Thin-film photovoltaic cell and method for manufacturing said photovoltaic cell

Abstract

Thin-film photovoltaic cell, which comprises a substrate (2) of transparent material, susceptible of being traversed by solar radiation, a first transparent electrode (3) placed on the substrate (2), a photo-active layer (4) placed on the first electrode (3), and a second electrode (5) placed on the photo-active layer (4). In addition, the photovoltaic cell comprises at least one bypass diode (6), which is arranged at a corresponding through opening (43) attained on the photo-active layer (4), so as to be placed on the non-irradiated side of the photovoltaic cell.

Description

[0001] THIN-FILM PHOTOVOLTAIC CELL AND METHOD FOR MANUFACTURING SAID PHOTOVOLTAIC CELL

[0002] DESCRIPTION

[0003] Field of application

[0004] The present invention regards a thin-film photovoltaic cell and a method for attaining said photovoltaic cell, according to the preamble of the respective independent claims.

[0005] The present photovoltaic cell is intended to be connected in series to other photovoltaic cells in order to form a photovoltaic module adapted to convert the solar radiation into electrical energy. Therefore, the photovoltaic cell, object of the present invention, and its attainment method are inserted in the field of production of modules for photovoltaic plants.

[0006] State of the art

[0007] As is known, a photovoltaic module is composed of multiple photovoltaic cells connected in series, which are capable of converting the light radiation coming from the sun into electrical energy.

[0008] In particular, a photovoltaic cell comprises a light radiation absorber layer, generally made of a semiconductor material, interposed between a positive electrode and a negative electrode, which allow the circulation of the generated electric current.

[0009] The most widespread photovoltaic cells on the market in recent years provide for an absorber layer made of crystalline silicon, made in a wafer, whose thickness is comprised in an interval of 100 - 200 micrometers.

[0010] For the purpose of reducing to a minimum the use of material for making the absorber layer, thin- film photovoltaic cells have been developed, which provide for an absorber layer provided with a thickness comprised between tens of nanometers and a few micrometers.

[0011] In particular, the absorber layer of the aforesaid thin-film photovoltaic cells can be made of amorphous silicon, cadmium telluride, copper-indium-gallium selenide, gallium arsenide, perovskite, etc.

[0012] Such thin-film photovoltaic cells comprise a substrate of transparent material, e.g. glass, on which the following are placed in sequence: a first layer of conductor material which forms a first electrode (positive or negative), the absorber layer, and a second layer of conductor material which forms a second electrode (with polarity opposite that of the first electrode).

[0013] In particular, the first electrode of a photovoltaic cell is connected to the second electrode of the successive photovoltaic cell, so as to make a series of photovoltaic cells which has a greater voltage at its ends than that of the single cells, so as to increase the voltage generated by the photovoltaic module and therefore reduce the resistive losses thereof.

[0014] Nevertheless, one drawback of the aforesaid connection in series of the photovoltaic cells is due to the possible partial shading of the module, where even only one of the cells of the series is darkened.

[0015] Indeed, when there is a shading on a photovoltaic cell, or generally when the illumination on the various cells is not uniform, the cells that receive less irradiation produce less electric current than the other cells of the module. Yet due to their connection in series, the total current of the module is limited, as is therefore the electrical energy production.

[0016] In addition, since the connection in series obliges the circulation of the same electric current in all of the module cells, a cell that is not producing electrical power since it is shaded will actually absorb power rather than generate it, inducing an inversion of the polarization at the ends of the cell (a phenomenon known with the name of reverse bias), which can lead to the reversal of the polarity of the voltage at the ends of the module, in particular when such module is inserted within a photovoltaic system comprising multiple modules.

[0017] In such circumstance, the shaded photovoltaic cell acts as a heating element, which is overheated due to the transiting electric current (phenomenon known with the name of hot-spot).

[0018] The above-described phenomena lead to a degradation, even with temporary effects, of the photovoltaic cell, negatively affecting the duration and the efficiency thereof, and, in extreme cases, to the breakage thereof, even permanent.

[0019] In order to avoid such phenomena, it is known to connect a bypass diode in parallel to a module of photovoltaic cells, such bypass diode provided with an anode and a cathode, connected respectively to the negative electrode and to the positive electrode of the module, such that the bypass diode itself is reversely polarized during the normal operation of the module (when all the photovoltaic cells of the module itself are uniformly irradiated) and is directly polarized when the module takes on a negative voltage. In this condition, the current passes through the bypass diode parallel to the module, therefore preventing the damage of the shaded photovoltaic cells, as is described in Vieira, Romenia G., et al. “A comprehensive review on bypass diode application on photovoltaic modules.” Energies 13.10 (2020): 2472.

[0020] In particular, as described in Ni, Zhenyi, et al. “Evolution of defects during the degradation of metal halide perovskite solar cells under reverse bias and illumination.” Nature Energy 7.1 (2022): 65-73, the threshold voltage beyond which the diode is directly polarized is sufficiently low to allow the conduction of the diode before the photovoltaic cells are degraded.

[0021] Nevertheless, the integration of the bypass diodes in the thin-film photovoltaic cells has in practice shown that it is not free of drawbacks.

[0022] A first drawback is represented by the fact that the integration of the bypass diodes in the thin-film photovoltaic cells is complex, since the connections in series of the latter for the formation of the module does not provide for the presence of conductors, rather than of monolithic type. A further drawback is represented by the fact that the thin-film photovoltaic cells have a low breakdown voltage due to the reduced thickness of the thin-film cell itself and, therefore, the diodes generally used in the silicon photovoltaic cells are ineffective in preventing the attainment of such breakdown voltage.

[0023] A further drawback is represented by the additional cost of the discrete bypass diodes that must be used for protecting each thin-film cell.

[0024] In order to protect the thin-film photovoltaic cells from the phenomenon of reverse polarization, various solutions have been proposed which provide for the use of a bypass diode.

[0025] For example, the patent application WO 2008030019 provides for attaining two superimposed layers of thin-film photovoltaic cells, in which one of the two layers, in specific conditions, carries out the function of bypass diode with protection of the single photovoltaic cells.

[0026] Otherwise, the patent application WO 2010077952 provides for positioning the bypass diode in an external zone with respect to the photovoltaic cell, precisely between the latter and a rear protective sheet of the panel, so as to be able to use the rear conductive surface of the photovoltaic cell as thermal dissipator for the bypass diode.

[0027] The patent application KR 20130139493 provides that the bypass diode be placed vertically above a photovoltaic cell attained on a printed circuit board, and which is connected through conductors to such printed circuit board, which is therefore common to the bypass diode and the photovoltaic cell.

[0028] The patent application WO 2013058724 provides for attaining the bypass diodes on the substrate semiconductor which composes the photovoltaic cell by means of the deposition of alternated superimposed doping zones, to be attained for example via laser or by means of printing techniques.

[0029] The patent application WO 2023094560 describes the attainment of a bypass diode integrated between two thin-film photovoltaic cells, by using deposition techniques typical for this type of technology.

[0030] The patent application WO 2023015994 also regards an integrated attainment of the bypass diode but specifically of perovskite type.

[0031] The patent application JP 2005268719 A describes a thin-film cell provided with a bypass diode which is placed between two adjacent cells, at an interruption opening of the second electrode which is attained for allowing the connection in series between two cells.

[0032] Nevertheless, the abovementioned solutions are invasive from a structural standpoint or, when integrated in the thin-film photovoltaic cell, require a particularly complex attainment, with significant energy expenditure of the photovoltaic cell itself.

[0033] Presentation of the invention In this situation, the problem underlying the present invention is therefore that of overcoming the drawbacks manifested by the photovoltaic cells of known type, by providing a thin-fdm photovoltaic cell and a method for attaining said photovoltaic cell which allow integrating a bypass diode within the structure of the photovoltaic cell itself in a simple and inexpensive manner.

[0034] A further object of the present invention is to provide a thin-film photovoltaic cell which integrates a bypass diode that allows a correction operation thereof, reducing the risk of hot-spot phenomena.

[0035] A further object of the present invention is to provide a thin-film photovoltaic cell which is long- lasting and provided with reduced degradation over time.

[0036] A further object of the present invention is to provide a thin-film photovoltaic cell and a method for attaining the same, which allow arranging bypass diodes without reducing the exposed surface area of the photovoltaic cell itself and therefore preventing losses via shading.

