JP2015142001A - Method for manufacturing photoelectric conversion device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photoelectric conversion device with high photoelectric conversion efficiency.SOLUTION: A photoelectric conversion device 11 comprises an electrode layer 2, a first semiconductor layer 3 of a first conductivity type arranged on the electrode layer 2 and including a group I-III-VI compound and an additive element made of at least one of a bismuth element and an antimony element, and a second semiconductor layer 4 arranged on the first semiconductor layer 3 and having a second conductivity type different from the first conductivity type. When the first semiconductor layer 3 is trisected in a thickness direction and a first region 3a, a second region 3b, and a third region 3c are allocated in this order from the second semiconductor layer side, the concentration distribution of the additive element in the thickness direction of the first semiconductor layer 3 has a maximum value in the first region 3a or the second region 3b, and the concentration of the additive element decreases as the additive element approaches an interface with the second semiconductor layer 4 from the site indicating the maximum value.

Description

The present invention relates to a photoelectric conversion device including a semiconductor layer containing an I-III-VI group compound.

As a photoelectric conversion device used for photovoltaic power generation or the like, there is one using a semiconductor layer containing a chalcopyrite-structured I-III-VI group compound such as CIS or CIGS (for example, see Patent Document 1). The chalcopyrite structure I-III-VI group compound has a high light absorption coefficient, and is suitable for reducing the thickness, area, and manufacturing cost of the photoelectric conversion device. The chalcopyrite structure group I-III-VI Research and development of next-generation solar cells using a semiconductor layer containing a compound is underway.

Such a photoelectric conversion device comprises a substrate such as glass, a lower electrode such as Mo, a CIGS layer (a semiconductor layer containing a I-III-VI group compound), and a buffer layer such as a sulfur-containing zinc mixed crystal compound. And an upper electrode such as ZnO are laminated in this order. This buffer layer is formed by crystal growth on the light absorption layer by a CBD (Chemical Bath Deposition) method.

  In recent years, photoelectric conversion devices are required to further improve photoelectric conversion efficiency. As a method for increasing the photoelectric conversion efficiency of the photoelectric conversion device described above, Non-Patent Document 1 discloses that after depositing antimony or bismuth on a lower electrode, a CIGS layer is formed thereon. Thereby, the crystal grain size of the CIGS layer can be increased.

JP-A-8-330614

T. Nakada, Y. Honishi, Y. Yatsushiro, and H. Nakakoba “Impacts of Sb and Bi Incorporations on CIGS Thin Films and Solar Cells” Proc. 37th IEEE Photovoltaic Specialist Conf. (Seattle, June 2011)

The photoelectric conversion device containing the I-III-VI group compound is always required to improve the photoelectric conversion efficiency. In the method of Non-Patent Document 1, although the photoelectric conversion efficiency of the semiconductor layer containing the I-III-VI group compound is improved to some extent, there is a limit to further improvement of the photoelectric conversion efficiency.

  The present invention has been made in view of the above problems, and an object thereof is to provide a photoelectric conversion device having high photoelectric conversion efficiency.

The photoelectric conversion device according to one embodiment of the present invention includes an electrode layer and an additive element which is disposed on the electrode layer and includes an I-III-VI group compound and at least one of a bismuth element and an antimony element. A first semiconductor layer of a first conductivity type, and a second semiconductor layer of a second conductivity type different from the first conductivity type disposed on the first semiconductor layer, One semiconductor layer is equally divided into three in the thickness direction, and the first region, the second region, and the third region are sequentially formed from the second semiconductor layer side.
When the region is a region, the distribution of the concentration of the additive element in the thickness direction of the first semiconductor layer has a maximum value in the first region or the second region, and the second region from the portion showing the maximum value. The concentration of the additive element decreases as it approaches the interface with the semiconductor layer.

  ADVANTAGE OF THE INVENTION According to this invention, the photoelectric conversion efficiency of a photoelectric conversion apparatus can be improved.

It is a perspective view which shows an example of a photoelectric conversion apparatus. It is sectional drawing of the photoelectric conversion apparatus of FIG. It is sectional drawing which shows typically the mode in the middle of manufacture of a photoelectric conversion apparatus. It is sectional drawing which shows typically the mode in the middle of manufacture of a photoelectric conversion apparatus. It is sectional drawing which shows typically the mode in the middle of manufacture of a photoelectric conversion apparatus. It is sectional drawing which shows typically the mode in the middle of manufacture of a photoelectric conversion apparatus. It is sectional drawing which shows typically the mode in the middle of manufacture of a photoelectric conversion apparatus. It is sectional drawing which shows typically the mode in the middle of manufacture of a photoelectric conversion apparatus. It is a graph which shows the density | concentration distribution of the additive element in a 1st semiconductor layer. It is a graph which shows distribution of the II group element diffused in the 1st semiconductor layer.

  Hereinafter, a method for manufacturing a photoelectric conversion device according to an embodiment of the present invention will be described in detail with reference to the drawings.

