JP5634315B2 - Metal substrate with insulating layer and photoelectric conversion element - Google Patents

Description

  The present invention relates to a metal substrate with an insulating layer and a photoelectric conversion element suitable for applications such as a solar cell using the metal substrate with an insulating layer.

  In CIGS solar cells, glass substrates are generally used as substrates, but solar cells using metal substrates such as stainless steel plates in addition to glass substrates have also been reported as light-weight and flexible solar cells. Has been. A solar cell using a metal substrate can be applied to a wide range of uses because the substrate can be reduced in weight and flexibility. In addition, since the metal substrate has resistance to a high temperature process of 400 ° C. or higher, high efficiency of the solar cell can be expected.

  In an integrated solar cell, since it is necessary to connect a plurality of unit cells in series on a substrate, it is essential to provide an insulating layer on the metal substrate. As a method for forming an insulating layer, for example, Patent Document 1 describes a method for forming an insulating layer by a sol-gel method. However, the sol-gel method has to be a thick film having a thickness of 10 to 100 μm, and pinholes and bubbles are easily generated. In addition, it is difficult to obtain a thick film having a uniform composition on the surface and inside. As a countermeasure against this, Patent Document 1 describes a method in which another insulating layer is formed on this insulating layer by sputtering or liquid phase deposition. However, the manufacturing cost increases because the number of processes and the materials increase. There is a problem of becoming higher.

  Patent Document 2 proposes a method in which insulating fine particles are applied and baked in addition to a paint, but insulating properties cannot be ensured unless a thick film is applied. When the insulating layer is a thick film, bubbles enter, and the bubbles expand at high temperatures, causing irregularities in the substrate. Patent Document 3 describes a method for solving this problem by providing a hole for removing air bubbles in advance in the substrate. However, providing a hole in the substrate causes unevenness on the front surface side, or moisture enters from the back surface. There is a problem from the viewpoint of the original reliability of the solar cell.

  By the way, soda lime glass has been widely used as a glass substrate in compound solar cells conventionally, when sodium is diffused into the photoelectric conversion semiconductor layer when forming the photoelectric conversion semiconductor layer, it contributes to improvement in power generation efficiency. Based on knowledge. However, when a metal substrate is used as a solar cell substrate, there is a problem that conversion efficiency does not increase because sodium cannot be supplied from the substrate.

  In Patent Document 4, an attempt is made to provide a glass layer on a metal substrate to ensure insulation when the metal substrate is used and to supply sodium from the substrate. Although sodium diffusion is performed from the provided glass layer, since the glass layer described in Patent Document 4 is as thick as 10 to 100 μm, pinholes and bubbles are easily generated and it cannot be said that the insulating layer is perfect.

As a general technique for supplying alkali metal ions to the photoelectric conversion semiconductor layer, for example, Na ₂ Se is used in Patent Documents 5 and 6, Na ₂ O ₂ is used in Patent Document 7, and Na ₂ S is used in Patent Document 8. A method of co-evaporation with an element constituting a photoelectric conversion semiconductor layer is described. Patent Document 9 discloses a method of depositing sodium phosphate on molybdenum (Mo), Patent Document 10 discloses a method of forming an alkali layer by immersing in Na ₂ MoO ₄ , and Patent Document 11 discloses Na ₂ S or Na. A method for forming an alkali layer by dipping in ₂ Se is described.

JP 2004-158511 A JP 2001-185747 A JP 2007-305875 A JP 2006-80370 A Japanese Patent Laid-Open No. 10-74966 Japanese Patent Laid-Open No. 10-74967 JP-A-9-55378 Japanese Patent Application Laid-Open No. 10-125941 Japanese Patent Laid-Open No. 2006-210424 JP 2005-1117012 A JP 2003-318424 A

  As described above, the method of providing an insulating layer on a metal substrate described in Patent Documents 1 to 4 is difficult to obtain a uniform insulating film on the inside and the surface of the film because a thick film is applied and fired by the sol-gel method. Furthermore, since bubbles, pinholes, and the like are generated during firing, there is a problem that defects are caused and it is difficult to reliably maintain insulation.

