CN100431178C - Photoelectric module and manufacturing method thereof - Google Patents

Abstract

The invention relates to a photoelectric module comprising a front plate (2) and a back plate (3). In addition, an organic seal (4) is disposed between the plates and defines an inner sealed volume (5), which is maintained at a subatmospheric pressure and which contains the photovoltaic cell (1). The aforementioned seal (4) is an organic part, such as thermoplastic or polybutylene. According to the method of the invention, a low barometric pressure is generated by means of pumping. The method may include inert gas purge, hypobaric pressure build-up and pressure seal (P1). The method may also comprise: partial sealing of the module, leaving two openings in the seal (4); flushing of the internal volume with inert gas by means of the two openings; establishment of a low atmospheric pressure; and, subsequently, Block the opening.

Description

Photoelectric module and manufacturing method thereof

field of invention

The invention relates to a photovoltaic module comprising an assembly of photovoltaic cells arranged side by side between a front plate and a back plate, and a tight internal volume arranged between said plates and defined at a pressure lower than atmospheric pressure A seal, the photovoltaic cell is arranged in the closed internal volume.

Background technique

Traditionally, to manufacture photovoltaic modules, photovoltaic cells are covered with a network of electrodes and connected to each other by soldered metal strips. The assemblies thus formed are then placed between two polymer plates which themselves are held between two glass substrates. The assembly is then heated to about 120° C. to greatly soften the polymer in order to make it transparent and airtight and to ensure the mechanical consistency of the modules. However, hermeticity, in particular against the penetration of moisture, is generally not achieved over the long term.

This type of manufacturing method consumes large quantities of very expensive tin-based, lead-based and zinc-based fluxes. Soldering itself is an expensive, mechanically complex operation that requires rotating the battery and involves a non-negligible risk of damaging the battery.

To achieve hermeticity of the module, non-mineral seals can be deposited around all cells or the spaces remaining between the glass substrates can be filled with organic resins.

Document WO 03/038911 describes a method for the manufacture of a photovoltaic module comprising an assembly of photovoltaic cells arranged side by side between a front and a back plate. Mineral seals disposed between the plates define a hermetic interior volume in which all cells are disposed. The sealing operation is carried out at a temperature between 380°C and 480°C for a period of less than 30 minutes. During sealing, the sealing material softens considerably and creates a tightly closed inner volume with respect to the outside, which prevents any moisture from entering the module during its entire use. The pressure of the internal volume is about one atmosphere at the sealing temperature. After cooling to room temperature, the final pressure is lower, in the range of 400 mbar. A negative pressure with respect to the outside is therefore automatically formed inside the module and causes a force to be exerted on the cells through the front and back plates. This force ensures contact between the battery and the connecting conductors deposited on the front and back plates without soldering having to be carried out between the battery and the connecting conductors. However, applying a temperature of about 400° C. tends to impair the quality of photovoltaic cells currently available on the market.

Photovoltaic cells can be formed on bulk silicon substrates cut into wafers having a thickness of several hundred micrometers. The substrate may be formed of a semiconductor layer, single crystal silicon or polycrystalline silicon deposited on a glass or ceramic substrate. It has a network of narrow electrodes on its surface, usually made of silver or aluminum, structured to allow current to flow to one or more main electrodes, also made of silver or aluminum, with a width of 1 to several millimeters .

In known photovoltaic modules, a rear connection conductor associated with a first cell is connected to a front connection conductor associated with an adjacent second cell. If the module comprises more than two cells, the back connection conductor of the second cell is then connected to the front connection conductor of the next cell so that all cells are electrically connected in series. In fact, the back connecting conductor of a cell and the front connecting conductor associated with an adjacent cell can be formed by one and the same interconnecting conductor. The connection conductors of the terminal cells serve as outer connectors.

An assembly of photovoltaic cells in matrix form may include transverse connecting conductors electrically connecting the cells in parallel. Usually, the lateral connection conductors formed by the copper core and the tin-lead alloy deposited on the surface are soldered to the connection area of the battery with the tin-lead alloy. The connecting conductors can also be obtained by depositing a silver paste according to the desired pattern on the support plate of the module, followed by annealing at high temperature.

In document DE-A-4128766, front and back connecting conductors are formed on the inner faces of the front and back glass substrates, facing the position of each cell. The connecting conductors are then soldered to the cells and to interconnection elements configured to connect the cells in series. The spaces remaining between the glass substrates are then filled with organic resin.

Furthermore, in some known batteries (US patent 6384317), the positive and negative poles of the battery are arranged on one of its faces, in particular on its back.

