JP6115806B2 - Photovoltaic device - Google Patents

Description

  The present invention relates to a photovoltaic device, and more particularly to a photovoltaic device in which a plurality of photovoltaic elements are formed on a support substrate.

  Conventionally, development of photovoltaic elements that convert light energy into electrical energy has been energetically performed in various fields. For example, research and practical application of photovoltaic elements (apparatuses) using crystalline silicon such as single crystal silicon and polycrystalline silicon have been actively conducted.

  In recent years, the development of back contact type (back junction type) photovoltaic elements has also been advanced. In this type of photovoltaic device, the surface opposite to the light-receiving surface (light incident surface) is formed only on the light-receiving surface side by a texture layer, antireflection, and a passivation layer for preventing carrier recombination. In particular, a PN junction and a collector electrode are formed, and a high conversion efficiency can be obtained by removing a loss due to the element structure as much as possible.

  Furthermore, a photovoltaic device is disclosed in which a plurality of photovoltaic elements are bonded on a base substrate (support substrate) via an insulating layer (see, for example, Patent Document 1).

JP 2010-283339 A

  When joining a photovoltaic element to a support substrate, when joining a photovoltaic element made of crystalline silicon and a support substrate made of a glass plate by conventional Van der Waals force or hydrogen bonding, the bonding force is It is relatively weak, and there is a high possibility that the joint is peeled off due to external force during manufacturing, temperature change, exposure to a vacuum atmosphere, etc., and long-term reliability is low.

  A photovoltaic device of a back junction type, comprising a glass plate, and a photovoltaic element that is disposed on the glass plate and has a crystalline semiconductor layer that generates electric power in response to incidence of light. And at least a part of the light incident surface of the photovoltaic element.

  According to the present invention, by joining the photovoltaic element and the glass plate by fusion bonding, both of these can be made stronger than in the case of using conventional van der Waals force or hydrogen bonding. Can be joined.

It is sectional drawing which shows the structure of the photovoltaic apparatus in the 1st Embodiment of this invention. It is sectional drawing which shows the manufacturing method of the photovoltaic apparatus in the 1st Embodiment of this invention. It is sectional drawing which shows the manufacturing method of the photovoltaic apparatus in the 1st Embodiment of this invention. It is sectional drawing which shows the manufacturing method of the photovoltaic apparatus in the 1st Embodiment of this invention. It is sectional drawing which shows the manufacturing method of the photovoltaic apparatus in the 1st Embodiment of this invention. It is sectional drawing which shows the manufacturing method of the photovoltaic apparatus in the 1st Embodiment of this invention. It is sectional drawing which shows the manufacturing method of the photovoltaic apparatus in the 1st Embodiment of this invention. It is sectional drawing which shows the manufacturing method of the photovoltaic apparatus in the 1st Embodiment of this invention. It is sectional drawing which shows the manufacturing method of the photovoltaic apparatus in the 1st Embodiment of this invention. It is sectional drawing which shows the manufacturing method of the photovoltaic apparatus in the 1st Embodiment of this invention. It is sectional drawing which shows the manufacturing method of the photovoltaic apparatus in the 1st Embodiment of this invention. It is sectional drawing which shows the manufacturing method of the photovoltaic apparatus in the 1st Embodiment of this invention. It is sectional drawing which shows the manufacturing method of the photovoltaic apparatus in the 1st Embodiment of this invention. It is a top view which shows the structure of the photovoltaic apparatus in the 1st Embodiment of this invention. It is an enlarged plan view which shows the fusion | melting joining area | region of the photovoltaic apparatus in the 1st Embodiment of this invention. It is an enlarged plan view which shows the fusion | melting joining area | region of the photovoltaic apparatus in the 2nd Embodiment of this invention. It is an enlarged plan view which shows the fusion | melting joining area | region of the photovoltaic apparatus in the 3rd Embodiment of this invention. It is sectional drawing which shows the structure of the photovoltaic apparatus in the 4th Embodiment of this invention.

