JP2009164250A - Method of forming conduction separating portion of transparent conductive oxide film, and multi-junction photoelectric conversion device manufactured by using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of forming a conduction separating portion of a transparent conductive oxide film in which a decrease in power generation efficiency can be suppressed by dividing an intermediate contact layer without affecting a base layer and suppressing a current leak from the intermediate contact layer. <P>SOLUTION: Disclosed is the method of forming the conduction separating portion of the transparent conductive oxide film in which the conduction separating portion is formed on the transparent conductive oxide film forming the intermediate contact layer 11 of a thin-film solar cell module 1, the method being characterized in that an etchant for etching the transparent conductive oxide film is jetted in fine droplets by an ink jetting method to adhere to a position of the transparent conductive oxide film where an intermediate separating groove 23 is formed. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for forming a conductive separation portion of a transparent conductive oxide film and a multi-junction photoelectric conversion device manufactured using the same.

  Conventionally, a multijunction photoelectric conversion device, for example, a multijunction comprising a top cell that is a photoelectric conversion layer using amorphous silicon (a-Si) and a bottom cell that is a photoelectric conversion layer using microcrystalline silicon (μc-Si). Type thin-film silicon solar cell, the intermediate contact layer sandwiched between the top cell and the bottom cell reflects the short wavelength light that is not absorbed by the top cell to the top cell side, thereby increasing the amount of power generated by the top cell. have. The intermediate contact layer is formed using a transparent conductive oxide such as ZnO or ITO as a main component.

This multi-junction thin film silicon solar cell constitutes an integrated module in which a plurality are integrated and each connected in series. That is, each of the plurality of silicon solar cells is electrically connected to the transparent electrode layer of the silicon solar cell in which the back electrode layer is adjacent.
The connection is performed by filling the connection groove that penetrates the top cell, the intermediate contact layer, and the bottom cell with the components constituting the back electrode.
The transparent conductive oxide constituting the intermediate contact layer has conductivity. Therefore, since the intermediate contact layer and the connection groove are also electrically connected, there is a problem that power generated in the top cell and the bottom cell leaks from the connection groove through the intermediate contact layer.

When the current leaks in this way, the power generation performance is reduced correspondingly. Therefore, it has been desired to provide a method for suppressing the current leak through the intermediate contact layer. As this method, a method of processing a separation groove for separating the intermediate contact layer is widely used.
The separation groove is desirably as narrow as possible in order to suppress power generation loss. For this reason, as shown in Patent Document 1 and Patent Document 2, for example, a method of irradiating a laser beam condensed on the intermediate contact layer and removing it is generally used.

These form separation grooves that reach the transparent electrode layer through the intermediate contact layer and the top cell by laser light (Patent Document 1), or form separation grooves that include a part of the top cell from the intermediate contact layer ( Patent Document 2).
Since the intermediate contact layer is transparent, the top cell made of a-Si substantially absorbs the laser beam. The laser light is absorbed by the a-Si of the top cell to be converted into heat, resulting in a very high temperature locally. As a result, the intermediate contact layer is scattered by the evaporation pressure generated by the decomposition of hydrogen or the like that has melted and bonded to the a-Si, thereby forming a separation groove.

Further, although the target is not the intermediate contact layer, as a method for patterning the film, for example, a method shown in Patent Document 3 or Patent Document 4 has been proposed.
Patent Document 3 discloses that a transparent conductive ink containing ultrafine particles formed of an oxide-based transparent conductive material is ejected from a nozzle to form a transparent conductive layer only in a necessary portion. The pattern is formed by not forming the transparent conductive layer at the place to be removed.
In Patent Document 4, a polymer hot-melt ink that serves as an etching mask is applied to a metal oxide film such as tin oxide by inkjet, and hydrogen is generated with metal powder and an etching solution, which is covered with the mask. A portion of the metal oxide film not formed is removed to form a pattern.

JP 2002-261308 A JP 2006-313872 A JP 09-320363 A JP 2000-31131 A

  By the way, what forms a separation groove | channel by the laser beam as shown in patent document 1 and patent document 2 becomes very high locally because a laser beam is absorbed by a-Si which forms a top cell. Therefore, a-Si has undergone a structural change due to atomic diffusion in the peripheral portion of the groove, resulting in deterioration of power generation performance, and the top cell itself may have a low resistance and become a current leakage path. Although what is shown in Patent Document 2 reduces the range affected by heat on the separation groove, this is not sufficient, and there is a need for a method of processing the separation groove that does not generate a new current leakage path. It was.

