WO2012093187A1 - P-i-n-type multijunction photovoltaic material, photovoltaic ceramic device comprising said material and methods for the production of the material and device - Google Patents

Abstract

The invention relates to a P-I-N-type photovoltaic material characterised in that it comprises at least three P-I-N semiconductor junctions stacked in tandem, the P, I and N layers of which comprise hydrogenated monocrystalline silicon contained in an amorphous silicon matrix. Moreover, each of the P and N layers of each P-I-N junction has a specific composition. Said material can be used to produce photovoltaic devices with a ceramic base, preferably traditional materials used in the construction industry. The invention also relates to the method for obtaining the aforementioned photovoltaic material, as well as to the method for conditioning the surface of the ceramic base and the enamel used for said conditioning, which has a novel and inventive composition.

Description

 MULTIUNION PHOTOVOLTAIC MATERIAL TYPE P-I-N, PHOTOVOLTAIC CERAMIC DEVICE INCLUDING IT AND METHODS OF OBTAINING THE SAME TECHNICAL FIELD OF THE INVENTION

 The present invention is framed in the field of photovoltaic energy production, that is, the direct transformation of solar radiation into electrical energy, specifically the semiconductor materials used to produce said energy when integrated into devices such as cells solar. More specifically, the invention is part of the field of application of these photovoltaic devices in the manufacture of ceramic products of the construction industry, such as tiles, tiles or ventilated facade panels.

 BACKGROUND OF THE INVENTION

 The application of photovoltaic materials and solar cells on the surface (face view) of supports of a ceramic nature is widely known in the construction industry. In the literature you can find works aimed at the development of the semiconductor material itself and its manufacturing process (US5646050 and US5246505), as well as the ceramic support in which it is integrated

(JP2002246621 and JP2002293644) or of the way in which both, active element and constructive element, combine with each other - mechanical incorporation, recessed in ceramics ...-

(JP2007186856, JP2006019768, ES2153796 and its certificate of addition ES2158830).

Among the photovoltaic devices applied for this purpose, the present invention is directed specifically to the PIN-type solar cells, which are composed of two thin layers, P and N, doped with various elements and between which a third intrinsic semiconductor layer is integrated. Among the semiconductor materials used in the manufacture of PIN-type photovoltaic cells on supports Ceramic silicon is common, currently being of special interest for its properties the use of amorphous silicon (US5646050, US6635307 and US5246505) and, to a lesser extent, microcrystalline silicon.

 These solar cells can be of the simple type

(WO2008 / 120251) or multilayer (EP0660422A3), depending on the number of P-I-N type junctions that each cell comprises, and are usually deposited on a layer of a contacting metal, for example silver (WO2008 / 120251). The union or PIN-type junctions of the solar cell, when integrated into ceramic facade supports that are outdoors, are usually protected against atmospheric agents by means of protective layers of different nature and one or more encapsulating layers are coated (WO2008 / 120251 ).

 In the face of common procedures for obtaining these photovoltaic ceramic devices, such as the joining by adhesives of the cell or solar cells to the surface of the support (ES2153796 and ES2158830), today the interest is focused on developing integral methods of manufacturing such devices, aimed at how to directly grow (or deposit) the photovoltaic element on the support to achieve greater cohesion and achieve greater energy efficiency, generally by means of Plasma-enhanced chemical vapor deposition or Chemical Steam Phase deposition techniques PECVD, in English).

Among the works developed in this area, the one by Iencinella et al. (Thin-film solar cells on commercial ceramic tiles (2009); Solar Energy Materials and solar cells, 93: 206-210), for constituting one of the prior art documents closest to the present invention, which describes a process of deposition of a photovoltaic element type PI-N on a porcelain stoneware substrate by means of PECVD, in which to solve possible problems of short circuits associated with the roughness of the stoneware a layer of ITO between the surface of the same and the metal contact, in addition to establishing an arrangement of the contacts as a grid. It is also worth mentioning the international patent application WO2008 / 120251, belonging to the same authors, where a process of construction of a solar tile from a ceramic of porosity less than 0.5% is disclosed, depositing the metal contacts (from Ag ) on the surface of the support, a single active union type PIN (by deposition of plasma-assisted amorphous silicon), and then the frontal contact (also of Ag).

Another alternative method for manufacturing solar roof tiles is described in international patent application WO2005 / 045942, where: a) the support is treated with a phosphor silicate vitreous coating; b) a transparent conductive oxide layer (Sn0 ₂ and / or ln ₂ 0 ₃ ) is deposited on said coating as a bottom contact; c) the PIN junction is increased by PECVD; and d) an upper TCO contact similar to the lower one is deposited and e) the assembly is protected with a transparent encapsulating layer.

 Likewise, the patent EP0729190, which can be considered the state of the art closest to the present invention, consists in a process of deposition of a multi-junction photovoltaic material type PIN in tandem by means of PECVD of amorphous silicon and aggregates of microcrystalline silicon using in addition various components Dopants and barrier layers of the solar cell.

However, the works focused from this perspective are not abundant due to the numerous problems posed by the methodology. On the one hand, technical difficulties are due to 1) the roughness and porosity of the conventional (commercial) ceramic building elements used, in relation to the thickness of the photovoltaic element, which worsens the adhesion of both components and usually produces short circuits that destroy the device. On the other hand, 2) a migration usually occurs of contaminants (for example, sodium) from ceramics to photovoltaic material, which decreases its efficiency. This is joined by 3) environmental and health problems linked to certain doping components that are used, as well as 4) the need to find new doping and semiconductor materials (or their possible combinations) that improve the energy production of the solar cell , since the devices known so far have performance and durability problems due to the poor adequacy of the PIN photovoltaic material to the substrate.

 In order to solve these drawbacks, the present invention proposes multiple solutions at different scales by developing a process for obtaining a multilayer photovoltaic material that is integrated into a conventional ceramic support, such as those used in the construction industry (by for example, ceramic tiles or ventilated façade ceramic panels), to obtain a more economical, efficient and easy-to-use ceramic photovoltaic module or device:

 - the composition of the multilayer photovoltaic material type P-I-N has been improved, both in terms of semiconductor material and doping materials;

- an improved process of deposition and growth of the photovoltaic material by means of PECVD has been designed; Y

- A mechanism for conditioning and coating the surface of the ceramic support has been developed prior to the deposition of the semiconductor material, mainly through an enamelling formulation of a novel composition, in order to reduce its roughness and prevent the migration of contaminants.

In essence, from the obtaining of a semiconductor material type PIN of several thin layers of amorphous silicon (a-Si: H) and microcrystalline (yc-Si: H) hydrogenated and of a novel formulation enamel that serves as a barrier in the coating of conventional ceramic supports (commercial), the present invention seeks to integrate photovoltaic utilization facilities into traditional architecture by means of integrated and multifunctional devices of long duration and easy maintenance, which minimize the economic and operational impact.

