Method for producing a solar cell having an integral cover glass and the resulting cell

Abstract

A method for manufacturing a solar cell includes the steps of providing a solar cell (100) having an active surface (105a) intended to be exposed to sunlight in use for photovoltaic conversion, and forming a protection against low-energy protons and other radiation harmful to the solar cell corresponding to the active surface, the step of forming a resin layer (110; 210) and forming a layer of protective material (115; 215b) on top of the resin layer by deposition of a material.

Description

[Technical Field]

[0001] The present invention relates generally to the field of solar cells and their manufacture. As is known, solar cells or photovoltaic cells are solid-state (semiconductor) electrical / electronic devices that convert the energy of sunlight incident on them into electricity by the photovoltaic effect. Solar cells are a type of photovoltaic cell, defined as devices whose electrical properties, such as current and voltage, change when exposed to light. In particular, the present invention relates to a method for manufacturing solar cells with protection against low-energy protons (and other harmful radiation), and to solar cells obtained by such a manufacturing method. [Background technology]

[0002] Solar cells, especially those intended for use in space (hereinafter briefly "space solar cells") or at high altitudes, require protection that can shield them from low-energy protons (and other harmful radiation) and protect them mechanically.

[0003] Currently, typical protection for solar cells consists of a cerium-doped borosilicate glass (the so-called "cover glass" or "cover slip"), individually glued to the active surface of each solar cell (the active surface of a solar cell is the surface intended to be exposed to sunlight during use) using a transparent resin that reduces the mechanical stress between the glass and the solar cell itself.

[0004] US Patent No. 5,949,999 describes a flexible hybrid cover glass for spacecraft solar panels, consisting of droplets of fused silica or cerium-doped borosilicate glass embedded in a matrix of conventional adhesive for glass.

[0005] Patent Document 2 describes a radiation-stable screen for use in space applications or at high altitudes. The screen includes a plurality of overlapping planar glass flakes held in a lamellar matrix of a flexible polymeric material. Each flake is composed of a radiation-stable glass suitable for use in space or at high altitudes. The flakes are aligned in the lamellar direction of the matrix.

[0006] Patent Document 3 discloses a lightweight photovoltaic device for use in stratospheric and outer space applications. The device includes a protective surface coating on its light-incident side. The protective coating is formed of a material that does not adversely affect the photovoltaic properties of the solar cell and protects the solar cell from the harsh conditions of the stratospheric or outer space environment in which the photovoltaic device is adapted to be used, and remains substantially unchanged when exposed to the harsh environment of the stratosphere or outer space. The protective coating is made of a spray-coated silicone-based material and has a thickness of 0.01 to 2 mils (2.54 x 10 -4 The thickness ranges from 0.05 mm to 0.05 mm. Silicone-based overcoats are prepared by a chemical spray process using commercially available spray coating equipment. The coating is then cured at elevated temperatures. A suitable silicone-based material is DOW CORNING® 1-2620 (low VOC conformal coating or dispersion) diluted with DOW CORNING® OS-30 solvent. An additional layer of transparent conductive material is deposited on top of the silicone layer to provide additional protection in space environments, i.e., adding protection from UV radiation as well as allowing static electricity to escape, helping to prevent destructive ESD events. The transparent conductive layer may include a layer of indium tin oxide (ITO) or zinc oxide (ZnO).

[0007] Patent Document 4 discloses that solar cells, particularly those deployed in space, require a coating to protect the solar cells from damage caused by solar radiation. This document discloses a protective coating that is a polyimide that has the required combination of properties: colorless, transparent, relatively non-brittle, highly thermally stable, and readily transmits solar radiation without appreciable degradation. The coating is heat resistant, does not degrade significantly when exposed to ultraviolet light, and is highly effective at repelling low-energy proton particles. The protective polyimide coating is a polymer with repeating structural units. Anti-reflective coatings (TiO X and Al2O3, Ta2O5, or SiO X A polyimide coating (combined with an amine) is deposited directly on the active surface of the cell before applying a protective polyimide coating. A primer coating (a silane adhesion promoter such as aminopropyltrimethoxysilane) is applied on top of the antireflective coating before applying the polyimide coating. The primer coating improves the adhesion of the polyimide coating to the solar cell, particularly to the top surface of the antireflective coating.

