JP2013065818A - Method for manufacturing photoelectric conversion device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photoelectric conversion device which has high photoelectric conversion efficiency by easily and satisfactorily bonding a transparent conductive film onto a semiconductor layer containing a metal chalcogenide.SOLUTION: A method for manufacturing a photoelectric conversion device 11 comprises the steps of: producing a first semiconductor layer 3 having a first conductivity type on a lower electrode layer 2; producing a semiconductor layer 4 having a second conductivity type different from the first conductivity type and containing a metal chalcogenide, on the first semiconductor layer 3; applying a film forming liquid containing an acid or a base, an indium compound, and a tin compound onto the second semiconductor layer 4 to produce a film; and heating the film to form it into a transparent conductive film 5.

Description

  The present invention relates to a method for manufacturing a photoelectric conversion device having a transparent conductive film.

  As a photoelectric conversion device used for photovoltaic power generation or the like, a first semiconductor layer as a light absorption layer, a second semiconductor layer including a metal chalcogenide formed on the first semiconductor layer, And a transparent conductive film formed on the semiconductor layer.

Examples of the semiconductor material used for the first semiconductor layer include chalcopyrite-based I-III-VI group compounds such as CIS and CIGS, and II-VI group compounds such as CdTe. In addition, examples of the metal chalcogenide used for the second semiconductor layer include II-VI group compounds such as ZnS and III-VI group compounds such as In ₂ S ₃ . Moreover, as a transparent conductive film, Z
There are nO and ITO.

  In order to improve the electrical connection between the respective layers, it is preferable to sufficiently remove impurities between the respective layers to enhance the bonding property between the respective layers. Patent Document 1 describes that after forming a buffer layer by film formation in a solution, the surface of the buffer layer is washed to remove impurities, and then a transparent conductive film is formed by sputtering or the like. .

International Publication No. 2008/120306

  However, in the method using cleaning as in Patent Document 1, the number of cleaning steps increases and the manufacturing process becomes complicated. In addition, the surface of the buffer layer changes in quality between the cleaning and the formation of the transparent conductive film, and as a result, it is difficult to sufficiently increase the photoelectric conversion efficiency.

  An object of the present invention is to provide a photoelectric conversion device having a high photoelectric conversion efficiency by easily and satisfactorily bonding a transparent conductive film on a semiconductor layer containing a metal chalcogenide.

  According to one embodiment of the present invention, there is provided a method for manufacturing a photoelectric conversion device, the step of forming a first semiconductor layer having a first conductivity type on a lower electrode layer, and the first conductivity on the first semiconductor layer. Forming a second semiconductor layer having a second conductivity type different from the mold and containing metal chalcogenide, and a film containing either an acid or a base, an indium compound, and a tin compound on the second semiconductor layer A step of applying a forming solution to prepare a film, and a step of heating the film to form a transparent conductive film.

  According to the present invention, a photoelectric conversion device having high photoelectric conversion efficiency can be easily manufactured.

It is a perspective view which shows an example of embodiment of a photoelectric conversion apparatus. It is sectional drawing of the photoelectric conversion apparatus of FIG.

  Hereinafter, a method for manufacturing a photoelectric conversion device according to an embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a perspective view showing a photoelectric conversion device manufactured by using the method for manufacturing a photoelectric conversion device according to one embodiment of the present invention, and FIG. 2 is a cross-sectional view thereof. The photoelectric conversion device 11 includes a substrate 1, a lower electrode layer 2, a first semiconductor layer 3, a second semiconductor layer 4, and a transparent conductive film 5.

  The first semiconductor layer 3 has a first conductivity type, and the second semiconductor layer 4 has a second conductivity type different from the first conductivity type. Charge separation of positive and negative carriers generated by light irradiation in the first semiconductor layer 3 and the second semiconductor layer 4 having different conductivity types can be performed satisfactorily. For example, if the first semiconductor layer 3 is p-type, the second semiconductor layer 4 is n-type. Alternatively, the first semiconductor layer 3 may be n-type and the second semiconductor layer 4 may be p-type. Note that another layer such as a buffer layer may be interposed between the first semiconductor layer 3 and the second semiconductor layer 4.

