JP2012222267A - Solar cell and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solar cell and manufacturing method thereof capable of improving conversion efficiency.SOLUTION: The solar cell includes a photoelectric conversion part and a substrate of which the photoelectric conversion part is formed on one surface, and which has recesses on a rear face of the one surface and is curved so as to become convex on a side having recesses. The method of manufacturing the solar cell includes: a recess forming step for forming a recess on one surface of the substrate; a photoelectric conversion part forming step for forming the photoelectric conversion part on the rear surface of the one surface of the substrate; and a curving step for curving the substrate, on which the photoelectric conversion part is formed, so as to become convex on the side having recesses.

Description

  The present invention relates to a solar cell and a manufacturing method thereof.

  Solar cells have the advantage that the amount of carbon dioxide emission per unit of power generation is small and fuel for power generation is unnecessary. Therefore, it is expected as an energy source for suppressing global warming, and among the solar cells that have been put into practical use, single-junction solar cells having a pair of pn junctions using single-crystal silicon or polycrystalline silicon are provided. It has become mainstream.

  As a technique related to such a solar battery, for example, Patent Document 1 includes a solar battery cell, a sealing substrate that seals the solar battery cell, and a reflector that reflects incident light toward the solar battery cell. A solar cell module in which a reflection plate is detachably fixed to a sealing substrate is disclosed. Patent Document 2 discloses a solar cell in which an electrode formed by firing a conductive material on the surface of a semiconductor substrate and a notch portion for residual stress relaxation in which no electrode is present are disclosed. In addition, Non-Patent Document 1 that discloses a technique related to a Si field effect transistor describes that in-plane mobility of electrons and holes increases in Si having tensile strain in the (001) plane. Yes.

JP 2011-14842 A JP 2000-114556 A

Toshiba Review, 2000, Vol. 55, No. 9, p. 54-57

  As disclosed in Non-Patent Document 1, in Si having tensile strain in the (001) plane, the in-plane mobility of electrons and holes increases. Therefore, if tensile strain can be applied in the direction in which the electrons and holes generated in the photoelectric conversion layer (light absorption layer) of the solar cell move, the mobility of the electrons and holes can be increased. It is considered possible to improve the conversion efficiency. Here, in the Si field effect transistor disclosed in Non-Patent Document 1, Si is grown on SiGe having a lattice constant larger than that of Si, and strain is applied to Si. However, since it is necessary to connect the photoelectric conversion layer and the electrode in the solar cell, it is difficult to apply the technique disclosed in Non-Patent Document 1 to the solar cell as it is. Further, according to the technique disclosed in Patent Document 1, it is considered that the maintainability can be improved because the reflection plate is detachably fixed to the sealing substrate. Although it is considered that a thin film solar cell can be applied to the solar cell module according to Patent Document 1, the application of tensile strain to the thin film solar cell is not studied in Patent Document 1. In addition, in a solar cell using polycrystalline silicon assumed in Patent Document 2, since the wafer is damaged or cracked when the wafer is warped, Patent Document 2 describes warping by reducing the distortion of the wafer. Techniques for preventing this are disclosed. Therefore, even if the techniques disclosed in Patent Document 1, Patent Document 2, and Non-Patent Document 1 are combined, it is difficult to provide a solar cell with increased mobility of electrons and holes. It has been difficult to provide a solar cell with improved conversion efficiency.

  Then, this invention makes it a subject to provide the solar cell which can improve conversion efficiency, and its manufacturing method.

In order to solve the above problems, the present invention takes the following means. That is,
A first aspect of the present invention includes a photoelectric conversion unit and a substrate having a photoelectric conversion unit formed on one surface, the substrate having a recess on the back surface of the one surface, and the recess It is a solar cell characterized by being curved so that the side having the protrusion becomes convex.

  The photoelectric conversion part in this invention contains the layer corresponded to the photoelectric conversion layer (light absorption layer) of what is called a thin film type solar cell. The photoelectric conversion layer of the thin-film solar cell is thinner than the photoelectric conversion layer of the solar cell using single crystal silicon or polycrystalline silicon, and thus is not easily damaged even if it is bent. It is possible to apply a compressive stress in the in-plane direction of the photoelectric conversion unit and to apply a tensile stress in the thickness direction of the photoelectric conversion unit by curving so that the side having the recess becomes convex. It becomes possible. By applying tensile stress in the thickness direction of the photoelectric conversion part, it is possible to increase the mobility when electrons and holes generated in the photoelectric conversion part move in the thickness direction of the photoelectric conversion part. become. By increasing the mobility of electrons and holes, the conversion efficiency can be improved. Therefore, the solar cell which can improve photoelectric conversion efficiency can be provided by setting it as this form.

  In the first aspect of the present invention, it is preferable that the recess has a circular arc cross section. By adopting such a configuration, in addition to the above effects, it becomes easy to suppress damage to the substrate.

  In the first aspect of the present invention, the linear expansion coefficient of the substrate is preferably smaller than the linear expansion coefficient of the photoelectric conversion portion. By adopting such a configuration, it becomes possible to apply compressive stress in the in-plane direction of the photoelectric conversion unit and tensile stress in the thickness direction of the photoelectric conversion unit when the temperature of the solar cell rises. It is possible to suppress a decrease in conversion efficiency.

