JP2014192338A - Method of manufacturing photoelectric conversion device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photoelectric conversion device having high photoelectric conversion efficiency.SOLUTION: A method of manufacturing the photoelectric conversion device sequentially performs: a preparation step of preparing a substrate 100 in which a film M containing an organic compound, a group I-B element, and a group III-B element is formed on an electrode layer 2; a thermal decomposition step of heating the substrate 100 to thermally decompose the organic compound; a first heating step of heating the substrate 100 in a heating furnace 101 filled with a first atmospheric gas containing at least one of hydrogen and an inert gas; an exhaust step of exhausting the first atmospheric gas in the heating furnace 101; and a second heating step of filling the heating furnace 101 with a second atmospheric gas containing a chalcogen element, and heating the substrate 100, thereby making the film M into a semiconductor layer containing a group I-III-VI compound.

Description

The present invention relates to a method for manufacturing a photoelectric conversion device using a semiconductor layer containing an I-III-VI group compound.

As a photoelectric conversion device used for photovoltaic power generation or the like, a semiconductor layer containing an I-III-VI group compound such as CuInSe ₂ (CIS) or Cu (In, Ga) Se ₂ (CIGS) is used as a light absorption layer. There exists what formed buffer layers, such as a II-VI group compound, on this light absorption layer (refer to patent documents 1).

As a method for manufacturing a semiconductor layer containing such an I-III-VI group compound, there is a method for manufacturing a semiconductor layer using a complex compound of an element constituting the semiconductor layer. For example, in Patent Document 2, a single source precursor (Single Source Precursor) which is a complex compound in which Cu, Se and In or Ga are present in one organic compound is used. The formation of a semiconductor layer made of a group compound is described.

Japanese Patent Laid-Open No. 08-330614 US Pat. No. 6,992,202

  In recent years, the demand for photoelectric conversion devices has been increasing, and further improvement in the photoelectric conversion efficiency of the photoelectric conversion devices is desired. The photoelectric conversion efficiency of a photoelectric conversion device is likely to depend on the manufacturing process of the semiconductor layer, and promoting crystallization of the semiconductor layer well is one of the important factors for improving the photoelectric conversion efficiency.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a photoelectric conversion device with high photoelectric conversion efficiency by performing good crystallization of a semiconductor layer.

A manufacturing method of a photoelectric conversion device according to one embodiment of the present invention includes a preparation step of preparing a substrate on which an organic compound, a group containing an IB group element, and a group III-B element are formed on an electrode layer, A pyrolysis step of thermally decomposing the organic compound by heating the substrate; a first heating step of heating the substrate in a heating furnace filled with a first atmospheric gas containing at least one of hydrogen and an inert gas; An exhausting step of exhausting the first atmosphere gas in the heating furnace, and filling the inside of the heating furnace with a second atmosphere gas containing a chalcogen element and heating the substrate, the film is made I-III
A second heating step for forming a semiconductor layer containing a -VI group compound is sequentially performed.

  According to the said aspect of this invention, it becomes possible to provide a photoelectric conversion apparatus with high photoelectric conversion efficiency.

It is a perspective view which shows an example of the photoelectric conversion apparatus produced using the manufacturing method of the photoelectric conversion apparatus which concerns on one Embodiment of this invention. It is sectional drawing of the photoelectric conversion apparatus of FIG. It is sectional drawing which shows typically the mode in the middle of manufacture of a photoelectric conversion apparatus. It is sectional drawing which shows typically the mode in the middle of manufacture of a photoelectric conversion apparatus. It is sectional drawing which shows typically the mode in the middle of manufacture of a photoelectric conversion apparatus. It is sectional drawing which shows typically the mode in the middle of manufacture of a photoelectric conversion apparatus. It is sectional drawing which shows typically the mode in the middle of manufacture of a photoelectric conversion apparatus. It is sectional drawing which shows typically the mode in the middle of manufacture of a photoelectric conversion apparatus. It is sectional drawing which shows typically the mode in the middle of manufacture of a photoelectric conversion apparatus.

  Hereinafter, a method for manufacturing a photoelectric conversion device according to an embodiment of the present invention will be described with reference to the drawings. In the drawings, parts having similar configurations and functions are denoted by the same reference numerals, and redundant description is omitted in the following description. Further, the drawings are schematically shown, and the sizes, positional relationships, and the like of various structures in the drawings are not accurately illustrated.