[0037] Brief description of the drawings

[0038] The technical characteristics of the invention, according to the aforesaid objects, can be clearly seen in the contents of the below-reported claims and the advantages thereof will be more evident in the following detailed description, made with reference to the enclosed drawings, which represent several merely exemplifying and non-limiting embodiments of the invention, in which:

[0039] - figure 1 shows a simplified scheme of a photovoltaic module provided with photovoltaic cells, object of the present invention;

[0040] - figure 2a shows a schematic plan view of a portion of the aforesaid photovoltaic module comprising several cells of the latter (which represents the detail II of figure 1);

[0041] - figure 2b shows a schematic plan view of the portion of the photovoltaic module in accordance with a different embodiment of the invention;

[0042] - figures 2c, 2d and 2e show a schematic plan view of the detail II of figure 1 in accordance with corresponding different embodiments of the invention;

[0043] - figure 3 shows a section view of the photovoltaic cells of figure 2a, in accordance with the trace III - III of figure 2a itself;

[0044] - figures 4a and 4b show the section of figure 3 indicating the electric current and voltages in two respective operative conditions of the photovoltaic cell (direct polarization and reverse polarization, respectively);

[0045] - figure 5 a shows the detail V of figure 3 relative to the layers of a photovoltaic cell, in accordance with a first embodiment variant in which the photovoltaic cell is arranged with structure p-i-n;

[0046] - figure 5b a detail relative to the layers of a photovoltaic cell in accordance with a second embodiment variant in which the photovoltaic cell is arranged with structure n-i-p;

[0047] - figure 6 shows a schematic representation of the layers of a bypass diode integrated in the present photovoltaic cell;

[0048] - figure 7a shows a schematic sectional representation of a first embodiment of the bypass diode, in accordance with a version applied to a photovoltaic cell with structure p-i-n (which represents the detail VII of figure 3);

[0049] - figure 7b shows a schematic sectional representation of the first embodiment of the integrated bypass diode, in accordance with a version applied to a photovoltaic cell with structure n-i-p;

[0050] - figure 8a shows a schematic sectional representation of a second embodiment of the bypass diode, in accordance with a version applied to a photovoltaic cell with structure p-i-n;

[0051] - figure 8b shows a schematic sectional representation of the second embodiment of the bypass diode, in accordance with a version applied to a photovoltaic cell with structure n-i-p;

[0052] - figure 9a shows a schematic sectional representation of a third embodiment of the bypass diode, in accordance with a version applied to a photovoltaic cell with structure p-i-n;

[0053] - figure 9b shows a schematic sectional representation of the third embodiment of the bypass diode, in accordance with a version applied to a photovoltaic cell with structure n-i-p;

[0054] - figure 10a shows a schematic sectional representation of a fourth embodiment of the bypass diode, in accordance with a version applied to a photovoltaic cell with structure p-i-n;

[0055] - figure 10b shows a schematic sectional representation of the fourth embodiment of the bypass diode, in accordance with a version applied to a photovoltaic cell with structure n-i-p;

[0056] - figure 11 shows a schematic sectional representation of the bypass diode of the detail XI of the embodiment of the invention of figure 2e, according to the trace XI - XI of figure 2e itself;

[0057] - figure 12 shows a first section view of the photovoltaic cells of figure 2d, in accordance with the trace XII - XII of figure 2d itself;

[0058] - figure 13 shows a second section view of the photovoltaic cells of figure 2d, in accordance with the trace XIII - XIII of figure 2d itself.

[0059] Detailed description of a preferred embodiment

[0060] With reference to the enclosed drawings, reference number 1 overall indicates a thin-film photovoltaic cell, according to the present invention, and such photovoltaic cell 1 is advantageously intended to be connected in series to other photovoltaic cells 1 in order to form a photovoltaic module 100.

[0061] With reference to the scheme of figure 1, the photovoltaic module 100 comprises multiple photovoltaic cells 1 connected in series, in a per se conventional manner, such that at the ends of the series, there is a voltage equal to the sum of the voltages at the ends of the single photovoltaic cells 1. The thin-film photovoltaic cell 1 comprises a substrate 2 of at least partially transparent material, susceptible of being traversed by solar radiation, such as for example glass, transparent plastic or transparent metal.

[0062] In particular, the substrate 2 is transparent at least to part of the solar radiation.

[0063] With reference for example to figure 3, the photovoltaic cell 1 also comprises a first electrode 3, at least partially transparent, which is placed on the substrate 2 and is susceptible of being traversed by the solar radiation coming from the substrate 2.

[0064] Advantageously, the first electrode 3 is made of an electrically conductive material.

[0065] In particular, the first electrode 3 is transparent at least to part of the solar radiation to which the material of the substrate 2 is transparent, such that at least part of the solar radiation that traverses the substrate 2 is able to also traverse the first electrode 3.

[0066] The photovoltaic cell 1 also comprises a photo-active layer 4, which is provided with a first side 41, which is placed on the first electrode 3 and is susceptible of receiving the solar radiation for the generation of electric current, and with an opposite second side 42, in particular directed in opposite direction with respect to the first side 41.

[0067] Advantageously, the photo-active layer 4 comprises a solar radiation absorber material, made for example of hybrid metal halide perovskite, cadmium telluride, copper-indium-gallium selenide or amorphous silicon, or comprising a heterojunction of organic semiconductors, or of III-V semiconductor materials, such as for example gallium arsenide.

[0068] In particular, in the event in which the absorber material of the photo-active layer 4 is obtained with hybrid metal halide perovskite, the perovskite is a material with perovskite crystalline structure and chemical formula ABX3, in which:

[0069] A is a cation like methylammonium (MA), formamidinium (FA), cesium (Cs), rubidium (Rb), potassium (K) or other monovalent cations, or a combination of these;

[0070] B is a bivalent metal such as lead (Pb), tin (Sn) or others, or a combination of these;

[0071] X is an anion, more commonly a halogen such as iodide (I), bromide (Br), chloride (Cl), or a combination of these.

[0072] Advantageously, the photo-active layer 4 comprises two selective conductor layers, per se known and therefore not illustrated in the enclosed figures. In particular, the absorber material of the photo-active layer 4 is interposed between the two selective conductor layers.

[0073] The photovoltaic cell 1 also comprises a second electrode 5, which is placed on the second side 42 of the photo-active layer 4 and is arranged for being electrically connected to the first electrode 3 of a further photovoltaic cell connected in series to the photovoltaic cell 1.

[0074] In particular, such electrical connection in series between two consecutive thin-film photovoltaic cells 1 is of monolithic type, with the second and the first electrode 5, 3 which are placed in direct contact with each other, without the presence of electrical connectors, such as for example cables. Advantageously, the second electrode 5 is made of an electrically conductive material and, preferably, is at least partially transparent, for example in the event in which the photovoltaic cell 1 is of semitransparent or bifacial type.

[0075] In particular, the aforesaid substrates 2, first electrode 3, photo-active layer 4 and second electrode 5 are deposited on each other, forming a layer structure of per se known type.

[0076] As illustrated for example in the examples of figures 2a-2b, the photovoltaic cell 1 is mainly extended with thinned form on a lying plane thereof, and is provided with a perimeter edge 11 which delimits the extension thereof on such lying plane.

[0077] Advantageously, each photovoltaic cell 1 is extended (preferably with elongated form) along an extension direction L and is extended, transverse to such extension direction L, between a first lateral flank 12 and a second lateral flank 13, each of which, in particular, is side-by-side the corresponding adjacent photovoltaic cell 1 of the module 100.

[0078] One of the two electrodes 3, 5 forms the negative electrode N of the photovoltaic cell 1, while the other forms the positive electrode P of the photovoltaic cell 1 itself.

[0079] In particular, with negative electrode N and positive electrode P it is intended the polarization of the first and second electrode 3, 5 during the normal operation of the photovoltaic cell 1, when the latter is irradiated by the solar radiation and produce electrical energy, and, therefore, is directly polarized.

[0080] More in detail, one of the two selective conductor layers of the photo-active layer 4 is arranged for extracting electrons from the absorber material and is advantageously placed at the negative electrode N.

[0081] In particular, the other of the two selective conductor layers of the photo-active layer 4 is arranged for extracting electron holes from the absorber material and is advantageously placed at the positive electrode P.

[0082] In particular, in accordance with a first embodiment variant (illustrated for example in the detail of figure 5a), the photovoltaic cell 1 has structure p-i-n, in which the first electrode 3 is the positive electrode P and the second electrode 5 is the negative electrode N.

[0083] Otherwise, in accordance with a second embodiment variant (illustrated for example in the detail of figure 5b), the photovoltaic cell 1 has structure n-i-p, in which the first electrode 3 is the negative electrode N and the second electrode 5 is the positive electrode P.

