JP5667027B2 - Solar cell submodule, method for manufacturing the same, and substrate with electrode - Google Patents

Description

  The present invention relates to a solar cell submodule constituting a solar cell module, a method for manufacturing the same, and a substrate with electrodes used for the solar cell submodule.

A photoelectric conversion element including a photoelectric conversion layer and an electrode connected to the photoelectric conversion layer is used for applications such as solar cells. Conventionally, in the case of solar cells, Si-based solar cells using bulk single crystal Si or polycrystalline Si, or thin-film amorphous Si have been mainstream, but research and development of Si-independent compound semiconductor solar cells has been made. ing. As compound semiconductor solar cells, there are known bulk systems such as GaAs systems and thin film systems such as CIGS systems composed of group Ib elements, group IIIb elements and group VIb elements. CIGS has the general formula _{Cu 1-z In 1-x} Ga x Se 2-y S y ( where, 0 ≦ x ≦ 1,0 ≦ y ≦ 2,0 ≦ z ≦ 1) compound represented by the Semiconductor Yes, CIS is when x = 0, and CIGS when x> 0. In this specification, CIGS includes CIS.

  In manufacturing a CIGS photoelectric conversion element, the problem of delamination between stacked layers is important. In particular, when manufacturing by a roll-to-roll system, peeling is more likely to occur due to the load applied to the film during transport. The reduction of peeling contributes to improving the yield in manufacturing and also contributes to the improvement of photoelectric conversion efficiency characteristics.

The cause of delamination in a substrate-type CIGS photoelectric conversion element configured such that the light receiving surface is stacked on the substrate from the back electrode side is mainly the CIGS that is the photoelectric conversion layer and the back electrode It is said that the MoSe ₂ layer formed at the interface with the Mo layer is to be formed in a c-axis oriented layer with respect to the back electrode.

In Non-Patent Document 1, since the bond between the layers of the MoSe ₂ layer formed in a layered form is a weak bond due to van der Waals force, the adhesion between the Mo layer formed with the MoSe ₂ layer in a layered form and the CIGS film is Mentioned to be weak.

As schematically shown in FIG. 11, when a CIGS layer is formed on the surface of a body-centered cubic Mo layer (left figure), Se enters the Mo layer and a hexagonal MoSe ₂ layer is formed (right). Figure). The MoSe ₂ layer has a hexagonal layered structure and, for example, easily slips along the layer surface between Se layers indicated by phantom lines, and as a result, peeling easily occurs.

It is known that when a CIGS layer is formed on a Mo electrode, a MoSe ₂ layer having a thickness of about 200 nm or more is formed at the interface between the _two layers when a selenization method is used. The MoSe in order to reduce delamination by _two layers, a method of inhibiting the production of MoSe ₂ layer during CIGS layer formed using the selenization method has been discussed in Patent Documents 1, 2, and 3 and the like.

On the other hand, it is reported that the presence of the MoSe ₂ layer between the Mo layer and the CIGS layer forms an ohmic contact between the Mo layer and the MoSe ₂ layer, and is responsible for improving the efficiency of the solar cell. ing. It has also been proposed to improve the conversion efficiency by forming a semiconductor layer such as ZnO on the Mo layer instead of the MoSe ₂ layer (Patent Documents 4, 5, etc.).

JP-A-6-188444 JP-A-9-321326 JP 2009-289955 A JP 2006-13028 A JP 2007-335625 A

Thin Sold Films Vol480-481 p.433-438

As described above, Patent Documents 1 to 3 disclose a method for suppressing the MoSe ₂ layer when the CIGS layer is formed by a selenization method. On the other hand, when the CIGS layer is formed by the vapor deposition method, the generated MoSe ₂ layer is about 50 nm, which is thinner than the case of the selenization method. Although it seems that the formation of elements on non-flexible substrates such as glass substrates has not been a major problem, roll-to-roll systems using flexible substrates have been proposed to improve handling and productivity. In the case of application to element manufacturing, it has been found that even when the thickness is about 50 nm, the problem of peeling becomes significant when a layered MoSe ₂ layer is formed. At present, a method for suppressing the MoSe ₂ layer generated when forming the CIGS layer using the vapor deposition method has not been established yet.

  When the back electrode is composed of a transition metal other than Mo and the photoelectric conversion layer is composed of a chalcogen-containing compound semiconductor such as an Ib-IIIb-VIb compound semiconductor or an IIb-VIb compound semiconductor, a transition metal dichalcogenide layer Is generated between the back electrode and the photoelectric conversion layer, and the same problem occurs.

  The present invention has been made in view of the above circumstances, and has a substrate with an electrode that has high adhesion to a compound semiconductor photoelectric conversion layer to be formed and is unlikely to peel off, and a photoelectric conversion element formed using the same It aims at providing the solar cell submodule provided with. Moreover, this invention aims at providing the manufacturing method of the compound semiconductor type solar cell submodule which can suppress formation of a transition metal dichalcogenide layer, when forming a photoelectric converting layer by a vapor deposition method. It is.

The substrate with an electrode of the present invention is a substrate with an electrode used for a chalcogen-containing compound semiconductor-based photoelectric conversion element, and includes a conductive layer mainly composed of a single transition metal on the substrate,
At least a surface layer opposite to the substrate of the conductive layer is a layer containing the transition metal nitride.

  In this specification, “a conductive layer containing a single transition metal as a main component” means that nitrogen and unavoidable impurities contained in the surface layer may be included.

  The nitrogen content relative to the transition metal in the nitride-containing layer is preferably 5 at% or more. In such a configuration, the reflectance of the surface layer with respect to light of a predetermined wavelength can be 95% or less of the reflectance of the single transition metal. The reflectance of the surface layer is more preferably 90% or less of the reflectance of the single transition metal.

  In the present specification, the “reflectance of a single transition metal” is defined as the reflectance of a flat surface that is made of a single transition metal (may contain inevitable impurities) and has good surface smoothness.

