JP2019079916A - Back-contact type solar battery module - Google Patents

Abstract

To provide a solar battery module of a back-contact type solar battery, which can ensure both of a conversion performance of photoelectric conversion in a solar battery module and UV light durability.SOLUTION: A solar battery module 20 comprises an intrinsic semiconductor layer 12U formed by a hydrogenated amorphous silicon-based film layer, a low-reflection layer 16 composed of an insulative layer, and a light-receiving side sealant 21U which are disposed on one another on the side of a light-receiving face 11SU of a semiconductor substrate 11. The amount of a UV absorber to be added to a mass of the light-receiving side sealant 21U is less than 0.010 mass%. The hydrogenated amorphous silicon layer has a thickness Ta of 15 nm or more and 50 nm or less.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a back contact solar cell module.

  A common solar cell is a double-sided electrode type in which electrodes are disposed on both sides (light receiving side and back side) of a semiconductor substrate, but as disclosed in Patent Document 1 as a solar cell without shielding loss due to electrodes these days. A back contact (back electrode) type solar cell in which an electrode is disposed only on the back surface has been developed.

  Further, in practical use, the solar cell is disposed between the light receiving side protection member and the back side protection member and sealed with a sealing material disposed between the both protection members and the solar cell, It is considered as a battery module. In this module, a UV absorber is usually added to the encapsulant.

  If such an ultraviolet absorber is not added, the sealing material is deteriorated or damaged under the influence of ultraviolet light, and various members included in the solar cell are also affected by moisture or the like that infiltrates from ultraviolet light or cracks of the sealing material. As a result, the performance of the solar cell module is degraded.

International Publication 2015-060432

  However, although the ultraviolet light durability of the solar cell module is improved when the ultraviolet light absorber is added to the sealing material, the amount of light received by the solar cell is decreased due to the ultraviolet light absorber, and photoelectric conversion in the solar cell module Conversion efficiency declines.

  The present invention has been made to solve the above-mentioned problems. And the objective is to provide the solar cell module which secured simultaneously the conversion performance and the ultraviolet light durability of the photoelectric conversion in a solar cell module.

  In a back contact type solar cell module in which a back contact type solar cell in which different types of electrode layers are disposed on one side of a main surface of a semiconductor substrate according to the present invention is sealed with a sealing material The hydrogenated amorphous silicon-based thin film layer, the insulating layer, and the light-receiving side sealing material are disposed so as to overlap with each other on the light-receiving surface side which is the main surface on the side. The ultraviolet absorber added is less than 0.010% by mass, and the thickness Ta of the hydrogenated amorphous silicon layer is 15 nm or more and 50 nm or less.

  According to the back contact type solar cell module of the present invention, the conversion performance of photoelectric conversion and the ultraviolet light durability are simultaneously secured.

These are sectional drawings of a back contact type solar cell module. These are top views which show the back surface side of a back contact type solar cell. These are typical sectional drawings of a back contact type solar cell module. These are typical top views of a back contact type solar cell module. These are graphs which show the photoelectric conversion characteristic and ultraviolet-ray durability of a solar cell module of sample A. These are graphs which show the photoelectric conversion characteristic and ultraviolet-ray durability of a solar cell module of sample B. These are graphs which show the photoelectric conversion characteristic and ultraviolet-ray durability of a solar cell module of sample C. These are graphs which show the photoelectric conversion characteristic and ultraviolet-ray durability of a solar cell module of sample D.

  One embodiment of the present invention will be described as follows, but the present invention is not limited thereto. In addition, although hatching, a member code | symbol, etc. may be abbreviate | omitted for convenience, in this case, another drawing shall be referred. Also, the dimensions of the various members in the drawings have been adjusted for the sake of convenience.

  3 and 4 show a back contact type solar cell module 20 in which a back contact type solar cell 10 in which different types of electrode layers are disposed on one side of the main surface of a semiconductor substrate is sealed with a sealing material 21. FIG. In detail, the solar cell module 20 includes at least a sealing material 21 (light receiving side sealing material 21U, back side sealing material 21B), a light receiving side protective member 22, a back side protective member 23, and a back contact type solar cell Including ten.

  In FIGS. 3 and 4, a solar cell module 20 in which a plurality of solar cells 10 are electrically connected by a wiring member 25 for connection is illustrated. And, an assembly of the electrically connected solar cells 10 as shown in these figures may be referred to as a solar cell string.

  Further, the solar cell 10 includes a front surface and a back surface, and in the present specification, the front surface side is referred to as a front side, and the back surface side opposite to the front side is referred to as a back surface. Then, for convenience, the front side will be described as a side (light receiving side) that is to receive light more positively than the back side, and the back side not actively receiving light will be described as a non-light receiving side.

  Therefore, as shown in FIG. 3, the solar cell module 20 includes the solar cell 10, and the light receiving side sealing member 21U and the light receiving side protective member 22 in this order on the light receiving side with reference to the solar cell 10. On the other side opposite to the light receiving side, the rear side sealing member 21B and the rear side protection member 23 are arranged in this order in an overlapping manner.