  Although the supply technology of alkali metal ions described in Patent Documents 5 to 9 is based on vapor deposition, in the case of co-vapor deposition with the elements constituting the photoelectric conversion semiconductor layer, alkali metal elements are deposited at the same time in the formation of the microcrystalline film. This is considered to increase crystal defects, and there is a problem that it is difficult to form a high-quality semiconductor layer with few defects compared to the alkali metal diffusion method. Further, Patent Documents 10 and 11 provide an alkali layer by dipping, but in the case of dipping, an alkali metal exists only on the surface and diffuses not only in the upper semiconductor layer but also downward in the subsequent vapor deposition process or annealing process. Therefore, there is a problem that it is difficult to control the surface concentration of the alkali metal.

  In particular, when anodized aluminum is used as an insulating layer, it has a porous structure with a large specific surface area, so that the influence of alkali metal diffusion on the pore surface is large. In addition, there is a problem that the surface of the pores becomes a path for leakage current due to the adsorption of moisture in the atmosphere, and the insulating property is lowered.

  As described above, when manufacturing an integrated solar cell submodule, it is actually difficult to provide an insulating layer on a metal substrate so as to ensure insulation. In addition, there has been no technology capable of stably diffusing alkali metal ions with respect to the photoelectric conversion semiconductor layer.

  This invention is made | formed in view of the said situation, and when using a metal substrate, the metal substrate with an insulating layer which can ensure insulation reliably, and the photoelectric conversion element using this metal substrate with an insulating layer are provided. It is intended to provide.

The metal substrate with an insulating layer of the present invention is characterized by having an insulating oxide film formed by anodic oxidation on a metal substrate and a spin-on glass film on the insulating oxide film.
The spin-on glass film is preferably made of at least one selected from polysilazane, methylsiloxane, polysilsesquioxane, Si-based metalloxane polymer, Ti-based metalloxane polymer, and silicate.

The 10 μm square average surface roughness of the spin-on glass film surface is preferably 10 nm or less.
The spin-on glass film preferably has a thickness of 0.1 to 10 μm.

The metal substrate is preferably a substrate containing at least one metal selected from aluminum, iron, zirconium, titanium, magnesium, copper, niobium and tantalum.
The metal substrate is preferably a clad material in which one or both surfaces of aluminum, stainless steel, or steel plate are integrated with an aluminum plate.

The spin-on glass film preferably contains alkali metal ions.
The alkali metal ion is preferably a sodium ion.
The compound containing sodium ions is preferably at least one compound selected from NaF, Na ₃ AlF ₆ , Na ₂ (MoO ₄ ), Na ₂ CO ₃ , Na ₂ O, and sodium silicate.

  The photoelectric conversion element of the present invention is formed on the above metal substrate with an insulating layer.

  The metal substrate with an insulating layer of the present invention has an insulating oxide film formed by anodic oxidation on a metal substrate, and a spin-on glass film on the insulating oxide film. Since the irregularities and defects generated during the film formation can be smoothed after the defects are compensated for by the spin-on glass film, it is possible to ensure the insulation. In particular, since the spin-on glass film is a thin film as compared with an insulating film formed by a conventional sol-gel method, it becomes a homogeneous film upon firing, and a high-quality insulating film can be obtained.

  The photoelectric conversion element using the metal substrate with an insulating layer of the present invention as a substrate smoothes the unevenness of the semiconductor layer formed on the metal substrate with an insulating layer and the microcrystalline grains at the junction of the photoelectric conversion semiconductor layer. Therefore, it is possible to suppress the leakage current due to the non-uniformity of the junction and to further improve the conversion efficiency.

  In addition, since the metal substrate with an insulating layer of the present invention is covered with a porous layer generated when an insulating oxide film is formed by a spin-on glass film, the material of the semiconductor layer and the photoelectric conversion layer is used as the liquid phase of the precursor. Even when it is formed by coating, or by applying fine particles of photoelectric conversion materials such as semiconductors and CIGS, the precursor or compound fine particles do not enter the porous layer, so that a decrease in insulation is suppressed and material loss is reduced. Since it can be reduced, a semiconductor element and a photoelectric conversion element can be manufactured at low cost.

  Furthermore, since the pores of the anodic oxide film having a porous structure are blocked, the apparent specific surface area is greatly reduced. As a result, current leakage due to moisture adsorbed inside the pores can be reduced, and insulation can be improved. Thus, even when a semiconductor element and a photoelectric conversion element are integrated, an element with low loss, low power consumption, and high conversion efficiency can be manufactured. As another effect, when used as a substrate for a CIGS solar cell, even if an alkali metal supply layer is provided on the top and vapor deposition or annealing is performed, diffusion of alkali metal to the pore surface can be suppressed. The surface concentration of the alkali metal can be easily controlled.

