JP5730729B2 - Substrate with transparent electrode - Google Patents

Description

  The present invention mainly includes transparent electrodes and back electrodes of single crystal silicon-based or non-single-crystal silicon solar cells, transparent intermediate layers of hybrid solar cells, transparent electrodes of compound semiconductor solar cells, touch panels, PDPs, LCDs, and electroluminescence. (EL) Display materials, low dielectric constant films used in compound semiconductor high-speed devices, surface acoustic wave elements, window glass coatings for the purpose of cutting infrared rays, gas sensors, prism sheets utilizing nonlinear optics, transparent magnetic materials, optical recording The present invention relates to a transparent electrode capable of achieving high conductivity and durability in materials such as an element, an optical switch, an optical waveguide, an optical splitter, a photoacoustic material, and a high-temperature heating heater material.

  In a substrate with a transparent electrode used for a solar cell, an electroluminescence lighting device, a touch panel, etc., there are “conductivity”, “transparency”, and “durability” as important elements. As a substrate with a transparent electrode, a substrate having a transparent electrode on the substrate is generally used. As such a transparent electrode, transparent conductive oxide such as indium tin oxide (ITO), tin oxide, and zinc oxide is used. Things are widely used. Among them, ITO is an excellent material as a transparent conductive material, and is currently widely used as a transparent conductive oxide layer. However, there is a possibility that indium as a raw material may be depleted, and there is an urgent need to search for a material that can replace ITO in terms of resources and cost.

  As a material replacing such ITO, zinc oxide (ZnO), which is advantageous in terms of cost, has attracted attention. However, ZnO has a problem that reliability, that is, durability against water or air is poor, and in particular, conductivity easily changes.

  In general, zinc oxide is known to have a large “oxygen deficiency”, which is a cause of electrical conductivity. Due to this oxygen deficiency, it is assumed that reliability is low. Therefore, as a method for producing a highly reliable zinc oxide transparent electrode, there is a method of developing conductivity that does not depend on oxygen deficiency. For this reason, many studies have been made to improve the durability and conductivity of ZnO.

  As seen in Patent Document 1, it is well known that conductivity is improved by introducing aluminum in a zinc oxide transparent electrode. In general, about 2.0% by weight of aluminum oxide is doped to conduct electricity. The sex is secured. However, free electron absorption or free electron reflection derived from the conductive carriers generated thereby occurs, and as a result, the transparency may be lowered. For this reason, it is expected that the doping amount of aluminum is as small as possible. However, when the doping amount is as low as about 1.0% by weight, there is a problem that the conductivity sufficient to function as a transparent electrode cannot be obtained. .

  In addition, it is generally known that silicon oxide is doped to improve durability. In Patent Document 1, a zinc oxide-based transparent conductive film doped with aluminum oxide and silicon oxide is used. Patent Document 2 describes that conductivity and durability are improved by using a substrate with a transparent electrode having 0.50 to 2.75% by weight of silicon dioxide.

  However, in Patent Document 1, since the amount of aluminum oxide added is as large as about 2.0% by weight, there is a problem that the transmittance is lowered due to the influence of free electron absorption as described above. Here, in Patent Document 1, a transparent conductive film having a thickness of about 1 μm is used, and it is presumed that the conductivity and reliability are ensured. However, there is a problem that the transmittance is lowered due to the thick film thickness. Further, in Patent Document 2, since only silicon oxide is added to ZnO, the durability is excellent, but there is still room for improvement from the viewpoint of improving conductivity.

  In general, a transparent conductive oxide layer such as zinc oxide or indium tin oxide has a film thickness substantially proportional to conductivity, and the conductivity increases as the film thickness increases. It is known that when the film thickness is increased, the crystallinity is improved depending on the film forming process, and the carrier concentration is increased and the mobility is increased. On the other hand, as the film thickness increases, the transparency deteriorates. Thus, since conductivity and transparency are often in a trade-off relationship with each other, it is difficult to achieve both at a high level. Further, as the film thickness becomes thinner, the durability tends to decrease, and improving the durability with a thin film is an essential issue for obtaining a high-performance transparent electrode.

  In Patent Document 3, a transparent electrode substrate is formed by stacking two transparent conductive films of ZnO (AZO) having aluminum oxide and ZnO (SZO) having silicon oxide on the substrate, and making SZO amorphous. It is described that the durability is improved while maintaining the electrical conductivity. However, although the substrate with a transparent electrode has a thin transparent conductive film and a high transmittance, the doping amount of silicon oxide is as large as about 10% by weight, and the conductivity is improved (that is, the resistance is reduced). There is still room for improvement from the point of view.

