JP2014187089A - Photoelectric conversion module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve moisture resistance reliability of a photoelectric conversion module.SOLUTION: A photoelectric conversion module 200 includes: a first substrate 20; a first sealing material 21 disposed on the first substrate 20; a photoelectric conversion unit 11 disposed on a central part of an upper surface of the first sealing material 21; a second sealing material 22 which is disposed on the first sealing material 21, seals the photoelectric conversion unit 11, and has a larger water diffusion coefficient than the first sealing material 21; and a second substrate 23 disposed on the second sealing material 22.

Description

  The present invention relates to a photoelectric conversion module in which a photoelectric conversion part is sealed with a sealing material.

  In recent years, photovoltaic power generation that converts light energy into electric energy has attracted attention as energy problems and environmental problems become more serious.

  A photoelectric conversion module used for solar power generation has a semiconductor portion including a semiconductor capable of photoelectric conversion. Examples of such a semiconductor layer include a thin film semiconductor layer and a crystal semiconductor layer. As the thin film semiconductor layer, there are compound semiconductor thin films such as CIS (copper indium selenide) and CIGS (copper indium gallium selenide), amorphous silicon thin films, and the like. In addition, examples of the crystalline semiconductor layer include polycrystalline silicon and single crystal silicon.

  In the photoelectric conversion part having such a semiconductor layer, the photoelectric conversion characteristics are easily deteriorated by moisture. Therefore, moisture is prevented from entering the photoelectric conversion portion by sealing the photoelectric conversion portion between sealing materials such as ethylene vinyl acetate copolymer (hereinafter referred to as EVA) (see Patent Document 1). ).

JP 2006-179626 A

  The photoelectric conversion module is always required to improve moisture resistance. In the said photoelectric conversion module, the penetration | invasion of a water | moisture content to a photoelectric conversion part cannot fully be suppressed, and the further improvement in moisture resistance is desired.

  This invention is made | formed in view of the said subject, and aims at the improvement of the moisture resistance of a photoelectric conversion module.

  A photoelectric conversion module according to one embodiment of the present invention includes a first substrate, a first sealing material disposed on the first substrate, and a photoelectric conversion disposed on an upper surface central portion of the first sealing material. A second sealing material having a water diffusion coefficient larger than that of the first sealing material, the second sealing material being disposed on the first sealing material and sealing the photoelectric conversion unit, and the second sealing material And a second substrate disposed thereon.

  According to the photoelectric conversion module according to one embodiment of the present invention, the moisture resistance reliability of the photoelectric conversion module is improved.

It is a perspective view which shows the whole photoelectric conversion part. It is a principal part expansion perspective view of a photoelectric conversion part. It is sectional drawing of the photoelectric conversion part of FIG. It is sectional drawing of a photoelectric conversion module.

  Hereinafter, a photoelectric conversion module according to an embodiment of the present invention will be described in detail with reference to the drawings. Note that the drawings are schematically shown, and the sizes and positional relationships of various structures in the drawings are not accurately illustrated. 1 to 4 also have right-handed XYZ coordinates with the X-axis being the alignment direction of photoelectric conversion cells, which will be described later. First, a photoelectric conversion unit that is a part of the photoelectric conversion module will be described.

<Configuration of photoelectric conversion unit>
FIG. 1 is a perspective view illustrating the entire photoelectric conversion unit 11. 2 is an enlarged perspective view of a main part of the photoelectric conversion unit 11, and FIG. 3 is an XZ sectional view thereof. The photoelectric conversion unit 11 includes a support substrate 1 and a plurality of photoelectric conversion cells 10 provided on the support substrate 1 so as to be arranged along the X-axis direction. The photoelectric conversion cell 10 includes a lower electrode layer 2, a first semiconductor layer 3 having a first conductivity type, a second semiconductor layer 4 having a second conductivity type different from the first conductivity type, The upper electrode layer 5 is laminated in order. For example, if the first conductivity type is p-type, the second conductivity type is n-type, and vice versa. These first semiconductor layer 3 and second semiconductor layer 4 form a photoelectric conversion layer capable of separating charges well.

