JP2011151182A - Photoelectric conversion apparatus, and method of manufacturing the same - Google Patents

Abstract

A photoelectric conversion device in which output power is improved by suppressing leakage current and a method for manufacturing the photoelectric conversion device are provided.
A photoelectric conversion device includes a lower electrode layer, a first semiconductor layer provided on the lower electrode layer, and a conductivity type different from that of the first semiconductor layer provided on the first semiconductor layer. A second semiconductor layer; an upper electrode layer including an indium oxide-based material provided on the second semiconductor layer; and an indium oxide-based material provided between the second semiconductor layer and the upper electrode layer. And an intermediate conductive layer having a higher electrical resistivity than the upper electrode layer.
[Selection] Figure 2

Description

  The present invention relates to a photoelectric conversion device and a method for manufacturing the photoelectric conversion device.

  As a photoelectric conversion device used for photovoltaic power generation or the like, there is one in which a light absorption layer is formed by a chalcopyrite-based I-III-VI group compound semiconductor such as CIGS having a high light absorption coefficient (for example, Patent Documents). 1). CIGS has a high light absorption coefficient and is suitable for reducing the thickness, area, and cost of photoelectric conversion devices, and research and development of next-generation solar cells using the photoelectric conversion device is being promoted.

  Such a chalcopyrite photoelectric conversion device has a configuration in which a plurality of photoelectric conversion cells are arranged in a plane. This photoelectric conversion cell includes a lower electrode such as a metal electrode on a substrate such as glass, a photoelectric conversion layer that is a semiconductor layer including a light absorption layer and a buffer layer, and an upper electrode such as a transparent electrode and a metal electrode. Are stacked in this order. The plurality of photoelectric conversion cells are electrically connected in series by electrically connecting the upper electrode of one adjacent photoelectric conversion cell and the lower electrode of the other photoelectric conversion cell by a connecting conductor. ing.

JP 2007-311578 A

  In a chalcopyrite photoelectric conversion device, when a thin buffer layer has defects such as pinholes, a leakage current is generated between the transparent electrode and the light absorption layer, resulting in a decrease in output power.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a photoelectric conversion device in which output power is improved by suppressing leakage current and a method for manufacturing the photoelectric conversion device.

  In order to solve the above problems, a photoelectric conversion device according to a first aspect includes a lower electrode layer, a first semiconductor layer provided on the lower electrode layer, and a first semiconductor layer provided on the first semiconductor layer. A second semiconductor layer having a conductivity type different from that of the first semiconductor layer; an upper electrode layer including an indium oxide-based material provided on the second semiconductor layer; the second semiconductor layer and the upper electrode layer; And an intermediate conductive layer including an indium oxide-based material and having a higher electrical resistivity than the upper electrode layer.

  The method for manufacturing a photoelectric conversion device according to the second aspect is different from the first semiconductor layer on the first semiconductor layer and the first formation step of forming the first semiconductor layer on the lower electrode layer. A second forming step of forming a conductive second semiconductor layer; a third forming step of forming an intermediate conductive layer containing an indium oxide-based material on the second semiconductor layer by sputtering; and the third forming step. In an atmosphere having a second oxygen partial pressure lower than the first oxygen partial pressure of the atmosphere in which the process is performed, the intermediate conductive layer includes an indium oxide-based material and has an electrical resistivity lower than that of the intermediate conductive layer. And a fourth forming step of forming the upper electrode layer by a sputtering method.

  According to the present invention, generation of leakage current in the photoelectric conversion device is suppressed. Thereby, the output power in the photoelectric conversion device is improved.

It is a top view which shows the structure of a photoelectric conversion apparatus. It is sectional drawing which shows the structure of a photoelectric conversion apparatus. It is sectional drawing which shows the mode in the middle of manufacture of a photoelectric conversion apparatus. It is sectional drawing which shows the mode in the middle of manufacture of a photoelectric conversion apparatus. It is sectional drawing which shows the mode in the middle of manufacture of a photoelectric conversion apparatus. It is sectional drawing which shows the mode in the middle of manufacture of a photoelectric conversion apparatus. It is sectional drawing which shows the mode in the middle of manufacture of a photoelectric conversion apparatus. It is sectional drawing which shows the mode in the middle of manufacture of a photoelectric conversion apparatus. It is sectional drawing which shows the mode in the middle of manufacture of a photoelectric conversion apparatus. It is a figure which shows the relationship between the oxygen partial pressure at the time of a sputtering, and the specific resistance of ITO. It is a figure which shows the relationship between the oxygen partial pressure at the time of a sputtering, and the sheet resistance of ITO. It is a figure which shows the voltage-current characteristic of the photoelectric conversion apparatus in which an intermediate conductive layer exists. It is a figure which shows the voltage-current characteristic of the photoelectric conversion apparatus in which an intermediate conductive layer does not exist. It is sectional drawing which shows the structure of the photoelectric conversion apparatus which concerns on a modification. It is sectional drawing which shows the mode in the middle of manufacture of the photoelectric conversion apparatus which concerns on a modification. It is sectional drawing which shows the mode in the middle of manufacture of the photoelectric conversion apparatus which concerns on a modification. It is sectional drawing which shows the structure of the photoelectric conversion apparatus which concerns on a modification.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

<(1) Schematic configuration of photoelectric conversion device>
FIG. 1 is a top view illustrating a configuration of a photoelectric conversion device 20 according to an embodiment of the present invention. 2 is a cross-sectional view of the photoelectric conversion device 20 taken along the section line II-II in FIG. 1, that is, an xz cross-sectional view of the photoelectric conversion device 20 at the position indicated by the one-dot chain line in FIG.

