JP7633622B2 - Photoelectric conversion element, power generation device - Google Patents

Description

The present invention relates to a photoelectric conversion element and a power generation device using the photoelectric conversion element.

In conventional photoelectric conversion elements, one of the electrodes is a transparent electrode made of tin-doped indium oxide (ITO), and the other electrode is an opaque electrode made of a metal material such as Al, Au, Ag, Cu, Ni, Pt, or an Mg alloy (see, for example, Patent Document 1).

JP 2013-218924 A

However, light irradiated through the transparent electrode passes through the photoelectric conversion layer, but is absorbed or reflected by the opaque electrode. As a result, the photoelectric conversion element blocks light from reaching anything behind it in the direction of light irradiation, making it impossible to effectively utilize the light energy.

In view of the above situation, the present invention aims to provide a photoelectric conversion element that allows light to pass through to the rear of the element, and a power generation device that uses the photoelectric conversion element.

The present invention has been made to solve the above problems, and the photoelectric conversion element of the present invention comprises a first electrode made of a first electrode material having optical transparency, a second electrode containing a conductive nanostructure and made of a second electrode material having optical transparency, and a photoelectric conversion layer located between the first electrode and the second electrode, and when the direction in which the first electrode, the photoelectric conversion layer, and the second electrode are stacked is defined as the stacking direction, the first electrode and the second electrode are arranged shifted in an orthogonal direction perpendicular to the stacking direction, and the photoelectric conversion layer, the first electrode, and the second electrode are overlapped when viewed from the stacking direction, a second region in which the photoelectric conversion layer and the first electrode overlap when viewed from the stacking direction, but the photoelectric conversion layer and the second electrode do not overlap, and a third region in which the photoelectric conversion layer and the second electrode overlap when viewed from the stacking direction, but the photoelectric conversion layer and the first electrode do not overlap.

The photoelectric conversion element of the present invention is also characterized in that the second electrode material contains poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) (PEDOT-PSS) or polyaniline.

The photoelectric conversion element of the present invention is also characterized in that the nanostructure includes a metal nanowire.

The power generating device of the present invention further comprises: a first electrode made of a first electrode material having optical transparency;
The photoelectric conversion element includes a plurality of photoelectric conversion elements each having a second electrode that contains a conductive nanostructure and is made of a second electrode material that is optically transparent, and a photoelectric conversion layer located between the first electrode and the second electrode, and the photoelectric conversion element is characterized in that when the direction in which the first electrode, the photoelectric conversion layer, and the second electrode are stacked is defined as a stacking direction, the first electrode and the second electrode of the photoelectric conversion element are arranged so as to be shifted in an orthogonal direction perpendicular to the stacking direction, and the photoelectric conversion element has a first region in which the photoelectric conversion layer, the first electrode, and the second electrode overlap when viewed from the stacking direction, a second region in which the photoelectric conversion layer and the first electrode overlap when viewed from the stacking direction, but the photoelectric conversion layer and the second electrode do not overlap, and a third region in which the photoelectric conversion layer and the second electrode overlap when viewed from the stacking direction, but the photoelectric conversion layer and the first electrode do not overlap. Further, in the power generation device of the present invention, each of the multiple photoelectric conversion elements is arranged so that the stacking directions are parallel to each other, and the multiple photoelectric conversion elements are arranged so that the photoelectric conversion layer of one of the photoelectric conversion elements adjacent to each other in the arrangement direction of the multiple photoelectric conversion elements and at least one of the second region and the third region of the other adjacent photoelectric conversion element overlap in the arrangement direction .

In addition, in the power generation device of the present invention, the multiple photoelectric conversion elements are arranged so that the second electrode is located further back than the first electrode in the direction of light irradiation.

Moreover, the power generation device of the present invention is further characterized in that it comprises a holding section that holds the multiple photoelectric conversion elements so that the photoelectric conversion layer of one of the photoelectric conversion elements adjacent to each other in the arrangement direction of the multiple photoelectric conversion elements and at least one of the second region and the third region of the other adjacent photoelectric conversion element overlap in the arrangement direction, and when a position at which each of the multiple photoelectric conversion elements is held by the holding section is defined as a holding position, a plurality of first connection sections that are arranged at each of the holding positions and contact the first electrode of the photoelectric conversion element located at the holding position to electrically connect an external circuit to the photoelectric conversion element, and a plurality of second connection sections that are arranged at each of the holding positions and contact the second electrode of the photoelectric conversion element located at the holding position to electrically connect the external circuit to the photoelectric conversion element.

In addition, in the power generating device of the present invention, the first electrode and the second electrode have a non-overlapping region in the stacking direction that does not overlap the photoelectric conversion layer, and the first connection parts and the second connection parts are arranged so as to be electrically connected to the non-overlapping region.

According to the photoelectric conversion element of the present invention, the two electrodes are optically transparent, allowing the irradiated light to pass through. As a result, the photoelectric conversion element behind it can generate power from the transmitted light, increasing the amount of power generated per unit area. In addition, according to the power generation device of the present invention, the amount of power generated per unit area can be increased by overlapping photoelectric conversion elements having two optically transparent electrodes.

