JP4985209B2 - Thin film solar cell manufacturing equipment - Google Patents

Description

  The present invention relates to an apparatus for manufacturing a thin film solar cell in which a metal thin film serving as an electrode is formed on the surface of a strip-like flexible film substrate, and more specifically, a film by a guide roll in an intermediate chamber provided between film forming chambers. The present invention relates to an apparatus for manufacturing a thin-film solar cell that prevents generation of wrinkles on a substrate.

  Currently, clean energy research and development is underway from the standpoint of environmental protection. Among them, solar cells are attracting attention because their resources (sunlight) are infinite and pollution-free.

  Thin film solar cells are expected to become the mainstream of future solar cells because they are thin and lightweight, inexpensive to manufacture, and easy to increase in area.

  Conventional thin-film solar cells have used glass substrates, but research and development of flexible solar cells using plastic films and metal films has been promoted in terms of weight reduction, workability, and mass productivity. Taking advantage of this flexibility, mass production became possible by a roll-to-roll method or a stepping roll method.

  In the above thin film solar cell, a plurality of photoelectric conversion elements (or cells) formed by laminating a metal electrode layer, a photoelectric conversion layer made of a thin film semiconductor layer, and a transparent electrode layer on a flexible electrically insulating film substrate are formed. . The voltage required for the metal electrode of the first photoelectric conversion element and the transparent electrode of the last photoelectric conversion element by repeatedly connecting the metal electrode of one photoelectric conversion element and the transparent electrode of the adjacent photoelectric conversion element. Can be output.

  Such a photoelectric conversion element and its series connection are formed by forming an electrode layer and a photoelectric conversion layer, patterning each layer, and a combination procedure thereof. The configuration and manufacturing method of the solar cell are described in, for example, (Patent Document 1 and Patent Document 2).

  FIG. 3 shows a conceptual diagram of the structure of the thin film solar cell described in Patent Document 2. FIG. 3 is a perspective view of a flexible thin film solar cell using a plastic film as a substrate. The unit photoelectric conversion element 62 formed on the front surface of the substrate 61 and the connection electrode layer 63 formed on the back surface of the substrate 61 are each completely separated into a plurality of unit units, and are formed by shifting the separation positions.

  For this reason, the current generated in the photoelectric conversion layer 65, which is an amorphous semiconductor portion of the element 62, is first collected in the transparent electrode layer 66, and then on the back surface through the current collecting holes 67 formed in the transparent electrode layer region. It leads to the connection electrode layer 63, and further to the outside of the transparent electrode layer region of the element adjacent to the element through the connection hole 68 for series connection formed outside the transparent electrode layer region of the element in the connection electrode layer region. The extended lower electrode layer 64 is reached, and both elements are connected in series.

  The simplified manufacturing process of the thin film solar cell is shown in FIGS. Using the plastic film 71 as a substrate (step (a)), a connection hole 78 is formed in this (step (b)), and a first electrode layer (lower electrode) 74 and a third electrode layer (connection electrode) are formed on both sides of the substrate. After (part) 73 is formed (step (c)), a current collecting hole 77 is formed at a position away from the connection hole 78 by a predetermined distance (step (d)). The formation of the first electrode layer 74 and the third electrode layer 73 in the step (c) is performed in two stages by inverting the substrate 71 in a film forming apparatus described later. Both electrode layers 74 and 73 are formed by growing. Thereby, an electrical connection between the two electrode layers is obtained.

  Next, a semiconductor layer 75 to be a photoelectric conversion layer and a transparent electrode layer 76 to be a second electrode layer are sequentially formed on the first electrode layer 74 (step (e) and step (f)), A fourth electrode layer (connection electrode layer) 79 is formed on the three-electrode layer 73 (step (g)). Thereafter, the thin film on both sides of the substrate 71 is separated using a laser beam to form a series connection structure as shown in FIG.

  In the process of FIG. 4, in steps (a), (b) and (d), the substrate is processed in the atmosphere, but the other steps are processed in a vacuum film forming apparatus which will be described later. . Therefore, in the case of the above steps, in the subsequent steps of steps (b) and (d), the substrate is processed in the atmosphere and then introduced into the vacuum container of the vacuum film forming apparatus. In addition, the formation of the first electrode layer 74 and the third electrode layer 73 in the step (c) is performed in two stages by inverting the substrate 71 as described above. Is once taken out into the atmosphere and again introduced into the vacuum vessel.

