JP5517696B2 - Photoelectric conversion device and method for manufacturing photoelectric conversion device - Google Patents

Description

  The present invention relates to a photoelectric conversion device using a compound semiconductor and a manufacturing method thereof.

  As a solar cell, there is a photoelectric conversion device including a light absorption layer made of an I-III-VI group compound semiconductor such as CIS or CIGS. In this photoelectric conversion device, for example, a first electrode layer made of, for example, Mo is formed on a substrate made of soda lime glass, and the I-III-VI group compound is formed on the first electrode layer. A light absorption layer made of a semiconductor is formed. Further, a transparent second electrode layer made of ZnO or the like is formed on the light absorption layer via a buffer layer made of ZnS, CdS or the like.

  Such a buffer layer is chemically deposited in an aqueous solution by a solution deposition method called a chemical bath deposition method (CBD method), and then modified by annealing.

Japanese Patent No. 3249342

  However, the photoelectric conversion device has a problem in that when the photoelectric conversion device is used for solar power generation or the like, the photoelectric conversion efficiency is lowered and the moisture resistance is low.

  The present invention has been completed in view of the above-described conventional problems, and an object thereof is to provide a highly moisture-resistant photoelectric conversion device that can maintain high photoelectric conversion efficiency.

A photoelectric conversion device according to an embodiment of the present invention includes a mixed crystal compound of a metal chalcogenide, a metal oxide, and a metal hydroxide, and the total number of atoms of the chalcogen element and the oxygen element constituting the metal chalcogenide the atomic ratio of chalcogen elements much larger than the atomic number ratio of the oxygen element, atomic ratio of the oxygen element has comprises a first semiconductor layer is not more than 10 atom% in the first semiconductor The layer is bonded to a second semiconductor layer having a different conductivity type .

  A method for producing a photoelectric conversion device according to an embodiment of the present invention includes a step of producing a raw material solution containing an organic solvent, a metal salt, a chalcogen element-containing compound, and an organic onium salt, and using a support as the raw material. Contacting the solution, and depositing a first semiconductor layer containing a metal chalcogenide on the support.

  According to the present invention, it is possible to provide a highly reliable photoelectric conversion device that can maintain high photoelectric conversion efficiency.

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

  Hereinafter, a photoelectric conversion device and a manufacturing method thereof according to the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a cross-sectional view illustrating an example of an embodiment of a photoelectric conversion device of the present invention. The photoelectric conversion device 10 includes a support B, a first semiconductor layer 4, and a first electrode layer 5. In the present embodiment, an example in which the support B is composed of the substrate 1, the second electrode layer 2, and the second semiconductor layer 3 is shown, but the present invention is not limited thereto, and the support is not limited thereto. B may be composed of the substrate 1 and the second electrode layer 2 and have the first semiconductor layer 4 on the second electrode layer 2. In this embodiment, the second semiconductor layer 3 is a light absorption layer and the first semiconductor layer 4 is a buffer layer. However, the present invention is not limited to this.

  In FIG. 1, a plurality of photoelectric conversion devices 10 are formed side by side. The photoelectric conversion device 10 includes a third electrode layer 6 provided on the substrate 1 side of the second semiconductor layer 3 so as to be separated from the second electrode layer 2. The first electrode layer 5 and the third electrode layer 6 are electrically connected by the connection conductor 7 provided in the second semiconductor layer 3. The third electrode layer 6 is integrated with the second electrode layer 2 of the adjacent photoelectric conversion device 10. With this configuration, adjacent photoelectric conversion devices 10 are connected in series. In one photoelectric conversion device 10, the connection conductor 7 is provided so as to penetrate the second semiconductor layer 3 and the first semiconductor layer 4, and the second electrode layer 2 and the first electrode layer are provided. Photoelectric conversion is performed between the second semiconductor layer 3 and the first semiconductor layer 4 sandwiched between the first semiconductor layer 4 and the second semiconductor layer 3.

  The substrate 1 is for supporting the photoelectric conversion device 10. Examples of the material used for the substrate 1 include glass, ceramics, resin, and metal.

