PHOTOVOLTAIC MODULE PROVIDED WITH A H2O GAS PERMEATION BARRIER LAYER

Abstract

A photovoltaic module including: several photovoltaic cells disposed side by side, and electrically connected to each other, an encapsulating assembly, configured to encapsulate the photovoltaic cells, and a barrier layer disposed at an interface between the encapsulating assembly and at least one photovoltaic cell, the barrier layer being configured to at least partially cover the at least one photovoltaic cell, and to have an O.sub.2 gas transmission rate lower than that of the encapsulating assembly, and a water vapor transmission rate less than or equal to 10.sup.-2 g/m.sup.2/day measured at 38° C. and 85% humidity level, so as to form a barrier to the transmission of water vapor and O.sub.2 gas.

Claims

1. A photovoltaic module comprising: several photovoltaic cells disposed side by side, and electrically connected to each other, an encapsulating assembly, configured to encapsulate the photovoltaic cells, and a barrier layer disposed at an interface between the encapsulating assembly and at least one photovoltaic cell, the barrier layer being configured to at least partially cover the at least one photovoltaic cell, and to have an O.sub.2gas transmission rate lower than that of the encapsulating assembly, and a water vapor transmission rate less than or equal to 10.sup.-2 g/m /day measured at 38° C. and 85% humidity level, so as to form a barrier to the transmission of water vapor and O.sub.2gas, and wherein a surface of the barrier layer has hydroxyl bonds.

2. The photovoltaic module according to claim 1, wherein the barrier layer layer comprises a material selected from silicon oxides, titanium oxides, alumina, or a multilayer stack of several of these materials.

3. The photovoltaic module module according to claim 1, wherein the barrier layer layer has a thickness comprised between 15 and 50 nm.

4. The photovoltaic module according to claim 1, wherein the at least one photovoltaic cell comprises at least one sensitive layer layer which is capable of degrading in the presence of humidity and/or O.sub.2gas, and wherein the barrier layer layer at least partially covers the at least one sensitive layer layer.

5. The photovoltaic module according to claim 1, wherein the photovoltaic cells each have a separate substrate and are electrically connected to each other by electrical contacts comprising at least one electrical connection tape deposited on the barrier layer of each of the photovoltaic cells cells so as to form an electrical interconnection network, the electrical interconnection network being connected respectively to the cathode and to the anode of the photovoltaic module module by a first output electrical connection and a second output electrical connection deposited on the barrier layer layer.

6. The photovoltaic module according to claim 1,wherein the photovoltaic cells (1a) are formed on a common substrate and are electrically connected to each other by an internal interconnection network, the recovery of contacts between the internal interconnection network, the cathode and the anode of the photovoltaic module module are produced respectively by a first output electrical connection and a second output electrical connection deposited on the barrier layer layer.

7. The photovoltaic module according to claim 1, which further comprises a first protective layer layer and a second opposite protective layer the first protective layer and the second protective layer layer being laminated on either side of the encapsulating assembly, wherein are encapsulated the photovoltaic cells, the electrical contacts and the barrier layer layer.

8. The photovoltaic module according to claim 1, which further comprises a gasket disposed against a peripheral side edge of the encapsulating assembly.

9. A method for manufacturing a photovoltaic module according to claim 1, wherein the barrier layer is produced by an atomic layer deposition method.

10. The method for manufacturing a photovoltaic module according to claim 9, wherein the atomic layer deposition method is completed by a cycle consisting of a H.sub.2O oxidizing agent pulse so as to obtain hydroxyl bonds on the surface of the barrier layer, followed by a purge with an inert gas.

11. The method for manufacturing a photovoltaic module according to claim 9, which comprises a step i) of electrically connecting the photovoltaic cells to each other by depositing an electrical connection tape on the barrier layer of each of the photovoltaic cells and/or a step ii) of recovery of the contacts carried out by forming a first output electrical connection and a second output electrical connection on the barrier layer.

12. The method for manufacturing a photovoltaic module according to claim 9, which comprises: a step j) of forming a multilayer structure formed successively by: the first protective layer, at least one first encapsulation film, the photovoltaic cells electrically connected to each other, at least one second encapsulation film, and a second protective layer, and a step k) of laminating the multilayer structure obtained in step j) so as to form the encapsulating assembly from the first encapsulation film and the second encapsulation film, the encapsulating assembly, configured to encapsulate the photovoltaic cells, being disposed between the first and second protective layers.

Description

[0066] Other aspects, objects and advantages of the present invention will appear better on reading the following description of two embodiments thereof, given by way of non-limiting example and made with reference to the appended drawings. In the remainder of the description, for the sake of simplification, identical, similar or equivalent elements of the different embodiments bear the same reference numerals. The figures do not necessarily respect the scale of all the elements represented so as to improve their readability and in which:

[0067] FIG. 1 represents a schematic sectional view of a portion of a photovoltaic module of thin-layer cells according to a first embodiment of the invention.

[0068] FIG. 2 represents an enlarged schematic view of a thin-layer cell according to the embodiment of FIG. 1.

