JP2013074147A - Photoelectric conversion device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photoelectric conversion device which reduces the deterioration in photoelectric conversion efficiency.SOLUTION: A photoelectric conversion device comprises: a substrate 1; an electrode layer provided on the substrate 1; and a photoelectric conversion layer 3 provided on the electrode layer. The electrode layer is made of a plurality of crystal grains 2p which are aligned continuously in a columnar manner in the thickness direction of the electrode layer to thereby form a bent portion 2c.

Description

  The present invention relates to a photoelectric conversion device.

  As a photoelectric conversion device used for solar power generation or the like, there is one in which cells corresponding to a plurality of photoelectric conversion bodies are provided on one substrate. In this cell, for example, an electrode layer, a semiconductor film containing a compound semiconductor, and an upper electrode are stacked in this order. This electrode layer is known to be produced by sputtering a metal thin film such as molybdenum (Mo). (For example, Patent Document 1 and Patent Document 2)

JP 2006-80371 A Japanese Patent Laid-Open No. 2006-210424

  By the way, when the electrode layer of a photoelectric conversion apparatus is produced with thin films, such as a metal, a cooling process may be performed after a heat processing in the formation process of an electrode layer. At this time, stress is generated due to the difference in thermal expansion coefficient between the substrate and the electrode layer, and there is a possibility that a crack occurs in the electrode layer. Due to the progress of the cracks in the electrode layer, the series resistance component of the photoelectric conversion device may increase and the photoelectric conversion efficiency may decrease.

  One object of the present invention is to provide a photoelectric conversion device that reduces a decrease in photoelectric conversion efficiency.

  A photoelectric conversion device according to an embodiment of the present invention includes a substrate, an electrode layer provided on the substrate, and a photoelectric conversion layer provided on the electrode layer. The electrode layer is composed of a plurality of crystal grains, and the crystal grains are arranged in a column shape in the thickness direction of the electrode layer so as to have a curved portion.

  According to the photoelectric conversion device according to one embodiment of the present invention, the progress of cracks in the thickness direction of the electrode layer can be reduced. Thereby, since increase of the series resistance component of a photoelectric conversion apparatus can be reduced, the fall of photoelectric conversion efficiency can be made small.

It is a top view which shows typically the structure of the photoelectric conversion apparatus which concerns on one Embodiment of this invention. It is sectional drawing in the position shown with the dashed-dotted line II-II in FIG. It is a figure which expands and shows typically the XZ section of the laminated body which consists of a board | substrate, a lower electrode layer (electrode layer), and a photoelectric converting layer. It is a flowchart which shows the manufacturing flow of a photoelectric conversion apparatus. 2 is a cross-sectional view schematically showing a configuration of a sputtering apparatus for forming a lower electrode layer 2. FIG. It is a figure which expands and shows typically the XZ section of the laminated body which consists of a board | substrate which concerns on other embodiment, a lower electrode layer (electrode layer), and a photoelectric converting layer. It is a figure which expands and shows typically the XZ section of the laminated body which consists of a board | substrate which concerns on other embodiment, a lower electrode layer (electrode layer), and a photoelectric converting layer.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the drawings, parts having the same configuration and function are denoted by the same reference numerals, and redundant description is omitted in the following description. Further, the drawings are schematically shown, and the sizes, positional relationships, and the like of various structures in the drawings are not accurately illustrated. 1 to 3, 6, and 7, a right-handed XYZ coordinate system in which the arrangement direction of photoelectric conversion cells 10 (the left-right direction in the drawing of FIG. 1) is the X-axis direction is attached.

<(1) Schematic configuration of photoelectric conversion device>
<(1-1) Schematic configuration of photoelectric conversion device>
As shown in FIG. 1 or FIG. 2, the photoelectric conversion device 100 includes a substrate 1 and a plurality of photoelectric conversion cells 10 arranged in a plane on one main surface of the substrate 1. Adjacent photoelectric conversion cells 10 are separated by a groove P3. That is, in the photoelectric conversion device 100, a plurality of photoelectric conversion cells 10 are arranged on one main surface of the substrate 1 via the groove portion P3 along a predetermined arrangement direction (+ X direction in the present embodiment). In FIG. 1, for convenience of illustration, the groove portion P <b> 1 is seen through the upper surface and is indicated by a dotted line. In FIG. 1, only a part of the three photoelectric conversion cells 10 is shown. However, in the photoelectric conversion device 100, a large number (for example, eight) of photoelectric conversion cells 10 may be arranged in a plane (two-dimensionally) in the horizontal direction of the drawing. For example, electrodes for obtaining a voltage and a current by power generation may be provided at both ends in the X-axis direction of the photoelectric conversion device 100. In the photoelectric conversion device 100, for example, a large number of photoelectric conversion cells 10 may be arranged in a matrix.

