JP2007179941A - Light emitting element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To increase luminance in light emission in a light emitting element. <P>SOLUTION: The light emitting element includes: first and second electrodes; electrolyte containing light emitting pigment; a porous layer which is in contact with at least the first or second electrode and provided with a compound sintered body of an oxide selected from ITO, MoO<SB>2</SB>, WO<SB>2</SB>, RuO<SB>2</SB>, IrO<SB>2</SB>, ReO<SB>3</SB>, LiTi<SB>2</SB>O<SB>4</SB>, Li<SB>2</SB>V<SB>2</SB>O<SB>4</SB>, SrVO<SB>3</SB>, SrCrO<SB>3</SB>, SrRuO<SB>3</SB>, or NaCo<SB>2</SB>O<SB>4</SB>and TiO<SB>2</SB>. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a light emitting device utilizing an electrochemical reaction.

  Light emitting devices utilizing electrochemical reactions have been known for over 30 years. Electrochemiluminescence is a reduction reaction between the oxidant produced in this oxidation reaction, with some of the luminescent dye in the electrolyte being oxidized on the plus (+) pole and the other being reduced on the minus (-) pole. This is a phenomenon accompanied by the generation of phosphorescence when the excited species produced by collision with the produced reductant in the electrolyte returns to the original ground state luminescent dye.

A light emitting device in which a ruthenium complex, which is a luminescent dye, is dissolved in acetonitrile as an electrolyte, a SnO ₂ / F transparent conductive film formed on a glass substrate is used as a cathode, and a titania porous layer is formed on the cathode. Are known. When the light emitting element is driven by a DC voltage, the light emission luminance is improved as compared with the case where there is no titania porous layer (see Patent Document 1 and Non-Patent Document 1).
JP 2005-302332 A S.okamoto et.al, “Increase in Electrochemiluminescence Intensities by Use of Nanoporous TiO2 Electrodes”, Journal of The Electrochemical Society, July 12 2005, 152 (8) A1677-A1681

  As a result of intensive studies, the present inventors have found that the mechanism for improving the light emission luminance by the titania porous layer is considered to be described below.

  First, since the porous layer has a large surface area, the redox reaction sites of the luminescent dye increased, and the emission luminance was improved.

  Next, titania that forms the porous layer is an n-type semiconductor, and since the respective electron levels of titania and the luminescent dye are close to each other, the interaction between the two is strong, and the redox reaction of the luminescent dye does not occur. It was promoted and the luminance was improved.

  Further, when the electrolyte is a molten salt having a high viscosity, the oxidant and reductant of the luminescent dye generated in the vicinity of the electrode is prevented from diffusing by the porous layer and remains in the micropores of the porous layer. For this reason, both become easy to collide and light emission brightness improves. The fact that this mechanism is supported is that when the electrolyte is a molten salt, the luminance of light emission is further improved when the light emitting element is driven with an AC voltage. This is because when the AC voltage drive is performed, the oxidant and the reductant generated on the same electrode collide more efficiently than the DC voltage drive.

  However, the emission luminance is still insufficient. This seems to be partly due to the large electrical resistance of the titania porous layer and the large voltage loss due to the voltage drop in the porous layer portion.

  In view of the above circumstances, an object of the present invention is to improve the light emission luminance of a light emitting element.

The light-emitting element of the present invention is in contact with at least one of the first and second electrodes, the electrolyte containing a light-emitting dye, and the first and second electrodes, and includes ITO, MoO ₂ , WO ₂ , RuO ₂ , IrO. ₂ , a porous oxide having a mixed sintered body of an oxide selected from ReO ₃ , LiTi ₂ O ₄ , Li ₂ V ₂ O ₄ , SrVO ₃ , SrCrO ₃ , SrRuO ₃ , and NaCo ₂ O ₄ and TiO _2. And a layer.

  An object of the present invention is to provide a light emitting element with improved light emission luminance.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, the same code | symbol shall be attached | subjected to a common structure through embodiment, and the overlapping description is abbreviate | omitted. Each figure is a schematic diagram for promoting explanation and understanding of the invention, and its shape, dimensions, ratio, and the like are different from those of an actual device. However, these are in consideration of the following explanation and known techniques. The design can be changed as appropriate.

