WO2022185485A1 - Transparent electrode, method for producing same, and electronic device using transparent electrode - Google Patents

Abstract

[Problem] To provide: a transparent electrode which is not susceptible to migration of silver, while having high resistance; a method for producing this transparent electrode; and an electronic device which uses this transparent electrode. [Solution] A transparent electrode 100 according to one embodiment of the present invention is provided with a multilayer structure in which a transparent base material 101, a conductive silver-containing layer 102 and a conductive oxide layer 103 are sequentially stacked; if T800 and T600 are respective total light transmittances of the transparent electrode 100 at the wavelengths of 800 nm and 600 nm, the transmittance ratio T800/T600 is 0.85 or more; and the silver-containing layer 102 is continuous. This electrode is able to be produced by: (a) forming the conductive silver-containing layer 102 on the transparent base material 101; (b) forming the conductive oxide layer 103 on the silver-containing layer 102, thereby forming a multilayer film; and (c) forming a sulfur-containing silver compound layer by bringing the multilayer film into contact with sulfur or a sulfur compound.

Description

Transparent electrode, manufacturing method thereof, and electronic device using transparent electrode

An embodiment of the present invention relates to a transparent electrode, an element using the same, and a method for manufacturing the element.

Energy consumption has been increasing in recent years, and demand for alternative energy to replace conventional fossil energy is increasing as a countermeasure against global warming. Attention is focused on solar cells as a source of such alternative energy, and the development thereof is underway. The application of solar cells to various uses has been investigated, and flexibility and durability of solar cells are particularly important in order to accommodate various installation locations. The most basic single-crystal silicon solar cells are expensive and difficult to make flexible, and organic solar cells and organic-inorganic hybrid solar cells, which have been attracting attention in recent years, have room for improvement in terms of durability.

In addition to such solar cells, photoelectric conversion elements such as organic EL elements and optical sensors are being studied with the aim of making them more flexible and improving their durability. In such devices, an indium-doped tin oxide film (ITO film) is usually used as a transparent positive electrode. ITO films are usually formed by sputtering or the like, but in order to obtain high conductivity, they generally require high-temperature sputtering and high-temperature annealing after sputtering, and are often inapplicable to organic materials.

In addition, ITO/silver alloy/ITO, which has low resistance and high transparency, is sometimes used as the transparent electrode. However, in electrodes containing such silver alloys, silver ions tend to migrate easily. Therefore, in an electronic device having an electrode containing a silver alloy, when migrated silver ions reach the element active portion inside the device, the element activity itself may be lowered.

Japanese Patent Publication No. 2002-540459

In view of the problems described above, the present embodiment provides a highly durable transparent electrode that is resistant to silver ion migration, a method for producing the same, and an electronic device (such as a photoelectric conversion element) using the transparent electrode. .

A transparent electrode according to an embodiment has a laminated structure in which a transparent substrate, a first conductive silver-containing layer, and a conductive oxide layer are laminated in this order,
The transparent electrode has a total transmittance ratio _T800 / _T600 of 0.85 or more, where T800 and T600 are transmittances at wavelengths of ₈₀₀ nm and ₆₀₀ nm, respectively;
Moreover, the silver-containing layer is continuous when the cross section of the transparent electrode is observed with a scanning electron microscope.

A method for making a transparent electrode according to an embodiment includes:
(a) forming a conductive silver-containing layer on a transparent substrate;
(b) forming a first conductive oxide layer on the silver-containing layer to form a film stack; and (c) contacting the film stack with sulfur or a sulfur compound. It is a thing.

An electronic device according to an embodiment comprises the transparent electrode, the active layer, and the counter electrode.

4 is a conceptual diagram showing the structure of a transparent electrode according to the embodiment; FIG. FIG. 4 is a conceptual diagram showing the structure of another transparent electrode according to the embodiment; FIG. 4 is a conceptual diagram showing the structure of still another transparent electrode according to the embodiment; 4A and 4B are conceptual diagrams showing a method for manufacturing a transparent electrode according to the embodiment; 1 is a conceptual diagram showing the structure of a photoelectric conversion element (solar cell) according to an embodiment; FIG. 1 is a conceptual diagram showing the structure of a photoelectric conversion element (organic EL element) according to an embodiment; FIG. Cross-sectional SEM images of transparent electrodes in Example 1 and Comparative Example 1 (80,000 times). FIG. 5 is a conceptual diagram showing the structure of a photoelectric conversion element (solar cell) of Example 5;

The embodiment will be described in detail below with reference to the drawings.

[Embodiment 1]
First, the configuration of the transparent electrode according to the first embodiment will be described with reference to FIG. FIG. 1 is a schematic configuration diagram of a transparent electrode 100 according to this embodiment.

This transparent electrode has a laminated structure of a silver-containing layer 102 and a first conductive oxide layer 103 on a transparent substrate 101 . All of these layers are electrically conductive and all are light transmissive. The transparent electrode has a transmittance ratio _T800 / _T600 of 0.85 or more, where T800 and T600 are the total transmittance at wavelengths of ₈₀₀ nm and ₆₀₀ nm, respectively, and the cross section of the transparent electrode is a scanning type. The silver-containing layer is characterized by being continuous when observed with an electron microscope, where total transmittance is the transmittance including linearly transmitted light and backscattered light, using an integrating sphere. measured.

Materials for the base material 101 include resin materials such as polyethylene terephthalate (hereinafter referred to as PET) and polyethylene naphthalate (hereinafter referred to as PEN). The substrate is preferably planarized. Further, the total transmittance of the transparent substrate alone at 550 nm is preferably 85% or more.