  Patent Document 1 and Patent Document 4 describe that the bonding of devices is improved by changing the amounts of silicon oxide and aluminum oxide contained in the ZnO film in the film thickness direction. However, when changing the doping amount in the film thickness direction, it is necessary to use a large number of targets, which is problematic from the viewpoint of productivity. As described above, it has been difficult to produce a substrate with a transparent electrode that is excellent in durability, conductivity, and transparency.

JP 2002-217429 A WO2010 / 026899 JP 2010-21010 A Japanese Patent Laid-Open No. 5-110125

  In the present invention, even when the film thickness is reduced by using a transparent conductive oxide layer mainly composed of zinc oxide to which a predetermined amount of aluminum oxide and silicon oxide is added, It aims at providing the board | substrate with a transparent electrode excellent in durability, especially durability.

  In order to solve the above-mentioned problems, the present inventors have conducted intensive studies, and as a result, a transparent conductive oxide layer mainly composed of zinc oxide doped with a predetermined amount of aluminum oxide and silicon oxide is used as a transparent electrode. It has been found that by using it, it is possible to produce a substrate with a transparent electrode that is excellent in durability, conductivity, and transparency. That is, the present invention relates to the following.

(1) In a substrate with a transparent electrode having a transparent conductive oxide layer containing zinc oxide as a main component on the substrate, the transparent conductive oxide layer contains 1.2% by weight or more and 2.1% by weight of silicon oxide. Hereinafter, the aluminum oxide is contained in an amount of 0.2 wt% or more and less than 1.0 wt%, and the resistivity of the transparent conductive oxide layer is 4.5 × 10 ⁻³ Ωcm or less, and 85 ° C. When the temperature change (R) is T = 300K and the film thickness (d) is 20 nm ≦ d ≦ 120 nm when the film is left for 1000 hours in an environment of 85% RH,
ΔR = a × exp (−b × d / T) +1.0
[1.2 ≦ a ≦ 3.0, 15 ≦ b ≦ 45, a and b are real numbers] (Formula 1)
A substrate with a transparent electrode, characterized in that:

  (2) The substrate with a transparent electrode according to (1), wherein the change in resistivity before and after being left for 1000 hours in an environment of 85 ° C. and 85% RH is 0.8 to 1.2.

(3) R ₃₀ / R ₁₀₀ = 0.9 to 1.4 is satisfied when the change in resistivity before and after the wet heat durability test at a film thickness of 30 nm and 100 nm is R ₃₀ and R ₁₀₀ , respectively. (1) The board | substrate with a transparent electrode in any one of (2).

  According to the present invention, “durability”, “transparency”, and “conductivity”, which are particularly important elements in solar cells, touch panels, electroluminescent electrode substrates, etc., have good characteristics even when the film thickness is reduced. It becomes possible to provide the substrate with a transparent electrode shown.

It is a typical section schematic diagram of a substrate with a transparent electrode. It is a figure showing the relational expression which shows the film thickness and resistance change of the transparent electrode in this invention.

The present invention relates to "a substrate with a transparent electrode having a transparent conductive oxide layer mainly composed of zinc oxide on a substrate, wherein the transparent conductive oxide layer contains 1.2% by weight or more of silicon oxide and 2.1% by weight. The transparent conductive oxide layer has a resistivity of 4.5 × 10 −3 Ωcm or less and 85 ° C. For the change in resistivity ΔR when left for 1000 hours in an environment of 85% RH, when the wet heat durability of ΔR is normalized to a film thickness d = 100 nm, the temperature (T) is T = 300 K, the film thickness ( When d) is 20 nm ≦ d ≦ 120 nm,
ΔR = a × exp (−b × d / T) +1.0
[1.2 ≦ a ≦ 3.0, 15 ≦ b ≦ 45, a and b are real numbers] (Formula 1)
It is related with the board | substrate with a transparent electrode characterized by satisfy | filling.

  In the present invention, a transparent electrode substrate having both durability, conductivity and transparency can be obtained by adding a predetermined amount of silicon oxide and aluminum oxide to a transparent conductive oxide layer mainly composed of zinc oxide. It was found that it can be produced.