  Further, for example, a mode in which the shape of the upper surface of each photoelectric conversion cell 10 is approximately rectangular and the shape of the upper surface of the photoelectric conversion device 100 is approximately square may be employed. In addition, the shape of the upper surface of each photoelectric conversion cell 10 does not need to be substantially rectangular, and may be other shapes. Further, the shape of the upper surface of the photoelectric conversion device 100 does not have to be generally square, and may be other shapes. However, in the photoelectric conversion apparatus 100, the conversion efficiency is improved if a large number of photoelectric conversion cells 10 are arranged in a high-density plane.

  The conversion efficiency indicates a rate at which sunlight energy is converted into electric energy in the photoelectric conversion device 100. For example, the conversion efficiency can be derived by dividing the value of the electric energy output from the photoelectric conversion device 100 by the value of the energy of sunlight incident on the photoelectric conversion device 100 and multiplying by 100.

<(1-2) Basic configuration of photoelectric conversion cell>
Each photoelectric conversion cell 10 includes a lower electrode 2 as an electrode layer, a photoelectric conversion layer 3, an upper electrode layer 4, and a linear conductive portion 5. Each photoelectric conversion cell 10 is provided with a groove part P1 and a groove part P2. And in the photoelectric conversion apparatus 100, the main surface in the side in which the linear conductive part 5 was provided becomes a light-receiving surface.

  The substrate 1 supports a plurality of photoelectric conversion cells 10. Examples of the main material included in the substrate 1 include glass, ceramics, resin, and metal. Here, it is assumed that the substrate 1 is blue plate glass (soda lime glass) having a thickness of about 1 to 3 mm. Moreover, you may contain either one of potassium and sodium in glass. Thereby, when the light absorption layer 31 is comprised with the I-III-VI group compound semiconductor mentioned later, since the carrier concentration of the photoelectric converting layer 3 can be increased, the conversion efficiency of the photoelectric converting layer 3 can be improved.

  The lower electrode layer 2 is a conductive layer provided on one main surface of the substrate 1 on the + Z side. As shown in FIG. 2, the lower electrode layer 2 is arranged on one main surface of the substrate 1 with a gap (groove portion P <b> 1) therebetween. As the main material included in the lower electrode layer 2, various conductive metals such as molybdenum, aluminum, titanium, tantalum, and gold can be employed. In the above metal, molybdenum hardly reacts with a group VI element such as selenium, and therefore, deterioration that may be caused by the selenium is unlikely to occur. Moreover, the thickness of the lower electrode layer 2 is about 0.2-1 micrometer or less, for example. The detailed structure of the lower electrode layer 2 will be described later.

  The photoelectric conversion layer 3 is provided on the lower electrode layer 2 and includes a light absorption layer 31 and a buffer layer 32 that are sequentially stacked. Since the light absorption layer 31 and the buffer layer 32 are layers mainly including a semiconductor, the photoelectric conversion layer 3 is a layer mainly including a semiconductor (also referred to as a semiconductor layer).

  The light absorption layer 31 is provided on the main surface (also referred to as one main surface) on the + Z side of the lower electrode layer 2 and mainly includes a semiconductor having a first conductivity type (here, p-type conductivity type). Including. The thickness of the light absorption layer 31 is, for example, about 1 to 3 μm or less. The light absorption layer 31 mainly includes, for example, an I-III-VI group compound semiconductor. Thereby, the light absorption layer 31 can be thinned, and the conversion efficiency can be increased at a low cost with a small amount of material. The I-III-VI group compound semiconductor is a semiconductor mainly containing an I-III-VI group compound.

Here, as the I-III-VI group compound, 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). ). Examples of the I-III-VI group compounds 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), and Cu. A material such as (In, Ga) (Se, S) ₂ (also referred to as diselene, copper indium gallium sulfide, gallium, or CIGSS) may be employed. Here, the light absorption layer 31 shall mainly contain CIGS.