  The sealing material 21 seals and protects the solar cell 10, and between the surface on the light receiving side of the solar cell 10 and the light receiving side protection member 22, and the surface on the back side of the solar cell 10 and the back side protection member It intervenes between 23 and Hereinafter, the sealing material 21 covering the light receiving side of the solar cell 10 may be referred to as a light receiving side sealing material 21U, and the sealing material 21 covering the rear side of the solar cell 10 may be referred to as a rear side sealing material 21B.

  The shapes of the light-receiving side sealing material 21U and the back side sealing material 21B are not particularly limited, and examples thereof include a sheet shape. If it is a sheet form, it is because it is easy to coat the surface and the back of a planar solar cell 10.

  Although it does not specifically limit as a material of the sealing material 21, It is preferable if it has the characteristic (light transmission) which permeate | transmits light. Moreover, it is preferable that the material of the sealing material 21 has adhesiveness for bonding the solar cell 10, the light receiving side protection member 22 and the back side protection member 23.

  Such materials include, for example, ethylene / vinyl acetate copolymer (EVA), ethylene / α-olefin copolymer, ethylene / vinyl acetate / triallyisocyanurate (Evat), polyvinyl butyrate (PVB), acrylic Examples of the resin include translucent resins such as resins, urethane resins, and silicone resins. The material of the light receiving side sealing material 21U and the material of the back side sealing material 21B may be the same or different.

  In addition, it is preferable that the light receiving side sealing material 21U include a wavelength conversion agent that converts ultraviolet light and emits visible light. When such a wavelength conversion agent is contained, the ultraviolet light which did not contribute to the power generation of the solar cell 10 is converted into visible light which contributes to the power generation, so the power generation amount of the solar cell 10 and hence the solar cell module 20 Increases.

  The material of the wavelength conversion agent is not particularly limited, and examples thereof include metal complexes containing rare earth elements having fluorescence of visible light, organic dyes, inorganic phosphors, and the like. In addition, such a wavelength conversion agent is disperse | distributed to resin used as the material of the sealing material 21, and the sealing material 21 to which the wavelength conversion agent was disperse | distributed is obtained by shape | molding the resin in a sheet form etc. .

  The light receiving side protection member 22 covers the surface (light receiving surface) of the solar cell 10 via the light receiving side sealing material 21U to protect the solar cell 10. The shape of the light-receiving side protective member 22 is not particularly limited, but is preferably plate-like or sheet-like from the viewpoint of indirectly covering the planar light-receiving surface.

  The material of the light receiving side protection member 22 is not particularly limited, but like the sealing material 21, a material having translucency and resistance to ultraviolet light is preferable, for example, glass or Transparent resin such as acrylic resin or polycarbonate resin can be mentioned. In addition, the surface of the light receiving side protective member 22 may be processed to be uneven, or may be covered with an anti-reflection coating layer. Under these conditions, it is difficult for the light receiving side protection member 22 to reflect the received light and to guide more light to the solar cell 10.

  The back side protection member 23 covers the back side of the solar cell 10 via the back side sealing material 21 B to protect the solar cell 10. The shape of the back side protection member 23 is not particularly limited, but in the same manner as the light receiving side protection member 22, a plate or sheet is preferable from the viewpoint of indirectly covering the planar back surface.

  Although it does not specifically limit as a material of the back side protection member 23, A material (high water impermeability) which prevents penetration of water etc. is preferable. For example, the laminated body of resin films, such as a polyethylene terephthalate (PET), polyethylene (PE), an olefin resin, a fluorine-containing resin, or a silicone resin, and metal foil, such as aluminum foil, is mentioned.

  A solar cell module 20 including a plurality of solar cells 10 as shown in FIGS. 3 and 4 includes a wiring member 25 for connection (hereinafter also referred to as connection wiring 25). The connection wiring 25 is used for the connection of the electrodes in the adjacent solar cells 10, the connection of the solar cell strings, or the connection with the extraction wiring from the solar cell string to the external device.

  In the back side electrode type solar cell 10 as shown in FIG. 3 and FIG. 4, the connection wiring 25 is bridged across the back sides of the solar cell 10 and is bonded to the back side with a solder or a conductive adhesive. Specifically, the connection wiring 25 is connected to a bus bar portion (described later) in the electrode layer of the solar cell 10.

  Although the material of the connection wiring 25 is not particularly limited, metals such as copper, aluminum, silver, gold, or an alloy containing these may be mentioned. In addition, a metal with a covering layer in which a conductive layer such as gold, silver, tin, or solder is coated on the surface of a metal such as copper, aluminum, silver, gold, or an alloy containing these is the material of the connection wiring 25. It does not matter.

  In addition, the manufacturing method of the solar cell module 20 is not specifically limited. For example, the back side protection member 23, the back side sealing member 21B, the solar cell 10 (solar cell string), the light receiving side sealing member 21U, and the light receiving side protection member 22 are stacked in this order, and It may be sealed by heating and pressurizing at a predetermined temperature and pressure.