The silver-containing layer must contain silver, and may be silver or a silver alloy containing silver. In general, silver alloys tend to have a low ratio _T800 / _T600 when the silver content is low. Therefore, the silver content is preferably high, and the silver-containing layer is most preferably made of silver. .

The film thickness of the silver-containing layer 102 is appropriately adjusted according to the transparency and conductivity, but the film thickness is preferably 4 to 20 nm. If it is less than 4 nm, the resistance tends to increase, and if it exceeds 20 nm, the transparency tends to decrease. The film thickness of the silver-containing layer is more preferably 5-15 nm, still more preferably 6-10 nm. The silver-containing layer 101 can be produced by, for example, sputtering or vapor deposition, but is preferably produced by sputtering.

As for the oxide constituting the first conductive oxide layer (hereinafter sometimes referred to as the first oxide layer or oxide layer) 103, any generally known oxide, transparent It is possible to select a material that has good properties such as conductivity and conductivity. Specifically, indium doped tin oxide (hereinafter referred to as ITO), fluorine doped tin oxide (hereinafter referred to as FTO), aluminum doped zinc oxide (hereinafter referred to as AZO) and the like. Among these, ITO is preferable because it easily forms a layer with high flatness, has a zeta potential close to 0 at neutral pH, and has little interaction with cations and anions.

　These oxides generally often contain an amorphous structure. Having an amorphous structure is preferable because it facilitates the formation of a continuous, uniform and flat film. Also, the thickness of the oxide layer is preferably 30 to 200 nm. If the film thickness of the oxide layer is less than 30 nm, the resistance tends to increase, and if it is more than 200 nm, the transparency decreases and the production takes a long time. The film thickness of the oxide layer is more preferably 35-100 nm, more preferably 40-70 nm.

The oxide layer 103 can be produced, for example, by sputtering at a low temperature. The amorphous oxide film can be partially crystallized by annealing to form a mixture (amorphous-containing oxide layer).

FIG. 2 is a conceptual diagram of another transparent electrode according to the embodiment. This transparent electrode is further provided with a second conductive oxide layer (hereinafter sometimes referred to as a second oxide layer) 104 between the substrate 101 and the silver-containing layer 102 . The oxide forming the second oxide layer 104 can be selected from the oxides described for the first oxide layer 103 above. The first oxide layer 103 and the second oxide layer 104 may have the same composition or may have different compositions.

From the viewpoint of transparency and conductivity, the first oxide layer 103 and the second oxide layer 104 are preferably made of ITO. That is, the transparent electrode according to the embodiment preferably has a laminated structure of ITO/silver-containing layer/ITO.

FIG. 3 is a conceptual diagram of still another transparent electrode according to the embodiment. The oxide layer 103 may have minute non-uniformities 105 . Since such non-uniform portions tend to cause migration of silver, they are preferably blocked with sulfur-containing silver compound 106 or the like. Non-uniform portions include not only gaps and openings as shown in FIG. 3, but also areas where the density is lower than the surrounding area. Non-uniformity can also be observed using, for example, a scanning electron microscope or a transmission electron microscope. According to these electron microscopes, in addition to voids and openings, regions with low oxide densities are observed to be darker than their surroundings due to less electron scattering. Specifically, a Carl Zeiss ULTRA55 microscope (observation voltage: 2.0 kV, magnification of 80,000 times) as a field emission scanning electron microscope and a Hitachi High Technology H-9500 microscope (magnification of 200 times) as a transmission electron microscope 10,000 times) can be used.

The combination of the silver-containing layer and the first oxide layer, and optionally the second oxide layer and the sulfur-containing silver compound 106 may be referred to as a conductive layer for convenience.

Assuming that the transparent electrode according to the embodiment has a total transmittance at a wavelength of 800 nm as T ₈₀₀ and a total transmittance at a wavelength of 600 nm as T ₆₀₀ , the ratio T ₈₀₀ /T ₆₀₀ (hereinafter sometimes referred to as R _t ) is 0.85 or more. is. If the silver of the silver-containing transparent electrode is close to pure silver, the decrease in light transmittance at long wavelengths can be reduced. When _Rt is 0.85 or more, light on the long wavelength side can be transmitted, and the energy conversion efficiency of the solar cell can be increased. More preferably, _Rt is 0.88 or more, still more preferably 0.9 or more. If the ratio _Rt is less than 0.85, the migration resistance tends to increase, but the light transmittance of the entire transparent electrode tends to decrease, which is not preferable. Also, when _Rt is small, electrical resistance tends to be large.

In order to increase _Rt , it is effective to increase the silver content of the silver-containing layer. Therefore, the silver-containing layer is preferably made of pure silver. On the other hand, when the silver content of the silver-containing layer is high, migration tends to occur and deterioration tends to occur. From this point of view, the silver content in the silver-containing layer is preferably 90-100 atom %, more preferably 96-99 atom %, based on the number of atoms in the silver-containing layer.

It should be noted that a transparent electrode having a laminated structure of a silver-containing layer and an oxide layer has been conventionally known. And there may have been some of which the silver-containing layer had a high silver content. However, in such a transparent electrode, the migration of silver ions cannot be controlled, and as a result, the durability of the transparent electrode and the electronic device containing it is often insufficient.

The transparent electrode according to the embodiment achieves suppression of migration of silver ions by adopting a continuous silver-containing layer as the silver-containing layer. When the silver-containing layer is continuous, even when an electronic device such as a solar cell is driven for a long period of time, migration of silver is unlikely to occur, and the life tends to be long.

