JP5902592B2 - Method for manufacturing photoelectric conversion device - Google Patents

Description

  The present invention relates to a photoelectric conversion device in which a plurality of photoelectric conversion cells are electrically connected.

  As a photoelectric conversion device used for solar power generation or the like, there is one in which a plurality of photoelectric conversion cells are provided on a substrate (for example, Patent Document 1).

  Such a photoelectric conversion device is a photoelectric conversion cell in which a lower electrode layer such as a metal electrode, a photoelectric conversion layer containing a metal chalcogenide such as CIGS, and a transparent conductive film are laminated in this order on a substrate such as glass. However, a plurality of them are arranged in a plane. The plurality of photoelectric conversion cells are electrically connected in series by connecting the transparent conductive film of one adjacent photoelectric conversion cell and the other lower electrode layer with a connection conductor.

  The photoelectric conversion device is always required to improve the photoelectric conversion efficiency. In order to increase the photoelectric conversion efficiency of a photoelectric conversion device using a photoelectric conversion layer containing a metal chalcogenide, it is proposed to use a substrate containing an alkali metal element such as sodium and diffuse the alkali metal element from this substrate into the photoelectric conversion layer (For example, Patent Document 2).

JP 2000-299486 A JP 2004-047917 A

  When diffusing the alkali metal element from the substrate, the amount of the alkali metal element diffusing into the photoelectric conversion layer through the lower electrode layer made of Mo or the like and the gap between the lower electrode layers pass through the photoelectric layer without passing through the lower electrode layer. A difference is likely to occur depending on the amount of the alkali metal element diffusing into the conversion layer. Therefore, if an attempt is made to increase the diffusion amount of the alkali metal element to the photoelectric conversion layer on the lower electrode layer, the diffusion amount of the alkali metal element in the photoelectric conversion layer located near the gap between the lower electrode layers becomes excessive, and the photoelectric conversion layer Peeling easily occurs. Therefore, it is difficult to increase the photoelectric conversion efficiency.

  One object of the present invention is to improve the photoelectric conversion efficiency of a photoelectric conversion device.

A method of manufacturing a photoelectric conversion device according to an embodiment of the present invention includes a step of providing a first lower electrode layer and a second lower electrode layer on a substrate containing an alkali metal element at a first concentration with a gap therebetween, and Forming a high resistance layer containing an alkali metal element at a second concentration lower than the first concentration in the gap; and heating the substrate from above the first lower electrode layer onto the high resistance layer. And forming a semiconductor layer containing metal chalcogenide over the second lower electrode layer. The step of forming the high resistance layer is performed in the step of forming the semiconductor layer.
The high resistance layer is formed so that the amount of alkali metal element diffusing into the semiconductor layer through the first lower electrode layer and the amount of alkali metal diffusing into the semiconductor layer through the high resistance layer are approximated. It is a process to do.

  ADVANTAGE OF THE INVENTION According to this invention, the photoelectric conversion efficiency of a photoelectric conversion apparatus can be improved.

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 a plane perspective view 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.

  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. FIG. 3 is a perspective view of the photoelectric conversion device of FIG. 1 viewed from the upper surface side (+ Z side). 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.

  In the photoelectric conversion device 11, a plurality of photoelectric conversion cells 10 are provided on the substrate 1. Although only two photoelectric conversion cells 10 are shown in FIGS. 1 to 3 for convenience of illustration, in the actual photoelectric conversion device 11, the X-axis direction in the drawing, or further in the Y-axis direction in the drawing. Many photoelectric conversion cells 10 may be arranged in a plane (two-dimensionally).