  The solar cell 10 will be described in detail below. The schematic cross-sectional view of FIG. 1 represents a solar cell 10 using a semiconductor substrate 11 made of silicon. The solar cell 10 is a so-called heterojunction crystalline silicon solar cell, and is a back contact type (back electrode type) solar cell 10 in which the electrode layer 17 is disposed only on the back surface of the solar cell 10.

  The solar cell 10 includes a semiconductor substrate 11, an intrinsic semiconductor layer 12 (12U, 12p, 12n), a conductive semiconductor layer 13 (p-type semiconductor layer 13p, an n-type semiconductor layer 13n), a low reflection layer 16, and an electrode layer 17 (Transparent electrode layer 18, metal electrode layer 19) is included.

  In the following, for convenience, “p” / “n” may be added to the end of the member numbers for members individually associated with the p-type semiconductor layer 13p or the n-type semiconductor layer 13n. Further, as in p-type and n-type, in different types of conductivity types, one conductivity type may be referred to as “first conductivity type”, and the other conductivity type may be referred to as “second conductivity type”.

  The semiconductor substrate 11 may be a substrate formed of single crystal silicon or a substrate formed of polycrystalline silicon. Hereinafter, a single crystal silicon substrate will be described as an example.

  The conductivity type of the semiconductor substrate 11 is such that holes are introduced to silicon atoms even in an n-type single crystal silicon substrate containing an impurity (for example, phosphorus atom) for introducing electrons to silicon atoms. Although it may be a p-type single crystal silicon substrate having an impurity (for example, boron atom), hereinafter, an n-type semiconductor substrate 11 which is said to have a long carrier life will be described as an example.

  Further, from the viewpoint of closing the received light, the semiconductor substrate 11 has peaks (convex) and valleys (convex) on at least the light receiving side (light receiving surface 11SU side) of the surfaces of the two main surfaces 11S (11SU, 11SB). Preferably, there is a texture structure formed by The texture structure (concave and convex surface) is formed, for example, by anisotropic etching applying the difference between the etching rate of the (100) plane and the etching rate of the (111) plane in the semiconductor substrate 11.

  Further, the thickness of the semiconductor substrate 11 is preferably 250 μm or less. The measurement direction in the case of measuring the thickness is perpendicular to the average surface of the semiconductor substrate 11 (the average surface means the surface of the entire substrate independent of the texture structure). Therefore, hereinafter, the vertical direction, that is, the direction in which the thickness is measured is referred to as the thickness direction.

  When the thickness of the semiconductor substrate 11 is 250 μm or less, the amount of silicon used is reduced, so that the silicon substrate can be easily secured, and cost reduction can also be achieved. In addition, a back contact structure in which holes and electrons generated by photoexcitation in the silicon substrate are recovered only on the back surface side is preferable from the viewpoint of free travel of each exciton.

  On the other hand, if the thickness of the semiconductor substrate 11 is excessively small, mechanical strength may be reduced, external light (sunlight) may not be sufficiently absorbed, and the short circuit current density may be reduced. Therefore, the thickness of the semiconductor substrate 11 is preferably 50 μm or more, and more preferably 70 μm or more. When the texture structure is formed on the main surface 11S of the semiconductor substrate 11, the thickness of the semiconductor substrate 11 is represented by the maximum distance between the straight lines connecting the apexes of the projections on the light receiving side and the back side. Be done.

  The intrinsic semiconductor layer 12 (12U, 12p, 12n) covers both main surfaces 11S (11SU, 11SB) of the semiconductor substrate 11 to perform surface passivation while suppressing impurity diffusion into the semiconductor substrate 11. Note that the term "intrinsic (i-type)" is not limited to completely intrinsic ones that do not contain a conductive impurity, and a very small amount of n-type impurities or p-types can be used as long as the silicon-based layer can function as an intrinsic layer. Also included are "weak n-type" or "weak p-type" substantially intrinsic layers that contain impurities.

  The material of the intrinsic semiconductor layer 12 is not particularly limited, but is preferably an amorphous silicon-based thin film, and more preferably a hydrogenated amorphous silicon-based thin film layer containing silicon and hydrogen.

  The method for forming the intrinsic semiconductor layer 12 is not particularly limited, but is preferably the plasma CVD (Chemical Vapor Deposition) method.

  When these thin films are deposited by CVD on a semiconductor substrate 11 formed of single crystal silicon, passivation of the substrate surface can be effectively performed while suppressing diffusion of impurities into single crystal silicon. Further, in the plasma CVD method, by changing the hydrogen concentration in the film of the intrinsic semiconductor layer 12 in the film thickness direction, it is possible to form an energy gap profile that is effective for carrier recovery.

As conditions for forming a thin film by plasma CVD, for example, a substrate temperature of 100 ° C. to 300 ° C., a pressure of 20 Pa to 2600 Pa, and a high frequency power density of 0.003 W / cm ^{2 to} 0.5 W / cm ² are preferable. is there.

In the case of a hydrogenated amorphous silicon-based thin film, as a source gas used for forming a thin film, a silicon-containing gas such as SiH ₄ or Si ₂ H ₆ or a mixture of these gases and H ₂ Is preferred.

