Method and manufacturing of sealed monolithic photoelectrochemical systems and a sealed monolithic photoelectrochemical system

IS 2 256 247 T3

DESCRIPTION

Method and fabrication of sealed monolithic photoelectrochemical systems and a sealed monolithic photoelectrochemical system.

Technical field

The present invention relates to a method for manufacturing sealed monolithic photoelectrochemical systems according to the preamble of claim 1 of the patent, and in particular to a method for manufacturing monolithic photoelectrochemical systems comprising a substrate, a pattern, located on that substrate , of a porous structure comprising a photo-electrode, an insulating layer and a counter-electrode, wherein the porous structure is filled with electrolyte before the pattern of the porous structure is encapsulated between the substrate and the backplane formed by sealing material.

The present invention also relates to a sealed monolithic photoelectrochemical system according to the preamble of claim 16 of the patent.

Previous technique

Previously, from WO 97/16838, a method for manufacturing monolithic photoelectrochemical cells was known. In this method, photoelectrochemical cells are formed by means of patterns of conductive material that are applied to a transparent electrically insulated material. Next, a porous structure is provided by successively applying a porous semiconductor layer, a porous insulator layer, and a porous conductor layer. Upon application of the porous structure, a liquid electrolyte is provided thereto. The porous structure is also covered with an insulating cover layer.

However, a number of problems have been found to arise in sealing monolithic photoelectrochemical systems. On the other hand, cells have been found to be sensitive to moisture and impurities, because the presence of moisture and impurities has a considerable effect on the long-term stability of the system. On the other hand, it is important that the sealing along the outer edge of the cells effectively prevents the leakage or dissipation of, on the one hand, electrolyte coming from inside the cells and, on the other hand, impurities and moisture coming from the outside towards the inside cells.

Various methods have been tried to seal monolithic photoelectrochemical systems, in which electrolyte is placed to seal, such as gluing or joining two rollers holding them together by pressing. None of the methods that have been previously tested have resulted in photoelectrochemical systems with sufficiently good long-term characteristics and with a sufficiently low degree of deficiency of cell behavior during the sealing process, which has resulted in industrial manufacturing photoelectrochemical systems more difficult.

Brief description of the invention

The object of the invention is to provide a method for manufacturing sealed monolithic photoelectrochemical systems, in which the risk of the presence of moisture and impurities in the cell after sealing is reduced, the long-term stability of the cells is increased and the sealing has a high degree of impermeability with respect to the environment.

These objects are achieved by a method according to the characterizing part of claim 1 of the patent. The sealant material comprises a plastic that melts and is attached to a frontal plane, formed by a substrate and cells located on the substrate. Due to the fact that the sealing material is heated and pressed, sealing is obtained along the pattern edge of the porous structure. The border means, on the one hand, the inner border that separates the individual cells of a certain group of cells and, on the other, the external border that separates a group of cells from the environment. Since the plastic layer is very flexible when heated, a good and very tight seal is obtained, reducing the risk of moisture and impurities penetrating and increasing the long-term stability of the system. The sealing method according to the invention also reduces the risk that the performance of the cells is reduced during the manufacturing process.

In a preferred embodiment of the invention, the monolithic photoelectrochemical system is subjected to overpressure, allowing the evacuation of moisture and gases from the porous structure. This gives rise to the possibility of obtaining a cleaner and therefore more stable product in the long term.

In a preferred embodiment of the invention, the front and rear planes are pressed together by a flexible pressing device. By pressing the front plane and the back plane together with a flexible pressing device, a good seal is provided along the edge of the applied cell pattern. Good sealing is provided both along the inner edge between the individual cells and the outer edge surrounding the cells. Sealing between cells, this is the inner edge, reduces the risk of leakage between cells, and sealing around the cell pattern, this is the outer edge, reduces the risk of dirt and debris. moisture from the outside penetrates inside the cells.