  1 to 3, a plurality of lower electrode layers 2 are arranged in a plane on a substrate 1. Among the adjacent lower electrode layers 2, one upper electrode layer 2 a (hereinafter also referred to as the first lower electrode layer 2 a) to the other lower electrode layer 2 b (hereinafter also referred to as the second lower electrode layer 2 b). The first semiconductor layer 3 and the second semiconductor layer 4 having a conductivity type different from that of the first semiconductor layer 3 are provided. A connection conductor 7 is provided on the second lower electrode layer 2 b so as to electrically connect the second lower electrode layer 2 b and the second semiconductor layer 4. By including at least the lower electrode layer 2 (the first lower electrode layer 2a and the second lower electrode layer 2b), the first semiconductor layer 3, the second semiconductor layer 4, and the connection conductor 7, one photoelectric A conversion cell 10 is configured. Adjacent photoelectric conversion cells 10 are electrically connected by the second lower electrode layer 2b. With such a configuration, the adjacent photoelectric conversion cells 10 are connected in series to form a photoelectric conversion device 11. .

  In addition, although the photoelectric conversion apparatus 11 in this embodiment assumes what light injects with respect to the 1st semiconductor layer 3 from the 2nd semiconductor layer 4 side, it is not limited to this, The board | substrate 1 The light may be incident from the side.

  The substrate 1 supports the 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 substrate 1, blue plate glass (soda lime glass) having a thickness of about 1 to 3 mm may be used.

  The lower electrode layer 2 (the first lower electrode layer 2a and the second lower electrode layer 2b) is a conductor such as Mo, Al, Ti, or Au provided on the substrate 1. The lower electrode layer 2 is formed to a thickness of about 0.2 μm to 1 μm using a known thin film forming method such as sputtering or vapor deposition. A gap P1 between the first lower electrode layer 2a and the second lower electrode layer 2b may be 20 to 200 μm, for example.

  The high resistance layer 6 is interposed in the gap P1 between the first lower electrode layer 2a and the second lower electrode layer 2b. The high resistance layer 6 is a material whose electric resistivity is 100 times higher than that of the first semiconductor layer 3 described later. Thereby, generation | occurrence | production of the leakage current between the 1st lower electrode layer 2a and the 2nd lower electrode layer 2b is reduced, and the photoelectric conversion efficiency of the photoelectric conversion apparatus 11 is raised. Examples of the high resistance layer 6 include glass such as silicate glass and quartz glass, inorganic compounds such as silica, alumina, and titania, and organic resins such as polyimide.

The first semiconductor layer 3 is a first conductivity type semiconductor layer and functions as a light absorption layer. In the present embodiment, the first semiconductor layer 3 is assumed to be a p-type semiconductor layer having a thickness of, for example, about 1 μm to 3 μm, but is not limited thereto. The first semiconductor layer 3 mainly contains metal chalcogenide. The phrase “mainly containing metal chalcogenide” means containing 70 mol% or more of metal chalcogenide. A metal chalcogenide is a compound of a metal element and a chalcogen element. The chalcogen element refers to S, Se, or Te among VI-B group elements (also referred to as group 16 elements). As the metal chalcogenide, for example, I-III-VI group compounds, I-II-IV-VI group compounds, II-VI group compounds and the like may be used. From the viewpoint that high photoelectric conversion efficiency can be obtained even with a thin film of about 1 μm to 3 μm, an I-III-VI group compound or an I-II-IV-VI group compound may be used as the metal chalcogenide.

The I-III-VI group compound is a compound of a group IB element (also referred to as a group 11 element), a group III-B element (also referred to as a group 13 element), and a group VI-B element. Examples of the I-III-VI group compound include CuInSe ₂ (also referred to as copper indium selenide, CIS), Cu (In, Ga) Se ₂ (also referred to as copper indium selenide / gallium, CIGS), Cu ( In, Ga) (Se, S) ₂ (also referred to as diselene, copper indium sulphide, gallium, or CIGSS). Alternatively, the first semiconductor layer 3 may be composed of a multi-component compound semiconductor thin film such as copper indium selenide / gallium having a thin film of selenite / copper indium sulfide / gallium layer as a surface layer.