  Examples of the conductive semiconductor layer 13 include a p-type semiconductor layer 13p and an n-type semiconductor layer 13n. As shown in FIG. 1, the p-type semiconductor layer 13p is formed on a part of the back surface 11SB side of the semiconductor substrate 11 via the intrinsic semiconductor layer 12p, and the n-type semiconductor layer 13n is the back surface 11SB of the semiconductor substrate 11. It is formed on the other part of the side via the intrinsic semiconductor layer 12n. That is, between the p-type semiconductor layer 13 p and the n-type semiconductor layer 13 n and the semiconductor substrate 11, the intrinsic semiconductor layers 12 p and 12 n are interposed as intermediate layers. The manufacturing method of the conductive semiconductor layer 13 is not particularly limited, but like the intrinsic semiconductor layer 12, it is preferable to use the plasma CVD method.

  The p-type semiconductor layer 13p and the n-type semiconductor layer 13n are formed in a comb shape on the back surface 11SB side of the semiconductor substrate 11 as shown in the plan view of FIG. 2 (the electrode layer 17 is omitted for convenience).

  Describing in detail, the p-type semiconductor layer 13p includes a comb back E13p and a plurality of comb teeth T13p arranged in parallel while intersecting the comb back E13p. The n-type semiconductor layer 13n includes a comb back E13n and a plurality of comb teeth T13n arranged in parallel while crossing the comb back E13n. The comb teeth T13p and the comb teeth T13n are alternately arranged. The p-type semiconductor layer 13p and the n-type semiconductor layer 13n are disposed so as to be electrically separated.

  The p-type semiconductor layer 13p is a silicon layer to which p-type dopant (such as boron) is added, and is formed on the intrinsic semiconductor layer 13p. For example, a p-type hydrogenated amorphous silicon layer, a p-type amorphous silicon carbide layer, or a p-type amorphous silicon oxide layer can be mentioned. The p-type semiconductor layer 13p is preferably formed of amorphous silicon from the viewpoint of suppression of impurity diffusion or reduction in series resistance. In addition, since the p-type amorphous silicon carbide layer and the p-type amorphous silicon oxide layer are wide gap low refractive index layers, they are preferable in that optical loss can be reduced.

  The n-type semiconductor layer 13n is a silicon layer to which n-type dopant (such as phosphorus) is added, and is formed on the intrinsic semiconductor layer 13n. The n-type semiconductor layer 13n is also preferably formed of an amorphous silicon layer, similarly to the p-type semiconductor layer 13p.

  The low reflective layer [insulating layer] 16 is formed on the intrinsic semiconductor layer 12U on the light receiving side, and suppresses the reflection of the light received by the solar cell 10. The material of the low reflection layer 16 is not particularly limited as long as it is a light transmitting material that transmits light and is an insulating material, and examples thereof include silicon oxide and silicon nitride. The method of producing the low reflective layer 16 is not particularly limited, but like the intrinsic semiconductor layer 12, the plasma CVD method is preferable.

  The electrode layer 17 is formed so as to cover the p-type semiconductor layer 13p or the n-type semiconductor layer 13n, and is electrically connected to the semiconductor layers 13p and 13n. Thus, the electrode layer 17 functions as a transport layer which leads carriers generated in the p-type semiconductor layer 13p or the n-type semiconductor layer 13n.

  The electrode layer 17 may be formed of only a metal having high conductivity, but the viewpoint of electrical connection with the p-type semiconductor layer 13p and the n-type semiconductor layer 13n, or both of the metals that are electrode materials. From the viewpoint of suppressing atomic diffusion into the semiconductor layers 13p and 13n, an electrode layer formed of a transparent conductive oxide is provided between the metal electrode layer and the p-type semiconductor layer 13p and the n-type semiconductor layer 13n. Preferred.

  In the present specification, an electrode layer formed of a transparent conductive oxide is referred to as a transparent electrode layer 18, and a metal electrode layer is referred to as a metal electrode layer 19. Further, in the p-type semiconductor layer 13p and the n-type semiconductor layer 13n, the electrode layer 17 formed on the comb backs E13p and E13n is a bus bar portion, and the electrode layer 17 formed on the comb teeth T13p and T13n is a finger portion, It may be called (see FIG. 2).

  The transparent electrode layer 18 is not particularly limited as to the material, but, for example, zinc oxide or indium oxide, or various metal oxides to indium oxide, such as titanium oxide, tin oxide, tungsten oxide, or molybdenum oxide Etc. may be added in an amount of 1% by weight or more and 10% by weight or less.

  The thickness of the transparent electrode layer 18 is preferably 50 nm or more and 200 nm or less. As a method of forming the transparent electrode layer 18 suitable for such a film thickness, for example, physical vapor deposition (PVD) such as sputtering, Alternatively, a chemical vapor deposition (MOCVD) method utilizing a reaction of an organometallic compound and oxygen or water may, for example, be mentioned.

  The material of the metal electrode layer 19 is not particularly limited, and examples thereof include silver, copper, aluminum, and nickel.

