JP7324499B2 - Groove forming method and groove forming apparatus - Google Patents

Description

The present invention provides a layered structure that includes a first layer, a second layer formed over the first layer, and a third layer formed over the second layer. The present invention relates to a groove forming method and a groove forming apparatus for forming grooves by laser processing layers simultaneously.

A thin-film solar cell is constructed by laminating a lower electrode layer, a semiconductor layer, and an upper electrode layer on a glass substrate.
An example of the manufacturing process of a thin-film solar cell will be described.
First, a glass substrate is prepared.
A bottom electrode layer is then formed on the glass substrate.
Next, the lower electrode layer is patterned by grooving (process P1).

A semiconductor layer is then formed over the patterned bottom electrode layer.
Next, the semiconductor layer is patterned by groove processing (P2 process).
A top electrode layer is then formed over the patterned semiconductor layer.
Finally, the upper electrode layer and the semiconductor layer are patterned by grooving (process P3).

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

Japanese Unexamined Patent Application Publication No. 2011-189408

The upper electrode layer is made of, for example, a transparent conductive oxide (TCO) that is transparent to light in a specific range of wavelengths. Therefore, when the P3 process is performed by laser scribing, the following problems may occur.
In other words, the laser light that has passed through the upper electrode layer is mainly absorbed by the semiconductor layer, and therefore part of the semiconductor layer evaporates to generate gas. This gas causes the upper electrode layer to separate from the semiconductor layer, resulting in deterioration of the quality of the thin-film solar cell.
Such an example will be specifically described with reference to FIGS. 12 and 13. FIG. FIG. 12 is a schematic plan view showing the P3 process of the reference example. FIG. 13 is a plane photograph of the reference example after the P3 process. As shown in FIG. 12, when dividing grooves 41 are formed in the transparent conductive film 27 (upper electrode layer) and the underlying light absorbing layer (not shown) by laser processing, part of the light absorbing layer evaporates. This produces gas. As a result, as shown in FIG. 13, the transparent conductive film peels off at a plurality of locations around the dividing groove in plan view.

It is an object of the present invention to provide a layered structure comprising a first layer, a second layer formed over the first layer, and a third layer formed over the second layer. An object of the present invention is to reduce peeling of the third layer in a groove forming method and a groove forming apparatus for forming grooves by laser processing the third layer at the same time.

A plurality of aspects will be described below as means for solving the problem. These aspects can be arbitrarily combined as needed.

A groove forming method according to one aspect of the present invention is applied to a layered structure including a first layer, a second layer formed on the first layer, and a third layer formed on the second layer. Then, the second layer and the third layer are simultaneously laser-machined to form grooves. This grooving method comprises the following steps.
⊚ A first step of forming an air passage penetrating to the second layer in a part of the third layer where the groove is to be formed.
⊚ A second step of forming grooves by performing laser processing on the planned groove formation locations of the second layer and the groove formation planned locations of the third layer after the first step.
In this method, since the ventilation path is formed in advance in the first step, when the second layer and the third layer are laser-processed in the second step, the gas generated from the second layer is released from the ventilation path to the outside. go out to As a result, delamination of the third layer is reduced.
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.

The groove may be elongated in one direction.
In the first step, the ventilation path may be formed along the groove-formed portion of the third layer.
In this method, the gas generated from the second layer is efficiently discharged to the outside through the air passage.

In a first step, the air passages may be formed along both longitudinal edges of the third layer where the grooves are to be formed.
In this method, the gas generated from the second layer is efficiently discharged to the outside through the air passage.

In the first step, the ventilation path may be formed along the widthwise center of the third layer where the groove is to be formed.
In this method, the gas generated from the second layer is efficiently discharged to the outside through the air passage.

The first step may be performed by laser processing.
In this method, since the first step and the second step are performed by laser processing, a common laser processing apparatus can be used.

Another aspect of the present invention is a grooving apparatus having a layer structure including a first layer, a second layer formed over the first layer, and a third layer formed over the second layer. On the other hand, this apparatus forms grooves by laser processing the second layer and the third layer at the same time.
The apparatus has a first processing device and a second processing device. The first processing device forms an air passage penetrating to the second layer in a portion of the third layer where the groove is to be formed. The second processing device forms grooves by performing laser processing on the planned groove formation locations of the second layer and the groove formation planned locations of the third layer.
In this apparatus, since the first processing device forms the ventilation path, when the second layer and the third layer are laser-processed by the second processing device, the gas generated from the second layer is released from the ventilation path to the outside. go out to As a result, delamination of the third layer is reduced.
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.