  The second electrode layer 2 and the third electrode layer 6 are made of a conductor such as Mo, Al, Ti, or Au, and are formed on the substrate 1 by a sputtering method or a vapor deposition method.

The second semiconductor layer 3 is an I-III-VI group compound semiconductor, an II-VI group compound semiconductor, or the like, and functions as a light absorption layer that absorbs light and generates charges. The second semiconductor layer 3 is not particularly limited, but is preferably an I-III-VI group compound semiconductor from the viewpoint that high photoelectric conversion efficiency can be obtained even with a thin layer of 10 μm or less. Group I-III-VI compound semiconductors are group IB elements (also referred to as group 11 elements), group III-B elements (also referred to as group 13 elements) and group VI-B elements (16
Compound semiconductor), which has a chalcopyrite structure and is called a chalcopyrite compound semiconductor (also called a CIS compound semiconductor). Examples of the I-III-VI group compound semiconductor include Cu (In, Ga) Se ₂ (also referred to as CIGS), Cu (In, Ga) (Se, S) ₂ (also referred to as CIGSS), and CuInS ₂ (CIS). Also called). Cu (In, Ga) Se ₂ refers to a compound mainly composed of Cu, In, Ga, and Se. Cu (In, Ga) (Se, S) ₂ refers to a compound mainly composed of Cu, In, Ga, Se, and S.

The II-VI compound semiconductor is a compound semiconductor of a II-B group element (also referred to as a group 12 element) and a VI-B group element. Examples of II-VI group compound semiconductors include ZnS, ZnSe,
ZnTe, CdS, CdSe, CdTe etc. are mentioned.

Such a second semiconductor layer 3 can be formed by the following method. First, a raw material element (for example, an IB group element, an II-B group element, an III-B group element, a VI-B group element, etc.) is formed into a film shape by sputtering or vapor deposition, or a film shape is formed by applying a raw material solution. To form a precursor containing raw material elements. The second semiconductor layer 3 made of a semiconductor can be formed by heating the precursor. Alternatively, a metal element (for example, an IB group element, an II-B group element, an III-B group element, etc.) is formed into a film like the above to form a precursor, and this precursor is converted into a VI-B group It can also be formed by heating in a gas atmosphere containing an element.

  The first semiconductor layer 4 is formed on the second semiconductor layer 3 and functions as a buffer layer that is heterojunction with the second semiconductor layer 3. The second semiconductor layer 3 and the first semiconductor layer 4 are preferably of different conductivity types. For example, when the second semiconductor layer 3 is a p-type semiconductor, the first semiconductor layer 4 is an n-type semiconductor. It is. The thickness of the first semiconductor layer 4 is preferably 10 to 200 nm from the viewpoint of transmitting incident light and allowing it to enter the second semiconductor layer 3 satisfactorily. Further, from the viewpoint of reducing the leakage current, the first semiconductor layer 4 is preferably a layer having a resistivity of 1 Ω · cm or more.

The first semiconductor layer 4 includes a mixed crystal compound of a metal chalcogenide, a metal oxide, and a metal hydroxide. The metal chalcogenide is a compound composed of a chalcogen element and a metal. The chalcogen element refers to S, Se, or Te among the VI-B group elements. Examples of such compound semiconductors include II-VI group compound semiconductors and III-VI group compound semiconductors (III-VI group compound semiconductors are compound semiconductors of III-B group elements and VI-B group elements). ). Examples of II-VI group compound semiconductors include ZnS, ZnSe, ZnTe, and C.
Examples thereof include dS, CdSe, CdTe. Examples of the III-VI compound semiconductor include Ga ₂ S ₃ , Ga ₂ Se ₃ , Ga ₂ Te ₃ , In ₂ S ₃ , In ₂ Se ₃ , and In ₂ Te ₃ .

In the case where the second semiconductor layer 3 is an I-III-VI group compound semiconductor, the first semiconductor layer 4 is CdS, ZnS or In ₂ S ₃ from the viewpoint of increasing the photoelectric conversion efficiency by a good pn junction. It is preferable that Also, in terms of not containing toxic substances to the environment, it is preferable that ZnS or _In 2 _{S 3.} In particular, In ₂ S ₃ is preferable from the viewpoint of further improving moisture resistance.

