WO2019230686A1

WO2019230686A1 - Solar battery element and solar battery module

Info

Publication number: WO2019230686A1
Application number: PCT/JP2019/021007
Authority: WO
Inventors: 順次荒浪; 誠一郎稲井
Original assignee: 京セラ株式会社
Priority date: 2018-05-29
Filing date: 2019-05-28
Publication date: 2019-12-05
Also published as: JPWO2019230686A1

Abstract

This solar battery element includes a semiconductor substrate, an antireflection film, a passivation film, a protective layer, and an electrode. The semiconductor substrate has a first surface, a second surface, and side surfaces. The antireflection film is located on the first surface of the semiconductor substrate. The passivation film is located on the second surface. The protective layer is located on the passivation film and is thicker than the antireflection film. The electrode has: a first portion that is located on a first region of the protective layer; and a second portion that is located inside a through hole that passes successively through the passivation film and the protective layer, and is connected to the semiconductor substrate. The protective layer has a base material portion and a plurality of granules. The plurality of granules includes a plurality of first granules that is frequently present in a first diameter range, and a plurality of second granules that is frequently present in a second diameter range that is different from the first diameter range. Each of the first granules has a refractive index that is closer to that of the semiconductor substrate than that of the base material.

Description

Solar cell element and solar cell module

The present disclosure relates to a solar cell element and a solar cell module.

The solar cell element includes, for example, a PERC (Passivated Emitter and Rear Cell) type solar cell element in which a passivation film is present between a semiconductor substrate and a back electrode.

For this PERC type solar cell element, for example, aiming to improve photoelectric conversion efficiency, a back electrode is locally present on the back side of the semiconductor substrate, and light incident on the back side as well as the front side is also used for power generation. (For example, refer to the description of JP-T-2016-523442). In other words, solar cell elements and solar cell modules of a type (also referred to as a double-sided light receiving type) that use light incident on both the front surface and the back surface for power generation have been proposed.

A solar cell element and a solar cell module are disclosed.

One aspect of the solar cell element includes a semiconductor substrate, an antireflection film, a passivation film, a protective layer, and an electrode. The semiconductor substrate has a first surface, a second surface located on the opposite side of the first surface, and a side surface located in a state where the first surface and the second surface are connected. The antireflection film is located on the first surface side of the semiconductor substrate. The passivation film is located on the second surface. The protective layer is located on the passivation film and has a larger thickness than the antireflection film. The electrode is electrically connected to the semiconductor substrate in a first portion located on the first region of the protective layer, and in a through hole in a state of continuously passing through the passivation film and the protective layer. And a second portion located in a connected state. The protective layer has a base material portion and a plurality of granular materials. The plurality of granular materials are a plurality of first granular materials present in a first particle size range at a frequency higher than outside the first particle size range, and a second particle size different from the first particle size range. A plurality of second granular materials that are present at a higher frequency than outside the second particle size range. The refractive index of each of the first granular materials is closer to the refractive index of the semiconductor substrate than the refractive index of the base material portion.

One aspect of the solar cell module includes a first protective member, a second protective member, a solar cell portion, and a filler. The first protective member has translucency. The second protective member has translucency. The solar cell unit is located between the first protective member and the second protective member. The filler is located between the first protective member and the second protective member so as to cover the solar cell portion from the first protective member side and the second protective member side, and has translucency. Have. The solar cell unit includes a plurality of the solar cell elements according to the one aspect.

FIG. 1 is a plan view showing an appearance of an example of the solar cell module according to the first embodiment viewed from the front side. FIG. 2 is a diagram showing a virtual cut surface of an example of the solar cell module according to the first embodiment along the line II-II in FIG. Fig.3 (a) is a top view which shows the external appearance seen from the 1st element surface side of an example of the solar cell element which concerns on 1st Embodiment. FIG.3 (b) is a top view which shows the external appearance seen from the 2nd element surface side of an example of the solar cell element which concerns on 1st Embodiment. FIG. 4A is a diagram showing a virtual cut surface of an example of the solar cell element according to the first embodiment taken along line IVa-IVa in FIGS. 3A and 3B. FIG. 4B is a diagram showing a virtual cut surface of an example of the solar cell element according to the first embodiment along the line IVb-IVb in FIGS. 3A and 3B. FIG. 4C is a diagram showing a virtual cut surface of an example of the solar cell element according to the first embodiment along the line IVc-IVc in FIGS. 3A and 3B. FIG. 5 is a cross-sectional view schematically showing one configuration example of the protective layer according to the first embodiment. FIG. 6 is a cross-sectional view schematically showing three paths through which light enters the solar cell element in the cut surface of an example of a part of the solar cell module according to the first embodiment in the VI part of FIG. 2. FIG. 7A to FIG. 7D are cross-sectional views illustrating states in the middle of manufacturing the solar cell element according to the first embodiment. FIG. 8 is a cross-sectional view schematically showing one configuration example of the protective layer according to the second embodiment. FIG. 9A is a cross-sectional view schematically showing a configuration example of the first region of the protective layer according to the third embodiment. FIG. 9B is a cross-sectional view schematically showing a configuration example of the second region of the protective layer according to the third embodiment.

For example, a so-called PERC type solar cell element in which a passivation film exists between a semiconductor substrate and a back electrode is known. As the passivation film, for example, an aluminum oxide thin film that can be formed by a film forming method such as atomic layer deposition (ALD) is applied.

For this PERC type solar cell element, for example, a back electrode is locally present on the back side of the semiconductor substrate, and light incident on the back side as well as the front side is used for power generation, thereby improving photoelectric conversion efficiency. It is possible to make it. In other words, a solar cell element and a solar cell module of a type (double-sided light receiving type) that uses light incident on both the front surface and the back surface for power generation can be considered.

Here, with respect to the double-sided light receiving solar cell element, for example, it is conceivable to reduce reflection of light irradiated to the back surface by making a fine uneven structure (texture) exist on the back surface side. However, for example, if a fine concavo-convex structure is present on the back side of a double-sided light receiving solar cell element, carriers are likely to recombine on the back side of the solar cell element, and the photoelectric conversion efficiency may be reduced.

Also, for example, there may be a protective layer that protects the passivation film located on the back surface of the semiconductor substrate. For the protective layer, for example, a silicon nitride thin film that can be formed using a plasma-enhanced chemical vapor deposition (PECVD) method or a sputtering method is applied. Here, for example, on the back side of the solar cell element, if there is no fine uneven structure, multiple reflection of light may occur due to the presence of the protective layer. Here, for example, there may be light in a wavelength range in which multiple reflection is likely to occur, such as light in a relatively short wavelength range of 600 nanometers (nm) or less of sunlight. Thereby, for example, in the double-sided light receiving solar cell element, the ratio of the light used for photoelectric conversion in the semiconductor substrate out of the light irradiated on the back surface does not increase, and the photoelectric conversion efficiency is difficult to improve.

Therefore, the present inventors have created a technology capable of improving the photoelectric conversion efficiency for the double-sided light receiving solar cell element and the solar cell module.

Hereinafter, each of the first to third embodiments will be described with reference to the drawings. In the drawings, parts having similar configurations and functions are denoted by the same reference numerals, and redundant description is omitted in the following description. The drawings are shown schematically. FIGS. 1 to 9B each have a right-handed XYZ coordinate system. In this XYZ coordinate system, the direction along the pair of sides of the front surface 1fs of the solar cell module 100 is the + X direction, the direction along the other pair of sides of the front surface 1fs is the + Y direction, the + X direction and the + Y direction. The normal direction of the front surface 1fs that is orthogonal to both is the + Z direction.

<1. First Embodiment>
<1-1. Solar cell module>
The solar cell module 100 according to the first embodiment will be described with reference to FIGS. 1 to 6.

As shown in FIGS. 1 and 2, the solar cell module 100 has a light receiving surface (also referred to as a front surface) 1fs on which light is mainly incident, and a back surface 1bs located on the opposite side of the front surface 1fs. In the first embodiment, the front surface 1fs faces the + Z direction. The back surface 1bs faces the −Z direction. For example, the + Z direction is set to a direction toward the sun going south. In the example of FIG. 1, the front surface 1fs has a rectangular shape.

As shown in FIGS. 1 and 2, the solar cell module 100 includes, for example, a solar cell panel Pn1. As shown in FIG. 2, the solar cell module 100 may include, for example, a terminal box J1. The terminal box J1 is located on, for example, the back surface 1bs of the solar cell panel Pn1, and can output the electricity obtained by the power generation in the solar cell panel Pn1 to the outside. The solar cell module 100 may include a frame 106, for example. The frame 106 is located along the outer periphery of the solar cell panel Pn1, for example, and can protect the outer periphery of the solar cell panel Pn1. Here, for example, a sealing material having a low moisture permeability such as a butyl resin may be filled between the outer peripheral portion of the solar cell panel Pn1 and the frame 106.

As shown in FIGS. 1 and 2, the solar cell panel Pn1 includes, for example, a first protection member 101, a second protection member 102, a solar cell portion 103, a filler 104, and a packing portion 105. I have. Here, for example, the first protection member 101 and the second protection member 102 are positioned so as to sandwich the solar cell portion 103. The 1st protection member 101 is located in the state which comprises front surface 1fs of solar cell panel Pn1, for example. The 2nd protection member 102 is located in the state which constitutes back side 1bs of solar cell panel Pn1, for example.

The first protective member 101 is a member having translucency. For example, the first protective member 101 has translucency with respect to light in a specific range of wavelengths. The wavelength in this specific range includes, for example, the wavelength of light that can be photoelectrically converted by the solar cell unit 103. Thereby, for example, the light applied to the front surface 1fs can transmit the first protective member 101 toward the solar cell unit 103. Here, for example, if the wavelength in the specific range includes the wavelength of light with high irradiation intensity constituting sunlight, the photoelectric conversion efficiency of the solar cell module 100 can be improved. For example, a flat glass plate having a refractive index of about 1.4 to 1.8 is applied to the first protection member 101. As shown in FIGS. 1 and 2, the first protective member 101 has a first plate surface F1, a second plate surface F2, and a first outer peripheral surface S1. The second plate surface F2 is in a state facing the opposite direction to the first plate surface F1. The first outer peripheral surface S1 is in a state of connecting the first plate surface F1 and the second plate surface F2. In the solar cell module 100 according to the first embodiment, the first plate surface F1 is in a state of constituting the front surface 1fs. The thickness of the first protective member 101 is set to, for example, about 1 millimeter (mm) to about 5 mm. In the example of FIG. 1, the outer shape of the first protective member 101 is rectangular when viewed from the front surface 1 fs side. The 1st protection member 101 which has the said structure can protect the solar cell part 103 from the front 1fs side with high rigidity and low moisture permeability, for example.

