JP2008004574A - Solar battery cell and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solar battery cell that cannot be cracked easily in a later process, or the like even if a thin silicon semiconductor substrate is used. <P>SOLUTION: The solar battery cell comprises: the silicon semiconductor substrate, and an aluminum electrode formed at a non-light-reception surface side of the silicon semiconductor substrate. The aluminum electrode comprises: an aluminum sintered layer formed by applying and baking paste containing aluminum to the non-light-reception surface side of the silicon semiconductor substrate, and a conductive organic resin layer formed on the aluminum sintered layer by conductive paste containing a conductive particle and an organic resin. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a solar battery cell and a manufacturing method thereof, and more particularly to a solar battery cell in which an aluminum electrode is formed on the back surface of a silicon semiconductor substrate and a manufacturing method thereof.

  Solar cells are desired to be put into practical use more widely as clean energy sources that are safe and have a low environmental impact. In particular, in order to promote the spread of solar cells that are configured using a silicon semiconductor substrate, it is necessary to promote weight reduction and cost reduction. In response to this demand, research and development for reducing the thickness of solar cells has been repeated.

  FIG. 5 is a diagram schematically showing a cross-sectional structure of a general solar battery cell 101. As shown in FIG. 5, in the silicon semiconductor substrate 102, an n-type impurity layer 104 is formed on the light receiving surface side of the p-type silicon semiconductor substrate 103, and an antireflection film 106 and a grid electrode 107 are formed on the n-type impurity layer 104. Is formed.

  On the other hand, an aluminum electrode 108 as a back electrode is formed on the back side of the silicon semiconductor substrate 102. In the aluminum electrode 108, an aluminum silicon mixed layer 109 and an aluminum layer 110 are formed in this order from the silicon semiconductor substrate 102 side.

In general, the aluminum electrode 108 is formed by applying an aluminum-containing paste to the back surface of the p-type silicon semiconductor substrate 103 and baking it. Also, this firing, the aluminum-containing paste to the p-type silicon semiconductor substrate 103 and the aluminum is diffused, ^{p +} layer (or ^{p ++} layer) 105 is formed.

By the presence of the p ⁺ layer 105, a so-called BSF (Back Surface Field) effect can be obtained, and the collection efficiency of carriers generated in the p-type semiconductor substrate 103 can be increased. That is, among the minority carriers generated in the p-type silicon semiconductor substrate 103, the carriers directed to the back electrode are repelled in the surface direction by the p ⁺ layer 105 forming an internal electric field and serving as a barrier, and the photocurrent is generated at the surface electrode. As a result, photovoltaic power and photocurrent are increased and conversion efficiency is improved.

  For example, such a solar battery cell 101 is connected in series using a plurality of wirings, for example, and then sandwiched entirely from the light-receiving surface side and the back surface side by a light-transmitting substrate and a back sheet, respectively. A solar cell module is formed by fixing the periphery in the planar direction with a module frame.

  As described above, the aluminum electrode 108 in the solar battery cell 101 is formed by applying an aluminum-containing paste on the back surface of the p-type silicon semiconductor substrate 103 by screen printing and firing in an oxidizing atmosphere. ing. At this time, in order to obtain a desired BSF effect, it is necessary to apply a thick aluminum-containing paste and fire it.

  However, when the aluminum-containing paste is applied thickly, the aluminum electrode 108 becomes thicker. For this reason, when the silicon semiconductor substrate 102 is thinned to reduce the weight of the solar battery cell 101, the ratio of the thickness of the aluminum electrode 108 to the thickness of the silicon semiconductor substrate 102 increases.

  As a result, when cooled to room temperature after firing to form the aluminum electrode 108, internal stress is generated due to the difference in thermal expansion coefficient between aluminum or aluminum silicon alloy and silicon, and the silicon semiconductor substrate 102. Warpage occurs, and it becomes easy to break in a post-process or the like for manufacturing a solar cell module.

  In order to solve such a problem, several methods have been proposed. For example, a method has been proposed in which after a back electrode is formed on a silicon semiconductor substrate, the surface of the back electrode is partially etched in the thickness direction (see, for example, Patent Document 1). However, this method has a problem that the manufacturing process becomes complicated.