In the surface layer, when the amount of nitrogen contained in the transition metal is small, the content in the transition metal can be evaluated by XPS (X-ray photoelectron spectroscopy) or SIMS (secondary ion mass spectrometer). Furthermore, when the nitrogen content is about 20 at.% Or more, transition metal nitrides (M ₂ N, where M is a transition metal) are formed in the transition metal. Also, the nitrogen content can be confirmed.

  The predetermined wavelength is preferably 532 nm or 1064 nm. The transition metal is preferably Mo.

The solar cell submodule of the present invention is a solar cell submodule formed by electrically connecting a plurality of solar cells on a substrate, on the substrate with an electrode of the present invention,
A photoelectric conversion element having a laminated structure of a photoelectric conversion layer made of a compound semiconductor containing chalcogen and a transparent electrode is provided.

  In the solar cell submodule of the present invention, the chalcogen-containing compound semiconductor is preferably a compound semiconductor containing a group Ib element, a group IIIb element and a group VIb element.

  In the solar cell submodule of the present invention, the group Ib element is Cu, the group IIIb element is at least one selected from the group consisting of Al, Ga and In, and the group VIb element is Se. Or it is preferable that it is S.

The method for producing the solar cell submodule of the present invention includes:
A solar cell submodule comprising a photoelectric conversion element having a laminated structure of a conductive layer mainly composed of a transition metal element, a photoelectric conversion layer composed of a compound semiconductor containing chalcogen, and a transparent conductive layer on a substrate. A manufacturing method comprising:
A conductive layer forming step of forming a conductive layer mainly composed of a single transition metal on the substrate;
A conductive layer nitriding step of forming a nitride of the transition metal on a surface layer of the conductive layer;
Removing a part of the conductive layer using a laser to form a substrate with an electrode having a separation groove; and
And a photoelectric conversion layer forming step of forming the photoelectric conversion layer on the substrate with electrodes by a vapor deposition method.

  In the conductive layer nitriding step, the transition metal nitride may be formed by nitrogen plasma treatment or by reactive sputtering under a condition in which nitrogen is mixed in the sputtering gas. .

  In the conductive layer removal step, the wavelength of the laser is preferably 532 nm or 1064 nm. The transition metal is preferably Mo.

  The substrate with an electrode of the present invention is a substrate with an electrode used for a chalcogen-containing compound semiconductor-based photoelectric conversion element, and includes a conductive layer mainly composed of a single transition metal on the substrate, and at least the substrate of the conductive layer The surface layer on the opposite side is a layer containing a transition metal nitride. According to such a configuration, when the chalcogen-containing compound semiconductor photoelectric conversion layer is formed on the conductive layer by vapor deposition, the formation of a transition metal dichalcogenide thin film in the vicinity of the film formation surface of the conductive layer is suppressed. Can do.

When the transition metal dichalcogenide thin film represented by the MoSe ₂ layer is uniformly formed on the back electrode (conductive layer) in a layered manner, the adhesion of the photoelectric conversion layer in the photoelectric conversion element is lowered. Therefore, according to the present invention, in the photoelectric conversion element and the solar cell submodule using the photoelectric conversion element, it is possible to improve the conversion efficiency by increasing the adhesion of the photoelectric conversion layer and reducing the defective portion due to the decrease in adhesion. And the yield can be further improved.

  In addition, when forming an integrated solar cell sub-module formed by electrically connecting a plurality of solar cells on a substrate, separation is performed to form a separation groove on the back electrode. After the back electrode in the region is removed by laser scribing, a photoelectric conversion layer is formed. In laser scribing, the higher the laser beam absorption rate of the workpiece, the lower the output power of the laser can be used. However, the back electrode, which is a metal layer, has low laser beam absorption rate (high reflectance). It is difficult to form a separation groove satisfactorily without a residue with a low-power laser with little damage to the base of the back electrode.

  In the substrate with electrodes of the present invention, since the surface layer contains nitride, the reflectance of the laser (light) is lower than that of the portion not containing. Therefore, according to the present invention, when forming the integrated solar cell submodule that requires the formation of a separation groove on the back electrode, a low-power laser with little damage to the base of the back electrode can be used without residue. The separation groove of the back electrode can be formed satisfactorily.

Schematic structure sectional drawing which shows one Embodiment of the photoelectric conversion element provided with the board | substrate with an electrode of this invention Schematic structure sectional drawing which shows other embodiment of the photoelectric conversion element of the example of a design change of this invention Schematic diagram showing how Se enters the molybdenum nitride layer Schematic sectional view showing a specific example of a substrate The schematic diagram which shows the processability of the laser scribe in the board | substrate with an electrode of this invention, and the board | substrate with a conventional metal electrode Sectional drawing which shows the structure of the solar cell submodule of one Embodiment concerning this invention. The figure which shows the wavelength dependence of the reflectance of the molybdenum electrode layer surface of an Example and a comparative example. The figure which shows the adhesive evaluation result of an Example and a comparative example The figure which shows the X-ray crystal structure analysis result of the molybdenum electrode layer surface of an Example and a comparative example Shows the _{N 2} volume relationship in the film which has been deposited and _{N 2} ratio Ar in the reactive sputtering method (Fig.9 literature Shih) Schematic showing how Se enters the molybdenum layer

  Hereinafter, with reference to drawings, the photoelectric conversion element concerning the embodiment of the present invention and its manufacturing method are explained.

  FIG. 1 is a cross-sectional view illustrating a schematic configuration of an electrode-equipped substrate 1 and a photoelectric conversion element 2 having the same according to the present embodiment. Further, FIG. 2 shows a schematic cross-sectional view of a photoelectric conversion element 2 ′ of a design change example provided with a substrate 1 with electrodes. In FIG. 2, the scale of each component in the drawing is appropriately different from the actual one. It is different.