  In the photoelectric conversion unit 11, the upper electrode layer 5 of one adjacent photoelectric conversion cell 10 and the lower electrode layer 2 of the other photoelectric conversion cell 10 are electrically connected via a connection conductor 6. With such a configuration, adjacent photoelectric conversion cells 10 are connected in series. And in the edge part of the photoelectric conversion part 11, the connection electrode 2a electrically connected with one electrode of the photoelectric conversion cell 10 group connected in series is provided, and a photoelectric conversion part is provided in this connection electrode 2a. 11 is connected to a wiring conductor 13a for electrical connection to the outside. Similarly, a connection electrode 2b that is electrically connected to the other electrode of the group of photoelectric conversion cells 10 connected in series is provided at the opposite end of the photoelectric conversion unit 11, and this connection electrode 2b is provided. A wiring conductor 13b for making an electrical connection to the outside of the photoelectric conversion unit 11 is connected.

  2 and 3, only two photoelectric conversion cells 10 are shown for convenience of illustration, but the actual photoelectric conversion unit 11 includes a plurality of photoelectric conversion cells 10 in the X-axis direction of the drawings. They are arranged in a plane (two-dimensional). Furthermore, a plurality of photoelectric conversion cells 10 may be arranged in a plane in the Y-axis direction of the drawing.

  The support substrate 1 has a flat plate shape having a first main surface, and supports a plurality of photoelectric conversion cells 10 on the first main surface. Examples of the material used for the support substrate 1 include glass, ceramics, resin, and metal. As the support substrate 1, for example, 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 conductor such as Mo, Al, Ti, or Au provided on the support 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.

  The first semiconductor layer 3 is a semiconductor layer having the first conductivity type. The first semiconductor layer 3 has a thickness of about 1 μm to 3 μm, for example. The material of the first semiconductor layer 3 is not particularly limited, and a thin film semiconductor layer such as a compound semiconductor thin film or an amorphous silicon thin film can be used. In view of having a relatively high photoelectric conversion efficiency, as the first semiconductor layer 3, for example, metal chalcogenides such as I-III-VI group compounds, I-II-IV-VI group compounds, II-VI group compounds and the like are used. May be used.

An I-III-VI group compound is a group IB element (also referred to as a group 11 element) and a group III-B element (1
It is a compound of a group 3 element) and a VI-B group element (also referred to as a group 16 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 selenide / copper indium sulfide / gallium as a surface layer. The I-III-VI group compound has a relatively high light absorption coefficient, and good photoelectric conversion efficiency can be obtained even if the first semiconductor layer 3 is thin.

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. The second semiconductor layer 4 may be formed by stacking a material different from that of the first semiconductor layer 3 on the first semiconductor layer 3, or the surface portion of the first semiconductor layer 3 may be other than the first semiconductor layer 3. It may be modified by elemental doping.

The second semiconductor layer 4 includes CdS, ZnS, ZnO, In ₂ S ₃ , In ₂ Se ₃ , In (OH, S), (Zn, In) (Se, OH), and (Zn, Mg) O. Etc. 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. Note that In (OH, S) refers to a mixed crystal compound in which In exists as hydroxide and sulfide. (Zn, In) (Se, OH) refers to a mixed crystal compound in which Zn and In exist as selenides and hydroxides. (Zn, Mg) O refers to a mixed crystal compound in which Zn and Mg are present as oxides.

  As shown in FIGS. 2 and 3, the 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 carriers generated in the first semiconductor layer 3 and the second semiconductor layer 4 are extracted well. 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.

  Further, as shown in FIGS. 2 and 3, a collecting electrode 7 may be further formed on the upper electrode layer 5. The current collecting electrode 7 is for taking out the carriers generated in the first semiconductor layer 3 and the second semiconductor layer 4 more satisfactorily. For example, as shown in FIG. 2, the collector electrode 7 is formed in a linear shape from one end of the photoelectric conversion cell 10 to the connection conductor 6. As a result, the current generated in the first semiconductor layer 3 and the fourth semiconductor layer 4 is collected by the current collecting electrode 7 via the upper electrode layer 5, and is supplied to the adjacent photoelectric conversion cell 10 via the connection conductor 6. Good conductivity.

The collector electrode 7 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 7 may have a plurality of branched portions.

  The collector electrode 7 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.

  2 and 3, the connection conductor 6 is a conductor provided in a groove that penetrates (divides) the first semiconductor layer 3, the second semiconductor layer 4, and the second electrode layer 5. The connection conductor 6 can be made of metal, conductive paste, or the like. In FIG. 2 and FIG. 3, the collector electrode 7 is extended to form the connection conductor 6, but the present invention is not limited to this. For example, the upper electrode layer 5 may be stretched.

  In order to extract the current generated by the photoelectric conversion of the photoelectric conversion unit 11 as described above to the outside of the photoelectric conversion module 200, the wiring conductors 13a and 13b are electrically connected to the photoelectric conversion unit 11 as shown in FIG. ing.