  Hereinafter, typical embodiments of the substrate with a transparent electrode according to the present invention will be described. FIG. 1 shows a typical schematic diagram of a substrate with a transparent electrode of the present invention. That is, a substrate with a transparent electrode (that is, a substrate + a transparent electrode) in which a transparent conductive oxide layer 2 is formed as a transparent electrode on the substrate 1 is shown.

  About the said board | substrate 1 in this invention, it uses properly by an application and is not specifically limited, such as a hard or soft material. For example, hard materials include single crystal silicon substrates, non-single crystal silicon substrates, oxides such as glass and sapphire, compound semiconductor substrates such as gallium nitride and gallium arsenide, copper-indium-selenium (CIS), and copper-indium. -Gallium-selenium (CIGS) etc. can be used. On these CIS and CIGS, cadmium sulfide (CdS), zinc sulfide (ZnS), and zinc oxide (ZnO) may be formed as a buffer layer. Specific examples of the glass include alkali glass, borosilicate glass, and non-alkali glass.

  When a soft material is used as a substrate, it can be used for a touch panel, for example. In addition, it is applicable to a flexible organic EL device. When used for a touch panel, any method such as a resistive film method or a capacitance method can be adopted as long as a transparent electrode can be applied. Examples of the soft material include a thermoplastic resin and a thermosetting resin. Examples of the thermoplastic resin include acrylic resin, polyester, polycarbonate resin, polyolefin, and cycloolefin polymer. Examples of the thermosetting resin include polyurethane. Among these, the substrate 1 mainly composed of a cycloolefin polymer (COP) that is particularly excellent in optical isotropy and water vapor blocking properties is preferable.

  Examples of COP include norbornene polymers, copolymers of norbornene and olefins, and polymers of unsaturated alicyclic hydrocarbons such as cyclopentadiene. From the viewpoint of water vapor barrier properties, it is preferable that the main chain and side chain of the constituent molecules do not contain a functional group having a large polarity, such as a carbonyl group or a hydroxyl group. In addition, from the viewpoint of excellent heat resistance, polyethylene naphthalate (PEN), polyethersulfone (PES), or the like can be used as the soft material. These can be used alone or in combination as appropriate.

  The thickness when the soft material as described above is used as the substrate 1 can be arbitrarily selected depending on the purpose of use, and preferably about 0.03 mm to 3.0 mm. When the thickness of the substrate is 0.03 mm or more, it is preferable from the viewpoint of handling and strength. In addition, when the thickness of the substrate is 3.0 mm or less, the weight is light and does not affect the thickness of the device, so that it can be used for portable devices and the like, and is preferable from the viewpoint of transparency and cost.

  When the single crystal or non-single-crystal silicon substrate is used as the substrate 1 in the present invention, the single-crystal or non-single-crystal silicon substrate may be intrinsic, but preferably doped with an impurity by an ion implantation method or the like. be able to.

  In crystalline silicon solar cells, crystalline silicon is generally doped p-type or n-type, and the transparent electrode (that is, transparent conductive oxide layer 2) of the present invention is used as a transparent electrode on top of this. Thus, the conversion efficiency can be improved. The doping is not particularly limited, but boron is typical for p-type, and phosphorus and antimony are typical for n-type. It can also be used as a transparent electrode of a so-called heterojunction crystal silicon solar cell in which amorphous silicon is formed on these single crystal silicon substrates.

  Heterojunction type crystalline silicon solar cells, for example, formed by depositing amorphous intrinsic silicon 3 to 200 nm, further conductive doped amorphous silicon 1 to 30 nm on a single crystal silicon substrate, A transparent electrode and a collector electrode formed in this order can be used.

  The thickness of the single crystal silicon substrate or the non-single crystal silicon substrate may be appropriately selected according to the purpose such as use, but is generally preferably in the range of 80 to 1000 μm, and more preferably in the range of 100 to 700 μm. When the single crystal silicon substrate is used as a photoelectric conversion layer or a carrier transport layer of a solar cell, a large amount of light can be generated by taking in a large amount of light into the photoelectric conversion layer. The thickness of the silicon substrate is preferably 80 μm or more because a sufficient amount of light can be secured for photoelectric conversion. The thickness of 1000 μm or less is preferable from the viewpoint of diffusion and extraction of photoinduced carriers.