In addition, for example, a thin aluminum-containing paste is applied to the entire back surface of the silicon semiconductor substrate, and the aluminum-containing paste is applied again to the portion to be thickened, and then fired to form a back electrode with two or more thicknesses. Has been proposed (see, for example, Patent Document 2). Furthermore, a method has been proposed in which back electrodes are formed in a lattice pattern on the back surface of a silicon semiconductor substrate (see, for example, Patent Document 3). In addition, a method has been proposed in which backside electrodes are formed in stripes having different thicknesses on the backside of a silicon semiconductor substrate (see, for example, Patent Document 4). Furthermore, a method of forming a back electrode in a rectangular shape on the back surface of a silicon semiconductor substrate has been proposed (see, for example, Patent Document 5). However, by any of these methods, there is a problem that the formation of the p ⁺ layer that brings about the BSF effect becomes non-uniform and the conversion efficiency decreases.
JP 2002-353476 A JP 2002-217435 A JP 2002-141533 A JP 2002-141534 A JP 2002-141546 A

As described above, in the solar battery cell, there is a problem that, when the thickness of the silicon semiconductor substrate is generally reduced, warpage is likely to occur, and cracking is likely to occur in a subsequent process. In addition, various methods have been proposed to suppress the occurrence of warping that causes cracking. However, in any case, the manufacturing process becomes complicated, or the formation of the p ⁺ layer that brings about the BSF effect becomes uneven. Therefore, there is a problem that the conversion efficiency is not necessarily sufficient.

  The present invention has been made to solve the above-described problem, and even when a thin silicon semiconductor substrate is used, a solar battery cell capable of suppressing cracks in the silicon semiconductor substrate in a post-process and the like, and It aims at providing the manufacturing method.

  The solar battery cell of the present invention is a solar battery cell comprising a silicon semiconductor substrate and an aluminum electrode formed on the non-light-receiving surface side of the silicon semiconductor substrate, the aluminum electrode being non-light-receiving of the silicon semiconductor substrate. Conductivity formed from a conductive paste containing an aluminum sintered layer formed by applying and baking an aluminum-containing paste on the surface side, and conductive particles and an organic resin formed on the aluminum sintered layer. It consists of an organic resin layer.

The electrical resistivity of the conductive organic resin layer is preferably 1 × 10 ⁻⁵ Ω · cm or less, and a protective film is preferably further provided on the conductive organic resin layer.

  The conductive organic resin layer and the protective film are formed by laminating a sheet-like laminate in which the conductive organic resin layer is previously formed on the protective film on the aluminum sintered layer. It is preferable.

  The thickness of the silicon semiconductor substrate is preferably 200 μm or less, and the thickness of the aluminum sintered layer is preferably 20% or less of the thickness of the silicon semiconductor substrate.

  The manufacturing method of the photovoltaic cell of the present invention includes a step of forming an aluminum sintered layer by baking after applying an aluminum-containing paste on a silicon semiconductor substrate, and containing conductive particles and an organic resin on the protective film. And a step of laminating a sheet-like laminate on which the conductive organic resin layer made of the conductive paste is formed on the aluminum sintered layer.

  According to the solar cell of the present invention, the aluminum electrode formed on the silicon semiconductor substrate is made of an aluminum sintered layer formed by firing an aluminum-containing paste, and a conductive paste containing conductive particles and an organic resin. By comprising the conductive organic resin layer to be formed, the silicon semiconductor substrate can be strengthened by the conductive organic resin layer, and cracking of the silicon semiconductor substrate in a subsequent process or the like can be effectively suppressed. In addition, since the silicon semiconductor substrate can be reinforced by the conductive organic resin layer, a thinner silicon semiconductor substrate can be used, and the solar cell can be reduced in thickness and weight.

  Moreover, according to the manufacturing method of the photovoltaic cell of this invention, after apply | coating an aluminum containing paste on a silicon semiconductor substrate, the process of forming an aluminum sintered layer by baking, and electroconductive particle and organic on a protective film And a step of laminating a sheet-like laminate on which the conductive organic resin layer made of a conductive paste containing a resin is formed on the aluminum sintered layer, the crack of the silicon semiconductor substrate is suppressed. In addition, it is possible to easily manufacture a solar battery cell that can be reduced in thickness and weight.