The I-II-IV-VI group compound includes an IB group element, an II-B group element (also referred to as a group 12 element), an IV-B group element (also referred to as a group 14 element), and a VI-B group element. It is a compound semiconductor. Examples of the I-II-IV-VI group compound include Cu ₂ ZnSnS ₄ (also referred to as CZTS) and Cu ₂ ZnSnS _4-x Se _x (also referred to as CZTSSe. Note that x is a number greater than 0 and smaller than 4. And Cu ₂ ZnSnSe ₄ (also referred to as CZTSe).

  The II-VI group compound is a compound semiconductor of a II-B group element and a VI-B group element. CdTe etc. are mentioned as a II-VI group compound.

  The second semiconductor layer 4 is a semiconductor layer having a second conductivity type different from that of the first semiconductor layer 3. By electrically connecting the first semiconductor layer 3 and the second semiconductor layer 4, a photoelectric conversion layer capable of taking out charges well is formed. For example, if the first semiconductor layer 3 is p-type, the second semiconductor layer 4 is n-type. The first semiconductor layer 3 may be n-type and the second semiconductor layer 4 may be p-type. The second semiconductor layer 4 may be a multilayer structure including a high resistance layer.

As the second semiconductor layer 4, CdS, ZnS, ZnO, In ₂ S ₃ , In ₂ Se ₃ , I
n (OH, S), (Zn, In) (Se, OH), (Zn, Mg) O, and the like. In this case, the second semiconductor layer 4 is formed with a thickness of 10 to 200 nm by, for example, a chemical bath deposition (CBD) method. In (OH, S) refers to a compound mainly containing In, OH, and S. (Zn, In) (Se, OH) refers to a compound mainly containing Zn, In, Se, and OH. (Zn, Mg) O refers to a compound mainly containing Zn, Mg and O.

  As shown in FIGS. 1 and 2, an upper electrode layer 5 may be further provided on the second semiconductor layer 4. The upper electrode layer 5 is a layer having a lower resistivity than the second semiconductor layer 4, and it is possible to take out charges generated in the first semiconductor layer 3 and the second semiconductor layer 4 satisfactorily. From the viewpoint of further increasing the photoelectric conversion efficiency, the resistivity of the upper electrode layer 5 may be less than 1 Ω · cm and the sheet resistance may be 50 Ω / □ or less.

  The upper electrode layer 5 is a 0.05 to 3 μm transparent conductive film such as ITO or ZnO. In order to improve translucency and conductivity, the upper electrode layer 5 may be composed of a semiconductor having the same conductivity type as the second semiconductor layer 4. The upper electrode layer 5 can be formed by sputtering, vapor deposition, chemical vapor deposition (CVD), or the like.

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

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

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

  1 and 2, the connection conductor 7 is a conductor provided in a groove P <b> 2 that penetrates (divides) the first semiconductor layer 3, the second semiconductor layer 4, and the upper electrode layer 5. The connection conductor 7 can be made of metal, conductive paste, or the like. In FIG. 1 and FIG. 2, the collector electrode 8 is extended to form the connection conductor 7, but the present invention is not limited to this. For example, the upper electrode layer 5 may be stretched.

<(2) Method for Manufacturing Photoelectric Conversion Device>
4 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. 4 to 9 shows a state in the middle of manufacturing a portion corresponding to the cross-section shown in FIG.

  First, a substrate 1 containing an alkali metal element such as Na or K (an alkali metal element means a group 1 element excluding hydrogen) at a first concentration (total concentration of alkali metal elements contained in the substrate 1). Prepare. The first concentration may be, for example, 0.8 to 16.5 atom%. With such a concentration, when the first semiconductor layer 3 is formed, the alkali metal element in the substrate 1 can be favorably diffused to promote crystal growth of the first semiconductor layer 3. As the substrate 1, for example, blue plate glass (soda lime glass) can be used.

  Then, a lower electrode layer 2 made of Mo or the like is formed on substantially the entire surface of the substrate 1 by using a sputtering method or the like. Then, a groove-like gap P <b> 1 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 substrate 1 immediately below the formation target. The gap P1 can be formed by, for example, 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. 4 is a diagram illustrating a state after the gap P1 is formed.