IS 2 256 247 T3

Another object of the invention is to provide a sealed monolithic photoelectrochemical system comprising an effective protective barrier against the entry of moisture and impurities into cells from the environment, in which the risk of degradation of cell function during encapsulation is reduced. , and it is possible that the cells have sufficiently good long-term stability characteristics. These objects are achieved by a sealed monolithic photoelectrochemical system in accordance with the characterizing part of claim 16 of the patent. By means of a sealing material comprising at least a first layer formed by a plastic film, a bond is provided between the front plane and the back plane of the photoelectrochemical system, which reduces the risk of moisture penetrating the cells and also reduces the risk of the electrolyte flowing out of the cell and coming into contact with the adjacent cell. Since the plastic layer is very flexible in the hot state, a good and very tight seal is obtained, the risk of moisture penetrating is reduced and thus the long-term stability of the system is increased.

In a preferred embodiment, the sealing material comprises at least a second layer, which constitutes a barrier layer and has appropriate properties to prevent the penetration of moisture and dirt into the cell from the environment. This type of sealing material is especially suitable, because the risk of defective long-term system stability is reduced.

Description of the figures

The invention is described below with reference to the figures of the accompanying drawings, in which

Fig. 1 shows a cross section of a sealed monolithic photoelectrochemical system comprising a number of cells,

Fig. 2 shows another embodiment of a monolithic photoelectrochemical system, in which the series connection between the number of cells is carried out by alternating interconnection of terminal walls,

Fig. 3 shows a group of cells applied to the substrate,

Fig. 4 shows a flow chart of the monolithic photoelectrochemical system sealing process,

Fig. 4A shows a flow chart of a group of processes by parts in the sealing processes shown in Figure 4,

Fig. 5 shows the pressing of a photoelectrochemical system by means of a flexible diagram,

Fig. 6 shows a soft pressing head,

Fig. 7 shows a two-chamber system for pressing a photoelectrochemical system,

Fig. 8 shows a photoelectrochemical system with a two-part sealant material, and

Fig. 9 shows a photoelectrochemical system with the outer areas strongly pressed against each other.

Ways of carrying out the invention

In Figure 1, a cross-section of a sealed monolithic 1-photoelectrochemical system is shown comprising a number of cells 2A, 2B, 2C. Each cell 2A, 2B, 2C constitutes a porous structure and comprises a photoelectrode 6, an insulating layer 7 and a counter electrode 8. Cells 2A, 2b, 2C or porous structures are applied on the substrate in a pattern. The pattern is surrounded by a border that consists of an inner border that separates individual cells from each other and an outer border that surrounds a group of cells that make up the pattern. WO 97/16838 describes an example of such a system, the description of which is incorporated in its entirety herein.

The monolithic photoelectrochemical system 1 comprises photoelectrodes in the form of nanoporous photoelectrodes 6 built on the substrate. The substrate comprises a support layer 3 of completely or partially transparent material and also a thin conductive layer 4 which is applied to the support layer 3. The support layer 3 can be made of glass or plastic, in which case the photoelectric system can be designed flexibly to some extent. Each photoelectrode 6 is placed on the conductive thin layer. The conductive layer is divided into a pattern of fine dividing lines in which the conductive layer is peeled away, subsequently forming a group of mutually isolated cells. Preferably, the pattern consists of a group of elongated rectangles, but may of course be arbitrarily designed, although preferably it is a pattern to cover the surface. Figure 2 shows an example of a suitable pattern, and the photoelectrochemical system 2 is seen from above.

According to the embodiment shown in Figure 2, the pattern of the porous structure as a group of rectangular cells 2A-2D. The cells are arranged long edge to long edge. In this case, the outer edge is formed by a rectangle 40 that surrounds the group of cells and the inner edge is formed by a group of parallel lines 41 that separate the cells from each other. A group of cells is connected in series in a known way, for example as indicated below. Other patterns are also raised to cover the surface,

ES 2 256 247 T3 for example, a group of hexagons. However, the preferred embodiment with rectangles allows simple series connection between cells. In order to make a series connection between cells in a simple way, the cell layers are arranged in the embodiment shown in Figure 1, where the cells are interconnected edge to edge as follows: the photoelectrode 6 extends up to one edge of the cell conducting layer 4, while the other edge is left free. The dividing lines 5 are designed with a width such that there is no risk of the photoelectrode coming into contact with the adjacent cell.

