JP6539010B1 - Solar cell element - Google Patents

Abstract

The solar cell element includes a semiconductor substrate, a passivation layer, a protective layer, and an electrode layer. The passivation layer is located on the first surface of the semiconductor substrate. The protective layer is located on the passivation layer. The electrode layer is located on the protective layer and contains a glass component. The protective layer has a plurality of convex portions located on the surface on the electrode layer side. Each of the plurality of convex portions has a concave portion on the electrode layer side. A glass component is located in the internal space of the concave portion.

Description

  The present disclosure relates to a solar cell element.

  As a solar cell element, there is a PERC (Passivated Emitter and Rear Cell) type solar cell element (see, for example, the description of JP-A-2013-4944). In this solar cell element, the passivation layer is located on the back surface of the semiconductor substrate. Furthermore, the back side current collection electrode is located on the passivation layer or on the protective layer located on the passivation layer.

  A solar cell element is disclosed.

  One aspect of a solar cell element includes a semiconductor substrate, a passivation layer, a protective layer, and an electrode layer. The passivation layer is located on the first surface of the semiconductor substrate. The protective layer is located on the passivation layer. The electrode layer is located on the protective layer and includes a glass component. The protective layer has a plurality of convex portions located on the surface on the electrode layer side. Each of the plurality of convex portions has a concave portion on the electrode layer side. The glass component is located in the internal space of the concave portion.

FIG. 1 is a plan view showing the appearance of the front side of an example of the solar cell element according to the first embodiment. FIG. 2: is a top view which shows the external appearance of the back surface side of an example of the solar cell element which concerns on 1st Embodiment. FIG. 3: is a figure which shows an example of the virtual cut surface part of the solar cell element which followed the III-III line of FIG. 1 and FIG. FIG. 4A is an enlarged view showing an example of a virtual cut surface portion of the portion P1 of FIG. FIG.4 (b) is an enlarged view which shows an example of the virtual cut surface part of the part P11 of Fig.4 (a). FIG. 5A is an enlarged view showing an example of a virtual cut surface portion of the portion P1 of FIG. 3. FIG.5 (b) is an enlarged view which shows an example of the virtual cut surface part of the part P11 of Fig.5 (a). Fig.6 (a) is a figure for demonstrating the conditions of the peel test about the solar cell element which concerns on one reference example. FIG.6 (b) is a figure which shows the result of the peeling test about the solar cell element which concerns on one reference example. FIG. 7 is an enlarged view showing an example of a virtual cut surface portion of the portion P12 of FIG. 5 (a). FIGS. 8 (a) to 8 (f) each show an example of a virtual cut surface portion corresponding to the virtual cut surface portion of FIG. 3 in a state in the middle of manufacturing the solar cell element according to the first embodiment. FIG. FIG. 9 is a view for explaining an example of the structure of the protective layer according to the first embodiment. Fig.10 (a) is an enlarged view which shows an example of the virtual cutting plane part of the part corresponding to the part P11 of Fig.4 (a) among the solar cell elements which concern on 2nd Embodiment. FIG.10 (b) is an enlarged view which shows an example of the virtual cutting plane part of the part corresponding to the part P11 of Fig.5 (a) among the solar cell elements which concern on 2nd Embodiment. FIG. 11 is a view for explaining an example of the structure of the protective layer according to the second embodiment. FIG. 12 is a plan view showing the appearance of the back surface side of an example of the solar cell element according to the third embodiment. FIG. 13 is a plan view showing an appearance of a front side of an example of a solar cell module according to a third embodiment. FIG. 14 is a view showing an example of a virtual cross section of the solar cell element taken along line XIV-XIV in FIG. FIG. 15 is a view showing an example of a virtual cut surface part corresponding to the virtual cut surface part of FIG. 14 in a state where the solar cell module according to the third embodiment is being manufactured. FIG. 16A is an enlarged view showing an example of a virtual cut surface portion of the portion P16 of FIG. FIG. 16B is an enlarged view showing a first example of a virtual cut surface portion of a portion corresponding to the portion P16 of FIG. 3 in the solar cell element according to a modification. FIG. 16C is an enlarged view showing a second example of a virtual cut surface portion of a portion corresponding to the portion P16 of FIG. 3 in the solar cell element according to one modification. Fig.17 (a) is an enlarged view which shows the 1st example of the virtual cutting plane part of the part corresponding to the part P16 of FIG. 3 among the solar cell elements which concern on another one modification. FIG. 17B is an enlarged view showing a second example of a virtual cut surface portion of a portion corresponding to the portion P16 of FIG. 3 in a solar cell element according to another modification. FIG. 17C is an enlarged view showing a third example of a virtual cut surface portion of a portion corresponding to the portion P16 of FIG. 3 in a solar cell element according to another modification.

  When a PERC type solar cell element is manufactured, for example, a passivation layer, a protective layer, and a back electrode are formed in this order on the back surface of the semiconductor substrate. The protective layer is formed of, for example, an oxide film formed of silicon oxide or the like, a nitride film formed of silicon nitride or the like, or a film in which an oxide film and a nitride film are stacked. This protective layer is formed, for example, by a wet process or a dry process. In the wet process, for example, a coating method for applying and drying an insulating paste containing a siloxane resin is applied. For the dry process, for example, chemical vapor deposition (CVD), plasma-enhanced chemical vapor deposition (PECVD), sputtering or the like is applied.

  By the way, in order to improve the photoelectric conversion efficiency in a solar cell element, the fine concavo-convex structure (texture) for reducing reflection of irradiated light may be formed in the front side of a semiconductor substrate, for example. In this case, a texture is formed on the semiconductor substrate by performing wet etching using, for example, an alkaline aqueous solution such as sodium hydroxide or an acidic aqueous solution such as hydrofluoric-nitric acid. At this time, texture may be formed on the entire surface including the back surface as well as the front surface of the semiconductor substrate.

  As described above, if there is an unevenness such as texture on the back surface of the semiconductor substrate, the unevenness is easily generated on the surface of the passivation layer and the protective layer formed on the back surface of the semiconductor substrate. Here, for example, a paste containing metal powder mainly containing aluminum, a glass component, and an organic vehicle (also referred to as a metal paste) is applied onto the protective layer, and the metal paste is fired to form the back surface side. It may form a collecting electrode. In this case, the distribution of the components of the metal paste tends to be biased due to the presence of irregularities on the surface of the protective layer. For this reason, the adhesion strength of the current collection electrode with respect to the protective layer tends to be uneven. Thereby, there exists a possibility that partial peeling of a current collection electrode may arise on a protective layer. Specifically, for example, it is easy for the fluid glass component and the organic vehicle to flow into the lower part in the direction of gravity such as over the convex portion of the protective layer and between the metal powder and over the concave portion of the protective layer. . For this reason, there exists a possibility that partial peeling of a current collection electrode may arise on the convex-shaped part of a protective layer. And when a current collection electrode exfoliates from a protective layer, exfoliation of a current collection electrode advances on the back side of a solar cell element, and there is a possibility that the efficiency of current collection in the back side of a solar cell element may fall. As a result, the photoelectric conversion efficiency in the solar cell element may be reduced.

  Then, in order to reduce the partial peeling of the current collection electrode on a protective layer, it is possible to, for example, increase the content rate of the glass component in a metal paste. However, when the content of the glass component in the metal paste is increased, fire through (fired penetration) of the protective layer by the metal paste tends to occur at the time of firing the metal paste. For this reason, there exists a possibility that the photoelectric conversion efficiency in a solar cell element may fall by the fall of the passivation effect in the back surface side of a solar cell element.

  Moreover, in order to make it hard to produce fire through of the protective layer by a metal paste with respect to said point, it is possible to enlarge the thickness of a protective layer, for example. However, when the thickness of the protective layer is increased, stress caused by expansion and contraction with temperature change tends to be increased between the semiconductor substrate and the protective layer during firing of the metal paste and when using the solar cell element. Thus, the protective layer may be peeled off from the back surface side of the semiconductor substrate. In addition, for example, if the stress generated between the semiconductor substrate and the protective layer increases due to expansion and contraction accompanying the temperature change of the protective layer, the warpage of the solar cell element may increase, and the solar cell element may be cracked or broken. There is. As a result, the photoelectric conversion efficiency in the solar cell element may be reduced.

  Therefore, the present inventors have created a technology that can improve the photoelectric conversion efficiency of a PERC type solar cell element.

  Hereinafter, various embodiments will be described based on the drawings. In the drawings, portions having similar configurations and functions are denoted by the same reference numerals, and redundant description will be omitted in the following description. The drawings are schematically shown. The XYZ coordinate system of the right-handed system is attached to FIGS. 1 to 6 (a), 7 and 9 to 17 (c). In this XYZ coordinate system, the longitudinal direction of the first output extraction electrode 7a is the + Y direction, the short direction of the first output extraction electrode 7a is the + X direction, and the sun is orthogonal to both the + X direction and the + Y direction. The normal direction of the front surface 10 fs of the battery element 10 is the + Z direction.

<1. First embodiment>
<1-1. Schematic Configuration of Solar Cell Element>
The schematic configuration of the solar cell element 10 according to the first embodiment will be described based on FIGS. 1 to 3. In FIG. 3, the texture intentionally formed on the second surface 1 fs of the semiconductor substrate 1 is drawn in a large size for convenience. On the other hand, in FIG. 3, the texture formed on the first surface 1 bs of the semiconductor substrate 1 is omitted so as to fit the actual size. The solar cell element 10 according to the first embodiment is a PERC type solar cell element.

  As shown in FIGS. 1 to 3, the solar cell element 10 mainly includes a light receiving surface (also referred to as a front surface) 10 fs, and a surface (also referred to as a back surface) 10 bs located on the opposite side of the front surface. And. In the example of FIGS. 1 to 3, the front surface 10 fs faces the + Z direction, and the back surface 10 bs faces the −Z direction.

  The solar cell element 10 includes, for example, a semiconductor substrate 1, a passivation layer 4, an antireflection layer 5, a protective layer 6, a front electrode 7, and a back electrode 8.

  The semiconductor substrate 1 has a first surface 1 bs, a second surface 1 fs, and a third surface 1 ss. The first surface 1 bs is located on the back surface 10 bs side. The second surface 1 fs is located on the front surface 10 fs side. In other words, the first surface 1 bs and the second surface 1 fs are located in directions opposite to each other. The third surface 1ss is located in a state in which the first surface 1bs and the second surface 1fs are connected. In other words, the third surface 1 ss is an end surface in a state of forming the outer peripheral edge of the semiconductor substrate 1. In the example of FIGS. 1 to 3, the first surface 1 bs is in the state of being oriented in the −Z direction. The second surface 1 fs is in the state of facing the + Z direction. The semiconductor substrate 1 has a flat form having a thickness along the + Z direction. For this reason, the first surface 1 bs and the second surface 1 fs are in the state of constituting the plate surface of the semiconductor substrate 1 along the XY plane.

