A solar cell comprising a plurality of porous layers and a charge-carrying medium penetrating the porous layers.

MX435053BActive Publication Date: 2026-06-12EXEGER OPERATIONS AB

Patent Information

Authority / Receiving Office: MX · MX
Patent Type: Patents
Current Assignee / Owner: EXEGER OPERATIONS AB
Filing Date: 2023-06-23
Publication Date: 2026-06-12

AI Technical Summary

Technical Problem

Dye-sensitized solar cells face challenges in maintaining the integrity of the electrolyte during manufacturing and long-term use, including evaporation, leakage, and inefficient charge transport due to the need for vacuum filling and the compromise between mechanical support and resistive losses in solid substrates.

Method used

A solar cell design featuring a stack of porous layers supported by a porous substrate with a charge-conducting medium that penetrates through the layers, utilizing capillary forces to retain the medium and facilitate uniform distribution, reducing the need for vacuum filling and enhancing mechanical resilience.

Benefits of technology

The design prolongs the operational life of the solar cell by maintaining the charge-conducting medium, accelerates production, and reduces resistive losses while providing mechanical flexibility and durability.

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Abstract

The present invention relates to a solar cell (1a) comprising a stack of porous layers, a support substrate (2) for supporting the stack, and a charge-carrying medium (7) penetrating through the porous layers. The stack comprises a porous light-absorbing layer (3), a first porous conductive layer (4) including conductive material for extracting photogenerated electrons from the light-absorbing layer, a porous counter electrode (6) including conductive material, and a separation layer (5) made of electrically insulating porous material and disposed between the conductive layer (4) and the counter electrode (6), wherein the conductive layer (4) is disposed closer to the light-absorbing layer (3) than the counter electrode (6). The support substrate (2) is porous, and the charge-carrying medium (7) penetrates through the support substrate (2).

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Description

A solar cell comprising a plurality of porous layers and a charge-carrying medium penetrating the porous layers. TECHNICAL FIELD The present invention relates to solar cells for converting light energy into electrical energy comprising a plurality of porous layers and a charge-conducting medium penetrating the porous layers. BACKGROUND Solar cells for converting light into electrical energy, comprising a plurality of porous layers, are well known in the art. Dye-sensitized solar cells (DSSCs) comprising a porous light-absorbing layer, porous conductive layers, and a porous insulating layer are known to have high potential for industrial-scale manufacturing using established manufacturing methods such as screen printing, inkjet printing, or slot coating. The industrial-scale manufacturing of dye-sensitized solar cells involves processing large areas of thin layers of solar cell components. These components undergo several processing stages, such as printing, heat treatments, vacuum treatments, and chemical treatments during manufacturing. Therefore, the solar cell architecture is crucial for managing the processing of the components mechanically and performing the various treatments without damaging the underlying components. The solar cell architecture is also important for the overall performance of the solar cell. One common method for manufacturing dye-sensitized solar cells is a roll-to-roll process.In EnergyTrend 20180614 Keys to mass production of flexible solar cells: Cell encapsulation and durability” the researchers describe that the flexible DSSC produced by a roll-to-roll manufacturing process can be commercialized due to the efficiency of the production method. In a roll-to-roll process, the solar cell comprises a solid substrate, such as a flexible conductive sheet, which can be placed on a conveyor belt and act as a mechanically stable substrate for the positioning of other solar cell components. US patent 8658455 describes a roll-to-roll process having a flexible substrate onto which a T1O2 layer is formed, and the T1O2 layer is sintered, dyed, and charged. MA / a / k'UZ J / UU / O / 4 with electrolyte, after which a second flexible substrate is added on top to seal the sandwich-type DSSC. The sealing stage, which also involves the roll-to-roll process, is said to reduce the risk of leakage or evaporation of the liquid electrolyte. Flexible conductive sheets are available, such as sheets of titanium, stainless steel, or other metals, or sheets coated with conductive polymers or thin films of conductive glass. One problem with roll-to-roll manufacturing of dye-sensitized solar cells is that some processes, such as heat treatments or vacuum treatments, must take place as the conveyor belt passes through the ovens or chemical treatment boxes. This requires space and time for these processes. Another method for manufacturing a dye-sensitized solar cell is described in EP2834823B1, which shows a monolithic dye-sensitized solar cell in which all component layers are porous. A porous insulating