Soldering the conductors and assembling the battery is a hindrance since it is a long and expensive operation that damages the battery and results in high manufacturing costs.

Contents of the invention

The purpose of the present invention is to overcome these disadvantages and, in particular, to achieve modules exhibiting good long-term hermeticity and to simplify the manufacturing method of photovoltaic modules so that their manufacture can preferably be carried out at room temperature while reducing manufacturing costs.

According to the invention, this object is achieved by the appended claims, and in particular by the seal being a flexible organic seal.

Description of drawings

Other advantages and characteristics will become more apparent from the following description of specific embodiments of the invention, given by way of non-limiting examples only and in conjunction with the accompanying drawings, in which:

1 and 2 show the assembly steps of a particular embodiment of the method for the manufacture of photovoltaic modules according to the invention.

3 and 4 show a particular embodiment of the evacuation step of the method for the manufacture of a photovoltaic module according to FIG. 2 in cross-section along the line A-A.

5 and 6 show two particular embodiments of photovoltaic modules according to the invention.

7 and 8 show two specific embodiments of the method for the manufacture of photovoltaic modules according to the invention.

Figures 9 and 10 show a particular embodiment of a photovoltaic module according to the invention in cross-section along line B-B and in bottom view, respectively.

11 and 12 show various specific embodiments of interconnecting conductors of photovoltaic modules according to the invention.

Detailed ways

FIG. 1 shows the assembly of a photovoltaic cell 1 and an organic seal 4 arranged side by side between a front sheet 2 and a back sheet 3 . For assembly, plates 2 and 3 and photovoltaic cell 1 are kept parallel to each other. In order to protect the photovoltaic cell 1 during assembly, the cell may be pre-fixed on one of the plates, for example on the back plate 3 , prior to the assembly of the plates 2 and 3 , as the corresponding electrical interconnection conductors may be. For example, they can be pre-glued by means of solvent-free organic glues, for example by derivatives of the polyvinyl family. The glue can consist of the same material as the organic seal 4 , for example a polybutene derivative. An organic seal 4 may then be deposited on one of the plates 2 and 3 , for example on the front plate 2 , around the set of photovoltaic cells 1 . The front sheet 2 and the back sheet 3 are then sealed by means of an organic seal 4, which may be thermoplastic, for example of the polybutene family. The organic seal 4 may be made of any organic material capable of providing an effective barrier to moisture and gases, especially oxygen. The closed inner volume 5 is filled with an inert gas. The inert gas may consist of any gas, pure or mixed, compatible with the material of the components arranged in the closed volume, such as argon. The gas concentration, in particular the argon concentration, can be determined by spectroscopic analysis, which enables the gas pressure and gas composition within the closed inner volume 5 to be controlled.

During assembly, the module assembly is pressed, preferably by applying a pressure P1 on the plates 2 and 3 , as shown in FIG. 2 . In this way, the organic seal 4 defines a closed inner volume 5 in which all photovoltaic cells 1 are arranged. The material of the organic seal 4 is preferably of the polybutene family, free of solvents, eg polyisobutylene. After it has been assembled and pressed, the polybutylene seal remains flexible and at the interface with the plates 2 and 3 its color, initially dull black, changes to a glossy black which makes a tight seal if required properties can be checked. Although the seal retains some flexibility, the mechanical properties of the seal remain unchanged. The step of pressing the module thereby enables the thickness of the module to be controlled.

According to the invention, a negative pressure is created by evacuation to ensure a sufficient contact pressure to achieve the electrical conduction necessary for a good functioning of the module without soldering of the interconnecting contacts between the cells. In a first particular embodiment of the manufacturing method shown in FIGS. 3 and 4 , evacuation is performed after sealing of the module. The suction can generate a negative pressure of up to 0.5 bar in the closed inner volume 5 . Evacuation (schematically indicated by dashed arrows) is performed, for example, by means of a piercing tool, for example by means of a syringe 6 passing through the organic seal 4 and connected to an external aspirating device (not shown). The piercing tool is dimensioned so that when it is removed, the seal is not compromised. In Figure 3, the syringe 6 is inserted into the organic seal 4 near the corner of the module. The residual flexibility of the organic seal means that the small opening through which the syringe enters will automatically close when the syringe is removed. As shown in Figure 4, when the syringe 6 is removed, the application of a pressure P2 on the two vertical faces 7a and 7b of the seal on each side of the opening through which the syringe enters enables the closure of this opening and ensures the tightness of the seal sex. Before generating the underpressure, the method preferably includes a purging step with an inert gas, which can be carried out by means of two injectors, the first injector evacuating and the second injector simultaneously supplying the inert gas.

