JP5023457B2 - Organic thin film solar cell - Google Patents

Description

  The present invention relates to a high-efficiency organic thin film solar cell, and more particularly to an organic thin film solar cell including an organic semiconductor layer in which a plurality of organic semiconductor films are stacked.

  An organic thin film solar cell is a solar cell in which an organic thin film having an electron donating function and an electron accepting function is disposed between two different electrodes, and a manufacturing process compared to an inorganic solar cell typified by silicon or the like. Is easy, and has the advantage that the area can be increased at low cost. However, since the photoelectric conversion efficiency is low, it is difficult to put it to practical use, and in the organic thin film solar cell, increasing the photoelectric conversion efficiency is the biggest issue.

As a general organic thin film solar cell, for example, a transparent substrate, a transparent electrode layer, an organic semiconductor layer that functions as an electron donor and an electron acceptor, and a metal electrode layer are sequentially laminated. In the organic thin-film solar cell in which a plurality of layers are laminated in this way, the smoothness and adhesion at the interface between the layers greatly affect the performance of the solar cell. Since the extraction of electric charges in organic thin-film solar cells is not actively assisted by an external electric field, the presence of slight defects or barriers in the charge transfer path greatly impairs the characteristics of the solar cell. This is because the interface resistance caused by the smoothness and adhesion at the interface becomes a defect and a barrier.
In addition, in an organic thin film solar cell, a plurality of organic semiconductor films may be stacked as the organic semiconductor layer. In such a case, the interface state between the organic semiconductor films greatly affects the performance of the solar cell.

  Here, generally, when the contact area between the upper and lower organic semiconductor films increases, the movement of electric charges becomes smooth, and the performance of the solar cell tends to be improved. However, when a plurality of organic semiconductor films are stacked by the vapor deposition method, the surface state of the film varies, and there is a problem that the smoothness and adhesion at the interface between the organic semiconductor films are low. In addition, it is possible to form an organic semiconductor film by a coating method, but it is a limit to stacking up to two layers, and it is technically difficult to stack three or more organic semiconductor films (See, for example, Non-Patent Document 1). Accordingly, there is no practical means for increasing the contact area between the upper and lower organic semiconductor films.

Also, a method of laminating an organic semiconductor film by a coating method on an organic semiconductor film formed by vapor deposition when laminating a p-type organic semiconductor film and an n-type organic semiconductor film has been proposed (for example, non-patent literature) 2). According to this method, when the coating liquid is applied onto the lower organic semiconductor film, which is a deposited film, the organic semiconductor material is slightly eluted from the lower organic semiconductor film into the solvent in the coating liquid. The semiconductor film surface is roughened. As a result, the interface between the upper and lower organic semiconductor films is intricate, so that the pn junction area can be increased and the photoelectric conversion efficiency can be improved.
However, this method increases the pn junction area, and does not increase the contact area to facilitate charge transfer.

C.W.Tang, “Two-layer organic photovoltaic cell”, Applied Physics Letters, vol.48, No.2, p.183-185 (1986) A. Fujii, H. Mizukami, T. Umeda, T. Shirakawa, Y. Hashimoto and K. Yoshino, “Solvent dependence of interpenetrating interface formation in organic conducting polymer and C60”, Jpn. J. Appl. Phys., 43, p.8312-8315 (2004)

  The present invention has been made in view of the above problems, and its main object is to provide a highly efficient organic thin-film solar cell with good charge extraction efficiency.

  In order to achieve the above object, the present invention provides an organic semiconductor layer having a substrate, a first electrode layer formed on the substrate, and at least two photoelectric conversion layers formed on the first electrode layer. And a second electrode layer formed on the organic semiconductor layer, wherein the interface between the photoelectric conversion layers has irregularities, and the organic thin film solar cell I will provide a.

  According to the present invention, since the interface between the photoelectric conversion layers has irregularities, the contact area between the adjacent photoelectric conversion layers increases, and the charge transfer between the photoelectric conversion layers becomes smooth, so that the charge extraction efficiency can be improved. it can. Thereby, the photoelectric conversion efficiency can be improved.

  In the above invention, the organic semiconductor layer may further have a charge extraction promoting layer. For example, when a charge extraction promoting layer is formed between the photoelectric conversion layer and the first electrode layer or the second electrode layer, a resistance barrier at the interface between the photoelectric conversion layer and the first electrode layer or the second electrode layer. This is because the charge can be taken out efficiently.

  The present invention also provides a substrate, a first electrode layer formed on the substrate, an organic semiconductor layer formed on the first electrode layer and having a photoelectric conversion layer and a charge extraction promoting layer, and the organic semiconductor layer. An organic thin film solar cell having a second electrode layer formed thereon, wherein the interface between the photoelectric conversion layer and the charge extraction promoting layer has irregularities I will provide a.

  According to the present invention, since the interface between the photoelectric conversion layer and the charge extraction facilitating layer has irregularities, the contact area between the photoelectric conversion layer and the charge extraction facilitating layer is increased, and charge transfer between the photoelectric conversion layer and the charge extraction facilitating layer is performed. Therefore, the charge extraction efficiency can be improved. For example, when a charge extraction promoting layer is formed between the photoelectric conversion layer and the first electrode layer or the second electrode layer, at the interface between the photoelectric conversion layer and the first electrode layer or the second electrode layer. The resistance barrier can be reduced, and charges can be taken out efficiently. Thereby, it is possible to improve photoelectric conversion efficiency.

  In the present invention, the organic semiconductor layer is preferably a coating film. That is, the organic semiconductor layer is preferably formed by a coating method. This is because, for example, coating unevenness is caused by using a coating liquid having a relatively high viscosity, so that a layer having irregularities on the surface can be formed. In addition, when a coating liquid is further applied onto such a layer having irregularities on the surface, the fluidity is good, so that the upper layer can be formed so as to adhere to the irregularities on the surface. Thereby, while being able to form a lower layer so that the interface between layers may have an unevenness | corrugation, the adhesiveness between layers can be improved.

  In the present invention, a hole extraction layer may be formed between the first electrode layer and the organic semiconductor layer. This is because when the first electrode layer is an anode, the hole extraction efficiency from the organic semiconductor layer to the anode is increased by providing the hole extraction layer.

  Furthermore, the present invention provides a first electrode layer forming step of forming a first electrode layer on a substrate, and applying a lower layer forming coating liquid having a predetermined viscosity on the first electrode layer to form a lower layer. An organic semiconductor layer forming step for forming an organic semiconductor layer having at least two layers, the lower layer forming step for forming a coating film, and the upper layer forming step for forming an upper layer film on the lower layer coating film; And a second electrode layer forming step of forming a second electrode layer on the organic semiconductor layer. A method of manufacturing an organic thin film solar cell is provided.

  According to the present invention, coating unevenness is caused by using a coating solution for forming a lower layer having a predetermined viscosity, so that a coating film having irregularities on the surface can be formed. Next, when a film is further formed on a coating film having irregularities on such a surface, the contact area between the upper and lower films increases, and the movement of charges between the photoelectric conversion layers becomes smooth, thereby improving the charge extraction efficiency. Can do. Therefore, a highly efficient organic thin film solar cell can be obtained.

  In the said invention, it is preferable that the said upper layer formation process is a process of apply | coating the coating liquid for upper layer formation on the said lower layer coating film, and forming an upper layer coating film. If it is such a process, the upper layer forming coating solution can be applied to follow the surface irregularities on the lower layer coating film having irregularities on the surface as described above. It is because it can raise.

  Moreover, in the said invention, it is preferable that the said lower layer forming coating liquid contains the organic-semiconductor material whose weight average molecular weight is 100,000 or more. This is because when the weight average molecular weight of the organic semiconductor material is in the above range, it is possible to suppress the organic semiconductor material in the lower layer coating from being eluted into the solvent in the upper layer forming coating solution. In addition, since the conventional method does not use a difference in solubility in a solvent to laminate, there is an advantage that the type of solvent used for the upper layer forming coating liquid and the constituent material of the upper layer film are not limited. .

  In the present invention, since the interface between adjacent photoelectric conversion layers or the interface between the photoelectric conversion layer and the charge extraction promoting layer has irregularities, the contact area between the layers is increased and the charge transfer is facilitated. There is an effect that the conversion efficiency can be improved.

Hereinafter, the organic thin-film solar cell and the manufacturing method thereof of the present invention will be described in detail.
A. Organic Thin Film Solar Cell The organic thin film solar cell of the present invention can be divided into two embodiments depending on the configuration of the organic semiconductor layer. The first embodiment of the organic thin film solar cell of the present invention is characterized in that the organic semiconductor layer has at least two photoelectric conversion layers, and the interface between the photoelectric conversion layers has irregularities. In addition, the second embodiment of the organic thin film solar cell of the present invention is characterized in that the organic semiconductor layer has a photoelectric conversion layer and a charge extraction promoting layer, and the interface between the photoelectric conversion layer and the charge extraction promotion layer has irregularities. . In the following, each embodiment will be described separately.

1. First Embodiment A first embodiment of the organic thin film solar cell of the present invention is a substrate, a first electrode layer formed on the substrate, and at least two layers of photoelectric conversion formed on the first electrode layer. An organic thin film solar cell comprising an organic semiconductor layer having a layer and a second electrode layer formed on the organic semiconductor layer, wherein the interface between the photoelectric conversion layers has irregularities It is what.

The organic thin film solar cell of this embodiment will be described with reference to the drawings.
FIG. 1 is a schematic cross-sectional view showing an example of an organic thin film solar cell of this embodiment. In the example shown in FIG. 1, an organic thin-film solar cell 10 is obtained by sequentially laminating a first electrode layer 2, an organic semiconductor layer 3, and a second electrode layer 4 on a substrate 1. The organic semiconductor layer 3 has two photoelectric conversion layers 13a and 13b, and the interface between the photoelectric conversion layers 13a and 13b has irregularities.

According to this embodiment, since the interface between the photoelectric conversion layers has irregularities, the contact area between the adjacent photoelectric conversion layers increases, and the movement of charges between the photoelectric conversion layers becomes smooth, so that the charge extraction efficiency is improved. In addition, when the refractive indexes of adjacent photoelectric conversion layers are different from each other, light scattering effect and light confinement effect can be obtained by the unevenness of the interface, so that light can be used effectively. Therefore, it is possible to achieve high photoelectric conversion efficiency.
Hereinafter, each structure of such an organic thin film solar cell is demonstrated.

(1) Organic semiconductor layer The organic semiconductor layer used in the present embodiment has at least two photoelectric conversion layers. Here, the “photoelectric conversion layer” refers to a member that contributes to charge separation of the organic thin film solar cell and has a function of transporting the generated electrons and holes toward the electrode layers in opposite directions.

  In this embodiment, the photoelectric conversion layer may be an electron hole transporting layer having electron accepting property and electron donating property, and an electron transporting layer having electron accepting property and a hole transporting layer having electron donating property. And may be laminated. For example, in FIG. 1, when the photoelectric conversion layer 13a is a laminate of an electron transport layer and a hole transport layer, the photoelectric conversion layer 13a includes a hole transport layer 17a and an electron transport layer 17b as illustrated in FIG. It will have. In FIG. 2, since the side in contact with the photoelectric conversion layer 13b is the electron transport layer 17b, there are irregularities on the surface of the electron transport layer 17b. However, even if the side in contact with the photoelectric conversion layer 13b is the electron transport layer, holes are present. Since it may be a transport layer, although not shown, when the side in contact with the photoelectric conversion layer 13b is a hole transport layer, irregularities exist on the surface of the hole transport layer side.

In this embodiment, the organic semiconductor layer has a plurality of photoelectric conversion layers, and at least one interface among the adjacent photoelectric conversion layers may be uneven. Specifically, the center line average roughness (Ra) is preferably in the range of 10 nm to 1 μm at the interface between the photoelectric conversion layers, and in particular, in the range of 10 nm to 500 nm, particularly in the range of 10 nm to 300 nm. Is preferred. That is, it is preferable that the center line average roughness (Ra) of the surface of the photoelectric conversion layer as a lower layer in the uneven surface is in the above range. This is because if the center line average roughness is smaller than the above range, the adhesion between the photoelectric conversion layers is lowered, and the contact area may be reduced. Moreover, it is because it is difficult to form the photoelectric converting layer whose surface centerline average roughness is smaller than the said range by the apply | coating method. On the other hand, if the center line average roughness is larger than the above range, the effect of increasing the contact area may not be sufficiently obtained.
The centerline average roughness (Ra) was measured using an atomic force microscope (Nanoscope IIIa manufactured by Beeco Instruments (DI)) under the conditions of a scan range: 10 μm and a scan speed: 0.4 Hz. Value.