[0084] In particular, in a per se conventional manner, the polarity of the first and of the second electrode 3, 5 (when the photovoltaic cell 1 generates electrical energy) is given by the nature of the photoactive layer 4, and in particular by the arrangement of the two selective semiconductor layers, which determine the direction of the current generated by the photo-active layer 4 when the latter is irradiated by the solar radiation.

[0085] In operation, when the photo-active layer 4 is irradiated by the solar radiation, the photovoltaic cell 1 is directly polarized and produces electrical energy.

[0086] Advantageously, as described in detail hereinbelow, the first electrode 3 of a photovoltaic cell 1 is electrically connected to the second electrode 5 of a successive photovoltaic cell 1 and, preferably, the second electrode 5 of the photovoltaic cell 1 itself is electrically connected to the first electrode 3 of a preceding photovoltaic cell 1, in order to obtain the connection in series of the photovoltaic cells 1 of the photovoltaic module 100.

[0087] Advantageously, in order to attain the connection in series between multiple thin-film photovoltaic cells 1, with reference for example to figure 3, each photovoltaic cell 1 (preferably except for the first and / or the last of the series) is provided, at the second lateral flank 13, and preferably also at the first lateral flank 12, with a connection zone 14 which electrically connects in series the second lateral flank 13 to the first lateral flank 12 of a successive photovoltaic cell 1.

[0088] More in detail, the connection zone 14 contains a first interruption opening Pl, placed to separate the first electrode 3 of the photovoltaic cell 1 and the first electrode 3 of a successive photovoltaic cell 1.

[0089] In particular, the first interruption opening Pl is of through type and is preferably made on the first electrode 3, longitudinally along the extension direction L of the photovoltaic cell 1 itself, more in detail transverse (and preferably orthogonal) with respect to a flanking direction of the photovoltaic cells 1 in series which form the module 100.

[0090] Advantageously, the connection zone 14 contains a second interruption opening P2, placed to separate the photo-active layer 4 of the photovoltaic cell 1 and the photo-active layer 4 of the successive photovoltaic cell 1.

[0091] In particular, the second interruption opening P2 is of through type and is preferably made along the photo-active layer 4, in proximity to the first interruption opening Pl and parallel (according to the extension direction L) to the latter, and, more in detail, closer to the adjacent photovoltaic cell 1 than the first interruption opening Pl.

[0092] Advantageously, the connection zone 14 contains a third interruption opening P3, placed to separate the second electrode 5 of the photovoltaic cell 1 and the second electrode 5 of the successive photovoltaic cell 1.

[0093] In particular, the third interruption opening P3 is of through type and is preferably made along the second electrode 5, in proximity to the second interruption opening P2 and parallel to the latter and, more in detail, closer to the adjacent photovoltaic cell 1 than the first and second interruption openings PI, P2.

[0094] Advantageously, the connection zone 14 contains a conductor element 15, which is extended in the second interruption opening P2 and is placed as an electrical connection between the second electrode 5 of the photovoltaic cell 1 and the first electrode 3 of the successive photovoltaic cell 1, in order to ensure the electrical connection in series between two adjacent photovoltaic cells 1.

[0095] Preferably, in accordance for example with figure 3, the conductor element 15 is the second electrode 5, which is extended in the second interruption opening P2 up to being in contact with the first electrode 3.

[0096] In this manner, the first electrodes 3 of two adjacent photovoltaic cells 1, which have the same polarity (as do the second electrodes 5 of two adjacent photovoltaic cells 1), are electrically insulated from each other, ensuring as single electrical contact between the two adjacent photovoltaic cells 1 that between the first and the second electrode 3, 5 at the second opening P2. Advantageously, the bypass diode 6 is placed outside the connection zone 14.

[0097] In operation, when a photovoltaic cell 1 of the photovoltaic module 100 is shaded, the latter does not produce electrical energy. Nevertheless, the electric current produced by the other photovoltaic cells 1 of the photovoltaic module 100 itself also circulates in the shaded photovoltaic cell 1, which, not producing electrical energy, is reversely polarized, with the first electrode 3 and the second electrode 5 which take on reverse polarity with respect to the polarity taken on in the normal operation (i.e., when the photovoltaic cell 1 produce electrical energy).

[0098] The photovoltaic cell 1 also comprises at least one bypass diode 6, and in particular multiple bypass diodes 6, as is visible for example in figures 2a and 2b.

[0099] With reference for example to figure 3, the bypass diode 6 comprises an anode 61 electrically connected to the negative electrode N of the photovoltaic cell 1 and a cathode 62 electrically connected to the positive electrode P of the photovoltaic cell 1 itself.

[0100] In particular, the bypass diode 6 is arranged for allowing, therethrough, the passage of electric current between the first electrode 3 and the second electrode 5 when the photovoltaic cell 1 is reversely polarized.

[0101] In other words, the bypass diode 6 is connected to the photovoltaic cell 1 so as to be reversely polarized when the photovoltaic cell 1 is directly polarized (i.e., when it produces electrical energy) and to be directly polarized when the photovoltaic cell 1 is reversely polarized (i.e., when it does not produce electrical energy, for example due to a shading of the photovoltaic cell 1 itself).

[0102] In accordance with the idea underlying the present invention, the photo-active layer 4 is provided with a through opening 43 which is extended in a through maimer from the first side 41 to the second side 42 of the photo-active layer 4, in particular with axis orthogonal to the lying plane of the photovoltaic cell 1.

[0103] In other words, the through opening 43 is extended along the thickness of the photo-active layer 4, leading to both sides 41, 42 of the latter.

[0104] Advantageously, the through opening 43 is separate from the first interruption opening Pl, from the second interruption opening P2 and from the third interruption opening P3.

[0105] In particular, the through opening 43 is misaligned, with respect to the aforesaid axis, from the first, second and third interruption opening Pl, P2, P3.

[0106] Advantageously, the through opening 43 is placed within the perimeter edge 11 of the photovoltaic cell 1 and is spaced therefrom. Advantageously, the through opening 43 has area at least of several orders of magnitude smaller than the extension of the photovoltaic cell 1 on its lying plane.

[0107] In addition, the bypass diode 6 is at least partially arranged within the through opening 43 in a manner such to connect the first electrode 3 to the second electrode 5.

[0108] In this manner, the bypass diode 6 is integrated within the structure of the photovoltaic cell 1, resulting electrically connected in parallel to the photovoltaic cell 1 itself, in particular between the first and the second electrode 3, 5.

[0109] In particular, the aforesaid arrangement of the bypass diode 6 allows obtaining a thin-film photovoltaic cell 1 which is compact and does not require the presence of a bypass diode outside the latter.

[0110] Advantageously, the thin-film photovoltaic cell 1 thus obtained is easy to connect in series with other photovoltaic cells 1, since it does not require the further connection of an external bypass diode. Indeed, as discussed in the discussion of the prior art, the arrangement of an external bypass diode is hard to apply in a thin-film photovoltaic cell, since the latter does not provide for electrical connectors such as cables.

[0111] Advantageously, the bypass diode 6 of the photovoltaic cell 1 is arranged on the photovoltaic cell 1 without having to make openings or holes on the substrate 2 and / or on the first electrode 3, therefore preventing the reduction of the surface area of the photovoltaic cell 1 itself that is exposed to solar radiation.

[0112] In operation, with reference for example to figure 4a which represents the section of several photovoltaic cells 1 with structure p-i-n of a photovoltaic module 100, when the photovoltaic cell 1 is irradiated by the solar radiation, this is directly polarized. In particular, the electric current flows from the negative electrode N (which in the embodiment variant illustrated in figure 4 is the second electrode 5) to the opposite positive electrode P (which in the embodiment variant illustrated in figure 4 is the first electrode 3) of the same photovoltaic cell 1 through the photoactive layer 4.

[0113] More in detail, in such condition in which the photovoltaic cell 1 is irradiated by the solar radiation and, therefore, produces electrical energy, the photovoltaic cell 1 itself is directly polarized (in the embodiment variant of figure 4a with structure p-i-n, the first electrode 3 is the positive electrode P and the second electrode 5 is the negative electrode N).

[0114] In such condition, the bypass diode 6 is reversely polarized, with the anode 61 electrically connected to the negative electrode N and the cathode 62 electrically connected to the positive electrode P and, therefore, does not conduct electric current, which, as described above, flows from the negative electrode N to the positive electrode P through the photo-active layer 4.

[0115] Otherwise, with reference for example to figure 4b, when the photovoltaic cell 1 is shaded (even partially) so as to not generate electrical energy, the photovoltaic cell 1 itself is reversely polarized, i.e. it is the negative electrode N (which in the embodiment variant illustrated in figure 4 is the second electrode 5) that takes on positive potential, and the positive electrode P (which in the embodiment variant illustrated in figure 4 is the first electrode 3) takes on negative potential.