  The thickness of the metal electrode layer 19 is preferably 20 μm to 80 μm. As a method of forming the metal electrode layer 19 suitable for such a film thickness, a printing method in which material paste is ink jetted or screen printed, or a plating method Can be mentioned. However, the present invention is not limited to this, and in the case of employing a vacuum process, vapor deposition or sputtering may be employed.

  The widths of the comb teeth T13p and T13n of the p-type semiconductor layer 13p and the n-type semiconductor layer 13n are preferably substantially the same as the widths of the metal electrode layers 19p and 19n formed thereon. However, the present invention is not limited to this, and the widths of the metal electrode layers 19p and 19n may be narrower than the widths of the comb teeth T13p and T13n. In addition, the metal electrode layers 19p and 19n may be wider than the width of the comb-tooth portions T13p and T13n as long as leakage between the metal electrode layers 19p and 19n is prevented.

  When the intrinsic semiconductor layer 12, the conductive semiconductor layer 13, the low reflective layer 16, and the electrode layer 17 are stacked on the semiconductor substrate 11, passivation at each bonding interface, defects in the semiconductor layer and the interface thereof Annealing treatment is performed for the purpose of suppression of generation of levels and crystallization of the transparent conductive oxide in the transparent electrode layer 18.

  As the annealing treatment, for example, the semiconductor substrate 11 in which each layer is disposed is put into an oven heated to 150 ° C. or more and 200 ° C. or less, and the heat treatment can be mentioned. In this case, although the atmosphere in the oven may be the atmosphere, more effective annealing can be performed by using hydrogen or nitrogen. Further, the annealing process may be an RTA (Rapid Thermal Annealing) process in which the semiconductor substrate 11 on which each layer is arranged is irradiated with infrared rays using an infrared heater.

  Here, the light receiving surface 11SU side which is the main surface of the semiconductor substrate 11 in the back contact type solar cell module 20 as described above will be described in detail.

  In the solar cell module 20, the intrinsic semiconductor layer 12U formed of a hydrogenated amorphous silicon-based thin film layer on the light receiving surface 11SU side of the semiconductor substrate 11, the low reflection layer 16 which is an insulating layer, and the light receiving side sealing material 21U is arranged in piles. And the ultraviolet absorber added with respect to the mass of 21 B of light receiving side sealing materials is less than 0.010 mass%, Preferably it is less than 0.008 mass%, More preferably, it is less than 0.005 mass% . In addition, the thickness Ta of the intrinsic semiconductor layer 12U is 15 nm or more and 50 nm or less, preferably 30 nm or more and 50 nm or less.

  As described above, when the amount of the ultraviolet absorber is less than 0.01% by mass with respect to the mass of the light receiving side sealing member 21U, the decrease in the amount of received light due to the ultraviolet absorber is unlikely to occur. It is difficult to reduce the efficiency. On the other hand, a large amount of ultraviolet light passes through the light receiving side sealing material 21U because the ultraviolet light absorber does not exist or is very small.

  However, on the light receiving side of the semiconductor substrate 11, an intrinsic semiconductor layer 12U formed of a hydrogenated amorphous silicon-based thin film layer and a low reflective layer 16 which is an insulating layer are laminated. Therefore, these two layers suppress the influence of ultraviolet light on the semiconductor substrate 11. The thickness Ta of the intrinsic semiconductor layer 12U in the two layers is 15 nm or more and 50 nm or less.

  Within the range of this specific thickness, the intrinsic semiconductor layer 12U blocks the ultraviolet rays entering along with the low reflective layer 16 and prevents it from reaching the semiconductor substrate 11 as much as possible. In addition, when the thickness of the intrinsic semiconductor layer 12U is too large, the short circuit current in the solar cell module 20 becomes large and the conversion efficiency also decreases, and such a range is suppressed as well. .

  That is, such a solar cell module 20 suppresses the decrease in conversion efficiency due to the increase in thickness of the intrinsic semiconductor layer 12U to a certain degree while securing the ultraviolet light durability, and there is a trade-off relationship between the ultraviolet light durability and the conversion efficiency You can balance the two performances. On the other hand, if it is less than the lower limit of this thickness range, the conversion efficiency of photoelectric conversion becomes relatively high, but the ultraviolet light durability can not be secured. If it exceeds the upper limit, the conversion efficiency is excessive even though the ultraviolet light durability is secured. It will

  In addition, content of a ultraviolet absorber is measured, for example using LC / MS (liquid chromatograph mass spectrometry).

  The UV absorber is not particularly limited as long as it is an additive for absorbing UV light, and examples thereof include benzotriazole UV absorbers, benzophenone UV absorbers, triazine UV absorbers, Examples thereof include cyanoacrylate-based ultraviolet absorbers, oxanilide-based ultraviolet absorbers, salicylate-based ultraviolet absorbers, formamidine-based ultraviolet absorbers, benzoate-based ultraviolet absorbers, and salicylic acid-based ultraviolet absorbers.

  In addition, such a ultraviolet absorber is disperse | distributed to resin used as the material of 21 U of light-receiving side sealing materials, and the resin is made into a sheet form etc., The light-receiving side sealing material to which the ultraviolet absorber was disperse | distributed 21 U is obtained.