<First Embodiment>
As shown in the sectional view of FIG. 1, the photovoltaic device 100 according to the first embodiment includes a glass plate 10, a passivation layer 12, a base Si layer 14, an n-type heavily doped region 16, an i-type amorphous Si layer. 18, a p-type amorphous Si layer 20, a transparent electrode 22, and a back electrode 24 (first back electrode 24n, second back electrode 24p).

  In the present embodiment, the photovoltaic device 100 includes a plurality of back-junction photovoltaic elements 102, and an electrode for taking out the electric power generated by the photovoltaic elements 102 to the outside is opposite to the light receiving surface. Are provided only on the main surface (hereinafter referred to as the back surface).

  Here, the light receiving surface means a main surface on which light is mainly incident in the photovoltaic element 102, and specifically, a surface on which most of the light incident on the photovoltaic element 102 is incident. It is. Further, the back surface means a surface opposite to the light receiving surface of the photovoltaic element 102.

  Specifically, the base Si layer 14 is single-crystal Si having an n-type conductivity, a crystal axis of <100>, a specific resistance of 8 to 12 Ωcm, and a thickness of 60 μm. However, the applicable range of the present invention is not limited to this, and the conductivity types of the base Si layer 14, the n-type heavily doped region 16, the i-type amorphous Si layer 18 and the p-type amorphous Si layer 20 are all reversed. May be.

  The passivation layer 12 is provided on the light receiving surface side surface of the base Si layer 14. The passivation layer 12 plays a role of terminating dangling bonds (dangling bonds) on the surface of the base Si layer 14 and suppresses carrier recombination. By providing the passivation layer 12, it is possible to suppress loss of generated current due to carrier recombination on the light receiving surface side of the photovoltaic element.

  The passivation layer 12 may include, for example, a silicon nitride layer (SiN), and more preferably has a stacked structure of a silicon oxide layer (SiOx) and silicon nitride. For example, a structure in which a silicon oxide layer and a silicon nitride layer are sequentially stacked with a thickness of 30 nm and 40 nm, respectively, may be used.

The heavily doped region 16 is an n ⁺ region in which a dopant containing phosphorus (P) is diffused at a high concentration in the base Si layer 14 (a region where an n-type dopant is doped at a higher concentration than the base Si layer 14). ). The diffusion depth of the dopant in the heavily doped region 16 is preferably 10 to 500 nm, and most preferably 50 to 100 nm. The dopant diffusion concentration is preferably in the range of 1 × 10 ²⁰ to 2 × 10 ²¹ atoms / cm ³ , and within these ranges, the dopant concentration is substantially reduced by recombination of carriers in the n ⁺ region. Electric power can be extracted outside without causing deterioration in characteristics.

  The base Si layer 14 and the heavily doped region 16 form a first conductivity type contact (base contact) region in which the crystalline materials are homo-joined.

The i-type amorphous Si layer 18 and the p-type amorphous Si layer 20 include an amorphous phase or a microcrystalline phase in which minute crystal grains are precipitated in the amorphous phase. In the present embodiment, the i-type amorphous Si layer 18 and the p-type amorphous Si layer 20 are made of amorphous silicon containing hydrogen. The i-type amorphous Si layer 18 is a substantially intrinsic amorphous silicon layer. The p-type amorphous Si layer 20 is an amorphous silicon layer to which a p-type dopant is added. The p-type amorphous Si layer 20 is a semiconductor layer having a higher doping concentration than the i-type amorphous Si layer 18. For example, the i-type amorphous Si layer 18 is not intentionally doped, and the doping concentration of the p-type amorphous Si layer 20 may be about 10 ¹⁸ / cm ³ .

  The film thickness of the i-type amorphous Si layer 18 is made thin so as to suppress light absorption as much as possible. Specifically, it may be 1 nm to 50 nm, for example, 10 nm. The thickness of the p-type amorphous Si layer 16 is made thin so that light absorption can be suppressed as much as possible, while it is made so thick that the open circuit voltage (Voc) of the photovoltaic element becomes sufficiently high. For example, it may be 1 nm to 50 nm, for example, 10 nm.