Hereinafter, modes for carrying out the present invention will be described.
FIG. 1 is a cross-sectional view showing an example of a solar battery cell 1 of the present invention. As shown in FIG. 1, a silicon semiconductor substrate 2, n-type impurity layer 4 is formed on the light receiving surface of the p-type silicon semiconductor substrate 3, p ⁺ layer on the back side (non-light-receiving surface side) (or p ⁺⁺ layer ) 5 is formed. An antireflection film 6 and a grid electrode 7 are formed on the light receiving surface side of the silicon semiconductor substrate 2.

  On the other hand, an aluminum sintered layer 8 is formed on the back side of the silicon semiconductor substrate 2. The aluminum sintered layer 8 is an aluminum silicon mixed layer 9 and an aluminum layer 10 in this order from the silicon semiconductor substrate 2 side. A conductive organic resin layer 11 made of a conductive paste containing conductive particles and an organic resin is formed on the aluminum sintered layer 8. Here, what consists of the aluminum sintered layer 8 and this electroconductive organic resin layer 11 is the aluminum electrode 12 in this invention.

  In the solar cell 1 of the present invention, by providing such a conductive organic resin layer 11, the conductive organic resin layer 11 can be used as an electrode and used to reinforce the silicon semiconductor substrate 2. Can do. For this reason, even when an excessive stress is applied to the silicon semiconductor substrate 2 of the solar battery cell 1 in a post-process or the like for manufacturing the solar battery module, the crack of the silicon semiconductor substrate 2 can be suppressed.

  In particular, when the silicon semiconductor substrate 2 is thinned to a thickness of, for example, 200 μm or less in order to reduce the weight of the solar battery cell 1, a large warp is likely to occur in the silicon semiconductor substrate 2 when forming the aluminum sintered layer 8, Although it becomes easy to crack at a post-process etc., the crack in the silicon semiconductor substrate 2 at a post-process etc. can be effectively suppressed by providing such a conductive organic resin layer 11.

  In the solar cell 1 of the present invention, as shown in FIG. 2, it is preferable to further provide a protective film 13 made of an organic resin film on the conductive organic resin layer 11. By providing such a protective film 13, the silicon semiconductor substrate 2 can be further strengthened. For this reason, even when an excessive stress is applied to the silicon semiconductor substrate 2 of the solar cell 1 in a post-process or the like for manufacturing the solar cell module, the crack of the silicon semiconductor substrate 2 can be further effectively suppressed.

  In the solar battery cell 1 shown in FIG. 2, the protective film 13 is provided on the substantially entire surface of the conductive organic resin layer 11, but connection with other solar battery cells for manufacturing a solar battery module, etc. Therefore, a through hole penetrating in the thickness direction may be provided in a part of the protective film 13.

  The silicon semiconductor substrate 2 used in the present invention preferably has a thickness of 200 μm or less from the viewpoint of reducing the thickness and weight of the solar battery cell 1. When the silicon semiconductor substrate 2 is such a thin one, particularly when the aluminum sintered layer 8 is formed, a large warp is likely to occur, and the silicon semiconductor substrate 2 is liable to be cracked in a subsequent process or the like. However, by providing the conductive organic resin layer 11 and further the protective film 13 on such a material, it is possible to more effectively suppress cracks in the post-process and the like.

  Amorphous or crystalline silicon can be applied as the silicon semiconductor substrate 2, but it is preferable to use crystalline silicon. The crystalline silicon may be either single crystal or polycrystalline. A texture structure may be formed on the light receiving surface side of the silicon semiconductor substrate 2 in order to increase the power generation efficiency of the solar battery cell 1.

The thickness of the p ⁺ layer 5 in the silicon semiconductor substrate 2 is preferably 6 μm or more. When the thickness of the p ⁺ layer 5 is less than 6 μm, the BSF effect is remarkably lowered. The upper limit value of the thickness of the p ⁺ layer 5 is not necessarily limited as long as it does not cause a warp or the like generated in the silicon semiconductor substrate 2, but is preferably about 40 μm.

The surface resistance of the p ⁺ layer 5 is preferably 12Ω / □ or less. When the surface resistance of the p ⁺ layer 5 exceeds 12 Ω / □, the BSF effect is significantly reduced. The lower limit value of the surface resistance of the p ⁺ layer 5 is not necessarily limited, but about 1.0Ω / □ is sufficient.