substrate made of woven and non-woven glass fibers acts as a support structure during manufacturing, and porous conductive metal layers are printed on both sides of the insulating substrate. On one side, the porous conductive layer is printed with a T1O2 layer, and on the other side, a catalyst is applied. The T1O2 layer is dipped with a dye, and an electrolyte is added as the cells are cut into pieces suitable for laminating the protective film.During the process stages involving heat treatments, vacuum treatments, or various chemical treatments, the working workpiece is completely porous, and multiple workpieces can be stacked on top of each other without obstructing, for example, the escape of released gases. The porous insulating substrate used as a support substrate in manufacturing will be the insulating layer between the working electrode and the counter electrode in the final solar cell. Therefore, the thickness of the porous insulating substrate will be a compromise between making the insulating layer thin enough to reduce resistive losses in the solar cell and making the porous substrate thick enough to achieve sufficient mechanical properties to serve as a support structure. During manufacturing, the support structure must be rotated to print on both sides of the support. EP1708301 describes a dye-sensitized solar cell with an architecture that includes a stack of porous layers arranged on top of each other, electrolyte positioned integrally in the pores of the porous layers, and a support structure to support the stack of porous layers made of ceramic, metal, resin, or glass. MA / a / zuzo / uu ro / 4 Another problem with dye-sensitized solar cells relates to the evaporation or depletion of the electrolyte solution or possible electrolyte leakage, especially during long-term use of the solar cell. SUMMARY The objective of the present invention is to overcome, at least in part, the above problem and provide an improved solar cell. This objective is achieved by means of a solar cell as defined in claim 1. The solar cell comprises a stack of porous layers arranged one on top of the other, a charge-carrying medium that penetrates through the porous layers, and a support substrate to hold the porous layers. The plurality of porous layers comprises a light-absorbing layer, a first conductive layer containing conductive material for extracting photogenerated electrons from the light-absorbing layer, a counter electrode containing conductive material, and a separation layer made of electrically insulating porous material and arranged between the first conductive layer and the counter electrode. The stack of porous layers is arranged on top of the support substrate, which is porous, and the charge-carrying medium penetrates through the porous support substrate. The stack of porous layers consists of active layers, meaning they are involved in energy production. The charge-carrying medium must be able to penetrate the stack of active porous layers to allow charge transport between the light-absorbing layer and the counter electrode. The support substrate is not an active layer in the solar cell; that is, it is not involved in energy production. The primary function of the support substrate is to provide support for the stack of active layers. The support substrate is porous, and the charge-carrying medium penetrates the substrate's pores, as well as the pores of the solar cell's porous layers. Due to the substrate's porosity, these pores act as a reservoir for the charge-carrying medium. Therefore, the total volume of charge-carrying medium in the solar cell increases. Consequently, if the charge-carrying medium in the solar cell decreases due to leakage or evaporation, the time until the total charge-carrying medium content reaches a minimum level and the solar cell ceases to function is prolonged. The thicker the substrate and the greater the porosity, the larger the reservoir of charge-carrying medium. Since the support substrate is not involved in power generation, its thickness is not critical and does not affect power generation. MA / a / k'UZ J / UU / O / 4 Another advantage of the porous substrate is that it makes it easier to achieve uniform filling of the charge-carrying medium in the solar cell during manufacturing. This is a problem when manufacturing thin, wide solar cells. For example, the area of the solar cell might be 1 m² and the thickness 0.2 mm. The charge-carrying medium has to infiltrate the porous layers of the large solar cell, and ideally, all the pores in the porous layers should be filled with the charge-carrying medium. Because of the porous substrate on the underside of the solar cell, the charge-carrying medium can be introduced from the bottom and, through capillary action, fill most of the pores in the porous layers of the stack with the charge-carrying medium. Another advantage of the porous substrate is that it eliminates the need to vacuum-fill the cell with a conductive medium, as in the previous technique. Vacuum filling is time-consuming and requires additional equipment. Another advantage of the porous substrate is that it retains the conductive medium through capillary forces, thus preventing it from spilling. Therefore, in the event of solar cell breakage, the conductive medium will remain