JP5341297B2 - Compound single crystal solar cell and method for producing compound single crystal solar cell - Google Patents

Description

  The present invention relates to a compound single crystal solar cell and a method for producing a compound single crystal solar cell, and more particularly to a compound single crystal solar cell and a method for producing a compound single crystal solar cell that can simplify an electrode forming step.

  Among solar cells, as a solar cell having high power generation efficiency and suitable for a space solar cell, there is a compound semiconductor solar cell in which a compound semiconductor single crystal layer is stacked on a semiconductor substrate. It is important to reduce the mass of space solar cells, and a technology has been developed to reduce the thickness of a semiconductor substrate that does not function as a solar cell, or to reduce the weight by removing the substrate.

  Conventionally, in a thinned compound semiconductor solar battery, damage to the solar battery has occurred in a process after electrode formation such as a sealing process due to irregularities generated during electrode formation and inter-cell connection. In order to avoid this, a method has been developed in which electrodes having different polarities are formed on the side on which sunlight is incident to reduce unevenness that occurs during electrode formation and inter-cell connection (Patent Document 1).

9 and 10 are schematic cross-sectional views of the compound solar cell of Patent Document 1. FIG. 9 includes a p-type Ge substrate 1 / n-type Ge layer 2 / n-type GaAs layer 3 / n-type InGaP layer 4 / p-type AlGaAs layer 5 / p-type InGaP layer 6 / p-type GaAs layer 7 / n. Type GaAs layer 8 / n type AlInP layer 9 / n type InGaP layer 10 / p type AlGaAs layer 11 / p type AlInP layer 12 / p type InGaP layer 13 / n type InGaP layer 14 / n type AlInP layer 15 / n type GaAs 10 is a p-type InGaP layer 27 / p-type AlGaAs layer 28 / p-type AlInP layer 29 / p-type InGaP layer 30 / n-type InGaP layer 31 / n-type AlInP layer 32 /. The first electrode 17 and the second electrode 18 are formed on the semiconductor layer composed of the n-type GaAs layer 33 by vapor deposition, and the Ag ribbon wirings 22 and 23 are connected to each other. Compared with the structure in which the first electrode 17 and the second electrode 18 having different polarities are formed on the light incident surface side of the solar cell, and electrodes / wirings are formed on both the front and back surfaces of the solar cell, the electrode and the wiring The unevenness caused by is reduced.
Japanese Patent Application No. 2005-168124

  However, in the case of the solar cell structure of Patent Document 1, the first electrode 17 is on the n-type GaAs layer 16, the second electrode 18 is on the p-type Ge substrate 1 (FIG. 9), or the first electrode 17 is n-type GaAs. On the layer 33, the second electrode 18 is formed on a semiconductor having a different conductivity type from that on the p-type AlGaAs layer 28 (FIG. 10). For this reason, the first electrode 17 has a structure in which Au—Ge (100 nm) / Ni (20 nm) / Au (100 nm) / Ag (5000 nm) are sequentially stacked, and the second electrode 18 has Au (30 nm) / It was necessary to use a material different from the structure in which Ag (5000 nm) was sequentially laminated, and two electrode formation steps were required even though the electrodes were provided on the same side of the semiconductor layer.

  This invention is made | formed in view of said point, and it aims at providing the structure and manufacturing method of a compound single crystal solar cell which can simplify an electrode formation process more.

In order to achieve the above object, the present invention includes a first semiconductor laminate including a photoelectric conversion layer and having an upper surface of a first conductivity type,
A cap layer formed on the upper surface of the first semiconductor laminate;
A first electrode having a first polarity formed on the upper surface of the cap layer;
A first semiconductor layer of a first conductivity type formed on the lower surface of the first semiconductor laminate and having an exposed surface, a part of which is exposed on the upper surface side;
A second electrode having a second polarity formed on the exposed surface;
One of the interfaces of the layers located between the lowermost layer of the photoelectric conversion layer and the first semiconductor layer is electrically joined by a tunnel junction,
Said first semiconductor layer and the cap layer, Ri n-type GaAs Tona,
The first electrode and the second electrode were compound single crystal solar cells formed from the same material .

