JPWO2019167227A1 - Photoelectric conversion element and photoelectric conversion module - Google Patents

Abstract

It is an object of the present invention to provide a photoelectric conversion element capable of efficiently photoelectrically converting incident light and a photoelectric conversion module including the photoelectric conversion element. The photoelectric conversion element according to the present invention is formed by at least a transparent substrate (2), a first transparent electrode (3) formed on the transparent substrate (2), and a laminate formed on the first transparent electrode (3). Three photoelectric conversion layers (7, 8, 9) and a second transparent electrode (5) formed on the uppermost photoelectric conversion layer (9) of each photoelectric conversion layer (7, 8, 9) are provided. Each of the photoelectric conversion layers (7, 8, 9) has a light absorption layer (12), and the photoelectric conversion layer (8) is not in contact with the first transparent electrode (3) and the second transparent electrode (5). The light absorption layer (12) is a light absorption layer (12) of the photoelectric conversion layer (7) in contact with the first transparent electrode (3) and a light absorption layer of the photoelectric conversion layer (9) in contact with the second transparent electrode (5). Bandgap smaller than layer (12).

Description

  The present invention relates to a thin-film stacked photoelectric conversion element in which a plurality of photoelectric conversion layers are stacked, and a photoelectric conversion module including the photoelectric conversion element, and in particular, a photoelectric conversion element capable of receiving light on both opposing surfaces and a photoelectric conversion element including the photoelectric conversion element. Regarding the conversion module.

  In recent years, the introduction of solar power plants has been actively promoted. Demand for solar cells is expected as one of important distributed power sources, and demand is also expected for residential power generation applications. Furthermore, in the IoT (Internet of Things), in which various information is collected using a large number of sensors and the collected data is analyzed and used as big data, the solar cell needs to secure the operation power supply of a large number of sensors. In view of the above, attention has been paid to an energy harvesting element that does not require wiring cost.

  When a solar cell is used as an energy harvesting element in a house, an office, a factory, or the like, it is necessary to generate electricity with weak indoor lighting, unlike an outdoor place such as a solar power plant. In this case, a crystalline silicon solar cell generally used outdoors has a problem that the conversion loss of the photoelectric conversion when the incident light amount is reduced is large. Therefore, a thin-film solar cell using an amorphous silicon or organic thin film for a photoelectric conversion layer, whose conversion efficiency is unlikely to be reduced even with weak incident light, is used.

  In a thin-film silicon-based photoelectric conversion element represented by a solar cell using amorphous silicon, a thin-film stacked-type photoelectric conversion element in which two or more photoelectric conversion layers are stacked has been devised as one method for improving conversion efficiency. ing. In a thin-film laminated photoelectric conversion element, a photoelectric conversion layer having a large band gap is provided on the light incident side, and the photoelectric conversion layer has a band gap that decreases in order from the photoelectric conversion layer to the side opposite to the light incident side. By providing the layer, it is possible to efficiently perform photoelectric conversion over a wide wavelength range of incident light (for example, see Patent Document 1).

  In addition, in order to increase the output of the solar cell module, a solar cell module that adopts a double-sided light-receiving type, which is a structure that captures not only light incident from the front but also light incident on the back due to reflection from the surrounding environment etc. It has been devised (for example, see Patent Document 2).

JP 2002-237608 A Japanese Patent Application Laid-Open No. 2000-243989

  Conventionally, even for a photoelectric conversion element of a thin film lamination type having a high conversion efficiency, even if a structure capable of receiving light on both opposing surfaces in order to capture light incident from a plurality of light sources such as indoors as much as possible, There is a problem that the band gap arrangement is not optimal for the light incident from the back side, and the conversion efficiency of the photoelectric conversion is reduced.

  Patent Literature 1 is based on the premise that light is incident from one direction, and has a problem that light such as indoor lighting that enters from various directions cannot be incident on the photoelectric conversion element. Patent Document 2 discloses a module structure that allows light to enter from both sides. In this module structure, a back electrode of a thin-film laminated photoelectric conversion element as disclosed in Patent Document 1 is provided. Even if the material is changed and arranged, there is a problem that light incident from the back side cannot be efficiently photoelectrically converted. Thus, conventionally, there is room for improvement in the efficiency of photoelectric conversion.

  The present invention has been made to solve such a problem, and it is an object of the present invention to provide a photoelectric conversion element capable of efficiently performing photoelectric conversion on incident light and a photoelectric conversion module including the photoelectric conversion element. Aim.

  In order to solve the above problems, a photoelectric conversion element according to the present invention includes a transparent substrate, a first transparent electrode formed on the transparent substrate, and at least three photoelectric layers stacked on the first transparent electrode. A conversion layer, and a second transparent electrode formed on the uppermost photoelectric conversion layer of the photoelectric conversion layers. Each photoelectric conversion layer has a light absorbing layer, and includes a first transparent electrode and a second transparent electrode. The light absorption layer of the photoelectric conversion layer not in contact with the electrode has a smaller band gap than the light absorption layer of the photoelectric conversion layer in contact with the first transparent electrode and the light absorption layer of the photoelectric conversion layer in contact with the second transparent electrode.

  According to the present invention, a photoelectric conversion element includes: a transparent substrate; a first transparent electrode formed on the transparent substrate; at least three photoelectric conversion layers formed by stacking on the first transparent electrode; A second transparent electrode formed on the uppermost photoelectric conversion layer of the conversion layers, wherein each photoelectric conversion layer has a light absorbing layer and is not in contact with the first transparent electrode and the second transparent electrode. The light absorbing layer has a smaller band gap than the light absorbing layer of the photoelectric conversion layer in contact with the first transparent electrode and the light absorbing layer of the photoelectric conversion layer in contact with the second transparent electrode. It can be converted.

  The objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description and the accompanying drawings.

FIG. 1 is a cross-sectional view illustrating an example of a configuration of a photoelectric conversion element according to a first embodiment of the present invention. FIG. 2 is a cross-sectional view illustrating an example of a configuration of a photoelectric conversion layer according to Embodiment 1 of the present invention. FIG. 3 is a diagram illustrating an example of an energy band structure of a photoelectric conversion layer according to the first embodiment of the present invention. It is a figure showing an example of a wavelength spectrum of light of a white LED. FIG. 3 is a diagram illustrating an example of an energy band structure of each photoelectric conversion layer according to the first embodiment of the present invention. It is a figure showing an example of a wavelength spectrum of light of a white LED. FIG. 9 is a diagram illustrating an example of a result obtained by simulating output characteristics of a photoelectric conversion element when amorphous silicon carbide is used as a light absorption layer. FIG. 3 is a diagram illustrating an example of incident light intensity dependence of an open circuit voltage and a short circuit current of the photoelectric conversion element according to the first embodiment of the present invention. FIG. 7 is a cross-sectional view illustrating an example of a configuration of a photoelectric conversion element according to a second embodiment of the present invention. FIG. 9 is a cross-sectional view illustrating an example of a configuration of a photoelectric conversion element according to a third embodiment of the present invention. FIG. 4 is a diagram for explaining the behavior of electrons and holes in each photoelectric conversion layer according to the first embodiment of the present invention. FIG. 10 is a diagram for explaining the behavior of electrons and holes in each photoelectric conversion layer according to the third embodiment of the present invention. FIG. 13 is a cross-sectional view illustrating an example of a configuration of a photoelectric conversion module according to Embodiment 4 of the present invention. FIG. 13 is a cross-sectional view illustrating an example of a configuration of a photoelectric conversion module according to Embodiment 4 of the present invention. FIG. 13 is a top view illustrating an example of a configuration of a photoelectric conversion module according to Embodiment 4 of the present invention. FIG. 13 is a cross-sectional view illustrating an example of a configuration of a photoelectric conversion module according to Embodiment 5 of the present invention. FIG. 14 is a cross-sectional view illustrating an example of a configuration of a photoelectric conversion module according to Embodiment 6 of the present invention. FIG. 14 is a cross-sectional view illustrating an example of a configuration of a photoelectric conversion module according to Embodiment 6 of the present invention. It is A1-A2 sectional drawing of FIG. FIG. 14 is a cross-sectional view illustrating an example of a configuration of a photoelectric conversion module according to Embodiment 7 of the present invention. It is sectional drawing which shows an example of a structure of the photoelectric conversion element by base technology. It is a figure showing an example of the energy band structure of each photoelectric conversion layer by a base technology. It is a figure showing an example of the energy band structure of each photoelectric conversion layer by a base technology.