The light-emitting element according to this embodiment includes at least two electrodes, that is, a first electrode and a second electrode. The first and second electrodes are disposed in one cell and are electrically insulated from each other. Further, a porous layer is formed so as to be in contact with at least one of the first and second electrodes. This porous layer is made of ITO (tin-doped indium oxide), MoO ₂ , WO ₂ , RuO ₂ , IrO ₂ , ReO ₃ , LiTi ₂ O ₄ , Li ₂ V ₂ O ₄ , SrVO ₃ , SrCrO ₃ , It has a mixed sintered body of an oxide selected from SrRuO ₃ and NaCo ₂ O ₄ and TiO ₂ (titania). As will be described later in detail, the present inventors have found that the emission luminance can be improved by forming a porous layer using this mixed sintered body.

  Note that when a porous layer is formed on one electrode, the porous layer is electrically insulated from the other electrode. Moreover, when forming a porous layer on both electrodes, the porous layer on each electrode is electrically insulated from each other.

  Hereinafter, the structure of the element, the porous layer, the first and second electrodes, the electrolyte, and the driving method will be described in this embodiment.

(Element structure)
The first and second electrodes are disposed so as to be electrically insulated from each other. The first and second electrodes are plate-shaped, sheet-shaped, or film-shaped, and may be opposed to each other with a desired distance. The first and second electrodes may be electrically insulative and arranged on the same substrate with a desired distance.

  First, the former will be described with reference to FIG. FIG. 1 is a schematic cross-sectional view illustrating an example of the structure of a light-emitting element.

  As shown in FIG. 1, a porous layer 3 is formed on the second electrode 2. A spacer 4 is interposed at a position sandwiching the porous layer 3 between the first electrode 1 and the second electrode 2. By the spacer 4, the first and second electrodes 1 and 2 face each other at a desired distance and are insulated from each other. An electrolyte 5 is filled in a space provided by the first and second electrodes 1 and 2 and the spacer 4. The first and second electrodes 1 and 2 and the spacer 4 are sealed with a sealing material (not shown).

  In FIG. 1, the porous layer 3 is formed only on the second electrode 2, but of course, the porous layer 3 may also be formed on the first electrode 1.

  Next, the latter will be described with reference to FIG. FIG. 2 is a schematic perspective view illustrating an example of the structure of the light emitting element.

  As shown in FIG. 2, the first and second electrodes 1 and 2 are formed on the first substrate 6 so as to have alternate comb shapes. A porous layer 3 is formed between the first and second electrodes 1 and 2 so as to be in contact with the first and second electrodes 1 and 2, respectively. The second substrate 7 covers the first and second electrodes 1 and 2. An electrolyte (not shown) is filled in a space provided by the first and second substrates 6 and 7 and a spacer (not shown). That is, the electrolyte is interposed between the first and second electrodes 1 and 2. The first and second substrates 6 and 7 and the spacer are sealed with a sealing material (not shown).

  In FIG. 2, the porous layer 3 is formed in contact with both the first and second electrodes 1, 2. Of course, the porous layer 3 is in contact with only the first electrode 1 or only the second electrode 2. The quality layer 3 may be formed.

  Examples of the sealant include an epoxy resin and an ionomer resin that is a thermoplastic resin. If an ionomer resin or the like is used, it can be avoided that the sealing material is eluted into the electrolyte and the emission of the pigment is inhibited.

(Porous layer)
The porous layer, ITO (indium _{tin-doped), MoO 2, WO 2,} RuO 2, IrO 2, ReO 3, LiTi 2 O 4, Li 2 V 2 O 4, SrVO 3, SrCrO 3, SrRuO ₃ and a mixed sintered body of an oxide selected from NaCo ₂ O ₄ and TiO ₂ (titania). Luminance can be improved by forming a porous layer using this mixed sintered body.

As in Patent Document 1 and Non-Patent Document 1, when the porous layer is formed of only TiO ₂ , electrons are easily exchanged between the porous layer and the luminescent dye, but the electrical resistance of the porous layer is large, The voltage loss due to the voltage drop in the porous layer portion becomes large, and the luminance is lowered. On the other hand, when the porous layer is formed only from the above-described highly conductive oxide, the electrical resistance of the porous layer is small, but the electron levels involved in the oxidation-reduction reaction between this oxide and the luminescent dye are separated. In addition, it is difficult for electrons to be exchanged between the porous layer and the luminescent dye, resulting in a decrease in luminance.

