JP2010177266A - Method for manufacturing tandem type thin film solar cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a tandem type thin film solar cell without breakage of a pn junction of a lower cell. <P>SOLUTION: The manufacturing method of the tandem type thin film solar cell 100 including a plurality of photoelectric conversion units stacked on a substrate 10, includes a first electrode layer film formation process of forming a first electrode layer of a photoelectric conversion unit, a precursor layer film formation process of forming a plurality of semiconductor precursor layers on the formed first electrode layer, a second electrode layer film formation process of forming a second electrode layer on the formed semiconductor precursor layers, and a precursor layer diffusion process of producing a crystal of a semiconductor by heating semiconductor precursor layers of a plurality of photoelectric conversion units each having a semiconductor precursor layer formed between a first electrode layer and a second electrode layer after stacking the photoelectric conversion units. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a tandem thin film solar cell, and more particularly to a method for manufacturing a tandem thin film solar cell suitable for a CIS semiconductor.

  In recent years, a multi-junction (tandem) solar cell in which two or more pn junctions are formed has been proposed as one method for increasing the efficiency of solar cells. For example, in the case of a two-junction solar cell, a semiconductor material having a relatively large forbidden band is arranged in a cell near the light incident side (top cell), and a forbidden band is located far from the light incident side (bottom cell). It has a structure in which a semiconductor material with a small width is arranged. When such a structure is employed, when sunlight is irradiated, short-wavelength light energy is absorbed in the top cell, and long-wavelength light that passes through the top cell is absorbed in the bottom cell, so that sunlight is wasted. Can be used efficiently.

  As for the tandem solar cell, for example, in Patent Document 1, a first conductive power generation film, i-type power generation film, and amorphous Si made of amorphous Si or crystalline Si through a conductive oxide film on one main surface of a substrate is disclosed in Patent Document 1. A solar cell is described in which cells formed by sequentially forming a second conductivity type power generation film made of crystalline Si are stacked in multiple stages. Further, Patent Document 2 describes a multi-junction solar cell having an immediately upper layer formed on a Ge substrate and a plurality of growth layers stacked on the immediately upper layer.

JP 2004-128083 A JP 2007-189025 A

  By the way, expectations for solar cells are increasing as part of global warming countermeasures. In particular, CIS solar cells using chalcopyrite type compound semiconductors are attracting attention because of their high photoelectric conversion efficiency, excellent long-term stability, and relatively low cost. At present, a conversion efficiency of 20% is achieved with a small area cell, and about 15% is achieved with a large area module.

As a method for producing a CIS solar cell, a precursor layer made of copper (Cu), indium (In), or a compound thereof is usually formed on a back electrode formed on a substrate, and the substrate is heated to 500 ° C. After the CIS-based absorption layer is obtained by reacting the precursor layer with selenium in hydrogen selenide (He ₂ Se) gas while heating to the extent, a buffer layer made of CdS, ZnS or the like is formed by a solution growth method. Subsequently, a surface electrode layer such as ITO or AZO is formed. As the CIS-based absorption layer, Cu (Ga, In) Se _{2 in} which a part of In in CuInSe ₂ is substituted with Ga or CuIn (S, Se) _{2 in} which a part of Se is substituted with S is usually used. ing.

  Although the limit of the conversion efficiency of such a CIS solar cell is estimated to be about 22%, according to the latest simulation results, a conversion efficiency of 26 to 28% can be realized when a two-junction tandem solar cell is used. It is reported. Therefore, it can be said that the CIS tandem solar cell has high expectations.

However, there is a problem that the conventional method for manufacturing a two-junction tandem solar cell is not suitable for a CIS solar cell. That is, as described above, since the CIS-based absorption layer is usually formed at a high temperature of 450 ° C. to 550 ° C., after forming the lower cell of the two-junction tandem solar cell, the upper cell is continuously formed thereon. When directly forming a film, the pn junction of the lower cell is destroyed due to the influence of heat at the time of forming the upper cell, resulting in a problem that the performance of the solar cell deteriorates.
Further, in a general CIS solar cell manufacturing process, at least two types of sputtering devices, a heating reactor, and a solution growth tank are required. Moreover, since the use of H ₂ Se gas is toxic gas, it is necessary to toxic gas treatment apparatus and special safety measures. In addition, since an aqueous solution of alkali is used in the solution growth method, an alkali treatment facility is required.