1 is a cross-sectional view of a power generating device in which photoelectric conversion elements are connected in parallel according to an embodiment of the present invention. 1A is a cross-sectional view of a modified example of the photoelectric conversion element according to the embodiment of the present invention, and FIG. 1B is a cross-sectional view of a power generating device in which another modified example of the photoelectric conversion element according to the embodiment of the present invention is connected in series. 1 is a cross-sectional view of a power generating device in which photoelectric conversion elements are connected in series according to an embodiment of the present invention. FIG. 2 is a perspective view of an output device of the power generation device according to the embodiment of the present invention. (A) is an output circuit for connecting photoelectric conversion elements of a power generating device in parallel according to an embodiment of the present invention. (B) is an output circuit for connecting photoelectric conversion elements of a power generating device in series according to an embodiment of the present invention. (C) is an output circuit for connecting photoelectric conversion elements of a power generating device in series and in parallel according to an embodiment of the present invention. 1A is a perspective view of a photoelectric conversion element used in an experiment on a photoelectric conversion element, FIG. 1B is a plan view of the photoelectric conversion element used in an experiment on a photoelectric conversion element, and FIG. 1C is a plan view of two photoelectric conversion elements used in an experiment on a photoelectric conversion element when stacked. 1 is a graph showing the transmittance of second electrode materials A to D.

The following describes an embodiment of the present invention with reference to the attached drawings. Figures 1 to 6 show an example of an embodiment of the invention, and parts in the figures that are given the same reference numerals as in Figure 1 represent the same items.

<Overall composition>
A power generating device 1 according to an embodiment of the present invention will be described with reference to Fig. 1. The power generating device 1 according to the present embodiment includes a plurality of photoelectric conversion elements 2 and an output device 3.

<Photoelectric conversion element>
With reference to FIG. 1, a photoelectric conversion element 2 in an embodiment of the present invention will be described. In this embodiment, the photoelectric conversion element 2 is configured in a sheet shape and is configured to have flexibility. The photoelectric conversion element 2 includes a first electrode 10, a second electrode 11, a photoelectric conversion layer 12, a functional layer (metal alkoxide-containing layer) 13, a substrate 14, a sealing portion 15, and a substrate 16. As shown in FIG. 1, the photoelectric conversion element 2 is stacked on the substrate 14 in the order of the first electrode 10, the functional layer 13, the photoelectric conversion layer 12, and the second electrode 11. The stacking direction A of each layer of the photoelectric conversion element 2 (hereinafter referred to as the layer stacking direction) is described below as coinciding with the thickness direction of the sheet-like photoelectric conversion element 2 or the surface perpendicular direction of the plane of the sheet-like photoelectric conversion element 2.

The photoelectric conversion element 2 does not have to be configured in a sheet shape, and furthermore, it does not have to be flexible.

<First Electrode and Second Electrode>
One of the first electrode 10 and the second electrode 11 corresponds to an anode, and the other corresponds to a cathode. The first electrode 10 is made of a first electrode material having electrical conductivity and optical transparency. Examples of the first electrode material include transparent materials having electrical conductivity. More specifically, examples of the first electrode material include conductive metal oxides such as tin-doped indium oxide (ITO), IGZO (composed of In (indium), Ga (gallium), Zn (zinc), and O (oxygen)), gallium-doped zinc oxide (GZO), fluorine-doped tin oxide (FTO), antimony-doped tin oxide (ATO), and aluminum-doped zinc oxide (AZO). In this embodiment, the first electrode 10 is made of the first electrode material as a transparent electrode (first transparent electrode).

The first electrode 10 is formed, for example, by forming a single layer or a plurality of layers of materials on a substrate 14 made of an insulator, as shown in FIG. 1. In this embodiment, the first electrode 10 may be formed, for example, by forming a film of the first electrode material on the substrate 14 by a film forming method such as a sputtering method or a vacuum deposition method, or by applying a first electrode material solution, in which the first electrode material is dissolved in a predetermined solvent, as an ink solution onto the substrate 14, or by printing the first electrode material on the substrate 14 with an inkjet printer.

The substrate 14 is preferably made of a light-transmitting material such as polycarbonate, and is particularly preferably made of a transparent material with high light transmittance. In this embodiment, the photoelectric conversion element 2 is configured to be flexible. For this reason, the substrate 14 is preferably configured in a sheet shape from a flexible and insulating material such as polycarbonate. The substrate 14 may also be configured in a sheet shape from a non-flexible material such as glass.

The second electrode 11 is made of a second electrode material that is conductive and optically transparent. The second electrode material includes a nanostructure. Specifically, the second electrode material is made of a conductive polymer compound and a nanostructure. In this embodiment, the second electrode 11 is made of the second electrode material as a transparent electrode (second transparent electrode).

Examples of conductive polymer compounds include poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) (hereinafter referred to as PEDOT-PSS) and polyaniline. Nanostructures refer to nanoscale structures such as nanorods, nanowires, nanoparticles, and nanostereostructures (tetrapod-type and marshmallow-type). Specific examples of nanostructures include metal nanowires such as silver nanowires (AgNW).

Metal nanowires (silver nanowires) are mixed into the PEDOT-PSS solution at a predetermined mass ratio (for example, a mass ratio of 1:1), and a predetermined process is performed to disperse the metal nanowires (silver nanowires) appropriately in the PEDOT-PSS solution, creating a mixed solution of the PEDOT-PSS solution and the metal nanowires (silver nanowires). When the mixed solution is applied to the photoelectric conversion layer 12 and dried, a layer of the second electrode 11 with high light transmittance is formed. The same is true when the metal nanowires (silver nanowires) are mixed into a polyaniline solution. Note that the second electrode 11 may be constructed by stacking multiple materials on the photoelectric conversion layer 12, as long as high light transmittance can be ensured.