<Configuration of photoelectric conversion device>
FIG. 1 is a perspective view illustrating a photoelectric conversion device manufactured using the method for manufacturing a photoelectric conversion device according to an embodiment, and FIG. 2 is a cross-sectional view of the photoelectric conversion device. The photoelectric conversion device 11 includes a substrate 1, a first electrode layer 2, a first semiconductor layer 3 containing an I-III-VI group compound, a second semiconductor layer 4, and an upper electrode layer 5. It is out.

  The first semiconductor layer 3 and the second semiconductor layer 4 have different conductivity types, and the charge separation of positive and negative carriers generated by light irradiation in the first semiconductor layer 3 and the second semiconductor layer 4 is excellent. It can be carried out.

  Moreover, although the photoelectric conversion apparatus 11 in this embodiment has shown what the light injects from the upper electrode layer 5 side, it is not limited to this, The light may inject from the board | substrate 1 side. .

  1 and 2, a plurality of lower electrode layers 2 are arranged in a plane on a substrate 1. 1 and 2, the plurality of lower electrode layers 2 include lower electrode layers 2 a to 2 c that are arranged at intervals in one direction. A first semiconductor layer 3 is provided from the lower electrode layer 2a through the substrate 1 to the lower electrode layer 2b. In addition, a second semiconductor layer 4 having a conductivity type different from that of the first semiconductor layer 3 is provided on the first semiconductor layer 3. Further, the connection conductor 6 is provided on the lower electrode layer 2 b along the surface (side surface) of the first semiconductor layer 3 or penetrating the first semiconductor layer 3. The connection conductor 6 electrically connects the second semiconductor layer 4 and the lower electrode layer 2b. The lower electrode layer 2, the first semiconductor layer 3, and the second semiconductor layer 4 constitute one photoelectric conversion cell 10, and adjacent photoelectric conversion cells 10 are connected in series via the connection conductor 6. Thus, the photoelectric conversion device 11 with high output is obtained.

The substrate 1 is for supporting the photoelectric conversion cell 10. Examples of the material used for the substrate 1 include glass, ceramics, resin, and metal. As the substrate 1, for example, blue plate glass (soda lime glass) having a thickness of about 1 to 3 mm can be used.

  The lower electrode layer 2 (lower electrode layers 2a, 2b and 2c) is a conductor such as Mo, Al, Ti or Au provided on the substrate 1. The lower electrode layer 2 is formed to a thickness of about 0.2 μm to 1 μm using a known thin film forming method such as sputtering or vapor deposition.

The first semiconductor layer 3 is a semiconductor layer mainly containing an I-III-VI group compound. “Containing mainly an I-III-VI group compound” means containing 70 mol% or more of an I-III-VI group compound. The first semiconductor layer 3 has a thickness of about 1 μm to 3 μm, for example. I-III-VI group compound semiconductors are Group 11 elements (also referred to as Group I-B elements), Group 13 elements (also referred to as Group III-B elements), and Group 16 elements (also referred to as Group VI-B elements). This compound semiconductor has a chalcopyrite structure and is called a chalcopyrite compound semiconductor. Examples of the I-III-VI group compound semiconductor include Cu (In, Ga) Se ₂ (also referred to as CIGS), Cu (In, Ga) (Se, S) ₂ (also referred to as CIGSS), and CuInSe ₂ (CIS). Also). Cu (In, Ga) Se ₂ refers to a compound mainly composed of Cu, In, Ga, and Se. Cu (In, Ga) (Se, S) ₂ refers to a compound containing Cu, In, Ga, Se, and S as main components.

  The first semiconductor layer 3 contains an additive element composed of at least one of a bismuth element (Bi) and an antimony element (Sb). The average molar concentration of the additive element contained in the first semiconductor layer 3 (when Bi and Sb are both included in the first semiconductor layer 3, the total average molar concentration of Bi and Sb) is the first semiconductor layer The average molar concentration of group 13 elements contained in 3 is about 0.001 to 0.1 times the average molar concentration. Note that the average molar concentration of the additive element contained in the first semiconductor layer 3 is, for example, an elemental analysis by secondary ion mass spectrometry (SIMS) while etching the first semiconductor layer 3 in the thickness direction (Z direction). It can obtain | require by calculating the average value of the thickness direction from the result performed.

  In addition, as shown in FIG. 2, when the first semiconductor layer 3 is equally divided into three in the thickness direction, the first region 3a, the second region 3b, and the third region 3c are sequentially formed from the second semiconductor layer 4 side. In addition, the concentration distribution of the additive element in the thickness direction (Z direction) of the first semiconductor layer 3 has a maximum value in the first region 3a or the second region 3b. Further, the concentration of the additive element decreases as the distance from the portion showing the maximum value approaches the interface with the second semiconductor layer 4. An example of the concentration distribution of such an additive element is shown by a solid line (sample 1) in FIG. FIG. 9 shows an example in which CIGS is used as the first semiconductor layer 3 and Bi is used as the additive element. In FIG. 9, the depth on the horizontal axis indicates the distance from the interface between the first semiconductor layer 3 and the second semiconductor layer 4. Here, the maximum value of the concentration distribution is the concentration at the inflection point at which the concentration distribution of the additive element changes from increasing to decreasing in the thickness direction of the first semiconductor layer 3.