  Furthermore, when alkali metal ions are included in the spin-on glass film, alkali metal ions can be diffused and supplied to the photoelectric conversion semiconductor layer, and a photoelectric conversion element with high photoelectric conversion efficiency can be obtained.

It is a schematic sectional drawing which shows one Embodiment of the photoelectric conversion element of this invention. It is the elements on larger scale which show one embodiment of a spin-on glass film. It is the elements on larger scale which show another embodiment of a spin-on glass film. It is the elements on larger scale which show another embodiment of a spin-on glass film | membrane. It is a histogram which shows the withstand voltage measurement result of a spin-on glass film | membrane (presence / absence). It is a SEM photograph of the board | substrate with which the anodic oxide film was formed. It is an atomic force microscope photograph (AFM) of the spin-on glass film surface. It is an electron micrograph of a CIGS crystal.

  Hereinafter, the metal substrate with an insulating layer of the present invention will be described taking a photoelectric conversion element as an example. FIG. 1 is a schematic cross-sectional view showing an embodiment of a photoelectric conversion element of the present invention. In addition, in order to make it easy to visually recognize, the scales and the like of each component are appropriately changed from actual ones. As shown in FIG. 1, the photoelectric conversion element 1 includes an insulating oxide film 20 formed by anodic oxidation on a metal substrate 10, a spin-on glass film 30, a lower electrode 40, and holes and electrons by light absorption. A photoelectric conversion semiconductor layer 50 that generates a pair, a buffer layer 60, a translucent conductive layer (transparent electrode) 70, and an upper electrode (grid electrode) 80 are sequentially stacked.

As the metal substrate 10, a material in which a metal oxide film generated on the surface of the metal substrate by anodic oxidation becomes an insulator can be used. Specifically, at least selected from aluminum (Al), iron (Fe), zirconium (Zr), titanium (Ti), magnesium (Mg), copper (Cu), niobium (Nb) and tantalum (Ta). A substrate containing one metal or an alloy of the above metals is preferred. In particular, a clad material in which one or both surfaces of aluminum, stainless steel, or steel plate are integrated with an aluminum plate is more preferable from the viewpoint of easy formation of anodization and high durability. In the case of an integrated clad material with both surfaces sandwiched between aluminum plates, it is possible to suppress substrate warpage due to the difference in thermal expansion coefficient between aluminum and the oxide film (Al ₂ O ₃ ), and film peeling due to this. Therefore, it is more preferable.

  For the substrate, cleaning treatment / polishing smoothing treatment, if necessary, for example, a degreasing step for removing the adhering rolling oil, a desmut treatment step for dissolving the smut on the surface of the aluminum plate, and roughening the surface of the aluminum plate It is preferable to use one subjected to a roughening treatment step.

  The insulating oxide film 20 formed by anodic oxidation (hereinafter also referred to as anodic oxide film 20) is obtained by forming an insulating oxide film having a plurality of pores by anodic oxidation. Secured. Anodization can be performed by immersing the substrate 10 as an anode in an electrolyte together with a cathode, and applying a voltage between the anode and the cathode. Carbon, aluminum, or the like is used as the cathode.

The anodic oxidation conditions depend on the type of electrolyte used. For example, the electrolyte concentration is 0.1 to 2 mol / L, the liquid temperature is 5 to 80 ° C., the current density is 0.005 to 0.60 A / cm ² , and the voltage is 1 to 200 V. Any electrolysis time in the range of 3 to 500 minutes is suitable. The electrolyte is not particularly limited, and an acidic electrolytic solution containing one or more acids such as sulfuric acid, phosphoric acid, chromic acid, oxalic acid, malonic acid, sulfamic acid, benzenesulfonic acid, and amidosulfonic acid is preferable. Used. When such an electrolyte is used, an electrolyte concentration of 0.2 to 1 mol / L, a liquid temperature of 10 to 80 ° C., a current density of 0.05 to 0.30 A / cm ² , and a voltage of 30 to 150 V are preferable.

  The thickness of the base material 10 and the anodic oxide film 20 is not particularly limited. Considering the mechanical strength of the substrate 10 and reduction in thickness and weight, for example, the thickness of the base material 10 before anodization is preferably 0.05 to 0.6 mm, and more preferably 0.1 to 0.3 mm. Considering the insulating properties, mechanical strength, and reduction in thickness and weight of the substrate, the thickness of the anodic oxide film 20 is preferably 0.1 to 100 μm, for example.