Moreover, it is preferable that the surface unevenness | corrugation of the photoelectric converting layer used as a lower layer is an unevenness | corrugation of gentle inclination. This is because if the unevenness has a steep slope, the adhesion between the photoelectric conversion layers is lowered, and the contact area may be reduced.
Furthermore, it is preferable that the surface roughness of the photoelectric conversion layer as a lower layer is small. In general, the surface roughness (surface properties) can be represented by roughness and swell as illustrated in FIG. Roughness refers to surface irregularities with relatively small intervals, and undulation refers to surface undulations with relatively large intervals. If the roughness is too large, the adhesion between the photoelectric conversion layers may be reduced, and the contact area may be reduced.

  The number of stacked layers of the photoelectric conversion layer may be two or more, but is preferably about 2 to 5 layers, more preferably 2 or 3 layers. It is because the transmittance | permeability of an organic-semiconductor layer will fall when there are too many laminations, and the utilization efficiency of light will fall.

  For example, in the case where three or more photoelectric conversion layers are stacked, it is only necessary that at least one of the interfaces of adjacent photoelectric conversion layers has unevenness. For example, as shown in FIG. 4, the interfaces of all the photoelectric conversion layers 13a, 13b, and 13c may have irregularities.

  The organic thin film solar cell of this embodiment is one in which at least two photoelectric conversion layers are directly laminated. In the organic thin film solar cell in which a plurality of photoelectric conversion layers are directly laminated in this way, materials having different absorption wavelength regions can be used for each photoelectric conversion layer, so that the entire organic thin film solar cell has an absorption wavelength region. Can be spread. In addition, when a material having the same absorption wavelength region is used for each photoelectric conversion layer, an organic thin film solar cell having a plurality of photoelectric conversion layers is compared with an organic thin film solar cell having only one photoelectric conversion layer. Then, since the thickness is increased, it is considered that the absorbance can be increased as the thickness increases. Therefore, by directly laminating a plurality of photoelectric conversion layers, it is possible to produce an organic thin film solar cell that can generate power over a wide wavelength range and can realize high photoelectric conversion efficiency.

Here, FIG. 6 shows an example of an organic thin film solar cell. In the organic thin-film solar cell S having a configuration in which the photoelectric conversion layer 22 is sandwiched between the two electrode layers 21 and 23, the current J is generated by irradiating the light energy L in the photoelectric conversion layer 22, and the electromotive force of V Is obtained (FIG. 6A). When two organic thin film solar cells S are connected in series and irradiated with 2 L of light energy, the light energy equivalent to each of the two organic thin film solar cells S (= 2L / 2 = L) Can be obtained, a double electromotive force (= 2V) can be obtained (FIG. 6B). That is, if any of the plurality of organic thin-film solar cells connected in series can absorb light, the electromotive force increases accordingly.
In the present embodiment, for example, by directly laminating the photoelectric conversion layers 22a and 22b, an electromotive force of 2V can be obtained in the same level as when two organic thin film solar cells are connected in series. It is expected (FIG. 6 (c)). Therefore, the photoelectric conversion efficiency can be increased, and more ideally, a plurality of organic thin film solar cells can be used as a single organic thin film solar cell, instead of being connected in series.

  In this embodiment, the organic semiconductor layer may further have a charge extraction promoting layer. An example of an organic thin film solar cell having a charge extraction promoting layer is shown in FIG. In the organic thin film solar cell 10 shown in FIG. 7, the first electrode layer 2, the organic semiconductor layer 3, and the second electrode layer 4 are sequentially stacked on the substrate 1, and the organic semiconductor layer 3 is the charge extraction promoting layer 15. And two photoelectric conversion layers 13a and 13b are laminated. Electrons and holes are generated in the photoelectric conversion layers 13a and 13b, respectively, and the electrons and holes move in the opposite directions toward the first electrode layer 2 or the second electrode layer 4, respectively. In this case, since the charge extraction promoting layer 15 is formed between the photoelectric conversion layer 13a and the first electrode layer 2, the resistance barrier at the interface between the photoelectric conversion layer 13a and the first electrode layer 2 can be reduced. It is possible to take out charges efficiently.

  FIG. 8 shows another example of the organic thin film solar cell having the charge extraction promoting layer. In the organic thin film solar cell 10 shown in FIG. 8, the 1st electrode layer 2, the organic-semiconductor layer 3, and the 2nd electrode layer 4 are laminated | stacked in order on the board | substrate 1, and the organic-semiconductor layer 3 is the photoelectric converting layer 13a. The charge extraction promoting layer 15 and the two photoelectric conversion layers 13b and 13c are laminated. Electrons and holes are generated in the photoelectric conversion layers 13a, 13b, and 13c, respectively, and the electrons and holes move in the opposite directions toward the first electrode layer 2 or the second electrode layer 4, respectively. In this case, since the charge extraction promoting layer 15 is formed between the photoelectric conversion layer 13a and the photoelectric conversion layer 13b, the resistance barrier at the interface between the photoelectric conversion layer 13a and the photoelectric conversion layer 13b can be reduced. Since the charge easily moves from the photoelectric conversion layer 13b to the photoelectric conversion layer 13a, the charge extraction efficiency can be improved.

  Thus, when the charge extraction promoting layer is formed, the resistance barrier at the interface between the layers becomes loose, and the extraction of charges can be promoted. Further, since it is possible to facilitate the extraction of charges, there is an advantage that it is not necessary to separately provide a conventional charge extraction layer (a hole extraction layer or an electron extraction layer).

Further, when the charge extraction promoting layer is formed, the interface between the photoelectric conversion layer and the charge extraction promoting layer may have irregularities. In this case, the center line average roughness (Ra) of the interface between the photoelectric conversion layer and the charge extraction promoting layer is preferably in the range of 10 nm to 1 μm, more preferably in the range of 10 nm to 500 nm, and still more preferably in the range of 10 nm to 300 nm. Is within. This is because the charge extraction efficiency can be further increased by increasing the contact area between the photoelectric conversion layer and the charge extraction promoting layer.
Hereinafter, the photoelectric conversion layer and the charge extraction promoting layer that constitute the organic semiconductor layer, and the layer configuration of the organic semiconductor layer will be described.

(I) Photoelectric Conversion Layer As described above, the photoelectric conversion layer used in this embodiment may be an electron hole transport layer having electron accepting properties and electron donating properties, and electron transport having electron accepting properties. A layer and a hole transport layer having an electron donating property may be laminated. Hereinafter, the electron hole transport layer, the electron transport layer, and the hole transport layer will be described.

(Electron hole transport layer)
The electron hole transport layer used in this embodiment contains an electron donating organic semiconductor material and an electron accepting organic semiconductor material. The electron hole transport layer is a layer having both electron accepting and electron donating functions, and charge separation is generated by using a pn junction formed in the electron hole transport layer, so that photoelectric conversion alone is performed. Acts as a layer.

  In order to generate charges efficiently, it is preferable that the electron-donating organic semiconductor material and the electron-accepting organic semiconductor material are uniformly dispersed in the electron-hole transport layer. At this time, the mixing ratio of the electron-donating organic semiconductor material and the electron-accepting organic semiconductor material is appropriately adjusted to an optimal mixing ratio depending on the type of the organic semiconductor material to be used.

The electron-donating organic semiconductor material is not particularly limited as long as it has a function as an electron donor, but it is preferable that the film can be formed by a coating method. A conductive polymer material is preferable.
Here, the conductive polymer is a so-called π-conjugated polymer, and is composed of a π-conjugated system in which double bonds or triple bonds containing carbon-carbon or heteroatoms are alternately linked to single bonds, and has semiconducting properties. Is shown. In the conductive polymer material, π conjugation is developed in the polymer main chain, so that charge transport in the main chain direction is basically advantageous. In addition, the conductive polymer material can be easily formed by a coating method by using a coating solution in which the conductive polymer material is dissolved or dispersed in a solvent. There is an advantage that it can be manufactured at low cost without requiring expensive equipment.

Examples of the electron-donating conductive polymer material include polyphenylene, polyphenylene vinylene, polysilane, polythiophene, polycarbazole, polyvinyl carbazole, porphyrin, polyacetylene, polypyrrole, polyaniline, polyfluorene, polyvinyl pyrene, polyvinyl anthracene, and derivatives thereof. And copolymers thereof, phthalocyanine-containing polymers, carbazole-containing polymers, organometallic polymers, and the like.
Among the above, thiophene-fluorene copolymer, polyalkylthiophene, phenylene ethynylene-phenylene vinylene copolymer, phenylene ethynylene-thiophene copolymer, phenylene ethynylene-fluorene copolymer, fluorene-phenylene vinylene copolymer A thiophene-phenylene vinylene copolymer is preferably used. This is because the energy level difference is appropriate for many electron-accepting organic semiconductor materials.
For example, a phenylene ethynylene-phenylene vinylene copolymer (Poly [1,4-phenyleneethynylene-1,4- (2,5-dioctadodecyloxyphenylene) -1,4-phenyleneethene-1,2-diyl-1,4- ( 2,5-dioctadodecyloxyphenylene) ethene-1,2-diyl]) is described in detail in Macromolecules, 35, 3825 (2002) and Micromol. Chem. Phys., 202, 2712 (2001).

In addition, the electron-accepting organic semiconductor material is not particularly limited as long as it has a function as an electron acceptor, but it is preferable that the film can be formed by a coating method. It is preferable that the conductive conductive polymer material. This is because the conductive polymer material has the advantages as described above.
Examples of the electron-accepting conductive polymer material include polyphenylene vinylene, polyfluorene, and derivatives thereof, and copolymers thereof, or carbon nanotubes, fullerene derivatives, CN group or CF ₃ group-containing polymers, and their it can be mentioned -CF ₃ substituted polymer. Specific examples of the polyphenylene vinylene derivative include CN-PPV (Poly [2-Methoxy-5- (2′-ethylhexyloxy) -1,4- (1-cyanovinylene) phenylene]), MEH-CN-PPV (Poly [2 -Methoxy-5- (2′-ethylhexyloxy) -1,4- (1-cyanovinylene) phenylene]) and the like.

  Alternatively, an electron-accepting organic semiconductor material doped with an electron-donating compound, an electron-donating organic semiconductor material doped with an electron-accepting compound, or the like can be used. Among these, a conductive polymer material doped with an electron donating compound or an electron accepting compound is preferably used. Conductive polymer materials are basically advantageous in charge transport in the direction of the main chain because of the development of π conjugation in the polymer main chain, and are doped with electron-donating compounds and electron-accepting compounds. This is because electric charges are generated in the π-conjugated main chain, and the electrical conductivity can be greatly increased.

Examples of the electron-accepting conductive polymer material doped with the electron-donating compound include the above-described electron-accepting conductive polymer material. As the electron-donating compound to be doped, for example, a Lewis base such as an alkali metal such as Li, K, Ca, or Cs or an alkaline earth metal can be used. The Lewis base acts as an electron donor.
Examples of the electron-donating conductive polymer material doped with the electron-accepting compound include the above-described electron-donating conductive polymer material. As the electron-accepting compound to be doped, for example, a Lewis acid such as FeCl ₃ (III), AlCl ₃ , AlBr ₃ , AsF ₆ or a halogen compound can be used. In addition, Lewis acid acts as an electron acceptor.

  As the film thickness of the electron-hole transport layer, the film thickness generally employed in bulk heterojunction organic thin film solar cells can be employed, and is adjusted as appropriate depending on whether the surface has irregularities. For example, when the electron hole transport layer has irregularities on one surface and becomes a lower layer when laminating, and when the electron hole transport layer has irregularities on both surfaces, when formed by a coating method The thickness is preferably such that uneven coating occurs. In addition, for example, when the electron-hole transport layer has irregularities on one surface and becomes an upper layer when laminated, the thickness is preferably such that the lower surface irregularities can be filled. Specifically, it can be set within a range of 0.2 nm to 3000 nm, and preferably within a range of 1 nm to 600 nm. This is because if the film thickness is thicker than the above range, the volume resistance in the electron-hole transport layer may increase, and it may be difficult to form irregularities. On the other hand, if the film thickness is thinner than the above range, light may not be sufficiently absorbed, it may be difficult to form irregularities, and it may be difficult to fill the underlying surface irregularities.