  In the first aspect of the present invention, the photoelectric conversion unit includes a first electrode and a second electrode arranged in parallel with each other in a thickness direction of the photoelectric conversion unit, and a first electrode and a second electrode. A photoelectric conversion layer disposed between the photoelectric conversion unit, the photoelectric conversion unit includes a power generation unit and a non-power generation unit, the first electrode and the second electrode are connected by the non-power generation unit, and the first electrode And a first groove penetrating in the thickness direction of the first electrode on one side of the connection location of the second electrode, and the second electrode on the other side of the connection location of the first electrode and the second electrode. The non-power generation part has a second groove penetrating in the thickness direction, and the non-power generation unit is defined by the first groove and the second groove arranged so as to sandwich the connection portion of the first electrode and the second electrode, and is adjacent to the non-power generation unit L2 = nL1 (n is a positive integer), where L1 is the central spacing in the width direction of the portion and L2 is the length in the width direction of the recess. Arbitrariness. By adopting such a configuration, it becomes possible to position a portion (convex portion) corresponding to the boundary between adjacent concave portions on the back side of the non-power generating portion, so that tensile stress is applied in the thickness direction of all the power generating portions. It becomes possible to do. Therefore, it becomes easy to improve a photoelectric conversion efficiency by setting it as this form.

  According to a second aspect of the present invention, there is provided a recess forming step for forming a recess on one surface of the substrate, a photoelectric conversion portion forming step for forming a photoelectric conversion portion on the back surface of the one surface of the substrate, and a photoelectric conversion portion. And a bending step of bending the formed substrate so that the side on which the concave portion is formed is convex.

  According to the 2nd aspect of this invention, it becomes possible to manufacture the solar cell concerning the said 1st aspect of this invention. By forming the photoelectric conversion portion so that the concave portion is curved so as to be convex, a tensile stress can be applied in the thickness direction of the photoelectric conversion portion. Therefore, according to the 2nd aspect of this invention, the manufacturing method of the solar cell which can improve a photoelectric conversion efficiency can be provided.

  In the second aspect of the present invention, the recess forming step is preferably a step of forming a recess having an arcuate cross section. By adopting such a configuration, in addition to the above effects, it becomes easy to suppress damage to the substrate.

  In the second aspect of the present invention, the linear expansion coefficient of the substrate is preferably smaller than the linear expansion coefficient of the photoelectric conversion portion. By producing a solar cell using such a substrate and a photoelectric conversion unit, compressive stress is applied in the in-plane direction of the photoelectric conversion unit and tensile stress is applied in the thickness direction of the photoelectric conversion unit when the temperature of the solar cell rises. Therefore, it is possible to suppress a decrease in conversion efficiency when the temperature rises.

  In the second aspect of the present invention, the photoelectric conversion part forming step includes a first electrode forming step of forming a first electrode on the back surface of the surface of the substrate on which the recess is formed, and a step of forming the first electrode. A first groove forming step for forming a first groove penetrating in the thickness direction, a photoelectric conversion layer forming step for forming a photoelectric conversion layer on the surface of the first electrode in which the first groove is formed, and a photoelectric conversion formed Photoelectric conversion by forming a groove in the layer to expose a part of the surface of the first electrode, and forming a second electrode on the surface of the photoelectric conversion layer and the first electrode from which part of the surface is exposed. A second electrode forming step for forming a second electrode on the surface of the layer and connecting the first electrode and the second electrode; and a second groove for forming a second groove penetrating the thickness direction of the formed second electrode. And a first groove disposed so as to sandwich the connection portion of the first electrode and the second electrode, When the interval in the width direction between adjacent non-power generation parts defined by two grooves is L1, and the length of the recesses in the width direction is L2, the second groove forming step is L2 = nL1 (n is a positive value) It is preferable that the second groove is formed so as to be an integer. By adopting such a configuration, it becomes possible to position a portion corresponding to the boundary between adjacent recesses on the back side of the non-power generation unit, so it is possible to apply tensile stress in the thickness direction of all power generation units become. Therefore, it becomes easy to improve a photoelectric conversion efficiency by setting it as this form.

  ADVANTAGE OF THE INVENTION According to this invention, the solar cell which can improve conversion efficiency, and its manufacturing method can be provided.

1 is a cross-sectional view of a solar cell 10. FIG. It is a bottom view of board | substrate 1 '. It is a side view of the board | substrate 1 'and the photoelectric conversion part 2'. It is a figure which expands and shows the site | part enclosed with the dotted line of FIG. It is a figure explaining the board | substrate 1 and the photoelectric conversion part 2. FIG. 2 is a flowchart illustrating a method for manufacturing solar cell 10. FIG. It is a figure which shows the relationship between the curvature of a photoelectric conversion part, and conversion efficiency.