  Moreover, a metal oxide and a metal hydroxide are the metal oxide and hydroxide which comprise the said metal chalcogenide.

The first semiconductor layer 4 includes a mixed crystal compound of a metal chalcogenide, a metal oxide, and a metal hydroxide, and contains the chalcogen element in the total number of atoms of the chalcogen element and the oxygen element constituting the metal chalcogenide. The atomic ratio is larger than the atomic ratio of oxygen element. When the number of atoms of the chalcogen element in the mixed crystal compound is K and the number of atoms of oxygen is O, the atom number ratio P _K of the chalcogen element is K / (K + O) (atom%), The atomic ratio P _O is O / (K + O) (atom%).

With such a structure, moisture resistance of the photoelectric conversion device can be increased. That is, when the first semiconductor layer is formed by a solution deposition method using a conventional aqueous solution, in addition to the metal chalcogenide, it contains many metal oxides and metal hydroxides, and oxygen atoms in the first semiconductor layer. The number ratio _PO is about 70 atom%. When a large amount of metal oxide or metal hydroxide is contained in this manner, the ratio of the metal oxide and the metal hydroxide easily changes due to the influence of moisture, thereby changing the semiconductor characteristics of the first semiconductor layer. As a result, it becomes difficult to maintain the photoelectric conversion efficiency of the photoelectric conversion device high, and the moisture resistance becomes low. In contrast, in the photoelectric conversion device of this embodiment, by the atomic ratio P _O of the first semiconductor layer 4 oxygen lower than the atomic number ratio of chalcogen element, it is excellent in moisture resistance Can do. The atomic number ratio _{P O} of oxygen Ru der following 10 atom%.

Such a first semiconductor layer 4 is formed by, for example, the following solution deposition method. First, a raw material solution containing an organic solvent, a metal salt, a chalcogen element-containing compound, and an organic onium salt is prepared. Next, the second semiconductor layer 3 is brought into contact with the raw material solution, thereby
A first semiconductor layer 4 is deposited on the semiconductor layer 3. In the production of the first semiconductor layer 4, the temperature of the raw material solution is set to 30 ° C. to 100 ° C., and the time during which the second semiconductor layer 3 is brought into contact with the raw material solution is about 5 minutes to 180 minutes. The second semiconductor layer 3 is brought into contact with the raw material solution by immersing the second semiconductor layer 3 in the raw material solution or by applying the raw material solution onto the second semiconductor layer 3.

  The metal salt used in the raw material solution contains a metal and acid salt that is a raw material of the metal chalcogenide that constitutes the first semiconductor layer 4, and a metal that is a raw material of the metal chalcogenide that constitutes the first semiconductor layer 4 And a complex of a ligand. The metal salt is preferably an organic metal salt using an organic acid or an organic metal complex using an organic ligand in order to increase the solubility in an organic solvent. The concentration of the metal salt in the raw material solution is preferably 0.001 to 1M.

  Examples of such organic metal salts include salts of organic acids such as acetic acid and propionic acid with metals such as zinc and indium. Examples of the organometallic complex include zinc acetylacetonate and indium acetylacetonate.

  The chalcogen element-containing compound used for the raw material solution is a compound containing a chalcogen element that is a raw material for the metal chalcogenide that forms the first semiconductor layer 4. The chalcogen element-containing compound is preferably a chalcogen element-containing organic compound that is an organic compound containing a chalcogen element in order to increase the solubility in an organic solvent. Examples of the chalcogen element-containing organic compound include thioamides such as thioacetamide and thioformamide, and thiourea. The concentration of the chalcogen element-containing compound in the raw material solution is preferably 0.001 to 1M.