The thickness of the aluminum sintered layer 8 formed on the back side of the silicon semiconductor substrate 2 is relative to the total thickness of the silicon semiconductor substrate 2 (p-type silicon semiconductor substrate 3, n-type impurity layer 4 and p ⁺ layer 5). And preferably 20% or less ((thickness of aluminum sintered layer 8 / thickness of silicon semiconductor substrate 2) × 100 ≦ 20 [%]).

  When the thickness of the aluminum sintered layer 8 exceeds the above thickness ratio, when the aluminum sintered layer 8 is formed on the back side of the silicon semiconductor substrate 2, a large warp occurs in the silicon semiconductor substrate 2, and the silicon semiconductor The substrate 2 is easily broken. In particular, when the thickness of the silicon semiconductor substrate 2 is as thin as 200 μm or less, this is remarkable. In the present invention, the thickness of the aluminum sintered layer 8 is set to 20% or less of the thickness of the silicon semiconductor substrate 2, so that even when the thickness of the silicon semiconductor substrate 2 is 200 μm or less, the occurrence of warpage is reduced. And can be made difficult to break.

  The conductive organic resin layer 11 formed on the aluminum sintered layer 8 is made of a conductive paste containing conductive particles and an organic resin. Specifically, it is formed by drying a conductive paste containing conductive particles and an organic resin, and fusing or curing by heating.

  The thickness of the conductive organic resin layer 11 is not necessarily limited. However, when the protective film 13 is not provided, the thickness is set to 10 μm or more from the viewpoint of effectively suppressing cracking of the silicon semiconductor substrate 2 in a subsequent process or the like. It is preferable. Moreover, it is preferable that the upper limit of thickness shall be 50 micrometers or less from a viewpoint of weight reduction or thickness reduction.

  Moreover, when providing the protective film 13, since the silicon semiconductor substrate 2 is mainly strengthened by the protective film 13 and the crack in a post process etc. is suppressed, the thickness of the conductive organic resin layer 11 is as described above. It may be thinner than that without the protective film 13 and may be 5 μm or more. Moreover, it is preferable that the upper limit of thickness shall be 30 micrometers or less from a viewpoint of weight reduction or thickness reduction.

The conductive organic resin layer 11 also serves as an electrode in addition to strengthening the silicon semiconductor substrate 2 or bonding the protective film 13 to the silicon semiconductor substrate 2 (aluminum sintered layer 8). Therefore, the electrical resistivity is preferably as small as possible, and is preferably 1 × 10 ⁻⁵ Ω · cm or less. In addition, from the viewpoint of thermal stability in post-processes such as wiring connection, the conductive organic resin layer 11 preferably has a glass transition temperature of 200 ° C. or higher.

  The organic resin constituting the conductive organic resin layer 11, that is, the organic resin constituting the conductive paste is at least one resin selected from a thermosetting resin and a thermoplastic resin. The thermosetting resin or thermoplastic resin is not necessarily limited, and a known thermosetting resin or thermoplastic resin is used.

  Examples of specific thermosetting resins and thermoplastic resins include, for example, epoxy resins, phenoxy resins, phenol resins, urethane resins, polyimide resins, polyvinyl butyral, polyvinyl acetal, polyvinyl formal, polyamide, polyacetal, polycarbonate, modified polyphenylene oxide. , Polybutylene terephthalate, reinforced polyethylene terephthalate, polyarylate, polysulfone, polyethersulfone, polyetherimide, polyamideimide, polyphenylene sulfide, polyether ketone and the like. These resins may be used alone or in combination of two or more.

  Examples of the conductive particles include metal powders such as silver powder, copper powder, nickel powder, and aluminum powder. Among these, aluminum powder is preferable because it is excellent in lightness and corrosion resistance and has good electrical conductivity. Moreover, it is preferable that content of electroconductive particle is 70 weight% or more in the whole electroconductive organic resin layer 11. FIG. If the content of the conductive particles in the conductive organic resin layer 11 is less than the above content, the electrical resistivity of the conductive organic resin layer 11 may not be as described above, which is not preferable.

  Moreover, the protective film 13 should just be a well-known organic resin film, for example, a polyimide film, a polyethylene film, a polyethylene terephthalate film, a polypropylene film, a polyvinyl chloride film etc. are mentioned. Among these, a polyimide film is preferable from the viewpoint of heat resistance.

