JPH03166772A - Manufacture of thin film solar cell - Google Patents

Abstract

PURPOSE:To enhance an efficiency by sequentially laminating a film made of boron by a thermal CVD method, then an amorphous silicon i-type layer film by a thermal CVD method and further an amorphous silicon n-type layer film by a plasma CVD method on a board. CONSTITUTION:A film 2 made of boron by a thermal CVD method, then an a-Si i-type layer film 4 by a thermal CVD method on the film 2 and further an a-Si n-type layer film 5 by a plasma CVD method on the film 4 are sequentially laminated on a board 1. Here, since the film 4 is formed by the thermal CVD method, a deterioration of the film quality due to light irradiation is suppressed, boron deposited in advance is thermally diffused in the film 4 at a high temperature at the time of forming the film 4, and a p-type layer 3 is formed on the part of the layer 4 at the side of the board. Further, a pin type a-Si solar cell is eventually formed together with the film 5 formed by the plasma CVD method at a low temperature. Thus, a thin film solar cell having high efficiency is obtained.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for manufacturing a thin film solar cell that performs charge conversion using a pin junction structure made of an amorphous silicon (hereinafter abbreviated as a-Si) thin film. ．． [Prior Art] Thin-film solar cells using amorphous semiconductors, especially a-31 thin films, have the advantages of being easy to increase in area and requiring low raw material costs, and are expected to be used as low-cost solar cells. ing. Usually, this a-St solar cell is made of SnO. A transparent conductive film made of transparent and conductive materials such as
On top of that, plasma C using plasma glow discharge decomposition
p-type by VD method. l type. It is manufactured by sequentially laminating n-type a-31 layers and further forming metal electrodes made of M, ^g, etc. by vacuum evaporation or sputtering. [
Problems to be Solved by the Invention Regarding a-Sl solar cells, one of the biggest problems that currently requires improvement is the problem of reduced efficiency under light irradiation. In other words, a-
There is a well-known phenomenon known as the Stepler-Wronski effect, in which the film quality of the 31 film, especially the L layer, deteriorates due to light irradiation, and this is the main cause of the decrease in efficiency. On the other hand, the a-Sl film formed by thermal CVD has little deterioration in film quality due to light. Therefore, if this film is applied to the L layer of a solar cell, an a-Si solar cell with almost no light deterioration can be formed. It is expected that you will be able to discipline yourself. However, it is not possible to produce an efficient a-Si solar cell simply by replacing the conventional l-layer film produced by plasma CVD with a single-layer film produced by thermal CVD, which exhibits less photodeterioration. This is because thermal CVD is generally performed in the following manner. Generally, to form a 1-layer film by the thermal CVD method, the substrate to be coated is placed on a support stand in a He or Hz atmosphere at atmospheric pressure or reduced pressure in a reaction chamber, and the film temperature is raised to 450 to 500°C. After warming,
A reactive gas is introduced and decomposed, and an a-Si film is deposited on the substrate. SdL is used as a reaction gas for a-Sill film, and it is optionally mixed with He or H2.
Use by diluting with For this reason, conventional plasma CV
The p layer that was prominent in the D method. When attempting to form the L layer of the L layer and the N layer using thermal CVD, which causes less photodeterioration, the following problems occur. In other words, plasma CVD requires approximately 200
Thermal CVD is carried out at a relatively low temperature of 45°C as mentioned above.
Since the process is carried out at a high temperature of 0 to 500°C, after forming the p-layer film by plasma CVD, l! When attempting to form an L-layer film using icVD, the hydrogen atoms and impurities in the p-layer are thermally diffused, changing the properties of the p-layer itself, resulting in efficient thick film formation. I can't get batteries. Therefore, in order to apply a single-layer film produced by thermal CVD with less photodeterioration to the A-51 solar cell, it is necessary to change not only the method of manufacturing the L-layer film but also the overall device structure and manufacturing method. At this time, it is extremely important to make the manufacturing method as simple as possible in consideration of mass production. An object of the present invention is to provide a method for manufacturing a thin-film solar cell that can suppress deterioration caused by light by using a thermal CVD method for a single-layer film, and prevent a decrease in efficiency due to deterioration of other layer films. It's about doing. [Means for Solving the Problems] In order to achieve the above object, the present invention provides a
- When forming a pin junction structure made of a thin Sl film, a film made of boron is deposited on the substrate by thermal CVD, and then a single layer of A-31 is deposited on the film made of boron by thermal CVD. Then, a-St nllll! is further deposited on the L layer film by plasma CVD method. are deposited sequentially. [Function] Since the l-layer film is formed using the thermal CVD method, deterioration of the film quality due to light irradiation is suppressed. Due to the high temperature during this five-layer membrane formation, the boron deposited in advance is thermally diffused into the l layer, and
A p-type layer is formed on the substrate side of the layer film. Finally, a pln-type a-Sl solar cell is completed by combining the n-layer film with a plasma CVD method performed at low temperatures. [Example] An example of the present invention will be described below with reference to the figures.