  The electrode-equipped substrate 1 includes a substrate 10 and a conductive layer 20 formed on the substrate 10. The conductive layer 20 is mainly composed of a single transition metal M, and is composed of a metal layer 21 formed on the substrate 10 side and a surface layer 22 of the conductive layer 20 containing a nitride of the transition metal M. ing.

  The photoelectric conversion element 2 includes a substrate 1 with an electrode, a photoelectric conversion layer 30 made of a chalcogen-containing compound semiconductor formed on the conductive layer 20 of the substrate 1 with an electrode, a buffer layer 40 and a window layer 50 on the photoelectric conversion layer 30. And a photoelectric conversion element of a substrate type in which the transparent electrode 60 is sequentially stacked, and the photoelectric conversion layer 30 is formed so as to be in contact with the conductive layer 20. In the example shown in FIG. 1, an extraction electrode (grid electrode) 70 is further provided on the transparent electrode 60.

  The surface layer 22 of the conductive layer 20 contains a nitride of the transition metal M, that is, the surface layer of the conductive layer 20 is nitrided, whereby the photoelectric conversion layer 30 made of a chalcogen-containing compound semiconductor is formed on the conductive layer 20. When vapor deposition is performed, a transition metal dichalcogenide thin film composed of chalcogen (VIb group element) which is a constituent element and a transition metal element is uniformly formed between the conductive layer 20 and the photoelectric conversion layer 30. Can be suppressed.

  The transition metal M that is the main component of the conductive layer 20 is not particularly limited as long as it is a transition metal that can be used as an electrode. In particular, Mo, W, and combinations thereof are preferable, and Mo is particularly preferable. The film thickness of the conductive layer 20 is not limited and is preferably about 200 to 1000 nm.

  Of the conductive layer 20, the surface layer 22 containing nitride is preferably about several nm to 200 nm. The thickness of the surface layer 22 is desirably about 20% or less with respect to the total thickness of the conductive layer 20.

  The nitrogen content in the surface layer 22 is preferably 5 at.% Or more, and more preferably 20 at.% Or more. However, if the content of nitrogen is too large, the electrical resistance becomes too large and the photoelectric conversion efficiency may be lowered. Therefore, the content is preferably 50 at.% Or less.

In addition, although it is preferable that nitrogen is uniformly contained in the surface layer 22, there may be a part where the nitrogen is not partially contained in the surface layer 22. The size of each part not containing nitrogen is preferably 100 nm ² or less.

The inventors have found that when nitrogen is contained in the surface layer, formation of a transition metal dichalcogenide thin film in that portion can be suppressed. Since the transition metal dichalcogenide thin film having a layered structure typified by the MoSe ₂ layer is uniformly formed on the back electrode, the adhesion in the photoelectric conversion element is lowered, so that the generation of the transition metal dichalcogenide thin film is suppressed. In this way, it is possible to suppress peeling.

  By making the surface layer 22 of the conductive layer a layer containing a nitride of the transition metal M, the VIb group element (chalcogen) is less likely to enter the crystal lattice of the transition metal compared to the case of a simple transition metal layer. Therefore, it is considered that generation of a transition metal dichalcogenide thin film having a layered structure can be suppressed.

  In addition, the effect of suppressing the formation of a transition metal dichalcogenide thin film can be similarly expected by using oxygen instead of nitrogen to form an oxide transition metal layer. Is not preferred because of its high resistivity and consequently hindering the improvement of the photoelectric conversion rate.

  On the other hand, for example, while Mo has a resistance of several tens of μΩ · cm, the resistance value varies depending on the nitriding condition, but Mo nitride has a resistance of about several hundred μΩ · cm. The low efficiency does not increase so much with respect to the layer, and the role as an electrode can be maintained.

  By providing the surface layer 22 including the nitride of the transition metal M, the formation of the transition metal dichalcogenide layer can be suppressed during the formation of the photoelectric conversion layer. However, there is a portion where the degree of nitridation is small and nitrogen is not partially included. In some cases, depending on the ratio, chalcogen enters the surface layer 22 to form a transition metal dichalcogenide-containing layer 22a containing nitrogen in part of the surface layer (FIG. 2).

  FIG. 3 schematically shows a state in which chalcogen enters the nitride-containing layer 22 by taking an example in which the transition metal M is Mo and the chalcogen is Se. When CIGS is formed on the molybdenum nitride layer as shown in the left of FIG. 3, Se enters the molybdenum nitride layer as shown in the right of FIG. However, since nitrogen is contained, Se does not enter into a regular layer shape, and it is considered that a layer structure that causes slipping is not formed. Since a structure in which slip occurs is not formed, it is possible to suppress a decrease in adhesion.

  From the viewpoint of adhesion, the transition metal dichalcogenide layer is preferably 10 nm or less.

  In the photoelectric conversion element 2 ′, a transition metal dichalcogenide thin film made of a transition metal M and a chalcogen is partially formed in the transition metal chalcogenide-containing layer 22a. As described above, since the transition metal dichalcogenide thin film is uniformly formed on the back electrode in a layered manner, the adhesion in the photoelectric conversion element is lowered. It may be formed as long as it is 50% or less with respect to the area of the region where the conversion layer 30 is formed.

  If the region where the transition metal dichalcogenide thin film is formed is 50% or less, the effect of suppressing the decrease in adhesion can be sufficiently obtained.

  On the other hand, as described in the section of “Background Art”, the transition metal dichalcogenide layer contributes to the improvement of photoelectric conversion efficiency by ohmic contact. Therefore, from the viewpoint of this ohmic contact, a transition metal dichalcogenide thin film is almost formed. It is preferable to form about 10% or more than not.

  Considering both the above viewpoints of adhesion and ohmic contact, a more preferable range of the region where the transition metal dichalcogenide thin film is formed is 20% to 30%.

  In the integrated solar cell submodule (see FIG. 6 for the configuration), which is formed by electrically connecting a plurality of solar cells on a substrate, as described above, the back electrode (conductive In order to form a separation groove in the layer, it is necessary to form a photoelectric conversion layer on the back electrode with the separation groove after forming the separation groove by removing the back electrode in the separation region by laser scribing.