On the other hand, in the present embodiment, the emission luminance can be improved by using the above-described mixed sintered body of oxide and TiO ₂ (titania). This is presumably because the electrical resistance of the porous layer was reduced and electrons could be exchanged quickly between the porous layer and the luminescent dye. Here, usually, when different substances are mixed and sintered, the sinterability is lowered, the electron transfer at the interface between the two hardly occurs, and the electric resistance increases. However, the combination of the above-described oxide and TiO ₂ has high sinterability because of the oxides, and the electron transfer at the interface between the two is rapid.

Further, the above-described oxide and TiO ₂ have acid groups on the particle surface, and it is difficult to decompose and deteriorate the molten salt. On the other hand, for example, a metal has an alkali group such as a hydroxyl group on the surface thereof, and when a voltage is applied, the molten salt is attracted to the charged metal and may be decomposed or deteriorated by the alkali group. . Therefore, the above-described oxide and TiO ₂ are particularly preferable when a molten salt is used as the electrolyte.

The oxide and TiO ₂ described above are preferably granular. The oxide and TiO ₂ described above are stable even in nano-sized fine particles, and are easy to handle industrially. On the other hand, for example, nano-sized fine particles of single metal are easily oxidized and difficult to handle.

The average particle diameter of the oxide and TiO ₂ particles is preferably 1 nm or more and 10 μm or less. This is because when the particle size is smaller than 1 nm, handling becomes difficult, and when the particle size is larger than 10 μm, the surface area of the porous layer is decreased, and thus the redox reaction of the luminescent dye is difficult to occur. A more preferable range is 10 nm or more and 100 nm or less.

The ratio of the average particle diameter of the above-mentioned oxide to the average particle diameter of TiO ₂ is preferably 0.7 or more and 1.3 or less. Since the average particle diameter of both is mixed and sintered within this range, the above-described synergistic effect becomes more remarkable. The ratio of the average particle diameter of the oxide to the average particle diameter of TiO ₂ is more preferably 0.9 or more and 1.1 or less.

  In addition, the average particle diameter of the particle | grains used for a porous layer can be analyzed from an electron microscope (TEM) observation or an X-ray diffraction peak.

The weight ratio (X) of TiO _{2 to} the total of TiO ₂ and the above oxides is preferably 20 (wt%) ≦ X ≦ 60 (wt%). If X is less than 20%, the effect of easily exchanging electrons with the luminescent dye is reduced. If X is more than 60%, the electrical resistance of the porous layer increases and the voltage drop in the porous layer portion. This is because the voltage loss due to is increased.

ITO is most preferable as the oxide described above. TiO ₂ and ITO are excellent in mutual sinterability, the electron transfer at the interface between them is rapid, and the increase in electrical resistance can be further reduced. Moreover, since both are transparent, it is easy to efficiently take out phosphorescence generated in the light emitting element to the outside. From these, the emission luminance can be particularly increased.

The weight ratio (X) of TiO _{2 to} the total of TiO ₂ and ITO is preferably 5 (wt%) ≦ X ≦ 95 (wt%). In particular, the weight ratio (X) of TiO _{2 to} the total of TiO ₂ and ITO is preferably 40 (wt%) ≦ X ≦ 60 (wt%). If X is less than 40 wt%, the effect of easily transferring electrons between TiO 2 and the luminescent dye is reduced. If X is more than 60 wt%, the electrical resistance of the porous layer is increased, resulting in a voltage drop in the porous layer portion. This is probably because the voltage loss becomes large.