 DESCRIPTION OF THE INVENTION

General description

 The main object of the present invention resides in a thin layer PIN type photovoltaic material based on crystalline amorphous silicon (or what is the same, amorphous silicon with microcrystalline cores), suitable for integration on a ceramic substrate or piece in order to obtain an improved efficiency photovoltaic device (panel). Specifically, said photovoltaic material is composed of three or more PIN-type junctions stacked in tandem on one another, comprising hydrogenated microcrystalline silicon contained in an amorphous silicon matrix (which can be represented as a-Si: H / yc-Si: H ) as a semiconductor material.

 The at least three layers P and three layers N further comprise boron and phosphorus as doping agents, respectively. However, while the layer I of all the joints in the series consists essentially of the aforementioned silicon, the composition of each of the at least three layers P and the at least 3 layers N differs between them; in its essential composition, the P layer of the second P-I-N junction further comprises arsenic, while the P layer of the third P-I-N junction further comprises gallium. On the other hand, the N layer of the second P-I-N junction further comprises gallium, and the N layer of the third P-I-N junction further comprises arsenic. To facilitate the interpretation of the text, the composition of the material disclosed is illustrated in Table 1 below.

Table 1. Essential composition of the multi-layer photovoltaic material type PIN object of the invention Essential components

 Photovoltaic material

 Semiconductor A. dopants

 FIRST LAYER P B

FIRST LAYER I

FIRST LAYER N P

SECOND LAYER P B + As

 SECOND LAYER I a-Yes: H / c-Si: H *

 SECOND LAYER N P + Ga

 THIRD LAYER P B + Ga

 THIRD LAYER I

THIRD LAYER N P + As

 * hydrogenated microcrystalline silicon in an amorphous silicon matrix

If the photovoltaic material comprises more than 3 semiconductor junctions type P-I-N as mentioned, which is the minimum defined for said material, the doping sequence in the odd and even junctions is analogous to that represented in Table 1.

The improvement proposed by this photovoltaic material compared to others known in the field lies not only in the type of silicon used, but also in the use of arsenic and gallium as doping agents. Regarding the first, it should be noted that thanks to the microcrystallinity of the Si it is possible to obtain materials with a narrow effective band space compared to those already known, also allowing greater stability and resistance to light than amorphous silicon, being the layers intrinsic semiconductors I relatively thin. As for the latter, it has been proven that within this composition and together with the other components listed, both doping agents improve the performance and give greater stability to the PIN-type joints. It has thus been possible to obtain an improved photovoltaic material in open circuit voltage and with greater efficiency in the production of photovoltaic energy, having achieved values around 19 mA / cm ² as a short-circuit current and 0.78 as a fill factor, values at least similar to those theoretically predictable for amorphous semiconductors. As for the open circuit voltage, a value that approximates that corresponding to the physical properties of the individual layers has been obtained. The improvement in performance parameters is achieved thanks to the aggregate contribution of the different unions that make up the tandem, which collaborate independently without interfering with each other. The thickness of the individual layers is also critical in order to achieve the aggregate effect.

 These essential components can preferably be combined in different proportions, as will be seen in the Detailed Description of the invention, and the photovoltaic material in question can be obtained by a sequential process (i.e., forming a PIN junction over another PIN junction and so on ) of Chemical Deposition in Phase Steam Supported by Plasma, from the injection into a series of gases inside an ultra-high vacuum reactor.

 The photovoltaic material described in this application can be specifically supported on a conventional ceramic substrate, the assembly giving rise to a photovoltaic ceramic device that is also part of the present invention, since it is novel. In addition, the use of photovoltaic material to coat ceramic substrates is another object of the present application.

Likewise, the method of obtaining the photovoltaic material disclosed here is another object of protection of this application. Said method comprises forming (growing) sequentially and in tandem (that is, mounted on top of each other) by means of Chemical Deposition in Steam Phase Supported by Plasma each of the P, I and N type layers of each of the PIN type joints that they make up the photovoltaic material, from the first P-type layer of the first PIN-type junction to the last N-type layer of the last PIN-type junction, dosing into an ultra-empty reactor chamber at least the following gases: SiCH ₄ , H ₂ , B ₂ H ₆ , PH ₃ , CH ₄ , Ga (CH ₃ ) ₃ and AsH ₃ , and applying a high frequency electromagnetic field. The preferred parameters and conditions with which said method is carried out are described in the following section.

 As mentioned when discussing the background of the present invention, another object thereof is a method of conditioning a ceramic substrate that is used in the manufacture of photovoltaic devices, and which comprises coating the surface of said substrate with a Sodium-free enamel and which in its formulation comprises at least borax, anatase, zinc oxide, metallic zinc powder, boron oxide and feldspar, before firing the ceramic substrate.

 The ceramic substrate itself obtainable from this procedure, as well as the enamelling formulation itself and its use to coat ceramic substrates are also encompassed in this invention. It has been proven that the developed enamel works optimally as a barrier layer that prevents the migration of harmful species (chemical elements) from the ceramic substrate to the photovoltaic material that is deposited on it. In addition, it allows to obtain an ideal morphology on the surface of the substrate, to achieve a micropore free roughness.

Detailed description

 Starting from the essential invention described in the previous section, a preferred embodiment thereof has been developed in which each of the at least three P-I-N type semiconductor junctions comprised in the photovoltaic material in question has the following formulation:

 - hydrogenated microcrystalline silicon contained in an amorphous silicon matrix in a percentage between 92% and 96%, including both limits;

- boron in a percentage between 1.1% and 2.8%, including both limits; Y phosphorus in a percentage between 2.4% and 3.6% including both limits;

 - the second and third unions type P-I-N also comprising nanostructured gallium arsenide in a percentage between 0.3% and 1.2%, including both limits.

Regardless of their formulation, and preferably, the at least three P-IN semiconductor junctions of the photovoltaic material are sequentially obtained in tandem (one after the other, stacked) by Plasma-backed Chemical Phase Deposition from the mixture of at least the following gases: SiCH ₄ , H ₂ , B ₂ H ₆ , PH ₃ , CH ₄ , Ga (CH ₃ ) ₃ and AsH ₃ , which are dosed into a chamber of an ultra-high vacuum reactor in the that a high frequency electromagnetic field is applied.

 When the plasma state is formed in the gas between the two electrodes where the electric field has been applied, the radicals form a layer on the heated electrode (or surface to be treated) and thus form layers P, I and N of the first junction, the P, I and N layers of the second junction on the N layer of the first, the P, I and N layers of the third junction on the N layer of the second, and so on in case there were more of three unions.

