Patent Application
20150287859
The present invention relates to a method for manufacturing a thin-layer photovoltaic device.
More particularly, it relates to a method for manufacturing a photovoltaic device comprising the following steps:
The photovoltaic device obtained with such a method finds a particular application in the field of glazing called solar glazing or glazing called photovoltaic glazing, in which the substrate is constituted of a transparent glass substrate—or transparent glazing—with interconnected and more or less spaced photovoltaic cells so as to choose the best ratio between the light or the overall transparency and the energy performance. The glazing can be of the double or triple glazing type, in the form of a laminated, insulating glazing, etc.
However, the present invention is not limited to such an application and other substrates can be considered with such a method, as for example by using a substrate made of organic material, a substrate made of plastic material or polymers-based substrate, a substrate made of treated glass, for example of frosted, tinted, opaque glass, etc., a metal substrate, a substrate made of construction material, for example of concrete, of composite material, etc., optionally covered with a paint layer and/or a protective layer.
The object of the present invention is to apply, over the substrate, a series of thin layers forming a photovoltaic film defining several interconnected photovoltaic cells which are shaped to let pass part of the light in order to confer to the photovoltaic film some transparency which ensures the visibility of a portion of the substrate. Thus the photovoltaic film offers opaque areas and transparent areas which respectively allow hiding and exposing the substrate from the outside. For the following description, an area of the photovoltaic film is considered as transparent insofar as it easily lets light pass therethrough and clearly allows to distinguish the substrate through its thickness.
The Integration of photovoltaic devices in a building is facing several constraints: the photovoltaic surface that may be used on a roof and/or a facade, the cost, the dimensions of the photovoltaic devices which should preferably be standardized in order to comply with the standards and usages in the field of construction, the installation of the photovoltaic devices with constraints of insulation, sealing, mechanical strength, wind resistance, etc. and the aesthetics of the photovoltaic devices particularly in an integration on a facade.
To address these constraints, it is known to use photovoltaic devices called thin-layer or “thin film” photovoltaic devices, using a photoactive layer absorbing in the solar spectrum, with a thickness ranging from a few atoms of thickness to about ten micrometers, made based on semi-conductive inorganic material, in particular based on Cu2S/CdS, of a-Si:H (hydrogenated amorphous silicon), CdTe (cadmium telluride), and CuInSe2 (Copper Indium Selenium or CIS), CuInGaSe2 (Copper Indium Galium Selenium or CIGS).
These thin-layer photovoltaic devices based on inorganic materials belong to the second generation, after the first generation based on crystalline silicon, and before the third generation based on organic materials.
The organic photovoltaic materials are naturally transparent, however, they have limited lifespans, generally in the order of a few thousands hours, and low electrical efficiencies or performances (efficiency in the order of 5 to 9% against 15 to 20% for the inorganic photovoltaic materials of the second generation), which are incompatible with an integration in a building.
The inorganic photovoltaic materials do not have intrinsic properties of transparency, and only the layout of the photovoltaic cells over the substrate will confer to the photovoltaic film a required transparency in order to be able to partly see the substrate through the film. Indeed, these inorganic photovoltaic materials have a very high light absorption level, for example, with an absorption of 99% of the light reaching the surface of the CIGS material on the first micrometer thickness. Thus, for the CIGS, a thickness of material that is larger than one micron leads to a layer that is opaque to the light.
The present invention thus focuses on the realization of the layout of the photovoltaic cells made based on thin layers of inorganic photovoltaic material.
Generally, in a thin-layer photovoltaic device, the photovoltaic film is composed of a superposition of layers comprising a first conductive layer forming a rear electrical contact, a second photoactive layer absorbing in the solar spectrum and based on inorganic material, a third layer made of transparent conductive material forming a front electrical contact.
The third front contact layer may for example be constituted of a double-film layer of zinc oxide (ZnO) doped with elements of the group III such as aluminum, and it presents the highest possible luminous transmission in the range of wavelength related to the second photoactive layer. It is known to use an intermediate thin layer, called window or “buffer” layer, between the second and the third layer, generally based on CdS (cadmium sulfide), ZnS, ZnSe, SnIn2Se4, Zn1-xMgxO, In2S3, etc.