  As described above, a method for producing a thin film of the thin film solar cell includes a roll-to-roll method or a stepping roll method. Both types are equipped with a substrate transport means by a plurality of rolls, the former is a method of continuously forming a film on a substrate that moves continuously in each film forming chamber, and the latter is stopped simultaneously in each film forming chamber. A method is employed in which a film is formed on a substrate and the substrate portion after film formation is sent to the next film formation chamber.

  The stepping roll type film forming apparatus is excellent in that the characteristics of each thin film can be obtained stably because gas mutual diffusion between adjacent film forming chambers can be prevented. It is described in Document 3 and Patent Document 4.

  FIG. 5 shows an example of a configuration of a vacuum film forming apparatus of a stepping roll film forming system having a plurality of film forming chambers in a common vacuum chamber. The apparatus shown in FIG. 5 is an unwinder chamber 90 for unwinding a flexible substrate, and a film forming chamber as a plurality of independent processing spaces for forming a metal electrode layer, a photoelectric conversion layer, a transparent electrode layer, and the like. 80 and a winding winder chamber 91, and the substrate 92 is configured to be deposited in a plurality of deposition chambers 80 while being rolled out from the core 82 and wound on the core 83. The common chamber 81 houses a plurality of film forming chambers 80 therein.

  In the film formation chamber, film formation is performed by sputtering film formation or plasma chemical vapor deposition (hereinafter referred to as plasma CVD method). For example, in the stepping roll method for forming a film by the plasma CVD method, the film formation chamber is opened, the substrate frame is moved, the film formation chamber is sealed, the raw material gas is introduced, the pressure is controlled, the discharge is started, the discharge is finished, the raw material gas is stopped, the gas is generated. The operation consisting of opening the membrane chamber is repeated.

  FIG. 6 shows an example of a schematic structure of the film forming chamber described in Patent Document 4. 6A and 6B are schematic cross-sectional views when the film formation chamber is opened and sealed, respectively. A box-shaped lower film-forming chamber wall 121 and an upper film-forming chamber wall 122 are arranged opposite to each other on the upper and lower sides of the flexible substrate 100 that is intermittently transferred. An independent processing space comprising a chamber and an upper film forming chamber is configured. In this example, the lower film forming chamber includes a high voltage electrode 131 connected to a power source 140, and the upper film forming chamber includes a ground electrode 132 with a built-in heater 133.

  At the time of film formation, as shown in FIG. 6B, the upper film formation chamber wall 122 is lowered, and the ground electrode 132 holds the substrate 100 and is attached to the opening side end surface of the lower film formation chamber wall 121. Contact the material 141. As a result, an airtightly sealed film formation space 143 communicating with the exhaust pipe 142 is formed from the lower film formation chamber wall 121 and the substrate 100. In the film formation chamber as described above, by applying a high frequency voltage to the high voltage electrode 131, plasma is generated in the film formation space 143, and a source gas introduced from an introduction pipe (not shown) is decomposed on the substrate 100. For example, a photoelectric conversion layer can be formed into a film.

  On the other hand, the roll-to-roll method is excellent in mass productivity because the substrate is continuously moved between rolls provided in the horizontal direction or between the rolls provided in steps in the vertical direction to perform a plurality of film forming operations continuously. ing. The configuration of the apparatus is described in, for example, Patent Literature 5 as a substrate that is continuously moved to rolls provided in steps in the vertical direction.

  About the structure of the apparatus of the roll-to-roll system which moves a board | substrate continuously between the rolls provided in the horizontal direction regarding the film-forming apparatus by sputtering, the schematic structure is shown in FIG. A reaction chamber as a vacuum chamber, a vacuum exhaust system, a sputtering gas supply system, and the like are not shown.