  Especially when using a metal substrate with an insulating layer, the upper back electrode layer (conductive layer) must be removed by laser scribing so as not to damage the underlying insulating layer. The laser is preferably low energy. When the insulating layer is damaged or scribed up to the insulating layer, the CIGS layer and the metal substrate are brought into conduction and cannot be integrated on the substrate.

  The conductive layer 20 of the electrode-equipped substrate 1 has a surface layer 22 containing a transition metal M nitride, that is, the surface layer of the conductive layer 20 is nitrided. The reflectance of the surface layer 22 with respect to light is lower than that of the portion (metal layer 21) that does not include the light (see the example described later and FIG. 7).

  FIG. 5 schematically shows the state of laser scribing. As shown in the right diagram of FIG. 5, in a mode in which a layer containing nitride is not provided on the surface, the laser light absorption is low, so that processing with a low-power laser that does not damage the underlying layer of the conductive layer 20 is performed. difficult. If the conductive layer remains in the separation groove of the electrode layer as shown in the right diagram of FIG. 5, electrical leakage may occur between cells in the solar cell module, resulting in poor performance.

  The left figure of FIG. 5 is the schematic diagram which showed a mode that laser scribe was performed to the conductive layer 20 of the board | substrate 1 with an electrode of this embodiment. As described above, since the surface layer 22 of the conductive layer 20 is a layer containing nitride, the laser light absorption rate is high. Therefore, even in a low-power laser that does not damage the underlying layer of the conductive layer 20, The laser irradiated portion of the layer 20 can be removed satisfactorily.

  In the laser scribe of the conductive layer 20, since the ablation occurs even if the absorption rate of the surface layer 22 is high, the conductive layer 20 in the separation groove forming region can be removed well with a lower output laser. (See examples below).

  As described above, the substrate with electrode 1 has a higher absorption rate of laser light in the region where the separation groove is formed than the conventional back surface electrode. By using the substrate with electrode 10 in the module, the separation groove of the conductive layer 20 can be satisfactorily formed without residue with a low-power laser with little damage to the base of the conductive layer 20.

  Below, the detail of each layer which comprises the board | substrate 1 with an electrode other than the above-mentioned back electrode (conductive layer 20) and the photoelectric converting layers 2 and 2 'is demonstrated.

(substrate)
The substrate 10 is not particularly limited, and for example, a glass substrate, an anodized aluminum substrate, a flexible substrate such as a resin substrate, or the like can be used.

  FIG. 4 is a schematic cross-sectional view of specific forms 10A and 10B of an anodized substrate which is a preferred embodiment of the substrate 10. As shown in FIG. The substrates 10A and 10B are substrates obtained by anodizing at least one surface side of the base material 11. The base material 11 is a composite base material in which an Al base material containing Al as a main component is combined with at least one surface side of an Fe base material containing Fe as a main component (for example, SUS). Alternatively, a base material in which an Al film mainly composed of Al is formed on at least one surface side of an Fe material mainly composed of Fe is preferable.

The substrate 10A shown in the left diagram of FIG. 4 is one in which the anodic oxide film 12 is formed on both surfaces of the base material 11, and the substrate 10B shown in the right diagram in FIG. Is formed. The anodic oxide film 12 is a film mainly composed of Al ₂ O ₃ . In order to suppress the warpage of the substrate due to the difference in thermal expansion coefficient between Al and Al ₂ O ₃ and the film peeling due to this in the device manufacturing process, as shown in the left diagram of FIG. More preferably, the anodic oxide film 12 is formed on both surfaces.

  Anodization can be performed by a known method in which a base material 11 that has been subjected to cleaning treatment, polishing smoothing treatment, or the like as necessary is immersed in an electrolyte together with a cathode, and a voltage is applied between the anode and the cathode.

  The thickness of the base material 11 and the anodic oxide film 12 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 11 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 12 is preferably 0.1 to 100 μm, for example.

  Further, the substrate 10 may be one in which a soda lime glass (SLG) layer is provided on the anodic oxide film 12. By providing the soda lime glass layer, Na can be diffused in the photoelectric conversion layer. When the photoelectric conversion layer contains Na, the photoelectric conversion efficiency can be further improved.

(Photoelectric conversion layer)
The main component of the photoelectric conversion layer 30 is not particularly limited as long as it is a chalcogen-containing compound semiconductor. The chalcogen-containing compound semiconductor includes at least one compound semiconductor (at least one II-VI group semiconductor) composed of a group IIb element and a group VIb element, and a group Ib element, a group IIIb element, and a group VIb element. Examples include at least one compound semiconductor (at least one I-III-VI group semiconductor), and preferably at least one I-III-VI group semiconductor.

  Examples of II-VI group semiconductors include CdTe.

As the I-III-VI group semiconductor, at least one Ib group element selected from the group consisting of Cu and Ag,
At least one group IIIb element selected from the group consisting of Al, Ga and In;
Examples include at least one compound semiconductor composed of at least one VIb group element selected from the group consisting of S, Se, and Te.

As the compound semiconductor,
CuAlS ₂ , CuGaS ₂ , CuInS ₂ ,
CuAlSe ₂ , CuGaSe ₂ ,
AgAlS ₂ , AgGaS ₂ , AgInS ₂ ,
AgAlSe ₂ , AgGaSe ₂ , AgInSe ₂ ,
AgAlTe ₂ , AgGaTe ₂ , AgInTe ₂ ,
Cu (In, Al) Se ₂ , Cu (In, Ga) (S, Se) ₂ ,
Cu _1-z In _1-x Ga _x Se _2-y S _y (where 0 ≦ x ≦ 1, 0 ≦ y ≦ 2, 0 ≦ z ≦ 1) (CI (G) S),
Examples include Ag (In, Ga) Se ₂ and Ag (In, Ga) (S, Se) ₂ .
In particular, CuInGaSe ₂ is preferable.