<(1) Configuration of photoelectric conversion device>
FIG. 1 is a perspective view showing an example of a photoelectric conversion device 11 manufactured by using a method for manufacturing a photoelectric conversion device according to an embodiment of the present invention. FIG. 2 is an XZ sectional view of the photoelectric conversion device 11 of FIG. 1 to 9 are provided with a right-handed XYZ coordinate system in which the arrangement direction of photoelectric conversion cells 10 (the horizontal direction in the drawing in FIG. 1) is the X-axis direction.

  The photoelectric conversion device 11 has a configuration in which a plurality of photoelectric conversion cells 10 are arranged in parallel on a support 1. In FIG. 1, only two photoelectric conversion cells 10 are shown for convenience of illustration, but an actual photoelectric conversion device 11 has a large number of photoelectric conversion cells in the X-axis direction of the drawing or further in the Y-axis direction of the drawing. The conversion cells 10 are arranged two-dimensionally (two-dimensionally).

Each photoelectric conversion cell 10 includes a lower electrode layer 2, an I-III-VI group compound semiconductor layer 3 (hereinafter,
I-III-VI group compound semiconductor layer is also referred to as first semiconductor layer), second semiconductor layer 4,
An upper electrode layer 5 and a collecting electrode 7 are mainly provided. In the photoelectric conversion device 11, the main surface on the side where the upper electrode layer 5 and the collecting electrode 7 are provided is a light receiving surface. In addition, the photoelectric conversion device 11 is provided with three types of groove portions such as first to third groove portions P1, P2, and P3.

  The support 1 supports a plurality of photoelectric conversion cells 10 and is made of, for example, a material such as glass, ceramics, resin, or metal. For example, as the support 1, blue plate glass (soda lime glass) having a thickness of about 1 to 3 mm may be used.

  The lower electrode layer 2 is a conductive layer provided on one main surface of the support 1. For example, molybdenum (Mo), aluminum (Al), titanium (Ti), tantalum (Ta), or gold (Au) ) Or a laminated structure of these metals. The lower electrode layer 2 has a thickness of about 0.2 to 1 μm and is formed by a known thin film forming method such as a sputtering method or a vapor deposition method.

The I-III-VI group compound semiconductor layer 3 (first semiconductor layer 3) as a light absorption layer is provided on the main surface (also referred to as one main surface) on the + Z side of the lower electrode layer 2. This is a semiconductor layer having one conductivity type (here, p-type conductivity type), and has a thickness of about 1 to 3 μm. The first semiconductor layer 3 is a semiconductor layer containing an I-III-VI group compound. The I-III-VI group compound is a group IB element (also referred to as group 11 element), a group III-B element (also referred to as group 13 element), and a group VI-B element (also referred to as group 16 element). It is a compound containing. The first semiconductor layer 3 contains a sulfur element (S) and a selenium element (Se) as VI-B group elements. I-
Examples of III-VI group compounds include Cu (In, Ga) (Se, S) ₂ (also referred to as diselene / sulfur copper indium / gallium, CIGSS), CuIn (Se, S) ₂ (diselen / sulfur). And copper indium chloride (also referred to as CISS), CuGa (Se, S) ₂ (also referred to as diselenium copper gallium sulfide and CGSS), and the like.

In addition, the 1st semiconductor layer 3 does not need to contain a sulfur element and a selenium element in the front part of the thickness direction. For example, in a portion of the first semiconductor layer 3 on the lower electrode layer 2 side, Cu (In, Ga) Se ₂ (also called copper indium selenide / gallium, CIGS), CuInSe ₂ (copper indium diselenide, CIS), CuGaSe ₂ (also referred to as copper gallium selenide, CGS), or the like.

  The second semiconductor layer 4 is a semiconductor layer provided on one main surface of the first semiconductor layer 3. The second semiconductor layer 4 has a conductivity type (here, n-type conductivity type) different from that of the first semiconductor layer 3. By joining the first semiconductor layer 3 and the second semiconductor layer 4, positive and negative carriers generated by photoelectric conversion in the first semiconductor layer 3 are favorably separated. Note that semiconductors having different conductivity types are semiconductors having different conductive carriers. Further, when the conductivity type of the first semiconductor layer 3 is p-type as described above, the conductivity type of the second semiconductor layer 4 may be i-type instead of n-type. Furthermore, there may be a mode in which the conductivity type of the first semiconductor layer 3 is n-type or i-type and the conductivity type of the second semiconductor layer 4 is p-type.