  The semiconductor substrate 1 also has a first semiconductor layer 2 and a second semiconductor layer 3. The first semiconductor layer 2 is in a state of being constituted by a semiconductor having a first conductivity type. The second semiconductor layer 3 is in a state of being constituted by a semiconductor having a second conductivity type opposite to the first conductivity type. The first semiconductor layer 2 is located in a portion of the semiconductor substrate 1 on the first surface 1 bs side. The second semiconductor layer 3 is located in the surface layer portion of the semiconductor substrate 1 on the second surface 1 fs side. In the example of FIG. 3, the second semiconductor layer 3 is located on the first semiconductor layer 2.

  Here, for example, it is assumed that the semiconductor substrate 1 is a silicon substrate. In this case, a polycrystalline or single crystal silicon substrate is employed as the silicon substrate. The silicon substrate is, for example, a thin substrate having a thickness of 250 μm or less or 150 μm or less. The silicon substrate has, for example, a rectangular outer edge shape in plan view. If the semiconductor substrate 1 having such a shape is adopted, the gaps between the solar cell elements 10 may be small when the solar cell module 10 is manufactured by arranging the plurality of solar cell elements 10.

  Also, for example, when the first conductivity type is p-type and the second conductivity type is n-type, the p-type silicon substrate is, for example, boron as a dopant element in polycrystalline or single crystal silicon crystal. Alternatively, it may be manufactured to contain an impurity such as gallium. In this case, the n-type second semiconductor layer 3 can be generated by diffusing an impurity such as phosphorus as a dopant in the surface layer portion on the second surface 1 fs side of the p-type silicon substrate. At this time, the semiconductor substrate 1 in which the p-type first semiconductor layer 2 and the n-type second semiconductor layer 3 are stacked can be formed. Thus, the semiconductor substrate 1 has a pn junction located at the interface between the first semiconductor layer 2 and the second semiconductor layer 3.

  As shown in FIG. 3, the second surface 1 fs of the semiconductor substrate 1 may have, for example, a fine uneven structure (texture) for reducing the reflection of the irradiated light. At this time, the height of the convex portion of the texture is, for example, about 0.1 μm to 10 μm. The distance between the apexes of adjacent protrusions is, for example, about 0.1 μm to about 20 μm. In the texture, for example, the recess may be substantially spherical, or the protrusion may be pyramidal. The “height of the convex portion” described above is, for example, a straight line passing through the bottom of the recess in FIG. 3 as a reference line, and from the reference line in a direction (here, + Z direction) perpendicular to the reference line. It is the distance to the top of the convex part.

Furthermore, the semiconductor substrate 1 has a third semiconductor layer 2bs. The third semiconductor layer 2 bs is located in the surface layer portion of the semiconductor substrate 1 on the first surface 1 bs side. The conductivity type of the third semiconductor layer 2bs is the same as the conductivity type of the first semiconductor layer 2 (p type in this embodiment). The concentration of the dopant contained in the third semiconductor layer 2 bs is higher than the concentration of the dopant contained in the first semiconductor layer 2. The third semiconductor layer 2 bs forms an internal electric field on the side of the first surface 1 bs of the semiconductor substrate 1. Thereby, in the vicinity of the first surface 1 bs of the semiconductor substrate 1, recombination of minority carriers generated in the semiconductor substrate 1 by photoelectric conversion in response to light irradiation can be reduced. As a result, a decrease in photoelectric conversion efficiency in the solar cell element 10 does not easily occur. The third semiconductor layer 2bs may be formed, for example, by diffusing a dopant element such as aluminum in the surface layer portion of the semiconductor substrate 1 on the first surface 1bs side. At this time, the concentration of the dopant element contained in the first semiconductor layer 2 is about 5 × 10 ¹⁵ atoms / cm ³ to 1 × 10 ¹⁷ atoms / cm ^3, and the concentration of the dopant element contained in the third semiconductor layer 2 bs is And 1 × 10 ¹⁸ atoms / cm ³ to 5 × 10 ²¹ atoms / cm ³ or so. The third semiconductor layer 2 bs is present at a contact portion between the second current collection electrode 8 b described later and the semiconductor substrate 1.

  The passivation layer 4 is located on at least the first surface 1 bs of the semiconductor substrate 1. The passivation layer 4 can reduce recombination of minority carriers generated by photoelectric conversion in response to light irradiation in the semiconductor substrate 1. As a material of the passivation layer 4, for example, one or more kinds of materials selected from aluminum oxide, zirconium oxide, hafnium oxide, silicon oxide, silicon nitride, silicon oxynitride and the like are employed. The passivation layer 4 is, for example, in a state of being constituted by one layer or two or more layers containing different materials. In this case, the passivation layer 4 can be formed by, for example, a CVD method or an atomic layer deposition (ALD) method. Here, it is assumed that the passivation layer 4 contains aluminum oxide. In this case, the aluminum oxide has a negative fixed charge. Therefore, minority carriers (in this case, electrons) generated on the first surface 1 bs side of the semiconductor substrate 1 by the field effect are generated from the interface (first surface 1 bs) between the p-type first semiconductor layer 2 and the passivation layer 4. It is kept away. Thereby, the recombination of minority carriers in the vicinity of the first surface 1 bs of the semiconductor substrate 1 can be reduced. For this reason, the photoelectric conversion efficiency of the solar cell element 10 can be improved. The thickness of the passivation layer 4 is, for example, about 3 nm to 100 nm. The passivation layer 4 may be located, for example, on the second surface 1 fs of the semiconductor substrate 1. The passivation layer 4 may also be located, for example, on the third surface 1 ss as an end face connecting the second surface 1 fs of the semiconductor substrate 1 and the first surface 1 bs.

  The antireflection layer 5 can reduce the reflectance of light irradiated to the front surface 10 fs of the solar cell element 10. As a material of the antireflective layer 5, for example, silicon oxide, aluminum oxide or silicon nitride is adopted. The refractive index and thickness of the antireflective layer 5 are conditions (also referred to as low reflection conditions) in which the reflectance is low with respect to light in a wavelength range that can be absorbed by the semiconductor substrate 1 and contribute to power generation. It can be appropriately set to a value that can be realized. For example, it is conceivable to set the refractive index of the antireflective layer 5 to about 1.8 to 2.5 and to set the thickness of the antireflective layer 5 to about 20 nm to 120 nm.

  The protective layer 6 is located on the passivation layer 4 located on the first surface 1 bs of the semiconductor substrate 1. The protective layer 6 can protect the passivation layer 4. As a material of the protective layer 6, for example, one or more kinds of materials selected from silicon oxide, silicon nitride, silicon oxynitride and the like are employed. The protective layer 6 is located on the passivation layer 4 in a state having a desired pattern. The protective layer 6 has a gap penetrating the protective layer 6 in the thickness direction (here, the + Z direction). This gap may be, for example, a hole in a state in which the periphery along the first surface 1 bs forms a closed through hole, or at least a part of the periphery along the first surface 1 bs It may be a slit-like hole in an open state. For example, as shown in FIG. 2, when the protective layer 6 is seen through the plan view from the back surface 10 bs side, it is assumed that the protective layer 6 has a plurality of holes CH1. Here, when the protective layer 6 is seen through the plan view from the back surface 10bs side, each hole CH1 may be in a dot (dot) shape or in a band (line) shape. The diameter or width of the hole CH1 is, for example, about 10 μm to 500 μm. The pitch of the holes CH1 is, for example, about 0.3 mm to 3 mm. The pitch of the holes CH1 is, for example, the distance between the centers of the holes CH1 adjacent to each other when the protective layer 6 is seen through the plane from the back surface 10bs side. In the example of FIG. 2, 110 holes CH1 are present. However, the combination of the size, shape, and number of the holes CH1 may be appropriately adjusted. For this reason, the number of the holes CH1 may be, for example, one or more.

  By the way, for example, on the passivation layer 4 formed on the first surface 1 bs of the semiconductor substrate 1, the protective layer 6 has a desired pattern of insulating paste by a coating method such as a spray method, a coater method or a screen printing method. It is formed by being dried after being applied to have. The protective layer 6 may be formed directly on the passivation layer 4 or the antireflective layer 5 directly on the third surface 1 ss of the semiconductor substrate 1, for example. At this time, the leakage current in the solar cell element 10 can be reduced by the presence of the protective layer 6.

  Here, for example, when forming a second current collection electrode 8b described later on the protective layer 6, a metal paste (a first metal paste containing a metal powder mainly composed of aluminum, a glass component, and an organic vehicle) Is applied and baked on the protective layer 6 so as to have a desired shape. The main component means a component having the largest ratio (also referred to as a content ratio) of the contained components. At this time, the first metal paste applied directly on the passivation layer 4 causes a fire through of the passivation layer 4 in the hole portion CH1 of the protective layer 6, and the second surface 1bs of the semiconductor substrate 1 The collecting electrode 8b is directly connected. As a result, the passivation layer 4 and the protective layer 6 are in a state of having a plurality of holes CH1 positioned respectively in a state of penetrating the passivation layer 4 and the protective layer 6. At this time, for example, the third semiconductor layer is formed by diffusing aluminum contained in the first metal paste located in the plurality of holes CH1 into the surface layer portion of the first surface 1bs of the semiconductor substrate 1 Two bs are formed. Also, for example, if the thickness of the protective layer 6 is sufficiently larger than the thickness of the passivation layer 4, the first metal paste is used as the passivation layer 4 in the portion covered with the protective layer 6 in the passivation layer 4. Do not fire through. Thereby, in the solar cell element 10, the passivation layer 4 can be present on the first surface 1 bs of the semiconductor substrate 1 in a pattern corresponding to the desired pattern of the protective layer 6.

  The thickness of the protective layer 6 is, for example, about 0.5 μm to 10 μm. The thickness of the protective layer 6 depends on the composition of the insulating paste to be described later for forming the protective layer 6, the shape of the first surface 1bs of the semiconductor substrate 1, and the firing conditions at the time of forming the second collector electrode 8b. , Is set appropriately.

  The front surface electrode 7 is located on the second surface 1 fs side of the semiconductor substrate 1. The surface electrode 7 has the 1st output extraction electrode 7a and several linear 1st current collection electrodes 7b, as FIG. 1 and FIG. 3 show.

  The first output lead electrode 7 a can take out the carrier obtained by photoelectric conversion according to the irradiation of light in the semiconductor substrate 1 to the outside of the solar cell element 10. As the first output lead-out electrode 7a, a bus bar electrode having, for example, an elongated rectangular shape is employed in plan view of the front surface 10 fs. The length (also referred to as the width) of the first output lead electrode 7a in the short direction is, for example, about 0.3 mm to 2.5 mm. At least a part of the first output lead-out electrode 7a is in a state of being electrically connected in a state of intersecting with the first current collection electrode 7b.