  Although the thickness of the protective film 13 is not necessarily limited, It is preferable to set it as 10 micrometers or more from a viewpoint of suppressing the crack of the silicon semiconductor substrate 2 in a post process etc. more effectively. Moreover, it is preferable that the thickness of the protective film 13 shall be 50 micrometers or less from a viewpoint of suppressing the increase in the thickness and weight of the photovoltaic cell 1 whole.

  Next, the manufacturing method of the photovoltaic cell 1 of this invention is demonstrated. First, a single crystal silicon substrate manufactured by a pulling method or a polycrystalline silicon substrate manufactured by a casting method is prepared. As such a single crystal silicon substrate or a polycrystalline silicon substrate, a substrate having a thickness of 200 μm or less as described above is preferably used. When the silicon substrate is p-type, an n-type impurity layer 4 for forming a pn junction is formed on the p-type silicon substrate 3.

  Further, an aluminum-containing paste layer is formed by applying an aluminum-containing paste on the entire back surface side (p-type silicon substrate 3 side) of the p-type silicon substrate 3 on which the n-type impurity layer 4 is formed by using a screen printing method. Form.

At this time, the aluminum-containing paste layer is formed as thin as possible within a range in which the p ⁺ layer 5 having a predetermined BSF effect can be formed in order to suppress warpage in the p-type silicon substrate 3 and the like generated by firing described later. It is preferable to do. Specifically, as described above, the aluminum sintered layer 8 with respect to the total thickness of the finally obtained silicon semiconductor substrate 2 (p-type silicon semiconductor substrate 3, n-type impurity layer 4 and p ⁺ layer 5). It is preferable to adjust the thickness of the aluminum-containing paste layer so that the thickness of the aluminum-containing paste layer is 20% or less.

  The composition of the aluminum-containing paste is not necessarily limited, but includes at least aluminum powder, and additionally contains glass frit, organic vehicle, and the like. As the aluminum powder, those having an average particle diameter of 2 to 20 μm are suitably used, and commercially available atomized powder is suitably used as such an aluminum powder.

  On the other hand, on the light-receiving surface side of the p-type silicon substrate 3, a silver paste is printed and dried using a screen printing method to form a silver paste layer.

Thereafter, the silver paste layer and the aluminum paste layer formed on each of the light receiving surface side and the back surface side are baked together. By this firing, aluminum in the aluminum-containing paste layer is diffused as impurities into the p-type silicon substrate 3, and a p ⁺ layer 5 containing high-concentration impurities is formed on the back side of the p-type silicon substrate 3. Moreover, the aluminum paste layer on the back side becomes an aluminum sintered layer 8 (aluminum silicon mixed layer 9 and aluminum layer 10).

The firing temperature is preferably 600 ° C. or higher and 850 ° C. or lower, and more preferably 650 ° C. or higher and 800 ° C. or lower. If the firing temperature is less than 600 ° C., the p ⁺ layer 5 that brings about the BSF effect may not be sufficiently formed. In particular, when the aluminum-containing paste layer is formed thin in order to suppress warping in the p-type silicon substrate 3 and the like that occurs during firing, the formation of the p ⁺ layer 5 tends to be insufficient. When the firing temperature exceeds 850 ° C., the difference in thermal expansion coefficient between aluminum and silicon becomes remarkably large, and the warp in the p-type silicon substrate 3 after firing tends to be large. In such firing, the firing temperature, by adjusting the atmosphere during thickness and firing the aluminum-containing paste layer or the like, for example, with the thickness of the p ⁺ layer 5 can be more than 6 [mu] m, the p ⁺ layer 5 The surface resistance can be 12 Ω / □ or less.

  Then, on the silicon semiconductor substrate 2 on which the aluminum sintered layer 8 is formed, the conductive organic resin layer 11 or the conductive organic resin layer 11 and the protective film 13 are formed on the aluminum sintered layer 8.

  When the conductive organic resin layer 11 is provided alone, for example, a conductive paste containing conductive particles and an organic resin is applied to substantially the entire surface of the aluminum sintered layer 8, dried, and then heated. Then, the conductive organic resin layer 11 can be provided on the aluminum sintered layer 8 by fusing or curing.