 More preferably, the gases are dosed into the reactor chamber with the following flow rates:

^• SiCH ₄ : flow rate between 25 ncc / min and 47 ncc / min, including both limits;

H ₂ : flow rate between 110 ncc / min and 186 ncc / min, including both limits;

· B ₂ H ₆ : flow rate between 12 ncc / min and 19 ncc / min, including both limits;

PH ₃ : flow rate between 14 ncc / min and 19 ncc / min, including both limits;

CH ₄ : flow rate between 43 ncc / min and 47 ncc / min, including both limits; Ga (CH ₃ ) ₃ : flow rate between 2 ncc / min and 5 ncc / min, including both limits; and AsH ₃ : flow rate between 4 ncc / min and 8 ncc / min, including both limits.

 On the other hand, when the photovoltaic material in question is obtained by Chemical Deposition in Steam Phase supported by Plasma, this process can be preferably carried out according to the following parameters:

 - Frequency of the electromagnetic field: 13.56 MHz. ; - Electrode temperature where layers P, I and N of the P-I-N type junctions are deposited: between 300 ° C and 400 ° C, including both limits;

 - RF power: between 50 and 100 w, including both limits;

 - Pressure: between 0.1 mbar and 10 mbar, including both limits; Y

 - Distance between electrodes: between 10 mm and 35 mm, including both limits.

 More preferably still, the P-I-N type junctions are deposited with a deposition rate between 0.1 nm / sec and 2 nm / sec, both limits included.

 Preferably, in any of the above variants, each PIN type junction of the photovoltaic material has a thickness between 150 nm and 210 nm, including both limits, the thickness of each of its three layers P, I and N being comprised between 50 nm and 70 nm, including both limits, that is, what could be called "thin layer".

In a preferred embodiment of the invention, the photovoltaic material in any of its variants is further defined as comprising a metallic contact layer, on which the at least three semiconductor PIN-type junctions are deposited sequentially (i.e. the layer metallic would be in direct contact with the P layer of the first PIN junction). Said metal contact layer is preferably Ni-Mo and has a thickness between 2 and 3 microns, including both limits.

 In another more preferred embodiment, the photovoltaic material further comprises at least one transparent layer of a conductive oxide coating of the last semiconductor junction type PIN, which is supported on the first two (ie, said transparent layer will be in direct contact with the Layer n of the last PIN type junction deposited). Preferably, the transparent layer of a conductive oxide has a thickness between 200 and 300 nm, including both limits. Also preferably, said layer is indium tin oxide (commonly referred to as ITO).

 And in another still more preferred embodiment, the photovoltaic material further comprises at least one polymeric sheet of a transparent, moisture and air-tight optical polymer (protective encapsulation), which covers all the photovoltaic material (i.e., on the previous transparent layer ). The polymeric layer has a preferable thickness between 80 and 100 microns, including both limits. Also preferably, said encapsulated layer is EVA (vinyl ethyl acetate).

 More preferably still, the photovoltaic material is characterized in that it additionally comprises at least one layer of transparent epoxy on the polymeric sheet. In this way, the tightness and lasting resistance of the layer is guaranteed without compromising the properties of the cell by ionic diffusion.

As stated above, this photovoltaic material is preferably designed to cover ceramic substrates, so that its use allows to obtain photovoltaic ceramic devices, which for example may be applicable to the construction industry. Therefore, the present invention encompasses the use of said material to coat ceramic substrates, as well as a device photovoltaic ceramic characterized in that it comprises at least one photovoltaic material as described above, in any of its variants, supported on a substrate of a ceramic nature. Preferably, said substrate is a porcelain tile (more preferably with a vitreous finish) or a non-porous ceramic, of those commonly used in the construction industry, and which can be selected from roof tiles, tiles, rustic tiles and ventilated facade panels, among other enclosures.

 Another object of the present invention is the method of obtaining a photovoltaic material as described herein, characterized in that it comprises at least the following steps:

form the P-type layer of the first PIN-type semiconductor junction on a previously heated support by means of a Chemical Steam Phase Deposition on a previously heated medium, dosing at least the following gases into a chamber of an ultra-high vacuum reactor: SiCH ₄ , H ₂ , B ₂ H ₆ , PH ₃ , CH ₄ , Ga (CH ₃ ) ₃ and AsH ₃ , and applying a high frequency electromagnetic field;

Y

 - deposit sequentially (one after another, stacked), in the same manner indicated in the previous stage, the layers type I and N of the first joint type P-I-N; then the layers type P, I and N of the second joint type P-I-N; and then the layers type P, I and N of the third joint type P-I-N; and so on, depending on the number of P-I-N type joints desired.

 In a preferred embodiment of the method, the gases are dosed into the reactor with the following flow rates:

SiCH ₄ : flow rate between 25 ncc / min and 47 ncc / min, including both limits;

· H ₂ : flow rate between 110 ncc / min and 186 ncc / min, including both limits;

B ₂ H ₆ : Flow rate between 12 ncc / min and 19 ncc / min, including both limits;

PH ₃ : flow rate between 14 ncc / min and 19 ncc / min, including both limits;

CH ₄ : flow rate between 43 ncc / min and 47 ncc / min, including both limits;

Ga (CH ₃ ) ₃ : flow rate between 2 ncc / min and 5 ncc / min, including both limits; and · AsH ₃ : flow rate between 4 ncc / min and

8 ncc / min, including both limits.

 The flow rate selected will depend on the specific conditions that are desired for the P-I-N type junctions that are obtained from the procedure.

 It should be noted that the method may comprise a stage of cleaning the reactor circuits between successive depositions of layers, using Helium gas as a purge. Said Helium gas can be dosed with a flow rate between 20 ncc / min. And 50 ncc / min, and would not be part of the composition of the photovoltaic material.

 Also preferably, the Chemical Steam Phase Deposition supported by Plasma is carried out according to the following parameters:

 - Frequency of the electromagnetic field: 13.56 MHz. (that is, it is done with a radio frequency equipment that works at 13.56 MHz.);

 - Temperature of the support where layers P, I and N of the P-I-N type junctions are deposited (that is, at which it is previously heated before growing the semiconductor junctions): between 300 ° C and

400 ° C, including both limits;

 - RF power: between 50 and 100 w, including both limits;

Pressure: between 0.1 mbar and 10 mbar, including both limits; Y - Distance between electrodes: between 10 mm and 35 mm, including both limits.

 Preferably, each of the P, I and N type layers of each P-I-N semiconductor junction is deposited with a deposition rate between 0.1 nm / sec and 0.2 nm / sec, including both limits.

 On the other hand, each PIN type connection obtained by the method described here preferably has a thickness between 150 nm and 210 nm, including both limits, the thickness of each of its three layers P, I and N being between 50 nm and 70 nm, including both limits.

 In another preferred embodiment, the method disclosed herein in any of the variants mentioned further comprises the following step:

 - depositing a metallic contact layer on the support, prior to the formation of the P-type layer of the first semiconductor union type PIN that is deposited on said metallic layer, which preferably has a thickness between 2 and 3 microns, including both limits, being more preferably of

1 miera.

