JP6791156B2 - Organic photoelectric conversion element and organic thin film solar cell module - Google Patents

Description

The present invention relates to an organic photoelectric conversion element and an organic thin film solar cell module including the organic photoelectric conversion element.

In recent years, organic thin-film solar cells have been actively studied. In particular, as an organic thin-film solar cell, it is possible to use a transparent resin substrate having flexibility. Therefore, the organic thin-film solar cell can be installed on the wall surface, window glass, etc. of a building by taking advantage of its flexibility and light weight as compared with the conventional solar cell using a crystalline silicon substrate or a glass substrate. It is being considered. Assuming that the organic thin-film solar cell is installed on the wall surface or window glass of the building, the wall surface or window glass of the building is easily noticeable. Therefore, the organic thin-film solar cell module also has an appearance color such as color tone. It is considered necessary to attach importance to it.

As a method of adjusting the color tone of an organic thin-film solar cell, for example, Patent Document 1 describes a method of arranging a light absorption layer behind a photoelectric conversion layer when viewed from the light receiving surface side to absorb a specific wavelength. It is disclosed. Further, Patent Document 2 discloses that a wide range of colors of the dial can be selected by setting the refractive index and the thickness of the transparent electrode and the photoelectric conversion layer to specific values.

Japanese Unexamined Patent Publication No. 2006-278878 Japanese Unexamined Patent Publication No. 2001-217444

In the first place, organic thin-film solar cells are required to have high conversion efficiency for practical use. In addition, taking advantage of its flexibility and light weight as described above, it is being considered to install it on the wall surface of a building, window glass, etc., and the current situation is that designability is also emphasized.
From the viewpoint of high efficiency, it is preferable to form the lower transparent electrode constituting the organic thin-film solar cell not only by using a transparent oxide conductor having high resistance but also by using a metal layer having low resistance. However, when a metal layer is used, a new problem arises in which the reflected light of the metal layer may cause unwanted red or yellow interference colors to stand out when it is generally assumed to be installed in windows or building materials. ..

The new problem could not be solved by the technique disclosed in Patent Documents 1 and 2 which disclose a method for adjusting a color tone. Further, in Patent Document 1, since the light absorption layer is arranged inside the solar cell (transparent electrode layer and counter electrode layer), for example, the light absorption layer acts as an internal resistance of the solar cell, and the power generation efficiency and life of the solar cell. There was a risk of impairing the characteristics of the solar cell, such as a decrease in the value of the solar cell. Further, in Patent Document 2, in order to determine the thickness of the transparent electrode and the photoelectric conversion layer in order to adjust the appearance color, the optimum film thickness of the transparent electrode and the photoelectric conversion layer is selected in order to exhibit the performance as a solar cell. This could not be done, for example, the resistance of the transparent electrode would increase, the amount of light absorbed by the photoelectric conversion layer would decrease, etc., which would reduce the power generation efficiency of the solar cell, which could impair the characteristics of the solar cell.

The present invention solves such a new problem, and does not impair the characteristics of the solar cell, particularly prevents the solar cell from exhibiting yellow or red color, while relating to the color of the organic active layer. Instead, it is an object of the present invention to provide an organic photoelectric conversion element and an organic thin film solar cell module which can be adjusted to a desirable bluish color as the appearance color of the surface of the solar cell and can improve the design.

As a result of diligent studies to solve the above problems, the present inventor has found that when the organic thin-film solar cell module is viewed from the front from the transparent substrate side, the poor design that exhibits yellow or red color is the transparent substrate of the organic photoelectric conversion element. It has been found that this is due to the transparent electrode existing between the organic active layer and the organic active layer, and is particularly remarkable when the transparent electrode contains a metal layer.

That is, a part of the light incident on the transparent substrate of the organic photoelectric conversion element is reflected by the metal layer of the transparent electrode, and light interference occurs between the incident light and the reflected light, and under specific conditions, yellow or red color is produced. An interference color is produced.

Since this interference color is generated outside the organic active layer and is generated on the light incident surface side having a high light intensity, the light intensity is higher than the reflected color generated in the organic active layer. Therefore, it is considered that the appearance color of the organic thin-film solar cell module is strongly influenced by the optical interference generated between the transparent substrate and the transparent electrode of the organic photoelectric conversion element, particularly between the transparent substrate and the metal layer.

Therefore, by adjusting the distance between the transparent substrate of the organic photoelectric conversion element and the metal layer, it is possible to prevent the appearance color of the photoelectric conversion element from being yellow or red due to the interference color of yellow or red. Furthermore, it has been found that the appearance color of the organic photoelectric conversion element can be easily adjusted to a desired bluish color regardless of the color tone of the organic active layer by making the bluish interference color stand out, and the present invention is completed. I arrived. Further, since the present invention adjusts the film thickness of the layer other than the organic active layer that directly contributes to the power generation efficiency, it is possible to prevent the characteristics of the solar cell from being significantly deteriorated.

That is, the present invention is as follows.
[1] An organic photoelectric conversion element in which a transparent substrate, a lower transparent electrode including a metal layer, an organic active layer, and an upper electrode are sequentially laminated.
The following equation (1) in any of the integers in which the optical path length (n × d) between the transparent substrate and the metal layer, which is represented by the distance d between the transparent substrate and the metal layer and the refractive index n, is 0 or more. An organic photoelectric conversion element characterized by satisfying 1).
480 nm ≧ 4 × (n × d) ÷ (2 × m + 1) ≧ 380 nm …… (1)
[2] The organic photoelectric conversion element according to [1], which includes an undercoat layer between the transparent substrate and the metal layer.
[3] The organic photoelectric conversion according to [1] or [2], wherein the lower transparent electrode includes a transparent conductive layer, and the transparent conductive layer is arranged between the transparent substrate and the metal layer. element.
[4] The organic photoelectric conversion element according to [2] or [3], wherein the thickness of the undercoat layer is 10 nm or more and 5000 nm or less.
[5] The organic photoelectric conversion element according to [3] or [4], wherein the thickness of the transparent conductive layer is 5 nm or more and 200 nm or less.
[6] The organic photoelectric conversion element according to any one of [1] to [5], wherein the thickness of the metal layer is 1 nm or more and 20 nm or less.
[7] An organic thin-film solar cell module including the organic photoelectric conversion element according to any one of [1] to [6].

According to the present invention, the appearance color of the surface of the solar cell is adjusted to a bluish color while suppressing the solar cell from exhibiting yellow or red without impairing the characteristics of the solar cell, thereby improving the design. An organic photoelectric conversion element to be obtained can be provided. Further, it is possible to provide an organic thin-film solar cell module including the organic photoelectric conversion element, which suppresses yellow or red color and has improved design.

FIG. 1 is a cross-sectional view schematically showing the configuration of an organic photoelectric conversion element according to an embodiment of the present invention. FIG. 2 is a diagram showing the relationship between the optical path length and the phase of light. FIG. 3 is a cross-sectional view schematically showing the configuration of the organic thin-film solar cell module according to the embodiment of the present invention.

Hereinafter, the present invention will be described in detail by showing embodiments and examples, but the present invention is not limited to the following embodiments and examples, and is arbitrarily limited to the extent that the gist of the present invention is not deviated. Can be changed and implemented.