The continuity of such a silver-containing layer can be evaluated by observing the cross section of the transparent electrode using a scanning electron microscope (hereinafter sometimes referred to as SEM). When a sample is observed with an SEM, the sample is irradiated with an electron beam. When the silver-containing layer is irradiated with an electron beam, electrons tend to stay on the surface of the sample, so an electric field is generated. This electric field tends to cause migration of silver. Then, when silver migration occurs, discontinuous regions are formed in the silver-containing layer. In embodiments, such a silver-containing layer in which no discontinuous regions are identified by SEM is said to be continuous. Since such SEM observation can be considered as accelerated observation of migration of silver in the transparent electrode or electronic device, it can also be applied to prediction of the lifetime of the transparent electrode or electronic device.

In the embodiment, the silver-containing layer being continuous means that five randomly selected cross sections of the transparent electrode are observed with an SEM at a magnification of 80,000 times and have a length of 1.4 μm. It means that there are two or less discontinuous regions in the silver-containing layer of . In embodiments, preferably no discontinuous regions are observed. Note that the discontinuous region is observed as a black shadow with a major axis of 15 nm or more in the SEM image.

According to the studies of the present inventors, such discontinuous regions are likely to be formed when the oxide layer formed on the silver-containing layer has uneven portions. Generally, an oxide layer is formed by sputtering or the like, but it is difficult to form a dense oxide layer without non-uniform portions. For this reason, in a general transparent electrode, the oxide layer often includes minute non-uniform portions. In that case, it is believed that the migration of silver is facilitated in the non-uniform portion where a part of the silver-containing layer is not sufficiently covered with a uniform and dense oxide layer, and a discontinuous region is formed in the silver-containing layer. be done.

In such a transparent electrode having an oxide layer with non-uniform portions, it is preferable to block the non-uniform portions in order to maintain the continuity of the silver-containing layer. Specifically, the silver-containing layer below the uneven portion can be modified with a highly stable compound, or a highly stable compound layer can be provided. Such highly stable compounds include sulfur-containing silver compounds. A typical example of such a sulfur-containing silver compound is silver sulfide, but compounds containing metals other than silver or chalcogens other than sulfur may also be used. A compound obtained by reacting a metal such as silver with an alkylthiol or the like may also be used.

In order to close the uneven portions of the oxide layer, it is convenient to bring sulfur or a sulfur compound into contact with the silver or silver alloy below the uneven portions to form a sulfur-containing silver compound (details will be described later). Generally, sulfur or sulfur compounds are likely to contact the entire lower portion of the uneven portion, so that the entire lower portion is likely to be coated with the sulfur-containing silver compound. With such a method, the entire surface of the silver-containing layer is coated with either a uniform and dense oxide layer or a layer of a stable sulfur-containing silver compound to prevent migration of silver ions from the silver or silver alloy layer. Suppressed.

In embodiments, it is preferable to have a graphene layer on top of the oxide layer. In an embodiment, the graphene layer has a structure in which one to several layers of sheet-shaped graphene are laminated. The number of laminated graphene layers is not particularly limited, but it is preferably 1 to 6 layers, and 2 to 4 layers so that sufficient transparency, conductivity, or ion shielding effect can be obtained. It is more preferable to have

The graphene preferably has a structure in which a polyalkyleneimine, particularly a polyethyleneimine chain, such as shown in the following formula, is bonded to the graphene skeleton. It is also preferred that some of the carbons in the graphene skeleton are substituted with nitrogen.

In the above formula, a polyethyleneimine chain is exemplified as a polyalkyleneimine chain. The number of carbon atoms contained in the alkyleneimine unit is preferably from 2 to 8, and polyethyleneimine containing a unit with 2 carbon atoms is particularly preferred. In addition to linear polyalkyleneimine, polyalkyleneimine having a branched chain or cyclic structure can also be used. Here, n (the number of repeating units) is preferably 10-1000, more preferably 100-300.

Graphene is preferably unsubstituted or nitrogen-doped. Nitrogen-doped graphene is preferred when a transparent electrode is used as the cathode. The doping amount (N/C atomic ratio) can be measured by X-ray photoelectron spectrum (XPS), and is preferably 0.1 to 30 atom %, more preferably 1 to 10 atom %. The graphene layer has a high shielding effect, prevents deterioration of metal oxides and metals by preventing diffusion of acids and halogen ions, and can prevent impurities from entering the photoelectric conversion layer from the outside. Furthermore, since the nitrogen-substituted graphene layer (N-graphene layer) contains nitrogen atoms, it has a high acid trapping ability, and thus has a higher shielding effect.

Also, in embodiments, it is preferable to further have a third inorganic oxide layer on the first oxide layer or on the graphene layer. The third inorganic oxide includes TiO ₂ , SnO ₂ , WO ₃ , NiO, MoO ₃ , ZnO, V ₂ O ₅ and the like. A conductive oxide may be further laminated. These third inorganic oxide films function as barrier layers, insulating layers, buffer layers, etc. in transparent substrates or electronic devices. The ratio of metal to oxygen in the third inorganic oxide does not necessarily have to be stoichiometric.

[Embodiment 2]
FIG. 4 shows a conceptual diagram of a method for producing a transparent electrode according to the embodiment. This production method is
(a) forming a conductive silver-containing layer on a transparent substrate;
(b) forming a first conductive oxide layer over the silver-containing layer to form a film stack; and (c) contacting the film stack with sulfur or a sulfur compound. .