[0069] FIG. 3 represents a schematic view from above of a portion of a photovoltaic module of thin-layer cells according to the embodiment of FIG. 1.

[0070] FIG. 4 represents a schematic sectional view of a portion of a photovoltaic module of tandem cells according to a second embodiment of the present invention.

[0071] FIG. 5 represents an enlarged schematic view of a tandem cell according to the embodiment of FIG. 4.

[0072] FIG. 6 represents a schematic view from above of a portion of a photovoltaic module of tandem cells according to the embodiment of FIG. 4.

[0073] FIG. 7 represents the results of experimental measurements of the adhesion strength of an encapsulating assembly on an alumina barrier layer according to different barrier layer deposition recipes.

[0074] FIG. 8 represents the results of experimental measurements of efficiency of different cells comprising electrical contacts deposited before or after the deposition of the alumina barrier layer.

[0075] As illustrated in the figures, the invention relates to a photovoltaic module 100 comprising photovoltaic cells 1a, formed and on a common substrate 11 (FIGS. 1 to 3) or photovoltaic cells 1b each having a separate substrate and disposed side by side (FIGS. 4 to 6), the module 100 comprising a barrier layer 3 covering at least in part the side edges and one face of the photovoltaic cells 1a,b, itself being encapsulated by an encapsulating assembly 2.

[0076] In a first embodiment illustrated in FIGS. 1 to 3, the photovoltaic module 100 is formed of several thin-layer photovoltaic cells 1a, formed on a common substrate, an encapsulating assembly 2, and an alumina barrier layer 3 disposed at the interface between the encapsulating assembly 2 and the photovoltaic cells 1a. More precisely, the barrier layer 3 covers the photovoltaic cells 1a so as to form a barrier to the transmission of water vapour, O.sub.2 gas, or even ammonia or acetic acid (FIG. 2). The barrier layer 3 is made of alumina and has indeed transmission rates for water vapor and O.sub.2 gas lower than those of the encapsulating assembly 2. The barrier layer 3 is deposited by ALD over a thickness of approximately 30 nm so as to present a WVTR rate less than or equal to 10.sup.-2 g/m.sup.2/day measured at 38° C. under a humidity rate of 85%. According to different efficiency needs of the barrier layer, the thickness of the layer varies between 15 and 50 nm.

[0077] This barrier layer 3 deposited by ALD is dense, it has few defects so that a fine thickness is sufficient to form a barrier to the transmission of the majority of gases. The production of electrical contacts remains possible through this fine thickness, as developed hereinbelow.

[0078] According to possible embodiments, the barrier layer 3 is made of alumina, silicon oxide, titanium oxide, or formed from a multilayer stack of several of these materials.

[0079] In this first embodiment, the cells 1a comprise a sensitive layer 4, that is to say a layer 4 which is capable of degrading more or less rapidly in the presence of water vapor and/or O.sub.2 gas, for example a sensitive layer 4 from perovskite or organic material. In this case, the barrier layer 3 covers said sensitive layer 4, without however being in direct contact with the latter. The enlargement of FIG. 2 illustrates in detail the covering of the sensitive layer 4 when it is an active layer located within a stack of layers forming the photovoltaic cell. It is possible to observe in particular that the barrier layer 3 covers at least partially the side edges 8, 9 of each of the cells and at least the rear face 6 of the cell 1a. Indeed, the protection of the front face 5 of the cell is already ensured at the time of its formation: the thin-layer cell 1a comprising the perovskite layer is formed from a support 11 intended to form the front face 5 of the cell (FIG. 2). This support 11 meets transparency criteria and it is also selected to ensure the function of the first protective layer 11, in particular against the permeation of H.sub.2O and O.sub.2 gases. The support is then selected so as to have a WVTR rate of less than 10.sup.-2 g/m.sup.2/day. It may consist of a glass plate, or of a highly gas-barrier flexible film such as the 510-F film from 3M®.

[0080] Insofar as the rear face 6 of the cell 1a is protected by the alumina barrier layer 3, the second protective layer 13 disposed on the rear face 6 of the module may be chosen to have a higher WVTR rate, for example lower than or equal to 1 g/m.sup.2/day (FIG. 1).

[0081] According to a particularity of this embodiment, the cells 1a are electrically connected to each other by an internal interconnection network, the recovery of contacts between the internal interconnection network and the cathode, and mutually between the internal interconnection network and the anode of the photovoltaic module 100 is produced respectively by a first output electrical connection 15 and a second output electrical connection 15′deposited on the barrier layer 3 (step ii). FIG. 3 notably illustrates the output electrical connections 15 deposited on the barrier layer 3. These are electrically conductive adhesive tapes, sensitive to pressure and configured to connect the internal interconnection network between the cells 1a to the cathode and to the anode.

[0082] A first encapsulation film and a second encapsulation film from ionomer or a combination of EVA and from ionomer are each deposited on one face of the photovoltaic cells so as to form the encapsulating assembly 2 during a subsequent step k) of lamination.