  Moreover, in the solar cell module 20, the thickness Tb of the low reflective layer 16 is preferably 30 nm or more and 200 nm or less, and more preferably 50 nm or more and 100 nm or less.

  Within this specific thickness range, the low reflective layer 16, like the intrinsic semiconductor layer 12 U, suppresses the decrease in conversion efficiency due to the increase in thickness to a certain level while securing the ultraviolet light durability. Moreover, since the light receiving side sealing material 21U does not contain the ultraviolet light absorber or is a trace amount, the thickness of the low reflection layer 16 even if a crack or the like is generated in the light receiving side sealing material 21U due to the ultraviolet deterioration. If Tb is in the above-mentioned range, the water etc. which infiltrates from a crack etc. are blocked. As a result, the durability of the solar cell module 20 is improved.

  On the other hand, when the thickness of the low reflection layer 16 is outside the specific range, it is difficult to be a solar cell module in which both performances of UV durability and conversion efficiency are well balanced as described above. Below the lower limit, the low reflective layer 16 can not ensure insulation, and can not easily play the role of a sacrificial layer for the etching solution in the patterning of the conductive semiconductor layer 13 or the electrode layer 17. If the upper limit is exceeded, the low reflective layer 16 can not ensure light transmission and it is difficult to play a role as an antireflective layer.

  The relationship (Tb / Ta) between the thickness Tb of the insulating low reflection layer 16 and the thickness Ta of the intrinsic semiconductor layer 12U formed of the hydrogenated amorphous silicon-based thin film layer is 0.5 <Tb / It is preferable that Ta <14.0, more preferably 0.8 <Tb / Ta <8.0, and still more preferably 1.0 <Tb / Ta <5.0.

  Within such a range, both of the intrinsic semiconductor layer 12U and the low reflective layer 16 maintain the ultraviolet light durability in a well-balanced manner, and suppress the decrease in conversion efficiency due to the increase in thickness to a certain level.

  Moreover, in the solar cell module 20, a wavelength conversion agent may be added to the light receiving side sealing material 21U. Even in the case of such a solar cell module 20, in the same manner as described above, the balance between the UV durability and the conversion efficiency can be maintained.

  The present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the claims. That is, an embodiment obtained by combining technical means appropriately modified within the scope of the claims is also included in the technical scope of the present invention.

  EXAMPLES Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited by these examples.

<Evaluation>
[Evaluation of film thickness]
The film thicknesses of various layers in the solar cell module were observed and measured at a magnification of 100,000 using an SEM (field emission scanning electron microscope S4800, manufactured by Hitachi High-Technologies Corporation).

[Evaluation of conversion efficiency]
The conversion efficiency (Eff (%)) of the solar cell module was measured by irradiating standard sunlight of AM (air mass) 1.5 with a light quantity of 100 mW / cm ² by a solar simulator.

[UV durability test]
After measuring the conversion efficiency of the solar cell module (conversion efficiency Ea%), using a xenon lamp, light including ultraviolet light is applied to the solar cell module for 150 hours under the conditions of a light quantity of 300 mW / cm ² and a sample temperature of 70 ° C. After irradiation, the conversion efficiency was measured again (conversion efficiency Eb%). And ratio (Eb / Ea) of conversion efficiency before and behind ultraviolet irradiation was made into evaluation data of ultraviolet endurance of a solar cell module.

<Manufacture of solar cell module>
First, as a semiconductor substrate, a single crystal silicon substrate having a thickness of 200 μm having a pyramidal texture structure on both principal surfaces was adopted. Then, this single crystal silicon substrate was introduced into a CVD apparatus, and an intrinsic semiconductor layer made of a hydrogenated amorphous silicon-based thin film was formed on the front main surface to be a light receiving surface.

In addition, the thickness of this intrinsic semiconductor layer was suitably set according to the below-mentioned sample. In addition, as film forming conditions, the substrate temperature is 150 ° C., the pressure is 120 Pa, the SiH ₄ / H ₂ flow ratio is 3/10, and the power density is 0.011 W / cm ² .

Next, a semiconductor substrate having an intrinsic semiconductor layer formed on the front side was introduced into a CVD apparatus, and a low reflection layer was formed of insulating silicon nitride on the intrinsic semiconductor layer. The thickness of this low reflective layer was 60 nm. The film forming conditions were a substrate temperature of 150 ° C., a pressure of 120 Pa, an NH ₃ / SiH ₄ / H ₂ flow ratio of 1/1/40, and a power density of 0.011 W / cm ² .

  Subsequently, the semiconductor substrate was introduced into a CVD apparatus, and an intrinsic semiconductor layer made of a hydrogenated amorphous silicon-based thin film was formed on the back surface of the semiconductor substrate. The thickness of this intrinsic semiconductor layer is 8 nm. The film forming conditions were the same as those of the intrinsic semiconductor layer formed on the front main surface of the semiconductor substrate.

