JP3560109B2 - Method and apparatus for manufacturing thin film photoelectric conversion element - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method and an apparatus for manufacturing a thin-film photovoltaic element such as a solar cell using a flexible film substrate.
[0002]
[Prior art]
One of the typical thin film photovoltaic elements is an amorphous silicon (hereinafter abbreviated as a-Si) solar cell. This solar cell is generally formed by laminating a metal electrode layer, an a-Si layer as a power generation layer, a transparent electrode layer, and the like on a flexible film substrate. At present, issues relating to a-Si solar cells include lower cost and higher efficiency.
[0003]
Mass production is very effective for cost reduction. As a manufacturing method for improving mass productivity, for example, Suzuki, K .; Et al., "Technical Digest of the International PVSEC-1 (1984) p. 191" or Ovshinsky, S.M. R. By p. 577. The method is a method in which a strip-shaped film substrate is rolled into a loading chamber, a thin film photoelectric conversion element having a multilayer structure is continuously formed through a plurality of reaction chambers, and is rolled out in a loading chamber. This is called a roll-to-roll process. The roll-to-roll process is an excellent manufacturing method capable of forming a film with good uniformity on a long belt-like film substrate under a certain condition.
[0004]
As a method other than the roll-to-roll process, see Ichikawa, Y .; Devised a stepping roll process in “IEEE 1st World Conference on Photovoltaic Energy Conversion (1994) p. 441”. In this method, there are a plurality of independent film forming chambers having a movable heater and a frame in a common vacuum chamber, and in each of the film forming chambers, a flexible film substrate is sandwiched between the frames to perform vacuum sealing. To form a film. After film formation, the film substrate is transported intermittently (steps) like a one-frame or one-frame photo film to build a laminated structure.
[0005]
[Problems to be solved by the invention]
However, in the roll-to-roll process, although the film thickness and the film quality are good because the continuous film formation is performed, a manufacturing apparatus having a structure in which a plurality of film formation chambers are connected is used, and a film substrate for passing the film substrate therebetween is used. Due to the openings, it is impossible to continuously perform steps having greatly different conditions such as the degree of vacuum. In addition, there is a problem that a source gas (particularly a doping gas) introduced into a certain film formation chamber is mixed into another film formation chamber and causes deterioration of solar cell characteristics.
[0006]
On the other hand, in the stepping roll process, it is possible to independently control so-called film forming conditions such as a source gas type and a pressure in each film forming chamber. Therefore, it is possible to solve the problem of mixing the raw material gas into another film formation chamber without impairing mass productivity. In addition, it is possible to install the film forming mechanisms of the chemical vapor deposition method and the sputtering method, which have completely different film forming conditions, in the same vacuum chamber, and the power generation layer and the electrode layer can be formed in the same apparatus. The modification of the electrode layer interface structure has been achieved. For example, in a solar cell manufactured by a roll-to-roll process, the fill factor was 0.54 and the conversion efficiency was 7.2%, whereas in a solar cell manufactured by a stepping roll process, the fill factor was , 0.62, and a conversion efficiency of 8.1%.
[0007]
However, the stepping roll process has the following problems due to the operation of pinching the film by the movable heater.
One is that film formation must be performed at once in a large portion (one unit) of a film formation chamber surrounded by a movable heater and a frame. It is very difficult to form a uniform film over a large area, and the film forming conditions and the like tend to be limited.
[0008]
The other is a film sandwiching portion, where a minute film deformation occurs due to thermal expansion of the film substrate or the like, causing unevenness in film thickness and film quality in this portion.
These problems become more prominent as the area is increased. In addition, the unevenness of each layer of the solar cell also affects the characteristics of the solar cell. Therefore, in order to obtain a solar cell having a large area and excellent characteristics, more and more uniform film formation is important.
[0009]
In view of the above problems, an object of the present invention is to provide a manufacturing method and a manufacturing apparatus having both the excellent uniform film forming property of a roll-to-roll process and the advantage of independent operation of a film forming chamber of a stepping roll process. It is in.