In order to form an intermediate contact layer having a separation groove so as not to affect the top cell, it is conceivable to use the method disclosed in Patent Document 3.
However, this method is a method of forming a transparent conductive oxide film by an ink jet discharge method. However, when forming a separation groove with a small groove width, that is, when a region where a transparent conductive oxide film is not formed is small. However, since the film forming portion is increased accordingly, there is a problem that it takes a long time for the film forming process.

It is also conceivable to use the method disclosed in Patent Document 4.
However, this method requires a step of forming an etching mask before etching and a step of removing the etching mask after etching, which requires extra work time. In addition, when forming a separation groove having a groove width as small as possible, that is, when a region where a transparent conductive oxide film is not formed is small, the range of the etching mask is widened. When applied to the separation groove, there is a problem that it takes a lot of work time.
Further, when an intermediate contact layer is formed, a transparent electrode layer composed of substantially the same material is formed. Therefore, when etching is performed by immersing in an etching solution, the transparent electrode layer is formed from the periphery of the substrate. There exists a problem that an etching liquid acts on an electrode layer and damages a transparent electrode layer.

  In view of the above problems, the present invention provides a transparent conductive oxide film that can divide an intermediate contact layer without affecting the underlying layer, suppress current leakage in the surface direction from the intermediate contact layer, and suppress a decrease in power generation efficiency. It is an object of the present invention to provide a conductive separation portion forming method and a conductive separation portion forming apparatus.

In order to achieve the above object, the present invention provides the following means.
The method for forming a conductive separation portion of a transparent conductive oxide film according to the present invention is a method for forming a conductive separation portion of a transparent conductive oxide film in which a conductive separation portion is formed on a transparent conductive oxide film constituting an intermediate contact layer in a multi-junction photoelectric conversion device. An etching solution that erodes the transparent conductive oxide film is ejected in the form of fine droplets by an ink jet method, and is deposited on the transparent conductive oxide film at a position where the conductive separation portion is formed.

According to the present invention, since the etching solution is ejected by the ink jet method, it can be accurately deposited at a predetermined position. When the sprayed etching solution is deposited on the transparent conductive oxide film, the etching solution erodes the deposited portion of the transparent conductive oxide film to form a recess.
Since the etching solution is deposited on the transparent conductive oxide film at a position where the conductive separation portion is formed, a concave portion is formed along the conductive separation portion. At this time, by adjusting the amount of the etching solution to be deposited, the concave portion from which the transparent conductive oxide film has been completely removed can be formed.

  Etching of the etching solution is a chemical reaction and may generate heat during the reaction. Even in this case, a material that is much smaller than the heat generated by the laser beam can be selected. Therefore, the intermediate contact layer is divided by forming a conductive separation portion, that is, for example, a groove-shaped division groove in the intermediate contact layer without causing a new current leakage path by affecting the underlayer due to heat. be able to. As a result, current leakage from the intermediate contact layer in the surface direction can be suppressed or prevented, and a decrease in power generation efficiency of the multi-junction photoelectric conversion device can be suppressed.

Further, since the etching solution is deposited in the form of fine droplets, the range in which one drop of the etching solution erodes is limited. As a result, even in the case of a groove-shaped conductive separation portion having a narrow width, which is formed in a narrow range, etching can be performed by directly applying an etching solution without masking. The process of forming and the process of removing the etching mask are unnecessary, and the working time can be reduced accordingly.
As described above, after forming the intermediate contact layer, a conductive separation portion formed in a narrow range can be formed. Therefore, an efficient film forming method can be used for forming the intermediate contact layer, and a multi-junction photoelectric film can be used. The work time required for manufacturing the converter can be reduced.

In the case where the intermediate contact layer has a crystal structure, the crystal grain boundary is more easily eroded by the etching solution than the crystal part, and is eroded earlier than the crystal part. Thus, the erosion due to etching proceeds from the crystal grain boundary, so that the erosion of the crystal grain boundary ends before the erosion of the crystal portion ends. As a result, adjacent crystal parts are separated and are not in contact with each other, so that the conduction is cut off or becomes difficult. In this case, since the transparent conductive oxide film is not completely removed, that is, current leakage from the intermediate contact layer can be suppressed even when the crystal portion is partially left, the power generation of the multi-junction photoelectric conversion device can be performed with a small amount of etchant. Reduction in efficiency can be suppressed.
This is particularly effective when the transparent conductive oxide film is formed of columnar crystals such as ZnO (zinc oxide) in which the crystals extend in the vertical direction.