The second layer, called absorber, is made based on semi-conductive inorganic materials of type the I-III-VI, such as for example the CIGS, often referenced as chalcogenides materials.
The first layer is deposited over the substrate and has both ohmic properties to ensure an optimal recovery of the charges emitted by the second photoactive layer as well as optical properties to ensure reflection toward the second layer of the portion of the luminous spectrum that is not absorbed in direct transmission.
In the field of solar glazing based on thin layers of inorganic photovoltaic material, it is known to make the solar glazing by depositing, in a uniform manner, a photovoltaic film on the glass substrate, through superposition of the aforementioned thin layers, then by removing, through mechanical engraving or laser, strips in the photovoltaic film, which allows to obtain opaque and parallel photovoltaic strips, presenting a width in the order of centimeter and regularly spaced from one other with a spacing equivalent to the width of the strips; the cells being interconnected at their ends, the interconnections being generally hidden by the frame of the glazing.
Thus, the overall transparency of the glazing is in the order of 50%, but these photovoltaic strips, distributed in a linear array with a resolution in the order of centimeter, offer a real visual discomfort for the building users who look through the glazing.
The present invention aims to propose a method for manufacturing a thin-layer photovoltaic device made with a photovoltaic film based on semi-conductive inorganic material, of the second generation, which allows to control the geometry of the photovoltaic cells with a resolution lower than the millimeter, and preferably in the order of micrometer or even less or of ten micrometers, in order to obtain a film with a controlled transparency between 10 and 90% and a visual comfort resulting from a high resolution which provides the perception of a quasi-uniformity of the layout of the opaque layers.
To this end, it proposes a method for manufacturing a thin-layer photovoltaic device, comprising the following steps:
The use of such a mask deposited by printing is really advantageous to obtain the desired resolutions in the distribution of perforations. Thanks to this printing technique (over the substrate, over a resin layer or over the first layer, as explained later), it is possible to guarantee micrometric dimensions of the perforations and micrometric spacings between the perforations.
In accordance with the invention, the mask serves therefore to make perforations at least in the first layer and in the second layer, to obtain a controlled transparency of the photovoltaic film.
According to one possibility of the invention, the sequence called main sequence is carried out, including the following steps:
The third transparent layer does not modify the transparency and thus may cover the bare areas of the substrate in the orifices passing through the first layer.
It may be considered to provide for several modes of use of the mask.
According to a first use of the mask, the following first sequence is carried out:
Afterwards, the steps of the above-mentioned main sequence are resumed.
According to a second use of the mask, the following second sequence is carried out:
Following this second sequence, two options may be considered.
In a first option, following the deposition of the first conductive layer, the remaining islets of insolated resin are eliminated, leaving over the substrate only but the first conductive layer presenting negative orifices of the mask. Afterwards, the steps of the above-mentioned main sequence are resumed.
In a second option, following the deposition of the first conductive layer:
In this second option, the second and third layers are uniformly deposited, preferably by vaporization, and not in a selective manner as in the case of the first option.
According to a third use of the mask, the following sequence is carried out:
Thus, the mask is deposited directly over the substrate, and no longer on a resin layer as in the first and second uses. Following this sequence, two options may be considered.
In a first option, following the deposition of the first conductive layer, the mask is eliminated, leaving over the substrate only but the first conductive layer presenting positive orifices of the mask. Afterwards, the steps of the above-mentioned main sequence are resumed, in this case:
In a second option, following the deposition of the first conductive layer:
Advantageously, the mask presents secondary areas defining a positive or a negative of separating strips between the cells.
Thus, the mask is advantageously utilized to directly prepare the separating between the photovoltaic cells.
Advantageously, the perforations are arranged in compliance with the following geometric characteristics:
Thus, the photovoltaic cells are perforated, at least over the thickness of the first and second layers (the third layer being transparent), and these perforations are distributed, in a quasi-uniform manner, in each cell with a resolution comprised between 5 nanometers and 400 micrometers, guaranteeing, for the human eye, a quasi-uniform perception of the outer surface of the film, with a controlled transparency of the film which insures visibility of the support through the film.
Indeed, the resolving power of the eye (minimum distance which should exist between two contiguous points so that they are correctly discerned) is of about one minute of arc, namely 0.017°, which corresponds to a minimum distance of about 600 micrometers for an image located at a distance of 2 meters from the eye.