Furthermore, when forming the pn junction, it is necessary to maintain the temperature of the substrate at a low temperature of about 200 ° C. to 300 ° C. for a long time. Further, in the vapor phase selenization method, it is necessary to expose a thin film having a composition as a precursor to the selenium-containing gas while heating for several tens of minutes to several hours, and thus a long film formation time is required. .
Thus, in the conventional method for manufacturing a two-junction tandem solar cell, each layer of the CIS-based tandem solar cell is consistently formed at a high speed, and both the upper cell and the lower cell have good crystallinity and pn. At present, it is not possible to have an absorption layer that forms a bond.

  An object of the present invention is to provide a method for manufacturing a tandem thin film solar cell from which a CIS tandem thin film solar cell can be obtained without destroying the pn junction of the lower cell.

  According to this invention, it is a manufacturing method of a tandem-type thin film solar cell provided with the some photoelectric conversion unit laminated | stacked on the board | substrate, Comprising: The 1st electrode layer film-forming process which forms the 1st electrode layer of a photoelectric conversion unit A precursor layer forming step of forming a plurality of semiconductor precursor layers on the formed first electrode layer; and a second step of forming a second electrode layer on the formed semiconductor precursor layer After laminating a plurality of photoelectric conversion units in which a semiconductor precursor layer is formed between the electrode layer forming step and the first electrode layer and the second electrode layer, the semiconductor precursor layer of the photoelectric conversion unit is There is provided a method for producing a tandem-type thin film solar cell, characterized by comprising a precursor layer diffusion step of heating and generating semiconductor crystals.

Here, in the method for manufacturing a tandem thin film solar cell to which the present invention is applied, the first electrode layer, the plurality of semiconductor precursor layers, and the second electrode layer of the plurality of photoelectric conversion units constituting the tandem thin film solar cell are: These are preferably formed by sputtering.
Further, in the method of manufacturing a tandem thin film solar cell to which the present invention is applied, in the precursor layer diffusion step, a plurality of semiconductor precursor layers are mutually diffused by melt diffusion to generate semiconductor crystals. Is preferred.

Moreover, in the manufacturing method of the tandem-type thin film solar cell to which the present invention is applied, it is preferable that the semiconductor generated by the precursor layer diffusion step is composed of crystals of chalcopyrite type compounds.
Furthermore, the semiconductor produced by the precursor layer diffusion step preferably contains at least copper (Cu), indium (In), and selenium (Se).

  According to the present invention, a CIS tandem thin film solar cell can be obtained without destroying the pn junction of the lower cell.

It is a figure explaining the outline | summary of the manufacturing method of the tandem-type thin film solar cell to which this Embodiment is applied. It is a figure explaining an example of the tandem-type thin film solar cell manufactured by the manufacturing method of this Embodiment. It is a figure explaining the process of preparing the lower cell. It is a figure explaining the process of laminating | stacking upper cell II on lower cell I.

  Hereinafter, embodiments of the present invention will be described in detail. In addition, this invention is not limited to the following embodiment, It can implement by changing variously within the range of the summary. Further, the drawings to be used are for explaining the present embodiment and do not represent the actual size.

  FIG. 1 is a diagram for explaining the outline of a method for manufacturing a tandem-type thin film solar cell to which the present embodiment is applied. As shown in FIG. 1, in the manufacturing method of the tandem-type thin film solar cell to which the present embodiment is applied, a sputtering apparatus is used, and first, the back surface constituting the first photoelectric conversion unit (lower cell) on the insulating substrate. A multilayer film such as an electrode layer and a semiconductor precursor layer is formed by sputtering (lower cell multilayer film forming step). Next, without removing the insulating substrate on which the lower cell is formed from the sputtering apparatus, a multilayer film such as a semiconductor precursor layer of the second photoelectric conversion unit (upper cell) is subsequently formed on the lower cell by sputtering. (Upper cell multilayer film forming step). The semiconductor precursor layer preferably contains selenium (Se). In addition, you may laminate | stack a photoelectric conversion unit further as needed.