  In addition, for example, in a thin-film silicon solar cell having a transparent electrode layer, one or more non-single-crystal silicon photoelectric conversion units, and a back electrode in this order on a glass substrate, the transparent electrode layer, the photoelectric conversion unit, and the back surface The transparent conductive oxide layer 2 of the present invention can be applied as a transparent electrode inserted between the electrodes.

  When glass or sapphire is used as the substrate 1 in the present invention, the thickness of the substrate 1 can be arbitrarily selected depending on the purpose of use, but it is 0.5 mm to 4.5 mm in consideration of the balance between handling and weight. It can be illustrated as a preferred range. A substrate such as glass having a thickness of 0.5 mm or more is preferable from the viewpoint of strength and the like. In addition, when the thickness is 4.5 mm or less, the weight is light and does not affect the thickness of the device, so that it can be used for portable devices and the like, and is preferable from the viewpoint of transparency and cost.

  The most important feature of the transparent conductive oxide layer 2 in the present invention is that it has a transparent conductive oxide mainly composed of zinc oxide, and the transparent conductive oxide contains predetermined amounts of silicon oxide and aluminum oxide. It is to contain. Use of such a transparent conductive oxide layer 2 makes it possible to improve both durability and conductivity. This is presumably because the silicon oxide can improve the durability in addition to imparting conductivity, and can further improve the conductivity by adding aluminum oxide which is a group 13 element.

  The reason why durability is improved by silicon oxide is not clear, but by introducing silicon oxide with strong covalent bond to zinc oxide, which has strong ion binding, it is durable against external environment, especially moisture. Is estimated to improve. The reason why the conductivity is improved by aluminum oxide is thought to be that electrons, which are conductive carriers, can be injected by introducing an appropriate amount of aluminum oxide, which is a group 13 element, into zinc, which is a group 12 element.

Examples of the group 13 element include boron, aluminum, gallium, and indium. In the present invention, the conductive carrier injection is less than gallium and indium.
Aluminum is used from the viewpoint of improving the conductivity by improving the mobility. Here, “having zinc oxide as a main component” means that the transparent electrode, that is, the transparent conductive oxide layer 2 contains more than 50% by weight of zinc oxide, preferably 70% by weight or more, wt% or more, still more preferably at least 90 wt%.

  In the transparent conductive oxide mainly composed of zinc oxide in the present invention, the addition amount of silicon oxide and aluminum oxide is 1.2 wt% or more and 2.1 wt% or less and 0 wt%, respectively, with respect to the transparent conductive oxide. .2% by weight or more and less than 1.0% by weight.

  When silicon oxide is 1.2% by weight or more, it is preferable from the viewpoint of durability, and when it is 2.1% by weight or less, it is preferable from the viewpoint of conductivity. Moreover, when aluminum oxide is 0.2 weight% or more, it is preferable from an electroconductive viewpoint, and when less than 1.0 weight%, it is preferable from a transparency viewpoint.

  Here, as described above, it has been considered that the aluminum oxide needs to be 1.0% by weight or more from the viewpoint of electrical conductivity. It has been found that conductivity can be secured. This is presumed to be due to the “co-doping effect” with silicon oxide because it has a predetermined amount of silicon oxide in addition to aluminum oxide in the present invention.

  That is, by setting the addition amounts of silicon oxide and aluminum oxide in the above range, it is possible to produce a transparent electrode excellent in durability, conductivity, and transparency even when the film thickness is reduced. Further, silicon oxide is preferably 1.5% by weight or more, and more preferably 2.0% by weight or less. Aluminum oxide is preferably 0.3% by weight or more, and preferably 0.7% by weight or less. By setting it as this range, the transparent electrode more excellent in durability, electroconductivity, and transparency can be produced.

  In the transparent conductive oxide layer in the present invention, it is preferable that the addition amount of silicon oxide and aluminum oxide is substantially uniform in the film thickness direction. That is, it is preferable that there is no concentration distribution. By using such a transparent conductive oxide layer, uniform conduction in the film thickness direction is possible. This is a very important factor when the transparent conductive oxide layer is considered as one electrode. This is because, in various devices, if the conductivity of the electrode is not uniform, the difficulty in controlling the conductivity and designing the device increases. From the viewpoint of productivity, it is preferable that the film thickness is substantially uniform in the film thickness direction. The addition amount can be measured by X-ray photoelectron spectroscopy in the film thickness direction, secondary ion mass spectrometry, or the like.