  The film thickness of the photoelectric conversion layer 30 is not particularly limited, and is preferably 1.0 to 3.0 μm and particularly preferably 1.5 to 2.5 μm.

(Buffer layer)
The buffer layer 40 is a layer mainly composed of CdS, ZnS, Zn (S, O), and Zn (S, O, OH). The film thickness of the buffer layer 40 is not particularly limited, preferably 10 nm to 0.5 μm, and more preferably 15 to 200 nm.

(Window layer)
The window layer 50 is an intermediate layer that captures light. The composition of the window layer 50 is not particularly limited, and i-ZnO or the like is preferable. The film thickness of the window layer 50 is not particularly limited, and is preferably 15 to 200 nm. The window layer is an arbitrary layer and may be a photoelectric conversion element without the window layer 50.

(Transparent electrode)
The transparent electrode 60 is a layer that takes in light and functions as an electrode. The composition of the transparent electrode 60 is not particularly limited, and ZnO, ITO (indium tin oxide), SnO ₂ , and combinations thereof are preferable. Such a material is preferable because of its high light transmittance and low resistance. The second electrode 22 is obtained by adding a dopant capable of becoming a desired conductivity type to these materials. Examples of the dopant include elements such as Ga, Al, and B, and n-ZnO such as ZnO: Al is preferable. The film thickness of the transparent electrode 60 is not particularly limited, and is preferably 50 nm to 2 μm.

  The transparent electrode 60 may have a single layer structure or a laminated structure such as a two-layer structure. The second electrode 60 is formed by laminating an i layer having an i-type conductivity type and an n-layer having an n-type conductivity type (the conductivity type is a p-type depending on the entire layer configuration) from the buffer layer 40 side. A two-layer structure is preferred.

(Extraction electrode)
The extraction electrode 70 is an electrode for efficiently extracting electric power generated between the back electrode 20 and the transparent electrode 60 to the outside.

  The main component of the extraction electrode 70 is not particularly limited, and examples thereof include Al. The film thickness of the extraction electrode 70 is not particularly limited and is preferably 0.1 to 3 μm.

(Other configurations)
The photoelectric conversion elements 2, 2 ′ can include arbitrary layers other than those described above as necessary. For example, when an anodized substrate is used as the substrate, an adhesion layer (buffer layer), an alkali barrier layer, or the like is provided between the substrate 10 and the back electrode 20 as necessary to enhance the adhesion between the layers. Can be provided. For the alkali barrier layer, see JP-A-8-222750.

The photoelectric conversion elements 2 and 2 ′ can be preferably used as solar cells.
For example, a solar cell submodule can be formed by integrating a large number of the photoelectric conversion elements 2 and 2 ′, and a cover glass, a protective film, and the like can be attached as necessary to obtain a solar cell.

  In addition, in a solar cell (submodule) in which a large number of photoelectric conversion elements (cells) are integrated, it is not necessary to provide an extraction electrode for each cell, and among cells connected in series, a cell serving as a power extraction end Is provided. An integrated solar cell includes, for example, a process of forming each layer on a substrate by a roll-to-roll method using a flexible long substrate, and a patterning (scribing) process for integration. It is formed through an element forming process, a process of cutting the element-formed substrate into one module, and the like. In addition, when manufacturing by the roll-to-roll method, since the scribing process and the winding process of the substrate in each processing process are involved, the problem of peeling between the conductive layer and the photoelectric conversion layer is more remarkable. Therefore, the photoelectric conversion element of the present invention having high adhesion between the conductive layer and the photoelectric conversion layer is very effective.

In addition, the electric conversion element using the board | substrate 1 with an electrode of this invention is applicable not only to a solar cell but other uses, such as CCD.
<Solar cell sub-module and manufacturing method thereof>

  A solar cell submodule according to an embodiment of the present invention and a manufacturing method thereof will be described with reference to FIG. FIG. 6 is a schematic configuration diagram of the solar cell submodule 3 of the present embodiment. In order to facilitate visual recognition, the scales of the constituent elements of each part are appropriately changed and shown.

  The solar cell submodule 3 shown in FIG. 6 is formed by electrically connecting a plurality of solar cells C in series on a substrate, and the chalcogen is formed on the substrate 1 with an electrode according to the present invention. A photoelectric conversion element 2 (cell C) having a laminated structure of a transparent electrode 60 and a photoelectric conversion layer 30 made of a compound semiconductor containing a buffer layer 40 between the photoelectric conversion layer 30 and the transparent electrode 60. And the window layer 50, and the current generated in the photoelectric conversion layer 30 when the cell C is irradiated with light is taken out by the transparent electrode 60 and the back electrode 20.

  The solar cell submodule 3 is an integrated solar cell submodule formed by electrically connecting a plurality of solar cells C in series on a substrate 10. In FIG. A first groove 71, a second groove 72 that penetrates the photoelectric conversion layer 30, the buffer layer 40, and the window layer 50, a second that penetrates the photoelectric conversion layer 30, the buffer layer 40, the window layer 50, and the transparent electrode 60. 3 open groove portions 73 are formed.

  With the above configuration, a structure in which the elements are separated into a large number of cells C by the first to third groove portions 71 to 73 is obtained. Moreover, the structure which the transparent electrode 60 of a certain cell C connected in series with the back surface electrode 20 of the adjacent cell C by filling the transparent electrode 60 in the 2nd groove part 72 is obtained.

  The aspect of each component is as described in the description of the photoelectric conversion elements 2 and 2 '.

Further, the solar cell submodule 3 includes a conductive layer film forming step for forming a conductive layer 20 (21) mainly composed of a transition metal on the substrate 10,
A conductive layer nitriding step of forming a transition metal M nitride on the surface layer 22 of the conductive layer 20;
A conductive layer removing step of removing a part of the conductive layer 20 using a laser to form the electrode-equipped substrate 1 ′ having the separation groove 71;
And a photoelectric conversion layer forming step of forming the photoelectric conversion layer 30 on the substrate with electrode 1 ′ by a vapor deposition method. Hereinafter, the procedure will be described more specifically.