  The inventors of the present invention specifically improve the conversion efficiency by increasing the mobility of electrons and holes in the photoelectric conversion layer by applying tensile strain to the photoelectric conversion layer of the solar cell to which the electrodes are connected. We examined various configurations. As a result, (1) using a substrate having a recess, (2) forming a photoelectric conversion layer on the back side of the recess (or the back side of the surface on which the recess is to be formed), and (3) the substrate After forming the photoelectric conversion layer, it was found that the conversion efficiency can be improved by bending the substrate and the photoelectric conversion layer so that the concave side of the substrate is convex. Furthermore, the present inventors can increase the mobility of electrons and holes that move toward the electrodes by arranging (4) a pair of electrodes so as to be parallel to the thickness direction of the photoelectric conversion layer. As a result, it becomes easy to improve the conversion efficiency, and (5) the conversion efficiency is improved by making the boundary (convex part) of the adjacent concave part on the back side of the non-power generation part in the photoelectric conversion layer. I found it easier. In addition, the present inventors can (6) configure the substrate with a material having a smaller linear expansion coefficient than the photoelectric conversion layer, thereby suppressing a decrease in conversion efficiency of the solar cell when the temperature rises. And (7) It has also been found that breakage of the substrate can be suppressed by making the cross section of the concave portion into an arc shape. Based on these findings, the present inventors have completed the present invention.

  The present invention will be described below with reference to the drawings. In the drawings, only a part of a similar configuration provided in plural may be denoted by reference numerals, and in the description related to the present invention, “′” is denoted by reference numerals of components before being bent. In addition, the form shown below is an illustration of this invention and this invention is not limited to the form shown below.

  FIG. 1 is a cross-sectional view illustrating a solar cell 10 of the present invention. 1 is the thickness direction of the photoelectric conversion unit 2. In order to facilitate understanding of the overall image of the present invention, the photoelectric conversion unit 2 and the frame 3 are simplified in FIG. As shown in FIG. 1, the solar cell 10 includes a substrate 1 that is curved so as to protrude downward, a photoelectric conversion unit 2 formed on the upper side of the substrate 1, the substrate 1, and photoelectric conversion. Frames 3 and 3 for supporting and fixing the edges of the portion 2. On the lower surface of the substrate 1, a plurality of recesses 1x, 1x,. A protective film 4 is disposed on the upper side of the photoelectric conversion unit 2, and the photoelectric conversion unit 2 and the protective film 4 are joined by a sealing resin 5 filled between the photoelectric conversion unit 2 and the protective film 4. Has been. A back sheet 6 is disposed below the substrate 1, and the substrate 1 and the back sheet 6 are joined together by a sealing resin 7 filled between the substrate 1 and the back sheet 6. . In the solar cell 10, the substrate 1 is made of a material having a smaller linear expansion coefficient than the material constituting the photoelectric conversion unit 2.

  FIG. 2 is a bottom view of the substrate (substrate 1 ′) before being bent. The back / front direction in FIG. 2 is the thickness direction of the substrate 1 ′. As shown in FIG. 2, the plurality of recesses 1x, 1x,... Formed in the lower surface of the substrate 1 'has a groove shape extending in the vertical direction on the paper surface of FIG.

  FIG. 3 is a side view schematically showing the substrate (substrate 1 ′) and the photoelectric conversion unit (photoelectric conversion unit 2 ′) before being bent. FIG. 4 is an enlarged view of the portion of FIG. 3 surrounded by a dotted line. 3 and 4 is the thickness direction of the photoelectric conversion unit 2 '. As shown in FIGS. 3 and 4, the photoelectric conversion unit 2 ′ includes a back electrode 2a ′ formed on the top surface of the substrate 1 ′, and a photoelectric conversion layer 2b ′ formed on the top surface of the back electrode 2a ′. And a transparent electrode 2c ′ formed on the upper surface of the photoelectric conversion layer 2b ′. In the back electrode 2a ′, there are formed first grooves 2d ′, 2d ′,... Extending through the thickness direction of the back electrode 2a ′ and extending in the back / front direction of FIG. . Further, in the photoelectric conversion layer 2b ′, grooves 2e ′, 2e ′,... Extending through the thickness direction of the photoelectric conversion layer 2b ′ and extending in the back / front direction of FIG. 4 are formed at predetermined intervals. .. And a portion of the transparent electrode 2c ′ is disposed in the grooves 2e ′, 2e ′,... So that the back electrode 2a ′ and the transparent electrode 2c ′ are connected at predetermined intervals. Further, the photoelectric conversion layer 2b ′ and the transparent electrode 2c ′ have second grooves 2f ′, 2f ′,... Extending through the thickness direction and extending in the back / front direction of FIG. Is formed. Are defined by first grooves 2d ′, 2d ′,... And second grooves 2f ′, 2f ′,... Formed so as to sandwich a portion where the back electrode 2a ′ and the transparent electrode 2c ′ are connected. The non-power generation parts 2g ′, 2g ′,... Are the non-power generation parts 2g ′, 2g ′,. The distance between the centers of the adjacent non-power generation portions 2g ′ and 2g ′ in the left-right direction (width direction) in FIG. 4 is L1, and the width of the recess 1x ′ in the left-right direction (width direction) in FIG. Is L2 in the substrate 1 ′ and the photoelectric conversion unit 2 ′. And the convex part 1y ', 1y', ... used as the boundary of adjacent recessed part 1x ', 1x', ... exists in the lower side of the non-power generation part 2g ', 2g', ... as shown in FIG. is doing.

