JPH04369869A - Solar cell and manufacture thereof - Google Patents

Abstract

PURPOSE:To enable a solar cell to be enhanced in characteristics, where cells can be integrated on the same insulating substrate. CONSTITUTION:A solar cell of this design is provided with a first P-type silicon crystal layer 2 provided onto an insulating substrate, an insulating layer 3 formed on the silicon crystal layer 2, and a second P-type silicon crystal layer 4 provided onto the insulating layer 3 coming into contact with the first P-type silicon crystal layer 2 through openings 35 provided to the insulating layer 3. A photocurrent generated in the second silicon crystal layer 4 by light incident on the layer 4 is taken out through the first P-type silicon crystal layer 2 through the intermediary of the openings 35 provided to the insulating layer 3.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a solar cell in which a thin film crystal cell for photoelectric conversion is provided on an insulating substrate, and a method for manufacturing the same, and more particularly to a solar cell in which a plurality of thin film crystal cells can be integrated on the same substrate, and a method for manufacturing the same. The present invention relates to a manufacturing method thereof.

0002

2. Description of the Related Art FIG. 12 shows, for example, the 20th IEEE Photovoltaic Specialists Conference (1988) Conference Record, Volume 2, Page 1406 (The C
Oference Record of the 20
th IEEE Photovoltaic Spec
ialists Conference, 1988,
Volume 2, pp. 1406) is a cross-sectional view showing the manufacturing process of a conventional solar cell formed by melting and recrystallizing a silicon layer on an insulating film. 301 is an opening provided in the SiO2 film 300, and 401 is the SiO2 film 30.
402 is a silicon layer formed by heating and melting the polycrystalline silicon layer 401, and 403 is a large-grain or single-crystal silicon layer formed by resolidifying the molten silicon layer 402.

Next, the manufacturing process will be explained. First, as shown in FIG. 12(a), a thermal oxidation method or chemical vapor deposition (CVD) process is performed on a silicon substrate 100.
SiO2 film 300 using
is formed, and an opening 301 is provided in the SiO2 film 300 using photolithography and etching techniques. Next, Figure 12(b)
), a silicon layer 401 is grown on the entire surface of the wafer using the CVD technique. Here, this silicon layer 40
1 is a polycrystalline silicon layer. Next, the silicon layer 401 is heated to form a molten silicon layer 402 as shown in FIG. 12(c). Silicon layer 402 is in contact with substrate 1 through opening 301 . This silicon layer 402 is recrystallized to form a large grain size or single crystal silicon layer 403 on the SiO2 film 300 as shown in FIG. 12(d). Thereafter, a pn junction is formed in the silicon layer 403 by impurity diffusion, etc., and electrodes are further formed on the entire back surface of the substrate 100 and a part of the surface of the silicon layer 403, thereby completing the solar cell structure.

Next, the operation will be explained. silicon layer 4
The light incident from the surface of 03 generates carriers in the silicon layer 403, and one polarity of the generated photocurrent is from the surface electrode formed on the silicon layer 403, and the other polarity is from the opening of the SiO2 film 300. It passes through the substrate 100 via 301 and is taken out from the back electrode.

In this conventional example, a conductive substrate 10
Since the silicon layer 403 serving as a functional layer is provided on the substrate, it is not possible to divide the functional area on the substrate to form an integrated cell.

FIG. 13 shows, for example, Japanese Patent Application Laid-Open No. 55-124274.
13(a) is a cross-sectional view, and FIG. 13(b) is a diagram showing the structure of a conventional integrated solar cell disclosed in the publication.
is a perspective view. In the figure, 101 is an insulating substrate made of transparent glass or the like, 102 is a first electrode made of a transparent conductive film divided into stripes on the substrate 101, and 103 is a power generator made of amorphous silicon. The layer 104 is a second electrode provided on the power generation layer 103, and the layer 105 is a protective insulating film formed to cover the element surface.

Next, the operation will be explained. Light incident from the back surface of the substrate 101 passes through the first electrode 102 and generates carriers within the amorphous silicon layer 103. One polarity of the generated photocurrent is extracted from the first electrode 102 and the other polarity is extracted from the second electrode 104.

In this conventional example, an integrated cell is realized in which a plurality of functional regions are formed on an insulating substrate. Here, in this conventional example, amorphous silicon is used as the power generation layer 103, which can be formed under heating at about 300°C. Therefore, for the substrate and substrate side electrodes,
An insulating substrate made of glass or the like that does not have high-temperature resistance and a transparent conductive film are used.