  According to this structure, since the first electrode and the second electrode are formed on the semiconductor layer of the same conductivity type, the first electrode and the second electrode can be formed of the same material at the same time. The process can be simplified.

  In the present invention, it is preferable that the tunnel junction is formed at an interface between the first semiconductor stacked body and the first semiconductor layer.

  In the present invention, the main material of the first semiconductor layer and the layer constituting the upper surface of the first semiconductor stacked body are preferably the same.

  In the present invention, it is desirable that a second semiconductor stacked body made of a single crystal semiconductor having the first conductivity type is formed on the lower surface of the first semiconductor layer.

In the present invention, the second semiconductor stacked body may include a single crystal semiconductor substrate.
In the present invention, it is desirable that a conductive film is formed on the lower surface of the second semiconductor laminate.

In the present invention, the conductive film is preferably made of a transparent conductive material.
In the present invention, the conductive film preferably includes a metal film .

The present invention also includes a step of forming a second semiconductor stacked body including one or more semiconductor layers on the upper surface of the single crystal semiconductor substrate;
Forming a first semiconductor layer of a first conductivity type on the upper surface of the second semiconductor laminate;
Forming a first semiconductor stacked body including a photoelectric conversion layer on an upper surface of the first semiconductor layer and having an upper surface side of the first conductivity type;
Forming an exposed surface that exposes a portion of the upper surface of the first semiconductor layer by etching away a portion of the first semiconductor stack; and
Forming a first conductivity type cap layer on the upper surface of the first semiconductor laminate;
Simultaneously forming a first electrode having a first polarity on the upper surface of the cap layer and a second electrode having a second polarity on the exposed surface of the first semiconductor layer;
Including
Said first semiconductor layer and the cap layer, Ri n-type GaAs Tona,
The first electrode and the second electrode are made of the same material and are formed from the same direction .

  According to this manufacturing method, since the first electrode and the second electrode can be formed on the same conductivity type semiconductor layer facing the same direction, the first electrode and the second electrode can be simultaneously formed of the same material. .

  In the present invention, the first semiconductor layer is preferably lattice-matched with the single crystal semiconductor substrate.

The present invention preferably includes a step of removing the single crystal semiconductor substrate .

According to the present invention, the first semiconductor stacked body including the photoelectric conversion layer and having the upper surface of the first conductivity type, the cap layer formed on the upper surface of the first semiconductor stacked body, and the first layer formed on the upper surface of the cap layer. A first electrode having one polarity; a first semiconductor layer of a first conductivity type formed on a lower surface of the first semiconductor multilayer body and having an exposed surface partially exposed on the upper surface side; and on the exposed surface A second electrode having a second polarity formed, and one of the interfaces of the layer located between the lowermost layer of the photoelectric conversion layer and the first semiconductor layer is electrically connected by a tunnel junction. are bonded, said first semiconductor layer and the cap layer, Ri n-type GaAs Tona, the first electrode and the second electrode was a compound single crystal solar cell formed from the same material. With the above structure, the first electrode and the second electrode are formed on the same conductivity type semiconductor layer from the same direction, and therefore can be formed simultaneously with the same electrode material in the electrode formation process, simplifying the manufacturing process. it can.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic cross-sectional view of a compound single crystal solar cell according to this embodiment.

  A cap layer 102 having the first conductivity type is formed on at least a part of the upper surface 101a having the first conductivity type of the first semiconductor stacked body 101 including the photoelectric conversion layer. A first electrode 103 having a first polarity is formed on at least a part of the upper surface 102 a of the cap layer 102.

  A first semiconductor layer 104 having the first conductivity type is formed on the lower surface 101b of the first semiconductor stacked body 101, and a part of the upper surface thereof has an exposed exposed surface 104a. A second electrode 105 having a second polarity is formed on the exposed surface 104a. The first polarity and the second polarity are different from each other and are either positive or negative.