  With such a configuration, the photoelectric conversion efficiency of the photoelectric conversion device 11 can be increased. This is due to the following reason.

  The additive element tends to increase the crystal grain size in the first semiconductor layer 3 and tends to cause defects of the group 11 element. A group 12 element or a group 13 element having a higher valence than the group 11 element with respect to the surface of the first semiconductor layer 3 having such a defect of the group 11 element (surface opposite to the lower electrode layer 2). Can contact these Group 12 elements and Group 13 elements well into the first semiconductor layer 3 to fill the defects of the Group 11 elements. As a result, a pn homo bond is formed in the first semiconductor layer 3, and the photoelectric conversion efficiency can be further increased.

However, if the group 12 element or the group 13 element is excessively contained in the first semiconductor layer 3 having such a defect of the group 11 element, the characteristics of the pn junction tend to deteriorate. In addition, when the group 12 element or the group 13 element excessively diffuses in the thickness direction of the first semiconductor layer 3 and reaches the vicinity of the lower electrode layer 2, the p-type characteristics of the first semiconductor layer 3 tend to deteriorate. There is.

  Therefore, in this embodiment, the concentration distribution of the additive element has a maximum value in the first region 3a or the second region 3b, so that the surface of the first semiconductor layer 3 (the second semiconductor layer 4). The group 12 element or the group 13 element can be favorably diffused from the surface of the first semiconductor layer 3 to the vicinity of the portion showing the maximum value. Further, since the concentration distribution of the additive element decreases from the portion showing the maximum value toward the lower electrode layer 2 side, the group 12 element or group 13 from the portion showing the maximum value to the lower electrode layer 2 side is reduced. It is possible to suppress the diffusion of the element and prevent the group 12 element or the group 13 element from excessively diffusing to the lower electrode layer 2 side. Furthermore, since the concentration of the additive element decreases as it approaches the interface with the second semiconductor layer 4 from the portion showing the maximum value, the diffusion of the group 12 element or the group 13 element easily occurs. It is possible to prevent the group 12 element or the group 13 element from being excessively contained in the surface portion 3 (the vicinity of the second semiconductor layer 4 in the first semiconductor layer 3). From the above, a pn homojunction can be satisfactorily formed in the first semiconductor layer 3, and the photoelectric conversion efficiency of the photoelectric conversion device 11 is improved.

  On the other hand, in the conventional configuration such as Non-Patent Document 1, Bi and Sb are formed in the vicinity of the lower electrode layer in order to form the first semiconductor layer after depositing Bi and Sb on the lower electrode layer. Although many of them exist, they are less likely to be present on the surface side than the center of the thickness on the second semiconductor layer side. Therefore, the group 12 element or the group 13 element is difficult to diffuse into the first semiconductor layer, and it is difficult to form a pn homojunction in the first semiconductor layer 3 as described above. Therefore, it is difficult to increase the photoelectric conversion efficiency with the conventional configuration.

  Here, as a supply source of the group 12 element or the group 13 element diffused with respect to the first semiconductor layer 3, there can be various supply sources as follows.

As a first supply source, when the second semiconductor layer 4 includes at least one of a group 12 element and a group 13 element, the second semiconductor layer 4 can be a supply source. In the case where the second semiconductor layer 4 includes a plurality of layers, any one of the layers may include at least one of a group 12 element and a group 13 element. For example, the buffer layer 4a includes CdS, ZnS, In ₂ S ₃ or the like. Alternatively, the upper electrode layer 4b includes one containing ZnO, In ₂ O ₃ or the like. Such a group 12 element such as Cd or Zn or a group 13 element such as In is heated by a heating process in the process of manufacturing the photoelectric conversion device 11, or a temperature rise due to heat generated by light irradiation or the like when using the photoelectric conversion device. Thus, diffusion from the buffer layer 4a into the first semiconductor layer 3 or from the upper electrode layer 4b through the buffer layer 4a into the first semiconductor layer 3 is performed.

  As the second supply source, the first semiconductor layer 4 is manufactured and then the surface of the first semiconductor layer 4 is separately supplied with a substance containing a group 12 element or a group 13 element. It can be done. That is, after the first semiconductor layer 4 is manufactured, a process for diffusing a group 12 element or a group 13 element in the first semiconductor layer 4 is performed. As such a process, for example, by bringing the first semiconductor layer 3 into contact with a liquid in which a compound of a group 12 element or a group 13 element is dissolved, the group 12 element or group 13 element in the liquid is converted into the first semiconductor. There is a method of diffusing in the layer 3. Further, as another method, a group 12 element or a group 13 element is deposited on the surface of the first semiconductor layer 3 as a simple substance or a compound by vapor deposition or the like, and this is heated so that the group 12 element or the group 13 element is deposited. There is a method of diffusing in the first semiconductor layer 3. As another method, heating is performed while bringing an organometallic compound such as diethyl zinc into contact, and a group 12 element or a group 13 element is diffused into the first semiconductor layer 3 on the surface of the first semiconductor layer 3. There is.

