WO2012036146A1 - Crystalline solar cell and manufacturing method therefor - Google Patents

Abstract

This crystalline solar cell has: a planar crystalline substrate that contains p-type or n-type monocrystalline or polycrystalline silicon and can perform photoelectric conversion; a first semiconductor layer that is disposed on the light-receiving-surface side of the crystalline substrate and contains amorphous or microcrystalline silicon; a second semiconductor layer that is disposed on the back side of the crystalline substrate, opposite the light-receiving-surface side, and contains amorphous or microcrystalline silicon of the conductivity type opposite that of the first semiconductor layer; and a first silicon oxide layer disposed either between the crystalline substrate and the first semiconductor layer or between the crystalline substrate and the second semiconductor layer.

Description

Crystal solar cell and manufacturing method thereof

The present invention relates to a crystalline solar cell and a method for manufacturing the same.
This application claims priority on the basis of Japanese Patent Application No. 2010-204734 for which it applied to Japan on September 13, 2010, and uses the content here.

Solar cells that generate power using solar energy are power generation systems that are expected as alternative technologies for fossil fuels. In addition, solar cells tend to rapidly increase production from the viewpoint of preserving the global environment. For this reason, solar cells having various structures and configurations have been actively developed. Among them, crystalline silicon (Si) solar cells are most commonly produced due to performance such as photoelectric conversion efficiency and superior manufacturing costs.

As a structure of the photoelectric conversion element in the crystalline silicon solar cell, for example, a back contact structure having no electrode on the light receiving surface, a pin structure using a heterojunction of single crystal silicon and amorphous silicon, and the like are known. . By adopting such various structures, the conversion efficiency of the crystalline silicon solar cell is improved.

In recent years, a so-called HIT (Heterojunction with Intrinsic Thin-Layer) type solar cell that can improve photoelectric conversion efficiency by improving semiconductor junction characteristics is known. As described in Patent Document 1, for example, a HIT type solar cell includes a crystalline semiconductor substrate of one conductivity type (for example, n-type) and an amorphous semiconductor of other conductivity type (for example, p-type). A semiconductor junction is formed by the layers. In this semiconductor junction, an amorphous semiconductor layer that is substantially intrinsic is interposed between a crystalline semiconductor substrate of one conductivity type and an amorphous semiconductor layer of another conductivity type.
Thus, improvement of the photoelectric conversion efficiency of a solar cell (crystalline silicon solar cell) is a very important theme, and its research is being carried out every day.

Japanese Unexamined Patent Publication No. 2010-34162

The present invention has been devised in view of the above circumstances, and an object thereof is to provide a solar cell and a method for manufacturing the solar cell that further improve photoelectric conversion characteristics.

The present invention employs the following means in order to solve the above problems and achieve the object. That is,
[1] A crystalline solar cell according to one embodiment of the present invention includes a flat crystalline substrate containing p-type or n-type single crystal or polycrystalline silicon and having a photoelectric conversion function; and light reception of the crystalline substrate A first semiconductor layer disposed on a surface side and containing amorphous or microcrystalline silicon; and disposed on a back surface side opposite to the light-receiving surface of the crystalline substrate and having a non-conductive type opposite to the first semiconductor layer A first semiconductor layer disposed between one of the crystalline substrate and the first semiconductor layer and between the crystalline substrate and the second semiconductor layer; And a silicon oxide layer.

[2] The crystalline solar cell according to [1], wherein the second is disposed between the crystalline substrate and the first semiconductor layer and between the crystalline substrate and the second semiconductor layer. The silicon oxide layer may be disposed.

[3] In the crystalline solar cell according to [1], the thickness of the first silicon oxide layer may be 10 to 30 mm.

[4] In the crystalline solar cell according to [1], a side surface of the crystalline substrate may be covered with a third silicon oxide layer.

[5] The crystalline solar cell according to [1], wherein the transparent conductive film is disposed on at least one of the light receiving surface side of the first semiconductor layer and the back surface side of the second semiconductor layer; And a comb-shaped electrode disposed on the film.

[6] In the crystalline solar cell according to [1], a white coating film or a reflective layer that reflects light transmitted from the back surface side of the crystalline substrate toward the crystalline substrate side is formed of the second semiconductor layer. It may be provided on the back side.

[7] In the crystalline solar cell according to [1], a back electrode may be arranged so as to cover the back side of the second semiconductor layer.

[8] A method for manufacturing a crystalline solar cell according to one embodiment of the present invention includes a crystalline solar cell having a photoelectric conversion function and including a planar crystalline substrate containing p-type or n-type single crystal or polycrystalline silicon. A method of manufacturing a battery, comprising: forming a first silicon oxide layer on a light-receiving surface side of the crystalline substrate or on a back surface side opposite to the light-receiving surface; and first including amorphous or microcrystalline silicon Forming a semiconductor layer on the light receiving surface side, and forming a second semiconductor layer containing amorphous or microcrystalline silicon having a conductivity type opposite to that of the first semiconductor layer on the back surface side. .

[9] In the method for manufacturing a crystalline solar cell according to [8], the first silicon oxide layer may be formed with a thickness of 10 to 30 mm.

[10] The method for producing a crystalline solar cell according to [8] above, between the step of forming the first silicon oxide layer and the step of forming the first semiconductor layer and the second semiconductor layer. A step of exposing the surface of the first silicon oxide layer to plasma containing a desired process gas may be provided.

[11] A crystalline solar cell according to one embodiment of the present invention includes a flat crystalline substrate containing p-type or n-type single crystal or polycrystalline silicon and having a photoelectric conversion function; and light reception of the crystalline substrate A first semiconductor layer disposed on a surface side and containing amorphous or microcrystalline silicon; and disposed on a back surface side opposite to the light-receiving surface of the crystalline substrate and having a non-conductive type opposite to the first semiconductor layer A first semiconductor layer disposed between one of the crystalline substrate and the first semiconductor layer and between the crystalline substrate and the second semiconductor layer; A silicon carbide layer of;
Have

[12] In the crystalline solar cell according to [11], the second is provided between the crystalline substrate and the first semiconductor layer and between the crystalline substrate and the second semiconductor layer. The silicon carbide layer may be arranged.

[13] In the crystalline solar cell according to [11], a side surface of the crystalline substrate may be covered with a third silicon carbide layer.