  The wiring conductors 13a and 13b are electrically connected to the connection electrode portions 2a and 2b connected to the photoelectric conversion cell 10, respectively. The other ends of the wiring conductors 13a and 13b are led out of the photoelectric conversion module 200, and the power generated by the photoelectric conversion module 200 is output to an external circuit via the wiring conductors 13a and 13b. It becomes.

  For the wiring conductors 13a and 13b, for example, a metal foil such as copper (Cu) having a thickness of about 0.1 to 0.5 mm and a width of about 1 to 7 mm is used. Also. The surface of the metal foil may be coated with tin, nickel, aluminum, solder, or the like by plating or the like in order to improve electrical connection with the connection electrode portions 2a and 2b.

<Configuration of photoelectric conversion module>
Next, the photoelectric conversion module will be described in detail. FIG. 4 is a cross-sectional view of a photoelectric conversion module 200 according to an embodiment.

  As shown in FIG. 4, the photoelectric conversion module 200 includes a first substrate 20, a first sealing material 21, a second sealing material 22, and a second substrate 23 stacked in this order, and a first sealing material. The photoelectric conversion unit 11 is sealed between 21 and the second sealing material 22. That is, the first sealing material 21 and the second sealing material 22 cover the photoelectric conversion unit 11 from above and below at the center of these interfaces and are in close contact with each other around the photoelectric conversion unit 11. In addition, the second sealing material 22 has a larger water diffusion coefficient than the first sealing material 21, and the photoelectric conversion unit 11 is a semiconductor layer that performs photoelectric conversion (the first semiconductor layer 3 and the second semiconductor layer 2). The side on which the semiconductor layer 4) is provided is in contact with the second sealing material 22, and the first substrate 1 side is in contact with the first sealing material 21.

  With such a configuration, the moisture resistance reliability of the photoelectric conversion module 200 is improved. That is, when the conventional photoelectric conversion module is used in a high humidity environment, moisture tends to enter the sealing material, and the photoelectric conversion unit 11 tends to deteriorate due to the entered moisture. On the other hand, in the photoelectric conversion module 200 of the above embodiment, even if moisture enters the second sealing material 22, the water diffusion coefficient of the first sealing material 21 in close contact with the second sealing material 22 is low. Since it is smaller than the second sealing material 22, it becomes easier for moisture to be held by the first sealing material 21, and it is possible to effectively reduce the progress of moisture to the photoelectric conversion unit 11.

  From the viewpoint of maintaining the moisture that has entered the photoelectric conversion module 200 well and maintaining good sealing performance, the water diffusion coefficient of the second sealing material 22 is the diffusion coefficient of the first sealing material 21. It may be 2 to 2000 times.

  As such first sealing material 21 and second sealing material 22, various resins are combined in such a manner that the diffusion coefficient of the first sealing material 21 is smaller than the diffusion coefficient of the second sealing material 22. Use it. A combination of different diffusion coefficients is a copolymer using the same composition, but may be a combination of copolymer resins having a different diffusion coefficient by changing the composition ratio, or a combination of resins having different compositions. May be.

For example, in the case of a butyl rubber sealing material, there is one having a diffusion coefficient at 40 ° C. of 3.03 × 10 ⁻⁸ cm ² / sec. Further, some ethylene vinyl acetate copolymers (EVA) have a diffusion coefficient of 2.08 × 10 ⁻⁷ cm ² / sec at 40 ° C. In addition, some cyclic olefin polymers have a diffusion coefficient at 40 ° C. of 1.37 × 10 ⁻⁵ cm ² / sec. Moreover, if it is a polystyrene type sealing material, there exists a thing with the diffusion coefficient in 40 degreeC of 1.45 * 10 < ^-5 > cm < ² > / sec.

The diffusion coefficient of water in the first sealing 21 and the second sealing portion 22 can be measured as follows. First, a part of each sealing member is formed into a sheet having a thickness t to produce a test piece. Next, the amount of moisture that permeates the test piece is measured using a method based on JIS K 7192 B. At this time, a graph is created in which values are plotted with the time (sec) from the start of moisture permeation as the horizontal axis and the integrated value (g / cm ² ) of the permeated water amount as the vertical axis. In this graph, for a region where a line obtained by plotting numerical values has a substantially constant slope, linear approximation is performed using the least square method, and a time intersecting with the horizontal axis is obtained. This time is set as a delay time θ. Then, the diffusion coefficient of each sealing member is calculated by fitting the numerical values of the delay time θ and the thickness t to D = t ² / (6θ), which is a calculation formula for the diffusion coefficient D.