  The first current collecting electrode 7 b can collect carriers obtained by photoelectric conversion according to the light irradiation in the semiconductor substrate 1. Each first current collecting electrode 7 b is, for example, a linear electrode having a width of about 20 μm to 200 μm. In other words, the width of each first current collecting electrode 7b is smaller than the width of the first output lead electrode 7a. The plurality of first current collection electrodes 7b are located, for example, in a state of being spaced apart from each other by about 1 mm to 3 mm. The thickness of the surface electrode 7 is, for example, about 3 μm to 30 μm. Such a surface electrode 7 is formed by, for example, applying a metal paste (also referred to as a second metal paste) containing metal particles containing silver as a main component to a desired shape by screen printing or the like. Can be formed by firing. Further, for example, the auxiliary electrode 7c having the same shape as that of the first collecting electrode 7b is located along the edge portions respectively present on the + X direction side and the −X direction side of the semiconductor substrate 1 The first collecting electrodes 7b may be electrically connected to each other.

  The back electrode 8 is located on the first surface 1 bs side of the semiconductor substrate 1. The back surface electrode 8 has the 2nd output extraction electrode 8a and the 2nd current collection electrode 8b, as FIG. 2 and FIG. 3 show.

  The second output lead electrode 8 a is located on the first surface 1 bs side of the semiconductor substrate 1. The second output extraction electrode 8 a is an electrode for extracting carriers obtained by photoelectric conversion in the solar cell element 10 to the outside of the solar cell element 10. The thickness of the second output lead-out electrode 8a is, for example, about 3 μm to 20 μm. The width of the second output lead-out electrode 8a is, for example, about 1.3 mm to 7 mm. When the second output lead-out electrode 8a contains silver as a main component, the second output lead-out electrode 8a is, for example, a metal paste (third metal paste) containing a metal powder mainly containing silver, a glass component and an organic vehicle The third metal paste may be formed by firing after the coating is applied to a desired shape by screen printing or the like.

  The second current collection electrode 8 b is located on the protective layer 6 on the first surface 1 bs side of the semiconductor substrate 1. The second current collection electrode 8 b is in a state of being electrically connected to the semiconductor substrate 1. Specifically, the second current collection electrode 8b includes an electrode layer 8bl and a connection portion 8bc. The electrode layer 8 bl is a layered portion located on the protective layer 6. Connecting portion 8 bc electrically connects electrode layer 8 bl to first surface 1 bs of semiconductor substrate 1 at a plurality of holes CH 1 positioned respectively in a state of penetrating through passivation layer 4 and protective layer 6. It is the part located in the state where it is doing.

  The second current collection electrode 8 b can collect carriers obtained by photoelectric conversion in the semiconductor substrate 1 according to the light irradiation on the first surface 1 bs side of the semiconductor substrate 1. The second current collection electrode 8 b is located in a state electrically connected to at least a part of the second output extraction electrode 8 a. The thickness of the electrode layer 8bl in the second current collection electrode 8b is, for example, about 15 μm to 50 μm. When the second current collection electrode 8b contains aluminum as a main component, for example, after the first metal paste is applied in a desired shape, the second current collection electrode 8b is fired by baking the first metal paste. It can be formed.

  Furthermore, the second current collection electrode 8 b has, for example, the same shape as the first current collection electrode 7 b on the first surface 1 bs of the solar cell element 10 and is connected to the second output extraction electrode 8 a It may be located in the state. If such a structure is adopted, light incident on the back surface 10 bs of the solar cell element 10 can also be used for photoelectric conversion in the solar cell element 10. Thereby, for example, the output of the solar cell element 10 can be improved. The light incident on the back surface 10bs can be generated, for example, by the reflection of sunlight on the ground or the like.

<1-2. Structure on Back Side of Solar Cell>
The structure on the back surface 10bs side of the solar cell element 10 according to the first embodiment will be described based on FIGS. 4 (a) and 4 (b). Here, for example, after removing the back surface electrode 8 of the solar cell element 10 by etching using hydrochloric acid or the like, observing the surface shape of the protective layer 6 with an optical microscope or a scanning electron microscope (SEM: Scanning Electron Microscope) Can. In addition, for example, after cutting the solar cell element 10 and removing a portion having distortion and flaws due to cutting on the cut surface of the solar cell element 10 by etching using hydrochloric acid or the like, the cross section of the protective layer 6 is observed by SEM or the like. can do.

  As shown in FIG. 4A, for example, the protective layer 6 has a plurality of convex portions 6p located on the surface of the second current collection electrode 8b on the electrode layer 8bl side. In other words, for example, the plurality of convex portions 6 p are located on the surface of the protective layer 6 opposite to the surface on which the passivation layer 4 is located. Here, the surface of the protective layer 6 opposite to the surface on which the passivation layer 4 is located is the surface of the protective layer 6 on which the electrode layer 8 b 1 is located. In the first embodiment, the protective layer 6 has a plurality of convex portions 6 p and a non-convex portion 6 ap, which are located on the electrode layer 8 bl side of the second collecting electrode 8 b. The non-convex portion 6 ap is a portion other than the plurality of convex portions 6 p, which is located on the surface of the protective layer 6 on the electrode layer 8 bl side. In other words, the surface of the protective layer 6 on the electrode layer 8 bl side has a concavo-convex structure including the convex portion 6 p and the non-convex portion 6 ap. In the example of FIG. 4A, each convex portion 6p is positioned in a state of projecting in the -Z direction with reference to the non-convex portion 6ap.

  Also, for example, in a mode as shown in FIG. 5A, the protective layer 6 is located on the surface of the second current collection electrode 8b on the electrode layer 8bl side, and the convex portion 6p, and the convex shape You may have non-convex-shaped parts 6ap other than the part 6p. In other words, for example, the convex portion 6 p and the non-convex portion 6 ap are located on the surface of the protective layer 6 opposite to the surface on which the passivation layer 4 is located. In the example of FIG. 5A, each convex portion 6p is positioned so as to protrude in the -Z direction with reference to the non-convex portion 6ap.

  The concavo-convex structure on the surface of the protective layer 6 may be derived from, for example, the concavo-convex structure 1 rg of the first surface 1 bs of the semiconductor substrate 1. In the example of FIG. 4A and FIG. 5A, in the first surface 1bs of the semiconductor substrate 1, a portion (also referred to as a recess) 1r located in a state of being recessed in the + Z direction, and in the -Z direction. There is a portion (also referred to as a convex portion) 1p positioned in a protruding state. The concavo-convex structure 1 rg is in a state of being configured to have the concave portion 1 r and the convex portion 1 p. Therefore, for example, the passivation layer 4 and the protective layer 6 having a small thickness are formed in this order on the concavo-convex structure 1 rg, so that the electrode layer 8 bl of the protective layer 6 is to be formed. A concavo-convex structure corresponding to the concavo-convex structure 1 rg of the semiconductor substrate 1 may be formed on the surface.

  In the first embodiment, in the semiconductor substrate 1, as described above, the above-described fine on the second surface 1 fs side by wet etching using an alkaline aqueous solution such as sodium hydroxide or an acidic aqueous solution such as fluoronitric acid. An uneven structure (texture) is formed. For example, when the concavo-convex structure is formed on the second surface 1 fs side, the concavo-convex structure 1 rg may be formed on the first surface 1 bs side of the semiconductor substrate 1.

  Also, as shown in FIGS. 4B and 5B, each of the plurality of convex portions 6p in the protective layer 6 has one or more concave shapes on the electrode layer 8bl side of the second current collection electrode 8b. It has a portion 6pr. Thus, the convex portion 6p has a plurality of concave portions 6pr. In FIG. 4B, six concave portions 6pr located in the convex portion 6p are drawn. In FIG. 5 (b), seven concave portions 6pr located in the convex portion 6p are drawn. In such a concave portion 6pr, for example, an organic filler is contained in the insulating paste used when forming the protective layer 6, and the organic filler is thermally decomposed when the insulating paste is dried. The filler may be formed as a trace of the extinguished area.

  In the internal space SC1 of the concave portion 6pr, a part of the electrode layer 8bl of the second collecting electrode 8b is located. In other words, a component (also referred to as an electrode component) in a state of constituting the electrode layer 8bl of the second current collection electrode 8b is located in the internal space SC1 of the concave portion 6pr. The electrode component contains at least a glass component. This glass component may be derived from, for example, the glass component contained in the first metal paste used when forming the second current collection electrode 8b.

  By the way, when, for example, the content of the glass component contained in the first metal paste to be applied on the protective layer 6 is temporarily reduced when forming the second current collection electrode 8b, the protective layer 6 and the second current collection are The adhesion to the electrode 8b is reduced. For example, as described below, four types of experimental solar cell elements 110 (see FIGS. 6A and 6B) are manufactured as samples, and the adhesion of the second current collection electrode 108b to the protective layer 106 is obtained. Experiments were conducted. As a result, it was confirmed that when the content of the glass component contained in the first metal paste decreases, the adhesion of the second current collection electrode 108b to the protective layer 106 decreases.

  In producing four types of experimental solar cell elements 110, first, a polycrystalline silicon substrate having rectangular front and back surfaces with a side of about 156 mm and a thickness of about 200 μm was prepared. A passivation layer of about 50 nm was formed by the ALD method on the back surface side of this polycrystalline silicon substrate, and a protective layer 106 was formed on this passivation layer. At this time, an insulating paste containing a siloxane resin, an organic solvent, and a plurality of inorganic fillers is applied by a coater method on the passivation layer, and dried at about 270 ° C. to have a thickness of about 1 μm. The protective layer 106 was formed. Next, a first metal paste containing a metal powder containing aluminum (Al) as a main component, a glass component, and an organic vehicle was applied to substantially the entire surface of the protective layer 106 by screen printing. Here, four types of first metal pastes were used in which the content of the glass component was four levels of 2% by mass, 3.5% by mass, 4% by mass, and 5% by mass. Furthermore, a third metal paste containing a metal powder containing silver as a main component, an organic vehicle, and a glass frit was applied by screen printing to a pattern of the second output extraction electrode 108a. Then, by firing the first metal paste and the third metal paste under the condition that the maximum temperature is about 740 ° C. and the heating time is about one minute (min), the second output extraction electrode 108 a and the second output extraction electrode 108 a A back electrode 108 including the two current collection electrodes 108 b was formed. Thereby, samples of solar cell elements 110 for four types of experiments were produced.