(Electron transport layer)
The electron transport layer used in this embodiment contains an electron-accepting organic semiconductor material.
The electron-accepting organic semiconductor material is not particularly limited as long as it has a function as an electron acceptor, but it is preferable that the film can be formed by a coating method. A conductive polymer material is preferable. This is because the conductive polymer material has the advantages as described above. Specific examples include the same electron-accepting conductive polymer materials used for the electron-hole transport layer.

  The film thickness of the electron transport layer is appropriately adjusted depending on whether the surface has irregularities. For example, when the electron transport layer has unevenness on one surface and becomes a lower layer when laminated, and when the electron transport layer has unevenness on both surfaces, uneven coating occurs when formed by a coating method. It is preferable that the thickness is such that it occurs. For example, when the electron transport layer has irregularities on one surface and becomes an upper layer when laminated, the thickness is preferably such that the surface irregularities of the lower layer can be filled. Specifically, it can be set within a range of 0.1 nm to 1500 nm, and preferably within a range of 1 nm to 300 nm. This is because if the film thickness is larger than the above range, the volume resistance in the electron transport layer may be increased, and it may be difficult to form irregularities. On the other hand, if the film thickness is thinner than the above range, light may not be sufficiently absorbed, it may be difficult to form irregularities, and it may be difficult to fill the underlying surface irregularities.

(Hole transport layer)
The hole transport layer used in this embodiment contains an electron donating organic semiconductor material.
The electron-donating organic semiconductor material is not particularly limited as long as it has a function as an electron donor, but it is preferable that the film can be formed by a coating method. A conductive polymer material is preferable. This is because the conductive polymer material has the advantages as described above. Specifically, the same materials as the electron-donating conductive polymer material used for the electron-hole transport layer can be given.

  The thickness of the hole transport layer is appropriately adjusted depending on whether the surface has irregularities. For example, when the hole transport layer has irregularities on one surface and becomes a lower layer when laminating, and when the hole transport layer has irregularities on both surfaces, it is applied when formed by a coating method The thickness is preferably such that unevenness occurs. In addition, for example, when the hole transport layer has irregularities on one surface and becomes an upper layer when laminated, the thickness is preferably such that the lower surface irregularities can be filled. Specifically, it can be set within a range of 0.1 nm to 1500 nm, and preferably within a range of 1 nm to 300 nm. This is because if the film thickness is thicker than the above range, the volume resistance in the hole transport layer may increase, or the formation of irregularities may be difficult. on the other hand. This is because if the film thickness is thinner than the above range, light may not be sufficiently absorbed, it may be difficult to form unevenness, and it may be difficult to fill the underlying surface unevenness.

(Ii) Charge extraction accelerating layer The charge extraction accelerating layer used in this embodiment has either electron donating property or electron accepting property, and is on the anode side with respect to the photoelectric conversion layer in which at least two layers are laminated. The function is appropriately selected depending on whether it is disposed on the cathode side or on the cathode side. In the case where the charge extraction promoting layer is disposed on the anode side with respect to the photoelectric conversion layer in which at least two layers are laminated, a layer having an electron donating property is used so that holes can be easily extracted. On the other hand, when the charge extraction promoting layer is disposed on the cathode side with respect to the photoelectric conversion layer in which at least two layers are laminated, a layer having an electron accepting property is used so that electrons can be easily extracted.

  The charge extraction promoting layer having electron donating property is the same as the hole transporting layer, and the charge extraction promoting layer having electron accepting property is the same as the electron transporting layer. Description is omitted.

(Iii) Layer structure of organic semiconductor layer The organic semiconductor layer used in the present embodiment has at least two photoelectric conversion layers, and the photoelectric conversion layer may be an electron-hole transport layer, The electron transport layer and the hole transport layer may be laminated. Further, the combination of the electron hole transport layer and the stack of the electron transport layer and the hole transport layer is not particularly limited. For example, a plurality of electron hole transport layers may be stacked, or an electron transport layer and a hole transport layer may be repeatedly stacked in this order. The transport layer and the hole transport layer may be laminated. Furthermore, the organic semiconductor layer may have a charge extraction promoting layer.

  The combination of these layers is not particularly limited. As an example in which a plurality of photoelectric conversion layers are laminated, (1) photoelectric conversion layer (electron hole transport layer) / photoelectric conversion layer (electron hole transport layer); (2) photoelectric conversion layer (hole transport layer) (Electron transport layer) / photoelectric conversion layer (hole transport layer / electron transport layer); (3) photoelectric conversion layer (electron hole transport layer) / photoelectric conversion layer (hole transport layer / electron transport layer); (4 ) Photoelectric conversion layer (hole transport layer / electron transport layer) / photoelectric conversion layer (electron hole transport layer); (5) Photoelectric conversion layer (electron hole transport layer) / photoelectric conversion layer (electron hole transport layer) / Photoelectric conversion layer (electron hole transport layer); (6) Photoelectric conversion layer (hole transport layer / electron transport layer) / Photoelectric conversion layer (hole transport layer / electron transport layer) / Photoelectric conversion layer (hole transport) Layer / electron transport layer); (7) photoelectric conversion layer (hole transport layer / electron transport layer) / photoelectric conversion layer (electron hole transport layer) / photoelectric conversion layer (electron hole transport layer); (8) Electrical conversion layer (electron hole transport layer) / photoelectric conversion layer (hole transport layer / electron transport layer) / photoelectric conversion layer (electron hole transport layer); (9) Photoelectric conversion layer (electron hole transport layer) / Photoelectric conversion layer (electron hole transport layer) / photoelectric conversion layer (hole transport layer / electron transport layer); (10) Photoelectric conversion layer (hole transport layer / electron transport layer) / photoelectric conversion layer (hole transport layer) Electron transport layer) / photoelectric conversion layer (electron hole transport layer); (11) Photoelectric conversion layer (hole transport layer / electron transport layer) / photoelectric conversion layer (electron hole transport layer) / photoelectric conversion layer (positive) Hole transport layer / electron transport layer); (12) photoelectric conversion layer (electron hole transport layer) / photoelectric conversion layer (hole transport layer / electron transport layer) / photoelectric conversion layer (hole transport layer / electron transport layer) And the like.

Further, as an example in which a plurality of photoelectric conversion layers and charge extraction promoting layers are laminated, (13) charge extraction promoting layer (electron donating property) / photoelectric conversion layer (electron hole transport layer) / photoelectric conversion layer ( (14) photoelectric conversion layer (electron hole transport layer) / photoelectric conversion layer (electron hole transport layer) / charge extraction promotion layer (electron acceptability); (15) charge extraction promotion layer ( Electron donating property) / photoelectric conversion layer (electron hole transport layer) / photoelectric conversion layer (electron hole transport layer) / charge extraction promoting layer (electron accepting property); (16) charge extraction promoting layer (electron donating property) / Photoelectric conversion layer (electron hole transport layer) / photoelectric conversion layer (electron hole transport layer) / photoelectric conversion layer (electron hole transport layer); (17) Photoelectric conversion layer (electron hole transport layer) / photoelectric conversion layer (Electron hole transport layer) / photoelectric conversion layer (electron hole transport layer) / charge extraction promoting layer (electron acceptability); (1 ) Charge extraction promoting layer (electron donating property) / photoelectric conversion layer (electron hole transport layer) / photoelectric conversion layer (electron hole transport layer) / photoelectric conversion layer (electron hole transport layer) / charge extraction promotion layer (electrons) Receptivity); and the like.
For example, “A / B / C” indicates that A, B, and C are laminated in this order.

  Among the above combinations, the photoelectric conversion layer (electron hole transport layer) / photoelectric conversion layer (electron hole transport layer) / photoelectric conversion layer (electron hole transport layer) is preferable. This is because high photoelectric conversion efficiency can be expected by effective use of light by stacking the photoelectric conversion layers. A combination of charge extraction promoting layer (electron donating property) / photoelectric conversion layer (electron hole transporting layer) / photoelectric conversion layer (electron hole transporting layer) / charge extraction promoting layer (electron accepting property) is also preferable. This is because high photoelectric conversion efficiency can be expected by promoting charge extraction by the charge extraction promoting layer.

  When a plurality of photoelectric conversion layers (an electron hole transport layer, or a hole transport layer and an electron transport layer) are stacked, light can be effectively used as described above. In this case, when the organic semiconductor materials used for the multiple layers of photoelectric conversion layers have different absorption wavelength regions, the absorption wavelength region can be expanded, and used for the multiple layers of photoelectric conversion layers. When the organic semiconductor material has the same absorption wavelength region, the absorbance can be increased.

In order to realize effective use of light, an absorption wavelength region of an electron donating organic semiconductor material or an electron accepting organic semiconductor material may be appropriately selected. Since the electron-hole transport layer contains an electron-donating organic semiconductor material and an electron-accepting organic semiconductor material, either the electron-donating organic semiconductor material or the electron-accepting organic semiconductor material is a predetermined one. Any material having an absorption maximum wavelength may be used. In the hole transport layer and the electron transport layer, the hole transport layer contains an electron-donating organic semiconductor material, and the electron transport layer contains an electron-accepting organic semiconductor material. Any one of the electron-donating organic semiconductor material and the electron-accepting organic semiconductor material used for the electron transporting layer may have a predetermined absorption maximum wavelength.
At this time, when the electron-donating organic semiconductor material has a predetermined absorption maximum wavelength, the electron-accepting organic semiconductor material forms a pn junction with the electron-donating organic semiconductor material to separate charges. There is no particular limitation as long as it causes the problem. Similarly, when the electron-accepting organic semiconductor material has a predetermined absorption maximum wavelength, the electron-donating organic semiconductor material forms a pn junction with the electron-accepting conductive polymer material. There is no particular limitation as long as it causes charge separation.

  When electron donating organic semiconductor materials having different absorption wavelength regions are used for the electron hole transport layer and the hole transport layer, each electron donating property is used to absorb sunlight (white light) over a wide range. It is preferable that the absorption maximum wavelength of the organic semiconductor material is different by about 50 nm or more.

In this case, it is particularly preferable that three layers of photoelectric conversion layers (electron hole transport layer, or hole transport layer and electron transport layer) are laminated. For example, an electron-donating organic semiconductor material having an absorption maximum wavelength in the red wavelength region is used for the first layer, and an electron-donating organic semiconductor material having an absorption maximum wavelength in the green wavelength region is used for the second layer. This is because sunlight (white light) can be absorbed in a wider range by using an electron-donating organic semiconductor material having an absorption maximum wavelength in the blue wavelength region.
Specifically, (a) electron hole transport layer / electron hole transport layer / electron hole transport layer; (b) hole transport layer / electron transport layer / hole transport layer / electron transport layer / positive Hole transport layer / electron transport layer; (c) hole transport layer / electron transport layer / electron hole transport layer / electron hole transport layer; (d) electron hole transport layer / hole transport layer / electron transport layer / (E) electron hole transport layer / electron hole transport layer / hole transport layer / electron transport layer; (f) hole transport layer / electron transport layer / hole transport layer / electron transport layer (G) hole transport layer / electron transport layer / electron hole transport layer / hole transport layer / electron transport layer; (h) electron hole transport layer / hole transport layer / electron transport Layer / hole transport layer / electron transport layer; and the like.

  In this embodiment, the interface between adjacent photoelectric conversion layers should just have an unevenness | corrugation among the interfaces of each layer in an organic-semiconductor layer. In addition, when there are a plurality of interfaces between adjacent photoelectric conversion layers, it is sufficient that at least one of the interfaces has irregularities. Furthermore, the interface between the photoelectric conversion layer and the charge extraction promoting layer may have irregularities.

(Iv) Method for Forming Organic Semiconductor Layer In this embodiment, the method for forming the organic semiconductor layer may be any method capable of stably laminating each layer, and whether to form a layer having irregularities on the surface. It is appropriately selected depending on the above. For example, when forming a layer having irregularities on the surface, any method that can form irregularities may be used. Specifically, the surface irregularities are obtained by applying a coating liquid having a relatively high viscosity and drying gently. A layer having a surface may be formed by applying a coating liquid by a roll coating method, and adjusting an air flow blown from a dryer in the initial stage of drying to a undried coating surface, thereby applying a desired uneven state. May be formed. Furthermore, a layer having surface irregularities can be formed by post-processing. For example, a method of pressing a plate having a desired fine structure on a soft coating surface formed by a microprinting method, a method of cutting an unnecessary portion by blasting, and forming a desired uneven state, etc. .