[0008] (Non-Patent Document 1) describes the development of a proprietary transparent conductive oxide (TCO) coating for use on flexible cover glass materials such as UVR / AR (UV reflector and wide-band anti-reflection) and pseudomorphic glass (PMG) and other silicone-based covers. The coatings deposited on the flexible substrate materials underwent mechanical and space environment durability testing. The coated flexible substrates were then integrated (CIC'd) with active IMMs and other battery types.

[0009] Non-Patent Document 2 discloses that a key area for improving solar cell efficiency is optimizing antireflective coatings (ARCs) to allow more light to be converted, which theoretically could improve solar cell efficiency by 0.5%. Various ARC designs have been investigated, with the most promising approaches being based on multilayer or graded index approaches. These approaches have been theoretically and experimentally optimized to increase photocurrent within the spectral range of 300–1880 nm.

[0010] The applicant has identified that the protective glasses currently used to protect solar cells, particularly solar cells for space or high altitude applications, have several drawbacks, including a lack of flexibility and high integration costs.

[0011] The protective glass used must have specific properties depending on the specific type of solar cell and the specific application of the solar cell itself. Therefore, the protective glass must be customized and specially made. This is expensive both in terms of supply time and costs (so-called "recurring costs") inherent in glass designs that sometimes differ in properties such as size. Furthermore, the entire process of manufacturing the protective glass and applying it to the solar cell is completely decoupled from the manufacturing process of the solar cell itself (which is based on semiconductor technology).

[0012] With regard to Patent Document 3, the applicant has realized that protection against the harsh conditions in the stratosphere or outer space environments is provided by a coating made of a spray-coated silicone-based material. An additional layer of transparent conductive material (ITO or ZnO) deposited on top of the silicone layer provides enhanced protection from UV radiation and is specifically designed to allow static electricity to escape, helping to prevent destructive ESD events, and therefore is electrically conductive.

[0013] Applicant has observed that the use of conductive oxides such as ITO and ZnO limits the thickness of the protective layer that can be formed and does not compromise the transparency of the protective layer to sunlight, which would adversely affect the conversion efficiency of the solar cell. Therefore, protection against low-energy protons is limited. Furthermore, the use of transparent conductive materials limits the selection of suitable materials, preventing the selection of materials with better refractive indices.

[0014] With regard to Patent Document 4, the applicant has realized that protection of the solar cell is provided by the polyimide coating. The primer coating is not for protecting the solar cell, but serves to enhance the adhesion of the polyimide coating to the solar cell (particularly to the top surface of the anti-reflective coating). The applicant further points out in Patent Document 4 that a thin (thickness less than 1 μm) anti-reflective coating layer (TiO X and Al2O3, Ta2O5, or SiO X It has been noted that the anti-reflective coating is deposited directly onto the active surface of the cell prior to application of the polyimide protective coating, i.e., the anti-reflective coating is underneath the polyimide coating (and underneath the primer coating).

[0015] In Non-Patent Document 1, the applicant noted that the coatings deposited on PMG and other silicone-based covers (Figure 1 of the document) are thin layers whose purpose is to protect solar cells from exposure to atomic oxygen and UV radiation. The coatings must withstand (not protect against) the ionizing radiation present in the space environment (gamma rays, X-rays, and charge carriers (electrons and protons) trapped by the Earth's magnetic field). Anti-reflective or UV-reflective coatings are typically thin (Figures 2 and 3 of the document report transparent conductive oxide (TCO) coating thicknesses of 8 nm, 15 nm, and 16 nm, demonstrating that an increase in the thickness of the TCO coating by just a few nanometers (from 8 nm to 15-16 nm) already significantly reduces the coating's spectral transmittance in the 300-500 nm wavelength range).

[0016] Non-Patent Document 2 deals with anti-reflective coatings deposited directly on the active surface of solar cells. The purpose of the anti-reflective coating is to minimize the reflection of sunlight. The applicant observes that anti-reflective coatings that are anti-reflective are typically thin. [Prior art documents] [Patent documents]

[0017] [Patent Document 1] U.S. Patent No. 8,974,899 [Patent Document 2] US Patent Application Publication No. 2014 / 0007924 [Patent Document 3] US Patent Application Publication No. 2008 / 173349 [Patent Document 4] International Publication No. 84 / 02529 [Non-patent literature]

