JP2011056514A - Method of manufacturing photoelectric conversion element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a photoelectric conversion element by which the heat damage to a transparent electrically conductive film and the crack of a glass substrate caused by a laser beam are suppressed and the focusing of the laser beam is consequently facilitated. <P>SOLUTION: In the method of manufacturing the photoelectric conversion element which has a scribing step of forming a scribe 30 on a film 13 including the transparent electrically conductive film 12 which is formed on the glass substrate 11, the scribing step is performed with a laser beam 15 induced with water jet 16 having a diameter of ≤100 μm and the laser beam 15 is emitted from the side of the film 13 toward the side of the glass substrate 11. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a photoelectric conversion element, and more particularly to a method for manufacturing a photoelectric conversion element having a scribing step of forming a groove in a film including a transparent conductive film on a substrate with a laser beam. The present invention is useful for the manufacture of photoelectric conversion elements such as solar cells.

The clean energy market represented by photovoltaic power generation is expanding on a global scale, and in particular, the solar cell market is expanding year by year. Accordingly, a solar cell with higher power generation efficiency is demanded. A solar cell is a power device that can directly convert light energy into electric power, and a photoelectric conversion element is used. A photoelectric conversion element is a semiconductor element that utilizes the “photovoltaic effect” in which electrons are generated by absorbing light energy at a PN junction of a semiconductor, and a light emitting diode (LED) that emits light when a voltage is applied. Is the reverse mechanism.
The photoelectric conversion element has a thin plate shape called a “solar cell panel”, and is formed by integrating a thin transparent glass substrate and a thin layered semiconductor element. Briefly explaining the structure of a general solar cell panel, a transparent electrode layer (transparent conductive film), a P-type semiconductor layer, an I-type semiconductor layer, an N-type semiconductor layer, and a back electrode layer are laminated on a glass substrate in this order. The sunlight incident from the glass substrate passes through the transparent conductive film, is absorbed by the I-type semiconductor layer, and generates electrons.

An example of the structure of the photoelectric conversion element is shown in FIG. In the photoelectric conversion element 10 shown in FIG. 5, a transparent conductive film 12, an amorphous silicon layer 53, a crystalline silicon layer 54, and a back electrode layer 55 are sequentially laminated on the back surface of a glass substrate 11. Here, in FIG. 5, the photoelectric conversion element 10 is depicted upside down, the lower side being the surface of the photoelectric conversion element 10, and the upper side being the back surface of the photoelectric conversion element 10.
The transparent conductive film 12 is a zinc oxide-based transparent conductive film, and is a layer for reducing light reflection and increasing internal power generation. A texture 57 is formed on the back surface side of the transparent conductive film 12. Yes. The texture 57 is fine unevenness and forms a pyramid shape.
The amorphous silicon layer 53 is called a “top cell” and is a layer for absorbing sunlight having a short wavelength, and includes a p layer 60 (P-type semiconductor), an i layer 61 (active layer), and an n layer 62 (N Are stacked in the order of type semiconductor).
The crystalline silicon layer 54 is called a “bottom cell” and is a layer for absorbing sunlight having a long wavelength, and includes a p layer 65 (P-type semiconductor), an i layer 66 (active layer), and an n layer 67 (N Are stacked in the order of type semiconductor).
The back electrode layer 55 is a layer for reflecting sunlight, and is laminated in the order of a ZnO layer 70 (zinc oxide layer) and an Ag layer 71 (silver layer).

By the way, in the manufacturing process of the photoelectric conversion element, there is a scribing process for forming a groove called “scribe” in the transparent conductive film. Briefly, a laser beam (hereinafter referred to as a dry laser) that propagates in a gas is irradiated between a portion where the transparent conductive film is desired to be removed or a portion where electrical insulation is desired. Then, the dry laser is absorbed by the transparent conductive film and instantaneously becomes thermal energy to sublimate the transparent conductive film at the irradiated location, thereby forming a groove in the transparent conductive film. A series of dry laser irradiation points is “scribe”.
Incidentally, the output energy of the dry laser is adjusted by a laser oscillator or the like. The focus of the dry laser is adjusted by adjusting the distance (Z direction distance) between the laser oscillation focus lens (optical lens) and the glass substrate surface.
Patent Document 1 discloses a method for processing a transparent conductive film of a solar cell using a dry laser.
Further, Patent Document 2 discloses a processing method for cutting a silicon wafer into a plurality of chips using a laser beam incident on a liquid jet.