Note that the maximum value in the first region 3a or the second region 3b of the concentration distribution of the additive element does not necessarily have to be the maximum value of the concentration of the additive element in the entire thickness direction of the first semiconductor layer 3. Further, the concentration distribution of the additive element may also have other local maximum values in the third region 3c. This is because, for example, even if the concentration distribution of the additive element has a maximum value or a maximum value in the third region 3c, it has a maximum value in the first region 3a or the second region 3b as described above. Therefore, it is possible to prevent the group 12 element or the group 13 element from diffusing beyond the portion having the maximum value. In addition, since the third region 3c has a large distance from the surface of the first semiconductor layer 3, it is also related to the difficulty in diffusing group 12 elements or group 13 elements.

  Further, the concentration distribution of the additive element in the thickness direction of the first semiconductor layer 3 may show a minimum value in the vicinity of the interface with the second semiconductor layer 4. With such a configuration, it is possible to reduce the excessive inclusion of the group 12 element or the group 13 element in the vicinity of the interface between the first semiconductor layer 3 and the second semiconductor layer 4. A good homo pn junction can be formed inside the semiconductor layer 3.

  Further, in the concentration distribution of the additive element, the decrease rate in the direction from the portion showing the maximum value toward the second semiconductor layer 4 is larger than the decrease rate in the direction from the portion showing the maximum value toward the lower electrode layer 2 side. May be. With such a configuration, it is possible to reduce the excessive inclusion of a group 12 element or a group 13 element in a portion closer to the second semiconductor layer 4 than a portion showing the maximum value of the first semiconductor layer 3. A good homo pn junction can be formed inside the first semiconductor layer 3.

  Further, the first semiconductor layer 3 may have a plurality of holes in the vicinity of the portion showing the maximum value. Thus, when it has a void | hole, it becomes easy for a 12th group element and a 13th group element to diffuse through the interface of the crystal grain and void | hole which comprise the 1st semiconductor layer 3, and a 1st semiconductor It is possible to easily form a good pn junction inside the layer 3.

  The second semiconductor layer 4 is a semiconductor layer having a second conductivity type different from that of the first semiconductor layer 3. When the first semiconductor layer 3 and the second semiconductor layer 4 are electrically joined to each other, a photoelectric conversion layer from which charges can be favorably extracted is formed. For example, if the first semiconductor layer 3 is p-type, the second semiconductor layer 4 is n-type. The first semiconductor layer 3 may be n-type and the second semiconductor layer 4 may be p-type. Further, the second semiconductor layer 4 may be a multi-layer stack made of different semiconductor materials. A part of the laminate may be a high resistance layer having a higher electrical resistivity than the others. In the present embodiment, an example is shown in which the second semiconductor layer 4 is a stacked body of a buffer layer 4a that forms a heterojunction with the first semiconductor layer 3 and an upper electrode layer 4b that has a lower electrical resistivity than the buffer layer 4a. ing.

The buffer layer 4a is a layer that performs a heterojunction with the first semiconductor layer 3, and has a thickness of, for example, 5 to 200 nm. Examples of the buffer layer 4a include CdS, ZnS, ZnO, In ₂ S ₃ , In ₂ Se ₃ , In (OH, S), (Zn, In) (Se, OH), and (Zn, Mg) O. It is done. The buffer layer 4 is formed with a thickness of 10 to 200 nm by, for example, a chemical bath deposition (CBD) method or the like. In (OH, S) refers to a mixed crystal compound containing In as a hydroxide and a sulfide. (Zn, In) (Se, OH) refers to a mixed crystal compound containing Zn and In as selenides and hydroxides. (Zn, Mg) O refers to a compound containing Zn and Mg as oxides.

  The upper electrode layer 4 b is a layer having a lower electrical resistivity than the second semiconductor layer 4, and functions as an electrode layer that favorably extracts charges generated in the first semiconductor layer 3. From the viewpoint of further increasing the photoelectric conversion efficiency, the resistivity of the upper electrode layer 4b may be less than 1 Ω · cm and the sheet resistance may be 50 Ω / □ or less.

For the upper electrode layer 4b, for example, a metal oxide semiconductor such as ZnO, In ₂ O ₃ and SnO ₂ can be adopted. These metal oxide semiconductors may contain any element of Al, B, Ga, In, F, and the like. Specific examples of the metal oxide semiconductor containing such an element include, for example, AZO (Aluminum Zinc Oxide) and BZO (Boron Zinc Oxide).
GZO (Gallium Zinc Oxide), IZO (Indium Zinc Oxide), ITO (Indium Tin Oxide), FTO (Fluorine tin Oxide), and the like.

