Groove forming method and groove forming device

Abstract

The present invention relates to a method and apparatus for forming grooves, wherein the second and third layers of a layer structure (thin-film solar cell) comprising a first layer, a second layer (semiconductor layer) formed on the first layer, and a third layer (transparent electrode layer) formed on the second layer are simultaneously laser processed to form grooves, thereby reducing peeling of the third layer. In the P3 process, the light absorbing layer (25) and the transparent conductive film (27) of the layer structure comprising a back electrode layer (23), a light absorbing layer (25) formed on the back electrode layer (23), and a transparent conductive film (27) formed on the light absorbing layer (25) are simultaneously laser processed to form third dividing grooves (27a). In the first process, a ventilation channel (33) penetrating to the light absorbing layer (25) is formed in a portion of the transparent conductive film (27) where the groove is to be formed. In the second process, after the first process, the portion (25b) of the light absorbing layer (25) where the groove is to be formed and the portion (27b) of the transparent conductive film (27) where the groove is to be formed are laser processed to form the third dividing grooves (27a).

Description

Technical Field

[0001] The present invention relates to a method and apparatus for forming grooves by simultaneously laser processing the second and third layers of a layer structure including a first layer, a second layer formed on the first layer, and a third layer formed on the second layer to form grooves. Background Art

[0002] The thin-film solar cell is constructed by laminating a lower electrode layer, a semiconductor layer, and an upper electrode layer on a glass substrate.

[0003] An example of a thin-film solar cell manufacturing process will be described.

[0004] First, a glass substrate is prepared.

[0005] Next, a lower electrode layer is formed on the glass substrate.

[0006] Then, the lower electrode layer is patterned by groove processing (P1 step).

[0007] Next, a semiconductor layer is formed on the patterned lower electrode layer.

[0008] Then, the semiconductor layer is patterned by groove processing (P2 step).

[0009] Next, an upper electrode layer is formed on the patterned semiconductor layer.

[0010] Finally, the upper electrode layer and the semiconductor layer are patterned by groove processing (P3 step).

[0011] A solar cell processing method is known in which the above-mentioned steps P1, P2, and P3 are performed by laser scribing (for example, see Patent Document 1).

[0012] Prior art literature

[0013] Patent Literature

[0014] Patent Document 1: Japanese Patent Application Laid-Open No. 2011-189408.

[0015] Problems to be solved by the invention

[0016] The upper electrode layer is made of, for example, a transparent conductive oxide (TCO) that is translucent to light within a specific wavelength range. Therefore, when the P3 process is performed by laser scribing, the following problems may occur.

[0017] That is, the laser light transmitted through the upper electrode layer is mainly absorbed by the semiconductor layer, causing a portion of the semiconductor layer to evaporate and generate gas. This gas causes the upper electrode layer to separate from the semiconductor layer, resulting in a decrease in the quality of the thin-film solar cell.

[0018] use Figure 12 and Figure 13 Let's illustrate this example. Figure 12 It is a schematic plan view showing the P3 step of the reference example. Figure 13 This is a top view photograph showing the reference example after the P3 process. Figure 12 As shown in FIG. 1 , when the dividing grooves 41 are formed in the transparent conductive film 27 (upper electrode layer) and the light absorbing layer (not shown) thereunder by laser processing, part of the light absorbing layer evaporates to generate gas. As a result, as shown in FIG. Figure 13 As shown in FIG. 1 , the transparent conductive film is peeled off in a plurality of portions around the dividing grooves in a plan view. Summary of the Invention

[0019] The object of the present invention is to reduce the peeling of the third layer in a method for forming a groove and a device for forming a groove, in which a groove is formed by simultaneously laser processing the second layer and the third layer of a layer structure comprising a first layer, a second layer formed on the first layer, and a third layer formed on the second layer.

[0020] Solutions to Problems

[0021] Hereinafter, a plurality of embodiments will be described as solutions to the problems. These embodiments can be arbitrarily combined as needed.

[0022] One aspect of the present invention relates to a method for forming a groove, comprising simultaneously laser processing the second and third layers of a layer structure comprising a first layer, a second layer formed on the first layer, and a third layer formed on the second layer to form a groove. The method comprises the following steps.

[0023] ◎In the first step, a ventilation channel is formed in a portion of the third layer where the groove is to be formed, penetrating to the second layer.

[0024] ◎The second step is to form grooves by laser processing the portion of the second layer where the grooves are to be formed and the portion of the third layer where the grooves are to be formed after the first step.