Next, the compound constituting the semiconductor precursor layer formed on the lower cell and the upper cell, respectively, by heating the insulating substrate in which the lower cell and the upper cell are laminated, using a heating device (for example, light irradiation with a halogen lamp or the like). The semiconductor crystal is formed by heating to the melting point of the semiconductor (annealing step). In this embodiment mode, it is only necessary to use one sputtering device and one heating device. Also, no toxic gas treatment facility or waste liquid treatment facility is required. Furthermore, since the number of processes is small, the cost can be significantly reduced.
Next, the tandem thin film solar cell in this embodiment will be described.

FIG. 2 is a diagram illustrating an example of a tandem thin film solar cell manufactured by the manufacturing method of the present embodiment. Here, a two-junction tandem thin film solar cell in which two photoelectric conversion units (lower cell and upper cell) are stacked will be described as an example.
In the method for manufacturing a tandem thin film solar cell to which the present embodiment is applied, first, a tandem solar cell precursor 100A shown in FIG. 2A is prepared, and then this tandem solar cell precursor 100A. Is heat-treated to produce a tandem-type thin film solar cell 100 shown in FIG.

  A tandem solar cell precursor 100A shown in FIG. 2A includes a lower cell (first photoelectric conversion unit) I formed on a substrate 10 and an upper cell (second photoelectric layer) stacked on the lower cell I. Photoelectric conversion unit) II. The lower cell I includes a back electrode layer (first electrode layer) 20 formed on a substrate 10 made of an insulating material, a first semiconductor precursor layer 30 formed on the back electrode layer 20, a first The first buffer layer 40 is formed on the semiconductor precursor layer 30, and the first transparent conductive film (second electrode layer) 50 is formed on the first buffer layer 40.

The first semiconductor precursor layer 30 of the lower cell I is formed by laminating a plurality of precursor layers (31, 32,... 36, 37) made of a compound semiconductor. Specifically, a precursor layer for p-type semiconductor formation, a precursor layer for diffusion control, and a precursor layer for n-type semiconductor formation. A plurality of p-type semiconductor forming precursor layers and n-type semiconductor forming precursor layers are sequentially stacked with a diffusion control precursor layer interposed therebetween.
Here, in this embodiment, when a Cu-In-Se based semiconductor is employed as the compound semiconductor, the p-type semiconductor forming precursor layer is a precursor layer that easily forms a p-type semiconductor by melt diffusion, The precursor layer for forming an n-type semiconductor is a precursor layer that easily forms an n-type semiconductor. The diffusion control precursor layer is a layer for controlling mutual diffusion of the p-type semiconductor formation precursor layer and the n-type semiconductor formation precursor layer. As will be described later, each layer is formed by sputtering using a sputtering apparatus.

Next, the upper cell II includes a second semiconductor precursor layer 60 formed on the first transparent conductive film 50 of the lower cell I and a second buffer layer formed on the second semiconductor precursor layer 60. 70 and a second transparent conductive film 80 formed on the second buffer layer 70.
In the present embodiment, the first transparent conductive film 50 of the lower cell I also serves as the back electrode (first electrode layer) of the upper cell II that is the second photoelectric conversion unit. The second transparent conductive film 80 constitutes the second electrode layer of the upper cell II that is the second photoelectric conversion unit.
Similar to the first semiconductor precursor layer 30 of the lower cell I, the second semiconductor precursor layer 60 of the upper cell II is a p-type semiconductor formation precursor layer, a diffusion control precursor layer, and an n-type semiconductor formation precursor. A plurality of precursor layers (61, 62,... 66, 67) made of body layers are laminated. Each layer is formed by sputtering using a sputtering apparatus.

  Next, the tandem-type thin film solar cell 100 shown in FIG. 2 (b) is manufactured by heat-treating the tandem-type solar cell precursor 100A shown in FIG. 2 (a). The tandem thin film solar cell 100 is composed of a lower cell I and an upper cell II. The lower cell I includes a first semiconductor layer 300 formed by melting and diffusing the first semiconductor precursor layer 30 (see FIG. 2A), and the upper cell II includes a second semiconductor precursor layer 60. The second semiconductor layer 600 is formed by melting and diffusing (see FIG. 2A). Further, a comb-shaped electrode (negative electrode) 90 is provided on the second transparent conductive film 80 side of the upper cell II for current collection.