The second protective member 102 is a member having translucency, similar to the first protective member 101. For example, the second protective member 102 has a light-transmitting property with respect to light in a specific range of wavelengths, like the first protective member 101. Thereby, for example, the light applied to the back surface 1bs can be transmitted through the second protective member 102 toward the solar cell unit 103. For this reason, for example, not only the light irradiated to the front surface 1fs but also the light irradiated to the rear surface 1bs is used for photoelectric conversion in the solar cell unit 103. In other words, the solar cell module 100 is a solar cell module of a type (double-sided light receiving type) that uses light incident on both the front surface 1fs and the back surface 1bs for power generation. For example, a flat glass plate having a refractive index of about 1.4 to 1.8 is applied to the second protective member 102. As shown in FIGS. 1 and 2, the second protective member 102 has a third plate surface F3, a fourth plate surface F4, and a second outer peripheral surface S2. The third plate surface F3 is in a state of facing the second plate surface F2 of the first protective member 101. The fourth plate surface F4 is in a state facing the opposite direction to the third plate surface F3. The second outer peripheral surface S2 is in a state where the third plate surface F3 and the fourth plate surface F4 are connected. In the solar cell module 100 according to the first embodiment, the fourth plate surface F4 is in a state of constituting the back surface 1bs. The thickness of the second protective member 102 is set to about 1 mm to 5 mm, for example. In the example of FIG. 1, the outer shape of the second protective member 102 is a rectangular shape when seen in a plan view from the front surface 1 fs side. The 2nd protection member 102 which has the said structure can protect the solar cell part 103 from the back surface 1bs side with high rigidity and low moisture permeability, for example.

The solar cell unit 103 is located, for example, in an area A0 (also referred to as an inter-plate area) between the first protection member 101 and the second protection member 102. As shown in FIG. 1, the solar cell unit 103 includes, for example, a plurality of solar cell elements 1. In the first embodiment, the plurality of solar cell elements 1 are positioned in a two-dimensional array. In the example of FIGS. 1 and 2, the plurality of solar cell elements 1 are positioned in a state of being planarly arranged so as to be positioned along the second plate surface F 2 of the first protection member 101. The solar cell unit 103 includes, for example, a plurality of first wiring members W1 and a plurality of second wiring members W2. The solar cell unit 103 includes, for example, a plurality (eight in this example) of solar cell strings St1. The solar cell string St1 includes, for example, a plurality (here, seven) solar cell elements 1 and a plurality of first wiring members W1. The plurality of first wiring members W1 are in a state in which, for example, the solar cell elements 1 adjacent to each other among the plurality of solar cell elements 1 are electrically connected to each other. The plurality of second wiring members W2 are in a state in which solar cell strings St1 adjacent to each other among the plurality of solar cell strings St1 are electrically connected to each other. In the example of FIG. 1, the second wiring member W2 connected to the solar cell string St1 located at the end in the −X direction and the second wiring material W2 connected to the solar cell string St1 located at the end in the + X direction. The wiring member W 2 is positioned in a state of being drawn out of the solar cell module 100. Here, the two second wiring members W2 are positioned in a state of being pulled out of the solar cell module 100 through, for example, a hole positioned so as to penetrate the second protective member 102. Yes.

The filler 104 is positioned so as to cover the solar cell unit 103 in the inter-plate region A0 between the first protective member 101 and the second protective member 102. In the first embodiment, the filler 104 is positioned so as to be filled in the inter-plate area A0 between the first protection member 101 and the second protection member 102, for example. The filler 104 includes, for example, a portion (also referred to as a first filling portion) 104u located on the front surface 1fs side and a portion (also referred to as a second filling portion) 104b located on the back surface 1bs side. The 1st filling part 104u is located so that the whole surface by the side of the 1st protection member 101 of the solar cell part 103 may be covered, for example. The 2nd filling part 104b is located so that the whole surface by the side of the 2nd protection member 102 of the solar cell part 103 may be covered, for example. For this reason, the solar cell part 103 exists in the state enclosed so that it might be pinched | interposed by the 1st filling part 104u and the 2nd filling part 104b, for example. Thereby, the attitude | position of the solar cell part 103 can be maintained by presence of the filler 104, for example.

Moreover, the filler 104 has translucency, for example. Here, for example, if both the first filling portion 104u and the second filling portion 104b constituting the filling material 104 have translucency, incident light from the front surface 1fs side and incident light from the back surface 1bs side. Both can reach the solar cell unit 103. As the material of the filler 104, for example, a material having a refractive index close to or substantially the same as that of the first protective member 101 and the second protective member 102 and excellent in translucency for light in a specific range of wavelengths is applied. Is done. Specifically, the material of the filler 104 includes, for example, one or more of polyester resins such as ethylene vinyl acetate copolymer (EVA), triacetyl cellulose (TAC), and polyethylene naphthalate (PEN). The material is applied. Here, for example, if the first protective member 101 and the first filling portion 104u are close or have substantially the same refractive index, the light irradiated to the front surface 1fs is the first protective member 101 and the first protective member 101u. It is difficult to reflect at the interface with the filling portion 104u and easily reaches the solar cell portion 103. Further, for example, if the second protective member 102 and the second filling portion 104b are close or have substantially the same refractive index, the light irradiated to the back surface 1bs is the second protective member 102 and the second filling member. It is difficult to reflect at the interface with the portion 104 b and easily reaches the solar cell portion 103.

The packing part 105 is located along the annular part (it is also called annular opening part) A0p opened with respect to external space among the board | plate area | regions A0, for example. In 1st Embodiment, the packing part 105 is located so that the outer peripheral part of the area | region containing the solar cell part 103 and the filler 104 may be enclosed, for example. Here, the packing part 105 is located so that the area | region from the 1st protection member 101 to the 2nd protection member 102 may be filled up, for example. Here, for example, if the packing part 105 has a moisture permeability lower than that of the filler 104, the packing part 105 can seal a portion along the outer peripheral part of the inter-plate region A0. . Thereby, the packing part 105 can reduce the penetration | invasion of the water | moisture content etc. toward the solar cell part 103 from the exterior of the solar cell module 100, for example. For example, a butyl resin, a polyisopropylene resin, an acrylic resin, or the like is applied to the material of the packing unit 105. The material of the packing unit 105 may include a metal such as copper or solder or a non-metal such as glass as long as the material has low moisture permeability. The packing part 105 may be, for example, one obtained by bonding a copper foil by soldering, or one obtained by melting glass with a laser or the like and then solidifying it. Alternatively, a white or transparent resin may be applied to the material of the packing unit 105 so as not to hinder light capture in the solar cell unit 103.

<1-2. Solar cell element>
Each of the plurality of solar cell elements 1 can convert light energy into electrical energy, for example. As shown in FIGS. 3A and 3B, each of the plurality of solar cell elements 1 is a surface (also referred to as a first element surface) Sf1 positioned on the front (front) surface side. And a surface (also referred to as a second element surface) Sf2 located on the opposite side of the first element surface Sf1. In the example of FIGS. 3A and 3B, the first element surface Sf1 faces the + Z direction, and the second element surface Sf2 faces the −Z direction. In this case, for example, the first element surface Sf1 is a front surface on which light is mainly incident, and the second element surface Sf2 is a rear surface on which light is not incident than the front surface.

In the first embodiment, as shown in FIGS. 3A to 4C, each of the plurality of solar cell elements 1 includes a semiconductor substrate 2, an antireflection film 3, a passivation film 4, and a protection film. A layer 5, a front electrode 6, and a back electrode 7 are provided. In the solar cell element 1, for example, the front electrode 6 is located at a part on the first element surface Sf1 side, and the back electrode 7 is located at a part on the second element surface Sf2 side. For this reason, the solar cell element 1 according to the first embodiment is a type (double-sided light receiving type) solar cell element that uses light incident on both the first element surface Sf1 and the second element surface Sf2 for power generation.

<1-2-1. Semiconductor substrate>
As shown in FIGS. 4A to 4C, the semiconductor substrate 2 has a first surface 2u, a second surface 2b, and a side surface 2s. The second surface 2b is located on the opposite side to the first surface 2u. The side surface 2s is located in a state where the first surface 2u and the second surface 2b are connected. In the example of FIGS. 4A to 4C, the first surface 2u is positioned in the + Z direction, and the second surface 2b is positioned in the −Z direction.

The semiconductor substrate 2 includes, for example, a region (also referred to as a first semiconductor region) 21 having a first conductivity type, and a region (also referred to as a second semiconductor region) 22 having a second conductivity type opposite to the first conductivity type. Have. The first semiconductor region 21 is located on the second surface 2b side of the semiconductor substrate 2, for example. For example, the second semiconductor region 22 is located in the surface layer portion of the semiconductor substrate 2 on the first surface 2u side. Here, for example, when the first conductivity type is p-type, the second conductivity type is n-type. For example, when the first conductivity type is n-type, the second conductivity type is p-type. Thereby, the semiconductor substrate 2 has a pn junction located at the interface between the first semiconductor region 21 and the second semiconductor region 22.

Here, for example, it is assumed that the semiconductor substrate 2 is a silicon substrate. In this case, for example, a polycrystalline or single crystal silicon substrate is employed as the silicon substrate. The silicon substrate has, for example, a thickness of 250 micrometers (μm) or less or 150 μm or less. The silicon substrate has a rectangular outer shape in plan view, for example. If the semiconductor substrate 2 having such a shape is employed, the gap between the solar cell elements 1 can be reduced when the solar cell module 100 is manufactured by arranging the plurality of solar cell elements 1.

Here, for example, when the first conductivity type is p-type and the second conductivity type is n-type, for example, boron or gallium as a dopant element is added to a polycrystalline or single crystal silicon crystal. By adding impurities, a p-type silicon substrate can be manufactured. In this case, the n-type second semiconductor region 22 can be generated by diffusing impurities such as phosphorus as an n-type dopant in the surface layer portion on the first surface 2u side of the p-type silicon substrate. Here, the semiconductor substrate 2 in which the p-type first semiconductor region 21 and the n-type second semiconductor region 22 are stacked can be formed.

Here, the first surface 2u of the semiconductor substrate 2 may have, for example, a fine uneven structure (texture) for reducing reflection of irradiated light.