[14] The crystalline solar cell according to [11], wherein the transparent conductive film is disposed on at least one of the light receiving surface side of the first semiconductor layer and the back surface side of the second semiconductor layer; And a comb-shaped electrode disposed on the film.

[15] In the crystalline solar cell according to [11], a white coating film or a reflective layer that reflects light transmitted from the back surface side of the crystalline substrate toward the crystalline substrate side is formed of the second semiconductor layer. It may be provided on the back side.

[16] In the crystalline solar cell according to [11], a back electrode may be arranged so as to cover the back side of the second semiconductor layer.

[17] A method for manufacturing a crystalline solar cell according to one embodiment of the present invention includes a crystalline solar cell having a photoelectric conversion function and including a planar crystalline substrate containing p-type or n-type single crystal or polycrystalline silicon. A method of manufacturing a battery, comprising: forming a silicon carbide layer on a light receiving surface side of the crystalline substrate or a back surface opposite to the light receiving surface; and an amorphous material having a conductivity type opposite to or the same as the crystalline substrate. Or forming a first semiconductor layer made of microcrystalline silicon on the light receiving surface side, and forming a second semiconductor layer made of amorphous or microcrystalline silicon having a conductivity type opposite to that of the first semiconductor layer on the back surface side. And comprising;

[18] The method for manufacturing a crystalline solar cell according to [17], wherein the carbonization is performed between the step of forming the silicon carbide layer and the step of forming the first semiconductor layer and the second semiconductor layer. You may provide the process of performing the process which exposes the surface of a silicon layer to the plasma which consists of desired process gas.

[19] A crystalline solar cell according to one embodiment of the present invention includes a flat crystalline substrate containing p-type or n-type single crystal or polycrystalline silicon and having a photoelectric conversion function; and light reception by the crystalline substrate. A first semiconductor layer disposed on a surface side and containing amorphous or microcrystalline silicon; and disposed on a back surface side opposite to the light-receiving surface of the crystalline substrate and having a non-conductive type opposite to the first semiconductor layer A second semiconductor layer containing crystalline or microcrystalline silicon; and disposed between one of the crystalline substrate and the first semiconductor layer and between the crystalline substrate and the second semiconductor layer. A first aluminum oxide layer formed thereon.

[20] The crystalline solar cell according to [19], wherein the second is provided between the crystalline substrate and the first semiconductor layer and between the crystalline substrate and the second semiconductor layer. An aluminum oxide layer may be provided.

[21] In the crystalline solar cell according to [19], a side surface of the crystalline substrate may be covered with a third aluminum oxide layer.

[22] The crystal solar cell according to [19], wherein the transparent conductive film disposed on at least one of the light receiving surface side of the first semiconductor layer and the back surface side of the second semiconductor layer; And a comb-type electrode disposed on the conductive film.

[23] In the crystalline solar cell according to [19], a white coating film or a reflective layer that reflects light transmitted from the back surface side of the crystalline substrate toward the crystalline substrate side is formed of the second semiconductor layer. It may be provided on the back side.

[24] In the crystalline solar cell according to [19], a back electrode may be arranged so as to cover the back side of the second semiconductor layer.

[25] A method for manufacturing a crystalline solar cell according to one embodiment of the present invention includes a crystalline solar cell having a photoelectric conversion function and including a planar crystalline substrate containing p-type or n-type single crystal or polycrystalline silicon. A method of manufacturing a battery, comprising: forming an aluminum oxide layer on a light receiving surface side of the crystalline substrate or on a back surface opposite to the light receiving surface; Or forming a first semiconductor layer made of microcrystalline silicon on the light receiving surface side, and forming a second semiconductor layer made of amorphous or microcrystalline silicon having a conductivity type opposite to that of the first semiconductor layer on the back surface side. And have;

[26] The method for manufacturing a crystalline solar cell according to [25] described above, wherein the oxidation is performed between the step of forming the aluminum oxide layer and the step of forming the first semiconductor layer and the second semiconductor layer. You may provide the process of performing the process which exposes the surface of an aluminum layer to the plasma which consists of desired process gas.

According to the crystalline solar cell according to the above [1] to [7], it is interposed between the crystalline substrate and the first semiconductor layer and between the crystalline substrate and the second semiconductor layer. Since the first silicon oxide layer is disposed, a tunnel current flows. This reduces the interface state density at one of the interface between the crystalline substrate and the first semiconductor layer and the interface between the crystalline substrate and the second semiconductor layer. For this reason, the band in the said interface curves, and a passivation effect arises. As described above, it is possible to provide a crystalline solar cell with improved photoelectric conversion characteristics.

In the method for manufacturing a crystalline solar cell according to the above [8] to [10], the first semiconductor layer and the second semiconductor layer are formed after the first silicon oxide layer is formed on the light receiving surface side or the back surface side of the crystalline substrate. By forming the semiconductor layer, the above-described passivation effect occurs. Thereby, it becomes possible to stably produce a crystalline solar cell with improved photoelectric conversion characteristics.
In particular, in the case of the method for producing a crystalline solar cell according to [10] above, a crystalline solar cell with further improved photoelectric conversion characteristics can be obtained by performing plasma treatment on the surface of the first silicon oxide layer.

In addition, according to the crystalline solar cell described in [11] to [16] above, between the crystalline substrate and the first semiconductor layer and between the crystalline substrate and the second semiconductor layer. Since the first silicon carbide layer is disposed on one side, a tunnel current flows. This reduces the interface state density at one of the interface between the crystalline substrate and the first semiconductor layer and the interface between the crystalline substrate and the second semiconductor layer. For this reason, the band in the said interface curves, and a passivation effect arises. As described above, it is possible to provide a crystalline solar cell with improved photoelectric conversion characteristics.

In the method for manufacturing a crystalline solar cell according to [17] to [18], the first semiconductor layer and the second semiconductor layer are formed after the first silicon carbide layer is formed on the light receiving surface side or the back surface side of the crystalline substrate. By forming the semiconductor layer, the above-described passivation effect can be obtained. Thereby, it becomes possible to stably produce a crystalline solar cell with improved photoelectric conversion characteristics.
In particular, in the case of the method for producing a crystalline solar cell according to [18] above, a crystalline solar cell with further improved photoelectric conversion characteristics can be obtained by subjecting the surface of the first silicon carbide layer to plasma treatment.