FIG. 14 shows, for example, the technical abstracts of the 3rd International Photovoltaic Science and Engineering Conference (1987).
451 pages (Technical Digest, 3r
d International Photovolt
aic Science and Engineering
ngConference, 1987, pp. 45
1) is a perspective view showing the structure of a conventional integrated solar cell disclosed in 1), in which 201 is an insulating substrate;
02 is a substrate side electrode, 203 is a crystalline semiconductor layer serving as a power generation layer, and 204 is a grid electrode formed on the surface of the semiconductor layer 203.

In this conventional example, a plurality of recesses are formed on an insulating substrate 201 that can withstand high-temperature processes for forming a crystalline semiconductor layer, and a substrate-side electrode 202 is formed at the bottom of the recess. A crystalline semiconductor layer 203 is directly formed on the semiconductor layer 203, a pn junction is provided on the surface of the semiconductor layer 203, and then a grid electrode 204 is formed.

FIG. 15 shows, for example, the 9th European Communities Photovoltaic Solar Energy Conference (1989) Proceedings, page 700 (9th E.C. Photovoltaic Energy Conference).
rgy Conference, 1989, pp.
700) is a diagram showing the structure of a conventional integrated solar cell, in which 501 is an insulating substrate;
02 is a barrier layer, 503 is a first electrode placed on the substrate side, 504 is a crystalline semiconductor layer serving as a power generation layer, and 505 is a second electrode formed on the surface and side surfaces of the semiconductor layer 504.

In this conventional example, a barrier layer 50 is formed on an insulating substrate 501 that can withstand high-temperature processes for forming a crystalline semiconductor layer.
After forming a plurality of striped first electrodes 503 on this barrier layer 502, a power generation layer consisting of a crystalline semiconductor layer 504 is directly formed on the electrodes 503, and further, the surface of the semiconductor layer 504 is A second electrode is formed on the side surface and connected to the first electrode 503 of the adjacent functional area.

[0013]

[Problems to be Solved by the Invention] Conventional solar cells capable of forming integrated cells have been constructed as described above, and have had the following problems. First, in the conventional solar cell shown in FIG. 13, since the power generation layer is formed of amorphous silicon, there is a problem that its performance is inferior to that of a power generation layer formed of silicon crystal. Also, Figure 1
The structure shown in No. 3 has a problem in that the power generation layer cannot be formed of silicon crystal because the substrate and the substrate-side electrode cannot withstand high-temperature processes.

Furthermore, in the conventional solar cells shown in FIGS. 14 and 15, the power generation layer is formed of a crystalline semiconductor, but since the crystal is grown in full contact with the substrate side electrode, the power generation layer In the high-temperature process of forming the solar cell, impurities enter the power generation layer from the substrate-side electrode, which causes a problem in that the characteristics of the solar cell deteriorate.

The present invention was made in order to solve the above-mentioned problems, and provides a structure and structure of a solar cell that can improve the characteristics of a solar cell in which a plurality of cells can be integrated on one substrate. The purpose of this study is to obtain a manufacturing method for the same.

[0016]

[Means for Solving the Problems] A solar cell according to the present invention includes: a first semiconductor layer provided on an insulating substrate; an insulating layer provided on the first semiconductor layer; a second semiconductor layer mainly composed of the same material as the first semiconductor layer provided on the insulating layer so as to be in contact with the first semiconductor layer at an opening provided in the insulating layer; One polarity of a photocurrent generated in the second semiconductor layer due to the incidence of light passes through the opening of the insulating layer to the first semiconductor layer.
The semiconductor layer is taken out through the semiconductor layer.

Further, the method for manufacturing a solar cell according to the present invention includes forming a first semiconductor layer on an insulating substrate, forming an insulating layer on the first semiconductor layer, and forming the first semiconductor layer on the insulating layer. a second semiconductor layer having the same material as the first semiconductor layer as a main component and connected to the first semiconductor layer at the opening on the insulating layer; It is designed to form a .

[0018]

[Operation] In the present invention, the first semiconductor layer provided on the insulating substrate, the insulating layer provided on the first semiconductor layer, and the first semiconductor layer provided in the opening provided in the insulating layer are provided. A second semiconductor layer mainly composed of the same material as the first semiconductor layer provided on the insulating layer so as to be in contact with the first semiconductor layer.
, and one polarity of the photocurrent generated in the second semiconductor layer due to the incidence of light is taken out through the first semiconductor layer through the opening of the insulating layer. It is possible to obtain a high-performance solar cell on an insulating substrate without the inclusion of impurities that deteriorate characteristics in the second semiconductor layer serving as a conversion layer.

