emitting element 1G, at least the light emitting layer 15 of the first conductive layer 12, the second conductive layer 13, and the light emitting layer 15 is configured by adding a rare earth element (Tb) to an oxide. In the light emitting element 1B, at least the light emitting layer 15 of the first conductive layer 12, the second conductive layer 13, and the light emitting layer 15 is configured by adding rare earth element (Ce) to an oxide.

  The electrode layers 11 of the light emitting elements 1R, 1G, and 1B may be formed separately from each other, for example, as shown in FIG. 12, or may be formed integrally with each other, for example, as shown in FIG. It may be. When the substrate 10 has insulating properties, the electrode layers 11 of the light emitting elements 1R, 1G, and 1B do not directly contact the first conductive layer 12 as shown in FIG. 14, for example. It is preferable to have the region 11A. In that case, the region 11A can be used as an electrode pad connected to an external device. Further, even when the substrate 10 has conductivity, the electrode layer 11 is provided with a region 11A that does not directly contact the first conductive layer 12, and the region 11A serves as an electrode pad that connects to an external device. It is possible to use. When the substrate 10 has conductivity, a metal layer (not shown) is newly provided on the back surface of the substrate 10 and the metal layer can be used as a common electrode for each of the light emitting elements 1R, 1G, and 1B. Is possible.

  In the display device 3 according to this application example, in each of the light emitting elements 1R, 1G, and 1B, at least one of a pn junction layer (the first conductive layer 12 and the second conductive layer 13) or a pin junction layer (the first conductive layer 12). Among the second conductive layer 13 and the light emitting layer 15), at least the light emitting layer 15 is formed by adding a rare earth element to an oxide. As a result, when electrons and holes are injected by applying voltage to the pn junction layer or pin junction layer, the rare earth element is excited by the energy generated by the combination of the injected electrons and holes, and the rare earth element is excited. Light emission occurs at a wavelength corresponding to the energy released when returning from the state to the ground state. Accordingly, for example, red light is generated in the light emitting element 1R to which Eu is added, green light is generated in the light emitting element 1R to which Tb is added, and blue light is generated in the light emitting element 1B to which Ce is added.

  Here, as described above, the conductive oxide used in each of the light emitting elements 1R, 1G, and 1B has a property of being extremely less deteriorated by moisture and oxygen than the organic material. Furthermore, in each light emitting element 1R, 1G, 1B, a heterostructure is used as a light emitting mechanism. Therefore, in this application example, the device life is longer than the organic EL device, and the manufacturing cost can be kept low. Moreover, the structure is simple like the organic EL element, and it is suitable for weight reduction and thickness reduction.

<Modification>
In the application example, the light emitting elements 1R, 1G, and 1B that emit light of each color are provided on the substrate. However, the light emitting element 1 that emits light of a single color may be provided. For example, an element that emits white light may be provided as the light-emitting element 1 that emits a single color. In this case, for example, RGB color filters can be provided on the light emission side of the light emitting element 1. This color filter has a red filter on the light emitting surface of one light emitting element 1, a green filter on the light emitting surface of the other light emitting element 1, and the light emitting surfaces of the remaining light emitting elements 1. Has a blue filter.

  Further, for example, a light emitting element 1 that emits blue light may be provided that emits blue light. In this case, for example, it is possible to provide RGB color conversion filters on the light emission side of the light emitting element 1. This color conversion filter has a conversion layer for converting blue to red on the light emitting surface of one light emitting element 1, and has a conversion layer for converting blue to green on the light emitting surface of another light emitting element 1. The light emitting surface of the remaining light emitting element 1 has a non-conversion layer that transmits blue light.

  Moreover, although the case where the light emitting element 1 of the said embodiment and the said modified example was applied to the display apparatus was illustrated in the said application example and its modification, it applies to other devices, such as a backlight and an illuminating device. Of course it is also possible.

  In the application example and the modification example, the case where the light emitting element 1 is used as the light source of the display device 3 has been described. However, it is of course possible to use the light emitting element 2 of the second embodiment.

  DESCRIPTION OF SYMBOLS 1,1R, 1G, 1B, 2 ... Light emitting element, 3 ... Display apparatus, 10, 40 ... Board | substrate, 11, 14 ... Electrode layer, 11A ... Area | region, 12 ... 1st conductivity type layer, 13 ... 2nd conductivity type layer 15, 44 ... light emitting layer, 16 ... base layer, 20 ... display panel, 30 ... pixel, 41 ... graphite layer, 42 ... first conductive conductive ZnO layer, 43 ... second conductive conductive ZnO layer.