  FIG. 5 is a diagram illustrating the curved substrate 1 and the photoelectric conversion unit 2. 5 is the thickness direction of the photoelectric conversion unit 2. In FIG. 5, the photoelectric conversion unit 2 is shown in a simplified manner. For example, as shown in FIG. 5, the substrate 1 ′ and the photoelectric conversion unit 2 ′ shown in FIG. 3 are placed on the members 8 and 8 arranged at an interval so that the concave portions 1x and 1x are formed by their own weight. ,... And the side having the convex portions 1y, 1y,... (Hereinafter sometimes referred to as “the back side of the substrate 1”) can be curved so as to be convex. When the back surface side of the substrate 1 is curved so as to be convex, compressive stress is applied to the in-plane direction of the photoelectric conversion unit 2 (in other words, the direction parallel to the top surface of the curved substrate 1; the same applies hereinafter). Is done. Since the photoelectric conversion unit 2 is an elastic body, a tensile stress is applied in the thickness direction of the photoelectric conversion unit 2 in a state where compressive stress is applied in the in-plane direction of the photoelectric conversion unit 2. As described above, by applying a tensile stress, the mobility of electrons and holes in the direction in which the tensile stress is applied can be increased. Therefore, according to the solar cell 10 including the substrate 1 and the photoelectric conversion unit 2, holes that are directed from the photoelectric conversion layer 2 b to the transparent electrode 2 c can be formed without providing a layer such as a SiGe layer like a field effect transistor. Since mobility and mobility of electrons traveling from the photoelectric conversion layer 2b to the back electrode 2a can be increased, conversion efficiency can be improved.

  In general, the conversion efficiency of solar cells decreases with increasing temperature. However, the solar cell 10 has the substrate 1 made of a material having a smaller linear expansion coefficient than the material constituting the photoelectric conversion unit 2. Since the substrate 1 is less likely to expand than the photoelectric conversion unit 2, when the temperature of the solar cell 10 increases, the expansion of the photoelectric conversion unit 2 is suppressed by the substrate 1, and as a result, the photoelectric conversion unit 2 is compressed in the in-plane direction. Stress is applied, and tensile stress is applied in the thickness direction of the photoelectric conversion unit 2. Here, by applying a tensile stress in the thickness direction of the photoelectric conversion unit 2, the mobility of holes from the photoelectric conversion layer 2b to the transparent electrode 2c, and from the photoelectric conversion layer 2b to the back electrode 2a. It becomes possible to increase the mobility of the electrons going. Therefore, according to the solar cell 10, it becomes possible to suppress the fall of the conversion efficiency accompanying a temperature rise.

  The solar cell 10 having such a feature can be manufactured through, for example, each step shown in FIG. Specifically, a recessed portion forming step (S1), a photoelectric conversion portion forming step (S2), a bending step (S3), a back sheet disposing step (S4), a protective film disposing step (S5), Through the frame disposing step (S6), the solar cell 10 can be manufactured.

  The recess forming step (hereinafter also referred to as “S1”) is a step of forming the recesses 1x ′, 1x ′,... On one surface of the substrate 1 ′. The shape of S1 is not particularly limited as long as the recesses 1x ', 1x', ... can be formed on one surface (back surface) of the substrate 1 '. S1 can be a step of forming recesses 1x ′, 1x ′,... Having a 5 mm width in an arcuate section by irradiating the back surface of a quartz glass substrate with a thickness of several mm, for example.

  In the photoelectric conversion portion forming step (hereinafter, sometimes referred to as “S2”), after the end of S1, the surface of the substrate 1 ′ where the recesses 1x ′, 1x ′,... Are not formed (recesses 1x ′, 1x ′). ,... Is a step of forming the photoelectric conversion part 2 ′ on the surface opposite to the surface on which. The form of S2 is not particularly limited as long as the photoelectric conversion portion 2 'can be formed on the surface of the substrate 1'. S2 is a step of forming the back electrode 2a ′, a step of forming the first grooves 2d ′, 2d ′,... Penetrating through the thickness direction of the back electrode 2a ′, and the first grooves 2d ′, 2d ′,. Step of forming photoelectric conversion layer 2b ′ after formation, step of forming grooves 2e ′, 2e ′,... Penetrating through the thickness direction of photoelectric conversion layer 2b ′, and transparent after formation of grooves 2e ′, 2e ′,. The step of forming the electrode 2c ′ and the step of forming the second grooves 2f ′, 2f ′,... After the formation of the transparent electrode 2c ′ are included. The back electrode 2a 'can be formed on the surface of the substrate 1' by sputtering or the like, for example. Further, the first grooves 2d ′, 2d ′,... Can be formed by, for example, a laser scribe method. Further, the photoelectric conversion layer 2b 'can be formed by, for example, a chemical vapor deposition method (CVD method) or the like. Further, the grooves 2e ', 2e', ... can be formed by, for example, a laser scribing method or the like. The transparent electrode 2c 'can be formed by, for example, a sputtering method. Further, the second grooves 2f ′, 2f ′,... Can be formed by, for example, a mechanical scribe method. Since the solar cell 10 has L1 = L2, the first grooves 2d ', 2d', ..., the grooves 2e ', 2e', ... and the second grooves 2f ', 2f', ... are formed at intervals of 5 mm. It ’s fine. Further, the widths of the first grooves 2d ', 2d', ..., the grooves 2e ', 2e', ... and the second grooves 2f ', 2f', ... are not particularly limited, and are, for example, about several tens of micrometers. be able to.