 The method may also comprise the following stage:

- coating the multi-junction photovoltaic material by selective deposition of a transparent layer of a conductive oxide, ITO, after the deposition of the N layer of the last photovoltaic junction on all other layers. Said coating layer preferably has a thickness between 200 and 300 nm, including both limits.

 In a third possibility, the method may comprise the stage of:

- encapsulate all the multi-junction photovoltaic material, by forming a polymeric sheet of an optical transparent polymer (preferably, EVA), air and moisture tight. The sheet or layer Polymeric must be suitable for sealing and mechanical protection, and must possess the necessary optical transparency for the visible spectrum. Preferably, it has a thickness between 80 and 100 microns, including both limits, and being more preferably 100 microns.

 In a preferred embodiment, the method of obtaining the photovoltaic material comprises the three steps described above.

 As for the metal contact layer, it is preferably deposited by an electrode-free chemical deposition process that comprises at least immersing the surface of the support in a hot bath having the following formulation:

 · At least one source of metal ions,

^• at least one reducing agent,

^• at least one complex agent, and

^• at least one stabilizer,

the bath temperature being between 80 ° C and 85 ° C, including both limits, and the duration of the bath being between 3 and 5 minutes, including both limits. In a preferred embodiment, the reducing agent is hydrated sodium hypophosphite of the formula NaH ₂ P0 ₂ · H ₂ 0; the complexing agent is ammonium hydroxide; and the stabilizers are gluconic acid and sodium tartrate.

 This process offers metallic layers with high corrosion resistance, since the deposited nanoparticles have very particular physical and chemical characteristics, due to their small size.

Among all the options, the metal layer is preferably Ni-Mo, since it has the appropriate electrical and corrosion resistance properties to act as a rear contact of the photovoltaic material. In this specific case, the sources of metal ions would be nickel sulfate and molybdenum sulfate. If the electrode-free chemical deposition process described here is applied to deposit the metal layer on the substrate, it is advisable and preferable to selectively catalyze the surface of the support prior to said deposition of the metal layer, such that thanks to the location of the Catalyst The deposition of the metallic layer is selective, thus achieving an optimal contact distribution for the performance and segmentation of photovoltaic materials. Said selective catalysis is optionally carried out with a catalyst comprising palladium in suspension and applied to the surface of the substrate for 30 minutes, subsequently activating said surface at a temperature between 190 ° C and 200 ° C including both limits, during a time between 120 and 150 minutes including both limits.

 In any of the options described, it is recommended and preferable to heat the surface of the metallic support (that is, after having deposited the metal layer) until reaching a temperature between 250 and 300 ° C including both limits, before depositing the photovoltaic material on said metallic contact layer.

As for the coating of the multi-junction photovoltaic material by selective deposition of a transparent layer of a conductive oxide, in a preferred embodiment said coating is carried out by sputtering in a cathodic spray at a pressure between 10 ^{~ 6} and 10 ^{~ 8} mbar, including both limits.

For its part, the encapsulation is carried out by thermal softening of the vacuum polymer, at a pressure less than 10 ^{~ 6} , and more preferably at a pressure between 10 ^{~ 6} and 10 ^{~ 8} mbar, including both limits.

Since in a preferred embodiment the stages of metallization, coating and encapsulation can take place in the same method of obtaining the material Photovoltaic, the present invention contemplates any combination of the characteristics given for all of them.

 Optionally, after the encapsulation stage of the photovoltaic material, it is protected by spraying and polymerizing a transparent epoxy layer, at a temperature between 220 ° C and 250 ° C, including both limits (preferably, in the oven).

 Another object of the present invention is the photovoltaic material obtainable from the method described above, in any of its variants.

 Likewise, the invention described herein is directed to a method of conditioning a ceramic substrate as a support for manufacturing photovoltaic devices, characterized in that it comprises at least the following steps:

 - depositing a sodium-free enamel on the surface of the ceramic substrate and whose formulation comprises at least borax, anatase, zinc oxide, metallic zinc powder, boron oxide and feldspar; Y

 - cook the glazed ceramic substrate.

 Through this process, it is intended to provide the substrate surface with a barrier composition and ensure adequate morphology for the subsequent deposition of photovoltaic materials. In addition, adhesion between both elements, substrate and photovoltaic material is favored

 Preferably, the enamel comprises the following components in percentage by weight of dry powder:

 - 99% pure ZnO powder in anatase form, in a percentage between 20% and 30%, including both limits;

 - 99% pure anatase, in a percentage between 20% and 30%, including both limits, and coinciding with the percentage of ZnO;

- commercial quartz, in a percentage between 10% and 30%; - sodium-free potassium feldspar, in a percentage between 10% and 20%;

 - commercial borax, in a percentage between 20% and 30%;

 - Zn metal powder, in a percentage between

5% and 8%; Y

 water, at least one dispersant, at least one binder and at least one plasticizer,

and has an average granulometry equal to or less than 2 microns.

 Cooking of the material after the deposition of the enamel is preferably carried out between 1000 ° C and 1100 ° C including both limits, and preferably for a minimum period between 1 and 2 hours including both limits. More preferably, cooking is carried out at a temperature of 1100 ° C for 1 hour.

 Also optionally, after the firing step of the enameled surface of the substrate, said surface is selectively catalyzed. Said selective catalysis is carried out with a catalyst comprising palladium in suspension and applied on the surface of the ceramic substrate for 30 minutes, subsequently activating said surface at a temperature between 190 and 200 ° C including both limits, for a time between 120 and 150 minutes including both limits.

 It is recommended and preferable that, after selective catalysis, a metallic contact layer is deposited on the substrate surface, on which a photovoltaic material is deposited.

It is also preferable, for an optimal development of the invention, that at the microstructural level the tile has closed porosity and polished finish. Also preferably, the ceramic substrate may be a porcelain stoneware or a non-porous ceramic of those used in construction. More preferably the porcelain stoneware or Non-porous ceramics are selected from tiles, tiles, ventilated facade ceramic panels and other similar enclosures.

 The present invention covers the ceramic substrate obtainable from this conditioning method to obtain photovoltaic devices.

 As can be seen, the described method of conditioning a ceramic substrate can be perfectly combined with the method of obtaining a photovoltaic material discussed above, so that the conditioning of the substrate would be carried out first, and then the deposition of the photovoltaic material on said enameled substrate.

 In fact, the method of conditioning the substrate is especially preferred to obtain a photovoltaic device such as the one described herein.