  The upper electrode layer 4b is formed to have a thickness of 0.05 to 3.0 [mu] m by sputtering, vapor deposition, chemical vapor deposition (CVD), or the like.

  Further, as shown in FIGS. 1 and 2, a current collecting electrode 7 may be further formed on the upper electrode layer 4b. The collecting electrode 7 is for taking out charges generated in the first semiconductor layer 3 more satisfactorily. For example, as shown in FIG. 1, the collector electrode 7 is formed in a linear shape from one end of the photoelectric conversion cell 10 to the connection conductor 6. As a result, the current generated in the first semiconductor layer 3 is collected to the current collecting electrode 7 via the upper electrode layer 4 b, and the adjacent photoelectric conversion cell 10 is successfully energized via the connection conductor 6.

  The collector electrode 7 may have a width of 50 to 400 μm from the viewpoint of increasing the light transmittance to the first semiconductor layer 3 and having good conductivity. The current collecting electrode 7 may have a plurality of branched portions.

  The collector electrode 7 is formed, for example, by printing a metal paste in which a metal powder such as Ag is dispersed in a resin binder or the like in a pattern and curing it.

  1 and 2, the connection conductor 6 is a conductor provided in a groove that penetrates the first semiconductor layer 3, the buffer layer 4a, and the upper electrode layer 4b. The connection conductor 6 can be made of metal, conductive paste, or the like. In FIG. 1 and FIG. 2, the collector electrode 7 is extended to form the connection conductor 6, but the present invention is not limited to this. For example, the upper electrode layer 4b may be extended.

<Method for Manufacturing Photoelectric Conversion Device>
3 to 8 are cross-sectional views schematically showing a state during the manufacture of the photoelectric conversion device 11. Each of the cross-sectional views shown in FIGS. 3 to 8 shows a state in the middle of manufacturing a portion corresponding to the cross-section shown in FIG.

  First, the lower electrode layer 2 made of Mo or the like is formed on substantially the entire surface of the cleaned substrate 1 using a sputtering method or the like. Then, the first groove portion P1 is formed from the linear formation target position along the Y direction on the upper surface of the lower electrode layer 2 to the upper surface of the substrate 1 immediately below the formation position. The first groove portion P1 can be formed by, for example, a scribe process in which a groove process is performed by irradiating a formation target position while scanning with a laser beam such as a YAG laser. FIG. 3 is a diagram illustrating a state after the first groove portion P1 is formed.

  After forming the first groove portion P1, a complex film in which a group 11 element and a group 13 element are present in an organic complex state on the lower electrode layer 2 is produced. And this thermal decomposition film 3a is produced by heating this complex membrane | film | coat and carrying out the thermal decomposition removal of the organic component of said organic complex.

  The complex film can be produced by applying a raw material solution in which a group 11 element and a group 13 element are present in an organic complex state. As the raw material solution, an organic complex in which an organic ligand is coordinated to a group 11 element, an organic complex in which an organic ligand is coordinated to a group 13 element, or the like can be used. An organic complex is a compound in which an organic ligand having a group having a lone pair of electrons is coordinated to a metal element. Examples of such an organic ligand include a compound having a carboxyl group, an alkoxy group, a thiol group, or a selenol group, and an acetylacetone compound.

From the viewpoint of further promoting the formation of the I-III-VI group compound, an organic chalcogen compound may be used as the organic ligand. An organic chalcogen compound is an organic compound containing a chalcogen element, and is an organic compound having a covalent bond between a carbon element and a chalcogen element. The chalcogen element is sulfur (S), selenium (Se) and tellurium (Te) among group 16 elements. Examples of the organic chalcogen compound include thiol, sulfide, disulfide, selenol, selenide, diselenide, tellurol, telluride, ditelluride and the like.

  As such an organic complex, an organic complex in which an organic chalcogen compound is bonded to a Group 11 element (hereinafter referred to as a Group 11 complex), an organic complex in which an organic chalcogen compound is bonded to a Group 13 element (hereinafter referred to as a Group 13 complex), Alternatively, an organic complex in which a group 11 element, a group 13 element, and an organic chalcogen compound are combined to form one complex molecule (hereinafter referred to as a single source complex. Note that the single source complex is described in US Pat. No. 6,992,202. No. specification can be referred to)). By using the organic complex in which the organic chalcogen compound is coordinated in this way, each metal element and the chalcogen element of the organic chalcogen compound are brought close to each other, so that the chalcogenization reaction of each metal element is more likely to proceed.

  Moreover, the solvent used for a raw material solution should just be a thing which can melt | dissolve the said organic complex, For example, polar solvents, such as alcohol and amines, can be used.

  As a method of applying the raw material solution onto the lower electrode layer 2, for example, spin coating, screen printing, dipping, spray coating, die coating, or the like can be used.