The light absorption layer 31 may be, for example, a thin film of a multicomponent compound semiconductor such as copper indium selenide / gallium having a thin film mainly containing diselen / copper indium sulfide / gallium as a surface layer. The light absorption layer 31 may mainly contain, for example, a II-VI group compound semiconductor. The II-VI group compound semiconductor is a semiconductor mainly containing a II-VI group compound. The II-VI group compound is a compound mainly containing a II-B group (also referred to as a group 12 element) and a VI-B group element. However, if the light absorption layer 31 mainly contains an I-III-VI compound semiconductor, the photoelectric conversion efficiency (also referred to as photoelectric conversion efficiency) in the photoelectric conversion layer 3 can be increased. Moreover, the light absorption layer 31 may be a CZTS-based material including, for example, copper (Cu), zinc (Zn), tin (Sn), and sulfur (S). An example of such a CZTS compound semiconductor is Cu ₂ ZnSnS ₄ . Since the CZTS compound semiconductor does not use rare metal unlike the I-III-VI compound semiconductor, it is easy to secure the material.

  The light absorption layer 31 can be formed by a vacuum process such as sputtering or vapor deposition. The light absorption layer 31 can also be formed by a process called a coating method or a printing method. In the application method or the printing method, for example, a complex solution of elements mainly contained in the light absorption layer 31 is applied on the lower electrode layer 2, and then drying and heat treatment are performed. By using a process called a coating method or a printing method, the cost for manufacturing the photoelectric conversion device 100 can be reduced.

The buffer layer 32 is provided on the main surface (also referred to as one main surface) on the + Z side of the light absorption layer 31, and has a second conductivity type (here, n) different from the first conductivity type of the light absorption layer 31. Mainly including a semiconductor having a conductive type). Note that semiconductors having different conductivity types are semiconductors having different conductive carriers. Moreover, the conductivity type of the light absorption layer 31 may be n-type, and the conductivity type of the buffer layer 32 may be p-type. Here, a heterojunction region is formed between the light absorption layer 31 and the buffer layer 32. For this reason, in the photoelectric conversion cell 10, photoelectric conversion can occur in the light absorption layer 31 and the buffer layer 32 that form the heterojunction region.

The buffer layer 32 mainly includes a compound semiconductor. Examples of the compound semiconductor included in the buffer layer 32 include cadmium sulfide (CdS), indium sulfide (In ₂ S ₃ ), zinc sulfide (ZnS), zinc oxide (ZnO), indium selenide (In ₂ Se ₃ ), In (OH, S), (Zn, In) (Se, OH), (Zn, Mg) O, and the like may be employed. If the buffer layer 32 has a resistivity of 1 Ω · cm or more, the generation of leakage current can be suppressed. The buffer layer 32 can be formed by, for example, a chemical bath deposition (CBD) method or the like.

  The buffer layer 32 has a thickness in the normal direction (+ Z direction) of one main surface of the light absorption layer 31. This thickness is set to 10 to 200 nm or less, for example. If the thickness of the buffer layer 32 is 100 to 200 nm or less, the buffer layer 32 is less likely to be damaged when the upper electrode layer 4 is formed on the buffer layer 32 by a sputtering method or the like.

  The upper electrode layer 4 is provided on the + Z side main surface (also referred to as one main surface) of the buffer layer 32. The upper electrode layer 4 is provided on one main surface of the buffer layer 32 and is, for example, a transparent conductive layer (also referred to as a transparent conductive layer) having an n-type conductivity. The upper electrode layer 4 serves as an electrode (also referred to as an extraction electrode) that extracts charges generated in the photoelectric conversion layer 3. The upper electrode layer 4 mainly includes a material having a lower resistivity than the buffer layer 32. The upper electrode layer 4 may include what is called a window layer, and may include a window layer and a transparent conductive layer.

The upper electrode layer 4 mainly includes a transparent and low resistance material having a wide forbidden band width. As such a material, for example, a metal oxide semiconductor such as zinc oxide (ZnO), a compound of zinc oxide, indium oxide containing tin (ITO), and tin oxide (SnO ₂ ) can be employed. The zinc oxide compound only needs to contain any one element of aluminum, boron, gallium, indium, and fluorine.

  The upper electrode layer 4 can be formed by sputtering, vapor deposition, chemical vapor deposition (CVD), or the like. The thickness of the upper electrode layer 4 may be, for example, 0.05 to 3 μm or less. Here, if the upper electrode layer 4 has a resistivity of less than 1 Ω · cm and a sheet resistance of 50 Ω / □ or less, electric charges are favorably extracted from the photoelectric conversion layer 3 through the upper electrode layer 4. Can be.

