JP2014239086A - Process of manufacturing organic thin-film solar cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a process of manufacturing an organic thin-film solar cell with which work safety is secured and conversion efficiency and a yield are improved.SOLUTION: The process of manufacturing an organic thin-film solar cell, having a plurality of photoelectric conversion elements each of which is constituted of at least a bottom electrode, an active material layer, and an upper electrode on a substrate, includes depositing the active material layer by a coating method in a state where the bottom electrode constituting each photoelectric conversion element is mutually electrically connected.

Description

  The present invention relates to a method for manufacturing a solar cell, and particularly relates to a method for manufacturing an organic thin film solar cell that is suitably used when an organic thin film solar cell is manufactured using a coating method.

Organic thin-film solar cells are generally composed of a plurality of unit cells (hereinafter sometimes referred to as photoelectric conversion elements). In the manufacturing process, after forming each layer to form a unit cell A method of patterning by laser scribing or a method of forming each layer using a mask is employed.
Patent Document 1 describes a manufacturing example of an organic solar cell in which a lower electrode is formed using a mask and a plurality of photoelectric conversion elements are connected in series. Patent Document 2 proposes a method in which a lower transparent electrode is processed by a laser and connected in series. These methods are different in their means, but in any case, before the organic layer which is an active layer is formed, the lower electrode constituting the cell is completely electrically insulated from the lower electrode of the adjacent cell. The

JP 2006-237165 A JP 2010-287800 A

When the present inventors examined, when the organic thin film solar cell was produced by the method described in patent document 1 or patent document 2, the lower electrode formed and patterned on the substrate might be charged, respectively. found. The charging of the lower electrode significantly hinders uniform film formation when an organic layer or other layer is laminated on the lower electrode. If a non-uniform film is formed, not only the appearance is impaired, but the organic thin film solar cell itself cannot exhibit its original performance. In addition, when an organic layer is formed as an active layer by a coating method, a flammable organic solvent is used and coating is performed in a dry room environment. It may happen and there are concerns about safety.
This invention solves the said problem, and makes it a subject to provide the manufacturing method of the organic thin-film solar cell excellent in conversion efficiency and productivity.

  The inventors of the present invention have made extensive studies to solve the above problems, and in the process of manufacturing an organic thin film solar cell having a monolithic structure in which photoelectric conversion elements are connected in series, the lower electrodes constituting each photoelectric conversion element are The inventors have found that the above problem can be solved by forming an active layer while being electrically connected to each other, and have completed the present invention.

The present invention is a method for producing an organic thin-film solar cell having a plurality of photoelectric conversion elements composed of at least a lower electrode, an active layer, and an upper electrode on a substrate,
In the organic thin film solar cell manufacturing method, the active layer is formed by a coating method in a state where lower electrodes constituting each photoelectric conversion element are electrically connected to each other.
The lower electrodes are preferably separated from each other by patterning the lower electrode after forming the upper electrode.
The patterning is preferably performed by laser scribe.

  According to the present invention, when manufacturing an organic thin film solar cell having a monolithic structure, the charging of the lower electrode formed on the substrate can be greatly reduced, and the active layer is formed uniformly on the lower electrode without unevenness. It becomes possible. As a result, an organic thin-film solar cell with improved conversion efficiency and yield can be provided. In addition, work safety can be improved.

It is an upper surface schematic diagram of the serial array which concerns on the prior art which has a monolithic structure where the several thin film photoelectric conversion cell was connected in series. It is an upper surface schematic diagram showing the manufacturing method of the serial array concerning this embodiment which has a monolithic structure where a plurality of thin film photoelectric conversion cells were connected in series. It is an upper surface schematic diagram showing the manufacturing method of the serial array concerning this embodiment which has a monolithic structure where a plurality of thin film photoelectric conversion cells were connected in series. It is sectional drawing which shows the conventional manufacturing method of the serial array which has a monolithic structure, and shows the AA 'direction cross section in FIG. It is sectional drawing which shows the manufacturing method which concerns on this embodiment of the serial array which has a monolithic structure, and shows the BB 'direction cross section in FIG. It is a cross-sectional schematic diagram which shows the specific aspect of the patterning which concerns on this embodiment. It is a schematic diagram showing the general layer structure of an organic thin film solar cell. It is a schematic diagram showing the general layer structure of a solar cell. It is a schematic diagram showing the general layer structure of a solar cell module.

Hereinafter, the present invention will be described in detail while showing specific embodiments. However, the present invention is not limited to the following description, and those skilled in the art will readily understand that the form and details can be variously changed without departing from the spirit and scope of the present invention. Note that in the structures of the present invention described below, the same portions or portions having similar functions are denoted by the same reference numerals in different drawings, and description thereof is not repeated.
In the method for producing an organic thin film solar cell of the present invention, the substrate may be handled individually as a single wafer, or may be handled by a roll-to-roll continuous conveyance operation. In either case, it is preferable to ground the lower electrode during coating film formation. From the viewpoint of productivity, the roll-to-roll method is preferable.

The manufacturing method of the organic thin-film solar cell which concerns on the embodiment of this invention includes the process of forming an active layer into a film by the apply | coating method in the state in which the lower electrode which each photoelectric conversion element has was electrically connected.
The organic thin-film solar cell manufactured by this embodiment has one or more series arrays of a monolithic structure in which a plurality of photoelectric conversion elements are connected in series. An organic thin film solar cell having a monolithic structure can be manufactured through a step of forming at least a lower electrode, an active layer, and an upper electrode on the substrate, and a step of dividing the formed film. In order to form such a monolithic structure, a series array is formed in addition to patterning of the lower electrode for forming an open groove in a portion necessary for connecting adjacent photoelectric conversion elements in series. Therefore, it is necessary to pattern the lower electrode for forming an insulating groove for the purpose. One serial array may be formed on one substrate, or a plurality of direct arrays may be formed. The plurality of series arrays can be formed by providing an insulating groove so that the plurality of series arrays are electrically insulated from each other by the patterning.