After applying the organic seal 4 , the closed inner volume 5 is kept at a pressure significantly below atmospheric pressure, which causes a force to be exerted on the photovoltaic cell 1 through the front plate 2 and the back plate 3 . This force ensures contact between the cells and the connecting conductors implementing the electrical connection between the cells without having to deposit any solder between the cells and the connecting conductors. The material forming the connecting conductor can be copper-based, copper alloy or any other high-conductivity metal material that ensures good contact with the photovoltaic cell 1 under negative pressure.

The hermeticity of the organic seal 4 is obtained after pressing the front and back plates, which are present at the periphery of the entire module. The thickness of the seal, determined by the amount of organic material deposited and the pressure at which the seal is performed, then remains constant. Since the method is performed at room temperature, it is compatible with all photovoltaic cells.

The organic seal 4 , in particular when it is made of polybutene, retains a certain elasticity after application. As shown in Figure 5, a reinforcement system 8 may be arranged around the seal 4 to increase the reliability of the module.

The front plate 2 and the back plate 3 may both be glass plates, for example made of soda-lime glass having a thickness of 1.6 to 6 mm, typical values of 3 mm to 4 mm for the front plate 2 and 2 mm to 4 mm for the back plate 3 production. Advantageously, the glass is clear or colorless glass, ie contains a small amount of iron, since such glass transmits light very well. Glass can also undergo thermal hardening to increase its mechanical strength. However, the front plate 2 of the photovoltaic module is preferably made of glass, while the back plate 3 is made of a rigid plate, insulating at least on the surface, made of plastic or metal, such as aluminum or surface treated so that it does not conduct electricity on the surface Stainless steel. Such a board enables photovoltaic cells to be protected while considerably reducing weight (up to 2 times).

Furthermore, the method may comprise a step of chemical etching of the glass front, for example alkaline etching, carried out before the module is assembled, so as to roughen the inner face 9 of the front glass, ie the face facing the photovoltaic cells 1 , as shown in FIG. 5 . In this way, the radiation reflected by the photovoltaic cells 1 is partially recycled by multiple reflections on different areas of the surface of the front plate 2 . This treatment can be carried out by anisotropic etching of the glass, the outer surface of the front plate 2 being protected so as to give a texture to the inner face 9 of the front plate 2 . This technique enables to obtain an increase in the efficiency of the photovoltaic module. The texturing can also be performed by hardening the glass after protecting the outer surface of the glass, for example by chemical etching.

Furthermore, between the photovoltaic cells 1 and the back plate 3 and/or between the photovoltaic cells 1, the photovoltaic module shown in FIG. ) basically corresponds to radiation in the visible spectral band. Substance 10 includes, for example, polymethyl methacrylate (PMMA) and/or metal salts and/or pigments formed from a compound mainly containing lanthanum-based, erbium-based, terbium-based, neodymium-based and praseodymium-based rare earths , mixed oxides of alkali metals or metals belonging to the alkaline earth metals. These oxides convert ultraviolet radiation into visible radiation having a wavelength comprised between 550 nm and 650 nm. Thus the efficiency of the photovoltaic module can be increased. The absorption of infrared radiation enables the operating temperature of the photovoltaic cell to be lowered.

In a second particular embodiment of the manufacturing method, shown in Figure 7, the method comprises in sequence: assembly and partial sealing of the modules, leaving two openings 13a and 13b in the seal 4; by means of the two openings 13a and 13b , flushing the inner volume with an inert gas, schematically indicated by dashed arrow 14 . The negative pressure is then generated by suction via the two openings 13a and 13b. After pumping, the two openings 13a and 13b are closed without weakening the negative pressure. It is also possible to close one of the openings 13 after purging and to evacuate by means of the other opening 13 and then close it.

In a third particular embodiment of the manufacturing method, shown in FIG. 8 , the method sequence includes the assembly of the modules and, in a tight enclosure 17 , purging with inert gas and establishing a negative pressure by evacuation. The sealing of the front panel 2 and the back panel 3 is then performed by pressing 18 the seal 4 , which is arranged between the two preformed parts 19 and 20 , which enables a closed enclosure 17 to be established.

The modules according to the invention can be of large size, the glass having a corresponding thickness, and no frame has to be added to it.

The invention is applicable to any type of photovoltaic module, including modules comprising photovoltaic cells 1 each having positive and negative electrodes arranged on the same side of the cell, as described above.

The photovoltaic module shown in FIG. 9 comprises photovoltaic cells 1 arranged side by side between the inner faces of the front plate 2 and the back plate 3 . For clarity, only three batteries 1a, 1b and 1c are shown in FIG. 9 . The positive and negative terminals of each battery are provided on its back.