  The organic onium salt used in the raw material solution is for accelerating metal chalcogenization, and examples thereof include onium salts of organic acids. Examples of the organic acid include acetic acid and propionic acid. An onium salt is a compound formed by a compound having an electron pair not involved in a chemical bond and coordinated with another cationic compound by the electron pair. For example, an ammonium salt, a phosphonium salt, and Examples include sulfonium salts. From the viewpoint of ease of formation of the first semiconductor layer 4 and removal of unreacted components after the formation of the first semiconductor layer 4, the organic onium salt is, for example, acetic acid or propionic acid. An ammonium salt of a lower organic carboxylic acid is preferred. The concentration of the organic onium salt in the raw material solution is preferably 0.1 to 5M.

  As the organic solvent used for the raw material solution, an organic solvent capable of dissolving the above metal salt, chalcogen element-containing compound and organic onium salt is used. Examples of the organic solvent include pyridine, aniline, dimethyl sulfoxide, and isopropanol. These organic solvents may be mixed solvents.

  The raw material solution preferably has a low water content of 0.1 M or less. Thereby, when depositing the 1st semiconductor layer 4, it can suppress that a metal oxide and a metal hydroxide arise. From the viewpoint of reducing the content of water in the raw material solution, the organic solvent used in the raw material solution is preferably free of hydroxyl groups such as alcohol. As a result, it is effective that an organic solvent containing a hydroxyl group reacts with an organic acid (for example, an organic acid having a carboxyl group or a sulfo group) constituting a metal salt or an organic onium salt used in the raw material solution to desorb water. Can be suppressed.

  More preferably, the organic solvent used for the raw material solution is a nitrogen-containing aromatic compound. The nitrogen-containing aromatic compound is an organic compound in which at least one of the constituent elements of the aromatic ring is nitrogen, and examples thereof include pyridine. Such a nitrogen-containing organic solvent does not contain a hydroxyl group, can reduce the content of water in the raw material solution, stabilizes the metal from which the nitrogen unshared electron pair is a raw material, and has a good chalcogenation reaction Can be promoted.

  Moreover, it is preferable that the desiccant is added to the raw material solution. Thereby, the content rate of water can be reduced more. As the desiccant, those used for desiccants of organic solvents can be used. For example, molecular sieves and zeolites are suitable.

  The first electrode layer 5 is a 0.05 to 3.0 μm transparent conductive film such as ITO or ZnO. The first electrode layer 5 is formed by sputtering, vapor deposition, chemical vapor deposition (CVD), or the like. The first electrode layer 5 is a layer having a resistivity lower than that of the first semiconductor layer 4, and is for taking out charges generated in the second semiconductor layer 3. From the viewpoint of taking out charges well, it is preferable that the resistivity of the first electrode layer 5 is less than 1 Ω · cm and the sheet resistance is 50 Ω / □ or less.

  In order to increase the absorption efficiency of the second semiconductor layer 3, the first electrode layer 5 is preferably light-transmissive to the absorbed light of the second semiconductor layer 3. The first electrode layer 5 has a thickness of 0.05 to 0.5 μm from the viewpoint of enhancing the light transmittance and at the same time enhancing the light reflection loss prevention effect and the light scattering effect, and further favorably transmitting the current generated by the photoelectric conversion. Thickness is preferred. From the viewpoint of preventing light reflection loss at the interface between the first electrode layer 5 and the first semiconductor layer 4, the refractive indexes of the first electrode layer 5 and the first semiconductor layer 4 are equal. preferable.

  A plurality of photoelectric conversion devices 10 can be arranged and electrically connected to form a photoelectric conversion module 11. In order to easily connect adjacent photoelectric conversion devices 10 in series, as shown in FIG. 1, the photoelectric conversion device 10 is separated from the second electrode layer 2 on the substrate 1 side of the second semiconductor layer 3. A third electrode layer 6 is provided. The first electrode layer 5 and the third electrode layer 6 are electrically connected by the connection conductor 7 provided in the second semiconductor layer 3.

  The connection conductor 7 is preferably formed and integrated simultaneously when forming the first electrode layer 5. Thereby, the process can be simplified and the reliability of electrical connection with the first electrode layer 5 can be improved.

  The connection conductor 7 is formed so as to connect the first electrode layer 5 and the third electrode layer 6 and to divide each second semiconductor layer 3 of the adjacent photoelectric conversion device 10. With such a configuration, photoelectric conversion can be satisfactorily performed in the adjacent second semiconductor layers 3 and current can be extracted in series connection.