In addition, according to the crystalline solar cell described in [19] to [24] above, oxidation is performed between the crystalline substrate and the first semiconductor layer, or between the crystalline substrate and the second semiconductor layer. Since the aluminum layer is disposed, a tunnel current flows. Thereby, the interface state density in one of the interface between the crystalline substrate and the first semiconductor layer and the crystal substrate and the second semiconductor layer is reduced. For this reason, the band in the said interface curves, and a passivation effect arises. As described above, it is possible to provide a crystalline solar cell with improved photoelectric conversion characteristics.

In the method for manufacturing a crystalline solar cell according to the above [25] to [26], the first semiconductor layer and the second semiconductor layer are formed after the aluminum oxide layer is formed on the light receiving surface side or the back surface side of the crystalline substrate. By forming, the passivation effect mentioned above arises. Thereby, it becomes possible to stably produce a crystalline solar cell with improved photoelectric conversion characteristics.
In particular, in the case of the method for producing a crystalline solar cell according to [26] above, a crystalline solar cell with further improved photoelectric conversion characteristics can be obtained by subjecting the surface of the aluminum oxide layer to plasma treatment.

It is sectional drawing which shows typically one structural example (1st embodiment) of the crystalline solar cell of this invention. It is sectional drawing which shows typically the example of 1 structure (2nd embodiment) of the crystalline solar cell of this invention. It is sectional drawing which shows typically the example of 1 structure (3rd embodiment) of the crystalline solar cell of this invention. It is sectional drawing which shows typically the example of 1 structure (4th embodiment) of the crystal solar cell of this invention.

Hereinafter, a first embodiment of a crystalline solar cell (crystalline silicon solar cell) according to the present invention will be described with reference to the drawings.

<First embodiment>
FIG. 1 is a cross-sectional perspective view schematically showing one structural example of the crystalline solar cell of the present invention.
As shown in FIG. 1, a crystalline solar cell 1A (1) includes a crystalline substrate (base) 10, a first silicon oxide layer (20a) 20, a first semiconductor layer 11, a second semiconductor layer 12, and a transparent conductive material. The film 13, the first electrode 14, the transparent conductive film 15, and the second electrode 16 are roughly configured. The light receiving side of the crystalline solar cell 1A (1) is defined as a light receiving surface 1α, and the surface facing the light receiving surface 1α (the side opposite to the light receiving surface 1α) is defined as a back surface 1β.

The crystalline substrate 10 is a semiconductor substrate having a photoelectric conversion function. As the crystalline substrate 10, for example, a flat substrate having a thickness of 50 μm to 200 μm and containing p-type or n-type single crystal or polycrystalline silicon (Si) can be used. As such a substrate, a wafer cut from a single crystal silicon ingot formed by a pulling method, a wafer cut from a polycrystalline silicon ingot formed by a casting technique, or the like can be used.

The first silicon oxide layer 20a is made of silicon oxide (SiOx or SiOx: H, where 0 <x ≦ 2), and includes a surface 10a on the light-receiving surface 1α side and a surface 10b on the back surface 1β side of the crystalline substrate 10. It is formed so as to cover at least one. Thus, the first silicon oxide layer 20a is arranged between one of the crystalline substrate 10 and the first semiconductor layer 11 and between the crystalline substrate 10 and the second semiconductor layer 12. Yes.
In the example shown in FIG. 1, the silicon oxide layer 20 is disposed between the crystalline substrate 10 and the second semiconductor layer 12. However, the present invention is not limited to this, and the crystalline substrate 10 and the second semiconductor layer 12 are arranged. A first silicon oxide layer 20 a may be disposed between the semiconductor layer 11.

The thickness of the first silicon oxide layer 20a is not particularly limited as long as the tunnel current flows. Specifically, such a thickness is preferably in the range of 10 to 30 mm, for example. When the thickness of the first silicon oxide layer 20a is less than 10 mm, the curvature of the band becomes small and the passivation effect becomes small, which is not good. On the other hand, when the thickness of the first silicon oxide layer 20a exceeds 30 mm, the tunnel current is reduced, and the photoelectric conversion efficiency is thus reduced. Therefore, a preferable range of the thickness of the first silicon oxide layer 20a is 10 to 30 mm.

The first semiconductor layer 11 containing amorphous or microcrystalline silicon opposite to or the same conductivity type as the crystalline substrate 10 is disposed on the light receiving surface 1α side of the crystalline substrate 10.
For example, when a substrate made of n-type silicon is used as the crystalline substrate 10, the first semiconductor layer 11 includes p-type amorphous silicon (pa-Si), p-type microcrystalline silicon (p-μc-Si). N-type amorphous silicon (na-Si) and n-type microcrystalline silicon (n-μc-Si) are included.

The second semiconductor layer 12 containing amorphous or microcrystalline silicon having a conductivity type opposite to that of the first semiconductor layer 11 is disposed on the back surface 1β side of the crystalline substrate 10.
For example, when the first semiconductor layer 11 is p-type, the second semiconductor layer 12 contains n-type amorphous silicon (na-Si) or n-type microcrystalline silicon (n-μc-Si). .

The transparent conductive film 13 is made of a conductive material having optical transparency (transmits sunlight), and is disposed on the light receiving surface 1α side of the first semiconductor layer 11.
Examples of the constituent material of the transparent conductive film 13 include a transparent conductive film mainly composed of zinc oxide in addition to an electrically conductive oxide such as zinc oxide, tin oxide, and indium oxide in which oxygen defects are controlled. ATO (Sb-doped SnO ₂ ), FTO, which is a transparent conductive film mainly composed of tin oxide, such as AZO (Al-doped ZnO), BZO (B-doped ZnO), FZO (F-doped ZnO), and GZO (Ga-doped ZnO). (F-doped SnO ₂ ) or the like, ITO (Sb-doped In ₂ O ₃ ), IFO (F-doped In ₂ O ₃ ), or the like, which is a transparent conductive film mainly composed of indium oxide, can be used. Moreover, as a constituent material of the transparent conductive film 13, so-called TAOS (transparent amorphous oxide semiconductor) including IGZO (InGaZnO) which can obtain high mobility may be used.
Particularly suitable as a constituent material of the transparent conductive film 13 is a SnO ₂ or ZnO-based material formed by thermal CVD or MOCVD. The transparent conductive film 13 made of these materials has irregularities called textures formed on the surface thereof. For this reason, light easily scatters on the surface of the transparent conductive film 13. Then, the optical path is bent by the transparent conductive film 13 disposed on the light incident side or the reflection side, and the distance passing through the crystalline substrate 10 becomes longer. For this reason, carrier generation efficiency improves and a photoelectric conversion characteristic improves further.