Further, in the present invention, a first semiconductor layer is formed on an insulating substrate, an insulating layer is formed on the first semiconductor layer, and the first semiconductor layer is exposed to the insulating layer. A second semiconductor layer is formed on the insulating layer, the second semiconductor layer being connected to the first semiconductor layer in the opening and having the same material as the first semiconductor layer as a main component. Therefore, even if the second semiconductor layer serving as the photoelectric conversion layer and the first semiconductor layer serving as the lower electrode are mixed, the characteristics do not deteriorate, and a high-performance solar cell can be obtained easily. It is possible to fabricate integrated solar cells.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view showing the structure of a solar cell according to an embodiment of the present invention. In the figure, 1 is an insulating substrate made of alumina or the like, 2 is a first p-type semiconductor layer formed on the substrate 1, 3 is an insulating layer formed on the first semiconductor layer 2; 35
4 is an opening provided in the insulating layer 3, 4 is a second p-type semiconductor layer formed on the insulating layer 3, and 44 is a second p-type semiconductor layer 4.
This is an n-type region formed by diffusion or the like. Here, the thickness of the first p-type semiconductor layer is about 2 to 3 microns, the thickness of the insulating layer 3 is about several thousand angstroms to 1 micron, and the thickness of the second p-type semiconductor layer is about 20 to 30 microns.

Next, the manufacturing process will be explained. FIG. 3 is a diagram showing the manufacturing process of the solar cell in FIG. 1, and in the diagram,
The same reference numerals as in FIG. 1 indicate the same or corresponding parts. First, Figure 3
A first film with a thickness of 2 to 3 microns as shown in FIG. 3(b) is formed by CVD or the like on an insulating substrate 1 made of alumina or the like shown in FIG. 3(a).
A p-type polysilicon layer 2 is formed. Next, as shown in FIG. 3(c), the first p-type polysilicon layer 2 is also coated by CVD or the like.
As shown in FIG. 2, an insulating layer 3 having a thickness of approximately several thousand angstroms to 1 micron is formed. Thereafter, using photolithography and etching techniques, an opening 35 is formed in the insulating layer 3 as shown in FIG. 3(d). As shown in FIG. 3(e), 2.
A second p-type polysilicon layer 4 having a thickness of about 0 to 30 microns is formed.

Note that the first and second p-type polysilicon layers 2
, 4 is generally used as the doping impurity. The doping impurity concentration is controlled so that the resistivity of the second p-type polysilicon layer 4 is generally about 1 Ω·cm. On the other hand, since the first p-type polysilicon layer 2 functions as an electrode, its specific resistance must be made sufficiently low. For this reason, the impurity concentration of the first p-type polysilicon layer 2 is made higher than that of the second p-type polysilicon layer 4.

After forming the second p-type polysilicon layer 4, the surface of the p-type polysilicon layer 4 is diffused with phosphorus (P) or ion-implanted with arsenic (As) as shown in FIG. 3(f).
) The solar cell shown in FIG. 1 is completed by forming the n-type region 44 and obtaining the pn junction necessary for photoelectric conversion. In practical use, a surface electrode is formed on the n-type region 44, and an antireflection film (not shown) or the like is further provided on the surface of the n-type region 44 as necessary.

