JP2012064734A - Manufacturing method of photoelectric conversion device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress a light absorption layer from peeling and to provide a photoelectric conversion device with excellent reliability.SOLUTION: A manufacturing method of a photoelectric conversion device having a light absorption layer comprises: a first step of preparing a first material having a metallic oxide including a group I-B element and a group III-B element; a second step of forming a precursor layer of the light absorption layer by applying a solution prepared by dissolving a second material having a metallic salt including the same element as the group I-B element or the group III-B element and the first material in the solvent in which the metallic salt dissolves to a substrate 1; and a third step of reducing the metallic oxide by heat-treating the precursor layer.

Description

  The present invention relates to a method for manufacturing a photoelectric conversion device having a chalcogen compound semiconductor layer.

  As a solar cell, there is one using a photoelectric conversion device including a light absorption layer composed of a chalcogen compound semiconductor layer such as an I-III-VI group compound semiconductor such as CIS or CIGS. In this photoelectric conversion device, for example, an electrode layer made of, for example, Mo is formed on a substrate made of soda-lime glass, and a light absorption layer made of an I-III-VI group compound semiconductor is formed on this electrode layer. Is formed.

  Examples of a method for manufacturing such a light absorption layer include the following. First, Mo is formed from an aqueous ink obtained by mixing a powder composed of an oxide of a group I-B element and an oxide of a group III-B element and a liquid containing a dispersant composed of water and an organic material. After coating on the substrate, the oxide is reduced to form a precursor layer. Thereafter, this precursor layer is heated in a selenium atmosphere, which is a gaseous chalcogen element, to selenide the precursor layer to form a I-III-VI group compound semiconductor (for example, a patent is disclosed). Reference 1).

JP-A-11-171880

  However, in the method described in Patent Document 1, since the dispersant is composed of an organic material, when selenization is performed at a relatively high temperature, the organic material located between adjacent powders volatilizes, and the powder It was easy for gaps to occur. Therefore, in the light absorption layer produced by the above method, many voids are formed in the light absorption layer, and the light absorption layer is easily peeled off from the substrate.

  The present invention has been completed in view of the above-described conventional problems, and an object of the present invention is to provide a photoelectric conversion device that suppresses peeling of the light absorption layer and has excellent reliability.

  The manufacturing method of the photoelectric conversion device according to the first embodiment of the present invention includes a first step of preparing a first raw material having a metal oxide containing a group I-B element and a group III-B element, and the I- A second raw material having a metal salt containing the same element as the group B element or the III-B group element and a solution obtained by dissolving the first raw material in a solvent in which the metal salt is dissolved, applied onto a substrate, A second step of forming a precursor layer of the light absorption layer; and a third step of heat-treating the precursor layer to reduce the metal oxide.

  Moreover, the manufacturing method of the photoelectric conversion device according to the second embodiment of the present invention includes a first raw material having a metal oxide containing a group IB element and a metal oxide containing a group III-B element. 1 step, a second raw material having a metal salt containing the same element as the group IB element or the group III-B element, and a solution obtained by dissolving the first raw material in a solvent in which the metal salt dissolves, A second step of coating the substrate and forming a precursor layer of the light absorption layer; and a third step of heat-treating the precursor layer to reduce the metal oxide.

  According to the method for manufacturing a photoelectric conversion device according to the first and second embodiments of the present invention, since the light absorption layer can be made relatively dense, the occurrence of peeling of the light absorption layer from the substrate or the like is suppressed. In addition, reliability can be improved.

It is a perspective view which shows an example of the photoelectric conversion apparatus produced with the manufacturing method of the photoelectric conversion apparatus which concerns on embodiment of this invention. It is sectional drawing of the photoelectric conversion apparatus of FIG. It is sectional drawing which shows the other example of the photoelectric conversion apparatus produced with the manufacturing method of the photoelectric conversion apparatus which concerns on embodiment of this invention.

  Below, the manufacturing method of the photoelectric conversion apparatus which concerns on embodiment of this invention is demonstrated. First, an embodiment of a photoelectric conversion device manufactured by a manufacturing method according to an embodiment of the present invention will be described.

  The photoelectric conversion device 10 includes a substrate 1, a first electrode layer 2, a first semiconductor layer 3, a second semiconductor layer 4, and a second electrode layer 5. In the present embodiment, an example in which the first semiconductor layer 3 is a light absorption layer and the second semiconductor layer 4 is a buffer layer bonded to the first semiconductor layer 3 is shown, but the present invention is not limited thereto. Alternatively, the light absorption layer including the second semiconductor layer 4 may be used. In addition, the photoelectric conversion device 10 may receive light from the second electrode layer 5 side, but is not limited thereto, and if the substrate 1 and the first electrode layer 2 are translucent, The light may be incident from the substrate 1 side. Alternatively, light may be incident from both the substrate 1 side and the second electrode layer 5 side.