The patterning of the lower electrode in the conventional method for manufacturing a thin film solar cell will be described with reference to FIGS.
FIG. 1 is a schematic top view of a conventional serial array having a monolithic structure in which a plurality of unit cells are connected in series. FIG. 1 (a) shows patterning of the lower electrode laminated on the substrate. In order to connect the photoelectric conversion elements in series in the vertical direction of FIG. 1A, the lower electrode is patterned in a direction perpendicular to the series connection direction. A first open groove 41 is formed by this patterning. Similarly, in order to form a series array, the lower electrode is patterned to form the insulating open grooves 46.
The insulating open groove 46 is formed not only in the direction perpendicular to the series connection direction but also in the parallel direction. The first open grooves 41 and the insulating open grooves 46 completely separate the lower electrodes constituting each photoelectric conversion element from the other lower electrodes (islandization of the lower electrodes) and are electrically insulated from each other. State (hereinafter sometimes referred to as a state of being not electrically connected). Thereafter, the active layer and the upper electrode are formed and patterned to produce the serial arrays 30 and 30 'as shown in FIG.

FIG. 3 shows a cross-sectional view in the AA ′ direction in FIG.
FIG. 3A is a cross-sectional view in the AA ′ direction in FIG. 1A, showing a patterning process of the lower electrode performed after forming the lower electrode on the substrate, and FIG. It is sectional drawing of the AA 'direction in 1 (b), and shows the patterning process after upper electrode formation.

As described above, in the conventional method for manufacturing an organic thin film solar cell, the lower electrodes constituting the photoelectric conversion elements are separated from each other even between the formed series arrays, and are electrically insulated from each other. An active layer was formed. However, when the lower electrode constituting each photoelectric conversion element is separated from each other and not electrically connected, an organic material is applied on the lower electrode to form an active layer. It was found that the film could not be formed and unevenness occurred.
That is, in the conventional method, since the lower electrodes constituting the photoelectric conversion element are separated from each other and electrically insulated, the lower electrode is charged due to generation of static electricity or the like. Then, when an active layer or other layer is coated on the lower electrode while the lower electrode is charged, the lower electrode is charged to repel the ink for coating and form a uniform film. Will not be possible and unevenness will occur. Further, if the active layer becomes uneven, not only the appearance of the organic thin film solar cell is impaired, but each photoelectric conversion element itself cannot exhibit its original performance. Furthermore, when manufacturing a photoelectric conversion element constituting an organic thin-film solar cell by a coating method, a flammable organic solvent is used and coating is performed in a dry room environment. There is a possibility that an electrostatic explosion may occur, and there is a concern about safety.

On the other hand, in FIG. 2A showing the embodiment of the present invention, only the first groove 41 for connecting the photoelectric conversion elements in series is formed before the step of forming the active layer by the coating method. The lower electrode is patterned so as to be formed, and the patterning for forming the series array is not performed. Therefore, each lower electrode constituting the photoelectric conversion element is electrically connected without being separated from each other between the formed series arrays. Therefore, even if static electricity or the like is generated, the lower electrode is discharged. No charging occurs. Therefore, even if an active layer is applied and formed on the lower electrode, the ink is not repelled by the electric charge, and the active layer can be uniformly formed, thereby providing a photoelectric conversion element with improved conversion efficiency and yield. it can. In the present invention, the state in which the lower electrodes constituting each photoelectric conversion element are electrically connected to each other means that the lower electrodes are patterned to form a series array as shown in FIG. In a state before performing, the lower electrodes constituting each photoelectric conversion element are not separated from each other (is not formed into islands), or the separated lower electrodes constituting each photoelectric conversion element have a surface resistance. It means a state in which they are connected to each other through members having a rate of 100Ω / sq or less. For example, when the lower electrodes constituting each photoelectric conversion element, which are completely separated from each other by patterning, are connected to each other via a zinc oxide layer having a surface resistivity of 100 Ω / sq or more, each photoelectric conversion The lower electrodes constituting the element are not considered to be electrically connected to each other.
Then, as shown in FIGS. 2B and 2C, after the upper electrode is formed, the lower electrode is patterned again to form the insulating open groove 45. Thus, the lower electrode is completely separated from other lower electrodes, and a series array is formed.

Hereinafter, specific embodiments of the present invention will be further described with reference to the drawings.
<1. Patterning>
FIG. 4 shows a manufacturing process of an organic thin film solar cell having a plurality of photoelectric conversion elements according to this embodiment. On the other hand, FIG. 3 is the figure shown about the manufacturing method of the organic thin-film solar cell based on a prior art.
Examples of a method of patterning each layer constituting the photoelectric conversion element include a method of processing with a laser scriber or a mechanical scribe after the formation of a uniform layer. Further, a layer having a specific pattern shape may be formed using mask film formation or screen printing, and the present invention is not limited to the illustrated embodiment. However, in order to secure a wider effective element area, it is preferable to perform patterning by laser scribe capable of fine processing. Below, the manufacturing method of the organic thin-film solar cell which has the serial array which patterned by the laser scribe and serialized the unit cell is illustrated.

In the step of FIG. 4A, an open groove is formed by patterning the surface of the lower electrode of the laminate in which the substrate and the lower electrode are laminated by laser scribing.
4A, a serial connection portion of the lower electrode 32 having the first open groove 41 on the substrate 31 can be formed. The width | variety of the 1st open groove 41 is 5 micrometers or more normally, Preferably it is 10 micrometers or more, More preferably, it is 25 micrometers or more, Usually 1000 micrometers or less, Preferably it is 500 micrometers or less, More preferably, it is 300 micrometers or less, More preferably, it is 100 micrometers or less. The method for forming the first groove 41 is not limited to laser scribe, and other methods include mechanical scribe. Further, the lower electrode 32 may be formed so as to provide the first groove 41 by using a method such as lift-off, mask film formation, gravure printing, screen printing, and ink jet. At this time, the first open grooves 41 only for the portions necessary for the series connection of the unit cells are formed, and patterning for forming the series array is not performed, and the lower electrode 32 constituting the photoelectric conversion element is replaced with the other It is important to keep it electrically connected to the lower electrode.