  The photoelectric conversion device 20 has a configuration in which a plurality of photoelectric conversion cells 10 are arranged in parallel on a substrate 1. In FIG. 1, only two photoelectric conversion cells 10 are shown for convenience of illustration, but in an actual photoelectric conversion device 20, in the horizontal direction of the drawing, or further in the vertical direction of the drawing perpendicular thereto, A large number of photoelectric conversion cells 10 are arranged in a plane (two-dimensionally). 1 and other drawings after FIG. 1 are provided with a right-handed xyz coordinate system in which the arrangement direction of photoelectric conversion cells 10 (the horizontal direction in the drawing) is the x-axis direction.

  Each photoelectric conversion cell 10 mainly includes a lower electrode layer 2, a light absorption layer 3, a buffer layer 4, an intermediate conductive layer 6, an upper electrode layer 7, a grid electrode 8, and a connection portion 9. In the photoelectric conversion device 20, the main surface on the side where the upper electrode layer 7 and the grid electrode 8 are provided is the light receiving surface side.

  Further, the photoelectric conversion device 20 is provided with three types of groove portions, that is, a first groove portion P1, a second groove portion P2, and a third groove portion P3.

  The substrate 1 is for supporting a plurality of photoelectric conversion cells 10. Examples of the material used for the substrate 1 include glass, ceramics, resin, and metal. Here, a blue plate glass (soda lime glass) having a thickness of about 1 to 3 mm is used as the substrate 1.

  The lower electrode layer 2 is a metal such as Mo (molybdenum), Al (aluminum), Ti (titanium), Ta (tantalum), or Au (gold) provided on one main surface of the substrate 1, or these It is a conductor layer made of a metal laminate structure. 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 light absorption layer 3 is a semiconductor layer having a p-type conductivity type and made of a chalcopyrite (also referred to as CIS) I-III-VI group compound provided on the lower electrode layer 2. The light absorption layer 3 has a thickness of about 1 μm to 3 μm.

Here, the I-III-VI group compound is a group IB element (also referred to as a group 11 element), a group III-B element (also referred to as a group 13 element), and a group VI-B element (also referred to as a group 16 element). ) And a compound. Examples of the I-III-VI group compound include CuInSe ₂ (also referred to as copper indium selenide, CIS), Cu (In, Ga) Se ₂ (also referred to as copper indium diselenide / gallium, CIGS), Cu ( In, Ga) (Se, S) ₂ (also referred to as diselene, copper indium gallium sulfide, gallium, CIGSS). The light absorption layer 3 may be formed of a multi-component compound semiconductor thin film such as copper indium selenide / gallium having a thin film of selenite / copper indium sulfide / gallium as a surface layer.

  The light absorption layer 3 may be a semiconductor layer made of a II-VI group compound. The II-VI group compound is a compound semiconductor of a group II-B (also referred to as a group 12 element) and a group VI-B element. However, from the viewpoint of increasing the photoelectric conversion efficiency, it is preferable to use an I-III-VI compound semiconductor which is a chalcopyrite compound semiconductor.

  Such a light absorption layer 3 can be formed by a so-called vacuum process such as a sputtering method or a vapor deposition method, and a solution containing the constituent elements of the light absorption layer 3 is applied onto the lower electrode layer 2, and then It can also be formed by a so-called coating method or printing method in which drying and heat treatment are performed. However, from the viewpoint of suppressing the manufacturing cost of the photoelectric conversion device 20, the latter process is preferably used.

  The buffer layer 4 is a semiconductor layer provided on the light absorption layer 3 and having an n type conductivity type different from the conductivity type of the light absorption layer 3. The buffer layer 4 is provided in a mode of heterojunction with the light absorption layer 3 when the light absorption layer 3 is composed of an I-III-VI group compound semiconductor. In the photoelectric conversion cell 10, photoelectric conversion occurs in the light absorption layer 3 and the buffer layer 4 constituting the heterojunction, and thus the light absorption layer 3 and the buffer layer 4 are the photoelectric conversion layer 5. In addition, the structure of the photoelectric converting layer 5 is not limited to this, The semiconductor layer of a different conductivity type may be a homojunction. Here, semiconductors having different conductivity types are semiconductors having different conductive carriers.

The buffer layer 4 is made of, for example, CdS (cadmium sulfide), In ₂ S ₃ (indium sulfide), ZnS (zinc sulfide), ZnO (zinc oxide), In ₂ Se ₃ (indium selenide), In (OH, S). , (Zn, In) (Se, OH), and (Zn, Mg) O. From the viewpoint of reducing leakage current, the buffer layer 4 preferably has a resistivity of 1 Ω · cm or more.

  The buffer layer 4 is preferably formed to a thickness of 10 nm to 200 nm, preferably 100 nm to 200 nm. Thereby, the fall of the photoelectric conversion efficiency in high temperature, high humidity conditions is suppressed especially effectively. The buffer layer 4 is formed by, for example, a chemical bath deposition (CBD) method.

The intermediate conductive layer 6 is an n-type transparent conductive film provided on the buffer layer 4. From another viewpoint, the intermediate conductive layer 6 is provided between the buffer layer 4 and the upper electrode layer 7. The intermediate conductive layer 6 is made of a material having an electrical resistivity (specific resistance) higher than that of the upper electrode layer 7. Specifically, the intermediate conductive layer 6 preferably has a sheet resistance of 1 × 10 ³ Ω / □ to 1 × 10 ⁷ Ω / □ in consideration of necessary specific resistance and conductivity.