  Moreover, when providing the conductive organic resin layer 11 and the protective film 13, it can carry out as follows. First, as shown in FIG. 3, the conductive organic resin layer 11 is formed on the protective film 13 by applying a conductive paste containing conductive particles and an organic resin in advance on the protective film 13 and drying it. The formed sheet-like laminate 20 is manufactured.

  Thereafter, the sheet-like laminate 20 is placed on the aluminum sintered layer 8 of the silicon semiconductor substrate 2 on which the aluminum sintered layer 8 is formed so that the conductive organic resin layer 11 side is the aluminum sintered layer 8 side. Place in contact. Furthermore, the conductive organic resin layer 11 is fused or cured by heating them, and the protective film 13 is fixed on the aluminum sintered layer 8.

  When providing the through-hole of the thickness direction in the protective film 13, the sheet-like laminated body 20 is manufactured, for example using the protective film 13 by which the through-hole was previously provided, and this was sintered aluminum layer 8 as mentioned above. It is fixed on the silicon semiconductor substrate 2 on which is formed.

  Further, for example, the sheet-like laminate 20 is manufactured using the protective film 13 having no through-hole, and fixed on the silicon semiconductor substrate 2 on which the aluminum sintered layer 8 is formed as described above, and then on the surface. You may form a through-hole by removing a part of exposed protective film 13 using a commercially available laser processing machine.

  The conductive paste used to form the conductive organic resin layer 11 is one in which conductive particles are contained in at least one of a thermosetting resin and a thermoplastic resin. The conductive paste can contain a curing agent, a curing accelerator, a solvent, and other additives.

  The thermosetting resin and the thermoplastic resin are not necessarily limited, and known thermosetting resins or thermoplastic resins can be used.

  Examples of specific thermosetting resins and thermoplastic resins include, for example, epoxy resins, phenoxy resins, phenol resins, urethane resins, polyimide resins, polyvinyl butyral, polyvinyl acetal, polyvinyl formal, polyamide, polyacetal, polycarbonate, modified polyphenylene oxide. , Polybutylene terephthalate, reinforced polyethylene terephthalate, polyarylate, polysulfone, polyethersulfone, polyetherimide, polyamideimide, polyphenylene sulfide, polyether ketone and the like. These resins may be used alone or in combination of two or more.

  Examples of the conductive particles include metal powders such as silver powder, copper powder, nickel powder, and aluminum powder. Among these, aluminum powder is preferable because it is excellent in lightness and corrosion resistance and has good electrical conductivity.

The conductive paste containing the conductive particles and the organic resin is such that the electrical resistivity of the conductive organic resin layer 11 after being fused or cured by heating is 1 × 10 ⁻⁵ Ω · cm or less. It is preferably adjusted. Further, the conductive paste containing conductive particles and organic resin is adjusted so that the glass transition temperature of the conductive organic resin layer 11 after being fused or cured by heating is 200 ° C. or higher. Is preferred.

  In order to set the electrical resistivity of the conductive organic resin layer 11 within the above range, for example, the content of the conductive particles in the conductive organic resin layer 11 after being fused or cured by heating is 70% by weight or more. Thus, the composition of the conductive paste is adjusted. Further, in order to set the glass transition temperature of the conductive organic resin layer 11 after being fused or cured by heating to 200 ° C. or higher, for example, an organic resin having a glass transition temperature after curing of 200 ° C. or higher is selected. This can be done.

  Hereinafter, the present invention will be described in more detail with reference to examples.

(Examples 1-4)
First, a p-type silicon substrate 3 having an n-type impurity layer 4 formed on the light receiving surface side was prepared by a known method. The p-type silicon substrate 3 on which the n-type impurity layer 4 is formed on the light receiving surface side has a size of 5 inches (127 mm) × 5 inches (127 mm) and a thickness as shown in Table 1. It is what has.

  Then, an aluminum-containing paste is applied to the back side of the p-type silicon substrate 3 using a 180-mesh screen printing plate, dried and then fired, and the aluminum sintered layer 8 (aluminum) is applied to the back side of the p-type silicon substrate 3. A silicon mixed layer 9 and an aluminum layer 10) were formed.