contained within the porous substrate and will not leak out. Another advantage of having the porous layers stacked on a porous support substrate, instead of a solid support substrate as in the prior art, is that it facilitates the fabrication of large solar cells. This is because it allows gas to be emitted through the substrate during vacuum sintering of the solar cell, and also during air sintering. In air sintering, combustion gases must be removed in later stages when the layers comprise titanium dioxide (T1O2) and are sintered with air, and the combustion gases from the organic substances must be eliminated by combustion. Therefore, solar cell production is accelerated. The solar cell is preferably a monolithic cell. A monolithic solar cell is characterized by the fact that all porous layers are deposited directly or indirectly onto the same support substrate. By having a porous support substrate beneath the porous active layers, the fabrication of the monolithic solar cell structure can benefit from the advantageous procedure of stapling the workpieces during the manufacturing process. Another benefit of having a support substrate beneath the active layers, upon which the active layers are formed, is that there is no need to rotate the workpiece during manufacturing. Another advantage of the present invention is that the separation layer made of electrically insulating porous material is not defined by the support substrate. The porous separation layer between the electrically conductive porous layers can be formed by an impressioning process. MA / a / ZUZO / UU / O / 4 cost-effective and can be manufactured with a variety of materials. The thickness of the separation layer can be designed to optimize the efficiency of the solar cell. According to one aspect, the solar cell comprises an encapsulation that encapsulates the porous layers, the support substrate, and the conductive medium, and the porous layers are arranged on one side of the support substrate, and an opposite side of the support substrate faces the encapsulation. Each of the porous layers and the supporting substrate contains pores. The charge-carrying medium penetrates through the pores of the porous layers and the supporting substrate. The charge-carrying medium is integrally positioned within the pores of both the porous layers and the supporting substrate. The average pore size of the multiple porous layers is smaller than the average pore size of the supporting substrate, resulting in stronger capillary forces within the pores of the porous layers compared to those in the supporting substrate. Because the pore size in the porous layers above the supporting substrate is smaller than the pore size in the supporting substrate, the capillary force in the porous layers will preferentially pump the charge-carrying medium upwards, where capillary forces are stronger than those in the supporting substrate.This action is analogous to a capillary pump. This means that, in the presence of a leak of charge-carrying medium in the upper active layers, the charge-carrying medium will preferentially be pumped from the reservoir upwards to the active layers, and the support substrate will act as a reservoir supplying charge-carrying medium to the active layers. The sizes of the pores in the substrate and porous layers can be measured, for example, using a scanning electron microscope (SEM). According to one aspect, at least 80% of the pores in the support substrate are larger than 3 μm, and at least 80% of the pores in the porous layers are smaller than 3 μm. Preferably, at least 90% of the pores in the support substrate are larger than 3 μm, and at least 90% of the pores in the porous layers are smaller than 3 μm. Preferably, at least 80% of the pores in the support substrate are between 3 μm and 10 μm, and / or with maximum preference, at least 90% of the pores in the support substrate are between 3 μm and 10 μm. Thus, the pores in the porous layers are typically in the submetric range, i.e., below 3 μm, and the pores in the support substrate are typically in the micrometric range, i.e., 3–10 μm.The difference in pore size between the support substrate and the porous layers causes the capillary forces in the porous layers to be stronger than the capillary forces in the support substrate, and consequently the charge-conducting medium will be pumped upwards to the active layers if 5. MA / a / k'UZ J / UU / O / 4 reduces the content of charge-conducting medium in the active layers of the solar cell. According to one aspect, the thickness of the support substrate is at least 20 µm, preferably at least 30 µm, and with the maximum preference at least 50 µm. The thicker the substrate, the greater the deposition of charge-conducting medium. According to one aspect, the thickness of the support substrate is between 20 pm and 200 pm. According to one aspect, the porosity of the support substrate is at least 50%, and preferably at least 70%, with the highest preference being at least 80%. The higher the porosity, the greater the deposition of charge-carrying medium. According to one aspect, the porosity of the support substrate is between 50% and 90%, and preferably between 70% and 90%. According to one aspect, the support substrate comprises woven and / or non-woven microfibers. A microfiber