<Organic photoelectric conversion element 1>
FIG. 1 is a cross-sectional view schematically showing the configuration of the organic photoelectric conversion element 1 according to the embodiment of the present invention. The organic photoelectric conversion element 1 includes a transparent substrate 2, an undercoat layer 3, a lower transparent electrode 7 in which a first transparent conductive layer 4, a metal layer 5, and a second transparent conductive layer 6 are sequentially laminated, and an organic active layer. 8 and the upper electrode 9 are sequentially laminated.
The organic photoelectric conversion element according to the present embodiment is organic regardless of the color tone of the organic active layer, while suppressing the appearance color of the organic photoelectric conversion element from exhibiting yellow or red when observed from the transparent substrate 2 side. The appearance color of the photoelectric conversion element can be adjusted to a bluish color, and the design can be improved.

Usually, it is considered that the color of the organic active layer 8 is dominant in the appearance color of the organic photoelectric conversion element. The reason for this is that while the organic active layer 8 is colored to absorb light in the visible light region, the layers other than the organic active layer 8 are colorless and transparent so that the organic active layer 8 can efficiently absorb light. This is because it is considered to be preferable. However, according to the study by the present inventors, when the organic photoelectric conversion element is actually observed from the transparent substrate 2 side, the organic photoelectric conversion element exhibits an unfavorable appearance color such as red or yellow due to light interference. It turned out that there may be cases. The following are possible reasons for this.

As will be described later, when the lower transparent electrode 7 is generally formed with a metal layer 5 having a high reflectance, a large amount of reflected light is generated in the metal layer 5. Further, some layers may be formed between the metal layer 5 and the transparent substrate 2. For example, in the embodiment according to FIG. 1, an undercoat layer 3 and a transparent conductive layer 6 forming a lower transparent electrode are formed between the transparent substrate 2 and the metal layer 5. Therefore, depending on the film thickness of these layers, an optical interference effect due to the reflected light of the metal layer 5 may occur in the layers. Specifically, in the organic photoelectric conversion element 1 of the present embodiment, an example of interference of incident light will be described with reference to FIG.

When light is incident on the transparent substrate 2 of the organic photoelectric conversion element 1 in the direction perpendicular to the transparent substrate 2, the transparent substrate 2 is represented by the distance (thickness) d and the refractive index n between the transparent substrate 2 and the metal layer 5. The reflected light of the wavelength λ calculated by substituting the optical path length (n × d) between the metal layer 5 and the metal layer 5 into the following equation (a) is enhanced by the optical interference condition. That is, the reflected light of the wavelength λ affects the appearance color of the organic photoelectric conversion element.
2 × n × d = (2 × m + 1) × λ ÷ 2 (m is an integer of 0 or more) …… (a)
Since the metal layer 5 generally has a higher refractive index than the undercoat layer 3 and the first transparent conductive layer 4 existing on the surface of the metal layer 5, the formula (a) is based on the reflection in the metal layer 5. This equation assumes that the phase of light is shifted by 180 °.

When the incident light that is not reflected at the interface between the transparent substrate 2 and the undercoat layer 3 is reflected by the metal layer 5 (incident light 1), the incident light reflected at the interface between the transparent substrate 2 and the undercoat layer 3 (incident light 2). ) Is 2 × n × d as shown on the left side of the equation (a), and when this is (2m + 1) × λ / 2, the phases of the light match and the light strengthens each other. Become. In the present embodiment, the appearance of the organic photoelectric conversion element with a tint of appearance means that the light intensifies each other in the range of visible light. That is, in the above equation (a), when the optical path length (n × d) between the transparent substrate 2 and the metal layer 5 is selected so that λ = 380 nm to 780 nm theoretically, the visible light region Since the light inside interferes, the appearance color of the organic photoelectric conversion element is affected by the interference color.

For example, in the above formula (a), when the optical path length (n × d) is selected so that λ is 380 nm or more and 480 nm or less, the bluish interference color becomes conspicuous in the organic photoelectric conversion element. On the other hand, as the optical path length (n × d) increases, unwanted interference colors such as yellow and red become conspicuous. That is, when the optical path length (n × d) between the transparent substrate 2 and the metal layer 5 becomes a specific value, the interference color in the specific visible light becomes conspicuous, and the interference color is converted to organic photoelectric conversion. It will affect the appearance color of the element.

In the above equation (a), as m increases, that is, as the value of n × d increases, the number of interference waves appearing in the visible light region increases, and the maximum peak of the reflectance increases. That is, as m becomes larger, many reflected colors tend to be mixed, and the interference color of a specific primary color becomes inconspicuous. In particular, when m is 4 or more, the interference color of a specific primary color becomes inconspicuous. Therefore, when m is any integer of 0 or more and 3 or less, the value of n × d is such that the appearance color becomes bluish. It is considered that the appearance of the organic photoelectric conversion element and the organic thin-film solar cell module can be adjusted to a desirable bluish color by adjusting.

As a result of various studies including the above formula (a) and Examples, the organic photoelectric conversion element 1 is a transparent substrate represented by the distance (total thickness) d between the transparent substrate 2 and the metal layer 5 and the refractive index n. By satisfying the following equation (1) in any of the integers where m is 0 or more, the optical path length (n × d) between the solar cell and the metal layer makes the solar cell yellow or red without impairing the characteristics of the solar cell. It has been found that the appearance color of the surface of the solar cell can be adjusted to a desired bluish color regardless of the color tone of the organic active layer while suppressing the display.
480 nm ≧ 4 × (n × d) ÷ (2 × m + 1) ≧ 380 nm …… (1)

The equation (1) is satisfied by any of the integers in which m is 0 or more, but as described above, when the value of m is 4 or more, the interference color of a specific primary color becomes inconspicuous. Therefore, by satisfying the above equation (1) when m is any of an integers of 0 or more and 3 or less, the appearance color of the organic photoelectric conversion element can be changed while suppressing the organic photoelectric conversion element from exhibiting yellow or red. It is possible to adjust to a bluish color.

The film thickness d in the formula (1) can be measured by, for example, a spectroscopic ellipsometer, an optical interference type film thickness meter, a stylus type step meter, an atomic force microscope, a transmission electron microscope, a scanning electron microscope, or the like. it can.
The refractive index n in the formula (1) can be measured by using, for example, an Abbe refractive index meter, a Prufrich refractive index meter, a digital refractive index meter, or the like according to the method described in JIS K0062. It can also be measured by a prism coupler method, an immersion method, or a spectroscopic method. Although the refractive index n varies depending on the wavelength, in the present invention, the refractive index n is at a wavelength of 485 nm because the wavelength dependence of the refractive index of transparent materials such as those used for the undercoat layer and the transparent conductive layer is small. It is assumed that the refractive index n is used. Specific examples of the spectroscopic method are as described in Applied Physics Vol. 65, No. 11, pp. 1125 to 1130, a) a method obtained by optical simulation using spectral reflectance and spectral transmittance, and b) spectroscopy. There is a method to obtain by ellipsometry.

When two or more types of layers such as the undercoat layer 3 and the first transparent conductive layer 4 are laminated between the transparent substrate 2 and the metal layer 5, n × d in the above formula (1). Can be calculated according to the following formula (b).
_{n × d = Σ (n i} × d i) ...... (b)
(N _i and d _i respectively mean refractive index and film thickness of the i-th layer material from the transparent substrate 2 side.)