  The size of the conductive separation portion formed by etching can be adjusted by the film thickness of the transparent conductive oxide film and the deposition amount of the etching solution. The deposition amount of the etching solution is adjusted by the size of the droplet, the content of the etching component, the number of jets, and the like.

  In the above invention, a diluted acid or alkali solution may be used as the etching solution.

The transparent conductive oxide is generally known to be dissolved (corroded) in an acid solution or an alkali solution. Therefore, an appropriate acid solution or alkali solution is selected for the transparent conductive oxide of interest.
As the acid, hydrochloric acid, acetic acid, phosphoric acid, citric acid, oxalic acid, nitric acid, sulfuric acid and the like are used, and as the alkali, sodium hydroxide, potassium hydroxide, ammonium hydroxide (ammonia water) and the like are used.
In order to adjust the etching rate, a solvent such as an alcohol such as IPA (isopropyl alcohol) may be added to the acid solution or the alkali solution.

  In the invention described above, a viscosity adjusting material for adjusting the viscosity may be added to the etching solution.

If it does in this way, even if it is an etching liquid of the viscosity which is not suitable for an inkjet method, it can be used by adding a viscosity modifier. Moreover, since the spreading | diffusion at the time of deposition can be prescribed | regulated by an etching liquid with a viscosity, the deposition range of an etching liquid can be adjusted and the magnitude | size of a conductive isolation | separation part can be adjusted.
As the viscosity adjusting material, for example, PVA (polyvinyl alcohol) or the like is used.

  Moreover, in the said invention, it is suitable for the injection of the said etching liquid by the said inkjet method to be performed in multiple places simultaneously.

  If it does in this way, since the process of the electroconductive isolation | separation part is simultaneously performed in multiple places, work time can be reduced. That is, the conductive separation portion can be processed efficiently.

In this case, the etching solution is supplied, for example, by holding the substrate on which the transparent conductive oxide film constituting the intermediate contact layer in the multi-junction photoelectric conversion device is formed on the uppermost surface and eroding the transparent conductive oxide film. Using an apparatus in which an inkjet head attached with a nozzle that ejects the etching liquid in the form of fine droplets is opposed to the holding member and can be relatively repositioned within the surface of the holding member, the etching liquid is discharged from the nozzle. Do this by spraying. Then, a predetermined conductive separation portion is formed by changing the relative positional relationship between the inkjet head and the holding portion.
By providing a plurality of inkjet heads and / or providing a plurality of nozzles in the inkjet head, it is possible to spray the etching solution at a plurality of locations at the same time.

  A multi-junction photoelectric conversion device according to the present invention is manufactured using the above-described method for forming a conductive separation portion of a transparent conductive oxide film.

  It is possible to divide the intermediate contact layer by forming a conductive separation portion, that is, for example, a groove-shaped dividing groove in the intermediate contact layer without causing a new current leakage path by affecting the underlayer by heat. Since the method for forming a conductive separation part of a transparent conductive oxide film is used, current leakage from the intermediate contact layer can be suppressed or prevented, and a decrease in power generation efficiency of the multijunction photoelectric conversion device can be suppressed.

According to the present invention, the etching solution that erodes the transparent conductive oxide film is ejected in the form of fine droplets by the ink jet method, and is deposited on the position where the conductive separation portion of the transparent conductive oxide film is formed. The intermediate contact layer can be divided without.
Thereby, current leakage from the intermediate contact layer can be suppressed or prevented, so that reduction in power generation efficiency of the multi-junction photoelectric conversion device can be suppressed.

Embodiments of the present invention will be described below with reference to the drawings.
[First embodiment]
A method for forming a conductive separation portion of a transparent conductive oxide film according to a first embodiment of the present invention will be described with reference to FIGS.
FIG. 1 is a partial cross-sectional view schematically showing a cross section of a thin film solar cell module (multi-junction photoelectric conversion device) 1 manufactured by using the conductive separation portion forming method according to the present embodiment. The thin film solar cell module 1 has a structure in which thin film solar cells 5 are connected in series in a tandem manner on a substrate 3.