  The base Si layer 14, the i-type amorphous Si layer 18, and the p-type amorphous Si layer 20 form a second conductivity type contact (emitter contact) region heterojunctioned.

  Here, since the heterojunction forming the second conductivity type contact (emitter contact) has higher electric resistance than the homojunction, in order to obtain high conversion efficiency, the area of the first conductivity type contact region is set to It is preferable to form the pattern so as to be smaller than the area of the two conductivity type contact region.

  The transparent electrode 22 is a translucent conductive oxide film containing indium oxide as a main component, and serves as a starting point for the growth of the back electrode 24 formed thereafter by plating.

  The back electrode 24 is preferably formed by a plating method such as nickel or an alloy of nickel and iron, but aluminum, silver, copper, or a metal paste containing these can also be used. On the back side of the layer 14, they are provided over substantially the entire surface at equal intervals of 2 mm. Here, the interval between the combs of the comb-shaped electrodes formed by the back electrode 24 is 2 mm in the present embodiment, but may be narrower than this, and the interval of 2 mm satisfies the allowable output characteristics. The range is selected to be the maximum (the number of combs is the minimum).

  The glass plate 10 and the photovoltaic element 102 are melt-bonded in the melt-bonding area A in the outer peripheral area of the photovoltaic element 102. The melt bonding method will be described later.

  Next, a method for manufacturing the photovoltaic device 100 will be described. 2A to 2J show a method for manufacturing the photovoltaic device 100 according to the first embodiment.

  The substrate 26 is made of a crystalline semiconductor material. For example, a semiconductor substrate such as silicon, polycrystalline silicon, gallium arsenide (GaAs), or indium phosphide (InP) is used. In this embodiment mode, an example in which a single crystal silicon substrate is used as the substrate 26 is described. Therefore, the n-type heavily doped region 16, the base Si layer 14, the i-type amorphous Si layer 18 and the p-type amorphous Si layer 20 described later are also silicon layers. However, the substrate 26 may be made of a material other than silicon, and these layers may be made of a material other than the silicon layer.

A porous layer (brittle layer) 26a is formed on one main surface of the substrate 26 (FIG. 2A). The porous layer 26a can be formed by anodic oxidation or the like. The electrolyte used for anodization can be, for example, a mixed solution of hydrofluoric acid and ethanol, or a mixed solution of hydrofluoric acid and hydrogen peroxide solution. The current density of the anodic oxidation may be 5 mA / cm ² or more and 600 nA / cm ² or less, for example, about 10 mA / cm ² .

The base Si layer 14 is formed on the porous layer 26a of the substrate 26 (FIG. 2B). The base Si layer 14 can be formed by chemical vapor deposition (CVD). The base Si layer 14 is formed by epitaxial growth using the porous layer 26a as a seed layer, and forms a homojunction region in which crystalline semiconductor layers are joined to each other. For example, the film can be formed by heating the substrate 26 to 950 ° C. and supplying dichlorosilane (SiH ₂ Cl ₂ ) diluted with hydrogen (H ₂ ) as a source gas. The flow rates of hydrogen (H ₂ ) and dichlorosilane (SiH ₂ Cl ₂ ) are, for example, 0.5 (l / min) and 180 (l / min), respectively.

A passivation layer 12 is formed on the base Si layer 14 (FIG. 2C). The passivation layer 12 can be formed by plasma enhanced chemical vapor deposition (PECVD) in which a raw material gas obtained by mixing oxygen (O ₂ ) or nitrogen (N ₂ ) with silane (SiH ₄ ) is supplied as a plasma.

  After forming the passivation layer 12, the glass plate 10 is joined to the passivation layer 12 (FIG. 2D). At this time, as shown in the plan view of FIG. 3, the base Si layer 14 is joined and modularized so that the plurality of photoelectric conversion elements 102 are arranged on one main surface of the glass plate 10. The example of FIG. 3 shows an example in which 24 base Si layers 14 are bonded to one glass plate 10 to form a module. In FIGS. 1 and 2, sectional views of two photoelectric conversion elements 102 included in the modularized photovoltaic device 100 are representatively shown.