First, in step (a), the transparent substrate 101 is prepared. The transparent substrate 101 is preferably smooth, and prior to the formation of the silver-containing layer, it can be subjected to smoothing treatment such as polishing or corona treatment. Then, a conductive silver-containing layer 102 is formed on the transparent substrate. The silver-containing layer can be formed by any conventionally known method. For example, silver or a silver alloy can be formed by sputtering or vapor deposition. A uniform sputtering method is particularly preferable because the silver-containing layer can be easily formed.

Next, in step (b), a conductive oxide layer 103 is formed on the silver-containing layer 102 to form a laminated film. The oxide layer 103 can be formed, for example, by sputtering at low temperature. An amorphous oxide layer can be formed by low-temperature sputtering, and the amorphous oxide can be partially crystallized by annealing to form a mixture (amorphous oxide layer). Annealing is preferably performed in a high-temperature atmosphere or laser annealing. This oxide layer 103 is formed on the silver-containing layer 102 uniformly, ie as a non-patterned uniform film. However, when an oxide layer is formed by a general method, it is common that uneven portions 105 are inevitably formed on the surface.

Then, in step (c), the formed laminated film is brought into contact with sulfur or a sulfur compound. As a result, the silver or silver alloy under the uneven portion 105 reacts with sulfur or a sulfur compound to form a sulfur-containing silver compound 106 to form a sulfur-containing silver compound layer. For the sake of convenience, the silver-containing layer is sometimes covered with the sulfur-containing silver compound layer, but in reality, part of the silver in the silver-containing layer reacts with the sulfur compound to form the sulfur-containing silver compound. Therefore, as shown in FIG. 3, part of the silver-containing layer becomes a sulfur-containing silver compound layer, and with the reaction, the sulfur-containing silver compound layer becomes larger in volume than part of the silver-containing layer before the reaction. To increase.

The method of contacting sulfur or a sulfur compound with the laminated film is not particularly limited, but a method of contacting a gas or liquid containing sulfur or a sulfur compound is used. More specifically, (c1) contacting the laminated film with a sulfur vapor gas;
(c2) contacting the laminated film with hydrogen sulfide gas, or (c3) contacting the laminated film with an aqueous solution of hydrogen sulfide or sodium sulfide,
method is adopted.

The method (c1) is a method of heating sulfur powder to generate a sulfur vapor gas containing clusters of sulfur atoms, blowing the gas onto the laminated film, or placing the laminated film in an atmosphere of the gas. . This gas reacts with the silver or silver alloy exposed at the bottom of the uneven portion to form stable silver sulfide. The temperature for heating the sulfur powder is preferably 50°C to 300°C. The sulfur vapor gas is preferably generated in dry air or dry nitrogen.

A step of blowing nitrogen may be further included in order to remove unreacted sulfur adsorbed on the surface of the transparent electrode.

The method (c2) is a method of blowing hydrogen sulfide gas onto the laminated film or placing the laminated film in the gas atmosphere. Hydrogen sulfide can be produced by any method, but it can be produced by using hydrogen sulfide gas recovered from the exhaust gas discharged from the plant, or by reacting methane and sulfur in the presence of a catalyst. can.

The method (c3) is a method of immersing the laminated film in an aqueous solution of a sulfur compound such as hydrogen sulfide or sodium sulfide or spraying the aqueous solution onto the laminated film. Since hydrogen sulfide is generally poorly soluble in water, it is preferable to use a highly water-soluble sulfur compound such as sodium sulfide. In addition, since the silver-containing layer is susceptible to oxidation when an aqueous solution is used, it is preferable to dry the layer in an atmosphere with a low oxygen content after contact with the aqueous solution.

By adjusting the content of the sulfur-containing compound in the gas or aqueous solution in step (c1), (c2) or (c3), an appropriate sulfur-containing silver compound layer can be formed. Furthermore, it is preferable to observe the sulfur concentration in the gas or aqueous solution and adjust the contact conditions according to the observed concentration. Production stability can be enhanced by controlling the detection reaction time and temperature while observing the sulfur concentration.

The production method according to the embodiment may further include a step of forming another layer. An example of such another layer is the second oxide layer described above. That is, prior to step (a), a second conductive oxide layer may be formed.

In addition, the manufacturing method according to the embodiment may further include step (d) of stacking the graphene layers described above after step (c).

The step of laminating the graphene layers can be performed by any method. For example, a method of forming a graphene film on another support and transferring it onto an oxide film can be employed. Specifically, an unsubstituted single-layer graphene film is formed by a CVD method using methane, hydrogen, and argon as reaction gases and using a copper foil as a base catalyst layer. single-layer graphene can be transferred onto the laminated film. A plurality of single-layer graphene layers can be laminated on the laminated film by repeating the same operation. At this time, it is preferable to form two to four graphene layers. Graphene in which some carbons are substituted with boron may be used instead of unsubstituted graphene. Boron-substituted graphene can be similarly prepared using BH ₃ , methane, hydrogen, and argon as reactant gases.

In addition, the manufacturing method according to the embodiment can further have step (e) of laminating a third inorganic oxide layer before or after step (c). Step (e) may be performed after step (d). Inorganic oxides include TiO ₂ , SnO ₂ , WO ₃ , NiO, MoO ₃ , ZnO, V ₂ O ₅ and the like. These inorganic oxide films are generally formed by a sputtering method, a vapor deposition method, a sol-gel method, or the like. The ratio of metal to oxygen in these inorganic oxides is not necessarily stoichiometric.