 The invention also comprises, by its novel and inventive nature, a dry powder (flux) formulation for the enamelling of ceramic substrates, characterized in that it lacks sodium and comprises at least the following ceramic powder products (i.e., the formulation is consisting of a mixture of ceramic powders containing the following components): borax, anatase, zinc oxide, metallic zinc powder, boron oxide and feldspar. Said formulation in one of its preferred embodiments, comprises the following components in percentage by weight of dry powder:

 - 99% pure ZnO powder in anatase form, in a percentage between 20% and 30%, including both limits;

 - 99% pure anatase, in a percentage between 20% and 30%, including both limits, and coinciding with the percentage of ZnO;

- commercial quartz, in a percentage between 10% and 30%; - sodium-free potassium feldspar, in a percentage between 10% and 20%;

 - commercial borax, in a percentage between 20% and 30%; Y

 - Zn metal powder, in a percentage between

5% and 8%.

 Preferably the formulation, which is presented in the form of dry powder, has an equal average particle size

0 less than 2 microns. Therefore, it is optionally subjected to a grinding process.

 Preferably, the formulation further incorporates water for the milling process, and at least one dispersant, at least one binder and at least one plasticizer. Thanks to these components, the formulation is presented in the form of a slip, which facilitates its application on the surface of the substrate (a slip is understood as a suspension formed by inorganic oxides in a liquid medium, said medium being composed of water, dispersants, binders and plasticizers.

 It is logical to think that the enamelling formula developed here can be used as an enamel in a method of conditioning a ceramic substrate in accordance with the present specification to obtain photovoltaic devices, since it has advantageous properties when functioning as a barrier layer for the migration of harmful species from ceramics to the photovoltaic material itself that is deposited on it. Thus, after the application of the enamel or enamelling formula on the surface of the ceramic substrate, the assembly is subjected to cooking, preferably between 1000 ° C and 1100 ° C including both limits, and preferably for a minimum period between

1 and 2 hours including both limits. More preferably, cooking is carried out at a temperature of 1,100 ° C for 1 hour.

For the preparation of the formulation in the form of slip, it is recommended but not mandatory to follow the following premises:

 - the proportion between the dry powder that is incorporated into the slip and the organic components should be as high as possible;

 - the amount of water to keep the slip stable must be as low as possible;

 - the amount of dispersant must be adjusted to be adequate to ensure the stability of the suspension; - the proportion between binder and plasticizer must be adequate to obtain a flexible, resistant and easy to handle tape; Y

 - the rheological behavior must be adequate in order to obtain sheets without defects.

 The packaging of the particles in the enamelling formulation depends on the particle size distribution of the oxides. Thus, a very small particle size makes the surface area high which requires a high concentration of additives. In addition, during the drying stage, the dispersed particles join together to form a dense body where the small particles occupy the interstices between the large ones, hence a bimodal size distribution will improve the packing. Preferably, a greater proportion of solids with an adequate size distribution in the slip will increase the packing of the particles in the formulation sheet that is prepared.

 The function of each of the formulation additives are as follows:

- Dispersant: keep the suspension stable, because it makes the repulsive forces superior to those of attraction. The addition of the dispersant produces a decrease is the viscosity of the slip and allows to work with a higher solids content.

- Binder: provide resistance to the sheet in green and thus facilitate its handling and storage because it remains in the green sheet forming organic bridges between the ceramic particles that cause strong adhesion after evaporation of the solvent. The addition of binder to the slip produces other effects, such as better wetting, settling delay and a tolerable increase in the viscosity of the slip.

 Plasticizers: confer sufficient plasticity and flexibility to the green tape for easy handling and storage. They are substances of low molecular weight compared to the binder and are soluble in the solvent.

The at least one dispersant is optionally derived from ammonium salts of NH ₄ PA polyacrylic acids in a proportion less than 1% by weight of the dry powder; the at least one binder is preferably an acrylic polymer (preferably, latex) in proportions between 1.5% and 3% by weight of the dry powder, including both limits; and the plasticizer is preferably benzylbutylphthalate in a proportion comprised between 3% and 5% by weight of the dry powder, including both limits.

 The formulation may additionally comprise polyethylene glycol in a proportion of 2.5% by weight of the dry powder and cyclohexanone in a proportion of 0.5% by weight of the dry powder.

 The formulation is manipulated within the established ranges to adapt the enamel dilatometry to the properties of the ceramic substrate.

 Preferably, when presented as a slip, the enamel layer or enamelling formula is applied to the surface of the ceramic substrate by tape casting. It is advisable to guarantee a thickness of the enamel layer of 1 mm. after the cooking stage.

In a preferred embodiment, the preparation of the Slipper follows the scheme shown in Figure 1, which is summarized below:

 - preparing a suspension comprising the ceramic powder mixture (enamelling formulation) already described prepared in the form of a slip by adding water and at least one dispersant, subjecting the slip to grinding;

 - add the at least one binder and the at least one plasticizer in this order and mix, to obtain the slip; Y

 - deaerate, strain and dry the slip.

 In this way, a green sheet of enamelling or enamel formulation is obtained.

 In the first stage, a deflocculated suspension is actually prepared. The object of the dispersion of the mill is to break the weak agglomerates that have formed as a result of the high surface area of the ceramic particles, while the suspension is homogenized and the particle size distribution is adapted. The characteristics of this slip are critical for the later stages of the tape casting process because they influence the viscosity of the suspension and the packaging of the sheet. At this point, high solids suspensions with low viscosity are required to facilitate mixing and dispersion.

 In the second stage, mixing and homogenization of the binder and plasticizer is carried out in the slip. The technical characteristics of some binders indicate that it is necessary to avoid mixing by grinding or by very energetic means, called high shear, due to the breakage of the polymer chains. This stage is preferably performed by mechanical agitation on blades. The addition of casting additives causes an increase in the viscosity of the slip.

The order of addition of the additives (dispersant, binder, plasticizer, etc.) to the slip (which is it can be called casting) is critical, because on the surface there is competitive adsorption of the additives, according to studies conducted for non-aqueous systems. Thus, when the dispersant is added last, the viscosity increases with respect to when it is added first because if the other organic components are added they must first be desorbed before the dispersant is adsorbed on the surface. Desorption is a very slow process and therefore prevents adsorption of the dispersant on the surface of the powder which decreases its effectiveness.

After the grinding and mixing stages, a third deaeration stage follows in order to eliminate the possible occluded bubbles inside the slip because air bubbles cause defects in the sheet. Superficial "punctures" are the most common defects that result in cracking after drying. The preferable technique is vacuum deaeration. This deaeration optionally occurs in a vacuum hood (preferably up to 10 ^{~ 5} bar) where the bubbling is very vigorous during the initial stage, and decreases as the occluded air disappears. Very viscous slippers are much harder to deaerate than low viscosity slippers, so a longer time is required.

 Once the slip is deaerated, it is prepared for casting using preferably an industrial tape casting system (or "tape casting").

 After the deposition of the enamel layer on the ceramic substrate, it is dried in the environment, to then be cooked following the above indications.