  Next, as shown in FIG. 4B, the lower buffer layer 33, the active layer 34, and the upper buffer layer 35 are sequentially formed on the lower electrode 32 (hereinafter, the lower buffer layer 33, the active layer 34, and the upper buffer layer). 35 may be collectively referred to as a photoelectric conversion layer). When the lower buffer layer 33 is formed on the entire surface of the lower electrode 32, the first open groove 41 is filled with the material of the lower buffer layer 33. When the lower buffer layer 33 is patterned on the lower electrode 32, the first open groove 41 may not be filled with the material of the lower buffer layer 33. In this embodiment, an example in which the lower buffer layer 33, the active layer 34, and the buffer layer 35 are formed is shown, but this embodiment is not limited to this. That is, each photoelectric conversion element constituting the organic thin film solar cell according to the present invention is required to provide at least the active layer 34 among the above-described layers, and does not provide the lower buffer layer 33 and the upper buffer layer 35. Also good.

Next, as shown in FIG. 4C, the active layer 34 and the upper buffer layer 35 formed on the lower buffer layer 33 are in the vicinity of several tens of μm to 1 mm so as not to overlap the first open groove 41. A second open groove 42 reaching the lower electrode 32 at a certain distance is formed. The formation method of the 2nd open groove 42 is not limited to the laser scribing method, You may carry out by methods, such as a mechanical scribing. Further, the lower buffer layer 33, the active layer 34, and the upper buffer layer 35 may be formed so as to provide the second groove 42 by a method such as lift-off, mask film formation, gravure printing, screen printing, and ink jet. . The width of the second open groove 42 is usually 5 μm or more, preferably 10 μm or more, more preferably 25 μm or more, still more preferably 50 μm or more, and usually 1000 μm or less, preferably 500 μm or less, more preferably 200 μm or less, more preferably 100 μm or less. The wavelength of the laser forming the second groove 42 is usually 20
The upper limit is usually 1200 nm or less, preferably 900 nm or less, and more preferably 600 nm or less. As a result, the lower buffer layer 33, the active layer 34, and the upper buffer layer 35 are separated into strips.

  Next, as shown in FIG. 4D, the upper electrode 36 is formed. The second open groove 42 is filled with the material of the upper electrode 36. Since the second open groove 42 is for connecting the upper electrode of the unit cell to the lower electrode 32 of the adjacent unit cell, it must reach a depth reaching the lower electrode 32 of the adjacent unit cell. . The lower electrode may not exist in the second open groove 42.

  Thereafter, as shown in FIG. 4E, a third open groove 43 is formed in the upper electrode 36, the upper buffer layer 35, the active layer 34, and the lower buffer layer 33, and divided into unit cells. The formation method of the 3rd groove 43 is not limited to a laser scribe, You may use a mechanical scribe etc. Further, the upper electrode 36 may be formed only at a specific location by a method such as lift-off, gravure printing, screen printing, and ink jet, and electrically connected to the lower electrode 32 of the adjacent unit cell. Since the third groove 43 divides the upper electrode 36 of the adjacent unit cell, it may stop in the middle of the active layer 34 without penetrating the active layer 34, and further from the active layer 34 to the lower buffer layer 33. May penetrate into the lower electrode 32. Since the upper electrode 36 of each unit cell is electrically connected to the lower electrode 32 of the adjacent unit cell by the material of the upper electrode 36 filling the inside of the second open groove 42, a series array in which the unit cells are connected in series. Is obtained.

At this time, insulative grooves 45 are formed in the upper electrode 36, the upper buffer layer 35, the active layer 34, the lower buffer layer 33, and the lower electrode 32 in order to form a series array. The method for forming the insulating groove 45 is not limited to patterning by laser scribing, and a method such as mechanical scribing can be used.
As shown in FIG. 2, FIG. 4 (e) shows a cross section in a direction parallel to the series connection direction of a plurality of unit cells constituting the series array, and insulation is opened in a direction perpendicular to the series connection method. Although the groove 45 is formed, patterning is performed so as to form the insulating open groove 45 also in the parallel direction. As a result, the lower electrode constituting the unit cell is separated from the lower electrode constituting the other unit cell to form a series array. As described above, in this embodiment, after forming the upper electrode 36, the insulating open grooves 45 are formed and patterning is performed to form a series array. However, the patterning order is the upper electrode. It is not limited after the formation. For example, after the active layer 34 or the upper buffer layer 35 is formed, the patterning may be performed, and then the upper electrode 36 may be formed. That is, the order of the steps for performing the patterning is not limited as long as it is possible to finally manufacture a series array as long as the active layer 34 is formed. However, since the lower buffer layer, the active layer, the upper buffer layer, and the upper electrode 36 can be patterned at a time, the patterning is preferably performed after the upper electrode is formed.

The insulating open grooves 45 may be formed as a series of open grooves by one laser scribing as shown in FIG. 4 (e), for example, formed as two-stage open grooves as shown in FIG. May be.
In the two-stage groove mode shown in FIG. 5, grooves are formed in the photoelectric conversion layer other than the lower electrode 32 and the upper electrode 36 as shown in FIG. 5A (first groove forming step), and thereafter As shown in FIG. 5B, an insulating groove 45 is formed by forming a groove in the lower electrode 32 (second groove forming step).

When the insulating groove 45 is formed by a single laser scribe, it is necessary to increase the laser intensity with respect to the layer to be patterned. However, burrs or dust may occur during laser scribe. There is a case. However, by forming the insulating groove 45 by the first groove forming step and the second groove forming step, the laser intensity suitable for each layer can be selected, and the generation of burrs and dust is suppressed. be able to.
Further, by forming the insulating groove 45 separately in the first groove forming step and the second groove forming step, for example, the width of the groove in the lower electrode and the width of the groove in the active layer can be freely set. Can be adjusted. Therefore, bending strength, tensile strength, and the like can be adjusted by adjusting the width of each groove in consideration of the hardness of the active layer and the lower electrode.
In addition, in this way, by forming the insulating groove 45 by the first groove forming step and the second groove forming step, in the insulating groove 45, in the photoelectric conversion layer or the upper electrode 36, As long as the width of the groove in the lower electrode 32 is reduced with respect to the width, the width of the groove in the lower electrode 36 can be freely adjusted. Therefore, in the case of an organic thin film solar cell having a structure in which the lower electrode 32 is colored and incident light enters from the upper electrode 36 side, the colored lower electrode 32 and an active layer having transparency are observed when observed from the upper electrode 36 side. A new design can be imparted.