[Embodiment 3-1]
A configuration of a photoelectric conversion element according to one embodiment of the third electronic device will be described with reference to FIG. FIG. 3 is a schematic configuration diagram of a solar cell 500 (photoelectric conversion element) according to this embodiment. The photovoltaic cell 500 is an element having a function as a photovoltaic cell that converts light energy such as sunlight L incident on the cell into electric power. A solar cell 500 includes a photoelectric conversion layer 503 provided on the surface of a conductive layer 502 on a substrate 501, and a counter electrode 504 provided on the side of the photoelectric conversion layer 503 opposite to the conductive layer 502. ing. Here, the conductive layer 502 is similar to that shown in the first embodiment.

The photoelectric conversion layer 503 is a semiconductor layer that converts light energy of incident light into power to generate current. The photoelectric conversion layer 503 generally comprises a p-type semiconductor layer and an n-type semiconductor layer. As a photoelectric conversion layer, a laminate of a p-type polymer and an n-type material, perovskite RNH ₃ PbX ₃ (X is a halogen ion, R is an alkyl group, etc.), a silicon semiconductor, InGaAs, GaAs, chalcopyrite, CdTe, InP Inorganic compound semiconductors such as SiGe-based and Cu ₂ O-based semiconductors, quantum dot-containing type, and dye-sensitized transparent semiconductors may also be used. In either case, the efficiency is high, and deterioration of the output can be further reduced.

A buffer layer may be inserted between the photoelectric conversion layer 503 and the conductive layer 502 to promote or block charge injection.

The counter electrode 504 is usually an opaque metal electrode or carbon electrode, but a transparent electrode according to the embodiment may also be used. Another charge buffer layer or charge transport layer may be inserted between the counter electrode 504 and the photoelectric conversion layer 503 .

Examples of anode buffer layers and charge transport layers include vanadium oxide, PEDOT/PSS, p-type polymer, 2,2′,7,7′-Tetrakis[N,N-di(4-methoxyphenyl)amino]-9, A layer made of 9′-spirobifluorene (hereinafter referred to as Spiro-OMeTAD), nickel oxide (NiO), tungsten trioxide (WO ₃ ), molybdenum trioxide (MoO ₃ ), or the like can be used. The ratio of metal to oxygen in the inorganic oxide is not necessarily stoichiometric.

On the other hand, lithium fluoride (LiF), calcium (Ca), 6,6′-phenyl-C ₆₁ -butyric acid methyl ester (6,6′-phenyl _-C61 -butyric acid methyl ester, C60-PCBM), 6,6'-phenyl-C71-butyric acid methyl ester ₍ 6,6'-phenyl-C71-butyric acid methyl ester, hereinafter referred to as C70-PCBM), Indene-C _{60 bisadduct} (hereinafter referred to as ICBA), cesium carbonate (Cs ₂ CO ₃ ), titanium dioxide (TiO ₂ ), poly[(9,9-bis(3′-(N ,N-dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctyl-fluorene)] (hereinafter referred to as PFN), Bathocuproine (hereinafter referred to as BCP), zirconium oxide ( ZrO), zinc oxide (ZnO), tin oxide (SnO ₂ ), polyethynimine, and the like can be used. The ratio of metal to oxygen in the inorganic oxide is not necessarily stoichiometric.

A brookite-type titanium oxide layer can be provided between the photoelectric conversion layer and the transparent electrode layer. Titanium oxide is known to have three crystal structures: rutile, anatase, and brookite. In the embodiment, it is preferable to use a layer containing brookite-type titanium oxide. This brookite-type titanium oxide layer has the effect of suppressing migration of halogen from the photoelectric conversion layer to the conductive layer and migration of metal ions from the conductive layer to the photoelectric conversion layer. Therefore, it is possible to extend the life of the electrodes and the electronic device. Such a brookite-type titanium oxide layer preferably comprises brookite-type titanium oxide nanoparticles, specifically, particles having an average particle size of 5 to 30 nm. Here, the average particle size was measured with a particle size distribution analyzer. Such brookite-type nanoparticles are commercially available from, for example, Kojundo Chemical Laboratory.

An electrode having a structure similar to that of the conductive layer 502 may be used as the counter electrode 504 . In addition, the counter electrode 504 may contain unsubstituted planar single-layer graphene. Unsubstituted single-layer graphene can be produced by a CVD method using methane, hydrogen, and argon as reaction gases and using a copper foil as an underlying catalyst layer. For example, after the thermal transfer film and monolayer graphene are pressure-bonded, the copper is melted and the monolayer graphene is transferred onto the thermal transfer film. A plurality of monolayer graphene layers can be laminated on the thermal transfer film by repeating the same operation, producing 2 to 4 graphene layers. A counter electrode can be formed by printing a current-collecting metal wiring on this film using a silver paste or the like. Graphene in which some carbons are substituted with boron may be used instead of unsubstituted graphene. Boron-substituted graphene can be similarly prepared using BH ₃ , methane, hydrogen, and argon as reactant gases. These graphenes can also be transferred from thermal transfer films onto suitable substrates such as PET.

Also, these monolayer or multilayer graphenes may be doped with tertiary amines as electron donor molecules. An electrode made of such a graphene film also functions as a transparent electrode.
For example, a poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonic acid) composite (PEDOT/PSS) film may be formed as a hole injection layer on the counter electrode. This film may be, for example, 50 nm thick.

The solar cell according to the embodiment can have a structure sandwiched between transparent electrodes on both sides. A solar cell having such a structure can efficiently utilize light from both sides. The energy conversion efficiency is generally 5% or more, and it is characterized by long-term stability and flexibility.

Also, an ITO glass transparent electrode can be used as the counter electrode 504 instead of the graphene film. In this case, the flexibility of the solar cell is sacrificed, but light energy can be utilized with high efficiency. Also, stainless steel, copper, titanium, nickel, chromium, tungsten, gold, silver, molybdenum, tin, zinc, or the like may be used as the metal electrode. In this case, transparency tends to decrease.