The comb-shaped first electrode 14 is formed on the light receiving surface 1α side of the transparent conductive film 13.
As a constituent material of the first electrode 14, a conductive material may be appropriately selected according to the structure and process design of the crystalline solar cell 1A (1). As such a constituent material, for example, aluminum can be used for the purpose of suppressing power loss, or a low resistance material such as silver can be used.

The transparent conductive film 15 is disposed on the back surface 1β side of the second semiconductor layer 12.
As a constituent material of the transparent conductive film 15, for example, zinc oxide, tin oxide, indium tin oxide (ITO) or the like is used.
The comb-shaped second electrode 16 is formed on the back surface 1β side of the transparent conductive film 15. As a constituent material of the second electrode 16, a conductive material may be appropriately selected according to the structure and process design of the crystalline solar cell 1A (1). As such a constituent material, for example, aluminum can be used for the purpose of suppressing power loss, or a low resistance material such as silver can be used.

In addition, a white coating film or a reflective layer is formed so as to cover the back surface 1β side of the second semiconductor layer 12 and the second electrode 16.
This white coating film or reflective layer is a layer (film) for reflecting light transmitted from the back surface 10b side of the crystalline substrate 10 to the crystalline substrate 10 side. Here, the case where the white coating film 17 is formed on the first electrode 16 will be described as an example.

The white coating film 17 is a white coating film having a high reflectance in the absorption wavelength region of the crystalline substrate 10. As a white component of the white coating film 17, for example, a compound composed of at least one selected from the group consisting of barium sulfate, magnesium oxide, and titanium oxide can be used.
The white coating film 17 is formed by applying a white paint composed of fine particles of the white component, a binder, and a solvent to the back surface side of the second semiconductor layer 12. The white coating film 17 having such a configuration functions as a reflecting surface that diffusely reflects a part of light (sunlight) transmitted through the crystalline substrate 10 toward the back surface 10b side of the crystalline substrate 10.

When the surface (light receiving surface) on the surface 1α side of the crystalline solar cell 1A (1) receives sunlight, the sunlight incident from the surface is absorbed by the crystalline substrate 10. However, if the thickness of the crystalline substrate 10 is thin in order to reduce the amount of raw material used on the crystalline solar cell 1, the amount of light that cannot be absorbed by the crystalline substrate 10 increases. For this reason, a part of sunlight easily passes through the crystalline substrate 10.
When part of sunlight passes through the crystalline substrate 10 in this way, part of sunlight passes through the second semiconductor layer 12 and the transparent electrode 15 and reaches the white coating film 17. Under the present circumstances, the light which reached | attained the white coating film 17 is reflected toward the surface 1 alpha side by the light reflectivity which the white coating film 17 has. The light reflected by the white coating film 17 passes through the transparent electrode 15 and the second semiconductor layer 12 again and is absorbed by the crystalline substrate 10. That is, part of the light transmitted through the crystalline substrate 10 is converted into electric energy by the light reflecting function of the white coating film 17.

Thus, the use efficiency of light in the crystalline solar cell 1 can be improved by providing the white coating film 17 having a light reflection function.
The constituent material, film thickness, position, etc. of the white coating film 17 can be changed according to the optical characteristics of the crystalline substrate 10, the first electrode 14, and the second electrode 16, which are other constituent requirements. By appropriately selecting the configuration of such a white coating film 17, reuse of transmitted light can be more appropriately realized. Therefore, it is possible to improve the light utilization efficiency without forcing the crystalline substrate 10, the first electrode 14, and the second electrode 16 to change the constituent materials and design rules.

When a silicon substrate is used as the crystalline substrate 10, the above-described white coating film 17 is preferably configured to have a reflectance of 90% or more particularly in a wavelength region of 500 nm to 1200 nm. If the white coating film 17 has such a reflectance, the light that can be absorbed again by the crystalline substrate 10 can be efficiently reflected from the light transmitted through the crystalline substrate 10.

Further, when a reflective layer is provided in place of the white coating film 17, this reflective layer can be composed of a film of aluminum, silver, copper or the like, for example.

In such a crystalline solar cell 1A (1), when the surface (light receiving surface) on the light receiving surface 1α side of the crystalline solar cell 1A (1) is irradiated with sunlight (arrows in FIG. 1), it enters from the light receiving surface. Sunlight passes through the transparent conductive film 13, passes through the first semiconductor layer 11, and further reaches the surface 10 a of the crystalline substrate 10. At this time, the surface 10a of the crystalline substrate 10 functions as a light receiving surface that receives sunlight. Then, the sunlight transmitted through the crystalline substrate 10 enters the second semiconductor layer 12.
Thus, when sunlight passes through each layer of the crystalline solar cell 1A (1), the light absorbed in each part of the crystalline substrate 10 generates electrons and holes that are carriers. Then, the generated carriers are separated into the first semiconductor layer 11 and the second semiconductor layer 12 according to the potential gradient of the pn junction or the heterojunction portion that is the junction portion between the crystalline substrate 10 and the second semiconductor layer 12. The The carriers separated in this way are collected from the first electrode 14 and the second electrode 16 and thereby converted into electric energy. That is, the light absorbed by the crystalline substrate 10 is converted into electric energy by the photoelectric conversion function of the crystalline substrate 10.

At this time, in the crystalline solar cell 1 </ b> A (1) of the present invention, between the crystalline substrate 10 and the first semiconductor layer 11 and between the crystalline substrate 10 and the second semiconductor layer 12. Since the first silicon oxide layer 20a is disposed, a tunnel current flows through the first silicon oxide layer 20a. For this reason, higher energy carriers are collected from the first electrode 14 or the second electrode 16. As a result, the crystalline solar cell 1A (1) of the present invention has further improved photoelectric conversion characteristics.