 BRIEF DESCRIPTION OF THE FIGURES

Figure 1. Flow chart of preferred preparation of an enamelling or enamel formulation sheet according to the present invention. EXAMPLES OF EMBODIMENT OF THE INVENTION

 A preferred embodiment of the invention will now be described, by way of example and on a non-limiting basis. In order to give cohesion to the examples and illustrate the unity of all processes / products disclosed herein, the preparation of a photovoltaic device comprising, in its most preferred embodiment, all possible elements and their components is shown below. optimal conditions.

Example 1-. Obtaining an enamelling formulation of a ceramic substrate that will be used as supports to prepare a photovoltaic device.

 An enamelling formulation is prepared with the following components:

 - 99% pure ZnO powder in anatase form, in a percentage of 22%;

 - 99% pure anatase, in a percentage coinciding with the percentage of ZnO (22%);

 - commercial quartz, in a percentage of 12%;

 - sodium-free potassium feldspar, in a percentage of 11.5%;

 - commercial borax, in a percentage of 20%;

 - Zn metal powder, in a percentage of 6%;

 - Water;

 - a derivative of ammonium salts of polyacrylic acids

NH ₄ PA as dispersant, in a proportion less than 1% by weight of the dry powder;

 - an acrylic polymer as a binder, in a proportion of 2% by weight of the dry powder;

 - benzylbutylphthalate as a plasticizer, in a proportion of 4% by weight of the dry powder; Y

 - polyethylene glycol in a proportion of 2.5% by weight of the dry powder and cyclohexanone in a proportion of 0.5%.

The formulation is presented as a slip, suitable for tape casting on the ceramic substrate, and which is prepared as follows:

- preparing a suspension comprising the ceramic powder mixture described (enamelling formulation), the ammonium salts derivative of NH ₄ PA polyacrylic acids and water, and grinding;

 - add the binder and plasticizer in this order and mix by mechanical agitation on blades, to obtain the casting slip; Y

- deaerate in a vacuum hood (at 10 ^{~ 5} bar), strain through an industrial system of tape casting, and dry the slip into the environment (30 minutes at 20 ° C and with relative humidity not exceeding 70%).

 Example 2- Enameling of a ceramic substrate by the formulation prepared in Example 1, to prepare a support.

 As a ceramic substrate, a ceramic tile was selected, one of those commonly used in the construction industry, trying to have a closed porosity and polished finish at the structural level.

 The ceramic formulation obtained in Example 1 was applied to the exposed surface of the tile using the industrial tape casting system.

 After enameling the surface, the ceramic substrate was subjected to cooking at a temperature of 1100 ° C for 1 hour. After cooking, it was found that the enamel layer had a thickness of at least 1 mm over the entire surface of the substrate.

 Example 3-. Deposition of a metallic contact layer on the enameled surface of the ceramic support prepared in Example 2.

Once the enameled ceramic product was cooked, the previously enameled ceramic surface was metallized to obtain a contact layer with the photovoltaic material to be deposited on the ceramic support. However, before the metallizing stage the enameled surface of the ceramic support was subjected to selective catalysis. The catalyst used is formulated based on Palladium using 0.5 gr of Palladium Acetate, dissolved in two drops of ammonium. In addition, a 50% solution of polymer type B70, B90 or the like in ethanol is created. In this way, by introducing the palladium dissolved in the ammonium into this solution, a suspension of Palladium is generated. The catalysis of the surface is carried out by applying the catalyst suspension on the ceramic for 30 minutes. Finally, the dry surface is activated in an oven at 200 ° C for 2 hours.

 Subsequently, the previously glazed and catalyzed substrate surface was metallized.

 The metal layer is Mi-No and was deposited by an electrode-free or "electroless" process, following the following formulation of the hot bath in which the enameled surface of the substrate is submerged:

 - Source of metal ions (Ni ions, Mo): nickel sulfate in 1.77 M solution and molybdenum sulfate in simultaneous 1 M solution;

- Reducing agents: The reduction of nickel is carried out with the presence of one or more reducing agents in the solution. In this case, hydrated sodium hypophosphite (NaH ₂ P02 · Η ₂ 0) is used in an amount of 3 gr. per liter of dissolution.

 - Agents complexed before: Nickel ions in aqueous solution interact with a certain number of molecules, this being the coordination number, which in the case of divalent nickel can be two, 4 and 6.

Thus 5 g of ammonium hydroxide are added per liter of solution.

 - Stabilizers: 7 gr. of gluconic acid and 6 gr. of sodium tartrate per liter of solution.

The temperature of the bath is 85 ° C. The pottery is introduced in the hot bath, until a metallic layer of 1 thick thickness is formed in 3 minutes.

 Example 4-. Deposition of a photovoltaic material according to the present invention by Chemical Deposition in Steam Phase supported by Plasma, on a ceramic support prepared according to Example 3.

 Following Examples 1, 2 and 3, the ceramic substrate is in a position to be used as a support for a photovoltaic material type P-I-N.

 Thus, the support is introduced into an ultra high vacuum reactor chamber and deposited on an electrode, heating to 300 ° C, after which the photovoltaic material begins to form on the metal contact layer of the ceramic substrate by deposition. Steam Phase Chemistry supported by Plasma. The deposition or growth of the material is carried out sequentially, layer by layer; first, the P layer of the first P-I-N type joint, followed by the I layer and the N layer, then the P layer of the second P-I-N type joint, followed by the layer and the N layer; and so on until depositing the layer N of the third joint P-I-N that forms the semiconductor material.

 The deposition is carried out by dosing the following gases inside the chamber, modulating the flow rate within the ranges indicated:

SiCH ₄ : flow rate between 25 nec / min and 47 nec / min, including both limits;

H ₂ : flow rate between 110 nec / min and 186 nec / min, including both limits;

B ₂ H ₆ : flow rate between 12 nec / min and 19 nec / min, including both limits;

PH ₃ : flow rate between 14 nec / min and 19 nec / min, including both limits;

CH ₄ : flow rate between 43 nec / min and 47 nec / min, including both limits;

Ga (CH ₃ ) ₃ : flow rate between 2 ncc / min and 5 ncc / min, including both limits; and AsH ₃ : Flow rate between 4 ncc / min and 8 ncc / min, including both limits.

 The plasma is generated by means of a radio frequency equipment that works at 13.56 MHz, with a deposition rate that ranges between 0.1 and 0.2 nm / sec. The RF Power is between 50 and 100 w, including both limits; Pressure, between 0.1 mbar and 10 mbar, including both limits; and the distance between electrodes is between 10 mm and 35 mm, including both limits. The thickness of each of the deposited layers P, I and N varies between 50 nm and 70 nm each, thus varying the thickness of each junction between 150 and 210 nm. this thickness being adequate to consider that a thin layer photovoltaic material has been obtained.

 In this way, the total compatibility of the photovoltaic material with the ceramic substrate is ensured.

Example 5-. Coating of the photovoltaic device obtained in Example 4.