  Further, in the first groove forming step, the width of the groove in the photoelectric conversion layer or the upper electrode is made larger in advance than the width of the groove in the lower electrode 32 to be formed in the second groove forming step. By doing so, it becomes possible to cope with the laser scribe blur in the second groove forming step, and the manufacturing yield of the organic thin film solar cell can be improved. From this viewpoint, the width of the groove in the photoelectric conversion layer or the upper electrode 36 is preferably smaller than the width of the groove in the lower electrode 32. In particular, the width of the groove in the lower electrode is preferably smaller than the width of the groove in the organic layer.

The width of the groove formed in the lower electrode 32 is usually 5 μm or more, preferably 25 μm or more, particularly preferably 50 μm or more, usually 1000 μm or less, and 500 μm or less. More preferably, it is particularly preferably 150 μm or less. On the other hand, the width of the groove in the photoelectric conversion layer such as the active layer 34 or the upper electrode 36 is usually 25 μm or more, preferably 50 μm or more, particularly preferably 150 μm or more, and usually 2000 μm or less. More preferably, it is 1000 μm or less, and particularly preferably 500 μm or less. The ratio of the width of the groove in the photoelectric conversion layer or the upper electrode 36 to the width of the groove in the lower electrode 32 is preferably greater than 1, more preferably 2 or more, and particularly preferably 5 or more. On the other hand, it is preferably 200 or less, more preferably 100 or less, and particularly preferably 10 or less.
Note that the shape of the insulating groove 45 shown in FIG. 5B (a method for forming the groove by two steps) is applied only to the insulating grooves in the direction parallel to the series connection direction of the unit cells in FIG. Alternatively, it may be applied only to the insulating groove in the direction perpendicular to the series connection direction, or may be applied to the insulating groove in both directions.

Laser scribing of the lower electrode may be performed from the laminated surface side of the substrate on the laminated body in which the electrode and / or active layer is laminated on the substrate, or by laser irradiation from the opposite side of the laminated surface, that is, the substrate side. , You may go. From the relationship with the depth of focus, it is preferable to perform laser scribing of the lower electrode from the laminated surface side of the substrate.
Thus, a series array (organic thin film solar cell) in which unit cells are connected in series can be obtained. As shown in FIG. 4 (f), the obtained series array can take out the generated electricity by installing a collecting wire 37 on the upper electrode 36.

In addition, the film-forming method of each layer in manufacture of the photoelectric conversion element which comprises an organic thin film solar cell is normally formed into a film by the dry process or the apply | coating method. Examples of the dry process include vapor deposition, sputtering, and CVD. The coating method means a process in which a film is formed by dissolving or dispersing a material in a solution and removing the solvent.
These film forming methods can be appropriately selected depending on the type of layer to be formed. In the present invention, at least the active layer 34 is formed by a coating method because charging of the lower electrode can be suppressed as much as possible. It is preferable to form a film. The coating method used for forming the active layer 34 is not particularly limited, and specifically, a wire bar coating method, a blade coating method, a die coating method, a slit die coating method, a reverse roll coating method, and a gravure coating method. Kiss coating method, roll brushing method, spray coating method, air knife coating method, pipe doctor method, impregnation / coating method, curtain coating method, flexographic printing, inkjet and the like. The lower buffer layer 33 is also preferably formed by a coating method because the effects of the present invention can be obtained. More preferably, the lower buffer layer 33, the active layer 34, and the upper buffer layer are all formed by a coating method.
As the film forming means, known means capable of performing the above-described film forming method can be used. Examples of the dry process include a sputtering apparatus, a vapor deposition apparatus, and a CVD apparatus. Examples of the coating method include a coating device and a printing device. When the film forming means according to this embodiment is a coating method, the film forming means preferably includes a drying device in addition to the coating device.

When a coating method is used as a method for forming each layer, an organic solvent is used for the coating solution. Organic solvents are easily charged with static electricity and may ignite due to static electricity. The present invention is suitable when a coating method is used because electricity can be released even if the lower electrode is charged in the manufacturing process. It is also suitable for manufacturing in a ring atmosphere where static electricity is likely to occur, such as in a dry room.
The dry room usually has a dew point of −30 ° C. or lower, more preferably −35 ° C. or lower, particularly preferably −38 ° C. or lower, and further preferably −40 ° C. or lower.

<2. Roll-to-roll system>
In the present embodiment, it is preferable from the viewpoint of productivity to adopt the roll-to-roll method, and only a part may be implemented by the roll-to-roll method.
The roll-to-roll method is a method in which a flexible substrate wound in a roll shape is fed out and processed intermittently or continuously while being wound up by a take-up roll. . Since it is possible to batch-process long substrates of kilometer order, mass production can be easily performed.

  The roll-to-roll method has attracted attention as a method for efficiently mass-producing electronic devices that have been produced by the sheet-to-sheet (sheet-fed) method so far, and has recently been developed for various uses. The roll-to-roll method has advantages in terms of manufacturing technology that enables cost reduction and high productivity compared to the sheet-to-sheet process. Specifically, in the roll-to-roll system, flexible substrates flow continuously between devices, so we can expect significant cost reductions in manufacturing process energy, personnel, factory space, logistics, etc. It is a more versatile production technology that takes the environment and energy into consideration.