  The problem of voltage loss due to the voltage drop in the porous layer portion is particularly serious when the electrolyte is a molten salt. For this reason, the effect of the present embodiment is particularly suitable when a molten salt is used for the electrolyte. This is considered to be based on the following factors. When an organic solvent such as acetonitrile is used for the electrolyte, since the viscosity is low, the luminescent dye oxidized and reduced on the porous surface diffuses quickly. On the other hand, when the molten salt is used as the electrolyte, the viscosity of the molten salt is high, so that the diffusion of the luminescent dye oxidized and reduced on the porous layer surface is slow. The oxidation / reduction reaction rate of the luminescent dye increases as the voltage on the surface of the porous layer increases and the diffusion rate of the luminescent dye increases. In the case of an organic solvent, the voltage drop at the porous layer portion is large, that is, the diffusion rate is large even when the voltage at the porous surface is small. Can maintain a good oxidation / reduction reaction rate. On the other hand, in the case of molten salt, if the diffusion rate is small and the voltage on the porous layer surface is further reduced due to the voltage drop of the porous layer portion, the absolute value of the oxidation / reduction reaction rate becomes very small. Therefore, the effect of improving the electrical resistance of the porous layer portion appears remarkably when a molten salt is used for the electrolyte.

(First and second electrodes)
As shown in FIG. 1, when the first electrode and the second electrode are opposed to each other with a desired distance, a transparent electrode is used for each of the first electrode and the second electrode, or one of them is made of carbon. It is possible to form from a non-transparent electrode such as a sheet, a metal substrate or an alloy substrate and to form the other from a transparent electrode.

  The non-transparent electrode will be described. The carbon sheet is not particularly limited as long as the carbon material functions as a conductive component. As the metal substrate, gold, silver, platinum, copper, aluminum, silicon, nickel, iron, titanium, or the like can be used, but is not limited thereto. Examples of the alloy include those containing at least one metal selected from the group consisting of gold, silver, platinum, copper, aluminum, silicon, nickel, iron, and titanium, and stainless steel. It is not limited to. Of these, gold, platinum, nickel, and stainless steel are preferable. Thereby, the emission intensity can be further improved.

  The transparent electrode preferably includes a transparent conductive film that absorbs less visible light and has conductivity. The transparent conductive film is preferably an ITO (indium oxide doped with tin) film, a tin oxide film doped with fluorine, or a zinc oxide film doped with fluorine or indium. Further, from the viewpoint of improving conductivity and preventing an increase in resistance, it is desirable to wire a low-resistance metal matrix in combination with a transparent electrode.

  It is desirable that the transparent electrode further includes a support substrate for supporting the transparent conductive film. In order to make the surface opposite to the surface on which the transparent conductive film of the supporting substrate is formed function as a light emitting surface, it is preferable to use a transparent substrate that absorbs less visible light, such as a glass substrate or a plastic substrate. .

  When the first electrode and the second electrode are arranged on the same insulated substrate as shown in FIG. 2, the first and second electrodes are made of the same materials as described above with reference to FIG. It is possible. The board | substrate 6 which arrange | positions the 1st electrode and the 2nd electrode, and the board | substrate 7 opposite to the board | substrate 6 may be a normal transparent substrate which does not comprise electroconductivity, such as glass and a plastics.

(Electrolytes)
The electrolyte of the light-emitting device of the present invention contains a light-emitting dye having a reversible redox structure and a solvent such as an organic solvent, a molten salt, or a gel.

  However, when the electrolyte is an organic solvent such as acetonitrile, since the solvent is volatile, durability and environmental resistance are low. Therefore, a non-volatile and stable molten salt, or a gel that does not leak the electrolyte is more preferable. .

  Examples of the organic solvent include carbonates such as propylene carbonate, ethylene carbonate, vinylene carbonate, and methylpropyl carbonate; esters such as ethyl propionate, γ-butyrolactone, γ-valerolactone, and δ-valerolactone; and ethylene glycol. Examples thereof include ethers such as dimethyl ether and ethylene glycol diethyl ether, and solvents selected from the group consisting of various solvents obtained by introducing substituents such as fluorine into these compounds. Among them, propylene carbonate, ethylene carbonate or vinylene carbonate is preferable, but is not particularly limited. The type of organic solvent can be one type or two or more types.

溶融塩のカチオン種は特に限定されないが、イミダゾリウムイオン、ピリジニウムイオン、4級アンモニウムイオンなどを用いることができる。中でも、Ｎ−メチル−Ｎ−プロピルピペリジニウムイオン、Ｎ−メチル−Ｎ−イソプロピルピペリジニウムイオン、Ｎ−ブチル−Ｎ−メチルピペリジニウムイオン、Ｎ−イソブチル−Ｎ−メチルピペリジニウムイオン、Ｎ−ｓｅｃ−ブチル−Ｎ−メチルピペリジニウムイオン、Ｎ−（２−メトキシエチル）−Ｎ−メチルピペリジニウムイオン、Ｎ−（２−エトキシエチル）−Ｎ−メチルピペリジニウムイオンが好ましい。 The molten salt includes a structure represented by the following general formula (1).