Next, a semiconductor substrate having an intrinsic semiconductor layer formed on the backside main surface was introduced into a CVD apparatus, and a p-type semiconductor layer made of a p-type hydrogenated amorphous silicon-based thin film was formed on the intrinsic semiconductor layer. The thickness of this p-type semiconductor layer was 10 nm. As film forming conditions, the substrate temperature is 150 ° C., the pressure is 60 Pa, the SiH ₄ / B ₂ H ₆ flow ratio is 100/2, and the input power density is 0.01 W / cm ² .

  Furthermore, a resist film was formed on the p-type semiconductor layer, and patterned by photolithography, and the p-type semiconductor layer and the intrinsic semiconductor layer were etched using the resist pattern layer. After this, the semiconductor substrate was washed.

  Subsequently, the cleaned semiconductor substrate was introduced into a CVD apparatus, and an intrinsic semiconductor layer made of a hydrogenated amorphous silicon-based thin film was formed on the p-type semiconductor layer and the exposed backside principal surface. The film thickness and the film formation conditions were the same as those of the intrinsic semiconductor layer immediately below the p-type semiconductor layer.

Next, an n-type semiconductor layer made of an n-type hydrogenated amorphous silicon-based thin film was formed on the intrinsic semiconductor layer. The thickness of this n-type semiconductor layer is 10 nm. The film forming conditions were as follows: substrate temperature: 150 ° C., pressure: 60 Pa, SiH ₄ / PH ₃ flow ratio: 100/1, input power density: 0.01 W / cm ² .

  Furthermore, a resist film was formed on the n-type semiconductor layer, and patterned by photolithography, and the n-type semiconductor layer and the intrinsic semiconductor layer on the p-type semiconductor layer were etched using the resist pattern layer. After this, the semiconductor substrate was washed.

Subsequently, a transparent electrode layer of indium tin oxide (ITO, refractive index: 1.9) was formed on the patterned p-type semiconductor layer and n-type semiconductor layer. The thickness of the transparent electrode layer was 80 nm. Further, in this film formation, indium oxide was used as a target, and a film was formed by applying a power density of 0.5 W / cm ² in an argon atmosphere at a substrate temperature: room temperature and a pressure: 0.2 Pa.

  Furthermore, a resist film is formed on the transparent electrode layer, patterned by photolithography, and the transparent electrode layer is etched using the resist pattern layer, and the transparent electrode layer on the p-type semiconductor layer, n-type It separated from the transparent electrode layer on the semiconductor layer. After this, the semiconductor substrate was washed.

  Then, after screen-printing with silver paste using the screen plate corresponding to an electrode pattern on the transparent electrode layer, it was made to dry at 150 degreeC, and the metal electrode layer was formed.

  The back contact type solar cell completed through the above steps was modularized in a state of being electrically connected by connection wiring. Specifically, on the back side protection member, a back side sealing material made of EVA (ultraviolet absorber is appropriately set) is disposed, and further, a plurality of back contact type solar electrically connected by connection wiring on the back side sealing material. I placed the battery. Subsequently, a light-receiving side sealing material made of EVA (no ultraviolet light absorber) is disposed on the solar cell string, and a light-receiving side protective member made of glass is further disposed thereon, and laminated at 140 ° C. The solar cell module of the back contact type solar cell was manufactured.

<About UV absorber>
Ultraviolet absorber (material name: benzo) added to the light receiving side sealing material with a thickness of 20 nm of the intrinsic semiconductor layer made of a hydrogenated amorphous silicon-based thin film formed on the front main surface to be a light receiving surface 7 types of samples (A1 in which the triazole derivative is not included, 0.005% by mass, 0.008% by mass, 0.010% by mass, 0.012% by mass, 0.015% by mass, and 0.03% by mass) -A7) was created.

  Then, the conversion efficiency (%) and the ultraviolet light durability (%) of this sample were measured (see Table 1 and FIG. 5). In addition, conversion efficiency compared the other sample on the basis of the value in sample A1 without an ultraviolet absorber (that is, it displayed as 100% if it is the same value as A1). Moreover, the measurement of conversion efficiency measured the sample after the completion of the ultraviolet light resistance test.

  From Table 1 and FIG. 5, when the ultraviolet absorber exceeded 0.010 mass%, the conversion efficiency dropped sharply. From this, it was found that although it would not naturally cause a decrease in the conversion efficiency if the ultraviolet absorber was not contained, the addition of up to 0.010 mass% would not adversely affect the conversion efficiency. .

<On the thickness and low reflection layer of hydrogenated amorphous silicon thin film layer>
Hydrogenated amorphous silicon system formed on the front side main surface which becomes 0.30 mass% of ultraviolet absorber (material name: benzotriazole derivative) added with respect to the mass of the light receiving side sealing material Twelve samples (B1-B12) were prepared in which the thickness of the thin film intrinsic semiconductor layer was set to 3 nm, 5 nm, 8 nm, 10 nm, 13 nm, 15 nm, 20 nm, 25 nm, 30 nm, 40 nm, 50 nm, and 60 nm.

Then, the conversion efficiency (%) and the ultraviolet light durability (%) of this sample were measured (see Table 2 and FIG. 6). In addition, conversion efficiency compared the other sample on the basis of the value in sample B4 without an ultraviolet absorber (that is, it displayed as 100% if it is the same value as B4). Moreover, the measurement of conversion efficiency measured the sample after the completion of the ultraviolet light resistance test.