  For the formation of the transparent conductive oxide layer 2 in the present invention, for example, sputtering, metal organic chemical vapor deposition (MOCVD), thermal CVD, plasma CVD, molecular beam epitaxy (MBE), pulse laser, etc. Examples thereof include a deposition method (PLD).

  At this time, the film forming temperature is not particularly limited as long as it does not reach the glass transition temperature of the substrate. In general, it is known that a transparent conductive oxide film is formed at a higher temperature to improve conductivity because crystallinity is improved. For this reason, it is preferable to form the film at as high a temperature as possible, and it is more preferable that the film is close to the glass transition temperature of the substrate as described above. On the other hand, it is preferable to form a film at room temperature from the viewpoint of productivity. In particular, in the case of a film substrate capable of roll-to-roll film formation, the effect on productivity at room temperature film formation is clear.

  The substrate with a transparent electrode in which the transparent conductive oxide layer 2 is formed on the substrate 1 made of glass or a soft material having a high softening (melting) temperature is subjected to an annealing process in order to increase conductivity and light transmittance. be able to.

  The annealing atmosphere is preferably a vacuum or an inert gas atmosphere. By annealing in the above atmosphere, thermal oxidation of the transparent conductive oxide, which can occur when annealing is performed under an active gas such as an oxygen atmosphere, can be prevented, and a decrease in conductivity can be suppressed. For example, the annealing temperature when zinc oxide is used as the transparent conductive oxide is preferably not less than the temperature at which the crystallinity of zinc oxide is improved and not more than the melting temperature of the substrate. Specifically, a favorable substrate with a transparent electrode can be produced by annealing at about 200 to 450 ° C., more preferably 220 to 300 ° C.

  The film thickness of the transparent conductive oxide layer 2 is preferably in the range of 10 to 500 nm, more preferably in the range of 15 to 200 nm, and particularly preferably in the range of 30 to 100 nm. By using a transparent conductive oxide layer having a thickness in this range, a substrate with a transparent electrode having both high transparency and conductivity can be produced.

  In the present invention, “durability” means a change in resistivity before and after the wet heat durability test shown below. That is, “excellent in durability” means that there is little change in resistivity before and after the wet heat durability test.

The resistivity of the transparent electrode (transparent conductive oxide layer) in the present invention is 4.5 × 10 ⁻³ Ωcm or less before and after the wet heat durability test. The resistivity is more preferably 3.2 × 10 ⁻³ Ωcm or less. Further, it is preferably 5 × 10 ⁻⁵ Ωcm or more. By making the resistivity within the above range, it is considered that when various devices are produced, a transparent electrode having a low resistance loss due to the transparent conductive oxide layer, that is, a highly conductive electrode can be produced.

  In addition, the transparent electrode (transparent conductive oxide layer) in the present invention has a change in resistivity of 0.8 to 1 when left for 1000 hours under the conditions of 85 ° C. and 85% RH (after wet heat durability test). 2 is preferable, and 0.9 to 1.1 is more preferable. By making the change in resistivity within the above range, a transparent electrode with stable quality can be expected. Here, the change in resistivity means (resistivity after wet heat durability test) / (resistivity before wet heat durability test).

Further, the transparent electrode (transparent conductive oxide layer) in the present invention has a resistivity change ΔR when left in an environment of 85 ° C. and 85% RH for 1000 hours, a temperature (T) of T = 300K, a film When the thickness (d) is 20 nm ≦ d ≦ 120 nm, the following (Equation 1) is satisfied.
ΔR = a × exp (−b × d / T) +1.0
[1.2 ≦ a ≦ 3.0, 15 ≦ b ≦ 45, a and b are real numbers] (Formula 1)

Here, ΔR is a value obtained by standardizing wet heat durability with a film thickness d = 100 nm, and a temperature (T) is a temperature at the time of resistance measurement. Further, a is a coefficient relating to the magnitude of resistance change, and b is a coefficient relating to the degree of dependence on the film thickness and temperature. Here, the temperature (T) is a temperature at the time of resistance measurement, and (Equation 1) can be expressed as follows by substituting T = 300K.
ΔR = a × exp (−b × d / 300) +1.0

ΔR is the change in resistivity at each film thickness d of 20 nm ≦ d ≦ 120 nm normalized by the film thickness d = 100 nm, and a is a coefficient relating to the magnitude of the resistance change, b Is a coefficient related to the degree of dependence on the film thickness and temperature. Here, “standardized with a film thickness d = 100 nm” means a change in resistivity (referred to as R _L ) before and after the wet heat durability test when the film thickness d = Lnm (20 nm ≦ L ≦ 120 nm). It means a value obtained by calculating a relative value with respect to the change in resistivity (R ₁₀₀ ) at d = 100 nm.