is a fiber that has a diameter less than 10 pm and greater than 1 nm. According to one aspect, the support substrate comprises inorganic fibers. According to one aspect, the support substrate comprises at least one of the following: glass fibers, ceramic fibers, and carbon fibers. According to one aspect, microfibers have a diameter between 0.2 pm and 10 pm, preferably between 0.2 pm and 5 pm, with greater preference between 0.2 pm and 3 pm, and with the maximum preference between 0.2 and 1 pm. According to one aspect, the support substrate comprises a layer of woven microfibers. The woven microfibers are flexible, and consequently, the solar cell becomes flexible. According to one aspect, the support substrate comprises a layer of non-woven microfibers arranged on top of a layer of woven microfibers. Both the woven and non-woven microfibers are flexible, and consequently, the solar cell becomes flexible. The non-woven microfibers act as a spring damper, effectively absorbing and dampening incoming mechanical energy and distributing it over a larger area, thereby reducing localized impact. An advantage of having the porous layers stacked on a substrate comprising a layer of woven and non-woven microfibers is that the support substrate absorbs shocks and is therefore more mechanically resistant when the solar cell is subjected to, for example, mechanical bending, torsion, stretching, or impact.This is an advantage when the solar cell is integrated into consumer products, such as headphones, remote controls, and cell phones. MA / a / k'UZ J / UU / O / 4 According to one aspect, the non-woven microfiber layer is positioned closer to the counter electrode than the woven microfiber layer. Preferably, the non-woven microfiber layer is positioned adjacent to the counter electrode. According to another aspect, the woven microfiber layer is positioned closer to the counter electrode than the non-woven microfiber layer. Preferably, the woven microfiber layer is positioned adjacent to the counter electrode. According to one aspect, the woven microfiber layer comprises threads with holes formed between them, and at least some of the non-woven microfibers accumulate in the holes between the threads. According to one aspect, the thickness of the separation layer is between 3 µm and 50 µm, and preferably between 4 µm and 20 µm. It is desirable to make the separation layer as thin as possible to reduce resistive losses in the solar cell and, consequently, improve its efficiency. However, if the separation layer becomes too thin, there is a risk of short-circuiting between the conductive layer and the counter electrode. According to one aspect, the separation layer comprises electrically insulating porous material. Preferably, the electrically insulating material is made of electrically insulating particles. Such a separation layer can be manufactured by applying several layers of insulating particles on top of each other to achieve the desired thickness. Therefore, it is possible to control the thickness of the separation layer, and the thickness can be selected according to the requirement. According to one aspect, these electrically insulating particles consist of an insulating material. According to one aspect, these electrically insulating particles comprise a core of semiconductor material and an outer layer of an electrically insulating material covering the core. According to one aspect, the insulating material of the outer layer of the insulating particles comprises one or more of the materials in the group consisting of alumina (Al₂O₃), zirconium oxide (ZrO₂), silicon oxide (S₁O₂), and aluminosilicate. Aluminosilicate is, for example, Al₂S₁O₅. According to one aspect, the insulating material of the outer layer of the insulating particles is one or more of the materials in the group consisting of alumina (Al₂O₃), zirconium oxide (ZrO₂), silicon oxide (S₁O₂), and aluminosilicate. Aluminosilicate is, for example, Al₂S₁O₅. According to one aspect, the semiconductor material in the core of the insulating particle comprises titanium dioxide (T1O2). MA / a / ZUZO / UU / O / 4 According to one aspect, the semiconductor material in the core of the insulating particle is titanium dioxide (T1O2). According to one aspect, the electrically insulating material of the insulating particles comprises one or more of the materials in the group consisting of alumina (Al₂O₃), zirconium oxide (ZrCl₂), silicon dioxide (S₁O₂), and aluminosilicate. Aluminosilicate is, for example, Al₂S₁O₅. According to another aspect, the insulating material may be glass. From one perspective, the electrically insulating material of the insulating particles is one or more of the materials in the group consisting of alumina (Al₂O₃), zirconium oxide (ZrO₃), silicon dioxide (S₁O₂), and aluminosilicate. Aluminosilicate is, for example, Al₂S₁O₅. From another perspective, the insulating material can be glass. According to one aspect, the charge-conducting medium is a liquid electrolyte. Certain conductive media, such as complex copper electrolytes and complex cobalt electrolytes, can have very low electrical conductivity, resulting in very large electrical resistive losses. This low electrical conductivity stems from the fact that the electrolytes contain large ions with a slow