FIG. 4 is a diagram showing another example of the manufacturing process of the solar cell shown in FIG. 1. In the diagram, the same reference numerals as in FIG. 1 indicate the same or corresponding parts. First, as shown in FIG. 4(b), a first p-type polysilicon layer 2 having a thickness of 2 to 3 microns is formed on an insulating substrate 1 made of alumina or the like shown in FIG. 4(a) by CVD or the like. Next, on the first p-type polysilicon layer 2,
A protective film 30 is formed by a VD method or the like as shown in FIG. 4(c), and while heating the substrate 1, the polysilicon layer 2 is further heated from the surface of the protective film 30 to perform area melting recrystallization. (d) As shown in (d), a semiconductor layer 2' is formed in which the crystal grain size of the polysilicon layer 2 is increased or made into a single crystal. After that, the protective film 30 is removed, and an insulating film 3 is newly formed on the semiconductor layer 2'.
) An opening 35 is formed as shown in FIG. Here, insulating film 3
Therefore, it is also possible to use the protective film 30 as it is instead of forming a new one. Opening 3 like this
4(f) by CVD method etc. on the insulating layer 3 provided with 5.
As shown in FIG.
A mold polysilicon layer 4 is formed. Next, a protective film 5 is formed on the second polysilicon layer 4 by a CVD method or the like as shown in FIG. 4(g), and while heating the substrate 1, the polysilicon layer 4 is further heated from the surface of the protective film 5. The polysilicon layer 4 is formed into a semiconductor layer 4 in which the crystal grain size of the polysilicon layer 4 is increased or made into a single crystal by performing region melt recrystallization.
′ is formed. Then, on the surface of the p-type semiconductor layer 4', as shown in FIG.
(i) By forming the n-type region 44 and obtaining the pn junction necessary for photoelectric conversion, the solar cell shown in FIG. 1 is completed. According to the manufacturing method shown in FIG.
Since the crystal grain size of the second semiconductor layer is increased by melt recrystallization or made into a single crystal, the performance of the solar cell can be further improved.

FIG. 5 is a diagram showing still another example of the manufacturing process of the solar cell shown in FIG. 1. In the diagram, the same reference numerals as in FIG. 1 indicate the same or corresponding parts. First, the insulating substrate 1 made of alumina or the like shown in FIG. 5(a) is coated with the material shown in FIG.
A first p-type polysilicon layer 2 is formed as shown in FIG.
An insulating layer 3 is formed on the first p-type polysilicon layer 2 by CVD or the like as shown in FIG. 5(c). Thereafter, an opening 35 is formed in the insulating layer 3 as shown in FIG. 5(d). CVD is performed on the insulating layer 3 provided with the opening 35 in this way.
A second p-type polysilicon layer 4 is formed by a method or the like as shown in FIG. 5(e). Next, a protective film 5 is formed on the second polysilicon layer 4 by CVD or the like as shown in FIG. 5(f).
While heating the substrate 1, the first and second polysilicon layers 2 and 4 are further heated from the surface of the protective film 5 to perform region melting and recrystallization, as shown in FIG. 5(g). 1. The crystal grain size of the second polysilicon layers 2 and 4 is increased,
Alternatively, single-crystal semiconductor layers 2' and 4' are formed. Then, an n-type region 44 is formed on the surface of the p-type semiconductor layer 4' as shown in FIG. 5(h) to obtain a p-n junction necessary for photoelectric conversion, thereby completing the solar cell shown in FIG. 1. According to the manufacturing method shown in FIG. 5, similar to the manufacturing method shown in FIG. 4, the crystal grain sizes of the first and second semiconductor layers are increased by melt recrystallization or made into single crystals. It is possible to further improve the performance of solar cells. Furthermore, the first and second
Since the semiconductor layers are melted and recrystallized at one time, the number of melting and recrystallization steps can be reduced compared to the manufacturing method shown in FIG.

Next, the operation of the solar cell produced in this manner will be explained. Light incident from the surface of the second p-type semiconductor layer 4 on which the n-type region 44 is formed is transmitted to the semiconductor layer 4.
Carriers are generated inside, and one polarity of the generated photocurrent is transmitted from a surface electrode (not shown) formed on the n-type region 44.
The other polarity is taken out through the first p-type semiconductor layer 2 through the opening 35 in the insulating layer 3 .

[0027] Here, the insulating layer 3 is manufactured as follows:
In the process of forming the second p-type semiconductor layer 4, etc., the first p-type semiconductor layer 4 is
type semiconductor layer 2 and second p-type semiconductor layer 4 or the p-type impurity doped in the first p-type semiconductor layer 2 at a high concentration diffuses into the second p-type semiconductor layer 4. This serves to prevent the specific resistance of the first p-type semiconductor layer 2 from increasing due to a decrease in the impurity concentration in the first p-type semiconductor layer 2, and also during operation. , as shown by the arrows L1 and L2 in FIG.
interface with the type semiconductor layer 4 or the first p-type semiconductor layer 2
The second p layer, which is a photoelectric conversion layer, is reflected at the interface with
By confining it within the type semiconductor layer 4, it plays the role of improving conversion efficiency.