A solar cell can have an ultraviolet blocking layer and a gas barrier layer. Specific examples of UV absorbers include 2-hydroxy-4-methoxybenzophenone, 2,2-dihydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxy-2-carboxybenzophenone, 2-hydroxy-4-n- Benzophenone compounds such as octoxybenzophenone; 2-(2-hydroxy-3,5-di-tert-butylphenyl)benzotriazole, 2-(2-hydroxy-5-methylphenyl)benzotriazole, 2-(2-hydroxy benzotriazole-based compounds such as 5-tertiary-octylphenyl)benzotriazole; and salicylic acid ester-based compounds such as phenyl salicylate and p-octylphenyl salicylate. It is desirable for these to cut ultraviolet rays of 400 nm or less.

As the gas barrier layer, a layer that blocks water vapor and oxygen is particularly preferable, and a layer that hardly allows water vapor to pass through is particularly preferable. For example, layers made of inorganic substances such as SiN, SiO ₂ , SiC, SiO _x N _y , TiO ₂ and Al ₂ O ₃ , ultra-thin glass, and the like can be suitably used. Although the thickness of the gas barrier layer is not particularly limited, it is preferably in the range of 0.01 to 3000 μm, more preferably in the range of 0.1 to 100 μm. If the thickness is less than 0.01 μm, sufficient gas barrier properties tend not to be obtained. The water vapor permeation amount (water vapor permeability) of the gas barrier layer is preferably 100 g/m ² ·d to 10 ^-6 g/m ² ·d, more preferably 10 g/m ² ·d to 10 ^-5 g/m ² · d, more preferably 1 g/m ² ·d to 10 ^-4 g/m ² ·d. Incidentally, the moisture permeability can be measured based on JIS Z0208 or the like. A dry method is suitable for forming the gas barrier layer. Methods for forming a gas barrier layer with gas barrier properties by a dry method include resistance heating deposition, electron beam deposition, induction heating deposition, vacuum deposition methods such as assisted methods using plasma or ion beams, reactive sputtering methods, and ion beams. Sputtering method, sputtering method such as ECR (electron cyclotron) sputtering method, physical vapor deposition method (PVD method) such as ion plating method, chemical vapor deposition method (CVD method) using heat, light, plasma, etc. ) and the like. Among them, the vacuum vapor deposition method, in which a film is formed by a vapor deposition method under vacuum, is preferred.

When the transparent electrode according to the embodiment has a substrate, the type of substrate is selected according to the purpose. For example, as the transparent substrate, an inorganic material such as glass, or an organic material such as PET, PEN, polycarbonate, or PMMA is used. In particular, it is preferable to use a flexible organic material because the transparent electrode according to the embodiment becomes highly flexible.

The solar cell of this embodiment can also be used as an optical sensor.

[Embodiment 3-2]
A configuration of a photoelectric conversion element according to a third embodiment will be described with reference to FIG. FIG. 6 is a schematic configuration diagram of an organic EL element 600 (photoelectric conversion element) according to this embodiment. The organic EL element 600 is an element that functions as a light-emitting element that converts electrical energy input to this element into light L. As shown in FIG. The organic EL element 600 includes a photoelectric conversion layer (light-emitting layer) 603 provided on the surface of a conductive layer 602 on a substrate 601, and a counter electrode 604 provided on the side of the photoelectric conversion layer 603 opposite to the conductive layer 602. and

The conductive layer 602 here is the same as that shown in the first embodiment. The photoelectric conversion layer 603 is an organic thin film layer that recombines charges injected from the conductive layer 602 and charges injected from the counter electrode 604 to convert electrical energy into light. The photoelectric conversion layer 603 usually consists of a p-type semiconductor layer and an n-type semiconductor layer. A buffer layer is provided between the photoelectric conversion layer 603 and the counter electrode 604 to promote or block charge injection, and another buffer layer may be provided between the photoelectric conversion layer 603 and the conductive layer 602. . The counter electrode 604 is usually a metal electrode, but a transparent electrode may be used.

(Example 1)
A transparent electrode 700A having a structure corresponding to FIG. 2 is produced. Amorphous-containing ITO layer (hereinafter referred to as a-ITO layer) 704A (45-52 nm)/silver-containing layer 702A (5-8 nm)/a-ITO layer 703A (45-52 nm) on PET film 701A having a thickness of 100 μm. A transparent electrode 700A having a conductive layer having a laminated structure is formed by a sputtering method. The surface resistance is 7-9Ω/□. It is left in a glass container at 80° C. for 10 minutes with sulfur powder in dry air. The surface resistance and transmission spectrum do not change. A cross-sectional SEM of the obtained transparent electrode is measured. Specifically, an FE-SEM (Field Emission Scanning Electron Microscope, manufactured by Carl Zeiss, Model ULTRA55) can be used for measurement at an observation voltage of 2.0 kV and a magnification of 80,000. The obtained cross-sectional image is as shown in FIG. 7(A). In FIG. 7A, silver-containing layer 702A is continuous. 705A is a metal coating layer for SEM measurement. The ratio _Rt is 0.92. When the response power is measured by cyclic buttonmetry for 5 minutes at -0.5 to 0.8 V (against silver-silver chloride electrode) in salt water containing 0.03 wt%, the increase in surface resistance is 10% or less. and is resistant to ion migration.