That is, when a plurality of layers are present between the transparent substrate 2 and the metal layer 5, it is preferable that the following equation (2) is satisfied by any of the integers in which m is 0 or more.
_{480 ≧ 4 × Σ (n i} × d i) ÷ (2 × m + 1) ≧ 380 ...... (2)

As described above, when the value of m is 4 or more, the specific interference color tends to be inconspicuous. Therefore, the interference color of yellow or red is suppressed and the color tone of the organic active layer is irrelevant. If you want the appearance color of the organic photoelectric conversion element is adjusted to bluish color, m in the case of 0 to 3 integer that light path lengths Σ (n _i × d _i) is satisfy formula (2) preferable.

Among them, in the present invention, as will be described later, it is preferable to have the undercoat layer 3 in order to improve the adhesion between the transparent substrate 2 and the lower transparent electrode 7. Further, in order to improve the durability of the metal layer 5 constituting the lower transparent electrode 7, it is preferable to have a first transparent conductive layer 4 below the metal layer 5. That is, it is particularly preferable to have the undercoat layer 3 and the first transparent conductive layer 4 from the transparent substrate 2 side between the transparent substrate 2 and the metal layer 5. Therefore, when the thickness of the undercoat layer 3 is d ₁ , the refractive index of the undercoat layer 3 is n ₁ , the thickness of the first transparent conductive layer 4 is d ₂ , and the refractive index of the first transparent conductive layer 4 is n _2. , The optical path length (d ₁ × n ₁ + d ₂ × n ₂ ) satisfies the following equation (3) in any of the integers in which m is 0 or more, so that the characteristics of the solar cell are not impaired. It is preferable because the appearance color of the surface of the solar cell can be adjusted to a bluish color and the design can be improved while suppressing the appearance of yellow or red.
480 ≧ 4 × (n ₁ × d ₁ + n ₂ × d ₂ ) ÷ (2 × m + 1) ≧ 380 …… (3)

As in the above equation (2), when the value of m is 4 or more, the specific interference color becomes inconspicuous. Therefore, when m is any integer of 0 or more and 3 or less, the optical path length ( It is preferable that n ₁ × d ₁ + n ₂ × d ₂ ) satisfies the above equation (3).

Hereinafter, each component or layer of the organic photoelectric conversion element 1 according to the embodiment of the present invention shown in FIG. 1 will be described.

<Transparent substrate 2>
The transparent substrate 2 is a member that supports the organic photoelectric conversion element 1. The material of the transparent substrate 2 is not limited as long as it can be supported by laminating the layers constituting the organic photoelectric conversion element 1.

Examples of the material of the transparent substrate 2 include glass, quartz, and a transparent resin material. Specific examples of the transparent resin material include polyethylene terephthalate, polyethylene naphthalate, polyether sulfone, polyimide, nylon, polystyrene, polyvinyl alcohol, ethylene vinyl alcohol copolymer, fluororesin, polyvinyl chloride, polyethylene, polypropylene, and cyclic resin. Examples thereof include organic materials such as polyolefin, cellulose, acetyl cellulose, polyvinyl chloride, aramid, polyphenylene sulfide, polyurethane, polycarbonate, poly (meth) acrylic resin, phenol resin, epoxy resin, polyarylate, and polynorbornene. Among these, the transparent substrate 2 is preferably flexible from the viewpoint of the degree of freedom in installing the organic thin-film solar cell module including the organic photoelectric conversion element 1. The material having flexibility is not particularly limited, but polyethylene terephthalate, polyethylene naphthalate, polyimide, and poly (meth) acrylic resin are preferable in terms of ease of forming the organic photoelectric conversion element 1.

As the material of the transparent substrate 2, one kind may be used, or two or more kinds may be used in any combination and ratio. Further, the material of the transparent substrate 2 may be impregnated with reinforcing fibers such as carbon fiber and glass fiber to reinforce the mechanical strength.

The visible light transmittance of the transparent substrate 2 as defined by JIS R 3106 is usually 70% or more, preferably 80% or more. The thickness of the transparent substrate 2 is not particularly limited as long as it satisfies the above visible light transmittance, but from the viewpoint of ease of handling, it is usually 20 μm or more, preferably 50 μm or more, while it is usually 1000 μm or less, preferably 1000 μm or less. Is 500 μm or less, more preferably 200 μm or less.

<Undercoat layer 3>
The undercoat layer 3 is mainly arranged between the transparent substrate 2 and the lower transparent electrode 7, and has a function of improving the adhesion between the transparent substrate 2 and the lower transparent electrode 7. The organic photoelectric conversion element 1 shown in FIG. 1 is an embodiment in which the undercoat layer 3 is used, but it is not always essential. The undercoat layer 3 is preferably transparent in order to efficiently inject light into the organic active layer 8. The fact that the undercoat layer 3 is transparent means that the visible light transmittance defined by JIS R 3106 is 70% or more, and is preferably 80% or more.

The refractive index n ₁ of the undercoat layer 3 at a wavelength of 485 nm is not particularly limited, but is usually 1.4 or more and 2.0 or less, and the above formulas (1) to (3) and the formulas described later are usually used. It may be appropriately designed so as to satisfy (4).

Further, in a case that satisfies the above equation (1) to (3), the refractive index _{n 1} at the wavelength 485nm of the undercoat layer 3 is of refractive index _{n 3} and the first transparent conductive layer at a wavelength of 485nm of the transparent substrate 2 485nm It is preferable that the refractive index is smaller than n ₂ . The reason for this is that the Fabry-Perot interference efficiently causes optical interference between the transparent substrate 2 and the metal layer 5, and the interference color in the undercoat layer is enhanced, so that the appearance color of the organic photoelectric conversion element is further improved. This is because it is easy to adjust. In particular, the refractive index n ₁ of the undercoat layer 3 is the refractive index of the transparent substrate 2 so that the organic active layer 8 can efficiently absorb light while appropriately adjusting the appearance color of the organic photoelectric conversion element by light interference. n less than _3, and the difference between the refractive index _{n 1} and the refractive index _{n 3} of the transparent substrate 2 of the undercoat layer 3 _(n 3 -n ₁₎ is preferably 0.1 or more, 0. It is preferably 2 or more, while it is preferably 0.4 or less, and particularly preferably 0.3 or less.

As the material of the undercoat layer 3, for example, a substance produced by hydrolysis of a resin such as an acrylic resin, a polyester resin, a polyamide resin, or an organic silicon compound such as a hard coating agent SHC900 manufactured by Momentive Performance Materials. (Hydrogens), fine particles of inorganic substances such as silica, etc.

Among these, the undercoat layer 3 is preferably formed from a hydrolysis product of an organosilicon compound for the purpose of further improving the adhesion to the lower transparent electrode 7. When a hydrolysis product of an organosilicon compound is used, an acrylic resin, a polyester resin, a polyamide resin, and an epoxy resin are used together for the purpose of improving the adhesion strength with the transparent substrate 2 and the mechanical strength of the undercoat layer 3. May be good.

Further, for the purpose of improving the adhesion between the undercoat layer 3 and the lower transparent electrode 7, it is also preferable to contain inorganic substance fine particles having a diameter of 100 nm or less. When inorganic substance fine particles having a diameter of 100 nm or less are used, it is desirable to use them together with an acrylic resin, a polyester resin, and a polyamide resin for the purpose of improving the adhesion strength with the transparent substrate 2 and the mechanical strength of the undercoat layer 3.
Silica is particularly desirable as the inorganic substance fine particles having a diameter of 100 nm or less. The reason for this is that since the refractive index of silica is close to that of acrylic resin, diffuse reflection is small and it is easy to obtain a transparent undercoat layer 3.
When acrylic resin, polyester resin, polyamide resin, etc. are used, they may be crosslinked.