  The electrode forming apparatus shown in FIG. 7 is a type that horizontally transports a film substrate, and a film substrate unwinding roll 151 and a winding roll 152 are also horizontally disposed. In the apparatus shown in FIG. 7, the film substrate 153 is transported between the heater 154 that also serves as a ground electrode and the application electrode 155 that has a target. The film substrate 153 is electrode-formed by sputtering while being heated in a non-contact manner by a heater from the back side.

  In the electrode forming apparatus shown in FIG. 7, an example in which a plurality of (three) targets are provided is shown. This is an example in which the electrode layer is formed as a laminated film of a plurality of materials. In the case of forming with a single metal such as, one target is sufficient.

  According to the apparatus shown in FIG. 7, it is possible to form an electrode on one side of the film substrate by carrying the film substrate once. When electrode formation is performed on both sides, after the electrode formation on one side is completed, the apparatus is opened to the atmosphere, the film substrate is inverted and set, evacuated again, and then degassed. Then, electrode formation is performed.

  By the way, when transporting such a film substrate, since the width of the film substrate is considerable, slack or wrinkles occur during transport, so the film substrate unwinding roll and take-up roll shaft are placed vertically. Thus, a method of transporting the film substrate in a vertically placed state is adopted. In this case, the film substrate is transported between the heater also serving as the ground electrode and the application electrode having the target, and electrode formation is performed.

In such a film formation chamber for forming an electrode layer, film formation is performed in a state where the film is evacuated by a vacuum pump and heated to about 300 ° C. by a heater (Patent Document 6). ).
Japanese Patent Laid-Open No. 10-233517 JP 2000-223727 A JP-A-6-292349 JP-A-8-250431 Japanese Patent Publication No. 7-38378 JP 2000-307139 A

  The film forming chamber for forming this electrode layer is divided into a plurality of film forming chambers and sequentially transports the film substrate, but in the middle of the film forming chamber, in order to prevent loosening of the film substrate, etc. An intermediate chamber provided with a guide roll is provided to convey the film substrate at a constant speed. Film formation was performed on the film substrate at a high temperature of about 300 ° C. by a heater in the previous film formation chamber, which was not preferable because wrinkles were generated when the film substrate was fed by a guide roll. The temperature of this film substrate is usually about 177 ° C. In the heated film substrate, the elongation due to thermal expansion becomes a mountain on the guide roll and buckles due to the inner ring difference, which causes the generation of conveyance wrinkles. I was invited. In particular, when an electrode on the power generation layer side (also referred to as the back surface) is provided on one side of the film substrate, the electrode is formed in comparison with the film surface when forming the electrode on the opposite side (also referred to as the back surface). Since the emissivity of the electrode surface provided with is low, the temperature history of the film is greatly different when forming the back surface compared to when forming the back surface, and the film temperature is difficult to cool. And the malfunction which the conveyance wrinkle which contacts a guide roll in the state with high film temperature generate | occur | produced had arisen.

  An object of the present invention is to solve the above-mentioned problems, and to provide a thin-film solar cell manufacturing apparatus that can prevent conveyance wrinkles due to guide rolls and improve workability.

In order to solve the above problems, the present invention feeds a strip-shaped flexible film substrate wound around an unwinding roll to a plurality of film forming chambers maintained in a substantially vacuum state, and faces the film forming chambers to each other. Discharge between the arranged ground electrode and the application electrode having the target material to form a metal thin film to be an electrode on the surface of the film substrate under constant heating, and to form a film substrate on which the metal thin film is formed In the thin-film solar cell manufacturing apparatus configured to be wound by a winding roll, an intermediate chamber provided with a guide roll for transporting the film substrate is provided between the film forming chambers, and is provided in a stage preceding the intermediate chamber. The temperature of the film substrate sent from the film formation chamber is reduced by the temperature of the film substrate before reaching the guide roll in the intermediate chamber after leaving the film formation chamber. So So as to reduce to below, from the outlet of the film forming chamber provided in front of the intermediate chamber to the setting of the distance to the guide roll.
The present invention also provides a ground electrode disposed in a manner facing the film formation chamber by feeding a strip-shaped flexible film substrate wound around an unwinding roll to a plurality of film formation chambers maintained in a substantially vacuum state. And an applied electrode having a target material, a metal thin film to be an electrode is formed on the surface of the film substrate under constant heating, and the film substrate on which the metal thin film is formed is wound by a winding roll. In the thin-film solar cell manufacturing apparatus, an intermediate chamber provided with a guide roll for transporting the film substrate is provided between the film formation chambers, and radiation is directed toward the film substrate on the inner surface of the intermediate chamber. Extending the heat absorption plate having a high rate, the temperature of the film substrate sent from the film forming chamber provided in the previous stage of the intermediate chamber is set to reach the guide roll of the intermediate chamber after leaving the film forming chamber. on the film substrate By degrees is reduced, so reducing to a boundary temperature or below to wrinkles, from the outlet of the film forming chamber provided in front of the intermediate chamber to the setting of the distance to the guide roll .