[0025] In this method, since the ventilation channels are pre-formed in the first step, when the second and third layers are laser processed in the second step, the gas generated from the second layer is discharged to the outside through the ventilation channels. As a result, the third layer is less likely to peel off.

[0026] The layer structure may be a thin film solar cell, the second layer may be a semiconductor layer, and the third layer may be a transparent electrode layer.

[0027] The slot may extend long in one direction.

[0028] In the first step, the ventilation channel may be formed along a portion of the third layer where the groove is to be formed.

[0029] In this method, the gas generated from the second layer is efficiently discharged to the outside through the ventilation channel.

[0030] In the first process, the ventilation channel may be formed along two long edges of the portion of the third layer where the groove is to be formed.

[0031] In this method, the gas generated from the second layer is efficiently discharged to the outside through the ventilation channel.

[0032] In the first step, the ventilation channel may be formed along the center in the width direction of the portion of the third layer where the groove is to be formed.

[0033] In this method, the gas generated from the second layer is efficiently discharged to the outside through the ventilation channel.

[0034] The first step can be performed by laser processing.

[0035] In this method, since the first step and the second step are performed by laser processing, a common laser processing device can be used.

[0036] Another aspect of the present invention relates to a groove forming apparatus that forms grooves by simultaneously laser processing the second and third layers of a layer structure including a first layer, a second layer formed on the first layer, and a third layer formed on the second layer.

[0037] The apparatus includes a first processing device and a second processing device. The first processing device forms a vent passage extending through a portion of the third layer where the groove is to be formed. The second processing device forms the groove by laser processing the portion of the second layer where the groove is to be formed and the portion of the third layer where the groove is to be formed.

[0038] In this device, since the ventilation channel is formed by the first processing device, when the second processing device laser processes the second and third layers, the gas generated from the second layer is discharged to the outside through the ventilation channel. As a result, the peeling of the third layer is reduced.

[0039] The slot may extend long in one direction.

[0040] The first processing device may form the ventilation channel along a portion of the third layer where the groove is to be formed.

[0041] In this device, the gas generated from the second layer is efficiently discharged to the outside through the ventilation channel.

[0042] The first processing device may form the ventilation channel along two long edges of the portion of the third layer where the groove is to be formed.

[0043] In this device, the gas generated from the second layer is efficiently discharged to the outside through the ventilation channel.

[0044] The first processing device may form the ventilation channel along the center in the width direction of the portion of the third layer where the groove is to be formed.

[0045] In this device, the gas generated from the second layer is efficiently discharged to the outside through the ventilation channel.

[0046] The first processing device can also perform laser processing.

[0047] In this apparatus, since the first processing device and the second processing device perform laser processing, a common laser processing device can be utilized.

[0048] Effects of the Invention

[0049] In the groove forming method and groove forming apparatus of the present invention, when the second and third layers are laser processed, gas generated from the second layer is exhausted to the outside through the vent channel, resulting in reduced peeling of the third layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 It is a schematic diagram of the laser processing apparatus of the first embodiment.

[0051] Figure 2 It is a schematic cross-sectional view showing the steps of manufacturing the solar cell according to the first embodiment.

[0052] Figure 3 It is a schematic cross-sectional view showing the state before the P3 step.

[0053] Figure 4 This is a schematic cross-sectional view showing the first step of the P3 step.

[0054] Figure 5 It is a schematic plan view showing the first step of the P3 step.

[0055] Figure 6 It is a schematic cross-sectional view showing the second step of the P3 step.

[0056] Figure 7 This is a top view of the first embodiment after the P3 process.

[0057] Figure 8 This is a schematic cross-sectional view showing the first step of the P3 step of the second embodiment.

[0058] Figure 9It is a schematic plan view showing the first step of the P3 step.

[0059] Figure 10 This is a schematic cross-sectional view showing the first step of the P3 step.

[0060] Figure 11 This is a top view of the second embodiment after the P3 process.

[0061] Figure 12 It is a schematic plan view showing the P3 step of the reference example.

[0062] Figure 13 This is a top view photograph of the reference example after the P3 process. DETAILED DESCRIPTION

[0063] 1. First Implementation

[0064] (1) Overall structure of laser processing equipment

[0065] Figure 1 The entire structure of a laser processing apparatus 1 (an example of a first processing apparatus and a second processing apparatus) according to an embodiment of the present invention is shown. Figure 1 It is a schematic diagram of a laser processing apparatus according to a first embodiment of the present invention.