As described above, the thickness of the undercoat layer 3 may be selected in consideration of the optical path length between the transparent substrate 1 and the metal layer 5. In the present embodiment, in order to improve the adhesion with the lower transparent electrode 7, the film thickness of the undercoat layer 3 is preferably 10 nm or more, more preferably 50 nm or more, while cracks occur. It is preferably 5 μm or less, more preferably 1 μm or less, further preferably 500 nm or less, particularly preferably 300 nm or less, and most preferably 200 nm or less in order to prevent the above.

<Lower transparent electrode 7 and upper electrode 9>
One of the lower transparent electrode 7 and the upper electrode 9 is an anode that collects holes generated in the organic active layer 8, and the other is a cathode that collects electrons generated in the organic active layer 8. The lower transparent electrode 7 may be an anode and the upper electrode 9 may be a cathode, or the lower transparent electrode 7 may be a cathode and the upper electrode 9 may be an anode.

In the embodiment according to FIG. 1, the lower transparent electrode 7 is formed by sequentially laminating a first transparent conductive layer 4, a metal layer 5, and a second transparent conductive layer 6. That is, the first transparent conductive layer 4 is laminated between the undercoat layer 3 and the metal layer 5, and the second transparent conductive layer 6 is laminated between the metal layer 5 and the organic active layer 8. There is. Normally, the lower transparent electrode 7 can be formed of a single transparent conductive layer, but the transparent conductive layer formed of a metal oxide tends to have high resistance. Therefore, in the present invention, the lower transparent electrode 7 is formed to have the metal layer 5 in order to improve the conductivity. That is, in the present invention, the lower transparent electrode 7 may include at least a metal layer, and may be a single layer of the metal layer 5 or a laminate of the metal layer 5 and the transparent conductive layer, but the lower transparent electrode 7 In order to improve the durability of the metal layer, it is preferable to have a laminated structure of a metal layer and a transparent conductive layer. Among them, as shown in FIG. 1, a laminated structure in which transparent conductive layers are arranged on both sides of the metal layer. Is preferable.

<First transparent conductive layer 4 and second transparent conductive layer 6>
The materials of the first transparent conductive layer 4 and the second transparent conductive layer 6 may be the same or different. The material used for the first transparent conductive layer 4 and the second transparent conductive layer 6 is preferably one having excellent transparency and conductivity. Here, excellent transparency means that when a thin film having a film thickness of about 100 nm is formed, the visible light transmittance of the thin film is 60% or more, and excellent conductivity means that the film thickness is about 100 nm. thin film upon the formation of a surface resistance value of the thin film is meant that at 1 × 10 ⁷ Ω / □ or less. The surface resistance value may be adjusted by doping with impurities.

Examples of the material that can be suitably used for the first transparent conductive layer 4 and the second transparent conductive layer 6 include metal oxides. For example, tin-doped indium oxide (ITO), zinc-doped indium oxide (IZO), tungsten-doped indium oxide (IWO), gallium-doped indium oxide (IGO), cadmium and tin. oxide (CTO), aluminum oxide _{(Al 2 O} 3), zinc oxide (ZnO), oxides of zinc and aluminum (AZO), tin oxide and zinc (ZTO), magnesium oxide (MgO), oxide Thorium (ThO ₂ ), tin oxide (SnO ₂ ), lanthanum oxide (La ₂ O ₃ ), indium oxide (In ₂ O ₃ ), niobium oxide (Nb ₂ O ₃ ), antimony oxide (Sb ₂ O ₃ ), oxidation Zinc oxide (ZrO ₂ ), cerium oxide (CeO ₂ ), titanium oxide (TiO ₂ ), bismuth oxide (Bio ₂ ) and the like.
Further, a highly transparent sulfide having a high refractive index may be used. Specific examples thereof include zinc sulfide (ZnS), cadmium sulfide (CdS), and antimony sulfide (Sb ₂ S ₃ ). In particular, tin-doped indium oxide (ITO), zinc-doped indium oxide (IZO), tungsten-doped indium oxide (IWO), gallium-doped indium oxide (IGO), tin and zinc. Amorphous oxides such as oxide (ZTO) are preferred.

The crystal transition temperature (Tc) of the first transparent conductive layer 4 and the second transparent conductive layer 6 is usually 150 ° C. or higher, preferably 180 ° C. or higher, and more preferably 200 ° C. or higher. When the crystal transition temperature (Tc) of the transparent conductive thin film layer is 150 ° C. or higher, the surface unevenness of the transparent conductive layer does not occur when the organic photoelectric conversion element is formed on the transparent plastic substrate, which is preferable. The crystal transition temperature can be measured by a measuring method such as differential thermal analysis.

The thickness of the first transparent conductive layer 4 and the second transparent conductive layer 6 takes into consideration the transmittance and / or reflectance of the entire lower transparent electrode 7 and the organic photoelectric conversion element 1 and the electrical conductivity of the lower transparent electrode 7. Can be adjusted arbitrarily. In particular, when the organic photoelectric conversion element 1 is a transmission type (see-through type) photoelectric conversion element, it is preferable to select the organic photoelectric conversion element 1 in consideration of the transmittance and reflectance of the entire lower transparent electrode 7 and the organic photoelectric conversion element 1. ..

In particular, when the lower transparent electrode has the first transparent conductive layer 4, the thickness of the first transparent conductive layer 4 is selected in consideration of the interference of light between the metal layer 5 and the transparent substrate 2 as described above. There is a need to. In particular, when the organic photoelectric conversion element has the undercoat layer 3 and the first transparent conductive layer, the film thickness of the first transparent conductive layer 4 takes into consideration the relationship with the film thickness of the undercoat layer 3. Then design it. However, for the following reasons, the film thickness of the first transparent conductive layer 4 is preferably 5 nm or more, more preferably 10 nm or more, more preferably 20 nm or more, and preferably 200 nm or less. It is more preferably 100 nm or less, and particularly preferably 60 nm or less. If the thickness of the first transparent conductive layer 4 is too small, the first transparent conductive layer 4 is not uniformly formed, and the metal layer 5 is oxidatively deteriorated to lose its luster, and the light interference effect tends to be impaired. At the same time, electrical resistance may increase. On the other hand, if the film thickness of the first transparent conductive layer 4 is too large, the first transparent conductive layer 4 is usually formed by a vacuum deposition method such as a sputtering method or a CVD method. In this case, the transparent conductive layer 4 has a high density. Since the conductive layer is formed, the first transparent conductive layer 4 is likely to be cracked due to the stress. As a result, oxygen infiltrates into the first lower transparent electrode 7, and the metal layer 5 tends to be oxidatively deteriorated.

When the lower transparent electrode 7 has the second transparent conductive layer 6, the thickness of the second transparent conductive layer 6 is usually 20 nm or more, preferably 30 nm or more, while usually 60 nm or less, although there is no particular limitation. .. On the other hand, when it is not more than the above upper limit, flexibility can be ensured and the production speed does not decrease, which is preferable.

The refractive indexes of the first transparent conductive layer 4 and the second transparent conductive layer 6 at 485 nm are not particularly limited, but are usually 1.3 or more, respectively, while the organic active layer 8 suppresses the interfacial reflectance. In order to be able to absorb light efficiently, 2.5 or less is preferable, and 2.2 or less is more preferable. In particular, the refractive index n ₂ of the first transparent conductive layer 4 is preferably selected so as to satisfy the above formulas (1) to (3) and the later formula (4).

