JPH0149019B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application] The present invention relates to a method for dividing an amorphous solar cell into cells having a predetermined shape using laser light.

[Prior art] Amorphous silicon semiconductor films can be deposited uniformly over a wide area at low substrate temperatures by glow discharge decomposition using silane gas, etc., and can be applied to various substrates such as glass, polymer films, ceramic plates, metal foils, etc. Because the substrate can be selected, it is widely studied as a semiconductor film for solar cells. As a basic structure of an amorphous silicon solar cell, a laminated structure of a metal electrode layer/amorphous silicon semiconductor layer/transparent electrode layer provided on the above-mentioned various substrates is known.

Taking advantage of the characteristics of amorphous silicon layer deposition, it is easy to install a solar cell with the above basic structure over a large area, but as it is, the maximum output voltage is around 0.6 to 5 V regardless of the area, which is necessary for power applications. It is not possible to obtain an output voltage of 100V or more. In order to obtain such a practical voltage, a method is to install a predetermined number of small-area solar cells on a small-area substrate, and then connect a predetermined number of these cells in series, or a large-area solar cell placed on a large-area substrate. A method is to divide the substrate into cells of a predetermined small area by etching or the like without damaging it, and then connect a predetermined number of the cells in series. A method is known in which solar cells are deposited and then a predetermined number of the cells are connected in series. Among these methods, these methods are not suitable for mass production that takes advantage of the characteristics of amorphous silicon layer deposition, and the steps of series connection and modularization become complicated. This method is possible by combining resist coating and etching, but it requires many steps such as resist coating, exposure, cleaning, and etching, and is not suitable for manufacturing solar cells in large quantities at low cost. . In this method, the solar cell constituent layers are generally deposited one after another by placing a metal mask in close contact with the substrate, but when increasing the area, the difference in thermal expansion coefficient between the substrate and the mask makes it difficult to deposit each layer. Adhesion between the substrate and the mask deteriorates, often causing the deposited components to wrap around in each layer, making it impossible to obtain a good divided pattern. Furthermore, in the case of division by the mask deposition method, it is difficult to align the mask, and it is difficult to reduce the error to about 0.5 mm or less.

[Purpose of the Invention] The present invention has been made to solve the above-mentioned drawbacks of the conventional method, and is capable of producing a large-area amorphous solar cell formed on a large-area substrate at high speed through a simple process without damaging the substrate. It is an object of the present invention to provide a method for dividing an amorphous solar cell that can be divided into arbitrary shapes.

[Structure and operation of the invention] That is, the present invention provides a laminated structure of a metal electrode layer, an amorphous silicon semiconductor layer, and a transparent electrode layer, in which an amorphous silicon semiconductor layer is used as a photovoltaic layer, on a substrate. When dividing the amorphous solar cell into predetermined patterns by irradiating laser light onto the surface of the amorphous solar cell and moving the irradiation point along a predetermined pattern, the metal electrode layer of the pattern is preliminarily processed. and an amorphous silicon semiconductor layer or an interface between an amorphous silicon semiconductor layer and a transparent electrode layer, an insulating polymer resin layer is formed in advance. .

The above-mentioned present invention was made as follows. In the division processing method using laser light, by adjusting the optical system, the width of the division part can be freely changed between several tens of microns to several hundred microns, and
By using a computer control system and programming a predetermined pattern in advance, it is possible to divide into arbitrary shapes accurately and with good reproducibility. Furthermore, by using mirror movement within the optical system or optical fiber glasses, solar cells on a continuously running wide substrate film can also be divided, and a dividing process with good overall productivity can be realized.
Therefore, we irradiated the laser beam and performed the dividing process, and found that simply scanning the laser beam along a predetermined pattern and patterning would cause thermal damage to the area around the irradiated area, and in particular, the amorphous silicon layer would crystallize. It was revealed by Raman spectrum measurement that this occurs. When the silicon layer crystallizes, the dark conductivity of that part increases and it loses its pin junction characteristics and no longer exhibits a rectifying effect. Therefore, it was found that the electromotive force generated in the solar cell is lost in the crystallized region, resulting in a decrease in the solar cell characteristics after patterning.

Furthermore, as a result of electron microscopic observation of the cross section of the divided portion, it was observed that the lower metal electrode and the upper transparent electrode layer were melted and bonded, and this point was also found to be a cause of deterioration of the solar cell characteristics.