  A spin-on glass (SOG) is a thin glass film, used for relaxing a step in an interlayer insulating film formed on a semiconductor wiring and filling a groove between wirings. It is possible to compensate for defects by closing the pores generated during the formation of, and filling in irregularities and defects.

  The spin-on glass film 30 is at least one selected from polysilazane, methylsiloxane, polysilsesquioxane, Si-based metalloxane polymer, Ti-based metalloxane polymer, and silicate (hereinafter referred to as “spin-on glass film material”). And a plurality of the above may be mixed. More specifically, it is preferable to add a solvent such as 30 to 70% by mass of butanol, ethanol, toluene, benzene, xylene to 5 to 50% by mass of the spin-on glass film material.

The alkali metal ions contained in the spin-on glass film are preferably sodium ions. The compound containing sodium ions is preferably at least one compound selected from NaF, Na ₃ AlF ₆ , Na ₂ (MoO ₄ ), Na ₂ CO ₃ , Na ₂ O, and sodium silicate. Since these compounds have low hygroscopicity and low toxicity and corrosivity, they can be used stably. In addition, Na ₂ MoO ₄ (sodium molybdate) described in Patent Document 10 is concerned about a problem that a film produced due to high crystallinity is easy to peel off, but the above compound has a problem of peeling. Does not happen.

  The amount of the compound containing sodium ions is preferably in the range of 1 to 10% by mass with respect to the total material of the spin-on glass film. When the amount is less than 1% by mass, the effect of diffusing sodium ions in the photoelectric conversion semiconductor layer cannot be expected or the effect is weak. On the other hand, adding more than 10% by mass is undesirable because it increases crystal defects in the microcrystal of the semiconductor layer.

The spin-on glass film 30 is coated with a coating liquid in which the above spin-on glass film material and an alkali metal ion source are dispersed in a solvent, and then baked in air at 100 to 150 ° C. in an inert gas atmosphere such as N ₂ . It can be produced by firing at 300 to 500 ° C. for 30 to 60 minutes. By this firing, the spin-on glass film becomes dense and becomes a silicon oxide film. The film thickness of the spin-on glass film is preferably in the range of 0.1 to 10 μm, more preferably 0.5 to 5.0 μm. In the case of a film thicker than 10 μm, it is difficult to obtain a homogeneous film on the surface and inside of the film, and there is a problem that bubbles are left behind due to insufficient conversion into a silicon oxide film or difficulty in removing the solvent during baking. On the other hand, when the thickness is smaller than 0.1 μm, it becomes difficult to compensate for the defects by filling the irregularities and defects generated when the anodic oxide film 20 is formed. The method for applying the coating liquid onto the substrate is not particularly limited. For example, a doctor blade method, a wire bar method, a gravure method, a spray method, a dip coating method, a spin coating method, a capillary coating method, or the like is used. be able to.

  2 to 4 are partially enlarged views of the substrate, the anodic oxide film, and the spin-on glass film. As shown in these figures, the anodic oxide film 20 has a porous structure, but the spin-on glass film 30 does not penetrate into the porous structure of the anodic oxide film 20 as shown in FIG. Only the surface of 20 may be covered, or as shown in FIG. 3, a composite structure penetrating into the porous structure of the anodic oxide film 20 may be taken. Further, as shown in FIG. 4, the spin-on glass film 30 penetrates only near the pore surface of the porous structure of the anodic oxide film 20, and does not have to penetrate up to the vicinity of the bottom of the pore.

  The structure of the spin-on glass film 30 depends on whether the solution applied to the surface of the anodized film can enter the pores. In general, the penetration of liquid into the pores is determined by the pore diameter, surface tension, solution viscosity, and the like, as shown by the Lucas-Washburn equation. For example, since anodized aluminum has a relatively high hydrophilicity, when an aqueous solution having a relatively low viscosity is used as the coating solution, it is considered that the solution penetrates to the bottom of the pores immediately after coating. That is, FIG. 2 shows a high viscosity, FIG. 4 shows a medium viscosity, and FIG. 4 shows a low viscosity. In order to obtain the structure of the embodiment of FIG. 3, the viscosity of the coating solution is preferably 20 mPa · s or less, and particularly preferably 10 mPa · s or less.