The second electrode 11 may be formed by forming a film on the photoelectric conversion layer 12 using a film forming method such as sputtering or vacuum deposition, or may be formed by applying a second electrode material solution containing the second electrode material as an ink solution onto the photoelectric conversion layer 12, or by printing it onto the photoelectric conversion layer 12 using an inkjet printer.

The sealing portion 15 protects the photoelectric conversion element 2 by sealing the first electrode 10, the functional layer 13, the photoelectric conversion layer 12, and the second electrode 11 stacked on the substrate 14, for example, with a resin or the like. The sealing portion 15 is preferably made of a material having optical transparency, and is particularly preferably made of a transparent material having high optical transparency. In addition, the sealing portion 15 is preferably made of a material having flexibility.

In addition, when, for example, another layer (e.g., a hole transport layer, etc.) is laminated on the photoelectric conversion layer 12 on the side opposite the functional layer 13, the second electrode 11 is laminated on that other layer.

<Photoelectric conversion layer>
The photoelectric conversion layer 12 generates electrons and holes due to light incident from the outside. The photoelectric conversion layer 12 is formed between the first electrode 10 and the second electrode 11. When light is incident, excitons are generated in the photoelectric conversion layer 12, and electrons and holes are generated. For example, when the first electrode 10 functions as a cathode and the second electrode 11 functions as an anode, the electrons move to the first electrode 10 side through the functional layer 13 functioning as an electron transport layer, and the holes move to the second electrode 11 side. As a result, a current (photoexcited current) flows in an external circuit (not shown) connected to the second electrode 11 and the first electrode 10.

The photoelectric conversion layer 12 contains an n-type semiconductor material and a p-type semiconductor material. The junction between the n-type semiconductor material and the p-type semiconductor material in the photoelectric conversion layer 12 may be a planar heterojunction having a planar junction interface, or a bulk heterojunction in which the materials are mixed three-dimensionally.

The photoelectric conversion layer 12 in this embodiment contains a metal alkoxide. The metal alkoxide acts as an n-type semiconductor. The output voltage of the photoelectric conversion element 2 is determined by the difference between the LUMO of the n-type semiconductor and the HOMO of the p-type semiconductor. Since the values of LUMO and HOMO are band gap energy, when the band gap energy of the metal alkoxide as an n-type semiconductor is large, the LUMO of the n-type semiconductor becomes large, and a high output voltage can be obtained. In order to obtain a high output voltage, it is preferable that the metal alkoxide used in the photoelectric conversion layer 12 has a band gap energy of 3.5 eV or more.

As the metal alkoxide used in the photoelectric conversion layer 12, for example, titanium alkoxide (general formula: Ti(OR) _n ), zinc-based zinc alkoxide, diethyl zinc, titania or zinc oxide fine particles are preferable. As the titanium alkoxide, for example, titanium isopropoxide is preferable.

In addition, the n-type semiconductor in the photoelectric conversion layer 12 may contain at least one of fullerene, fullerene derivative, oxide semiconductor, and other electron-accepting compounds in addition to metal alkoxide. That is, the n-type semiconductor in the photoelectric conversion layer 12 may be composed of only metal alkoxide, or may be composed of a mixture of metal alkoxide and the above-mentioned electron-accepting compounds. In addition, when the n-type semiconductor is composed of only metal alkoxide, it may contain other n-type semiconductors that are unintentionally contained during the manufacturing process. In addition, examples of the oxide semiconductor include inorganic compound particles of zinc oxide and titanium oxide. In addition, the n-type semiconductor in the photoelectric conversion layer 12 may contain at least one of fullerene, fullerene derivative, oxide semiconductor, and other electron-accepting compounds instead of metal alkoxide. Examples of the oxide semiconductor include inorganic compound particles of zinc oxide and titanium oxide, but are not limited thereto.

Examples of p-type organic semiconductors include polyvinylcarbazole and its derivatives, polysilane and its derivatives, polysiloxane derivatives having aromatic amines in the side chain or main chain, polyaniline and its derivatives, polythiophene and its derivatives, polypyrrole and its derivatives, polyphenylenevinylene and its derivatives, polythienylenevinylene and its derivatives, polyfluorene and its derivatives, etc.

<Functional layer (metal alkoxide-containing layer)>
The functional layer 13 is formed between the first electrode 10 and the second electrode 11. In particular, the functional layer 13 is preferably formed between the photoelectric conversion layer 12 and the first electrode 10 so as to be adjacent to both layers. Then, for example, when the first electrode 10 is a cathode, the functional layer 13 functions as an electron transport layer that efficiently transports electrons generated in the photoelectric conversion layer 12 to the first electrode 10. In this case, the functional layer 13 is preferably formed of a material with high electron mobility. Examples of materials with high electron mobility include metal alkoxides (e.g., titanium alkoxides) and poly(3-hexylthiophene-2,5-diyl) (P3HT), which is a polythiophene derivative. In addition, the functional layer 13 has a rectifying effect that does not allow holes generated in the photoelectric conversion layer 12 to flow to the first electrode 10. Note that, for example, when the first electrode 10 is an anode, the functional layer 13 functions as an electron transport layer that efficiently transports holes generated in the photoelectric conversion layer 12 to the first electrode 10. In this case, the functional layer 13 is preferably made of a material with high hole mobility.