  If the buffer layer 32 and the upper electrode layer 4 have a property (also referred to as light transmittance) that allows light to easily pass through the wavelength band of light that can be absorbed by the light absorption layer 31, the light absorption layer 31. Decrease in light absorption efficiency in can be suppressed. Moreover, if the thickness of the upper electrode layer 4 is 0.05 to 0.5 μm or less, the light transmittance in the upper electrode layer 4 can be improved, and at the same time, the current generated by the photoelectric conversion can be transmitted well. Further, if the absolute refractive index of the upper electrode layer 4 and the absolute refractive index of the buffer layer 32 are substantially the same, the incident light loss caused by the reflection of light at the interface between the upper electrode layer 4 and the buffer layer 32 is reduced. Can be reduced.

The linear conductive portion 5 is a linear electrode portion provided on the + Z side main surface (also referred to as one main surface) of the upper electrode layer 4. The linear conductive portion 5 includes a plurality of current collecting portions 5a, connecting portions 5b, and hanging portions 5c. The plurality of current collectors 5a are separated in the Y-axis direction, and each current collector 5a extends in the X-axis direction. The connecting portion 5b is provided in the Y-axis direction, and each current collecting portion 5a is connected. The drooping part 5c is connected to the lower part of the connecting part 5b, and is connected to the lower electrode layer 2 extended from the adjacent photoelectric conversion cell 10 through the groove part P2.

  The current collector 5 a plays a role of collecting charges generated in the photoelectric conversion layer 3 and taken out in the upper electrode layer 4. By providing the current collector 5a, the conductivity of the upper electrode layer 4 is supplemented, so that the upper electrode layer 4 can be thinned. As a result, it is possible to achieve both the securing of charge extraction efficiency and the improvement of light transmittance in the upper electrode layer 4. In addition, if the linear electroconductive part 5 mainly contains the metal which was excellent in electroconductivity, such as silver, the conversion efficiency in the photoelectric conversion apparatus 100 can improve. Moreover, as a metal contained in the linear conductive part 5, copper, aluminum, nickel, etc. may be sufficient, for example.

  The charges collected by the upper electrode layer 4 and the plurality of current collecting portions 5a are transmitted to the adjacent photoelectric conversion cell 10 through the connecting portion 5b and the hanging portion 5c. Thereby, in the photoelectric conversion apparatus 100, the adjacent photoelectric conversion cells 10 are electrically connected in series. Specifically, the drooping portion 5c electrically connected to the current collector 5a of one photoelectric conversion cell 10 and the lower electrode layer 2 of the other photoelectric conversion cell 10 are electrically connected in series. It is connected to the.

  Moreover, if the width | variety of the current collection part 5a is 50-400 micrometers, the fall of the incident amount of the light to the light absorption layer 31 may be suppressed, ensuring the favorable electroconductivity between the adjacent photoelectric conversion cells 10. FIG. The interval between the plurality of current collectors 5a provided in one photoelectric conversion cell 10 may be about 2.5 mm, for example.

<(1-3) Arrangement of groove and its role>
The groove part P1 extends linearly in the Y-axis direction. By arranging one or more of the groove portions P1, the plurality of electrode layers 2 are separated in the X-axis direction. That is, the groove part P1 corresponds to a gap provided between adjacent electrode layers. In FIG. 2, two electrode layers 2 are shown. The extending part of the light absorption layer 31 arranged immediately above is embedded in the groove part P1. That is, the light absorption layer 31 is disposed so as to cover the gap (groove portion P1) located between the electrode layers. Thereby, in the adjacent photoelectric conversion cell 10, the lower electrode layer 2 of one photoelectric conversion cell 10 and the lower electrode layer 2 of the other photoelectric conversion cell 10 are electrically separated. The width of the groove part P1 may be about 40 to 400 μm or less, for example.

  The groove portion P2 is provided from one main surface of the upper electrode layer 4 to the upper surface of the lower electrode layer 2, and extends linearly in the Y-axis direction. For this reason, the groove portion P2 separates the stacked portion in which the photoelectric conversion layer 3 and the upper electrode layer 4 are stacked in the X-axis direction. That is, the groove part P <b> 2 is provided so as to penetrate the photoelectric conversion layer 3 in a direction perpendicular to one main surface of the substrate 1.