Also, the first silicon oxide layer 20a is disposed between the crystalline substrate 10 and the first semiconductor layer 11 and between the crystalline substrate 10 and the second semiconductor layer 12. As a result, the interface state density is decreased and the band at the interface is curved. As a result, a passivation effect is generated, and the crystalline solar cell 1A (1) of the present invention has improved photoelectric conversion characteristics.

Further, the first silicon oxide layer 20a is disposed between the crystalline substrate 10 and the first semiconductor layer 11 and between the crystalline substrate 10 and the second semiconductor layer 12. This reduces the number of defects at the silicon / silicon oxide interface. For this reason, it is possible to bend the band without additional doping.

Note that the thickness of the first semiconductor layer 11 and the thickness of the second semiconductor layer 12 described above are such that the p-type semiconductor layer (for example, the first semiconductor layer 11) is relatively thick, and the n-type semiconductor. A structure in which the layer forming the layer (for example, the second semiconductor layer 12) is relatively thin is preferable. If the thicknesses of the first semiconductor layer 11 and the second semiconductor layer 12 are changed in this way, the carrier generated in the p-type semiconductor layer (for example, the first semiconductor layer 11) is regenerated. Coupling is reduced and conversion efficiency is improved.

<Second embodiment>
Next, a second embodiment of the present invention will be described.
FIG. 2 is a cross-sectional view schematically showing a configuration example of the solar battery 1B (1) of the present embodiment. In the following description, portions different from the above-described first embodiment will be mainly described, and description of portions similar to the first embodiment will be omitted.

In the crystalline solar cell 1B (1) of the second embodiment, both the crystalline substrate 10 and the first semiconductor layer 11 and the crystalline substrate 10 and the second semiconductor layer 12 are One silicon oxide layer 20a or the second silicon oxide layer 20b is provided. Here, for example, a first silicon oxide layer 20 a is provided between the crystalline substrate 10 and the first semiconductor layer 11, and a second silicon oxide layer is provided between the crystalline substrate 10 and the second semiconductor layer 12. An example in which the layer 20b is provided is shown.

As described above, the first silicon oxide layer 20a or the second silicon oxide layer 20a is formed between the crystalline substrate 10 and the first semiconductor layer 11 and between the crystalline substrate 10 and the second semiconductor layer 12. By disposing the silicon oxide layer 20b, more high energy carriers are collected. For this reason, it becomes possible to further improve the photoelectric conversion efficiency of the solar cell 1B (1).

<Third embodiment>
Next, a third embodiment of the present invention will be described. FIG. 3 is a cross-sectional view schematically showing a configuration example of the solar battery 1C (1) of the present embodiment. In the following description, portions different from the above-described first embodiment will be mainly described, and description of portions similar to the first embodiment will be omitted.

In the first embodiment described above, the transparent conductive film 15 is disposed on the second semiconductor layer 12, and the first electrode 16 formed in a comb shape is disposed on the transparent conductive film 15. On the other hand, in the crystalline solar cell 1C (1) of the third embodiment, the back surface electrode 16 is arranged so as to cover the entire surface of the second semiconductor layer 12 on the back surface 1β side.

<Fourth embodiment>
Next, a third embodiment of the present invention will be described. FIG. 4 is a cross-sectional view schematically showing a configuration example of the solar battery 1D (1) of the present embodiment. In the following description, portions different from the above-described first embodiment will be mainly described, and description of portions similar to the first embodiment will be omitted.

In the crystalline solar cell 1D (1) of the fourth embodiment, in addition to both between the crystalline substrate 10 and the first semiconductor layer 11 and between the crystalline substrate 10 and the second semiconductor layer 12, Side surface 10c of crystalline substrate 10 is covered with silicon oxide layer 20 (third silicon oxide layer 20c).
Thus, by providing the third silicon oxide layer 20c also on the side surface 10c of the crystalline substrate 10, the surface defects of the crystalline substrate 10 are further reduced. For this reason, it is possible to further increase the photoelectric conversion efficiency.

Next, a method for manufacturing the above-described solar cell (crystal solar cell) will be described. The crystalline solar cell 1A (1) of the first embodiment is formed by the following manufacturing process, for example.

<First embodiment>
First, fine unevenness on the surface called texture (not shown) is formed on the crystalline substrate 10 (substrate made of silicon) by wet etching or dry etching. Next, a cleaning process is performed on the surface of the crystalline substrate 10.
Next, a silicon oxide film 20 is formed on the surface of the crystalline substrate 10 on which the texture is formed. The method for forming the silicon oxide film 20 on the surface of the crystalline substrate 10 is not particularly limited. Examples of such methods include thermal oxidation with water vapor or oxygen, and deposition methods such as plasma CVD and ALD (atomic layer deposition). Among them, as a method for forming a high-quality ultrathin oxide film with good controllability, for example, a method described in Japanese Patent Application Laid-Open No. 2002-064093 can be used.

Specifically, such a method has a basic configuration, for example, a method in which the semiconductor substrate (crystalline substrate) 10 is immersed in an oxidizing chemical solution and is oxidized. Thereby, an extremely thin oxide film is formed on the surface of the crystalline substrate 10. As described above, the thickness of the oxide film can be easily controlled by immersing the crystalline substrate 10 in the oxidizing chemical solution and performing the chemical oxidation treatment.
Note that it is desirable to perform a process of removing a natural oxide film or impurities on the surface of the crystalline substrate 10 before the crystalline substrate 10 is immersed in the oxidizing chemical solution. This makes it possible to stably form a high quality ultrathin oxide film.

Then, if necessary, this oxide film may be modified by heat treatment in an inert gas atmosphere. By performing the heat treatment on the oxide film in this manner, the leakage current density is reduced. Usually, a chemically oxidized oxide film before heat treatment is in a suboxide state, that is, a state in which oxygen is deficient. For this reason, the oxide film in this state tends to have a large leakage current. However, by performing the heat treatment in this way, the suboxide can be reduced, and the interface between the substrate and the oxide film can be made smooth by the heat treatment. For this reason, the leakage current density of the oxide film can be reduced. However, in the manufacturing process of the crystalline solar cell 1, there is no practical problem even if this heat treatment is not performed.

