JP2012015234A - Method of manufacturing photoelectric conversion device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photoelectric conversion device having a high photoelectric conversion efficiency.SOLUTION: A method of manufacturing a photoelectric conversion device 10 includes a method of manufacturing a chalcogen compound semiconductor layer. The method of manufacturing a chalcogen compound semiconductor layer includes a heating step for heating a precursor layer provided on a substrate A and including a metal element under a chalcogen element-containing atmosphere to make a chalcogen compound semiconductor layer including the metal and chalcogen elements. The heating step includes a first step for heating under an atmosphere including the chalcogen elements of a first concentration, and a second step for heating under an atmosphere including the chalcogen elements of a second concentration lower than the first concentration after the first step.

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, a back electrode is formed on a substrate made of soda lime glass, for example, an electrode layer made of Mo is formed, and a light absorption layer made of an I-III-VI group compound semiconductor is formed on this electrode layer. 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.

As a method for manufacturing such a light absorption layer, a IB group element and a III-B group element are deposited individually or simultaneously to form a precursor layer, and this precursor layer is formed into a gaseous chalcogen element (VI A method of crystallizing a precursor layer by heating while supplying a -B group element) or a chalcogen compound to form an I-III-VI group compound semiconductor is disclosed.

JP-A-5-267704

A photoelectric conversion device having higher photoelectric conversion efficiency is desired. However, in the method described in Patent Document 1, chalcogenization of the precursor layer containing the IB group element and the III-B group element is difficult to proceed, and it is difficult to obtain a high photoelectric conversion efficiency. When heat treatment is performed at a relatively high temperature in order to promote chalcogenization, although the chalcogenization is promoted, the adhesion between the I-III-VI group compound semiconductor and the electrode layer is deteriorated, and the photoelectric conversion efficiency is increased. Have difficulty.

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

  In the method of manufacturing a photoelectric conversion device according to an embodiment of the present invention, a precursor layer containing a metal element provided on a substrate is heated in an atmosphere containing a chalcogen element, and the metal element and the chalcogen element are heated. A manufacturing method of a photoelectric conversion device including a heating step for forming a chalcogen compound semiconductor layer, wherein the heating step includes a first step of heating in an atmosphere containing the chalcogen element at a first concentration, and the first step. And a second step of heating in an atmosphere containing the chalcogen element at a second concentration lower than the first concentration.

  ADVANTAGE OF THE INVENTION According to this invention, a photoelectric conversion apparatus with high photoelectric conversion efficiency can be provided.

It is sectional drawing which shows an example of embodiment of the photoelectric conversion apparatus produced by this invention. It is a perspective view of the photoelectric conversion apparatus of FIG. It is sectional drawing which shows the other example of embodiment of the photoelectric conversion apparatus produced by this invention. It is a graph which shows an example of the manufacturing conditions in the manufacturing method of the photoelectric conversion apparatus of this invention.

  FIG. 1 is a perspective view showing an example of an embodiment of a photoelectric conversion device manufactured by the method for manufacturing a photoelectric conversion device of the present invention, and FIG. 2 is a sectional view thereof. 3 is a cross-sectional view showing another example of the embodiment of the photoelectric conversion device manufactured by the method for manufacturing the photoelectric conversion device of the present invention (in FIG. 3, the same parts as those in FIGS. Sign). The photoelectric conversion device 10 includes a base A, a first electrode layer 2, a first semiconductor layer 3, a second semiconductor layer 4, and a second electrode layer 5. In this embodiment, the substrate A is shown to include the substrate 1 and the first electrode layer 2 formed on the surface thereof, but is not limited thereto. In this embodiment, an example is shown 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, but the present invention is not limited thereto. Alternatively, the second semiconductor layer 4 may be a light absorption layer. 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. 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. Examples of the chalcogen compound semiconductor include an I-III-VI compound semiconductor, a II-VI group compound semiconductor, and a III-VI group compound semiconductor.

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.

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

The III-VI compound semiconductor is a compound semiconductor of a III-B group element and a VI-B group element. Examples of III-VI group compound semiconductors include In ₂ S ₃ , In ₂ Se ₃ , and In ₂ T.
e ₃ , Ga ₂ S ₃ , Ga ₂ Se ₃ , Ga ₂ Te _{3 and the} like.

Such a first semiconductor layer 3 is produced, for example, as follows. First, a metal element (for example, an IB group element and an III-B group element, or an II-B group element constituting the chalcogen compound semiconductor layer is formed on the substrate 1 having the first electrode layer 2 by vapor deposition, sputtering, or the like. ) To form a precursor. Alternatively, a precursor is formed by applying a raw material solution containing a metal element (for example, an IB group element and an III-B group element or an II-B group element) on the substrate 1 having the first electrode layer 2. To do. These precursors may contain a VI-B group element. These precursors may be a plurality of laminated bodies having different composition ratios.

Next, this precursor layer is heated in an atmosphere containing a chalcogen element. The atmosphere containing a chalcogen element may be a gas atmosphere of a chalcogen element such as Se or a gas atmosphere of a chalcogen compound such as H ₂ Se, or a mixed gas atmosphere of these gases and a reducing gas such as hydrogen. Or a mixed gas atmosphere of these gases and an inert gas such as nitrogen or argon.