The intermediate conductive layer 6 includes, for example, at least one of indium oxide containing tin (ITO: In ₂ O ₃ —SnO ₂ ) and indium oxide containing zinc (IZO: In ₂ O ₃ —ZnO). It is formed using a metal oxide semiconductor containing an indium oxide-based material as a main component. Thus, in the intermediate conductive layer 6, both high transparency and high conductivity are realized by using an indium oxide-based material.

  Further, the intermediate conductive layer 6 is formed to a thickness of 0.025 μm to 0.1 μm by sputtering, vapor deposition, chemical vapor deposition (CVD), or the like.

  Due to the presence of the intermediate conductive layer 6, the occurrence of leakage current between the upper electrode layer 7 and the light absorption layer 3 is suppressed.

  The upper electrode layer 7 is a transparent conductive film having an n-type conductivity provided on the intermediate conductive layer 6. The upper electrode layer 7 is provided as an electrode for extracting charges generated in the photoelectric conversion layer 5 through the intermediate conductive layer 6. The upper electrode layer 7 is made of a material having a lower resistivity than the buffer layer 4 and the intermediate conductive layer 6. The upper electrode layer 7 includes what is called a window layer. When a transparent conductive film is further provided in addition to the window layer, these are regarded as the upper electrode layer 7 together.

  The upper electrode layer 7 is made of a transparent and low resistance material having a wide forbidden band, for example, indium oxide containing at least one of indium oxide containing tin (ITO) and indium oxide containing zinc (IZO). It is composed of a metal oxide semiconductor whose main component is a system material. As described above, in the upper electrode layer 7, as in the case of the intermediate conductive layer 6, both high transparency and high conductivity are realized by using an indium oxide-based material.

  The upper electrode layer 7 is formed to a thickness of 0.05 μm to 3.0 μm by sputtering, vapor deposition, CVD, or the like. In particular, when the intermediate conductive layer 6 and the upper electrode layer 7 are formed of an indium oxide-based material containing the same kind of metal oxide by sputtering or the like, in an atmosphere in the sputtering apparatus (for example, in a chamber). By changing the oxygen partial pressure, the specific resistance can be made different between the intermediate conductive layer 6 and the upper electrode layer 7. Specifically, the specific resistance is increased by increasing the oxygen partial pressure.

  From the viewpoint of taking out charges from the photoelectric conversion layer 5 through the intermediate conductive layer 6, the upper electrode layer 7 has a resistivity of less than 1 Ω · cm and a sheet resistance of 50 Ω / □ or less. It is preferable.

  The buffer layer 4, the intermediate conductive layer 6, and the upper electrode layer 7 are preferably made of a material that has optical transparency with respect to the wavelength region of light absorbed by the light absorption layer 3. Thereby, a decrease in light absorption efficiency in the light absorption layer 3 due to the provision of the buffer layer 4, the intermediate conductive layer 6, and the upper electrode layer 7 is suppressed.

  In addition to increasing light transmission, it also increases the effect of preventing loss due to light reflection (light reflection loss) and the effect of scattering light (light scattering effect), and further transmits the current generated by photoelectric conversion well. From the viewpoint of doing, the upper electrode layer 7 preferably has a thickness of 0.05 to 0.5 μm. From the viewpoint of preventing light reflection loss at the interface between the upper electrode layer 7 and the intermediate conductive layer 6 and at the interface between the intermediate conductive layer 6 and the buffer layer 4, the buffer layer 4, the intermediate conductive layer 6, and the upper electrode The absolute refractive index of the layer 7 is preferably substantially the same.

  The grid electrodes 8 are provided apart from each other in the y-axis direction, and each of the current collectors 8a extends in the y-axis direction and is connected to each of the current collectors 8a extending in the x-axis direction. It is the electrode which has electroconductivity provided with the connection part 8b to perform. The grid electrode 8 is made of a metal such as Ag, for example.

  The current collector 8 a plays a role of collecting charges generated in the photoelectric conversion layer 5 and taken out in the upper electrode layer 7. By providing the current collector 8a, the upper electrode layer 7 can be thinned. Since the upper electrode layer 7 is provided above the light absorption layer 3, it is desirable that the upper electrode layer 7 be formed as thin as possible in order to increase the light transmittance. Efficiency is reduced. Therefore, by providing the current collector 8a, the charge extraction efficiency is ensured, and the light transmittance of the upper electrode layer 7 can be improved.

  The electric charges collected by the grid electrode 8 and the upper electrode layer 7 are transmitted to the adjacent photoelectric conversion cell 10 through the connection part 9 provided in the second groove part P2. The connecting portion 9 is constituted by an extending portion 7a of the upper electrode layer 7 and a hanging portion 8c from the connecting portion 8b formed thereon. Thereby, in the photoelectric conversion apparatus 20, one lower electrode layer 2 of the adjacent photoelectric conversion cell 10 and the other upper electrode layer 7 and the grid electrode 8 are connected to each other by the connection portion 9 provided in the second groove portion P2. The connection conductor is electrically connected in series.

  The grid electrode 8 has a width of 50 μm to 400 μm from the viewpoint of minimizing the reduction in the light receiving area that affects the amount of light incident on the light absorption layer 3 while ensuring good conductivity. Is preferred.