Among these, the organic semiconductor layer forming method is preferably a coating method using a coating solution. That is, the photoelectric conversion layer and the charge extraction promoting layer are preferably coating films. As described above, for example, application unevenness is caused by using a coating liquid having a relatively high viscosity, so that a layer having irregularities on the surface can be formed. In addition, when a coating liquid is further applied on a layer having irregularities on such a surface, the fluidity of the coating liquid is good, so that the coating liquid can be applied so as to follow the irregularities on the surface. This is because the adhesion can be improved.
In addition, since the formation method of the organic-semiconductor layer by the apply | coating method is described in detail in the section of "B. Manufacturing method of an organic thin film solar cell" mentioned later, description here is abbreviate | omitted.

(2) First Electrode Layer The material for forming the first electrode layer used in the present embodiment is not particularly limited as long as it has conductivity, but the light irradiation direction and the formation of the second electrode layer described later. It is preferable to select appropriately considering the work function of the material.
For example, when the material for forming the second electrode layer is a material having a low work function, the material for forming the first electrode layer is preferably a material having a high work function. Examples of the material having a high work function include Au, Ag, Co, Ni, Pt, C, ITO, SnO ₂ , fluorine-doped SnO ₂ , and ZnO.
Further, when the substrate side is the light receiving surface, the first electrode layer is preferably a transparent electrode. In this case, what is generally used as a transparent electrode can be used. Specifically, In—Zn—O (IZO), In—Sn—O (ITO), ZnO—Al, Zn—Sn—O, and the like can be given.

In this embodiment, the total light transmittance of the first electrode layer is 85% or more, preferably 90% or more, and particularly preferably 92% or more. When the substrate side is a light-receiving surface, the first electrode layer can sufficiently transmit light because the total light transmittance of the first electrode layer is in the above range, and light is efficiently transmitted by the photoelectric conversion layer. It is because it can absorb.
The total light transmittance is a value measured using an SM color computer (model number: SM-C) manufactured by Suga Test Instruments Co., Ltd. in the visible light region.

In the present embodiment, the sheet resistance of the first electrode layer is preferably 20 Ω / □ or less, more preferably 10 Ω / □ or less, and particularly preferably 5 Ω / □ or less. This is because if the sheet resistance is larger than the above range, the generated charge may not be sufficiently transmitted to the external circuit.
The sheet resistance is measured based on JIS R1637 (low-efficiency test method for fine ceramic thin film: 4-probe method) using a surface resistance meter (Loresta MCP: 4-terminal probe) manufactured by Mitsubishi Chemical Corporation. It is the value.

The first electrode layer may be a single layer or may be laminated using materials having different work functions.
As the film thickness of the first electrode layer, when it is a single layer, the film thickness is within a range of 0.1 to 500 nm, particularly within a range of 1 nm to 300 nm when it is composed of a plurality of layers. Preferably there is. If the film thickness is smaller than the above range, the sheet resistance of the first electrode layer may become too large, and the generated charge may not be sufficiently transmitted to the external circuit. On the other hand, if the film thickness is larger than the above range, This is because the total light transmittance is lowered and the photoelectric conversion efficiency may be lowered.

  The first electrode layer may be formed on the entire surface of the substrate or may be formed in a pattern.

(3) Second electrode layer The second electrode layer used in the present embodiment is an electrode facing the first electrode layer. The material for forming the second electrode layer is not particularly limited as long as it has conductivity, but may be appropriately selected in consideration of the light irradiation direction, the work function of the material for forming the first electrode layer, and the like. preferable.
For example, when the substrate side is a light receiving surface, the first electrode layer is a transparent electrode. In such a case, the second electrode layer may not be transparent.
In the case where the first electrode layer is formed using a material having a high work function, the second electrode layer is preferably formed using a material having a low work function. Specific examples of the material having a low work function include Li, In, Al, Ca, Mg, Sm, Tb, Yb, Zr, and LiF.

The second electrode layer may be a single layer or may be laminated using materials having different work functions.
When the second electrode layer is a single layer, the film thickness is in the range of 0.1 nm to 500 nm, particularly 1 nm to 500 nm. It is preferable to be within the range of 300 nm. If the film thickness is smaller than the above range, the sheet resistance of the second electrode layer may become too large, and the generated charge may not be sufficiently transmitted to the external circuit. On the other hand, if the film thickness is larger than the above range, This is because the total light transmittance is lowered and the photoelectric conversion efficiency may be lowered.

  Further, the second electrode layer may be formed on the entire surface of the photoelectric conversion layer or may be formed in a pattern.

(4) Substrate The substrate used in this embodiment is not particularly limited, whether it is transparent or opaque. For example, when the substrate side is a light receiving surface, it is transparent. A substrate is preferred. The transparent substrate is not particularly limited, and for example, a non-flexible transparent rigid material such as quartz glass, Pyrex (registered trademark), synthetic quartz plate, or a transparent resin film, an optical resin plate, etc. The transparent flexible material which has flexibility can be mentioned.

  In the present invention, among the above, the substrate is preferably a flexible material such as a transparent resin film. Transparent resin films are excellent in processability, and are useful in the realization of organic thin-film solar cells that reduce manufacturing costs, reduce weight, and are difficult to break, and expand the applicability to various applications such as application to curved surfaces. is there.

(5) Hole extraction layer In this embodiment, a hole extraction layer may be formed between the organic semiconductor layer and the anode. When the first electrode layer is an anode, for example, a hole extraction layer 5 is formed between the organic semiconductor layer 3 and the first electrode layer 2 as shown in FIG. When the second electrode layer is an anode, although not shown, a hole extraction layer is formed between the organic semiconductor layer and the second electrode layer.

  The hole extraction layer is a layer provided so that holes can be easily extracted from the organic semiconductor layer to the anode. As a result, the efficiency of extracting holes from the organic semiconductor layer to the anode is increased, so that the photoelectric conversion efficiency can be improved.

The material used for such a hole extraction layer is not particularly limited as long as it is a material that stabilizes extraction of holes from the organic semiconductor layer to the anode. Specifically, doped polyaniline, polyphenylene vinylene, polythiophene, polypyrrole, polyparaphenylene, polyacetylene, conductive organic compounds such as triphenyldiamine (TPD), or electron donation such as tetrathiofulvalene, tetramethylphenylenediamine, etc. An organic material that forms a charge transfer complex composed of an organic compound and an electron-accepting compound such as tetracyanoquinodimethane and tetracyanoethylene. Also, a thin film of metal such as Au, In, Ag, Pd, etc. can be used. Furthermore, a thin film of metal or the like may be formed alone or in combination with the above organic material.
Among these, polyethylenedioxythiophene (PEDOT) and triphenyldiamine (TPD) are particularly preferably used.

  The film thickness of the hole extraction layer is preferably in the range of 10 nm to 200 nm when the organic material is used, and in the range of 0.1 nm to 5 nm in the case of the metal thin film. It is preferable.

(6) Electron extraction layer In this embodiment, an electron extraction layer may be formed between the organic semiconductor layer and the cathode. When the second electrode layer is a cathode, for example, an electron extraction layer 6 is formed between the organic semiconductor layer 3 and the second electrode layer 4 as shown in FIG. When the first electrode layer is a cathode, an electron extraction layer is formed between the organic semiconductor layer and the first electrode layer, although not shown.

  The electron extraction layer is a layer provided so that electrons can be easily extracted from the organic semiconductor layer to the cathode. Thereby, since the electron extraction efficiency from the organic semiconductor layer to the cathode is increased, the photoelectric conversion efficiency can be improved.

  The material used for such an electron extraction layer is not particularly limited as long as it is a material that stabilizes the extraction of electrons from the organic semiconductor layer to the cathode. Specifically, conductive organic compounds such as doped polyaniline, polyphenylene vinylene, polythiophene, polypyrrole, polyparaphenylene, polyacetylene, triphenyldiamine (TPD), or electron donation such as tetrathiofulvalene, tetramethylphenylenediamine, etc. An organic material that forms a charge transfer complex composed of an organic compound and an electron-accepting compound such as tetracyanoquinodimethane and tetracyanoethylene. Moreover, the metal dope layer with an alkali metal or alkaline-earth metal is mentioned. Suitable materials include bathocuproin (BCP) or bathophenantrone (Bphen) and metal doped layers such as Li, Cs, Ba, Sr.

(7) Other constituent members The organic thin-film solar cell of this embodiment may have the constituent members mentioned later as needed other than the constituent members described above. For example, the organic thin film solar cell of this embodiment includes a protective sheet, a filler layer, a barrier layer, a protective hard coat layer, a strength support layer, an antifouling layer, a high light reflecting layer, a light containment layer, an ultraviolet / infrared blocking layer, a sealing layer. You may have functional layers, such as a stop material layer. In addition, an adhesive layer may be formed between the functional layers depending on the layer configuration.

(I) Protective sheet In this embodiment, the protective sheet may be formed on the 2nd electrode layer. A protective sheet is a layer provided in order to protect the organic thin-film solar cell of this invention from the external environment.

  Examples of the material used for the protective sheet include a metal plate or metal foil such as aluminum, a fluorine resin sheet, a cyclic polyolefin resin sheet, a polycarbonate resin sheet, a poly (meth) acrylic resin sheet, a polyamide resin sheet, and a polyester. And a composite sheet obtained by laminating and laminating a weather-resistant film and a barrier film.

  The thickness of the protective sheet is preferably in the range of 20 μm to 500 μm, and more preferably in the range of 50 μm to 200 μm.

Further, the protective sheet may have a barrier property as described in the section of the barrier layer described later.
Furthermore, the design properties can be imparted to the protective sheet by coloring or the like. At this time, it may be colored by kneading the pigment into the protective sheet or the like, for example, by laminating a colored layer such as a blue hard coat layer.

(Ii) Filler layer In this embodiment, a filler layer may be formed between the second electrode layer and the protective sheet. A filler layer is a layer provided in order to adhere the back surface side of an organic thin film solar cell, ie, a 2nd electrode layer, and the said protective sheet, and to seal an organic thin film solar cell.

  As such a filler layer, what is generally used as a filler layer of a solar cell should just be mentioned, for example, ethylene-vinyl acetate copolymer resin is mentioned.

  Moreover, it is preferable that the thickness of the said filler layer exists in the range of 50 micrometers-2000 micrometers, and it is more preferable that it exists in the range of 200 micrometers-800 micrometers. This is because when the thickness is less than the above range, the strength is reduced, and conversely, when the thickness is greater than the above range, cracks and the like are likely to occur.

(Iii) Barrier layer In this embodiment, a barrier layer may be formed on the surface of the substrate or the surface of the protective sheet. Moreover, when the said board | substrate or the said protective sheet consists of multiple layers, you may provide a barrier layer between each layer. The barrier layer used in this embodiment is a transparent layer, and is a layer provided to prevent the entry of oxygen and water vapor from the outside and protect the organic thin film solar cell of the present invention.

The barrier layer has an oxygen permeability of 5 cc / m ² / day / atm or less, preferably 0.1 cc / m ² / day / atm or less. On the other hand, the lower limit of the oxygen transmission rate is set to 5.0 × 10 ⁻³ cc / m ² / day / atm from the accuracy of the measuring apparatus. The oxygen permeability is a value measured under conditions of 23 ° C. and 90% Rh using an oxygen gas permeability measuring device (manufactured by MOCON, OX-TRAN 2/21).
Further, the water vapor permeability of the barrier layer is 5 g / m ² / day or less under the conditions of 37.8 ° C. and 100% Rh, and preferably 0.01 g / m ² / day or less. Furthermore, under the conditions of 40 ° C. and 90% Rh, the water vapor transmission rate is preferably 1 g / m ² / day or less, and the lower limit of the water vapor transmission rate is 5.0 × 10 ⁻³ g / ^d from the accuracy of the measuring apparatus. Let m ² / day. The water vapor transmission rate is a value measured using a water vapor transmission rate measurement device (manufactured by MOCON, PERMATRAN-W 3/33).

The material for forming the barrier layer is not particularly limited as long as the above-described barrier property can be obtained, and examples thereof include inorganic oxides, metals, and sol-gel materials. Specifically, as the inorganic oxide, silicon oxide (SiO _x ), aluminum oxide (Al _n O _m ), titanium oxide (TiO ₂ ), yttrium oxide, boron oxide (B ₂ O ₃ ), calcium oxide (CaO) ), Silicon oxynitride carbide (SiO _x N _y C _z ), etc., examples of the metal include Ti, Al, Mg, Zr, etc., and examples of the sol-gel material include siloxane-based sol-gel materials. These materials may be used alone or in combination of two or more.