The photoelectrode 6 is covered by a porous layer of an insulator 7, which extends over one edge of the conductive layer and insulates the photoelectrode 6 from the porous counter electrode 8 which is located in the insulator 7. Preferably, the insulator 7 may also constitute a diffuse reflector that reflects the light that has passed through the photoelectrode 6 without being absorbed in it, increasing the degree of absorption of the system.

In a preferred embodiment, the counter electrode 8 is applied in such a way that it essentially covers the insulator 7 and extends to the layer on an adjacent cell not covered by the insulator 7. In this way, cells connected in series are created, entering contact 11, with 12 providing only for the first and last in a group of interconnected cells.

The counter electrodes 8 of the respective cells are separated by an interspace 9. It is important that the cells are isolated from each other so that the electrolyte cannot get out of the electrodes or the insulator and come into contact with the electrodes of the different cells. In order to ensure that this does not happen, the interspace can be filled with an insulating material. In a preferred embodiment, the insulating material is formed by parts of sealing material 10 that is subjected to pressing within the gap 9.

Before the photoelectrochemical system 1 is sealed, the photoelectrode 6 absorbs an active substance, for example a dye that absorbs light. Furthermore, the electrolyte is supplied to the porous structure formed by the photoelectrode 6, insulator 7 and counter electrode 8. In a preferred embodiment, the electrolyte is supplied by means of a printing process, suitably screen printing. Using this method, the correct amount of electrolyte can be supplied, so that the porous structure of each cell is filled but without exceeding the filling capacity. If too much electrolyte is supplied, there is a risk that the electrolyte will move into the gap 9 between the cells, leading to a risk of short-circuiting between the cells. In another embodiment, the electrolyte is delivered by allowing the porous structure to adsorb the electrolyte during the delivery process.

In another embodiment, shown in Figure 3, the serial connection between a number of cells 2A, 2B and 2C is carried out through the terminal walls of the cells which are connected as described below. In this embodiment, the cells are in a pattern in which each cell is rectangular and has two long sides and two end walls. The cells are formed on a substrate with a layer 4 of conductive material. The cells are isolated from each other by channels 5 of the conductive material that has been etched. Each cell comprises an anode 6 made of porous material, and in the present case this anode is formed by a light-sensitive photoelectrode. An insulator 7 of porous material is applied to the anode 6. A counter electrode 8 of porous material is applied to said insulator 7. In order to carry out the series connection between the cells, they are connected in such a way that the anode of one cell is connected to the counter electrode of the next cell. In the embodiment shown in Figure 2, this is accomplished by etched channels 5 that are designed in a zig-zag pattern, producing an L-shaped pattern of conductive surfaces consisting of a group of Ls , which have a rear part 13 and a foot 14, facing each other so that the protrusion of one L tends to be located directly adjacent to the next L. The photoelectrode 6 is located entirely within the rear part, that is to say the elongated part, of an L-shaped area. The insulator 7 is positioned so that it covers the photoelectrode and extends slightly over the foot 14 of the L-shaped area of ​​an adjacent cell, that is to say the insulator 7 acts as a bridge in the etched channel 5 within a zone corresponding to the width of the cell. The series connection is carried out by the counter electrode 8 of a cell which is allowed to extend into the conductive layer 4 of an adjacent cell. In the embodiment shown in Figure 3, this is accomplished by means of the counter electrode 8 extending into the foot 14 of an L-shaped area of ​​an adjacent cell. Figure 3 also shows an encapsulating material 10A and a cover layer 10B which together constitute a sealing material 10. In a preferred embodiment, the encapsulating material 10 is formed by an adhesion layer 19A, and a cover layer 10B which is formed by an adhesion layer 19B and a barrier layer 19C.

After the electrolyte has been supplied to the porous structure, the photoelectrochemical system 1 is sealed by means of a sealing material 10 according to the invention, using a method described below with respect to Figure 4.