As described above, in this example, the lower electrode on the insulating substrate is made of the first semiconductor layer 2 whose main component is the same material as the second semiconductor layer 4 that performs photoelectric conversion. Therefore, when growing the photoelectric conversion layer on the bottom electrode,
Impurities that degrade photoelectric conversion characteristics do not enter the photoelectric conversion layer from the lower electrode, and crystal growth of the photoelectric conversion layer can be performed at high temperatures, making it possible to create solar cells on insulating substrates with excellent characteristics. realizable.

Next, a second embodiment of the present invention will be described. FIG. 2 is a cross-sectional view showing the structure of a solar cell according to a second embodiment of the present invention. In the figure, the same reference numerals as those in FIG. This is a barrier layer made of a silicon oxide film, a silicon nitride film, etc., provided between the two.

The manufacturing process of this embodiment is a step of forming a barrier layer 11 made of a silicon oxide film, a silicon nitride film, etc. on the substrate 1 before forming the first semiconductor layer 2 on the insulating substrate 1. The other manufacturing steps are completely the same as those of the first embodiment.

By adopting the structure of the first embodiment, it is possible to prevent impurities from entering the photoelectric conversion layer from the lower electrode, but when crystal-growing the photoelectric conversion layer on the lower electrode, the insulating substrate 1 It is conceivable that impurities therein mix into the first semiconductor layer 2 constituting the lower electrode, and this impurity further mixes into the photoelectric conversion layer, deteriorating the photoelectric conversion characteristics. In addition to the structure of the solar cell according to the first embodiment, the solar cell according to the second embodiment further includes a barrier made of a silicon oxide film, a silicon nitride film, etc. between the insulating substrate 1 and the first semiconductor layer 2. The structure includes a layer 11, which prevents impurities in the insulating substrate 1 from being mixed into the first semiconductor layer 2 constituting the lower electrode during crystal growth of the photoelectric conversion layer on the lower electrode. can be prevented.

Next, a third embodiment of the present invention, an integrated solar cell, will be explained. 6 and 7 are cross-sectional process diagrams showing the manufacturing process of an integrated solar cell according to a third embodiment of the present invention, and in these figures, the same reference numerals as in FIG. 1 represent the same or corresponding parts. The manufacturing process of the third embodiment will be explained below. First, as shown in FIG. 6(b), a first p-type polysilicon layer 2 is formed on an insulating substrate 1 made of alumina or the like shown in FIG. 6(a). Next, as shown in FIG. 6C, a separation groove 50 is formed in the first p-type polysilicon layer 2 to divide the first p-type polysilicon layer 2 into a plurality of regions. Next, as shown in FIG. 6(d), an insulating layer 3 is formed over the entire surface of the substrate. After this, using photolithography and etching techniques, the image shown in FIG. 6(e) was created.
An opening 35 is formed in the insulating layer 3 as shown in FIG. As shown in FIG. 6(f), a second p-type polysilicon layer 4 is formed on the insulating layer 3 in which the opening 35 is formed in this way. Next, a protective film 5 is formed on the second polysilicon layer 4 as shown in FIG. , 4 is heated to perform area melting recrystallization, and as shown in FIG. Semiconductor layers 2' and 4' are formed. Next, as shown in FIG. 6(i), a separation groove 55 corresponding to the separation groove 50 is formed in the second p-type polysilicon layer 4', and the second p-type polysilicon layer, which is a photo-electric conversion layer, is formed. 4' is divided into a plurality of regions corresponding to each region of the first p-type polysilicon layer 2 divided into a plurality of regions by the separation trench 50. After this, as shown in FIG. 7(a), the protective layer 5 other than one end of each region of the divided second p-type polysilicon layer 4' and the insulating layer 3 exposed at the bottom of the isolation trench 55 are removed. do. In this state, n-type impurities are diffused from the surface side, and as shown in FIG.
), an n-type region 44 is formed to obtain a pn junction necessary for photoelectric conversion. Then, as shown in FIG. 7(c), the separation groove 55 is filled with a conductive paste 6 such as aluminum paste or silver paste, and the first paste exposed at the bottom of the separation groove is removed.
By connecting the type polysilicon layer 2' and the n-type region 44 on the surface of the second p-type polysilicon layer 4' in the adjacent region, a structure in which each region of the divided solar cell is connected in series is created. obtain.