The second semiconductor layer 4 includes, for example, cadmium sulfide (CdS), indium sulfide (In ₂ S ₃ ), zinc sulfide (ZnS), zinc oxide (ZnO), indium selenide (In ₂ Se ₃ ), In (OH , S), (Zn, In) (Se, OH), and (Zn, Mg) O. From the viewpoint of reducing current loss, the second semiconductor layer 4 can have a resistivity of 1 Ω · cm or more. The second semiconductor layer 4 is formed by, for example, a chemical bath deposition (CBD) method or the like.

  The second semiconductor layer 4 has a thickness in the normal direction of one main surface of the first semiconductor layer 3. This thickness is set to, for example, 10 to 200 nm.

  The upper electrode layer 5 is a transparent conductive film provided on the second semiconductor layer 4, and is an electrode that extracts charges generated in the first semiconductor layer 3. The upper electrode layer 5 is made of a material having a lower resistivity than the second semiconductor layer 4. The upper electrode layer 5 includes what is called a window layer, and when a transparent conductive film is further provided in addition to the window layer, these may be regarded as an integrated upper electrode layer 5.

The upper electrode layer 5 mainly includes a material having a wide forbidden band, transparent, and low resistance. As such a material, for example, a metal oxide semiconductor such as ZnO, In ₂ O ₃ and SnO ₂ can be adopted. These metal oxide semiconductors may contain any element of Al, B, Ga, In, F, and the like. Specific examples of the metal oxide semiconductor containing such an element include, for example, AZO (Aluminum Zinc Oxide), GZO (Gallium Zinc Oxide),
Examples include IZO (Indium Zinc Oxide), ITO (Indium Tin Oxide), and FTO (Fluorine tin Oxide).

  The upper electrode layer 5 is formed to have a thickness of 0.05 to 3.0 μm by sputtering, vapor deposition, chemical vapor deposition (CVD), or the like. Here, from the viewpoint of good charge extraction from the first semiconductor layer 3, the upper electrode layer 5 has a resistivity of less than 1 Ω · cm and a sheet resistance of 50Ω / □ or less. Can do.

The second semiconductor layer 4 and the upper electrode layer 5 can be made of a material having a property (also referred to as light transmittance) that allows light to easily pass through the wavelength region of light absorbed by the first semiconductor layer 3. Thereby, a decrease in light absorption efficiency in the first semiconductor layer 3 caused by providing the second semiconductor layer 4 and the upper electrode layer 5 is reduced.

  In addition, from the viewpoint of improving the light transmittance, the effect of preventing loss of light reflection and the light scattering effect, and further transmitting the current generated by the photoelectric conversion, the upper electrode layer 5 can have a thickness of 0.05 to 0.5 μm. Further, from the viewpoint of reducing the light reflection loss at the interface between the upper electrode layer 5 and the second semiconductor layer 4, the absolute refractive index is substantially between the upper electrode layer 5 and the second semiconductor layer 4. It can be made the same.

  The collecting electrodes 7 are spaced apart in the Y-axis direction, and each extend in the X-axis direction. The collector electrode 7 is an electrode having conductivity, and is made of a metal such as silver (Ag), for example.

  The collecting electrode 7 plays a role of collecting charges generated in the first semiconductor layer 3 and taken out in the upper electrode layer 5. If the current collecting electrode 7 is provided, the upper electrode layer 5 can be thinned.

  The charges collected by the collector electrode 7 and the upper electrode layer 5 are transmitted to the adjacent photoelectric conversion cell 10 through the connection conductor 6 provided in the second groove portion P2. For example, the connection conductor 6 is constituted by a portion extending in the Y-axis direction of the current collecting electrode 7 as shown in FIG. Thereby, in the photoelectric conversion apparatus 11, one lower electrode layer 2 of the adjacent photoelectric conversion cell 10 and the other collector electrode 7 are electrically connected via the connection conductor 6 provided in the second groove portion P2. Connected in series. In addition, the connection conductor 6 is not limited to this, You may be comprised by the extension part of the upper electrode layer 5. FIG.