An example is shown in C of FIG. On the contrary,
After investigating various solutions, we found that an electrically insulating polymer resin layer was interposed between the amorphous silicon semiconductor layer and the metal electrode layer or between the amorphous silicon semiconductor layer and the transparent electrode layer of the amorphous solar cell. They discovered that by doing so, it is possible to prevent short circuits between the transparent electrode layer, the crystallized amorphous silicon semiconductor layer, and the metal electrode layer, and it is possible to prevent the deterioration of the solar cell characteristics after division, and have arrived at the present invention. .

By the way, in the above study, the present inventors found that by making the polymer resin layer opaque to laser light, the entire layer could be cut by using a high power laser beam, and by using a low power laser beam, the polymer resin layer could be cut by the laser beam. It was discovered that only the layer located on the irradiated side could be cut. Therefore, by providing an opaque polymer resin layer, it is possible to selectively cut the surface layer only on the irradiated side and cut the front and back layers including the opposite side by simply changing the power of the laser beam, allowing two types of cutting to be performed in one layer. This allows for patterning.

The details of the present invention will be explained below.

From the above point, it is necessary that the electrically insulating polymer resin layer formed along the pattern has a width slightly wider than the dividing width of the laser beam so as to prevent short-circuiting of the dividing surface after the dividing process using the laser beam. or,
When the thickness of the polymer layer is 1 μm or less, it is a metal electrode layer,
Short circuits between the transparent electrode layers cannot be prevented, and if the thickness exceeds 50 μm, a step will occur, making it difficult to deposit the transparent electrode layer and form a collection electrode in a subsequent process.

The polymer resin layer includes epoxy resin,
Polyamide resin, polyimide resin, polyester resin, etc. can also be used. In addition, when providing on the interface, a screen printing method or the like can be applied.

Furthermore, the polymer resin layer may be transparent or opaque to laser light. When cutting and dividing layers including the polymer resin layer on the side opposite to the laser irradiation side, a transparent material has the advantage that the power of the laser beam required is smaller. On the other hand, when the polymer resin layer is opaque, there is an advantage that selective cutting can be performed by selecting the power of the laser beam, as described above, to cut the surface layer only on the laser irradiation side and cut the front and back layers including the opposite side. This is achieved by simply providing one layer of polymer resin between the transparent electrode layer and the electromotive force layer in the aforementioned amorphous solar cell according to a predetermined pattern, and dividing the pattern up to the metal electrode layer and forming the transparent electrode layer. It is possible to divide the pattern into only one pattern, which has a very large effect on patterning and modularization.

In any case, when dividing with a laser, it is possible to divide into any shape by selecting the optimum power. The laser may be light in a wavelength range that can be absorbed by each of the constituent layers, and light with a wavelength of 0.2 to 2 μm is used. Preferably, a YAG laser, which is currently widely used industrially, is used.

Incidentally, the amorphous solar cell to which the present invention can be applied is not particularly limited, and may be one having an amorphous silicon semiconductor layer as an electromotive force layer, but from the viewpoint of productivity, an electrically insulating substrate, more preferably a flexible solar cell may be used. It is preferable that the film be continuously formed on a flexible elongated substrate.

In addition, the divided amorphous solar cells are divided into 120
Heat treatment in air at a temperature of .degree. C. to 200.degree. C. has the effect of preventing performance degradation of the solar cell after division, and it is preferable to perform the heat treatment after division.

The present invention will be explained below based on examples.

FIG. 1 is a side sectional view of an amorphous silicon solar cell according to an example. In this example, a polymer film suitable for mass production is used as the substrate 1, in which the solar cell constituent layers can be sequentially deposited on a long running substrate by a roll-to-roll method. As the polymer film, any polymer film having the heat resistance necessary for amorphous silicon deposition may be used, but polyethylene terephthalate (PET) film, polyimide film, etc. are preferably used. The example in the diagram is
It uses PET film.

As the metal electrode layer 2, an Al layer 2a of about 0.5 μm is used.
An Al/stainless steel laminate was used in which stainless steel layers 2b of about 300 Å to 10 Å were sequentially deposited using a sputtering method.

The amorphous silicon semiconductor layer 3 of the photovoltaic layer adopts a well-known pin-type structure, and is formed into a metal electrode layer using a glow discharge decomposition method using silane gas, etc., similar to that disclosed in Japanese Patent Application Laid-Open No. 59-34668. Deposited on 2.

Next, as the electrically insulating polymer resin layer 5 provided at the interface between the amorphous silicon semiconductor 3 and the transparent electrode layer 4, epoxy resin is divided into parts on the amorphous silicon semiconductor layer 3 using a screen printing method using a laser. do. It was provided in a predetermined pattern shape with a thickness of 10 μm.