In a first step 20 of the method, a sealing material 12 is applied to the substrate 3 in such a way that it completely covers the cells 2A-2C and their porous structure, to form a sealed monolithic photoelectric system comprising a frontal plane formed by said substrate and the porous structure, and a back plane formed by the sealing material. The sealant material comprises at least one layer of plastic, preferably a thermoplastic such as, for example, polyethylene-methacrylic acid, which upon heating is intended to adhere to the underlying substrate and, if appropriate, to the porous structure located on the substratum. In a preferred embodiment, the sealing material is formed by a laminated material, with an adhesion plastic layer and a barrier layer with low or no permeability to liquids and air, for example a sheet of aluminum foil. In another preferred embodiment, the sealing material comprises on the one hand an adhesion plastic layer that is intended, as before, to be

ES 2 256 247 T3 one to the substrate, and secondly a laminated material formed by a plastic layer and a laminated material layer in which the plastic material is intended to adhere to said adhesion layer. The plastic layer is attached to the aluminum layer in a manner known to those skilled in the art, for example by gluing. By using an intermediate layer, a good bond is achieved as the more flexible adhesion layer takes the shape of the backing more efficiently than the less flexible aluminum layer.

In order to ensure that adequate airtightness is obtained against the ingress of liquid through the edge of the adhesion layer, the adhesion layer, in a preferred embodiment, is designed with a thickness of less than 50 pm and, in a more preferred embodiment, with a thickness of less than 30 pm. With such thicknesses, a layer is obtained that is thin enough that the edge of intense flow does not have a negative impact on the long-term stability of the enclosed cells, while the thickness is large enough to result easy to handle.

In a second step 21 of the method, the sealing material is pressed together with the substrate and with the cells located on the substrate. The sealing is carried out by means of a front plane formed by said substrate and the porous structure and a rear plane formed by the sealing material that is being subjected to pressing while it is heated, producing the fusion of the adhesion layer together with the plane. front, and resulting in sealing along the edge of the pattern. The seal isolates the individual cells from each other along the inner edge of the pattern, thus preventing leakage of the electrolyte between the cells and also isolating the group of cells whose pattern it constitutes from the surrounding environment at the outer edge. of the pattern and, in this way, prevents the entry of dirt or moisture into the cells. The following are alternative preferred embodiments of pressing.

Furthermore, Figure 4A symbolically shows certain preferred piecewise processes during sealing 21. In a first piecewise process 22, an adhesion plastic layer is first placed in front of the front plane, and on top of it a laminated material formed by a layer of adhesion, preferably plastic, and a barrier layer, preferably aluminum. In the case where the use consists of a plastic layer and an aluminum layer, the plastic layer is bonded to the aluminum layer in a way well known to the person skilled in the art, for example by gluing. By using an intermediate layer, a good bond is achieved as the more flexible adhesion layer takes the shape of the backing more efficiently than the less flexible aluminum layer. Figure 8 shows the front plane 19, the adhesion layer 19A and the barrier layer of the adhesion layer 19B and the barrier layer 19C. The adhesion layer 19B has the function of joining the barrier layer 19C and the adhesion layer 19A. Preferably, the adhesion layer is formed of a thermoplastic.

In a second piecewise process 23, the face plane and the sealing material are subjected to overpressure, which makes it possible to reduce the presence of dirt and moisture inside the cells.

In a third piecewise process 24, the face plane and the sealing material are pressed by a flexible pressing device, resulting in a good seal around both the inner and outer edges.

In order to achieve an even better seal around the outer edge, said edge can even be pressed further, with a strong pressing device in a piecewise process 25, slightly outside the cells, for example 2-5 mm from the edge of the cells. This pressing thinns any layer of adhesion 19A present, thus reducing the risk of ingress of dirt or moisture from the environment once bonding has occurred. Figure 9 shows a group of cells being pressed by a strong pressing device to give rise to two zones 26A and 26B that essentially surround the cell cluster 2A-2D. In a zone 26C, 26D around each of the contacts 11, 12, the cell cluster is not pressed in order to prevent the aluminum layer in the barrier layer from being pressed together with the conductive layer on the substrate. In order to avoid any contouring between the conductive layer and the aluminum layer in zones 26A and 26B, which can negatively affect cell grouping, these zones are separated by etched channels 26E and 26F, the areas being in those that take place the strong pressing electrically isolated from the total grouping of cells.