The groove may be elongated in one direction.
The first processing device may form the ventilation path along the groove formation scheduled location of the third layer.
In this device, the gas generated from the second layer is efficiently discharged to the outside through the air passage.

The first processing device may form the ventilation path along both longitudinal edges of the third layer where the groove is to be formed.
In this device, the gas generated from the second layer is efficiently discharged to the outside through the air passage.

The first processing device may form the ventilation path along the widthwise center of the third layer where the groove is to be formed.
In this device, the gas generated from the second layer is efficiently discharged to the outside through the air passage.

The first processing device may perform laser processing.
In this device, since the first processing device and the second processing device perform laser processing, a common laser processing device can be used.

In the grooving method and the grooving apparatus according to the present invention, gas generated from the second layer goes out through the air passage when the second layer and the third layer are laser-processed. As a result, delamination of the third layer is reduced.

1 is a schematic diagram of a laser processing apparatus according to a first embodiment; FIG. 4A to 4C are schematic cross-sectional views showing stepwise the manufacturing process of the solar cell of the first embodiment. FIG. 4 is a schematic cross-sectional view showing the state before the P3 process; FIG. 4 is a schematic cross-sectional view showing the first step of the P3 step; FIG. 4 is a schematic plan view showing the first step of the P3 step; FIG. 4 is a schematic cross-sectional view showing a second step of the P3 step; Plane photograph after P3 process of 1st Example. FIG. 10 is a schematic cross-sectional view showing the first step of the P3 step of the second embodiment; FIG. 4 is a schematic plan view showing the first step of the P3 step; FIG. 4 is a schematic cross-sectional view showing the first step of the P3 step; Plane photograph after P3 process of 2nd Example. FIG. 4 is a schematic plan view showing the P3 process of the reference example; Plane photograph after P3 process of a reference example.

1. First Embodiment (1) Overall Configuration of Laser Processing Apparatus FIG. 1 shows the overall configuration 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. FIG. 1 is a schematic diagram of a laser processing apparatus according to a first embodiment of the present invention.

A laser processing apparatus 1 includes a laser device 3 . The laser device 3 has a laser oscillator 15 for irradiating a substrate 21 (described later) with laser light, and a laser controller 17 . A laser control unit 17 can control the driving of the laser oscillator 15 and the laser power.
The laser device 3 has a transmission optical system 5 that transmits laser light to a mechanical drive system, which will be described later. The transmission optical system 5 has, for example, a condenser lens 19, a plurality of mirrors (not shown), a prism (not shown), and the like.

The laser processing apparatus 1 has a driving mechanism 11 that changes the converging angle of laser light by moving the position of the lens in the optical axis direction.
The laser processing apparatus 1 has a processing table 7 on which the substrate 21 is placed. The processing table 7 is moved by a table driving section 13 . The table drive unit 13 has a moving device (not shown) that horizontally moves the processing table 7 with respect to a bed (not shown). The moving device is a known mechanism having guide rails, motors, and the like.

The laser processing apparatus 1 has a control section 9 . The control unit 9 has a processor (eg, CPU), a storage device (eg, ROM, RAM, HDD, SSD, etc.), and various interfaces (eg, A/D converter, D/A converter, communication interface, etc.). computer system. 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).
The control unit 9 may be composed of a single processor, or may be composed of a plurality of independent processors for each control.

The controller 9 can control the laser controller 17 . The controller 9 can control the drive mechanism 11 . The control section 9 can control the table driving section 13 .
The control unit 9 is connected to a sensor for detecting the size, shape and position of the substrate 21, sensors and switches for detecting the state of each device, and an information input device (not shown).

(2) Structure of Solar Cell The structure of the solar cell 20 will be described with reference to FIG. The solar cell 20 is, for example, a perovskite-type thin-film solar cell module using a perovskite crystal compound for a semiconductor layer. 2A to 2C are schematic cross-sectional views showing stepwise the manufacturing process of the solar cell of the first embodiment.

The solar cell 20 is shown in FIG.2(g).
The solar cell 20 includes a substrate 21, a back electrode layer 23 (an example of a first layer), a perovskite crystal compound layer (light absorption layer) 25 (an example of a second layer), and a transparent conductive film 27 (an example of a third layer). An example), and a back electrode layer 23 , a light absorption layer 25 and a transparent conductive film 27 are sequentially laminated on a substrate 21 .