  Then, as shown in FIG. 6A, for each of the samples of the four types of experimental solar cell elements 110, ethylene vinyl acetate is provided in a region Aa0 surrounded by a two-dot chain line on the second current collection electrode 108b. It stuck, heating resin of copolymer (EVA). Then, an experiment was conducted to confirm whether or not the second current collection electrode 108 b is peeled off from the protective layer 106 by peeling off the EVA resin from the second current collection electrode 108 b. At this time, as shown in FIG. 6 (b), the content of the glass component in the first metal paste used for the preparation is 4 mass% and 5 among the samples of the four types of experimental solar cell elements 110. It was found that the second current collection electrode 108 b was not peeled off from the protective layer 106 for the sample that was% by mass. On the other hand, if the content of the glass component in the first metal paste used for preparation is as low as 3.5 mass% and 2 mass%, it is recognized that the second current collection electrode 108 b peels off from the protective layer 106 It was done. From this experimental result, it was confirmed that when the content of the glass component contained in the first metal paste decreases, the adhesion of the second current collection electrode 108b to the protective layer 106 decreases. Thereby, it was found that if the content of the glass component in the first metal paste is increased, the adhesion between the protective layer 106 and the metal particles in the second current collection electrode 108b is enhanced due to the presence of the glass component.

  On the other hand, in the solar cell element 10 according to the first embodiment, the concave portion 6pr is present in the convex portion 6p present on the surface of the protective layer 6. Therefore, for example, when the first metal paste is applied on the protective layer 6 to form the second current collecting electrode 8b, the convex portion 6p may be formed even if the surface of the protective layer 6 has an uneven structure. The glass component and the like in the first metal paste penetrate into the existing concave portion 6pr. Therefore, for example, when forming the configuration shown in FIG. 4A and FIG. 5A, in the first metal paste located on the convex portion 6p, the glass component, the organic vehicle, etc. It becomes difficult for the fluid component including Y to flow out in the direction along the direction of gravity (the + Z direction in the example of FIG. 4A and FIG. 5A). Thereby, in the 1st metal paste located on convex-shaped part 6p, content of a glass component does not reduce easily. As a result, when the second current collection electrode 8 b is formed, the distribution of the components of the first metal paste applied on the protective layer 6 is less likely to be biased. At this time, for example, the adhesion of the second current collection electrode 8b on the protective layer 6 is unlikely to be uneven. And when baking a 1st metal paste, adhesiveness improves between the protective layer 6 and the metal particle in the 2nd current collection electrode 8b in convex part 6p by presence of a glass component in concave part 6pr. obtain. Further, for example, when a part of the second current collection electrode 8b enters the concave portion 6pr of the protective layer 6, a so-called anchor effect can also be generated. Thereby, the adhesion of the second current collection electrode 8 b to the protective layer 6 can be improved. As a result, for example, partial peeling of the second current collection electrode 8 b from the protective layer 6 does not easily occur. Therefore, the photoelectric conversion efficiency in the PERC solar cell element 10 can be improved.

  Here, for example, when the protective layer 6 is seen through in plan from the electrode layer 8bl side of the second current collection electrode 8b, the diameter of the concave portion 6pr present on the surface of the protective layer 6 is, for example, 0.1 μm to It is about 10 μm. In this case, for example, when firing the first metal paste, a glass component in a molten state in the first metal paste can easily enter the concave portion 6pr. As a result, the adhesion of the second current collection electrode 8b to the protective layer 6 can be improved.

  Here, for example, the depth of the concave portion 6pr present on the surface on the electrode layer 8bl side of the second current collection electrode 8b of the protective layer 6 is, for example, about 0.1 μm to 1 μm. . Here, for example, when the depth of the concave portion 6pr is smaller than the height of the convex portion 6p, the component of the first metal paste applied on the protective layer 6 when forming the second current collecting electrode 8b. Distribution is less likely to occur. As a result, for example, the adhesion of the second current collection electrode 8 b on the protective layer 6 is unlikely to be uneven. In addition, here, for example, if the thickness (also referred to as the minimum film thickness) of the protective layer 6 in the portion where the concave portion 6pr is present in the protective layer 6 is about 0.5 μm or more, passivation by the protective layer 6 is performed. The function of protecting the layer 4 can be secured.

  By the way, here, as shown in FIGS. 4 (b) and 5 (b), for example, the distance between adjacent concave portions 6pr among the plurality of concave portions 6pr present in the convex portion 6p The first distance is also referred to as D1. As the first distance D1, for example, a distance between centers of adjacent concave portions 6pr is adopted. The first distance D1 may be, for example, an average value of distances between centers of adjacent concave portions 6pr, or even a distance between adjacent concave portions 6pr (also referred to as a separation distance). It may be an average value of the separation distance between adjacent concave portions 6pr. Further, as shown in FIGS. 4A and 5A, for example, the distance (also referred to as a second distance) between adjacent convex portions 6p among the plurality of convex portions 6p is D2. . As the second distance D2, for example, the distance between the centers or the apexes of adjacent convex portions 6p is adopted. The second distance D2 may be, for example, an average value of distances between centers or apexes of adjacent convex portions 6p, or may be a distance between adjacent convex portions 6p. It may be an average value of the separation distances of the adjacent convex portions 6p. Further, as shown in FIGS. 2 and 3, for example, a distance (also referred to as a third distance) between adjacent connection portions 8bc among a plurality of connection portions 8bc existing in a plurality of hole portions CH1 is D3. I assume. As the third distance D3, for example, the distance between the centers of adjacent connection portions 8bc is adopted. The third distance D3 may be, for example, an average value of distances between centers of adjacent connection portions 8bc, or may be a separation distance between adjacent connection portions 8bc, or adjacent connection portions 8bc. The average value of the separation distances of In this case, for example, if the first distance D1 is shorter than any of the second distance D2 and the third distance D3, the adhesion of the second current collection electrode 8b to the protective layer 6 can be sufficiently improved. As a result, for example, partial peeling of the second current collection electrode 8 b from the protective layer 6 does not easily occur. Therefore, the photoelectric conversion efficiency in the PERC solar cell element 10 can be improved. Furthermore, here, for example, adjacent concave portions 6pr may be connected to each other. In this case, the adhesion of the second current collection electrode 8b to the protective layer 6 can be further improved. As a result, for example, partial peeling of the second current collection electrode 8 b from the protective layer 6 is less likely to occur.

Here, for example, when the surface on the electrode layer 8bl side of the protective layer 6 is viewed in plan, the ratio of the concave portion 6pr to the area of the unit area in the convex portion 6p is about 5% to 40%. Thus, the adhesion of the second current collection electrode 8b to the protective layer 6 can be easily improved. Here, for example, after the back electrode 8 of the solar cell element 10 is removed by etching with hydrochloric acid or the like, the surface of the protective layer 6 on the electrode layer 8 bl side is observed by SEM. The plane can be viewed in plan. The unit area is set, for example, in the range of 10 μm ² to 20 μm ² .

  Furthermore, here, as shown in, for example, FIGS. 4B and 7, the non-convex portion 6ap of the protective layer 6 also has one or more concave portions 6pr, similarly to the convex portion 6p. It may be Thereby, for example, a plurality of concave portions 6pr may exist over a wide range in the portion of the protective layer 6 on the electrode layer 8bl side of the second current collection electrode 8b. Then, for example, in the internal space SC1 of the concave portion 6pr of the non-convex portion 6ap, an electrode component including a glass component in a state of constituting the electrode layer 8bl of the second current collection electrode 8b is positioned . If such a configuration is adopted, the distribution of the components of the first metal paste applied onto the protective layer 6 is less likely to be uneven when the second current collection electrode 8 b is formed. Thereby, for example, on the back surface 10 bs side of the solar cell element 10, the distribution of the adhesion between the protective layer 6 and the second current collection electrode 8 b is unlikely to be biased. As a result, for example, partial peeling of the second current collection electrode 8 b from the protective layer 6 does not easily occur. Therefore, the photoelectric conversion efficiency in the PERC solar cell element 10 can be improved.

<1-3. Insulating paste>
In the first embodiment, for example, two types of insulating pastes are used to form the protective layer 6. The two types of insulating pastes include a first insulating paste and a second insulating paste.

  Each of the first insulating paste and the second insulating paste contains, for example, a siloxane resin, an organic solvent, and a plurality of fillers. The siloxane resin is a siloxane compound having a Si-O-Si bond (siloxane bond). Specifically, as the siloxane resin, for example, a low molecular weight resin having a molecular weight of 10,000 or less, which is produced by hydrolyzing alkoxysilane or silazane or the like and condensation polymerization, is employed.

  Here, the plurality of fillers in the first insulating paste include fillers (also referred to as inorganic fillers) whose main component is an inorganic material. The plurality of fillers in the second insulating paste contain a filler whose main component is an organic material (also referred to as an organic filler). The plurality of fillers in the second insulating paste may contain an inorganic filler.

<1-4. Production of insulating paste>
<1-4-1. Production of first insulating paste>
The first insulating paste can be manufactured as follows.

  First, a mixed solution is prepared by mixing a siloxane resin precursor, water, an organic solvent, a catalyst, and a filler.

  As a precursor of a siloxane resin, for example, a silane compound having a Si-O bond or a silazane compound having a Si-N bond may be employed. These compounds have the property of causing hydrolysis (also referred to as hydrolyzability). Moreover, the precursor of a siloxane resin becomes a siloxane resin by hydrolyzing and producing condensation polymerization.

  The silane compound is represented by the following general formula 1.

(R1) _n Si (OR2) _(4-n) (general formula 1).

N in the general formula 1 is, for example, an integer of 0, 1, 2 or 3. Further, R1 and R2 in formula 1 is a methyl group (-CH ₃₎ and ethyl group _(-C 2 _{H 5)} alkyl groups such as _{(-C m H 2m + 1)} or phenyl group _(-C 6 _{H 5),} etc. Represents a carbon-hydrogen group such as Here, m is a natural number.

Here, the silane compound includes, for example, a silane compound in which at least R 1 has an alkyl group (also referred to as an alkyl group-based silane compound). Specifically, examples of alkyl group silane compounds include methyltrimethoxysilane (CH ₃ -Si- (OCH ₃ ) ₃ ) and dimethyldimethoxysilane ((CH ₃ ) ₂ -Si- (OCH ₃ ) _2. ), Triethoxymethylsilane (CH ₃ -Si- (OC ₂ H ₅ ) ₃ ), diethoxydimethylsilane ((CH ₃ ) ₂ -Si- (OC ₂ H ₅ ) ₂ ), trimethoxypropylsilane ((CH ₃ ) _{3 O) 3 -Si- (CH 2} ) 2 CH 3), triethoxy propyl silane _{((C 2 H 5 O)} 3 -Si- (CH 2) 2 CH 3), hexyl trimethoxysilane _((CH 3 O ) _3- Si- (CH ₂ ) ₅ CH ₃ ), triethoxyhexylsilane ((C ₂ H ₅ O) ₃ -Si- (CH ₂ ) ₅ CH ₃ ), triethoxyoctyl Silane _{((C 2 H 5 O)} 3 -Si- (CH 2) 7 CH 3) and decyl trimethoxysilane _{((CH 3 O) 3 -Si-} (CH 2) 9 CH 3) can be mentioned.