  First, the substrate 10 is prepared, and the conductive layer 20 is formed on the substrate 10.

  As already described, the conductive layer 20 includes the layer 22 containing nitride on the surface layer. The method for forming the nitride-containing layer 22 can be broadly divided into a method in which the conductive layer 20 is formed and then the surface is nitrided to form the metal layer 21 and the nitride-containing layer 22, and the metal layer 21. There are two types of methods of forming a nitride-containing layer 22 after the film is formed.

  The method for producing the conductive layer 20 (metal layer 21) not containing nitride is not particularly limited, but is preferably a sputtering method. For example, Mo is used as the transition metal, and a Mo layer (transition metal layer) is formed on the substrate 10 by sputtering (conductive layer deposition step).

  Next, when the metal layer 21 and the nitride-containing layer 22 are formed by nitriding the surface, the surface of the conductive layer (Mo layer) 20 not containing nitride is subjected to nitrogen plasma treatment or the like. The surface of the Mo layer is nitrided. Thereby, the conductive layer 20 containing nitrogen can be formed on the surface layer of the Mo layer (conductive layer nitriding step). In such a method, the penetration depth of nitrogen is at most several nanometers to 10 nm from the surface, and the boundary between the first conductive layer 21 and the second conductive layer 22 cannot be visually observed in an image such as an electron microscope. However, if composition analysis is performed in the depth direction from the surface side, it can be confirmed that nitrogen is contained in a region of several nm to 10 nm of the surface layer.

In the case where the nitride-containing layer 22 is formed after the metal layer 21 is formed, nitrogen (N ₂ ) is mixed into the sputtering gas (Ar) on the metal layer 21. By performing reactive sputtering, the nitride-containing layer 22 (molybdenum nitride layer 22) is formed (conductive layer nitriding step). In this method, the thickness of the surface layer 22 can be set to a desired thickness by adjusting the film formation time of sputtering. The thickness of the molybdenum nitride layer 22 is preferably up to about 100 nm.

  Next, a part of the conductive layer 20 is removed by laser scribing to form an electrode-equipped substrate 1 ′ having a separation groove 71 (conductive layer removing step).

  The laser used for laser scribing is not particularly limited, and lasers from ultraviolet light to infrared light can be used. In particular, a pulse laser having a wavelength of 1064 nm and its second harmonic, 532 nm, is preferable because of its high versatility. As described above, since the surface layer 22 is a layer containing nitride, the electrode-equipped substrate 1 has a high absorption rate of laser light. As shown in the examples described later, the electrode-equipped substrate 1 can form the separation groove 71 without leaving a residue after scribing using a 532 nm Nd: YAG pulse laser.

  Next, a chalcogen-containing compound semiconductor photoelectric conversion layer 30 is formed on the substrate with electrode 1 ′ (nitride-containing layer 22) by a vapor deposition method (photoelectric conversion layer forming step). Here, a case where a CuInGaSe layer is formed will be described as an example.

  Of the vapor deposition methods, the multi-source simultaneous vapor deposition method is particularly suitable. Typical methods include a three-step method (JRTuttle et.al, Mat.Res.Soc.Symp.Proc., Vol.426 (1996) p.143., Etc.) and the EC group simultaneous deposition method ( L. Stolt et al .: Proc. 13th ECPVSEC (1995, Nice) 1451.).

  In the three-stage method, In, Ga, and Se are first vapor-deposited at a substrate temperature of 400 ° C. in a high vacuum, then heated to 500 to 560 ° C., and Cu and Se are simultaneously vapor-deposited, followed by In, Ga, and Se. Are further deposited simultaneously to obtain a graded band gap CIGS film with a forbidden band width inclined. The EC group method is an improved version of the Bayer method developed by Boeing, which deposits Cu-rich CIGS in the early stage of vapor deposition and In-rich CIGS in the latter half of the process so that it can be applied to the in-line process. The Bayer method is described in W. E. Devaney, W. S. Chen, J. M. Stewart, and R. A. Mickelsen: IEEE Trans. Electron. Devices 37 (1990) 428.

Both the three-stage method and the EC group co-evaporation method use a CI-rich CIGS film composition in the film growth process and utilize liquid phase sintering with phase separated liquid phase Cu _2-x Se (x = 0 to 1). Therefore, there is an advantage that the CIGS film having a large particle size and excellent crystallinity is formed. Furthermore, in recent years, in order to improve the crystallinity of the CIGS film, various methods in addition to this method have been studied, and these may be used.

In order to improve the crystallinity of the CIGS film, as a method of improving the above method,
a) a method using ionized Ga (H. Miyazaki, et.al, phys.stat.sol. (a), Vol.203 (2006) p.2603, etc.),
b) Method of using cracked Se (68th Japan Society of Applied Physics Academic Lecture Proceedings (Autumn 2007, Hokkaido Institute of Technology) 7P-L-6 etc.),
c) Method using radicalized Se (Proceedings of the 54th Japan Society of Applied Physics (Aoyama Gakuin University) 29P-ZW-10 etc.)
d) A method using a photoexcitation process (the 54th Japan Society of Applied Physics Academic Lecture Proceedings (Spring 2007 Aoyama Gakuin University) 29P-ZW-14 etc.) is known.

During the formation of the photoelectric conversion layer, Se, which is the VIb element of the CIGS layer, reacts with Mo to partially form the MoSe ₂ layer 25.

  After the formation of the photoelectric conversion layer 30, the buffer layer 40 is formed on the photoelectric conversion layer 30. As the buffer layer 40, for example, CdS is formed by a CBD method (chemical bath deposition method) or the like.