  The first semiconductor layer 104 is electrically connected to the photoelectric conversion layer included in the first semiconductor stacked body 101 via a tunnel junction.

  With the above structure, the first electrode 103 and the second electrode 105 are formed on the same conductivity type semiconductor layer from the same direction. Therefore, the same electrode material can be formed at the same time in the electrode forming step. Can be simplified.

  The tunnel junction may be provided in the first semiconductor stacked body 101, but is preferably provided at the interface between the first semiconductor stacked body 101 and the first semiconductor layer 104.

  When a tunnel junction is provided at the interface between the first semiconductor stacked body 101 and the first semiconductor layer 104, the carrier concentration of the lowermost layer 101c of the first semiconductor stacked body 101 and the first semiconductor layer 104 is high. The electrical resistance of the first semiconductor layer 104 is kept low. In this structure, since the current generated in the photoelectric conversion layer in the first semiconductor stacked body 101 flows in the in-plane direction of the first semiconductor layer 104 and is collected by the second electrode 105, the electric resistance of the first semiconductor layer 104 Is effective to reduce the series resistance.

  Moreover, it is desirable that the upper surface 101 a having the first conductivity type of the first semiconductor stacked body 101 and the main material of the first semiconductor layer 104 be the same. In the process of simultaneously forming the first electrode 103 and the second electrode 105 with the same material, if the main material of the semiconductor material that is the base for forming both electrodes is the same, the process conditions that can reduce the contact resistance are the same, The condition selection becomes easy.

In the present embodiment, each of the first electrode 103 and the second electrode 105 is made of an opaque material such as metal or a transparent conductive material such as ZnO (zinc oxide), SnO ₂ (tin oxide) or ITO (Indium Tin Oxide). Can do.

  In addition, as shown in FIG. 2, the second semiconductor stacked body 106 may be further stacked on the lower surface 104 b of the first semiconductor layer 104. The second semiconductor stacked body 106 is made of one or more single crystal semiconductors having the same conductivity type as the first semiconductor layer 104, and may include a single crystal semiconductor substrate.

  In the process of manufacturing the compound single crystal solar cell of this embodiment, it is desirable that the semiconductor film is epitaxially grown on the single crystal semiconductor substrate, and this is lattice-matched with the single crystal semiconductor substrate. A single crystal semiconductor substrate is a substrate for growing a semiconductor layer at the start of manufacturing a compound single crystal solar cell, and can be left after the solar cell is manufactured. Further, it can be removed by a method such as etching or ELO (epitaxial lift-off).

  By forming the second semiconductor stacked body 106 on the single crystal semiconductor substrate and then stacking the first semiconductor layer 104, lattice mismatch between the single crystal semiconductor substrate and the first semiconductor layer 104 can be relaxed, The quality of the epitaxial layer (the first semiconductor layer 104, the first semiconductor stacked body 101) above the first semiconductor layer 104 can be improved, such as reducing crystal defects.

Further, as shown in FIG. 3, it is desirable that a conductive film 107 is formed on the lower surface 106 b of the second semiconductor stacked body 106. The conductive film 107 may be a transparent conductive material such as ZnO (zinc oxide), SnO ₂ (tin oxide) or ITO (Indium Tin Oxide), an opaque material such as metal, or a laminate of these. The conductive film 107 may be provided on at least a part of the lower surface 106b of the second semiconductor stacked body 106, and is preferably provided on the entire surface.

  With the above structure, part of the current generated in the photoelectric conversion layer in the first semiconductor stacked body 101 flows in the stacking direction through the first semiconductor layer 104 and the second semiconductor stacked body 106, and in the conductive film 107 with low electrical resistance. After flowing in the in-plane direction of the solar cell through, it is possible to take a path collected by the second electrode 105 through the second semiconductor stacked body 106 and the first semiconductor layer 104, reducing the series resistance of the portion through which the output current flows can do. When the conductive film 107 is provided on the entire surface of the lower surface 106b of the second semiconductor stacked body 106, this effect becomes the largest and is more desirable.