[0116] In such condition, the bypass diode 6, being connected with its own anode 61 to the negative electrode N of the photovoltaic cell 1 and with its own cathode 62 to the positive electrode P of the photovoltaic cell 1 itself, is directly polarized and therefore the current of the photovoltaic module 100 passes through the bypass diode 6 itself.

[0117] Advantageously, the bypass diode 6 comprises a first conductor layer 63, of electrically conductive material, which is placed at the anode 61 of the bypass diode 6 and is connected to the negative electrode N of the photovoltaic cell 1.

[0118] Advantageously, the bypass diode 6 also comprises a second conductor layer 64, of electrically conductive material, which is placed at the cathode 62 of the bypass diode 6 and is connected to the positive electrode P of the photovoltaic cell 1.

[0119] Advantageously, the bypass diode 6 also comprises at least one semiconductor layer 65, of semiconductor material, which is interposed between the first conductor layer 63 and the second conductor layer 64.

[0120] Preferably, the semiconductor material constituting the semiconductor layer 65 is provided with high electrical mobility, e.g. greater than 5 cm2 / (V s) for the majority charge carriers and a low concentration of charge carriers, e.g. less than 1017cm'3for the majority charge carriers.

[0121] More in detail, the semiconductor material constituting the semiconductor layer 65 can be gallium oxide, tin oxide, zinc oxide, indium oxide or a combination of such oxides, or amorphous silicon.

[0122] In particular, as is visible in the examples of figures 7a-10b, at least one of the first conductor layer 63, second conductor layer 64 and semiconductor layer 65 is at least partially placed in the through opening 43 in order to connect the first electrode 3 to the second electrode 5 through the bypass diode 6.

[0123] In this manner, the bypass diode 6 is integrated in the structure of the photovoltaic cell 1, more in detail at least partially extended in the photo-active layer 4, at the through opening 43 made on the later.

[0124] Advantageously, the first conductor layer 63 or the second conductor layer 64 of the bypass diode 6 is formed by a portion of the second electrode 5 of the photovoltaic cell 1.

[0125] In particular, the first conductor layer 63 of the bypass diode 6 is formed by a portion of the second electrode 5 when the later is the negative electrode N (as provided for in the photovoltaic cell 1 with structure p-i-n).

[0126] More in detail, the second conductor layer 64 of the bypass diode 6 is formed by a portion of the second electrode 5 when the later is a positive electrode P (as provided for in the photovoltaic cell 1 with structure n-i-p).

[0127] For example, in accordance with the versions illustrated in figures 5a, 7a, 8a, 9a and 10a, in which the photovoltaic cell 1 has structure p-i-n, a portion of the second electrode 5 (corresponding to the negative electrode N of the photovoltaic cell 1) forms the first conductor layer 63 of the bypass diode 6.

[0128] Otherwise, in accordance with the versions illustrated in figures 5b, 7b, 8b, 9b and 10b, in which the photovoltaic cell 1 has structure n-i-p, a portion of the second electrode 5 (corresponding to the positive electrode P of the photovoltaic cell 1) forms the second conductor layer 64 of the bypass diode 6.

[0129] Advantageously, in accordance with the first, second and third embodiment of the bypass diode 6 illustrated in figures 7a to 9b, the photovoltaic cell 1 comprises an additional conductor layer 7, of electrically conductor material, which in particular is at least partially placed on the semiconductor layer 65, and forms the conductor layer (first 63 or second 64) which is not formed by the first electrode 5.

[0130] Such additional conductor layer 7 is at least partially extended within the through opening 43 and is electrically connected to the first electrode 3.

[0131] In particular, the additional conductor layer 7 has the same polarity as the first electrode 3, i.e. in the embodiment versions on figures 5a, 7a, 8a, 9a and 10a (with photovoltaic cell 1 with structure p-i-n) forms the second layer 64 (placed at the cathode 62) of the bypass diode 6. In the second embodiment variant of figures 5b, 7b, 8b, 9b and 10b (with photovoltaic cell 1 with structure n-i- p) forms the first layer 63 (placed at the anode 61) of the bypass diode 6.

[0132] In particular, the additional conductor layer 7 is electrically connected to the first electrode 3 by means of direct contact (as in the examples of figures 8a-8b and 9a-9b), or by means of ohmic contact (as in the examples of figures 7a-7b, where a semiconductor is interposed, as discussed in detail hereinbelow).

[0133] Advantageously, in accordance with the aforesaid embodiments from the first to the third (illustrated in figures 7a to 9b), the second electrode 5 of the photovoltaic cell 1 is provided with a first through hole 51, which is aligned with the through opening 43 of the photo-active layer 4 and is traversed by the additional conductor layer 7.

[0134] In particular, the additional conductor layer 7 traverses both the first through hole 51 and (at least partially) the through opening 43 in order to be electrically connected to the first electrode 3.

[0135] In this manner, the bypass diode 6 is extended between the second electrode 5 and the additional conductor layer 7 (the latter electrically connected to the first electrode 3), and is therefore electrically connected in parallel to the photovoltaic cell 1.

[0136] Advantageously, in accordance with the first, second and fourth embodiment of the bypass diode 6 respectively illustrated in figures 7a-7b, 8a-8b and lOa-lOb, the semiconductor layer 65 is at least partially extended within the through opening 43.

[0137] Preferably, in such embodiments the semiconductor layer 65 is at least partially in contact with the photo-active layer 4 and, advantageously, with the first electrode 3.

[0138] In particular, the photo-active layer 4 is provided with a thickness region 44, which laterally delimits the through opening 43.

[0139] More in detail, the semiconductor layer 65 of the bypass diode 6 is extended within the through opening 43 at least to cover the thickness region 44.

[0140] Advantageously, in accordance with the first and second embodiment of the bypass diode 6 respectively illustrated in figures 7a-7b and 8a-8b, the semiconductor layer 65, within the through opening 43, is placed to separate between the photo-active layer 4 and the additional conductor layer 7.

[0141] Advantageously, in accordance with the first embodiment of the bypass diode 6 illustrated in figures 7a-7b, the at least one semiconductor layer 65, within the through opening 43, is interposed between the first electrode 3 and the additional conductor layer 7.

[0142] In particular, in accordance with such first embodiment, the semiconductor layer 65 is placed in the through opening 43 to close the latter at the first side 41 of the photo-active layer 4, more in detail in contact with (and interposed between) the first electrode 3 and with the additional conductor layer 7.

[0143] Preferably, the semiconductor layer 65 of the bypass diode 6 forms, in the zone in which it is interposed between the first electrode 3 and the additional conductor layer 7, an ohmic contact both with the first electrode 3 and with the additional conductor layer 7.

[0144] In this manner, the semiconductor layer 65 ensures the electrical connection between the first electrode 3 and the additional conductor layer 7 notwithstanding the physical interposition between the latter and, consequently, the additional conductor layer 7 is situated substantially at the same potential as the first electrode 3.

[0145] Advantageously, in such embodiment, the bypass diode 6 is a Schottky diode, as described in detail hereinbelow.

[0146] Advantageously, in accordance with the second and third embodiment of the bypass diode 6 respectively illustrated in figures 8a-8b and 9a-9b, the semiconductor layer 65 is provided with a second through hole 66, which is aligned with the through opening 43 and with the first through hole 51 and is traversed by the additional conductor layer 7 that comes into (direct) contact with the first electrode 3.

[0147] Advantageously, in accordance with the second embodiment of the bypass diode 6 illustrated in figures 8a-8b, on the second through hole 66, and, more in detail, at the first side 41 of the photoactive layer 4, a portion of the first electrode 3 faces, such portion in contact with the additional conductor layer 7.

[0148] In this manner, the collection of electric charge reaches an optimal level due to the direct contact between the first electrode 3 and the additional conductor layer 7.

[0149] In accordance with the third embodiment of the bypass diode 6 illustrated in figures 9a-9b, the semiconductor layer 65 is placed on a zone of the second electrode 5 adjacent to the through opening 43, substantially without entering within the latter.

[0150] In particular, in accordance with such third embodiment, the second through hole 66 made on the semiconductor layer 65 is provided with a width substantially coinciding with the width of the through opening 43 made on the photo-active layer 4 and, preferably, with the width of the first through hole 51 made on the second electrode 5.

[0151] More in detail, the semiconductor layer 65 is provided with a first internal edge 67, which delimits the second through hole 66 and, preferably, the second electrode 5 is provided with a second internal edge 52, which delimits the first through hole 51.