Next, as a transparent electrode layer 4, an indium oxide (ITO) layer is deposited to a thickness of about 600 Å by electron beam evaporation or sputtering, and an epoxy resin layer ITO with a PETAl/SUS amorphous silicon pin pattern shown in FIG. An amorphous solar cell with this structure was obtained.

Note that the amorphous silicon solar cell is not limited to the above-mentioned structure, but may also include, for example, a ceramic plate as the substrate 1,
A glass plate or a metal foil provided with an insulating layer on the surface can be used, and a long flexible substrate to which continuous film formation and division processing can be applied is particularly advantageous. or,
The metal electrode layer 2 provided thereon also includes Ti, Ag,
Single metals and alloy metals such as W, Pt, Ni, C ₀ , chromium, and nichrome can be used. In addition to pin, the structure of the amorphous silicon semiconductor layer 3 of the electromotive force layer is
In addition to multilayer tandem structures such as pin/pin, pin/pin/pin, narrow band gap or wide band gap amorphous silicon semiconductor layers such as amorphous silicon germanium and amorphous silicon carbide. You can also use it from time to time. Further, as the transparent electrode layer 4, a known transparent conductive layer such as tin oxide or cadmium stannate can be used.

Next, the 10 cm x 10 cm square cell of the amorphous solar cell with the epoxy resin layer ITO structure with the PETAl/SUS amorphous silicon pin patterned in the above-mentioned Fig. 1 was heated with a YAG laser to form a highly electrically insulating, highly electrically insulating cell made of an epoxy resin layer. The molecular resin layer 5 was scanned to melt and evaporate the solar cell components to form a groove 6 up to the metal electrode layer 2 as shown in FIG. 1, and the cell was divided into two 5 cm x 10 cm square cells. The YAG laser is a Q-switch pulse laser with an average laser power of 0.8W.
Irradiate the surface of the solar cell with a pulse frequency of 2KHz,
Scanning was performed at a speed of 80 mm/sec.

The current-voltage characteristics of the 5 cm x 10 cm square cell after division were as shown in B in Figure 3. A in the same figure is 10cm x before division.
These are the characteristics of a 10 cm square cell, and C is the characteristic of a comparative example in which a conventional amorphous solar cell with the same configuration as the above example but without a polymer resin layer was decomposed using a YAG laser.

From the figure, it is clear that according to the present invention, it is possible to divide the cell without substantially degrading the cell performance.

Further, when the cell of Example after division was heat-treated in air at 150° C. for 30 minutes, the characteristics were almost the same as those of A in FIG. 3 before division. It was confirmed that almost the same results were obtained up to 200°C.

[Brief explanation of drawings]

Figure 1 is a side sectional view of the solar cell used in the example.
FIG. 2 is a graph of voltage-current characteristics of a solar cell showing the results of an example. 1: Substrate, 2: Metal electrode layer, 3: Amorphous silicon semiconductor layer, 4: Transparent electrode layer, 5: Electrically insulating polymer resin layer.

Claims (1)

[Claims] 1. An amorphous silicon semiconductor layer as a photovoltaic layer,
When dividing an amorphous solar cell in which a laminated structure of a metal electrode layer, an amorphous silicon semiconductor layer, and a transparent electrode layer is formed on a substrate into a predetermined pattern using laser light, the metal electrode layer of the pattern and the transparent electrode layer are separated in advance. A method for dividing an amorphous solar cell, comprising forming an electrically insulating polymer resin layer at the interface of a crystalline silicon semiconductor layer or the interface between an amorphous silicon semiconductor layer and a transparent electrode layer. 2. The method for dividing an amorphous solar cell according to claim 1, wherein the polymeric resin layer is opaque to laser light. 3 The thickness of the insulating polymer resin layer is 1μ or more and 50μ
A method for dividing an amorphous solar cell according to claim 1 or 2 below. 4. Heat the amorphous solar cell after splitting to 120°C to 200°C.
Claim 1, in which heat treatment is performed in the air of
The method for dividing an amorphous solar cell according to item 2 or 3. 5. The method for dividing an amorphous solar cell according to claim 1, 2, 3, or 4, wherein the amorphous solar cell is formed on an insulating substrate. 6. The amorphous solar cell according to claim 1, 2, 3, 4, or 5, wherein the amorphous solar cell is continuously formed on a long flexible substrate. How to divide and process quality solar cells.