The first transparent conductive layer 4 and the second transparent conductive layer 6 have a specific resistance of usually 1 × 10 ^-7 Ω · cm or more, preferably 1 × 10 ^-6 Ω · cm or more, while usually 5 × 10 ^{It is -3} Ω · cm or less, preferably 1 × 10 ^-4 Ω · cm or less.

Although the lower transparent electrode 7 is transparent, it is preferably highly transparent from the viewpoint of conversion efficiency, and is usually 60% or more, preferably 70% or more. The upper limit is not particularly limited, but is usually 90% or less.

The transmittance of the lower transparent electrode 7 can be measured using an ultraviolet-visible near-infrared spectrophotometer and a film sample holder. As for the measurement result, the transmittance from a wavelength of 380 nm to 900 nm is calculated according to JIS R 3106: 1998, and the transmittance of the lower transparent electrode 7 is calculated as the average of the transmittances in these wavelength regions.

<Metal layer 5>
The material of the metal layer 5 is not particularly limited, and examples thereof include metals such as platinum, gold, silver, aluminum, chromium, nickel, copper, titanium, magnesium, calcium, barium, and sodium, or alloys of these metals. Be done. Of these, a material having high electrical conductivity is preferable, and silver is particularly preferable. Silver is most preferably used because it has a specific resistance of about 1.59 × ^10-6 Ω · cm, is excellent in electrical conductivity, and has excellent visible light transmittance in a thin film.

The thickness of the metal layer 5 is preferably 1 nm, more preferably 5 nm or more in order to improve the electrical conductivity, while the organic active layer 8 efficiently absorbs light and improves the conversion efficiency. In addition, it is preferably 20 nm or less, and more preferably 10 nm or less.

The thickness of the entire lower transparent electrode 7 may be adjusted by determining the film thickness of each layer in consideration of optical characteristics and electrical characteristics, but is usually 10 nm or more, preferably 60 nm or more, while usually, It is 300 nm or less, preferably 200 nm or less, and particularly preferably 100 nm or less.

<Upper electrode 9>
The upper electrode 9 can be formed of any conductive material. Examples of the material of the upper electrode 9 are metals such as platinum, gold, silver, aluminum, chromium, nickel, copper, titanium, magnesium, calcium, barium and sodium or alloys thereof; metals such as indium oxide and tin oxide. Oxides or alloys thereof (ITO, etc.); Conductive polymers such as polyaniline, polypyrrole, polythiophene, and polyacetylene; Acids such as hydrochloric acid, sulfuric acid, and sulfonic acid, Lewis acids such as FeCl ₃ , and iodine are added to the conductive polymer. Containing dopants such as halogen atoms such as halogen atoms and metal atoms such as sodium and potassium; conductive composite materials in which conductive particles such as metal particles, carbon black, fullerene, and carbon nanotubes are dispersed in a matrix such as a polymer binder. , Materials exemplified for the lower transparent electrode 7 and the like can be mentioned.

In particular, when the lower transparent electrode 7 is used as a cathode for collecting electrons and the upper electrode 9 is used as an anode for collecting holes, a material having a deep work function should be used as the material constituting the upper electrode 9. Is preferable. On the other hand, when the lower transparent electrode 7 is used as an anode and the upper electrode 9 is used as a cathode for collecting electrons, it is preferable to use a material having a shallow work function as the material constituting the upper electrode 9. By optimizing the work function, holes and electrons generated by light absorption can be well collected. By providing a buffer layer as described later, the lower transparent electrode 7 and the upper electrode 9 can be formed of the same material.
Further, by making the upper electrode 9 a transparent electrode similar to the lower transparent electrode 7, a transmission type (see-through type) organic photoelectric conversion element can be obtained. In particular, in the present invention, it is effective in a transmission type organic photoelectric conversion element that requires high designability.

The method for forming each layer constituting the lower transparent electrode 7 and the upper electrode 9 is not particularly limited, and the lower transparent electrode 7 and the upper electrode 9 can be formed by a known method. For example, it can be formed by a dry process such as vacuum deposition or sputtering. It can also be formed by a wet process or the like using a conductive ink or the like. At this time, any conductive ink can be used, and for example, a metal particle dispersion liquid or the like can be used. Further, the lower transparent electrode 7 and / or the upper electrode 9 may be improved in characteristics such as electrical characteristics and wet characteristics by surface treatment.

<Organic active layer 8>
The organic active layer 8 usually contains a p-type organic semiconductor compound and an n-type semiconductor compound. 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 organic photoelectric conversion element receives light, the light is absorbed by the organic 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 taken out from the electrode.

The layer structure of the organic active layer is a thin film laminated type in which a p-type semiconductor compound layer and an n-type semiconductor compound layer are laminated, and a bulk hetero having a layer (i layer) in which a p-type semiconductor compound and an n-type semiconductor compound are mixed. Examples thereof include a structure in which a layer (i layer) in which a bonded type or p-type semiconductor compound and an n-type semiconductor compound are mixed, and a p-type semiconductor compound layer and / or an n-type semiconductor compound layer are laminated. Of these, a bulk heterojunction type having a layer (i layer) in which a p-type semiconductor compound and an n-type semiconductor compound are mixed is preferable.

The film thickness of the organic active layer 8 is not particularly limited, but is usually 10 nm or more, preferably 50 nm or more, more preferably 100 nm or more, while usually 1000 nm or less, preferably 500 nm or less, more preferably 400 nm or less. It is particularly preferably 200 nm or less. When the film thickness of the organic active layer 8 is 10 nm or more, the uniformity of the film is maintained and short circuits are less likely to occur, which is preferable. Further, when the thickness of the organic active layer 8 is 1000 nm or less, it is preferable in that the internal resistance is small and the electrodes are not too far apart and the charge diffusion is good.

The color tone of the organic active layer 8 is not particularly limited, but the present invention is particularly effective when the appearance color of the organic photoelectric conversion element is yellow to red, which is not desirable. Specifically, the present invention is particularly effective when using an organically active layer having a hue angle in the range of −60 ° to 110 ° as defined in Z 8781-4: 2013. The reason for this is that, as described above, in the present invention, even if the organic active layer exhibits such a color tone, the appearance color is adjusted to a bluish color by adjusting the optical path length between the transparent substrate 2 and the metal layer 5. Because it can be done.

The p-type organic semiconductor compound is not particularly limited, and examples thereof include a p-type low molecular weight organic semiconductor compound and a p-type organic semiconductor polymer. Among them, when the organic active layer 8 is of the bulk heterojunction type, it is preferable to use a p-type organic semiconductor polymer having excellent film forming properties.

Specifically, the p-type semiconductor polymer is preferably a semiconductor polymer obtained by copolymerizing two or more kinds of monomer units, and specifically, a π-electron conjugation containing an acceptor-type structural unit and a donor-type structural unit. It is preferably heavy.

More specific examples of p-type semiconductor polymers include the polythiophene-thienothiophene copolymer described in Nature Materials, 2006, 5, 328, and the polythiophene-diketopyrrolopyrrole described in WO 2008/000664. Copolymer, Adv. Mater. , 2007, 4160. Polythiophene-thiazolothiazole copolymer, Nature Materials, 2007, 6,497, polythiophene copolymers such as PCPDTBT, etc., International Publication No. 2011/028827. Examples thereof include a copolymer containing benzodithiophene and a copolymer of thienothiophene and benzodithiophene described in International Publication No. 2011/011545. In addition, the conjugated polymer compounds described in International Publication No. 2013/180243 Pamphlet, International Publication No. 2013/065855 Pamphlet and the like can also be mentioned. In addition, derivatives of these polymers and polymers that can be synthesized by combining the monomers listed here can also be used in the same manner. Substituents of these polymers and monomers can be appropriately selected in order to control solubility, crystallinity, film forming property, HOMO energy level, LUMO energy level and the like.