The connection of the positive pole of a battery to the negative pole of an adjacent battery is achieved very simply by means of at least one interconnecting conductor formed by a metal strip, for example deposited on the back plate before the battery is mounted in place, for example by screening 3 Strips of silver paste on the inner face. The electrical interconnection of the cells can also be done by means of metal conductors prefixed with glue on the back plate of the module.

In Figures 9 and 10, the metal strip 11a deposited on the back plate 3 is positioned on the area connecting the positions of the two adjacent cells 1a and 1b so as to be on the back of the cells 1a and 1b respectively with the positive and positive poles of the cells 1a and 1b. The negative terminal of battery 1b is in contact. In Fig. 10, this region appears as a step. A silver paste strip 11b connecting the positive terminal of the battery 1b to the negative terminal of the battery 1c is provided on the back plate 3 in a similar manner. In this way, a network of interconnecting conductors 11 is formed on the backplane 3 before the cells are mounted in place. When the back side is not optically active, there is no limit to the light transmission of the back sheet 3, and the network pattern of silver paste strips 11 is chosen so that the conductivity is maximized. According to a first alternative embodiment, the width of the silver paste strips 11 is large, eg each silver paste strip 11 can have a width comprised between 3 mm and 10 mm, more generally comprised between 3 mm and 5 mm.

Interconnects can also be prepared through screens when the positive and negative terminals of the battery are arranged on the front and back plates, respectively.

According to the path described below, the seal 4 is deposited on one of the plates 2 and 3 or on both plates, ie along the four sides.

In the particular embodiment of FIG. 10 , the organic seal 4 is located at the periphery of the common surface of both the front and back plates 2 and 3 . It is arranged on the periphery of the backplane 3 in such a way, except on the left side of the backplane 3, to allow access to the external connection conductor 12 from the outside. For example, the outer connection conductors 12 of the terminal cells ( 1 a and 1 c ) may protrude outward beyond the seal 4 .

As mentioned above, the seal 4 may then be arranged between the front plate 2 and the back plate 3, at the periphery of the module, thereby defining a closed inner volume in which all the cells 1 are arranged.

The seal 4 has a thickness of several hundreds of micrometers, which depends inter alia on the thickness of the battery 1, which must be added to the thickness of the metal strip 11 forming the interconnecting conductor, which is formed on the front face of the back plate 3 by placing the battery 1a The positive terminal of the battery 1b is connected to the negative terminal of the adjacent battery 1b to connect the batteries 1 in series.

In FIG. 11, an interconnect conductor 15 connects the front surface of a first battery 1a and the back surface of an adjacent second battery 1b. The interconnect conductor 15 is formed of a rigid material that retains its overall electrical conductivity, such as an alloy of copper and manganese or of hardened copper. The first wavy end 16 a is arranged between the front surface of the first battery 1 a and the inner surface of the front plate 2 . The second wavy end 16 b is arranged between the back surface of the second battery 1 b and the inner surface of the back plate 3 . In the particular embodiment shown in Fig. 12, the intermediate portion of the interconnecting conductor arranged between adjacent cells 1a and 1b is not corrugated. In an alternative embodiment, one of the ends 16 may be realized without corrugations.

In a similar manner, the corrugated interconnecting conductor 15 may be used to connect the positive and negative terminals of two adjacent single-sided cells, ie each cell has its positive and negative terminals arranged on the same side of the cell. Such corrugations enable improved contact between the battery 1 and the interconnecting conductor 15 by means of the spring effect.

The interconnecting conductors 15 formed of rigid material connecting the photovoltaic cells 1 to each other may have any cross-sectional shape, such as a U-shaped, W-shaped or V-shaped cross-section, as shown in FIG. A spring effect is obtained between. The spring effect compensates for changes in the thickness of the battery and/or of the front and back plates as well as changes due to thermal expansion of the elements making up the module, thus making it possible to limit the risk of damage to the battery while ensuring that the contact between the battery 1 and the interconnecting conductors 15 Constant electrical contact. The interconnect conductor 15 may also be helical.

The method according to the invention can be applied to the manufacture of photovoltaic modules and thus solar generators comprising square, rectangular or circular photovoltaic cells, the characteristic dimensions of which can range from a few centimeters to tens of centimeters. The battery is preferably a square battery with sides having dimensions comprised between 8 cm and 30 cm.