The thickness of the barrier layer is appropriately selected depending on the type of material used and the like, but is preferably in the range of 10 nm to 1000 nm. If the film thickness is smaller than the above range, sufficient barrier properties may not be obtained. If the film thickness is larger than the above range, it takes a long time for film formation.
In addition, the barrier layer may be a single layer or a stack of a plurality of layers. In the case of laminating a plurality of layers, they may be directly laminated or bonded together.

  Examples of the method for forming the barrier layer include vapor deposition methods such as a PVD method and a CVD method such as a sputtering method and an ion plating method, a roll coating method, and a spin coating method. Moreover, you may combine these methods.

Furthermore, the barrier layer is not particularly limited as long as it has the above-described barrier property, but it is preferable to have a vapor deposition layer formed by a vapor deposition method because of its high barrier property.
The vapor deposition layer is not particularly limited as long as it is a layer formed by a vapor deposition method, and may be a CVD method or a PVD method. When the vapor deposition layer is formed by a CVD method such as a plasma CVD method, it is possible to form a dense and high barrier layer, but the PVD method is preferable from the viewpoint of manufacturing efficiency and cost. . Examples of the PVD method include a vacuum vapor deposition method, a sputtering method, and an ion plating method. Among these, the vacuum vapor deposition method is preferable from the standpoint of barrier properties. Examples of the vacuum deposition method include a vacuum deposition method using an electron beam (EB) heating method, a vacuum deposition method using a high frequency dielectric heating method, and the like.

In addition, the material for the vapor deposition layer is preferably a metal or an inorganic oxide, Ti, Al, Mg, Zr, silicon oxide, aluminum oxide, silicon oxynitride, aluminum oxynitride, magnesium oxide, zinc oxide, indium oxide, oxide Tin, yttrium oxide, B ₂ O ₃ , CaO and the like can be mentioned, among which silicon oxide is preferable. This is because the layer made of silicon oxide has high barrier properties and transparency.

  The thickness of the vapor-deposited layer varies depending on the type and configuration of the material used and is appropriately selected, but is preferably in the range of 5 nm to 1000 nm, particularly 10 nm to 500 nm. This is because if the thickness of the deposited layer is thinner than the above range, it may be difficult to obtain a uniform layer, and the barrier property may not be obtained. Moreover, when the thickness of the vapor deposition layer is thicker than the above range, the barrier property may be remarkably impaired due to a crack in the vapor deposition layer due to an external factor such as pulling after film formation. . Moreover, it takes time to form and productivity is also lowered.

An anchor layer may be formed as a base layer for the barrier layer. This is because the barrier properties and weather resistance can be improved. Examples of the material for forming the anchor layer include an adhesive resin, an inorganic oxide, an organic oxide, and a metal.
Examples of the method for forming the anchor layer include PVD methods such as sputtering and ion plating, CVD, roll coating, and spin coating. Moreover, you may combine these methods. Of these, in-line coating during film formation is preferred. This is because it is excellent in mass productivity and can improve the adhesion of the anchor layer.

(Iv) Protective hard coat layer In this embodiment, a protective hard coat layer may be provided on the outermost surface of the organic thin film solar cell. The protective hard coat layer has ultraviolet shielding properties and weather resistance. In order to protect the organic thin film solar cell from the external environment, it protects the organic semiconductor layer and prevents deterioration of the organic semiconductor material contained in the organic semiconductor layer. It is a layer provided for the purpose.

The material for forming the protective hard coat layer is not particularly limited as long as it has ultraviolet shielding properties and weather resistance. For example, acrylic resin, fluorine resin, silicon resin, melamine resin, polyester resin And polycarbonate resins. These resins may be used alone or in combination of two or more.
Moreover, you may add a light resistance additive to the said resin. Examples of the light-resistant additive include a light stabilizer (HALS) and an ultraviolet absorber (UVA).

  The thickness of the protective hard coat layer is preferably in the range of 0.5 μm to 20 μm. If the film thickness is thinner than the above range, the ultraviolet shielding property and weather resistance may be insufficient, and if the film thickness is thicker than the above range, the coating process becomes difficult and the mass productivity may be inferior. .

  Examples of the method for forming the protective hard coat layer include PVD methods such as sputtering and ion plating, CVD, roll coating, and spin coating. Moreover, you may combine these methods. Of these, the roll coating method is preferably used. This is because the roll coating method is excellent in mass productivity and can form a protective hard coat layer having excellent ultraviolet shielding and weather resistance.

Further, an anchor layer may be formed as a base layer of the protective hard coat layer. This is because the weather resistance can be increased.
Examples of the method for forming the anchor layer include PVD methods such as sputtering and ion plating, CVD, roll coating, and spin coating. Moreover, you may combine these methods. Of these, in-line coating during film formation is preferred. This is because it is excellent in mass productivity and can improve the adhesion of the anchor layer.

(V) Strength Support Layer In this embodiment, a strength support layer may be formed inside the protective hard coat layer. The strength support layer may be formed at any position as long as it is inside the protective hard coat layer, but is preferably provided between the functional layers. Moreover, the function of the strength support layer may be imparted to the substrate itself.

The strength support layer is excellent in heat resistance, heat and humidity resistance, hydrolysis resistance, and transparency.
As heat resistance, when a heat resistance test is performed for 72 hours at a temperature of 100 ° C., it is preferable that the rate of decrease in power generation efficiency after the heat resistance test before the heat resistance test is within 10%. Furthermore, when the heat resistance test held at a temperature of 125 ° C. for 72 hours is performed, the rate of decrease in power generation efficiency after the heat resistance test with respect to before the heat resistance test is preferably within 10%. The heat resistance test shall comply with JIS C60068-2-2.
Moisture and heat resistance is determined when a moisture and heat resistance test is performed in which the organic thin-film solar cell is maintained for 96 hours or more in a constant temperature and humidity chamber environment adjusted to a temperature of 40 ° C. or higher and a humidity of 90% RH or higher in advance. It is preferable that the reduction rate of the power generation efficiency after the wet heat resistance test before the test is within 10%. Furthermore, when a moisture and heat resistance test for holding an organic thin film solar cell for 500 hours or more in a constant temperature and humidity chamber environment adjusted to a temperature of 80 ° C. or higher and a humidity of 80% RH or higher in advance is performed. The rate of decrease in power generation efficiency after the wet heat resistance test is preferably within 10%. In addition, according to JIS C60068-2-3, the moisture and heat resistance test shall be evaluated using an environmental testing machine “HIFLEX α series FX424P” manufactured by Enomoto Kasei Co., Ltd.
As the transparency, the total light transmittance is preferably 70% or more, more preferably 85% or more. The total light transmittance is a value measured in the visible light region using an SM color computer (model number: SM-C) manufactured by Suga Test Instruments Co., Ltd.
This is because the organic thin-film solar cell is required to have excellent heat resistance, moisture heat resistance, and permeability.

  Examples of the material for forming the strength support layer include silicone resins, acrylic resins, cyclic polyolefin resins, syndiotactic polystyrene (SPS) resins, polyamide (PA) resins, polyacetal (POM) resins, and modified polyphenylenes. Ether (mPPE) resin, polyphenylene sulfide (PPS) resin, fluorine resin (polytetrafluoroethylene (PTEE), ethylene-tetrafluoroethylene copolymer (ETFE), polychlorotrifluoroethylene (PCTFE), fluorine Ethylene propylene (FEP)), polyether ether ketone (PEEK) resin, liquid crystal polymer (LCP), polyether nitrile (PEN) resin, polysulfone (PSF) resin, polyether sulfone (PES) resin, poly Relate (PAR) resin, polyamideimide (PAI) resin, polyimide (PI) resin, polyethylene terephthalate (PEN), polypropylene (PP), acrylonitrile / butadiene / styrene copolymer (ABS), biaxially oriented polystyrene ( OPS), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polycarbonate (PC), polyester (PE), polyacrylonitrile (PAN) and the like. Also, weathering grades of these resins can be used. Further, these resins may be further reinforced by combining with glass fiber or the like.

  The thickness of the strength support layer is preferably in the range of 10 μm to 800 μm, and particularly preferably in the range of 100 μm to 400 μm. This is because if the film thickness is thinner than the above range, sufficient strength may not be obtained, and if the film thickness is thicker than the above range, processing in the manufacturing process may be difficult.

(Vi) Adhesive layer In the present embodiment, an adhesive layer may be formed between the respective layers according to the layer configuration.
The adhesive layer is excellent in heat resistance and wet heat resistance.
As heat resistance, when a heat resistance test is performed for 72 hours at a temperature of 100 ° C., it is preferable that the rate of decrease in power generation efficiency after the heat resistance test before the heat resistance test is within 10%. Furthermore, when the heat resistance test held at a temperature of 125 ° C. for 72 hours is performed, the rate of decrease in power generation efficiency after the heat resistance test with respect to before the heat resistance test is preferably within 10%.
Moisture and heat resistance is determined when a moisture and heat resistance test is performed in which the organic thin-film solar cell is maintained for 96 hours or more in a constant temperature and humidity chamber environment adjusted to a temperature of 40 ° C. or higher and a humidity of 90% RH or higher in advance. It is preferable that the reduction rate of the power generation efficiency after the wet heat resistance test before the test is within 10%. Furthermore, when a moisture and heat resistance test for holding an organic thin film solar cell for 500 hours or more in a constant temperature and humidity chamber environment adjusted to a temperature of 80 ° C. or higher and a humidity of 80% RH or higher in advance is performed. The rate of decrease in power generation efficiency after the wet heat resistance test is preferably within 10%.
This is because the organic thin film solar cell is required to have excellent heat resistance and heat and humidity resistance. The heat resistance test and the moist heat resistance test are the same as those described above.

  Examples of the material for forming the adhesive layer include silicone resins, rubber resins, acrylic resins, polyester urethane resins, vinyl acetate resins, polyvinyl alcohol resins, phenol resins, melamine resins, hot melt resins, polyurethanes. Resin, polyolefin resin, epoxy resin, styrene butadiene resin and the like. Also, weathering grades of these resins can be used.

  The film thickness of the adhesive layer is preferably in the range of 1 μm to 200 μm, particularly in the range of 2 μm to 20 μm. This is because if the film thickness is thinner than the above range, the strength may be inferior, and if the film thickness is thicker than the above range, processing in the manufacturing process may be difficult.

  Examples of the method for forming the adhesive layer include a dry laminating method and a melt extrusion laminating method. Moreover, you may laminate | stack through an adhesive sheet. Preferably, a dry lamination method by roll coating is used. This is because this method is excellent in mass productivity and good adhesion can be obtained.

2. Second Embodiment A second embodiment of the organic thin film solar cell of the present invention is a substrate, a first electrode layer formed on the substrate, and a photoelectric conversion layer and charge extraction formed on the first electrode layer. An organic thin-film solar cell having an organic semiconductor layer having an accelerating layer and a second electrode layer formed on the organic semiconductor layer, wherein the interface between the photoelectric conversion layer and the charge extraction accelerating layer Is characterized by having irregularities.

The organic thin film solar cell of this embodiment will be described with reference to the drawings.
FIG. 10 is a schematic cross-sectional view showing an example of the organic thin film solar cell of this embodiment. In the example shown in FIG. 10, the organic thin film solar cell 10 is obtained by sequentially laminating a first electrode layer 2, an organic semiconductor layer 3, and a second electrode layer 4 on a substrate 1. The organic semiconductor layer 3 has the photoelectric conversion layer 13 and the charge extraction promoting layer 15, and the interface between the photoelectric conversion layer 13 and the charge extraction promoting layer 15 has irregularities.

  According to this embodiment, since the interface between the photoelectric conversion layer and the charge extraction promoting layer has irregularities, the contact area between the photoelectric conversion layer and the charge extraction promoting layer is increased, and the charge between the photoelectric conversion layer and the charge extraction promoting layer is reduced. Since the movement becomes smooth, the charge extraction efficiency is improved. Further, when the refractive indexes of the photoelectric conversion layer and the charge extraction promoting layer are different, the light scattering effect and the light confinement effect can be obtained by the unevenness of the interface, so that light can be used effectively. Therefore, it is possible to achieve high photoelectric conversion efficiency.

  Since the substrate, the first electrode layer, the second electrode layer, and other components are the same as those described in the first embodiment, description thereof is omitted here. Hereinafter, the organic semiconductor layer will be described.