diffusion rate. When a liquid electrolyte is charged, the charges move with Brownian motion, meaning they move randomly due to collisions with rapidly moving atoms or molecules in the liquid. Copper and cobalt have relatively large ions that move slowly and therefore exhibit low conductivity. The efficiency of using such electrolytes is greatly improved by maintaining a short distance between the counter electrode and the light-absorbing layer.The present invention makes it possible to choose the thickness of the separation layer and, consequently, to select a suitable distance between the counter electrode and the light-absorbing layer depending on the electrolyte. According to one aspect, the conductive medium comprises copper complexes. An advantage of using copper complexes for charge transport is that the conductive medium will not be toxic. It has been demonstrated that using copper as a conductive medium produces a very high resulting photovoltage. The solar cell according to the invention allows the use of copper complexes because the distance between the counter electrode and the light-absorbing layer can be shortened. According to another aspect, the charge-carrying medium comprises iodide (Γ) and triiodide (I.i). Another object of the present invention is to provide a method for producing the solar cell: The method comprises: - provide a porous support substrate, - deposit a porous counter electrode onto the porous support substrate, IVIA / a / ZUZO / UU / O / 4 - deposit a porous separation layer on the counter electrode, - deposit a porous conductive layer over the separation layer, - deposit a porous light-absorbing layer on the conductive layer, - introduce a charge-conducting medium into the cell and the support substrate until the charge-conducting medium penetrates the support substrate and the cell, — seal the solar cell. According to one aspect, depositing the porous counter electrode comprises depositing a second porous conductive layer and a porous catalytic layer on top of the second conductive layer. According to one aspect, the charge-conducting medium is introduced into the side of the support substrate that faces away from the stack, so that the support substrate and the stack are impregnated with the charge-conducting medium. The deposition of the porous counter electrode, the porous separation layer, the first porous conductive layer, and the porous light-absorbing layer are carried out, for example, by a spraying or printing technique, such as inkjet printing or screen printing. BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be explained in more detail by describing different embodiments of the invention and with reference to the accompanying figures. Figure 1 shows a cross-section of an example of a solar cell according to the invention. Figure 2 shows a cross-section of another example of a solar cell according to the invention. Figure 3 shows an SEM image of a cross-section through an example of an embodiment of the invention. Figure 4 shows an SEM image of a cross-section through another example of a modality of the invention. Figure 5 shows a block diagram of an example of a method for manufacturing the solar cell according to the invention. DETAILED DESCRIPTION The aspects of this description will be described more fully below. MA / a / k'UZ J / UU / O / 4 Reference to the accompanying drawings. The solar cell device can, however, be implemented in many different ways and should not be interpreted as limited to the aspects set forth in this description. Equal numbers in the drawings refer to equal elements. Figure 1 shows a cross-section through an example of a solar cell 1a according to the invention. The solar cell comprises a support substrate 2 and a stack 12 of porous layers 3-6 arranged on the support substrate 2. The stack 12 of porous layers comprises a light-absorbing layer 3, which serves as the working electrode, a conductive layer 4 made of conductive porous material, which serves as the current collector, a separation layer 5 comprising electrically insulating porous material, and a counter electrode 6 comprising porous conductive material. The counter electrode 6 is formed on one side of the porous substrate 2. In this example, the counter electrode is a porous conductive layer. The separation layer 5 is arranged between the counter electrode 6 and the conductive layer 4.The separation layer 5 serves to physically and electrically separate the conductive layer 4 and the counter electrode 6 to prevent a direct electrical short circuit between them. In this example, the separation layer 5 is formed over the counter electrode 6, and the conductive layer 4 is formed over the separation layer 5. The light-absorbing layer 3 is placed on top of the conductive layer 4. The first conductive layer 4 includes conductive material to extract photogenerated electrons from the light-absorbing layer 3. The light-absorbing layer 3 can be fabricated in different ways. For example, the light-absorbing layer can comprise dye molecules adsorbed on the surfaces of semiconductor particles, dye clusters, or grains made of a semiconductor material, such as silicon. Porous layers 3-6 are active layers, meaning they are involved in energy production. Support substrate 2 is not an active layer in the solar