  1 and 2, the photoelectric conversion device 11 is formed by arranging a plurality of photoelectric conversion cells 10. 1 and FIG. 2, only two photoelectric conversion cells 10 are shown for convenience of illustration. However, in the actual photoelectric conversion device 11, there are many in the left-right direction of the drawing or a direction perpendicular thereto. The photoelectric conversion cells 10 may be arranged two-dimensionally (two-dimensionally).

  1 and 2, a plurality of lower electrode layers 2 are arranged in a plane on a substrate 1. Among the adjacent lower electrode layers 2, a first semiconductor layer 3, a second semiconductor layer 4, and a transparent conductive film 5 are provided from one lower electrode layer 2a to the other lower electrode layer 2b. On the lower electrode layer 2b, a connection conductor 7 is provided so as to electrically connect the lower electrode layer 2b and the transparent conductive film 5. These lower electrode layer 2, first semiconductor layer 3, second semiconductor layer 4, transparent conductive film 5 and connection conductor 7 constitute one photoelectric conversion cell 10. The adjacent photoelectric conversion cells 10 are connected to each other by the lower electrode layer 2b. With such a configuration, the adjacent photoelectric conversion cells 10 are connected in series.

  The substrate 1 is for supporting the photoelectric conversion cell 10. Examples of the material used for the substrate 1 include glass, ceramics, resin, and metal. As the substrate 1, for example, blue plate glass (soda lime glass) having a thickness of about 1 to 3 mm can be used.

  The lower electrode layer 2 (lower electrode layers 2a, 2b) is a conductor such as Mo, Al, Ti, or Au provided on the substrate 1. The lower electrode layer 2 is formed to a thickness of about 0.2 μm to 1 μm using a known thin film forming method such as sputtering or vapor deposition.

The first semiconductor layer 3 has a first conductivity type and is a semiconductor layer having a thickness of about 1 μm to 3 μm, for example. Examples of the first semiconductor layer 3 include silicon, II-VI group compounds, I-III-VI group compounds, and I-II-IV-VI group compounds.

  The II-VI group compound is a compound semiconductor of a II-B group (also referred to as a group 12 element) and a VI-B group element (also referred to as a group 16 element). Examples of II-VI group compounds include CdTe.

An I-III-VI group compound is a group IB element (also referred to as a group 11 element) and a group III-B element (1
Compound of group VI-B). Examples of the I-III-VI group compound include CuInSe ₂ (also referred to as copper indium selenide, CIS), Cu (In, Ga) Se ₂ (also referred to as copper indium selenide / gallium, CIGS), Cu ( In, Ga) (Se, S) ₂ (also referred to as diselene / copper indium / gallium / CIGSS). Alternatively, the first semiconductor layer 3 may be composed of a multi-component compound semiconductor thin film such as copper indium selenide / gallium having a thin film of selenite / copper indium sulfide / gallium layer as a surface layer.

The I-II-IV-VI group compound is a compound of a group IB element, a group II-B element, a group IV-B element (also referred to as a group 14 element), and a group VI-B element. Examples of the I-II-IV-VI group compound include Cu ₂ ZnSnS ₄ (also referred to as CZTS), Cu ₂ ZnSn (S, Se) ₄ (also referred to as CZTSSe), and Cu ₂ ZnSnSe ₄ (also referred to as CZTSe). Can be mentioned.

  The first semiconductor layer 3 can be formed by a so-called vacuum process such as a sputtering method or an evaporation method, or can be formed by a process called a coating method or a printing method. A process referred to as a coating method or a printing method is a process in which a complex solution of constituent elements of the first semiconductor layer 3 is applied onto the lower electrode layer 2 and then dried and heat-treated.