[0010]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present invention provides a thin film photoelectric conversion element in which a plurality of thin films having different properties are continuously laminated on a belt-shaped flexible film substrate while transporting the substrate to form a photoelectric conversion layer. In the manufacturing method, a laminated film is formed while using a cassette having at least one roll wound with a flexible film substrate, and sequentially mounting and detaching the cassette in independent film forming chambers for forming each layer. It shall be.
[0011]
By doing so, since each film is formed by a roll-to-roll process and in a film forming chamber independent of each other, it is possible to prevent the raw material gas from being mixed into another film forming chamber.
The manufacturing apparatus includes a cassette having at least one roll wound with a flexible film substrate, a plurality of independent film forming chambers for forming each layer, and the cassette is sequentially mounted and demounted in each film forming chamber. And moving means for performing the operation.
[0012]
By doing so, a film can be formed by a roll-to-roll process in a plurality of independent film forming chambers, and the stacked film can be formed by transferring between the film forming chambers by the moving means.
In particular, it is preferable that the cassette has two winding shafts.
As long as it has two winding shafts, there is no need to provide a roll on the film forming chamber side, and a drive device is sufficient.
[0013]
Each of the film forming chambers may be arranged around a common vacuum chamber provided with the cassette moving means, or each of the film forming chambers may be arranged in series.
If each of the film forming chambers is arranged around the common vacuum chamber provided with the moving means, cassettes can be transferred between the common vacuum chamber and each of the film forming chambers. Sex can be maintained. In addition, even when the respective film forming chambers are arranged in series, if the cassette is transferred between the adjacent film forming chambers except during the film forming, the independence between the film forming chambers can be maintained.
[0014]
Further, a film formation chamber formed by a chemical vapor deposition method and a film formation chamber formed by a sputtering method are provided.
The chemical vapor deposition method is a film forming method most suitable for forming a photoelectric conversion layer, and the sputtering method is a film forming method most suitable for forming an electrode film, and it is important to provide both methods.
Further, a pretreatment chamber for performing plasma treatment and vacuum heating treatment of the substrate is provided.
[0015]
Plasma treatment and vacuum heat treatment are extremely important in cleaning the substrate surface and forming a high-quality film.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
In order to solve the above-mentioned problems, the present invention provides a film forming method and a film forming apparatus capable of completely suppressing mutual diffusion of source gases between film forming chambers while performing all film forming by a uniform roll-to-roll process. Is devised. Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[Example 1]
FIG. 2 is a perspective view of the transport cassette 4 for transporting the flexible film substrate 1 used in the manufacturing apparatus of the present invention. Reference numeral 2 denotes a roll around which the flexible film substrate 1 is wound around a winding shaft 11. Reference numeral 12 denotes a case for holding two rolls 2, and a window 3 is provided in a portion corresponding to a film forming position of the flexible film substrate 1. Reference numeral 13 denotes a projection for rotating the winding shaft 11. A window 3a for inserting an electrode or the like at the time of film formation is also provided behind the case 12.
[0017]
As the flexible film substrate 1, a resin film such as aramid, polyether sulfone (PES), polyethylene naphthalate (PEN), polyethylene terephthalate (PET), or polyimide is used. Depending on the structure, a metal film may be used. The outer dimensions of the case 5 are about 800 × 400 mm, the height is 600 mm, and the window 6 for film formation is 100 × 500 mm.
[0018]
FIG. 1 is a schematic plan view showing the configuration of the manufacturing apparatus of the present invention. There is a common vacuum chamber 9 at the center, around which a preparation chamber 5, a pretreatment chamber 6, an electrode film formation chamber 7, and a semiconductor layer film formation chamber 8 are arranged. The common vacuum chamber 9 is also provided with a moving device 14 for inserting and withdrawing the roll cassette 4 into each chamber.