  Embodiments of the present invention will be described below with reference to the drawings.

<Prerequisite technology>
The base technology of the embodiment of the present invention will be described.

  FIG. 21 is a cross-sectional view illustrating an example of the configuration of the photoelectric conversion element 40 according to the base technology.

  As shown in FIG. 21, a first transparent electrode 42 is formed on a transparent substrate 41. On the first transparent electrode 42, a first photoelectric conversion layer 43, a second photoelectric conversion layer 44, and a third photoelectric conversion layer 45 are sequentially laminated. The second transparent electrode 46 is formed on the third photoelectric conversion layer 45.

  FIG. 22 is a diagram illustrating an example of the energy band structure of each of the photoelectric conversion layers 43, 44, and 45 according to the base technology. Note that FIG. 22 illustrates an example in which the structure of Patent Document 1 is applied to the photoelectric conversion element 40 illustrated in FIG. The photoelectric conversion element 40 having the energy band structure illustrated in FIG. 22 receives light incident from one direction.

  In FIG. 22, Eg1 indicates the band gap of the first photoelectric conversion layer 43, Eg2 indicates the band gap of the second photoelectric conversion layer 44, and Eg3 indicates the band gap of the third photoelectric conversion layer 45. EL indicates the light energy of the incident light. As shown in FIG. 22, a first photoelectric conversion layer 43, a second photoelectric conversion layer 44, and a third photoelectric conversion layer 45 are formed such that the band gap becomes smaller in order from the transparent substrate 41 side which is the light incident side. I have. That is, the relationship of Eg1> Eg2> Eg3 holds.

  In such a configuration, of the incident light, light having high light energy is absorbed by the first photoelectric conversion layer 43 having the largest band gap Eg1, and photoelectric conversion is performed. In addition, light having low light energy among the incident light is absorbed by the second photoelectric conversion layer 44 and the third photoelectric conversion layer 45 whose band gap is smaller than that of the first photoelectric conversion layer 43, and photoelectric conversion is performed. As described above, the photoelectric conversion element having the energy band structure illustrated in FIG. 22 can efficiently perform photoelectric conversion over a wide wavelength range of incident light.

  The photoelectric conversion element having the energy band structure illustrated in FIG. 22 is based on the assumption that light is incident from one direction. However, for example, when a photoelectric conversion element is used in a house indoors, an office, or a factory, unlike the outdoors such as a solar power plant, light incident from indoor lighting installed in various places is assumed. However, the photoelectric conversion element having the energy band structure shown in FIG. 22 has a problem that light such as room lighting that enters from various directions cannot be photoelectrically converted efficiently.

  FIG. 23 is a diagram illustrating an example of the energy band structure of each of the photoelectric conversion layers 43, 44, and 45 according to the base technology. FIG. 23 illustrates an example in which the structure of Patent Document 2 is applied to the photoelectric conversion element 40 illustrated in FIG. In the photoelectric conversion element 40 having the energy band structure shown in FIG. 23, light enters both opposing surfaces.

  In FIG. 23, Eg1 indicates the band gap of the first photoelectric conversion layer 43, Eg2 indicates the band gap of the second photoelectric conversion layer 44, and Eg3 indicates the band gap of the third photoelectric conversion layer 45. ELR indicates the light energy of the rear incident light. Here, the back side incident light refers to light incident from the second transparent electrode 46 side. The relationship between the energy gaps of the photoelectric conversion layers 43, 44, and 45 is the same as that in FIG. Although not shown, light also enters from the transparent substrate 41 side.

  In the configuration shown in FIG. 23, the light incident on the back surface is absorbed by the third photoelectric conversion layer 45 having the smallest band gap Eg3, and photoelectric conversion is performed. At this time, energy for ELR-Eg3 is lost. As described above, the photoelectric conversion element having the energy band structure shown in FIG. 23 can efficiently perform photoelectric conversion on incident light incident from the transparent substrate 41 side, but efficiently perform photoelectric conversion on backside incident light. Can not do it. In addition, considering the characteristics of LED (Light Emitting Diode) light sources that have been widely adopted due to recent demands for energy saving, it is considered that the influence of the above-described loss increases.

  The embodiment of the present invention has been made to solve such a problem, and will be described in detail below.

<First Embodiment>
<Structure>
FIG. 1 is a cross-sectional view illustrating an example of a configuration of a photoelectric conversion element 1 according to Embodiment 1 of the present invention.

  As shown in FIG. 1, a first transparent electrode 3 is formed on a transparent substrate 2 which is a support substrate. On the first transparent electrode 3, a first photoelectric conversion layer 7, a second photoelectric conversion layer 8, and a third photoelectric conversion layer 9 are sequentially laminated and formed. The first photoelectric conversion layer 7, the second photoelectric conversion layer 8, and the third photoelectric conversion layer 9 constitute the photoelectric conversion region 4. The second transparent electrode 5 is formed on the third photoelectric conversion layer 9. A sealant 6 is formed on the second transparent electrode 5.

  The transparent substrate 2 is made of a material that can withstand a process of forming a photoelectric conversion layer at about 100 ° C. to 300 ° C., such as glass, plastic, or a resin sheet.

  The first transparent electrode 3 and the second transparent electrode 5 are made of a metal oxide such as tin oxide, titanium oxide, indium tin oxide, magnesium oxide, and zinc oxide, and are formed by sputtering, metal organic chemical vapor deposition (Metal Organic Chemical Vapor Deposition). : MOCVD) method or an evaporation method.