The thin-film solar cell module 1 has a tin oxide film (SnO ₂ ) on a translucent substrate 3 (at least 1 m on a side, for example: 1.4 m × 1.1 m × 3 mm to 4 mm soda glass substrate). A transparent electrode layer 7 which is a transparent and conductive layer as a main component is formed.
On the transparent electrode layer 7, a top cell 9 which is a photoelectric conversion layer made of amorphous silicon (a-Si) having a pin structure is formed. The top cell 9 has a higher resistance than the intermediate contact layer 11 and generates electric power from light in a specific wavelength region by the photovoltaic effect.

  On the top cell 9, an intermediate contact layer 11 having a function of reflecting a part of light incident from the substrate 3 side and transmitting a part thereof is formed. The intermediate contact layer 11 is composed, for example, of a zinc oxide (GZO; transparent conductive oxide) film doped with gallium Ga as a main component.

On the intermediate contact layer 11, a bottom cell 13 which is a photoelectric conversion layer made of microcrystalline silicon (μc-Si) having a pin structure is formed. The bottom cell 13 absorbs light in a wavelength range different from the wavelength range of light converted by the top cell 9 to generate electric power.
On the bottom cell 13, a laminated structure of a metal material such as silver (Ag), titanium (Ti) or aluminum (Al), or a conductive oxide film such as ITO or ZnO and a metal material such as silver, titanium or aluminum. A back electrode layer 15 made of is formed.

The thin-film solar cell module 1 includes a transparent electrode separation groove 17 that has an opening on the transparent electrode layer 7 and a bottom surface on the substrate 3, and divides the transparent electrode layer 7, a back electrode layer 15, and a bottom cell 13. Having an opening at the interface between the transparent electrode film 7 and the top cell 9, a connection groove 19 having a bottom surface at the interface between the transparent electrode film 7 and the top cell 9, and an opening at the surface of the back electrode layer 15. A cell separation groove 21 having a bottom surface at the interface and an intermediate separation groove (conductive separation portion) 23 for separating the intermediate contact layer 11 are provided.
The transparent electrode separation groove 17, the connection groove 19, the cell separation groove 21, and the intermediate separation groove 23 are provided in parallel to each other and extend in a direction perpendicular to the paper surface of FIG.

A material constituting the top cell 9 is embedded in the transparent electrode separation groove 17, and the divided transparent electrode layers 7 are electrically insulated from each other.
The cell separation groove 21 is provided at a location different from the transparent electrode separation groove 17. The cell separation groove 21 divides the top cell 9, the intermediate contact layer 11, the bottom cell 13, and the back electrode layer 15 between the adjacent thin film solar cells 5.
The cell separation grooves 21 electrically insulate the back electrode layers 15 and the intermediate contact layers 11 between the adjacent thin film solar cells 5.

  The connection groove 19 is provided between the transparent electrode separation groove 17 and the cell separation groove 21. The connection groove 19 is filled with a material constituting the back electrode layer 15 and electrically connects the back electrode layer 15 and the transparent electrode layer 7 of the adjacent thin-film solar battery cell 5. That is, the adjacent thin film photovoltaic cells 5 are electrically connected in series.

  The intermediate separation groove 23 is provided between the transparent electrode separation groove 17 and the connection groove 19. The intermediate separation groove 23 separates the intermediate contact layer 11. The intermediate separation groove 23 has an opening at the interface between the intermediate contact layer 11 and the bottom cell 13 and has a bottom surface at the interface between the intermediate contact layer 11 and the bottom cell 13. A material constituting the bottom cell 13 is embedded in the intermediate separation groove 23 to electrically insulate the divided intermediate contact layers 11 from each other.

Hereinafter, the manufacturing process of the thin film solar cell module 1 will be described mainly with respect to the method for forming the intermediate separation groove 23.
First, a film mainly composed of tin oxide (SnO ₂ ) is formed on the substrate 3 as the transparent electrode layer 7 at a film thickness of about 500 nm to 800 nm and about 500 ° C. using a thermal CVD apparatus. At this time, a texture with appropriate unevenness is formed on the surface of the transparent electrode layer 7.
Further, an alkali barrier film (not shown) may be formed between the substrate 3 and the transparent electrode layer 7. As the alkali barrier film, a silicon oxide film (SiO ₂ ) is formed at a temperature of about 500 ° C. in a thermal CVD apparatus at 50 nm to 150 nm.

Thereafter, the substrate 3 is placed on an XY table, and the first harmonic (1064 nm) of the YAG laser is incident from the film surface side of the transparent electrode layer 7.
The laser power is adjusted so as to be suitable for the processing speed, and the transparent electrode layer 7 is moved relative to the direction perpendicular to the serial connection direction of the thin-film solar cells 5 by moving the substrate 3 and the laser light relatively transparent. An electrode separation groove 17 is formed. The transparent electrode separation groove 17 is laser etched into a strip shape having a predetermined width (for example, about 6 mm to 15 mm).