JP 2006-121011 A Special Table 2007-537881

In the transparent conductive film processing method disclosed in Patent Document 1, it is not easy to adjust the output of the dry laser. For example, when the output of the dry laser is too low, a “film residue” is generated in which the removal of the transparent conductive film becomes insufficient, and it becomes difficult to ensure the scribe insulation. Also, if the output of the dry laser is too high, thermal energy is applied to the periphery of the scribe formation area, and in the transparent conductive film made of zinc oxide, etc., "thermal damage" occurs, in which the scribe edges are melted. There is a risk. In particular, when a zinc oxide-based transparent conductive film is used, since zinc oxide has poor heat resistance, the edge portion is heated and melted by absorption heat generated by application of a laser beam, so that there is a problem that “thermal damage” becomes large. In addition, the processable area where “film residue” does not occur and “thermal damage” does not occur is called a process window. However, a zinc oxide-based transparent conductive film is made of another material (for example, tin oxide or indium tin oxide-based). Since the occurrence of “thermal damage” is more significant than that of the transparent conductive film), the process window tends to be narrowed. Furthermore, if the output of the dry laser is excessive, there is a risk of “cracking” in the glass substrate in addition to “thermal damage”.
Further, it is not easy to focus the distance of the dry laser in the Z direction. This is because the depth of focus (allowable range of focus) between the laser oscillation focus lens (optical lens) and the glass substrate surface is shallow. For example, in a large glass substrate, if the glass substrate itself is warped, the focus of the dry laser will be “deviation” or “blurred”, resulting in poorly shaped scribes or residue on the scribe edges. The processing state of scribes becomes worse, such as the occurrence of a large amount. Or when the flatness of the processing-table surface which mounts a glass substrate is bad, it is the same as the above, and it is difficult to keep the processing precision of a scribe constant. For this reason, after the scribe process, a cleaning process for removing the scribe residue is essential.
In Patent Document 2, there is no description regarding the manufacture of a photoelectric conversion element.

  In view of the above-described present situation, an object of the present invention is to provide a method for manufacturing a photoelectric conversion element that suppresses thermal damage of a transparent conductive film and breakage of a glass substrate due to a laser beam and facilitates focusing of the laser beam.

  Invention of Claim 1 for solving the said subject is a manufacturing method of the photoelectric conversion element which has a scribe process which forms a groove | channel in the film | membrane containing the transparent conductive film formed into a film on the board | substrate, The said scribe process is A method for producing a photoelectric conversion element, wherein a groove is formed by irradiating a laser beam guided by a water jet having a diameter of 100 μm or less and irradiating the laser beam from a film side toward a substrate side.

The method for producing a photoelectric conversion element of the present invention includes a scribing process for forming a groove in a film including a transparent conductive film formed on a substrate, and the scribing process is induced with a water jet having a diameter of 100 μm or less. The groove is formed by irradiating the laser beam to the substrate side from the film side. The method for producing a photoelectric conversion element of the present invention prevents thermal damage to the transparent conductive film and breakage of the glass substrate caused by laser light, and makes it unnecessary to focus laser light.
“Laser beam induced by water jet” has a high cooling effect by water and can prevent thermal damage of the transparent conductive film and cracking of the glass substrate.
Further, the laser beam uses a “water jet”, so that optical focusing is unnecessary and processing accuracy is high. For this reason, almost no scribe residue is generated, and a small amount of the residue can be washed away by a water jet. That is, the residue cleaning step that has been conventionally performed after the scribing step may be unnecessary.

  Invention of Claim 2 is a manufacturing method of the photoelectric conversion element of Claim 1 whose diameter of a water jet is 30-50 micrometers.

  With this configuration, the scribe process can be performed more precisely.

  Invention of Claim 3 is the manufacturing method of the photoelectric conversion element of Claim 1 or 2 characterized by the water used for a water jet being acidic or alkaline.

  With this configuration, chemical cleaning with acid or alkali can be performed simultaneously with physical cleaning with a water jet during the scribing process.

  The output energy of the laser beam is preferably 1 to 40 W at the irradiation point on the film.

  The wavelength of the laser beam is preferably 1064 nm which is the fundamental wave of the YAG laser, 532 nm which is the second harmonic, or 355 nm which is the third harmonic.

The manufacturing method of the photoelectric conversion element of this invention is suitable for the process of a zinc oxide type transparent conductive film (Claim 6).
Here, the “zinc oxide-based transparent conductive film” is a transparent conductive film containing zinc oxide as a main component, and includes a substance such as a dopant as necessary.

  The substrate may have irregularities on at least one surface thereof (Claim 7). In other words, for the purpose of preventing the reflection of sunlight, the substrate may be subjected to uneven processing. At this time, the transparent conductive film formed on the glass substrate has an anchor effect (increased adhesion strength by entering the uneven surface). Firmly adheres to the unevenness of the substrate. For this reason, it is preferable to process with “a laser beam guided by a water jet”, which has a wider process window than a dry laser.

  According to the method for producing a photoelectric conversion element of the present invention, it is possible to prevent thermal damage of the transparent conductive film and cracking of the glass substrate due to the laser beam in the scribe process. In addition, since laser beam focusing is not required, the processing accuracy is high. Furthermore, the cleaning process of the residue after the scribing process becomes unnecessary, which is convenient.

