JPH0519990B2 - - Google Patents

Description

[Detailed description of the invention]

[Field of Application] The present invention relates to a method for manufacturing an integrated amorphous silicon thin film solar cell. More specifically, a plurality of partitioned metal electrode layers stacked on the same substrate,
The present invention relates to a method for manufacturing an integrated solar cell in which a cell consisting of an amorphous silicon layer and a transparent electrode layer is connected. [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 deposited on 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. The basic structure of an amorphous silicon solar cell is a laminated structure of metal electrode layer/amorphous silicon semiconductor layer/transparent electrode layer provided on the various substrates mentioned above. Utilizing the characteristics of amorphous silicon layer deposition, JP-A-59
A large area where a metal electrode layer is provided using the roll-to-roll method disclosed in Publication No. 34668 or the three-chamber separation formation method published in Japan Journal of Applied Physics, Vol. 21, No. 3, page 413 (1982). It is easy to deposit an amorphous silicon layer on a long substrate. Further, it is also easy to provide the transparent electrode layer of the other current extraction electrode over a large area. However, in order for the above-mentioned laminate to function as a solar cell, it is necessary to attach lead terminals to the metal electrode layer and the transparent electrode layer. Furthermore, in order to obtain an output voltage of several tens of volts or more, which is necessary for practical use, the solar cell provided on the large-area substrate is divided by a laser scribing method, etc., and then the adjacent metal electrode layer and transparent electrode layer are separated. It is necessary to connect them in series. In such a case, a method is usually used in which the lowest metal electrode layer is exposed and then connected to the adjacent upper electrode layer or lead extraction electrode. Methods for exposing this metal electrode layer include: using a metal mask during deposition of the amorphous silicon layer; removing the silicon layer using wet or dry etching after depositing the amorphous silicon layer; A method has been used in which after deposition, only the silicon layer is selectively melted and evaporated by laser irradiation to remove it. Among these methods, the method is not only unsuitable for long, large-area roll-to-roll methods, but also for the three-chamber separation method, thermal expansion of the substrate and mask occurs during the heating process during amorphous silicon deposition. Due to the deterioration of adhesion due to the difference in ratio, the amorphous silicon component wraps around, making it difficult to obtain a good pattern and making it difficult to expose the electrically good surface of the metal layer. 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 the other method, due to the high temperature required to melt the silicon layer, the metal electrode layer made of a high-melting point metal is also damaged, making it impossible to expose the electrically good metal layer surface. The reality is that it is not possible to selectively remove only the silicon layer with low melting point metals such as metals. [Object of the invention] The present invention eliminates the above-mentioned drawbacks and provides a method for bonding a connecting electrode to a metal electrode surface for taking out lead terminals on a large-area substrate or connecting divided solar cells in series. The purpose of this invention is to provide a simple method for manufacturing an integrated solar cell. [Structure and operation of the invention] The above-mentioned objects are achieved by the present invention as described below.
That is, the present invention provides an integrated solar cell in which cells are stacked on the same substrate and are made up of a plurality of partitioned metal electrode layers, an amorphous silicon semiconductor layer serving as a photovoltaic layer, and a transparent electrode layer. In the manufacturing method, after forming a connection electrode made of a highly conductive material in a predetermined pattern on each cell or its lead extraction electrode part, the connection part of the connection electrode is irradiated with laser light to remove the connection part. A thin film solar cell characterized by melting all layers of a metal electrode layer, an amorphous silicon layer serving as a photovoltaic layer, a transparent electrode layer, and a connecting electrode, and ohmic bonding the metal electrode layer and the connecting electrode. This is the connection method. In addition, the connection part of the above-mentioned connection electrode is specifically a connection electrode part or a lead extraction electrode part formed by dividing the transparent electrode layer for connection with an adjacent cell, which will be described later. As a result of various studies in order to eliminate the above-mentioned drawbacks of the conventional method, the present invention described above was developed by irradiating a laser beam onto two metal layers sandwiching an amorphous silicon semiconductor layer, thereby forming an amorphous silicon semiconductor layer. This was done based on the discovery that when the metal layers are melted, a good ohmic bond is formed between the two metal layers, although the irradiated center portion evaporates slightly. As mentioned above, the present invention simply forms connection electrodes at the connection points,
Since it is only necessary to irradiate the laser beam, there is no need for a step to expose the metal electrode surface as in the conventional method, and electrical connection with the metal electrode surface can be formed very simply and by a dry process. It is unclear why laser light can electrically connect an amorphous silicon layer and a metal layer with a transparent electrode layer sandwiched therein, but as the amorphous silicon crystallizes by melting, the metal forming the metal layer It is believed that this is because the electrical resistance of the cross-sectional area irradiated with the laser beam is reduced, and a good ohmic junction is formed. The details of the present invention will be specifically explained below. As the electrically insulating substrate of the present invention, any substrate made of an electrically insulating material can be used, and specifically, a polymer film, a ceramic plate, a glass plate, or a metal foil with an insulating layer provided on the surface can be used. Preferably, however, a polymeric film is used which allows the constituent layers to be deposited one after another by a roll-to-roll method on a long, moving substrate and is suitable for mass production. The polymer film may be any polymer film that has the heat resistance necessary for amorphous silicon deposition, but polyethylene terephthalate (PET) film, polyethylene naphthalate film, and polyimide film, which have excellent mechanical properties, are preferably used. etc. are used. The metal electrode layer provided on the substrate may be a layer mainly composed of a metal with good electrical conductivity such as A or Ag and a melting point of 1000°C or less, or a layer with good electrical conductivity of 1000°C or less with this layer.