  As shown in the enlarged plan view of FIG. 4, the glass plate 10 and the base Si layer 14 are melt-bonded in the melt-bonding region A in the outer peripheral region of the base Si layer 14. In the photovoltaic device 100 of the present embodiment, the fusion bonding region A is provided so as to surround the effective power generation region D of the photoelectric conversion element 102.

  As shown in FIG. 2D, the melt-bonded region A is formed by irradiating the laser beam B from the glass plate 10 side. The laser beam B is preferably a femtosecond laser beam. That is, the laser beam B preferably has a pulse width of 1 nanosecond or less. Further, it is preferable that the laser beam B has a wavelength at which absorption occurs in at least one of the glass plate 10 and the base Si layer 14. For example, it is preferable that the laser beam B has a wavelength of 800 nm. Further, the laser beam B is preferably irradiated at an energy density and a scanning speed sufficient to melt at least a part of the glass plate 10 and the base Si layer 14. For example, the laser beam B is preferably irradiated with a pulse energy of 10 microjoules (μJ) per pulse. The laser beam B is preferably scanned at a scanning speed of 10 mm / min.

  In the present embodiment, the fusion bonding region A is provided so as to surround the peripheral edge of the photovoltaic element 102 in a single manner, but the present invention is not limited to this. For example, when it is desired to further strengthen the bonding, the periphery of the photovoltaic element 102 may be provided so as to be double-wrapped, or may be provided in a lattice shape over the entire photovoltaic element 102. .

  Further, the passivation layer 12 is not essential, and the base Si layer 14 and the glass plate 10 may be directly joined.

  2D to 2J are shown upside down in FIGS. 2A to 2C for easy understanding. It should be noted that a mask is applied so that a film is not formed in a region between the plurality of photovoltaic elements 102 when each film is formed as described below, or is removed by etching or the like after the film is formed. do it.

Next, the substrate 26 is separated using the porous layer 26a (FIG. 2E). For example, the substrate 26 and the glass plate 10 can be separated from the porous layer 26a by adsorbing the substrate 26 and the glass plate 10 with a vacuum chuck and pulling them apart. Further, the substrate 26 can be separated from the porous layer 26a portion by spraying a water jet from the side surface of the substrate 26 onto the porous layer 26a. If part of the porous layer 26a remains, the porous layer 26a may be removed by etching with hydrofluoric acid in which hydrofluoric acid (HF) and nitric acid (HNO ₃ ) are mixed.

An i-type amorphous Si layer 18, a p-type amorphous Si layer 20, and a transparent electrode 22 are formed on the base Si layer 14 separated from the substrate 26 (FIG. 2F). The i-type amorphous Si layer 18 and the p-type amorphous Si layer 20 can be formed by PECVD of a silicon-containing gas such as silane (SiH ₄ ). While supplying a silicon-containing gas such as silane (SiH ₄ ) and supplying high-frequency power from a high-frequency power source to a high-frequency electrode, a raw material gas plasma is generated, and the raw material is supplied from the plasma onto the base Si layer 14 to form silicon. A thin film is formed. The source gas is mixed with a dopant-containing gas such as boron (B ₂ H ₆ ) as necessary. The transparent electrode 22 can be formed using a sputtering method or the like. The i-type amorphous Si layer 18, the p-type amorphous Si layer 20, and the transparent electrode 22 are formed on the entire surface of the base Si layer 14.

  The i-type amorphous Si layer 18, the p-type amorphous Si layer 20, and the transparent electrode 22 formed on the entire surface are patterned (FIG. 2G). At this time, the i-type amorphous Si layer 18, the p-type amorphous Si layer 20 and the transparent electrode 22 formed on the glass plate 10 around the base Si layer 14 are also removed. Patterning can be performed using an etching paste. The i-type amorphous Si layer 18, the p-type amorphous Si layer 20, and the transparent electrode 22 are removed by applying an etching paste containing phosphoric acid in a desired pattern by screen printing or the like. In addition, an etchant containing hydrochloric acid (HCl) may be used for etching the transparent electrode 22. Further, an etchant containing hydrofluoric acid (HF) may be used for etching the i-type amorphous Si layer 18 and the p-type amorphous Si layer 20.