  In addition, when the conductive film 107 is formed of a transparent conductive material, or when an opaque material such as a metal is partially formed and transmits light, the light can be incident from any of the upper and lower surfaces. good. Such a light transmission type solar cell can be used as a mechanical stack type solar cell by stacking with other solar cells having different band gaps.

  In the case where the conductive film 107 includes an opaque conductive material such as metal, when light is incident from the upper surface side, sunlight is reflected by the opaque conductive material portion of the conductive film 107, and again, the first semiconductor laminate 101 Since it is absorbed by the photoelectric conversion layer, the effect of improving the output current of the solar cell can be obtained.

  In this example, a method for producing a compound single crystal solar cell of the present invention will be described with reference to the drawings. FIG. 4 shows a manufacturing process of the compound single crystal solar cell of this example.

  An n-type GaAs substrate 401 was used as the single crystal semiconductor substrate 401, and a compound semiconductor single crystal layer was sequentially formed on the n-type GaAs substrate 401 by epitaxial growth using the MO-CVD method (a). Specifically, first, an n-type GaAs buffer layer 402 having a thickness of 3 μm and an n-type InGaP buffer layer 403 having a thickness of 0.02 μm are formed on a disk-shaped n-type GaAs substrate 401 having a diameter of 50 mm doped with Si. did. Next, an n-type GaAs first semiconductor layer 104 having a thickness of 0.02 μm was formed on the n-type InGaP buffer layer 403. The first semiconductor layer 104 is desirably lattice-matched with the substrate 401. By lattice matching, it is possible to grow a high-quality film while suppressing generation of crystal defects. Next, a p-type AlGaAs layer 404 having a thickness of 0.02 μm was formed on the n-type GaAs first semiconductor layer 104. Here, the n-type GaAs first semiconductor layer 104 and the p-type AlGaAs layer 404 form a tunnel junction.

  The tunnel junction is a tunnel junction located between the first semiconductor layer 104 and the photoelectric conversion layer, which is one of the characteristics of the present invention.

  Next, a first semiconductor laminate 101 including the p-type AlGaAs layer 404 and having a photoelectric conversion layer constituting a two-junction solar cell was formed. First, a p-type InGaP layer having a thickness of 0.1 μm was formed as a back surface field layer on the p-type AlGaAs layer, and a p-type GaAs layer having a thickness of 3 μm was formed as a base layer on the p-type InGaP layer. Thereafter, an n-type GaAs layer having a thickness of 0.1 μm was formed as an emitter layer on the p-type GaAs layer, and an n-type AlInP layer having a thickness of 0.03 μm was formed as a window layer on the n-type GaAs layer.

  The p-type InGaP layer (back surface field layer) / p-type GaAs layer (base layer) / n-type GaAs layer (emitter layer) / n-type AlInP layer (window layer) constitutes a GaAs bottom cell layer, and a p-type GaAs layer ( The base layer) and the n-type GaAs layer (emitter layer) function as a photoelectric conversion layer of the GaAs bottom cell.

  Subsequently, an n-type InGaP layer having a thickness of 0.02 μm was formed on the n-type AlInP layer, and a p-type AlGaAs layer having a thickness of 0.02 μm was formed on the n-type InGaP layer. Here, the n-type InGaP layer and the p-type AlGaAs layer form a tunnel junction. This tunnel junction is for electrically joining the GaAs bottom cell and an InGaP top cell described later, and is a tunnel located between the first semiconductor layer 104 and the photoelectric conversion layer, which is one of the features of the present invention. It is not joining.

  Further, a p-type AlInP layer having a thickness of 0.03 μm was formed as a back surface field layer on the p-type AlGaAs layer, and a p-type InGaP layer having a thickness of 0.5 μm was formed as a base layer on the p-type AlInP layer. Next, an n-type InGaP layer having a thickness of 0.05 μm was formed as an emitter layer on the p-type InGaP layer, and an n-type AlInP layer having a thickness of 0.03 μm was formed as a window layer on the n-type InGaP layer.