It is preferable that the functional layer 13, which has an electron transport function, contains a metal alkoxide (e.g., titanium alkoxide). The metal alkoxide in the functional layer 13 serves as an n-type semiconductor and quickly moves electrons to the first electrode 10. In addition, the functional layer 13 and the photoelectric conversion layer 12 have a metal alkoxide as a common component. As a result, the ratio of metal alkoxides contacting each other between the functional layer 13 and the photoelectric conversion layer 12 is increased, so that the contact resistance between the layers is reduced. The higher the content ratio of metal alkoxide in the functional layer 13 and the photoelectric conversion layer 12, the lower the contact resistance. In addition, since interpenetration of the metal alkoxide occurs between the layers, the mechanical strength of the photoelectric conversion layer 12 and the functional layer 13 is improved. As a result, peeling between the photoelectric conversion layer 12 and the functional layer 13 is less likely to occur. From this viewpoint, it is preferable that the functional layer 13 is mainly composed of a metal alkoxide, or is composed only of a metal alkoxide (including unavoidable components that are unintentionally included during the manufacturing process). In addition, it is preferable to use non-crystalline metal alkoxide in the functional layer 13, rather than crystalline metal alkoxide. This is to solve the problem of low toughness of crystalline metal alkoxide. In addition, the thickness of the functional layer 13 is preferably about 100 nm or less. If the thickness of the functional layer 13 is made too thick, the electrons cannot reach the first electrode 10 and are deactivated. If the thickness of the functional layer 13 is made too thin, the surface of the first electrode 10 cannot be covered. For this reason, in order to enable the electrons to reach the first electrode 10 quickly and obtain a high output current, the thickness of the functional layer 13 is appropriate to be about 100 nm or less. Note that when the n-type semiconductor in the photoelectric conversion layer 12 is not a metal alkoxide but is made of a material containing at least one of fullerene, fullerene derivative, oxide semiconductor, and other electron-accepting compound, the functional layer 13 that performs the electron transport function may be made of other materials instead of metal alkoxide.

<Configuration of photoelectric conversion element>
The photoelectric conversion element 2 is formed by stacking a first electrode 10, a functional layer 13, a photoelectric conversion layer 12, and a second electrode 11 in this order on a substrate 14. The second electrode 11 side is sealed with a sealing portion 15 and covered with a substrate 16. The substrate 16 is preferably made of the same material as the substrate 14.

As shown in FIG. 1, the photoelectric conversion element 2 has a first electrode side overlapping region 21 where the first electrode 10 overlaps with the photoelectric conversion layer 12, and a second electrode side overlapping region 22 where the second electrode 11 overlaps with the photoelectric conversion layer 12 in the layer stacking direction A of the photoelectric conversion element 2. In the first electrode side overlapping region 21 in this embodiment, the first electrode 10 also overlaps with the functional layer 13 in the layer stacking direction A. In the second electrode side overlapping region 22 in this embodiment, a partial region of the second electrode 11 also overlaps with the functional layer 13 in the layer stacking direction A.

In this embodiment, the first electrode 10 has a first electrode side non-overlapping region 23 that does not overlap with the photoelectric conversion layer 12 in the layer stacking direction A. In this embodiment, the second electrode 11 has a second electrode side non-overlapping region 24 that does not overlap with the photoelectric conversion layer 12 in the layer stacking direction A.

In FIG. 1, if the direction in which the second electrode 11 and the first electrode 10 are shifted while being perpendicular to the layer stacking direction A is defined as the width direction (hereinafter referred to as the element width direction) W of the photoelectric conversion element 2, the first electrode side non-overlapping region 23, the first electrode side overlapping region 21, the second electrode side overlapping region 22, and the second electrode side non-overlapping region 24 are arranged in order in the element width direction W. The first electrode side non-overlapping region 23 and the second electrode side non-overlapping region 24 are convex in the direction away from the first electrode side overlapping region 21 and the second electrode side overlapping region 22, respectively, starting from the ends of the first electrode side overlapping region 21 and the second electrode side overlapping region 22 along the element width direction W. In addition, the first electrode side overlapping region 21 and the second electrode side overlapping region 22 have partial overlapping regions in the layer stacking direction A.

2(A), the photoelectric conversion element 2 may have a plurality of photoelectric conversion elements shown in FIG. 1, which are connected in series. In this embodiment, the first electrode 10 in the first electrode side non-overlapping region 23 and the second electrode 11 in the second electrode side non-overlapping region 24 are provided to ensure that the photoelectric conversion layer 12 and the functional layer 13 do not come into contact with the first electrode 10 and the second electrode 11 while connecting the first connection portion 18 and the second connection portion 19 only to the first electrode 10 and the second electrode 11, respectively. Therefore, if the photoelectric conversion element 2 is configured to connect only the first electrode 10 and the second electrode 11 to the first connection portion 18 and the second connection portion 19, as shown in FIG. 2(B), the second electrode side non-overlapping region 24 and the first electrode side non-overlapping region 23 are not provided, and the first electrode 10, the second electrode 11, the photoelectric conversion layer 12, and the functional layer 13 may be entirely overlapped. Such a configuration is also included in the scope of the present invention. In other words, the photoelectric conversion element 2 may have any structure as long as the first electrode 10, the second electrode 11, the first connection portion 18, and the second connection portion 19 can be connected, respectively.