The substrate 21 is a portion that serves as a base on which the back electrode layer 23, the light absorption layer 25, and the transparent conductive film 27 are formed. The substrate 21 is made of, for example, 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, about several millimeters.

Back electrode layer 23 is a layer that functions as one electrode of solar cell 20 and is formed on substrate 21 . The back electrode layer 23 is made of, for example, molybdenum (Mo), titanium (Ti), or chromium (Cr). The thickness of the back electrode layer 23 is, for example, about several tens of nm to several μm.
The back electrode layer 23 is divided by first dividing grooves 23a provided along the direction perpendicular to the paper surface. The width of the first dividing groove 23a is, for example, about several tens to several hundred μm.

The light absorption layer 25 is a portion that photoelectrically converts irradiated sunlight or the like. The electromotive force generated by the photoelectric conversion of the light absorption layer 25 can be taken out as current from electrode ribbons (copper foil ribbons) attached to the back electrode layer 23 and the transparent conductive film 27 by soldering or the like.
The light absorbing layer 25 is a layer made of a p-type semiconductor, and is formed on the back electrode layer 23 and in the first dividing grooves 23a. The light absorption layer 25 is divided by second division grooves 25a provided along the direction perpendicular to the plane of the drawing. The width of the second dividing groove 25a is, for example, about several tens to several hundred μm.
As the light absorption layer 25, for example, a semiconductor compound made of an inorganic compound or an organic-inorganic compound can be used. Examples of the inorganic semiconductor compounds include CIGS (CuInGaSe)-based compounds, CZTS (CuZnS)-based compounds, and CdTe-based compounds. Examples of the organic-inorganic semiconductor compounds include lead halide-based perovskites (e.g., CH ₃ NH ₃ PbI ₃ ) and other perovskite crystalline compounds. The thickness of the light absorption layer 25 is, for example, about several micrometers to several tens of micrometers.

The transparent conductive film 27 is a layer that functions as the other electrode of the solar cell 20 . The transparent conductive film 27 is a transparent layer made of an n-type semiconductor, is formed on the light absorption layer 25 and in the second division groove 25a, and forms a pn junction with the light absorption layer 25. As shown in FIG. The transparent conductive film 27 is made of, for example, a zinc oxide thin film (ZnO) or an ITO thin film. When a zinc oxide-based thin film (ZnO) is used, it is preferable to add boron (B), aluminum (Al), gallium (Ga), or the like as a dopant so that the resistance can be lowered. The thickness of the transparent conductive film 27 is, for example, about several micrometers to several tens of micrometers.
The transparent conductive film 27 is preferably made of a material having a property (also referred to as light transmittance) that easily transmits light in the wavelength range of light absorbed by the light absorption layer 25 .

The light absorbing layer 25 and the transparent conductive film 27 are divided by a third dividing groove 27a provided along the direction perpendicular to the plane of the drawing. The width of the third dividing groove 27a is, for example, about several tens to several hundred μm. Each portion divided by the third dividing groove 27a constitutes a plurality of cells 31. As shown in FIG. The transparent conductive film 27 formed in the third dividing groove 27a of the predetermined cell 31 is electrically connected to the back electrode layer 23 of the adjacent cell 31 through the third dividing groove 27a. That is, the plurality of cells 31 divided by the third dividing grooves 27a are connected in series.

(3) Method for Manufacturing Solar Cell Next, a method for manufacturing the solar cell 20 will be described.
(3-1) Formation of Back Electrode Layer As shown in FIG. 2(a), a substrate 21 is prepared. to form a film.

(3-2) Step P1 As shown in FIG. 2(c), the first dividing grooves 23a are formed in the back electrode layer . The first dividing grooves 23a divide the back electrode layer 23 along the direction perpendicular to the plane of the drawing. The surface of the substrate 21 is exposed in the first dividing grooves 23a. Specifically, the first dividing grooves 23a are formed by irradiating a portion of the back electrode layer 23 with a pulsed laser beam L1 using the laser processing apparatus 1, thereby forming the portion of the back electrode layer 23 irradiated with the laser beam. 23 is removed and formed.

(3-3) Formation of Light Absorbing Layer As shown in FIG. 2D, the light absorbing layer 25 is formed on the back electrode layer 23 and in the first dividing grooves 23a. The light absorption layer 25 is formed by, for example, a printing method, a sputtering method, or a vapor deposition method.