There are various methods for imparting functions, processes, materials, etc. according to the roll-to-roll method, depending on the purpose. For the functionalization, surface treatment (mechanical treatment), laser processing (patterning), laminating (functional film laminating), coating (wet / dry), printing (flexo, gravure, letterpress, ink jet, ink printing) and the like. Among these, there are wet coating and dry coating, and wet coating is a manufacturing method in which a monomer or polymer (polymer) solution is applied on a substrate and dried and cured. Fluorine-based coatings for developing functions such as chemical properties, heat resistance, and low friction properties, and conductive film coatings for the purpose of conductivity, IR cut, antistatic, etc. have already been put into practical use. These are the most suitable processes for the roll-to-roll method because the function needs to be uniformly applied to the entire surface of the substrate.

  The size of the roll that can be used in the roll-to-roll method is not particularly limited as long as it can be handled by a roll-to-roll manufacturing apparatus, but the outer diameter is usually 5 m or less, preferably 3 m or less. Preferably, it is 1 m or less, usually 10 cm or more, preferably 20 cm or more, more preferably 30 cm or more. The outer diameter of the roll core is usually 4 m or less, preferably 3 m or less, more preferably 0.5 m or less, usually 1 cm or more, preferably 3 cm or more, more preferably 5 cm or more, still more preferably 10 cm or more, particularly preferably 20 cm or more. When these diameters are not more than the above upper limit, it is preferable in terms of high handleability of the roll, and when it is more than the lower limit, the layer formed in each of the following steps is less likely to be broken by bending stress. Is preferable. The width of the roll is usually 5 cm or more, preferably 10 cm or more, more preferably 20 cm or more, and is usually 5 m or less, preferably 3 m or less, more preferably 2 m or less. When the width is not more than the upper limit, it is preferable from the viewpoint of high handleability of the roll, and when the width is not less than the lower limit, the degree of freedom of the size of the photoelectric conversion element is preferable.

<3. Photoelectric conversion layer>
Next, the configuration of the photoelectric conversion element according to the embodiment of the present invention will be described.
The photoelectric conversion element used in this embodiment usually has at least a pair of electrodes, an active layer that exists between the electrodes, and an electron extraction layer that exists between the active layer and one of the electrodes. FIG. 6 shows a general layer structure of the photoelectric conversion element. A photoelectric conversion element 107 illustrated in FIG. 6 includes a photoelectric conversion element substrate 106, a lower electrode 101 serving as a cathode, an electron extraction layer 102, an active layer 103 (a layer including a p-type semiconductor compound and an n-type semiconductor material), holes. It has a layer structure in which an extraction layer 104 and an upper electrode 105 as an anode are sequentially formed. In FIG. 6, the lower electrode 101 exists above the upper electrode 105. In this specification, the upper electrode and the lower electrode refer to the upper electrode and the lower electrode when the photoelectric conversion element substrate 106 is the bottom. The electrode laminated on the solar cell element substrate is referred to as a lower electrode. In addition, the electron extraction layer 102, the active layer 103, and the hole extraction layer 104 may be collectively referred to as a photoelectric conversion layer.

The photoelectric conversion element has a solar cell element substrate (hereinafter also simply referred to as an element substrate) serving as a support. That is, an electrode and an active layer are formed on the element substrate.
The material of the element substrate is not particularly limited as long as it is a film substrate. Preferable examples of the material of the element substrate include polyethylene terephthalate, polyethylene naphthalate, polyethersulfone, polyimide, nylon, polystyrene, polyvinyl alcohol, ethylene vinyl alcohol copolymer, fluororesin film, polyolefin such as vinyl chloride or polyethylene; Insulating organic materials such as cellulose, polyvinylidene chloride, aramid, polyphenylene sulfide, polyurethane, polycarbonate, polyarylate, polynorbornene or epoxy resin; paper materials such as paper or synthetic paper; metals such as stainless steel, titanium or aluminum Examples thereof include composite materials such as those coated or laminated on the surface.

  Among these materials, from the viewpoint of heat resistance, polyethylene naphthalate, polyethersulfone, polyimide, fluororesin film, polyphenylene sulfide, polyarylate, or surface for imparting insulating properties to metals such as stainless steel, titanium or aluminum. Particularly preferred are composite materials such as those coated or laminated.

The shape of the element substrate is a film. Moreover, although there is no restriction | limiting in the film thickness of an element substrate, Usually, 5 micrometers or more, Preferably it is 10 micrometers or more, More preferably, it is 20 micrometers or more, On the other hand, it is 1 mm or less normally, Preferably it is 500 micrometers or less, More preferably, it is 200 micrometers or less. It is preferable that the thickness of the substrate is 5 μm or more because the possibility that the strength of the photoelectric conversion element is insufficient is reduced. The film thickness of the element substrate is preferably 1 mm or less because the cost is suppressed and the weight does not increase.

  The electrode has a function of collecting holes and electrons generated by light absorption. Therefore, the pair of electrodes includes an electrode suitable for collecting holes (hereinafter also referred to as an anode) and an electrode suitable for collecting electrons (hereinafter also referred to as a cathode). Is preferably used. Any one of the pair of electrodes may be translucent, and both may be translucent. However, in the case of a see-through solar cell which is a preferred embodiment of the present invention, both Must be translucent and have transparency. Translucency means that sunlight passes through 40% or more. Further, the solar light transmittance of the transparent electrode is preferably 70% or more in order to allow light to reach the active layer through the transparent electrode. The light transmittance can be measured with a normal spectrophotometer.

  The anode is an electrode generally made of a conductive material having a work function higher than that of the cathode and having a function of smoothly extracting holes generated in the active layer.

  Examples of materials for the anode include conductive metal oxides such as nickel oxide, tin oxide, indium oxide, indium tin oxide (ITO), indium-zirconium oxide (IZO), titanium oxide, indium oxide, and zinc oxide; Examples thereof include metals such as gold, platinum, silver, chromium and cobalt, or alloys thereof. These substances are preferable because they have a high work function, and further, a conductive polymer material represented by PEDOT: PSS in which a polythiophene derivative is doped with polystyrene sulfonic acid can be stacked. When laminating such a conductive polymer, the work function of this conductive polymer material is high, so even if it is not a material with a high work function as described above, it is suitable for cathodes such as Al and Mg. Metals can also be widely used. PEDOT: PSS in which a polythiophene derivative is doped with polystyrene sulfonic acid, or a conductive polymer material in which polypyrrole, polyaniline, or the like is doped with iodine or the like can also be used as an anode material. When the anode is a transparent electrode, it is preferable to use a light-transmitting conductive metal oxide such as ITO, zinc oxide or tin oxide, and ITO is particularly preferable.