  The spin-on glass film 30 preferably has a 10 μm square average surface roughness Ra of 10 nm or less on the surface thereof. Here, the 10 μm square average surface roughness of the spin-on glass film surface of 10 nm or less means that the surface roughness of all parts of the spin-on glass film surface is 10 nm or less. When the thickness is larger than 10 nm, it is difficult to reliably ensure insulation because the irregularities and defects generated during the formation of the anodic oxide film 20 cannot be compensated. This flatness can be evaluated by various methods such as observation with an SEM and measurement with an atomic force microscope. In the present invention, an atomic force microscope (manufactured by Seiko Instruments, probe: SI-DF20, The flatness was evaluated using the average surface roughness in the measurement area of 10 μm square using a measurement frequency of 1 Hz.

  The component of the lower electrode (back electrode) 40 is not particularly limited, and Mo, Cr, W, and combinations thereof are preferable, and Mo or the like is particularly preferable. The film thickness of the lower electrode (back electrode) 40 is not limited and is preferably about 200 to 1000 nm.

  The photoelectric conversion semiconductor layer 50 is a compound semiconductor-based photoelectric conversion semiconductor layer, and is not particularly limited as a main component (the main component means a component of 20% by mass or more), and high photoelectric conversion efficiency is obtained. A compound semiconductor, a compound semiconductor having a chalcopyrite structure, or a compound semiconductor having a defect stannite structure can be preferably used.

As a chalcogen compound (compound containing S, Se, Te),
II-VI compounds: ZnS, ZnSe, ZnTe, CdS, CdSe, CdTe, etc.
I-III-VI ₂ group _{compounds: CuInSe 2, CuGaSe 2, Cu} (In, Ga) Se 2, CuInS 2, CuGaSe 2, Cu (In, Ga) (S, Se) 2 , etc.,
Preferable examples include I-III ₃ -VI ₅ group compounds: Cull ₃ Se ₅ , CuGa ₃ Se ₅ , Cu (ln, Ga) ₃ Se _{5 and the} like.

As a compound semiconductor having a chalcopyrite structure and a defect stannite structure,
I-III-VI ₂ group _{compounds: CuInSe 2, CuGaSe 2, Cu} (In, Ga) Se 2, CuInS 2, CuGaSe 2, Cu (In, Ga) (S Se) 2 , etc.,
Preferred examples include I-III ₃ -VI ₅ group compounds: CuIn ₃ Se ₅ , CuGa ₃ Se ₅ , Cu (In, Ga) ₃ Se _{5 and the} like.
In the above description, (In, Ga) and (S, Se) are (In _1-x Ga _x ) and (S _1-y Se _y ) (where x = 0 to 1, y = 0-1).

The method for forming the photoelectric conversion semiconductor layer is not particularly limited. For example, a CI (G) S-based photoelectric conversion semiconductor layer containing Cu, In, (Ga), and S can be formed using a method such as a selenization method or a multi-source evaporation method.
The film thickness of the photoelectric conversion semiconductor layer 50 is not particularly limited, and is preferably 1.0 to 3.0 μm, particularly preferably 1.5 to 2.0 μm.

  The buffer layer 60 is not particularly limited, but CdS, ZnS, Zn (S, O) and / or Zn (S, O, OH), SnS, Sn (S, O) and / or Sn (S, O, OH). A metal sulfide containing at least one metal element selected from the group consisting of Cd, Zn, Sn, and In, such as InS, In (S, O) and / or In (S, O, OH). Is preferred. The thickness of the buffer layer 40 is preferably 10 nm to 2 μm, and more preferably 15 to 200 nm.

The translucent conductive layer (transparent electrode) 70 is a layer that captures light and functions as an electrode that is paired with the lower electrode 40 and through which the current generated in the photoelectric conversion layer 50 flows. The composition of the translucent conductive layer 70 is not particularly limited, and n-ZnO such as ZnO: Al is preferable. The film thickness of the translucent conductive layer 70 is not particularly limited, and is preferably 50 nm to 2 μm.
The upper electrode (grid electrode) 80 is not particularly limited, and examples thereof include Al. The film thickness of the upper electrode 80 is not particularly limited and is preferably 0.1 to 3 μm.

The photoelectric conversion element of this invention can be preferably used for a solar cell etc. If necessary, a cover glass, a protective film, or the like can be attached to the photoelectric conversion element 1 to form a solar cell.
Hereinafter, the photoelectric conversion element of the present invention will be described in more detail with reference to examples.