cell; that is, it is not involved in energy production. Support substrate 2 supports the stack of porous layers 3-6. Additionally, support substrate 2 allows the counter electrode 6 to be printed onto it during solar cell fabrication. Porous layers 3-6 are arranged on one side of support substrate 2. Each of the porous layers formed on the support substrate has a large number of pores. The solar cell also comprises a charge-conducting medium 7 that penetrates the pores of the porous layers 3-6 to allow charge transport between the light-absorbing layer 3 and the counter electrode 6. The support substrate 2 is also porous and includes pores. The charge-conducting medium 7 penetrates the pores of the support substrate 2 as well as the pores of the porous layers 3-6 of the solar cell. Due to the porosity of the support substrate 2, the pores of the support substrate function as a reservoir for the charge-conducting medium. IVIA / a / ZUZO / UU / O / 4 In one respect, the average pore size of porous layers 3-6 in stack 12 is smaller than the average pore size of support substrate 2, so the capillary forces in the pores of porous layers 3-6 are stronger than the capillary forces in support substrate 2. The difference in pore size between support substrate 2 and porous layers 3-6 makes the capillary forces in the porous layers stronger than the capillary forces in support substrate 2, and consequently, the charge-conducting medium 7 will be pumped upwards to the active layers 3-6 if the charge-conducting medium content in the active layers of the solar cell is reduced. Preferably, at least 80% of the pores in support substrate 2 are larger than 3 pm, and at least 80% of the pores in the porous layers are smaller than 3 pm. More preferably, at least 90% of the pores in support substrate 2 are larger than 3 pm, and at least 90% of the pores in porous layers 3-6 are smaller than 3 pm. For example, at least 80% of the pores in support substrate 2 are between 3 pm and 10 pm. The thicker the support substrate 2, the greater the charge-carrying medium deposit on the solar cell. Typically, the thickness of support substrate 2 is between 20 µm and 200 µm. Preferably, the thickness of the support substrate is at least 30 µm. Greater porosity in the support substrate results in greater deposition of the charge-carrying medium. 7. Preferably, the porosity of the support substrate is at least 50%, and ideally at least 70%. If the support substrate is too porous, its mechanical strength will be too low. Preferably, the porosity of the support substrate is between 50% and 90%. The solar cell further comprises an encapsulation 10 that encapsulates the porous layers 3-6, the support substrate 2, and the conductive medium 7. The stack 12 of porous layers is arranged on one side of the support substrate 2, and an opposite side of the support substrate faces the encapsulation 10. The stack of porous layers 12 may include other porous layers arranged between the porous layers 36. For example, there may be a porous catalytic layer arranged between the support substrate 2 and the counter electrode 6, or between the counter electrode 6 and the separation layer 5, as shown in Figure 1. In addition, there may be a porous reflective layer arranged between the conductive layer 4 and the light-absorbing layer 3. The same conditions mentioned above regarding pore size apply to all layers in the stack of porous layers 12, regardless of the number of layers. MA / a / ZUZO / UU / O / 4 Figure 2 shows a cross-section of another example of solar cell Ib according to the invention. Solar cell Ib comprises a support substrate 2 and a stack 12 of porous layers 3 6 arranged on the support substrate 2. Solar cell Ib differs from solar cell a in that the counter electrode 6 of solar cell Ib comprises a second porous conductive layer 6a and a porous catalytic layer 6b formed on top of the porous conductive layer 6a. In this example, the support substrate 2 comprises a woven microfiber layer 2a and a nonwoven microfiber layer 2b disposed on the woven microfiber layer 2a. The counter electrode 6 is disposed on the nonwoven microfiber layer 2b. In this example, the porous conductive layer 6a of the counter electrode 6 is formed on the nonwoven microfiber layer 2b. Alternatively, the catalytic layer 6b is disposed on the nonwoven microfiber layer 2b. The woven microfiber layer 2a comprises yarns with holes formed between them, and at least some of the nonwoven microfibers accumulate in the holes between the yarns. Preferably, the microfibers of the nonwoven microfiber layer 6b have a diameter between 0.2 µm and 5 µm, to achieve pores larger than 1 µm. Document EP2834824BI describes methods for manufacturing a substrate 2 comprising woven and nonwoven microfibers. Solar cells Ia and Ib are monolithic. This means that all porous layers are deposited directly or indirectly onto the same support substrate. Solar cells Ia and Ib can be, for example, dye-sensitized solar cells (DSCs). Figure 3 shows an SEM image of a cross-section through an example of an embodiment of the invention showing the support substrate 2 comprising the woven microfiber layer 2a on top of the non-woven microfiber layer 2b. On the support substrate 2 is disposed the second porous conductive layer 6a, then the