  The first photoelectric conversion layer 7, the second photoelectric conversion layer 8, and the third photoelectric conversion layer 9 are formed by using a material that can perform photoelectric conversion. For example, in addition to an amorphous silicon-based material whose band gap can be controlled by changing a composition ratio, a polycrystalline silicon-based material or a microcrystalline silicon-based material is used, and a sputtering method, a plasma chemical vapor deposition (Chemical It is desirable to form the first photoelectric conversion layer 7, the second photoelectric conversion layer 8, and the third photoelectric conversion layer 9 by a vapor deposition (CVD) method. Examples of the amorphous silicon-based material include amorphous silicon, amorphous silicon oxide, amorphous silicon carbide, amorphous silicon nitride, and amorphous germanium. Further, the first photoelectric conversion layer 7, the second photoelectric conversion layer 8, and the third photoelectric conversion layer are formed using an organic molecular material such as fullerene or a π-conjugated polymer capable of controlling a wavelength band to be absorbed by a molecular structure. 9 may be formed.

  The sealant 6 is made of a resin material such as ethylene-vinyl acetate copolymer (EVA) in order to protect the photoelectric conversion element 1 from invasion of moisture, invasion of outside air, or physical damage.

  FIG. 2 is a cross-sectional view illustrating an example of the configuration of the photoelectric conversion layer 10. The photoelectric conversion layer 10 is representative of the first photoelectric conversion layer 7, the second photoelectric conversion layer 8, and the third photoelectric conversion layer 9 shown in FIG. That is, each of the first photoelectric conversion layer 7, the second photoelectric conversion layer 8, and the third photoelectric conversion layer 9 has the same configuration as the photoelectric conversion layer 10 shown in FIG.

  As shown in FIG. 2, the photoelectric conversion layer 10 includes a P-type semiconductor layer 11, a light absorption layer 12 made of an intrinsic semiconductor, and an N-type semiconductor layer 13. The light absorbing layer 12 is formed on the P-type semiconductor layer 11, and the N-type semiconductor layer 13 is formed on the light absorbing layer 12.

  FIG. 3 is a diagram illustrating an example of the energy band structure of the photoelectric conversion layer 10.

  As shown in FIG. 3, the electron-hole pairs generated by absorbing the incident light in the light absorbing layer 12 are generated by the electric field generated in the light absorbing layer 12 due to the potential difference between the P-type semiconductor layer 11 and the N-type semiconductor layer 13. Separated and taken out. At this time, if there is an energy difference between the light energy EL of the incident light and the band gap Eg of the light absorbing layer 12, the electrons having received the light energy of the EL are once excited to a higher energy level, Energy corresponding to EL-Eg corresponding to the difference between the level and the band gap Eg is emitted as heat. The energy released at this time is a loss during photoelectric conversion.

  FIG. 4 is a diagram illustrating an example of a wavelength spectrum of light of a white LED used as indoor lighting.

  Sunlight includes light of a wide range of energy having a wavelength of about 300 nm to 1200 nm. On the other hand, a white LED includes only light having a wavelength of about 400 nm to 700 nm and short wavelength light having relatively high energy. Therefore, when a photoelectric conversion layer having a small band gap is provided on the light incident side, the effect of photoelectric conversion loss due to this is considered to be much greater than when used outdoors.

  FIG. 5 is a diagram illustrating an example of an energy band structure in each of the first photoelectric conversion layer 7, the second photoelectric conversion layer 8, and the third photoelectric conversion layer 9 according to the first embodiment.

  As shown in FIG. 5, in the photoelectric conversion element 1 according to the first embodiment, the second photoelectric conversion layer 8 having the smallest band gap Eg2 includes the first photoelectric conversion layer 7, the second photoelectric conversion layer 8, and the second photoelectric conversion layer 8. It is formed at the center of the three photoelectric conversion layers 9. That is, the photoelectric conversion layer having the smallest band gap is formed at the center of the stacked photoelectric conversion layers in the stacking direction.

  Further, regarding the first photoelectric conversion layer 7 and the third photoelectric conversion layer 9 having the largest band gaps Eg1 and Eg3, the first photoelectric conversion layer 7 is formed so as to be adjacent to the first transparent electrode 3, and the third photoelectric conversion layer 7 is formed. The conversion layer 9 is formed so as to be adjacent to the second transparent electrode 5. With such a configuration, the first photoelectric conversion layer 7 and the second photoelectric conversion layer 8 having a smaller band gap than the first photoelectric conversion layer 7 are provided on the side where the incident light of the light energy EL is incident. Since they are formed in order, loss during photoelectric conversion can be reduced. In addition, the third photoelectric conversion layer 9 and the second photoelectric conversion layer 8 having a smaller band gap than the third photoelectric conversion layer 9 are sequentially formed on the side where the incident light of the light energy ELR is incident. Loss during photoelectric conversion can be reduced.

<Detailed Study of Photoelectric Conversion Element According to First Embodiment>
The results of a detailed study of the photoelectric conversion element according to the first embodiment by the inventors will be described.

  Assuming indoor use, a simulation of the structure of the photoelectric conversion element was performed when a white LED having a wavelength spectrum as shown in FIG. 6 was used as a light source. As shown in FIG. 6, most of the currently marketed white LEDs have a characteristic in which two peaks having wavelengths around 450 nm and 570 nm overlap each other.

  The thickness of the photoelectric conversion region 4 varies depending on what material is used for the first photoelectric conversion layer 7, the second photoelectric conversion layer 8, and the third photoelectric conversion layer 9, but the thickness of the first photoelectric conversion layer 7, Since the photocurrent generated by each of the second photoelectric conversion layer 8 and the third photoelectric conversion layer 9 needs to match, the absorption coefficient of the material used and the wavelength spectrum characteristics of the incident light as shown in FIG. And can be calculated based on

  Considering that all incident light is absorbed and used for photoelectric conversion, the light absorbing layer 12 needs to have a certain thickness. On the other hand, particularly in the light absorption layer 12 of the second photoelectric conversion layer 8 having the smallest band gap, when light does not reach the entire region of the light absorption layer 12, the region where the light does not reach has high resistance and the photoelectric conversion efficiency is high. Will decrease. Therefore, it is necessary to calculate the film thickness tmax at which the light absorption layer 12 of the second photoelectric conversion layer 8 can almost completely absorb the incident light, and make the film thickness of the second photoelectric conversion layer 8 not exceed the film thickness tmax. There is.

  It is considered that the thickest film thickness condition is a state in which each of the incident lights incident from both sides is completely absorbed by the second photoelectric conversion layer 8 and does not enter the subsequent stage. Therefore, since the film thickness condition is applied to each of the two sides as viewed from the second photoelectric conversion layer 8, it is desirable to design the upper limit of the thickness of the photoelectric conversion region 4 to be twice the film thickness tmax. . By substituting the absorption coefficient α and the film thickness t into the following equation (1) representing the transmittance T, it is possible to calculate the limit film thickness tmax that can absorb all the light of the target wavelength. A value twice as large as the film thickness tmax obtained by Expression (1) is the upper limit of the thickness of the photoelectric conversion region 4.

T = e− ^αt (1)

  For example, when the light absorption layer 12 of the second photoelectric conversion layer 8 is formed of amorphous silicon, the above equation (1) is calculated using the absorption coefficient α of the amorphous silicon. If the film thickness of the layer 12 is about 4000 nm, the amount of light entering the rear stage of the light absorption layer 12 of the second photoelectric conversion layer 8 is 10% or less. However, in the case of a photoelectric conversion element formed using an amorphous silicon-based material, considering that the built-in electric field is likely to decrease with an increase in film thickness, and that the voltage and the fill factor decrease, the photoelectric conversion region 4 It is desirable that the film thickness be 1000 nm or less.