(Flatness and withstand voltage by forming a spin-on glass film)
An aluminum substrate (thickness 300 μm) was anodized with a 0.5 M oxalic acid aqueous solution at 16 ° C. using a direct current power source under a voltage of 40 V to form an aluminum oxide film having a thickness of 10 μm. On top of this, VRL-1H-5K (Ti, Si-based metalloxane polymer) manufactured by Lhasa Kogyo Co., Ltd. was applied at 500 rpm to 1500 rpm with a spin coater, baked at 150 ° C. for 5 minutes on a hot plate in the air, and a heating device And cured at 400 ° C. for 60 minutes in an N ₂ atmosphere to form a spin-on glass film. The thickness of the spin-on glass film after curing was 1.0 μm. After forming the spin-on glass film, the surface was observed by SEM, and it was confirmed that the pores, small recesses, rolling streaks, etc. of the aluminum oxide film were filled with the spin-on glass film and were flattened.

  Two samples of 5 cm □ with this spin-on glass film were prepared, and two samples that were not to be formed (one with an aluminum oxide film only) were prepared, and a 3.6 mmφ gold electrode was formed on each by vacuum mask deposition. The withstand voltage was measured. The number of electrodes was 12 and 30 respectively. FIG. 5 shows a histogram of the results. In addition, the withstand voltage in FIG. 5 is shown as a relative value with the withstand voltage having no difference in frequency in the presence or absence of the spin-on glass film as Vp. When the measured values were collected, the withstand voltage increased by 6% on average by laminating the spin-on glass film, and the standard deviation was improved by 60% as compared to the case where the spin-on glass film was not laminated. Further, it can be seen from FIG. 5 that a metal substrate having a high-quality insulating layer can be manufactured because a layer with a low withstand voltage is entirely eliminated by laminating a spin-on glass film. .

Example 1
An aluminum substrate (thickness 300 μm) was anodized with an oxalic acid aqueous solution under the same conditions as described above to form an 18 μm thick aluminum oxide film. On top of this, an aqueous solution of Na ₂ CO ₃ was mixed with VRL-1H-5K (Ti, Si-based metalloxane polymer) manufactured by Lhasa Kogyo so that the sodium concentration was 5% by mass with respect to the metalloxane polymer and stirred. A spin-on glass film was formed by coating, baking, and curing the material under the same conditions as described above using a spin coater. After forming the spin-on glass film, fracture surface observation by SEM and surface property evaluation by atomic force microscope are performed, and the pores, small recesses, rolling streaks, etc. of the aluminum oxide film are filled with the spin-on glass film and are flattened. It was confirmed. On the formed spin-on glass film, a Mo electrode (thickness 0.8 μm) was formed by DC sputtering with a size of 3 cm × 3 cm.

A CIGS solar cell was formed on the Mo electrode. In this embodiment, granular raw materials of high-purity copper and indium (purity 99.9999%), high-purity Ga (purity 99.999%), and high-purity Se (purity 99.999%) were used as the evaporation source. . A chromel-alumel thermocouple was used as a substrate temperature monitor. After the main vacuum chamber is evacuated to 10 ⁻⁶ Torr (1.3 × 10 ⁻³ Pa), the deposition rate from each evaporation source is controlled, and the film thickness is about 530 ° C. under the film forming conditions. A 1.8 μm CIGS thin film was formed. Subsequently, a CdS thin film of about 90 nm was deposited as a buffer layer by a solution growth method, and a ZnO: A1 film of a transparent conductive film was formed thereon with a thickness of 0.6 μm by a DC sputtering method. Finally, an Al grid electrode was formed as an upper electrode by a vapor deposition method to produce a solar battery cell.

(Example 2)
A solar cell was produced in the same manner as in Example 1 using the substrate on which the spin-on glass film produced in the above (flattening and withstand voltage by forming the spin-on glass film) was formed.

Example 3
An aluminum / SUS430 substrate (aluminum 30 μm thick and SUS430 clad 100 μm thick) is anodized with a 1M malonic acid aqueous solution at 80 ° C. using a direct current power source at a voltage of 80 V and oxidized with a thickness of 10 μm. A film was formed. On top of this, a coating solution having the composition shown in Table 1 below was applied using a spin coater, and heat treatment was performed in air in an electric furnace at 200 ° C. for 30 minutes to laminate a spin-on glass film. The thickness of the spin-on glass film after the heat treatment was 1.9 μm. After forming the spin-on glass film, fracture surface observation by SEM and surface property evaluation by atomic force microscope are performed, and the pores, small recesses, rolling streaks, etc. of the aluminum oxide film are filled with the spin-on glass film and are flattened. It was confirmed. Using the substrate on which the spin-on glass film was formed, solar cells were produced in the same manner as in Example 1.