  The p-type InGaP layer is constituted by the p-type AlInP layer (back surface field layer) / p-type InGaP layer (base layer) / n-type InGaP layer (emitter layer) / n-type AlInP layer (window layer). The (base layer) and the n-type InGaP layer (emitter layer) function as a photoelectric conversion layer of the InGaP top cell.

  Further, an n-type GaAs cap layer 102 having a thickness of 0.5 μm was formed on the n-type AlInP window layer. As a result, the second semiconductor stacked body 106, the first semiconductor layer 104, the first semiconductor stacked body 101, and the cap layer 102 were stacked to form an InGaP top cell / GaAs bottom cell two-junction compound solar cell.

The above epitaxial growth temperature was about 700 ° C. Further, TMG (trimethylgallium) and AsH ₃ (arsine) are used as raw materials for growing the GaAs layer, and TMI (trimethylindium), TMG and PH ₃ (phosphine) are used as raw materials for growing the InGaP layer. ) Was used.

As raw materials for growing the AlInP layer, TMA (trimethylaluminum), TMI and PH ₃ are used. As an n-type impurity source for forming the n-type GaAs layer, the n-type InGaP layer and the n-type AlInP layer, SiH ₄ (monosilane) was used for each.

On the other hand, DEZn (diethyl zinc) was used as a p-type impurity source for forming the p-type GaAs layer, the p-type InGaP layer, and the p-type AlInP layer. Further, TMI, TMG, and AsH ₃ were used as raw materials for growing the AlGaAs layer, and CBr ₄ (carbon tetrabromide) was used as the p-type impurity source for forming the p-type AlGaAs layer. .

  Next, a resist is applied to the entire surface of the n-type GaAs cap layer 102, and the resist is left by photolithography to form a comb-shaped electrode, and then the n-type GaAs in the portion where the resist is opened with an ammonia-based etching solution. The layer was etched and the resist was removed using a suitable organic solvent (b). At this time, since the underlying n-type AlInP layer is not etched in an ammonia system, the etching automatically stops when the n-type GaAs layer is etched.

  Next, a resist is applied again on the entire surface, and the resist is removed again in accordance with a portion to be removed of the first semiconductor stacked body 101 by photolithography, and one of the first semiconductor stacked bodies 101 is removed with an ammonia-based and HCl-based etching solution. The portion was removed in a predetermined pattern until the surface of the p-type AlGaAs layer 404 was exposed (c), and the p-type AlGaAs layer 404 was removed with an HCl-based etchant (d).

By this step, a part of the n-type GaAs first semiconductor layer 104 can be exposed.
Next, the resist is removed using an appropriate organic solvent, a resist 406 is applied again on the entire surface, and the comb-shaped region where the n-type GaAs cap layer 102 remains by photolithography and the n-type GaAs first semiconductor layer The resist 406 was removed in accordance with the exposed portion 104 (e).

  Then, a 100 nm Au—Ge film, a 20 nm thick Ni film, a 100 nm thick Au film, and a 5000 nm thick Ag film as electrode materials 407 are sequentially deposited on the resist by lift-off. The resist was removed together with the resist to form the first electrode 103 and the second electrode 105 (f). Then, the compound single crystal solar cell containing the structure of this invention was manufactured by heat-processing.

  FIG. 5 shows a schematic cross-sectional view of a compound single crystal solar cell produced by this example. As described above, both the first electrode 103 and the second electrode 105 are simultaneously formed on the n-type GaAs layer, and the electrode forming process can be simplified.

  Further, the solar cell of this embodiment may be configured such that a conductive film 107 further including an opaque electrode such as a metal is formed on the lower surface of the n-type GaAs substrate 401 as shown in FIG. With this configuration, the conductive film 107 transmits light incident from the upper surface side and transmitted through the first semiconductor stacked body 101, the first semiconductor layer 104, the n-type InGaP layer 403, the n-type GaAs layer buffer layer 402, and the n-type GaAs substrate 401. It is reflected and absorbed again in the photoelectric conversion layer in the first semiconductor stacked body 101, and the output of the solar cell can be improved.