  Here, for example, when the alkyl group is a methyl group, an ethyl group or a propyl group, an alcohol as a by-product which has a small number of carbon atoms and is easy to volatilize may be generated when the precursor of the siloxane resin is hydrolyzed. Thereby, by-products are easily removed in the process described later. As a result, for example, when the protective layer 6 is formed, generation of pores due to evaporation of by-products hardly occurs, so that the protective layer 6 becomes dense, and the barrier property of the protective layer 6 can be improved.

  Here, for example, when the precursor of the siloxane resin has a phenyl group, the precursor of the siloxane resin is hydrolyzed and subjected to condensation polymerization, and byproducts generated by the hydrolysis and condensation polymerization of the phenyl group are removed. You may be used in the state made into the produced siloxane resin. Thereby, for example, the fluctuation of the viscosity of the insulating paste due to the reaction of hydrolysis and condensation polymerization of the siloxane resin is reduced, and the viscosity of the insulating paste is easily stabilized. Also, for example, if an insulating paste is formed by mixing a siloxane resin, an organic solvent and a filler in a state in which by-products are removed, the amount of by-products contained in the insulating paste is reduced. . For this reason, if such an insulating paste is generated, for example, in the case of applying the insulating paste by screen printing, it is reduced that the emulsion of the screen plate making is dissolved by a by-product. As a result, the dimension of the pattern of the screen plate making is less likely to change.

The silane compounds also include, for example, silane compounds in which R1 and R2 have both a phenyl group and an alkyl group. As such a silane compound, for example, trimethoxyphenylsilane (C ₆ H ₅ -Si- (OCH ₃ ) ₃ ), dimethoxydiphenylsilane ((C ₆ H ₅ ) ₂ -Si- (OCH ₃ ) ₂ ), Methoxytriphenylsilane ((C ₆ H ₅ ) ₃ -Si-OCH ₃ ), triethoxyphenylsilane (C ₆ H ₅ -Si- (OC ₂ H ₅ ) ₃ ), diethoxydiphenylsilane ((C ₆ H ₅₎ ) _2- Si- (OC ₂ H ₅ ) ₂ ), ethoxytriphenylsilane ((C ₆ H ₅ ) ₃ -Si-OC ₂ H ₅ ), triisopropoxyphenylsilane (C ₆ H ₅ -Si- (OCH) _{(CH 3) 2) 3)} , diisopropoxy diphenylsilane _{((C 6 H 5) 2} -Si- (OCH (CH 3) 2) 2) and Isopuropokishito Phenyl silane _{((C 6 H 5) 3} -Si-OCH (CH 3) 2) can be mentioned.

  Among these silane compounds, for example, if a silane compound containing two or more OR bonds is adopted, a siloxane bond (Si-O-Si bond) is generated by causing condensation polymerization after the silane compound is hydrolyzed. The number of) can be increased. This can increase the number of siloxane bond networks in the silicon oxide that forms the protective layer 6. As a result, the barrier properties of the protective layer 6 can be improved.

The silazane compound may be either an inorganic silazane compound or an organic silazane compound. Examples of the inorganic silazane compounds, for example, polysilazane _{(- (H 2 SiNH) -} ) and the like. Examples of organic silazane compounds include hexamethyldisilazane ((CH ₃ ) ₃ -Si-NH-Si- (CH ₃ ) ₃ ) and tetramethylcyclodisilazane ((CH ₃ ) ₂ -Si- (NH) _2. -Si- _{(CH 3) 2)} and tetraphenyl cyclo disilazane _{((C 6 H 5) 2} -Si- (NH) 2 -Si- (C 6 H 5) 2) , and the like.

Water is a liquid for hydrolyzing the precursor of the siloxane resin. For example, pure water is used as water. For example, water reacts to the bond of Si-OCH ₃ of the silane compound to form Si-OH bond and HO-CH ₃ (methanol).

  The organic solvent is a solvent for producing a paste containing a siloxane resin from a precursor of the siloxane resin. Moreover, the organic solvent can mix the precursor of siloxane resin, and water. As the organic solvent, for example, diethylene glycol monobutyl ether, methyl cellosolve, ethyl cellosolve, ethyl alcohol, 2- (4-methylcyclohex-3-enyl) propan-2-ol, 2-propanol or the like is used. Here, any one of these organic solvents and an organic solvent in which two or more organic solvents are mixed may be used.

The catalyst can control the rate of reaction as the precursor of the siloxane resin undergoes hydrolysis and condensation polymerization. For example, hydrolysis and condensation polymerization are caused to the Si-OR bond (for example, R is an alkyl group) contained in the precursor of the siloxane resin to form Si-O-Si bond and H ₂ O from two or more Si-OH bonds. The rate of reaction to produce (water) can be adjusted. As the catalyst, for example, one or more inorganic acids or one or more organic acids of hydrochloric acid, nitric acid, sulfuric acid, boric acid, phosphoric acid, hydrofluoric acid, acetic acid and the like are used. Further, as a catalyst, for example, one or more types of inorganic bases or one or more types of organic bases among ammonia, sodium hydroxide, potassium hydroxide, barium hydroxide, calcium hydroxide and pyridine may be used. Furthermore, the catalyst may be, for example, a combination of an inorganic acid and an organic acid, or a combination of an inorganic base and an organic base.

  The filler is, for example, an inorganic filler containing silicon oxide, aluminum oxide or titanium oxide.

  As for the mixing ratio of each material mixed here, for example, in the mixed solution after mixing all the materials, the concentration of the precursor of the siloxane resin becomes 7 mass% to 60 mass%, and the concentration of water is 5 mass % To 40 wt% (may be 10 wt% to 20 wt%), the concentration of the catalyst is 1 ppm to 1000 ppm, the concentration of the organic solvent is 5 wt% to 50 wt%, the concentration of the inorganic filler is 3 wt% to It is adjusted to be 30% by mass. With such a mixing ratio, for example, a siloxane resin produced by hydrolysis and condensation polymerization of a precursor of a siloxane resin can be contained in the insulating paste at an appropriate concentration. Also, for example, in the insulating paste, excessive increase in viscosity due to gelation does not easily occur.

  Thus, when the materials are mixed, the siloxane resin precursor and water react with each other to initiate hydrolysis of the siloxane resin precursor. Also, the precursor of the hydrolyzed siloxane resin causes condensation polymerization to begin to form the siloxane resin.

  Next, the mixed solution is stirred. Here, the mixed solution is stirred using, for example, a mix rotor or a stirrer. When the mixed solution is stirred, the hydrolysis of the precursor of the siloxane resin further proceeds. Also, the precursor of the hydrolyzed siloxane resin causes condensation polymerization, and the siloxane resin continues to be produced. For example, in the case of stirring with a mix rotor, the rotation conditions of the rotation roller of the mix rotor are set to about 400 rpm to 600 rpm, and the stirring conditions are set such that the stirring time is about 30 minutes to 90 minutes. When such stirring conditions are adopted, the precursor of the siloxane resin, water, the catalyst and the organic solvent can be uniformly mixed. In addition, when the mixed solution is stirred, for example, if the mixed solution is heated, hydrolysis and condensation polymerization of the precursor of the siloxane resin easily proceed. As a result, for example, the productivity can be improved by shortening the stirring time, and the viscosity of the mixed solution can be easily stabilized.

  Next, the first insulating paste can be manufactured by volatilizing water and the catalyst from the mixed solution. Here, for example, when the first insulating paste is applied by screen printing, the by-products and the organic solvent are also volatilized so that the emulsion of the screen is unlikely to melt and change in size. By-products include, for example, organic components such as alcohols generated by the reaction of a siloxane resin precursor with water.

  Here, for example, using a hot plate or a drying furnace, the processing temperature is about room temperature to 90 ° C. (may be about 50 ° C. to 90 ° C.) and the processing time is about 10 minutes to 600 minutes. The mixed solution after stirring is treated. By-products can be removed if the treatment temperature is within the above temperature range. Moreover, since the organic component which is a by-product is easily volatilized within the said temperature range, the improvement of productivity by shortening of processing time may be achieved. Here, for example, under reduced pressure, the by-product organic component is likely to be volatilized. As a result, productivity can be improved by shortening the processing time. Also, for example, when the mixed solution is stirred, the precursor of the siloxane resin remaining without being hydrolyzed may be further hydrolyzed.

<1-4-2. Production of second insulating paste>
The method for producing the second insulating paste can be realized, for example, by adding an organic filler to the mixed solution in place of all or part of the inorganic filler in the method for producing the first insulating paste described above. Here, for example, the organic filler is added to the mixed solution after volatilizing the by-products and the organic solvent in the mixed solution so that the dissolution of the organic filler by the by-product and the organic solvent in the mixed solution is less likely to occur. And the mixed solution may be stirred.

  Here, as the organic filler, for example, one containing as a main component a material that causes thermal decomposition at a temperature at which the second insulating paste is dried when forming the protective layer 6 is employed. The temperature at which the organic filler causes thermal decomposition is, for example, 300 ° C. or less. Such materials include acrylic materials and the like. The average particle size of the organic filler is, for example, about 1 μm or less. Here, for example, if about 5 parts by mass to about 20 parts by mass of the organic filler is added to 100 parts by mass of the mixed solution, the viscosity of the mixed solution and the concave portion 6pr formed in the protective layer 6 The number can be easily adjusted.

<1-5. Method of manufacturing solar cell element>
An example of the manufacturing method of the solar cell element 10 is demonstrated based on FIG. 8 (a)-FIG.8 (f).

  First, the step of preparing the semiconductor substrate 1 (also referred to as a first step) is performed. The semiconductor substrate 1 has a first surface 1 bs and a second surface 1 fs facing in the opposite direction to the first surface 1 bs.

  Here, for example, first, the semiconductor substrate 1 is prepared as shown in FIG. The semiconductor substrate 1 can be formed, for example, using the existing CZ method or casting method. Here, an example using a p-type polycrystalline silicon ingot manufactured by a casting method will be described. The ingot is sliced to a thickness of, for example, 250 μm or less to manufacture the semiconductor substrate 1. Here, for example, when a very small amount of etching is performed on the surface of the semiconductor substrate 1 with an aqueous solution such as sodium hydroxide, potassium hydroxide, hydrofluoric acid or fluoronitric acid, mechanical damage to the cut surface of the semiconductor substrate 1 And the contaminated layer can be removed. At this time, for example, a part of the above-described texture may be formed on the second surface 1 fs of the semiconductor substrate 1, and at least a part of the above-described uneven structure 1 rg may be formed on the first surface 1 bs of the semiconductor substrate 1.

  Next, as shown in FIG. 8B, the texture is formed on the second surface 1 fs of the semiconductor substrate 1. The texture can be formed by wet etching using an alkaline aqueous solution such as sodium hydroxide or an acidic aqueous solution such as hydrofluoric-nitric acid, or dry etching using a reactive ion etching (RIE) method or the like. At this time, for example, at least a part of the concavo-convex structure 1 rg described above may be formed on the first surface 1 bs of the semiconductor substrate 1.