  The film thickness of the anode is not particularly limited, but is usually 10 nm or more, preferably 20 nm or more, and more preferably 50 nm or more. On the other hand, it is usually 10 μm or less, preferably 1 μm or less, more preferably 500 nm or less. When the thickness of the anode is 10 nm or more, the sheet resistance is suppressed, and when the thickness of the anode is 10 μm or less, light can be efficiently converted into electricity without decreasing the light transmittance. When the anode is a transparent electrode, it is necessary to select a film thickness that can achieve both light transmittance and sheet resistance.

  The sheet resistance of the anode is not particularly limited, but is usually 1Ω / □ or more, on the other hand, 1000Ω / □ or less, preferably 500Ω / □ or less, more preferably 100Ω / □ or less.

  Examples of the anode forming method include a vacuum film forming method such as a vapor deposition method or a sputtering method, or a wet coating method in which an ink containing nanoparticles or a precursor is applied to form a film.

  The cathode is generally an electrode made of a conductive material having a low work function and having a function of smoothly extracting electrons generated in the active layer. The cathode is adjacent to the electron extraction layer.

Examples of cathode materials include platinum, gold, silver, copper, iron, tin, zinc, aluminum, indium, chromium, lithium, sodium, potassium, cesium, calcium, and magnesium, and alloys thereof; lithium fluoride And inorganic salts such as cesium fluoride and metal oxides such as nickel oxide, aluminum oxide, lithium oxide, and cesium oxide. These materials are preferable because they are materials having a low work function. Similarly to the anode, a material having a high work function can be used for the cathode by using an n-type semiconductor such as titania having conductivity as the electron extraction layer. From the viewpoint of electrode protection, the cathode material is preferably a metal such as platinum, gold, silver, copper, iron, tin, aluminum, calcium or indium, or an alloy using these metals such as indium tin oxide.

  The film thickness of the cathode is not particularly limited, but is usually 10 nm or more, preferably 20 nm or more, more preferably 50 nm or more. On the other hand, it is usually 10 μm or less, preferably 1 μm or less, more preferably 500 nm or less. When the film thickness of the cathode is 10 nm or more, the sheet resistance is suppressed, and when the film thickness of the cathode is 10 μm or less, light can be efficiently converted into electricity without decreasing the light transmittance. When the cathode is a transparent electrode, it is necessary to select a film thickness that achieves both light transmittance and sheet resistance.

  The sheet resistance of the cathode is not particularly limited, but is usually 1000Ω / □ or less, preferably 500Ω / □ or less, and more preferably 100Ω / □ or less. Although there is no restriction on the lower limit, it is usually 1Ω / □ or more.

  As a method for forming the cathode, there are a vacuum film formation method such as a vapor deposition method or a sputtering method, or a wet coating method in which an ink containing nanoparticles or a precursor is applied to form a film.

  Furthermore, the anode and the cathode may have a laminated structure of two or more layers. In addition, characteristics (electric characteristics, wetting characteristics, etc.) may be improved by performing surface treatment on the anode and the cathode.

  After laminating the anode and cathode, the photoelectric conversion element is usually heated in a temperature range of 50 ° C. or higher, preferably 80 ° C. or higher, and usually 300 ° C. or lower, preferably 280 ° C. or lower, more preferably 250 ° C. or lower. Is preferable (this step may be referred to as an annealing treatment step). By performing the annealing process at a temperature of 50 ° C. or higher, an effect of improving the adhesion between the layers of the photoelectric conversion element, for example, the adhesion between the electron extraction layer and the cathode and / or the electron extraction layer and the active layer is obtained. ,preferable. By improving the adhesion between the layers, the thermal stability and durability of the photoelectric conversion element can be improved. It is preferable to set the temperature of the annealing treatment step to 300 ° C. or lower because the possibility that the organic compound in the active layer is thermally decomposed is reduced. In the annealing treatment step, stepwise heating may be performed within the above temperature range.

  The heating time is usually 1 minute or longer, preferably 3 minutes or longer, and usually 3 hours or shorter, preferably 1 hour or shorter. The annealing treatment step is preferably terminated when the open-circuit voltage, the short-circuit current, and the fill factor, which are parameters of the solar cell performance, reach a constant value. Further, the annealing treatment step is preferably performed under normal pressure and in an inert gas atmosphere.

  The method for heating is not particularly limited, but preferred is a method using heating with hot air, irradiation with far infrared rays and / or near infrared rays, and an organic photoelectric conversion element may be placed on a heat source such as a hot plate, an oven or the like. You may put an organic photoelectric conversion element in the heating atmosphere. The heating may be performed batchwise or continuously, but is preferably performed continuously.

The photoelectric conversion element according to the embodiment of the present invention usually has an electron extraction layer between the cathode and the active layer. The photoelectric conversion element has a hole extraction layer between the active layer and the anode. Note that the electron extraction layer and the hole extraction layer are not essential components.

The electron extraction layer and the hole extraction layer are preferably disposed so as to sandwich the active layer between the pair of electrodes. That is, when the photoelectric conversion element includes both an electron extraction layer and a hole extraction layer, the upper electrode, the hole extraction layer, the active layer, the electron extraction layer, and the lower electrode can be arranged in this order. In this case, the upper buffer layer described above corresponds to the hole extraction layer, and the lower buffer layer corresponds to the electron extraction layer. When the photoelectric conversion element includes an electron extraction layer and does not include a hole extraction layer, the upper electrode, the active layer, the electron extraction layer, and the lower electrode can be arranged in this order. The stacking order of the electron extraction layer and the hole extraction layer may be reversed, or at least one of the electron extraction layer and the hole extraction layer may be composed of a plurality of different films.
Examples of the material, film thickness, and formation method of the electron extraction layer and the hole extraction layer include materials used for the electron extraction layer and the hole extraction layer described in International Publication WO2012 / 102390, for example.