(1) Organic Semiconductor Layer The organic semiconductor layer used in the present embodiment has a photoelectric conversion layer and a charge extraction promoting layer, and the interface between the photoelectric conversion layer and the charge extraction promotion layer has irregularities. Specifically, the center line average roughness (Ra) is preferably in the range of 10 nm to 1 μm at the interface between the photoelectric conversion layer and the charge extraction promoting layer, and more preferably in the range of 10 nm to 500 nm, particularly 10 nm to 300 nm. It is preferable to be within the range. That is, it is preferable that the center line average roughness (Ra) of the surface of the photoelectric conversion layer or charge extraction promoting layer as the lower layer at the interface where the center line average roughness (Ra) is in a predetermined range is in the above range. This is because if the center line average roughness is smaller than the above range, the adhesion between the photoelectric conversion layer and the charge extraction accelerating layer is lowered, and the contact area may be reduced. Further, it is difficult to form a photoelectric conversion layer or a charge extraction promoting layer having a surface center line average roughness smaller than the above range by a coating method. On the other hand, if the center line average roughness is larger than the above range, the effect of increasing the contact area may not be sufficiently obtained.
The method for measuring the center line average roughness (Ra) is the same as the method described in the first embodiment.

Moreover, it is preferable that the surface unevenness | corrugation of the photoelectric converting layer or electric charge extraction promotion layer used as a lower layer is an unevenness | corrugation of gentle inclination. This is because if the unevenness has a steep slope, the adhesion between the layers is lowered and the contact area may be reduced.
Furthermore, it is preferable that the surface roughness of the lower layer of the photoelectric conversion layer or the charge extraction promoting layer is small. If the roughness is too large, the adhesion between the layers may be lowered, and the contact area may be reduced.

In the organic thin-film solar cell of this embodiment, a photoelectric conversion layer and a charge extraction promoting layer are directly laminated. Examples of the organic thin-film solar cell of this embodiment are shown in FIGS. 11 and 12, respectively.
In the organic thin film solar cell 10 shown in FIG. 11, the first electrode layer 2, the organic semiconductor layer 3, and the second electrode layer 4 are sequentially laminated on the substrate 1, and the organic semiconductor layer 3 is formed as the charge extraction promoting layer 15a. The photoelectric conversion layer 13 and the charge extraction promoting layer 15b are directly laminated in this order. Electrons and holes are generated inside the photoelectric conversion layer 13, and the electrons and holes move in opposite directions toward the first electrode layer 2 or the second electrode layer 4. In this case, since the charge extraction promoting layers 15a and 15b are formed between the photoelectric conversion layer 13 and the first electrode layer 2 and the second electrode layer 4, respectively, the photoelectric conversion layer 13, the first electrode layer 2, and the first electrode layer 2 The resistance barrier at the interface with the two-electrode layer 4 can be reduced, and holes and electrons can be taken out efficiently.

  In the organic thin film solar cell 10 shown in FIG. 12, the 1st electrode layer 2, the organic-semiconductor layer 3, and the 2nd electrode layer 4 are laminated | stacked one by one on the board | substrate 1, and the organic-semiconductor layer 3 is the photoelectric converting layer 13a. The charge extraction promoting layer 15 and the photoelectric conversion layer 13b are directly laminated in this order. Electrons and holes are generated inside the photoelectric conversion layers 13a and 13b, and these electrons and holes move in the opposite directions toward the first electrode layer 2 or the second electrode layer 4, respectively. In this case, since the charge extraction promoting layer 15 is formed between the photoelectric conversion layers 13a and 13b, the resistance barrier at the interface between the photoelectric conversion layers 13a and 13b can be reduced, and the charge extraction efficiency can be improved. Is possible.

  Thus, when the charge extraction promoting layer is formed adjacent to the photoelectric conversion layer, the resistance barrier at the interface between the layers becomes loose, and the extraction of charges can be promoted. Further, since it is possible to facilitate the extraction of charges, there is an advantage that it is not necessary to separately provide a conventional charge extraction layer (a hole extraction layer or an electron extraction layer).

In this embodiment, a plurality of photoelectric conversion layers may be laminated. This is because light can be used effectively. In addition, about the lamination | stacking number of a photoelectric converting layer, it is the same as that of what was described in the said 1st embodiment.
In the case where a plurality of photoelectric conversion layers are stacked, an interface between adjacent photoelectric conversion layers may have unevenness. In this case, the center line average roughness (Ra) at the interface between adjacent photoelectric conversion layers is preferably in the range of 10 nm to 1 μm, more preferably in the range of 10 nm to 500 nm, and still more preferably in the range of 10 nm to 300 nm. . This is because the charge extraction efficiency can be further increased by increasing the contact area between adjacent photoelectric conversion layers.

  Since the photoelectric conversion layer and the charge extraction promoting layer are the same as those described in the first embodiment, description thereof is omitted here. Moreover, since the formation method of an organic-semiconductor layer is described in detail in the section of "B. Manufacturing method of an organic thin-film solar cell" mentioned later, description here is abbreviate | omitted. Hereinafter, the layer configuration of the organic semiconductor layer will be described.

(I) Layer structure of organic semiconductor layer The organic semiconductor layer used in the present embodiment has a photoelectric conversion layer and a charge extraction promoting layer. This photoelectric conversion layer may be an electron hole transport layer, or may be a laminate of an electron transport layer and a hole transport layer.

The combination of these layers is not particularly limited. For example, (1) Charge extraction promoting layer (electron donating property) / photoelectric conversion layer (electron hole transport layer); (2) Photoelectric conversion layer (electron hole transport layer) / charge extraction promoting layer (electron accepting property); 3) Charge extraction promoting layer (electron donating) / photoelectric conversion layer (electron hole transporting layer) / charge extracting promoting layer (electron accepting); (4) Charge extraction promoting layer (electron donating) / photoelectric conversion layer ( Hole transport layer / electron transport layer) / charge extraction promoting layer (electron accepting property); (5) photoelectric conversion layer (electron hole transport layer) / charge extraction promoting layer (electron donating property) / photoelectric conversion layer (electron positive layer) (6) photoelectric conversion layer (electron hole transport layer) / charge extraction promotion layer (electron acceptability) / photoelectric conversion layer (electron hole transport layer); (7) charge extraction promotion layer (electron donation) ) / Photoelectric conversion layer (electron hole transport layer) / photoelectric conversion layer (electron hole transport layer); (8) photoelectric conversion layer (electrons) Hole transport layer) / photoelectric conversion layer (electron hole transport layer) / charge extraction promoting layer (electron accepting property); (9) charge extraction promoting layer (electron donating property) / photoelectric conversion layer (electron hole transport layer) / Photoelectric conversion layer (electron hole transport layer) / charge extraction promoting layer (electron accepting property); (10) Charge extraction promoting layer (electron donating property) / photoelectric conversion layer (hole transport layer / electron transport layer); (11 ) Photoelectric conversion layer (hole transport layer / electron transport layer) / charge extraction promoting layer (electron accepting property); (12) charge extraction promoting layer (electron donating property) / photoelectric conversion layer (electron hole transport layer) / photoelectric Conversion layer (electron hole transport layer) / photoelectric conversion layer (electron hole transport layer); (13) Photoelectric conversion layer (electron hole transport layer) / photoelectric conversion layer (electron hole transport layer) / photoelectric conversion layer ( Electron hole transport layer) / charge extraction promoting layer (electron accepting); (14) charge extraction promoting layer (electron donating) / photoelectric Examples include combinations of exchange layer (electron hole transport layer) / photoelectric conversion layer (electron hole transport layer) / photoelectric conversion layer (electron hole transport layer) / charge extraction promoting layer (electron acceptability). .
For example, “A / B / C” indicates that A, B, and C are laminated in this order.

  Among the above combinations, charge extraction promoting layer (electron donating property) / photoelectric conversion layer (electron hole transporting layer) / charge extracting promotion layer (electron accepting property) or charge extraction promoting layer (electron donating property) / photoelectric A conversion layer (electron hole transport layer) / photoelectric conversion layer (electron hole transport layer) / charge extraction promoting layer (electron acceptability) is preferable. This is because high photoelectric conversion efficiency can be expected by promoting charge extraction by the charge extraction promoting layer.

  In the present embodiment, it is only necessary that the interface between the photoelectric conversion layer and the charge extraction promoting layer has irregularities among the interfaces of the layers in the organic semiconductor layer. Further, for example, as shown in FIGS. 11 and 12, when there are a plurality of interfaces between the photoelectric conversion layer and the charge extraction promoting layer, at least one of the interfaces may be uneven. Furthermore, the interface between adjacent photoelectric conversion layers may have irregularities.

B. Next, the manufacturing method of the organic thin film solar cell of this invention is demonstrated.
The organic thin film solar cell manufacturing method of the present invention includes a first electrode layer forming step of forming a first electrode layer on a substrate, and a lower layer formation having a viscosity in the range of 50 cps to 6000 cps on the first electrode layer. Organic semiconductor having at least two layers, including a lower layer forming step of forming a lower layer coating film by applying a coating liquid and an upper layer forming step of forming an upper layer layer on the lower layer coating layer An organic semiconductor layer forming step of forming a layer and a second electrode layer forming step of forming a second electrode layer on the organic semiconductor layer are characterized.

  In FIG. 13, an example of the manufacturing method of the organic thin-film solar cell of this invention is shown. In the present invention, first, the first electrode layer 2 is formed on the substrate 1 by an ion plating method (first electrode layer forming step, FIG. 13A). Next, a lower layer-forming coating solution having a predetermined viscosity is applied onto the first electrode layer 2 by a spin coating method to form a lower layer coating film 33a and dried (lower layer forming step, FIG. 13 ( b)). When the lower layer forming coating liquid is applied, the viscosity of the lower layer forming coating liquid is relatively high, so that the coating film 33a having waviness can be formed. Further, an upper film 33b is formed on the dried lower coating film 33a (upper layer forming step, FIG. 13C). Thus, the organic semiconductor layer 3 having the two layers of films 33a and 33b is formed (organic semiconductor layer forming step). Then, the second electrode layer 4 is formed on the organic semiconductor layer 3 by vapor deposition (second electrode layer forming step, FIG. 13D).

According to the present invention, coating unevenness is caused by using a coating solution for forming a lower layer having a predetermined viscosity, so that a coating film having irregularities on the surface can be formed. Next, when a film is further formed on a coating film having irregularities on such a surface, the contact area between the upper and lower films increases, and the movement of charges between the photoelectric conversion layers becomes smooth, thereby improving the charge extraction efficiency. Can do. Moreover, since the coating film which has an unevenness | corrugation on the surface can be formed, when a refractive index differs in an upper and lower film | membrane, a light-scattering effect and a light confinement effect can be acquired. Therefore, it is possible to manufacture a highly efficient organic thin film solar cell.
Hereinafter, each process in the manufacturing method of an organic thin film solar cell is demonstrated.

1. First electrode layer forming step The first electrode layer forming step in the present invention is a step of forming the first electrode layer on the substrate.
As a method for forming the first electrode layer, a general electrode forming method can be used, for example, a PVD method such as a vacuum deposition method, a sputtering method, an ion plating method, or a dry coating method such as a CVD method. Can be mentioned. Moreover, the wet coating method which apply | coats the coating liquid etc. which contain ITO microparticles | fine-particles can also be used.
Further, the patterning method of the first electrode layer is not particularly limited as long as it is a method capable of accurately forming the first electrode layer in a desired pattern, and examples thereof include a photolithography method. .
In addition, since it is the same as that of what was described in the term of the 1st electrode layer of said "A. organic thin film solar cell" about the other point of a 1st electrode layer, description here is abbreviate | omitted.

2. Organic semiconductor layer forming step The organic semiconductor layer forming step in the present invention includes a lower layer forming step of applying a lower layer forming coating liquid having a predetermined viscosity to form a lower layer coating film, and an upper layer on the lower layer coating film. And forming an organic semiconductor layer having at least two layers. Hereinafter, each step in the organic semiconductor layer forming step will be described.

(1) Lower layer formation process The lower layer formation process in this invention is a process of apply | coating the coating liquid for lower layer formation which has a predetermined | prescribed viscosity, and forming a lower layer coating film.

The lower layer forming coating solution used in the present invention has a viscosity in the range of 50 cps to 6000 cps, preferably in the range of 100 cps to 5000 cps, and more preferably in the range of 100 cps to 2000 cps. If the viscosity is smaller than the above range, it may be difficult to cause coating unevenness. If the viscosity is larger than the above range, the film thickness unevenness may become too large, which may reduce the contact area. is there.
The viscosity is a value measured using a single cylindrical rotational viscometer according to JIS Z 8803 (1991).