The cation species of the molten salt is not particularly limited, but imidazolium ions, pyridinium ions, quaternary ammonium ions, and the like can be used. Among them, N-methyl-N-propylpiperidinium ion, N-methyl-N-isopropylpiperidinium ion, N-butyl-N-methylpiperidinium ion, N-isobutyl-N-methylpiperidinium ion, N-sec- Butyl-N-methylpiperidinium ion, N- (2-methoxyethyl) -N-methylpiperidinium ion, and N- (2-ethoxyethyl) -N-methylpiperidinium ion are preferable.

The anion species of the molten salt is not particularly limited, but specifically, PF ₆ ⁻ , [PF ₃ (C ₂ F ₅ ) ₃ ] ⁻ , [PF ₃ (CF ₃ ) ₃ ] ⁻ , BF ₄ ⁻ , [BF ₂ (CF ₃ ) ₂ ] ⁻ , [BF ₂ (C ₂ F ₅ ) ₂ ] ⁻ , [BF ₃ (CF ₃ )] ⁻ , [BF ₃ (C ₂ F ₅ )] ⁻ , [B (COOCOO) ₂ ^{− _{] (BOB -), CF 3}} SO 3 - (Tf -), C 4 F 9 SO 3 - (Nf -), [(CF 3 SO 2) 2 N] - (TFSI -), [(C 2 F 5 ^{_{SO 2) 2 N] - (}} BETI -), [(CF 3 SO 2) (C 4 F 9 SO 2) N] -, [(CN) 2 N] - (DCA -), [(CF 3 SO 2 ) ₃ C] ⁻ , [(CN) ₃ C] ^{− and the} like can be used. Among these, BF ₄ ⁻ , [BF ₃ (CF ₃ )] ⁻ , [BF ₃ (C ₂ F ₅ )] ⁻ , BOB ⁻ , TFSI ⁻ and BETI ⁻ are preferable. Incidentally, BOB ^- is the meaning of bis (oxalato) borate, TFSI ^- is the meaning of bistrifluoromethylsulfonylimide, BETI ^- is the meaning of bis pentafluorophenyl imide.

  An organic solvent may be added to the molten salt. This is because the viscosity is lowered by adding an organic solvent, and the luminance of emitted light can be further improved. As the organic solvent, those mentioned above may be used.

  However, if a large amount of the organic solvent is added, there is a possibility that the characteristics of the molten salt, which is nonvolatile and stable, may not be utilized. Therefore, the amount of the organic solvent added is preferably 20% by volume or less of the electrolyte.

  In the case of a gel electrolyte, a gel-like electrolyte can be formed by mixing a heated polymer, a solvent, and a luminescent dye, injecting the mixture into a cell before the temperature drops, and lowering the temperature to room temperature. Examples of the polymer include, but are not limited to, polyethylene oxide, polyacrylonitrile, and polyvinylidene fluoride. Examples of the solvent include, but are not limited to, the above organic solvents and the above molten salts.

  The luminescent dye is not particularly limited, but is preferably a phosphorescent dye. The phosphorescent dye is preferably a heavy metal complex. As the heavy metal used, Ir, Tb, Yb, Nd, Er, Ru, Os, Re, or the like is used. The type of heavy metal in the complex can be one type or two or more types. As the ligand, a pyridine derivative, a bipyridyl derivative, a terpyridyl derivative, a phenanthroline derivative quinoline derivative, an acetylacetone derivative, a dicarbonyl compound derivative, or the like is used. Among these, a complex having Ru as a central metal is desirable. Thereby, high light emission luminance can be obtained.

(Driving method)
In the present invention, the light emitting element can be driven with a DC voltage or an AC voltage. As the waveform of the AC voltage, a rectangular wave is most preferable because the voltage can be applied to the light emitting element most efficiently.

  Examples will be described below, but the present invention is not limited to the examples described below unless the gist of the present invention is exceeded.