Next, components of the tandem solar cell precursor 100A and the tandem thin film solar cell 100 will be described.
As a material which comprises the board | substrate 10, metal films, such as stainless steel, an organic film, glass etc. are mentioned, for example. Although the magnitude | size of the board | substrate 10 is not specifically limited, In this Embodiment, length x width is 5 cm x 5 cm, and thickness is 0.5 mm.

  The material constituting the back electrode layer 20 is preferably a metal, and examples thereof include at least one metal selected from Mo, Ti, Cr, Al, Ag, Au, Cu, and Pt, or an alloy thereof. In this embodiment, the back electrode layer 20 is a metal thin film having a thickness of about 0.3 μm. The back electrode layer 20 can be formed on the substrate 10 by, for example, a vapor deposition method, a sputtering method, a CVD method (Chemical Vapor Deposition), or the like. In this embodiment mode, it is preferably formed by a sputtering method.

Examples of the semiconductor composing the first semiconductor layer 300 and the second semiconductor layer 600 include chalcopyrite type compound semiconductors containing elements of groups IB, IIIB, and VIB of the periodic table. A chalcopyrite type compound semiconductor is a semiconductor material called a chalcopyrite system that is used in place of silicon as a material of a light absorption layer of a solar cell and is made of Cu, In, Ga, Al, Se, S, or the like. Typical examples include Cu (In, Ga) Se ₂ , Cu (In, Ga) (Se, S) ₂ , CuInS _{2 and the} like, which are abbreviated as CIGS, CIGSS, and CIS, respectively.
In this embodiment mode, it is preferably formed using a Cu—In—Se semiconductor material having a chalcopyrite structure including copper (Cu), indium (In), and selenium (Se).
In the present embodiment, the thicknesses of the first semiconductor layer 300 and the second semiconductor layer 600 are in the range of 0.3 μm to 2 μm, respectively.

  Here, when a Cu—In—Se based semiconductor material containing copper (Cu), indium (In), and selenium (Se) is employed as a semiconductor constituting the first semiconductor layer 300 and the second semiconductor layer 600, The p-type semiconductor forming precursor layer constituting the first semiconductor precursor layer 30 and the second semiconductor precursor layer 60 of the tandem solar cell precursor 100A is made of copper (Cu) and selenium (which easily form a p-type semiconductor). It is preferable to form a film by a mixture with Se). The precursor layer for forming an n-type semiconductor is preferably a mixture of indium (In) and selenium (Se) that easily forms an n-type semiconductor.

Here, in the present embodiment, a Cu-In-Se-based semiconductor material having a small forbidden band width is disposed in the first semiconductor layer 300 of the lower cell I, and the second semiconductor layer 600 of the upper cell II is It is preferable to arrange a Cu—In—Se based semiconductor material having a relatively large forbidden bandwidth. Examples of the Cu—In—Se based semiconductor material of the lower cell I include CuInSe ₂ and Cu (In _1-x Ga _x ) Se ₂ containing low-concentration gallium. Examples of the Cu—In—Se based semiconductor material of the upper cell II include CuGaSe ₂ , Cu (In _1-x Ga _x ) Se ₂ , and Cu (In _1-x Ga _x ) (Se _1-y S _y ) _{2. , Ag (In 1-x Ga} x) Se 2, Ag (In 1-x Ga x) (Se 1-y S y) 2 and the like.

In the manufacturing method of the tandem-type thin film solar cell 100 to which the present embodiment is applied, the precursor for forming a p-type semiconductor is controlled by controlling the elemental composition, melting point and film thickness of the compound constituting the diffusion control precursor layer. It is possible to control the diffusion of the layer and the n-type semiconductor forming precursor layer by melt diffusion.
This is confirmed from the fact that when a Cu—In—Se based semiconductor material is used, a crystal peak is observed by X-ray diffraction measurement of the first semiconductor layer 300 and the second semiconductor layer 600 after melt diffusion. .
Moreover, the elemental composition of the compound which comprises the several precursor layer (31-37, 61-67: refer Fig.2 (a)) in two semiconductor precursor layers (30,60: refer Fig.2 (a)). By changing the film thickness and melting and diffusing them, a semiconductor layer having good crystallinity (300, 600: see FIG. 2B) can be generated and a pn junction can be formed at the same time. This will be described by taking as an example the case of adopting a CuInSe2-based compound which is one of chalcopyrite type compounds.