  The groove part P3 is provided from the upper surface of the photoelectric conversion cell 10 to the upper surface of the lower electrode layer 2, and extends in the Y-axis direction. The width of the groove P3 may be about 40 to 1000 μm or less, for example.

  When the photoelectric conversion device 100 is seen through from above the light receiving surface (here, + Z side), the groove portion P2 is provided between the groove portion P1 and the groove portion P3. In other words, the groove part P1, the groove part P2, and the groove part P3 are provided in this order in the + X direction. Further, in each photoelectric conversion cell 10, the photoelectric conversion layer 3 is provided from the top of the lower electrode layer 2 over the groove P <b> 1 to the top of the adjacent lower electrode layer 2. Here, the adjacent lower electrode layer 2 is the lower electrode layer 2 extending from the adjacent photoelectric conversion cell 10.

When the photoelectric conversion device 100 is seen through from above the light receiving surface (here, + Z side), the photoelectric conversion device 100 includes the groove portion P1 and the groove portion P2 and is sandwiched between the groove portion P1 and the groove portion P2. There are a region (also referred to as a connection region), a region sandwiched between the groove P2 and the groove P3, and a remaining region. This remaining area is an area contributing to power generation (also referred to as a power generation contribution area).

<(1-4) Structure of lower electrode layer 2 (electrode layer)>
The lower electrode layer 2 has a plurality of crystal grains 2p as shown in FIG. A grain boundary exists between the adjacent crystal grains 2p. The plurality of crystal grains 2p are connected in a columnar shape in the thickness direction (+ Z direction) of the lower electrode layer 2.

  The shape of the crystal grain 2p in the XY section is, for example, a substantially elliptical shape. At this time, the major axis of the crystal grain 2p is about 10 to 50 nm, and the minor axis is about 3 to 20 nm. The length of the crystal grain 2p in the + Z direction is about 0.2 to 1 μm. In addition, the shape of the XY cross section of the crystal grain 2p is not limited to an elliptical shape, and may be an elongated shape having an outer shape with straight lines and curves.

  Further, as shown in FIG. 3, the plurality of crystal grains 2p are arranged so that the shape of the XZ section has a curved portion 2c. Thus, when the crystal grains 2p are arranged so that the shape of the XZ cross section has the curved portion 2c, the arrangement shape of the plurality of crystal grains 2p in the YZ cross section does not have the curved portion 2c. On the other hand, when the crystal grains 2p are arranged so that the shape of the YZ cross section has the curved portion 2c, the arrangement shape of the plurality of crystal grains 2p in the XZ cross section does not have the curved portion 2c. In this way, the curved portion 2c that can be formed by connecting a plurality of crystal grains 2p in a columnar shape can be confirmed in either the XZ cross section or the YZ cross section. That is, the curved portion 2c is configured between the thickness direction of the lower electrode layer 2 (Z direction in the present embodiment) and a direction orthogonal to the thickness direction (X direction or Y direction in the present embodiment). One of the two cross sections can be identified.

  Thus, in the lower electrode layer 2 in the present embodiment, the progress of cracks generated between the crystal grain groups 2g formed of the crystal grains 2p arranged in a columnar shape can be reduced. Such cracks are likely to occur due to the stress generated by the difference in thermal expansion coefficient between the substrate 1 and the lower electrode layer 2. And the said crack tends to advance in the thickness direction of the lower electrode layer 2 through the grain boundary which exists between the adjacent crystal grain groups 2g. On the other hand, if the crystal grain group 2g is curved as in the present embodiment, it is possible to make it difficult for cracks to advance in the thickness direction of the lower electrode layer 2. That is, the progress of cracks is likely to stop in the curved portion 2c configured by an array of a plurality of crystal grains 2p. Thereby, since the increase in the series resistance component of the lower electrode layer 2 can be reduced, the fall of the photoelectric conversion efficiency of the photoelectric conversion apparatus 100 can be reduced. If the curved portion 2c forms an angle of about 120 to 170 degrees when viewed in a cross section where the curved portion 2c can be confirmed, the progress of cracks is likely to stop.

  From another viewpoint, in the XZ cross section or the YZ cross section, the grain boundary located between adjacent crystal grain groups 2g extends so as to be bent. Therefore, the sliding surface of the grain boundary can be formed in a direction different from the direction in which cracks tend to proceed (the thickness direction of the lower electrode layer 2). The progress of this crack can occur when the crystal grain 2p moves (slides). Therefore, if the slip surfaces of the grain boundaries are located in two different directions, the slip is unlikely to occur, so that cracks do not easily progress in the thickness direction of the lower electrode layer 2.