Here, as the aluminum-containing paste, one containing 60 to 75% by mass of aluminum powder, 0.3 to 5.0% by mass of glass frit, and 20 to 30% by mass of organic vehicle was used. Specifically, aluminum powder and B ₂ O ₃ —SiO ₂ —PbO glass frit are added to an organic vehicle in which ethyl cellulose is dissolved in a glycol ether organic solvent, and the mixture is mixed with a known mixer to contain aluminum. It is a paste. The thickness for applying the aluminum-containing paste was adjusted so that the thickness of the aluminum sintered layer 8 obtained by firing was as shown in Table 1. Firing was performed in an infrared firing furnace under the conditions of heating at a temperature rising rate of 400 ° C./min and holding at a temperature of 710 to 720 ° C. for 30 seconds.

  Thus, about the p-type silicon substrate in which the aluminum sintered layer 8 was formed, the cross section was actually observed with the optical microscope, and the thickness of the aluminum sintered layer 8 was measured ten places. The average value of the thickness of the aluminum sintered layer 8 is shown in the column “Thickness of the aluminum sintered layer” in Table 1.

Further, for the p-type silicon substrate 3 on which the aluminum sintered layer 8 was formed, the surface resistance of the p ⁺ layer 5 was measured. First, the aluminum sintered layer 8 was dissolved and removed by immersing the p-type silicon substrate 3 on which the aluminum sintered layer 8 was formed in an aqueous hydrochloric acid solution. Then, the surface resistance of the p-type silicon substrate 3 on which the p ⁺ layer 5 was formed was measured using a four-terminal surface resistance measuring instrument (RG-5 type sheet resistance measuring instrument manufactured by Napson). The measurement conditions were a voltage of 40 mV, a current of 1 mA, and a load applied to the surface of 200 gf (1.96 N). The measured values of the surface resistance are shown in the “Surface resistance” column of Table 1.

  Next, a polyimide film having a size substantially the same as that of the p-type silicon substrate 3 and a thickness of 25 μm was prepared as the protective film 13. A conductive paste containing conductive particles and an organic resin is applied on one main surface of the protective film 13 and dried to form the conductive organic resin layer 11 on the protective film 13 as shown in FIG. A sheet-like laminate 20 was obtained.

In addition, as a conductive paste containing conductive particles and an organic resin, the aluminum powder is in the range of 80 to 95% by mass, the imide-modified epoxy resin composition is in the range of 5 to 15% by mass, and the solvent is in the range of 5 to 10% by mass. What was blended and mixed in was used. This conductive paste has an electrical resistivity after curing of 9 × 10 ⁻⁶ Ω · cm and a glass transition temperature of 210 ° C. (DMA method). The thickness of the conductive paste applied was adjusted so that the thickness after adhering onto the aluminum sintered layer 8 of the p-type silicon substrate 3 was 20 μm.

  And on the aluminum sintered layer 8 of the p-type silicon substrate 3 which has the aluminum sintered layer 8 manufactured as mentioned above, the sheet-like laminated body 20 the conductive organic resin layer 11 side is the aluminum sintered layer 8 Arranged to be on the side. Furthermore, these were heat-processed at 170 degreeC, and the photovoltaic cell 1 by which the electroconductive organic resin layer 11 and the protective film 13 were provided in order on the aluminum sintered layer 8 as shown in FIG. 2 was manufactured.

(Examples 3 and 4)
In the same manner as in Examples 1 and 2, the p-type silicon substrate 3 on which the aluminum sintered layer 8 was formed was manufactured, and the thickness of the aluminum sintered layer 8 and the surface resistance of the p ⁺ layer 5 were measured. . Further, the same conductive particles and organic resin as those used in Examples 1 and 2 are applied to the entire surface of the aluminum sintered layer 8 of the p-type silicon substrate 3 having the aluminum sintered layer 8 manufactured in the same manner. The conductive paste contained was applied and cured by heat treatment at 170 ° C. to produce a solar battery cell 1 in which the conductive organic resin layer 11 was formed on the aluminum sintered layer 8 as shown in FIG.