  After forming the gap P1, the high resistance layer 6 containing the alkali metal element is formed in the gap P1 at a second concentration in which the concentration of the alkali metal element is lower than the first concentration. In addition, this 2nd density | concentration also includes the case where the alkali metal element is not included, and should just be about 0 to 0.9 times of the 1st density | concentration, More preferably, about 0 to 0.5 times. As such a high resistance layer 6, an alkali free glass paste etc. can be used, for example. And a high resistance layer is producible by apply | coating this alkali free glass paste in the gap | interval P1 by methods, such as screen printing. FIG. 5 is a diagram showing a state after the high resistance layer 6 is formed.

  After forming the high resistance layer 6, the first semiconductor layer 3 containing metal chalcogenide is formed on the lower electrode layer 2 and the high resistance layer 6 while heating the substrate 1. In addition, as a method for forming the first semiconductor layer 3 while heating the substrate 1, for example, first to third methods as described below can be employed. The first method is a method of forming the first semiconductor layer 3 by sputtering or vapor deposition while heating the substrate 1 at 400 to 600 ° C., for example. The second method is a method in which the first semiconductor layer 3 and the substrate 1 are heated at, for example, 400 to 600 ° C. after the first semiconductor layer 3 is formed by a sputtering method, a vapor deposition method, or the like. The third method is a method in which after forming a precursor layer to be the first semiconductor layer 3, the precursor layer and the substrate 1 are heated so that the precursor layer becomes the first semiconductor layer 3. .

  When the first semiconductor layer 3 is formed while heating the substrate 1 in this way, the alkali metal element contained in the substrate 1 is heated into the first semiconductor layer 3 via the lower electrode layer 2 or the high resistance layer 6. By diffusing, the growth of crystal grains of the first semiconductor layer 3 can be promoted by the alkali metal element. At that time, the amount of the alkali metal element diffused into the first semiconductor layer 3 through the lower electrode layer 2 by the high resistance layer 6 having a concentration of the alkali metal element lower than that of the substrate 1, and the high resistance layer 6. Thus, the difference from the amount of the alkali metal element diffusing into the first semiconductor layer 3 can be adjusted. As a result, it is possible to reduce the possibility that the first semiconductor layer 3 is likely to be peeled off due to the diffusion amount of the alkali metal element increasing locally in the first semiconductor layer 3 (particularly in the vicinity of the gap between the lower electrode layers 2). The photoelectric conversion device 11 having high photoelectric conversion efficiency can be obtained. FIG. 6 is a diagram showing a state after the first semiconductor layer 3 is formed.

  The amount of the alkali metal element diffused from the substrate 1 through the high resistance layer 6 to the first semiconductor layer 3 is adjusted by adjusting the thickness of the high resistance layer 6 and the concentration of the alkali metal element in the high resistance layer 6. Can be changed. Therefore, the amount of the alkali metal element that diffuses from the substrate 1 to the first semiconductor layer 3 via the lower electrode layer 2 and the alkali metal that diffuses from the substrate 1 to the first semiconductor layer 3 via the high resistance layer 6. These physical quantities may be adjusted so that the amounts of the elements approximate.

Here, the third method will be described below. The precursor layer in the third method can be produced, for example, by using a sputtering method or by applying a raw material solution. The precursor layer may be a layer containing a metal chalcogenide material constituting the first semiconductor layer 3, or may be a layer containing metal chalcogenide fine particles constituting the first semiconductor layer 3. For example, if the first semiconductor layer 3 is CIGS, the precursor layer may contain a Cu element, an In element, and a Ga element as a simple substance or a compound, and in addition to these metal elements, Se element may also be included. Alternatively, the precursor layer is CIG
S particles may be included.