Next, a p-layer film / i-layer film / n-layer film constituting the top cell 9 is sequentially formed by a plasma CVD apparatus at a reduced pressure atmosphere: 30 to 1000 Pa and a substrate temperature: about 200 ° C.
The top cell 9 is formed on the transparent electrode layer 7 using SiH ₄ gas and H ₂ gas as main raw materials. At this time, the transparent electrode separation groove 17 is filled with pin-type amorphous Si.
In the top cell 9, a p layer, an i layer, and an n layer are stacked in this order from the sunlight incident side. The structure and thickness of these layers are, for example, p layer: amorphous SiC doped with boron (B) as a main component and a film thickness of 10 nm to 30 nm, i layer: amorphous Si as a main component, and a film thickness of 200 nm to 350 nm, n Layer: Mainly composed of microcrystalline Si doped with phosphorus (P) and having a film thickness of 30 nm to 50 nm.
A buffer layer may be provided between the p-layer film and the i-layer film in order to improve the interface characteristics.

  Next, a ZnO (GZO) film doped with Ga (gallium) is formed on the top cell 9 with a film thickness of 20 nm to 100 nm, for example, by a sputtering apparatus, and the intermediate contact layer 11 is formed.

Thereafter, the substrate 3 is placed on the table 25 (the intermediate contact layer 11 is located on the upper surface), and an etching solution is sprayed from the nozzle 29 of the ink jet head 27 placed above the table 25.
As the etching solution, 0.05 to 30 wt% hydrochloric acid aqueous solution or 0.1 to 60 wt% acetic acid aqueous solution is used.
In addition, when the viscosity of an etching liquid is low and it is difficult to inject from the nozzle 29 effectively, you may adjust a viscosity by adding PVA (polyvinyl alcohol) etc., for example.

When this etching solution is deposited on the surface of the intermediate contact layer 11, the etching solution erodes the deposited portion of GZO. For example, when an aqueous hydrochloric acid solution is used, a reaction of ZnO + 2HCl → ZnCl ₂ + H ₂ O results in the formation of ZnCl ₂ and water that dissolve in water.
Although generated heat is generated, it is consumed by the latent heat of vaporization of water, and the temperature rise due to this is slight. Therefore, there is no possibility of changing the amorphous Si of the top cell 9.

  The appropriate amount of liquid (weight of one drop) of a normal industrial inkjet head nozzle is about 30 to 100 ng. For example, when a 15 wt% hydrochloric acid aqueous solution is used and 100 ng droplets are sprayed and deposited on a ZnO film and reacted, an opening 31 having a diameter of about 10 μm can be formed. By ejecting droplets that can erode the thickness of the intermediate contact layer 11, the opening 31 is formed to a thickness that reaches the interface with the top cell 9, as shown in FIG.

  Since amorphous Si constituting the top cell 9 does not dissolve in dilute hydrochloric acid, the groove is formed up to the inside of the top cell 9, that is, the top cell 9 is not damaged. If the etching solution is supplied excessively, the etching proceeds in the direction in which the diameter of the opening 31 is increased along the surface of the top cell 9. The hydrogen chloride gas contained in hydrochloric acid and the water produced by the reaction evaporate, and the hydrogen chloride gas naturally decreases, so the reaction stops immediately and there is no significant effect.

Since the amount of etching is determined by the acid concentration and the volume (or weight) of the droplets, the etching depth and the opening area can be controlled by adjusting them.
Accordingly, the acid concentration of the spraying etchant and the volume (or weight) of the droplets are appropriately set according to the film thickness of the intermediate contact layer 11 and the width of the intermediate separation groove 23.
For example, when a 20 wt% HCl aqueous solution is used as an etchant, 100 ng contains 3 × 10 ¹⁴ HCl molecules. When all of this reacts with ZnO, 1.5 × 10 ¹⁴ (3 × 10 ⁻⁹ cc in volume) ZnO from the reaction formula ZnO + 2HCl → ZnCl ₂ + H ₂ O will be subjected to the reaction. This corresponds to an opening having a diameter of about 200 μm with respect to ZnO having a thickness of 100 nm. Actually, the reaction heat is accompanied by a decrease in the ability of the etching solution due to evaporation of the generated water and volatilization of hydrogen chloride gas. Increasing the opening area can be achieved by increasing the volume or concentration of the droplet. In addition, since the power generation loss of the thin film solar cell module 1 can be suppressed, the width | variety of the intermediate separation groove 23 is so preferable that it is small.