Next, the operation will be explained. As in the case of the single cell shown in FIG.
The light incident from the surface of the p-type semiconductor layer 4 generates carriers in the semiconductor layer 4, and one polarity of the generated photocurrent is n.
On the mold region 44, the other polarity is extracted through the first p-type semiconductor layer 2 through the opening 35 of the insulating layer 3, and the other polarity extracted is transferred to the other side of the adjacent cell via the conductive paste 6. Connected to the polarity of Therefore, by forming a large number of cells on one substrate, a large amount of power can be generated.

As described above, in this example, the lower electrode on the insulating substrate is made of the first semiconductor layer 2 whose main component is the same material as the second semiconductor layer 4 that performs photoelectric conversion. Therefore, when growing the photoelectric conversion layer on the bottom electrode,
The integrated solar cell on an insulating substrate has excellent characteristics, since impurities that degrade the photoelectric conversion characteristics do not enter the photoelectric conversion layer from the lower electrode, and the crystal growth of the photoelectric conversion layer can be performed at high temperatures. Batteries can be realized.

Note that in the steps shown in FIGS. 6 and 7 above, the first
, the second polysilicon layers 2 and 4 are melted and recrystallized at once, but the first and second polysilicon layers 2 and 4 are formed in separate steps in the same manner as the manufacturing method shown in FIG. It may also be melted and recrystallized.

In addition, in the steps shown in FIGS. 6 and 7, the isolation trench 55 for isolating the second p-type polysilicon layer 4' is
In the fourth embodiment of the present invention shown in FIG. The separation trench 55 may be formed so as to span the separation trench 50 separating the first p-type polysilicon layer 2, as shown in FIG. It is exactly the same as the one produced.

FIG. 9 is a cross-sectional process diagram showing a part of the manufacturing process of an integrated solar cell according to a fifth embodiment of the present invention, and in these figures, the same reference numerals as in FIG. 1 indicate the same or corresponding parts. The manufacturing process of the fifth embodiment will be described below. A first p-type polysilicon layer 2 is formed on an insulating substrate 1, an isolation trench 50 is formed therein, an insulating layer 3 is formed, an opening 35 is further formed in the insulating layer 3, and a second p-type polysilicon layer 2 is formed on the insulating substrate 1. After forming a polysilicon layer 4 and heating the first and second polysilicon layers 2 and 4 to perform region melting and recrystallization, a second polysilicon layer 4 is formed.
The steps up to forming the isolation trench 55 in the mold polysilicon layer 4' are exactly the same as in the third and fourth embodiments. In this embodiment, instead of forming a pn junction by diffusion etc., CV
By D, n-type microcrystalline silicon is deposited on the second p-type polysilicon layer 4' to form a pn junction. second p
After forming the separation groove 55 in the type polysilicon layer 4' as shown in FIG. 9(a), each region of the divided second p-type polysilicon layer 4' is divided as shown in FIG. 9(b). The protective layer 5 is removed except on one end of the protective layer 5. In this state, as shown in FIG. 9(c), n-type microcrystalline silicon 44' is deposited over the entire surface of the substrate by CVD.
A transparent conductive film 45 is formed on the n-type microcrystalline silicon 44'. The reason why the transparent conductive film 45 is formed on the n-type microcrystalline silicon 44' is to compensate for the low lateral conductivity of microcrystalline silicon. The transparent conductive film 45 is made of tin oxide (SnO2).
or indium tin oxide (ITO). After this, as shown in Fig. 9(d), Fig. 9(b)
The protective layer 5 and the insulating layer 3 in the separation groove 55 portion left in the step of 2 are removed, and at the same time, the n
The mold microcrystalline silicon 44' and the transparent conductive film 45 are lifted off. The first p-type polysilicon layer 2' exposed at the bottom of the isolation trench, the n-type microcrystalline silicon 44' and the transparent conductive film 45 on the second p-type polysilicon layer 4' in the adjacent region.
By connecting these, a structure is obtained in which each region of the divided solar cell is connected in series. The operation of the completed integrated solar cell is exactly the same as that produced by the manufacturing method shown in FIGS. 6 and 7.

FIG. 10 is a cross-sectional process diagram showing a part of the manufacturing process of an integrated solar cell according to a sixth embodiment of the present invention.
In the figures, the same reference numerals as in FIGS. 6 and 7 indicate the same or corresponding parts. In the third embodiment described above, the divided second p
The n-type impurity is diffused with the protective layer 5 left on one end of each region of the type polysilicon layer 4', and the conductive paste is However, in the sixth embodiment, the n-type impurity is diffused with the protective film 5 completely removed, as shown in FIG. 10(a). After forming an n-type region 44 on the entire surface of the second p-type polysilicon layer 4' as shown in FIG. 10(b), an isolation groove 56 shown in FIG. 10(c) is formed by etching. This provides a structure in which the n-type regions of each cell are not connected to each other.