Further, for example, a third semiconductor region having a first conductivity type that is the same as the first conductivity type (for example, p-type) of the first semiconductor region 21 in the surface layer portion on the second surface 2b side of the semiconductor substrate 2. 23 may exist. Here, for example, if the concentration of the dopant contained in the third semiconductor region 23 is higher than the concentration of the dopant contained in the first semiconductor region 21, the third semiconductor region 23 will be the second semiconductor substrate 2. It functions as a BSF (Back Surface Field) layer that forms an internal electric field on the two-surface 2b side. Thereby, in the vicinity of the 2nd surface 2b of the semiconductor substrate 2, the recombination of the minority carrier produced by the photoelectric conversion according to light irradiation in the semiconductor substrate 2 can be reduced. As a result, the photoelectric conversion efficiency in the solar cell element 1 is hardly reduced. The third semiconductor region 23 can be generated, for example, by diffusing a dopant element such as aluminum in the surface layer portion of the semiconductor substrate 2 on the second surface 2b side.

<1-2-2. Antireflection film>
The antireflection film 3 is located, for example, on the first surface 2 u side of the semiconductor substrate 2. In the example of FIGS. 3A to 3C, the antireflection film 3 is located on the first surface 2u. For example, the antireflection film 3 can reduce the reflectance of the light applied to the first element surface Sf 1 of the solar cell element 1. As a material of the antireflection film 3, for example, silicon oxide, aluminum oxide, silicon nitride, or the like can be employed. The refractive index and the thickness of the antireflection film 3 are, for example, a condition where the reflectance is low with respect to light in a wavelength range that can be absorbed by the semiconductor substrate 2 and contribute to power generation in sunlight (also referred to as a low reflection condition). ) Is appropriately set to a value capable of realizing. Here, for example, the refractive index of the antireflection film 3 is about 1.8 to 2.5, and the thickness of the antireflection film 3 is about 50 nm to 120 nm. The antireflection film 3 can be formed using, for example, PECVD or sputtering.

<1-2-3. Passivation film>
The passivation film 4 is located on at least the second surface 2 b of the semiconductor substrate 2. In the first embodiment, the passivation film 4 is in contact with the second surface 2 b of the semiconductor substrate 2. For example, the passivation film 4 can reduce recombination of minority carriers generated by photoelectric conversion in response to light irradiation in the semiconductor substrate 2. As the material for the passivation film 4, for example, one or more materials selected from aluminum oxide, zirconium oxide, hafnium oxide, silicon oxide, silicon nitride, silicon oxynitride, and the like are employed. The passivation film 4 may be, for example, a single layer film of one kind of material, or may be a state in which two or more layers of different materials are laminated. Specifically, as the passivation film 4, for example, a single layer film of aluminum oxide or the like may be employed, or a film in which a silicon oxide film and an aluminum oxide film are stacked in the order of description. It may be adopted. The passivation film 4 can be formed by, for example, an ALD method. Here, the passivation film 4 can reduce minority carrier recombination by, for example, termination of dangling bonds on the second surface 2 b of the semiconductor substrate 2 and field effect. For example, when aluminum oxide is employed as the material for the passivation film 4, the aluminum oxide has a negative fixed charge. Therefore, minority carriers (electrons in this case) generated on the second surface 2b side of the semiconductor substrate 2 due to the field effect are generated from the interface (second surface 2b) between the p-type first semiconductor region 21 and the passivation film 4. Be kept away. Thereby, recombination of minority carriers in the vicinity of the second surface 2b of the semiconductor substrate 2 can be reduced. As a result, the photoelectric conversion efficiency of the solar cell element 1 can be improved. The thickness of the passivation film 4 is, for example, about 10 nm to 60 nm. The passivation film 4 may be located on the first surface 2u of the semiconductor substrate 2, for example. The passivation film 4 may be located on the side surface 2s that connects the first surface 2u and the second surface 2b of the semiconductor substrate 2, for example.

<1-2-4. Protective layer>
The protective layer 5 is located on the second surface 2b side of the semiconductor substrate 2, for example. In the first embodiment, the protective layer 5 is located on the passivation film 4 located on the second surface 2b of the semiconductor substrate 2, for example. If it says from another viewpoint, the protective layer 5 will be located between the passivation film 4 and the back surface electrode 7, for example. The protective layer 5 is in a state of covering the passivation film 4 on the passivation film 4. Thereby, the protective layer 5 can protect the passivation film 4, for example. In other words, when the solar cell element 1 is manufactured and when the solar cell element 1 is used, moisture and the like hardly reach from the outside of the solar cell element 1 to the passivation film 4 due to the presence of the protective layer 5. Thereby, the passivation film 4 is hardly deteriorated. The protective layer 5 may be formed on the side surface 2s of the semiconductor substrate 2, for example. In this case, the presence of the protective layer 5 makes it difficult for leak current to occur in the solar cell element 1.

The protective layer 5 is located on the passivation film 4 in a state having a desired pattern, for example. The protective layer 5 has a plurality of holes in a state of passing through the protective layer 5 in the thickness direction (here, the + Z direction). The plurality of holes are, for example, in a state of penetrating through the protective layer 5 among a plurality of holes (also referred to as through holes) 45h in a state of continuously penetrating the protective layer 5 and the passivation film 4. Part. Each through-hole 45h may be, for example, a hole forming a closed through-hole along the second surface 2b, or at least a part of the periphery along the second surface 2b is open. It may be a slit-shaped hole.

As shown in FIG. 5, the protective layer 5 includes a base material portion (also referred to as a base material portion) 5a and a plurality of granular bodies 5b. In the first embodiment, for example, the plurality of granular bodies 5b are positioned in a moderately dispersed state within the base material portion 5a. As a material of the base material part 5a, for example, a siloxane resin or the like is employed. A siloxane resin is a siloxane compound having a Si—O—Si bond (also referred to as a siloxane bond). Here, for example, the protective layer 5 can be formed by using a wet process in which an insulating paste is applied onto the passivation film 4 by a screen printing method and dried.

Here, as the insulating paste, for example, an insulating paste including a siloxane resin that is a raw material of the base material portion 5a, an organic solvent, and a large number of granular materials is applied. Here, as the siloxane resin, for example, a low molecular weight resin having a molecular weight of 15,000 or less, which is produced by hydrolyzing alkoxysilane or silazane and performing condensation polymerization, is employed. As the organic solvent, for example, a solvent in which a siloxane resin and a large number of particles are dispersed is employed. Examples of such organic solvents include diethylene glycol monobutyl ether, methyl cellosolve, ethyl cellosolve, ethyl alcohol, 2- (4-methylcyclohex-3-enyl) propan-2-ol, or 2-propanol. Or multiple types are applied. The large number of granular materials includes, for example, at least a plurality of granular materials 5b. The many granular materials include, for example, an inorganic filler (also referred to as a viscosity adjusting filler) for adjusting the viscosity of an insulating paste such as silicon oxide, aluminum oxide, or titanium oxide having an average particle diameter of 1000 nm or less. obtain. The average particle diameter here may be the average particle diameter of the primary particles or the average particle diameter of the secondary particles in which the secondary particles are aggregated. Here, for example, by appropriately adjusting the viscosity of the insulating paste, the insulating paste can be applied on the passivation film 4 in a desired pattern having a plurality of holes corresponding to the plurality of through holes 45h. Here, for example, in a large number of granules, the plurality of granules 5b and the viscosity adjusting filler may exist separately, and the plurality of granules 5b function as a viscosity adjusting filler. You may have.

Incidentally, as shown in FIG. 6, the solar cell module 100 is irradiated with light on both the front surface 1fs and the back surface 1bs. For example, the light irradiated to the front surface 1fs mainly passes through an optical path (also referred to as a first optical path) Rt1 that passes through the first protective member 101 and the first filling portion 104u and reaches the first element surface Sf1 of the solar cell element 1. obtain. The first optical path Rt1 may include, for example, a path in which the light applied to the front surface 1fs is reflected a plurality of times in the solar cell module 100 and reaches the first element surface Sf1. Further, for example, the light irradiated on the front surface 1fs may pass through a path (also referred to as a second optical path) Rt2 that is reflected once or more in the solar cell module 100 and reaches the second element surface Sf2. Further, for example, the light irradiated on the back surface 1bs mainly passes through the second protective member 102 and the second filling portion 104b and reaches the second element surface Sf2 of the solar cell element 1 (also referred to as a third optical path). Rt3 can be passed. Here, for example, if the front surface 1fs is positioned so as to face the sun going south, the amount of light passing through the first optical path Rt1 per day is the amount of light passing through the second optical path Rt2. It is assumed that it is about 50 times, that is, about 5 to 10 times the amount of light passing through the third optical path Rt3. Therefore, for example, in the double-sided light receiving solar cell element 1 and the solar cell module 100, while increasing the ratio of light used for photoelectric conversion of light passing through the first optical path Rt1 (also referred to as first light utilization rate), Increasing the proportion of light used for photoelectric conversion of light passing through the third optical path Rt3 (also referred to as third light utilization rate) can improve the photoelectric conversion efficiency.

Here, for example, if the protective layer 5 has a thickness larger than that of the antireflection film 3, visible light and near infrared rays hardly cause multiple reflection on the second element surface Sf 2 side of the solar cell element 1. can do. Thereby, for example, the third light utilization rate related to the third optical path Rt3 can be increased. In the first embodiment, for example, the protective layer 5 having a thickness significantly larger than that of the antireflection film 3 can be easily formed by, for example, applying and drying the insulating paste described above. The thickness of the protective layer 5 is set to, for example, about 600 nm to 20 μm. Thereby, for example, on the second element surface Sf2 side of the solar cell element 1, multiple reflection of light in a wavelength region of 1200 nm or less including visible light, near ultraviolet light, and near infrared light with high energy intensity of sunlight occurs. It becomes difficult. Further, for example, the performance of protecting the passivation film 4 of the protective layer 5 can be improved by increasing the thickness of the protective layer 5.

In the first embodiment, for example, as shown in FIG. 5, the plurality of granular bodies 5b include a plurality of first granular bodies 5b1 and a plurality of second granular bodies 5b2. Here, for example, in the particle size distribution indicating the relationship between the particle size and the number of granular materials, the plurality of first granular materials 5b1 are in the first particle size range (also referred to as the first particle size range). It exists more frequently than outside the range of one particle size. Specifically, for example, a configuration showing a peak indicating that the particle size distribution of the plurality of first granular materials 5b1 is present at the highest frequency within the first particle size range is conceivable. Here, for example, in the particle size distribution indicating the relationship between the particle size and the number of particles, the plurality of second particles 5b2 have a second particle size range (first value) different from the first particle size range. 2) is also present at a higher frequency than outside the second particle size range. Specifically, for example, a configuration showing a peak indicating that the particle size distribution of the plurality of second granular bodies 5b2 exists at the highest frequency within the second particle size range is conceivable. The measurement of the particle size distribution of the plurality of granular materials 5b included in the protective layer 5 can be executed by extracting the plurality of granular materials 5b from the solar cell element 1, for example. For example, if the material of the protective layer 5 is silicon oxide, the front electrode 6 and the back electrode 7 are melted using hydrochloric acid and then hydrofluoric acid. A method of melting the protective layer 5, the semiconductor substrate 2 and the like using, for example, is applied.