  In the heating of the precursor layer, as shown in FIG. 4, a first step of heating in an atmosphere containing a chalcogen element at a first concentration, and after the first step, the chalcogen element is added to the first step. A second step of heating in an atmosphere containing a second concentration lower than the concentration (in the graph of FIG. 4, the solid line indicates the temperature change of the precursor layer, and the dotted line indicates the chalcogen element in the atmosphere) Change in the concentration of Thereby, in the state which maintained the adhesiveness of the 1st semiconductor layer 3 and the 1st electrode layer 2 favorable, crystallization of the 1st semiconductor layer 3 can be accelerated | stimulated, and photoelectric conversion efficiency is improved. Can do. That is, crystallization is accelerated by increasing the temperature in an atmosphere containing a constant concentration of the chalcogen element, and the concentration of the chalcogen element is decreased when the crystallization progresses to some extent, thereby reducing the first semiconductor layer 3 and the first semiconductor layer 3. In the vicinity of the interface with the electrode layer 2, the supply of the chalcogen element is suppressed, so that high adhesion can be maintained, and crystallization is continuously performed on the upper surface side of the first semiconductor layer, so It can be increased.

  The second concentration in the atmosphere containing the chalcogen element is preferably 0.5 to 0.9 times the first concentration. Thereby, crystallization of the first semiconductor layer 3 can be favorably promoted while maintaining high adhesion.

When the first semiconductor layer 3 is made of CIGS, for example, in the first step, up to a maximum temperature (t ₃ = 500 to 600 ° C.) at a temperature rising rate of 5 to 30 ° C./min in an atmosphere containing Se vapor. Then, in the second step, the Se concentration is lowered to 0.5 to 0.9 times that in the first step, and heating is performed for 30 to 120 minutes.

Further, from the viewpoint of further improving the adhesion between the first semiconductor layer 3 and the first electrode layer 2, as shown in FIG. 4, the precursor is formed at the start of the second step or during the second step. The layer temperature (t ₂ ) should be lower than the maximum temperature (t ₃ ) of the first step. Preferably, in the second step, the temperature t ₂ is maintained at a constant temperature t ₂ for 10 to 90 minutes, and the temperature t ₂ to be maintained is lower by 25 to 150 ° C. than the maximum temperature t ₃ .

Further, as shown in FIG. 4, the first step includes a third step of maintaining the temperature of the precursor layer at a constant temperature t ₁ before the temperature of the precursor layer reaches the maximum temperature t _3. It is preferable. Thereby, chalcogenization can be favorably performed over the entire first semiconductor layer 3, and the photoelectric conversion efficiency can be further increased. From the viewpoint of favorably alloying the precursor layer and promoting chalcogenization, the temperature t ₁ is preferably lower by 100 to 250 ° C. than the maximum temperature t ₃ . The temperature maintained at this temperature _{t 1} good 10 to 60 minutes.

Further, after maintaining at this temperature t ₁ , when the maximum temperature t ₃ is reached, it is preferable to gradually or stepwise increase the concentration of the chalcogen element in the atmosphere. Thereby, the crystallization of the first semiconductor layer 3 is promoted, and the first semiconductor layer 3 has a smooth surface. Therefore, the second semiconductor layer 4 having a different composition can be favorably heterojunction with such a smooth surface, and a photoelectric conversion device with extremely high photoelectric conversion efficiency can be obtained.

  In FIG. 4, the heating of the precursor layer is started from the state where the gas containing the chalcogen element is supplied to the precursor layer, but the heating may be started simultaneously with the supply of the gas containing the chalcogen element. When the heating of the precursor layer is started from the state where the gas containing the chalcogen element is supplied to the precursor layer as shown in FIG. 4, the detailed reason is not known, but the grain growth of the chalcogen compound semiconductor is promoted. Probably, the chalcogenization proceeds well by heating with the chalcogen element spreading over the entire precursor layer.

In the production of the first semiconductor layer 3 using the heating step having the first step and the second step, the first semiconductor layer 3 is used as a precursor layer to be the first semiconductor layer 3. It is preferable to form a film by coating or the like with a raw material solution containing a metal element (for example, an IB group element, an III-B group element, or an II-B group element) as a raw material and a chalcogen element-containing organic compound. . In such a raw material solution, the chalcogen element-containing organic compound forms a precursor layer in a state of being well bonded to the metal element by a coordinate bond or the like, so that the chalcogenization of each metal element is good in the first step. Thus, the first semiconductor layer 3 having a desired composition can be easily manufactured.

  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 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 (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 photoelectric conversion device 10 uses the first semiconductor layer 3 as a light absorption layer, and a second semiconductor layer 4 is formed on the first semiconductor layer 3 with a thickness of 10 to 200 nm. A second electrode layer 5 is formed on the 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. Examples of the second semiconductor layer 4 include CdS, ZnS, ZnO, In ₂ Se ₃ , In (OH, S), (Zn, In) (Se, OH), and (Zn, Mg) O. For example, it is formed by a chemical bath deposition (CBD) method or the like. 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 second
The electrode layers 5 and the second semiconductor layer 4 preferably have the same refractive index.

  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. 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 (4)

Manufacture of a photoelectric conversion device comprising a heating step of heating a precursor layer containing a metal element provided on a substrate in an atmosphere containing a chalcogen element to form a chalcogen compound semiconductor layer containing the metal element and the chalcogen element A method,
The heating step includes a first step of heating in an atmosphere containing the chalcogen element at a first concentration, and a second concentration lower than the first concentration after the first step. And a second step of heating in an atmosphere containing the method of manufacturing a photoelectric conversion device.   2. The method for manufacturing a photoelectric conversion device according to claim 1, wherein the temperature of the precursor layer is set lower than the maximum temperature in the first step at the start of the second step or during the step.   3. The method of manufacturing a photoelectric conversion device according to claim 1, wherein the first step includes a third step of maintaining the temperature of the precursor layer at a constant temperature before reaching the maximum temperature. The photoelectric conversion device according to any one of claims 1 to 3, wherein the metal element includes an IB group element and an III-B group element, and the chalcogen compound semiconductor layer includes an I-III-VI group compound semiconductor. Manufacturing method.

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