  In the bending step (hereinafter, sometimes referred to as “S3”), the substrate 1 ′ on which the photoelectric conversion unit 2 ′ is formed is bent so that the back side of the substrate 1 ′ is convex after the end of S2. It is a process. The form of S3 is not particularly limited as long as it can be curved so that the back surface side of the substrate 1 'on which the photoelectric conversion unit 2' is formed is convex. S3 is, for example, by placing the substrate 1 ′ on which the photoelectric conversion unit 2 ′ is formed on the members 8 and 8 disposed at a predetermined interval so that the back surface side of the substrate 1 ′ is down. It can be set as the process of curving so that the back surface side of board | substrate 1 'in which photoelectric conversion part 2' is formed may become convex by dead weight.

  The back sheet disposing step (hereinafter sometimes referred to as “S4”) is a step of disposing the back sheet 6 on the back surface side of the curved substrate 1 after the end of S3. The form of S4 is not particularly limited as long as the back sheet 6 can be disposed on the back side of the substrate 1. In S4, for example, the back sheet 6 is placed on a mold having a concave portion with an arc-shaped cross section on the upper surface and a hole on the upper surface that enables vacuuming from the lower side. After placing the sealing resin sheet on the substrate, the substrate 1 on which the photoelectric conversion part 2 is formed is placed so that the sealing resin sheet and the substrate 1 are in contact with each other, and then heated using infrared rays while vacuuming. Thereby, it can be set as the process of joining the back sheet 6 and the board | substrate 1 through the sealing resin 7, and sealing. In addition, you may perform a back seat | sheet arrangement | positioning process after a protective film arrangement | positioning process, or simultaneously with a protective film arrangement | positioning process.

  In the protective film disposing step (hereinafter sometimes referred to as “S5”), the protective film 4 is formed on the surface side of the curved substrate 1 (photoelectric conversion unit 2 side; the same applies hereinafter) after the end of S4. Is a step of arranging If S5 can arrange | position the protective film 4 to the surface side of the board | substrate 1, the form will not be specifically limited. In S5, for example, a sealing resin sheet is placed on the upper surface of the photoelectric conversion unit 2, and the protective film 4 is placed on the sealing resin sheet. A mold having a hole on the lower surface on the lower surface is formed on the protective film 4 and then heated using infrared rays while vacuuming, whereby the protective film 4 and the photoelectric film are sealed via the sealing resin 5. It can be set as the process of joining and sealing with conversion part 2. In addition, you may perform a protective film arrangement | positioning process before a backsheet arrangement | positioning process or simultaneously with a backsheet arrangement | positioning process.

  In the frame disposing step (hereinafter sometimes referred to as “S6”), the substrate 1 and the photoelectric conversion unit are disposed by disposing the frames 3, 3,... This is a step of fixing 2 while being curved. The form of S6 is not particularly limited as long as the frame can be disposed on the edge of the curved structure manufactured through S1 to S5. S6 is, for example, a curved structure in which frames 3, 3,... Coated with a sealing material that also functions as an adhesive on the surface to be in contact with the protective film 4 or the back sheet 6 are manufactured through the above S1 to S5. It can be set as the process of attaching to the edge of a body and screwing the adjacent frames 3 and 3 together.

  The solar cell 10 can be manufactured through, for example, the above S1 to S6. As described above, the solar cell 10 that can be manufactured by S1 to S6 can improve the conversion efficiency, and can suppress a decrease in the conversion efficiency due to a temperature rise. Therefore, according to the present invention, there is provided a solar cell manufacturing method capable of improving the conversion efficiency and capable of manufacturing the solar cell 10 capable of suppressing a decrease in the conversion efficiency accompanying a temperature rise. be able to.

  In the said description regarding the manufacturing method of the solar cell of this invention, although the form which performs a photoelectric conversion part formation process after a recessed part formation process was illustrated, this invention is not limited to the said form. The manufacturing method of the solar cell of the present invention is a mode in which a recess forming step is performed after the photoelectric conversion portion forming step, that is, the substrate surface on which the photoelectric conversion portion is formed after the photoelectric conversion portion is formed on one surface of the substrate. It is also possible to form a recess on the back surface. However, from the viewpoint of making it possible to manufacture a solar cell that easily improves the conversion efficiency, it is preferable that the photoelectric conversion portion forming step be performed after the recess forming step.

  In the above description regarding the solar cell and the method for manufacturing the solar cell according to the present invention, the mode in which the recesses 1x, 1x,... Having a circular arc cross section are illustrated, but the present invention is not limited to this mode. The cross-sectional shape of the concave portion of the substrate may be a polygonal shape such as a quadrangle. However, from the standpoint of making it easy to suppress the breakage of the substrate, it is preferable to have a form in which a recess having an arcuate cross section is provided.

  Moreover, in the said description regarding the solar cell of this invention, and its manufacturing method, although the form using the board | substrate 1 comprised with the material whose linear expansion coefficient is smaller than the photoelectric conversion part 2 was illustrated, this invention is not limited to the said form. . The solar cell of the present invention and the solar cell manufactured by the solar cell manufacturing method of the present invention (hereinafter simply referred to as “the solar cell of the present invention”) have a constituent material and a linear expansion coefficient of the photoelectric conversion part. You may have the board | substrate comprised with the same material, and you may have the board | substrate comprised with the material whose linear expansion coefficient is larger than the constituent material of a photoelectric conversion part. However, from the standpoint of, for example, a configuration that can suppress / prevent a decrease in conversion efficiency when the temperature rises, it is preferable that the substrate is provided with a substrate made of a material having a smaller linear expansion coefficient than the photoelectric conversion unit.