<Arrangement of photoelectric conversion elements>
In conventional photoelectric conversion elements, only one electrode, the cathode or anode, is made of a transparent material with high light transmittance, and the other electrode is made of a metal material with low light transmittance. Therefore, when multiple photoelectric conversion elements are stacked along the layer stacking direction of the reference photoelectric conversion element, most of the light is absorbed or reflected by the photoelectric conversion element in the front row, and almost no light reaches the photoelectric conversion elements arranged second or later. As a result, almost no power is generated in the photoelectric conversion elements arranged second or later.

In the photoelectric conversion element 2 in this embodiment, not only the first electrode 10 but also the second electrode 11 are made of a transparent material with high light transmittance. Therefore, as shown in FIG. 1, as a result of arranging a plurality of photoelectric conversion elements 2 so as to be stacked along the layer stacking direction A of the reference photoelectric conversion element 2, even if the first electrode side overlapping region 21 and the second electrode side overlapping region 22 of adjacent photoelectric conversion elements 2 overlap in the layer stacking direction A, only a portion of the irradiated light is absorbed by the photoelectric conversion element 2 on the front side, but the remainder is transmitted and reaches the photoelectric conversion element 2 arranged on the back side. As a result, the amount of power generation per unit area as viewed from the layer stacking direction A is improved. In other words, even in a place with a limited installation area, if the photoelectric conversion elements 2 in this embodiment are stacked vertically at that place, the amount of power generation at that place can be increased. Therefore, the effect of the plurality of photoelectric conversion elements 2 in this embodiment is improved by arranging them so as to be stacked along the layer stacking direction A of the reference photoelectric conversion element 2.

In addition, fields where agricultural crops are grown are generally located in places where they are sufficiently exposed to sunlight. For this reason, by positioning the photoelectric conversion element 2 in this embodiment above the field, it is possible to receive sufficient sunlight while allowing a certain amount of sunlight to pass through. As a result, it is ensured that a sufficient amount of sunlight is irradiated onto the crops, and the photoelectric conversion element 2 can ensure sufficient power generation while also promoting the growth of the crops.

<Output device configuration>
The output device 3 in this embodiment is used when outputting to the outside electric power generated by the multiple photoelectric conversion elements 2. The photoelectric conversion elements 2 are detachably held by the output device 3. As shown in FIG. 1 , the output device 3 has a holding portion 17, multiple first connection portions 18, multiple second connection portions 19, and an output circuit 20.

<Holding part>
1, the holding unit 17 holds the multiple photoelectric conversion elements 2 so that the multiple photoelectric conversion elements 2 are stacked while the layer stacking direction A of the other photoelectric conversion elements 2 is parallel to the layer stacking direction A of the reference photoelectric conversion element 2 (hereinafter referred to as the reference layer stacking direction CA). The holding unit 17 is configured so that the photoelectric conversion elements 2 can be freely attached and detached. Therefore, even if some of the photoelectric conversion elements 2 are defective, it is sufficient to replace only that part.

In this embodiment, the photoelectric conversion elements 2 are arranged in such a manner that the reference layer stacking direction CA and the layer stacking direction A of each photoelectric conversion element 2 are approximately parallel. In this case, as shown in FIG. 1, when the photoelectric conversion elements 2 are connected in parallel, the photoelectric conversion elements 2 are arranged in such a manner that the first electrode 10 and the second electrode 11 of each photoelectric conversion element 2 are located on the same side. On the other hand, as shown in FIG. 3, when the photoelectric conversion elements 2 are connected in series, the photoelectric conversion elements 2 are arranged in such a manner that the first electrode 10 and the second electrode 11 of the adjacent photoelectric conversion elements 2 are located opposite each other in the layer stacking direction A. In addition, it is preferable to arrange the photoelectric conversion elements 2 in such a manner that the second electrode 11 is located further back than the first electrode 10 with respect to the light irradiation direction. This is to prevent the irradiation light from being reflected by the nanostructure before it reaches the photoelectric conversion layer 12.

In this embodiment, the holding unit 17 is configured by a housing 170 having a plurality of support parts 171 therein, as shown in FIG. 4. The housing 170 has, for example, a hollow rectangular parallelepiped shape with an opening 170A. The housing 170 is missing one of the faces of the rectangular parallelepiped shape, and this part becomes the opening 170A, opening the inside of the housing 170 to the outside.

The support portion 171 is for supporting the photoelectric conversion element 2 within the housing 170. The multiple support portions 171 are provided at equal intervals along the extension direction D (e.g., the height direction) of the housing 170.

In addition, between two adjacent support parts 171 in the extension direction D of the housing 170, an accommodation space S for accommodating the photoelectric conversion element 2 is formed. The accommodation space S is surrounded by an inner wall surface 170B of the housing 170 that extends unclosed along the circumferential direction around the central axis J of the housing 170 that extends in the extension direction D of the housing 170, and opposing surfaces 171A that face each other in the extension direction D of each of the two adjacent support parts 171 in the extension direction D of the housing 170. The unclosed portion of the inner wall surface 170B becomes the above-mentioned opening 170A of the housing 170.