Generally, CuInSe ₂ is a _Cu 2 SE50 mol% and _{an In} 2 _Se 3 50 mole% is a stable compound, can be obtained by reacting. Here, it is known that both Cu ₂ Se and In ₂ Se ₃ have a melting point higher than the melting point (986 ° C.) of CuInSe ₂ which is the final product in each binary phase diagram (for example, Cu ₂ Se has a melting point of 1,130 ° C.). Therefore, when diffusing the Cu 2 _Se and an In ₂ Se ₃ by heat treatment, it is possible that these compounds remains remain unreacted.
Therefore, by disposing a compound having a higher melting point than these compounds between the InSe compound layer and the CuSe compound layer, mutual diffusion of InSe and CuSe can be controlled. As a result, a chalcopyrite n-type Cu—In—Se film slightly lacking Cu is formed on the negative electrode side, while a chalcopyrite p-type Cu slightly lacking In is formed on the positive electrode side. It is considered that an -In-Se film is formed.

Furthermore, the relationship between the Se concentration and the melting point (° C.) of the Cu—Se compound is known to change rapidly when the Se concentration ranges from 33.3 at% to 52.5 at%. . Moreover, as for the relationship between Se concentration and melting | fusing point (degreeC) of an In-Se type compound, it is known that melting | fusing point changes rapidly in the range of Se concentration of 50at% -60at%.
By utilizing such properties of the Cu—Se compound and In—Se compound, the melting points of the p-type semiconductor forming precursor layer and the n-type semiconductor forming precursor layer are adjusted, and at the same time, the diffusion of each compound The direction and amount of diffusion can be controlled.

That is, the n-type semiconductor forming precursor layer is formed using an In—Se compound in which the melting point increases as the Se concentration increases in the range of Se concentration from 50 at% to 60 at%. In addition, the p-type semiconductor forming precursor layer is formed using a Cu—Se-based compound whose melting point is lowered when the Se concentration is increased in the Se concentration range of 33.3 at% to 52.5 at%. Then, by adjusting the concentration of Se contained in the diffusion control precursor layer, the respective melting points of the p-type semiconductor formation precursor layer and the n-type semiconductor formation precursor layer are controlled, and at the same time, the direction of diffusion and diffusion It is possible to control the amount.
As a result, a pn junction is formed in the first semiconductor layer 300 and the second semiconductor layer 600 generated by melting and diffusion of the plurality of precursor layers, and the width and depth direction of the depletion layer in the vicinity of the formed pn junction It is also possible to control the distribution of.

Next, the material which comprises the 1st transparent conductive film 50 and the 2nd transparent conductive film 80 is not specifically limited, In this Embodiment, the metal element chosen from periodic table IIB group, IIIB group, and IVB group A transparent conductive film material containing is used.
Specifically, for example, as a transparent conductive film material containing a metal element selected from Group IIB of the periodic table, AZO added with Al as a dopant to ZnO, GZO added with Ga as a dopant to ZnO, and In to ZnO. A zinc oxide based metal material such as IZO added as a dopant; a transparent conductive film material containing a metal element selected from Group IIIB of the periodic table is ITO (Indium Tin Oxide) in which Sn is added to In ₂ O ₃ as a dopant. Examples of the transparent conductive film material containing a metal element selected from Group IVB include tin oxide-based metal materials such as SnO ₂ to which a dopant is added.
Among these, zinc (Zn), indium (In), and tin (Sn) are preferable as the metal element. In this embodiment, it is preferable to form a film by sputtering using a metal material containing at least one selected from ZnO, ITO, and SnO ₂ .

In the present embodiment, the first transparent conductive film 50 is formed using an indium oxide-based metal material such as ITO. The second transparent conductive film 80 is formed using a zinc oxide-based metal material such as AZO, GZO, IZO. The thickness of the first transparent conductive film 50 and the second transparent conductive film 80 is about 0.5 μm to 1.5 μm in the present embodiment.
Here, in the present embodiment, the first transparent conductive film 50 and the second transparent conductive film 80 are formed as conductive thin films that are transparent and have high electrical conductivity. Specifically, it has a property that the transmittance is 80% or more in the visible light wavelength region of 380 nm to 780 nm, and the electrical resistivity is about 1 × 10 ⁻³ Ωcm or less.