  The i-type amorphous Si layer 18, the p-type amorphous Si layer 20, and the transparent electrode 22 may be patterned so that power can be collected as evenly as possible from the back surface of the photovoltaic element. For example, a comb-shaped pattern including fingers and bus bars that are generally applied to photovoltaic elements is preferable. In particular, a comb-shaped pattern alternately combined with the comb-shaped pattern of the n-type heavily doped region 16 is preferable.

  A doped layer 28 containing an n-type dopant is formed on the patterned transparent electrode 22, the exposed base Si layer 14, and the glass plate 10 (FIG. 2H). The doped layer 28 is used for diffusing an n-type dopant in the base Si layer 14. The doped layer 28 can be, for example, an amorphous silicon layer containing n-type dopant, phosphosilicate glass (PSG), or the like. The amorphous silicon layer can be formed by atmospheric pressure CVD or the like, and PSG can be formed by a coating method or the like. The thickness of the doped layer 28 is preferably about 300 nm, for example.

  After forming the doped layer 28, the n-type heavily doped region 16 is formed by the diffusion process of the dopant into the base Si layer 14 (FIG. 2I). Here, diffusion is performed only in the region where the i-type amorphous Si layer 18, the p-type amorphous Si layer 20, and the transparent electrode 22 are removed, that is, the region where the doped layer 28 is in direct contact with the base Si layer 14. Process.

  For example, the n-type heavily doped region 16 can be formed by irradiating only the target region with the laser beam C and diffusing the dopant into the base Si layer 14 by local heating with the laser beam C. For example, the laser light C may have a wavelength of 532 nm, a power of 0.89 W, and a scanning speed of 50 mm / s.

After the n-type heavily doped region 16 is formed, the unnecessary doped layer 28 is removed by etching (FIG. 2J). The doped layer 28 can be removed by, for example, nitrogen trifluoride (NF ₃ ) plasma etching.

  After removing the doped layer 28, a back electrode 24 is formed on the patterned transparent electrode 22 and the exposed base Si layer 14 (FIG. 2K). The back electrode 24 can be formed by a thin film forming method such as sputtering or plasma enhanced chemical vapor deposition (PECVD). Further, a metal layer may be laminated by electrolytic plating or the like. For example, nickel or an alloy of nickel and iron is formed by electrolytic plating. A metal layer is laminated | stacked by applying with an electroplating method, applying an electric potential to the electrode layer used as a seed layer. The back electrode 24 may be formed by applying aluminum, silver, copper, or a metal paste containing these.

  Next, a part of the back electrode 24 is removed, the back electrode 24 is divided, and the first back electrode 24n connected to the n-type heavily doped region 16 and the second back electrode connected to the transparent electrode 22 24p is formed (FIG. 2L). Further, the back electrodes 24 (the first back electrode 24n and the second back electrode 24p) adjacent to each other are also electrically separated.

  Thereafter, if necessary, the first back electrode 24n and the second back electrode 24p of the plurality of photovoltaic elements 102 arranged in parallel are connected by a conductive tab. Alternatively, the filler 30 may be applied to the back side of the photovoltaic element 102 and sealed with the sealing material 32. The filler 30 is preferably a resin material such as EVA. The sealing material 32 is preferably made of a material that is chemically stable, such as a glass plate, plastic, metal, or the like, and has a high structural strength.

  Since the photovoltaic device is used outdoors for a long time, it is necessary to prevent moisture from entering from the outside environment. By sealing the back surface of the photovoltaic element 102 with the filler 30 and the sealing material 32, both surfaces of the photovoltaic element 102 are protected by the sealing material 32 having a shielding performance from the external environment, and high reliability. Sex can be obtained. At this time, it is good also as a structure which provides a through-hole in the sealing material 32 (and filler 30), and takes out generated electric power through these.