By satisfy | filling the relationship of (Formula 1), the board | substrate with a transparent electrode excellent in wet heat durability and transparency can be produced. Here, the transmittance and the film thickness ^{conform to} Lambert-Beer's law “I = I ₀ × e ^−αd (I ₀ : incident light intensity, α: absorption coefficient, d: film thickness)”. The transparency can be controlled by setting the thickness within the range.

  As described above, in the present invention, silicon oxide and aluminum oxide are added in an amount of 1.2 wt% or more and 2.1 wt% or less and 0.2 wt% or more and less than 1.0 wt%, respectively, with respect to the transparent conductive oxide. By adding, a and b can satisfy the above range, that is, (Equation 1). In the present invention, by setting the values of a and b within the above ranges, high wet heat durability can be exhibited in a wide film thickness range.

  FIG. 2 shows the relationship between the film thickness (d) of the transparent electrode (transparent conductive oxide layer) in the present invention and the change in resistivity (ΔR) after standardization with a film thickness of 100 nm. That is, FIG. 2 shows the film thickness dependence of wet heat durability. That is, as shown in Comparative Example 2 or Comparative Example 5 in FIG. 2, when the transparent conductive oxide layer is about 20 nm and an extremely thin film, the change in resistivity generally tends to be extremely worse. It depends on the crystal structure of the transparent conductive oxide layer, and it is considered that the wet heat durability deteriorates because the crystal does not grow sufficiently at the above film thickness. In contrast, the transparent conductive oxide layer in the present invention has a small change in resistivity even when the film thickness is as thin as about 20 nm as shown in Example 1 in FIG.

On the other hand, when the values of a and b are out of the above ranges, for example, when a <1.2 and 50 <b, the film thickness dependency of ΔR becomes small, but generally the conductivity is poor. Tend to be.
This is considered to be related to the potential barrier between crystal grains because b is a coefficient related to temperature. When b is too large, the potential barrier becomes high, that is, the movement of electrons between crystal grains. This is expected to reduce the conductivity.

In the substrate with a transparent electrode in the present invention, R ₃₀ / R ₁₀₀ = 0.9 to 1.4 when the change in resistivity before and after the wet heat durability test at a film thickness of 30 nm and 100 nm is R ₃₀ and R ₁₀₀ , respectively. It is preferable to satisfy. In particular, when used as a thin transparent conductive oxide layer such as a touch panel, this value is preferably 0.9 to 1.2. Here, in general, the smaller the film thickness, the larger the change in resistivity, that is, the wet heat durability of the transparent conductive oxide layer is inferior, so that a substrate with a transparent electrode having excellent wet heat durability as in the present invention is effective. It becomes.

  Any method can be used for detecting the doping amount contained in the transparent conductive oxide layer 2 as long as it is a method usually used for elemental analysis. For example, atomic absorption analysis or fluorescent X-ray analysis is possible. Elemental analysis means such as X-ray photoelectron spectroscopy, Auger electron spectroscopy, and electron beam microanalyzer, and secondary ion mass spectrometry can be used. Above all, energy dispersive X-ray fluorescence analysis (EDX) is a relatively simple technique that can perform elemental analysis with high accuracy simultaneously with shape observation with a scanning electron microscope (SEM) or transmission electron microscope (TEM). preferable.

  The surface resistance of the substrate with a transparent electrode in the present invention varies depending on the application, but is used in a range of 10,000 Ω / □ or less. For example, when used for a touch panel, the surface resistance is 50 to 500 Ω / □ in a thin film silicon solar cell. When used, it can generally be used in the range of 5 to 2500 Ω / □.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. In the present invention, a resistivity meter Loresta GP MCT-610 (manufactured by Mitsubishi Chemical Corporation) was used for the surface resistance measurement. Spectral ellipsometer VASE (manufactured by JA Woollam) was used for the film thickness of each layer. Fitting was performed using the Tauc-Lorentz model. The transmittance was a haze meter NDH-5000 (manufactured by Nippon Denshoku). Elemental analysis was performed by attaching an EDX measurement unit to a field emission scanning electron microscope (FE-SEM) S-4800 (manufactured by Hitachi High-Technology Corporation). The uniformity of concentration was confirmed by measuring oxygen plasma as ions with a secondary ion mass spectrometer SIMS4100 (manufactured by CAMEA).