  After forming the precursor layer, the substrate 1 and the body layer are heated at 400 to 600 ° C., for example, to crystallize the precursor layer 3 into the first semiconductor layer 3. The atmosphere during the heating is a non-oxidizing gas atmosphere (the non-oxidizing gas includes an inert gas such as nitrogen and argon, a reducing gas such as hydrogen), a chalcogen gas atmosphere (as a chalcogen gas) May be hydrogen sulfide, sulfur vapor, hydrogen selenide, selenium vapor, hydrogen telluride, tellurium vapor, or the like, or a mixed atmosphere of a non-oxidizing gas and a chalcogen gas.

  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, cadmium acetate and thiourea are dissolved in ammonia water, and the substrate 1 that has been formed up to the formation of the first semiconductor layer 3 is immersed in the second semiconductor layer 3 so as to contain the second CdS on the first semiconductor layer 3. The semiconductor layer 4 can be formed.

  The upper electrode layer 5 is a transparent conductive film containing, for example, indium oxide (ITO) containing Sn as a main component, 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 forming the upper electrode layer 5, a groove portion for forming the connection conductor 6 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 the upper electrode layer 5. P2 is formed. 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 shifted in the X direction (+ X direction in the drawing) from the gap P1.

  After forming the groove part 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 the collector electrode 7 and the connection conductor 6 are formed, the photoelectric conversion cell 10 is divided from the linear formation target position of the upper surface of the upper electrode layer 5 to the upper surface of the lower electrode layer 2 immediately below The groove part P3 is formed. 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 manner, the photoelectric conversion device 11 shown in FIGS. 1 to 3 is manufactured by forming the third groove portion P3.

<Other examples of photoelectric conversion device>
The present invention is not limited to the above-described embodiment, and various modifications and improvements can be made without departing from the scope of the present invention. For example, the high resistance layer 6 may have a plurality of holes. Thus, when it has a void | hole, the diffusion path | route of an alkali metal element can be narrowed by a void | hole, Thereby, control of the alkali metal element from the board | substrate 1 to the 1st semiconductor layer 3 can be made easier. Further, when the high resistance layer 6 has holes as described above, light can be favorably reflected by a difference in refractive index between the solid portion of the high resistance layer 6 and the holes. Therefore, the light transmitted without being absorbed by the first semiconductor layer 3 can be reflected to the first semiconductor layer 3, and the photoelectric conversion efficiency is further increased. The high resistance layer 6 having such holes can be formed, for example, by using a sol-gel method or by solidifying the paste so that the holes remain using a paste containing glass particles.

1: Substrate 2: Lower electrode layer 2a: First lower electrode layer 2b: Second lower electrode layer 3: First semiconductor layer 4: Second semiconductor layer 5: Upper electrode layer 6: High resistance layer 7: Connecting conductor 8: Current collecting electrode 10: Photoelectric conversion cell 11: Photoelectric conversion device

Claims (4)

Providing a first lower electrode layer and a second lower electrode layer on a substrate containing an alkali metal element at a first concentration with a gap;
Forming a high resistance layer containing an alkali metal element at a second concentration lower than the first concentration in the gap;
Forming a semiconductor layer containing metal chalcogenide from above the first lower electrode layer to the second lower electrode layer through the high resistance layer while heating the substrate ,
The step of forming the high resistance layer includes an amount of an alkali metal element that diffuses into the semiconductor layer through the first lower electrode layer during the step of forming the semiconductor layer and the high resistance layer through the high resistance layer. A method for manufacturing a photoelectric conversion device, which is a step of forming the high resistance layer so that an amount of alkali metal diffusing into a semiconductor layer is approximated . The method for manufacturing a photoelectric conversion device according to claim 1, wherein a layer having a plurality of pores is used as the high resistance layer. The method for producing a photoelectric conversion device according to claim 1, wherein an I-III-VI group compound or an I-II-IV-VI group compound is used as the metal chalcogenide.   4. The method of manufacturing a photoelectric conversion device according to claim 1, wherein the first lower electrode layer and the second lower electrode layer include one containing molybdenum element. 5.

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