[0066] The laser processing apparatus 1 includes a laser device 3. The laser device 3 includes a laser oscillator 15 for irradiating a substrate 21 (described later) with laser light, and a laser control unit 17. The laser control unit 17 can control the driving of the laser oscillator 15 and the laser power.

[0067] The laser device 3 includes an optical transmission system 5 for transmitting laser light to a mechanical drive system described later. The optical transmission system 5 includes, for example, a condenser lens 19, a plurality of reflection mirrors (not shown), a prism (not shown), and the like.

[0068] The laser processing apparatus 1 includes a drive mechanism 11 that changes the focusing angle of laser light by moving the position of a lens in the optical axis direction.

[0069] The laser processing apparatus 1 includes a processing table 7 on which a substrate 21 is mounted. The processing table 7 is moved by a table drive unit 13. The table drive unit 13 includes a moving device (not shown) that moves the processing table 7 horizontally relative to a base (not shown). The moving device is a well-known mechanism including a guide rail, a motor, and the like.

[0070] The laser processing apparatus 1 includes a control unit 9. The control unit 9 is a computer system comprising a processor (e.g., a CPU), a storage device (e.g., a ROM, RAM, HDD, SSD, etc.), and various interfaces (e.g., an A / D converter, a D / A converter, a communication interface, etc.). The control unit 9 performs various control operations by executing programs stored in a storage unit (corresponding to part or all of the storage area of ​​the storage device).

[0071] The control unit 9 may be composed of a single processor or a plurality of independent processors for performing various controls.

[0072] The control unit 9 can control the laser control unit 17 , the drive mechanism 11 , and the console drive unit 13 .

[0073] Although not shown, the control unit 9 is connected to a sensor for detecting the size, shape, and position of the substrate 21 , a sensor and a switch for detecting the status of each device, and an information input device.

[0074] (2) Structure of solar cells

[0075] use Figure 2 The structure of the solar cell 20 will be described. The solar cell 20 is, for example, a perovskite thin-film solar cell module using a perovskite crystal compound as a semiconductor layer. Figure 2 It is a schematic cross-sectional view showing the steps of manufacturing the solar cell according to the first embodiment.

[0076] Figure 2 (g) represents the solar cell 20 .

[0077] The solar cell 20 includes: a substrate 21, a back electrode layer 23 (an example of a first layer), a perovskite crystalline compound layer (light absorption layer) 25 (an example of a second layer) and a transparent conductive film 27 (an example of a third layer), and the back electrode layer 23, the light absorption layer 25 and the transparent conductive film 27 are stacked in sequence on the substrate 21.

[0078] The substrate 21 serves as the base for forming the back electrode layer 23, the light absorbing layer 25, and the transparent conductive film 27. The substrate 21 is formed, for example, from a glass substrate such as soda-lime glass or low-alkali glass, a metal substrate such as stainless steel, or a resin substrate such as epoxy resin. The thickness of the substrate 21 is, for example, several millimeters.

[0079] The back electrode layer 23 functions as one electrode of the solar cell 20 and is formed on the substrate 21. The back electrode layer 23 is formed, for example, from molybdenum (Mo), titanium (Ti), or chromium (Cr). The thickness of the back electrode layer 23 is, for example, several tens of nanometers to several micrometers.

[0080] The back electrode layer 23 is divided by first dividing grooves 23a provided in a direction perpendicular to the paper surface. The width of the first dividing grooves 23a is, for example, several tens to several hundred μm.

[0081] The light-absorbing layer 25 performs photoelectric conversion on the incident sunlight, etc. The electromotive force generated by the photoelectric conversion in the light-absorbing layer 25 can be output to the outside in the form of current from electrode strips (copper foil strips) attached to the back electrode layer 23 and the transparent conductive film 27, respectively, using solder or the like.

[0082] Light-absorbing layer 25 is a layer composed of a p-type semiconductor and is formed on back electrode layer 23 and within first dividing grooves 23a. Light-absorbing layer 25 is divided by second dividing grooves 25a extending perpendicularly to the paper. The width of second dividing grooves 25a is, for example, approximately several tens to several hundred microns.

[0083] Light absorbing layer 25 can be made of, for example, a semiconductor compound composed of an inorganic compound or an organic-inorganic compound. Examples of such inorganic semiconductor compounds include CIGS (CuInGaSe) compounds, CZTS (CuZnS) compounds, and CdTe compounds. Examples of organic-inorganic semiconductor compounds include perovskite crystal compounds such as lead halide perovskites (e.g., CH3NH3PbI3). The thickness of light absorbing layer 25 is, for example, several micrometers to several tens of micrometers.