The above-mentioned piecewise processes can be combined individually to separately obtain preferred embodiments of the invention.

In a preferred embodiment, the pressing is carried out by means of a flexible pressing device. A flexible pressing device means that the pressing device is allowed to deform enough to access the interspaces between the cells, the sealing material being pressed against the frontal plane, so that the sealing material is pressed against cells and descends into the interspaces between cells and also surrounds the edges of the pattern. Figures 5, 6 and 7 show examples of embodiments of flexible pressing devices.

Figure 5 shows the pressing of a monolithic photoelectric system by means of a flexible diagram 15A. The photoelectrochemical system 1 is placed on a support 15B, and is subsequently covered by the flexible diagram 15A. Suitably, the flexible diagram may be made of rubber. Next, the photoelectrochemical system is subjected to pressing by means of diagram 15a, and heat is applied, and sealing is carried out. In a preferred embodiment, the pressing of the diagram 15A is carried out via the space 16 around the photoelectrochemical system 1 which is subjected to overpressure. The overpressure reduces the presence of moisture and impurities in the cells before

ES 2 256 247 T3 for sealing to take place, thus improving the quality of the cells. The bracket 15B can also be designed as a flexible diagram.

In a preferred embodiment, pressing takes place under a pressure that is obtained from flexible patterns surrounding the flexible photoelectrochemical system. By making use of a flexible diagram, a uniform pressing is obtained over the entire monolithic photoelectrochemical system and a good sealing in the aforementioned cell interspaces 9.

In a preferred embodiment, pressing is obtained by placing the monolithic photoelectrochemical system in the gap between two flexible patterns and subjecting said gap to overpressure, the pressure of the environment acting on the monolithic photoelectrochemical system. This overpressure also helps to reduce moisture and dirt in the porous structure before final sealing takes place.

Figure 6 shows an alternative embodiment in which the pressing is carried out by means of a pressing head 17 comprising a pressing surface 18 formed by a soft material, for example rubber, which presses the sealing material giving rise to the frontal plane, so that the sealing material is pressed against the cells and descends into the interspaces between the cells and also around the edges of the pattern. According to a preferred embodiment, this type of pressing can take place in a chamber subject to overpressure, making it possible to reduce the presence of dirt and moisture in the final finished product.

In an illustrative embodiment, the monolithic photoelectrochemical system is placed in an oven that heats the monolithic photoelectrochemical system to about 100 ° C, heating from room temperature occurring over a period of about 30 minutes. The material is then slowly cooled.

According to an alternative method, the photoelectrochemical system is sealed by means of the frontal plane and the sealing material, being placed in a chamber that is subjected to overpressure. According to a preferred embodiment, in order to allow evacuation to further reduce the presence of dirt and moisture, the front plane and the sealing material are separated by a gap for a period of time while being subjected to the overpressure.

When the face plane and the sealing material have reached the correct temperature, the face plane is pressed together with the sealing material.

In one embodiment of the invention, pressing is carried out using a two-part chamber as shown in Figure 7. Chamber 30 is formed by a shell 31 and comprises a first chamber part 34 and a second chamber part 35 separated by a flexible diagram 32. The photoelectrochemical system 33 to be joined is placed in one of the parts of the chamber. An air pump (not seen) is connected, or can be connected, to the manifold in order to make possible the evacuation of both the first part of the chamber and the second part of the chamber. For this, the envelope 31 can be provided with a communication path between the first and second chambers, the communication path comprising a check valve positioned so that the evacuation of the first and second chambers can be carried out simultaneously, but the air does not flow from the second to the first chamber when air is subsequently introduced in order to allow the pressing of the frontal plane and the sealing material of the photoelectrochemical system.

The invention is not limited to the embodiments described above, but can be varied within the scope of the following patent claims. In one embodiment, it is envisioned to encapsulate a configuration throughout a solar cell. In this case, different electrolytes are used for the configuration and for the solar cell, which are encapsulated simultaneously. Furthermore, both the front and rear planes may comprise additional layers; For example, a colored layer can be placed between the adhesion layer 19A and the adhesion layer 19B, in order to give rise to a desired product appearance, or alternatively it is possible to color these or other layers that are part of the product. .