  1 and 2, a photoelectric conversion device 10 is formed by arranging a plurality of photoelectric conversion cells 11. The photoelectric conversion cell 11 includes a third electrode layer 6 provided on the substrate 1 side of the first semiconductor layer 3 so as to be separated from the first electrode layer 2. The second electrode layer 5 and the third electrode layer 6 are electrically connected by the connection conductor 7 provided in the first semiconductor layer 3. In the form shown in FIGS. 1 and 2, the connection conductor 7 is mainly composed of a part of the second electrode layer 5. The third electrode layer 6 is integrated with the first electrode layer 2 of the adjacent photoelectric conversion cell 11. With this configuration, adjacent photoelectric conversion cells 11 are connected in series. In one photoelectric conversion cell 11, the connection conductor 7 is provided so as to penetrate the first semiconductor layer 3 and the second semiconductor layer 4, and the first electrode layer 2 and the second electrode layer are provided. The first semiconductor layer 3 and the second semiconductor layer 4 sandwiched between 5 and 5 perform photoelectric conversion.

  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 first 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 first semiconductor layer 3 includes a chalcogen compound semiconductor and is formed in a layer shape having a thickness of 1.0 to 2.5 μm, for example. A chalcogen compound semiconductor is a semiconductor containing a chalcogen element. A chalcogen element means S, Se, and Te among VI-B group elements. As a chalcogen compound semiconductor, an I-III-VI compound semiconductor etc. are mentioned, for example.

An I-III-VI compound semiconductor is a group of IB group elements (also referred to as group 11 elements), III-B group elements (also referred to as group 13 elements), and VI-B group elements (also referred to as group 16 elements). It is a compound semiconductor, has a chalcopyrite structure, and is called a chalcopyrite compound semiconductor (also called a CIS compound semiconductor). Examples of the I-III-VI 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 (also referred to as CIS). Say). 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. From the viewpoint that the photoelectric conversion efficiency can be increased even with a thin layer of 10 μm or less, the first semiconductor layer 3 is preferably such an I-III-VI compound semiconductor.

  Next, an embodiment of a method for manufacturing a photoelectric conversion device will be described.

First, a first raw material having a metal oxide containing a group I-B element and a group III-B element is prepared (first step). Metal oxides containing I-B group element and III-B group elements as the (material A), for _{example, CuIn X Ga 1-X O} 2-Y ( where, 0 <X ≦ 1,0 <Y <2) Examples of the composite oxide are as follows.

On the other hand, the first raw material may be a mixture (raw material B) of a metal oxide containing a group IB element and a metal oxide containing a group III-B element. The metal oxide containing I-B group element, for example, CuO, include copper oxide Cu ₂ O and the like. Examples of the metal oxide containing a III-B group element include indium oxide such as In ₂ O ₃ and InO, and gallium oxide such as Ga ₂ O ₃ and GaO.

  Such a 1st raw material has comprised the granular form with an average particle diameter of 0.03-3 micrometers. The first raw material may be a mixture of the raw material A and the raw material B.

  Next, a second raw material having a metal salt containing the same element (metal element) as the IB group element and the III-B group element of the first raw material is prepared. Examples of such metal salts include sulfates, nitrates, carbonates, and the like. Specifically, examples of the sulfate include copper sulfate, indium sulfate, and gallium nitrate. Examples of nitrates include copper nitrate, indium nitrate, and gallium nitrate. Examples of the carbonate include copper carbonate, indium carbonate, and gallium carbonate. Among the metal salts described above, nitrates are preferred from the viewpoint of being easily dissolved in various solvents and having a low single thermal decomposition temperature. Moreover, the average particle diameter of the metal salt is, for example, 0.03 to 3 μm. The metal salt may be a hydrate.

  Next, a solvent to be mixed with the first raw material and the second raw material is prepared. The solvent may be any solvent that volatilizes in the heat treatment step when reducing the first raw material and can dissolve the metal salt described above. The dissolution of a metal salt mainly means that the metal salt is divided into a cation and an anion in a solvent. Specifically, in the case of copper nitrate, it is divided into copper ions (cations) and nitrate ions (anions). Examples of such a solvent include water, methanol, ethanol, ethylene glycol, and the like.