The photoelectric conversion element 2 is configured to be insertable into the storage space S through the opening 170A. At this time, the photoelectric conversion element 2 is inserted into the storage space S in such a manner that its layer stacking direction A is parallel to the extension direction D of the housing 170, and its element width direction W is parallel to the width direction E of the housing 170 (hereinafter referred to as the housing width direction). At this time, when the output circuit 20 forms a parallel circuit, the photoelectric conversion element 2 is arranged in such a manner that the first electrode 10 in the first electrode side non-overlapping region 23 and the second electrode 11 in the second electrode side non-overlapping region 24 are on the same side as those of the other photoelectric conversion elements 2. Also, when the output circuit 20 forms a series circuit, the photoelectric conversion element 2 is arranged in such a manner that the first electrode 10 in the first electrode side non-overlapping region 23 and the second electrode 11 in the second electrode side non-overlapping region 24 of adjacent photoelectric conversion elements 2 are opposite to each other.

As shown in FIG. 4, the support portion 171 is composed of a pair of supports 172 that support the photoelectric conversion element 2 at both ends of the photoelectric conversion element 2 in the element width direction W. The support 172 is composed of, for example, a rod-shaped plate material that forms part of the inner wall surface 170B of the housing 170 and extends along the depth direction F of the housing 170 from the opening 170A of the housing 170 while contacting a pair of opposing surfaces 170C that face each other in the housing width direction E. The support 172 contacts the photoelectric conversion element 2 at the second electrode side non-overlapping region 24 and the first electrode side non-overlapping region 23 of the photoelectric conversion element 2 (both ends of the photoelectric conversion element 2 in the element width direction W and their vicinity in FIG. 1) to support the photoelectric conversion element 2.

In the support portion 171 configured as described above, the space between the opposing surfaces 172A of the pair of supports 172 facing each other in the housing width direction E is an empty space T in which nothing is placed, as shown in Figures 1 and 4. When light is irradiated from one side in the extension direction D of the housing 170, as shown in Figure 1, the light passes through the second electrode side overlapping region 22 and the first electrode side overlapping region 21 of the photoelectric conversion element 2 and proceeds to the next photoelectric conversion element 2. At this time, if something is placed in a position corresponding to the empty space T, the light will be absorbed or reflected there. To prevent this, the empty space T is provided.

<First Connection Portion and Second Connection Portion>
The multiple first connection parts 18 come into contact with the first electrode 10 of the photoelectric conversion element 2 inserted into the accommodation space S, and electrically connect the output circuit 20 and the first electrode 10 of the photoelectric conversion element 2. The multiple second connection parts 19 come into contact with the second electrode 11 of the photoelectric conversion element 2 inserted into the accommodation space S, and electrically connect the output circuit 20 and the second electrode 11 of the photoelectric conversion element 2.

When the photoelectric conversion element 2 is inserted into the storage space S, and the position where the photoelectric conversion element 2 is held by the housing 170 and the support portion 171 (holding portion 17) is defined as the holding position, the first connection portion 18 is disposed at a position where the first electrode 10 of the photoelectric conversion element 2 contacts the first connection portion 18 at the holding position. The second connection portion 19 is disposed at a position where the second electrode 11 of the photoelectric conversion element 2 contacts the second connection portion 19 at the holding position. The first connection portion 18 and the second connection portion 19 are also connected to the output circuit 20. In other words, the first connection portion 18 and the second connection portion 19 electrically connect the photoelectric conversion element 2 and the output circuit 20.

In this embodiment, the first connection portion 18 and the second connection portion 19 are provided for each storage space S, as shown in FIG. 4, and are provided so that they face each other in the housing width direction E. Specifically, the first connection portion 18 and the second connection portion 19 are provided on or near the inner wall surface 170B of the housing 170 that faces each other in the housing width direction E. Note that the first connection portion 18 and the second connection portion 19 may not face each other in the housing width direction E, but may be positioned at positions offset from each other in the depth direction F of the housing 170.

<Output circuit>
The output circuit 20 is an example of an external circuit connected to each photoelectric conversion element 2, and outputs the power generated by each photoelectric conversion element 2 to the outside. The output circuit 20 may connect each photoelectric conversion element 2 in parallel as shown in FIG. 5(A), may connect each photoelectric conversion element 2 in series as shown in FIG. 5(B), or may connect each photoelectric conversion element 2 in a mixed manner in series and parallel as shown in FIG. 5(C). In the output circuit 20 shown in FIG. 5(C), two columns of photoelectric conversion elements 2 connected in series are connected in parallel. In the output circuit 20 shown in FIG. 1, each photoelectric conversion element 2 is connected in parallel. In the output circuit 20 shown in FIG. 2(B) and FIG. 3, each photoelectric conversion element 2 is connected in series. In addition, in FIGS. 5(A) to 5(C), the "-" of the photoelectric conversion element 2 represents the first electrode 10, and the "+" of the photoelectric conversion element 2 represents the second electrode 11.

When each photoelectric conversion element 2 is connected in parallel, it is preferable to provide a backflow prevention diode 190 in series with each photoelectric conversion element 2, as shown in FIG. 5(A). This is to prevent current from flowing backwards. Note that the backflow prevention diode 190 is omitted in the output circuit 20 shown in FIG. 1.