According to a first possibility, the perforations are distributed over the surface of each cell according to a non-periodic distribution, in particular according to a non-periodic paving. For example, the perforations are distributed over the surface of each cell according to a random distribution, in particular according to a random paving.
According to a second possibility, the perforations are distributed over the surface of each cell according to a periodic distribution, in particular according to a periodic paving.
According to one characteristic, the perforations are distributed over the surface of each cell according to a virtual paving composed of a plurality of elementary photovoltaic units, juxtaposed without void and without encroachment so as to define the corresponding cell, each elementary unit being in the form of a geometric portion of the photovoltaic film delimited by a virtual outline and to which there is associated at least one perforation arranged in whole or in part inside said outline, each perforation being associated to one single elementary unit, and wherein each elementary unit presents a perforated surface, corresponding to the surface of the perforation(s) associated to said elementary unit in the main plane, which is comprised between 10 and 90% of the total surface of the elementary unit in this same main plane, preferably between 30 and 70%.
Thus, each photovoltaic cell is geometrically defined by a paving of elementary photovoltaic units and each of these present units is perforated so as to intrinsically offer the desired overall transparency. In this manner, the macroscopic photovoltaic cell presents the same transparency as its own elementary units which compose it.
According to another characteristic, each elementary unit presents dimensions in the main plane comprised between 10 and 800 micrometers.
In a particular embodiment, the substrate is constituted of a glass substrate, so as to make a photovoltaic or solar glazing.
Preferably, the first layer is an opaque metallic layer. This first layer is positioned on the substrate side, in particular directly in contact over the substrate.
Other characteristics and advantages of the present invention will appear upon reading the detailed description below, of several non-limiting implementation examples, with reference to the appended figures wherein:
a is a schematic front view of a photovoltaic device in accordance with the invention;
b is a schematic sectional view of the photovoltaic film of the device of
a is a schematic front view of a mask established according to a first orthogonal or square periodic paving;
b is a schematic front view of a mask established according to a second staggered or honeycomb periodic paving;
a is a schematic front view of a mask established according to a first non-periodic paving of the “pinwheel”-type,
a is a schematic front view of a mask established according to a second non-periodic paving of the random-type;
a to 12k represent schematic perspective views of a sequence for depositing, over a substrate, the first, second and third layers with through perforations (eight steps being illustrated,
With reference to
Referring to
Each cell 30 comprises a plurality of individual perforations 31 passing through either the first and second layers 4, 5, or the first, second and third layers 4, 5, 6; these perforations 30 thereby ensuring semi-transparency of the cells 30, the perforated areas being transparent to the visible light and the non-perforated areas being opaque to the visible light.
These perforations 31 are advantageously distributed over each cell 30 according to the following geometric conformation:
Thus, each cell 30 presents a transparency comprised between 10 and 90%, depending on the total surface occupied by the perforations 31 in the concerned cell 30. The dimensions of the perforations 31 and the distances between perforations are selected so as to offer a visual comfort in accordance with the resolving power of the eye, so that the human eye distinguishes little the perforations 31 in the cells 30 and sees a substantially uniform surface.
The following description is about the method for manufacturing such a photovoltaic device 1, starting from the substrate 2 over which it is desired to deposit the photovoltaic film 3 divided into perforated and interconnected cells 30; several variants may be considered.
This mask 8 will serve as a stencil which will allow to make the distribution of the perforations 31 on the first layer 4 according to the aforementioned geometric conformation, the main areas 81 of the mask 8 defining:
Working by printing, the mask 8 can take the shape of a masking material layer, such as ink, forming the negative or the positive of the perforations 31.
In the case of a mask 8 forming a positive of the perforations 31, the mask 8 includes, for each cell, a plurality of individual main areas 81 of masking material, distributed over each cell according to the following geometric conformation:
Thus, with a mask 8 forming a positive of the perforations 31, the mask 8, for each cell, is in the form of a plurality of main areas 81 spaced apart from each other (as illustrated in particular in
In the case of a mask 8 forming a negative of the perforations 31, the mask 8 includes, for each cell, contiguous main areas 81 framing individual perforations 83 distributed over each cell according to the following geometric conformation:
Thus, with a mask 8 forming a negative of the perforations 31, the mask 8, for each cell, is in the form of a continuous layer of masking material, in which there are provided perforations 83 spaced from each other (as visible in
In the first sequence illustrated in
In the second sequence illustrated in
In this second sequence, the optical characteristics of the mask 8 do not matter, in other words the mask 8 may or may not be opaque. Indeed, the mask 8 is used to form a physical barrier for the deposition of the first layer 4, without making use of an insolation step.