  Next, a solution obtained by mixing the first raw material, the second raw material, and the solvent is applied onto the substrate 1 and the second electrode layer 2 to produce a precursor layer of the light absorption layer (second step). Such application may be performed using, for example, a slit coater. The concentration of this solution is adjusted so that the first raw material is 1 to 30% by mass and the second raw material is 1 to 80 mol / L.

At this time, if the first raw material is mixed and adjusted more than the second raw material, irregularities mainly composed of the first raw material can be formed on the light receiving surface on which light is incident. Thereby, in such a form, since incident light is scattered and an optical path length becomes long, an electric current can increase and conversion efficiency can be improved. On the other hand, if the second raw material is blended and adjusted more than the first raw material, it is possible to reduce the occurrence of the above-described unevenness derived from the first raw material and form a smoother precursor layer.
Thereby, in such a form, since a denser precursor layer can be formed, for example, when a light absorption layer is formed by stacking a plurality of such precursor layers, the precursor located closest to the substrate 1 side. It is preferable from the viewpoint that the generation of leakage can be reduced by making the layer dense. Further, as described above, this coating may be performed a plurality of times depending on the thickness of the precursor layer. At this time, after coating once, a drying step may be added.

  Next, the metal oxide constituting the first raw material is reduced by heat-treating the precursor layer produced in the second step (third step). In such a reduction step (third step), the metal oxide is reduced to reduce oxygen, and the metal element of the group I-B element or group III-B element is taken out, whereby the next chalcogen element is obtained. This is performed to facilitate introduction into the precursor layer. Moreover, what is necessary is just to perform a 3rd process in the atmosphere of reducing gas like hydrogen, for example. At this time, in order to suppress the occurrence of a chemical reaction other than the reduction, a mixed gas obtained by mixing nitrogen, argon, or the like in addition to the reducing gas may be used. Moreover, what is necessary is just to set the heat processing in a 3rd process according to the magnitude | size of a precursor layer, For example, if it is a precursor layer whose thickness is 1-2 micrometers and an area is 1 square centimeter, it is 300 to 520 degreeC. What is necessary is just to carry out for 1 hour or more in the range.

  As described above, in the present embodiment, when the metal salt is dissolved in the solvent, the metal particles derived from the metal salt, which becomes a part of the light absorption layer, easily enter between the first raw materials. And when it heat-processes by a 3rd process, adjacent 1st raw materials can be combined through the said metal particle comprised with the same metal as this 1st raw material. Therefore, the precursor layer after the heat treatment can fill the gap between the first raw materials with the metal particles. As a result, the light absorption layer becomes relatively dense, and peeling from the substrate 1 and the first electrode layer 2 can be suppressed. In addition, in the present embodiment, the metal particles are likely to be deposited on the substrate 1 and the first electrode layer 2 due to the influence of gravity, and therefore, between the substrate 1 and the first electrode layer 2 and the light absorption layer. It is possible to reduce the generation of voids and improve the adhesion. That is, in this embodiment, the metal that is maintained in a metal salt state that is relatively easy to handle is mixed with a solvent to form a solution, whereby the metal that becomes a part of the light absorption layer is formed in the gap between the first raw materials. By positioning, voids in the light absorption layer are suppressed by filling the gap.

Next, this precursor layer is heated in an atmosphere containing a chalcogen element, and the chalcogen element is introduced into the precursor layer (fourth step). In addition, the atmosphere containing a chalcogen element may be a gas atmosphere of a chalcogen element alone such as Se (selenium) or a gas atmosphere of a chalcogen compound such as H ₂ Se, and a combination of these gases with a reducing gas such as hydrogen. It may be in a mixed gas atmosphere or a mixed gas atmosphere of these gases and an inert gas such as nitrogen or argon. And when this 4th process is a precursor layer containing copper, indium, and gallium, it should just heat up to the maximum temperature of 500 degreeC with the temperature increase rate of 5-30 degree-C / min in the atmosphere containing Se vapor | steam. . Through such steps, the first semiconductor layer 3 is manufactured.

  The fourth step is a precursor formed by applying a raw material solution obtained by mixing a chalcogen element-containing organic compound to a solution containing the first raw material and the second raw material on the substrate 1 and the first electrode layer 2. The layer may be heat treated. In such a raw material solution, the chalcogen element-containing organic compound forms a precursor layer in a state in which the chalcogen element-containing organic compound is well bonded to the metal element by a coordination bond or the like, which is preferable in that chalcogenization proceeds well. .