  Next, a ZnO layer, for example, is formed as the window layer 50 on the surface of the CdS buffer layer 40, and further, a layer from the predetermined position on the surface of the window layer 50 to the photoelectric conversion layer 30 (window layer 50, buffer layer 40, photoelectric layer). The conversion layer 30) is removed and the separation grooves 72 are patterned. The method for forming the separation groove 72 is not particularly limited, but can be formed by mechanical scribing or the like.

  Finally, as the transparent electrode 60, for example, an Al—ZnO layer is formed by sputtering from the upper surfaces of the separation grooves 72 and the window layer 50, and further, the separation grooves 73 for dividing the cells are patterned to form the solar cell submodule 3 Get.

When a flexible substrate is used as the substrate, each film forming step includes a supply roll (unwinding roll) formed by winding a long flexible substrate in a roll shape, and a film-formed substrate in a roll shape. It is preferable to use a so-called roll-to-roll method that uses a winding roll wound around.
(Design changes)

  The present invention is not limited to the above-described embodiment, and the design can be changed as appropriate without departing from the spirit of the present invention.

(Production of substrate with electrodes)
The sample of the Example of the photoelectric conversion element of this invention was produced with the following method.

  First, a 3 cm × 3 cm × 1.1 mm soda lime glass substrate was prepared and subjected to ultrasonic cleaning with acetone, ethanol, and pure water for 5 minutes each.

  Thereafter, the substrate was introduced into a sputtering apparatus, and Mo was sputtered on the substrate by DC sputtering at a DC power of 1 KW, an Ar gas pressure of 0.5 Pa, and a substrate temperature of room temperature. The film formation time was 35 min. Thereafter, the sputtering was temporarily interrupted, and nitrogen gas was introduced into the film forming chamber. At this time, the flow rate ratio between Ar gas and nitrogen gas was adjusted for each example while keeping the film forming pressure at 0.5 Pa (Table 1). When the gas pressure and flow rate can be adjusted, sputtering (reactive sputtering) is resumed and discharged for a predetermined time (Table 1). Molybdenum nitride is formed on the surface of the previously formed Mo layer to form the electrode of the present invention. An attached substrate was obtained. At this time, the Mo layer was 450 nm and the molybdenum nitride layer was 50 nm.

In the above procedure, the flow rate ratio of Ar gas and _{N 2} gas during the reactive sputtering, relative to Ar gas 1 was _{N 2} gas and the ratio of 0, 0.1, 0.3 . Here, when N ₂ gas is 0, sputtering is performed in an atmosphere containing only Ar gas, which is a comparative example that does not include molybdenum nitride.

Examples 1 to 3 are substrates with electrodes prepared under conditions of N ₂ gas of 0.1, 0.3, and 1, respectively. When the N ₂ gas is 1, the atmosphere is Ar: N ₂ = 1: 1.
(Evaluation)
<Measurement of reflectance and sheet resistance>

  About each obtained board | substrate with an electrode, the reflectance of the electrode surface was measured using the Hitachi U-4000 type spectrophotometer. The measurement was performed for each wavelength of 532 nm, 1064 nm, and 355 nm.

  Moreover, the sheet resistance value of the electrode surface of each electrode-attached substrate was measured by a four-probe method using a Mitsubishi Chemical resistivity meter Loresta.

  The measurement results of the reflectance and the sheet resistance value are shown in Table 1 together with the flow ratio of Ar gas and nitrogen gas and the discharge time of each example. In addition, a graph showing the wavelength dependence of the reflectance is shown in FIG.

  As shown in FIG. 7, it is confirmed that the reflectance decreases as the nitrogen content (nitrogen introduction amount) on the surface increases, and further, it is confirmed that the reflectance (absorption rate) can be arbitrarily determined by the degree of nitridation. It was done. FIG. 7 shows that it is 95% or less even at the lowest rate of decrease. In particular, the reduction rate is high in the infrared region, and a high effect was confirmed.

  Further, FIG. 7 shows that the wavelength dependence graph becomes flat as the nitridation degree increases. The flatter the graph, the less the change in reflectance due to the wavelength, and the higher the stability of the scribe processability.

  Further, Table 1 shows that the sheet resistance necessary for the element is ensured even when nitrogen is included in the surface layer.

<Cross cut test>
Next, ₂ μm of Cu (In _0.7 Ga _0.3 ) Se ₂ was formed as a photoelectric conversion layer (semiconductor layer) on the back electrode by a so-called three-stage method. The substrate temperature in the second and third stages in the three-stage method was set to 550 ° C. In addition, K cell (knudsen-Cell: Knudsen cell) was used as an evaporation source.

  Next, a CdS buffer layer is formed on the surface of the photoelectric conversion layer (CIGS layer) by a CBD method (chemical bath deposition method) to a thickness of 50 nm, and a ZnO layer as a window layer is formed thereon with a thickness of 50 nm. Further, an Al—ZnO layer as a transparent electrode was formed to a thickness of 300 nm by a sputtering method. Finally, an Al layer was formed on the surface of the Al—ZnO layer as an extraction electrode by a vapor deposition method.

  About the sample produced with each method of an Example and a comparative example, the crosscut test was done based on JIS specification (JIS-K5600). The cut interval was set to 1 mm, and the adhesion was judged based on the 25 grids after the adhesion (adhesion) test and the peeled state of the cut intersections. The number of peeled masses was evaluated as a percentage, and ranking was performed with 10 points indicating no peeling (100%) and 0 points indicating whole surface peeling (0%).

  About each Example and a comparative example, adhesive force (tape adhesive force) and a crosscut test evaluation value are shown in FIG. 8 using the some adhesive tape whose adhesive force is 0.5-24.5 N / 25mm.

  As shown in FIG. 8, the adhesion can be improved by providing a molybdenum nitride layer on the surface of the conductive layer as in the embodiment as compared with the case of only the molybdenum layer. Even in Example 1, there is a sufficient effect with respect to the comparative example. In particular, as in Example 2, when N = 0.3, the adhesion strength is significantly improved, and as N increases, the adhesion strength increases. It turns out that it improves.