[0084] The transparent conductive film 27 is a layer that functions as another electrode of the solar cell 20. The transparent conductive film 27 is a transparent layer formed of an n-type semiconductor. It is formed on the light absorbing layer 25 and within the second dividing groove 25a, forming a pn junction with the light absorbing layer 25. The transparent conductive film 27 is composed of, for example, a zinc oxide thin film (ZnO) or an ITO thin film. When using a zinc oxide thin film (ZnO), it is preferred because low resistance can be achieved by adding dopants such as boron (B), aluminum (Al), and gallium (Ga). The thickness of the transparent conductive film 27 is, for example, several μm to several tens of μm.

[0085] Furthermore, the transparent conductive film 27 is preferably made of a material having a property (also referred to as light transmittance) that easily transmits light corresponding to the wavelength region of light absorbed by the light absorbing layer 25 .

[0086] The light-absorbing layer 25 and the transparent conductive film 27 are divided by third dividing grooves 27a, which are arranged perpendicular to the paper. The width of the third dividing grooves 27a is, for example, approximately several tens to several hundred micrometers. Each section divided by the third dividing grooves 27a constitutes a plurality of cells 31. The transparent conductive film 27 formed within the third dividing grooves 27a of a given cell 31 is electrically connected to the back electrode layer 23 of the adjacent cell 31 across the third dividing grooves 27a. In other words, the plurality of cells 31 divided by the third dividing grooves 27a are connected in series.

[0087] (3) Method for manufacturing solar cells

[0088] Next, a method for manufacturing the solar cell 20 will be described.

[0089] (3-1) Formation of back electrode layer

[0090] like Figure 2 As shown in (a), prepare the substrate 21, as shown in Figure 2 As shown in (b), the back electrode layer 23 is formed on the substrate 21 by, for example, sputtering.

[0091] (3-2) P1 process

[0092] like Figure 2 As shown in (c), first dividing grooves 23a are formed in the back electrode layer 23. The first dividing grooves 23a divide the back electrode layer 23 in a direction perpendicular to the paper. The surface of the substrate 21 is exposed within the first dividing grooves 23a. Specifically, the first dividing grooves 23a are formed by irradiating a portion of the back electrode layer 23 with pulsed laser light L1 using the laser processing device 1, thereby removing the portion of the back electrode layer 23 irradiated with the laser light.

[0093] (3-3) Formation of Light Absorption Layer

[0094] like Figure 2 As shown in (d), the light absorbing layer 25 is formed on the back electrode layer 23 and in the first dividing grooves 23a. The light absorbing layer 25 is formed by, for example, printing, sputtering, or vapor deposition.

[0095] (3-4) P2 process

[0096] like Figure 2 As shown in (e), second dividing grooves 25a are formed in the light absorbing layer 25. The second dividing grooves 25a divide the light absorbing layer 25 in a direction perpendicular to the paper. The surface of the back electrode layer 23 is exposed within the second dividing grooves 25a. Specifically, the second dividing grooves 25a are formed by irradiating a portion of the light absorbing layer 25 with pulsed laser light L2 using the laser processing device 1, thereby removing the light absorbing layer 25 in the portion irradiated with the laser light.

[0097] (3-5) Formation of transparent conductive film

[0098] like Figure 2 As shown in FIG. 5 (f), a transparent conductive film 27 is formed on the light absorbing layer 25 and in the second dividing grooves 25a. The transparent conductive film 27 is formed by, for example, sputtering or vapor deposition.

[0099] (3-6) P3 process

[0100] like Figure 2 As shown in (g), third dividing grooves 27a are formed in the transparent conductive film 27. The third dividing grooves 27a divide the light absorbing layer 25 and the transparent conductive film 27 in a direction perpendicular to the paper. The surface of the back electrode layer 23 is exposed within the third dividing grooves 27a. Specifically, the third dividing grooves 27a are formed by irradiating the light absorbing layer 25 and the transparent conductive film 27 with pulsed laser light L3 using the laser processing device 1, thereby removing the light absorbing layer 25 and the transparent conductive film 27 in the irradiated portions.

[0101] Through the above steps, the solar cell 20 is completed.

[0102] (4) Detailed description of the P3 process

[0103] use Figures 3 to 7 , the P3 step as a groove forming method for forming the third dividing groove 27a will be described in detail. Figure 3 It is a schematic cross-sectional view showing the state before the P3 step. Figure 4 This is a schematic cross-sectional view showing the first step of the P3 step. Figure 5 It is a schematic plan view showing the first step of the P3 step. Figure 6 It is a schematic cross-sectional view showing the second step of the P3 step. Figure 7 This is a top view photograph showing the process after the P3 step of the first embodiment.