(Examples 4-A to D)
An aluminum / SUS430 substrate (aluminum 30 μm thick and SUS430 clad 100 μm thick) is anodized with a 1M malonic acid aqueous solution at 80 ° C. using a direct current power source at a voltage of 80 V and oxidized with a thickness of 10 μm. A film was formed to obtain a substrate. Sodium silicate (manufactured by Showa Chemical, No. 3 sodium silicate), lithium silicate (manufactured by Nissan Chemical Co., Ltd., trade name: lithium silicate 45) and water are mixed in a mass ratio shown in Table 2 below, and the coating solution is prepared. did. On the substrate, the coating solution was applied using a dip coater, and heat treatment was performed in an electric furnace in air to laminate a spin-on glass film. The lifting speed of the dip coater was adjusted from 0.03 m / s to 2.4 m / s to control the film thickness. After forming the spin-on glass film, fracture surface observation by SEM and surface property evaluation by atomic force microscope are performed, and the pores, small recesses, rolling streaks, etc. of the aluminum oxide film are filled with the spin-on glass film and are flattened. It was confirmed. Using the substrate on which the spin-on glass film was formed, solar cells were produced in the same manner as in Example 1.

(Comparative Example 1)
An aluminum substrate (thickness 300 μm) was anodized with a malonic acid aqueous solution under the same conditions as described above to form an aluminum oxide film having a thickness of 10 μm. On top of this, 0.2 μm of silica was formed by sputtering. After the formation of the silica film, fracture surface observation by SEM and surface property evaluation by an atomic force microscope were performed. Although the pores of the aluminum oxide film are blocked by the silica film, there are regular recesses corresponding to the positions of the pores, and the rolling streaks and the like remain in their original shapes. This shape is also apparent from FIG. Due to the unevenness, the 10 μm square average surface roughness exceeds 10 nm, and the smoothness is low. Using the substrate on which the sputter-deposited silica film was formed, solar cells were produced in the same manner as in Example 1.

(Comparative Example 2)
A solar cell was produced in the same manner as in Example 1 using the substrate on which only the aluminum oxide film produced by the above (planarization and withstand voltage by forming the spin-on glass film) was formed.

(Evaluation)
(Smoothness)
Using a Seiko Instruments atomic force microscope (model number SPA-400, probe: SI-DF20, measurement frequency 1 Hz), the surface of the spin-on glass film of the substrate produced in the example and the comparative example is in the range of 10 μm square. The average surface roughness was measured.

(Specific surface area of open holes)
The specific surface area of the open holes was evaluated by nitrogen adsorption measurement (BET). Each sample corresponding to 10 cm ² was cut out, and the specific surface area was measured with an automatic specific surface area measuring device (BELSORP-miniII) manufactured by Nippon Bell. In Comparative Example 2, which was only an anodized aluminum film, the specific surface area was 91 cm ² per cm ² of the 10 μm-thick film. On the other hand, in Examples 1, 2, 3, 4-A, B, C, D, and Comparative Example 1, all were below the measurement limit of the specific surface area and could not be measured. This indicates that the pores of the anodized film have become closed holes.

(Leakage current density)
In the measurement of insulating characteristics, Au having a thickness of 0.2 μm was provided on the insulating layer as an electrode by mask vapor deposition with a diameter of 3.5 mm, and a negative voltage of 200 V was applied to the Au electrode in an atmosphere at room temperature. A value obtained by dividing the leakage current by the Au electrode area (9.6 mm ² ) was defined as a leakage current density. Such a measurement was performed with nine Au electrodes provided on the same substrate, and the average value was taken as the leakage current density of each substrate.

(Energy conversion efficiency)
The solar cells (area 0.5 cm ² ) produced in the examples and comparative examples were irradiated with simulated sunlight of Air Mass (AM) = 1.5 and 100 mW / cm ² to measure energy conversion efficiency. The evaluation results are shown in Table 3. FIG. 6 shows SEM photographs of the substrates on which the spin-on glass films of Examples 4-A, 4-B, 4-D, Comparative Example 1 and Comparative Example 2 were formed (except for Comparative Example 2 in FIG. 6). FIG. 7 shows atomic force micrographs (AFM) of the surfaces of the spin-on glass films of Example 3 and Comparative Example 1. FIG. 7 shows the substrate observed obliquely, and Comparative Example 2 was observed from the vertical direction. .