  The current collecting electrode 5 has a width of 50 to 400 μm so that good conductivity is ensured and a decrease in the light receiving area that affects the amount of light incident on the first semiconductor layer 3 is minimized. Can be.

<(2) Method for Manufacturing Photoelectric Conversion Device>
3 to 9 are cross-sectional views each schematically showing a state during the manufacture of the photoelectric conversion device 11. Each of the cross-sectional views shown in FIGS. 3 to 9 shows a state in the middle of manufacturing a portion corresponding to the cross-section shown in FIG.

  First, the lower electrode layer 2 made of Mo or the like is formed on substantially the entire surface of the cleaned support 1 by sputtering or the like. Then, the first groove portion P1 is formed from the linear formation target position along the Y direction on the upper surface of the lower electrode layer 2 to the upper surface of the support body 1 immediately below the first formation portion P1. The first groove portion P1 can be formed, for example, by laser scribing, in which groove processing is performed by irradiating the formation target position while scanning with laser light from a YAG laser or the like. FIG. 3 is a diagram illustrating a state after the first groove portion P1 is formed.

  After forming the first groove P1, a coating M containing an organic compound, a group IB element and a group III-B element is formed on the lower electrode layer 2. Such a film M can be prepared as follows using a solution of an organic complex.

As the organic complex, an organic complex in which an organic ligand is coordinated to a group IB element such as copper or silver, an organic complex in which an organic ligand is coordinated to a group III-B element such as indium or gallium, or An organic ligand is coordinated to both a group I-B element and a group III-B element, and an organic compound having a group I-B element, a group III-B element, and an organic ligand in one molecule There are complexes.

In particular, an organic chalcogen compound may be used as the organic ligand from the viewpoint of satisfactorily producing the I-III-VI group compound. An organic chalcogen compound is an organic compound containing a chalcogen element, and is an organic compound having a covalent bond between a carbon element and a chalcogen element. A chalcogen element means S, Se, and Te among VI-B group elements. Examples of the organic chalcogen compound include thiol, sulfide, disulfide, thiophene, sulfoxide, sulfone, thioketone, sulfonic acid, sulfonic acid ester, sulfonic acid amide, selenol, selenide, diselenide, selenoxide, selenone, tellurol, telluride, ditelluride and the like. is there. In particular, thiol, sulfide, disulfide, selenol, selenide, diselenide, tellurol, telluride, and ditelluride may be used from the viewpoint of high coordination ability and easy formation of a stable complex with a metal element. Examples of organic complexes using organic chalcogen compounds as organic ligands include organic complexes in which organic chalcogen compounds such as phenyl selenol and ethane selenol are coordinated to group IB elements, phenyl selenol and ethane selenol. Organic chalcogen compounds such as organic coordinators coordinated with group III-B elements, or organic chalcogen compounds such as phenyl selenol and ethane selenol coordinated with both group IB elements and group III-B elements. There is a single source organic complex having a group IB element, a group III-B element and a selenium element in one molecule (see Patent Document 2).

  The above organic complex is dissolved in an organic solvent such as pyridine or aniline to prepare a raw material solution. Then, this raw material solution is deposited in the form of a film on the lower electrode layer 2 by, for example, a spin coater, screen printing, dipping, spraying, a die coater or the like to form a film M.

  Next, the organic component in the film M is removed by heating the film M at, for example, 50 to 350 ° C. to thermally decompose the organic compound in the film M. In addition, it is good also as the membrane | film | coat M which consists of a laminated body of multiple layers by repeating the process of forming the membrane | film | coat M using the above raw material solutions, and thermally decomposing the organic compound in this membrane | film | coat M. The laminate of the support 1, the lower electrode layer 2 and the film M produced as described above is hereinafter referred to as a substrate 100. FIG. 4 is a diagram showing a state (the state of the substrate 100) after performing the thermal decomposition process of the coating M. FIG.