The photovoltaic device obtained in the previous Example is subjected to coating by a transparent conductive layer of ITO by means of the sputtering technique. Previously, the individual areas and their interconnection will have been screened to achieve the electrical conditions of generation in the specific application (voltage and intensity).

The sputtering process takes place in a vacuum chamber. To avoid the residual gas causing considerable contamination in the deposited coatings it is necessary to achieve a high vacuum (high vacuum is considered for the sputtering process pressures below 10 ^{~ 6} mbar). The working pressure is achieved by introducing the process gas (argon) at a pressure of the order of 1.5 · 10 ^{~ 3} mbar.

The target that has been used is ITO. The compounds Stoichiometric form the ITO are ln ₂ 0 ₃ and Sn0 ₂ in concentrations of 90% and 10% by weight respectively. The purity of the ITO material used is 99.99%. The applied voltage is 500 V in direct current on the substrate heated to 200 ° C. This process is maintained until it reaches 1 millimeter thick (about 23 minutes).

Example 6-. Encapsulation and protection of the coated photovoltaic device obtained in Example 5.

Finally, the device or photovoltaic cell must be closed by an encapsulant. The encapsulation of the cell is carried out under vacuum (less than 10 ^{~ 6} bar) by means of EVA sheets of 100 microns thick heated to creep, and later sprayed (maximum final thickness 200 microns) and polymerization of a transparent epoxy layer ( Masterbond type) in oven at 250 ° C.

 In this way, the sealing and lasting resistance of the layer is guaranteed without compromising the properties of the photovoltaic device by ionic diffusion. Under these conditions, adequate sealing and durability are guaranteed.