[0018] [Non-Patent Document 1] Carol L. Martinez et al., "Test Results of Radiation Resistant Coatings Integrated with Flexible Substrate Materials and Active Solar Cells," 2016 IEEE 43rd Photovoltaic Specialists Conference (PVSC), June 5, 2016, pp. 2586-2591. [Non-patent document 2] Roberta Campesato et al., "Effective Coating for High Efficiency Triple Junction Solar Cells," 2019 European Space Power Conference (ESPC), September 30, 2019, pp. 1-5. Summary of the Invention [Problem to be solved by the invention]

[0019] Applicant was faced with the problem of identifying a solution to the problem of protecting solar cells from low energy protons (and other harmful radiation) encountered in the space environment and at high altitudes in the atmosphere, without the drawbacks associated with the use of protective glass. [Means for solving the problem]

[0020] Applicant has discovered that it is possible to provide protection to solar cells by forming (e.g., by depositing a material) directly on the active surface of the solar cell (the surface intended to be exposed to sunlight during use) one or more layers of protective material(s) suitable for protecting the solar cell from low-energy protons (and other harmful radiation) encountered in the space environment and at high altitudes in the atmosphere (e.g., at least 2 μm), which layer(s) are of an appropriate thickness (e.g., sufficient thickness (e.g., at least 2 μm) to stop protons having an energy of at least 200 KeV (0.2 MeV), which is transparent to electromagnetic radiation (e.g., solar radiation) within the frequency range at which the solar cell is capable of photovoltaic conversion, and which perform the same function as known protective glass).

[0021] Such a layer(s) of protective material can comprise or consist of an oxide layer (particularly a non-conductive oxide layer). For purposes of this disclosure, a "non-conductive" material is defined as a material having a conductivity of about 10 -3 Ω -1 m -1The term "material" should be intended to mean a material having an electrical conductivity less than 1000 .mu.m.

[0022] Examples of suitable non-conductive oxides that can be used as the protective material include silicon oxide (SiO2), aluminum oxide (Al2O3), tantalum oxide (Ta2O5), niobium oxide (Nb2O5), yttrium oxide (Y2O3), titanium oxide (TiO2), scandium oxide (Sc2O3), cerium oxide (CeO2), hafnium dioxide (HfO2), tin dioxide (SnO2), and LaTiO3.

[0023] In addition to non-conductive oxides, other non-conductive materials that are transparent in the frequency range used by solar cells to perform photovoltaic conversion of electromagnetic radiation (especially sunlight) can be used to form the layer(s) of protective material, such as, for example, magnesium fluoride (MgF2), cerium fluoride (CeF3), zinc sulfide (ZnS), silicon nitride (Si3N4), etc.

[0024] Such a layer(s) of protective material(s) can be formed (e.g., by deposition of a material) on the (active surface of) the solar cell directly or by interposing an adhesive layer (a layer of resin between the (active surface of) the solar cell and the layer(s) of protective material(s). It is also possible to form a combination of stacked layers of resin and protective material above the (active surface of) the solar cell (e.g., a layer of protective material formed (e.g., by deposition of a material) directly on the (active surface of) the solar cell, then a layer of resin formed on the layer of protective material, and an additional layer of protective material on the resin layer).

[0025] The use of non-conductive materials to form the protective layer allows for the formation of a relatively thick protective layer (thicker than when using a conductive oxide layer) while still ensuring a high level of transparency to electromagnetic radiation (especially solar radiation) within the frequency range at which the solar cell can perform photovoltaic conversion. Thicker protective layers are more effective at blocking low-energy protons and other radiation that are harmful to the solar cell.

[0026] Additionally, the use of a non-conductive material as the protective layer (instead of a conductive oxide layer) widens the range of suitable materials that can be selected and allows for better selection of the refractive index of the material selected to form the protective layer.

[0027] As mentioned above, the layer(s) of protective material can be formed, for example, by vapor deposition techniques (e.g., by utilizing any known technique of physical vapor deposition ("PVD"), such as thermal evaporation, electron gun, pulsed laser deposition ("PLD"), cathodic sputtering (or cathodic evaporation)).

[0028] The adhesive (resin) layer(s) can be made of the same type of resin typically used to bond cover glass to solar cells, and the resin used can be a transparent silicone adhesive material (e.g., a material commercially known as ELASTOSIL® S695 or S690, or an elastomeric silicone material commercially known as DC93-500 manufactured by Dow Corning®).