(3-4) Step P2 As shown in FIG. The second dividing groove 25a divides the light absorption layer 25 along the direction perpendicular to the plane of the drawing. The surface of the back electrode layer 23 is exposed in the second dividing groove 25a. Specifically, the second dividing groove 25a is formed by irradiating a portion of the light absorbing layer 25 with a pulsed laser beam L2 using the laser processing apparatus 1, thereby forming the portion of the light absorbing layer 25 irradiated with the laser beam. 25 is removed and formed.

(3-5) Formation of Transparent Conductive Film As shown in FIG. 2(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.

(3-6) Step P3 As shown in FIG. 2(g), the transparent conductive film 27 is formed with a third dividing groove 27a. The third dividing groove 27a divides the light absorption layer 25 and the transparent conductive film 27 along the direction perpendicular to the plane of the drawing. The surface of the back electrode layer 23 is exposed in the third dividing groove 27a. Specifically, the third dividing groove 27a is formed by irradiating a portion of the light absorption layer 25 and the transparent conductive film 27 with a pulsed laser beam L3 using the laser processing apparatus 1. A portion of the light absorption layer 25 and the transparent conductive film 27 is removed.
The solar cell 20 is completed through the above steps.

(4) Detailed Description of P3 Process The P3 process, which is a groove forming method for forming the third dividing grooves 27a, will be described in detail with reference to FIGS. 3 to 7. FIG. FIG. 3 is a schematic cross-sectional view showing the state before the P3 process. FIG. 4 is a schematic cross-sectional view showing the first step of the P3 step. FIG. 5 is a schematic plan view showing the first step of the P3 step. FIG. 6 is a schematic cross-sectional view showing the second step of the P3 step. FIG. 7 is a plane photograph after the P3 process of the first embodiment.

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

The P3 process has a first process and a second process that are executed from the initial state of FIG.
In the first step, as shown in FIGS. 4 and 5, the ventilation path 33 penetrating to the light absorption layer 25 is formed by the laser light L3a in a part of the groove formation planned portion 27b of the transparent conductive film 27. FIG. More specifically, the air passage 33 is formed along the center of the width direction of the groove-formed portion 27 b of the transparent conductive film 27 . The ventilation path 33 may be formed as a continuous linear opening (groove), or may be formed as an intermittent or discrete opening. It is preferably formed as a groove. In the first step, by controlling the focus position, output, irradiation beam diameter, scanning speed, etc. of the laser beam, only the third layer is processed and the second layer is not processed.
Since the first step is performed by laser processing as described above, the same laser processing apparatus 1 as that for the second step can be used.

In the second step, after the first step, as shown in FIG. 6, a groove formation planned portion 25b (FIG. 4) of the light absorption layer 25 and a groove formation planned portion 27b (FIG. 4) of the transparent conductive film 27 are irradiated with a laser beam L3b. ) is laser-processed, the third dividing groove 27a is formed.
In the above-described P3 process, since the air passage 33 is formed in advance in the first process, when the light absorbing layer 25 and the transparent conductive film 27 are laser-processed in the second process, the light absorbing layer 25 emits light. The gas to be discharged goes out from the air passage 33 to the outside. As a result, as shown in FIG. 7, peeling of the transparent conductive film 27 is reduced.

FIG. 7 is a photograph showing the results of Example 1 performed under the following conditions.
In the first embodiment, the wavelength of the laser light and the scanning speed are the same between the first step and the second step. Also, the laser output is large in the second step. Also, the processing Z position is just in focus with respect to the third layer in the first step, and defocused in the second step. As an example, the wavelength of laser light is 355 nm and the scanning speed is 500 mm/s. The laser output is 0.1 W in the first step (laser output in which only the first layer is processed and the second layer is not processed), and in the second step is 0.4 W (the second and third layers are processed). laser output). In the first step, a vent path is formed in the center of the processing width (formation of gas vent holes), and in the second step, the center of the processing width is laser-operated (patterning).

2. Second Embodiment In the first embodiment, the air passage 33 was formed along the widthwise center of the groove-formed portion 27b of the transparent conductive film 27. , the position, shape and number of air passages are not particularly limited.
Such an example will be described as a second embodiment with reference to FIGS. 8 to 11. FIG. FIG. 8 is a schematic cross-sectional view showing the first step of the P3 step of the second embodiment. FIG. 9 is a schematic plan view showing the first step of the P3 step. FIG. 10 is a schematic cross-sectional view showing the first step of the P3 step. FIG. 11 is a plane photograph after the P3 process of the second embodiment.