In the third sequence illustrated in
Starting from the end of any one of the three sequences described above with reference to
To deposit the second and third layers 5, 6 over such a first perforated layer 4, it may be considered to proceed as follows, with reference to
The deposition of the third layer 6 is carried out by evaporation, thereby covering the entire surface, including the perforations 31, which causes no prejudice because the third layer 6 is naturally transparent, furthermore, the step of electrodeposition guarantees that the second layer 5 entirely wraps the first layer 4, which prevents the third layer 6 from coming into contact with the first layer 4 and short-circuiting the cell.
In the case of the aforementioned three sequences using a mask 8, the mask 8 has been used only to make the perforations 31 in the first layer 4, before getting rid of it for proceeding to the deposition of the second layer 5 by electrodeposition.
However, it may be considered to provide variants wherein the mask 8 is preserved and removed only at the end of the process, after depositing the second and third layers 5.
In a first variant illustrated in
In a second variant illustrated in
In these two variants, the third layer 6 does not cover the perforations 31, because the mask 8 is removed after placing this third layer 6, thereby avoiding short circuit between the first and third layers 4, 6.
The following description is about the division of the photovoltaic film into several cells, and about the interconnection between two adjacent cells, with reference to
a and 12c illustrate each a substrate 2 over which a first layer 4 is deposited, with two cells 30 (
Several embodiments of the separating strips 32 can be considered, being specified that a separating strip 32 constitutes a perforated groove or notch in the first layer 4. Thus, the separating strip 32 is made in the same manner as the perforations 31.
In a first embodiment, the separating strip 32 is made by direct engraving, in the same manner as in the first sequence illustrated in
In a second embodiment, the separating strip 32 is made from a mask which presents secondary areas 82 defining a positive or a negative of the separating strips 32 between the cells, that is to say:
a illustrates the application of a positive mask 8 directly over the substrate (as in the second sequence illustrated in
b then illustrates the uniform application of the first layer 4 over the substrate 2 and the mask 8.
c illustrates the step of chemically eliminating the mask 8, leaving over the substrate 2 only but the first layer 4 presenting the perforations 31 and the separating strips 32. Note that the first layers 4 of all the cells 30 are electrically connected because the secondary areas 82 are not joined, leaving thus an electrical contact 42 between these cells 30 after removal of the mask 8. This electrical contact 42 between the cells 30 aims to facilitate the step of electrodepositing the second layer 5, because it is sufficient to polarize all cells 30 in an equivalent manner.
Starting from the first layer 4 with the perforations 31 and the separating strips 32, the following steps are carried out to deposit the second and third layers 5, 6 while ensuring the interconnection between the two cells 30:
It is to be noted that, if the second layer 5 is deposited by evaporation or spraying (instead of the deposition by electrodeposition illustrated in
a illustrates a substrate 2 over which a positive mask 8 has been deposited presenting main 81 and secondary 82 areas, and over which a first layer 4 has been deposited afterwards in a uniform manner, by spraying or by evaporation.
Starting from the situation of
The following description is about the geometric conformation of the perforations 31, in particular with reference to
Advantageously, the perforations 31 are distributed over the surface of each cell 30 according to a virtual paving composed of a plurality of elementary photovoltaic units, juxtaposed without void and without encroachment so as to define the corresponding cell 30. The principle is thus to define one or several basic pattern(s), defining one or several elementary unit(s), which will be repeated so as to entirely pave each cell 30, so that when managing transparency at the microscopic level (with the elementary units) transparency is managed at the macroscopic level (at the cell).
Each elementary unit is in the form of a geometric portion of the photovoltaic film 3, the dimensions of which in the main plane are comprised between 15 nanometers and 800 micrometers, delimited by a virtual outline (the outline of the pattern) and to which there is associated at least one perforation arranged in whole or in part inside said outline (the perforated surface in the elementary unit microscopically defining the perforated surface of the cell), each perforation being associated to one single elementary unit.