When the photoelectric conversion elements 2 are connected in series, it is preferable to connect a bypass diode 191 in parallel to each of the photoelectric conversion elements 2 as shown in FIG. 5(B). The bypass diode 191 bypasses the current at the defective part, for example, when an obstacle blocks the light to the photoelectric conversion element 2 or when a defect occurs in the photoelectric conversion element 2. Also, when the photoelectric conversion elements 2 are connected in series, it is preferable to provide a backflow prevention diode 190 in series with each photoelectric conversion element 2. This is to prevent the current from flowing backward. Note that the bypass diode 191 is omitted in the output circuit 20 shown in FIG. 2(B) and FIG. 3.

When the photoelectric conversion elements 2 are connected in a mixture of series and parallel, it is preferable to connect bypass diodes 191 in parallel to the series-connected parts and to connect backflow prevention diodes 190 in series to the parallel-connected parts, as shown in FIG. 5(C).

The power generated by each photoelectric conversion element 2 is output to the outside through the output circuit 20. Then, downstream of the output circuit 20, for example, a boost circuit (not shown) that boosts the voltage, or an inverter circuit (not shown) that performs DC-AC conversion, etc., are provided as necessary, so that a predetermined power is supplied to the outside. Note that the downstream side of the output circuit 20 may include circuits other than those described above.

<Experiments on photoelectric conversion elements A and B>
The inventors of the present application created photoelectric conversion elements A and B having the structures shown in Figures 6(A) and (B) and conducted experiments on the light absorption and power generation characteristics of the photoelectric conversion elements A and B. The photoelectric conversion element A is included in the embodiment of the present invention, and is a glass substrate with ITO (indium-doped tin oxide transparent conductive film) (substrate 14 with first electrode 10) on which a functional layer 13, a photoelectric conversion layer 12, and a second electrode 11 are formed in this order. The functional layer 13 in the photoelectric conversion element A was created by dropping a coating solution in which 2 wt% titanium isopropoxide was dissolved in isopropyl alcohol onto the glass substrate with ITO and forming a film by a spin coating method. Then, after the film formation, it was dried in the atmosphere at 120 ° C. for 10 minutes.

The photoelectric conversion layer 12 in the photoelectric conversion element A was prepared by dropping a coating solution in which the photoelectric conversion layer forming material was dissolved in chlorobenzene onto the functional layer and forming a film by spin coating. After the film was formed, it was dried for 10 minutes in the air at 120°C. The photoelectric conversion layer forming material may be a mixture of a polythiophene derivative (p-type semiconductor polymer compound), a fullerene derivative (PCBM), and a titanium alkoxide TiOx. As the polythiophene derivative, Poly(3-hexylthiophene)-regio-regular (purchased from Sigma-Aldrich) was used. As the titanium alkoxide, titanium isopropoxide was used.

The second electrode 11 in the photoelectric conversion element A was made by using a mixed solution in which PEDOT-PSS (purchased from Heraeus) and silver nanowires (purchased from Sigma-Aldrich) were mixed and dispersed in a mass ratio of 1:1 as the second electrode material, and the second electrode material was dropped onto the photoelectric conversion layer 12 and formed into a film by spin coating. After the film was formed, it was dried in air at 120°C for 10 minutes.

Photoelectric conversion element B was prepared as a comparative example, and like photoelectric conversion element A, a functional layer 13, a photoelectric conversion layer 12, and a second electrode 11 were formed in this order on a glass substrate (substrate 14 with a first electrode 10) with ITO (indium-doped tin oxide transparent conductive film). The functional layer 13 and the photoelectric conversion layer 12 were prepared using the same material and manufacturing method. On the other hand, the second electrode 11 was prepared by dropping the second electrode material onto the photoelectric conversion layer 12 and forming a film by a spin coating method using only PEDOT-PSS (purchased from Heraeus) as the second electrode material.

<Absorbance of Photoelectric Conversion Elements A and B>
The absorbance of photoelectric conversion elements A and B was measured for light with a wavelength of 500 nm using a spectrophotometer (UV-1800 manufactured by Shimadzu Corporation). In this case, if the absorbance of photoelectric conversion element A is C (Abs) and the absorbance of photoelectric conversion element B is D (Abs), C/D was 59(%). In other words, it can be seen that photoelectric conversion element A produced according to this embodiment had lower absorbance and transmitted 41(%) more light than photoelectric conversion element B.

<Power generation characteristics of photoelectric conversion elements A and B>
In addition, as shown in Fig. 6 (C), the photoelectric conversion element A and the photoelectric conversion element B were stacked so that the second electrode side overlapping region 22 of each was overlapped, and when light was irradiated from the substrate 14 side (from the back side to the front side of the paper surface of Fig. 6), the current value in the case of series connection and the voltage value in the case of parallel connection were measured. When the current value of the photoelectric conversion element A in the case of series connection is E (A) and the current value of the photoelectric conversion element B is F (A), E/F was 136 (%). This result revealed that the photoelectric conversion element A produced according to this embodiment transmits more light than the photoelectric conversion element B, and therefore generates more electricity.