By forming the oxide film in this way, a high-quality oxide film having a thickness of 0.3 to 3 nm with little leakage current can be easily formed on the surface of the crystalline substrate 10. In addition, the thickness of the oxide film can be easily controlled by adjusting the type and temperature of the oxidizing chemical solution in which the crystalline substrate 10 is immersed. This is because the film thickness of the ultrathin oxide film to be formed hardly changes when the time during which the crystalline substrate 10 is immersed in the chemical solution is longer than a certain time. In addition, since this fixed time changes with chemical | medical solutions, what is necessary is just to set suitably with the kind and temperature of a chemical | medical solution.

The type of the chemical solution is nitric acid, ozone-dissolved water, hydrogen peroxide solution, mixed solution of hydrochloric acid and hydrogen peroxide solution, mixed solution of sulfuric acid and hydrogen peroxide solution, mixed solution of ammonia and hydrogen peroxide solution, sulfuric acid And at least one chemical solution selected from a mixed solution of nitric acid, perchloric acid, and boiling water. This is because by using these chemical solutions, ultrathin oxide films having various thicknesses in the range of 0.3 to 3 nm can be formed with high film thickness controllability.

The inert gas is preferably at least one gas selected from nitrogen, argon, neon, hydrogen, or a mixed gas thereof. This is because, when heat treatment is performed using these inert gases, new oxidation does not occur in the oxide film due to heating. For this reason, a change in the thickness of the oxide film during the heat treatment can be prevented.

Further, the heating temperature of the inert gas in the heat treatment is desirably in the range of 500 to 1200 ° C. By heating the oxide film in this temperature range, the quality of the oxide film can be improved and the leakage current density can be reduced.
Thus, an oxide film (silicon oxide layer 20) is formed on the surface of the crystalline substrate 10 made of silicon.

When the oxide film is formed only on one surface (one surface, for example, the surface 10b) of the crystalline substrate 10, for example, the non-film-formed surface (the other surface, for example, the surface 10a) of the crystalline substrate 10 is masked. And the oxide film on the non-film-formed surface (the other surface) of the crystalline substrate 10 on which the oxide film is formed on both sides is removed by wet etching (single-side coating with a roller wetted with an etchant). Is used.

Next, the first semiconductor layer 11 and the second semiconductor layer 12 are formed. In addition, before the formation of the first semiconductor layer 11 and the second semiconductor layer 12, the surface of the silicon oxide layer 20 (first silicon oxide layer 20a) is exposed to plasma made of a desired process gas (hereinafter referred to as “plasma”). Also referred to as “processing”.
When the first semiconductor layer 11 or the second semiconductor layer 12 is a p-type semiconductor, a gas (for example, B ₂ H ₆ ) containing boron (B) is used as a process gas for plasma treatment. On the other hand, when the first semiconductor layer 11 or the second semiconductor layer 12 is an n-type semiconductor, a gas containing phosphorus (P) (for example, PH ₃ ) or the like is used as a process gas.
In this way, by subjecting the surface of the oxide film (first silicon oxide layer 20a) to a desired plasma, the plasma-treated surface of the oxide film (first silicon oxide layer 20a) The electrical barrier between the first semiconductor layer 11 or the second semiconductor layer 12 formed on the surface is lowered. For this reason, the rectification between the surface of the oxide film (first silicon oxide layer 20a) and the first semiconductor layer 11 or the second semiconductor layer 12 becomes high, and the flow of charge becomes smoother. As a result, power generation efficiency is improved. In other words, the process of exposing the surface of the oxide film (first silicon oxide layer 20a) to desired plasma contributes to the improvement of power generation efficiency.

Next, the first semiconductor layer 11 is formed on the surface 10a of the crystalline substrate 10 by performing a film forming process using, for example, a CVD method.
Next, the second semiconductor layer 12 is formed by performing a film forming process using, for example, a CVD method on the back surface 10b of the crystalline substrate 10 on which the silicon oxide layer 20 is formed.

Next, a film formation process using a sputtering method is performed on the surface of the first semiconductor layer 11 and the surface of the second semiconductor layer 12. As a result, the transparent conductive film 13 is formed on the front surface 1α side of the first semiconductor layer 11, and the transparent conductive film 15 is formed on the back surface 1β side of the second semiconductor layer 12.
Then, a film forming process using a sputtering method, a printing method, or a coating method is performed on the transparent conductive film 13 and the transparent conductive film 15. Thus, the first electrode 14 and the second electrode 16 are formed.

And the film-forming process is performed on the 2nd electrode 16 using the apply | coating method using a white coating material. Thereby, the white coating film 17 is formed.
As described above, a crystalline solar cell 1A (1) as shown in FIG. 1 is obtained.

<Second embodiment>
Hereinafter, the manufacturing method of crystalline solar cell 1B (1) of 2nd embodiment is demonstrated.
FIG. 2 is a cross-sectional view schematically showing a configuration example of the solar battery 1B (1) of the present embodiment. In the following description, portions different from the above-described first embodiment will be mainly described, and description of portions similar to the first embodiment will be omitted.

In the first embodiment described above, the oxide film (first silicon oxide layer 20a) is formed only on one surface (one surface, for example, the surface 10b) of the crystalline substrate 10, but the crystalline solar cell 1B ( In the manufacturing method 1), silicon oxide layers 20 (first silicon oxide layer 20a and second silicon oxide layer 20b) are formed on both surfaces ( surfaces 10a and 10b) of the crystalline substrate 10, respectively. Here, for example, an example is shown in which the first silicon oxide layer 20a is provided on the surface 10b and the second silicon oxide layer 20b is provided on the surface 10a.
Thus, the silicon oxide layer 20 (first silicon oxide layer) is formed between the crystalline substrate 10 and the first semiconductor layer 11 and between the crystalline substrate 10 and the second semiconductor layer 12, respectively. By forming the layer 20a and the second silicon oxide layer 20b), more high energy carriers can be collected. For this reason, it is possible to further increase the photoelectric conversion efficiency.

<Third embodiment>
Hereinafter, the manufacturing method of crystalline solar cell 1C (1) of 3rd embodiment is demonstrated.
FIG. 3 is a cross-sectional view schematically showing a configuration example of the solar battery 1C (1) of the present embodiment. In the following description, portions different from the above-described first embodiment will be mainly described, and description of portions similar to the first embodiment will be omitted.