This is presumably because MoSe ₂ is less likely to be formed as the amount of nitrogen contained in molybdenum nitride increases.

  The evaluation of the degree of nitridation in each example was performed on a film in which molybdenum nitride was formed on a substrate under the same conditions as in the above examples (film formation time was 45 min). As an evaluation method, an X-ray structural analysis using Cu as a tube was performed on the molybdenum nitride film, and a method of estimating the degree of nitridation using an ASTM card from a diffraction peak position by X-ray diffraction was adopted. The XRD spectrum of each example and comparative example is shown in FIG.

In FIG. 9, the (110) peak of Mo in the comparative example becomes broad and shifts to the left in Example 1 (N ₂ = 0.1). This is considered to be due to the distortion of the lattice due to N entering between the lattices of the body-centered cubic Mo crystal. On the other hand, in Example 2 (N ₂ = 0.3) and Example 3 (N ₂ = 1), the (111) peak of Mo ₂ N was observed, and the crystal structure was changed.

Regarding the flow ratio of Ar and N ₂ gas in the sputtering method and the N ₂ content in the deposited film, see “KK Shih and DB Dove, Properties of WN and Mo-N films prepared by reactive sputtering, J Vac. Sci. Technol. A 8 (3), May / Jun 1990, pp. 1359-1363 ”(fig. 9, shown in FIG. 10 of the present specification). The tendency obtained by the above method and the tendency described in this document have been confirmed to be substantially the same, and the validity of the present estimation method has been confirmed.
<Laser scribe>

Separation grooves were formed by laser scribing on the substrates with electrodes of the examples and comparative examples, and their processability was evaluated. As the laser, an Nd: YAG pulse laser having a wavelength of 532 nm was used. The pulse width was 25 ns, the scanning speed was 40 mm / s, and the laser intensity was 0.3 W / cm ² .

The separation groove formed by laser scribing was observed with an optical microscope to evaluate the presence or absence of Mo. In the evaluation, if there was any residual, it was judged unsuitable. In all the examples, there was no remaining, and in the comparative example, there was remaining.

DESCRIPTION OF SYMBOLS 1 Substrate with electrode 1 ′ Substrate with electrode with separation groove 2, 2 ′ Photoelectric conversion element 3 Solar cell submodule 10, 10A, 10B Substrate 11 Base material 12 Anodized film 20 Conductive layer (back electrode)
21 Metal layer 22 Layer containing nitride (nitride-containing layer, surface layer of conductive layer)
25 Transition metal dichalcogenide layer 30 Photoelectric conversion layer 40 Buffer layer 50 Window layer 60 Transparent electrode 70 Extraction electrode (grid electrode)
71, 71, 73 Separation groove

Claims (14)

A substrate with an electrode used for a chalcogen-containing compound semiconductor photoelectric conversion element,
Provided with a conductive layer mainly composed of a single transition metal on the substrate,
At least a surface layer of the conductive layer opposite to the substrate is a layer containing a nitride of the transition metal,
The content of the nitrogen to the transition metal in the layer containing the nitride of said transition metal is 5at% or more state, and are less 30 at%,
Electrode substrate with the transition metal and wherein the Mo der Rukoto.   2. The substrate with an electrode according to claim 1, wherein the thickness of the layer containing the transition metal nitride is 50 nm or less.   The substrate with an electrode according to claim 1, wherein a thickness of the layer containing the transition metal nitride is 10 nm or less.   The substrate with an electrode according to any one of claims 1 to 3, wherein a reflectance of the surface layer with respect to light having a predetermined wavelength is 95% or less of the reflectance of the single transition metal.   The substrate with an electrode according to claim 4, wherein the reflectance of the surface layer is 90% or less of the reflectance of the single transition metal.   6. The electrode-attached substrate according to claim 4, wherein the predetermined wavelength is 532 nm or 1064 nm. In a solar cell submodule formed by electrically connecting a plurality of solar cells in series on a substrate,
On the substrate with an electrode according to any one of claims 1 to 6 ,
A photoelectric conversion layer made of a compound semiconductor containing chalcogen;
A solar cell submodule comprising a photoelectric conversion element having a laminated structure with a transparent electrode. The solar cell submodule according to claim 7 , wherein the compound semiconductor contains a group Ib element, a group IIIb element, and a group VIb element. The Ib group element is Cu;
The group IIIb element is at least one selected from the group consisting of Al, Ga and In;
The solar cell submodule according to claim 8 , wherein the VIb group element is Se. A photoelectric conversion element having a laminated structure of a conductive layer mainly composed of Mo as a single transition metal , a photoelectric conversion layer made of a compound semiconductor containing chalcogen, and a transparent conductive layer on a substrate. It is a manufacturing method of the solar cell submodule in any one of 7-9 ,
A conductive layer forming step of forming the conductive layer on the substrate;
A conductive layer nitriding step of forming, on the surface layer of the conductive layer, a nitride of the transition metal having a nitrogen content of 5 at% to 30 at% with respect to the transition metal;
Removing a part of the conductive layer using a laser to form a substrate with an electrode having a separation groove; and
And a photoelectric conversion layer forming step of forming the photoelectric conversion layer on the substrate with electrodes by a vapor deposition method. 11. The method for manufacturing a solar cell submodule according to claim 10 , wherein the compound semiconductor contains a group Ib element, a group IIIb element, and a group VIb element. The method for manufacturing a solar cell submodule according to claim 10 or 11 , wherein, in the conductive layer nitriding step, the transition metal nitride is formed by nitrogen plasma treatment. In the conductive layer nitriding step, the sun according to the formation of nitrides of the transition metals, in claim 10 or 11, characterized in that under conditions of nitrogen was mixed in the sputtering gas is carried out by reactive sputtering Manufacturing method of battery submodule. The method of manufacturing a solar cell submodule according to claim 10 , wherein the laser has a wavelength of 532 nm or 1064 nm.