FIG. 11(a) is a cross-sectional view showing the structure of an integrated solar cell with a protection diode according to a seventh embodiment of the present invention. In the figure, the same reference numerals as in FIG. 10 indicate the same or equivalent parts, 62 is a region that functions as a protection diode, 60 is a groove separating the photoelectric conversion part and protection diode part 62 of each cell region, and 65 is an insulating film. . The manufacturing process consists of forming a first p-type polysilicon layer 2 on an insulating substrate 1, forming an isolation trench 50 in it, forming an insulating layer 3, and then forming an opening 35 in the insulating layer 3. After forming a second p-type polysilicon layer 4 and heating the first and second polysilicon layers 2 and 4 to perform region melting recrystallization, a separation groove is formed in the second p-type polysilicon layer 4'. The steps up to the formation of the protective film 55 are exactly the same as those in the third and fourth embodiments, and after that, the n-type impurity is diffused with the protective film 5 completely removed, as in the sixth embodiment. Thereafter, the end portions of predetermined cell regions are separated by etching grooves 60 to form protective diode portions 62, and the pn junctions of the photoelectric conversion portions exposed on the side walls of the separation grooves 60 are covered with an insulating film 65. Then, the conductive paste 6 connects the p-type layer 2', which is the lower electrode, with the n-type region 44 of the adjacent cell, and also connects these with the n-type region of the protection diode section 62. The p-type region and the n-type region on the surface of the photoelectric conversion section are connected. FIG. 11(b) is an equivalent circuit diagram of the integrated solar cell of FIG. 11(a), in which 70a is a photoelectric conversion section, 71a is a protection diode connected to the photoelectric conversion section, and 70b is an adjacent cell. This is the photoelectric conversion section of the area.

[0040] In an integrated solar cell, if part of a plurality of cell areas on the substrate falls into the shadow during actual use, the total generated voltage in the other cells will be the reverse voltage for the cell in the shade. It will be applied in the form of If this reverse voltage exceeds the withstand voltage of the element, the element will be destroyed. If the structure is such that each cell region has a protection diode connected in parallel with the photoelectric conversion section in that region in the opposite polarity direction as in this example, current flows through this protection diode, so that the photoelectric conversion part in the shadow is Since no reverse voltage is applied to the converter, damage to the element can be prevented. Note that this protection diode may not be provided for all cell regions, but may be provided for each several cells depending on the reverse breakdown voltage of the photoelectric conversion section.

[0041]

As described above, according to the present invention, the first semiconductor layer provided on the insulating substrate, the insulating layer provided on the first semiconductor layer, and the insulating layer provided on the insulating substrate. a second semiconductor layer mainly composed of the same material as the first semiconductor layer provided on the insulating layer so as to be in contact with the first semiconductor layer in the opening provided therein; Since one polarity of the photocurrent generated in the second semiconductor layer by the incidence of the photoelectric current is taken out through the first semiconductor layer through the opening of the insulating layer, the second semiconductor becomes the photoelectric conversion layer. It is possible to realize a high-performance solar cell without the inclusion of impurities that degrade characteristics in the layers, and since it is formed on an insulating substrate, it is possible to integrate multiple high-performance solar cells on one substrate. There are effects that can be obtained.

Further, in the present invention, a first semiconductor layer is formed on an insulating substrate, an insulating layer is formed on the first semiconductor layer, and the first semiconductor layer is exposed to the insulating layer. A second semiconductor layer is formed on the insulating layer, the second semiconductor layer being connected to the first semiconductor layer in the opening and having the same material as the first semiconductor layer as a main component. Therefore, even if the second semiconductor layer serving as the photoelectric conversion layer and the first semiconductor layer serving as the lower electrode are mixed, the characteristics do not deteriorate, and a high-performance solar cell can be obtained easily. This has the effect of making it possible to fabricate an integrated solar cell.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the structure of a solar cell according to a first embodiment of the present invention.

FIG. 2 is a sectional view showing the structure of a solar cell according to a second embodiment of the invention.

3 is a cross-sectional process diagram showing the manufacturing process of the solar cell of the example of FIG. 1. FIG.

4 is a cross-sectional process diagram showing another example of the manufacturing process of the solar cell of the embodiment shown in FIG. 1. FIG.