  The observation by SEM shown in FIG. 6 shows that the anodic oxide film has regular pores formed in the direction perpendicular to the surface of the film to form a porous layer. From Comparative Example 2 in which the anodized film was observed from the vertical direction, it can be seen that the pores of the porous layer exist as open holes on the surface of the anodized film. On the other hand, in Examples 4-A, 4-B, 4-D, and Comparative Example 1, there are no holes on the surface of the film, and the pores of the anodized film are closed holes.

  Further, from Table 3, the spin-on glass film surfaces of the examples all have a 10 μm square average surface roughness of 10 nm or less, and pores, irregularities and defects generated during the formation of the insulating oxide film formed by anodization. It can be seen that the film is smoothed by filling the film with a spin-on glass film to compensate for defects. And in the Example which provided the spin-on glass film | membrane with respect to the comparative example 2 which is only an anodic oxide film, a leak current fell from 1 to 3 digits, and the insulation improvement was confirmed. From the consideration combined with the result of the nitrogen adsorption measurement, it can be said that as an effect of blocking the pores of the anodized film, the adsorption of moisture and the like in the atmosphere is suppressed, and the insulation is surely ensured.

  As shown in Example 4-A, it can be seen that even when the film thickness of the spin-on glass film is 0.1 μm, the smoothness is maintained. In Comparative Example 2, since the depth (aspect ratio) with respect to the pore diameter of the anodic oxide film was large, the surface roughness could not be measured with an atomic force microscope.

  Further, as shown in Table 3, it can be seen that the metal substrate with an insulating layer of the present invention has high energy conversion efficiency as a whole, and the comparison between Example 2 and Comparative Example 2 shows that the photoelectric conversion efficiency is 2 only with or without the spin-on glass film. In Example 1 in which sodium was added to the spin-on glass, the photoelectric conversion efficiency nearly twice that of Comparative Example 2 without the spin-on glass film was obtained. The photoelectric conversion efficiency increased by 50% compared to Comparative Example 1 in which no addition was made. From this result, it can be seen that the photoelectric conversion efficiency was greatly improved by the smoothing, planarization effect, and sodium addition effect to the spin-on glass film in the present invention.

  8 is an electron micrograph of CIGS crystals of Example 4-A and Comparative Example 1. FIG. As is apparent from the electron micrographs of the two CIGS crystals, it can be seen that the grain size of the CIGS crystal is increased by using the metal substrate with an insulating layer of the present invention. Since the grain boundary is reduced by increasing the particle size, the number of carriers trapped by the grain boundary is reduced, and the energy conversion efficiency can be further improved.

1 Photoelectric conversion element 10 Substrate 20 Insulating oxide film (anodized film)
30 Spin-on glass film 40 Lower electrode (back electrode)
50 Photoelectric conversion semiconductor layer 60 Buffer layer 70 Translucent conductive layer (transparent electrode)
80 Upper electrode (grid electrode)

Claims (7)

A metal substrate with an insulating layer having an insulating oxide film formed by anodic oxidation on a metal substrate and a spin-on glass film on the insulating oxide film , wherein the spin-on glass film comprises polysilazane, methylsiloxane, polysil A metal substrate with an insulating layer, comprising at least one selected from sesquioxane, Si-based metalloxane polymer, Ti-based metalloxane polymer, and silicate, wherein the spin-on glass film contains sodium ions. Metal substrate with an insulation layer according to claim 1, wherein the 10μm square average surface roughness of the spin-on-glass film surface is 10nm or less. The metal substrate with an insulating layer according to claim 1 or 2, wherein the spin-on glass film has a thickness of 0.1 to 10 µm. The insulation according to claim 1 , wherein the metal substrate is a substrate containing at least one metal selected from aluminum, iron, zirconium, titanium, magnesium, copper, niobium and tantalum. Layered metal substrate. The metal substrate with an insulating layer according to any one of claims 1 to 4 , wherein the metal substrate is a clad material in which one or both surfaces of aluminum, stainless steel, or a steel plate are integrated with an aluminum plate. The compound containing sodium ions is at least one compound selected from NaF, Na ₃ AlF ₆ , Na ₂ (MoO ₄ ), Na ₂ CO ₃ , Na ₂ O, and sodium silicate. The metal substrate with an insulating layer according to any one of claims 1 to 5 . The photoelectric conversion device characterized by claim 1-6 and is formed to any one of claims insulating layer provided metal substrate.