  In addition, the thickness of the intrinsic semiconductor layer made of a hydrogenated amorphous silicon-based thin film formed on the main surface on the front side to be the light receiving surface without adding the ultraviolet absorber added to the mass of the light receiving side sealing material Similar to the samples B1 to B12, 12 samples (C1 to C12) were prepared.

  Then, the conversion efficiency (%) and the ultraviolet light durability (%) of this sample were measured (see Table 3 and FIG. 7). In addition, conversion efficiency compared the other samples on the basis of the value in sample B4 without an ultraviolet absorber as above-mentioned. Moreover, the measurement of conversion efficiency measured the sample after the completion of the ultraviolet light resistance test.

  From Table 2 and FIG. 6, when the ultraviolet absorber was added, samples B1 to B12 exhibited relatively high ultraviolet durability independently of the thickness of the intrinsic semiconductor layer. On the other hand, from Table 3 and FIG. 7, even if the ultraviolet absorber was not added, Samples C6 to C12 ensured the ultraviolet light durability if the thickness of the intrinsic semiconductor layer was 15 nm or more and 60 nm or less. However, when the thickness of the intrinsic semiconductor layer was 60 nm (sample C12), the conversion efficiency was inferior to the conversion efficiency of the reference value (sample B4).

  On the other hand, when the thickness of the intrinsic semiconductor layer is 5 nm or more and less than 15 nm, the conversion efficiency has a value higher than that of the sample B4, but the ultraviolet light durability is sharply reduced. From this, while the thickness Ta of the hydrogenated amorphous silicon layer is 15 nm or more and 50 nm or less, it exhibits higher conversion efficiency than the sample B4 to which the ultraviolet light absorber is added, and exhibits equivalent ultraviolet light durability. It turned out to do.

  In such a case, the relationship (Tb / Ta) between the thickness Tb of the insulating low reflective layer and the thickness Ta of the intrinsic semiconductor layer formed of the hydrogenated amorphous silicon-based thin film layer is 1.0. It was also found that <Tb / Ta <5.0.

<About wavelength conversion agent>
A sample of the thickness of the intrinsic semiconductor layer made of a hydrogenated amorphous silicon-based thin film formed on the main surface on the front side to be the light receiving surface is used as well as the light receiving side sealing material to which the wavelength converting agent is added without adding the ultraviolet absorber The sample (D1-D12) made into 12 types like B1-B12 was created.

  Then, the conversion efficiency (%) and the ultraviolet light durability (%) of this sample were measured (see Table 4 and FIG. 8). In addition, conversion efficiency compared the other sample on the basis of the value in sample B4 without an ultraviolet absorber (that is, it displayed as 100% if it is the same value as B4). Moreover, the measurement of conversion efficiency measured the sample after the completion of the ultraviolet light resistance test.

  From Table 4 and FIG. 8, even in the sample D to which the wavelength conversion agent was added, the result having the same tendency as the sample C was obtained. Therefore, it was found that the light converted by the wavelength conversion agent did not cause deterioration or the like on the semiconductor substrate or the like of the solar cell module.

10 Solar cells [back contact solar cells]
11 semiconductor substrate 11S principal surface of semiconductor substrate 11SU principal surface on the light receiving side of semiconductor substrate 11SB principal surface on the back side of semiconductor substrate 12 intrinsic semiconductor layer 12U intrinsic semiconductor layer [hydrogenated amorphous silicon based thin film layer]
12p intrinsic semiconductor layer 12n intrinsic semiconductor layer 13 conduction type semiconductor layer 13p p type semiconductor layer 13n n type peninsula layer 16 low reflective layer [insulation layer]
17 electrode layer 18 transparent electrode layer 19 metal electrode layer 20 solar cell module [back contact type solar cell module]
21 Sealing material 21U Light receiving side sealing material 21B Back side sealing material 22 Light receiving side protective member 23 Back side protective member 25 Wiring member

Claims (4)

In a back contact type solar cell module in which a back contact type solar cell in which different types of electrode layers are disposed on one side of a main surface of a semiconductor substrate is sealed with a sealing material,
A hydrogenated amorphous silicon-based thin film layer, an insulating layer, and a light-receiving side sealing material are arranged in an overlapping manner on the light-receiving surface side which is the other main surface of the semiconductor substrate,
The ultraviolet absorber added with respect to the mass of the light receiving side sealing material is less than 0.010 mass%,
The back contact type solar b-cell module, wherein the thickness Ta of the hydrogenated amorphous silicon layer is 15 nm or more and 50 nm or less.   The back contact type solar cell module according to claim 1, wherein a thickness Tb of the insulating layer is 30 nm or more and 200 nm or less.   The relationship (Tb / Ta) between the thickness Tb of the insulating layer and the thickness Ta of the hydrogenated amorphous silicon-based thin film layer is 0.5 <Tb / Ta <14.0. Back contact type solar cell module.   The back contact type solar cell module according to any one of claims 1 to 3, wherein a wavelength conversion agent is added to the light receiving side sealing material.

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