  In addition, it is preferable that at least the surface of the connecting portion 8b of the grid electrode 8 is formed of a material that reflects light in a wavelength region that is absorbed by the light absorption layer 3. Such a configuration is, for example, by adding metal particles such as silver having a high light reflectance to a translucent resin, or depositing a metal having a high light reflectance such as aluminum on the surface of the connecting portion 8b. Etc. can be formed. In this case, when the photoelectric conversion device 20 is modularized, the light reflected by the connecting portion 8b can be reflected again in the module and incident again on the light absorption layer 3. Increasing the incident amount leads to an improvement in photoelectric conversion efficiency in the photoelectric conversion device 20.

  Preferably, at least the current collector 8a of the grid electrode 8 preferably includes solder. Thereby, about the grid electrode 8, while the tolerance with respect to a bending stress is improved, an electrical resistance can be reduced more.

  More preferably, the grid electrode 8 includes two or more kinds of metals having different melting points, is heated at a temperature at which at least one kind of metal is not melted, and is melted at least one other metal and then cured by cooling. And is preferably formed. In this case, since the metal having a low melting point is melted in the formation process, the grid electrode 8 is densified and the resistance is reduced. At that time, the spread of the molten metal is suppressed by the high melting point metal which is not melted.

<(2) Photoelectric conversion device manufacturing process>
Next, a manufacturing process of the photoelectric conversion device 20 having the above configuration will be described. Hereinafter, a case where the light absorption layer 3 made of an I-III-VI group compound semiconductor is formed using a coating method or a printing method, and the buffer layer 4 is further formed will be described as an example.

  3 to 9 are cross-sectional views showing a state during the manufacture of the photoelectric conversion device 20. The cross-sectional views shown in FIG. 3 to FIG. 9 show a state in the middle of manufacturing a portion corresponding to the cross-section shown in FIG.

  First, as shown in FIG. 3, a 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 is preferably formed by scribe processing in which groove processing is performed by irradiating the formation target position while scanning with a YAG laser or other laser light. FIG. 4 is a diagram illustrating a state after the first groove portion P1 is formed.

  After the first groove portion P1 is formed, the light absorption layer 3 and the buffer layer 4 are sequentially formed on the lower electrode layer 2. FIG. 5 is a diagram illustrating a state after the light absorption layer 3 and the buffer layer 4 are formed.

  About the light absorption layer 3, the solution for forming the light absorption layer 3 is apply | coated to the surface of the lower electrode layer 2, and after forming a film | membrane by drying, this film | membrane is formed by heat-processing. The solution for forming the light absorption layer 3 is obtained by directly dissolving the group IB metal and the group III-B metal in a solvent (also simply referred to as a mixed solvent) containing a chalcogen element-containing organic compound and a basic organic solvent. Thus, the total concentration of the group I-B metal and the group III-B metal is 10 wt% or more. For the application of this solution, various methods such as spin coater, screen printing, dipping, spraying, and die coater can be applied.

  The chalcogen element-containing organic compound is an organic compound containing a chalcogen element. The chalcogen element refers to S, Se, or Te among VI-B group elements. Examples of the chalcogen element-containing organic compound include thiol, sulfide, disulfide, selenol, selenide, diselenide, tellurol, telluride, ditelluride and the like.

  For example, it is produced by directly dissolving bullion copper, bullion indium, bullion gallium, and bullion selenium in a mixed solvent in which benzeneselenol is dissolved to 100 mol% with respect to pyridine. A step in which the solution is applied by a blade method and dried to form a film, followed by heat treatment in an atmosphere of hydrogen gas is preferable.

  To directly dissolve a metal in a mixed solvent means to dissolve a single metal or alloy ingot directly into the mixed solvent and dissolve it. Drying is desirably performed in a reducing atmosphere. The drying temperature is, for example, 50 ° C to 300 ° C. The heat treatment is preferably performed in a reducing atmosphere so as to prevent oxidation and obtain a good I-III-VI compound semiconductor. The reducing atmosphere is desirably any of a nitrogen atmosphere, a forming gas atmosphere, and a hydrogen atmosphere. The heat treatment temperature is, for example, 400 ° C to 600 ° C.

  The buffer layer 4 is formed by a solution growth method (CBD method). For example, cadmium acetate and thiourea are dissolved in ammonia, and the substrate 1 having been subjected to the formation of the light absorption layer 3 is immersed therein, whereby the buffer layer 4 made of CdS is formed in the light absorption layer 3. This process is a suitable example.

  After the light absorption layer 3 and the buffer layer 4 are formed, an oxide containing at least one of, for example, indium oxide containing tin (ITO) and indium oxide containing zinc (IZO) is formed on the buffer layer 4. An intermediate conductive layer 6 mainly composed of an indium-based material is formed. The intermediate conductive layer 6 is formed by sputtering, vapor deposition, CVD, or the like. FIG. 6 is a diagram showing a state after the intermediate conductive layer 6 is formed.

  After the formation of the intermediate conductive layer 6, the second groove portion P2 is formed from the linear formation target position along the Y direction on the upper surface of the intermediate conductive layer 6 to the upper surface of the lower electrode layer 2 immediately below it. . The second groove portion P2 is formed, for example, by performing scribing using a scribe needle having a scribe width of about 40 μm to 50 μm continuously several times while shifting the pitch. Further, 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, two or more scribe needles may be fixed in a state where they are in contact with each other or close to each other, and may be formed by 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 shifted in the X direction from the first groove portion P1.