The active layer refers to a layer in which photoelectric conversion is performed, and usually includes an electrolytic solution containing a p-type semiconductor compound and an n-type semiconductor compound, or containing a dye and iodine ions.
The p-type semiconductor compound is a compound that works as a p-type semiconductor material, and the n-type semiconductor compound is a compound that works as an n-type semiconductor material. When the photoelectric conversion element receives light, the light is absorbed by the active layer, electricity is generated at the interface between the p-type semiconductor compound and the n-type semiconductor compound, and the generated electricity is extracted from the electrode.

  As the layer structure of the active layer, a thin film stacked type in which a p-type semiconductor compound layer and an n-type semiconductor compound layer are stacked, a bulk heterojunction type having a layer in which a p-type semiconductor compound and an n-type semiconductor compound are mixed, and p-type Examples thereof include a semiconductor compound layer, a layer (i layer) in which a p-type semiconductor compound and an n-type semiconductor compound are mixed, and an n-type semiconductor compound layer laminated. Among these, a bulk heterojunction type having a layer in which a p-type semiconductor compound and an n-type semiconductor compound are mixed is preferable.

  The thickness of the active layer is not particularly limited, but is usually 10 nm or more, preferably 50 nm or more, and is usually 2000 nm or less, preferably 1500 nm or less, more preferably 700 nm or less. It is preferable that the thickness of the active layer is equal to or more than the above lower limit because the uniformity of the film is maintained and short circuit is hardly caused. Moreover, it is preferable that the thickness of the active layer is not more than the above upper limit in that the internal resistance is reduced and the diffusion of charges is good without the electrodes being separated too much.

  A method for forming the active layer is not particularly limited, but it is preferable to form a film by a coating method. As the coating method, any method can be used. For example, wire bar coating method, blade coating method, die coating method, slit die coating method, reverse roll coating method, gravure coating method, kiss coating method, roll brush method, spray Examples thereof include a coating method, an air knife coating method, a pipe doctor method, an impregnation / coating method, a curtain coating method, flexographic printing, and an inkjet.

For example, the p-type semiconductor compound layer and the n-type semiconductor compound layer can be produced by applying a coating liquid containing a p-type semiconductor compound or an n-type semiconductor compound. Moreover, the layer in which the p-type semiconductor compound and the n-type semiconductor compound are mixed can be prepared by applying a coating solution containing the p-type semiconductor compound and the n-type semiconductor compound. As will be described later, the semiconductor compound precursor may be converted into a semiconductor compound after the coating liquid containing the semiconductor compound precursor is applied.
The p-type semiconductor compound included in the active layer is not particularly limited, and examples thereof include a low molecular organic semiconductor compound and a high molecular organic semiconductor compound. As a concrete example, for example, International Publication W
The p-type semiconductor compound described in O2012 / 102390 is mentioned. Further, specific examples of the n-type semiconductor compound contained in the active layer include the n-type semiconductor compound described in International Publication WO2012 / 102390.

The photoelectric conversion characteristics of the photoelectric conversion element can be obtained as follows. Irradiate the photoelectric conversion element with light of AM1.5G with a solar simulator at an irradiation intensity of 100 mW / cm ² ,
Measure current-voltage characteristics. From the obtained current-voltage curve, photoelectric conversion characteristics such as photoelectric conversion efficiency (PCE), short circuit current density (Jsc), open circuit voltage (Voc), fill factor (FF), series resistance, and shunt resistance can be obtained.

  Although there is no special restriction | limiting, the photoelectric conversion efficiency of a photoelectric conversion element is 1% or more normally, Preferably it is 1.5% or more, More preferably, it is 2% or more. On the other hand, there is no particular limitation on the upper limit, and the higher the better.

Moreover, as a method for measuring the durability of the photoelectric conversion element, a method for obtaining a maintenance ratio of the photoelectric conversion efficiency before and after exposing the photoelectric conversion element to the atmosphere can be mentioned.
(Maintenance rate) = (Photoelectric conversion efficiency after N hours of atmospheric exposure) / (Photoelectric conversion efficiency immediately before atmospheric exposure)

  In order to put a photoelectric conversion element into practical use, it is important to have high photoelectric conversion efficiency and high durability in addition to simple and inexpensive manufacture. From this viewpoint, the maintenance rate of photoelectric conversion efficiency before and after exposure to the atmosphere for one week is preferably 60% or more, more preferably 80% or more, and the higher the better.

<4. Solar cell>
The photoelectric conversion element 107 of the present invention is preferably used in a thin film solar cell as a solar cell element.
FIG. 7 is a cross-sectional view schematically showing a configuration of a thin film solar cell as one embodiment of the present invention. As shown in FIG. 7, the thin-film solar cell 14 of this embodiment includes a weather-resistant protective film 1, an ultraviolet cut film 2, a gas barrier film 3, a getter material film 4, a sealing material 5, and a photoelectric conversion element. 6, a sealing material 7, a getter material film 8, a gas barrier film 9, and a back sheet 10 are provided in this order. And light is irradiated from the side (lower side in the figure) where the weather-resistant protective film 1 is formed, and the photoelectric conversion element 6 generates electric power. In addition, when using a highly waterproof sheet such as a sheet obtained by bonding a fluororesin film on both surfaces of an aluminum foil as the back sheet 10 described later, the getter material film 8 and / or the gas barrier film 9 may not be used depending on the application. Good.
The materials, shapes, performances, and lamination methods of these encapsulant 5, backsheet 10 and various films are all as described in International Publication No. 2011/016430 or Japanese Patent Application Laid-Open No. 2012-191194. .