Here, for example, if the refractive index of each first granular body 5b1 is closer to the refractive index of the semiconductor substrate 2 than the refractive index of the base material part 5a, then the protective layer 5 is formed from the base material part 5a alone. However, the refractive index of the protective layer 5 may approach the refractive index of the semiconductor substrate 2 due to the presence of the plurality of first granular bodies 5b1. Thereby, for example, the light emitted from the back surface 1bs side to the second element surface Sf2 is less likely to be reflected in the region between the protective layer 5 and the semiconductor substrate 2, and is likely to enter the semiconductor substrate 2. In other words, for example, the third light utilization rate related to the third optical path Rt3 can be increased. As a result, for example, the photoelectric conversion efficiency in the solar cell element 1 can be improved.

Here, it is assumed that the semiconductor substrate 2 is a silicon substrate and the base material portion 5a of the protective layer 5 is a siloxane resin. In this case, for example, the refractive index of the semiconductor substrate 2 is about 3.4, and the refractive index of the base material portion 5a is about 1.5, which is equivalent to the refractive index of silicon oxide (SiO ₂ ). Here, as the material of the first granular body 5b1, for example, a material having a refractive index between the refractive index of the semiconductor substrate 2 (about 3.4) and the refractive index of the base material portion 5a (about 1.5). Adopted. Specifically, as the material of the first granular body 5b1, for example, titanium oxide (TiO ₂ ), ferric oxide (Fe ₂ O ₃ ), niobium oxide (Nb ₂ O ₅ ), zirconium oxide (ZrO ₂ ) and One or more of hafnium oxide (HfO ₂ ) may be employed. The refractive index of titanium oxide (TiO ₂ ) is about 2.5 to 2.7. The refractive index of ferric oxide (Fe ₂ O ₃ ) is about 3.0. The refractive index of niobium oxide (Nb ₂ O ₅ ) is about 2.7. The refractive index of zirconium oxide (ZrO ₂ ) is about 2.1. The refractive index of hafnium oxide (HfO ₂ ) is about 1.95. For example, if the material of the passivation film 4 is aluminum oxide, the refractive index of the passivation film 4 is about 1.76. Here, if the material of the base material part 5a of the protective layer 5 is a siloxane resin, the refractive index of the passivation film 4 is closer to the refractive index of the semiconductor substrate 2 than the refractive index of the base material part 5a.

Here, for example, if the upper limit value of the first particle size range relating to the plurality of first granular bodies 5b1 is 30 nm or less, the protective layer 5 has visible light and near infrared rays having high energy intensity in sunlight. Including light in a wavelength region of 1200 nm or less is difficult to occur. This phenomenon was confirmed by observing the protective layer 5 in which the first particle size range was variously changed. In this case, for example, the refractive index of the protective layer 5 is changed to the refractive index of the semiconductor substrate 2 by the first granular body 5b1 that hardly scatters the light irradiated to the second element surface Sf2 from the back surface 1bs side in the protective layer 5. Can be approached. Thereby, for example, the light applied to the second element surface Sf 2 is less likely to be reflected in the region between the protective layer 5 and the semiconductor substrate 2 and is likely to enter the semiconductor substrate 2. In other words, for example, the third light utilization rate related to the third optical path Rt3 can be increased. As a result, for example, the photoelectric conversion efficiency in the solar cell element 1 can be improved.

By the way, the semiconductor substrate 2 is thinned in accordance with a reduction in the amount of the material used, so that the semiconductor substrate 2 extends in the thickness direction (also referred to as the first thickness direction) of the semiconductor substrate 2 from the first surface 2u to the second surface 2b. Light that passes through the substrate 2 may be generated. For example, if the semiconductor substrate 2 is a silicon substrate, near-infrared rays in the wavelength region of 1000 nm or more of sunlight are likely to pass through the semiconductor substrate 2 according to the light absorption coefficient of silicon.

Therefore, for example, in the protective layer 5, the plurality of second granular bodies 5 b 2 are arranged in the thickness direction (first thickness direction) of the semiconductor substrate 2 from the first surface 2 u to the second surface 2 b. You may be in the state which scatters the light to permeate | transmit. In the first embodiment, the first thickness direction is the −Z direction. The light scattering includes Mie scattering that can occur, for example, when the plurality of second granular materials 5b2 have a refractive index different from that of the base material portion 5a. Here, for example, light transmitted through the semiconductor substrate 2 can be scattered by the plurality of second granular bodies 5b2 existing in the protective layer 5 and re-enter the semiconductor substrate 2 at various angles. In this case, for example, the re-incident light can be used for photoelectric conversion in the semiconductor substrate 2. Thereby, for example, the ratio of the light used for photoelectric conversion in the semiconductor substrate 2 out of the light irradiated to the first surface 2u of the semiconductor substrate 2 can be improved. In other words, for example, the first light utilization rate related to the first optical path Rt1 can be increased. As a result, for example, the photoelectric conversion efficiency in the solar cell element 1 can be improved. Here, for example, if the semiconductor substrate 2 is a silicon substrate, in the protective layer 5, a plurality of second granular bodies 5 b 2 may scatter near infrared rays that pass through the semiconductor substrate 2 in the first thickness direction. . In this case, for example, the near infrared light transmitted through the semiconductor substrate 2 is scattered by the plurality of second granular bodies 5b2 existing in the protective layer 5, and re-enters the semiconductor substrate 2 at various angles, so that the semiconductor substrate 2 2 can be used for photoelectric conversion.

Here, for example, a case where the lower limit value of the second particle size range related to the plurality of second granular materials 5b2 is set to a value higher than 30 nm is conceivable. In this case, in the protective layer 5, scattering of light in a wavelength region of 1200 nm or less including visible light and near infrared light having high energy intensity in sunlight can occur. Here, for example, as the lower limit value of the second particle size range increases, the protective layer 5 is less likely to scatter relatively short-wavelength near-ultraviolet rays and visible rays in light with high energy intensity among sunlight. . Thereby, for example, the protective layer 5 scatters light such as near-infrared light transmitted through the semiconductor substrate 2 out of light irradiated on the first element surface Sf1, and also irradiates the light irradiated on the second element surface Sf2. It is possible to transmit near-ultraviolet rays and visible rays to the semiconductor substrate 2. For this reason, for example, it is possible to improve the first light utilization rate related to the first optical path Rt1 and the third light utilization rate related to the third optical path Rt3 in a balanced manner. For example, it is possible to appropriately set which one of the first light utilization rate related to the first optical path Rt1 and the third light utilization rate related to the third optical path Rt3 is to be increased.

Here, for example, in the semiconductor substrate 2, a wavelength range in which a proportion of light that is equal to or greater than a preset threshold among the light applied to the first surface 2 u can be transmitted in the first thickness direction is the first wavelength range. And Further, for example, a wavelength range of light that can be absorbed by the semiconductor substrate 2 is set as a second wavelength range. In this case, for example, even if the degree of light scattering generated by the plurality of second granular bodies 5b2 in the protective layer 5 is in a state where it shows a peak in the wavelength region where the first wavelength region and the second wavelength region overlap. Good. In this state, for example, the light transmitted through the semiconductor substrate 2 is scattered by the plurality of second granular bodies 5b2 present in the protective layer 5, and easily reenters the semiconductor substrate 2 at various angles. Thereby, for example, the photoelectric conversion efficiency in the solar cell element 1 can be improved. Here, for example, a value of about 40% can be adopted as the threshold value. Further, the first wavelength range is a wavelength range corresponding to the light absorption coefficient and thickness of the semiconductor substrate 2, for example. The second wavelength range is, for example, a wavelength range corresponding to the light absorption coefficient of the semiconductor substrate 2.

For example, if the semiconductor substrate 2 is a silicon substrate, the first wavelength range is a wavelength range of about 900 nm to about 1000 nm or more according to the thickness (also referred to as plate thickness) of the silicon substrate, and the second wavelength range is 1120 nm. The wavelength range is less than about. Here, for example, it is assumed that the material of the protective layer 5 is silicon oxide having a refractive index of about 1.5, and the material of the second granular material 5b2 is titanium oxide having a refractive index of about 2.7. . In this case, for example, it is necessary to show the peak of the degree of light scattering in the wavelength range where the thickness of the silicon substrate, the lower limit value of the first wavelength range, and the first wavelength range and the second wavelength range overlap. And the lower limit value of the particle size of the plurality of second granular bodies 5b2 is as follows in the calculation.

For example, when the plate thickness is 50 μm, the lower limit value of the first wavelength region is about 930 nm, and the lower limit value of the particle diameters of the plurality of second granular bodies 5b2 is about 350 nm. For example, when the plate thickness is 100 μm, the lower limit of the first wavelength region is about 970 nm, and the lower limit of the particle size of the plurality of second granular bodies 5b2 is about 361 nm. For example, when the plate thickness is 115 μm, the lower limit value of the first wavelength region is about 980 nm, and the lower limit value of the particle size of the plurality of second granular materials 5b2 is about 364 nm. For example, when the plate thickness is 140 μm, the lower limit value of the first wavelength region is about 990 nm, and the lower limit value of the particle diameters of the plurality of second granular bodies 5b2 is about 367 nm. For example, when the plate thickness is 170 μm, the lower limit value of the first wavelength region is about 1000 nm, and the lower limit value of the particle size of the plurality of second granular materials 5b2 is about 370 nm. For example, when the plate thickness is 215 μm, the lower limit value of the first wavelength region is about 1010 nm, and the lower limit value of the particle size of the plurality of second granular bodies 5b2 is about 373 nm. For this reason, considering the practical thickness of the silicon substrate applied to the semiconductor substrate 2, for example, about 350 nm or more can be adopted as the lower limit value of the particle size of the plurality of second granular bodies 5b2. Here, for example, if the refractive index of the material of the second granular body 5b2 is a value smaller than 2.7 (for example, about 2.5 or about 2.2), the refraction of the material of the second granular body 5b2 is performed. The lower limit value of the particle diameters of the plurality of second granular bodies 5b2 may be larger than when the rate is 2.7. Here, for example, if the refractive index of the material of the second granular material 5b2 is a value larger than 2.7, a plurality of second granular materials 5b2 than the case where the refractive index of the material of the second granular material 5b2 is 2.7. The lower limit value of the particle size of the two granular bodies 5b2 may be large. Specifically, if the refractive index of the material of the second granular body 5b2 is 3, a value of about 220 nm or more may be adopted as the lower limit value of the particle size. In other words, a value of 220 nm or more can be adopted as the lower limit value of the second particle size range related to the plurality of second granular materials 5b2.