[0029] The layer(s) of protective material also protect the resin layer(s) from low energy protons and prevent the resin layer(s) from degrading due to exposure to low energy proton radiation.

[0030] According to one aspect of the present invention, there is provided a method for manufacturing a solar cell, comprising the steps of: providing a solar cell having an active surface intended to be exposed to sunlight for photovoltaic conversion in use; corresponding to said active surface, forming protection against low energy protons and other radiation harmful to solar cells. The step of forming the protection comprises: forming a resin layer; forming, over the resin layer, a layer of non-conductive protective material that is transparent in the electromagnetic radiation frequency range for which the solar cell is intended, by depositing material on top of the resin layer.

[0031] The step of forming by deposition of material includes one or more physical vapor deposition (PVD) processes, particularly thermal evaporation, electron beam, pulsed laser deposition (PLD), and sputtering.

[0032] In a possible embodiment, the resin layer can be formed directly on the active surface of the solar cell.

[0033] In a possible embodiment, the method comprises: The method may further comprise the step of forming, by deposition of material, another layer of protective material interposed between the resin layer and the active surface of the solar cell.

[0034] In a possible embodiment, the step of forming a layer of another protective material interposed between the resin layer and the active surface of the solar cell by depositing a material can include one or more physical vapor deposition (PVD) processes, such as thermal evaporation, electron beam, pulsed laser deposition (PLD), sputtering.

[0035] In a possible embodiment, the one or more layers of protective material may comprise or consist of oxide layers, in particular one or more layers of silicon oxide (SiO), aluminum oxide (AlO), tantalum oxide (TaO), niobium oxide (NbO), yttrium oxide (YO), titanium oxide (TiO), scandium oxide (ScO), cerium oxide (CeO), hafnium dioxide (HfO), tin dioxide (SnO), LaTiO, and other materials transparent in the frequency range used by solar cells to perform photoelectric conversion, including magnesium fluoride (MgF), cerium fluoride (CeF), zinc sulfide (ZnS), silicon nitride (SiN).

[0036] In a possible embodiment, said step of forming a resin layer may comprise a deposition process.

[0037] In a possible embodiment, the method may include forming alternating layers of resin and protective material repeated several times.

[0038] In a possible embodiment, the method may include forming an anti-reflective layer on top of the top protective layer.

[0039] Preferably, the layer of protective material, or at least one of the layers of protective material, has a thickness greater than about 2 μm.

[0040] According to another aspect of the present invention, there is provided a solar cell comprising an active surface intended to be exposed to sunlight in use for photovoltaic conversion, the active surface being provided with protection against low energy protons and other radiation harmful to the solar cell, the solar cell being obtainable by the manufacturing method according to the above aspect of the present invention.

[0041] The protection against low-energy protons and other harmful radiation can comprise at least one resin layer and, above the resin layer, at least one layer of protective material against low-energy protons and other radiation harmful to the solar cell, which is transparent to solar radiation in the frequency range used by the solar cell to perform photovoltaic conversion. The at least one layer of protective material is a layer of deposited non-conductive material that can be obtained by deposition of a material, for example, physical vapor deposition from the gas phase (physical vapor deposition (PVD)), for example, thermal evaporation, electron beam, pulsed laser deposition (PLD), sputtering.

[0042] The at least one layer of protective material may comprise or consist of an oxide layer, in particular one or more layers of silicon oxide (SiO2), aluminum oxide (Al2O3), tantalum oxide (Ta2O5), niobium oxide (Nb2O5), yttrium oxide (YO3), titanium oxide (TiO2), scandium oxide (Sc2O3), cerium oxide (CeO2), hafnium dioxide (HfO2), tin dioxide (SnO2), LaTiO3, and other materials transparent in the frequency range used by solar cells to perform photoelectric conversion, including magnesium fluoride (MgF2), cerium fluoride (CeF3), zinc sulfide (ZnS), silicon nitride (Si3N4).

[0043] Preferably, the at least one layer of protective material has a thickness greater than about 2 μm.

[0044] The layer(s) of protective material(s) perform the function of protecting the (active surface of) the solar cell, blocking low-energy protons and other radiation harmful to the solar cell encountered in the space environment and at high altitudes in the atmosphere. The layer(s) of resin help to reduce the mechanical stresses due to the different thermal expansion coefficients of the materials used, thus also ensuring better adhesion of the layer(s) of protective material to the surface of the device.