Single metals such as Ti, W, Pt, Co, Cr, nichrome, and stainless steel having a melting point of 0.degree. Further, these metal electrode layers preferably have a thickness of 0.3 μm or more from the viewpoint of reducing electrical resistance and mechanical strength. The amorphous silicon layer can be formed using any known photovoltaic layer, and is not particularly limited. Specifically, it can be formed using a plasma CVD method using glow discharge decomposition of a known silane gas, disilane gas, etc. There are pin-shaped laminated photovoltaic layers, etc.
The amorphous silicon photovoltaic layer may include not only multilayer tandem structures such as pin/pin, pin/pin/pin, but also narrow band gap structures such as amorphous silicon germanium and amorphous silicon carbide. Alternatively, a wide band gap semiconductor layer can be used as appropriate. Further, the transparent electrode layer is not particularly limited, and any known material can be used as is, and various metal oxides are preferably used. Specifically, a metal oxide layer such as indium oxide, tin oxide, tin cadmium oxide, indium tin oxide, or a laminate of a metal thin film and an oxide dielectric material is applied. A layer mainly made of gold, silver, copper, A, nickel, or an alloy thereof is used as a highly conductive connection electrode that serves as a collector electrode, an intercell connection electrode layer, or a lead extraction electrode layer. . This connection electrode is formed on the transparent electrode layer by patterning using a physical method such as a vacuum evaporation method or a sputtering method. In addition, the thin film at this time is 0.5μm
The above is preferable. The connecting electrode can also be provided by a chemical method such as plating, and the film thickness in this case is the same as described above. In addition, gold, silver, copper,
A. A method of applying a conductive resin using fine nickel powder by screen printing or the like can be applied. This screen printing method is desirable from the viewpoint of continuous productivity. The printed conductive layer needs to have a thickness of 5 μm or more for electrical resistance. Laser light with a wavelength of 0.2 to 2 μm is often used as long as it is in a wavelength range that can be absorbed by each constituent layer.
Preferably, it is currently widely used industrially.
A YAG laser is used. The laser beam is irradiated from above the above-mentioned connection electrode formed according to the connection pattern, but if the substrate is transparent to the laser beam, it can also be irradiated from the back side of the substrate through the substrate according to the pattern. I can do it. The laser power depends on the irradiation direction and also depends on the thickness of the highly conductive electrode layer, so it needs to be determined practically. , it is necessary to select a range in which all layers of the connection electrode layer are melted. In addition,
It is not necessary to melt the entire metal electrode layer or the connection electrode layer, and it is sufficient to melt at least a portion of the amorphous silicon layer side. As described above, the present invention forms a connection electrode on the part where it is necessary to connect to the lower metal electrode layer from above, and forms a good electrical connection from the upper part to the metal electrode layer by simply irradiating laser light. This eliminates the need for a step to expose the metal electrode surface as in the conventional method, and allows electrical connection to the metal electrode with a simple dry process, which has great practical effects in terms of productivity, reliability, etc. As is clear from its purpose, it is broadly applicable to all integrated solar cells that require such electrical connections. Examples of the present invention are shown below. [Example] A 100 μm thick polyethylene terephthalate film (PET) was used as the polymer film substrate 1. First, the film substrate 1 was mounted on a DC magnetron sputtering device, and an aluminum layer (A) of 0.4 μm and a stainless steel layer (SS) of 100 Å were successively deposited in an Ar atmosphere of 10 ^-3 torr. Layer 2 was provided on the long film substrate 1 (see Figure 3). Furthermore, a pin-type photovoltaic layer 3 of amorphous silicon is deposited on this PET/A/SS deposited body.
A boron (B)-doped P layer of 300 Å, an i-layer of 0.5 μm, and a phosphorus (P) doped layer were continuously formed over a large area in a long length using the roll-to-roll method disclosed in Publication No. 34668.
A doped n-layer was deposited to a thickness of 200 Å. In order to form a solar cell with three cells C connected in series on the same substrate, a large area of 10cm x 10cm PET/A was used.
/SS/ A black insulating paste is printed on the laminate of amorphous silicon layers using a screen printing method according to the cell division pattern, and a black insulating paste is printed around the division grooves during division according to the division pattern shown in Figure 1. An electrical insulating layer 4 was formed to prevent poor insulation between electrodes. Thereafter, a transparent electrode layer 5 made of indium oxide was uniformly deposited to a thickness of 600 Å thereon by electron beam evaporation. Next, by a laser scribing method using a YAG laser, it was divided into three cells C of 3.3 cm x 10 cm as shown in FIG. 1 as follows. That is,
YAG laser Q switch frequency 2KHz, power (peak value output) 1KW, beam diameter 100μm, scanning speed
3.2 cm/sec, a cell dividing groove 6 is formed by evaporating all layers except the substrate 1 along the electrical insulating layer 4 in order to divide the cell C, and a YAG laser is applied along the electrical insulating layer 4a. Only the power was set to 150 W, and other conditions were the same as above, and only the transparent electrode layer 5 was evaporated to form electrode dividing grooves 7 that separate the connecting electrode portions 5a, and cells were divided. After dividing, silver conductive resin was deposited to a thickness of 13 μm in the following pattern shown in Figure 2 using a screen printing method.
A collection electrode 8 and a lead extraction electrode 9 were formed. That is, the busbar portion 8a of the collecting electrode 8 is positioned on the connection electrode portion 5a so as to serve as a connection electrode, and the finger portions 8b are arranged in a pattern at predetermined intervals from the busbar portion 8a in a direction perpendicular to the busbar portion 8a. Note that the bus bar portion 8a of the cell C on the right side in the figure serves as an electrode for lead extraction. Next, in order to connect the three cells C in series, a YAG laser beam L having a power of 2 KW and the same conditions as above is irradiated onto the bus bar 8a of the collecting electrode 8 as shown in FIG. 3, and scanned over its entire length. did. By irradiating the laser beam, all the layers except the substrate are melted and mixed, as shown in FIG. 3, to form the metal electrode layer 2 and the bus bar portion 8a.
A good ohmic connection was formed between the electrode and the lead extraction electrode 9. This is clear from the results shown in Table 1, in which the solar cell module in which the three cells C obtained above were connected in series was measured at 100 mW/cm ² under an AM1 solar simulator. For comparison, a solar cell module with the same configuration was made using the mask method in all steps, and the results of measurements are also shown in Table 1.