  In the case of a stacked photoelectric conversion element in which a plurality of photoelectric conversion layers are electrically connected in series, such as the photoelectric conversion element 1 according to Embodiment 1, the photocurrent generated in each photoelectric conversion layer It is important that the design be made equal. Since the photoelectric conversion layers are connected in series, the voltage of the entire photoelectric conversion element 1 is the sum of the voltages generated by the photoelectric conversion layers. On the other hand, the current of the entire photoelectric conversion element 1 is limited to the value of the photoelectric conversion layer having the smallest current value among the photoelectric conversion layers. The current mismatch, which is the difference between the photocurrents generated between the photoelectric conversion layers, is re-coupled inside the photoelectric conversion element without being taken out of the photoelectric conversion element, resulting in heat loss.

  When determining the structure of the stacked photoelectric conversion element, it is necessary to design so that the photocurrent generated in each photoelectric conversion layer matches to reduce the loss due to the current mismatch. Is incident, and a plurality of photoelectric conversion layers are laminated to form a structure.

  On the other hand, as in the photoelectric conversion element 1 according to the first embodiment, each photoelectric conversion layer is positioned from the photoelectric conversion layer located at the center of the plurality of photoelectric conversion layers toward the transparent electrode formed on each of both surfaces. By adopting a structure in which the band gap of the conversion layer is symmetrically increased, it is not necessary to individually design each photoelectric conversion layer on each of the two surfaces on which light is incident. The structure in which the conversion layer is optimally designed can be directly applied to the other surface. However, for the photoelectric conversion layer located at the center of the plurality of photoelectric conversion layers, the light having the longest wavelength, that is, the light having the smallest light energy is incident from both surfaces on which the light is incident, so that the assigned incident energy is one side. It is necessary to design in consideration of the fact that the incident energy is doubled when light is incident only on the light.

When three photoelectric conversion layers of the first photoelectric conversion layer 7, the second photoelectric conversion layer 8, and the third photoelectric conversion layer 9 are used as in the photoelectric conversion element 1 according to the first embodiment, incident light is It is necessary to consider how to divide. Assuming a white LED light source as shown in FIG. 4, the total number of photons of light incident from one surface is about 1.7 × 10 ¹⁵ cm ⁻² . It is necessary to divide this into each of the first photoelectric conversion layer 7, the second photoelectric conversion layer 8, and the third photoelectric conversion layer 9 to perform current matching. The first photoelectric conversion layer 7 and the third photoelectric conversion layer 9 only need to be able to use ／ of the total number of photons of light incident from one surface. In the second photoelectric conversion layer 8, light is incident from both surfaces, so that it is sufficient that one-third of the total number of photons of light incident from one surface can be used. When this is applied to the wavelength of light, the first photoelectric conversion layer 7 and the third photoelectric conversion layer 9 use light having a wavelength shorter than 600 nm, and the second photoelectric conversion layer 8 uses light having a wavelength longer than 600 nm. Is used, the current values obtained from each of the first photoelectric conversion layer 7, the second photoelectric conversion layer 8, and the third photoelectric conversion layer 9 match. Therefore, the band gap of the first photoelectric conversion layer 7 and the third photoelectric conversion layer 9 is desirably 2.05 eV or less. When a material having a band gap higher than 2.05 eV is used for the first photoelectric conversion layer 7 and the third photoelectric conversion layer 9, the current obtained from the first photoelectric conversion layer 7 and the third photoelectric conversion layer 9 decreases, Is reduced, that is, the difference from the current obtained in the second photoelectric conversion layer 8 is a loss.

  When amorphous silicon having a band gap of about 1.7 eV is used for the second photoelectric conversion layer 8, almost all light emitted from the white LED can be absorbed by the second photoelectric conversion layer 8. Therefore, the above-described calculation of the photon split use can be applied as it is, and a material having a band gap of 1.7 eV to 2.05 eV can be used for the first photoelectric conversion layer 7 and the third photoelectric conversion layer 9. desirable. For example, by adjusting the carbon or oxygen content of amorphous silicon carbide or amorphous silicon oxide, the above band gap condition can be easily satisfied.

  FIG. 7 is a diagram illustrating an example of a result obtained by simulating the output characteristics of the photoelectric conversion element when the light absorption layer 12 is formed of amorphous silicon carbide. Specifically, the output of the photoelectric conversion element when monochromatic light having a wavelength of 600 nm is made incident on the first photoelectric conversion layer 7 and the third photoelectric conversion layer 9 having the light absorption layer 12 having a band gap of 2.05 eV. 9 shows an example of a result obtained by simulating characteristics. In FIG. 7, each value is normalized by the maximum value.

  As shown in FIG. 7, the current increases as the thickness of the light absorbing layer 12 increases, but recombination increases inside the light absorbing layer 12, so that when the thickness of the light absorbing layer 12 exceeds 400 nm, It is going down. The fill factor decreases as the thickness of the light absorbing layer 12 increases. Therefore, it can be seen that the photoelectric conversion efficiency increases when the thickness of the light absorption layer 12 is between 100 nm and 400 nm, and more preferably between 100 nm and 300 nm. Table 1 shows that the first photoelectric conversion layer 7 and the second photoelectric conversion layer 8 when the total film thickness of the photoelectric conversion region 4 is 500 nm or 750 nm under the condition that the light of the white LED having the same intensity is incident on both surfaces. 3 shows the result of calculating the film thickness of each light absorbing layer 12 at which the photocurrent obtained from each light absorbing layer 12 of the third photoelectric conversion layer 9 becomes equal. In Table 1, "total film thickness" indicates the total film thickness of the photoelectric conversion region 4, "first photoelectric conversion layer 7" indicates the film thickness of the light absorption layer 12 of the first photoelectric conversion layer 7, and "second film thickness". The “photoelectric conversion layer 8” indicates the thickness of the light absorption layer 12 of the second photoelectric conversion layer 8, and the “third photoelectric conversion layer 9” indicates the thickness of the light absorption layer 12 of the third photoelectric conversion layer 9. .

<Production method>
A method for manufacturing the photoelectric conversion element 1 according to the first embodiment will be described.

  First, zinc oxide as a material of the first transparent electrode 3 is formed on a non-alkali glass as the transparent substrate 2 by a metal organic chemical vapor deposition method so as to have a film thickness of 500 nm to 700 nm. Thereby, the first transparent electrode 3 is formed. The thickness of the first transparent electrode 3 can be appropriately changed based on the conductivity, transmittance, and light scattering characteristics of the first transparent electrode 3, but the photoelectric conversion region made of amorphous silicon formed later will be described. If the photoelectric conversion region 4 has a steep unevenness depending on the thickness of the film 4, a defect easily occurs inside the photoelectric conversion region 4, which causes a leak current. Therefore, in the first embodiment, the first transparent electrode 3 is formed to have a small film thickness so that the surface of the first transparent electrode 3 is flat.