The lower layer forming coating solution is obtained by dissolving or dispersing an organic semiconductor material in a solvent.
The organic semiconductor material preferably has a weight average molecular weight of 100,000 or more, more preferably 300,000 or more, and most preferably 500,000 or more. Moreover, it is preferable that a weight average molecular weight is 5 million or less, More preferably, it is 3 million or less. This is because if the weight average molecular weight is too small, the organic semiconductor material may be dissolved in the solvent in the upper layer forming coating solution. Conversely, if the weight average molecular weight is too large, the viscosity of the lower layer forming coating solution may become too high.

The weight average molecular weight is a value measured by gel permeation chromatography (GPC). The measurement conditions are shown below.
Measurement column: Shodex HF-2002 Styrene-divinylbenzene copolymer detector: Differential refractive index detector (RI) Shimadzu RID-6A
Ultraviolet absorption detector Measurement wavelength 254nm SPD-10A manufactured by Shimadzu Corporation
Measurement conditions: mobile phase chloroform
Flow rate 3ml / min
Injection method 2ml injection by syringe

  The organic semiconductor material is appropriately selected according to the layer to be formed. In the present invention, the lower layer coating film may be an electron hole transport layer constituting a photoelectric conversion layer, an electron transport layer or a hole transport layer, or a charge extraction promoting layer. Therefore, an organic semiconductor material corresponding to each layer is used. The organic semiconductor material used for each layer is the same as that described in the section of the organic semiconductor layer in the above-mentioned “A. Organic thin film solar cell”, and thus the description thereof is omitted here.

As a method of increasing the molecular weight so that the organic semiconductor material has a predetermined weight average molecular weight, a generally used method can be employed, for example, an oxidation polymerization method, an electrolytic polymerization method, a vapor deposition polymerization method, Examples include chemical polymerization and energy irradiation polymerization. The method for increasing the molecular weight is appropriately selected depending on the type of the organic semiconductor material.
For example, a method for increasing the molecular weight of polyphenylene vinylene (MDMO-PPV; poly (2-methoxy-5- (3 ′, 7′-dimethyloctyloxy) -1--4-phenylene vinylene) is described in Thin Solid Films, 363, The method described in 98-101 (2002) can be referred to.

  The lower layer forming coating solution may contain an organic semiconductor material and an insulating resin material, and these may be dissolved or dispersed in a solvent. When such a lower layer-forming coating solution is used, a lower layer containing an insulating resin material can be formed, so that the solvent resistance of the lower layer can be improved and the strength of the resulting lower layer can be improved. be able to.

The insulating resin material used in the present invention is not particularly limited as long as it improves the solvent resistance of the lower layer and increases the film strength. For example, a thermoplastic resin material, a thermosetting resin material, an ionization material is used. Examples include radiation curable resin materials.
Specific examples of the thermoplastic resin material include polypropylene, polyethylene, polystyrene, polyvinyl acetate, polyamide, polyvinyl chloride, polyurethane, polyethylene terephthalate, polyvinylidene chloride, and polyacrylonitrile.
Specific examples of the thermosetting resin material include phenol resin, melamine resin, urea resin, urethane resin, and epoxy resin.
Examples of the ionizing radiation curable resin material include an ultraviolet curable resin material and an electron beam curable resin material. Specific examples of the ultraviolet curable resin material include urethane acrylate, epoxy acrylate, ester acrylate, acrylate, epoxy, vinyl ether, oxetane, and the like. Specific examples of the electron beam curable resin material include unsaturated polyester, unsaturated acrylic, polyepoxy acrylate, urethane acrylate, polyester acrylate, polyether acrylate, polyene, and polythiol.

The weight average molecular weight of the insulating resin material is not particularly limited.
For example, when the organic semiconductor material has a predetermined weight average molecular weight, the weight average molecular weight of the insulating resin material may be smaller than the weight average molecular weight of the organic semiconductor material. This is because even if the weight average molecular weight of the insulating resin material is smaller than the weight average molecular weight of the organic semiconductor material, it is considered that the insulating resin material is hardly eluted into the upper layer forming coating solution. Although the reason for this is not clear, it is considered that the constituent material in the lower layer is less likely to elute as the entire lower layer by containing an organic semiconductor material having a weight average molecular weight in the above range.
For example, when the organic semiconductor material does not have the above-described weight average molecular weight, the insulating resin material preferably has a weight average molecular weight of 10,000 or more, more preferably 50,000 or more. Moreover, it is preferable that a weight average molecular weight is 3 million or less, More preferably, it is 1 million or less. This is because if the weight average molecular weight of the insulating resin material is too small, the insulating resin material may be dissolved in the solvent in the upper layer forming coating solution. Conversely, if the weight average molecular weight of the insulating resin material is too large, the viscosity of the lower layer forming coating solution may become too high.
The method for measuring the weight average molecular weight is the same as that described above.

  The solvent used in the lower layer forming coating solution is not particularly limited as long as it can dissolve or disperse the organic semiconductor material. Examples thereof include ketone solvents, alcohol solvents, ester solvents, ether solvents, aromatic hydrocarbon solvents, halogenated aliphatic and aromatic hydrocarbon solvents, and mixtures thereof. More specifically, cyclohexanone, acetone, methyl ethyl ketone, methanol, ethanol, butanol, amyl alcohol, butyl acetate, dibutyl ether, tetrahydrofuran, toluene, xylene, chlorobenzene, carbon tetrachloride, chloroform, methylene chloride, trichloroethylene and the like can be mentioned. These solvents can be used alone or in admixture of two or more.

  The coating method for the lower layer forming coating solution is preferably a method in which coating unevenness is likely to occur. For example, a die coating method, a spin coating method, a dip coating method, a roll coating method, a bead coating method, a spray coating method, a bar coating method. Examples thereof include a coating method, a gravure coating method, an ink jet method, a screen printing method, and an offset printing method. Of these, the spin coating method is preferably used. This is because this method is easy to form a wavy film.

  Moreover, after apply | coating the coating liquid for lower layer formation, a drying process is normally performed. As a drying method, a general drying method can be used, and for example, a heating method can be mentioned. As a heating method, specifically, a method of passing or standing in a device that heats the entire specific space such as an oven, a method of applying hot air, a method of heating directly by far infrared rays, or a hot plate A heating method or the like can be used. The heating temperature at this time is not particularly limited as long as it does not alter or modify the organic semiconductor material, and is usually set to be about 30 ° C. to 300 ° C., preferably Is in the range of 40 ° C to 150 ° C, more preferably 50 ° C to 110 ° C. Further, the heating time is appropriately adjusted.

(2) Upper layer forming step The upper layer forming step in the present invention is a step of forming an upper layer film on the lower layer coating film.
The method for forming the upper layer is not particularly limited as long as it is a method capable of forming a uniform film on the lower layer coating, but the upper layer forming coating solution is applied on the lower layer coating. It is preferable to form an upper coating film. If it is such a process, the coating liquid for upper layer formation can be applied on the lower layer coating film having the unevenness on the surface so as to follow the surface unevenness, and the adhesion between the upper and lower films can be improved. Because it can.

The upper layer forming coating solution used in the present invention is obtained by dissolving or dispersing an organic semiconductor material in a solvent.
The organic semiconductor material is appropriately selected depending on the layer to be formed. In the present invention, the upper film may be an electron hole transport layer constituting the photoelectric conversion layer, an electron transport layer or a hole transport layer, or a charge extraction promoting layer. Since it is good, the organic-semiconductor material according to each layer is used. The organic semiconductor material used for each layer is the same as that described in the section of the organic semiconductor layer in the above-mentioned “A. Organic thin film solar cell”, and thus the description thereof is omitted here.

  The solvent used in the upper layer forming coating solution is not particularly limited as long as it can dissolve or disperse the organic semiconductor material. In the present invention, since the organic semiconductor material in the lower layer has a large weight average molecular weight as described above, it is considered that the organic semiconductor material is hardly dissolved in a general solvent, and the solvent used in the upper layer forming coating solution is not limited. is there.

The solvent used in the upper layer forming coating solution may or may not be compatible with the solvent used in the lower layer forming coating solution. When the solvent in the upper layer forming coating liquid is not compatible with the solvent in the lower layer forming coating liquid, the organic semiconductor material contained in the lower layer is in contrast to the solvent in the upper layer forming coating liquid. Therefore, there is an advantage that the underlying organic semiconductor material is not eluted. On the other hand, when the solvent in the upper layer forming coating solution is compatible with the solvent in the lower layer forming coating solution, the organic semiconductor material contained in the lower layer is less than the solvent in the upper layer forming coating solution. As described above, since the weight average molecular weight of the lower organic semiconductor material is large, elution of the lower organic semiconductor material into the solvent in the upper layer forming coating liquid is suppressed. It is.
Therefore, when the solvent in the upper layer forming coating solution is compatible with the solvent in the lower layer forming coating solution, the effects of the present invention are remarkably exhibited.

  Specific examples of the solvent used for the upper layer forming coating solution include the same solvents as those used for the lower layer forming coating solution.

  The coating method of the upper layer forming coating liquid is not particularly limited, and for example, die coating method, spin coating method, dip coating method, roll coating method, bead coating method, spray coating method, bar coating method. , Gravure coating method, ink jet method, screen printing method, offset printing method and the like. Among these, a spin coating method or a die coating method is preferably used. This is because these methods can be formed with high precision so as to have a predetermined film thickness.

  Moreover, after apply | coating the said upper layer formation coating liquid, a drying process is normally performed. In addition, about the drying method, it is the same as that of what was described in the column of the lower layer formation process mentioned above.

(3) Others In the present invention, it is possible to laminate two or more layers by performing a lower layer forming step and an upper layer forming step.
For example, as shown in FIG. 4, when a three-layer film is laminated so that unevenness exists at all the interfaces of the three-layer films (13a, 13b, 13c), the first layer film is formed by the lower layer forming step. (13a) is formed, and then a second layer film (13b) is formed by a lower layer forming step, and finally a third layer film (13c) is formed by an upper layer forming step. By forming the first and second layer films (13a, 13b) using an organic semiconductor material or insulating resin material having a predetermined weight average molecular weight, it is possible to stably stack up to the third layer. It is. As described above, in order to form an unevenness at the interface of all the films in the organic semiconductor layer, it is possible to stack a plurality of layers by performing the lower layer forming step and the upper layer forming step.

  On the other hand, as shown in FIG. 5, for example, among the interfaces of the three-layer films (13a, 13b, 13c), the three-layer films are laminated so that there are irregularities only at the interface between the second and third layers. In this case, the second layer film (13b) can be formed by the lower layer forming step, the third layer film (13c) can be formed by the upper layer forming step, and the first layer film (13a) can be formed as follows. It can form by a 1st layer formation process.

In the first layer forming step, the film forming method is not particularly limited, and for example, a vapor deposition method or a coating method can be used.
When using the coating method which forms the coating film by apply | coating the coating liquid for 1st layer formation, the coating liquid for 1st layer formation contains the organic-semiconductor material whose weight average molecular weight is 100,000 or more. It is preferable. This is because, by using an organic semiconductor material having a predetermined weight average molecular weight, for example, the second layer film (13b) can be stably laminated on the first layer film (13a) in FIG.
Moreover, the coating liquid for 1st layer formation may contain an organic-semiconductor material and an insulating resin material. In this case as well, by using an insulating resin material, for example, the solvent resistance of the first film (13a) in FIG. 5 can be improved, and the second film (13b) can be laminated stably. Because it can be done.

  The viscosity of the first layer-forming coating solution is not particularly limited because it is not necessary to form a wavy film.

  The first layer-forming coating solution is obtained by dissolving or dispersing an organic semiconductor material in a solvent. Usually, after the first layer-forming coating solution is applied, a drying process is performed. The organic semiconductor material, the insulating resin material, the solvent, and the coating method and the drying process of the first layer forming coating solution are the same as those described in the column of the lower layer forming step, The description in is omitted.

  For example, the organic semiconductor layer 3 shown in FIG. 2 is also formed by laminating three layers so that irregularities exist only at the interface between the second layer and the third layer among the interfaces of the three layers (17a, 17b, 13b). Therefore, it can be formed as described above. As described in the section of the organic semiconductor layer of the above “A. Organic thin film solar cell”, in the case where a photoelectric conversion layer is formed by laminating an electron transport layer and a hole transport layer, the electron transport layer is formed as a single layer. The present invention is applied using the film and the hole transport layer as a single layer film.

  In addition, although not shown, when the three-layer film is laminated so that there is an unevenness only at the interface between the first and second layers, the first-layer film is formed by the lower layer formation process. The second layer film can be formed by the upper layer forming process, and the third layer film can be formed by the following second layer forming process.