In the first embodiment described above, the transparent conductive film 15 is formed on the second semiconductor layer 12, and the comb-shaped first electrode 16 is formed on the transparent conductive film 15. On the other hand, in the manufacturing method of the crystalline solar cell 1C (1) of the present embodiment, the back electrode 16 is formed so as to cover the entire surface of the second semiconductor layer 12 on the back surface 1β side.

<Fourth embodiment>
Hereinafter, the manufacturing method of crystalline solar cell 1D (1) of 4th embodiment is demonstrated.
FIG. 4 is a cross-sectional view schematically showing a configuration example of the crystalline solar cell 1D (1) of the present embodiment. In the following description, portions different from the above-described second embodiment will be mainly described, and description of portions similar to the second embodiment will be omitted.

In the second embodiment described above, the silicon oxide layer 20 (first silicon oxide layer 20a, second silicon oxide layer 20b) is formed so as to cover both surfaces ( surfaces 10a, 10b) of the crystalline substrate 10. On the other hand, in the manufacturing method of the crystalline solar cell 1D (1) of the present embodiment, the silicon oxide layer 20 (third silicon oxide layer 20c) is formed so as to cover the side surface 10c of the crystalline substrate 10.
As described above, the first silicon oxide layer 20a and the third silicon oxide layer 20c formed integrally with the second silicon oxide layer 20b are also disposed on the side surface 10c of the crystalline substrate 10, thereby forming a crystal. The surface defects of the conductive substrate 10 are further reduced. For this reason, it is possible to further increase the photoelectric conversion efficiency.

Table 1 shows the results of examining the power generation efficiency of the crystalline solar cell 1 having various configurations including the silicon oxide layer 20 described above.
In the “Silicon oxide layer 20” column of Table 1, “upper surface portion” refers to the surface 10 a of the crystalline substrate 10, that is, when the silicon oxide layer 20 is provided between the crystalline substrate 10 and the first semiconductor layer 11. Indicates. The “lower surface portion” refers to the case where the silicon oxide layer 20 is provided between the surface 10 b of the crystalline substrate 10, that is, between the crystalline substrate 10 and the second semiconductor layer 12. The “side surface portion” refers to the case where the silicon oxide layer 20 is provided on the side surface 10 c of the crystalline substrate 10. A circle indicates that the silicon oxide layer 20 is provided, and a cross indicates that the silicon oxide layer 20 is not provided.
Further, in the “plasma treatment” column of Table 1, “◯” means that a desired plasma treatment was performed, and “x” means that this plasma treatment was not performed.

From Table 1, the following points became clear.
(1) At least a part of the crystalline substrate 10 as compared with the case where the power generation efficiency of the crystal solar cell having the conventional configuration (the silicon oxide layer 20 according to the present invention is not provided at all) is examined (Experimental Example 1). The power generation efficiency of the crystalline solar cell 1 in which the silicon oxide layer 20 was provided on any one of the upper surface portion, the lower surface portion, and the side surface portion was improved.
(2) It was found that among the experimental examples 2, 3, 4, and 5, the power generation efficiency tends to increase as the number increases. In addition, from Experimental Examples 3, 4, and 5, it was found that the power generation efficiency tends to increase as the crystalline substrate 10 is more widely covered with the silicon oxide layer 20.
(3) Since the power generation efficiency of Experimental Example 6 increased compared to Experimental Example 5, it was found that plasma treatment contributed to the increase of power generation efficiency.

In the above, in the crystalline solar cell 1 of the present invention, between the crystalline substrate 10 and the first semiconductor layer 11 or between the crystalline substrate 10 and the second semiconductor layer 12, the silicon oxide layer 20 (SiOx, However, although the configuration example provided with 0 <x ≦ 2) has been described in detail, silicon carbide (SiCy or SiCy: H) is used instead of silicon oxide at the position where the silicon oxide layer 20 is provided in FIGS. However, even if a silicon carbide layer composed of 0 <y ≦ 1) or an aluminum oxide layer composed of aluminum oxide (AlOz or AlOz: H, where 0 <z ≦ 1.5) is provided, the same operation and effect are achieved. Can be obtained. That is, even when a silicon carbide layer or an aluminum oxide layer is provided on the surface of the crystalline substrate 10, the interface state density can be reduced. For this reason, the passivation effect by the curvature of a band arises in an interface. As described above, a crystalline silicon solar cell (crystalline solar cell 1) with improved photoelectric conversion characteristics can be provided.
In addition, when a silicon carbide layer or an aluminum oxide layer is provided instead of the silicon oxide layer 20, the above-described plasma treatment is effective, and power generation efficiency can be improved.

The crystal solar cell of the present invention has been described above, but the present invention is not limited to these examples, and can be appropriately changed without departing from the spirit of the invention.

The present invention is widely applicable to crystal solar cells.

1,1A, 1B, 1C, 1D Crystalline solar cell 10a, 10b Surface 10c Side surface 11 First semiconductor layer 12 Second semiconductor layer 13 Transparent conductive film 14 First electrode 15 Transparent conductive film 16 Second electrode 17 White coating film 20 Oxidation Silicon layer 20a First silicon oxide layer 20b Second silicon oxide layer 20c Third silicon oxide layer

Claims (26)