In the present embodiment, the first buffer layer 40 and the first transparent conductive film 50, and the second semiconductor layer 600 and the second transparent conductive film 80, respectively, Two buffer layers 70 are provided. In this case, the material constituting the first buffer layer 40 and the second buffer layer 70 is not particularly limited, in the present embodiment, it is preferable to use a InS 3, sulfides such as _ZnS. Thereby, defects generated at the interface between the first semiconductor layer 300 and the first transparent conductive film 50 and between the second semiconductor layer 600 and the second transparent conductive film 80 can be suppressed.

Next, each process of the manufacturing method of the tandem-type thin film solar cell to which this Embodiment is applied is demonstrated. FIG. 3 is a diagram illustrating a process of preparing the lower cell I.
As shown in FIG. 3A, in the preparation of the lower cell I which is the first photoelectric conversion unit of the two-junction tandem thin-film solar cell, first, an insulating substrate is used in a sputtering apparatus kept in a vacuum state. A back electrode layer (first electrode layer) 20 made of a metal material is formed on the substrate 10 by sputtering (first electrode layer forming step). Next, as shown in FIG. 3B, a first semiconductor precursor layer 30 in which a plurality of precursor layers are sequentially stacked is formed on the back electrode layer 20 by sputtering (precursor layer deposition). Process). Subsequently, as shown in FIG. 3C, a first buffer layer 40 is formed on the first semiconductor precursor layer 30 by sputtering, and then, as shown in FIG. A first transparent conductive film 50 (second electrode layer) made of a transparent conductive material is formed on one buffer layer 40 (second electrode layer film forming step). Each layer is formed in a sputtering apparatus consistently by sputtering.

Subsequently, a process of stacking the upper cell II will be described.
FIG. 4 is a diagram illustrating a process of stacking the upper cell II on the lower cell I. In the preparation of the upper cell II which is the second photoelectric conversion unit of the two-junction tandem thin film solar cell, as shown in FIG. 4A, it corresponds to the first electrode layer of the second photoelectric conversion unit by sputtering. On the 1st transparent conductive film 50 of the lower cell I, the 2nd semiconductor precursor layer 60 in which the several precursor layer was laminated | stacked in order is formed into a film (precursor layer film-forming process). Subsequently, as shown in FIG. 4B, the second transparent conductive film corresponding to the second buffer layer 70 and the second electrode layer of the second photoelectric conversion unit on the second semiconductor precursor layer 60 by sputtering. 80 are sequentially formed (second electrode layer forming step). As described above, each layer of the upper cell II is formed by sputtering in the sputtering apparatus.

Next, as shown in FIG. 4C, infrared rays 200 as electromagnetic waves are irradiated for a certain period of time from the second transparent conductive film 80 side, and the plurality of p-type semiconductor forming precursor layers and the diffusion control precursor described above. The first semiconductor precursor layer 30 and the second semiconductor precursor layer 60 composed of the body layer and the n-type semiconductor forming precursor layer are heated. In the present embodiment, a halogen lamp is preferable as the light source of the infrared ray 200.
The compounds contained in each of the p-type semiconductor forming precursor layer, the diffusion control precursor layer, and the n-type semiconductor forming precursor layer irradiated with the infrared rays 200 diffuse to each other by melt diffusion. Then, a first semiconductor layer 300 and a second semiconductor layer 600 made of a p-type semiconductor layer and an n-type semiconductor layer are formed in the lower cell I and the upper cell II, respectively.

  Here, the diffusion control precursor layer provided between the p-type semiconductor formation precursor layer and the n-type semiconductor formation precursor layer is adjacent to the p-type semiconductor formation precursor layer and the n-type semiconductor formation layer. It functions as a diffusion control layer for controlling interdiffusion with the precursor layer. Specifically, the diffusion control precursor layer melts and diffuses to increase the melting point of each interface between the adjacent p-type semiconductor formation precursor layer and the n-type semiconductor formation precursor layer, and thereby the p-type semiconductor. Diffusion of an element that generates a p-type semiconductor from the forming precursor layer side to the n-type semiconductor forming precursor layer side is suppressed.