catalytic layer 6b and on top of the catalytic layer the separation layer 5. On the separation layer 5 is disposed the first conductive layer 4 and on top of it the light-absorbing layer 3. Figure 4 shows an SEM image of a cross-section through another example of an embodiment of the invention showing a support substrate 2 comprising a layer of non-woven microfibers 2b on top of a layer of woven microfibers 2a. On the support substrate 2 is disposed the second porous conductive layer 6a, then the catalytic layer 6b and on top of the catalytic layer the separation layer 5. On the separation layer 5 is disposed the first conductive layer 4 and on top of it the light-absorbing layer 3. Preferably, the pore size of the light-absorbing layer 3 is equal to or less than the pore size of the first conductive layer 4, the pore size of the first conductive layer 4 is equal to or less than the pore size of the separation layer 5, and the pore size of the layer 12 MA / a / ZUZO / UU / O / 4 separation 5 is equal to or less than the pore size of the counter electrode layers 6, 6a, 6b. The pore size of the counter electrode 6, 6a, 6b is preferably smaller than the pore size of the support substrate 2, 2a, 2b. In one embodiment of the invention, the pore size in the stack 12 of porous layers decreases from the counter electrode 6 to the light-absorbing layer 3. For example, the pore size of the light-absorbing layer 3 is smaller than the pore size of the first conductive layer 4, the pore size of the first conductive layer 4 is smaller than the pore size of the separation layer 5, and the pore size of the separation layer 5 is smaller than the pore size of the counter electrode 6, 6a, 6b. The pore size of the counter electrode 6, 6a, 6b is smaller than the pore size of the support substrate 2, 2a, 2b. This embodiment will enhance the difference in capillary forces in the porous layers compared to the capillary forces in the support substrate 2. The light-absorbing layer 3 faces the incident light. The light-absorbing layer 3 can be fabricated in various ways. For example, the light-absorbing layer 3 may comprise a porous TiO2 layer deposited on the first conductive layer 4. The TiO2 layer may comprise TiO2 particles having dye molecules adsorbed onto their surfaces. In another example, the light-absorbing layer 3 comprises a plurality of grains of a doped semiconductor material, such as silicon, deposited on the conductive layer 4. The charge-carrying medium is integrally placed within the pores formed between the grains. The thickness of the light-absorbing layer 3 can vary and depends on the type of light-absorbing layer 3. The top side of the solar cell Ib must face the light to allow light to reach the light-absorbing layer 3. According to some interpretations, the light-absorbing layer is a porous layer of T1O2 nanoparticles with adsorbed organic or organometallic dye molecules, or natural dye molecules. However, the light-absorbing layer 3 can also comprise grains of a doped semiconductor material, for example, Si, CdTe, CIGS, CIS, GaAs, or perovskite. The conductive layer 4 serves as a back contact that extracts photogenerated charges from the light-absorbing layer 3. The porosity of the conductive layer 4 can preferably be between 30% and 85%. Depending on the material used for the conductive layer 4 and the manufacturing method employed, the thickness of the conductive layer 4 can vary between 1 pm and 50 pm. For example, the conductive layer 4 is made of a material selected from a group consisting of titanium, titanium alloys, nickel alloys, graphite, and amorphous carbon, or mixtures thereof. Most preferably, the conductive layer is made of titanium or a titanium alloy or mixtures thereof. MA / a / ZUZO / UU / O / 4 these. In such a case, the thickness of the conductive layer 4 is preferably between 4 pm and 30 pm. The separation layer 5 serves as an electrical barrier between the conductive layer 4 and the counter electrode 6 to prevent short circuits between them. The distance between the counter electrode 2 and the light-absorbing layer 3 depends on the thickness of the separation layer 5 and should be as small as possible to ensure the fastest possible charge transport between the counter electrode 2 and the light-absorbing layer 3, thereby reducing resistive losses in the solar cell. The thickness of the separation layer is, for example, between 3 pm and 50 pm, and preferably between 4 pm and 20 pm. The separation layer comprises electrically insulating porous material. For example, the separation layer comprises a porous layer of electrically insulating particles. For example, the insulating particles have a core of semiconductor material and an outer layer of electrically insulating material.For example, an insulating oxide layer forms on the surfaces of the semiconductor material. Conveniently, the semiconductor material is titanium dioxide (TiCb). The insulating material is, for example, alumina or silicon oxide. Alternatively, the entire particles can be made of insulating material, for example, alumina (Al₂O₃), silicon dioxide (S₁O₂), or zirconium oxide (ZrCh). The counter electrode 6 comprises a porous conductive layer 6a. The counter electrode typically also comprises a catalytic layer 6b. The counter electrode 6 may have a