  Further, the saturated water absorption rate of the second sealing material 22 may be smaller than the saturated water absorption rate of the first sealing material 21. As a result, the amount of moisture taken into the second sealing member 22 from the outside is reduced, and the retention of moisture by the first sealing material 21 is increased, making it difficult for moisture to further penetrate into the photoelectric conversion unit 11 side. it can.

  Moreover, the saturated water absorption rate of the 1st sealing material 21 and the 2nd sealing material 22 can be measured as follows. First, a part of each sealing member is formed into a sheet having a thickness t to produce a test piece. Next, the water vapor transmission rate (WVTR) and the diffusion coefficient D are determined using a method based on JIS K 7129 B. Next, the saturated water absorption rate of each sealing member is calculated by applying the values of the thickness t and the diffusion coefficient D to C = WVTR × t / D, which is a calculation formula for the saturated water absorption rate C.

Further, as shown in FIG. 4, a sealing material 24 may be provided so as to surround the first sealing material 21 and the second sealing material 22. The sealing material 24 is for further reducing the intrusion of moisture into the photoelectric conversion unit 11, and a member having lower moisture permeability than the first sealing material 21 and the second sealing material 22 is used. As such a sealing material 24, a resin such as polyethylene, an elastic body made of rubber such as butyl rubber or ethylene propylene rubber, or a mixture of the above-described resin and rubber can be used.

Further, as the sealing material 24, a polymer material in which an adsorbent is dispersed may be used. As such an adsorbent, those having the property of chemically adsorbing moisture may be used, or those having the property of physically adsorbing moisture may be used. The adsorbent that chemically adsorbs moisture has a property of chemically adsorbing with moisture and chemical reaction. For example, calcium oxide (CaO), sodium oxide (Na ₂ O), magnesium oxide (MgO), chloride calcium (CaCl _2), anhydrous sodium sulfate _(Na 2 _SO 4), and the like copper sulfate anhydrous salt (CuSO ₄₎ or calcium sulfate (CaSO _4). An adsorbent that physically adsorbs moisture adsorbs moisture by van der Waals force generated between the surface of the adsorbent and moisture. For example, molecular sieves such as zeolite, silica gel (SiO ₂ .nH ₂ O), inorganic materials having a porous surface such as alumina, allophane or activated carbon.

Further, from the viewpoint of further restricting the expansion and contraction of the first sealing material 21 and the second sealing material 22 to further increase the sealing reliability, the thermal expansion coefficient of the sealing material 24 is set to be the first sealing material 21. And it may be smaller than the thermal expansion coefficient of the second sealing material 22. For example, the linear expansion coefficient of the sealing material 24 may be 0.05 to 0.9 times the linear expansion coefficient of the first sealing material 21 and the second sealing material 22.

  Moreover, the 1st board | substrate 20 and the 2nd board | substrate 23 are for protecting the photoelectric conversion part 11, For example, glass, ceramics, resin, a metal, etc. are used. When light is incident on the photoelectric conversion unit 11 from the second substrate 23 side in the photoelectric conversion module 200, the second sealing material 22 and the second substrate 23 correspond to light used for photoelectric conversion of the photoelectric conversion unit 11. And may have translucency. As the 1st board | substrate 20 and the 2nd board | substrate 23, white tempered glass about 1-10 mm in thickness may be used, for example.

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

DESCRIPTION OF SYMBOLS 11: Photoelectric conversion part 20: 1st board | substrate 21: 1st sealing material 22: 2nd sealing material 23: 2nd board | substrate 24: Sealing material 200: Photoelectric conversion module

Claims (4)

A first substrate;
A first encapsulant disposed on the first substrate;
A photoelectric conversion unit disposed on a central portion of the upper surface of the first sealing material;
A second sealing material that is disposed on the first sealing material and seals the photoelectric conversion unit, and has a larger diffusion coefficient of water than the first sealing material;
A photoelectric conversion module comprising: a second substrate disposed on the second sealing material.   The photoelectric conversion module according to claim 1, wherein a saturation water absorption rate of the second sealing member is larger than a saturation water absorption rate of the first sealing member.   The photoelectric conversion module according to claim 1, further comprising a sealing material that covers side surfaces of the first sealing material and the second sealing material.   The photoelectric conversion module according to claim 1, wherein the second sealing material and the second substrate have translucency with respect to light that can be photoelectrically converted by the photoelectric conversion unit.

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