(Comparative example 1)
A transparent electrode having a conductive layer having a laminated structure of amorphous ITO layer 704B/silver-containing layer 702B/a-ITO layer 703B on PET film 701B in the same manner as in Example 1 except that it is not treated with sulfur vapor. 700B is produced and evaluated. The obtained cross-sectional image is as shown in FIG. 7(B). A large number of discontinuous regions 706B can be seen in the silver-containing layer 702B in the cross-sectional SEM photograph. In addition, when the response power is measured by cyclic buttonmetry for 5 minutes at -0.5 to 0.8 V (against silver-silver chloride electrode) in salt water containing 0.03 wt%, the surface resistance is 300Ω/□ or more. and have low resistance to ion migration.

(Example 2)
A transparent electrode 200 having the structure shown in FIG. 2 is produced. A conductive layer having a laminated structure of a-ITO layer (45-52 nm) / silver-containing layer containing silver and Pd alloy (5-8 nm) / a-ITO layer (45-52 nm) on a 100 μm thick PET film is created by the sputtering method. The surface resistance is 9-10Ω/□. This is left in a glass container for 10 minutes at 30° C. in dry air containing 1% hydrogen sulfide. A cross-sectional SEM of the obtained transparent electrode is measured. The silver-containing layer is uniform with no discontinuities. The surface resistance and transmission spectrum did not change from before sulfur treatment. The ratio _Rt is 0.85. When the response power is measured by cyclic buttonmetry for 5 minutes at -0.5 to 0.8 V (against silver-silver chloride electrode) in 0.03 wt% salt water, the increase in surface resistance is 1% or less. and is resistant to ion migration.

(Comparative example 2)
The amount of Pd is increased compared to Example 2 to produce a transparent electrode with a ratio _Rt of 0.83. . In this case, the light transmittance at 550 nm is 5% lower than that of Example 2, and the light transmittance is insufficient as a transparent electrode for solar cells.

(Example 3)
As in Example 1, a conductive layer having a laminated structure of a-ITO/silver-containing layer/a-ITO is formed on a 100 μm PET film by sputtering. The surface resistance is 7-9Ω/□. It is left in a glass container at 80° C. for 10 minutes with sulfur powder in dry air. A shielding layer is formed thereon by laminating an average of four layers of planar N-graphene films in which part of the carbon atoms are substituted with nitrogen atoms.

The shielding layer is created as follows. First, the surface of the Cu foil is heat-treated by laser irradiation and annealed to enlarge the crystal grains. Using this Cu foil as a base catalyst layer, using a mixed reaction gas of ammonia, methane, hydrogen, and argon (15:60:65:200 ccm) at 1000° C. for 5 minutes, a planar single-layer N-graphene was formed by a CVD method. Manufacture the membrane. At this time, a single-layer graphene film is mostly formed, but depending on the conditions, an N-graphene film having two or more layers is also partially formed. Further, it is treated at 1000° C. for 5 minutes under a mixture of ammonia and argon, and then cooled under argon. After pressing a thermal transfer film (150 μm thick) and a single layer N-graphene film, the single layer N-graphene film is transferred onto the thermal transfer film by immersing it in an ammonia alkaline cupric chloride etchant to dissolve Cu. By repeating the same operation, four monolayer graphene films are laminated on the thermal transfer film to obtain a multilayer N-graphene film.

After laminating the thermal transfer film on the a-ITO layer/silver-containing layer/a-ITO layer/PET film treated with sulfur vapor, the N-graphene film is formed by heating to form a-ITO/silver/a-ITO/PET. A shielding layer is produced by transferring onto a film.

The nitrogen content measured by XPS is 1-2 atom% under these conditions. The ratio of carbon atoms to oxygen atoms in the carbon material measured by XPS is 100-200.

A cross-sectional SEM of the obtained transparent electrode is measured. The silver-containing layer is uniform with no discontinuities. The ratio (R _t ) is 0.93. When the response power is measured by cyclic buttonmetry for 5 minutes at -0.5 to 0.8 V (against silver-silver chloride electrode) in 0.03 wt% salt water, the increase in surface resistance is 5% or less. and is resistant to ion migration.

(Example 4)
As in Example 1, a conductive layer having a laminated structure of a-ITO layer/silver-containing layer/a-ITO layer is formed on a 100 μm PET film by sputtering. The surface resistance is 7-9Ω/□. This is left in a glass container for 10 minutes at 30° C. in dry air containing 1% hydrogen sulfide.

An isopropanol solution containing 5 wt% niobium (V) butoxide with respect to titanium (IV) isopropoxide is applied with a bar coater. After drying at room temperature in nitrogen, it is dried on a hot plate at 130° C. in an atmosphere with a humidity of 20% to form an Nb-doped titanium oxide layer. When the response power is measured by cyclic buttonmetry for 5 minutes at -0.5 to 0.8 V (against silver-silver chloride electrode) in 0.03 wt% salt water, the increase in surface resistance is 2% or less. and is resistant to ion migration.

(Example 5)
A solar cell 800 shown in FIG. 8 is produced.

A conductive layer 802 is formed on a substrate 801 in the same manner as in the first embodiment. An aqueous solution of lithium fluoride is applied thereon as an electron injection layer 803 , then a toluene solution of C ₆₀ -PCBM is applied with a bar coater and dried to form an electron transport layer 804 . A chlorobenzene solution containing poly(3-hexylthiophene-2,5-diyl) and C ₆₀ -PCBM is applied with a bar coater and dried at 100° C. for 20 minutes to form a photoelectric conversion layer 805 .