The n-type semiconductor compound is not particularly limited, but specifically, a fullerene; a fullerene compound; a quinolinol derivative metal complex typified by 8-hydroxyquinoline aluminum; a diimide naphthalene tetracarboxylic acid, a diimide perylene tetracarboxylic acid, or the like. Condensed ring tetracarboxylic acid diimides; perylene diimide derivative, terpyridine metal complex, tropolone metal complex, flavonol metal complex, perinone derivative, benzimidazole derivative, benzoxazole derivative, thiazole derivative, benzthiazole derivative, benzothiasizole derivative, oxadiazole Derivatives, thiadiazole derivatives, triazole derivatives, aldazine derivatives, bisstyryl derivatives, pyrazine derivatives, phenanthroline derivatives, quinoxaline derivatives, benzoquinoline derivatives, bipyridine derivatives, borane derivatives; of condensed polycyclic aromatic hydrocarbons such as anthracene, pyrene, naphthacene or pentacene. Total fluoride; examples include single-layer carbon nanotubes and n-type polymers (n-type polymer semiconductor materials).

Among these, the n-type semiconductor compound is preferably a fullerene compound. As the fullerene compound, there are no particular restrictions, but for example, those described in publicly known documents such as International Publication No. 2011/016430 or Japanese Patent Application Laid-Open No. 2012-191194 can be used. Among the fullerene compounds, PC61BM or PC71BM is preferable. In addition, one of the above compounds may be used, or a mixture of a plurality of kinds of compounds may be used.

The method for producing the organic active layer 8 is not particularly limited, and the organic active layer 8 can be formed by any method according to the material used. For example, a vacuum film forming method such as a vapor deposition method or a sputtering method, or a coating method can be mentioned. Above all, it is preferable to use the coating method in order to improve the productivity. Any method can be used as the coating method, and for example, a spin coating method, a reverse roll coating method, a gravure coating method, a kiss coating method, a roll brushing method, a spray coating method, an air knife coating method, a wire barber coating method, etc. Examples include the pipe doctor method, the impregnation / coating method, and the curtain coating method.

For example, when the organic active layer 8 is a laminated type of a p-type semiconductor compound layer and an n-type semiconductor compound layer, a coating liquid containing a p-type semiconductor compound and a coating liquid containing an n-type semiconductor compound are applied, respectively. Can be made. When the organic active layer 8 is of the Berg heterojunction type having a layer in which a p-type semiconductor compound and an n-type semiconductor compound are mixed, a coating liquid containing the p-type semiconductor compound and the n-type semiconductor compound is prepared in advance. It can be produced by applying the coating liquid.
The organic active layer is preferably produced by roll-to-roll, in which case it is preferably formed by a coating method.

The organic photoelectric conversion element may have a layer other than the lower transparent electrode 7, the organic active layer 8, and the upper electrode 9. For example, the lower transparent electrode 7, the organic active layer 8, and / or the organic active layer 8 and the upper part. A buffer layer may be provided between the electrode 9 and the electrode 9. The buffer layer is a layer having a function of improving the efficiency of extracting electric charges from the organic active layer 8 to the anode and / or the cathode. The buffer layer can be classified into a hole extraction layer that improves the hole extraction efficiency and an electron extraction layer that improves the electron extraction efficiency. That is, when the lower transparent electrode 7 is used as a cathode and the upper electrode 9 is used as an anode, the buffer layer provided between the lower transparent electrode 7 and the organic active layer 8 is used as an electron extraction layer, and the organic active layer 8 and the upper electrode 9 are used. It is preferable that the buffer layer provided between the two is a hole extraction layer. On the other hand, when the lower transparent electrode 7 is used as an anode and the upper electrode 9 is used as a cathode, the buffer layer provided between the lower transparent electrode 7 and the organic active layer 8 is used as a hole extraction layer, and the organic active layer 8 and the upper electrode 9 are used. It is preferable that the buffer layer provided between the two is an electron extraction layer. The organic photoelectric conversion element may have only one of the electron extraction layer and the hole extraction layer.

The film thickness of the buffer layer (hole extraction layer and electron extraction layer) is not particularly limited and may be arbitrarily designed according to the material to be used, etc., but in order to improve the charge extraction efficiency, 0. It is preferably 1 nm or more, more preferably 1 nm or more, particularly preferably 10 nm or more, while it is preferably 400 nm or less, further preferably 200 nm or less.

The material of the hole extraction layer is not particularly limited, but specifically, a conductive polymer obtained by doping polythiophene, polyaniline, polypyrrole, polyacetylene, etc. with sulfonic acid / and / or iodine, molybdenum oxide, vanadium oxide, etc. Examples include copper oxide. Of these, poly (ethylenedioxythiophene): poly (styrene sulfonic acid) (PEDOT: PSS) is preferable.

The material of the electron extraction layer is not particularly limited, but is lithium fluoride, 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline, phosphine oxide compound, phosphine sulfide compound, zinc oxide, or titanium oxide. Can be mentioned. Of these, zinc oxide or titanium oxide is preferable as the material for the electron extraction layer.

The method for forming the electron extraction layer and the hole extraction layer is not particularly limited, and can be formed by any method according to the material to be used. For example, a vacuum vapor deposition method, a coating method and the like can be mentioned.

<Other layers>
The organic thin film semiconductor element 1 may have a layer other than the layer described above. For example, a barrier layer may be provided between the transparent substrate 2 and the lower transparent electrode 7. By having the barrier layer, degassing from the transparent substrate 2 is suppressed when the first transparent conductive layer 4 is formed, the film forming property of the first transparent conductive layer 4 is improved, and the heat resistance of the transparent substrate 2 is improved. It is preferable because it provides properties and plasma resistance.

The material of the barrier layer may be any material that can form a dense film, and there is no particular limitation, but specifically, silicon oxide, silicon nitride, silicon carbide, aluminum oxide, aluminum nitride, indium oxide, and oxidation. Examples thereof include transparent inorganic compounds such as tin and zinc oxide, or mixed compounds thereof. Among them, silicon oxide, silicon nitride and a mixture thereof, and aluminum oxide and aluminum nitride and a mixture thereof are preferable.

The thickness of the barrier layer is not particularly limited, but it may be uniform as long as it does not impair the transparency, maintains the gas barrier property, and secures the adhesion to the transparent substrate 2. In order to form a film, it is preferably 10 nm or more, more preferably 20 nm or more, while it is preferably 500 nm or less, further preferably 200 nm or less in order to prevent cracks from easily forming in the barrier layer. , Especially preferably 100 nm or less. On the other hand, when a barrier layer is provided between the transparent substrate 2 and the lower transparent electrode 7, the barrier layer also affects the optical interference between the transparent substrate 2 and the metal layer 5. Therefore, in consideration of the above formula (2), the barrier layer is provided so that the optical path length between the transparent substrate 2 and the lower transparent electrode 7 satisfies the following formula (4) at any of the integers m of 0 or more. It is preferable to adjust the film thickness.
480 ≧ 4 × (n ₁ × d ₁ + n ₂ × d ₂ + n ₄ × d ₄ ) ÷ (2 × m + 1) ≧ 380 …… (4)
In the formula _{(4), n 1, d} 1, n 2 and _{d 2} are _n 1, respectively formula (3) _in, d 1, and _{n 2} and _{d 2} synonymous, _{n 4} is the refractive index of the barrier layer Represents, and d ₄ represents the film thickness of the barrier layer.