  Thereafter, a comb-shaped electrode (negative electrode) 90 for collecting current is provided on the second transparent conductive film 80 by sputtering, and an electrode (positive electrode) is formed on the back electrode layer 20 by sputtering or printing a conductive paste. Installed (not shown), the tandem thin film solar cell 100 is manufactured.

  The direction in which the infrared ray 200 is irradiated is not necessarily limited to the second transparent conductive film 80 side. For example, if the substrate 10 is made of tempered glass that transmits the infrared ray 200, the infrared ray 200 is emitted from the substrate 110 side. It is also possible to irradiate.

In addition, the above description is only an example for demonstrating embodiment of this invention, and this invention is not limited to this embodiment.
The present invention can be applied to a photovoltaic device including a semiconductor layer composed of a plurality of elements and two electrode layers sandwiching the semiconductor layer, and a method for manufacturing a tandem thin film solar cell having such a structure. For example, a III-V group semiconductor typified by a Cd-Te system, an I-III-VI group semiconductor typified by a Cu-In-Se system, and an I-II typified by a Cu-Zn-Sn-S system compound The present invention can also be applied to an IV group semiconductor composed of two or more elements such as an -IV-VI group semiconductor, an II-IV-V group semiconductor, and a Si-Ge group.

As described above in detail, according to the method for manufacturing a tandem-type thin film solar cell to which the present invention is applied, a plurality of semiconductor precursor layers composed of elements contained in a semiconductor layer of a photoelectric conversion unit, and a semiconductor precursor By forming each layer other than the body layer in advance and then heating, the crystal of the semiconductor layer and the pn junction are simultaneously formed, thereby enabling high-speed consistent film formation.
The method for configuring the semiconductor precursor layer differs depending on each constituent element of each semiconductor layer. However, basically, at least three semiconductor precursor layers are provided to easily form an n-type semiconductor precursor. A body layer is provided on the negative electrode side, a p-type semiconductor precursor layer is provided on the positive electrode side, and a diffusion control layer for controlling interdiffusion of these layers is provided between these layers. Very important.

DESCRIPTION OF SYMBOLS 10 ... Board | substrate, 20 ... Back electrode layer, 30 ... 1st semiconductor precursor layer, 40 ... 1st buffer layer, 50 ... 1st transparent conductive film, 60 ... 2nd semiconductor precursor layer, 70 ... 2nd buffer layer, DESCRIPTION OF SYMBOLS 80 ... 2nd transparent conductive film, 90 ... Comb-shaped electrode (negative electrode), 100 ... Tandem-type thin film solar cell, 100A ... Tandem-type solar cell precursor, 200 ... Infrared, 300 ... 1st semiconductor layer, 600 ... 2nd semiconductor layer , I ... Lower cell, II ... Upper cell

Claims (5)

A method for producing a tandem thin film solar cell including a plurality of photoelectric conversion units stacked on a substrate,
A first electrode layer forming step of forming a first electrode layer of the photoelectric conversion unit;
A precursor layer film forming step of forming a plurality of semiconductor precursor layers on the formed first electrode layer;
A second electrode layer film forming step of forming a second electrode layer on the semiconductor precursor layer formed;
After laminating a plurality of the photoelectric conversion units in which the semiconductor precursor layer is formed between the first electrode layer and the second electrode layer, the semiconductor precursor layer of the photoelectric conversion unit is heated. And a precursor layer diffusion step for generating semiconductor crystals,
A method for producing a tandem-type thin-film solar cell.   2. The method of manufacturing a tandem thin-film solar cell according to claim 1, wherein the first electrode layer, the plurality of semiconductor precursor layers, and the second electrode layer are all formed by sputtering.   The method for producing a tandem-type thin film solar cell according to claim 1 or 2, wherein in the precursor layer diffusion step, the plurality of semiconductor precursor layers are diffused mutually by melt diffusion.   The method for producing a tandem thin film solar cell according to any one of claims 1 to 3, wherein the semiconductor produced by the precursor layer diffusion step is composed of crystals of chalcopyrite type compounds.   5. The semiconductor according to claim 1, wherein the semiconductor generated by the precursor layer diffusion step contains at least copper (Cu), indium (In), and selenium (Se). A method for producing a tandem thin film solar cell.

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