  Moreover, in the said description regarding the solar cell of this invention, and its manufacturing method, although the form which is L2 = L1 was illustrated, this invention is not limited to the said form. From the standpoint of making it possible to provide a solar cell that easily improves conversion efficiency and a method for manufacturing the solar cell by making it possible to uniformly apply tensile stress in the thickness direction of the power generation unit of all photoelectric conversion units, L2 = NL1 (n is a positive integer) is preferable. Even when L2 = 2L1 or L2 = 5L1, it is possible to position the convex portion that is the boundary between adjacent concave portions on the back side of the substrate on the back side of the non-power generation unit. It becomes possible to uniformly apply a tensile stress in the thickness direction of the power generation unit of all the photoelectric conversion units, and as a result, it becomes easy to improve the conversion efficiency. On the other hand, when L2 ≠ nL1 (n is a positive integer), at least a part of the convex portion that is the boundary between adjacent concave portions on the back surface side of the substrate is located on the back surface side of the power generation unit. Therefore, it becomes difficult to uniformly apply tensile stress in the thickness direction of all the power generation units. However, even in such a form, since the tensile stress is applied in the thickness direction to at least some of the power generation units, the conversion efficiency of the solar cell can be improved.

In this invention, the board | substrate 1 can use suitably the well-known board | substrate which can form the photoelectric conversion part of a thin film type solar cell. Examples of such a substrate material include quartz glass and tungsten coated with a SiO ₂ insulating film. In this invention, when setting it as the board | substrate 1 comprised with the material whose linear expansion coefficient is smaller than the photoelectric conversion part 2, according to the form (constituent material of the photoelectric conversion part 2) of the photoelectric conversion part 2, the constituent material of the board | substrate 1 May be selected as appropriate. For example, when the photoelectric conversion layer 2b is thin film Si, a material having a linear expansion coefficient smaller than that of Si having a linear expansion coefficient of about 3.0 × 10 ⁻⁶ [° C. ⁻¹ ] (for example, a linear expansion coefficient of about 5 (6 × 10 ⁻⁷ [° C. ⁻¹ ]) may be used as the constituent material of the substrate 1. In addition, for example, when the photoelectric conversion layer 2b is formed of a compound semiconductor having a linear expansion coefficient of about 9.0 × 10 ⁻⁶ [° C. ⁻¹ ], the linear expansion coefficient is about 4.3 × 10 ⁻⁶ [° C. ⁻¹ ] tungsten (tungsten coated with SiO ₂ insulating film) or the like may be used as the constituent material of the substrate 1.

  The back electrode 2a 'can be made of a known material that can be used for the back electrode of the thin film solar cell. Examples of such materials include Ag, Mo, Al, Cu, and Ti.

Moreover, photoelectric conversion layer 2b 'can be made into a well-known form as a photoelectric conversion layer of a thin film type solar cell. As the form that the photoelectric conversion layer 2b ′ can adopt, in addition to the thin film Si that behaves as a p-type semiconductor, a p-type semiconductor containing an Ib group element, an IIIb group element, and a VIb group element of the periodic table is used. it can. Such p-type semiconductors include Cu (In, Ga) Se ₂ (CIGS), Cu (In, Ga) (Se, S) ₂ (CIGSS), CuInS ₂ (CIS), and Cu (In, Al) Se. ₂ (CIAS), Cu ₂ ZnSnS ₄ (CZTS), and the like.

  The transparent electrode 2c 'can be made of a known material that can be used as a transparent electrode of a thin film solar cell. Examples of such a material include SnO, indium tin oxide (ITO), and the like, in addition to known n-type semiconductors (for example, ZnO to which B is added) containing IIb group elements and VIb group elements. .

  The first groove 2d 'is a groove formed for electrically connecting the photoelectric conversion layers 2b in series. The width of the first groove 2d '(the length in the left-right direction in FIG. 4) is not particularly limited, and can be, for example, about several tens of micrometers. Further, the interval between the adjacent first grooves 2d 'and 2d' is not particularly limited, and can be, for example, about several mm.

  Further, the groove 2e 'is a groove formed to connect the back electrode 2a and the transparent electrode 2c. The width of the groove 2e '(the length in the left-right direction in FIG. 4) is not particularly limited, and can be, for example, about several tens of micrometers. Further, the interval between the adjacent first grooves 2e 'and 2e' is not particularly limited, and can be, for example, about several mm.

  The second groove 2f 'is a groove formed to electrically connect the photoelectric conversion layers 2b in series. The width of the second groove 2f ′ (the length in the left-right direction in FIG. 4) is not particularly limited, and can be, for example, about several tens of μm. Further, the interval between the adjacent second grooves 2f 'and 2f' is not particularly limited, and can be, for example, about several mm.