Here, for example, as the upper limit value of the second particle size range related to the plurality of second granular bodies 5b2, a value about half or less of the thickness of the protective layer 5 can be adopted. Thereby, for example, the performance of protecting the passivation film 4 by the protective layer 5 can be ensured. For example, when the thickness of the protective layer 5 is 20 μm, the upper limit value of the second particle size range may be 10 μm.

Here, for example, as shown in FIG. 5, a plurality of second granular bodies 5b2 are arranged in the thickness direction of the protective layer 5 (also referred to as the second thickness direction). The granular material 5b2 may be included. In the first embodiment, the second thickness direction is the −Z direction. Here, for example, in the second thickness direction of the protective layer 5, light traveling in the second thickness direction out of the light scattered by the first second granular body 5 b 2 is the second second granular shape. It can be scattered by the body 5b2. Thereby, for example, the amount of light re-entering the semiconductor substrate 2 out of the light transmitted through the semiconductor substrate 2 can be increased. As a result, for example, the photoelectric conversion efficiency in the solar cell element 1 can be improved.

<1-2-5. Front electrode>
As shown in FIG. 3A and FIG. 4A to FIG. 4C, the front electrode 6 is located on the first surface 2u side of the semiconductor substrate 2, for example. In the first embodiment, the front electrode 6 is located on the first surface 2 u of the semiconductor substrate 2. The front electrode 6 includes, for example, a first output extraction electrode 6a and a first current collecting electrode 6b.

The first output extraction electrode 6 a is located on the first surface 2 u side of the semiconductor substrate 2. The 1st output extraction electrode 6a can take out the carrier obtained by the photoelectric conversion according to the irradiation of the light in the semiconductor substrate 2, for example to the exterior of the solar cell element 1. FIG. In the example of FIG. 3A and FIG. 4A to FIG. 4C, two first output extraction electrodes 6a are present on the first surface 2u side of the semiconductor substrate 2. Each first output extraction electrode 6a has a longitudinal direction along the first surface 2u. This longitudinal direction is the + Y direction. The length (also referred to as width) of the first output extraction electrode 6a in the short direction is, for example, about 1.3 mm to 2.5 mm. At least a part of the first output extraction electrode 6a is in a state of being electrically connected across the first collector electrode 6b.

The first current collecting electrode 6 b is located on the first surface 2 u side of the semiconductor substrate 2. The first current collecting electrode 6b can collect, for example, carriers obtained by photoelectric conversion according to light irradiation in the semiconductor substrate 2. In the example of FIG. 3A and FIG. 4A, a plurality of first current collecting electrodes 6 b exist on the first surface 2 u side of the semiconductor substrate 2. Each first current collecting electrode 6b has a longitudinal direction along the first surface 2u. This longitudinal direction is the + X direction. In other words, the plurality of first current collecting electrodes 6b have a so-called finger shape. Each first current collecting electrode 6b is a linear electrode having a width of about 20 μm to 200 μm, for example. In other words, the width of each first collector electrode 6b is smaller than the width of the first output extraction electrode 6a. The plurality of first current collecting electrodes 6b are positioned, for example, in a state where they are aligned with an interval of about 1 mm to 3 mm. The thickness of the front electrode 6 is, for example, about 10 μm to 40 μm.

The front electrode 6 having the above-described configuration can be formed by, for example, applying the first metal paste to a desired shape by screen printing or the like and then firing the first metal paste. The first metal paste contains, for example, metal particles mainly composed of silver, an organic vehicle, and glass frit. The main component means a component having the largest (high) content ratio (also referred to as a content ratio). Here, for example, the first metal paste is applied in a desired shape on the antireflection film 3. And when this 1st metal paste is baked, this 1st metal paste produces the baking penetration of the anti-reflective film 3. FIG. Thereby, the front electrode 6 in a state of being connected to the first surface 2u of the semiconductor substrate 2 can be formed.

The front electrode 6 may have an auxiliary electrode 6c having the same shape as the first current collecting electrode 6b, for example. For example, the auxiliary electrode 6c is located along each of the end in the + X direction and the end in the −X direction of the semiconductor substrate 2 so that the first current collecting electrodes 6b can be electrically connected to each other. .

<1-2-6. Back electrode>
As shown in FIGS. 3B and 4A to 4C, the back electrode 7 is located on the second surface 2b side of the semiconductor substrate 2, for example. The back electrode 7 includes, for example, a second output extraction electrode 7a and a second current collecting electrode 7b.

The second output extraction electrode 7 a is located on the second surface 2 b side of the semiconductor substrate 2. This 2nd output extraction electrode 7a is an electrode for taking out the carrier obtained by photoelectric conversion in the solar cell element 1 to the exterior of the solar cell element 1, for example. 3B, 4A, and 4C, two second output extraction electrodes 7a exist on the protective layer 5 on the second surface 2b side of the semiconductor substrate 2. Yes. Each second output extraction electrode 7a has a longitudinal direction along the second surface 2b. This longitudinal direction is the + Y direction. Each of the second output extraction electrodes 7a is composed of N (N is an integer of 2 or more) island-shaped electrode portions (also referred to as island-shaped electrode portions) arranged along the + Y direction as the longitudinal direction. ing. Here, N is four. In other words, on the second surface 2b side of the semiconductor substrate 2, there are two rows of island-like electrode portions arranged along the longitudinal direction (here, the + Y direction) of the second output extraction electrode 7a. . The second output extraction electrode 7a has a width direction that intersects the longitudinal direction. This width direction is the + X direction. The thickness of the second output extraction electrode 7a is, for example, about 10 μm to 40 μm. The width of the second output extraction electrode 7a is, for example, about 1.3 mm to 7 mm. At least a part of the second output extraction electrode 7a is in contact with and electrically connected to the second collector electrode 7b.

The second output extraction electrode 7a having the above-described configuration can be formed by, for example, applying the second metal paste into a desired shape by screen printing or the like and then firing the second metal paste. The second metal paste contains, for example, metal particles mainly composed of silver, an organic vehicle, and glass frit. Here, for example, the second metal paste is applied on the protective layer 5 in a desired shape.

The second current collecting electrode 7b is located on the second surface 2b side of the semiconductor substrate 2. For example, the second collector electrode 7b can collect carriers obtained by photoelectric conversion in the semiconductor substrate 2 according to light irradiation. In the example of FIG. 3B and FIG. 4A, a plurality of second current collecting electrodes 7b are present on the second surface 2b side of the semiconductor substrate 2. Each second current collecting electrode 7b has a longitudinal direction along the second surface 2b. This longitudinal direction is the + X direction. In other words, the plurality of second current collecting electrodes 7b also have a so-called finger-like form, similar to the plurality of first current collecting electrodes 6b described above. Each second current collecting electrode 7b is a linear electrode having a width of about 50 μm to 200 μm, for example. In other words, the width of each second current collecting electrode 7b is smaller than the width of the second output extraction electrode 7a. The plurality of second current collecting electrodes 7b are located, for example, in a state where they are aligned with an interval of about 1 mm to 3 mm.

The second current collecting electrode 7b has, for example, a first portion 7b1 and a second portion 7b2. The first portion 7b1 is located on the first region Ar1 of the protective layer 5. The second portion 7b2 is located in a state where it is electrically connected to the semiconductor substrate 2 in each of the plurality of through holes 45h in a state of continuously passing through the passivation film 4 and the protective layer 5. The thickness of the first portion 7b1 is, for example, about 10 μm to 40 μm. The first portion 7b1 and the second portion 7b2 are in an electrically connected state.

The second current collecting electrode 7b having the above-described configuration can be formed by, for example, applying the third metal paste into a desired shape by screen printing or the like and then firing the third metal paste. The third metal paste contains, for example, metal particles mainly composed of aluminum, an organic vehicle, and glass frit. Here, for example, the third metal paste is applied on the protective layer 5 and in the plurality of holes of the protective layer 5. And when this 3rd metal paste is baked, the 3rd metal paste located in the several hole part of the protective layer 5 produces baking penetration of the passivation film 4. FIG. Thereby, the 2nd part 7b2 in the state located in the some through-hole 45h can be formed. In this case, for example, aluminum in the third metal paste diffuses into the surface layer portion of the second surface 2b of the semiconductor substrate 2, and the third semiconductor region 23 as a BSF layer can be generated. On the other hand, in the third metal paste located on the protective layer 5, the first portion 7 b 1 can be formed on the protective layer 5 without causing the firing of the passivation film 4 due to the presence of the protective layer 5. As a result, the back electrode 7 can be formed.

<1-2-7. Connection between solar cell elements>
As shown in FIGS. 3A and 3B, for example, the first output extraction electrode 6 a of one solar cell element 1 and another solar cell adjacent to the one solar cell element 1. The second output extraction electrode 7a of the element 1 is in a state of being electrically connected by the first wiring member W1. In the example of FIG. 3A and FIG. 3B, the outer edge of the first wiring member W1 attached to each solar cell element 1 is virtually drawn with a two-dot chain line. For the first wiring member W1, for example, a metal having a linear or belt-like conductivity is applied. Specifically, for example, a copper foil having a thickness of about 0.1 mm to about 0.2 mm and a width of about 1 mm to about 2 mm covered with solder is applied to the first wiring member W1. The first wiring member W1 is positioned in a state where it is electrically connected to the first output extraction electrode 6a and the second output extraction electrode 7a, for example, by soldering.

<1-3. Manufacturing method of insulating paste>
The insulating paste used for forming the protective layer 5 can be produced, for example, by mixing a siloxane resin precursor, water, a catalyst, an organic solvent, and a large number of granular materials.

Specifically, first, a step of preparing a mixed solution (also referred to as a mixing step) is performed by mixing a siloxane resin precursor, water, a catalyst, and an organic solvent in a container.

Here, as the precursor of the siloxane resin, for example, a silane compound having a Si—O bond or a silazane compound having a Si—N bond is employed. These compounds have a property of causing hydrolysis (also referred to as hydrolyzability). The precursor of the siloxane resin is converted into a siloxane resin by hydrolysis and condensation polymerization. The silane compound is represented by the following general formula 1.

(R1) _4-d Si (OR2) _d .

D in the general formula 1 is an integer of any one of 1, 2, 3, and 4. R1 and R2 in the general formula 1 represent a carbon hydrogen group such as an alkyl group such as a methyl group and an ethyl group or a phenyl group.

Here, the silane compound includes, for example, a silane compound in which at least R1 includes an alkyl group (also referred to as an alkyl group-based silane compound). Specifically, as the alkyl group-based silane compound, for example, methyltrimethoxysilane, dimethyldimethoxysilane, triethoxymethylsilane, diethoxydimethylsilane, trimethoxypropylsilane, triethoxypropylsilane, hexyltrimethoxysilane, Examples include triethoxyhexylsilane, triethoxyoctylsilane, and decyltrimethoxysilane.