Here, the chalcogen element-containing organic compound is an organic compound containing a chalcogen element. When the chalcogen element is S, examples of the chalcogen element-containing organic compound include thiol, sulfide, disulfide, thiophene, sulfoxide, sulfone, thioketone, sulfonic acid, sulfonic acid ester, sulfonic acid amide, and the like and derivatives thereof. . Preferably, thiol, sulfide, disulfide and derivatives thereof are preferable from the viewpoint of satisfactory complex formation with an alkali metal. In particular, those having a phenyl group are preferred from the viewpoint of enhancing the coating property. As what has such a phenyl group, thiophenol, diphenyl sulfide, etc. and derivatives thereof are mentioned, for example.

  When the chalcogen element is Se, examples of the chalcogen element-containing organic compound include selenol, selenide, diselenide, selenoxide, selenone, and derivatives thereof. Preferably, from the viewpoint of forming a good complex with an alkali metal, serer, selenide, diselenide, and derivatives thereof are preferable. In particular, those having a phenyl group are preferred from the viewpoint of enhancing the coating property. Examples of those having such a phenyl group include phenyl selenol, phenyl selenide, diphenyl diselenide and the like and derivatives thereof.

  When the chalcogen element is Te, examples of the chalcogen element-containing organic compound include tellurol, telluride, ditelluride, and derivatives thereof.

  The raw material solution preferably further contains a Lewis basic organic compound. Thereby, the bond strength between the chalcogen element-containing organic compound and the metal element can be further increased, and a higher concentration raw material solution can be obtained. Thereby, a precursor layer having a desired thickness can be formed with a small number of coatings, and the process can be simplified.

  The Lewis basic organic compound is an organic compound having a functional group having an unshared electron pair. As such a functional group, a functional group having a VB group element having an unshared electron pair (also referred to as a Group 15 element) or a functional group having a VI-B group element having an unshared electron pair is preferable. Examples thereof include an amino group (which may be any of primary amine to tertiary amine), a carbonyl group, a cyano group, and the like. Specific examples of Lewis basic organic compounds include pyridine, aniline, triphenylphosphine, 2,4-pentanedione, 3-methyl-2,4-pentanedione, triethylamine, triethanolamine, acetonitrile, benzyl, benzoin and the like. And derivatives thereof. In particular, those having a boiling point of 100 ° C. or higher are preferable from the viewpoint of improving the coating property.

  The fourth step using such a chalcogen element-containing organic compound can be performed substantially simultaneously with the heat treatment in the third step. Further, the fourth step performed in the chalcogen element atmosphere may be performed substantially simultaneously with the heat treatment in the third step. Thus, it is preferable from the viewpoint of reducing the number of processes if the third process and the fourth process are performed simultaneously.

  The first semiconductor layer 3 manufactured through the first to fourth steps is formed with a thickness of 2 to 3 μm, for example.

  In the photoelectric conversion device 10, the second semiconductor layer 4 is formed with a thickness of 10 to 200 nm on the first semiconductor layer 3, and the second electrode layer 5 is formed on the second semiconductor layer 4. . Note that the second electrode layer 5 may be formed on the first semiconductor layer 3 without forming the second semiconductor layer 4. Alternatively, the second semiconductor layer 4 can function as an electrode without forming the second electrode layer 5.

The second semiconductor layer 4 is a semiconductor layer that forms a heterojunction with the first semiconductor layer 3. The first semiconductor layer 3 and the second semiconductor layer 4 are preferably of different conductivity types. For example, when the first semiconductor layer 3 is a p-type semiconductor, the second semiconductor layer 4 is i-type or It is an n-type semiconductor. Preferably, from the viewpoint of reducing leakage current, the second semiconductor layer is a layer having a resistivity of 1 Ω · cm or more. The second semiconductor layer 4 includes CdS, ZnS, ZnO, In ₂ Se ₃ , In (OH, S), (Zn, In) (Se, OH), and (Zn, M
g) O etc. are mentioned, for example, it forms by a chemical bath deposition (CBD) method etc. In (OH, S) refers to a compound mainly composed of In, OH, and S. (Zn, In) (Se, OH) refers to a compound mainly composed of Zn, In, Se, and OH. (Zn, Mg) O refers to a compound mainly composed of Zn, Mg and O. In order to increase the absorption efficiency of the first semiconductor layer 3, the second semiconductor layer 4 preferably has a light transmittance with respect to the wavelength region of light absorbed by the first semiconductor layer 3.