(Comparative Examples 1-5)
Aluminum was used in the same manner as in the above example, except that a p-type silicon substrate having a thickness as shown in Table 1 was used and the thickness of the aluminum sintered layer was as shown in Table 1. A p-type silicon substrate having a sintered layer was manufactured and used as a solar battery cell. And about this solar cell, each measurement of the thickness of an aluminum sintered layer and the surface resistance of a p ⁺ layer was performed. In addition, the photovoltaic cell manufactured here does not provide either the conductive organic resin layer or the protective film as provided in the examples.

  Next, the measurement of the amount of warpage and the ease of cracking were evaluated for the solar cells of the examples and comparative examples.

  For example, as shown in FIG. 4, the conductive organic resin layer 11 (Examples 3 and 4) or the protective film 13 (Examples 1 and 2) is exposed for the solar battery cell 1 of the example. With one side facing up, one end of the four corners of the solar battery cell 1 was pressed as indicated by an arrow, and the amount of lift x (including the thickness of the substrate) at one end located at the opposite corner was measured. Moreover, about the photovoltaic cell of the comparative example in which such a conductive organic resin layer and a protective film are not formed, it measured similarly by making the side which the aluminum sintered layer has exposed upwards. The measurement results are shown in the “warp” column of Table 1.

  Moreover, the evaluation of the ease of cracking was performed as follows. That is, 20 solar cells were used to make electrical connections and the like to manufacture a solar cell module, and the number of solar cells that were cracked in the manufacturing process was measured. The results are shown in the “crack” column of Table 1. In Table 1, “◯” indicates that no cracks occurred, “Δ” indicates that cracks occurred 3 or less, and “×” indicates that cracks exceeded 5 It shows that.

As is clear from Table 1, it was confirmed that the solar cells of the comparative example were more likely to crack as a whole. In Comparative Example 1, although the generation of cracks was suppressed because the thickness of the aluminum sintered layer was thin, it was recognized that the surface resistance of the p ⁺ layer was high and not practical. .

  On the other hand, it was recognized that the solar cell 1 of the example provided with the conductive organic resin layer 11 is less likely to crack. In particular, it was confirmed that the occurrence of cracking was suppressed in the solar cells 1 of Examples 1 and 2 in which the protective film 13 was provided together with the conductive organic resin layer 11.

Sectional drawing which shows an example of the photovoltaic cell of this invention. Sectional drawing which shows the other example of the photovoltaic cell of this invention. The figure which shows an example of the manufacturing method of the photovoltaic cell of this invention. The figure which showed typically the measuring method of curvature amount. Sectional drawing which shows an example of the conventional photovoltaic cell.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Solar cell, 2 ... Silicon semiconductor substrate, 3 ... p-type silicon semiconductor substrate, 4 ... n-type impurity layer, 5 ... p ⁺ layer, 6 ... Antireflection film, 7 ... Grid electrode, 8 ... Sintered aluminum layer , 9 ... Aluminum silicon mixed layer, 10 ... Aluminum layer, 11 ... Conductive organic resin layer, 12 ... Aluminum electrode, 13 ... Protective film

Claims (5)

A solar cell comprising a silicon semiconductor substrate and an aluminum electrode formed on the non-light-receiving surface side of the silicon semiconductor substrate,
The aluminum electrode includes an aluminum sintered layer formed by applying and baking an aluminum-containing paste on the non-light-receiving surface side of the silicon semiconductor substrate, and conductive particles and an organic resin formed on the aluminum sintered layer. And a conductive organic resin layer formed from a conductive paste containing a solar cell. The electrical conductivity of the conductive organic resin layer is 1 × 10 ⁻⁵ Ω · cm or less, and a protective film is further provided on the conductive organic resin layer. Solar cell.   The conductive organic resin layer and the protective film are formed by laminating a sheet-like laminate in which the conductive organic resin layer is previously formed on the protective film on the aluminum sintered layer. The solar battery cell according to claim 2.   The thickness of the said silicon semiconductor substrate is 200 micrometers or less, The thickness of the said aluminum sintered layer is 20% or less of the thickness of the said silicon semiconductor substrate, The any one of Claim 1 thru | or 3 characterized by the above-mentioned. Solar cells. Applying an aluminum-containing paste on a silicon semiconductor substrate and then baking to form an aluminum sintered layer;
And laminating a sheet-like laminate in which a conductive organic resin layer made of a conductive paste containing conductive particles and an organic resin is formed on a protective film on the aluminum sintered layer. The manufacturing method of the photovoltaic cell.

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