According to the first aspect, it is possible to prevent the occurrence of conveyance wrinkles generated on the film substrate by the guide roll. It is possible to prevent the occurrence of conveyance wrinkles generated on the film substrate even when the back surface is formed with electrodes formed on one side.
According to the second aspect, the heat of the film substrate can be diffused by the heat absorption plate having a high emissivity, and the temperature of the film substrate can be lowered.

Hereinafter, the illustrated embodiment will be described in detail with reference to the drawings.
FIG. 1 conceptually illustrates only the basic components for forming a thin-film electrode layer in a solar cell manufacturing apparatus. The reaction chamber, the sputtering gas supply system, the exhaust system, or the film substrate transfer means will be omitted.

  In FIG. 1, the thin-film electrode layer forming apparatus is a so-called roll-to-roll method, and includes a feed chamber 3 containing an unwinding roll 2 in which a strip-like flexible film substrate 1 is wound into a roll, and an electrode layer. A winding chamber 5 that houses a winding roll 4 for winding the film substrate 1 on which a metal thin film is formed, and the feeding chamber 3 and the winding chamber 5 are arranged in parallel, and the film substrate 1 is made of metal. A plurality of film forming chambers 6 for forming a thin film and an intermediate chamber 8 provided at a substantially intermediate position between the plurality of film forming chambers 6 and provided with guide rolls 7 for transporting the film substrate 1 are provided.

  The unwinding roll 2 and the winding roll 4 are arranged in the vertical direction, and convey the plurality of film forming chambers 6 and intermediate chambers 8 with the film substrate 1 standing up. An opening through which the film substrate 1 passes is formed. The feeding chamber 3 and the winding chamber 5 have a built-in mechanism (not shown) for applying a constant tension to the film substrate 1. The drive mechanism can be performed, for example, by incorporating a motor and a speed reducer in the winding chamber 5 and rotating the winding roll 4 at a constant speed. Further, the feeding chamber 3 may be provided with a mechanism for applying a constant braking so that the film substrate 1 is pulled out while maintaining a constant tension. The feeding chamber 3 and the winding chamber 5 are provided with an auxiliary roller 9 and a driving roller 10, respectively, and are controlled so that the driving roller 10 is driven and the conveyance of the film substrate 1 is maintained in an optimum state. The feeding chamber 3 and the winding chamber 5 are controlled by a control mechanism (not shown) so as to maintain a constant speed.

A vacuum device (not shown) is connected to the plurality of film forming chambers 6 and the intermediate chambers 8 and is evacuated so as to maintain a certain degree of vacuum of at least atmospheric pressure. The plurality of film forming chambers 6 are each provided with a ground electrode 12 having a built-in heater 11 on one side of the film substrate 1 to be conveyed, and on the other side, a high voltage connected to a DC power source V. A voltage electrode 13 is disposed. The heater 11 normally heats the film substrate 1 at a temperature of about 300 ° C. A DC power source V is connected to the ground electrode 12 and the high voltage electrode 13 in each film forming chamber 6, and a high voltage is applied between the ground electrode 12 and the high voltage electrode 13.
The high-voltage electrode 13 is formed by ionizing the introduced gas by discharge between the ground electrode 12 and sputtering a target such as silver, aluminum, or zinc oxide to form a metal thin film serving as an electrode on the surface of the film substrate 1. To form.