Each elementary unit presents a perforated surface, corresponding to the surface of the perforation(s) associated to the elementary unit in the main plane, which is comprised between 10 and 90% of the total surface of the elementary unit in this same main plane, preferably between 30 and 70%.
By working with a mask 8, paving of the elementary units is managed by managing paving of the above described main areas 81.
a, 2b, 3a and 3b illustrate positive masks 8 presenting circular-shaped main areas 81 (other shapes may of course be considered) distributed according to predefined paving.
With a positive mask 8, the main areas 81 of the mask 8 are distributed over the surface of each cell 30 according to a virtual paving composed of a plurality of patterns juxtaposed without void and without encroachment, each pattern being delimited by a virtual outline to which there is associated at least one main area 81 located in whole or in part inside said outline.
The pattern forms the smallest geometric element that allows constructing the mask 8 at a macroscopic scale by applying a given algorithm to this pattern (mainly a translation along two directions, a symmetry and a rotation), while integrating that the pattern should preferably offer the least interaction with the physiological mechanisms of the vision, and contribute to the best perceived uniformity of the photovoltaic device as well as to the best visual comfort.
Furthermore, it is important to note the following definition: the resolution of the mask 8 characterizes the smallest dimension of the basic pattern. However, the resolution has no impact on the level of transparency or on the energy efficiency of the photovoltaic film, but it may influence the way the eye perceives the transparency of this photovoltaic film and thus this resolution constitutes a potential factor of visual comfort or discomfort. In particular, the resolution intervenes on the perceived uniformity of the photovoltaic film, and the finest the resolution is, the more the perception of uniformity will be important.
In the implementation of a method for printing the mask 8, it is to be noted that the resolution of the mask 8 is still downwardly limited by the used printing technique. As an illustration, if the printing method presents an intrinsic resolution of 300 points per inch for drawing the pattern, this means that the basic printed point is in the order of at least 85 micrometers, so that such a printing method will not allow drawing patterns that are smaller than 100 micrometers. Hence, the intrinsic resolution of the method for printing the mask 8 automatically conditions the final resolution of the mask 8.
In a first embodiment of the mask 8 illustrated in
In a second embodiment of the mask 8 illustrated in
In order to avoid having periodic patterns which could reduce the visual comfort of the photovoltaic film, it may be considered to proceed with a non-periodic paving of the plane.
In a third embodiment of the mask 8 illustrated in
In a fourth embodiment of the mask 8 illustrated in
This random paving constitutes a variant of the periodic paving exposed above, with the aim of breaking periodicity, that is to say not obtaining parallel and regularly distributed disk lines; the principle being to scramble the distribution of the disks so that the eye cannot catch on any regular structure.
However, this random paving should comply with some constraints and statistical properties.
The first constraint consists in that the paving of patterns should ensure a constant level of transparency which is independent of the considered scale (unless, of course, falling below the basic pitch). In other words, this random paving should not lead to obtain too significant transparent or opaque areas so that the overall rendering is relatively uniform.
The second constraint comprises keeping a minimum distance between two neighboring disks 81, so as to be able to guarantee a deposition of the first layer 4 with a minimum width (depending on the capabilities of the printing technology of the mask 8 and/or the deposition technology of the thin layers) between two perforations 31.
In general, other shapes of the main areas 81 may be considered, not only the disk shape, as for example elliptical, rectanglar shapes, etc. The use of these other shapes might turn out to be interesting in particular for non-periodic paving, where the orientation of the basic pattern varies. As an example, an elliptical-shaped main area in a “pinwheel” paving would allow to access higher levels of transparency and contribute to visually scramble the pattern by varying the angle of the focal axis of the ellipse with the horizontal.
Furthermore, it may be considered to vary the dimensions of the main areas 81 over the substrate, in order to offer a gradient effect, for example, with a transparency that gradually increases from the bottom to the top or from the right to the left over the substrate.
Of course the aforementioned example of implementation is in no way limiting and other improvements and details can be brought to the photovoltaic device according to the invention, without departing from the scope of the invention where other pattern shapes can, for example, be made.
| Number | Date | Country | Kind |
|---|---|---|---|
| 12/60068 | Oct 2012 | FR | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/FR2013/052523 | 10/22/2013 | WO | 00 |