[0152] Advantageously, in accordance with the third embodiment, the thickness region 44 of the photoactive layer 4, the second internal edge 52 of the second electrode 5 and the first internal edge 67 of the semiconductor layer 65 are substantially superimposed on each other.

[0153] Advantageously, in accordance with such third embodiment of the bypass diode 6, the photovoltaic cell 1 comprises an insulating layer 8, made of an electrically insulating material, which is placed at least partially within the through opening 43, is extended to separate the photoactive layer 4 from the additional conductor layer 7.

[0154] In this manner, advantageously, the insulating layer 8 is capable of reaching possible chemicalphysical degradation processes of the photovoltaic cell 1 which could occur following direct contact between the photo-active layer 4 and the additional conductor layer 7.

[0155] Preferably, the insulating layer 8 covers the thickness region 44 of the photo-active layer 4 and, more in detail, second internal edge 52 of the second electrode 5 and the first internal edge 67 of the semiconductor layer 65. In particular, the insulating layer 8 covers a zone of the semiconductor layer 65 of the bypass diode 6 placed around the second through hole 66 of the semiconductor layer 65 itself.

[0156] Advantageously, the insulating layer 8 allows selecting from among a wider range the materials that will constitute the semiconductor layer 65 and, preferably, the first and the second electrode 3, 5 and the additional conductor layer 7, since it eliminates the potential due to undesired electrical conduction effects. More in detail, the insulating layer 8 further facilitates the collection of electric charge.

[0157] Advantageously, still in accordance with the third embodiment of the bypass diode 6, the insulating layer 8 is provided with a bottom opening 80, which is aligned with the through opening 43 and with the first through hole 51, and preferably with the second through hole 66, and is traversed by the additional conductor layer 7 which comes into contact with the first electrode 3. In particular, the first electrode 3 is provided with a contact zone 30, which faces the through opening 43, is not covered by the insulating layer 8 and is in contact with the additional conductor layer 7.

[0158] Advantageously, in accordance with the fourth embodiment of the bypass diode 6 illustrated in figures 10a- 10b, a portion of the second electrode 5 forms one of the conductor layers 63, 64 of the bypass diode 6, in particular it forms the first conductor layer 63 in the version of figure 10a (photovoltaic cell 1 with structure p-i-n), while it forms the second conductor layer 64 in the version of figure 10b (photovoltaic cell 1 with structure n-i-p).

[0159] In addition, the second electrode 5 is at least partially extended within the through opening 43 of the photo-active layer 4, covering it on the side of the second side 42 of the photo-active layer 4 itself.

[0160] In such fourth embodiment, the other conductor layer 63, 64 of the bypass diode 6 is formed by a portion of the first electrode 3 of the photovoltaic cell 1. In particular, the first electrode 3 forms the second conductor layer 64 in the version of figure 10a (photovoltaic cell 1 with structure p-i- n), while it forms the first conductor layer 63 in the version of figure 10b (photovoltaic cell 1 with structure n-i-p).

[0161] In addition, the semiconductor layer 65, at least within the through opening 43 of the photo-active layer 4, is interposed between the first electrode 3 and the second electrode 5 (preferably in direct contact with the latter), in this manner defining the bypass diode 6.

[0162] More in detail, in such fourth embodiment the second electrode 5 is placed to cover the semiconductor layer 65 of the bypass diode 6.

[0163] Advantageously, the bypass diode 6 is a Schottky diode, in which the semiconductor layer 65 defines, with the first conductor layer 63, a rectifying contact (which forms a Schottky barrier), and with the second conductor layer 64 defines an ohmic contact. Preferably, the material constituting the first conductor layer 63 employed for the rectifying contact has an extraction work at least 0.5 eV lower than the extraction work of the material constituting the semiconductor layer 65.

[0164] In this manner, the formation of the rectifying contact results simplified.

[0165] Preferably, the rectifying contact can be obtained by modifying a surface of the first conductor layer 63, and in particular the surface in contact with the semiconductor layer 65, by means of a surface modifier (e.g. employing organic molecules provided with reduced extraction work) or by means of oxides provided with reduced extraction work, such as for example silver oxide, copper oxide, molybdenum oxide, vanadium oxide, tungsten oxide, palladium oxide or a combination of such oxides, or by means of bidimensional materials such as for example materials with graphene base, MXene base, molybdenum sulfide base, or others by means of treatments with plasma.

[0166] Advantageously, the material constituting the second conductor layer 64 employed for the ohmic contact has an extraction work comparable with the extraction work of the material constituting the semiconductor layer 65.

[0167] For example, the second conductor layer 64 is made of metallic material such as silver, aluminum, copper or of conducive metallic oxides which have an extraction work comparable with the extraction work constituting the semiconductor layer 65.

[0168] Advantageously, in accordance with a different embodiment not illustrated in the enclosed figures, the bypass diode 6 is a junction diode p-n.

[0169] In particular, in such non-illustrated embodiment, the semiconductor layer 65 of the bypass junction diode p-n comprises a semiconductor layer p, which is in contact with the first conductor layer 63, and a semiconductor layer n, which is in contact with the second conductor layer 64 and forms, with the semiconductor layer p, a junction p-n.

[0170] Advantageously, the semiconductor layer p and the semiconductor layer n of the semiconductor layer 65 respectively define, with the first conductor layer 63 and with the second conductor layer 64, an ohmic contact.

[0171] Advantageously, as illustrated in the plan view of figures 2a-2b, the thin-film photovoltaic cell 1 comprises multiple bypass diodes 6 of the above-described type, in particular positioned according to a periodic scheme along the photovoltaic cell 1.

[0172] In this manner, when the photovoltaic cell 1 is shaded (and hence is reversely polarized) the current is divided onto multiple bypass diodes 6, reducing the overheating of the latter due an excessive circulation of current.

[0173] In accordance with an embodiment of the photovoltaic cell 1 illustrated in figure 2a, the latter comprises a plurality of bypass diodes 6, in particular five bypass diodes 6, aligned with each other. In accordance with a different embodiment of the photovoltaic cell 1 illustrated in figure 2b, the latter comprises a plurality of bypass diodes 6 placed on multiple rows, in particular three rows.

[0174] In particular, the surface covered by the bypass diodes 6 depends on the electrical characteristic of the latter, and, preferably, the distance between the bypass diodes 6 (and hence between the through openings 43) of a same photovoltaic cell 1 depends on the electrical conductivity of the first and second electrodes 3, 5.

[0175] More in detail, the periodic placement scheme of the bypass diodes 6 can be varied in order to minimize the resistive losses, or it can vary as a function of specific placement schemes in order to modify the aesthetics of the photovoltaic cell 1.

[0176] Advantageously, the above-described bypass diode 6 of the photovoltaic cell 1 is placed on one side of the cell not directly exposed to solar radiation.

[0177] In particular, the arrangement of the bypass diode 6 does not require making openings or holes on the substrate 2.

[0178] In this manner, the production of electrical energy of the photovoltaic cell 1 remains unchanged with respect to different structures which do not provide for the integration of the bypass diode 6 directly in the structure of the photovoltaic cell 1 itself.

[0179] Advantageously, in accordance with the embodiments illustrated in figures 2a and 2b, the form of the bypass diodes 6 - and in particular of the through openings 43 within which the bypass diodes 6 themselves are at least partially arranged - in plan view have polygonal shape, e.g. square. Otherwise, without departing from the protective scope of the present invention, the through openings 43 and the bypass diodes 6 have rectangular, circular or hexagonal shape.

[0180] In accordance with different embodiments of the photovoltaic cell 1 illustrated in figures 2c-2e, the bypass diodes 6 have elongated form, transverse with respect to the extension direction L of the photovoltaic cell 1, and advantageously parallel to the flanking direction of the photovoltaic cells 1 to form the module 100.

[0181] In particular, in accordance with the embodiment illustrated in figure 2c, each bypass diode 6 is extended on the photovoltaic cell 1 (transverse to the extension direction of the latter), between a first end thereof, placed in proximity to one of the lateral flanks, and an opposite second end, placed in proximity to the opposite lateral flank. In particular, in the embodiment of figure 2c, each bypass diode 6 is entirely contained in the surface of the corresponding photovoltaic cell 1 delimited by the perimeter edge 11.

[0182] In accordance with the embodiments of figures 2d and 2e, the bypass diode 6 has elongated form, transverse with respect to the extension direction L, from the first lateral flank 12 to the second lateral flank 13, advantageously able to be aligned with one of the bypass diodes 6 of the adjacent photovoltaic cell 1. In particular, in such examples, the bypass diodes 6 of one of the photovoltaic cells 1 are electrically separated from those of the adjacent photovoltaic cells 1.