<5. Application>
There is no restriction | limiting in the use of the thin film solar cell 14 mentioned above, It is arbitrary. For example, as schematically shown in FIG. 8, a solar cell module 13 in which a thin film solar cell 14 is provided on a certain base material 12 may be prepared and used by being installed at a place of use. As a specific example, when a building material plate is used as the base material 12, a thin film solar cell 14 is provided on the surface of the plate material to produce a solar cell panel as the solar cell module 13, and this solar cell panel is attached to the outer wall of the building. It can be installed and used.
The substrate 12 is a support member that supports the photoelectric conversion element 6. Examples of the material for forming the substrate 12 include inorganic materials such as glass, sapphire, and titania; polyethylene terephthalate, polyethylene naphthalate, polyethersulfone, polyimide, nylon, polystyrene, polyvinyl alcohol, ethylene vinyl alcohol copolymer, fluorine. Organic materials such as resin film, vinyl chloride, polyethylene, cellulose, polyvinylidene chloride, aramid, polyphenylene sulfide, polyurethane, polycarbonate, polyarylate, polynorbornene; paper materials such as paper or synthetic paper; metals such as stainless steel, titanium or aluminum For example, a composite material such as a material whose surface is coated or laminated in order to impart insulating properties can be used. In addition, 1 type may be used for the material of a base material, and 2 or more types may be used together by arbitrary combinations and a ratio. Moreover, carbon fiber may be included in these organic materials or paper materials to reinforce the mechanical strength.
When the example of the field | area which applies the thin film solar cell of this invention is given, as it exists in international publication 2011/016430 or Unexamined-Japanese-Patent No. 2012-191194, for example, it is a solar cell for building materials, a solar cell for motor vehicles, and interior use. It is suitable for use in solar cells, railroad solar cells, marine solar cells, airplane solar cells, spacecraft solar cells, home appliance solar cells, mobile phone solar cells, toy solar cells, and the like.

EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, it cannot be overemphasized that the technical scope of this invention is not limited only to the said Example.
<Example 1>
A serial array (organic thin-film solar cell (B5 size)) having a monolithic structure in which 10 columns of unit cells are connected in series was manufactured by the following method.
A PEN-lower electrode laminate in which a lower electrode (ITO-Ag-ITO) was laminated was used as a PEN substrate having a thickness of 125 μm (transmittance of 80% or more and sheet resistance of 15Ω / □ or less). Laser processing was performed on the surface of the multilayer body from the lower electrode side of the multilayer body using a laser whose beam shape was rectangular and the energy distribution was converted to flat (wavelength 532 nm, energy density 1.8 J / cm ² , laser shot overlap rate 10%, pulse width 20 nanoseconds). During laser processing, only a portion necessary for series connection of unit cells is formed, and the lower electrode is not made into an island, that is, the series array in which the lower electrode constituting each photoelectric conversion element is formed is electrically connected to each other. Connected to each other.
On top of this, a lower buffer layer (zinc oxide), an active layer (P3HT: C60 (ind) 2), and an upper buffer layer (PEDOT: PSS) (thickness 100 nm) are laminated by coating film formation, respectively. Laser processing was performed from the layer side (wavelength 532 nm, energy density 1.8 J / cm ² , laser shot overlap rate 10%, pulse width 20 nanoseconds). Here, the lower buffer layer, the active layer, and the upper buffer layer were separated so as to have a strip shape.
Further, an upper electrode (silver / 100 nm) was laminated, and laser processing was performed from the upper electrode side of the laminate (wavelength 266 nm, energy density 0.5 J / cm ² , laser shot overlap rate 10%, pulse width 20 nanometers). Seconds). In this process, open grooves were formed in the upper electrode, upper buffer layer, active layer, and lower buffer layer, and divided into unit cells. Subsequently, insulating grooves were formed in the upper electrode, the upper buffer layer, the active layer, the lower buffer layer, and the lower electrode in order to form an adjacent series array.
Each photoelectric conversion element of the organic thin-film solar cell obtained in this way was confirmed that the lower buffer layer, the active layer, and the upper buffer layer were uniformly formed in the laser groove and the surrounding area, and operated as a solar cell. did.

<Comparative Example 1>
An organic thin-film solar cell was manufactured in the same manner as in Example 1 except that patterning was performed so as to first separate the series arrays where the lower electrodes of the photoelectric conversion elements were formed. Observation of the manufactured organic thin-film solar cell revealed that coating unevenness around the laser groove portion of the lower electrode was noticeable especially in the formation of the active layer, and the state of thinning was confirmed. Moreover, when operation | movement was confirmed, it short-circuited and it did not operate | move as a solar cell.
As described above, a film can be uniformly formed by the manufacturing method according to the present invention, and further, a photoelectric conversion element that can be used as a solar cell can be manufactured.

DESCRIPTION OF SYMBOLS 1 Weatherproof protective film 2 Ultraviolet cut film 3,9 Gas barrier film 4,8 Getter material film 5,7 Sealing material 6 Photoelectric conversion element 10 Back sheet 12 Base material 13 Solar cell module 14 Thin film solar cell 101 Lower electrode 102 Electron take-out Layer 103 Active layer 104 Hole extraction layer 105 Upper electrode 106 Photoelectric conversion element substrate 107 Photoelectric conversion element 31 Solar cell element substrate (also simply referred to as a substrate)
32 Lower electrode 33 Lower buffer layer 34 Active layer 35 Upper buffer layer 36 Upper electrode 37 Current collector 41 First groove 42 Second groove 43 Third groove 44, 45, 46 Insulating groove

Claims (3)

A method for producing an organic thin-film solar cell having a plurality of photoelectric conversion elements, comprising at least a lower electrode, an active layer, and an upper electrode on a substrate,
A method for producing an organic thin-film solar cell, comprising forming the active layer by a coating method in a state where lower electrodes constituting each photoelectric conversion element are electrically connected to each other.   2. The method of manufacturing an organic thin film solar cell according to claim 1, wherein the lower electrodes are separated from each other by patterning the lower electrode after forming the upper electrode.   The method for producing an organic thin film solar cell according to claim 2, wherein the patterning is performed by laser scribing.

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