The intermediate chamber 8 is arranged in the middle of the plurality of film forming chambers 6, and a guide roll 7 for stably transporting the film substrate 1 at a constant distance L from the outlet of the film forming chamber 6 in the preceding stage. Has been placed. The guide roll 7 is composed of a plurality of rollers 7 a, 7 b, 7 d (three in the illustrated example), and is conveyed while maintaining tension on the film substrate 1. The roller 7b is supported so as to be movable up to a position 7c, and applies tension to the film substrate 1 by being pressed against the film substrate 1.
As for the position of the guide roll 7, the roller 7 a at the tip of the guide roll 7 is arranged at a certain distance from the outlet 6 b of the film forming chamber 6 in the preceding stage.

The temperature of the film substrate 1 exiting from the outlet 6b of the film formation chamber 6 in the previous stage normally reaches 230 ° C, and this temperature is cooled to a boundary temperature of 170 ° C where the wrinkles are generated or lower. The position of the guide roll 7 in the intermediate chamber 8 is set at a distance L.
Usually, the film substrate 1 is transported at a film transport speed of 1 m / min, and the distance at which the 230 ° C. film substrate 1 is lowered to 170 ° C. is about 0.6 m. The holding angle of the guide roll 7 is 51 °. Therefore, L = 0.6 m in this case.

  According to the embodiment, first, the vacuum apparatus is operated to hold the plurality of film forming chambers 6 and the intermediate chambers 8 in a vacuum state. The film forming chamber 6 is heated to a set temperature of about 300 ° C. by a ground electrode 12 having a built-in heater 11 and is kept in a high temperature vacuum state. And the unwinding roll 2 and the winding roll 4 are rotated by the action | operation of a drive device, and the film board | substrate 1 is conveyed at a film conveyance speed and about 1 m / min. The film substrate 1 drawn out from the unwinding roll 2 is wound around the winding roll 4 through a plurality of film forming chambers 6 and intermediate chambers 8. The film substrate 1 passing through the plurality of film forming chambers 6 passes between the ground electrode 12 and the high voltage electrode 13 in an upright state, and a vacuum is applied to one surface of the film substrate 1 by the discharge of the ground electrode 12 and the high voltage electrode 13. The metal foil film is formed by vapor deposition.

The film substrate 1 on which the metal foil film is formed in the film forming chamber 6 is at a high temperature of 177 ° C. or higher before entering the intermediate chamber 8, and is intermediate from the outlet of the film forming chamber 6 in the preceding stage of the intermediate chamber 8. The distance until the guide roll 7 of the chamber 8 is reached, about 0.6 m, is reduced to about 170 ° C. during the conveyance time. Thus, since the temperature is lowered to about 170 ° C. before the film substrate 1 is conveyed by the guide roll 7, the generation of wrinkles generated on the film substrate 1 can be prevented.
In particular, generation of wrinkles can be prevented even when the opposite surface (back surface) of the film substrate 1 on which the metal foil film has already been formed on one surface (back surface) is formed. Thus, the film substrate 1 having the metal foil film formed on both sides proceeds to the next step of forming the semiconductor layer.

  According to the above embodiment, the distance L from the outlet 6b of the film formation chamber 6 in the previous stage to the position reaching the guide roll 7 is set to the boundary temperature 170 ° C. at which the temperature of the film substrate 1 is generated from 177 ° C. Alternatively, since the distance is set to be cooled to a temperature lower than that, wrinkling of the film substrate 1 can be prevented. In particular, when forming the opposite surface (back surface) of the film substrate 1 on which the metal foil film has already been formed on one surface (back surface), generation of wrinkles can be prevented. When the film is transported at a speed of 1 m / min, generation of wrinkles can be prevented with L = 0.6 m. In addition, it has been confirmed that wrinkles do not occur up to 200 N (control upper limit) with respect to tension, which is one of the causes of wrinkles.