[0104] In the P3 process, the light absorbing layer 25 and the transparent conductive film 27 of the layer structure including the back electrode layer 23 (an example of the first layer), the light absorbing layer 25 formed on the back electrode layer 23 (an example of the second layer), and the transparent conductive film 27 formed on the light absorbing layer 25 (an example of the third layer) are simultaneously laser processed to form a third dividing groove 27a.

[0105] P3 process has Figure 3 The first process and the second process are executed starting from the initial state.

[0106] like Figure 4 and Figure 5As shown, in the first step, a vent channel 33 is formed in a portion of the transparent conductive film 27 where the groove is to be formed, using laser light L3a, penetrating to the light absorbing layer 25. More specifically, the vent channel 33 is formed along the widthwise center of the portion 27b of the transparent conductive film 27 where the groove is to be formed. The vent channel 33 can be formed as a continuous linear opening (groove), or as intermittent or discrete openings. A continuous groove is preferred for its effectiveness as a vent. In the first step, by controlling the laser focus position, output power, beam diameter, scanning speed, and other factors, it is possible to process only the third layer without processing the second layer.

[0107] As described above, since the first step is performed by laser processing, the same laser processing apparatus 1 as that for the second step can be utilized.

[0108] In the second process, after the first process, Figure 6 As shown, by using laser L3b to form the groove portion 25b ( Figure 4 ) and the groove-forming portion 27b of the transparent conductive film 27 ( Figure 4 ) is laser processed to form a third dividing groove 27a.

[0109] In the above-mentioned P3 step, since the vent channel 33 is formed in advance in the first step, when the light absorbing layer 25 and the transparent conductive film 27 are laser processed in the second step, the gas generated from the light absorbing layer 25 is discharged to the outside through the vent channel 33. As a result, Figure 7 As shown, the peeling of the transparent conductive film 27 is reduced.

[0110] also, Figure 7 These are photographs showing the results of the first example performed under the following conditions.

[0111] In the first embodiment, the wavelength and scanning speed of the laser are the same in the first process and the second process. In addition, the laser output power of the second process is larger. In addition, with respect to the processing Z position, the first process is precise focusing on the third layer, while the second process is defocusing. As an example, the wavelength of the laser is 355 nm and the scanning speed is 500 mm / s. The laser output power is 0.1 W in the first process (the laser output power for processing only the first layer, not the second layer), and is 0.4 W in the second process (the laser output power for processing the second and third layers). In the first process, the ventilation channel is formed in the center of the processing width (to form an exhaust hole), and in the second process, the laser operation (patterning) is performed on the center of the processing width.

[0112] 2. Second Implementation

[0113] In the first embodiment, the vent channel 33 is formed along the width center of the groove-forming portion 27 b of the transparent conductive film 27 . However, as long as gas can be sufficiently released during the second step, the position, shape, and number of the vent channels are not particularly limited.

[0114] use Figures 8 to 11 Such an example will be described as a second embodiment. Figure 8 This is a schematic cross-sectional view showing the first step of the P3 step of the second embodiment. Figure 9 It is a schematic plan view showing the first step of the P3 step. Figure 10 This is a schematic cross-sectional view showing the first step of the P3 step. Figure 11 This is a top view photograph showing the second embodiment after the P3 step.

[0115] P3 process has Figure 3 The first process and the second process are executed starting from the initial state.

[0116] like Figure 8 and Figure 9 As shown, in the first step, a vent channel 35 is formed by laser light L3a in a portion of the transparent conductive film 27 where the groove is to be formed, so as to penetrate the light absorbing layer 25. More specifically, the vent channel 35 is formed along the two long edges of the portion 27b where the groove is to be formed.

[0117] like Figure 10 As shown, in the second step, after the first step, the groove forming portion 25b of the light absorbing layer 25 and the groove forming portion 27b of the transparent conductive film 27 are laser processed by laser L3b to form third dividing grooves 27a.

[0118] In the above-mentioned P3 step, since the vent channel 35 is formed in advance in the first step, when the light absorbing layer 25 and the transparent conductive film 27 are laser processed in the second step, the gas generated from the light absorbing layer 25 is discharged to the outside through the vent channel 35. As a result, Figure 11 As shown, the peeling of the transparent conductive film 27 is reduced.