  After the second groove portion P2 is formed, an indium oxide-based material including at least one of indium oxide containing tin (ITO) and indium oxide containing zinc (IZO) is formed on the intermediate conductive layer 6, for example. A transparent upper electrode layer 7 mainly composed of the material is formed. The upper electrode layer 7 is formed by sputtering, vapor deposition, CVD, or the like. FIG. 8 is a view showing a state after the upper electrode layer 7 is formed.

  The intermediate conductive layer 6 and the upper electrode layer 7 are preferably formed by sputtering using the same material as a target in the same type of sputtering apparatus. Specifically, the intermediate conductive layer 6 and the upper electrode layer 7 having different specific resistances are formed by changing the oxygen partial pressure in the atmosphere in the chamber of the sputtering apparatus. More specifically, the oxygen partial pressure of the atmosphere in the chamber is set to a lower state than when the intermediate conductive layer 6 is formed, and the upper electrode layer 7 is formed on the intermediate conductive layer 6 by sputtering. Is done. The condition under which the specific resistance is adjusted between the intermediate conductive layer 6 and the upper electrode layer 7 by changing the oxygen partial pressure in the atmosphere in the chamber of the sputtering apparatus will be described later.

  After the upper electrode layer 7 is formed, the grid electrode 8 is formed. The grid electrode 8 is formed, for example, by printing a conductive paste in which a metal powder such as Ag is dispersed in a resin binder or the like, and drying and solidifying the pattern. Solidification includes the solidified state after melting when the binder used in the conductive paste is a thermoplastic resin, and after curing when the binder is a curable resin such as a thermosetting resin or a photocurable resin. The state of is also included. FIG. 9 is a diagram illustrating a state after the grid electrode 8 is formed.

  After the grid electrode 8 is formed, the third groove portion P3 is formed from the linear formation target position on the upper surface of the upper electrode layer 7 to the upper surface of the lower electrode layer 2 immediately below it. The width of the third groove portion P3 is preferably about 40 μm to 1000 μm, for example. Further, the third groove portion P3 is preferably formed by mechanical scribing similarly to the second groove portion P2. In this manner, the photoelectric conversion device 20 shown in FIGS. 1 and 2 is obtained by forming the third groove P3.

<(3) Adjustment of specific resistance by changing oxygen partial pressure in sputtering method>
Next, by changing the oxygen partial pressure in the chamber of the sputtering apparatus to form a film mainly composed of ITO, the specific resistances of the intermediate conductive layer 6 and the upper electrode layer 7 are adjusted to be different from each other. The conditions will be described with reference to experimental examples.

In the experiment illustrated here, indium oxide (In ₂ O ₃ ) and tin oxide (SnO ₂ ) are installed as targets in the chamber of the sputtering apparatus. A glass substrate having a square surface of 50 nm is placed on a turntable in the chamber, and after the chamber is evacuated, a mixed gas of argon (Ar) and oxygen (O ₂ ) is introduced into the chamber. Then, Ar is ionized and collides with the target. At this time, the blown-off target material adheres (physical adsorption) onto the glass substrate, thereby forming an ITO film (ITO film).

  As shown in Table 1 below, the glass substrate temperature (substrate temperature) is maintained at 180 ° C. to 200 ° C. and the atmosphere in the chamber is set as the sputtering method conditions when forming the ITO film. The pressure is maintained at 0.4 Pa. Furthermore, the voltage, current, and power of a direct current power supply (DC power supply) that applies voltage and current between the target of the sputtering apparatus and the turntable are held at 347 V, 3.76 A, and 1.3 kW, respectively.

Then, the electrical characteristics of the ITO film obtained by changing the ratio of the Ar content and the O ₂ content in the mixed gas introduced into the chamber were measured. The measurement results are shown in Table 2 below.

In Table 2 above, in order from the left, the ratio of the Ar content to the O ₂ content in the mixed gas introduced into the chamber during the formation of the ITO film (here, the Ar content is the O ₂ content). Divided by, simply referred to as the mixing ratio Ar / O ₂ ), the oxygen content (oxygen content) in the mixed gas, the thickness (film thickness) of the formed ITO film, and the ITO film The sheet resistance, the specific resistance of the ITO film, and the sheet resistance of the ITO film when the film thickness is 50 nm (also referred to as sheet resistance in terms of 50 nm thickness) are shown. Specifically, the oxygen content rate and the film in each case where the mixing ratio Ar / O ₂ was set to four levels (36.5 / 0.6, 36/4, 32/8, 30/10) Thickness, sheet resistance, specific resistance, and sheet resistance in terms of 50 nm thickness are shown.

As shown in Table 2 above, as the mixing ratio Ar / O ₂ decreases, that is, the oxygen content in the mixed gas increases, the sheet resistance of the ITO film, the specific resistance, and the sheet resistance in terms of 50 nm thickness increase. FIG. 10 is a line graph showing the relationship between the oxygen content of the mixed gas and the specific resistance of the ITO film, and FIG. 11 shows the relationship between the oxygen content of the mixed gas and the sheet resistance in terms of 50 nm thickness of the ITO film. It is a line graph shown. 10 and 11, the horizontal axis indicates the oxygen content of the mixed gas, in FIG. 10, the vertical axis indicates the specific resistance of the ITO film, and in FIG. 11, the vertical axis indicates the 50 nm-thick sheet of the ITO film. Indicates resistance.