  According to the present invention, the photovoltaic element 102 (base Si layer 14) and the glass plate 10 are bonded by fusion bonding, as compared with the conventional bonding using van der Waals force or hydrogen bonding. Thus, both of them can be bonded more firmly.

  Further, by arranging a plurality of photovoltaic elements 102 in a large-area glass plate 10, a plurality of isolated melt-bonding regions A are formed, and the curvature of each photovoltaic element 102 is curved due to thermal deformation. The amount of bending (deformation) as a whole can be suppressed. That is, it is effective for forming a large area photovoltaic device.

<Second Embodiment>
FIG. 5 is a plan view showing the configuration of the photovoltaic device 104 according to the second embodiment of the present invention. In the present embodiment, the fusion bonding region A is provided so that at least a part thereof is discontinuous in the peripheral portion of the photovoltaic element 102. Thereby, it joins so that a closed space may not be formed between the glass plate 10 and the photovoltaic element 102 by the fusion | melting joining area | region A. FIG.

  The photovoltaic device 104 is manufactured in a controlled atmosphere such as in a vacuum in most processes, but may be exposed to the atmosphere as necessary. At that time, if the air enters a slight gap between the glass plate 10 and the photovoltaic element 102, the glass plate 10 or the photovoltaic element 102 is damaged due to thermal expansion of the internal atmosphere in the subsequent heating step. There is a fear. According to the photovoltaic device 104 of the present embodiment, the atmosphere is released from an unbonded region that is not melt-bonded during heating, and damage to the glass plate 10 and the photovoltaic element 102 can be suppressed. .

  In the present embodiment, the melt-bonded region A has a configuration in which the corner of the photovoltaic element 102 is omitted, but the present invention is not limited to this. For example, a configuration in which a part of the peripheral edge of the photovoltaic element 102 is omitted may be employed.

<Third Embodiment>
FIG. 6 is a plan view showing the configuration of the photovoltaic device 106 according to the third embodiment of the present invention. In the present embodiment, the glass plate 10 and the photovoltaic element 102 are melt-bonded in a cross shape on these center lines. Thus, in this Embodiment, joining is performed so that the peripheral part of the photovoltaic element 102 may not be fixed by the fusion | melting joining area | region A. FIG.

  When the photovoltaic device 106 is manufactured and actually used in an outdoor environment, a temperature change of about several tens to 200 ° C. is accompanied. At this time, if the thermal expansion coefficients of the glass plate 10 and the photovoltaic element 102 are greatly different from each other, either of them may be greatly curved, and the glass plate 10 or the photovoltaic element 102 may be damaged. According to the photovoltaic device 106 of the present embodiment, the photovoltaic element 102 is melt-bonded in the vicinity of the center so that the peripheral edge portion is not fixed to the glass plate 10. Therefore, since the peripheral edge portion of the photovoltaic element 102 is mechanically free, deformation (curvature) due to thermal expansion does not occur, and damage can be suppressed even when subjected to a large temperature change.

  In the present embodiment, the melt-bonded region A is provided in a cross shape along the center line. However, the present invention is not limited to this. For example, it may be provided in a cross shape along a line connecting the corners of the photovoltaic element 102, or the back surface of the photovoltaic element 102 may be joined in a spot shape.

<Fourth embodiment>
FIG. 7 is a cross-sectional view showing the configuration of the photovoltaic device 108 according to the fourth embodiment of the present invention. In the present embodiment, fine irregularities 34 for light confinement are formed on the light receiving surface side surface of the photovoltaic region (effective region) 20 of the photovoltaic element 102.

  The irregularities 34 can be formed by subjecting the base Si layer 14 to anisotropic etching before forming the passivation layer 12. When the base Si layer 14 has a <100> crystal axis, an aqueous potassium hydroxide (KOH) solution can be used as an etchant for anisotropic etching. The size of the unevenness 34 is preferably larger than the wavelength of light used for photoelectric conversion in the photovoltaic element 102. The size of the irregularities 34 can be adjusted by the etchant concentration, etching time, temperature, and the like.