<(2) Manufacturing process of photoelectric conversion device>
Here, an example of a manufacturing process of the photoelectric conversion device 100 having the above configuration will be described. FIG. 4 is a flowchart illustrating the manufacturing flow of the photoelectric conversion apparatus 100. Hereinafter, a case where the light absorption layer 31 mainly including the I-III-VI group compound semiconductor is formed by using a coating method or a printing method and the buffer layer 32 is further formed will be described as an example.

  First, in step Sp1, a flat substrate 1 having a substantially rectangular board surface is prepared.

  In step Sp2, the lower electrode layer 2 is formed on substantially the entire main surface of the cleaned substrate 1 by using a sputtering method or a vapor deposition method.

  In this step Sp2, for example, the sputtering apparatus 200 shown in FIG. 5 is used. The sputtering apparatus 200 includes a load lock chamber 21, a film formation chamber 22, and an unload lock chamber 23. In these chambers, a transport mechanism 24 (24a to 24c), a gate valve 25 (25a to 25d), a supply line 26 (26a to 26c), and a vacuum pump 27 (27a to 27c) are provided.

  The load lock chamber 21 has a function of blocking the film formation chamber 22 from the external atmosphere. As a result, it is possible to secure a vacuum in the film forming chamber 22 and reduce the occurrence of contamination, and the efficiency of the film forming process is improved. The load lock chamber 21 accommodates the substrate 1 transferred from the outside of the sputtering apparatus 200 into the load lock chamber 21 by the transfer mechanism 24a. In the load lock chamber 21, the temperature of the substrate 1 can be raised by a heater 28 provided in the chamber.

  The film forming chamber 22 has a function of forming the lower electrode layer 2 on the substrate 1 by sputtering. Inside the film forming chamber 22, a sputtering target 29 made of a metal constituting the lower electrode layer 2 is disposed. The sputtering target 29 is disposed at a substantially central portion in the film forming chamber 22. A DC power supply 30 is provided outside the film forming chamber 22. The film forming chamber 22 is provided with a transport mechanism 24b for transporting the substrate 1 from the one end to the other end within the film forming chamber 22 at a predetermined speed. The transport mechanism 24b can change the speed, stop, reverse run, etc. during the film forming process.

  The unload lock chamber 23 has a function of blocking the film formation chamber 22 from the external atmosphere. As a result, it is possible to secure a vacuum in the film forming chamber 22 and reduce the occurrence of contamination, and the efficiency of the film forming process is improved. The unload lock chamber 23 accommodates the substrate 1 transferred from the film formation chamber 22 into the unload lock chamber 23. The substrate 1 is transferred to the outside of the sputtering apparatus 200 by the transfer mechanism 24c.

  The transport mechanism 24 (24a to 24c) has a mechanism for transporting the substrate 1 by, for example, a chain driven by a servo motor. Further, each transport mechanism 24 has a mechanism that can transfer the substrate 1 between the transport mechanisms.

  Next, the operation of the sputtering apparatus 200 will be described.

  First, the substrate 1 is set in the transport mechanism 24a so that the film formation surface is facing down. Next, nitrogen gas is supplied through the supply line 26 a in the load lock chamber 21 to return the load lock chamber 21 to atmospheric pressure. Next, the gate valve 25a is opened, and the substrate 1 is transferred into the rod lock chamber 21 by the transfer mechanism 24a. Next, the supply of nitrogen gas is stopped, the gate valve 25a is closed, and the inside of the load lock chamber 21 is reduced to a predetermined pressure by the vacuum pump 27a. Next, the temperature of the substrate 1 is raised to about 50 to 250 ° C. by the heater 28.

  Next, the gate valve 25 b is opened and closed, and the substrate 1 is transferred to the film formation chamber 22. Next, after the film formation chamber 22 is depressurized to a predetermined pressure by the vacuum pump 27b, the flow rate of argon (Ar) gas is controlled by a mass flow controller or the like, and introduced into the film formation chamber 22. Next, a voltage is applied between the sputtering target 29 and the substrate 1 by the DC power source 30 to start sputtering. At this time, the pressure inside the film forming chamber 22 may be about 0.1 to 10 Pa.