[0183] Advantageously, in accordance with figure 13, which shows the section view of the photovoltaic cells 1 of the embodiment of figure 2d according to the trace XIII-XIII, the connection zone 14 contains a fourth interruption opening P4 and a fifth interruption opening P5, which are placed as a separation between the additional conductor layer 7 of the photovoltaic cell 1 and the additional conductor layer 7 of the successive photovoltaic cell 1 and are placed aligned, respectively, with the first interruption opening Pl and with the third interruption opening P3 (in particular with respect to a plan view).

[0184] Preferably, at least one between the fourth and the fifth interruption openings P4, P5 and, in particular, both, as illustrated in the embodiment of figure 13, are placed as a separation also of the semiconductor layer 65 of the photovoltaic cell 1 from the semiconductor layer 65 of the successive photovoltaic cell 1.

[0185] More in detail, in the event in which the fifth interruption opening P5 is also placed to separate the semiconductor layer 65, this is placed in continuity with the third interruption opening P3 with which it is aligned.

[0186] Advantageously, the fourth and the fifth interruption openings P4, P5 allow the galvanic separation of the bypass diode 6 of a photovoltaic cell 1 from the bypass diode 6 of the successive photovoltaic cell 1.

[0187] In accordance with the embodiment of figure 13, the fourth and the fifth interruption opening P4, P5 are separated from each other by a portion of the additional conductor layer 7 and of the semiconductor layer 65.

[0188] Otherwise, in accordance with a different non-illustrated embodiment, the fourth and the fifth interruption openings P4, P5 are placed in continuity with each other and, therefore, a portion of the additional conductor layer 7 and of the semiconductor layer 65 is not present.

[0189] Advantageously, in accordance with the embodiment illustrated in figure 2e and in figure 11, the photovoltaic cell 1 is provided with at least one separation passage 31, which is made in a through manner in the first electrode 3, advantageously in the semiconductor layer 65 and / or in the additional conductor layer 7, in the portion of such layer or layers placed in the passage opening 42 of the photovoltaic cell 1.

[0190] In particular, according to the example of figure 2e, the separation passage 31 is extended in a through manner from the additional conductor layer 7 up to the first electrode 3. In particular, the removal of the semiconductor layer 65 is optional, the operation of the bypass diode 6 remaining unchanged.

[0191] Advantageously, the separation passage 31 is extended, length-wise, orthogonal to the main direction L of the photovoltaic cell 1, from one lateral flank to the other of the latter.

[0192] Advantageously, in accordance with such embodiment, each photovoltaic cell 1 is separated into multiple cell sections 101, so as to limit possible damage due to undesired phenomena of reverse bias to the single cell section 101 and not to the entire photovoltaic cell 1.

[0193] Advantageously, the photovoltaic module 100 comprises multiple photovoltaic cells 1 connected to each other in series, in which the first electrode 3 of each photovoltaic cell 1 is electrically connected respectively to the second electrode 5 of the successive photovoltaic cell 1 (to exclude the cells 1 at the end of the series).

[0194] In particular, as set forth above, the connection between the first electrode 3 of a photovoltaic cell 1 and the second electrode 5 of the successive photovoltaic cell 1 is of monolithic type.

[0195] Advantageously, the bypass diode 6 at least partially arranged within the through opening 43 of the photo-active layer 4 of the photovoltaic cell 1 allows connecting multiple photovoltaic cells 1 in series without resorting to external connections for arranging a bypass diode in parallel to the photovoltaic module 100, since each photovoltaic cell 1 is already provided with such bypass diode 6.

[0196] Also forming the object of the present invention is a method for attaining a photovoltaic cell 1 of the above-described type, regarding which the numerical references will be maintained for the sake of description simplicity.

[0197] Such method comprises a step of arranging a substrate 2 of at least partially transparent material, a first deposition step, in which a first electrode 3, at least partially transparent, is deposited on the substrate 2, and a second deposition step, in which a photo-active layer 4 is deposited on the first electrode 3.

[0198] The photo-active layer 4 has a first side 41 in contact with the first electrode 3, and an opposite second side 42.

[0199] The present method also comprises a third deposition step, in which a second electrode 5 is deposited on the second side 42 of the photo-active layer 4.

[0200] In particular, the aforesaid deposition step can provide for known deposition techniques, such as for example screen printing, spin coating, blade coating, slot die coating, thermal evaporation, sputtering coating, chemical vapor deposition, atomic layer deposition, close space sublimation, pulsed laser deposition or reactive plasma deposition, or physical or chemical depositions, or techniques that ensure a high precision in the definition of each layer and a uniformity over the entire area of deposition of the layer itself.

[0201] More in detail, the abovementioned deposition techniques can be employed both separately and combined with each other.

[0202] Advantageously, the definition of each layer can be obtained by means of selective deposition of the layer itself or by means of a selective removal, for example through laser devices or mechanical ablations.

[0203] The first electrode 3 is adapted to form the negative electrode N of the photovoltaic cell 1 and the second electrode 5 forms the positive electrode P of the photovoltaic cell 1, or vice versa, as a function of the specific structure (n-i-p or p-i-n) of the photovoltaic cell 1 that one wishes to obtain.

[0204] Advantageously, in the photovoltaic cell 1, at the second lateral flank 13, a connection zone 14 is obtained that electrically connects in series the second lateral flank 13 to the first lateral flank 12 of a successive photovoltaic cell 1.

[0205] In accordance with the idea underlying the present invention, the present method comprises a first deposition step, following at least the second step of depositing the photo-active layer 4, in which a part of the photo-active layer 4 is removed in order to obtain a through opening 43 which is extended in a through manner from the first side 41 to the second side 42 of the photo-active layer 4.

[0206] In particular, such first deposition step provides for the use of removal techniques such as, for example, laser ablation or chemical removal upon partial masking of the area affected by the process.

[0207] In addition, the present method comprises a formation of a bypass diode 6 at least partially arranged within the through opening 43, and comprising an anode 61 electrically connected to the negative electrode N of the photovoltaic cell 1 and a cathode 62 electrically connected to the positive electrode P of the photovoltaic cell 1 itself.

[0208] Advantageously, the bypass diode 6 comprises a first conductor layer 63, of electrically conductive material, which is placed at the anode 61 of the bypass diode 6 and is electrically connected to the negative electrode N of the photovoltaic cell 1.

[0209] In particular, the bypass diode 6 also comprises a second conductor layer 64, of electrically conductive material, which is placed at the cathode 62 of the bypass diode 6 and is electrically connected to the positive electrode P of the photovoltaic cell 1.

[0210] More in detail, the bypass diode 6 also comprises at least one semiconductor layer 65, of semiconductor material, which is interposed between the first conductor layer 63 and the second conductor layer 64.

[0211] Advantageously, in accordance with the attainment of the first, second and third embodiment respectively illustrated in figures 7a-7b, 8a-8b and 9a-9b, the first deposition step (of the photoactive layer 4) is executed after the third step of depositing the second electrode 5.

[0212] In particular, first the second electrode 5 is deposited on the second side 42 of the photo-active layer 4. Then, advantageously, the method provides for a second deposition step, in which a part of the second electrode 5 is removed at the through opening 43 in order to make a first through hole 51 aligned with the through opening 43. In particular, the second deposition step provides for the removal techniques mentioned above for the first deposition step, such as for example laser ablation or chemical removal upon partial masking of the area affected by the process.

[0213] After the second deposition step, the first deposition step is executed in order to attain the through opening 43 in the photo-active layer 4. Alternatively, the first and the second deposition steps are simultaneously executed.

[0214] Advantageously, the formation of the bypass diode 6 comprises a first step of covering the semiconductor layer 65, which is deposited at least on a zone of the second electrode 5 adjacent to the through opening 43.

[0215] Preferably, the formation of the bypass diode 6 comprises a second step of covering an additional conductor layer 7, preferably of electrically conductor material, which is deposited on the semiconductor layer 65 and, at least partially, within the through opening 43, and is electrically connected to the first electrode 3.

[0216] In particular, the first and the second covering step can provide for one of the deposition techniques employed in the deposition steps.

[0217] Advantageously, in accordance with the attainment of the first and second embodiment of the bypass diode 6 respectively illustrated in figures 7a-7b and 8a-8b, in the first covering step the semiconductor layer 65 is deposited in the through opening 43 at least to cover a thickness region 44 of the photo-active layer 4 which laterally delimits the through opening 43.

[0218] Advantageously, in accordance with the attainment of such first and second embodiment of the bypass diode 6, in the second covering step the additional conductor layer 7 is deposited on the semiconductor layer 65 which, in the through opening 43, separates the photo-active layer 4 from the additional conductor layer 7.