  Next, the first photoelectric conversion layer 7, the second photoelectric conversion layer 8, and the third photoelectric conversion layer 9 are formed on the first transparent electrode 3 such that the total film thickness of the photoelectric conversion region 4 is 750 nm. They are formed by sequentially stacking them by a vapor phase growth method. Table 2 shows the growth conditions for the light absorption layer 12 of each of the first photoelectric conversion layer 7, the second photoelectric conversion layer 8, and the third photoelectric conversion layer 9. In Table 2, “second photoelectric conversion layer 8” indicates the light absorption layer 12 of the second photoelectric conversion layer 8, and “first and third photoelectric conversion layers 7, 9” indicate the first photoelectric conversion layer 7 and the third photoelectric conversion layer 7. Each light absorption layer 12 of the photoelectric conversion layer 9 is shown.

As shown in Table 2, for the second photoelectric conversion layer 8, silane (SiH ₄ ) is used as a silicon source gas, and the source gas is diluted with hydrogen (H ₂ ) to form a light absorption layer made of amorphous silicon. 12 is formed. The first photoelectric conversion layer 7 and the third photoelectric conversion layer 9 use silane (SiH ₄ ) as a source gas of silicon, and use the source gas as compared with the time of forming the light absorption layer 12 of the second photoelectric conversion layer 8. Amorphous silicon carbide having a larger band gap than the light absorption layer 12 of the second photoelectric conversion layer 8 by diluting with a large amount of hydrogen (H ₂ ) and increasing the substrate temperature to introduce carbon dioxide (CO ₂ ). Is formed.

  The band gap of amorphous silicon carbide obtained under the growth conditions shown in Table 2 is about 0.2 eV larger than the band gap of amorphous silicon. The band gap of the amorphous silicon carbide forming the light absorption layer 12 of each of the first photoelectric conversion layer 7 and the third photoelectric conversion layer 9 is the band gap of the amorphous silicon forming the light absorption layer 12 of the second photoelectric conversion layer 8. Since it is 1.9 eV, which is 0.2 eV higher than the above, it is within the optimum value of the band gap of the first photoelectric conversion layer 7 and the third photoelectric conversion layer 9 described above.

  The P-type semiconductor layer 11 and the N-type semiconductor layer 13 in each of the first photoelectric conversion layer 7, the second photoelectric conversion layer 8, and the third photoelectric conversion layer 9 are formed under common conditions. The P-type semiconductor layer 11 is formed of wide band gap amorphous silicon carbide. The N-type semiconductor layer 13 is formed using microcrystalline silicon having high conductivity.

  Next, zinc oxide, which is a material of the second transparent electrode 5, is formed on the third photoelectric conversion layer 9 by metal organic chemical vapor deposition so as to have a thickness of 500 nm to 700 nm.

  FIG. 8 is a diagram illustrating an example of incident light intensity dependence of the open-circuit voltage and the short-circuit current of the photoelectric conversion element 1 according to the first embodiment of the present invention.

  As shown in FIG. 8, the short-circuit current strongly depends on the incident light intensity, but the open circuit voltage is kept at about 2 V even when the incident light intensity is low. When this is converted into a value per one layer of the first photoelectric conversion layer 7, the second photoelectric conversion layer 8, and the third photoelectric conversion layer 9, the voltage is 0.78 V, which is an open voltage of a general amorphous silicon solar cell. Is higher than 0.6V to 0.7V. That is, an effect is obtained by forming the first photoelectric conversion layer 7 and the third photoelectric conversion layer 9 having a large band gap on both sides of the second photoelectric conversion layer 8 having a small band gap. In addition, the deterioration of the characteristics of the photoelectric conversion element 1 caused by sandwiching the second photoelectric conversion layer 8 having a small band gap between the first photoelectric conversion layer 7 and the third photoelectric conversion layer 9 having a large band gap is caused under the present manufacturing conditions. Not seen.

  From the above, according to the first embodiment, in the photoelectric conversion element capable of receiving light on both opposing surfaces, the plurality of first photoelectric conversion layers 7, the second photoelectric conversion layers 8, and the third photoelectric conversion layers 9 are formed. The band gap of the light absorption layer 12 of the second photoelectric conversion layer 8 which is formed in a laminated manner and is located at the center is equal to that of the light absorption layer 12 of the first photoelectric conversion layer 7 in contact with the first transparent electrode 3 and the second light absorption layer. It is smaller than the band gap of the light absorption layer 12 of the third photoelectric conversion layer 9 in contact with the transparent electrode 5. Therefore, light incident from a plurality of light sources can be efficiently photoelectrically converted.

<Embodiment 2>
FIG. 9 is a cross-sectional view illustrating an example of the configuration of the photoelectric conversion element 14 according to Embodiment 2 of the present invention.

  As shown in FIG. 9, the photoelectric conversion element 14 includes a fourth photoelectric conversion layer 15 between the first photoelectric conversion layer 7 and the second photoelectric conversion layer 8, and the second photoelectric conversion layer 8 and the third photoelectric conversion layer 8. A feature is that a fifth photoelectric conversion layer 16 is provided between the layer and the layer 9. Other configurations are the same as those of the photoelectric conversion element 1 according to the first embodiment, and a detailed description thereof will not be repeated.

  The fourth photoelectric conversion layer 15 includes a plurality of fourth photoelectric conversion layers 151 to a fourth photoelectric conversion layer 15x. Each of the fourth to fourth photoelectric conversion layers 151 to 15x has the same configuration as the photoelectric conversion layer 10 shown in FIG. The band gap of each of the fourth photoelectric conversion layer 151 to the fourth photoelectric conversion layer 15x is formed so as to increase from the second photoelectric conversion layer 8 to the first photoelectric conversion layer 7. That is, the relationship of the band gap of the second photoelectric conversion layer 8 <the band gap of the fourth photoelectric conversion layer 151 <... <the band gap of the fourth photoelectric conversion layer 15x <the first photoelectric conversion layer 7 is satisfied.

  The fifth photoelectric conversion layer 16 includes a plurality of fifth photoelectric conversion layers 161 to fifth photoelectric conversion layers 16x. Each of the fifth to fifth photoelectric conversion layers 161 to 16x has the same configuration as the photoelectric conversion layer 10 shown in FIG. The band gap of each of the fifth photoelectric conversion layer 161 to the fifth photoelectric conversion layer 16x is formed so as to increase from the second photoelectric conversion layer 8 to the third photoelectric conversion layer 9. That is, the relationship of the band gap of the second photoelectric conversion layer 8 <the band gap of the fifth photoelectric conversion layer 161 <... <the band gap of the fifth photoelectric conversion layer 16x <the third photoelectric conversion layer 9 is satisfied.

  Table 3 shows that the first photoelectric conversion layer 7 and the second photoelectric conversion layer 8 when the total film thickness of the photoelectric conversion region 4 is 500 nm or 750 nm under the condition that the light of the white LED having the same intensity is incident on both surfaces. Of the thickness of each light absorption layer 12 in which the photocurrent obtained from each light absorption layer 12 of each of the third photoelectric conversion layer 9, the fourth photoelectric conversion layer 15, and the fifth photoelectric conversion layer 16 becomes equal Is shown.