  During sputtering, the substrate 1 is transferred from the gate valve 25b side to the gate valve 25c side by a transfer mechanism 24 at a predetermined speed of about 1 to 10 mm / sec. Thereby, the direction in which the metal particles sputtered fly toward the substrate 1 gradually changes. For example, as shown in FIG. 5, the direction in which the metal particles fly to the substrate 1 varies depending on the positions 1 </ b> A to 1 </ b> C of the substrate 1. First, when the substrate 1 is at the position 1A, the direction is the reverse of the traveling direction. Further, when the substrate 1 is at a position 1B in the vicinity of directly above the sputtering target 29, the direction is perpendicular to the traveling direction. When the substrate 1 is at the position 1C, the direction is the same as the traveling direction. The speed at which the substrate 1 passes through the position 1B immediately above the sputtering target 29 is faster than the speed at which it passes through the position 1A and the position 1C of the substrate. Thereby, the curved part 2c can be formed. At this time, the speed at which the substrate 1 passes through the position 1B may be about 1.2 to 1.6 times faster than the speed at which the substrate 1 passes through the positions 1A and 1C.

  As described above, by changing the flying direction of the metal particles with respect to the substrate 1 during the sputtering, the growth direction of the crystal grains 2p can be changed along with the flying direction. As a result, as shown in FIG. 3, the plurality of crystal grains 2p are arranged in a columnar shape in the thickness direction of the lower electrode layer 2 so as to have a curved portion 2c.

  Next, when the substrate 1 moves to the end of the film formation chamber 22, the sputtering is stopped and the inside of the unload lock chamber 23 is reduced to a predetermined pressure by the vacuum pump 27c. Next, the substrate 1 is moved into the unload lock chamber 23 by opening and closing the gate valve 25c. Next, the vacuum pump 27c is stopped, nitrogen gas is supplied through the supply line 26c, and the unload lock chamber 23 is returned to atmospheric pressure. Next, the gate valve 25d is opened, and the substrate 1 is transferred out of the unload lock chamber 23 by the transfer mechanism 24c.

  In the above description, the sputtering apparatus has been described as an example. However, a method of changing the direction in which the metal particles to be deposited fly may be applied to the vapor deposition method.

  In step Sp3, a straight line extends in one direction (in this case, the Y-axis direction shown in FIG. 1 and the like) from a predetermined formation target position on the upper surface of the lower electrode layer 2 to the upper surface of the substrate 1 immediately below it. The existing groove part P1 is formed. The groove P1 can be formed, for example, by irradiating a predetermined formation target position while scanning with a YAG laser or other laser light.

  In step Sp <b> 4, a film containing a metal element mainly contained in the light absorption layer 31 is formed on the lower electrode layer 2. The film can be formed, for example, by performing a drying process after a solution containing a metal element mainly contained in the light absorption layer 31 is applied on the lower electrode layer 2.

  In step Sp5, the heat treatment is performed on the film, so that the crystallization of the compound semiconductor in the film proceeds and the light absorption layer 31 is formed.

  In step Sp <b> 6, the buffer layer 32 is formed on the light absorption layer 31. Thereby, the photoelectric conversion layer 3 in which the light absorption layer 31 and the buffer layer 32 are laminated is formed. The buffer layer 32 may be formed by, for example, a chemical bath deposition (CBD) method. Specifically, for example, the buffer layer 32 mainly containing CdS can be formed by immersing the light absorption layer 31 in a solution prepared by dissolving cadmium acetate and thiourea in ammonia.

In step Sp7, in a region extending from a predetermined formation target position to the upper surface of the lower electrode layer 2 on the upper surface of the buffer layer 32, linearly extends in one direction (here, the Y-axis direction shown in FIG. 1 and the like). An extending groove P2 is formed. The groove part P2 can be formed by mechanical scribing using a scribe needle.

  In step Sp8, the upper electrode layer 4 is formed from the upper surface of the photoelectric conversion layer 3 to the inside of the groove portion P2. The upper electrode layer 4 can be formed by, for example, a sputtering method, a vapor deposition method, a chemical vapor deposition (CVD) method, or the like. Specifically, for example, the transparent upper electrode layer 4 mainly including ZnO added with Al is formed on the buffer layer 32. At this time, the drooping portion 4a of the upper electrode layer 4 is formed in the groove P2.

  In Step Sp9, the linear conductive portion 5 is formed from a predetermined formation target position on the upper surface of the upper electrode layer 4 to the inside of the groove portion P2. The linear conductive part 5 can be formed by, for example, printing so that the metal paste has a predetermined pattern, and solidifying the printed metal paste by drying.