  Next, another example of the embodiment of the photoelectric conversion device of the present invention will be described with reference to FIGS. FIG. 2 is a cross-sectional view of a photoelectric conversion device 20 according to another embodiment, and FIG. 3 is a perspective view of the photoelectric conversion device 20. 2 and 3 are different from the photoelectric conversion device 10 of FIG. 1 in that a collecting electrode 8 is formed on the first electrode layer 5. 2 and 3, the same components as those in FIG. 1 are denoted by the same reference numerals, and similarly to FIG. 1, a plurality of photoelectric conversion devices 20 are connected to constitute a photoelectric conversion module 21. The collecting electrode 8 is for reducing the electric resistance of the first electrode layer 5. From the viewpoint of enhancing light transmittance, it is preferable that the thickness of the first electrode layer 5 is as thin as possible. However, since the current collecting electrode 8 is provided on the first electrode layer 5, the current generated in the second semiconductor layer 3 can be efficiently taken out. As a result, the power generation efficiency of the photoelectric conversion device 20 can be increased.

For example, as shown in FIG. 3, the collector electrode 8 is formed in a linear shape from one end of the photoelectric conversion device 20 to the connection conductor 7. Thereby, the electric charge generated by the photoelectric conversion of the second semiconductor layer 3 is collected to the current collecting electrode 8 via the first electrode layer 5, and this is collected to the adjacent photoelectric conversion device 20 via the connection conductor 7. It can conduct well. Therefore, by providing the current collecting electrode 8, the current generated in the second semiconductor layer 3 can be efficiently extracted even if the first electrode layer 5 is thinned. As a result, power generation efficiency can be increased.

  The collector electrode 8 preferably has a width of 50 to 400 μm from the viewpoint of suppressing light from being blocked to the second semiconductor layer 3 and having good conductivity. The current collecting electrode 8 may have a plurality of branched portions.

  The collector electrode 8 can be 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.

  The photoelectric conversion device of the present invention was evaluated as follows.

  A plurality of sample substrates on which a Mo electrode as a second electrode layer and a CIGS layer as a second semiconductor layer were formed on a glass substrate were prepared.

  Next, three types of raw material solutions for forming the first semiconductor layer were prepared (first to third raw material solutions). The first raw material solution was prepared by dissolving zinc acetate in 0.025M, thioacetamide in 0.375M, and ammonium acetate in 2.5M in pyridine.

  The second raw material solution was prepared by dissolving pyridine in 0.025M indium acetate, 0.375M thioacetamide, and 2.5M ammonium acetate.

  The third raw material solution was prepared by dissolving zinc acetate in water to 0.025M, thiourea 0.375M, and aqueous ammonia 2.5M (ammonia concentration).

  Then, two of the sample substrates were immersed in the first raw material solution at 80 ° C. for 45 minutes to deposit a first semiconductor layer containing ZnS on the second semiconductor layer. One of the two sample substrates was designated as sample 1. The remaining one sheet was further annealed at 200 ° C. for 15 minutes. Sample 2 was annealed.

Similarly, the other two sample substrates were immersed in the above-mentioned second raw material solution at 80 ° C. for 45 minutes to deposit a first semiconductor layer containing In ₂ S ₃ on the second semiconductor layer. . One of the two sample substrates was designated as Sample 3. The remaining one sheet was further annealed at 200 ° C. for 15 minutes. Sample 4 was subjected to the annealing treatment.

  Similarly, the other two sample substrates were immersed in the third raw material solution at 80 ° C. for 45 minutes to deposit a first semiconductor layer containing ZnS on the second semiconductor layer. One of the two sample substrates was designated as sample 5. The remaining one sheet was further annealed at 200 ° C. for 15 minutes. Sample 6 was subjected to the annealing treatment.

Composition analysis of the first semiconductor layers of Samples 1 to 6 manufactured as described above was performed by X-ray photoelectron spectroscopy (XPS). The results are shown in Table 1. It was confirmed that Samples 1-6 all produced mixed crystal compounds containing metal chalcogenides, metal oxides and metal hydroxides. In Table 1, P _K indicates the atomic ratio of Zn in Samples 1, 3, and 4, and indicates the atomic ratio of In in Sample 2. _PO represents the atomic ratio of oxygen caused by oxides and hydroxides.