  In Table 3, “total film thickness” indicates the total film thickness of the photoelectric conversion region 4, “first photoelectric conversion layer 7” indicates the film thickness of the light absorption layer 12 of the first photoelectric conversion layer 7, “Photoelectric conversion layer 15” indicates the thickness of the light absorption layer 12 of the fourth photoelectric conversion layer 15, “second photoelectric conversion layer 8” indicates the thickness of the light absorption layer 12 of the second photoelectric conversion layer 8, The “fifth photoelectric conversion layer 16” indicates the thickness of the light absorption layer 12 of the fifth photoelectric conversion layer 16, and the “third photoelectric conversion layer 9” indicates the thickness of the light absorption layer 12 of the third photoelectric conversion layer 9. ing.

  From the above, according to Embodiment 2, the fourth photoelectric conversion layer 15 is formed between the first photoelectric conversion layer 7 and the second photoelectric conversion layer 8, and the second photoelectric conversion layer 8 and the third Since the fifth photoelectric conversion layer 16 is formed between the photoelectric conversion layer 9 and the first photoelectric conversion layer 7, the second photoelectric conversion layer 8, the third photoelectric conversion layer 9, the fourth photoelectric conversion layer 15, and Energy loss in each of the fifth photoelectric conversion layers 16 can be reduced as compared with the first embodiment. Here, the energy loss is represented by EL-Eg, where EL is the light energy of the incident light and Eg is the band gap of the photoelectric conversion layer.

  In the above description, for simplicity of calculation, the size of the energy gap, the thickness of each of the fourth photoelectric conversion layer 15 and the fifth photoelectric conversion layer 16, and the number of the photoelectric conversion layers are determined by the second photoelectric conversion layer. Although the case where the layer 8 is symmetrical with respect to the layer 8 has been described, the present invention is not limited to this. For example, only one of the fourth photoelectric conversion layer 15 and the fifth photoelectric conversion layer 16 may be formed. Further, the number of photoelectric conversion layers included in each of the fourth photoelectric conversion layer 15 and the fifth photoelectric conversion layer 16 does not necessarily need to be the same.

<Embodiment 3>
FIG. 10 is a cross-sectional view illustrating an example of the configuration of the photoelectric conversion element 17 according to Embodiment 3 of the present invention.

  As shown in FIG. 10, the photoelectric conversion element 17 includes a bonding layer 18 between the second photoelectric conversion layer 8 and the third photoelectric conversion layer 9. Other configurations are the same as those of the photoelectric conversion element 1 according to the first embodiment, and a detailed description thereof will not be repeated.

  FIG. 11 illustrates the behavior of electrons and holes in each of the first, second, and third photoelectric conversion layers 7, 8, and 9 of the photoelectric conversion element 1 according to the first embodiment. FIG. The photoelectric conversion element 1 according to the first embodiment does not include the bonding layer 18.

  As shown in FIG. 11, the energy level of the valence band in the N-type semiconductor layer 13 of the second photoelectric conversion layer 8 is higher than the energy level of the valence band in the P-type semiconductor layer 11 of the third photoelectric conversion layer 9. May also be present on the high energy side. In the stacked photoelectric conversion element, ideally, at the ends of the second photoelectric conversion layer 8 and the third photoelectric conversion layer 9, the electrons existing in the N-type semiconductor layer 13 of the second photoelectric conversion layer 8 and the second It is considered that electrical continuity is maintained by one-to-one recombination of holes existing in the P-type semiconductor layer 11 of the photoelectric conversion layer 9 adjacent to the two photoelectric conversion layers 8.

  However, when the energy levels of the first photoelectric conversion layer 7, the second photoelectric conversion layer 8, and the third photoelectric conversion layer 9 have a relationship as shown in FIG. Some holes remain in the interface of the second photoelectric conversion layer 8 without recombination of holes present in the semiconductor layer 11 with electrons present in the N-type semiconductor layer 13 of the second photoelectric conversion layer 8. In such a state, there is no hole recombination partner in the P-type semiconductor layer 11 of the second photoelectric conversion layer 8, and electron recombination in the N-type semiconductor layer 13 of the second photoelectric conversion layer 8. However, there is a possibility that recombination loss may occur due to these factors.

  In order to solve such a problem, as shown in FIG. 12, the photoelectric conversion element 17 according to the third embodiment has electrons and positive electrons between the second photoelectric conversion layer 8 and the third photoelectric conversion layer 9. A bonding layer 18 is formed to assist recombination with the holes. As shown in FIG. 12, the electrons of the second photoelectric conversion layer 8 and the holes of the third photoelectric conversion layer 9 are recombined at the trap level of the bonding layer 18.

  For the bonding layer 18, a P-type or N-type wide band gap semiconductor material having a valence band energy structure that hinders the movement of holes, or a material including many recombination levels inside the band gap is used. It is formed by this. Specifically, the bonding layer 18 is made of an amorphous silicon-based material doped with at least one of phosphorus and boron, a microcrystalline silicon-based material in which an amorphous silicon-based material is doped with a minute silicon-based crystal component, or a metal. The oxide is formed by a plasma enhanced chemical vapor deposition method, a sputtering method, an evaporation method, or the like. Examples of the amorphous silicon-based material include amorphous silicon, amorphous silicon oxide, and amorphous silicon carbide. Examples of the metal oxide include titanium oxide, tin oxide, zinc oxide, manganese oxide, and copper oxide. The bonding layer 18 may be a stack of metal oxides.

  When the bonding layer 18 is formed by a plasma enhanced chemical vapor deposition method, a sputtering method, or an evaporation method, the film formation rate of the bonding layer 18 is approximately several Å / sec. In addition, the thickness of the bonding layer 18 needs to be 1 nm or more in order to capture and recombine carriers. If the thickness of the bonding layer 18 is too large, the series resistance increases and light absorption loss occurs in the bonding layer 18. Therefore, the thickness of the bonding layer 18 is about the same as the P-type semiconductor layer 11 and the N-type semiconductor layer 13 in each of the first photoelectric conversion layer 7, the second photoelectric conversion layer 8, and the third photoelectric conversion layer 9. It is desirable that the thickness be 40 nm or less.

  From the above, according to the third embodiment, since the bonding layer 18 is formed between the second photoelectric conversion layer 8 and the third photoelectric conversion layer 9, the third photoelectric conversion layer having a large band gap is provided. Holes 9 can be prevented from remaining excessively in the second photoelectric conversion layer 8 having a small band gap, and recombination loss can be reduced.

<Embodiment 4>
FIG. 13 is a cross-sectional view illustrating an example of a configuration of a photoelectric conversion module 19 according to Embodiment 4 of the present invention.

  As shown in FIG. 13, the photoelectric conversion module 19 includes a photoelectric conversion element 20, a support member 21, and a cover 22. The photoelectric conversion element 20 corresponds to any of the photoelectric conversion elements described in Embodiments 1 to 3.

  The support member 21 supports the photoelectric conversion element 20 in a direction perpendicular to the ground plane. The support member 21 only needs to have strength enough to support the photoelectric conversion element 20 and attach the photoelectric conversion module 19 to the installation location. Further, as shown in FIG. 14, for example, a reflector 23 may be provided on the surface of the support 21 supporting the photoelectric conversion element 20. The reflection member 23 can be made of a metal plate, a white plastic, a reflection coating, a white paint, or the like. By providing the reflecting member 23, light incident on the reflecting member 23 can be reflected by the reflecting member 23 and incident on the photoelectric conversion element 20. That is, light incident on the photoelectric conversion element 20 can be increased.