  The frame 3 is a member used for the purpose of easily holding the curved substrate 1 and the photoelectric conversion unit 2. The present invention can be configured so that the frame is not used. However, from the viewpoint of improving the conversion efficiency by easily maintaining the curved state of the substrate 1 and the photoelectric conversion unit 2, the frame Is preferably used. The frame only needs to have a property (heat resistance, water resistance, etc.) that can withstand the use environment of the solar cell, and have a predetermined strength that maintains the curved state of the substrate 1 and the photoelectric conversion unit 2. Examples of the constituent material of the frame include aluminum and polycarbonate resin.

  Moreover, the protective film 4 can be comprised with the well-known material which can be used for the protective film of a thin film type solar cell. Examples of such materials include polycarbonate resin and polyethylene terephthalate resin.

  Moreover, the sealing resins 5 and 7 can use suitably the well-known resin which can be used when sealing a thin film type solar cell. Examples of such resins include ethylene vinyl acetate (EVA) resin and high Milan (“High Milan” is a registered trademark of Mitsui DuPont Polychemical Co., Ltd.).

  Moreover, the backsheet 6 can be comprised with the well-known material which can be used for the backsheet of a thin film type solar cell. Examples of such a material include polyethylene terephthalate resin and polyvinyl fluoride resin.

  In the said description regarding the solar cell of this invention, and its manufacturing method, photoelectric conversion layer 2b 'and transparent electrode 2c' contact directly, and the form which does not have a buffer layer between a photoelectric conversion layer and a transparent electrode is illustrated. However, the present invention is not limited to this form. In the solar cell and the manufacturing method thereof of the present invention, a known buffer layer used in a thin film solar cell may be appropriately interposed between the photoelectric conversion layer and the transparent electrode. Examples of the constituent material of such a buffer layer include CdS, ZnS, InS, and the like.

  Moreover, the solar cell of this invention may be provided with the condensing means which collects the light which injects into a photoelectric converting layer in addition to the said structure. In addition, the solar cell of the present invention may have a form in which light enters from one side of the photoelectric conversion layer (single-sided light receiving type), or a form in which light enters from both sides of the photoelectric conversion layer (double-sided light receiving type). It may be. In the case of a double-sided light receiving type, each of the pair of electrodes disposed so as to sandwich the photoelectric conversion layer may be made of a known conductive material that transmits light.

  In the present invention, the degree of curvature (curvature) of the substrate on which the photoelectric conversion part is formed is not particularly limited. As the curvature increases, it becomes easier to improve the conversion efficiency. On the other hand, if the curvature is too large, the photoelectric conversion unit and the substrate may be damaged. The magnitude of the curvature can be controlled by changing the depth h (depth in the vertical direction of the paper in FIG. 4) of the recesses 1x, 1x,. By increasing the depth h of the recesses 1x, 1x,..., It becomes easy to increase the curvature.

  In the present invention, the substrate only needs to be curved so that the side having the concave portion is convex, and the direction in which the substrate on which the photoelectric conversion portion is formed is bent (for example, the direction of the convex portion on the back surface of the substrate is shown in FIG. There is no particular limitation on whether to bend so as to be in the left-right direction of the paper surface or to be curved so as to be in the back / front direction of the paper surface in FIG. However, when the frame is attached only to a pair of opposite sides of the substrate, from the viewpoint of facilitating the installation of the solar cell provided with the frame, the pair of opposite sides to which the frame is attached and the direction of the convex portion on the back surface of the substrate are It is preferable to bend so as to be parallel.

  L2 = 5 mm grooves (corresponding to recesses 1x ′, 1x ′,...) Were produced by irradiating the back surface of quartz glass having a thickness of 2 mm (corresponding to substrate 1 ′, the same applies hereinafter) with laser. Next, an Ag thin film having a thickness of about 100 nm (corresponding to the back electrode 2a ′; the same applies hereinafter) is formed on the surface of the quartz glass by sputtering, and laser is applied to the upper surface of the Ag thin film at intervals of 5 mm by laser scribing. Through the process of irradiating, a patterning groove (corresponding to the first grooves 2d ′, 2d ′,..., Which is the same in the following) having an interval of 5 mm and a width of about 60 μm penetrating the thickness direction of the Ag thin film was formed. Thereafter, a thin film Si layer having a thickness of 2 μm (corresponding to the photoelectric conversion layer 2b ′; the same applies hereinafter) is formed on the upper surface of the Ag thin film in which the patterning groove is formed, and the thin film Si is formed by a laser scribing method. This is equivalent to patterning grooves (grooves 2e ′, 2e ′,... Having a width of about 5 μm and a width of about 60 μm penetrating through the thickness direction of the thin film Si layer through a process of irradiating the upper surface of the layer with a laser at intervals of 5 mm. ) Was formed. Thereafter, a SnO layer having a thickness of 1 μm (corresponding to the transparent electrode 2c ′; the same applies hereinafter) is formed on the upper surface of the thin film Si layer on which the patterning grooves are formed, and at intervals of 5 mm by a mechanical scribing method. A patterning groove (corresponding to the second grooves 2f ′, 2f ′,..., Which is the same below) having a width of about 60 μm penetrating the thickness direction of the SnO layer and the thin film Si layer was formed. Thus, the photoelectric conversion part 2 'was formed in the surface of the board | substrate 1' by forming the patterning groove | channel which penetrates the thickness direction of a SnO layer and a thin film Si layer.