  In this embodiment, a GaAs substrate 401 is used as the single crystal semiconductor substrate 401 and InGaP / GaAs is stacked as the photoelectric conversion layer, but sapphire, Ge, or the like may be used as the single crystal semiconductor substrate 401. The layer is not limited to InGaP / GaAs, and other materials may be used, and the photoelectric conversion layer may be a short junction or a multi-junction.

Furthermore, the tunnel junction provided between the first semiconductor stacked body 101 and the first semiconductor layer 104 in this embodiment may be provided in the first semiconductor stacked body 101. For example, as shown in FIG. 7, the lowermost layer 404 of the first semiconductor stacked body 101 is composed of a p ⁺⁺ type AlGaAs layer 404a, an n ⁺⁺ type GaAs layer 404b, and an n ⁺⁺ type InGaP layer 404c, and a p ⁺⁺ type AlGaAs layer 404a. The above-described effects of the present invention can also be achieved with a structure in which a tunnel junction is formed between the n ⁺⁺ type GaAs layers 404b.

  In this example, a method for manufacturing a solar cell of the present invention when further weight reduction is desired for space applications will be described. The following process was implemented about the solar cell after completion | finish of the process of the said FIG.

  First, an Ag ribbon 801 having a length of 10 mm, a width of 3 mm, and a thickness of 0.03 mm was electrically connected to the first electrode 103 and the second electrode 105, respectively, by welding.

  Thereafter, the n-type GaAs substrate 301 having a diameter of 50 mm was cut into a rectangular plate shape having a width of 20 mm and a length of 20 mm.

Further, as the antireflection film 802, a TiO2 film having a thickness of 55 nm and an Al2O3 film having a thickness of 85 nm were deposited.
Subsequently, a transparent adhesive 803 made of silicone is applied on the surface on which the first electrode 103 and the second electrode 105 on which sunlight is incident is formed, and a transparent protective material 804 made of glass having a thickness of 100 μm is applied. The transparent protective material was bonded by bonding to this and curing the transparent adhesive at a predetermined temperature.

  Thereafter, the surface of the transparent protective material was covered with a resist, and the n-type GaAs substrate 401 and the n-type GaAs layer buffer layer 402 were removed with an ammonia-based etching solution from the surface opposite to the side on which sunlight was incident. Then, a conductive film 107 is formed by sequentially depositing an Au film having a thickness of 30 nm and an Ag film having a thickness of 3000 nm on the surface of the thinned solar cell opposite to the side on which sunlight is incident, followed by heat treatment. A solar cell having a schematic cross-sectional view shown in FIG.

  The output voltage / current characteristics of the solar cell produced in this example were measured under air mass (AM) 1.5 conditions. As a result, the short-circuit current Isc was 39 mA, the open circuit voltage Voc was 2.47 V, the fill factor FF was 0.83, and the conversion efficiency Eff was 20%. Since the conversion efficiency Eff of the InGaP / GaAs solar cell having a structure in which the conventional back electrode is taken out from the P-type GaAs on the side where sunlight is incident is about 20%, the solar cell of this embodiment has a conventional conversion efficiency Eff. The process could be simplified while maintaining almost the same as the above.