  The cover 22 is provided so as to cover the entire photoelectric conversion element 20 and the support member 21 in order to protect the photoelectric conversion element 20 and the support member 21. The cover 22 is made of a translucent material such as glass or plastic. In FIG. 13, the shape of the cover 22 is a box shape, but may be any shape according to the design and ease of handling of the photoelectric conversion module. For example, the shape of the cover 22 may be a semicircular dome shape, a conical shape, a triangular pyramid shape, a quadrangular pyramid shape, or a spherical shape.

  The inside of the cover 22 may be hollow, but is not limited to this. For example, by filling the inside of the cover 22 with a high-molecular polymer used as a sealant for a photoelectric conversion element, the strength and durability of the photoelectric conversion module can be improved.

  In the photoelectric conversion module 19, for example, as shown in FIG. 14, a via hole or the like may be provided in the support member 21 and an extraction electrode 24 connected to the photoelectric conversion element 20 through the via hole. The power obtained by the photoelectric conversion by the photoelectric conversion element 20 is extracted to the outside via the extraction electrode 24.

  FIG. 15 is a top view of FIG. In FIG. 15, illustration of the support member 21 is omitted. As shown in FIG. 15, by providing the extraction electrode 24 along the surface of the photoelectric conversion element 20 on which light is incident, power can be extracted from the side surface of the photoelectric conversion module 19. Further, various sensors, an IC (Integrated Circuit) for signal processing, or a power storage element can be provided inside the photoelectric conversion module 19, for example, on the support member 21.

  As described above, according to the fourth embodiment, since the photoelectric conversion element 20 is supported in the direction perpendicular to the ground plane, light can be incident on both surfaces of the photoelectric conversion element 20.

  In the above, the case where the photoelectric conversion element 20 is provided in a direction perpendicular to the ground plane has been described. This is because when the photoelectric conversion element 20 is provided in a direction perpendicular to the ground plane, the photoelectric conversion element 20 is symmetrical in the left-right direction, so that the intensity of light incident on both surfaces can be easily designed. The photoelectric conversion element 20 can be provided obliquely with respect to the ground plane.

<Embodiment 5>
FIG. 16 is a cross-sectional view illustrating an example of a configuration of a photoelectric conversion module 25 according to Embodiment 5 of the present invention.

  As shown in FIG. 16, the photoelectric conversion module 25 includes a plurality of photoelectric conversion elements 26 and 27. Other configurations are the same as those of the fourth embodiment, and thus detailed description is omitted here.

  The photoelectric conversion elements 26 and 27 correspond to any of the photoelectric conversion elements described in Embodiments 1 to 3. The support member 21 supports each of the photoelectric conversion elements 26 and 27 in a direction perpendicular to the ground plane.

  Each of the photoelectric conversion elements 26 and 27 needs to be provided at a sufficient interval so that the photoelectric conversion elements 26 and 27 do not shade each other with respect to light from an external light source. Thereby, the output power with respect to the installation area of the photoelectric conversion elements 26 and 27 can be increased. In FIG. 16, the photoelectric conversion elements 26 and 27 are provided at both ends of the support member 21, but the invention is not limited to this. The photoelectric conversion elements 26 and 27 may be provided at any positions as long as they do not shadow each other. Further, the photoelectric conversion module 25 may include three or more photoelectric conversion elements. In this case as well, they may be provided at any positions as long as they do not become shadows.

  A high voltage output can be obtained by connecting the two photoelectric conversion elements 26 and 27 in series, and a high current output can be obtained by connecting the two photoelectric conversion elements 26 and 27 in parallel. Thereby, the characteristics of the electrical output of the photoelectric conversion module 25 can be changed.

  As described above, according to the fifth embodiment, since the plurality of photoelectric conversion elements 26 and 27 are supported in the direction perpendicular to the ground plane, light can be incident on both surfaces of the photoelectric conversion element 20. It becomes possible. In addition, by connecting the plurality of photoelectric conversion elements 26 and 27 in series or in parallel, it is possible to change the characteristics of the electrical output of the photoelectric conversion module 25.

<Embodiment 6>
FIG. 17 is a cross-sectional view illustrating an example of a configuration of a photoelectric conversion module 28 according to Embodiment 6 of the present invention.

  As shown in FIG. 17, the photoelectric conversion module 28 includes a photoelectric conversion element 29, a case 30, a mounting board 31, and a reflection member 23. The photoelectric conversion element 29 corresponds to any of the photoelectric conversion elements described in Embodiments 1 to 3. The reflecting member 23 corresponds to the reflecting member 23 described in the fourth embodiment.

  The photoelectric conversion element 29 is provided in the case 30 so as to be parallel to the reflector 23 with a space therebetween. In addition, in FIG. 17, the photoelectric conversion element 29 is provided in parallel with the reflection member 23, but is not limited thereto. For example, when light incident from a specific direction is dominant, the photoelectric conversion element 29 may be provided so as not to be parallel to the reflector 23, that is, to be inclined. Thereby, the light intensity incident on both surfaces of the photoelectric conversion element 29 can be made equal.

  In FIG. 17, the photoelectric conversion element 29 is provided directly on the case 30, but the present invention is not limited to this. For example, as shown in FIG. 18, a configuration may be adopted in which the photoelectric conversion element 33 is fixed by the support 34 inside the case 30. 19 is a cross-sectional view taken along line A1-A2 of FIG. 18, and is a view of FIG. 18 as viewed from below. As shown in FIG. 19, the four corners of the photoelectric conversion element 33 are supported by the support. Note that the number and shape of the supports 34 can be appropriately changed according to the size and shape of the photoelectric conversion element 33.

  From the above, according to the sixth embodiment, since the photoelectric conversion element 33 is provided in parallel with the reflector 23 with a space therebetween, the surface of the photoelectric conversion element 33 opposite to the reflector 23 is Light from a light source is incident, and light reflected by the reflector 23 is incident on the surface of the photoelectric conversion element 33 on the side of the reflector 23. Thereby, light can be incident on both surfaces of the photoelectric conversion element 33.

<Embodiment 7>
FIG. 20 is a cross-sectional view illustrating an example of a configuration of a photoelectric conversion module 35 according to Embodiment 7 of the present invention.

  As shown in FIG. 20, the photoelectric conversion module 35 is characterized by the shape of the reflection member 39 and the relationship between the photoelectric conversion element 36 and the reflection member 39. Other configurations are the same as those in the sixth embodiment, and thus detailed description is omitted here. The photoelectric conversion element 36 corresponds to any of the photoelectric conversion elements described in Embodiments 1 to 3. The reflecting member 23 corresponds to the reflecting member 23 described in the fourth embodiment.

  The reflection member 23 is curved in a concave shape with respect to the photoelectric conversion element 36, and can condense the light reflected by the reflection member 23 to the photoelectric conversion element 36. In addition, the area of the photoelectric conversion element 36 is smaller than the area of the reflector 39. Specifically, when the photoelectric conversion module 35 is viewed from above, the area Spv of the photoelectric conversion element 36 and the area Sref−Spv obtained by subtracting the area Spv of the photoelectric conversion element 36 from the area Sref of the reflective member 39 are substantially equal to each other. What is necessary is just to design so that it may become the same.