When the barrier layer is provided, the configuration of the organic photoelectric conversion element is not particularly limited, but the transparent substrate 2 / undercoat layer 3 / barrier layer / lower transparent electrode 7 / organic semiconductor layer 8 / upper electrode 9 or The transparent substrate 2 / barrier layer / undercoat layer 3 / lower transparent electrode 7 / organic semiconductor layer 8 / upper electrode 9 are preferable.

<Organic thin film solar cell module>
The photoelectric conversion element according to the above embodiment is preferably used as a solar cell module. The solar cell module is preferably sealed with a gas barrier layer or the like in order to prevent the organic photoelectric conversion element from being deteriorated by water, oxygen, or the like.

FIG. 3 is a cross-sectional view schematically showing the configuration of the organic thin-film solar cell module 10 according to the embodiment of the present invention. The organic thin-film solar cell module 10 includes, for example, an organic photoelectric conversion element 1, a sealing layer 11 provided on both sides of the organic photoelectric conversion element 1, and a gas barrier layer 12 provided on one side of the sealing layer 11, respectively. And have. Then, in the organic thin film solar cell module 10, for example, the organic photoelectric conversion element 1 generates electricity by irradiating light from the side where the gas barrier layer 12 is formed in the lower part of the drawing.

The material of the gas barrier layer 12 and the sealing layer 11 constituting the solar cell module 10 and the method of laminating these layers on the organic photoelectric conversion element are not particularly limited, and a well-known technique can be used. For example, those described in publicly known documents such as International Publication No. 2011/016430 or Japanese Patent Application Laid-Open No. 2012-191194 can be used.

Further, the configuration of the solar cell module is not limited to the structure shown in FIG. 3, and may be any structure as long as power can be generated by the photoelectric conversion element. In particular, FIG. 3 shows a structure in which a laminated body of the sealing layer 11 and the barrier layer 12 is provided on both sides of the organic photoelectric conversion element 1, but the sealing layer is provided only on one side of the organic photoelectric conversion element 1. The structure may be a structure in which a laminated body of 11 and the barrier layer 12 is provided. Further, in order to take out the electricity generated by the organic photoelectric conversion element 1 to the outside, it is preferable to provide a collecting wire on the organic photoelectric conversion element.

<Use>
The use of the organic thin-film solar cell module 10 is unlimited and arbitrary. Examples of fields in which the organic thin-film solar cell module 10 is applied include solar cells for building materials, solar cells for automobiles, solar cells for interiors, solar cells for railways, solar cells for ships, solar cells for airplanes, and solar cells for spacecraft. It is suitable for use in batteries, solar cells for home appliances, solar cells for mobile phones, solar cells for toys, and the like.

Specific examples include application as a solar cell for building materials to house roofing materials, rooftops, top lights, walls, windows, etc., application to interiors as an interior solar cell, and automobile bonnets and roofs as automobile solar cells. , Trunk lids, doors, front fenders, rear fenders, pillars, bumpers and rearview mirror surfaces, etc., as well as louvers, handrails, vegetable factories and parking lot exterior walls, highway sound insulation walls and water purification plants It can be applied to outer walls and the like. In particular, it is preferably used as a wind film applied to a window or a glass curtain wall applied to a glass wall.

The present invention will be described in more detail by way of examples, but the present invention is not limited to the description of the following examples as long as the gist of the present invention is not exceeded. First, the measurement test performed in this example will be described.

<Measurement of film thickness of undercoat layer>
The film thickness of the undercoat layer is determined by scratching with a spatula before heat curing to provide a step, then heating and curing at 140 ° C. for 15 minutes, and then sputtering silver to the step portion for about 5 nm to form a white interference. It was obtained by measuring the level difference of the stepped portion using a method surface shape measuring device VertScan (manufactured by Ryoka System).

<Measurement of refractive index>
The refractive indexes of the undercoat layer and the metal layer (indium oxide layer) were measured using a spectroscopic ellipsometer UVISEL (manufactured by HORIBA, Ltd.). The refractive index of the undercoat layer at a wavelength of 485 nm was 1.61. The refractive index of the first conductive layer (ITO layer) at a wavelength of 485 nm was 1.95.

<Observation of appearance color>
As for the appearance color of the organic thin-film solar cell module, an organic thin-film solar cell module having a size of 10 cm square was placed under a daylight fluorescent lamp having an illuminance of 700 lux, and the appearance color was determined at a position facing the organic thin-film solar cell module.

<Measurement of brightness index L ^* , a ^* , b ^* >
The appearance color and brightness indexes L ^* , a ^* , and b ^* were measured using a spectrocolorimeter CM-700d manufactured by Konica Minolta Co., Ltd. in accordance with JIS Z 8722 Condition C.

<Calculation of interference wavelength λ>
The interference wavelength λ between the silver layer, which is a metal layer, and the polyethylene naphthalate film, which is a transparent substrate, was calculated using the following formula (c), which is a modification of the above formula (a).
λ = 4 × (n × d) ÷ (2 × m + 1) …… (c)

<Example 1>
A 140 nm thick undercoat layer (Momentive hardcoat agent SHC900) is applied to one side of a polyethylene naphthalate film (Q65 manufactured by Teijin DuPont Film Co., Ltd., thickness 125 μm, refractive index 1.9 at a wavelength of 485 nm) by a bar coating method. It was formed and then heated in air at 140 ° C. for 15 minutes to cure.

Next, a laminated lower transparent electrode was formed by laminating the first indium oxide layer at 50 nm, the silver layer at 8 nm, and the second indium oxide layer at 30 nm in this order by a sputtering method on the undercoat layer.

Next, a copolymer composed of a zinc oxide layer having a zinc oxide layer of 50 nm as an electron extraction layer and an imidethiophene unit and a dithienosyrole unit as a p-type semiconductor polymer on a lower transparent electrode by a coating method: PCBM = An organic active layer composed of 2: 2.5 was laminated at 320 nm, and a PEDOT: PSS layer at 400 nm as a hole extraction layer was laminated in this order. The organic active layer exhibited a reddish gray color.

Next, a second electrode was formed by laminating a silver layer at 8 nm and an indium oxide layer at 40 nm on the organic semiconductor layer by a sputtering method to prepare an organic photoelectric conversion element.

Next, using an epoxy adhesive layer and a barrier film (Mitsubishi Resin View Barrier (R)), the barrier film, the adhesive layer, the organic photoelectric conversion element, the adhesive layer, and the barrier film were laminated. Then, the laminated body was heated at 140 ° C. for 1 hour to seal the organic photoelectric conversion element, and an organic thin film solar cell module was produced.

<Example 2>
An organic thin-film solar cell module was produced in the same manner as in Example 1 except that the thickness of the undercoat layer was 162 nm.

<Comparative example 1>
An organic thin-film solar cell module was produced in the same manner as in Example 1 except that the thickness of the undercoat layer was 178 nm.

<Comparative example 2>
An organic thin-film solar cell module was produced in the same manner as in Example 1 except that the thickness of the undercoat layer was set to 205 nm.