The roll cassette 4 is first placed in the preparation chamber 5, evacuated, and then placed in the common vacuum chamber 9. Therefore, the vacuum in the common vacuum chamber 9 is not broken, and contamination by the atmosphere can be avoided. Next, the roll cassette 4 is moved to the pre-processing chamber 6. Here, plasma processing and vacuum heating processing of the film substrate are performed. By exposing the film substrate 2 to plasma of argon gas or a mixed gas of argon gas and oxygen, the surface of the film substrate 2 is cleaned and activated. In addition, desorption of the adsorbed gas and the like on the surface of the film substrate 1 is performed by the vacuum heat treatment at about 300 ° C. Next, the layers are sequentially moved to the electrode film forming chamber 7 and further to the semiconductor layer film forming chamber 8 for forming a power generation layer made of, for example, a-Si, so that a laminated structure can be formed without exposure to the atmosphere. The plurality of electrode film forming chambers 7 and the plurality of semiconductor film forming chambers 8 are provided for forming a thick film and for forming a multilayer structure such as a pin by changing a doping gas or the like. It is. The electrodes are not limited to electrodes made of metal, and include transparent electrodes such as indium tin oxide (ITO).
[0019]
As described above, since each of the electrode film forming chambers 7 and the semiconductor layer film forming chamber 8 are operated independently, a laminated structure can be easily formed even when the film forming conditions of each layer are largely different. In particular, for electrode formation, sputtering performed at a high vacuum of 1 Pa or more is desirable. However, the electrode film forming chamber 7 performed at such a high vacuum is preferably a semiconductor formed by a chemical vapor deposition method at a lower vacuum. It can be installed together with the layer deposition chamber 8.
[0020]
In addition, since each semiconductor layer film forming chamber 8 is independent, it is possible to prevent characteristic deterioration caused by mixing of the source gas into another film forming chamber. As a result, the element interface structure and characteristics are improved, and a photoelectric conversion element having excellent performance can be manufactured. In the solar cell manufactured by the manufacturing method of the present invention, a conversion efficiency of 8.2% equivalent to that of the stepping roll process described above was obtained.
[0021]
Since film formation in each film forming chamber is equivalent to a roll-to-roll process, excellent uniform film formation is possible by achieving one-dimensional uniform discharge (in the width direction of the film substrate), and uniformity is achieved. The good thing is, of course. For example, the film thickness was within about 3% over about 400 m of one roll cassette. It can be seen that in the stepping roll process, the film thickness distribution on one film forming surface is about 6%, which is a great improvement. Since uniformity of discharge is easily obtained in this way, it is a very advantageous process for increasing the area.
[0022]
Although the manufacturing apparatus using this roll cassette is a highly productive apparatus, it has the advantage that the film forming chamber can be independently cleaned and maintained while the other film forming chambers are in operation. Time can be greatly reduced.
This roll cassette 4 can be applied not only to the formation of a laminated structure by the above-described manufacturing method but also to a modular device as it is.
[0023]
In the above embodiment, the case where the take-up shaft is two roll cassettes has been described. In this roll cassette, film formation and take-out of the roll cassette are possible regardless of which winding shaft the film substrate is wound on.
On the other hand, a roll cassette in which only one winding shaft is used and one end of the film substrate is taken out of the roll cassette is also conceivable. In that case, a winding shaft is also provided in the film forming chamber, and the film is formed while winding the film substrate around the winding shaft in the film forming chamber. However, after film formation, the film must be rewound on the winding shaft of the roll cassette.
[0024]
[Example 2]
FIG. 3 is a schematic plan view showing the configuration of another manufacturing apparatus of the present invention. A preparation room 5, a pretreatment room 6, an electrode film formation room 7, and a semiconductor layer film formation room 8 are arranged in series, and a take-out room 10 is further provided. In this case, although not shown, a moving device for transferring the roll cassette 4 is provided in each reaction chamber.
[0025]
After being inserted into the preparation chamber 5 and subjected to vacuum replacement, it is transferred to the pre-processing chamber 6 and subjected to plasma processing and heat treatment, and then introduced into the electrode film formation chamber 7 to form electrodes. Further, the semiconductor layer is transferred to the semiconductor layer deposition chamber 8 and a semiconductor layer is formed by the plasma CVD method. The roll cassette 4 repeats the sequential film formation and the movement to the next film formation chamber to form a laminated structure. Finally, it is transferred to the take-out chamber 10 and taken out into the atmosphere.