In addition, when the voltage value of the photoelectric conversion element A in the case of parallel connection is G (A) and the voltage value of the photoelectric conversion element B is H (A), G/H is 104 (%). This result reveals that the photoelectric conversion element A produced according to this embodiment transmits more light than the photoelectric conversion element B, and therefore generates more electricity. As shown in FIG. 6 (C), when viewed in plan from the layer stacking direction A, it is preferable from the viewpoint of improving the amount of electricity generated per unit area to stack the photoelectric conversion layers 12 of the photoelectric conversion elements A and B so that they overlap. When the photoelectric conversion elements A and B are arranged in this way, in the overlapping region where the second electrode 11 and the photoelectric conversion layer 12 overlap, a lot of light was absorbed or reflected by the second electrode 11, so that the power generation efficiency was low in the overlapping region. However, since the second electrode 11 in the photoelectric conversion elements A and B has a high light transmittance, high power generation efficiency can be maintained even in the overlapping region.

<Transmittance of Second Electrode Materials A to D>
The inventors of the present application have created second electrode materials A to D with different mixing ratios (mass ratios) of PEDOT-PSS and silver nanowires. Second electrode material A has a mixing ratio of PEDOT-PSS and silver nanowires of 1:1 by mass. Second electrode material B has a mixing ratio of PEDOT-PSS and silver nanowires of 1.5:1 by mass. Second electrode material C has a mixing ratio of PEDOT-PSS and silver nanowires of 2:1 by mass. Second electrode material D contains only PEDOT-PSS and does not contain silver nanowires. Note that second electrode material A corresponds to the second electrode material of photoelectric conversion element A, and second electrode material D corresponds to the second electrode material of photoelectric conversion element B.

The inventors of the present application used a spectrophotometer (UV-1800 manufactured by Shimadzu Corporation) to measure the transmittance (%) of second electrode materials A to D. The results are shown in the graph in Figure 7. In the graph in Figure 7, the horizontal axis represents the wavelength of the light irradiated from the spectrophotometer, and the vertical axis represents the transmittance (%). According to the graph in Figure 7, the transmittance generally increases in the order of second electrode material A, second electrode material B, second electrode material C, and second electrode material D. Furthermore, the transmittance of photoelectric conversion elements A to C is significantly higher than that of second electrode material D. Therefore, it can be seen that the transmittance is clearly improved when silver nanowires are mixed into PEDOT-PSS.

As is clear from the graph in FIG. 7, the transmittance is clearly better when the mass ratio of PEDOT-PSS to silver nanowires is smaller. When comparing second electrode material B with second electrode material C, the transmittance of both is approximately the same up to an irradiation light wavelength of about 400 (nm), but when the irradiation light wavelength exceeds 400 (nm), second electrode material B has a slightly higher transmittance than second electrode material C. When comparing second electrode material A with second electrode material B, the transmittance of second electrode material A is significantly higher than that of second electrode material B in the irradiation light wavelength range of 300 (nm) to 1000 (nm).

The photoelectric conversion element and power generation device of the present invention are not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.

REFERENCE SIGNS LIST 1 Power generation device 2 Photoelectric conversion element 3 Output device 10 First electrode 11 Second electrode 12 Photoelectric conversion layer 13 Functional layer 14, 16 Substrate 15 Sealing section 17 Holding section 18 First connection section 19 Second connection section 20 Output circuit 21 First electrode side overlapping region 22 Second electrode side overlapping region 23 First electrode side non-overlapping region 24 Second electrode side non-overlapping region 170 Housing 171 Support section 172 Support body

Claims (3)

A first electrode made of a first electrode material having optical transparency;
A second electrode including a conductive nanostructure and made of a second electrode material having optical transparency;
a photoelectric conversion layer located between the first electrode and the second electrode;
having
When the direction in which the first electrode, the photoelectric conversion layer, and the second electrode are stacked is defined as the stacking direction,
The first electrode and the second electrode are arranged to be shifted in an orthogonal direction perpendicular to the stacking direction,
a first region in which the photoelectric conversion layer, the first electrode, and the second electrode overlap when viewed from the stacking direction;
a second region in which the photoelectric conversion layer and the first electrode overlap each other when viewed from the stacking direction, but the photoelectric conversion layer and the second electrode do not overlap each other;
a third region in which the photoelectric conversion layer and the second electrode overlap each other when viewed from the stacking direction, but the photoelectric conversion layer and the first electrode do not overlap each other;
A plurality of photoelectric conversion elements having the same structure;
a holding section that holds the plurality of photoelectric conversion elements such that the photoelectric conversion layer of one of the photoelectric conversion elements adjacent to the plurality of photoelectric conversion elements in an arrangement direction of the photoelectric conversion elements and at least one of the second region and the third region of the other adjacent photoelectric conversion element overlap in the arrangement direction;
a plurality of first connection parts that are arranged at the respective holding positions, when the positions at which the plurality of photoelectric conversion elements are held by the holding parts are defined as holding positions, and that contact the first electrodes of the photoelectric conversion elements positioned at the holding positions to electrically connect an external circuit to the photoelectric conversion elements;
a plurality of second connection parts that are arranged at the respective holding positions and contact the second electrodes of the photoelectric conversion elements positioned at the respective holding positions to electrically connect the external circuit and the photoelectric conversion elements;
The present invention is characterized in that it comprises
Power generation equipment. The plurality of photoelectric conversion elements are arranged such that the second electrode is located deeper than the first electrode with respect to a light irradiation direction.
The power generating device according to claim 1 . The photoelectric conversion elements are arranged such that the stacking directions of the photoelectric conversion elements are parallel to each other.
The power generating device according to claim 1 .

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