Example 1
<Production of second electrode and porous layer>
A second electrode (transparent electrode) prepared by forming a fluorine-doped tin oxide thin film (sheet resistance 6 Ω / sq) having a thickness of about 1 μm on a glass substrate having a thickness of 1000 μm was prepared. On the other hand, Japan Aerosil Co. P25TiO ₂ (average particle size 21 nm), and Mitsui Kinzoku Co. of ITO powder (average particle size 20 nm), the weight ratio of TiO ₂ to the total amount of TiO ₂ and ITO (X) is, 5 wt % Was mixed with water to prepare a paste. This paste was applied on the fluorine-doped tin oxide thin film of the transparent electrode. After drying, baking was performed at 450 ° C. for 30 minutes to obtain a porous layer in which 20 μm thick TiO ₂ and ITO were mixed.

<Production of first electrode>
What formed the fluorine dope tin oxide thin film (sheet resistance 6 ohm / sq) on the glass substrate was prepared as a counter substrate (1st electrode).

<Production of light-emitting element>
The fluorine-doped tin oxide thin film of the first electrode was made to face the surface of the second electrode on the porous layer side. In the meantime, an ionomer resin HiMilan 1702 was interposed as a spacer so as to surround the porous layer, so that the first and second electrodes were opposed to each other with a distance of 150 μm. An electrolyte was injected between the first and second electrodes. As the electrolyte, 0.2 g of ruthenium (II) trisbipyridyl (PF ₆ ⁻ ) ₂ as a luminescent dye was dissolved in 1.1 g of acetonitrile as an organic solvent. Finally, the electrolyte inlet was sealed with an ionomer resin Himiran 1702.

<Measurement of emission luminance>
When a direct current voltage of 2.5 V was applied between the first and second electrodes and the luminance of the central part of the element in the range of about 1 mm in diameter was measured using Topcon BM-8, it was 8 cd / m ² . It emitted light. Table 1 shows the results and the results of Examples 2 to 7 and Comparative Examples 1 to 7 described later.

(Examples 2 to 5)
Luminance measurement was performed in the same manner as in Example 1 except that the ratio of X was changed to the values in Table 1.

(Comparative Example 1)
The luminance was measured in the same manner as in Example 1 except that the porous layer was formed only from the ITO powder described above.

(Comparative Example 2)
When the luminance was measured in the same manner as in Example 1 except that the porous layer was formed using only TiO _{2 as} described above, no light was emitted.

(Comparative Example 3)
When the luminance was measured in the same manner as in Example 1 except that the porous layer was not formed, no light was emitted.

(Example 6)
<Production of second electrode and porous layer> and <Production of first electrode> are the same as in Example 1.

<Production of light-emitting element>
The fluorine-doped tin oxide thin film of the first electrode was made to face the surface of the second electrode on the porous layer side. In the meantime, an ionomer resin HiMilan 1702 was interposed as a spacer so as to surround the porous layer, so that the first and second electrodes were opposed to each other with a distance of 150 μm. An electrolyte was injected between the first and second electrodes. In the electrolyte, 0.1 g of ruthenium (II) trisbipyridyl (PF ₆ ⁻ ) ₂ as a luminescent dye was dissolved in 1.0 g of 1-ethyl-3-methylimidazolium (TFSI ⁻ ), which is a molten salt. I used something. The electrolyte inlet was sealed with ionomer resin Himiran 1702.

<Measurement of emission luminance>
An AC rectangular wave voltage of 100 Hz was applied between the first and second electrodes, and brightness was measured in the center of the element and in a range of about 1 mm in diameter using a Topcon BM-8. The applied voltage of the rectangular wave was 0.5, 1, 1.5, 2, 2.5, 3, 3.5V. The result is shown in FIG. Table 1 shows the luminance at 2.5V.

(Comparative Example 4)
Luminance measurement was performed in the same manner as in Example 6 except that the porous layer was formed only from ITO powder. The results are shown in FIG. Table 1 shows the luminance at 2.5V.

(Comparative Example 5)
Luminance measurement was performed in the same manner as in Example 6 except that the porous layer was formed only with TiO ₂ . The results are shown in FIG. Table 1 shows the luminance at 2.5V.