5 is a cross-sectional process diagram showing still another example of the manufacturing process of the solar cell of the embodiment shown in FIG. 1. FIG.

FIG. 6 is a cross-sectional process diagram showing a part of the manufacturing process of an integrated solar cell according to a third embodiment of the present invention.

FIG. 7 is a cross-sectional process diagram showing a part of the manufacturing process of an integrated solar cell according to a third embodiment of the present invention.

FIG. 8 is a cross-sectional process diagram showing a manufacturing process of an integrated solar cell according to a fourth embodiment of the present invention.

FIG. 9 is a cross-sectional process diagram showing a manufacturing process of an integrated solar cell according to a fifth embodiment of the present invention.

FIG. 10 is a cross-sectional process diagram showing a manufacturing process of an integrated solar cell according to a sixth embodiment of the present invention.

FIG. 11 is a cross-sectional view and an equivalent circuit diagram showing the structure of an integrated solar cell according to a seventh embodiment of the present invention provided with a protection diode.

FIG. 12 is a cross-sectional process diagram showing a process for forming a conventional solar cell formed using a semiconductor melt recrystallization technique.

FIG. 13 is a diagram showing the structure of a conventional integrated solar cell.

FIG. 14 is a diagram showing the structure of another conventional integrated solar cell.

FIG. 15 is a diagram showing the structure of yet another conventional integrated solar cell.

[Explanation of symbols]

1 Insulating substrate 2 First semiconductor layer 3 Insulating layer 4 Second semiconductor layer 44 Bonding layer 5 Cap layer 6 Conductive paste 45 Transparent conductive film

Claims (9)

[Claims] 1. A first semiconductor layer provided on an insulating substrate, an insulating layer provided on the first semiconductor layer, and a first semiconductor layer provided in an opening provided in the insulating layer. a second semiconductor layer mainly composed of the same material as the first semiconductor layer provided on the insulating layer so as to be in contact with the first semiconductor layer; A solar cell characterized in that one polarity of the photocurrent is taken out through the first semiconductor layer through an opening in the insulating layer. 2. The solar cell according to claim 1, wherein the first semiconductor layer is provided on the insulating substrate with a barrier layer interposed therebetween. 3. The first semiconductor layer, the insulating layer, and the second semiconductor layer are formed on the insulating substrate by being divided into a plurality of regions, and the first semiconductor layer in one region is divided into a plurality of regions. 3. The solar cell according to claim 1, wherein the layer is connected to an extraction portion of the other polarity of the photocurrent in another region adjacent to the layer. 4. All or some of the plurality of regions include a protection diode configured using a part of the second semiconductor layer divided within the region. The solar cell according to claim 3. 5. Forming a first semiconductor layer on an insulating substrate, forming an insulating layer on the first semiconductor layer, and exposing the first semiconductor layer to the insulating layer. a step of providing an opening; and a step of forming a second semiconductor layer on the insulating layer, the second semiconductor layer being connected to the first semiconductor layer at the opening and having the same material as the first semiconductor layer as a main component. A method for manufacturing a solar cell, comprising: 6. A step of forming a first semiconductor layer on an insulating substrate, a step of dividing the first semiconductor layer into a plurality of regions, and a step of covering the first semiconductor layer with an insulating layer. and,
providing an opening at a predetermined location on the first semiconductor layer of the insulating layer; a step of forming a second semiconductor layer mainly composed of a material, a step of dividing the second semiconductor layer into a plurality of regions according to the region of the first semiconductor layer, and a step of dividing the second semiconductor layer into a plurality of regions according to the region of the first semiconductor layer; a step of electrically connecting the first semiconductor layer of a region to a current extraction portion of a polarity opposite to the first semiconductor layer side of another adjacent region. How to manufacture batteries. 7. The method of manufacturing a solar cell according to claim 5, further comprising the step of melting and recrystallizing the first and second semiconductor layers. 8. The method of manufacturing a solar cell according to claim 7, wherein the first and second semiconductor layers are melted and recrystallized simultaneously. 9. After dividing the second semiconductor layer by forming a dividing groove that reaches the insulating layer, the second semiconductor layer is divided into a surface portion of the second semiconductor layer including the side wall portion of the dividing groove. 2
9. The method for manufacturing a solar cell according to claim 6, further comprising forming a semiconductor layer having a conductivity type opposite to that of the semiconductor.