The invention is not limited to the specific embodiments described and shown above. In particular, strips of silver paste can be deposited on the inner face of the front plate. The invention is applicable to all types of photovoltaic cells, not only silicon, monocrystalline or polycrystalline photovoltaic cells, but also gallium arsenide cells, cells formed from silicon strips, cells formed from silicon beads inserted into conductive plates ), or photovoltaic cells formed by deposition and etching of thin films of silicon, copper/indium/selenium, or cadmium/tellurium on glass or ceramic plates.

Claims (20)

1. A photovoltaic module comprising: an assembly of photovoltaic cells (1) arranged side by side between a front plate (2) and a back plate (3); and a seal (4), which is arranged between the front plate (2) and the back plate Between the plates (3) and delimiting a closed internal volume (5) maintained at a pressure lower than atmospheric pressure, the photovoltaic cell (1) is arranged in the closed internal volume, the module is characterized in that the seal (4) is a flexible Organic seal. 2. Module according to claim 1, characterized in that the seal (4) is thermoplastic. 3. Module according to claim 2, characterized in that the seal (4) is of the polybutene family. 4. Module according to any one of claims 1 to 3, characterized in that it comprises a reinforcement system (8) arranged around the seal (4). 5. Module according to claim 1, characterized in that the front panel (2) is made of glass and the rear panel (3) is made of glass or a plate of plastic or surface-treated metal. 6. A module according to claim 1, characterized in that the module comprises a substance (10) which absorbs infrared and ultraviolet radiation and emits radiation in the visible spectral band substantially corresponding to the maximum of the absorption band of the photovoltaic cell (1). 7. The module according to claim 6, characterized in that the substance (10) comprises at least one material selected from the group consisting of: polymethylmethacrylate; metal salts; and mainly containing rare earths, alkali metals or belonging to alkaline earths A mixture of metal oxides of metals. 8. Module according to claim 1, characterized in that it comprises interconnecting conductors (15), formed of rigid material, connecting the photovoltaic cells (1) to each other and having a cross-sectional shape such that between the photovoltaic cells (1) and the corresponding A spring effect is obtained between said plates (2 and 3). 9. The module according to claim 8, characterized in that: the interconnecting conductor (15) connects the front of the first cell (1a) and the back of the adjacent second cell (1b), the first of the interconnecting conductor (15) One end (16a) is arranged between the front face of the first cell (1a) and the inner face of the front plate (2) and the second end (16b) of the interconnecting conductor (15) is arranged at the second cell (1b ) and the inner surface of the back plate (3), at least one of the first end and the second end is corrugated. 10. A method of manufacturing a photovoltaic module according to claim 1, characterized in that it comprises the deposition of the organic seal (4) and the formation of a negative pressure by evacuation, and It includes in sequence the assembly of the module and, in a closed enclosure, flushing with inert gas, creating a negative pressure by evacuating and pressing the seal (4) with the front (2) and back (3) to seal . 11. Method according to claim 10, characterized in that it comprises in sequence: assembly and partial sealing of the module so as to leave two openings in the seal (4); passage of the inner volume with inert gas by means of the two openings purging; creating said negative pressure by suction; and closing the opening. 12. A method according to claim 10, characterized in that after sealing of the module, a negative pressure in said closed internal volume (5) is created by suction by means of a piercing tool through the organic seal. 13. A method according to claim 10, characterized in that it comprises the control of the gas pressure and gas composition in the closed inner volume (5). 14. A method according to claim 10, characterized in that it comprises the step of pressing the module to control the thickness of the module. 15. The method according to claim 10, characterized in that, before the assembly of the plates (2 and 3), the photovoltaic cells (1) and the interconnecting conductors (15) connecting the photovoltaic cells (1) to each other are fixed on the on one of the boards (3). 16. A method according to claim 15, characterized in that, before assembly, the photovoltaic cell (1) and the interconnecting conductor (15) are fixed on one of the plates (3) by means of a solvent-free organic glue. 17. The method according to claim 16, characterized in that the solvent-free organic glue comprises polyethylene and polybutene derivatives. 18. A method according to claim 10, characterized in that the front panel (2) is made of glass, the method comprising a chemical treatment step of the front glass panel (2) before assembly so as to roughen the inner face of the front panel (2) . 19. A method according to claim 10, characterized in that each of the photovoltaic cells (1) has a positive pole and a negative pole arranged on the same side of the cell, before the cell (1) is assembled in place, the method comprises only the Depositing on the inner face of one of the plates (3) at least one metal strip (11) which connects the positive pole of said battery (1a) to the negative pole of an adjacent said battery (1b) thereby connecting said battery (1b) in series Battery. 20. A method according to claim 19, characterized in that said metal strip is formed by a silver paste strip (11) arranged to connect the positive pole of said battery (1a) and the negative pole of an adjacent said battery (1b).

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