[0219] Advantageously, in accordance with the attainment of the first embodiment of the bypass diode 6 illustrated in figures 4a-4b, in the first covering step the semiconductor layer 65 e deposited in the through opening 43, in particular at least to cover a zone of the first electrode 3 that faces the through opening 43.

[0220] More in detail, in the second covering step the additional conductor layer 7 is deposited on the semiconductor layer 65 which, in the through opening 43, is interposed between the first electrode 3 and the additional conductor layer 7.

[0221] In particular, the semiconductor layer 65 is placed in the through opening 43 at the first side 41, more in detail in contact with the first electrode 3 and with the additional conductor layer 7.

[0222] Preferably, the semiconductor layer 65 of the bypass diode 6 forms, at the first side 41, an ohmic contact both with the first electrode 3 and with the additional conductor layer 7, such that the additional conductor layer 7 is substantially situated at the same potential as the first electrode 3, thus ensuring the electrical connection between the first electrode 3 and the additional conductor layer 7 notwithstanding the physical interposition between the latter.

[0223] Advantageously, in accordance with the attainment of the second and third embodiments of the bypass diode 6 respectively illustrated in figures 8a-8b and 9a-9b, the formation of the bypass diode 6 comprises a step of attaining, in the semiconductor layer 65, a second through hole 66 aligned with the first through opening 43 and with the first through hole 51.

[0224] In particular, the formation of the bypass diode 6 provides for, in the second covering step, depositing the additional conductor layer 7 in a maimer such that the latter crosses the second through hole 66 in order to come into contact with the first electrode 3.

[0225] Advantageously, in accordance with the attainment of the third embodiment of the bypass diode 6 illustrated in figures 9a-9b, the formation of the bypass diode 6 comprises a covering step, in which an insulating layer 8, made of an electrically insulating material, is deposited in the through opening 43 at least to cover a thickness region 44 of the photo-active layer 4 which laterally delimits the through opening 43.

[0226] In particular, the formation of the bypass diode 6 comprises, in the second covering step, the deposition of the additional conductor layer 7 on the insulating layer 8 which, in the through opening 43, separates the photo-active layer 4 from the additional conductor layer 7.

[0227] More in detail, the first electrode 3 is provided with at least one contact zone 30 which faces the through opening 43, is not covered by the insulating layer 8 and is in contact with the additional conductor layer 7.

[0228] Advantageously, in accordance with the attainment of the fourth embodiment of the bypass diode 6 illustrated in figures 10a- 10b, the formation of the bypass diode 6 comprises a first step of covering the semiconductor layer 65, which is deposited in the through opening 43 to cover a zone of the first electrode 3 that faces the through opening 43 itself.

[0229] In particular, the third step of depositing the second electrode 5 is executed after the first covering step and, in such third deposition step, the second electrode 5 is deposited also within the through opening 43 on the semiconductor layer 65.

[0230] In this manner, the succession of the first electrode 3, the semiconductor layer 65 and the second electrode 5 within the through opening 43 forms the bypass diode 6.

[0231] Advantageously, in order to attain the connection in series between multiple thin-film photovoltaic cells 1, the present method provides for making, in the connection zone 14 of the photovoltaic cell 1, a first interruption opening Pl, preferably through, in order to separate the first electrode 3 of the photovoltaic cell 1 and the first electrode 3 of a successive photovoltaic cell 1. More in detail, the present method provides for making the first intermption opening Pl on the first electrode 3, longitudinally along the extension direction L of the photovoltaic cell 1 itself, in particular transverse (and more particularly orthogonal) to the flanking direction of the photovoltaic cells 1 that form the module 100.

[0232] Advantageously, the present method provides for making, in the connection zone 14, a second intermption opening P2, preferably of through type, in order to separate the photo-active layer 4 of the photovoltaic cell 1 and the photo-active layer 4 of the successive photovoltaic cell 1.

[0233] More in detail, the present method provides for making the second intermption opening P2 along the photo-active layer 4, in proximity to the first intermption opening Pl and parallel (according to the length-wise extension) to the latter, and, more particularly, closer to the adjacent photovoltaic cell 1 with respect to the first intermption opening Pl .

[0234] Advantageously, the present method provides for attaining a conductor element 15, in the second intermption opening P2, as an electrical connection between the second electrode 5 of the photovoltaic cell 1 and the first electrode 3 of the successive photovoltaic cell 1, in order to ensure the electrical connection in series between two adjacent photovoltaic cells 1.

[0235] Advantageously, the present method also provides for making, in the connection zone 14, a third intermption opening P3, preferably of through type, in order to separate the second electrode 5 of the photovoltaic cell 1 and the second electrode 5 of the successive photovoltaic cell 1.

[0236] More in detail, the method provides for making the third intermption opening P3 along the second electrode 5, in proximity to the second intermption opening P2 and parallel to the latter and, in particular, closer to the adjacent photovoltaic cell 1 with respect to the first and second intermption openings Pl, P2.

[0237] In this manner, the present method allows electrically insulating the first electrodes 3 of two adjacent photovoltaic cells 1, which have the same polarity (as do the second electrodes 5 of two adjacent photovoltaic cells 1), ensuring - as single electrical contact between the two adjacent photovoltaic cells 1 - that between the first and second electrodes 3, 5 at the second opening P2. Advantageously, for example so as to attain the electrical insulation between the bypass diodes 6 of elongated form illustrated in the embodiments of figures 2d and 2e of adjacent photovoltaic cells 1 connected in series, the present method provides for making a fourth and a fifth intermption opening P4, P5 in order to separate the additional conductor layer 7 of the photovoltaic cell 1 from the additional conductor layer 7 of the successive photovoltaic cell 1.

[0238] In particular, the fourth and the fifth intermption opening P4, P5 are aligned, with respect to a plan view, respectively to the first intermption opening Pl and to the third intermption opening P3.

[0239] Advantageously, the present method provides for making the fourth and the fifth intermption openings P4, P5 also in order to separate the semiconductor layer 65 of the photovoltaic cell 1 from the semiconductor layer 65 of the successive photovoltaic cell 1.

[0240] In accordance with the embodiment illustrated in figure 13, the present method provides for making the fourth and the fifth interruption openings P4, P5 separate from each other, in particular from a portion of additional conductor layer 7 and of semiconductor layer 65. Otherwise, in accordance with a different non-illustrated embodiment, the present method provides for obtaining the fourth and the fifth interruption openings P4, P5 in continuity with each other, as a single opening, therefore removing the aforesaid portion of additional conductor layer 7 and of semiconductor layer 65.

[0241] The photovoltaic cell 1 thus conceived and the method of attainment thereof therefore achieve the preset objects.

Claims

CLAIMS1. Thin-film photovoltaic cell (1), which comprises:- a substrate (2) of at least partially transparent material, susceptible of being traversed by solar radiation;- a first electrode (3), at least partially transparent, which is placed on said substrate (2) and is susceptible of being traversed by said solar radiation coming from said substrate (2);- a photo-active layer (4), which is provided with a first side (41), which is placed on said first electrode (3) and is susceptible of receiving said solar radiation for the generation of electric current, and with an opposite second side (42);- a second electrode (5), which is placed on the second side (42) of said photo-active layer (4) and is arranged for being electrically connected to the first electrode (3) of a further photovoltaic cell connected in series to said photovoltaic cell (1); wherein one of said first electrode (3) and second electrode (5) is a negative electrode (N), and the other of said first electrode (3) and second electrode (5) is a positive electrode (P);- at least one bypass diode (6), which comprises an anode (61) electrically connected to said negative electrode (N) and a cathode (62) electrically connected to said positive electrode (P); said photovoltaic cell (1) being characterized in that:- said photo-active layer (4) is provided with a through opening (43) which is extended in a through manner from the first side (41) to the second side (42) of said photo-active layer (4);- said bypass diode (6) is arranged, at least partially, within said through opening (43) in a manner such to connect said first electrode (3) to said second electrode (5).

2. Photovoltaic cell (1) according to claim 1, characterized in that said bypass diode (6) comprises:- a first conductor layer (63), which is placed at the anode (61) of said bypass diode (6);- a second conductor layer (64), which is placed at the cathode (62) of said bypass diode (6);- at least one semiconductor layer (65), which is interposed between said first conductor layer (63) and said second conductor layer (64); wherein at least one of said first conductor layer (63), said second conductor layer (64) and said at least one semiconductor layer (65) is placed at least partially in said through opening (43) in order to connect said first electrode (3) to said second electrode (5) through said bypass diode (6).