The second semiconductor layer 4 has a second conductivity type different from the first conductivity type, and is a semiconductor layer containing metal chalcogenide. A metal chalcogenide is a compound of a metal element and a chalcogen element. Moreover, a chalcogen element means S, Se, and Te among VI-B group elements. Examples of the metal chalcogenide contained in the second semiconductor layer 4 include II-VI group compounds and III-VI group compounds containing a chalcogen element as a VI-B group element. The second semiconductor layer 4 can be formed with a thickness of 10 to 200 nm by, for example, a chemical bath deposition (CBD) method or the like.

Examples of the II-VI group compound contained in the second semiconductor layer 4 include CdS and ZnS. Examples of the III-VI group compound contained in the second semiconductor layer 4 include In ₂ S ₃ . Such II-VI group compounds and III-VI group compounds may be mixed crystal compounds containing at least one of a metal oxide and a metal hydroxide in addition to a metal chalcogenide. The second semiconductor layer 4 may contain a mixed crystal compound of a II-VI group compound and a III-VI group compound.

  The transparent conductive film 5 has a thickness of 0.05 to 3.0 μm and is a film mainly containing ITO. The transparent conductive film 5 is a layer having a resistivity lower than that of the second semiconductor layer 4 and is used for taking out charges generated in the first semiconductor layer 3 and the second semiconductor layer 4. From the viewpoint of taking out charges well, the resistivity of the transparent conductive film 5 may be less than 1 Ω · cm and the sheet resistance may be 50 Ω / □ or less. The photoelectric conversion device 11 generates power by receiving light incident from the transparent conductive film 5 side and photoelectrically converting light transmitted through the transparent conductive film 5 and the second semiconductor layer 4 by the first semiconductor layer 3. It is.

  The transparent conductive film 5 is produced as follows. First, a film forming liquid containing either an acid or a base, an indium compound, and a tin compound is produced. This film-forming liquid is applied onto the second semiconductor layer 4 by, for example, a spin coater, screen printing, dipping, spraying, or a die coater to form a film. And the transparent conductive film 5 containing ITO is formed by heating this film | membrane at 200-600 degreeC, for example.

  Examples of indium compounds contained in the film forming liquid include indium salts such as indium chloride, indium nitrate, indium sulfate, indium acetate, indium oxalate, and indium formate. Further, as another indium compound, an indium complex such as indium acetylacetonate may be used.

  Examples of the tin compound contained in the film-forming liquid include tin salts such as tin chloride, tin nitrate, tin sulfate, tin acetate, and tin oxalate. Moreover, tin complexes such as tin acetylacetonate may be used as other tin compounds.

  As the indium compound and the tin compound, ITO (compound containing indium oxide and tin oxide) particles may be used. From the viewpoint of forming the transparent conductive film 5 with high conductivity, the average particle diameter of the ITO particles can be 10 to 200 nm. Moreover, such ITO particles may be used by mixing with at least one of the indium salt, indium complex, tin salt and tin complex.

  Examples of the solvent used in the film forming liquid include water and various organic solvents. And the said indium compound and a tin compound are melt | dissolved in a solvent so that it may become 50: 1-20 by the molar ratio of an indium element and a tin element.

  Further, the film forming liquid contains either an acid or a base. With such a configuration, when the film-forming liquid is applied onto the second semiconductor layer 4 to form a film, impurities on the second semiconductor layer 4 are washed by the acid or base contained in the film-forming liquid. As a result, the transparent conductive film 5 is formed. Therefore, it is not necessary to provide a separate cleaning process as in the prior art, and the process is simplified. Further, since the cleaning and the film formation proceed in the same process, the transparent conductive film 5 can be formed on the surface of the cleaned second semiconductor layer 4 in a good state. As a result, the electrical connection between the second semiconductor layer 4 and the transparent conductive film 5 becomes good, and the photoelectric conversion efficiency of the photoelectric conversion device 11 can be increased.

  From the viewpoint of improving the formation of the transparent conductive film 5, the content of the acid or base contained in the film-forming solution may be 0.1 to 0.7 mol / L.