  As shown in FIG. 10 and FIG. 11, when the oxygen content of the mixed gas is 10% or more, both the specific resistance of the ITO film and the sheet resistance in terms of 50 nm thickness rapidly increase as the oxygen content increases. That is, the specific resistance and sheet resistance of the ITO film can be increased by increasing the oxygen partial pressure of the mixed gas introduced into the chamber during sputtering.

Therefore, for example, it is possible to form the intermediate conductive layer 6 by forming the ITO film under the sputtering conditions in which the oxygen content of the mixed gas is 10% or more, and the oxygen content of the mixed gas is 0%. The upper electrode layer 7 can be formed by forming the ITO film under a condition close to. However, as described above, the sheet resistance of the intermediate conductive layer 6 is preferably 1 × 10 ³ Ω / □ to 1 × 10 ⁷ Ω / □ in consideration of necessary specific resistance and conductivity. . For this reason, when the intermediate conductive layer 6 is formed, it is preferable that the oxygen content of the mixed gas introduced into the chamber at the time of sputtering is set to about 10% to 25%.

  In the experimental example described above, when the ITO film is formed by the sputtering method, the substrate temperature is maintained at 180 ° C. to 200 ° C., but the ITO is formed on the glass substrate that is maintained at room temperature (about 25 ° C.) by the sputtering method. A method for forming a film, a method for forming an ITO film by further annealing, and the like are also conceivable.

However, as shown in Table 3 below, the ITO film formed by the sputtering method with the substrate temperature held at room temperature, and 180 after being formed by the sputtering method with the substrate temperature held at room temperature. In the ITO film formed by annealing at a temperature of 200 ° C. to 200 ° C., preferable electrical characteristics (sheet resistance of 1 × 10 ³ Ω / □ to 1 × 10 ⁷ Ω / □) as the intermediate conductive layer 6 are obtained. Absent.

  Specifically, when the film is formed at room temperature, the ITO film becomes amorphous and becomes too high in resistance, and in the method of performing annealing (after annealing), the resistance of the ITO film becomes too low. Therefore, the substrate temperature is preferably heated to about 180 ° C. to 200 ° C. during sputtering when forming the intermediate conductive layer 6.

In Table 3, from the left, the mixture ratio Ar / O _{2 of the} mixed gas introduced into the chamber when forming the ITO film, the oxygen content in the mixed gas, the substrate temperature during sputtering, and the formation The film thickness of the ITO film, the sheet resistance of the ITO film, and the specific resistance of the ITO film are shown.

<(4) Improvement of characteristics due to presence of intermediate conductive layer>
Next, improvement in characteristics of the photoelectric conversion device 20 due to the presence of the intermediate conductive layer 6 will be described with reference to specific examples.

  FIG. 12 and FIG. 13 are diagrams illustrating experimental results regarding differences in characteristics of the photoelectric conversion device depending on the presence or absence of the intermediate conductive layer 6. FIG. 12 shows voltage-current characteristics of the photoelectric conversion device 20 in which the intermediate conductive layer 6 exists, and FIG. 13 shows the photoelectric conversion device 20 in which the intermediate conductive layer 6 is omitted, that is, the intermediate conductive layer 6. The voltage-current characteristic of the photoelectric conversion device without the presence of the symbol is shown.

Here, in the photoelectric conversion device 20 in which the intermediate conductive layer 6 exists, the light absorption layer 3 is formed of CIGS, and the buffer layer 4 is formed of ZnS (zinc sulfide). Further, the intermediate conductive layer 6 is formed by sputtering under the condition that the substrate temperature is about 200 ° C., the sheet resistance is 1 × 10 ⁶ Ω / □ to 1 × 10 ⁷ Ω / □, and the film thickness is about It is a 50 nm ITO film. Further, the upper electrode layer 7 is formed by sputtering under the condition that the substrate temperature is about 200 ° C., the sheet resistance is 1 × 10 ¹ Ω / □ to 1 × 10 ² Ω / □, and the film thickness is about It is a 170 nm ITO film.

On the other hand, in the photoelectric conversion device in which the intermediate conductive layer 6 does not exist, the intermediate conductive layer 6 is not formed and the upper electrode layer is directly formed on the buffer layer 4 as compared with the photoelectric conversion device 20 in which the intermediate conductive layer 6 exists. It has the structure made. The upper electrode layer is formed by sputtering under the condition that the substrate temperature is about 200 ° C., the sheet resistance is 1 × 10 ¹ Ω / □ to 1 × 10 ² Ω / □, and the film thickness is about The ITO film is 220 nm (= 170 nm + 50 nm). That is, the film thickness of the upper electrode layer is substantially equal to the sum of the film thickness of the intermediate conductive layer 6 and the film thickness of the upper electrode layer 7 in the photoelectric conversion device 20 in which the intermediate conductive layer 6 exists.

  12 and 13, the horizontal axis indicates the voltage V between the two electrodes of the photoelectric conversion device, and the vertical axis indicates a value obtained by dividing the current flowing between the two electrodes of the photoelectric conversion device by the effective light receiving area (current density). J is shown. Furthermore, the voltage-current characteristic of the photoelectric conversion device when irradiated with light (during light irradiation) is indicated by a thick solid curve, and the voltage of the photoelectric conversion device when light is not irradiated (during no light irradiation) -The current characteristic (that is, the characteristic relating to the dark current) is shown by a thick dashed curve.

  As shown in FIG. 13, in the photoelectric conversion device in which the intermediate conductive layer 6 does not exist, the fill factor (FF) and the open circuit voltage are small due to the occurrence of leakage current, and the output power in the photoelectric conversion device is small.