<Comparative example 3>
An organic thin-film solar cell module was produced in the same manner as in Example 1 except that the thickness of the undercoat layer was 221 nm.

Wavelength λ at m0, 1, 2, 3 in the organic thin-film solar cell modules of Examples 1 to 2 and the organic thin-film solar cell modules of Comparative Examples 1 to 3 and the brightness index L ^* , a ^* , b ^* and the appearance color were measured. Table 1 shows the measurement results.

In Table 1, it is shown that the larger the a ^* value is, the stronger the redness is, and the smaller the a ^* value is, the stronger the greenness is. Further, it is shown that the larger the b ^* value, the stronger the yellowness, and the smaller the b ^* value, the stronger the bluishness. Therefore, in order to avoid the appearance color of the organic thin-film solar cell module becoming yellow or red, the a ^* value and the b ^* value should be as small as possible.

As can be seen from Table 1, the organic thin-film solar cell modules of Example 1 and Example 2 satisfying the formula (1) when m = 1 have a vivid appearance color as expected from the calculated λ value. It exhibited a bluish color, and both the a ^* value and the b ^* value of the brightness index were small. Further, the organic thin-film solar cell module in Comparative Example 3 exhibited a bright reddish color as expected from the calculated value of λ, and the brightness index a ^* value was large and the b ^* value was small.

The organic thin-film solar cell modules of Comparative Example 1 and Comparative Example 2 exhibited an undesired yellow color tone. The brightness index of Comparative Example 1 has a b ^* value that is almost the same as that of Comparative Example 2, but the a ^* value is small, indicating that Comparative Example 1 is more greenish than Comparative Example 2. Further, Comparative Example 2 has a larger a ^* value than Comparative Example 1, indicating that Comparative Example 2 is more yellowish than Comparative Example 1. This is the same as the color tone transition expected from the interference wavelength λ calculated in Comparative Example 1 and Comparative Example 2, and the appearance color of the organic thin-film solar cell module observed in these Examples and Comparative Examples was used. Although the organic semiconductor layer had a reddish gray color, it is shown that it is determined by the optical interference between the metal layer constituting the lower transparent electrode and the transparent substrate.

<Example 3>
An organic thin-film solar cell module was produced in the same manner as in Example 1 except that the thickness of the undercoat layer was 139 nm, and the appearance color was evaluated. In addition, the conversion efficiency (PCE) of the organic thin-film solar cell module was measured according to JIS C8934. The results obtained are shown in Table 2.

<Comparative example 4>
An organic thin-film solar cell module was produced in the same manner as in Example 1 except that the thickness of the undercoat layer was set to 240 nm, and the appearance color was evaluated. Further, the conversion efficiency (PCE) of the organic thin-film solar cell module was measured in the same manner as in Example 3. The results obtained are shown in Table 2.

Similar to the results in Table 1, the organic thin-film solar cell module according to Example 3 satisfying the above formula (1) when m = 1 is organic even though the organic active layer is reddish gray. thin-film solar cell module shows a brilliant blue appearance color, the Suga satisfy (1), greater than the 200nm thickness of the undercoat layer, the organic thin film solar cell module according to Comparative example 4, vivid The appearance color of reddish purple was shown. On the other hand, the conversion efficiencies of the organic thin-film solar cell modules according to Example 3 and Comparative Example 4 are both 4.0%, and the organic thin-film solar cell modules are adjusted so as to show a blue appearance color as in Example 3. However, the conversion efficiency did not decrease. Therefore, it can be seen that according to the present invention, it is possible to provide an organic thin film solar cell module exhibiting a desirable blue appearance color without lowering the conversion efficiency.

<Example 4>
A copolymer containing a naphthobistiaziazole unit and a benzodithiophene unit was used as the p-type semiconductor polymer, the film thickness of the PEDOT: PSS layer, which is a hole extraction layer, was changed to 150 nm, and the film thickness of the undercoat layer was further changed. An organic thin-film solar cell module was produced by the same method as in Example 1 except that the nm was set to 142 nm, and the appearance color was evaluated. The organic active layer had a green color. In addition, the conversion efficiency (PCE) of the organic thin-film solar cell module was measured according to JIS C8934. The results obtained are shown in Table 3.

<Comparative example 5>
An organic thin-film solar cell module was produced in the same manner as in Example 4, except that the film thickness of the undercoat layer was 176 nm, and the appearance color was evaluated and the conversion efficiency was measured. The results obtained are shown in Table 3.

<Comparative Example 6>
An organic thin-film solar cell module was produced in the same manner as in Example 4 except that the undercoat layer was not provided, and the appearance color was evaluated and the conversion efficiency was measured. The results obtained are shown in Table 3.

From the results in Table 3, the organic thin-film solar cell module according to Example 4 satisfying the formula (1) when m = 1 is an organic thin-film solar cell module even though the organic active layer is green. Can be confirmed to have a green-blue appearance color. On the other hand, in Comparative Example 5 which does not satisfy the formula (1), the appearance color of the organic thin-film solar cell module did not become a bluish color because the green interference color was conspicuous when m = 1. Similarly, Suga satisfy the equation (1), also an organic thin film solar cell module according to Comparative Example 6 not to have a undercoat layer, can not be interference color yellow is conspicuous, adjusted to the color of bluish It was. Therefore, to satisfy the equation (1), by having an undercoat layer is 200nm or less thick, it can be seen that to adjust the appearance color of the organic thin-film solar cell module to the color of bluish. Further, as in the results of Table 2, it can be seen that there is almost no difference in the conversion efficiency of each organic thin-film solar cell module. Therefore, according to the present invention, the color of the organic thin-film solar cell module can be adjusted to a bluish color while preventing a decrease in conversion efficiency.

1 ... Organic photoelectric conversion element, 2 ... Transparent substrate, 3 ... Undercoat layer, 4 ... First transparent conductive layer, 5 ... Metal layer, 6 ... Second transparent conductive layer, 7 ... Lower transparent Electrode, 8 ... Organic active layer, 9 ... Top electrode, 10 ... Organic thin-film solar cell module, 11 ... Sealing layer, 12 ... Gas barrier layer

Claims (6)

An organic photoelectric conversion element in which a transparent substrate , a lower transparent electrode including a metal layer, an organic active layer, and an upper electrode are sequentially laminated , and an undercoat layer is included between the transparent substrate and the metal layer. ,
The following formula (1) is used when the optical path length (n × d) between the transparent substrate and the metal layer, which is represented by the distance d between the transparent substrate and the metal layer and the refractive index n, is an integer whose m is 0 or more. ) meets, organic photoelectric conversion element, wherein the thickness of the undercoat layer is 200nm or less.
480 nm ≧ 4 × (n × d) ÷ (2 × m + 1) ≧ 380 nm ・ ・ ・ (1) The organic photoelectric conversion element according to claim 1, wherein the undercoat layer has a thickness of 10 nm or more. The organic photoelectric conversion element according to claim 1 or 2, wherein the lower transparent electrode includes a transparent conductive layer, and the transparent conductive layer is arranged between the transparent substrate and the metal layer. The organic photoelectric conversion element according to claim 3, wherein the thickness of the transparent conductive layer is 5 nm or more and 200 nm or less. The organic photoelectric conversion element according to any one of claims 1 to 4, wherein the thickness of the metal layer is 1 nm or more and 20 nm or less. An organic thin-film solar cell module including the organic photoelectric conversion element according to any one of claims 1 to 5.