  As an atmosphere at the time of producing such a thermal decomposition film 3a by heating such a complex film, for example, an inert gas atmosphere such as nitrogen or argon can be used. Moreover, the heating temperature at the time of producing this thermal decomposition film 3a can be 150-430 degreeC, for example. By this step, the pyrolysis film 3a becomes porous. FIG. 4 is a diagram showing a state after the thermal decomposition film 3a is produced.

Next, an additive element (at least one of Bi and Sb) is deposited on the surface of the pyrolysis film 3a in the form of a simple substance or a compound. Thereafter, the pyrolytic film 3a is heated in an atmosphere containing a chalcogen element to produce a first semiconductor layer 3 containing an I-III-VI group compound. Thus, by adding an additional element to the surface of the pyrolysis film 3a which is a porous state, it becomes easy for the additive element to easily diffuse into the pyrolysis film 3a. As a result, the distribution of the concentration of the additive element in the thickness direction of the first semiconductor layer 3 has a maximum value in the first region 3a or the second region 3b. The first semiconductor layer 3 in which the concentration of the additive element decreases as it approaches the surface on the opposite side can be produced. Note that the portion showing the maximum value of the concentration distribution of the additive element becomes a desired position in the thickness direction of the first semiconductor layer 3 by adjusting the time of the heating step in the atmosphere containing the chalcogen element. Can be. That is, as the time of the heating process in the atmosphere containing the chalcogen element becomes longer, the portion showing the maximum value of the concentration distribution of the additive element is from the surface of the first semiconductor layer 3 opposite to the lower electrode layer 2. Since there is a tendency to move to the lower electrode layer 2 side, this heating time may be adjusted.

The additive element deposited on the surface of the pyrolysis film 3a may be a single element or a compound such as an organic complex. Examples of a method for depositing the additive element on the surface of the pyrolysis film 3a in a simple substance or compound state include, for example, a film forming method such as vapor deposition or a complex solution containing the additive element in a state of an organic complex or the like. A method or the like can be used. From the viewpoint that the additive element can be easily deposited with simple equipment, a method of applying a complex solution in which the additive element exists in an organic complex state on the surface of the pyrolysis film 3a may be used.

  As the complex solution in which the additive element exists in the state of an organic complex, an organic complex in which an organic ligand is coordinated to the additive element can be used. An organic complex is a compound in which an organic ligand having a group having a lone pair of electrons is coordinated to a metal element. Examples of such an organic ligand include a compound having a carboxyl group, an alkoxy group, a thiol group, or a selenol group, and an acetylacetone compound.

From the viewpoint of further improving the crystallinity of the I-III-VI group compound, an organic chalcogen compound may be used as the organic ligand. As a result, the additive element is favorably chalcogenized, whereby the additive element is favorably incorporated into the I-III-VI group compound.

Examples of the organic complex in which an organic chalcogen compound is coordinated to such an additive element include those having a complex structure such as the structural formula (1). In the structural formula (1), M is Bi or Sb. L _{1 to} L ₃ are organic chalcogen compounds, and these may have different structures or the same structure. As a specific example of the structural formula (1), for example, there is a compound in which diethyldithiocarbamic acid is coordinated to an additive element as in the structural formula (2). In addition to the compound of the structural formula (2), there are Bi (SC ₆ H ₅ ) ₃ , Bi (SeC ₆ H ₅ ) ₃ , Sb (SC ₆ H ₅ ) ₃ , Sb (SeC ₆ H ₅ ) _{3 and the} like. . The compound of the structural formula (2) has a relatively high solubility in an organic solvent and good handleability.

The compounds of structural formula (1) and structural formula (2) are produced, for example, as follows. Here, an example in which M in the structural formula (2) is Bi is shown; however, other compounds can be manufactured by a similar method. First, a solution A is prepared by dissolving sodium diethyldithiocarbamate in methanol. Also, solution B is prepared by dissolving BiCl ₃ in methanol. Then, by mixing the solution A and the solution B, a precipitate containing the compound of the structural formula (2) is generated.

The amount of the complex solution applied to the surface of the pyrolysis film 3a is the amount of III-B contained in the pyrolysis film 3a.
It is sufficient that the molar concentration of the additive element (the total molar concentration when the additive element contains both Bi and Sb) is about 0.01 to 10% with respect to the molar concentration of the group element. As a method for applying the complex solution onto the pyrolysis film 3a, for example, spin coating, screen printing, dipping, spray coating or die coating can be used.