It is a schematic diagram explaining the structure and principle of a water jet induction type laser apparatus which can be used for the manufacturing method of the photoelectric conversion element of this invention. It is sectional drawing which shows the state of the transparent conductive film on the glass substrate used for a scribe process, (a) is the state before laser beam irradiation, (b) is the state at the time of laser beam irradiation, (c) is after laser beam irradiation completion | finish. Shows the state. It is a microscope picture which shows the result of the scribe process with respect to the transparent conductive film performed in the Example. It is a microscope picture which shows the result of the scribe process with respect to the transparent conductive film performed in the comparative example 1. It is a partially broken perspective view which shows the laminated structure of a photoelectric conversion element.

  Below, embodiment of the manufacturing method of the photoelectric conversion element of this invention is described in detail, referring drawings. In addition, the following description is for facilitating the understanding of the embodiment, and the present invention should not be understood to be limited thereby.

First, the structure of the water jet induction type laser apparatus which can be used for the manufacturing method of the photoelectric conversion element of this invention is demonstrated. A water jet guided laser apparatus 1 shown in FIG. 1 includes a laser oscillator 2, a focus lens 3, and a mixing chamber 4. As the water jet induction laser device 1, for example, LCS300 manufactured by SYNOVA is preferably used.
The laser oscillator 2 is a device for adjusting and irradiating the output energy of the laser beam 15, and is preferably composed of a YAG laser.
The focusing lens 3 increases the output energy of the laser beam 15 by narrowing the laser beam 15.
The mixing chamber 4 is a device for mixing the water 7 filled in the mixing chamber 4 and the laser beam 15 to generate a water jet guided laser 20 (laser beam guided by the water jet). The injection nozzle 6 is provided.
The opening 5 is a hole for introducing the laser beam 15 into the mixing chamber 4.
The jet nozzle 6 is for converting the water 7 into the water jet 16 and jetting it using the output energy of the laser beam 15.
As shown in the enlarged view of FIG. 1, the laser beam 15 is diffusely reflected in the water jet 16 ejected from the ejection nozzle 6, so that the laser beam 15 is confined in the water jet 16 while maintaining high output energy. The water jet induction laser 20 is obtained.

In the present embodiment, the scribing process is performed on the transparent conductive film 12 on the glass substrate 11 using the water jet induction laser device 1. The glass substrate 11 may be provided with irregularities for preventing reflection of sunlight on at least one surface thereof (not shown). Hereinafter, the scribe process will be described in detail with reference to FIGS.
First, a zinc oxide-based transparent conductive film 12 is formed on a glass substrate 11 by a chemical vapor deposition method (CVD method) or the like. Thereby, the transparent conductive film 12 is laminated on the glass substrate 11 as shown in FIG.

  Next, as shown in FIG. 2B, the water jet guided laser 20 having a diameter of 100 μm or less generated by the water jet guided laser apparatus 1 is moved from the transparent conductive film 12 side toward the glass substrate 11 side. The region P to be removed of the transparent conductive film 12 is irradiated. Then, the region P is sublimated with heat and removed. Although the diameter of the water jet 16 at this time should just be 100 micrometers or less, Preferably it is 30-50 micrometers, More preferably, it is 30-45 micrometers, More preferably, it is 35-45 micrometers. Further, the output energy of the laser beam 15 may be appropriately selected depending on the thickness of the transparent conductive film, but is preferably 1 to 40 W, more preferably 5 to 25 W, more preferably 5 to 5 at the irradiation point on the transparent conductive film 12. 10W. Further, the wavelength of the laser beam 15 may be appropriately selected depending on the type of the transparent conductive film. However, the fundamental wave of the YAG laser is 1064 nm (infrared), and the second harmonic is 532 nm (green light in visible light). Or 355 nm (ultraviolet light) which is the third harmonic. In particular, zinc oxide-based transparent conductive films have good light absorption characteristics in the order of the third harmonic, fundamental wave, and second harmonic, and workability at low output is easy, but production on a commercial basis was considered. In this case, since the third harmonic laser oscillator is very expensive, the processing with the fundamental wave is more preferable in consideration of the economy and the ease of processing.

  When the removal of the region P is completed, the water jet guided laser device 1 is stopped. As a result, a scribe 30 (groove) is formed in the transparent conductive film 12 as shown in FIG. At this time, since the water jet induction type laser is used in this embodiment, almost no scribe residue is generated, and a small amount of residue can be washed away by the water jet. Therefore, the subsequent cleaning process is unnecessary.