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

  In order to increase the absorption efficiency of the first semiconductor layer 3, it is preferable that the second electrode layer 5 has optical transparency with respect to the absorbed light of the first semiconductor layer 3. The second 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 transmitting the current generated by the photoelectric conversion. Thickness is preferred. From the viewpoint of preventing light reflection loss at the interface between the second electrode layer 5 and the second semiconductor layer 4, the refractive indexes of the second electrode layer 5 and the second semiconductor layer 4 are equal. preferable.

  The photoelectric conversion device 10 includes a plurality of photoelectric conversion cells 11 having a configuration in which the first and second semiconductor layers 3 and 4 are sandwiched between the first and second electrode layers 1 and 5 and are electrically connected to each other. It consists of In order to easily connect adjacent photoelectric converters 11 in series, as shown in FIG. 1 and FIG. 2, the photoelectric conversion cell 11 is connected to the first electrode layer 2 on the substrate 1 side of the first semiconductor layer 3. A third electrode layer 6 is provided so as to be spaced apart. The second electrode layer 5 and the third electrode layer 6 are electrically connected by the connection conductor 7 provided in the first semiconductor layer 3.

  The connection conductor 7 is made of a material having a lower electrical resistivity than the first and second semiconductor layers 3 and 4. Such a connection conductor 7 can be formed, for example, by forming a groove penetrating the first and second semiconductor layers 3 and 4 and forming a conductor in the groove. As such a conductor, for example, after forming a groove penetrating the first and second semiconductor layers 3, 4, the connection electrode 7 is formed by forming the upper electrode layer 5 also in this groove. Alternatively, the connection conductor 7 may be formed by filling the groove with a conductive paste (see FIG. 3). In FIG. 3, when the current collecting electrode 8 is formed with a conductive paste, the connection conductor 7 is formed by filling the conductive paste in the grooves penetrating the first and second semiconductor layers 3 and 4. That is, in the form shown in FIG. 3, a part of the collecting electrode 8 functions as the connection conductor 7. Alternatively, it is possible to form the first and second semiconductor layers 3 and 4 by modifying a part of the first and second semiconductor layers 3 and 4 to lower the electric resistivity without forming the groove as described above.

  Moreover, the photoelectric conversion apparatus 10 may have the collector electrode 8 formed on the second electrode layer 5 as shown in FIGS. The collecting electrode 8 is for reducing the electric resistance of the second electrode layer 5. 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 11 to the connection conductor 7. Thereby, the current generated by the photoelectric conversion of the first semiconductor layer 3 is collected through the second electrode layer 5 to the current collecting electrode 8, and this current is collected to the adjacent photoelectric conversion cell 11 through the connection conductor 7. It can conduct well. Therefore, by providing the current collecting electrode 8, the current generated in the first semiconductor layer 3 can be efficiently taken out even if the second 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 first 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.

  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: First electrode layer 3: First semiconductor layer 4: Second semiconductor layer 5: Second electrode layer 6: Third electrode layer 7: Connection conductor 8: Current collecting electrodes 10, 20 : Photoelectric conversion device 11, 21: Photoelectric conversion module

Claims (5)

A method of manufacturing a photoelectric conversion device having a light absorption layer,
A first step of preparing a first raw material having a metal oxide containing a group I-B element and a group III-B element;
A second raw material having a metal salt containing the same element as the group IB element or the group III-B element and a solution obtained by dissolving the first raw material in a solvent in which the metal salt is dissolved are applied onto a substrate. A second step of forming a precursor layer of the light absorption layer;
And a third step of reducing the metal oxide by heat-treating the precursor layer. A method of manufacturing a photoelectric conversion device having a light absorption layer,
A first step of preparing a first raw material having a metal oxide containing a group IB element and a metal oxide containing a group III-B element;
A second raw material having a metal salt containing the same element as the group IB element or the group III-B element and a solution obtained by dissolving the first raw material in a solvent in which the metal salt is dissolved are applied onto a substrate. A second step of forming a precursor layer of the light absorption layer;
And a third step of reducing the metal oxide by heat-treating the precursor layer.   The method for manufacturing a photoelectric conversion device according to claim 1, wherein nitrate is used as the metal salt.   4. The method according to claim 1, further comprising a fourth step of disposing the precursor layer in an atmosphere containing a chalcogen element and introducing the chalcogen element into the precursor layer. 5. A method for manufacturing a photoelectric conversion device.   The method for manufacturing a photoelectric conversion device according to claim 4, wherein the third step and the fourth step are performed simultaneously.

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