Example 1
Alkali-free glass (thickness 0.7 mm, trade name OA-10, manufactured by Nippon Electric Glass Co., Ltd.) was used as the substrate, and zinc-silicon-aluminum composite oxide (ASZO) 80 nm as a transparent conductive oxide layer on this substrate. A film was formed. The film formation conditions are as follows: the substrate temperature is room temperature, and a zinc-silicon-aluminum composite oxide (ASZO, composition ZnO: SiO ₂ : Al ₂ O ₃ = 97.5: 2.0: 0.5) is used as a target. Using argon as a gas at 100 sccm, a film was formed at a pressure of 0.2 Pa and a power density of 0.8 W / cm ² .

The sheet resistance of the transparent electrode (that is, the transparent conductive oxide layer) forming the transparent electrode substrate thus prepared was measured and found to be 400Ω / □ (resistivity: 3.2 × 10 ⁻³ Ωcm). ). Moreover, the board | substrate with a transparent electrode which changed the film thickness d of the transparent electrode 10 nm in the range of 20-120 nm on the same conditions as said film forming conditions except changing film forming time was produced.

  Similarly in the following Examples 2 to 16 and Comparative Examples 1 to 3, a substrate with a transparent electrode was produced by changing the film thickness of the transparent electrode by 10 nm in the range of 20 to 120 nm for each Example or Comparative Example. did.

(Examples 2-16, Comparative Examples 1-3)
As shown in Table 1 below, substrates with transparent electrodes were prepared by changing the composition ratio of zinc oxide, silicon oxide, and aluminum oxide. The wet heat durability test was conducted by leaving the substrates with transparent electrodes prepared in each of the examples and comparative examples in an environment of 85 ° C. and 85% RH for 1000 hours, and comparing the sheet resistance before and after that. At this time, the change in resistivity was determined as (change in resistivity) = (resistivity after wet heat durability test) ÷ (resistivity before wet heat durability test).

About the sample of Examples 1-16 and Comparative Examples 1-3, the film thickness and wet heat durability were evaluated, and each result was fitted by Formula 1. At this time, as described above, the sheet resistance is measured at a temperature T = 300K, and the change in resistivity (ΔR) at each film thickness (20 to 120 nm) is 1 at the film thickness d = 100 nm. It was standardized to 0.0. That is, for example, a change in resistivity (R ₂₀ ) when the film thickness d = 20 nm was obtained, and a relative value to the value at the film thickness d = 100 nm was used. Table 1 shows the values of a and b obtained from the above.
Moreover, the light transmittance (%) in Table 1 was measured at a film thickness of 80 nm.

Further, the ratio R ₃₀ / R ₁₀₀ was determined when the changes in resistivity before and after the wet heat durability test at film thicknesses of 30 nm and 100 nm were R ₃₀ and R ₁₀₀ , respectively. Table 2 shows the relationship between the film thickness and the change in resistivity (ΔR), that is, the relationship between the film thickness and wet heat durability.

  When Comparative Example 1 or Comparative Example 4 is compared with Examples, in Comparative Example 1 not containing aluminum oxide or Comparative Example 4 having 0.1% by weight, in Examples having less than 0.2 to 1.0% by weight, The resistivity dropped significantly. On the other hand, in Comparative Examples 3 and 5, the resistivity did not decrease despite the high aluminum oxide content of 1.0% by weight and 0.5% by weight, respectively. This is presumably because in Comparative Example 3, the amount of silicon oxide was as large as 4.0% by weight, and segregated silicon oxide hindered the transport of conductive carriers. In Comparative Example 5, it is considered that the amount of silicon oxide is as small as 1.0% by weight and the total doping amount is small.

  Further, when Comparative Example 2 or Comparative Example 5 is compared with Examples, Comparative Example 2 containing no silicon oxide or Comparative Example 5 having 1.0% by weight contains 1.2 to 2.1% by weight. Then, the change of resistivity became small.