[Table] As is clear from Table 1, the module using the manufacturing method of the present invention has the same efficiency and efficiency as the mask method.
The fill factor is shown, which indicates that a good ohmic connection is formed by the manufacturing method of the present invention. In addition, when we measured the atomic distribution in the cross section of the part of the fused connection part of the bus bar part 8a that was evaporated by the laser beam using electron probe microanalysis (EPMA), we found that the A atoms, which should be contained only in the metal electrode layer, and the connection Ag atoms, which should only be contained in the electrode, are mixed in the entire layer near the cross section of the part evaporated by laser beam irradiation, forming an ohmic junction between the metal electrode and the connection electrode. was confirmed. Note that similar results were obtained when using the same configuration as in this example and connecting by irradiating laser light from the PET film side of the substrate. In this case, since it was not necessary to melt the entire silver layer of the bus bar portion 8a of the connection electrode, the laser beam power of 500 W was sufficient.
Note that other conditions for the laser beam in this case are the same as described above.

[Brief explanation of the drawing]

Figure 1 is a surface view showing the cell division pattern of the solar cell used in the example, Figure 2 is a plan view showing the collecting electrode pattern of the solar cell, and Figure 3 is Figure 2AB.
FIG. 2 is a partial side cross-sectional view showing the structure of the solar cell along lines. DESCRIPTION OF SYMBOLS 1... Substrate, 2... Metal electrode layer, 3... Amorphous silicon layer, 5... Transparent electrode layer, 8... Collection electrode, 8a... Bus bar portion of connection electrode.

Claims (1)

[Claims] 1. An integrated solar cell in which cells are stacked on the same substrate and are made up of a plurality of partitioned metal electrode layers, an amorphous silicon layer serving as a photovoltaic layer, and a transparent electrode layer. In the manufacturing method, after forming a connection electrode made of a highly conductive material in a predetermined pattern on each cell or its lead extraction electrode part, the connection part of the connection electrode is irradiated with laser light to remove the connection part. An integrated solar device characterized by melting all layers of a metal electrode layer, an amorphous silicon layer serving as a photovoltaic layer, a transparent electrode layer, and a connecting electrode, and ohmic bonding the metal electrode layer and the connecting electrode. How to manufacture batteries. 2. The method for manufacturing an integrated solar cell according to claim 1, wherein the connection electrode is a busbar portion of a collecting electrode. 3. The method for manufacturing an integrated solar cell according to claim 1 or 2, wherein the connection electrode is made of gold, silver, copper, aluminum, nickel, or an alloy thereof. 4. Claim 1, wherein the metal electrode layer is a layer mainly made of a highly conductive metal having a melting point of 1000°C or less, or a laminate of the highly conductive metal and a metal thin film having a melting point of 1000°C or more. 2. The method for manufacturing an integrated solar cell according to item 2, item 3, or item 3. 5. The method for manufacturing an integrated solar cell according to claim 1, 2, 3, or 4, wherein the substrate is an electrically insulating material. 6. The method for manufacturing an integrated solar cell according to claim 5, wherein the substrate is a long polymer film.