  The present invention is not limited to the above-described embodiment. For example, as shown in FIG. 2, a plurality of fins (heat-absorbing plates) 15 and 16 having high emissivity are provided on the inner wall surface of the intermediate chamber 8. By extending the fins 15 and 16 toward both surfaces of the film substrate 1, the heat of the film substrate 1 can be lowered more quickly. In this case, the fins 15 and 16 may be formed only on one side of the inner wall surface of the intermediate chamber 8 and can be formed at one or more locations. Thereby, the distance L for lowering the film substrate 1 to about 170 ° C. can be shortened. Therefore, since the distance to the guide roll 7 can be shortened, the intermediate chamber 8 can be made a more compact structure. Further, the fins 15 and 16 are arranged in parallel with the film substrate, and the shape is not limited to a flat plate shape, but may be a ring shape or a radial shape, and the inside thereof may be hollow so as to be in contact with the outside air.

  Furthermore, in the said embodiment, although applied to the formation apparatus of the thin film electrode layer which forms a metal foil film on one side, it can also be applied to the formation apparatus of the thin film electrode layer which forms a metal foil film on both surfaces. In addition, it can be applied to a thin film electrode layer forming apparatus that transports the film substrate 1 in a horizontal state, and other modifications can be made without departing from the scope of the present invention. Absent.

It is a block diagram which shows the formation apparatus of the thin film electrode layer by embodiment of the manufacturing apparatus of the thin film solar cell of this invention. It is a block diagram which shows the modification of the formation apparatus of the thin film electrode layer by embodiment of the manufacturing apparatus of the thin film solar cell of this invention. It is a perspective view which shows the structure conceptual diagram of the conventional thin film solar cell. The simplified manufacturing process of the conventional thin film solar cell is shown, (a)-(g) is a conceptual sectional view showing each process. It is a conceptual sectional view showing a configuration of a conventional stepping roll film forming type vacuum film forming apparatus. An example of a schematic structure of a conventional film forming chamber is shown, and (a) and (b) are schematic cross-sectional views when the film forming chamber is opened and sealed, respectively. It is a conceptual diagram which shows the film-forming apparatus by the conventional sputtering.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Film substrate 2 Unwinding roll 3 Feeding chamber 4 Winding roll 5 Winding chamber 6 Film-forming chamber 7 Guide roll 8 Intermediate chamber 9 Auxiliary roller 10 Drive roller 11 Heater 12 Ground electrode 13 High voltage electrode 15, 16 Fin (heat absorption plate) )

Claims (2)

An application having a ground electrode and a target material, which are fed to a plurality of film forming chambers maintained in a substantially vacuum state, with a strip-like flexible film substrate wound around an unwinding roll, facing each other. A thin film solar in which a metal thin film that is discharged between the electrodes and formed on the surface of the film substrate is formed under constant heating, and the film substrate on which the metal thin film is formed is wound up by a winding roll In the battery manufacturing apparatus, an intermediate chamber provided with a guide roll for transporting the film substrate is provided between the film forming chambers, and the film substrate sent from the film forming chamber provided in the preceding stage of the intermediate chamber. temperature, that the temperature of the film substrate to reach the intermediate chamber of the guide rolls after leaving the film forming chamber is reduced, to reduce to a boundary temperature or below to wrinkles, the in Apparatus for manufacturing a thin-film solar cells from the outlet of the film forming chamber provided in front of the chamber, characterized in that setting the distance to the guide roll. An application having a ground electrode and a target material, which are fed to a plurality of film forming chambers maintained in a substantially vacuum state, with a strip-like flexible film substrate wound around an unwinding roll, facing each other. A thin film solar in which a metal thin film that is discharged between the electrodes and formed on the surface of the film substrate is formed under constant heating, and the film substrate on which the metal thin film is formed is wound up by a winding roll In the battery manufacturing apparatus, an intermediate chamber having a guide roll for transporting the film substrate is provided between the film forming chambers, and an endothermic plate having a high emissivity toward the film substrate is provided on the inner surface of the intermediate chamber. to extend the temperature of the film substrate fed from the film forming chamber provided in front of the intermediate chamber, after leaving the film forming chamber of the film substrate to reach the intermediate chamber of the guide roll temperature Decrease In, as reduced to boundary temperature or below to wrinkles, thin-film solar cell, wherein the outlet of the film forming chamber provided in front of the intermediate chamber that adjusts the distance of the guide roll Manufacturing equipment.

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