The atmosphere containing a chalcogen element used when producing the first semiconductor layer 3 containing the I-III-VI group compound by heating the pyrolysis film 3a coated with the complex solution is sulfur vapor, selenium vapor, tellurium vapor. May be a gas atmosphere such as hydrogen sulfide, hydrogen selenide or hydrogen telluride, or a mixed gas atmosphere containing a chalcogen element vapor or a chalcogen element hydride as described above in a non-oxidizing gas. May be. Examples of the non-oxidizing gas include inert gases such as nitrogen and argon, and reducing gases such as hydrogen. In particular, hydrogen may be used as the non-oxidizing gas from the viewpoint of further reducing the remaining rate of the organic component in the first semiconductor layer 3. In this case, the amount of the chalcogen element contained in the atmosphere is, for example, 10 ⁻⁶ times to 5 × 10 5 times the number of moles of the chalcogen element as the number of moles of atoms when the number of moles of hydrogen molecules per unit volume is G. ⁻² times, more preferably 10 ⁻⁵ times to 5 × 10 ⁻³ times G.

Moreover, the heating temperature of the pyrolysis film 3a in the atmosphere containing a chalcogen element is, for example, 400 to 650 ° C., and the heating time is, for example, 0.5 to 5 hours. FIG. 5 is a diagram illustrating a state after the first semiconductor layer 3 is manufactured.

  After forming the first semiconductor layer 3, the buffer layer 4 a and the upper electrode layer 4 b as the second semiconductor layer 4 are sequentially formed on the first semiconductor layer 3.

The buffer layer 4a can be formed by a solution growth method (also referred to as a CBD method). For example, indium chloride and thioacetamide are dissolved in water acidified with hydrochloric acid, and the substrate 1 that has been formed up to the formation of the first semiconductor layer 3 is immersed in this, whereby an In layer is formed on the first semiconductor layer 3. _A buffer layer 4 a containing ₂ S ₃ can be formed.

  The upper electrode layer 4b is, for example, a transparent conductive film containing AZO, BZO, or the like as a main component, and can be formed by a sputtering method, a vapor deposition method, a CVD method, or the like. FIG. 6 is a diagram showing a state after the buffer layer 4a and the upper electrode layer 4b are formed.

  After the formation of the upper electrode layer 4b, the second groove portion P2 is formed from the linear formation target position along the Y direction on the upper surface of the upper electrode layer 4b to the upper surface of the lower electrode layer 2 immediately below it. The second groove portion P2 can be formed, for example, by performing scribing using a scribe needle having a scribe width of about 40 to 50 μm continuously several times while shifting the pitch. Alternatively, the second groove portion P2 may be formed by scribing after the tip shape of the scribe needle is expanded to an extent close to the width of the second groove portion P2. Alternatively, the second groove part P2 may be formed by fixing two or more than two scribe needles in contact with each other or in proximity to each other and performing scribing once to several times. FIG. 7 is a diagram illustrating a state after the second groove portion P2 is formed. The second groove portion P2 is formed at a position slightly deviated in the X direction (+ X direction in the drawing) from the first groove portion P1.

  After forming the second groove P2, the current collecting electrode 7 and the connection conductor 6 are formed. For the collector electrode 7 and the connection conductor 6, for example, a conductive paste (also referred to as a conductive paste) in which a metal powder such as Ag is dispersed in a resin binder or the like is printed so as to draw a desired pattern. It can be formed by drying and solidifying. FIG. 8 is a view showing a state after the current collecting electrode 7 and the connection conductor 6 are formed.

  After forming the current collection electrode 7 and the connection conductor 6, the 3rd groove part P3 is formed from the linear formation object position of the upper surface of the upper electrode layer 4b to the upper surface of the lower electrode layer 2 just under it. The width | variety of the 3rd groove part P3 can be about 40-1000 micrometers, for example. Moreover, the 3rd groove part P3 can be formed by mechanical scribing similarly to the 2nd groove part P2. In this way, the photoelectric conversion device 11 shown in FIGS. 1 and 2 is manufactured by forming the third groove portion P3.

  Note that the present invention is not limited to the above-described embodiment, and various modifications may be made without departing from the scope of the present invention.

  Next, a method for manufacturing the photoelectric conversion device will be described with a specific example.

<Preparation of Sample 1>
First, a raw material solution for forming the first semiconductor layer was prepared. As the raw material solution, a solution obtained by dissolving a single source complex prepared in accordance with the description of US Pat. No. 6,992,202 in pyridine was used. In addition, as this single source complex, Cu, In and phenyl selenol formed one complex molecule, and Cu, Ga and phenyl selenol formed one complex molecule. The molar ratio of Cu, In and Ga in the raw material solution was set to Cu: In: Ga = 1: 0.6: 0.4.

  Next, what prepared the lower electrode layer which consists of Mo on the surface of the board | substrate comprised with glass was prepared. And the said raw material solution was apply | coated by this blade method on this lower electrode layer, the complex membrane | film | coat was formed, and the thermal decomposition membrane | film | coat was formed by heating this complex membrane | film | coat at 300 degreeC.

  Next, Bi was vapor-deposited on the surface of the pyrolysis film by an evaporation method. The number of moles of Bi deposited was 1% with respect to the total number of moles of group 13 elements in the pyrolysis film.