The surface of the stainless steel foil 806 with the insulating ceramic film formed on the opposite side is treated with dilute hydrochloric acid to remove the surface oxide film, and then an aqueous solution of graphene oxide is applied with a bar coater to form a graphene oxide film. Next, after drying at 90° C. for 20 minutes, the shielding layer 807 is made of a two-layer N-graphene film in which some of the carbon atoms of graphene oxide are replaced with nitrogen atoms by treating with hydrazine hydrate vapor at 110° C. for 1 hour. change to

An aqueous solution of PEDOT/PSS containing sorbitol is applied onto the N-graphene film 806 with a bar coater and dried at 100° C. for 30 minutes to form an adhesive layer 808 (50 nm thick) containing PEDOT/PSS.

The adhesive layer 808 is bonded onto the photoelectric conversion layer 804 at 90°C. An ultraviolet shielding ink containing 2-hydroxy-4-methoxybenzophenone is screen-printed on the PET surface opposite to the conductive layer to form an ultraviolet shielding layer 809 . A silica film is formed on the ultraviolet blocking layer by a vacuum deposition method to form the gas barrier layer 810, and the solar battery cell 800 is produced.

The resulting solar battery cell exhibits an energy conversion efficiency of 5% or more for 1 SUN of sunlight, and the efficiency deterioration is less than 3% even after being left outdoors for a month.

(Example 6)
Create an organic EL element. An aqueous solution of lithium fluoride is applied as an electron transport layer on the transparent electrode produced in Example 2, and tris(8-hydroxyquinoline) aluminum (Alq ₃ ) ( 40 nm) is vapor-deposited to produce a photoelectric conversion layer. N,N'-di-1-naphthyl-N,N'-diphenyl-1,1'-biphenyl-4,4'-diamine (hereinafter referred to as NPD) was deposited thereon to a thickness of 30 nm to transport holes. Layer 83 is made. A gold electrode is formed thereon by a sputtering method. Further, by sealing the periphery, an organic EL element is produced. The resulting organic EL device has little deterioration of the output light, and even after continuous operation for 1000 hours, the decrease in output is 4% or less.

DESCRIPTION OF SYMBOLS 100, 200, 300... Transparent electrode 101... Base material 102... Silver-containing layer 103... Oxide layer 104... Second oxide layer 105... Non-uniform portion 106... Sulfur-containing silver compound 500... Solar battery cell 501... Transparent base Material 502 Conductive layer 503 Photoelectric conversion layer 504 Counter electrode 600 Organic EL element 601 Transparent substrate 602 Conductive layer 603 Photoelectric conversion layer 604 Counter electrode 700A, 700B Transparent electrode 701A, 701B PET Films 702A, 702B Silver-containing layers 703A, 703B Amorphous-containing ITO layers 704A, 704B Amorphous-containing ITO layers 705A, 705B Metal coat layer 706B Discontinuous region 800 Transparent electrode 800 Solar cell 801 Transparent substrate 802... Conductive layer 803... Electron injection layer 804... Electron transport layer 805... Photoelectric conversion layer 806... Stainless foil 807... Shielding layer 808... Adhesive layer 809... Ultraviolet cut layer 810... Gas barrier layer

Claims (15)

A transparent electrode having a laminated structure in which a transparent substrate, a conductive silver-containing layer, and a first conductive oxide layer are laminated in this order,
The transparent electrode has a total transmittance ratio _T800 / _T600 of 0.85 or more, where T800 and T600 are transmittances at wavelengths of ₈₀₀ nm and ₆₀₀ nm, respectively;
The transparent electrode, wherein the silver-containing layer is continuous when a cross section of the transparent electrode is observed with a scanning electron microscope. The transparent electrode according to claim 1, wherein the silver-containing layer is made of silver or a silver alloy. The transparent electrode according to claim 1 or 2, wherein the oxide is indium-doped tin oxide, fluorine-doped tin oxide, or aluminum-doped zinc oxide. The transparent electrode according to any one of claims 1 to 3, wherein the first conductive oxide layer has a non-uniform portion, and the non-uniform portion is provided with a sulfur-containing silver compound layer. The transparent electrode according to any one of claims 1 to 4, wherein the entire surface of the silver-containing layer is covered with the oxide layer or the sulfur-containing silver compound layer. The transparent electrode according to any one of claims 1 to 5, further comprising a graphene layer or another oxide layer on the first conductive oxide layer. The transparent electrode according to any one of claims 1 to 6, further comprising a second conductive oxide layer between the transparent substrate and the silver-containing layer. (a) forming a conductive silver-containing layer on a transparent substrate;
(b) forming a first conductive oxide layer over the silver-containing layer to form a film stack; and (c) contacting the film stack with sulfur or a sulfur compound. , a method for producing a transparent electrode. The step (c) is
(c1) contacting the laminated film with a sulfur vapor gas;
(c2) contacting the laminated film with hydrogen sulfide gas, or (c3) contacting the laminated film with an aqueous solution of hydrogen sulfide or sodium sulfide;
9. The method of claim 8, comprising: The method according to claim 9, wherein in steps (c1), (c2) or (c3), the sulfur concentration in the gas or the aqueous solution is observed, and the contact conditions are adjusted according to the observed concentration. The method according to any one of claims 8 to 10, further comprising (d) stacking a graphene layer after step (c). The method according to any one of claims 8 to 11, further comprising the step of (e) laminating a third inorganic oxide layer before or after step (c). An electronic device comprising the transparent electrode according to any one of claims 1 to 7, an active layer, and a counter electrode. The electronic device according to claim 13, wherein the active layer is a photoelectric conversion layer. The electronic device according to claim 13 or 14, wherein the active layer contains halogen ions.

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