In step Sp10, a straight line is formed in one direction (here, the Y-axis direction shown in FIG. 1 and the like) in a region from a predetermined formation target position to the upper surface of the lower electrode layer 2 in the upper surface of the upper electrode layer 4. A groove portion P3 (see FIGS. 1 and 2) extending to is formed. Thereby, the photoelectric conversion apparatus 100 in which a plurality of photoelectric conversion cells 10 are arranged on the substrate 1 is obtained. The groove part P3 can be formed, for example, by mechanical scribing using a scribe needle or the like, similarly to the groove part P2.
<(3) 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.

  The array of crystal grains 2p may have a plurality of curved portions 2c. For example, as shown in FIG. 6, two curved portions 2 c formed by arranging a plurality of crystal grains 2 p may be provided along the thickness direction of the lower electrode layer 2. At this time, the two bending portions 2c provided along the thickness direction may be bent in the same direction. Thereby, since the progress of a crack can be stopped by the plurality of curved portions 2c, an increase in the series resistance component of the lower electrode layer 2 can be further reduced. In addition, the length in the Z direction of these two curved parts 2c may be substantially the same, and may differ. Moreover, the shape of the XZ cross section of these curved parts 2c may also differ.

  Such a lower electrode layer 2 may be formed by providing a plurality of sputtering targets 29 at positions spaced apart from each other in the sputtering apparatus used in step Sp <b> 2 and forming the lower electrode layer 2 by each sputtering target 29.

  The lower electrode layer 2 may be composed of a plurality of layers as shown in FIG. At this time, each layer is provided with a curved portion 2c. Thereby, since the progress of the crack can be stopped at the boundary surfaces of the plurality of curved portions 2c and the adjacent layers, the increase in the series resistance component of the lower electrode layer 2 can be further reduced. In addition, the thickness of each layer may be substantially the same, and may differ.

  For such a lower electrode layer 2, a plurality of film formation chambers 22 may be provided in the sputtering apparatus used in step Sp2, and the lower electrode layer 2 may be sequentially formed in each film formation chamber 22.

Further, the crystal grain 2p in the lower electrode layer 2 may have a bent portion where the crystal grain 2p itself is bent. Thereby, progress of a crack can be reduced also in the bent part of crystal grain 2p. Such a crystal grain 2p is obtained by increasing the moving speed of the substrate 1 when it is transported in the film forming chamber 22 to 10 to 20 mm / sec (please describe numerical values) in step Sp2, for example. Crystal growth along the Z direction of the grains 2p can be inhibited. Thereby, the crystal grain 2p comes to have a bent part. On the other hand, in step Sp2, the speed at which the substrate 1 passes through the position 1B may be set to be twice or more the speed at which the substrate 1 passes through the position 1A and the position 1C. Thereby, one crystal grain 2p is easily bent.

1: Substrate 2: Lower electrode layer (electrode layer)
2p: Crystal grain 2c: Curved part 2g: Crystal grain group 3: Photoelectric conversion layer 31: Light absorption layer 32: Buffer layer 4: Upper electrode layer 5: Linear conductive part 5a: Current collecting part 5b: Connection part 5c: Hanging Unit 10: Photoelectric conversion cell 12: Crystal grain 21: Load lock chamber 22: Film formation chamber 23: Unload lock chamber 24a-24c: Transfer mechanism 25a-25d: Gate valve 26a-26c: Supply line 27a-27c: Vacuum pump 28: heater 29: sputtering target 30: DC power supplies P1, P2, P3: groove 100: photoelectric conversion device 200: sputtering device

Claims (5)

A substrate,
An electrode layer provided on the substrate;
A photoelectric conversion layer provided on the electrode layer,
The photoelectric conversion device, wherein the electrode layer is composed of a plurality of crystal grains, and the crystal grains are arranged in a column shape in the thickness direction of the electrode layer so as to have a curved portion.   The photoelectric conversion device according to claim 1, wherein the crystal grain array includes a plurality of the curved portions, and the curved portions are curved in the same direction.   The photoelectric conversion device according to claim 1, wherein the electrode layer includes a plurality of layers, and each of the layers has the curved portion.   The photoelectric conversion device according to claim 1, wherein the crystal grain has a bent portion.   The photoelectric conversion device according to claim 1, wherein the electrode layer is made of molybdenum.

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