[0045] Thanks to the present invention, it is possible to achieve protection of solar cells against low-energy protons and other radiation harmful to solar cells through a method integrated into the conventional solar cell manufacturing process (based on semiconductor technology). The protection thus obtained is far more advantageous than that obtained by applying a conventional cover glass, since it does not present the problems associated with special sizing of the protective glass, especially in terms of area. Furthermore, the thickness of the protection can be easily adapted to the specific needs resulting from the specific application of the solar cell. As a result, the manufacturing costs of the solar cell are significantly reduced. Last but not least, the protection achieved by the layer(s) of protective material integrally formed with the solar cell ensures the flexibility of the solar cell itself (unachievable with conventional protective glass), a feature particularly useful in the case of thin solar cells.

[0046] These and other features of the invention, as well as these and other advantages, will become more apparent upon reading the following detailed description of some of its possible embodiments, given by way of example and in no way limiting, in which, for a better understanding, reference is made to the accompanying drawings, in which: [Brief explanation of the drawings]

[0047] [Figure 1A] 1 illustrates three stages of a method for manufacturing a solar cell according to one embodiment of the present invention. [Figure 1B] 1 illustrates three stages of a method for manufacturing a solar cell according to one embodiment of the present invention. [Figure 1C] 1 illustrates three stages of a method for manufacturing a solar cell according to one embodiment of the present invention. [Figure 2A] 4 illustrates four steps of a method for manufacturing a solar cell according to another embodiment of the present invention. [Figure 2B] 4 illustrates four steps of a method for manufacturing a solar cell according to another embodiment of the present invention. [Figure 2C] 4 illustrates four steps of a method for manufacturing a solar cell according to another embodiment of the present invention. [Figure 2D]4 illustrates four steps of a method for manufacturing a solar cell according to another embodiment of the present invention. [Figure 3] FIG. 10 illustrates the "cutoff" energy as a function of thickness and type of protective material used for certain types of exemplary protective materials. DETAILED DESCRIPTION OF THE INVENTION

[0048] It should be noted that the illustrations shown in the drawings are schematic and are not necessarily made to scale, in particular some details of the drawings may be greatly exaggerated (compared to their actual size) purely for illustrative purposes.

[0049] Referring to the drawings, FIGS. 1A-1C show three stages of a method for fabricating a solar cell according to one embodiment of the present invention.

[0050] Reference numeral 100 denotes a solar cell, such as a space solar cell. Solar cell 100 can be, for example, a cell of compounds of groups III and V of the periodic table of elements (a "III-V solar cell"), such as gallium arsenide (GaAs) or indium gallium phosphide (InGaP). Solar cell 100 can be a single-junction solar cell, i.e., one with a single p-n junction, or a multi-junction solar cell with two or more p-n junctions, for example a triple-junction solar cell (including three p-n junctions). The steps in the manufacturing process for solar cell 100 are known to those skilled in the art and will not be shown or described.

[0051] The solar cell 100 has an active surface 105a (the surface of the solar cell that is intended to be exposed to sunlight during use to enable the solar cell to perform photovoltaic conversion) and an opposite inactive surface 105b (that is not exposed to sunlight during use), and the solar cell 100 is attached to a support panel (not shown) corresponding to the inactive surface 105b.

[0052] As shown in FIG. 1B, a solar-transparent resin layer 110 is formed on the active surface 105 of the solar cell 100 (the surface of the solar cell intended to be exposed to sunlight during use). The resin can be, for example, the same type of resin used in the art to bond protective cover glass to solar cells. For example, the resin used can be a transparent silicone adhesive material, such as a material commercially known as Elastosil® S695 or S690, or an elastomeric silicone material commercially known as DC93-500 manufactured by Dow Corning®. The resin layer 110 can be formed, for example, by any deposition technique used for integrating space solar cells (using conventional steps known to those skilled in the art and therefore not described here). FIG. 1B also shows (highly exaggerated compared to actual dimensions) how, as a result of the deposition process of the resin layer 110, the material of the resin layer 110 protrudes from the edge of the active surface 105a of the solar cell 100 and descends along the sidewalls of the solar cell 100 itself, covering them (in a manner that gradually decreases with distance from the active surface 105). The resin layer 110 can have a thickness in the range of, for example, several tens of microns to approximately 100 μm.