Next, as shown in FIG. 8C, the second semiconductor layer 3 which is an n-type semiconductor region is formed in the surface layer portion on the second surface 1 fs side of the semiconductor substrate 1 having texture. The second semiconductor layer 3 is formed, for example, by applying a paste-like diphosphorus pentoxide (P ₂ O ₅ ) on the surface of the semiconductor substrate 1 to thermally diffuse phosphorus, or a gaseous oxychloride It can be formed by using a vapor phase thermal diffusion method using phosphorus (POCl ₃ ) as a diffusion source. The second semiconductor layer 3 is formed to have, for example, a depth of about 0.1 μm to 2 μm and a sheet resistance value of about 40 Ω / □ to 200 Ω / □.

For example, in the vapor phase thermal diffusion method, first, the semiconductor substrate 1 is subjected to heat treatment for about 5 minutes to 30 minutes at a temperature of about 600 ° C. to 800 ° C. in an atmosphere having a diffusion gas mainly containing POCl ₃ or the like. Phosphorous glass is formed on the surface of the semiconductor substrate 1. Thereafter, the semiconductor substrate 1 is subjected to heat treatment for about 10 minutes to about 40 minutes at a relatively high temperature of about 800 ° C. to 900 ° C. in an atmosphere of an inert gas such as argon or nitrogen. Thereby, phosphorus is diffused from the phosphorus glass to the semiconductor substrate 1, and the second semiconductor layer 3 is formed in the surface layer portion on the second surface 1 fs side of the semiconductor substrate 1.

  Here, when the second semiconductor layer 3 is formed, the second semiconductor layer may be formed on the side of the first surface 1 bs. In this case, the second semiconductor layer formed on the first surface 1 bs side is removed by etching. For example, the second semiconductor layer formed on the first surface 1 bs side can be removed by immersing a portion on the first surface 1 bs side of the semiconductor substrate 1 in an aqueous solution of hydrofluoric-nitric acid. Thereby, the region having the p-type conductivity type can be exposed on the first surface 1 bs of the semiconductor substrate 1. Thereafter, when the second semiconductor layer 3 is formed, the phosphorus glass attached to the second surface 1 fs side of the semiconductor substrate 1 is removed by etching. As described above, with the phosphorus glass remaining on the second surface 1 fs side, if the second semiconductor layer formed on the first surface 1 bs side is removed by etching, the second semiconductor layer 3 on the second surface 1 fs side is removed. Removal and damage can be reduced. At this time, the second semiconductor layer formed on the third surface 1 ss of the semiconductor substrate 1 may be removed together.

  Alternatively, for example, a diffusion mask may be formed in advance on the first surface 1 bs side of the semiconductor substrate 1, the second semiconductor layer 3 may be formed by a vapor phase thermal diffusion method or the like, and then the diffusion mask may be removed. In this case, since the second semiconductor layer is not formed on the first surface 1 bs side, the step of removing the second semiconductor layer on the first surface 1 bs side is unnecessary.

  By the above processing, the second semiconductor layer 3 which is an n-type semiconductor layer is located on the second surface 1 fs side, has texture on the second surface 1 fs, and has the concavo-convex structure 1 rg on the first surface 1 bs. The semiconductor substrate 1 including the one semiconductor layer 2 can be prepared.

  Next, the step of forming passivation layer 4 (also referred to as a second step) is performed. In the first embodiment, the passivation layer 4 is formed at least on the first surface 1 bs of the semiconductor substrate 1.

  Here, for example, as shown in FIG. 8 (d), aluminum oxide is mainly contained on the first surface 1 bs of the first semiconductor layer 2 and the second surface 1 fs of the second semiconductor layer 3. The passivation layer 4 is formed. In addition, the antireflective layer 5 is formed on the passivation layer 4. The antireflection layer 5 is made of, for example, a silicon nitride film or the like.

  Passivation layer 4 can be formed by, for example, a CVD method or an ALD method. According to the ALD method, for example, the passivation layer 4 can be formed all around the semiconductor substrate 1 including the third surface 1ss. In the step of forming the passivation layer 4 by the ALD method, first, the semiconductor substrate 1 on which the second semiconductor layer 3 is formed is placed in the chamber of the film forming apparatus. Then, in a state where the semiconductor substrate 1 is heated to a temperature range of about 100 ° C. to about 250 ° C., the following steps A to D are repeated a plurality of times to form a passivation layer 4 mainly containing aluminum oxide. Thereby, the passivation layer 4 having a desired thickness is formed.

  [Step A] An aluminum source such as trimethylaluminum (TMA) for forming aluminum oxide is supplied onto the semiconductor substrate 1 together with a carrier gas such as Ar gas or nitrogen gas. Thereby, the aluminum source is adsorbed on the entire periphery of the semiconductor substrate 1. The time for which the TMA is supplied is, for example, about 15 milliseconds (msec: msec) to about 3000 milliseconds. Here, at the start of step A, the surface of the semiconductor substrate 1 may be terminated with an OH group. In other words, the surface of the semiconductor substrate 1 may have a Si-O-H structure. This structure can be formed, for example, by treating the semiconductor substrate 1 with dilute hydrofluoric acid and then washing with pure water.

  [Step B] The inside of the chamber of the film forming apparatus is cleaned with nitrogen gas, whereby the aluminum source in the chamber is removed. Furthermore, among the aluminum raw materials physically and chemically adsorbed to the semiconductor substrate 1, aluminum raw materials other than the components chemically adsorbed at the atomic layer level are removed. The time for cleaning the inside of the chamber with nitrogen gas is, for example, about one second (sec) to several tens of seconds.

  [Step C] By supplying an oxidizing agent such as water or ozone gas into the chamber of the film forming apparatus, the alkyl group contained in TMA is removed and substituted by an OH group. Thereby, an atomic layer of aluminum oxide is formed on the semiconductor substrate 1. The time during which the oxidizing agent is supplied into the chamber is, for example, about 750 milliseconds to 1100 milliseconds. Also, for example, if hydrogen is supplied together with the oxidizing agent in the chamber, the hydrogen atoms are more easily contained in the aluminum oxide.

  [Step D] The oxidizing agent in the chamber is removed by cleaning the chamber of the film forming apparatus with nitrogen gas. At this time, for example, an oxidizing agent which does not contribute to the reaction at the time of formation of aluminum oxide at the atomic layer level on the semiconductor substrate 1 is removed. Here, the time during which the inside of the chamber is purified by nitrogen gas is, for example, about one second or more to several tens of seconds.

  Thereafter, by repeating a series of steps in which step A, step B, step C and step D are sequentially performed in this order, a layer of aluminum oxide having a desired film thickness is formed.

The antireflective layer 5 is formed, for example, using a PECVD method or a sputtering method. In the case of using the PECVD method, the semiconductor substrate 1 is previously heated to a temperature higher than the temperature during the formation of the antireflective layer 5. Thereafter, a mixed gas of silane (SiH ₄ ) and ammonia (NH ₃ ) is diluted with nitrogen (N ₂ ) gas, and the reaction pressure is set to about 50 Pa to 200 Pa, and the one that has been plasmatized by glow discharge decomposition is It is deposited on the heated semiconductor substrate 1. Thus, the antireflective layer 5 is formed on the semiconductor substrate 1. At this time, the film forming temperature is set to about 350 ° C. to 650 ° C., and the preheating temperature of the semiconductor substrate 1 is set to about 50 ° C. higher than the film forming temperature. Also, a frequency of about 10 kHz to 500 kHz is adopted as the frequency of the high frequency power source required for the glow discharge. Further, the flow rate of the gas is appropriately determined depending on the size of the reaction chamber and the like. For example, the flow rate of the gas may be in the range of about 150 milliliters / minute (sccm) to about 6000 milliliters / minute (sccm). At this time, the value (B / A) obtained by dividing the flow rate B of the ammonia gas by the flow rate A of the silane gas is in the range of 0.5 to 15.

  Next, the step of forming the protective layer 6 (also referred to as a third step) is performed. In the first embodiment, the protective layer 6 is formed by applying a solution so as to form a pattern including the hole CH1 on the passivation layer 4 at least on the first surface 1 bs side of the semiconductor substrate 1 and drying the solution. Is formed. At this time, by using, for example, the first insulating paste and the second insulating paste as the solution, the protective layer 6 having the plurality of concave portions 6pr can be formed.

  Such a protective layer 6 can be formed, for example, by the following process. Here, first, the first insulating paste is applied on the passivation layer 4. Next, a second insulating paste is applied on the layer of the first insulating paste applied on the passivation layer 4. Next, the maximum temperature of the first insulating paste and the second insulating paste after application is set to about 200 ° C. to 350 ° C. using a hot plate or a drying furnace, and the heating time is about 1 minute to 10 minutes. Dry under the conditions that are considered. At this time, as shown in FIG. 9, the first protective layer region 6a derived from the first insulating paste, and the second derived from the second insulating paste located on the first protective layer region 6a. And a protective layer region 6 b is formed. Here, the organic filler contained in the second insulating paste is thermally decomposed by the heat treatment at the time of drying. Thereby, the part which the organic filler lose | disappeared by thermal decomposition becomes concave part 6pr, and the protective layer 6 which has several concave part 6pr on the surface is formed.

  Also, such a protective layer 6 may be formed, for example, by the following process. Here, first, the first insulating paste is applied on the passivation layer 4. Next, a second insulating paste is applied on the layer of the first insulating paste applied on the passivation layer 4. Next, the organic filler contained in the second insulating paste does not undergo thermal decomposition, using the first insulating paste and the second insulating paste after application, using a hot plate or a drying furnace, etc., relatively It is dried at a low temperature (for example, about 100 ° C.). Next, an organic solvent is used to dissolve the organic filler located on the surface of the dried second insulating paste. Next, a drying process of evaporating the organic solvent is performed using a hot plate, a drying furnace, or the like. Thereby, a protective layer 6 having a plurality of concave portions 6pr on the surface is formed.

  Here, the first insulating paste and the second insulating paste described above are applied in a desired pattern on at least a part of the passivation layer 4 using, for example, a spray method, a coater method, a screen printing method, or the like. Thereby, for example, as shown in FIG. 8E, the protective layer 6 is formed on at least a part of the passivation layer 4.

  Next, a step of forming an electrode including the front surface electrode 7 and the back surface electrode 8 (also referred to as a fourth step) is performed. Here, for example, a material for electrode formation is disposed on the protective layer 6 and in the hole CH1, and the material for electrode formation is heated, whereby the back electrode 8 is formed. The back surface electrode 8 formed at this time includes the second output extraction electrode 8 a and the second current collection electrode 8 b. The second current collection electrode 8b includes an electrode layer 8bl and a connection portion 8bc.