  Next, the substrate 100 is placed in the heating furnace 101. The heating furnace 101 includes a heating device, and can heat the substrate 100 installed in the heating furnace 101. The heating furnace 101 also includes an inlet 102 for injecting atmospheric gas into the heating furnace 101 and an outlet 103 for discharging atmospheric gas in the heating furnace 101. The injection port 102 is connected to a pipe for flowing the atmospheric gas, and the atmospheric gas can be injected into the heating furnace 101 by opening the valve 102a. The exhaust port 103 is connected to a pipe for discharging the atmospheric gas, and the atmospheric gas can be discharged out of the heating furnace 101 by opening the valve 103a. FIG. 5 is a view showing a state where the substrate 100 is installed in the heating furnace 101.

  Then, a first heating step is performed in which the inside of the heating furnace 101 is filled with a first atmosphere gas containing at least one of hydrogen and an inert gas, and the substrate 100 is heated. The inert gas is a gas that does not cause a chemical reaction with the film M, and is, for example, nitrogen or argon. The first atmosphere may be a mixed gas of hydrogen and an inert gas. The heating temperature of the substrate 100 in the first heating step is set higher than the heating temperature in the thermal decomposition step of the coating M from the viewpoint of better removing organic components in the coating M. Also good. As a heating condition of the first heating step, for example, a condition in which the substrate 100 is heated at 350 to 450 ° C. for about 30 to 180 minutes can be employed.

  Further, after the first heating step, an exhausting step of exhausting the first atmospheric gas in the heating furnace 101 from the outlet 103 to the outside of the heating furnace 101 is performed. In the exhaust process, the first atmosphere gas may be discharged by reducing the pressure inside the heating furnace 101 to, for example, 100 Pa or less with a vacuum pump as shown in FIG. Alternatively, while discharging the first atmosphere gas from the discharge port 103, a new gas such as hydrogen or an inert gas (hereinafter, this new gas is referred to as a third atmosphere gas) is injected from the injection port 102 to heat the heating furnace 101. The first atmosphere gas may be discharged by replacing the inside with the third atmosphere gas. From the viewpoint of better discharging the first atmospheric gas, the inside of the heating furnace 101 may be evacuated by substituting the inside of the heating furnace 101 with the third atmospheric gas. Note that the vacuum in the exhaust process refers to a reduced pressure state of 100 Pa or less.

  In the exhaust process, the substrate 100 may be cooled to 200 ° C. or lower. As a result, it is possible to suppress the chemical reaction of the coating M from proceeding during the exhausting process to become a crystal body containing many defects.

  Next, the inside of the heating furnace 101 is filled with a second atmospheric gas containing a chalcogen element, the substrate 100 is heated at a temperature equal to or higher than the heating temperature of the first heating step, and the coating M contains an I-III-VI group compound. A second heating step for forming the first semiconductor layer 3 is performed. The second atmosphere gas contains a chalcogen element as, for example, sulfur vapor, selenium vapor, tellurium vapor, hydrogen sulfide, hydrogen selenide, hydrogen telluride, or the like. The second atmosphere gas may be only such a chalcogen element gas, or may be a mixed gas with hydrogen or an inert gas. As a method of filling the inside of the heating furnace 101 with the second atmosphere gas, a second atmosphere gas containing a chalcogen element may be injected from the injection port 102, or the metal 104 of the chalcogen element is previously added as shown in FIG. In addition to being placed in the heating furnace 101, hydrogen or an inert gas is injected from the inlet 102, and the metal 104 of the chalcogen element is vaporized when the substrate 101 is heated. You may make it mix with active gas. As a heating condition of the second heating step, for example, a condition in which the substrate 100 is heated at 450 to 600 ° C. for about 30 minutes to 10 hours can be employed.

  As described above, by sequentially performing the first heating step, the exhaust step, and the second heating step, the crystallization reaction can be promoted, and the photoelectric conversion efficiency can be increased. That is, since it is difficult to sufficiently remove the organic component in the thermal decomposition process of the film M, the remaining organic component is crystallized when only the second heating process is performed without performing the first heating process and the exhaust process. It becomes easy to inhibit. On the other hand, by performing the first heating step and the exhaust step, the organic components in the film M can be removed more favorably, and crystallization can be performed more favorably. That is, by exhausting the organic component released from the film M in the first heating step together with the first atmosphere, the organic component can be prevented from being mixed again in the film. FIG. 6 is a view showing a state after the coating M is made the first semiconductor layer 3.