  Thereafter, a P-type semiconductor layer, an I-type semiconductor layer, an N-type semiconductor layer, a back electrode layer, and the like are laminated in this order on the scribed transparent conductive film 12 (FIG. 2C) to thereby obtain a photoelectric conversion element. Can be manufactured. For example, the photoelectric conversion element 10 shown in FIG. 5 can be manufactured by sequentially laminating the amorphous silicon layer 53, the crystalline silicon layer 54, and the back electrode layer 55 on the transparent conductive film 12.

In addition, as the water 7, an acidic or alkaline thing can be used. Thereby, chemical cleaning with acid or alkali can be performed simultaneously with physical cleaning with water jet. Examples of the acidic liquid include nitric acid and hydrochloric acid. As the pH of the acidic solution, a nitric acid aqueous solution of 1.0 to 4.0, preferably 1.5 to 2.0 is used.
Examples of the alkaline liquid include sodium hydroxide and potassium hydroxide. As the pH of the alkaline liquid, an aqueous solution of sodium hydroxide of 9.0 to 11.0, preferably 9.5 to 10.5 is used.

  As described above, according to this embodiment, since the water jet induction laser 20 is used, the cooling effect by the water 7 is high, and thermal damage of the transparent conductive film 12 and cracking of the glass substrate 11 can be prevented. Further, the water jet induction laser 20 uses the water jet 16, so that optical focusing is unnecessary and processing accuracy is high. For this reason, almost no scribe residue is generated, and a small amount of scribe residue can be washed away by the water jet 16. In other words, the residue cleaning step that has been conventionally performed after the scribing step becomes unnecessary.

In the present embodiment, a zinc oxide-based one is used as the transparent conductive film 12, but the present invention is not limited to this, and also for manufacturing a photoelectric conversion element having a transparent conductive film made of another material. Can be applied. Examples of materials other than zinc oxide include tin oxide (SnO ₂ ) and indium tin oxide (ITO).

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples.

〔Example〕
After forming a zinc oxide-based transparent conductive film 12 on the glass substrate 11, a water jet induction laser 20 was irradiated from the transparent conductive film 12 side toward the glass substrate 15 side to form a scribe 30. At this time, the output energy of the laser beam 15 constituting the water jet induction laser 20 was 10.2 W at the irradiation point on the transparent conductive film 12, the diameter of the water jet 16 was 40 μm, and the processing speed was 1000 mm / sec.

[Comparative Example 1]
A scribe 30 was formed on the transparent conductive film 12 using a conventional dry laser. At this time, the output energy of the dry laser was 4.5 W at the irradiation point on the transparent conductive film 12, and the processing speed was 1000 mm / sec. The depth of focus of the dry laser (allowable range for focusing) is ± 0.2 mm.

  In FIG. 3, the microscope picture which shows the result of the scribe process with respect to the transparent conductive film performed in the Example is shown. In FIG. 4, the microscope picture which shows the result of the scribe process with respect to the transparent conductive film performed in the comparative example 1 is shown. Both magnifications are 200 times. As shown in FIG. 3, in the transparent conductive film of the example, the scribe 30 had a well-formed shape, and no scribe residue was observed. On the other hand, as shown in FIG. 4, the scribe residue 35 remained in the transparent conductive film of Comparative Example 1, and “thermal damage” in which the edge portion of the scribe 30 and the like were melted by heat occurred.

[Comparative Example 2]
When the output energy of the dry laser was set to 5.3 W at the irradiation point on the transparent conductive film 12 and the transparent conductive film 12 was irradiated, “breaking” occurred in the glass substrate 11.

7 Water 10 Photoelectric conversion element 11 Glass substrate (substrate)
12 Transparent conductive film 13 Film 15 Laser beam 16 Water jet 30 Scribe (groove)

Claims (7)

In the method of manufacturing a photoelectric conversion element having a scribe process for forming a groove in a film including a transparent conductive film formed on a substrate,
The scribing step is performed by a laser beam guided by a water jet having a diameter of 100 μm or less, and the groove is formed by irradiating the laser beam from the film side toward the substrate side.   The method for producing a photoelectric conversion element according to claim 1, wherein the diameter of the water jet is 30 to 50 μm.   The method for producing a photoelectric conversion element according to claim 1 or 2, wherein water used in the water jet is acidic or alkaline.   4. The method of manufacturing a photoelectric conversion element according to claim 1, wherein the output energy of the laser beam is 1 to 40 W at an irradiation point on the film.   5. The photoelectric conversion according to claim 1, wherein the wavelength of the laser beam is 1064 nm which is a fundamental wave of a YAG laser, 532 nm which is a second harmonic wave, or 355 nm which is a third harmonic wave. Device manufacturing method.   The method for producing a photoelectric conversion element according to claim 1, wherein the transparent conductive film is zinc oxide-based.   The method for producing a photoelectric conversion element according to claim 1, wherein the substrate has irregularities on at least one surface thereof.