[0053] 1C, a layer of protective material 115 is formed on resin layer 110. The layer of protective material 115 is transparent to sunlight (within the wavelength range for which the solar cell is intended to perform photovoltaic conversion) but can block low-energy protons and other radiation that is harmful to solar cell 100. Protective material layer 115 is a layer of non-conductive material. Protective material layer 115 can include or consist of a layer of a non-conductive oxide (e.g., silicon oxide (SiO2) or an oxide of another element, or other non-conductive material that is transparent in the frequency range used by the solar cell to perform photovoltaic conversion). For example, the layer of protective material 115 can include or consist of silicon oxide (SiO), as well as aluminum oxide (AlO), tantalum oxide (TaO), niobium oxide (NbO), yttrium oxide (YO), titanium oxide (TiO), scandium oxide (ScO), cerium oxide (CeO), hafnium dioxide (HfO), tin dioxide (SnO), LaTiO, indium tin oxide (also called indium-doped tin oxide or ITO), or other materials transparent within the frequency range used by the solar cell to perform photovoltaic conversion, such as, for example, magnesium fluoride (MgF), cerium fluoride (CeF), zinc sulfide (ZnS), silicon nitride (SiN), etc. The layer of protective material 115 has an appropriate thickness selected to provide the desired protection of the solar cell 100 during use.

[0054] The shielding power (so-called "stopping power") that the protective material layer 115 has against low-energy protons depends on the thickness of this layer as well as the density and atomic composition of the protective material used. The cutoff energy (the maximum proton energy that the material can completely shield) as a function of the thickness of the protective material layer 115 used can be obtained using models and calculation codes known in the literature (e.g., SRIM, www.srim.org). Figure 3 shows the cutoff energy performance as a function of the protective material layer thickness for three representative protective materials: SiO2, Al2O3, and Ta2O5.

[0055] For example, if the layer of protective material 115 has a thickness of at least 2 μm, protons with energies of 0.2 MeV or less will be shielded.

[0056] The layer of protective material 115 can be formed by a deposition technique using any known technique of physical vapor deposition (PVD), such as, for example, thermal evaporation, electron beam, pulsed laser deposition (PLD), cathodic sputtering (or cathodic evaporation, simply "sputtering"), etc. As with Figure 1B, Figure 1C also shows (in a highly exaggerated manner compared to the actual dimensions) how, as a result of the formation process by deposition of the layer of protective material 115, the material of the layer of protective material 115 protrudes from the edge of the active surface 105a of the solar cell 100, descends along the sidewalls of the solar cell 100 itself, and covers (in a manner that decreases with distance from the active surface 105) the same sidewalls (already covered by the material of the resin layer 110).

[0057] The fabrication of the solar cell involves conventional steps which will not be described as they are known to those skilled in the art.

[0058] The adhesive resin layer 110 does not essentially have a function of protecting the solar cell against low-energy protons. The presence of the adhesive resin layer 110 interposed between the layer of protective material 115 and the active surface 105a of the solar cell 100 helps to reduce mechanical stress between the layer of protective material 115 and the solar cell 100.

[0059] The layer 115 of protective material present above the resin layer 110, in addition to performing a protective function against low-energy protons and other radiation harmful to the solar cell 100, also avoids the phenomenon of yellowing ("darkening") of the resin layer 110, which may affect the resin layer 110 as a result of exposure to ultraviolet radiation during use of the solar cell. The layer 115 of protective material also protects the resin layer 110 from low-energy protons, avoiding degradation of the resin layer 110 due to exposure to low-energy proton radiation.

[0060] 2A-2D show four steps of a method for manufacturing a solar cell according to another embodiment of the present invention.