Here, for example, if the alkyl group is a methyl group, an ethyl group, or a propyl group, an alcohol as a by-product that has a small number of carbon atoms and easily volatilizes can be generated when the precursor of the siloxane resin is hydrolyzed. Thereby, it becomes easy to remove a by-product in a by-product removing step described later. As a result, for example, when the protective layer 5 is formed, vacancies are hardly generated due to evaporation of by-products, the protective layer 5 becomes dense, and the barrier property of the protective layer 5 can be improved. Moreover, since the by-product produced | generated by hydrolysis is a low-viscosity liquid, in a manufacturing process of the insulating paste until a by-product removal process, a mixed solution is hard to gelatinize.

Here, for example, when the precursor of the siloxane resin has a phenyl group, the precursor of the siloxane resin undergoes hydrolysis and condensation polymerization in advance, and by-products generated by hydrolysis and condensation polymerization of the phenyl group It may be mixed in the state of the siloxane resin from which is removed. Thereby, the fluctuation | variation of the viscosity of the insulating paste by the hydrolysis reaction of a siloxane resin can be reduced, for example. Also, for example, if an insulating paste is produced by mixing a siloxane resin, an organic solvent, and a large number of granular materials in a state where the by-products are removed, the amount of by-products contained in the insulating paste is reduced. Reduced. In this case, for example, when the insulating paste is applied by a screen printing method, the emulsion of the screen plate making is hardly dissolved by the by-product. As a result, the dimensions of the screen plate making pattern are less likely to vary.

Further, the silane compound includes, for example, a silane compound in which R1 and R2 include both a phenyl group and an alkyl group. Examples of such silane compounds include trimethoxyphenylsilane, dimethoxydiphenylsilane, methoxytriphenylsilane, triethoxyphenylsilane, diethoxydiphenylsilane, ethoxytriphenylsilane, triisopropoxyphenylsilane, and diisopropoxydiphenylsilane. And isopropoxytriphenylsilane.

Among these silane compounds, for example, when a silane compound containing two or more OR bonds is employed, a siloxane bond (Si—O—Si bond) formed by condensation polymerization after the silane compound is hydrolyzed. ) May increase. Thereby, the network of the siloxane bond in the silicon oxide which comprises the protective layer 5 increases, and the barrier property of the protective layer 5 can improve. For example, the silazane compound may be either an inorganic silazane compound or an organic silazane compound. Here, examples of the inorganic silazane compound include polysilazane. Examples of the organic silazane compound include hexamethyldisilazane, tetramethylcyclodisilazane, and tetraphenylcyclodisilazane.

Water can, for example, hydrolyze a precursor of a siloxane resin. For example, pure water is used as water. For example, when water reacts with a Si—OCH ₃ bond of a silane compound, a Si—OH bond and HO—CH ₃ (methyl alcohol) are generated.

As the organic solvent, for example, a siloxane resin precursor and water can be mixed. Moreover, the organic solvent can also play the role which disperse | distributes a siloxane resin and many granular materials, for example. Examples of the organic solvent include diethylene glycol monobutyl ether, methyl cellosolve, ethyl cellosolve, ethyl alcohol, 2- (4-methylcyclohex-3-enyl) propan-2-ol or 2-propanol. Here, any one of these organic solvents and an organic solvent obtained by mixing two or more organic solvents may be used.

The catalyst can control the rate of the reaction, for example, when the siloxane resin precursor undergoes hydrolysis and condensation polymerization. For example, the Si—OR bond (for example, R is an alkyl group) contained in the siloxane resin precursor is subjected to hydrolysis and condensation polymerization, so that two or more Si—OH can be converted into Si—O—Si bond and H _2. The rate of reaction to produce O (water) can be adjusted. As the catalyst, for example, one or more inorganic acids or one or more organic acids selected from hydrochloric acid, nitric acid, sulfuric acid, boric acid, phosphoric acid, hydrofluoric acid, and acetic acid are used. Further, as the catalyst, for example, one or more inorganic bases or one or more organic bases among ammonia, sodium hydroxide, potassium hydroxide, barium hydroxide, calcium hydroxide, pyridine, and the like may be used. Further, 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.

About the ratio of each material mixed at a mixing process, the precursor of a siloxane resin is 10 mass% to 90 mass%, and water is 5 mass% to 40 with respect to the total mass (100 mass%) of the mixed material, for example. The mass% (or 10 mass% to 20 mass%), the catalyst is 1 ppm to 1000 ppm, and the organic solvent is 5 mass% to 50 mass%. If the said ratio is employ | adopted, the siloxane resin which hydrolyzed the siloxane resin precursor and condensed and polymerized can be contained in an insulating paste by suitable mass ratio. Furthermore, an excessive increase in the viscosity of the insulating paste due to gelation is unlikely to occur.

In such a mixing step, the siloxane resin precursor and water react to start hydrolysis of the siloxane resin precursor. Also, the hydrolyzed siloxane resin precursor undergoes condensation polymerization, and siloxane resin begins to be produced.

Next, a step of stirring the mixed solution prepared in the mixing step using, for example, a mix rotor or a stirrer (also referred to as a first stirring step) is performed. Here, when the mixed solution is stirred, hydrolysis of the precursor of the siloxane resin further proceeds. Also, the hydrolyzed siloxane resin precursor undergoes condensation polymerization, and the siloxane resin continues to be produced. For example, when stirring is performed with a mix rotor, the rotation speed of the rotating roller of the mix rotor is set to about 400 rpm to 600 rpm, and the stirring time is set to about 30 minutes to 90 minutes. With such a setting, the siloxane resin precursor, water, catalyst and organic solvent can be mixed uniformly. In the first stirring step, for example, if the mixed solution is heated, hydrolysis and condensation polymerization of the precursor of the siloxane resin easily proceed. Thereby, for example, the viscosity of the mixed solution tends to be stable in a step after the first stirring step. Further, for example, hydrolysis and condensation polymerization of the precursor of the siloxane resin can easily proceed, and productivity can be improved by shortening the stirring time.

Next, a step of removing by-products from the mixed solution stirred in the first stirring step (also referred to as a by-product removing step) is performed. Here, for example, by-products of organic components such as alcohol generated by the reaction between the precursor of the siloxane resin and water, water and the catalyst are volatilized. Thereby, for example, when the insulating paste is stored or when the insulating paste is continuously applied, fluctuations in the viscosity of the insulating paste due to the volatilization of the organic component as a by-product are reduced. Further, when the insulating paste is applied using the screen printing method, the emulsion of the screen plate making becomes difficult to be dissolved by the organic component as a by-product. Thereby, the fluctuation | variation of the dimension of the pattern of screen plate-making can be reduced. In the byproduct removal step, the hydrolyzed siloxane resin precursor further undergoes condensation polymerization, and the siloxane resin continues to be generated. In the byproduct removal step, water and the catalyst are volatilized, and thereafter, the condensation polymerization reaction of the precursor of the siloxane resin is reduced, and the fluctuation of the viscosity of the mixed solution can be reduced.

In the by-product removing step, for example, using a hot plate or a drying furnace, the processing temperature is about room temperature to about 90 ° C. (or about 50 ° C. to about 90 ° C.), and the processing time is about 10 minutes to about 600 minutes. The mixed solution after stirring is processed under the conditions as follows. By-products can be removed by volatilization if the processing temperature is within the above temperature range. In the byproduct removal step, for example, not only an organic component such as methyl alcohol produced by the hydrolysis reaction but also an added catalyst can be removed by volatilization. Here, for example, if the by-product removing step is performed under reduced pressure, the organic components and catalysts that are by-products are likely to volatilize, and the processing time can be shortened. Further, for example, in the byproduct removal step, the precursor of the siloxane resin remaining without being hydrolyzed in the first stirring step may be further hydrolyzed.

Next, a step of adding a large number of granular materials to the mixed solution from which the by-products have been removed in the by-product removing step (also referred to as a granular material adding step) is performed. Here, the multiple granular materials include, for example, the plurality of granular materials 5b described above. The plurality of granules 5b include the plurality of first granules 5b1 and the plurality of second granules 5b2 described above. Furthermore, a plurality of granular materials may include a plurality of fillers (viscosity adjusting fillers) for adjusting the viscosity of the mixed solution. For example, an inorganic material such as silicon oxide is applied to the plurality of filler materials. Here, for example, a filler having a surface covered with an organic coating may be applied to the plurality of fillers. The organic coating material has, for example, a structure in which the number of carbon atoms in the main chain is 6 or more, or the total number of carbon atoms and silicon atoms in the main chain is 6 or more. A material different from the siloxane resin can be applied. In the granular material addition step, a large number of granular materials are added to the mixed solution so that the insulating paste after the production includes, for example, 3% by mass to 30% by mass (may be 5% by mass to 25% by mass).

Next, a step (also referred to as a second stirring step) of stirring the mixed solution to which the plurality of granular materials are added using, for example, a rotation / revolution mixer or the like is performed. Here, for example, when the mixed solution is agitated by a rotation / revolution mixer, the rotation speed of the rotation part and the revolution part is set to 800 rpm to 1000 rpm, and the stirring time is set to 1 minute to 10 minutes. Thereby, a some granular material can be uniformly disperse | distributed in a mixed solution.

Next, a step of stabilizing the viscosity of the mixed solution (also referred to as a viscosity stabilization step) is performed by storing the mixed solution after stirring in the second stirring step, for example, at room temperature for about 2 to 24 hours. To do. When the viscosity of the mixed solution is stabilized in the second stirring step, the viscosity stabilization step may be omitted.

An insulating paste can be produced by the series of steps described above.

In the above series of steps, for example, a large number of granular materials may be mixed at the same time in the mixing step. Thereby, the granule addition step and the second stirring step become unnecessary, and the productivity of the insulating paste is improved. Further, for example, when the insulating paste is applied by a spray method or the like, the byproduct removal step may be omitted. Further, for example, a siloxane resin having an alkyl group may be generated in the mixing step, and the siloxane resin having a phenyl group may be added in the granular material adding step.

<1-4. Manufacturing method of solar cell element>
An example of a method for manufacturing the solar cell element 1 will be described with reference to FIGS. 7 (a) to 7 (d).