[0119] in addition, Figure 11 This photograph shows the results of Example 2, performed under the same conditions as Example 1. While the second step is the same as the first embodiment in that laser scanning (patterning) is performed at the center of the processing width, the first step differs in that vent channels are formed at both ends of the processing width (vent hole formation step).

[0120] 3. Other Implementation Methods

[0121] While various embodiments of the present invention have been described above, the present invention is not limited to the aforementioned embodiments and various modifications can be made without departing from the spirit of the invention. In particular, the various embodiments and modifications described in this specification can be arbitrarily combined as needed.

[0122] The type of solar cell is not particularly limited, and the solar cell may be, for example, a silicon-based solar cell, a compound-based solar cell, or a perovskite-based solar cell.

[0123] The present invention is also applicable to layer structures other than solar cells. In particular, the present invention is preferably applicable to a layer structure in which the third layer is transparent and the second layer absorbs laser light.

[0124] The first step may also employ a mechanical scribing method in which a mechanical tool such as diamond is used to remove a portion of the thin film.

[0125] In the first step, the ventilation channel can be formed at any position within the processing width in a plan view.

[0126] In the first step, the ventilation channel may be formed continuously in a linear shape in plan view, may be formed intermittently, or may be formed by a combination of the two.

[0127] In the first step, the ventilation passage may be formed on a straight line in a plan view, may be formed in a curved shape in a plan view, or may be formed by combining the two.

[0128] Industrial applicability

[0129] The present invention can be widely applied to a method and apparatus for forming a groove by simultaneously laser processing the second and third layers of a layer structure including a first layer, a second layer formed on the first layer, and a third layer formed on the second layer to form a groove.

[0130] Description of Reference Numerals

[0131] 1: Laser processing equipment

[0132] 20: Solar cells

[0133] 21: Substrate

[0134] 23: Back electrode layer

[0135] 23a: First dividing groove

[0136] 25: Light absorption layer

[0137] 25a: Second dividing groove

[0138] 25b: Portion where groove is to be formed

[0139] 27: Transparent conductive film

[0140] 27a: Third split groove

[0141] 27b: Portion where groove is to be formed

[0142] 31: Unit

[0143] 33: Ventilation channel

[0144] 35: Ventilation channel

Claims

1. A method for forming a groove, comprising: simultaneously laser processing the second layer and the third layer of a layer structure including a first layer, a second layer formed on the first layer, and a third layer formed on the second layer to form a groove, the method comprising: In a first step, a ventilation channel is formed in a portion of the third layer where the groove is to be formed, penetrating to the second layer; and A second step is to form the groove by laser processing the portion of the second layer where the groove is to be formed and the portion of the third layer where the groove is to be formed after the first step. The layer structure is a thin film solar cell, the second layer is a semiconductor layer, and the third layer is a transparent electrode layer.

2. The method for forming a groove according to claim 1, wherein: The groove extends long in one direction, In the first step, the ventilation channel is formed along the portion of the third layer where the groove is to be formed.

3. The method for forming a groove according to claim 2, wherein: In the first process, the ventilation channel is formed along both long edges of the portion of the third layer where the groove is to be formed.

4. The method for forming a groove according to claim 2, wherein: In the first step, the ventilation channel is formed along the center in the width direction of the portion of the third layer where the groove is to be formed.

5. The method for forming a groove according to any one of claims 1 to 4, wherein: The first step is performed by laser processing.

6. An apparatus for forming a groove, wherein the groove is formed by simultaneously laser processing the second layer and the third layer of a layer structure including a first layer, a second layer formed on the first layer, and a third layer formed on the second layer, the apparatus comprising: a first processing device for forming a ventilation channel penetrating to the second layer in a portion of the third layer where the groove is to be formed; and a second processing device for forming the groove by laser processing the portion of the second layer where the groove is to be formed and the portion of the third layer where the groove is to be formed, The layer structure is a thin film solar cell, the second layer is a semiconductor layer, and the third layer is a transparent electrode film.

7. The groove forming device according to claim 6, wherein: The groove extends long in one direction, The first processing device forms the ventilation channel along the portion of the third layer where the groove is to be formed.

8. The groove forming device according to claim 7, wherein: The first processing device forms the ventilation channel along two long edges of the portion of the third layer where the groove is to be formed.

9. The groove forming device according to claim 7, wherein: The first processing device forms the ventilation channel along the center in the width direction of the portion of the third layer where the groove is to be formed.

10. The groove forming device according to any one of claims 6 to 9, wherein: The first processing device performs laser processing.

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