Subsequently, when the inkjet head 27 is moved by a distance slightly smaller than the diameter of the opening 31 and the etching solution is sprayed from the nozzle 29 at that position, the opening 31 can be formed in the adjacent position, and this is repeated. As shown in FIG. 4, an intermediate separation groove 23 can be formed.
Since the relative position between the intermediate contact layer 9 and the nozzle 29 may be moved, the table 25 or the substrate 3 may be moved with the inkjet head 27 fixed. Further, the inkjet head 27 and the table 25 or the substrate 3 may be moved together.

  At this time, as shown in FIG. 5, a plurality of, for example, two nozzles 29 may be provided adjacent to the inkjet head. In this case, the intermediate separation groove 23 is formed wider than that under the same conditions as in FIG. 4, so that the intermediate contact layer 11 can be more reliably separated.

In this way, the etching solution is ejected in the form of fine droplets from the nozzle 29 using the ink jet method, so that it can be accurately applied to a predetermined position, and a single drop of etching solution can be applied. The range of erosion is limited.
As a result, the narrow intermediate separation groove 23 can be accurately formed at a predetermined position, and the intermediate separation groove 23 can be formed without performing masking that has been used in the conventional photolithography method or the like. .
Therefore, the intermediate contact layer 11 can be reliably separated, and the process of forming the etching mask and the process of removing the etching mask are not required, and the working time can be reduced accordingly.

When one intermediate separation groove 23 is thus formed, the inkjet head 27 is moved by the cell pitch SP, and the adjacent intermediate separation groove 23 is formed by the above-described procedure (see FIG. 2). By repeating this, a predetermined number, for example, 90 intermediate separation grooves 23 are formed in the intermediate contact layer 11.
At this time, as shown in FIG. 6, a plurality of, for example, three inkjet heads 27 may be provided with a distance that is a multiple of the cell pitch SP. In this way, since the intermediate separation groove 23 can be processed simultaneously and in parallel by the respective ink jet heads, the working time can be shortened.
For example, if the number of grooves to be processed is 90 and the cell pitch is 10 mm, the inkjet heads 27 are installed so that the distance between them is 300 mm. What is necessary is that the working time can be reduced to one-third as compared with the case where the number of the inkjet heads 27 is one.

Further, as shown in FIG. 7, a plurality of, for example, three nozzles 29 may be provided in one inkjet head 27 separated by a distance of the cell pitch SP. In this way, since the intermediate separation groove 23 can be processed simultaneously by the nozzles 29, the working time can be shortened.
For example, in the same example as described above, when the three nozzles 29 are provided at an interval of 10 mm, the three intermediate separation grooves 23 can be processed by one movement of the inkjet head 27. It can be reduced to 1/3 compared to the one provided.
If a plurality of ink jet heads 27 are provided, and a plurality of nozzles 29 are provided in each ink jet head 27, higher speed processing can be performed.

In this embodiment, a hydrochloric acid solution is used as an etching solution, but a solution of acetic acid, phosphoric acid, citric acid, oxalic acid, nitric acid, sulfuric acid, or the like may be used. Moreover, you may use alkaline solutions, such as sodium hydroxide, potassium hydroxide, and ammonium hydroxide (ammonia water).
In order to adjust the etching rate, a solvent such as an alcohol such as IPA (isopropyl alcohol) may be added to the acid solution or the alkali solution.
Further, although the transparent conductive oxide of the intermediate contact layer 11 is ZnO, it may be ITO or SnO ₂ . Alternatively, a composite oxide in which these are used as a base material and another oxide is added may be used.
For ITO, an aqueous hydrochloric acid solution or an aqueous solution obtained by adding FeCl ₃ to an aqueous hydrochloric acid solution can be used as an etching solution.

When this etching operation is completed, the surface of the intermediate contact layer 11 is washed with water. Thus, ZnCl ₂ remaining as a residue can be dissolved and removed.
ZnCl ₂ has a melting point of 317 ° C. and can be removed by gasification in a high temperature vacuum.
Further, zinc acetate remaining as a residue when an acetic acid solution is used as an etching solution can be removed by washing with water.
In the case where water washing brings about oxidation of the top cell 9, for example, washing with IPA (isopropyl alcohol) may be performed using an ink jet method and self-evaporated with hot air of about 70 ° C. and dried. In this case, an etching solution that dissolves in IPA is used.