3. Photovoltaic cell (1) according to claim 2, characterized in that one of said first conductor layer (63) and said second conductor layer (64) of said bypass diode (6) is formed by a portion of the second electrode (5) of said photovoltaic cell (1).

4. Photovoltaic cell (1) according to claim 3, characterized in that it comprises an additional conductor layer (7), which forms the other of said first conductor layer (63) and said second conductor layer (64) of said bypass diode (6), is at least partially extended within said through opening (43) and is electrically connected to said first electrode (3); wherein said second electrode (5) is provided with a first through hole (51), which is aligned with said through opening (43) and is traversed by said additional conductor layer (7).

5. Photovoltaic cell (1) according to any one of the preceding claims 2 to 4, characterized in that said at least one semiconductor layer (65) is at least partially extended within said through opening (43).

6. Photovoltaic cell (1) according to claims 4 and 5, characterized in that said at least one semiconductor layer (65), within said through opening (43), is placed to separate between said photo-active layer (4) and said additional conductor layer (7).

7. Photovoltaic cell (1) according to claim 4, characterized in that said at least one semiconductor layer (65) is provided with a second through hole (66), which is aligned with said through opening (43) and with said first through hole (51) and is traversed by said additional conductor layer (7) which comes into contact with said first electrode (3).

8. Photovoltaic cell (1) according to claim 7, characterized in that it comprises an insulating layer (8), which is at least partially placed within said through opening (43), is extended to separate said photo-active layer (4) from said additional conductor layer (7) and is provided with a bottom opening (80), which is aligned with said through opening (43) and with said first through hole (51) and is traversed by said additional conductor layer (7) which comes into contact with said first electrode (3).

9. Photovoltaic cell (1) according to claim 3, characterized in that:- said second electrode (5) is at least partially extended within said through opening (43);- the other of said first conductor layer (63) and said second conductor layer (64) of said bypass diode (6) is formed by a portion of the first electrode (3) of said photovoltaic cell (1);- said semiconductor layer (65), within said through opening (43), is interposed between said first electrode (3) and said second electrode (5).

10. Photovoltaic cell (1) according to any one of the preceding claims, which is extended along an extension direction (L) and is extended, transverse to said extension direction (L), between a first lateral flank (12) and a second lateral flank (13); said photovoltaic cell (1) being characterized in that it is provided, at said second lateral flank (13), with a connection zone (14) that electrically connects in series said second lateral flank (13) to the first lateral flank (12) of a subsequent said photovoltaic cell (1).

11. Photovoltaic cell (1) according to claim 10, characterized in that said connection zone(14) contains:- a first interruption opening (Pl), placed to separate the first electrode (3) of said photovoltaic cell (1) and the first electrode (3) of one said subsequent photovoltaic cell (1);- a second interruption opening (P2), placed to separate the photo-active layer (4) of said photovoltaic cell (1) and the photo-active layer (4) of said subsequent photovoltaic cell (1);- a third interruption opening (P3), placed to separate the second electrode (5) of said photovoltaic cell (1) and the second electrode (5) of said subsequent photovoltaic cell (1);- a conductor element (15) extended in said second interruption opening (P2) and placed to electrically connect the second electrode (5) of said photovoltaic cell (1) and the first electrode (3) of said subsequent photovoltaic cell (1).

12. Photovoltaic cell (1) according to claims 4 and 11, characterized in that said bypass diode (6) has elongated form, transverse with respect to said extension direction (L), from said first lateral flank (12) to said second lateral flank (13); wherein said connection zone (14) contains a fourth interruption opening (P4) and a fifth interruption opening (P5), which are placed to separate the additional conductor layer (7) of said photovoltaic cell (1) and the additional conductor layer (7) of said subsequent photovoltaic cell(I) and are placed aligned, respectively, with said first interruption opening (Pl) and with said third interruption opening (P3).

13. Photovoltaic cell (1) according to any one of the preceding claims 10 to 12, characterized in that said at least one bypass diode (6) is placed outside said connection zone (14).

14. Photovoltaic cell (1) according to any one of the preceding claims, characterized in that it is mainly extended with thinned form on a lying plane thereof, and is provided with a perimeter edge(I I), which delimits the extension of said photovoltaic cell (1) on said lying plane; wherein said through opening (43) is placed within the perimeter edge (11) of said photovoltaic cell (1) and is spaced therefrom.

15. Photovoltaic cell (1) according to claim 14, characterized in that said through opening (43) has area at least several orders of magnitude smaller than the extension of said photovoltaic cell (1) on said lying plane.

16. Photovoltaic cell (1) according to claim 11 or 12, characterized in that said through opening (43) is distinct from said first intermption opening (Pl), from said second intermption opening (P2) and from said third intermption opening (P3).

17. Photovoltaic cell (1) according to claim 14 or 15 and claim 16, characterized in that said through opening (43) is extended with axis orthogonal to the lying plane of said photovoltaic cell (1) and is misaligned, with respect to said axis, from said first, second and third intermption opening (Pl, P2, P3).

18. Method for attaining a photovoltaic cell (1), and such method comprises:- a step of arranging a substrate (2) of at least partially transparent material;- a first deposition step, in which a first electrode (3), at least partially transparent, is deposited on said substrate (2);- a second deposition step, in which a photo-active layer (4) is deposited on said first electrode (3); wherein said photo-active layer (4) has a first side (41) in contact with said first electrode (3) and an opposite second side (42);- a third deposition step, in which a second electrode (5) is deposited on the second side (42) of said photo-active layer (4); wherein one of said first electrode (3) and second electrode (5) is a negative electrode (N), and the other of said first electrode (3) and second electrode (5) is a positive electrode (P); said method being characterized in that it comprises:- a first removal step, subsequent at least to said second deposition step, in which a part of said photo-active layer (4) is removed in order to obtain a through opening (43) which is extended in a through manner from the first side (41) to the second side (42) of said photoactive layer (4);- a formation of a bypass diode (6) arranged, at least partially, within said through opening (43), and comprising an anode (61) electrically connected to said negative electrode (N) and a cathode (62) electrically connected to said positive electrode (P).

19. Method for attaining a photovoltaic cell (1) according to claim 18, characterized in that said first removal step is subsequent to said third deposition step, and in that it comprises a second removal step, in which a part of said second electrode (5) is removed at said through opening (43) in order to obtain a first through hole (51) aligned with said through opening (43); wherein the formation of said bypass diode (6) comprises:- a first step of covering at least one semiconductor layer (65), which is deposited at least on a zone of said second electrode (5) adjacent to said through opening (43);- a second step of covering an additional conductor layer (7), which is deposited on said at least one semiconductor layer (65) and, at least partially, within said through opening (43), and is electrically connected to said first electrode (3).

20. Method for attaining a photovoltaic cell (1) according to claim 19, characterized in that, in said first covering step, said at least one semiconductor layer (65) is deposited in said through opening (43) at least to cover a thickness region (44) of said photo-active layer (4) which laterally delimits said through opening (43);in said second covering step, said additional conductor layer (7) is deposited on said at least one semiconductor layer (65) which, in said through opening (43), separates said photo-active layer (4) from said additional conductor layer (7).

21. Method for attaining a photovoltaic cell (1) according to claim 20, characterized in that in said first covering step, said at least one semiconductor layer (65) is deposited in said through opening (43); wherein the formation of said bypass diode (6) comprises:- a step of attaining, in said at least one semiconductor layer (65), a second through hole (66) aligned with said first through opening (43) and with said first through hole (51);- the deposition, in said second covering step, of said additional conductor layer (7) to cross through said second through hole (66) in order to come into contact with said first electrode (3).

22. Method for attaining a photovoltaic cell (1) according to claim 19, characterized in that the formation of said bypass diode (6) comprises:- a covering step, in which an insulating layer (8) is deposited in said through opening (43) at least to cover a thickness region (44) of said photo-active layer (4) which laterally delimits said through opening (43);- in said second covering step, the deposition of said additional conductor layer (7) on said insulating layer (8) which, in said through opening (43), separates said photo-active layer (4) from said additional conductor layer (7); said first electrode (3) being provided with at least one contact zone (30), which faces said through opening (43), is not covered by said insulating layer (8) and is contact with said additional conductor layer (7).

23. Method for attaining a photovoltaic cell (1) according to claim 18, characterized in that the formation of said bypass diode (6) comprises a first step of covering at least one semiconductor layer (65), which is deposited at least in said through opening (43) at least to cover a zone of said first electrode (3) which faces said through opening (43); wherein said third deposition step is executed after said first covering step and, in said third deposition step, said second electrode (5) is also deposited within said through opening (43) on said at least one semiconductor layer (65).

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