[0061] Starting with the solar cell 100 shown in FIG. 2A (as in the above embodiment, the solar cell 100 can be, for example, a GaAs or InGaP single-junction or multi-junction, e.g., III-V solar cell), a first layer of protective material 215a is formed on the active surface 105a of the solar cell 100, as shown in FIG. 2B. The layer of protective material 215a is transparent to sunlight (within the wavelength range for which the solar cell is intended to perform photovoltaic conversion). The layer of protective material 115a is a layer of non-conductive material. The layer of protective material 215a can, for example, comprise or consist of a layer of SiO or an oxide of another element, or a layer of other non-conductive material that is transparent within the range of frequencies used by the solar cell to perform photovoltaic conversion. In addition to silicon oxide (SiO), the layer of protective material 215a can include or consist of aluminum oxide (AlO), tantalum oxide (TaO), niobium oxide (NbO), yttrium oxide (YO), titanium oxide (TiO), scandium oxide (ScO), cerium oxide (CeO), hafnium dioxide (HfO), tin dioxide (SnO), LaTiO, or other materials that are transparent in the frequency range used by the solar cell to perform photovoltaic conversion, such as, for example, magnesium fluoride (MgF), cerium fluoride (CeF), zinc sulfide (ZnS), silicon nitride (SiN).

[0062] The thickness of the layer of protective material 215a can be sized as a function of the energy of the protons that the oxide layer must be able to block. The layer of protective material 215a can be formed, for example, by a deposition technique as described in the description of the previous embodiment. Figure 2B also shows (highly exaggerated compared to its actual size) that, as a result of the process of forming the layer of protective material 215a by deposition, the material of the layer of protective material 215a overlaps the edges of the active surface 105a of the solar cell 100 and descends along the sidewalls of the solar cell 100 itself, covering them (in a manner that gradually decreases with distance from the active surface 105a).

[0063] As shown in Figure 2C, a solar-transparent resin layer 210 is formed on the first layer of protective material 215a. The resin layer 210 can be made, for example, as described for the resin layer 110 of the previous embodiment. In this case, Figure 2C also shows (in a highly exaggerated manner compared to the actual dimensions) how, as a result of the formation process by deposition of the resin layer 210, the material of the resin layer 210 protrudes from the edge of the active surface 105a of the solar cell 100, descends along the sidewalls of the solar cell 100 itself, and covers (to a gradually decreasing extent moving away from the active surface 105) the sidewalls themselves (which are already covered by the material of the layer of protective material 215a).

[0064] As shown in Figure 2D, a second layer of solar-transparent protective material 215b is formed on the resin layer 210. The second layer of protective material 215b is a layer of non-conductive material. The second layer of protective material 215b can include or consist of, for example, SiO2 or an oxide of another element, or other non-conductive material that is transparent within the range of frequencies used by the solar cell to perform photovoltaic conversion. Also in this case, the layer of protective material 215b can include or consist of, in addition to SiO, aluminum oxide (AlO), tantalum oxide (TaO), niobium oxide (NbO), yttrium oxide (YO), titanium oxide (TiO), scandium oxide (ScO), cerium oxide (CeO), hafnium dioxide (HfO), tin dioxide (SnO), LaTiO, or other materials transparent within the frequency range used by the solar cell to perform photovoltaic conversion, such as, for example, magnesium fluoride (MgF), cerium fluoride (CeF), zinc sulfide (ZnS), silicon nitride (SiN), etc. The layer of protective material 215b can be formed, for example, by the same deposition technique used to form the first layer of protective material 215a. In Figure 2D, as a result of the process of forming the layer of protective material 215b by deposition, the material of the layer of protective material 215b is shown (in a highly exaggerated manner compared to the actual dimensions) overlapping the edge of the active surface 105a of the solar cell 100, descending along the sidewalls of the solar cell 100 itself, and covering (to a degree that gradually decreases as it moves away from the active surface 105) the sidewalls themselves (which are already covered by the material of the first layer of protective material 215a and the material of the resin layer 210).

[0065] The presence of the resin layer 210 helps to reduce mechanical stress between the layers of protective material 215 a and 215 b and the solar cell 100 .

[0066] The layers of protective material 215a and 215b perform a protective function for the solar cell 100 against low energy protons and other harmful radiation.

[0067] The second layer 215b of protective material covering the resin layer 210 avoids the phenomenon of yellowing (darkening) caused by exposure to ultraviolet radiation.

[0068] The layers 215a and 215b of protective material also protect the resin layer 210 from low energy protons, avoiding degradation of the resin layer 110 that can result from exposure to low energy proton radiation.

[0069] Other embodiments of the present invention are possible by repeating the structure shown in FIG. 2D, for example, by forming one or more other pairs of resin layer 210 and layer of protective material 215b above layer of protective material 215b.

[0070] The materials used to form the resin layers 110, 210 and the materials used to form the layers of protective material(s) 115, 215a, 215b may be different from the materials previously shown as examples, and the thicknesses of these layers may be different from those shown.