First, as shown in FIG. 7A, a semiconductor substrate 2 is prepared. For example, a substrate made of single crystal silicon or polycrystalline silicon is applied to the semiconductor substrate 2. The semiconductor substrate 2 is formed using, for example, an existing Czochralski method (CZ method) or a casting method. Here, for example, if the semiconductor substrate 2 is a p-type polycrystalline silicon substrate, boron or the like is added as a dopant element when a polycrystalline silicon ingot is produced using a casting method or the like. The resistivity of the ingot is adjusted from 1 ohm centimeter (Ω · cm) to about 5 Ω · cm. Next, the ingot is cut into, for example, a rectangular parallelepiped shape having a square bottom surface with a side of about 160 mm, and further sliced to a thickness of about 200 μm to produce the semiconductor substrate 2. Here, for example, a very small amount of etching is performed on the surface of the semiconductor substrate 2 with an aqueous solution such as sodium hydroxide, potassium hydroxide, hydrofluoric acid, or hydrofluoric acid to mechanically damage the cut surface of the semiconductor substrate 2. The received layer and the contaminated layer are removed. Here, the texture may be formed on the first surface 2u of the semiconductor substrate 2 by wet or dry etching. For wet etching, for example, etching using an alkaline aqueous solution such as sodium hydroxide or an acidic aqueous solution such as hydrofluoric acid is applied. For example, etching using a reactive ion etching (RIE) method or the like is applied to the dry etching.

Next, as illustrated in FIG. 7B, for example, the second semiconductor region 22 that is an n-type semiconductor region is generated in the surface layer portion of the first surface 2 u of the textured semiconductor substrate 2. The second semiconductor region 22 is formed into a gaseous state, for example, by applying a paste of phosphorous pentoxide (P ₂ O ₅ ) to the first surface 2u of the semiconductor substrate 2 to thermally diffuse phosphorus. It can be produced using a vapor phase thermal diffusion method using phosphorus oxychloride (POCl ₃ ) as a diffusion source. The second semiconductor region 22 has, for example, a depth of about 0.1 μm to 2 μm and a sheet resistance value of about 40Ω / □ to 200Ω / □. Here, for example, in the vapor phase thermal diffusion method, the semiconductor substrate 2 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 containing a diffusion source gas such as POCl _3. Then, phosphor silicon glass (PSG) is formed on the first surface 2 u of the semiconductor substrate 2. Thereafter, heat treatment is performed on the semiconductor substrate 2 for about 10 minutes to 40 minutes at a high temperature of about 800 ° C. to 900 ° C. in an atmosphere of an inert gas such as argon or nitrogen. Thereby, phosphorus diffuses from the PSG to the surface layer portion on the first surface 2 u side of the semiconductor substrate 2, and the second semiconductor region 22 is generated in the surface layer portion on the first surface 2 u side of the semiconductor substrate 2.

Here, for example, if the second semiconductor region is also generated on the second surface 2b side, the second surface 2b side of the semiconductor substrate 2 is immersed in an aqueous solution of fluoric nitric acid so that the second surface 2b side is immersed. The formed second semiconductor region is removed by etching. Thereby, for example, the first semiconductor region 21 having p-type conductivity may be exposed on the second surface 2 b of the semiconductor substrate 2. Thereafter, for example, PSG attached on the first surface 2u of the semiconductor substrate 2 during the generation of the second semiconductor region 22 is removed by etching. At this time, for example, the second semiconductor region formed on the side surface 2s of the semiconductor substrate 2 may also be removed. By the way, for example, a diffusion mask may be formed in advance on the second surface 2b side of the semiconductor substrate 2, and the diffusion mask may be removed after the second semiconductor region 22 is generated by a vapor phase thermal diffusion method or the like. In this case, the second semiconductor region is not generated on the second surface 2b side.

Next, as shown in FIG. 7C, a passivation film 4 mainly containing, for example, aluminum oxide is formed on at least the second surface 2 b of the semiconductor substrate 2. The passivation film 4 can be formed by, for example, an ALD method or a PECVD method. Here, for example, if the ALD method is used, the surface of the semiconductor substrate 2 can be more densely covered with the passivation film 4 without a gap. In the step of forming the passivation film 4 using the ALD method, first, the semiconductor substrate 2 on which the second semiconductor region 22 is formed is placed in the chamber of the film forming apparatus. Then, in a state where the semiconductor substrate 2 is heated in a temperature range of 100 ° C. to 250 ° C., a plurality of four steps of supplying the aluminum raw material, removing the aluminum raw material by exhaust, supplying the oxidizing agent, and removing the oxidizing agent by exhausting are performed Repeat once. As a result, a passivation film 4 mainly containing aluminum oxide is formed on the semiconductor substrate 2. Here, for example, trimethylaluminum (TMA) or triethylaluminum (TEA) is applied as the aluminum raw material. For example, water or ozone gas is applied as the oxidizing agent. If the ALD method is used, the passivation film 4 can be formed not only on the second surface 2 b of the semiconductor substrate 2 but also on the entire periphery of the semiconductor substrate 2 including the side surface 2 s of the semiconductor substrate 2. Here, for example, after applying an acid resistant resist to the passivation film 4 on the second surface 2b of the semiconductor substrate 2, an unnecessary portion of the passivation film 4 may be removed by etching using hydrofluoric acid or the like.

Further, as shown in FIG. 7C, an antireflection film 3 containing, for example, silicon nitride is formed on at least the first surface 2u of the semiconductor substrate 2. The antireflection film 3 is formed using, for example, a PECVD method or a sputtering method. When the PECVD method is used, the semiconductor substrate 2 is heated in advance to a temperature higher than the temperature during the formation of the antireflection film 3. Thereafter, for example, a mixed gas of silane (SiH ₄ ) and ammonia (NH ₃ ) is diluted with nitrogen (N ₂ ) gas, the reaction pressure is changed from 50 Pa to 200 Pa, and plasma is generated by glow discharge decomposition. Is deposited on the heated semiconductor substrate 2. Thereby, the antireflection film 3 is formed on the first surface 2 u of the semiconductor substrate 2. Here, the film formation temperature is, for example, about 350 ° C. to 650 ° C. The frequency of the high-frequency power source necessary for glow discharge is, for example, about 10 kHz to 500 kHz. The flow rate of the mixed gas is appropriately determined according to the size of the reaction chamber. The flow rate of the mixed gas is, for example, in the range of about 150 ml / min (sccm) to about 6000 ml / min (sccm). A value (B / A) obtained by dividing the flow rate B of ammonia gas by the flow rate A of silane gas is, for example, in the range of 0.5 to 15.

Next, as shown in FIG. 7C, a protective layer 5 containing silicon oxide or the like is formed on the passivation film 4 formed on the second surface 2 b of the semiconductor substrate 2. The protective layer 5 is, for example, applied on the passivation film 4 formed on the second surface 2b of the semiconductor substrate 2 so that an insulating paste has a desired pattern by a coating method such as a screen printing method. The insulating paste can be formed by drying. Here, the insulating paste containing the plurality of granular materials 5b described above is employed. For example, the protective layer 5 may be formed directly on the passivation film 4 or on the antireflection film 3 formed on the passivation film 4 on the side surface 2 s of the semiconductor substrate 2. In this case, the presence of the protective layer 5 can reduce, for example, a leakage current in the solar cell element 1.

Next, as shown in FIG. 7D, the above-described first metal paste Pa1, second metal paste Pa2, and third metal paste Pa3 are applied and baked using screen printing or the like. As shown in FIG. 3 (a) to FIG. 4 (c), the front electrode 6 and the back electrode 7 are formed.

Specifically, for example, the front electrode 6 including the first output extraction electrode 6a and the first collector electrode 6b is formed by applying the first metal paste Pa1 on the antireflection film 3 and baking it. For example, if the first metal paste is applied by screen printing, the first output extraction electrode 6a, the first current collecting electrode 6b, and the auxiliary electrode 6c included in the front electrode 6 can be formed in one step. Here, for example, after the application of the first metal paste Pa1, the first metal paste Pa1 may be dried by evaporating the solvent in the first metal paste Pa1 at a predetermined temperature. Firing of the first metal paste Pa1 is performed, for example, under the condition that the maximum temperature in the firing furnace is 600 ° C. to 850 ° C. and the heating time is about several tens of seconds to several tens of minutes. As a result, the first metal paste Pa 1 causes firing through the antireflection film 3, and the front electrode 6 is formed on the first surface 2 u side of the semiconductor substrate 2.

Also, for example, the second output extraction electrode 7a of the back electrode 7 is formed by applying the second metal paste Pa2 on the protective layer 5 and baking it. Application | coating of 2nd metal paste Pa2 is performed using screen printing etc., for example. Here, for example, after the application of the second metal paste Pa2, the second metal paste Pa2 may be dried by evaporating the solvent in the second metal paste Pa2 at a predetermined temperature. Firing of the second metal paste is performed, for example, under the condition that the maximum temperature in the firing furnace is 600 ° C. to 850 ° C. and the heating time is about several tens of seconds to several tens of minutes. Thereby, the second output extraction electrode 7 a is formed on the second surface 2 b side of the semiconductor substrate 2.

Also, for example, the second current collecting electrode 7b of the back electrode 7 is formed by applying the third metal paste Pa3 on the protective layer 5 and baking it. Application | coating of 3rd metal paste Pa3 is performed using screen printing etc., for example. Here, the third metal paste Pa3 is applied to the second surface 2b side of the semiconductor substrate 2 so as to be in contact with a part of the second metal paste Pa2 previously applied. At this time, the third metal paste Pa3 is applied to a part on the protective layer 5 formed on the passivation film 4 on the second surface 2b and a plurality of holes of the protective layer 5. Here, for example, after applying the third metal paste Pa3, the third metal paste Pa3 may be dried by evaporating the solvent in the third metal paste Pa3 at a predetermined temperature. For example, the third metal paste Pa3 is fired under the condition that the maximum temperature in the firing furnace is 600 ° C. to 850 ° C. and the heating time is several tens of seconds to several tens of minutes. For example, the third metal paste Pa3 is fired under the condition that the maximum temperature in the firing furnace is 600 ° C. to 850 ° C. and the heating time is several tens of seconds to several tens of minutes. Thereby, the 1st part 7b1 of the 2nd current collection electrode 7b is formed by baking of 3rd metal paste Pa3 on the protective layer 5. FIG. At this time, the third metal paste Pa3 on the protective layer 5 is blocked by the protective layer 5. In addition, by firing the third metal paste Pa3 in the plurality of holes of the protective layer 5, the third metal paste Pa3 causes firing of the passivation film 4 and is electrically connected to the first semiconductor region 21. Thereby, the second portion 7b2 of the second collector electrode 7b is formed on the second surface 2b side of the semiconductor substrate 2. At this time, the third semiconductor region 23 is also generated with the formation of the second portion 7b2.

In this way, the back electrode 7 including the second output extraction electrode 7a and the second collector electrode 7b can be formed.