(Example 7)
<Production of second electrode and porous layer> and <Production of first electrode> are the same as in Example 1.

<Production of light-emitting element>
The fluorine-doped tin oxide thin film of the first electrode was made to face the surface of the second electrode on the porous layer side. In the meantime, an ionomer resin HiMilan 1702 was interposed as a spacer so as to surround the porous layer, so that the first and second electrodes were opposed to each other with a distance of 150 μm. An electrolyte was injected between the first and second electrodes. As the electrolyte, 0.25 g of polyethylene oxide was heated at 80 ° C., and 1.5 g of propylene carbonate and 0.2 g of ruthenium (II) trisbipyridyl (PF ₆ ⁻ ) ₂ as a luminescent dye were mixed, After injecting the electrolyte into the cell, the temperature of the cell was lowered to room temperature to gel the electrolyte. The electrolyte inlet was sealed with ionomer resin Himiran 1702.

<Measurement of emission luminance>
An AC rectangular wave voltage of 100 Hz was applied between the first and second electrodes, and brightness was measured in the center of the element and in a range of about 1 mm in diameter using a Topcon BM-8. The applied voltage of the AC rectangular wave was 2.5V.

(Comparative Example 6)
Luminance measurement was performed in the same manner as in Example 7 except that the porous layer was formed only from ITO powder.

表１に示すように、実施例１〜５は比較例１〜３に比して、実施例６は比較例４〜５に比して、実施例７は比較例６〜７に比して、発光輝度が高い。したがって、本実施の形態の多孔質層を用いると、発光輝度が向上することがわかる。 (Comparative Example 7)
Luminance measurement was performed in the same manner as in Example 7 except that the porous layer was formed only with TiO ₂ .

As shown in Table 1, Examples 1-5 are compared with Comparative Examples 1-3, Example 6 is compared with Comparative Examples 4-5, and Example 7 is compared with Comparative Examples 6-7. , The emission brightness is high. Therefore, it can be seen that the emission luminance is improved by using the porous layer of the present embodiment.

In addition, Examples 3-5 have higher emission luminance than Examples 1-2. Therefore, it can be seen that the light emission luminance is further improved when the weight ratio (X) of TiO _{2 to} the total amount of TiO ₂ and ITO is 40 (wt%) ≦ X ≦ 60 (wt%).

  As shown in FIG. 3, Example 6 shows particularly excellent light emission luminance in a low voltage range of AC voltage 2 V or more and 3.5 V or less as compared with Comparative Examples 4 to 5. Therefore, it can be seen that this embodiment shows excellent light emission luminance in a low voltage region when a molten salt is used as the electrolyte. Here, low voltage driving is desirable for extending the life of the light emitting element. For this reason, this Embodiment can also contribute to lifetime extension.

  As mentioned above, although embodiment of this invention was described, this invention is not restricted to these, In the category of the summary of the invention as described in a claim, it can change variously. In addition, the present invention can be variously modified without departing from the scope of the invention in the implementation stage. Furthermore, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment.

Cross-sectional schematic diagram showing an example of the structure of a light-emitting element Schematic perspective view showing an example of the structure of a light-emitting element A graph showing the material dependence of the light emission luminance of the porous layer

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 1st electrode 2 2nd electrode 3 Porous layer 4 Spacer 5 Electrolyte 6 1st board | substrate 7 2nd board | substrate

Claims (3)

First and second electrodes;
An electrolyte containing a luminescent dye;
In contact with at least one of the first and second electrodes, ITO, MoO ₂ , WO ₂ , RuO ₂ , IrO ₂ , ReO ₃ , LiTi ₂ O ₄ , Li ₂ V ₂ O ₄ , SrVO ₃ , SrCrO ₃ And a porous layer having a mixed sintered body of TiO ₂ and an oxide selected from SrRuO ₃ and NaCo ₂ O ₄ . _2. The light emitting device according to claim 1, wherein a ratio of an average particle diameter of the oxide to an average particle diameter of the TiO ₂ is 0.7 or more and 1.3 or less. The oxide is ITO;
_3. The light emitting device according to claim 1, wherein a weight ratio (X) of the TiO _{2 to} a total of the TiO ₂ and the ITO satisfies 40 (wt%) ≦ X ≦ 60 (wt%). .

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