  Thereafter, the quartz glass having the photoelectric conversion portion formed thereon is placed on a member arranged at a predetermined interval so that the back surface side (the side on which the groove is formed) of the quartz glass is located, The quartz glass on which the conversion part was formed was curved so as to protrude downward. In this experiment, the degree of curvature (the curvature of the photoelectric conversion portion) was controlled by changing the depth h of the groove formed on the back surface of the quartz glass.

  After the quartz glass on which the photoelectric conversion part was formed was curved, IV measurement was performed according to JIS C8990 using a solar simulator. The results are shown in FIG. In FIG. 7, the horizontal axis represents the curvature [1 / m] of the photoelectric conversion unit, and the vertical axis represents the conversion efficiency [%] of the photoelectric conversion unit. In FIG. 7, the result of zero curvature is a result of performing IV measurement without curving the quartz glass on which the photoelectric conversion unit is formed. The result of the curvature of 3 [1 / m] corresponds to the case where the depth h of the groove formed on the back surface of the quartz glass is 1.4 mm, and the result of the curvature is 4.5 [1 / m]. This corresponds to the case where the depth h of the groove formed on the back surface of the quartz glass is 1.5 mm, and the result of the curvature of 4.8 [1 / m] is the depth h of the groove formed on the back surface of the quartz glass. Is equivalent to 1.42 mm.

  As shown in FIG. 7, the conversion efficiency can be improved by curving so that the back side of the quartz glass is convex, and the conversion efficiency is improved as the curvature of the photoelectric conversion portion is increased. In this investigation, when the curvature of the photoelectric conversion portion was 4.8 [1 / m] or more, the quartz glass was broken.

DESCRIPTION OF SYMBOLS 1, 1 '... Board | substrate 1x, 1x' ... Concave part 1y, 1y '... Convex part 2, 2' ... Photoelectric conversion part 2a '... Back surface electrode 2b' ... Photoelectric conversion layer 2c '... Transparent electrode 2d' ... 1st groove | channel 2e '... groove 2f' ... second groove 2g '... non-power generation part 2h' ... power generation part 3 ... frame 4 ... protective film 5, 7 ... sealing resin 6 ... back sheet 8 ... member 10 ... solar cell

Claims (8)

A photoelectric conversion part, and a substrate on which the photoelectric conversion part is formed on one surface,
The substrate has a recess on the back surface of the one surface,
A solar cell that is curved so that the side having the concave portion is convex. The solar cell according to claim 1, wherein a cross section of the recess is arcuate. The solar cell according to claim 1, wherein a linear expansion coefficient of the substrate is smaller than a linear expansion coefficient of the photoelectric conversion unit. The photoelectric conversion unit includes a first electrode and a second electrode arranged in parallel with each other in a thickness direction of the photoelectric conversion unit, and a photoelectric conversion layer disposed between the first electrode and the second electrode. And having
The photoelectric conversion unit has a power generation unit and a non-power generation unit,
The first electrode and the second electrode are connected by the non-power generation unit,
A first groove penetrating in a thickness direction of the first electrode on one side of a connection portion of the first electrode and the second electrode;
A second groove penetrating in a thickness direction of the second electrode on the other side of the connection portion of the first electrode and the second electrode;
The non-power generation part is defined by the first groove and the second groove arranged so as to sandwich the connection portion of the first electrode and the second electrode,
L2 = nL1 (n is a positive integer), where L1 is an interval in the center in the width direction of adjacent non-power generation parts, and L2 is a length in the width direction of the recess. Item 4. The solar cell according to any one of Items 1 to 3. A recess forming step of forming a recess on one surface of the substrate;
A photoelectric conversion part forming step of forming a photoelectric conversion part on the back surface of the one surface of the substrate;
A bending step of bending the substrate on which the photoelectric conversion unit is formed so that the side on which the concave portion is formed is convex;
A method for producing a solar cell, comprising: 6. The method for manufacturing a solar cell according to claim 5, wherein the recess forming step is a step of forming the recess having an arc shape in cross section. The method for manufacturing a solar cell according to claim 5, wherein a linear expansion coefficient of the substrate is smaller than a linear expansion coefficient of the photoelectric conversion unit. The photoelectric conversion part forming step includes:
A first electrode forming step of forming a first electrode on the back surface of the surface of the substrate on which the recess is formed;
A first groove forming step of forming a first groove penetrating the thickness direction of the formed first electrode;
A photoelectric conversion layer forming step of forming a photoelectric conversion layer on the surface of the first electrode in which the first groove is formed;
An exposing step of forming a groove in the formed photoelectric conversion layer to expose a partial surface of the first electrode;
The second electrode is formed on the surface of the photoelectric conversion layer by forming the second electrode on the surface of the photoelectric conversion layer and the first electrode from which a part of the surface is exposed. A second electrode forming step of connecting the second electrode;
A second groove forming step of forming a second groove penetrating the thickness direction of the formed second electrode,
L1 is the interval in the center in the width direction of the adjacent non-power generation parts, which is defined by the first groove and the second groove arranged so as to sandwich the connection portion of the first electrode and the second electrode. When the length in the width direction is L2, the second groove forming step is a step of forming the second groove so that L2 = nL1 (n is a positive integer). The manufacturing method of the solar cell of any one of Claims 5-7.