Claims

1. Photovoltaic material comprising a series of semiconductor connections type PIN, each consisting of a thin layer type P, an intrinsic thin layer type I and a thin layer type N superimposed over each other, characterized in that the multi-junction series is It consists of at least three semiconductor joints type PIN stacked in tandem, whose layers type P, I and N comprise hydrogenated microcrystalline silicon contained in an amorphous silicon matrix in its composition, and where also  - the P-type layer of the at least three junctions additionally comprises boron as a doping agent; the P-type layer of the second joint also containing arsenic and the P-type layer of the third joint further containing gallic- the type I layer of the at least three junctions is composed of hydrogenated microcrystalline silicon contained in an amorphous silicon matrix, and  - the N-type layer of the at least three junctions additionally comprises phosphorus as a doping agent; the N type layer of the second junction further containing gallium, and the N type layer of the third junction further containing arsenic. 2. Photovoltaic material according to claim 1, characterized in that each of the semiconductor junctions type P-I-N has the following formulation:  - hydrogenated microcrystalline silicon contained in an amorphous silicon matrix in a percentage between 92% and 96%, including both limits;  - boron in a percentage between 1.1% and 2.8%, including both limits; Y phosphorus in a percentage between 2.4% and 3.6% including both limits; - the second and third PIN-type joints also comprising nanostructured gallium arsenide in a percentage between 0.3% and 1, 2%, including both limits. 3 . Photovoltaic material according to any one of claims 1 6 2, characterized in that each PIN type joint has a thickness between 150 nm and 210 nm, including both limits, the thickness of each of its three layers P, I and N being comprised between 50 nm and 70 nm, including both limits. 4. Photovoltaic material according to any one of claims 1 to 3, characterized in that it comprises:  - at least one metallic contact layer, on which the at least three semiconductor junctions type P-I-N are sequentially deposited;  - at least one transparent layer of a coating conductor oxide of the last semiconductor junction type P-I-N, which is supported on the first two; Y  at least one polymeric sheet of a transparent, moisture and air tight optical polymer that covers all the photovoltaic material. 5. Photovoltaic material according to claim 4, characterized in that the at least one metallic contact layer is Ni-Mo and has a thickness between 2 and 3 microns, including both limits; the at least one transparent layer of a conductive oxide has a thickness between 200 and 300 nm, including both limits; and the at least one polymeric layer has a thickness between 80 and 100 microns, including both limits. 6. Photovoltaic material according to any one of claims 4 6 5, characterized in that in addition It comprises at least one layer of transparent epoxy on the polymeric sheet. 7. Photovoltaic ceramic device characterized in that it comprises at least one material according to any one of claims 1 to 6, supported on a ceramic substrate. 8. Ceramic photovoltaic device according to claim 7, characterized in that the ceramic substrate that acts as a support is a porcelain stoneware or a non-porous ceramic of those used in construction. 9. Ceramic photovoltaic device according to claim 8, characterized in that porcelain stoneware or non-porous ceramic are selected from tiles, tiles, ventilated façade ceramic panels and other similar enclosures. 10. Use of the photovoltaic material described according to any one of claims 1 to 6 to coat ceramic substrates. 11. Method of obtaining a photovoltaic ceramic device, comprising a ceramic support and a photovoltaic material according to any one of claims 1 to 6, characterized in that it comprises at least the following steps: form the P-type layer of the first PIN-type semiconductor junction on the previously heated ceramic support by means of Plasma-backed Chemical Deposition on Plasma, dosing at least the following gases into an ultra-high vacuum reactor chamber: SiCH ₄ , H ₂ , B ₂ H ₆ , PH ₃ , CH ₄ , Ga (CH ₃ ) ₃ and AsH ₃ , and applying a high electromagnetic field frequency; Y  - sequentially depositing one over the other, in the same manner indicated in the previous stage, the layers type I and N of the first joint type P-I-N; the P, I and N type layers of the second P-I-N type joint; and the layers type P, I and N of the third joint type P-I-N. 12. Method according to claim 11, characterized in that the gases are dosed into the reactor with the following flow rates: SiCH ₄ : flow rate between 25 ncc / min and 47 ncc / min, including both limits; H ₂ : flow rate between 110 ncc / min and 186 ncc / min, including both limits; · B ₂ H ₆ : flow rate between 12 ncc / min and 19 ncc / min, including both limits; PH ₃ : flow rate between 14 ncc / min and 19 ncc / min, including both limits; CH ₄ : flow rate between 43 ncc / min and 47 ncc / min, including both limits; Ga (CH ₃ ) ₃ : flow rate between 2 ncc / min and 5 ncc / min, including both limits; and AsH ₃ : flow rate between 4 ncc / min and 8 ncc / min, including both limits. 13. Method according to any one of claims 11 or 12, characterized in that the Plasma-backed Chemical Deposition in Steam Phase is carried out according to the following parameters:  - Frequency of the electromagnetic field: 13.56 MHz. ; - Temperature of the ceramic support where layers P, I and N of the joints type P-I-N are deposited: between 300 ° C and 400 ° C, including both limits; - RF power: between 50 and 100 w, included both limits;  Pressure: between 0.1 mbar and 10 mbar, including both limits; Y  - Distance between electrodes: between 10 mm and 35 mm, including both limits. 14. Method according to any one of claims 11 to 13, characterized in that each of the P, I and N layers of each P-I-N semiconductor junction is deposited with a deposition rate between 0.1 nm / sec and 0.2 nm / sec, including both limits. 15. Method according to any one of claims 11 to 14, characterized in that each PIN type joint has a thickness between 150 nm and 210 nm, including both limits, the thickness of each of its three layers P, I and N between 50 nm and 70 nm being included, including both limits . 16. Method according to any one of claims 11 to 15, characterized in that it further comprises the following steps:  depositing a metallic contact layer on the ceramic support, prior to the formation of the P-type layer of the first semiconductor junction type P-I-N that is deposited on said metallic layer,  - coating the multi-junction photovoltaic material by selective deposition of a transparent layer of a conductive oxide, ITO, after the deposition of the N layer of the last photovoltaic junction on all other layers; Y - encapsulate all coated multi-junction photovoltaic material, by forming a polymeric sheet of an optical transparent polymer, air tight and moisture tight. 17. Method according to claim 16, characterized in that the metal contact layer is deposited by means of an electrode-free chemical deposition process comprising at least immersing the surface of the ceramic support in a hot bath having the following formulation: ^• at least one source of metal ions, ^• at least one reducing agent, ^• at least one complex agent,  · At least one stabilizer, the bath temperature being between 80 ° C and 85 ° C, including both limits, and the duration of the bath being between 3 and 5 minutes, including both limits. 18. Method according to claim 17, characterized in that the metal layer is Ni-Mo. 19. Method according to claim 18, characterized in that the metal ion sources are nickel sulfate and molybdenum sulfate. 20. Method according to any one of claims 17 to 19, characterized in that the reducing agent is hydrated sodium hypophosphite of the formula NaH ₂ P0 ₂ · H ₂ 0; the complexing agent is ammonium hydroxide; and the stabilizers are gluconic acid and sodium tartrate. 21. Method according to any one of claims 16 to 20, characterized in that, prior to the deposition of the metallic contact layer on the ceramic support, the surface of said ceramic support is selectively catalyzed. 22. Method according to claim 21, characterized in that selective catalysis is carried out with a catalyst comprising palladium in suspension and applied on the surface of the ceramic support for 30 minutes, subsequently activating said surface at a temperature between 190 and 200 ° C including both limits, for a time between 120 and 150 minutes including both limits. 23. Method according to any one of claims 16 to 22, characterized in that before depositing the photovoltaic material on the metallic contact layer, the surface of the ceramic support already metallized is heated until reaching a temperature between 250 and 300 ° C including both limits . 24. Method according to any one of claims 16 to 23, characterized in that the metal contact layer has a thickness between 2 and 3 microns, including both limits; the transparent layer of a conductive oxide has a thickness between 200 and 300 nm, including both limits; and the polymeric layer has a thickness between 80 and 100 microns, including both limits. 25. Method according to any one of claims 16 to 24, characterized in that: - the coating of the multi-junction photovoltaic material by selective deposition of a transparent layer of a conductive oxide is carried out by sputtering under vacuum at a pressure between 10 ^{~ 6} and 10 ^{~ 8} mbar, including both limits; Y The encapsulation is carried out by thermal softening of the vacuum polymer, at a pressure between 10 ^{~ 6} and 10 ^{~ 8} mbar, including both limits. 26. Method according to any one of claims 16 a 25, characterized in that after encapsulation all photovoltaic material is protected by spraying and polymerizing a transparent epoxy layer, at a temperature between 220 ° C and 250 ° C, including both limits. 27. Method according to any one of claims 11 to 26, characterized in that it comprises a previous initial process for conditioning the ceramic support according to at least the following steps:  - deposit a sodium-free enamel on the surface of the ceramic support and whose formulation comprises at least borax, anatase, zinc oxide, metallic zinc powder, boron oxide and feldspar; Y  - cook the glazed ceramic substrate. 28. Method according to the preceding claim, characterized in that the enamel comprises the following components in percentage by weight of dry powder:  - 99% pure ZnO powder in the form of anatase, in a percentage between 20% and 30%, including both limits;  - 99% pure anatase, in a percentage between 20% and 30%, including both limits, and coinciding with the percentage of ZnO;  - commercial quartz, in a percentage between 10% and 30%;  - sodium-free potassium feldspar, in a percentage between 10% and 20%;  - commercial borax, in a percentage between 20% and 30%;  - Zn metal powder, in a percentage between 5% and 8%; Y - water, at least one dispersant, at least one binder and at least one plasticizer, and has an average particle size equal to or less than 2 microns. 29. Method according to any one of claims 27 or 28, characterized in that the enameled ceramic support is baked between 1000 ° C and 1100 ° C including both limits, for a minimum period between 1 and 2 hours including both limits. 30. A method according to any one of claims 27 to 29, characterized in that the ceramic support is a porcelain stoneware or a non-porous ceramic of those used in construction. 31. Method according to claim 30, characterized in that the porcelain stoneware or non-porous ceramic are selected from tiles, tiles, ventilated façade ceramic panels and other similar enclosures. 32. Photovoltaic ceramic device obtainable from a method according to any one of claims 11 to 31. 33. Enamelling formulation of the ceramic support used in the method described in claim 27, characterized in that it lacks sodium and comprises at least a mixture of ceramic powders with: borax, anatase, zinc oxide, metallic zinc powder, metal oxide Boron and feldspar. 34. Enameling formulation according to the preceding claim, characterized in that it comprises the following components in percentage by weight of dry powder: 99% pure ZnO powder in anatase form, in a percentage between 20% and 30%, including both limits;  - 99% pure anatase, in a percentage between 20% and 30%, including both limits, and coinciding with the percentage of ZnO;  - commercial quartz, in a percentage between 10% and 30%;  sodium-free potassium feldspar, in a percentage between 10% and 20%;  - commercial borax, in a percentage between 20% and 30%; Y  - Zn metal powder, in a percentage between 5% and 8%. 35. Enameling formulation according to the preceding claim, characterized in that it has an average particle size equal to or less than 2 microns. 36. Enameling formulation according to any one of claims 34 or 35, characterized in that it further comprises water, at least one dispersant, at least one binder and at least one plasticizer. 37. Enamelling formulation according to the preceding claim, characterized in that the at least one dispersant is derived from ammonium salts of NH ₄ PA polyacrylic acids in a proportion less than 1% by weight of the dry powder; the at least one binder is an acrylic polymer in proportions between 1.5% and 3% by weight of the dry powder, including both limits; and the plasticizer is benzylbutylphthalate in a proportion between 3% and 5% by weight of the dry powder, including both limits. 38. Enameling formulation according to any one of claims 33 to 37, characterized in that it comprises additionally polyethylene glycol in a proportion of 2.5% by weight of dry powder and cyclohexanone in a proportion of