FIG. 2 shows an apparatus for carrying out the manufacturing process shown in FIGS.
2. The plasma CvD chamber 23 and the rear chamber 24 are connected, and the substrate 1 supported on the support stand 25 can be moved by the transport rollers 26 through each chamber. The manufacturing process is as follows. Figure 1+8) Snow is deposited as a transparent electrode 12 on a glass plate 11 to a thickness of 5000 mm to prepare a substrate 1 for forming a solar cell. Figure 1 ~》 Open the valve 31 and put the substrate 1 into the front chamber, that is, the load lock chamber 21, which is exhausted through the exhaust valve 41. Then, open the partition valve 32 and put the substrate 1 into the front chamber, which is exhausted through the exhaust valve 41.
1. 62 into a thermal CVD chamber 22 equipped with a pressure of 5.
Heat to 480°C in an atmosphere of 1 JTorr. After evacuation, open the reaction gas introduction valve 51, and B*Hh+
A mixed gas of He was introduced, the pressure was adjusted to 50 Torr, and thermal CVD was performed for 20 seconds. In this step, a boron thin film 2 is formed on the transparent electrode l2 of the substrate 1. After the membrane formation, the gas introduction valve 5l is closed and the gas is exhausted via the exhaust valve 42. FIG. 1(C) Next, open the reaction gas introduction valve 51 again and introduce the mixed gas of SiJ6 and Be.
A thermal CVD method was performed at a pressure of Torr for 30 minutes to obtain l-type a-
51 film 4 is formed to a thickness of 5,000 layers. At this time, heat C
At the temperature of 480° C. used in the VD method, boron diffuses into the l-layer film 3, forming an extremely thin p-type layer 3. Figure 1 (dl) Next, after vacuuming, the partition valve 3
3, and the substrate 1 is carried into the plasma CVD chamber 23, which has a heater 63 and a high-frequency electric generator 8i64. Continuing,
After lowering the temperature in an atmosphere with a pressure of 50 Torr and bringing the substrate temperature to 200° C., the exhaust valve 43 is used to cool the substrate. to vacuum. Next, open the reaction gas introduction valve 52, and
Sine. Introduce the Pus mixed gas and increase the pressure to 0.5
Torr, a high frequency voltage of 13.56 MHz is applied to the high frequency electrode 64, and the n-layer film 5 is decomposed by glow discharge decomposition method.
300 people thick. Since this process is performed at a low temperature, there is no impurity diffusion from the n-layer film 5 to the single-layer film 4. FIG. 1(e) The substrate 1 is moved to the rear chamber 24 by opening the partition valve 34, and then taken out to the outside, M is vapor-deposited, the back electrode 6 is formed, and the solar cell is completed. The cell characteristics of the solar cell of this example are shown as &I71 in Figure 3. line 72
These are the characteristics of an a-SL solar cell in which only the l layer of the p layer, l layer, and n layer is formed by thermal CVD, and the p layer and n layer are formed by the conventional plasma CVD method. All of these characteristics are based on light irradiation of 100s+l1/1.
The efficiency of the thick VA battery shown by line 7l is 7.4%, and the efficiency of the solar cell shown by line 72 is 5.3%, indicating that the efficiency can be improved by the present invention. Furthermore, when these two solar cells were irradiated with light of 100 mW/1 for 100 hours, no deterioration was observed in either case. In addition, as for other manufacturing methods, p-layer and! Heat CV of both layers
Although it is possible to form the P layer using the D method, it is not possible to obtain a p-layer film with good performance using the thermal CVD method.For this reason, in a solar cell in which both the P layer and the L layer are formed using the thermal CVD method, the cost is 4%.
Only the following low efficiency was obtained. The above embodiment relates to a solar cell in which light enters from the substrate 1 side. For example, a substrate made of stainless steel is used, a pin junction structure is formed thereon in the same manner as in the above embodiment, and It is also possible to manufacture a solar cell in which a transparent electrode is attached to the top surface and light is incident from that surface. [Effects of the Invention] According to the present invention, by depositing a boron film and an a-Si l-layer film on a substrate by thermal CVD, a p-type layer can be formed on one surface of the l-layer film, which is less susceptible to photodeterioration. As a result, we were able to produce highly efficient thin-film solar cells. Moreover,
The formation of the boron film and the i-layer film by the above-mentioned thermal CVD method can be performed successively in the same equipment, and the time required to form a certain boron film is short, making for extremely simple manufacturing. It is a method.

[Brief explanation of the drawing]

Figure 1 shows the manufacturing process of one embodiment of the present invention.
2 is a sectional view of the apparatus used in the process shown in FIG. 1, and FIG. 3 is a voltage/current characteristic of the solar cell according to the example shown in FIG. 1 and the solar cell of the comparative example. This is a line diagram. 1: Substrate, 11: Glass plate, l2: Transparent electrode, 2: Boron film, 3: P-type layer, 4: a-Sll layer film, 5: a-Sl
n-layer film, 6: back electrode, 22: thermal CVD chamber, 23: plasma CVD chamber. 1st close

Claims (1)

[Claims] 1) When forming a pin junction structure made of an amorphous silicon thin film on a substrate, a film made of boron is deposited on the substrate by thermal CVD, and then a film made of boron is deposited on top of the film made of boron by thermal CVD.
1. A method for manufacturing a thin film solar cell, comprising sequentially depositing an i-layer film of amorphous silicon by the D method, and then an n-layer film of amorphous silicon by the plasma CVD method on the i-layer film.