Next, a microcrystalline silicon thin film as a bottom cell 13 is formed on the intermediate contact layer 11 with a plasma CVD apparatus at a reduced pressure atmosphere: 3000 Pa or less, a substrate temperature: about 200 ° C., and a plasma generation frequency: 40 MHz to 100 MHz. Crystal p layer film / microcrystal i layer film / microcrystal n layer film are sequentially formed.
Each layer constituting the bottom cell 13 has a microcrystalline p layer: a microcrystalline SiC doped with boron (B) as a main component and a film thickness of 10 nm to 50 nm, and a microcrystalline i layer: a microcrystalline Si as a main component, a film thickness of 1.2 μm. .About.3.0 .mu.m, microcrystalline n layer: mainly composed of microcrystalline Si doped with phosphorus (P) and having a thickness of 20 nm to 50 nm.

  In forming a microcrystalline silicon thin film, particularly a microcrystalline i-layer film, by plasma CVD, the distance d between the plasma discharge electrode and the surface of the substrate 3 is preferably 3 mm or more and 10 mm or less. If it is smaller than 3 mm, it is difficult to keep the distance d constant from the accuracy of each component device in the film forming chamber corresponding to the large substrate, and there is a possibility that the discharge becomes unstable because it is too close. When it is larger than 10 mm, it is difficult to obtain a sufficient film forming speed (1 nm / s or more), and the uniformity of the plasma is lowered and the film quality is lowered by ion bombardment.

  Thereafter, the substrate 3 is set on an XY table, and is incident from the substrate surface side using the second harmonic (532 nm) of the laser diode pumped YAG laser. Laser etching is performed so that the connection groove 19 is formed at a position of about 100 to 150 μm on the lateral side of the transparent electrode separation groove 17 by adjusting the laser power so that the pulse oscillation frequency is 10 to 20 kHz and the processing speed is appropriate.

  An Ag film / Ti film is formed as a back electrode layer 15 on the bottom cell 13 by a sputtering apparatus. The back electrode layer 15 is formed by laminating an Ag film: 200 to 500 nm, and a Ti film having a high anticorrosive effect: 10 to 20 nm for protecting the Ag film in this order. For the purpose of reducing contact resistance between the n layer of the bottom cell 13 and the back electrode layer 15 and improving light reflection, a GZO film is formed between the bottom cell 13 and the back electrode layer 15 with a film thickness of 50 to 100 nm using a sputtering apparatus. May be provided. Moreover, it is good also as Al film | membrane: 250 nm or more and 350 nm or less instead of Ti film | membrane. By using Ti as Al, it is possible to reduce the material cost while maintaining the anticorrosion effect.

  Thereafter, the substrate 3 is set on an XY table and is incident from the substrate 3 side using the second harmonic (532 nm) of the laser diode pumped YAG laser. The laser light is absorbed by the top cell 9, and the back electrode layer 15 is exploded and removed using the high gas vapor pressure generated at this time. Laser etching is performed so that the cell separation groove 21 is formed at a position of about 250 to 400 μm on the lateral side of the transparent electrode separation groove 17 by adjusting the laser power so that the processing speed is appropriate as pulse oscillation: 1 kHz to 10 kHz.

  Since the thin film solar cell module 1 formed in this way can divide the intermediate contact layer 11 without affecting the top cell (underlayer) 9, current leakage from the intermediate contact layer 11 in the plane direction Can be suppressed or prevented. Thereby, the fall of the power generation efficiency of the thin film solar cell module 1 can be suppressed.

[Second Embodiment]
Next, a second embodiment of the present invention will be described with reference to FIGS.
The basic configuration of this embodiment is the same as that of the first embodiment, but the method for forming the intermediate separation groove 23 is different from that of the first embodiment. Therefore, in the present embodiment, the difference will be mainly described, and description of other overlapping items will be omitted.
In addition, about the component same as 1st embodiment, the same code | symbol is attached | subjected and the description is abbreviate | omitted.

The ZnO film forming the intermediate contact layer is a columnar crystal extending in the vertical direction as shown in FIG.
At this time, the crystal grain boundary, which is the gap between the columnar crystals, has many defects and poor crystallinity, so that the etching rate is faster than the crystal part. When the etching solution is applied to the intermediate contact layer 11, the crystal grain boundary part is etched faster than the crystal part. Therefore, even if the crystal part remains, the crystal grain boundary part is etched as shown in FIG. Is done.