The P3 process has a first process and a second process that are executed from the initial state of FIG.
In the first step, as shown in FIGS. 8 and 9, a ventilation path 35 penetrating to the light absorption layer 25 is formed in a part of the groove formation planned portion 27b of the transparent conductive film 27 by the laser beam L3a. More specifically, the air passage 35 is formed along both longitudinal edges of the groove-formed portion 27 b of the transparent conductive film 27 .

In the second step, after the first step, as shown in FIG. 10, a groove formation planned location 25b of the light absorption layer 25 and a groove formation planned location 27b of the transparent conductive film 27 are laser-processed with a laser beam L3b. A third dividing groove 27a is formed.
In the P3 process described above, since the ventilation path 35 is formed in advance in the first process, when the light absorbing layer 25 and the transparent conductive film 27 are laser-processed in the second process, the light absorbing layer 25 emits light. The gas to be discharged goes out from the air passage 35 to the outside. As a result, as shown in FIG. 11, peeling of the transparent conductive film 27 is reduced.
FIG. 11 is a photograph showing the results of the second example performed under the same conditions as the first example. Compared to the first embodiment, the second step is the same in that the center of the processing width is laser-scanned (patterning). punch hole forming step).

3. Other Embodiments Although a plurality of embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various modifications are possible without departing from the gist of the invention. In particular, multiple embodiments and modifications described herein can be arbitrarily combined as required.
The type of solar cell is not particularly limited. The solar cell may be, for example, a silicon solar cell, a compound solar cell, or a perovskite solar cell.
The invention also applies to layer structures other than solar cells. In particular, the present invention is preferably applied to a layered structure in which the third layer has transparency and the second layer absorbs laser light.

In the first step, a mechanical scribing method that removes part of the thin film with a mechanical tool such as diamond may be used.
In the first step, the air passage may be formed at any position in the processing width in plan view.
In the first step, the ventilation path may be formed continuously linearly in a plan view, may be formed intermittently, or may be formed by combining both.
In the first step, the air passage may be formed in a straight line in plan view, may be formed in a curved shape, or may be formed by combining the two.

The present invention provides a layered structure that includes a first layer, a second layer formed over the first layer, and a third layer formed over the second layer. It can be widely applied to a groove forming method and a groove forming apparatus for simultaneously laser-processing layers to form grooves.

1: Laser processing device 20: Solar cell 21: Substrate 23: Back electrode layer 23a: First division groove 25: Light absorption layer 25a: Second division groove 25b: Groove formation plan location 27: Transparent conductive film 27a: Third division Groove 27b : Groove-formed portion 31 : Cell 33 : Ventilation path 35 : Ventilation path

Claims (10)

For a layered structure including a first layer, a second layer formed on the first layer, and a third layer formed on the second layer, the second layer and the third A groove forming method for simultaneously laser processing layers to form grooves,
a first step of forming an air passage penetrating to the second layer in a portion of the third layer where the groove is to be formed;
After the first step, a second step of forming the groove by performing laser processing on the planned groove formation location of the second layer and the groove formation planned location of the third layer;
wherein said layer structure is a thin film solar cell, said second layer is a semiconductor layer, and said third layer is a transparent electrode layer . The groove extends long in one direction,
2. The groove forming method according to claim 1 , wherein in said first step, said ventilation path is formed along said groove-forming planned portion of said third layer. 3. The method of forming grooves according to claim 2 , wherein in said first step, said air passages are formed along both longitudinal edges of said portion of said third layer where said grooves are to be formed. 3. The groove forming method according to claim 2 , wherein in said first step, said ventilation path is formed along the width direction center of said groove formation planned portion of said third layer. 5. The groove forming method according to claim 1, wherein said first step is performed by laser processing. For a layered structure including a first layer, a second layer formed on the first layer, and a third layer formed on the second layer, the second layer and the third A grooving device for simultaneously laser processing layers to form grooves,
a first processing device that forms an air passage penetrating to the second layer in a part of the groove formation scheduled location of the third layer;
a second processing device that forms the groove by performing laser processing on the planned groove formation location of the second layer and the groove formation planned location of the third layer;
with
The groove forming device , wherein 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 . The groove extends long in one direction,
7. The grooving apparatus according to claim 6 , wherein said first processing apparatus forms said ventilation path along said groove-forming planned portion of said third layer. 8. The grooving device according to claim 7 , wherein said first processing device forms said ventilation path along both longitudinal edges of said grooving planned portion of said third layer. 8. The groove forming apparatus according to claim 7 , wherein said first processing apparatus forms said ventilation path along the width direction center of said groove formation planned portion of said third layer. 10. The groove forming device according to claim 6 , wherein said first processing device performs laser processing.

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