And the 1st semiconductor layer containing CIGS was formed by heating the thermal decomposition film which adhered this bismuth complex at 550 degreeC for 1 hour. Note that a hydrogen gas atmosphere containing selenium was used as the atmosphere during the heating. The hydrogen gas atmosphere containing selenium is prepared by vaporizing metal selenium in heated hydrogen gas. The selenium content in the hydrogen gas atmosphere containing selenium was such that the number of moles of selenium atoms per unit volume was 5 × 10 ⁻⁵ times the number of moles of hydrogen molecules.

  Next, the substrate on which the first semiconductor layer is formed is immersed in a CBD solution made of an aqueous solution containing 7 mM cadmium iodide and 0.3 M thiourea and adjusted to pH 12.2 with aqueous ammonia. A second semiconductor layer containing CdS was formed over the first semiconductor layer.

  Then, an upper electrode layer made of ZnO doped with Al was formed by sputtering on the second semiconductor layer, whereby a photoelectric conversion device as Sample 1 was obtained.

<Preparation of Sample 2>
What prepared the lower electrode layer which consists of Mo on the surface of the board | substrate comprised with glass was prepared. And Bi was vapor-deposited on this lower electrode layer. The number of moles of Bi deposited was set to 1% with respect to the total number of moles of group 13 elements in the pyrolysis film to be produced later.

  Next, on the lower electrode layer on which this Bi is deposited, the raw material solution used in the preparation of Sample 1 is applied by a blade method to form a complex film, and this complex film is heated at 300 ° C. for thermal decomposition. A film was formed.

  Then, the pyrolysis film is heated under the same conditions as the sample 1 to produce the first semiconductor layer, and the second semiconductor layer and the upper electrode layer are produced under the same conditions as the sample 1 A photoelectric conversion device as Sample 2 was obtained. That is, the sample 2 is a comparative example having a configuration similar to that of the non-patent document 1.

<Secondary ion mass spectrometry of sample 1 and sample 2>
FIG. 9 and FIG. 10 show the results of elemental analysis performed on the samples 1 and 2 by secondary ion mass spectrometry (SIMS) in the depth direction while etching the first semiconductor layer of each sample.

  From the result of FIG. 9, in Sample 2, Bi was hardly present on the surface portion opposite to the lower electrode layer, and was unevenly distributed on the lower electrode layer side of the first semiconductor layer. On the other hand, Sample 1 contains Bi throughout the thickness direction of the first semiconductor layer, and it can be seen that there is a maximum value of the concentration distribution of Bi in the vicinity of 0.7 μm from the surface.

  Further, from the result of FIG. 10, it can be seen that Cd diffuses better to the inside of the first semiconductor layer in sample 1 than in sample 2.

  From the above, it can be considered that Bi as an additive element has a concentration distribution as in Sample 1 so that Cd as a Group 12 element can be diffused well into the first semiconductor layer.

<Photoelectric conversion characteristics>
Photoelectric conversion efficiency was measured for Sample 1 and Sample 2. The photoelectric conversion efficiency is measured using a steady light solar simulator as pseudo-sunlight. The light irradiation intensity on the light receiving surface of the photoelectric conversion device is 100 mW / cm ² and AM (air mass) is 1.5. Condition. As a result, it was found that the photoelectric conversion efficiency of sample 2 was 12%, whereas the photoelectric conversion efficiency of sample 1 was improved to 14%.

1: Substrate 2, 2a, 2b, 2c: Lower electrode layer 3: First semiconductor layer 3a: Pyrolysis film 4: Second semiconductor layer 4a: Buffer layer 4b: Upper electrode layer 6: Connection conductor 7: Current collector Electrode 10: Photoelectric conversion cell 11: Photoelectric conversion device

Claims (4)

An electrode layer;
A first semiconductor layer of a first conductivity type disposed on the electrode layer and including an I-III-VI group compound and an additive element comprising at least one of a bismuth element and an antimony element; A second semiconductor layer of a second conductivity type different from the first conductivity type disposed on the semiconductor layer,
When the first semiconductor layer is equally divided into three in the thickness direction, and the first region, the second region, and the third region are sequentially formed from the second semiconductor layer side, the first semiconductor layer in the thickness direction of the first semiconductor layer The concentration distribution of the additive element has a maximum value in the first region or the second region, and the concentration of the additive element decreases as it approaches the interface with the second semiconductor layer from a portion showing the maximum value. Photoelectric conversion device.   2. The photoelectric conversion device according to claim 1, wherein the concentration distribution of the additive element shows a minimum value in the vicinity of an interface with the second semiconductor layer.   The concentration distribution of the additive element is such that the reduction rate in the direction from the portion showing the maximum value toward the second semiconductor layer is larger than the reduction rate in the direction from the portion showing the maximum value toward the electrode layer. The photoelectric conversion device according to claim 1.   The photoelectric conversion device according to claim 1, wherein the first semiconductor layer has a plurality of holes in the vicinity of a portion exhibiting the maximum value.

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