  On the other hand, as shown in FIG. 12, for the photoelectric conversion device 20 in which the intermediate conductive layer 6 exists, the FF and the open-circuit voltage are increased by suppressing the leakage current, and the output power in the photoelectric conversion device 20 is improved. ing.

  That is, in the photoelectric conversion device 20 in which the intermediate conductive layer 6 exists, the generation of leakage current is suppressed and a larger output power can be obtained compared to the photoelectric conversion device in which the intermediate conductive layer 6 does not exist.

  As described above, in the photoelectric conversion device 20 according to the embodiment, the buffer layer 4 and the upper electrode layer 7 include an indium oxide-based material of the same type as the upper electrode layer 7 and more than the upper electrode layer 7. By providing the intermediate conductive layer 6 having a high electrical resistivity (specific resistance), the occurrence of leakage current is suppressed. Thereby, the output power in the photoelectric conversion device 20 is improved.

  The intermediate conductive layer 6 and the upper electrode layer 7 are preferably formed by sputtering using the same type of material as a target in the same type of sputtering apparatus. Thereby, for example, since it is not necessary to prepare different types of sputtering apparatuses, the manufacturing equipment and manufacturing process of the photoelectric conversion apparatus can be simplified. Furthermore, for example, the intermediate conductive layer 6 and the upper electrode layer 7 can be formed without causing the sputtering apparatus to be contaminated by sputtering using different materials.

<(5) Modification>
The present invention is not limited to the above-described embodiment, and various changes and improvements can be made without departing from the scope of the present invention.

  For example, in the above-described embodiment, the upper electrode layer 7 is formed after the formation of the second groove P2, but the present invention is not limited to this. For example, the upper electrode layer is formed before the formation of the second groove P2, and then the second groove and the third groove are formed at the same time by mechanical scribing or the like, and then the grid electrode is formed. Also good. In this case, for example, the surface of the intermediate conductive layer 6 is not contaminated by scraps or the like generated when the second groove is formed by mechanical scribing, so that deterioration of the surface of the intermediate conductive layer 6 is suppressed, The photoelectric conversion efficiency is further increased.

  Further, in this case, the intermediate conductive layer 6 and the upper electrode layer can be continuously formed. For this reason, in the same sputtering apparatus, the intermediate conductive layer 6 and the upper electrode layer are continuously formed by changing the oxygen partial pressure of the atmosphere in the sputtering apparatus (for example, in the chamber). May be. With such a configuration, the manufacturing apparatus and manufacturing process of the photoelectric conversion device can be further simplified, and the manufacturing cost of the photoelectric conversion device can be further reduced.

  FIG. 14 is a cross-sectional view showing a configuration of a photoelectric conversion device 20A manufactured by forming the upper electrode layer 7A before forming the second groove portion. As shown in FIG. 1, the structure of the photoelectric conversion device 20 </ b> A viewed from above is the same as the structure of the photoelectric conversion device 20 according to the one embodiment viewed from above. For this reason, the cross section of the photoelectric conversion device 20A shown in FIG. 14 corresponds to the cross section of the photoelectric conversion device 20A along the section line II-II in FIG.

  In the photoelectric conversion device 20A, compared to the photoelectric conversion device 20 according to the one embodiment, the second groove portion P2 is replaced with the second groove portion P2A having a different width, and the extending portion 7a is omitted from the upper electrode layer 7. The upper electrode layer 7A is replaced, the grid electrode 8 is replaced with a grid electrode 8A having a hanging part 8c having a different structure, and the connecting part 9 is replaced with a connecting part 9A including a hanging part 8cA having a different structure. It is a thing. With the replacement of these configurations, the photoelectric conversion cell 10 is changed to a photoelectric conversion cell 10A having a different configuration.

  15 and 16 are cross-sectional views showing a state in the middle of manufacturing the photoelectric conversion device 20A. Note that the cross sections shown in FIGS. 15 and 16 show a state in the middle of manufacturing a portion corresponding to the cross section of the photoelectric conversion device 20A shown in FIG. In addition, among the manufacturing process of the photoelectric conversion device 20A and a state in the middle of manufacturing, the film forming process of the lower electrode layer 2 (FIG. 3), the process of forming the first groove P1 (FIG. 4), the light absorption layer 3, and the buffer layer 4 The forming step (FIG. 5) and the forming step (FIG. 6) of the intermediate conductive layer 6 are the same as the manufacturing process of the photoelectric conversion device 20 and the state during the manufacturing. For this reason, below, the manufacturing process of 20 A of photoelectric conversion apparatuses after formation of the intermediate conductive layer 6 is demonstrated.

  After the intermediate conductive layer 6 is formed, an indium oxide-based material including at least one of indium oxide containing tin (ITO) and indium oxide containing zinc (IZO) is formed on the intermediate conductive layer 6, for example. A transparent upper electrode layer 7A mainly composed of the material is formed. The upper electrode layer 7A is formed by sputtering, vapor deposition, CVD, or the like, similar to the upper electrode layer 7 according to the one embodiment. Preferably, in the sputtering apparatus in which the intermediate conductive layer 6 is formed, the oxygen partial pressure in the sputtering apparatus (for example, in the chamber) is reduced, and the upper electrode layer 7A may be formed by sputtering. FIG. 15 is a diagram showing a state after the upper electrode layer 7A is formed.