1. a flat crystalline substrate containing p-type or n-type single crystal or polycrystalline silicon and having a photoelectric conversion function;
   A first semiconductor layer disposed on a light-receiving surface side of the crystalline substrate and containing amorphous or microcrystalline silicon;
   A second semiconductor layer disposed on a back surface opposite to the light receiving surface of the crystalline substrate and including amorphous or microcrystalline silicon having a conductivity type opposite to that of the first semiconductor layer;
   A first silicon oxide layer disposed between the crystalline substrate and the first semiconductor layer and between the crystalline substrate and the second semiconductor layer;
   A crystalline solar cell comprising:
2. The second silicon oxide layer is disposed on the other side between the crystalline substrate and the first semiconductor layer and between the crystalline substrate and the second semiconductor layer. Item 2. The crystalline solar cell according to Item 1.
3. 2. The crystalline solar cell according to claim 1, wherein the thickness of the first silicon oxide layer is 10 to 30 mm.
4. The crystalline solar cell according to claim 1, wherein a side surface of the crystalline substrate is covered with a third silicon oxide layer.
5. A transparent conductive film disposed on at least one of the light receiving surface side of the first semiconductor layer and the back surface side of the second semiconductor layer;
   A comb-shaped electrode disposed on the transparent conductive film;
   The crystal solar cell according to claim 1, further comprising:
6. The white coating film or the reflective layer that reflects light transmitted from the back surface side of the crystalline substrate to the crystalline substrate side is provided on the back surface side of the second semiconductor layer. 2. The crystalline solar cell according to 1.
7. 2. The crystalline solar cell according to claim 1, wherein a back electrode is disposed so as to cover the back side of the second semiconductor layer.
8. A method for producing a crystalline solar cell having a planar crystalline substrate having a photoelectric conversion function and containing p-type or n-type single crystal or polycrystalline silicon;
   Forming a first silicon oxide layer on the light receiving surface side of the crystalline substrate or on the back surface side opposite to the light receiving surface;
   A first semiconductor layer containing amorphous or microcrystalline silicon is formed on the light receiving surface side, and a second semiconductor layer containing amorphous or microcrystalline silicon having a conductivity type opposite to that of the first semiconductor layer is formed on the back surface side. Forming the step;
   A method for producing a crystalline solar cell, comprising:
9. The method for producing a crystalline solar cell according to claim 8, wherein the first silicon oxide layer is formed with a thickness of 10 to 30 mm.
10. Plasma including a desired process gas on the surface of the first silicon oxide layer between the step of forming the first silicon oxide layer and the step of forming the first semiconductor layer and the second semiconductor layer. The method for producing a crystalline solar cell according to claim 8, further comprising a step of exposing to water.
11. a flat crystalline substrate containing p-type or n-type single crystal or polycrystalline silicon and having a photoelectric conversion function;
    A first semiconductor layer disposed on a light-receiving surface side of the crystalline substrate and containing amorphous or microcrystalline silicon;
    A second semiconductor layer disposed on a back surface opposite to the light receiving surface of the crystalline substrate and including amorphous or microcrystalline silicon having a conductivity type opposite to that of the first semiconductor layer;
    A first silicon carbide layer disposed between one of the crystalline substrate and the first semiconductor layer and between the crystalline substrate and the second semiconductor layer;
    A crystalline solar cell comprising:
12. The second silicon carbide layer is disposed on the other side between the crystalline substrate and the first semiconductor layer and between the crystalline substrate and the second semiconductor layer. Item 12. The crystalline solar cell according to Item 11.
13. The crystalline solar cell according to claim 11, wherein a side surface of the crystalline substrate is covered with a third silicon carbide layer.
14. A transparent conductive film disposed on at least one of the light receiving surface side of the first semiconductor layer and the back surface side of the second semiconductor layer;
    A comb-shaped electrode disposed on the transparent conductive film;
    The crystal solar cell according to claim 11, further comprising:
15. The white coating film or the reflective layer that reflects light transmitted from the back surface side of the crystalline substrate to the crystalline substrate side is provided on the back surface side of the second semiconductor layer. 11. The crystalline solar cell according to 11.
16. The crystal solar cell according to claim 11, wherein a back electrode is disposed so as to cover the back side of the second semiconductor layer.
17. A method for producing a crystalline solar cell having a planar crystalline substrate having a photoelectric conversion function and containing p-type or n-type single crystal or polycrystalline silicon;
    Forming a silicon carbide layer on the light-receiving surface side of the crystalline substrate or on the back surface side opposite to the light-receiving surface;
    A first semiconductor layer made of amorphous or microcrystalline silicon opposite to or the same conductivity type as the crystalline substrate is formed on the light-receiving surface side, and amorphous or microcrystalline silicon opposite to the first semiconductor layer. Forming a second semiconductor layer comprising: on the back side;
    A method for producing a crystalline solar cell, comprising:
18. Between the step of forming the silicon carbide layer and the step of forming the first semiconductor layer and the second semiconductor layer, a step of subjecting the surface of the silicon carbide layer to plasma made of a desired process gas The manufacturing method of the crystalline solar cell of Claim 17 characterized by the above-mentioned.
19. a flat crystalline substrate containing p-type or n-type single crystal or polycrystalline silicon and having a photoelectric conversion function;
    A first semiconductor layer disposed on a light-receiving surface side of the crystalline substrate and containing amorphous or microcrystalline silicon;
    A second semiconductor layer disposed on a back surface opposite to the light receiving surface of the crystalline substrate and including amorphous or microcrystalline silicon having a conductivity type opposite to that of the first semiconductor layer;
    Comprising
    A first aluminum oxide layer disposed between the crystalline substrate and the first semiconductor layer and between the crystalline substrate and the second semiconductor layer;
    A crystalline solar cell comprising:
20. The second aluminum oxide layer is disposed on the other side between the crystalline substrate and the first semiconductor layer and between the crystalline substrate and the second semiconductor layer. Item 20. The crystalline solar cell according to Item 19.
21. The crystal solar cell according to claim 19, wherein a side surface of the crystalline substrate is covered with a third aluminum oxide layer.
22. A transparent conductive film disposed on at least one of the light receiving surface side of the first semiconductor layer and the back surface side of the second semiconductor layer;
    A comb-shaped electrode disposed on the transparent conductive film;
    The crystal solar cell according to claim 19, further comprising:
23. The white coating film or the reflective layer that reflects light transmitted from the back surface side of the crystalline substrate to the crystalline substrate side is provided on the back surface side of the second semiconductor layer. 19. The crystalline solar cell according to 19.
24. The crystal solar cell according to claim 19, wherein a back electrode is arranged so as to cover the back side of the second semiconductor layer.
25. A method for producing a crystalline solar cell having a planar crystalline substrate having a photoelectric conversion function and containing p-type or n-type single crystal or polycrystalline silicon;
    Forming an aluminum oxide layer on the light receiving surface side of the crystalline substrate or on the back surface opposite to the light receiving surface;
    A first semiconductor layer made of amorphous or microcrystalline silicon opposite to or the same conductivity type as the crystalline substrate is formed on the light-receiving surface side, and amorphous or microcrystalline silicon opposite to the first semiconductor layer. Forming a second semiconductor layer comprising: on the back side;
    A method for producing a crystalline solar cell, comprising:
26. Between the step of forming the aluminum oxide layer and the step of forming the first semiconductor layer and the second semiconductor layer, a step of exposing the surface of the aluminum oxide layer to plasma made of a desired process gas The method for producing a crystalline solar cell according to claim 25, comprising:

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