[0071] On top of the last layer of protective material (on top of the solar cell) one or more layers with anti-reflection properties can be deposited.

Claims

1. 1. A method for manufacturing a semiconductor space solar cell for use in space, comprising: providing a semiconductor solar cell having an active surface intended to be exposed to sunlight in use for photovoltaic conversion; corresponding to the active surface, forming a protection against low-energy protons having an energy of 200 KeV or less that are harmful to the semiconductor solar cell; In the method, The step of forming the protection comprises: forming an adhesive layer made of a resin; forming, over the resin adhesive layer, a continuous single deposited layer of a non-conductive protective material that is transparent in an electromagnetic radiation frequency range in which the semiconductor solar cell is intended to perform the photovoltaic conversion, by material deposition on the resin adhesive layer, the material deposition comprising a physical vapor deposition (PVD) process; the continuous single deposited layer of non-conductive protective material comprises or consists of an oxide layer; The method of claim 1, wherein the continuous single deposited layer of non-conductive protective material has a thickness greater than 2 μm.

2. The method of claim 1 , wherein the resin adhesive layer is formed directly on the active surface of the semiconductor solar cell.

3. 10. The method of claim 1, further comprising the step of forming, by material deposition, another layer of protective material interposed between the resin adhesive layer and the active surface of the semiconductor solar cell.

4. 4. The method of claim 3, wherein the step of forming a layer of another protective material interposed between the resin adhesive layer and the active surface of the semiconductor solar cell by material deposition comprises a physical vapor deposition "PVD" process.

5. The continuous single deposited layer of non-conductive protective material comprises: Yes ２ 、 Al ２ O ３ 、 That ２ Oh ５ 、 Nb ２ O ５ 、 Y ２ O ３ 、 TO ２ 、 Sc ２ O ３ 、 CeO ２ 、 HfO ２ 、 SnO ２ 、 Latit ３ 、 Another material transparent in the electromagnetic radiation frequency range utilized by the semiconductor solar cell to perform the photovoltaic conversion, which may be MgF ２ , CeF ３ , ZnS, or Si ３ N ４ 5. The method of claim 1, further comprising or consisting of one or more layers of other materials including

6. The method according to any one of claims 1 to 5, wherein the step of forming an adhesive layer of resin comprises a deposition process.

7. 7. The method of claim 1, further comprising forming a plurality of alternating layers of resin adhesive layers and layers of non-conductive protective material on the single continuous deposited layer of non-conductive protective material.

8. The method of any one of claims 1 to 6, further comprising forming an anti-reflective layer on the continuous single deposited layer of protective material.

9. The method of claim 3 , wherein the layer of another protective material has a thickness greater than 2 μm.

10. The method of any one of claims 1 to 9, wherein the physical vapor deposition (PVD) process comprises one or more of thermal evaporation, electron beam, pulsed laser deposition (PLD), sputtering.

11. The method of claim 1, wherein the semiconductor solar cell is a III-V solar cell of compounds from groups III and V of the periodic table of elements.

12. 12. The method of claim 11, wherein the semiconductor solar cell is a gallium arsenide (GaAs) or indium gallium phosphide (InGaP) cell.

13. 5. The method of claim 4, wherein the method of depositing the material between the resin adhesive layer and the active surface of the semiconductor solar cell to form the other layer of protective material comprises one of thermal evaporation, electron beam, pulsed laser deposition "PLD", and sputtering.

14. The method of claim 3 , wherein the other layer of protective material comprises or consists of an oxide layer.

15. The layer of another protective material may be Yes ２ 、 Al ２ O ３ 、 That ２ Oh ５ 、 Nb ２ O ５ 、 Y ２ O ３ 、 TO ２ 、 Sc ２ O ３ 、 CeO ２ 、 HfO ２ 、 SnO ２ 、 Latit ３ 、 Another material transparent in the electromagnetic radiation frequency range utilized by the semiconductor solar cell to perform the photovoltaic conversion, which may be MgF ２ , CeF ３ , ZnS, or Si ３ N ４ Other materials including 16. The method of claim 15, comprising or consisting of one or more layers of

16. The method of claim 7 , wherein the alternating layers have a top layer of a protective material, the method further comprising forming an anti-reflective layer on the top layer of the protective material.

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