  After the upper electrode layer 7A is formed, the second groove portion P2A and the third groove portion P3 are formed. The second groove portion P2A is formed from the linear formation target position along the Y direction on the upper surface of the upper electrode layer 7A to the upper surface of the lower electrode layer 2 immediately below it. The third groove portion P3 is formed from the formation target position slightly on the X side to the upper surface of the lower electrode layer 2 immediately below the formation target position related to the second groove portion P2A in the upper surface of the upper electrode layer 7A. The second groove P2A can be formed by the same method as the second groove P2 according to the above-described embodiment, and the third groove P3 can be formed by the same method as the third groove P3 according to the above-described embodiment. It is. FIG. 16 is a diagram illustrating a state after the second groove portion P2A and the third groove portion P3 are formed.

  After the second groove portion P2A and the third groove portion P3 are formed, the grid electrode 8A is formed. The grid electrode 8A can be formed by the same method as the grid electrode 8 according to the above-described embodiment. In this manner, the formation of the grid electrode 8 yields the photoelectric conversion device 20A shown in FIG.

  Further, for example, the intermediate conductive layer and the upper electrode layer may be formed after the formation of the second groove portion, and then the third groove portion and the grid electrode may be formed.

  FIG. 17 is a cross-sectional view illustrating a configuration of a photoelectric conversion device 20B manufactured by sequentially forming the intermediate conductive layer 6B and the upper electrode layer 7B after the formation of the second groove portion P2B. As shown in FIG. 1, the structure of the photoelectric conversion device 20 </ b> B viewed from above is the same as the structure of the photoelectric conversion device 20 according to the above embodiment viewed from above. For this reason, the cross section of the photoelectric conversion device 20B shown in FIG. 17 corresponds to the cross section of the photoelectric conversion device 20B along the section line II-II in FIG.

  In the photoelectric conversion device 20B, compared to the photoelectric conversion device 20 according to the above-described embodiment, the second groove portion P2 is replaced with a second groove portion P2B having a different width, and the intermediate conductive layer 6 has an extending portion 6aB. Replaced by the intermediate conductive layer 6B, the upper electrode layer 7 is replaced by the upper electrode layer 7B in which the extended portion 7a is an extended portion 7aB having a different shape, and the grid electrode 8 is a suspended portion in which the suspended portion 8c has a different shape. The connecting portion 9 is replaced with the grid electrode 8B which is the portion 8cB, and the connecting portion 9 is a hanging portion from the extending portion 6aB of the intermediate conductive layer 6B, the extending portion 7aB of the upper electrode layer 7B, and the connecting portion 8b formed thereon. It is replaced with a connecting portion 9B constituted by 8cB. With the replacement of these configurations, the photoelectric conversion cell 10 is changed to a photoelectric conversion cell 10B having a different configuration.

  Even if such a configuration is adopted, the intermediate conductive layer 6B and the upper electrode layer 7B can be continuously formed. For this reason, although the electrical resistance is somewhat increased by the extension portion 6aB of the intermediate conductive layer 6B being interposed, the manufacturing device and manufacturing process of the photoelectric conversion device are further simplified, and the manufacturing cost of the photoelectric conversion device is further increased. Reduction is possible.

DESCRIPTION OF SYMBOLS 1 Board | substrate 2 Lower electrode layer 3 Light absorption layer 4 Buffer layer 5 Photoelectric conversion layer 6, 6B Intermediate conductive layer 6aB, 7a, 7aB Extension part 7, 7A, 7B Upper electrode layer 8, 8A, 8B Grid electrode 8a Current collection part 8b Connecting portion 8c, 8cA, 8cB Hanging portion 9, 9A, 9B Connection portion 10, 10A, 10B Photoelectric conversion cell 20, 20A, 20B Photoelectric conversion device

Claims (5)

A lower electrode layer;
A first semiconductor layer provided on the lower electrode layer;
A second semiconductor layer having a conductivity type different from that of the first semiconductor layer provided on the first semiconductor layer;
An upper electrode layer including an indium oxide-based material provided on the second semiconductor layer;
An intermediate conductive layer that is provided between the second semiconductor layer and the upper electrode layer and includes an indium oxide-based material and has a higher electrical resistivity than the upper electrode layer;
A photoelectric conversion device comprising: A first forming step of forming a first semiconductor layer on the lower electrode layer;
Forming a second semiconductor layer having a conductivity type different from that of the first semiconductor layer on the first semiconductor layer;
A third forming step of forming an intermediate conductive layer containing an indium oxide-based material on the second semiconductor layer by a sputtering method;
In an atmosphere having a second oxygen partial pressure lower than the first oxygen partial pressure of the atmosphere in which the third forming step is performed, the intermediate conductive layer includes an indium oxide-based material and is more electrically than the intermediate conductive layer. A fourth forming step of forming an upper electrode layer having a low resistivity by a sputtering method;
A process for producing a photoelectric conversion device comprising: It is a manufacturing method of the photoelectric conversion device according to claim 2,
The atmosphere of the first and second oxygen partial pressures is
A method for manufacturing a photoelectric conversion device, comprising: an atmosphere in a sputtering device in which the third and fourth forming steps are performed. It is a manufacturing method of the photoelectric conversion device according to claim 2 or 3,
The third and fourth forming steps include
A method for manufacturing a photoelectric conversion device, which is performed in the same type of sputtering apparatus. A method for manufacturing a photoelectric conversion device according to any one of claims 2 to 4,
The third and fourth forming steps include
A method for manufacturing a photoelectric conversion device, which is performed continuously by changing an oxygen partial pressure in an atmosphere in the sputtering device in the same sputtering device.

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