  Here, for example, as shown in FIG. 8F, the surface electrode 7 and the back surface electrode 8 are formed.

  The surface electrode 7 is produced using, for example, a metal powder containing silver as a main component, an organic vehicle, and a second metal paste (also referred to as a silver paste) containing a glass frit. First, the second metal paste is applied to the second surface 1 fs side of the semiconductor substrate 1. In the first embodiment, the second metal paste is applied on the antireflection layer 5 formed on the passivation layer 4 on the second surface 1 fs. Here, the application of the second metal paste can be realized by, for example, screen printing. Then, after applying the second metal paste, the solvent in the second metal paste may be evaporated and dried at a predetermined temperature. If the second metal paste is applied by screen printing, for example, the first output extraction electrode 7a, the first current collection electrode 7b, and the auxiliary electrode 7c included in the surface electrode 7 can be formed in one step. Thereafter, for example, the surface metal 7 is fired by firing the second metal paste under the condition that the maximum temperature is set to 600 ° C. to 850 ° C. in the firing furnace and the heating time is set to about several tens seconds to several tens of minutes. Form.

  The second output lead-out electrode 8a included in the back surface electrode 8 is manufactured using, for example, a third metal paste (also referred to as silver paste) containing a metal powder containing silver as a main component, an organic vehicle, a glass frit and the like. As a method of applying the third metal paste to the semiconductor substrate 1, for example, a screen printing method can be used. After application of the third metal paste, the solvent in the third metal paste may be evaporated and dried at a predetermined temperature. Then, the second output extraction electrode is fired by firing the third metal paste under the condition that the maximum temperature is set to 600 ° C. to 850 ° C. in the firing furnace and the heating time is set to about several tens of seconds to several tens of minutes. 8 a is formed on the first surface 1 bs side of the semiconductor substrate 1.

  The second current collection electrode 8b included in the back surface electrode 8 is produced, for example, using a first metal paste (Al paste) containing a metal powder containing aluminum as a main component, an organic vehicle and a glass frit. First, the first metal paste is applied to the first surface 1 bs side of the semiconductor substrate 1 so as to be in contact with a part of the previously applied third metal paste. In the first embodiment, the first metal paste is applied on the protective layer 6 formed on the passivation layer 4 on the first surface 1 bs and in the hole CH1. At this time, the first metal paste may be applied to almost the entire surface on the first surface 1 bs side of the semiconductor substrate 1 except for a part of the portion where the second output lead-out electrode 8 a is formed. Here, the application of the first metal paste can be realized by, for example, screen printing. Further, at this time, the first metal paste also intrudes into the internal space SC1 of the plurality of concave portions 6pr of the protective layer 6.

  Here, after the application of the first metal paste, the solvent in the first metal paste may be evaporated and dried at a predetermined temperature. After that, for example, the second current collection is performed by firing the first metal paste under the condition that the maximum temperature is set to 600 ° C. to 850 ° C. in the firing furnace and the heating time is about several tens seconds to several tens of minutes. The electrode 8 b is formed on the first surface 1 bs side of the semiconductor substrate 1. At this time, an electrode component including the glass of the second current collection electrode 8b enters the internal space SC1 of the plurality of concave portions 6pr of the protective layer 6. Further, at this time, in the hole portion CH1, the first metal paste fires through the passivation layer 4 when it is fired, and is electrically connected to the first semiconductor layer 2. Thereby, the second current collection electrode 8b is formed. At this time, the third semiconductor layer 2bs is also formed along with the formation of the second current collection electrode 8b. However, at this time, the first metal paste on the protective layer 6 is blocked by the protective layer 6. Therefore, when the first metal paste is fired, the passivation layer 4 blocked by the protective layer 6 is hardly affected by the firing.

  Thus, the back electrode 8 can be formed. For this reason, in the first embodiment, the first metal paste and the third metal paste are employed as the material for forming the back electrode 8. Here, for example, the second output lead-out electrode 8a may be formed after the second current collection electrode 8b is formed. Even when the second output lead-out electrode 8a is in direct contact with the semiconductor substrate 1, for example, the passivation layer 4 is present between the second output lead-out electrode 8a and the semiconductor substrate 1, It does not have to be in contact. Further, the second output lead electrode 8 a may be formed on the protective layer 6. Further, the surface electrode 7 and the back surface electrode 8 may be formed by applying baking after simultaneously applying each metal paste. Thereby, the productivity of the solar cell element 10 can be improved. Further, in this case, the heat history applied to the semiconductor substrate 1 is reduced, so that the output characteristics of the solar cell element 10 can be improved.

<1-6. Summary of First Embodiment>
In the solar cell element 10 according to the first embodiment, for example, the glass in a state in which the electrode layer 8 bl of the second current collection electrode 8 b is formed in the concave portion 6 pr existing in the convex portion 6 p of the protective layer 6 An electrode component comprising the component is located. If such a configuration is adopted, for example, when the first metal paste is applied on the protective layer 6 to form the second current collecting electrode 8 b, the uneven structure exists on the surface of the protective layer 6. Also, the glass component or the like in the first metal paste intrudes into the concave portion 6pr present in the convex portion 6p. For this reason, for example, in the first metal paste located on the convex portion 6p, it is difficult for the fluid component including the glass component and the organic vehicle to flow out to a lower part in the gravity direction. Thereby, in the 1st metal paste located on convex-shaped part 6p, content of a glass component does not reduce easily. As a result, when the second current collection electrode 8 b is formed, the distribution of the components of the first metal paste applied on the protective layer 6 is less likely to be biased. At this time, for example, the adhesion of the second current collection electrode 8b on the protective layer 6 is unlikely to be uneven. Then, in the concave portion 6pr, the adhesion between the protective layer 6 and the metal particles in the second current collection electrode 8b can be improved in the convex portion 6p due to the presence of the glass component. In addition, for example, when a part of the second current collection electrode 8b enters the concave portion 6pr of the protective layer 6, a so-called anchor effect may occur. Thereby, the adhesion of the second current collection electrode 8 b to the protective layer 6 can be improved. As a result, for example, partial peeling of the second current collection electrode 8 b from the protective layer 6 does not easily occur. Therefore, the photoelectric conversion efficiency in the PERC solar cell element 10 can be improved.

<2. Other Embodiments>
The present disclosure is not limited to the above-described first embodiment, and various changes, improvements, and the like can be made without departing from the scope of the present disclosure.

<2-1. Second embodiment>
In the first embodiment, for example, as shown in FIGS. 10 (a) and 10 (b), the protective layer 6 has a plurality of air gaps 6vd located inside the protective layer 6. It may be Here, the diameter of the void 6vd is d4. In this case, for example, a mode in which the diameter d4 is shorter than any one of the second distance D2 between adjacent convex portions 6p and the third distance D3 between adjacent connection portions 8bc may be considered. Specifically, as the air gap 6vd, for example, a minute air gap having an internal space of a diameter d4 of about 0.1 μm to 1 μm is adopted. Furthermore, here, for example, in the portion where the concave portion 6pr and the void 6vd of the protective layer 6 exist, the thickness (minimum film thickness) of the protective layer 6 excluding the void 6vd is 0.5 μm. If it is about above, the function which protects passivation layer 4 by protective layer 6 may be secured.

  By the way, for example, when the protective layer 6 is formed and when the solar cell element 10 is used, the protective layer 6 may expand or contract according to the temperature change, and may cause contraction according to the condensation polymerization reaction of the protective layer 6 is there. At this time, stress may be generated between the protective layer 6 and a layer adjacent to the protective layer 6 (also referred to as an adjacent layer). On the other hand, for example, if a plurality of air gaps 6vd are located inside the protective layer 6, stress generated between the protective layer 6 and an adjacent layer in a state adjacent to the protective layer 6 occurs. , And may be relieved by the plurality of air gaps 6 vd in the protective layer 6. As a result, peeling does not easily occur between the protective layer 6 and the adjacent layer in a state adjacent to the protective layer 6. As a result, the photoelectric conversion efficiency in the PERC solar cell element 10 can be improved.

  Also, here, for example, the distance (also referred to as a fourth distance) between adjacent gap portions 6 vd among the plurality of void portions 6 vd is set to D4. As the fourth distance D4, for example, the distance between the centers of the adjacent air gaps 6vd is adopted. The fourth distance D4 may be, for example, the average value of the distance between the centers of the adjacent void portions 6vd, or the separation distance between the adjacent void portions 6vd, or the adjacent void portions 6vd. The average value of the separation distances of In this case, for example, it is conceivable that the fourth distance D4 is shorter than any one of the second distance D2 between adjacent convex portions 6p and the third distance D3 between adjacent connection portions 8bc. At this time, for example, the density of the plurality of air gaps 6 vd in the protective layer 6 is somewhat high. Thereby, for example, the stress generated between the protective layer 6 and the adjacent layer in a state adjacent to the protective layer 6 is easily relaxed by the plurality of voids 6 vd in the protective layer 6. For this reason, the photoelectric conversion efficiency in the PERC solar cell element 10 can be easily improved.

  The protective layer 6 having the plurality of voids 6 vd inside can be formed, for example, by the following process.

  Here, first, the first insulating paste is applied on the passivation layer 4. Next, a second insulating paste is applied on the layer of the first insulating paste applied on the passivation layer 4. Next, the first insulating paste is applied on the layer of the second insulating paste applied on the layer of the first insulating paste. Next, the second insulating paste is applied on the layer of the first insulating paste applied on the layer of the second insulating paste. Then, the layer of the first insulating paste, the layer of the second insulating paste, the layer of the first insulating paste, and the layer of the second insulating paste after application are dried using a hot plate or a drying furnace. At this time, as the drying conditions, a maximum temperature of about 200 ° C. to 350 ° C. at which the organic filler contained in the second insulating paste is thermally decomposed, and a heating time of about 1 minute to 10 minutes are adopted. Ru. At this time, as shown in FIG. 11, on the passivation layer 4, a first protective layer area 6a, a second protective layer area 6b, a third protective layer area 6c, and a fourth protective layer area 6d, Is formed in the state of being stacked in the order of this description. Here, the first protective layer region 6a and the third protective layer region 6c are formed by drying the first insulating paste. The second protective layer region 6b and the fourth protective layer region 6d are formed by drying the second insulating paste. At this time, the organic filler contained in the second insulating paste is thermally decomposed by the heat treatment at the time of drying. Thereby, a plurality of void portions 6vd are formed in the second protective layer region 6b by the disappearance of the organic filler, and a plurality of concave portions 6pr are formed in the surface of the fourth protective layer region 6d by the disappearance of the organic filler. As a result, a protective layer 6 having a plurality of concave portions 6pr on the surface and a plurality of voids 6vd on the inside can be formed.