When the crystal grain boundary portion is etched, the crystal grains 33 are in an isolated state or a crystal grain boundary is deeply cut. In other words, a gap is formed between the crystal grains 33. The grain size of the crystal grains 33 is about 0.1 to 0.3 μm.
That is, a recessed portion 35 having a gap between the crystal grains 33 is formed in a portion where the etching solution is deposited. In the recessed portion 35, the adjacent crystal grains 33 are separated from each other and are not in contact with each other, so that the conduction is cut off or becomes difficult.

The method for forming a conductive separation portion of a transparent conductive oxide film according to the present embodiment is performed in the same manner as in the first embodiment, but the amount of a substance involved in etching contained in the etching solution sprayed from the nozzle 29 is reduced. I have to.
For example, when a hydrochloric acid aqueous solution of 5 wt% (15 wt% in the first embodiment) is used and a 100 ng droplet is sprayed and deposited on a ZnO film, the recess 35 having a diameter of about 10 μm can be formed. .
The recess 35 is formed and connected to form the intermediate separation groove 23. In this case, as shown in FIG. 8, the intermediate separation grooves 23 may be formed by a plurality of rows of recessed portions 35.

Thus, in this embodiment, since the intermediate contact layer 11 can be substantially separated by a small amount of etching solution, current leakage from the intermediate contact layer 11 in the surface direction can be suppressed. In addition, the work time required for forming the intermediate separation groove 23 can be shortened. Further, since the amount of ZnCl _{2 to} be removed is reduced, the burden of cleaning can be reduced.
Thereby, the fall of the power generation efficiency of the thin film solar cell module 1 can be suppressed.

  The technical scope of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.

It is a fragmentary sectional view which shows roughly the cross section of the thin film solar cell module manufactured using the electrically conductive isolation | separation part formation method concerning 1st embodiment of this invention. It is a fragmentary sectional view which shows the implementation condition of the conductive isolation | separation part formation method concerning 1st embodiment of this invention. It is sectional drawing which shows the opening formed with the electrically conductive isolation | separation part formation method concerning 1st embodiment of this invention. It is a partial top view which shows the intermediate | middle separation groove formed with the electrically conductive separation part formation method concerning 1st embodiment of this invention. It is a fragmentary top view which shows another aspect of the intermediate | middle separation groove formed with the electrically conductive separation part formation method concerning 1st embodiment of this invention. It is a fragmentary top view which shows the state in which an intermediate | middle separation groove is formed with the electrically conductive separation part formation method concerning 1st embodiment of this invention. It is a fragmentary top view which shows another state in which an intermediate | middle separation groove is formed with the electrically conductive separation part formation method concerning 1st embodiment of this invention. It is a fragmentary top view which shows the intermediate separation groove formed with the electrically conductive separation part formation method concerning 2nd embodiment of this invention. It is sectional drawing which shows the state of an intermediate contact layer. It is sectional drawing which shows the state in which the intermediate separation groove was formed with the conductive separation part formation method concerning 2nd embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Thin film solar cell module 3 Substrate 11 Intermediate contact layer 23 Intermediate separation groove

Claims (5)

  A method for forming a conductive separation portion of a transparent conductive oxide film that forms a conductive separation portion on a transparent conductive oxide film that constitutes an intermediate contact layer in a multi-junction photoelectric conversion device, wherein an etching solution that erodes the transparent conductive oxide film is inkjetted A method for forming a conductive separation portion of a transparent conductive oxide film, wherein the conductive separation portion is ejected in the form of fine droplets by a method and deposited on the transparent conductive oxide film at a position where the conductive separation portion is formed.   The method for forming a conductive separation portion of a transparent conductive oxide film according to claim 1, wherein a diluted acid or alkali solution is used as the etching solution.   The method for forming a conductive separation portion of a transparent conductive oxide film according to claim 1, wherein a viscosity adjusting material for adjusting the viscosity is added to the etching solution.   The method for forming a conductive separation portion of a transparent conductive oxide film according to any one of claims 1 to 3, wherein the jetting of the etching solution by the ink jet method is performed at a plurality of locations at the same time. A multijunction photoelectric conversion device manufactured using the method for forming a conductive separation portion of a transparent conductive oxide film according to any one of claims 1 to 4.

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