  After the formation of the first semiconductor layer 3, the second semiconductor layer 4 and the upper electrode layer 5 are sequentially formed on the first semiconductor layer 3.

The second semiconductor layer 4 can be formed by a solution growth method (also referred to as a CBD method). For example, a metal material such as cadmium acetate or indium chloride and a sulfur material such as thiourea or thioacetamide are dissolved in a solvent such as water, and the substrate 1 that has been formed up to the formation of the first semiconductor layer 3 is immersed in this solution. Thus, the second semiconductor layer 4 containing CdS, In ₂ S _3, or the like can be formed on the first semiconductor layer 3.

  The upper electrode layer 5 is a transparent conductive film mainly composed of zinc oxide (AZO) containing aluminum, for example, and can be formed by a sputtering method, a vapor deposition method, a CVD method, or the like. FIG. 7 is a view showing a state after the second semiconductor layer 4 and the upper electrode layer 5 are formed.

After the upper electrode layer 5 is formed, the second groove portion P2 is formed from the linear formation target position along the Y direction on the upper surface of the upper electrode layer 5 to the upper surface of the lower electrode layer 2 immediately below it. The second groove portion P2 can be formed by, for example, mechanical scribing using a scribe needle. FIG. 8 is a diagram illustrating a state after the second groove portion P2 is formed. The second groove portion P2 is formed at a position slightly deviated in the X direction (+ X direction in the drawing) from the first groove portion P1.

  After forming the second groove P2, the current collecting electrode 7 and the connection conductor 6 are formed. For the collector electrode 7 and the connection conductor 6, for example, a conductive paste (also referred to as a conductive paste) in which a metal powder such as Ag is dispersed in a resin binder or the like is printed so as to draw a desired pattern. It can be formed by heating. FIG. 9 is a view showing a state after the current collecting electrode 7 and the connection conductor 6 are formed.

  After forming the current collection electrode 7 and the connection conductor 6, the 3rd groove part P3 is formed from the linear formation object position of the upper surface of the upper electrode layer 5 to the upper surface of the lower electrode layer 2 just under it. The width | variety of the 3rd groove part P3 can be about 40-1000 micrometers, for example. Moreover, the 3rd groove part P3 can be formed by a mechanical scribing process similarly to the 2nd groove part P2. In this way, the photoelectric conversion device 11 shown in FIGS. 1 and 2 is manufactured by forming the third groove portion P3.

  The present invention is not limited to the above-described embodiment, and various changes and improvements can be made without departing from the scope of the present invention.

1: Support 2: Lower electrode layer 3: First semiconductor layer 4: Second semiconductor layer 5: Upper electrode layer 10: Photoelectric conversion cell 11: Photoelectric conversion device 100: Substrate 101: Heating furnace 102: Atmospheric gas supply Mouth 103: Atmospheric gas outlet M: Film

Claims (5)

A preparatory step of preparing a substrate on which a film containing an organic compound, a group IB element and a group III-B element is formed on the electrode layer;
A thermal decomposition step of thermally decomposing the organic compound by heating the substrate;
A first heating step of heating the substrate in a heating furnace filled with a first atmospheric gas containing at least one of hydrogen and an inert gas;
An exhaust step of exhausting the first atmospheric gas in the heating furnace;
A photoelectric conversion device that sequentially performs a second heating step of filling the inside of the heating furnace with a second atmospheric gas containing a chalcogen element and heating the substrate to form the film into a semiconductor layer containing an I-III-VI group compound. Manufacturing method.   The method for manufacturing a photoelectric conversion device according to claim 1, wherein the exhausting step includes a step of evacuating the inside of the heating furnace.   The photoelectric conversion according to claim 2, wherein the exhausting step includes a step of evacuating the inside of the heating furnace after replacing the inside of the heating furnace with a third atmospheric gas containing at least one of hydrogen and an inert gas. Device manufacturing method.   The method for manufacturing a photoelectric conversion device according to claim 1, wherein the substrate is cooled in the exhausting step.   5. The method of manufacturing a photoelectric conversion device according to claim 1, wherein a heating temperature of the substrate in the first heating step is higher than a heating temperature of the substrate in the pyrolysis step.

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