  According to the present embodiment, the optical path length of incident light in the photovoltaic element 102 can be increased, and in that case, the bonding strength between the glass plate 10 and the photovoltaic element 102 is not impaired. It can be firmly joined.

  When anodic bonding of the photovoltaic element 102 and the glass plate 10 is performed, it is difficult to perform bonding if the unevenness 34 for confining light is formed on the light incident surface of the photovoltaic element 102. According to this embodiment, strong bonding can be realized even with the photovoltaic element 102 having an uneven surface. This is because the photovoltaic element 102 (the base Si layer 14) is melted including the unevenness 34 in the melt bonding. In the anodic bonding, the glass plate 10 and the photovoltaic element 102 (base Si layer 14) are sandwiched between two electrodes and heated in a temperature range of 200 ° C. or higher and 600 ° C. or lower while being evacuated to vacuum. In this bonding method, a voltage of 300 V to 1 kV is applied between the electrodes.

  In particular, it is preferable that the melt bonding region A of the photovoltaic element 102 is not provided with the unevenness 34 and remains flat. For example, it is possible to leave a flat portion by performing etching in a state where a mask having resistance to an etchant is provided in a region to be the melt bonding region A. By adopting such a configuration, bonding can be performed more reliably.

  Furthermore, a space between the fine unevenness 34 provided on the light receiving surface side surface of the photovoltaic element 102 and the glass plate 10 transmits light having an intermediate refractive index value between the glass plate 10 and the photovoltaic element 102. It is preferable to fill with a refractive index adjusting material 36 having a characteristic. The refractive index adjusting material 36 is preferably a material having a refractive index of 1.5 or more and 3.0 or less for the glass plate 10 and the base Si layer 14 made of silicon. For example, the refractive index adjusting material 36 is preferably made of silica or titanium oxide.

  As a result, the refractive index sequentially changes as the incident light progresses, and it becomes difficult to cause a reflection loss of the incident light, and the power generation efficiency of the photovoltaic element 102 can be increased.

  In addition, it is good also as a structure which combined the structure in 1st-4th embodiment suitably. For example, in the second to fourth embodiments, a configuration in which a plurality of photovoltaic elements 102 are bonded to the same glass plate 10 can be employed. Moreover, the structure which seals the back surface of the photovoltaic element 102 with the filler 30 and the sealing material 32 is employable.

  10 glass plate, 12 passivation layer, 14 base Si layer, 16 n-type heavily doped region, 18 i-type amorphous Si layer, 20 p-type amorphous Si layer, 22 transparent electrode, 24 back electrode, 24n n-type back electrode, 24p p-type back electrode, 26 substrate, 26a porous layer, 28 doped layer, 30 filler, 32 sealing material, 34 unevenness, 36 refractive index adjusting material, 100, 104, 106, 108 photovoltaic device, 102 photovoltaic element.

Claims (5)

A back junction type photovoltaic device,
A glass plate,
A photovoltaic element disposed on the glass plate and having a crystalline semiconductor layer that generates power in response to the incidence of light, and
At least a part of the light incident surface of the glass plate and the photovoltaic element has a melted portion where the glass plate and the crystalline semiconductor layer are melted , and the glass plate and the photovoltaic power at the melted portion. A photovoltaic device, wherein the light incident surface of the element is directly bonded. The photovoltaic device according to claim 1,
The photovoltaic device according to claim 1, wherein the melt-bonded portion is provided so as not to create a closed space between the glass plate and the photovoltaic element. The photovoltaic device according to claim 1 or 2,
A photovoltaic device, wherein the photovoltaic device has a light-receiving surface on the glass plate side, and is provided with unevenness in a region other than the melting portion . The photovoltaic device according to claim 3, wherein
A refractive index adjusting material having a refractive index between the refractive index of the photovoltaic element and the refractive index of the glass plate is provided between the unevenness provided in the photovoltaic element and the glass plate. A photovoltaic device characterized by comprising: The photovoltaic device according to any one of claims 1 to 4, wherein
A plurality of the photovoltaic elements are joined to the glass plate.

Images