  Specifically, as described above, Comparative Example 2 or Comparative Example 5 and Example 1 are described in FIG. When the film thickness is as thick as about 100 nm, the change in resistivity is about the same (ΔR = 1.00). However, as the film thickness becomes thinner, ΔR increases in Comparative Example 2 and Comparative Example 5. When the thickness was 20 nm, ΔR = 2.80 and 2.00, respectively. On the other hand, in Example 1, even when the film thickness was as thin as 20 nm, ΔR was small and ΔR = 1.50. Therefore, it is considered that a substrate with a transparent electrode excellent in durability could be produced by using the transparent electrode of the present invention.

  Here, in Comparative Example 2, the resistivity decreased despite the absence of silicon oxide, which is considered to be because the amount of aluminum oxide is as large as 3.0% by weight. In Comparative Example 3, the light transmittance was the lowest at 81.9%. This is considered to be due to the large amount of impurities, that is, silicon oxide = 4.0% by weight and aluminum oxide = 1.0% by weight.

  In addition, when the amount of silicon oxide is large, that is, in Comparative Examples 1, 3, and 4, the value of a tends to be smaller than 1.2, whereas when it is small, that is, in Comparative Example 2, the value of a tends to be larger than 3.0. was there.

  Among Examples, Examples 5 to 12 in which both the resistivity and the change in resistivity are small are considered to be more preferable. This is because the conductivity was improved (ie, the resistivity was lowered) due to the relatively high addition of 0.8% by weight of aluminum oxide, and the durability was improved (ie, the change in resistivity) because of the addition of silicon oxide. This is probably due to the fact that

From the viewpoint of resistivity, it can be seen that heating to 200 ° C. is better than room temperature.
As described above, this is considered to be because the crystallinity is improved by high-temperature heating and the conductivity is increased. On the other hand, in view of productivity, it can be seen that a substrate with a transparent electrode of appropriate quality can be produced even if the film is formed at room temperature. From the above, it is considered that by using the transparent electrode of the present invention, a substrate with a transparent electrode excellent in durability, conductivity, and transparency can be produced even when the film thickness is thin.

1 substrate 2 transparent conductive oxide layer

Claims (6)

In the substrate with a transparent electrode having a transparent conductive oxide layer mainly composed of zinc oxide on the substrate,
The transparent conductive oxide layer contains 1.2 wt% or more and 2.1 wt% or less of silicon oxide and 0.2 wt% or more and less than 1.0 wt% of aluminum oxide,
The resistivity of the transparent conductive oxide layer is 4.5 × 10 −3 Ωcm or less,
In addition, regarding the change in resistivity ΔR when left in an environment of 85 ° C. and 85% RH for 1000 hours , the wet heat durability of ΔR is normalized with a film thickness d = 100 nm .
When the temperature (T) is T = 300K and the film thickness (d) is 20 nm ≦ d ≦ 120 nm,
ΔR = a × exp (−b × d / T) +1.0
[1.2 ≦ a ≦ 3.0, 15 ≦ b ≦ 45, a and b are real numbers] (Formula 1)
A substrate with a transparent electrode, characterized in that: Changes in resistivity before and after the wet heat durability test at film thicknesses of 30 nm and 100 nm were respectively R ₃₀ And R ₁₀₀ R ₃₀ / R ₁₀₀ It satisfy | fills = 0.9-1.4, The board | substrate with a transparent electrode of Claim 1 characterized by the above-mentioned. The solar cell provided with the board | substrate with a transparent electrode of Claim 1 or 2. A heterojunction solar cell comprising the substrate with a transparent electrode according to claim 1 or 2,
As the substrate, a single crystal silicon substrate is used,
On the substrate, there is amorphous intrinsic silicon, conductive doped amorphous silicon, a transparent electrode and a collector electrode in this order,
A heterojunction solar cell in which the transparent conductive oxide layer is used as the transparent electrode. A thin-film silicon solar cell comprising the substrate with a transparent electrode according to claim 1 or 2,
As the substrate, a glass substrate is used,
On the substrate, a transparent electrode layer, one or more non-single crystal silicon photoelectric conversion units, and a back electrode in this order,
A thin film silicon solar cell in which the transparent conductive oxide layer is used as the transparent electrode layer. Having a transparent electrode between the non-single crystal silicon photoelectric conversion unit and the back electrode;
The thin film silicon solar cell according to claim 5, wherein the transparent conductive oxide layer is used as the transparent electrode.

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