In the second layer forming step, the film forming method is not particularly limited, and for example, a vapor deposition method or a coating method can be used.
When using the coating method in which the coating solution for forming the second layer is applied to form a coating film, the film may be formed in the same manner as in the upper layer forming step.

  Thus, in the present invention, a plurality of layers can be stacked by combining the lower layer forming step, the upper layer forming step, the first layer forming step, and the second layer forming step.

3. Second electrode layer forming step The second electrode layer forming step in the present invention is a step of forming a second electrode layer on the organic semiconductor layer.
As a method for forming the second electrode layer, a general electrode forming method can be used, for example, a PVD method such as a vacuum deposition method, a sputtering method, or an ion plating method, or a dry coating method such as a CVD method. be able to. Moreover, the wet coating method apply | coated using the metal paste etc. containing metal colloids, such as Ag, can also be used.
Further, the patterning method of the second electrode layer is not particularly limited as long as it can accurately form the second electrode layer in a desired pattern, and examples thereof include a photolithography method. .
In addition, since it is the same as that of what was described in the term of the 2nd electrode layer of said "A. organic thin film solar cell" about the other point of a 2nd electrode layer, description here is abbreviate | omitted.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has any configuration that has substantially the same configuration as the technical idea described in the claims of the present invention and that exhibits the same effects. Are included in the technical scope.

Hereinafter, the present invention will be specifically described with reference to examples.
[Example]
(Formation of first electrode layer)
A SiO ₂ thin film is formed on the surface of a polyethylene naphthalate (PEN) film substrate (thickness: 125 μm) by the PVD method, and an ITO film (film thickness: 150 nm, sheet resistance: 20Ω / sheet) as a transparent electrode on the upper surface of the SiO ₂ thin film. □) was formed by a reactive ion plating method using a pressure gradient plasma gun (power: 3.7 kW, film forming pressure: 0.3 Pa, film forming rate: 150 nm / min, substrate temperature: 20 ° C.). Later, patterning was performed by etching. Next, the substrate on which the ITO pattern was formed was cleaned using acetone, a substrate cleaning solution, and IPA.

(Formation of hole extraction layer)
A coating liquid for forming a hole extraction layer (conductive polymer paste; poly (3,4) -ethylenedioxythiophene aqueous dispersion) is produced by spin coating on the substrate on which the ITO pattern is formed. The film was formed and dried at 150 ° C. for 30 minutes to form a hole extraction layer (film thickness: 100 nm).

(Formation of organic semiconductor layer)
Next, the first electron-hole transport layer was formed. A 0.3 wt% chloroform solution of polyalkylthiophene (P3HT; poly-3-hexylthiophene-2,5-diyl (resiregular)) and polyphenylene vinylene (MDMO-PPV; poly (2-methoxy-5- (3 ′, 7'-dimethyloctyloxy) -1--4-phenylene vinylene)) (weight average molecular weight: 1,200,000) in 0.3 wt% chloroform solution and fullerene (PCBM; 1- (3-methoxycarbonyl) propyl-1-phenyl A 0.1 wt% chloroform solution of (6,6) -C ₆₀ ) is mixed at a weight ratio of 3: 5: 2, and the mixed solution is filtered through a filter paper having a diameter of 1 μm to form the first electron-hole transport layer. A coating solution was prepared.
This electron hole transport layer forming coating solution is applied onto the hole extraction layer by spin coating, and dried at 110 ° C. for 10 minutes to form a first electron hole transport layer (film thickness: 30 nm). Formed.

Further, a second electron-hole transport layer was formed. 0.3 wt% chloroform solution of polyphenylene vinylene (MDMO-PPV; poly (2-methoxy-5- (3 ′, 7′-dimethyloctyloxy) -1--4-phenylene vinylene)) (weight average molecular weight: 1,200,000) And a 0.1 wt% chloroform solution of fullerene (PCBM; 1- (3-methoxycarbonyl) propyl-1-phenyl (6,6) -C ₆₀ ) at a weight ratio of 5: 3. The solvent was removed from the mixed solution under reduced pressure and heating, and the solution was concentrated until the solution concentration became 1.5% while controlling the evaporation rate so that no solid content was precipitated. The obtained solution was filtered with a φ1 μm filter paper to prepare a coating solution for forming a second electron-hole transport layer. The viscosity of this electron hole transport layer forming coating solution was 50 cps.
A coating liquid for forming an electron hole transport layer is applied on the first electron hole transport layer by a spin coating method at a rotational speed of 2000 rpm, and the coating liquid partially remains on the coating surface. In a dry state, the substrate was dried from the substrate side at a temperature of 110 ° C. for 10 minutes under no wind to form a second electron-hole transport layer (film thickness: 30 nm). The surface of the electron-hole transport layer had irregularities, and the center line average roughness (Ra) was 60 nm.

Then, a third electron-hole transport layer was formed. A 0.3 wt% chloroform solution of polyalkylthiophene (P3HT; poly-3-hexylthiophene-2,5-diyl (resiregular)) and fullerene (PCBM; 1- (3-methoxycarbonyl) propyl-1-phenyl (6 , 6) -C ₆₀ ) 0.1 wt% chloroform solution is mixed at a weight ratio of 3: 1 and the mixed solution is filtered through a filter paper of φ1 μm to form a third layer electron hole transport layer forming coating solution. Was prepared.
This coating solution for forming an electron hole transport layer is applied onto the second electron hole transport layer by a spin coating method and dried at 110 ° C. for 10 minutes to form a third layer of electron hole transport layer (film). Thickness: 30 nm).

(Formation of second electrode layer)
Next, a Ca thin film (film thickness: 100 nm) and an Al thin film (film thickness: 500 nm) were sequentially formed on the organic semiconductor layer by a vapor deposition method to obtain a metal electrode.

(Production of organic thin film solar cells)
Finally, sealing was performed from above the metal electrode with a sealing glass material to produce a bulk heterojunction type organic thin film solar cell.

It is a schematic sectional drawing which shows an example of the organic thin film solar cell of this invention. It is a schematic sectional drawing which shows the other example of the organic thin film solar cell of this invention. It is explanatory drawing for demonstrating surface roughness. It is a schematic sectional drawing which shows the other example of the organic thin film solar cell of this invention. It is a schematic sectional drawing which shows the other example of the organic thin film solar cell of this invention. It is a schematic sectional drawing which shows the other example of the organic thin film solar cell of this invention. It is a schematic sectional drawing which shows the other example of the organic thin film solar cell of this invention. It is a schematic sectional drawing which shows the other example of the organic thin film solar cell of this invention. It is a schematic sectional drawing which shows the other example of the organic thin film solar cell of this invention. It is a schematic sectional drawing which shows the other example of the organic thin film solar cell of this invention. It is a schematic sectional drawing which shows the other example of the organic thin film solar cell of this invention. It is a schematic sectional drawing which shows the other example of the organic thin film solar cell of this invention. It is process drawing which shows an example of the manufacturing method of the organic thin film solar cell of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Substrate 2 ... 1st electrode layer 3 ... Organic-semiconductor layer 4 ... 2nd electrode layer 5 ... Hole extraction layer 6 ... Electron extraction layer 10 ... Organic thin-film solar cell 13, 13a, 13b, 13c ... Photoelectric conversion layer 15, 15a, 15b ... Charge extraction promoting layer

Claims (14)

A substrate; a first electrode layer formed on the substrate; an organic semiconductor layer formed on the first electrode layer and having at least two photoelectric conversion layers; and a first electrode formed on the organic semiconductor layer. An organic thin film solar cell having two electrode layers,
Interface between the photoelectric conversion layers have a bumpy,
The organic thin-film solar cell, wherein the at least two photoelectric conversion layers are formed directly on the first electrode layer, and an interface between the first electrode layer and the organic semiconductor layer does not have the unevenness .   A substrate, a first electrode layer formed on the substrate, a hole extraction layer formed on the first electrode layer, and at least two photoelectric conversion layers formed on the hole extraction layer. An organic thin-film solar cell having an organic semiconductor layer and a second electrode layer formed on the organic semiconductor layer,
  The interface between the photoelectric conversion layers has irregularities,
  The organic thin film solar cell, wherein the at least two photoelectric conversion layers are formed directly on the hole extraction layer, and an interface between the hole extraction layer and the organic semiconductor layer does not have the unevenness. The organic thin film solar cell according to claim 1 or claim 2, wherein the organic semiconductor layer has a further charge extraction promoting layer on the second electrode layer side of the photoelectric conversion layer of the at least two layers.   A substrate; a first electrode layer formed on the substrate; an organic semiconductor layer formed on the first electrode layer and having at least two photoelectric conversion layers; and a first electrode formed on the organic semiconductor layer. An organic thin film solar cell having two electrode layers,
  The interface between the photoelectric conversion layers has irregularities,
  The organic semiconductor layer further has a charge extraction promoting layer on the first electrode layer side of the at least two photoelectric conversion layers, and the interface between the charge extraction promotion layer and the photoelectric conversion layer does not have the unevenness. An organic thin film solar cell characterized by The organic thin-film solar cell according to claim 4 , wherein a hole extraction layer is formed between the first electrode layer and the organic semiconductor layer.   Of the two photoelectric conversion layers having irregularities at the interface, the lower photoelectric conversion layer contains an organic semiconductor material having a weight average molecular weight of 100,000 or more or an insulating resin material having a weight average molecular weight of 10,000 or more. The organic thin-film solar cell according to any one of claims 1 to 5, wherein A substrate, a first electrode layer formed on the substrate, an organic semiconductor layer formed on the first electrode layer and having a photoelectric conversion layer and a charge extraction promoting layer, and formed on the organic semiconductor layer An organic thin film solar cell having a second electrode layer,
The photoelectric conversion layer and the charge extraction promoting layer are laminated in this order, the interface of the photoelectric conversion layer and the charge extraction promoting layers have a concavo-convex on the first electrode layer,
The organic thin-film solar cell , wherein the photoelectric conversion layer is formed directly on the first electrode layer, and an interface between the first electrode layer and the organic semiconductor layer does not have the unevenness .   A substrate, a first electrode layer formed on the substrate, an organic semiconductor layer formed on the first electrode layer and having a photoelectric conversion layer and a charge extraction promoting layer, and formed on the organic semiconductor layer An organic thin film solar cell having a second electrode layer,
  The photoelectric conversion layer and the charge extraction promoting layer are sequentially laminated on the first electrode layer, and the interface between the photoelectric conversion layer and the charge extraction promoting layer has irregularities,
  The organic semiconductor layer further has a second charge extraction promoting layer on the first electrode layer side of the photoelectric conversion layer, and the interface between the second charge extraction promotion layer and the photoelectric conversion layer has the unevenness. Organic thin-film solar cell characterized by not having.   A substrate, a first electrode layer formed on the substrate, a hole extraction layer formed on the first electrode layer, and a photoelectric conversion layer and a charge extraction promotion layer formed on the hole extraction layer An organic thin-film solar cell having an organic semiconductor layer having a second electrode layer formed on the organic semiconductor layer,
  The photoelectric conversion layer and the charge extraction promoting layer are sequentially laminated on the first electrode layer, and the interface between the photoelectric conversion layer and the charge extraction promoting layer has irregularities,
  The organic thin-film solar cell, wherein the photoelectric conversion layer is formed directly on the hole extraction layer, and an interface between the hole extraction layer and the organic semiconductor layer does not have the unevenness.   The photoelectric conversion layer contains an organic semiconductor material having a weight average molecular weight of 100,000 or more or an insulating resin material having a weight average molecular weight of 10,000 or more. The organic thin film solar cell described. The organic thin film solar cell as claimed in any of claims to claim 10, wherein the organic semiconductor layer is a coating film. A first electrode layer forming step of forming a first electrode layer on the substrate;
A lower layer forming step of forming a lower layer coating film by applying a lower layer forming coating liquid having a viscosity in the range of 50 cps to 6000 cps on the first electrode layer, and an upper layer coating on the lower layer coating film An organic semiconductor layer forming step of forming an organic semiconductor layer having an upper layer forming step of forming a film and having at least two layers of films;
And a second electrode layer forming step of forming a second electrode layer on the organic semiconductor layer. The said upper layer formation process is a process of apply | coating the coating liquid for upper layer formation on the said lower layer coating film, and forming the upper layer coating film, The manufacturing of the organic thin film solar cell of Claim 12 characterized by the above-mentioned. Method. The method for producing an organic thin-film solar cell according to claim 13 , wherein the lower layer forming coating liquid contains an organic semiconductor material having a weight average molecular weight of 100,000 or more.

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