Claims (9)

A pn junction layer formed by bonding a p-type conductive layer and an n-type conductive layer to each other on a substrate, or a p-type conductive layer, an i-type conductive layer, and an n-type conductive layer are bonded in this order. A pin junction layer,
At least one of the p-type conductive layer and the n-type conductive layer included in the pn junction layer, or at least the i-type conductive layer of the p-type conductive layer, the i-type conductive layer, and the n-type conductive layer included in the pin junction layer is , Which is configured by adding rare earth elements to conductive oxide,
The conductive oxide is tin oxide, zinc oxide, nickel oxide, titanium oxide, tin-added indium oxide or indium oxide,
The light-emitting element, wherein the rare earth element is terbium, europium, cerium, or gadolinium. The light emitting device according to claim 1, wherein the substrate is a glass substrate, a quartz glass substrate, or a silicon substrate. The light emitting device according to claim 1, wherein the substrate has a graphite sheet in contact with the pn junction layer or the pin junction layer. A pn junction layer formed by bonding a p-type conductive layer and an n-type conductive layer to each other using a vapor deposition method or a mist CVD method on a substrate, or a p-type conductive layer, an i-type conductive layer, and an n-type Forming a pin junction layer constituted by joining the conductive layers in this order;
At least one of the p-type conductive layer and the n-type conductive layer included in the pn junction layer, or at least the i-type conductive layer of the p-type conductive layer, the i-type conductive layer, and the n-type conductive layer included in the pin junction layer is , Which is configured by adding rare earth elements to conductive oxide,
The conductive oxide is tin oxide, zinc oxide, nickel oxide, titanium oxide, tin-added indium oxide or indium oxide,
The method for manufacturing a light-emitting element, wherein the rare earth element is terbium, europium, cerium, or gadolinium. A pn junction layer formed by bonding a p-type conductive layer and an n-type conductive layer to each other on a substrate, or a p-type conductive layer, an i-type conductive layer, and an n-type conductive layer are bonded in this order. A pin junction layer,
The substrate has a graphite sheet on the outermost surface of the pn junction layer side or the pin junction layer side,
The p-type conductive layer and the n-type conductive layer included in the pn junction layer, or the p-type conductive layer, the i-type conductive layer, and the n-type conductive layer included in the pin junction layer mainly include zinc oxide and a rare earth A light-emitting element comprising no element. A plurality of light-emitting elements arranged two-dimensionally;
The light emitting element is
A pn junction layer configured by bonding a p-type conductive layer and an n-type conductive layer to each other, or a pin junction layer configured by bonding a p-type conductive layer, an i-type conductive layer, and an n-type conductive layer in this order. Have
At least one of the p-type conductive layer and the n-type conductive layer included in the pn junction layer, or at least the i-type conductive layer of the p-type conductive layer, the i-type conductive layer, and the n-type conductive layer included in the pin junction layer is , Which is configured by adding rare earth elements to conductive oxide,
The conductive oxide is tin oxide, zinc oxide, nickel oxide, titanium oxide, tin-added indium oxide or indium oxide,
The display panel, wherein the rare earth element is terbium, europium, cerium, or gadolinium. A plurality of light-emitting elements arranged two-dimensionally;
The light emitting element is
A pn junction layer formed by bonding a p-type conductive layer and an n-type conductive layer to each other on a substrate, or a p-type conductive layer, an i-type conductive layer, and an n-type conductive layer are bonded in this order. A pin junction layer,
The substrate has a graphite sheet on the outermost surface of the pn junction layer side or the pin junction layer side,
The p-type conductive layer and the n-type conductive layer included in the pn junction layer, or the p-type conductive layer, the i-type conductive layer, and the n-type conductive layer included in the pin junction layer mainly include zinc oxide and a rare earth A display panel characterized in that it is constructed without containing elements. A light-emitting panel having a plurality of light-emitting elements arranged two-dimensionally;
A drive circuit unit for driving the light emitting element,
The light emitting element is
A pn junction layer configured by bonding a p-type conductive layer and an n-type conductive layer to each other, or a pin junction layer configured by bonding a p-type conductive layer, an i-type conductive layer, and an n-type conductive layer in this order. Have
At least one of the p-type conductive layer and the n-type conductive layer included in the pn junction layer, or at least the i-type conductive layer of the p-type conductive layer, the i-type conductive layer, and the n-type conductive layer included in the pin junction layer is , Which is configured by adding rare earth elements to conductive oxide,
The conductive oxide is tin oxide, zinc oxide, nickel oxide, titanium oxide, tin-added indium oxide or indium oxide,
The light-emitting device, wherein the rare earth element is terbium, europium, cerium, or gadolinium. A light-emitting panel having a plurality of light-emitting elements arranged two-dimensionally;
A drive circuit unit for driving the light emitting element,
The light emitting element is
A pn junction layer formed by bonding a p-type conductive layer and an n-type conductive layer to each other on a substrate, or a p-type conductive layer, an i-type conductive layer, and an n-type conductive layer are bonded in this order. A pin junction layer,
The substrate has a graphite sheet on the outermost surface of the pn junction layer side or the pin junction layer side,
The p-type conductive layer and the n-type conductive layer included in the pn junction layer, or the p-type conductive layer, the i-type conductive layer, and the n-type conductive layer included in the pin junction layer mainly include zinc oxide and a rare earth A light-emitting device characterized in that the light-emitting device is configured not to contain an element.

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