  Here, for example, instead of the layer of the second insulating paste for forming the second protective layer region 6b of FIG. 11, a layer in which an organic binder is contained in the first insulating paste may be applied. In this case, for example, when drying the first insulating paste, the plurality of void portions 6vd are formed by volatilization of a part of the organic binders among the organic binders present in the layer of the first insulating paste. It can occur. Further, here, instead of the layer of the second insulating paste for forming at least one of the fourth protective layer region 6d of FIG. 11 and the second protective layer region 6b of FIG. A layer containing a binder may be applied. In this case, for example, when the first insulating paste is dried, the plurality of concave portions 6pr are formed by volatilization of a part of the organic binder among the organic binders present in the layer of the first insulating paste. It can occur.

2-2. Third embodiment>
In each of the above embodiments, for example, as shown in FIG. 12, when the protective layer 6 is seen through from the electrode layer 8bl side of the second current collection electrode 8b, the protective layer 6 is per unit area of the concave portion 6pr. The first region Ar1 and the second region Ar2 may have different numbers. Here, the first region Ar1 is located on the outer peripheral portion OP1 side of the solar cell element 10. The second region Ar2 is located on the central portion CP1 side of the solar cell element 10. The unit area is set to, for example, about 100 mm ² to 400 mm ² . The number per unit area of concave portions 6pr present in the first region Ar1 may be larger than the number per unit area of concave portions 6pr present in the second region Ar2. When such a configuration is employed, for example, on the back surface 10bs side of the solar cell element 10, the protective layer 6 and the second current collection electrode 8b in the portion on the outer peripheral portion OP1 side than the portion on the central portion CP1 side. Adhesion becomes high.

  The protective layer 6 having the first area Ar1 and the second area Ar2 may be formed, for example, when the second insulating paste is applied on the layer of the first insulating paste applied on the passivation layer 4. It can be formed by performing the following process. First, the second insulating paste is applied to a region corresponding to the first region Ar1. Next, a second insulating paste having a lower organic filler content than the already applied second insulating paste is applied to the area corresponding to the second area Ar2. Also, for example, in such a process, the second insulating paste is applied on the layer of the first insulating paste applied on the passivation layer 4 to form the first insulating paste and the second insulating paste. The drying may be performed when the second insulating paste is applied on the layer of the first insulating paste further applied on the layer of the second insulating paste. Thus, the protective layer 6 having the plurality of void portions 6vd and the first region Ar1 and the second region Ar2 can be formed.

  By the way, for example, as shown in FIG. 13 and FIG. 14, the solar cell modules 100 are positioned in a state in which the plurality of solar cell elements 10 are electrically connected in series by the wiring member Tb and aligned in a plane. Can be used in the form of In this solar cell module 100, a plurality of solar cell modules are covered with the sealing material 102 in the gap between the first protective member 101 and the second protective member 104 located in a state of facing each other. A portion (also referred to as a photoelectric conversion portion) 103 including the element 10 is located. Here, the solar cell module 100 has a surface (also referred to as a front surface) 100 fs that mainly receives light, and a surface (also referred to as a back surface) 100 bs that is located on the opposite side of the front surface 100 fs. In the solar cell module 100, the light transmitting plate-like second protection member 104 is positioned on the front surface 100 fs side, and the plate-like or sheet-like first protection member 101 is positioned on the back surface 100 bs. Also, the sealing material 102 located in the gap between the first protective member 101 and the second protective member 104 is located on the front surface 100 fs side with the first sealing material 102 b located on the back surface 100 bs side. And a second sealing material 102u.

  For example, as shown in FIG. 15, this solar cell module 100 includes a first protective member 101, a first sheet SH1, a photoelectric conversion unit 103, a second sheet SH2, and a second protective member 104. The laminated body laminated | stacked in order of this description may be manufactured by integrating by lamination process. The first sheet SH1 is a sheet-like material that is the source of the first sealing material 102b, and the second sheet SH2 is a sheet-like material that is the source of the second sealing material 102u. Here, when lamination processing of a laminated body is performed, the thickness of the sealing material 102 is large between several solar cell elements 10 comrades. For this reason, expansion and contraction of the sealing material 102 become large between the plurality of solar cell elements 10. Thereby, when lamination processing is performed, for example, on the back surface 10 bs side of the solar cell element 10, a large stress may be applied to a region along the outer peripheral portion OP1 of the back surface 10 bs. On the other hand, on the back surface 10bs side of the solar cell element 10 according to the third embodiment, the protective layer 6 and the second collection are formed in the first region Ar1 on the outer peripheral portion OP1 side than the second region Ar2 on the central portion CP1 side. The adhesion to the electrode 8 b is high. For this reason, for example, when the lamination process of a laminated body is performed, it is hard to peel off the 2nd current collection electrode 8b from the protective layer 6. As shown in FIG.

<2-3. Other>
In each of the above-described embodiments and various modifications, for example, the second output lead-out electrode 8 a located on the protective layer 6 may be an electrode layer containing a glass component. In this case, the glass component of the second output extraction electrode 8 a may be located in the internal space of the concave portion 6 pr of the protective layer 6. Thereby, by improving the adhesion of the second output lead electrode 8 a to the protective layer 6, the photoelectric conversion efficiency in the solar cell element 10 may be improved.

  In each of the above-described embodiments and the above-described various modifications, when the surface of the protective layer 6 on the electrode layer 8bl side is viewed in plan, the ratio of the concave portion 6pr to the area of the unit area in the convex portion 6p is 5% to 40. It is not limited to about%. This ratio is appropriately set according to, for example, the content of the glass component and the type of the glass component in the second current collection electrode 8 b or the first metal paste for forming the second current collection electrode 8 b. For example, the adhesion of the second current collection electrode 8b to the protective layer 6 can be easily improved. In other words, for example, even if this ratio is appropriately set to a range of a different ratio including a part or all of the range of about 5% to 40% or a range of a ratio different from about 5% to about 40% Good.

  In each of the above embodiments and the above various modifications, for example, as shown in FIG. 16A, the passivation layer 4 is positioned from the top of the first surface 1 bs to the top of the third surface 1 ss, and the protective layer 6 is Although it has been located on the passivation layer 4 located on the outer edge Ed1 of the surface 1bs, it is not limited thereto. For example, as shown in FIG. 16B, on the region (also referred to as the outer edge region) Ao1 along the outer edge Ed1 of the first surface 1bs of the first surface 1bs, the passivation layer 4 and the protective layer 6 Also, the antireflective layer 5 may not be located. In other words, the passivation layer 4 and the antireflective layer 5 located on the third surface 1ss and the passivation layer 4 and the protective layer 6 located on the first surface 1bs are separated on the outer peripheral area Ao1. It may be At this time, it is conceivable that the outer edge area Ao1 is located in the range of the distance L1 from the outer edge Ed1 of the first surface 1bs. The distance L1 may be, for example, about 0.5 mm to 2 mm. When such a configuration is adopted, for example, as shown in FIG. 16B, the second current collection electrode 8b may not be located on the outer edge area Ao1 of the first surface 1bs. As shown in FIG. 16C, the second current collection electrode 8b may be located on at least a part of the outer edge area Ao1 of the first surface 1bs. In addition, here, for example, as shown in FIGS. 17A to 17C, the third surface 1ss to the upper surface of a portion on the outer edge portion Ed1 of the outer edge region Ao1 of the first surface 1bs. Passivation layer 4 and anti-reflective film 5 may be located. At this time, it is conceivable that the passivation layer 4 and the anti-reflection film 5 are located in the range of the distance L2 from the outer edge portion Ed1 on the outer edge region Ao1. The distance L2 may be, for example, about 0.1 mm to 1 mm. When such a configuration is employed, for example, as shown in FIGS. 17A and 17B, a passivation layer is formed from the third surface 1ss to the outer surface area Ao1 of the first surface 1bs. The anti-reflection layer 5 may be positioned to a portion closer to the central portion of the first surface 1 bs than 4. Further, for example, as shown in FIG. 17C, both the passivation layer 4 and the anti-reflection film 5 may be located from the outer edge portion Ed1 to the portion of the distance L2 on the outer edge region Ao1. Also in the example shown in FIG. 17 (c), as shown in FIG. 16 (c) or FIG. 17 (b), the second current collection is performed on at least a part of the outer edge area Ao1 of the first surface 1bs. The electrode 8b may be located.

  It is needless to say that all or part of each of the above-described embodiments and various modifications may be combined as appropriate, as long as no contradiction arises.

REFERENCE SIGNS LIST 1 semiconductor substrate 1 bs first surface 1 fs second surface 1 p convex portion 1 r concave portion 1 ss third surface 2 first semiconductor layer 2 bs third semiconductor layer 3 second semiconductor layer 4 passivation layer 6 protective layer 6 ap non-convex portion 6 p convex portion 6pr recessed portion 6vd gap 8 back surface electrode 8a second output extraction electrode 8b second collecting electrode 8bc connection portion 8bl electrode layer 10 solar cell element 10bs, 100bs back surface 10fs, 100fs front surface Ar1 first region Ar2 second region CH2 hole portion CP1 Central part D1 First distance D2 Second distance D3 Third distance D4 Fourth distance OP1 Outer peripheral part SC1 Internal space d4 diameter

Claims (5)

A semiconductor substrate,
A passivation layer located on the first surface of the semiconductor substrate;
A protective layer located on the passivation layer,
An electrode layer comprising a glass component located on the protective layer,
The protective layer has a plurality of convex portions located on the surface on the electrode layer side,
The solar cell element, wherein each of the plurality of convex portions has a concave portion in which the glass component is located in the internal space on the electrode layer side. The solar cell element according to claim 1, wherein
The passivation layer and the protective layer have the passivation layer and a plurality of holes positioned through the protective layer, respectively.
The solar cell element is
A plurality of connecting portions positioned in a state of electrically connecting the electrode layer and the semiconductor substrate in the plurality of holes, respectively;
A plurality of the concave portions;
The first distance between adjacent concave portions of the plurality of concave portions is the second distance between adjacent convex portions among the plurality of convex portions and the adjacent connection among the plurality of connection portions. A solar cell element shorter than any of the 3rd distance of parts. A solar cell element according to claim 1 or 2,
The protective layer is located on the surface on the electrode layer side, and has a non-convex portion different from the plurality of convex portions.
The solar cell element, wherein each of the non-convex portions has a concave portion in which the glass component is located in the internal space on the electrode layer side. The solar cell element according to any one of claims 1 to 3, wherein
When the protective layer is seen through the protective layer and the semiconductor substrate from the electrode layer side, a first region located on the outer peripheral portion side of the solar cell element, and a central portion side of the solar cell element And a second region located at
The solar cell element, wherein the number per unit area of the concave portion present in the first region is larger than the number per unit area of the concave portion present in the second region. The solar cell element according to any one of claims 1 to 4, wherein
The solar cell element, wherein the protective layer has a plurality of air gaps located inside the protective layer.

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