  From Table 1, it was confirmed that Samples 1 to 4 had an oxygen atom number ratio as low as 10 atom% or less. On the other hand, it was confirmed that Samples 5 and 6 as comparative examples prepared by a solution precipitation method using a conventional aqueous solution had an oxygen atom number ratio exceeding 68 atom%.

  Next, for samples 1 to 6, a transparent first electrode layer made of an Al-doped zinc oxide film was formed on the first semiconductor layer by a sputtering method. Finally, an aluminum electrode (extraction electrode) was formed by vapor deposition to produce a photoelectric conversion device.

About these photoelectric conversion apparatuses, the time-dependent change of the photoelectric conversion efficiency in a high-temperature, high-humidity environment (temperature: 90 ° C., humidity: 95%) was measured. The photoelectric conversion efficiency was measured using a so-called stationary light solar simulator under the conditions where the light irradiation intensity on the light receiving surface of the photoelectric conversion device was 100 mW / cm ² and AM (air mass) was 1.5. .

  The initial photoelectric conversion efficiencies of Samples 1 to 6 all showed 10% or more. And in the samples 5 and 6 as comparative examples, the photoelectric conversion efficiency is reduced to about 20% of the initial photoelectric conversion efficiency and the performance is extremely deteriorated at an elapsed time of 0.5 hours in a high temperature and high humidity environment. I understood it. On the other hand, it was found that Samples 1 to 4 according to the present invention did not change the photoelectric conversion efficiency even at an elapsed time of 4 hours, were able to maintain the performance, and the humidity resistance was greatly improved.

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

1: Substrate 2: Second electrode layer 3: Second semiconductor layer 4: First semiconductor layer 5: First electrode layer 7: Connection conductor 8: Current collecting electrode 10, 20: Photoelectric conversion device 11, 21 : Photoelectric conversion module B: Support

Claims (10)

A mixed crystal compound of a metal chalcogenide, a metal oxide, and a metal hydroxide, wherein the atomic ratio of the chalcogen element to the total number of atoms of the chalcogen element and the oxygen element constituting the metal chalcogenide is the oxygen element. much larger than the atomic ratio of the number, the ratio of the number of atoms of oxygen element is provided with a first semiconductor layer is not more than 10 atom%, the first semiconductor layer and the second semiconductor layer in which the conductive type is different from the bonding A photoelectric conversion device characterized by being made . 2. The photoelectric conversion device according to claim 1 , wherein the metal chalcogenide includes at least one of a II-VI group compound semiconductor and a III-VI group compound semiconductor. The photoelectric conversion device according to claim 2 , wherein the metal chalcogenide includes ZnS or In ₂ S ₃ . It said second semiconductor comprises a group I-III-VI compound semiconductor, the photoelectric conversion device according to any one of claims 1 to 3. Producing a raw material solution containing an organic solvent, a metal salt, a chalcogen element-containing compound, and an organic onium salt;
Contacting a support with the raw material solution, and depositing a first semiconductor layer containing a metal chalcogenide on the support;
A process for producing a photoelectric conversion device, comprising: The method for producing a photoelectric conversion device according to claim 5 , wherein the organic solvent does not contain a hydroxyl group. The method for producing a photoelectric conversion device according to claim 6 , wherein the organic onium salt is an onium salt of an organic acid having a carboxyl group or a sulfo group. The method for producing a photoelectric conversion device according to claim 6 or 7 , wherein the metal salt is a salt of an organic acid having a carboxyl group or a sulfo group and a metal. The organic solvent is a nitrogen-containing aromatic compounds, process for producing a photovoltaic device according to any one of claims 6 to 8. The support has a second semiconductor layer having a conductivity type different from that of the first semiconductor layer;
The method for manufacturing a photoelectric conversion device according to claim 5, wherein the first semiconductor layer is deposited on the second semiconductor layer.

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