It is a schematic sectional drawing of the compound single crystal solar cell which concerns on this embodiment of this invention. It is a schematic sectional drawing of the compound single crystal solar cell which has a structure which laminated | stacked the 2nd semiconductor laminated body in this embodiment of this invention. It is a schematic sectional drawing of the compound single crystal solar cell which has a structure which laminated | stacked the electrically conductive film containing a 2nd semiconductor laminated body and a metal in this embodiment of this invention. It is a figure which shows the manufacturing process of the compound single crystal solar cell which concerns on Example 1 of this invention. It is a schematic sectional drawing of the compound single crystal solar cell manufactured in Example 1 of this invention. It is a schematic sectional drawing of the compound single crystal solar cell which has the structure which laminated | stacked the electrically conductive film in Example 1 of this invention. It is a schematic sectional drawing of the compound single crystal solar cell of the structure which formed the tunnel junction in the 1st semiconductor laminated body in Example 1 of this invention. It is a schematic sectional drawing of the compound single crystal solar cell manufactured in Example 2 of this invention. 1 is a schematic cross-sectional view of a compound single crystal solar cell according to Patent Document 1. FIG. 1 is a schematic cross-sectional view of a compound single crystal solar cell according to Patent Document 1. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 1st semiconductor laminated body 101a Upper surface of 1st semiconductor laminated body 101b Lower surface of 1st semiconductor laminated body 102 Cap layer 102a Upper surface of cap layer 103 1st electrode 104 1st semiconductor layer 104a Exposed surface of 1st semiconductor layer 105 2nd Electrode 106 Second semiconductor stacked body 106b Lower surface of second semiconductor stacked body 107 Conductive film 401 Single crystal semiconductor substrate 404 Lowermost layer of first semiconductor stacked body

Claims (11)

A first semiconductor laminate including a photoelectric conversion layer and having an upper surface of the first conductivity type;
A cap layer formed on the upper surface of the first semiconductor laminate;
A first electrode having a first polarity formed on the upper surface of the cap layer;
A first semiconductor layer of a first conductivity type formed on the lower surface of the first semiconductor laminate and having an exposed surface, a part of which is exposed on the upper surface side;
A second electrode having a second polarity formed on the exposed surface;
One of the interfaces of the layers located between the lowermost layer of the photoelectric conversion layer and the first semiconductor layer is electrically joined by a tunnel junction,
Said first semiconductor layer and the cap layer, Ri n-type GaAs Tona,
The first electrode and the second electrode are compound single crystal solar cells formed of the same material .   2. The compound single crystal solar cell according to claim 1, wherein the tunnel junction is formed at an interface between the first semiconductor stacked body and the first semiconductor layer.   3. The compound single crystal solar cell according to claim 1, wherein the main material of the first semiconductor layer and the layer constituting the upper surface of the first semiconductor stacked body are the same.   4. The compound unit according to claim 1, wherein a second semiconductor stacked body made of a single crystal semiconductor having a first conductivity type is formed on a lower surface of the first semiconductor layer. 5. Crystal solar cell.   The compound single crystal solar cell according to claim 4, wherein the second semiconductor stacked body includes a single crystal semiconductor substrate.   6. The compound single crystal solar cell according to claim 4, wherein a conductive film is formed on a lower surface of the second semiconductor stacked body. The compound single crystal solar cell according to claim 6, wherein the conductive film is made of a transparent conductive material.   The compound single crystal solar cell according to claim 6, wherein the conductive film includes a metal film. Forming a second semiconductor laminate composed of one or more semiconductor layers on the upper surface of the single crystal semiconductor substrate;
Forming a first semiconductor layer of a first conductivity type on the upper surface of the second semiconductor laminate;
Forming a first semiconductor stacked body including a photoelectric conversion layer on an upper surface of the first semiconductor layer and having an upper surface side of the first conductivity type;
Forming an exposed surface that exposes a portion of the upper surface of the first semiconductor layer by etching away a portion of the first semiconductor stack; and
Forming a first conductivity type cap layer on the upper surface of the first semiconductor laminate;
Simultaneously forming a first electrode having a first polarity on an upper surface of the cap layer, and a second electrode having a second polarity on an exposed surface of the first semiconductor layer,
Said first semiconductor layer and the cap layer, Ri n-type GaAs Tona,
The method for producing a compound single crystal solar cell, wherein the first electrode and the second electrode are formed of the same material and are formed from the same direction . The method of manufacturing a compound single crystal solar cell according to claim 9 , wherein the first semiconductor layer is lattice-matched with the single crystal semiconductor substrate. Compound single crystal solar method of manufacturing a battery according to any one of claims 9 or 10, characterized in that it comprises a step of removing the single crystal semiconductor substrate.

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