  Examples of the acid used for the film forming liquid include sulfuric acid, phosphoric acid, nitric acid, and hydrochloric acid. From the viewpoint of better cleaning the surface of the second semiconductor layer 4, an acid having an acid dissociation constant pKa in water of 2 or less may be used. From the viewpoint of making it unnecessary to leave unnecessary elements in the transparent conductive film 5, highly volatile hydrochloric acid or nitric acid may be used as the acid.

  In addition, hydrofluoric acid may be used as an acid used for the film forming liquid from the viewpoint of further enhancing the cleaning effect on oxide-based impurities.

  Examples of the base used in the film forming liquid include ammonia, ethylamine, diethylamine, and triethylamine. From the viewpoint of better cleaning the surface of the second semiconductor layer 4, a base having an acid dissociation constant pKa in water of 9 or more may be used. From the viewpoint of making it difficult for unnecessary elements to remain in the transparent conductive film 5, ammonia having high volatility may be used as a base.

  In the photoelectric conversion device 11, a collecting electrode 8 may be further formed on the transparent conductive film 5 as shown in FIGS. 1 and 2. The current collecting electrode 8 is for taking out charges generated in the first semiconductor layer 3 and the second semiconductor layer 4 more satisfactorily. For example, as shown in FIG. 1, the collector electrode 8 is formed in a linear shape from one end of the photoelectric conversion cell 10 to the connection conductor 7. As a result, the current generated in the first semiconductor layer 3 and the fourth semiconductor layer 4 is collected by the current collecting electrode 8 through the transparent conductive film 5, and is supplied to the adjacent photoelectric conversion cell 10 through the connection conductor 7. Good conductivity.

  The collector electrode 8 may have a width of 50 to 400 μm from the viewpoint of increasing the light transmittance to the first semiconductor layer 3 and having good conductivity. The current collecting electrode 8 may have a plurality of branched portions.

  The collector electrode 8 is formed, for example, by printing a metal paste in which a metal powder such as Ag is dispersed in a resin binder or the like in a pattern and curing it.

  1 and 2, the connection conductor 7 is a first semiconductor layer so as to electrically connect the transparent conductive film 5 (or the current collecting electrode 8) and the lower electrode layer 2 of the adjacent photoelectric conversion cell 10. 3 and a conductor provided across the second semiconductor layer 4. The connection conductor 7 can be made of metal, conductive paste, or the like. In FIG. 1 and FIG. 2, the collector electrode 8 is extended to form the connection conductor 7, but this is not limitative. For example, the transparent conductive film 5 may be stretched.

  Note that the present invention is not limited to the above-described embodiment, and various modifications may be made without departing from the scope of the present invention.

1: Substrate 2, 2a, 2b: Lower electrode layer 3: First semiconductor layer 4: Second semiconductor layer 5: Transparent conductive film 7: Connection conductor 8: Current collecting electrode 10: Photoelectric conversion cell 11: Photoelectric conversion device

Claims (7)

Producing a first semiconductor layer having the first conductivity type on the lower electrode layer;
Forming a second semiconductor layer having a second conductivity type different from the first conductivity type on the first semiconductor layer and including a metal chalcogenide;
Applying a film-forming liquid containing either an acid or a base, an indium compound and a tin compound on the second semiconductor layer to produce a film;
And a step of heating the film to form a transparent conductive film.   The method for manufacturing a photoelectric conversion device according to claim 1, wherein ITO particles are used as the indium compound and the tin compound.   The method for producing a photoelectric conversion device according to claim 1, wherein the acid has an acid dissociation constant in water of 2 or less.   The method for manufacturing a photoelectric conversion device according to claim 1, wherein hydrochloric acid or nitric acid is used as the acid.   The method for manufacturing a photoelectric conversion device according to claim 1, wherein hydrofluoric acid is used as the acid.   The method for producing a photoelectric conversion device according to claim 1, wherein the base has an acid dissociation constant of 9 or more in water. The method for manufacturing a photoelectric conversion device according to claim 1, wherein ammonia is used as the base.

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