[0083] The first protective layer 11 and the second protective layer 13 are then disposed on either side of the photovoltaic cells 1a and their electrical contacts 15, 15′ and the lamination step is carried out at a temperature less than or equal to 130° C. and a pressure of approximately 100 kPa (1000 mbar step k), without affecting cell performance as can be shown later in FIG. 8.

[0084] FIGS. 4 to 6 illustrate a second embodiment of the invention which differs from the first mode and in that the cells are, in particular, tandem cells 1b each having a separate substrate. These cells 1b comprise an active and sensitive layer 4 from perovskite disposed within an upper sub-cell 7. The barrier layer 3 is disposed so as to cover at least one front face 5 and side edges 8, 9 of the cell 1b (FIG. 5). The lower sub-cell comprising a silicon substrate, or a layer of CGIS on a support, forms an effective barrier to the permeation of H.sub.2O and O.sub.2 gases on the rear face 6 (FIG. 4).

[0085] Also visible in FIG. 6, the cells 1b are electrically connected to each other by electrical contacts comprising at least one electrical connection tape 14 (electrically conductive adhesive tapes) deposited on the barrier layer 3 of each of the cells 1b, so as to form an electrical interconnection network (step i). The electrical interconnection network is then connected respectively to the cathode and to the anode of the photovoltaic module 100 by a first output electrical connection 15 and a second output electrical connection 15′ deposited on the alumina barrier layer 3 (step ii or “recovery of contacts”) prior to formation of the encapsulating assembly 2.

[0086] The remainder of the method takes place according to the same concept as that of the cells 1a, an encapsulating assembly 2 is deposited in the form of a first encapsulation film and a second encapsulation film on either side of the cells 1b, two protective layers 11, 13 are disposed on either side of the structure 100 (multilayer structure formed in step j) and a lamination step is carried out (step k).

[0087] According to an arrangement not illustrated, a PIB seal is disposed against a peripheral side edge of the encapsulating assembly 2 before the arrangement of the first and second protective layers 11, 13 so as to reinforce the protection of the cells 1a and 1b.

[0088] In the two embodiments illustrated in FIGS. 1 to 6, the problem of the adhesion of the encapsulant, for example of EVA or of an ionomer, with the alumina barrier layer 3, arises. FIG. 7 illustrates the effects of different deposition formulas by ALD of the barrier layer 3 on the adhesion with an encapsulating assembly 2 based on ionomer. The y-axis illustrates the average strength over the width in N/cm and the x-axis references four different formulas. With the standard STD formula comprising the repetition of cycles including: a H.sub.2O pulse, a purge of H.sub.2O with N.sub.2, a TMA pulse and a purge of TMA with N.sub.2, the adhesion strength is very low. With formula V1 comprising the following cycles: TMA pulse and a purge of TMA with N.sub.2, a H.sub.2O pulse, a purge of H.sub.2O with N.sub.2, the adhesion strength is the best. The formula V2 combining the repetition of the cycles of the standard formula and a last cycle with a H.sub.2O pulse then a purge of H.sub.2O with N.sub.2 also gives very good results. The formula V3 using the cycles of the standard formula but comprising at the end of each cycle a H.sub.2O pulse followed by a purge of H.sub.2O with N.sub.2 leads to similar results. As indicated hereinabove, the probable explanation for the increase in adhesion, despite a deposition temperature below 130° C., lies in the formation of hydroxyl bonds at the surface of the barrier layer 3 and a purge making it possible to remove the reaction by-products.

[0089] FIG. 8 illustrates the results of experimental yield measurements carried out after the deposition of the barrier layer 3 and after the formation of the encapsulating assembly 2 from different cells. The measurements carried out on the first two cells show improved yields after formation of the encapsulating assembly 2 even if these barely exceed 5% (the y-axis represents the relative PCE). The measurements carried out on the third cell approach 10%. Finally, the measurements carried out on the fourth cell exceed 15% after formation of the encapsulating assembly 2. The notable difference between the first two cells and the last two cells lies in the fact that in the latter case, the electrical contacts 14, 15, 15′ were made on the barrier layer 3 whereas in the first two cases they were made before forming the barrier layer 3.

[0090] Thus, the present invention suggests a photovoltaic module 100 comprising a barrier layer 3 forming a barrier to the permeation of H.sub.2O gas which has barrier properties to water vapour, to O.sub.2 gases, to acetic acid and to ammonia. The gas barrier layer 3 is in fact a dense inorganic layer (non-porous, with low defect densities) in particular obtained by an ALD deposition technology. The barrier layer 3 is thus barely exposed to gas solubility problems. The latter may reverse the transmission behavior according to the gases (water and oxygen for example) in the case of organic materials, such as organic polymers. The barrier layer 3 according to the invention thus makes it possible to significantly improve the lifetime of the cells of a module 100, whether these cells 1 have a sensitive layer 4 or not. This barrier layer 3 does not interfere with the making of the electrical contacts 14, 15, which facilitates the manufacturing method and avoids the risk of leakage current.