  From the above, according to the seventh embodiment, the reflecting member 23 is curved concavely with respect to the photoelectric conversion element 36, and the area of the photoelectric conversion element 36 is smaller than that of the reflecting member 39. The photoelectric conversion module 35 is installed in a place where straight traveling light is dominant, for example, in an environment where simulated parallel light enters, or in an environment where a point light source such as a spotlight having only one light source enters. Even in this case, it is possible to make light of the same light intensity enter both surfaces.

  In the present invention, each embodiment can be freely combined, or each embodiment can be appropriately modified or omitted within the scope of the invention.

  Although the present invention has been described in detail, the above description is illustrative in all aspects and the present invention is not limited thereto. It is understood that innumerable modifications that are not illustrated can be assumed without departing from the scope of the present invention.

  REFERENCE SIGNS LIST 1 photoelectric conversion element, 2 transparent substrate, 3 first transparent electrode, 4 photoelectric conversion region, 5 second transparent electrode, 6 sealant, 7 first photoelectric conversion layer, 8 second photoelectric conversion layer, 9 third photoelectric conversion Layer, 10 photoelectric conversion layer, 11 P-type semiconductor layer, 12 light absorption layer, 13 N-type semiconductor layer, 14 photoelectric conversion element, 15 fourth photoelectric conversion layer, 16 fifth photoelectric conversion layer, 17 photoelectric conversion element, 18 junction Layer, 19 photoelectric conversion module, 20 photoelectric conversion element, 21 support material, 22 cover, 23 reflection material, 24 extraction electrode, 25 photoelectric conversion module, 26, 27 photoelectric conversion element, 28 photoelectric conversion module, 29 photoelectric conversion element, 30 Case, 31 installation substrate, 32 photoelectric conversion module, 33 photoelectric conversion element, 34 support, 35 photoelectric conversion module, 36 photoelectric conversion element, 37 case, 38 Installation substrate, 39 reflector, 40 photoelectric conversion element, 41 transparent substrate, 42 first transparent electrode, 43 first photoelectric conversion layer, 44 second photoelectric conversion layer, 45 third photoelectric conversion layer, 46 second transparent electrode.

Claims (12)

A transparent substrate (2);
A first transparent electrode (3) formed on the transparent substrate (2);
At least three photoelectric conversion layers (7, 8, 9) laminated on the first transparent electrode (3);
A second transparent electrode (5) formed on the uppermost photoelectric conversion layer (9) of the photoelectric conversion layers (7, 8, 9);
With
Each of the photoelectric conversion layers (7, 8, 9) has a light absorption layer (12),
The light absorbing layer (12) of the photoelectric conversion layer (8) that is not in contact with the first transparent electrode (3) and the second transparent electrode (5) is the photoelectric conversion that is in contact with the first transparent electrode (3). The band gap is smaller than that of the light absorbing layer (12) of the layer (7) and the light absorbing layer (12) of the photoelectric conversion layer (9) in contact with the second transparent electrode (5). , Photoelectric conversion element. The light-absorbing layer (12) of the photoelectric conversion layer (8) located at the center in the stacking direction of each of the photoelectric conversion layers (7, 8, 9) is formed of the photoelectric conversion layer (7, 8, 9). The light absorbing layer (12) having the smallest band gap,
The band gap of the light absorption layer (12) of each of the photoelectric conversion layers (7, 8, 9) is set at the center of the photoelectric conversion layer (7, 8, 9) in the stacking direction. 8), the photoelectric conversion layer (7) in contact with the first transparent electrode (3) and the photoelectric conversion layer (9) in contact with the second transparent electrode (5) are symmetrically increased. The photoelectric conversion element according to claim 1, wherein: Each of the photoelectric conversion layers (7, 8, 9) includes a P-type semiconductor layer (11), the light absorption layer (12) formed on the P-type semiconductor layer (11), and the light absorption layer ( 12) an N-type semiconductor layer (13) formed thereon;
The N-type semiconductor layer (13) of the photoelectric conversion layer (8) between two adjacent photoelectric conversion layers (8, 9), the band gap of the light absorption layer (12) being smaller; The light absorption layer (12) further includes a bonding layer (18) between the photoelectric conversion layer (9) and the P-type semiconductor layer (11) having the larger band gap. Item 3. The photoelectric conversion element according to item 1 or 2.   The bonding layer (18) is made of an amorphous silicon-based material doped with at least one of phosphorus and boron, a microcrystalline silicon-based material in which an amorphous silicon-based material is doped with a minute silicon-based crystal component, titanium oxide, oxide The photoelectric conversion element according to claim 3, wherein the photoelectric conversion element is made of any one of tin, zinc oxide, manganese oxide, and copper oxide.   The photoelectric conversion element according to claim 3, wherein the thickness of the bonding layer is from 1 nm to 40 nm.   Each of the photoelectric conversion layers (7, 8, 9) is made of one of amorphous silicon, amorphous silicon oxide, amorphous silicon carbide, amorphous silicon nitride, amorphous germanium, polycrystalline silicon, and microcrystalline silicon. The photoelectric conversion element according to claim 1, wherein: The light absorption layer (12) of the photoelectric conversion layer (8) that is not in contact with the first transparent electrode (3) and the second transparent electrode (5) is made of amorphous silicon;
The light absorption layer (12) of the photoelectric conversion layer (7) in contact with the first transparent electrode (3) and the light absorption layer (12) of the photoelectric conversion layer (9) in contact with the second transparent electrode (5). 12) The photoelectric conversion element according to claim 1, wherein the element (12) is made of an amorphous silicon-based material having a band gap of 1.7 eV to 2.05 eV. The light absorption layer (12) of the photoelectric conversion layer (8) that is not in contact with the first transparent electrode (3) and the second transparent electrode (5) is made of amorphous silicon;
The light absorption layer (12) of the photoelectric conversion layer (7) in contact with the first transparent electrode (3) and the light absorption layer (12) of the photoelectric conversion layer (9) in contact with the second transparent electrode (5). The photoelectric conversion element according to any one of claims 1 to 5, wherein (12) is made of amorphous silicon carbide or amorphous silicon oxide having a thickness of 100 nm to 400 nm. A photoelectric conversion element (20) according to any one of claims 1 to 8,
A support member (21) for supporting the photoelectric conversion element in a direction perpendicular to a ground plane;
A photoelectric conversion module comprising: There are a plurality of the photoelectric conversion elements (26, 27),
The photoelectric conversion module according to claim 9, wherein the support member (21) supports each of the photoelectric conversion elements (26, 27) in a direction perpendicular to a ground plane. A photoelectric conversion element (29) according to any one of claims 1 to 8,
A reflector (23) provided in parallel with the photoelectric conversion element (29) with a space therebetween;
A photoelectric conversion module comprising: The reflector (39) is concavely curved with respect to the photoelectric conversion element (36),
The photoelectric conversion module according to claim 11, wherein an area of the photoelectric conversion element (36) is smaller than an area of the reflector (39).

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