[0026]
Also in this manufacturing apparatus, since the electrode film forming chamber 7 and the semiconductor layer film forming chamber 8 are operated independently, a laminated structure can be easily formed even if the film forming conditions of each layer are largely different. For electrode formation, a film formation chamber by a sputtering method can be provided.
Further, since each semiconductor layer film forming chamber 8 is independent, deterioration of characteristics caused by mixing of the source gas into another film forming chamber can be prevented, and a photoelectric conversion element having excellent performance can be manufactured. Since the film formation in each film formation chamber is the same as the roll-to-roll process, it is needless to say that the uniformity is good.
[0027]
A manufacturing apparatus using this roll cassette is an apparatus having high productivity.
[0028]
【The invention's effect】
As described above, according to the present invention, in a method of manufacturing a thin film photoelectric conversion element using a flexible film substrate, a pretreatment of a manufacturing apparatus is performed using a roll cassette having a roll around which the flexible film substrate is wound as a unit. It is installed in a chamber and sequentially sent to the electrode deposition chamber or the semiconductor layer deposition chamber, and forms a laminated structure without exposure to the atmosphere to form a thin-film photoelectric conversion element. Provided are a manufacturing method and a manufacturing apparatus which have both advantages of film forming property and independent operation of a film forming chamber of a stepping roll process.
[0029]
In other words, since each deposition chamber is completely separated in vacuum, it is possible to connect processes having completely different deposition conditions and to prevent diffusion of source gas from other deposition chambers, thereby improving the element interface structure and characteristics. In addition, only one-dimensional uniform discharge (in the width direction of the film substrate) is achieved, and large area uniform film formation can be achieved at the same time.
[Brief description of the drawings]
FIG. 1 is a schematic plan view of a manufacturing apparatus according to the present invention. FIG. 2 is a perspective view of a roll cassette for transporting a flexible film substrate used in the manufacturing method of the present invention. FIG. 3 is a schematic view of another manufacturing apparatus according to the present invention. Plan view [Explanation of reference numerals]
DESCRIPTION OF SYMBOLS 1 Flexible film substrate 2 Roll 3 Processing window 3a Backside window 4 Roll cassette 5 Preparation room 6 Pretreatment room 7 Electrode film formation room 8 Semiconductor layer film formation room 9 Common vacuum room 10 Extraction room 11 Winding shaft 12 Case 13 Projection 14 Moving device

Claims (7)

A method for manufacturing a thin-film photoelectric conversion element, in which a plurality of thin films having different properties are continuously laminated on a belt-shaped flexible film substrate while transporting the substrate to form a photoelectric conversion layer, the flexible film substrate Using a cassette having at least one roll wound with a cassette, and sequentially mounting and detaching the cassette in independent film forming chambers for forming each layer, and forming a stacked film, Device manufacturing method. In a manufacturing apparatus of a thin film photoelectric conversion element for forming a photoelectric conversion layer by continuously laminating a plurality of thin films having different properties on a belt-shaped flexible film substrate while transporting the substrate, the flexible film substrate A cassette having at least one roll wound thereon, a plurality of independent film forming chambers for forming each layer, and moving means for sequentially attaching and detaching the cassette to and from each film forming chamber. For manufacturing thin film photoelectric conversion elements. 3. The apparatus according to claim 2, wherein the cassette has two winding shafts. 4. The apparatus according to claim 2, wherein each of the film forming chambers is arranged around a common vacuum chamber provided with a moving unit of the cassette. 5. The apparatus according to claim 2, wherein each of the film forming chambers is arranged in series. The apparatus for manufacturing a thin-film photoelectric conversion device according to claim 4, wherein a film formation chamber formed by a chemical vapor deposition method and a film formation chamber formed by a sputtering method are provided as a method of forming a layer. 7. The apparatus according to claim 6, further comprising a pre-processing chamber for performing plasma processing and vacuum heating processing of the substrate.

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