<1-5. Summary of First Embodiment>
In the solar cell element 1 according to the first embodiment, for example, the protective layer 5 has a larger thickness than the antireflection film 3. For this reason, for example, on the second element surface Sf2 side of the solar cell element 1, multiple reflections of visible light and near infrared light can be made difficult to occur. Thereby, for example, the third light utilization rate related to the third optical path Rt3 can be increased. Further, for example, by increasing the thickness of the protective layer 5, the performance of protecting the passivation film 4 by the protective layer 5 can be improved. Further, for example, the protective layer 5 includes the base material portion 5a and the plurality of first granular bodies 5b1 having a refractive index closer to the semiconductor substrate 2 than the base material portion 5a, so that the protective layer 5 is the base material. The refractive index of the protective layer 5 can approach the refractive index of the semiconductor substrate 2 as compared with the case where the material portion 5a is constituted alone. Thereby, for example, the light emitted from the back surface 1bs side to the second element surface Sf2 is not easily reflected in the region between the protective layer 5 and the semiconductor substrate 2, and is likely to enter the semiconductor substrate 2. In other words, for example, the third light utilization rate related to the third optical path Rt3 can be increased. As a result, for example, the photoelectric conversion efficiency in the solar cell element 1 can be improved.

In the solar cell module 100 according to the first embodiment, for example, if the refractive index of the base material portion 5a and the refractive index of the filler 104 are substantially the same, the position between the filler 104 and the semiconductor substrate 2 is set. The refractive index of the protective layer 5 is between the refractive index of the filler 104 and the refractive index of the semiconductor substrate 2. Thereby, for example, the light irradiated to the back surface 1bs is not easily reflected in the region between the filler 104 and the protective layer 5 and the region between the protective layer 5 and the semiconductor substrate 2, and enters the semiconductor substrate 2. It becomes easy. As a result, for example, the photoelectric conversion efficiency in the solar cell module 100 can be improved.

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

<2-1. Second Embodiment>
In the first embodiment, as the shape of the plurality of second granular bodies 5b2, for example, any shape such as a particle shape, a layer shape, a flat shape, a hollow shape, and a fiber shape may be adopted. For example, as shown in FIG. 8, a case where the plurality of second granular bodies 5b2 have an elongated cross section is conceivable. In this case, for example, the second granular body 5b2 has a virtual cut surface in a direction perpendicular to the longitudinal direction having a diameter of about several tens of nanometers and a length in the longitudinal direction of about 1 μm to several μm or less. Possible forms. Here, for example, if the second granular material 5b2 having an elongated shape is present in the base material portion 5a, the wavelength region corresponding to the length in the longitudinal direction of the second granular material 5b2 is present in the protective layer 5. Light scattering can occur. Therefore, for example, a plurality of second granular bodies 5b2 that can scatter light transmitted through the semiconductor substrate 2 without causing an excessive increase in the thickness of the protective layer 5 are present in the protective layer 5. Is possible. Thereby, for example, an increase in the amount of material used and an occurrence of cracks in the protective layer 5 due to an excessive increase in the thickness of the protective layer 5 can be reduced. As a result, for example, the photoelectric conversion efficiency in the solar cell element 1 can be easily improved.

<2-2. Third Embodiment>
In each of the first embodiment and the second embodiment, the first region Ar1 of the protective layer 5 includes, for example, a plurality of second granular bodies 5b2 as shown in FIG. The second region Ar2 different from the first region Ar1 of the layer 5 may have a plurality of first granular bodies 5b1 as shown in FIG. 9B. In this case, for example, in the first region Ar1 in the protective layer 5 where light from the back surface 1bs side of the solar cell element 1 is difficult to enter due to the presence of the second current collecting electrode 7b, the semiconductor substrate 2 from the front surface 1fs side. Is scattered by the presence of the plurality of second granular bodies 5b2 and re-enters the semiconductor substrate 2. Further, for example, in the second region Ar2 in which light is likely to enter from the back surface 1bs side of the solar cell element 1 in the protective layer 5, the light incident from the back surface 1bs side is caused by the presence of the plurality of first granular bodies 5b1. 2 is easy to enter. As a result, for example, the photoelectric conversion efficiency in the solar cell element 1 can be improved. In addition, although the semiconductor substrate 2 does not absorb, light that increases the temperature of the solar cell element 1 (for example, the temperature of the solar cell element 1 increases due to absorption by a base that supports the solar cell module 100 or a base on which a base such as roofing material or asphalt is installed) Further, far infrared rays having a wavelength exceeding 2 μm or the like) can be reflected by the protective layer 5 to reduce the temperature rise of the power generation environment. By doing in this way, the temperature rise of the solar cell module 100 can be suppressed and the actual power generation amount can be increased.

Here, for example, in the first region Ar1 of the protective layer 5, the plurality of first granular bodies 5b1 may or may not exist. In the second region Ar2 of the protective layer 5, a plurality of second granular bodies 5b2 may exist. In this case, the density of the plurality of first granules 5b1 and the density of the plurality of second granules 5b2 in the second region Ar2 of the protective layer 5 can be set as appropriate. Here, for example, if the density of the plurality of second granular bodies 5b2 in the second region Ar2 is increased, even if the light irradiated to the first element surface Sf1 is transmitted through the semiconductor substrate 2, It is scattered by the presence of the plurality of second granular bodies 5 b 2 and easily reenters the semiconductor substrate 2. In other words, for example, the first light utilization rate related to the first optical path Rt1 can be increased. Further, for example, if the density of the plurality of first granular bodies 5b1 in the second region Ar2 is increased, the light radiated from the back surface 1bs side to the second element surface Sf2 is between the protective layer 5 and the semiconductor substrate 2. It is difficult to reflect in this area, and it is easy to enter the semiconductor substrate 2. In other words, for example, the third light utilization rate related to the third optical path Rt3 can be increased. As a result, for example, the photoelectric conversion efficiency in the solar cell element 1 can be improved.

<3. Other>
In each of the first to third embodiments, the plurality of second granular bodies 5b2 may have a function as a viscosity adjusting filler, for example. Moreover, the some 1st granule 5b1 may have a function as a filler for viscosity adjustment, for example. For example, the protective layer 5 may or may not contain a viscosity adjusting filler different from the plurality of first granular bodies 5b1 and the plurality of second granular bodies 5b2.

In each of the first embodiment to the third embodiment, the plurality of second current collecting electrodes 7b have other forms such as a so-called honeycomb form instead of the so-called finger form. It may be.

In each of the first to third embodiments, for example, the packing unit 105 may not be present. Depending on the specifications of the solar cell module 100, the packing unit 105 is not necessarily required as a member sandwiched between the first protective member 101 and the second protective member 102. For example, an aluminum frame that is a member that reinforces the strength of the solar cell module 100 or a resin that seals the side surface of the solar cell module 100 may serve as the function of the packing unit 105.

In each of the first to third embodiments, the semiconductor substrate 2 may be, for example, a silicon substrate using amorphous silicon instead of single crystal or polycrystalline silicon.

In each of the first embodiment to the third embodiment, the semiconductor substrate 2 is not a silicon substrate, for example, four kinds of elements (so-called CIGS) of copper, indium, gallium, and selenium, or cadmium and tellurium. A substrate having a compound semiconductor using the two types of elements (so-called CdTe) may be used.

In each of the first to third embodiments, if, for example, zirconium oxide softer than titanium oxide is used as the material of the plurality of granular bodies 5b, the passivation film 4 is damaged by the application of the insulating paste. Hateful.

Needless to say, it is possible to combine all or part of the first to third embodiments and various modifications, as appropriate, within a consistent range.

DESCRIPTION OF SYMBOLS 1 Solar cell element 1bs Back surface 1fs Front surface 2 Semiconductor substrate 2b 2nd surface

2s Side surface

2u 1st surface 3 Antireflection film 4 Passivation film 5 Protective layer 5a Base material part 5b Granule 5b1 1st granule 5b2 2nd granule 6 Front Electrode 6a 1st output extraction electrode 6b 1st current collection electrode 6c Auxiliary electrode 7 Back electrode 7a 2nd output extraction electrode 7b 2nd current collection electrode 7b1 1st part 7b2 2nd part 45h Through-hole 100 Solar cell module 101 1st protection Member 102 Second protective member 103 Solar cell portion 104 Filler A0 Inter-plate region Ar1 First region Ar2 Second region

Claims

A semiconductor substrate having a first surface, a second surface positioned on the opposite side of the first surface, and a side surface positioned in a state where the first surface and the second surface are connected;
An antireflection film located on the first surface side of the semiconductor substrate;
A passivation film located on the second surface;
A protective layer located on the passivation film and having a thickness larger than that of the antireflection film;
Electrically connected to the semiconductor substrate in a first hole located above the first region of the protective layer, and in a through hole in a state of continuously passing through the passivation film and the protective layer; An electrode having a second portion located in a state of being
The protective layer has a base material portion and a plurality of granules,
The plurality of granular materials are a plurality of first granular materials present in a first particle size range at a frequency higher than outside the first particle size range, and a second particle size different from the first particle size range. A plurality of second granular bodies present in a range at a frequency higher than outside the second particle size range,
The refractive index of each said 1st granule is a solar cell element closer to the refractive index of the said semiconductor substrate than the refractive index of the said base material part.
The solar cell element according to claim 1,
The plurality of second granular materials are solar cell elements in a state in which light transmitted through the semiconductor substrate is scattered in a first thickness direction of the semiconductor substrate from the first surface toward the second surface.
The solar cell element according to claim 2,
A first wavelength region in which a proportion of light that is greater than or equal to a preset threshold value of light irradiated on the first surface is transmitted through the semiconductor substrate in the first thickness direction, and light that can be absorbed by the semiconductor substrate The solar cell element in a state where the degree of light scattering generated by the plurality of second granular materials exhibits a peak in a wavelength range overlapping with the second wavelength range.
The solar cell element according to claim 3, wherein
The lower limit of the second particle size range is a solar cell element that is 220 nm or more.
The solar cell element according to any one of claims 2 to 4, wherein
The plurality of second granular bodies are solar cell elements including two or more granular bodies arranged in a second thickness direction of the protective layer.
A solar cell element according to any one of claims 2 to 5,
The plurality of second granular bodies are solar cell elements having an elongated shape.
The solar cell element according to any one of claims 1 to 6,
The upper limit of the first particle size range is a solar cell element that is 30 nm or less.
The solar cell element according to any one of claims 1 to 7,
The first region of the protective layer has the plurality of second granular bodies,
The 2nd area | region different from the said 1st area | region of the said protective layer is a solar cell element which has the said some 1st granule.
A first protective member having translucency;
A second protective member having translucency;
A solar cell portion located between the first protective member and the second protective member;
A translucent filler located between the first protective member and the second protective member so as to cover the solar cell portion from the first protective member side and the second protective member side. And comprising
The said solar cell part is a solar cell module which has a some solar cell element as described in any one of Claims 1-8.