separate porous catalytic layer 6b or have catalytic particles integrated into the porous conductive layer 6a. The porosity of the counter electrode 6 may preferably be between 30% and 85%. Depending on the material used for the counter electrode 6 and the manufacturing method, the thickness of the counter electrode 6 may vary between 1 µm and 50 µm. For example, the counter electrode 6 is made of a material selected from a group consisting of titanium, titanium alloys, nickel alloys, graphite, and amorphous carbon, or mixtures thereof. Most preferably, the counter electrode 6 is made of titanium or a titanium alloy or mixtures thereof. In such a case, the thickness of the conductive layer 4 is preferably between 10 µm and 30 µm.To achieve a catalytic effect, the counter electrode 6 may include platinized particles of conductive metal oxides, such as platinized ITO, ATO, PTO and FTO, or platinized carbon black or graphite particles. The support substrate 2 can be a microfiber-based substrate, such as a glass microfiber substrate or a ceramic microfiber substrate. The support substrate 2 is suitably made of microfibers. A microfiber is a fiber with a diameter less than 10 pm and a length greater than 1 nm. Conveniently, the support substrate 2 comprises woven microfibers. The microfibers can be made of a refractory and inert material, such as glass, S1O2, Al2O3, and 14 MA / a / ZUZO / UU / O / 4 aluminosilicate. Organic microfibers are fibers made from organic materials such as polymers, for example, polycaprolactone, PET, PEO, etc., or cellulose, for example, nanocellulose (MFC) or wood pulp. The support substrate 2 may comprise woven microfibers and non-woven microfibers arranged on top of the woven microfibers. Conveniently, the support substrate 2 comprises fiberglass. For example, the porous support substrate may be made of woven and non-woven fiberglass. The thickness of the support substrate 2 is conveniently between 10 µm and 1 mm. Such a layer provides the required mechanical strength. The charge-carrying medium 7 is integrally placed within the pores of the porous layers 3-6 and the pores of the support substrate 2 and transfers charges between the counter electrode 6 and the light-absorbing layer 3. The conductive medium 7 can be any suitable conductive medium, such as a liquid, a gel, or a solid material like a semiconductor. Examples of electrolytes include liquid electrolytes, such as those based on iodide (I) / triiodide (If) ions or cobalt complexes as a redox couple, or gel electrolytes, or ordinary polymer electrolytes. Preferably, the conductive medium is a liquid electrolyte, such as an electrolyte based on an ionic liquid, a copper complex, or a cobalt complex. Solar cells must be properly sealed to prevent leakage of the charge-carrying medium. For example, a solar cell is supplied by a package (10) that encloses the solar cell unit. However, the package must be penetrated in some way to allow access to the energy produced by the solar cell. Although these penetrations are sealed, there is a risk of slow leakage of the charge-carrying medium from the solar cell. Leaks can also occur from the sealed edges of the package. Slow leakage of the charge-carrying medium will cause a gradual decline in the efficiency of the solar cell. When the charge-carrying medium content in the solar cell has reached a minimum level, the cell's ability to convert light into electricity will decrease. This process can take several months or even years, depending on the quality of the package and the sealing. The encapsulation 10 acts as a barrier to protect the solar cell from the surrounding atmosphere and to prevent evaporation or leakage of the charge-carrying medium from inside the cell. The encapsulation 10 may include a top sheet covering one upper side of the solar cell and a bottom sheet covering one lower side of the solar cell. The top sheet on the upper side of the solar cell covers the light-absorbing layer and must be transparent to allow light to pass through. One lower side of the support substrate 2 faces the bottom sheet of the encapsulation 10. The photoabsorbing layer 3 faces the top sheet of the encapsulation 10. The top sheets and 15 ML / a / ZUZ J / UU { O í 4 lower are, for example, made of a polymeric material. The edges of the top and bottom sheets are sealed. According to one aspect, the solar cell package 10 comprises a plurality of penetration openings (not shown in the figures) to allow access to the energy produced by the solar cell. The penetration openings receive wires for electrical connection to the first conductive layer 4 and the counter electrode 6. The penetration openings can be arranged in connection with the first conductive layer 4 and the counter electrode 6. Preferably, the penetration openings are arranged on the side of the package positioned below the support substrate 7. Figure 5 shows a block diagram of an example of a method for manufacturing the solar cell according to the invention. The method in Figure 5 comprises the following steps: S1: provide a porous support substrate 2, S2: deposit a porous counter electrode 6 onto the porous support substrate 2, S3: deposit a porous separation layer 5 on the counter electrode 6, S4: deposit a first porous conductive layer 4 on the separation layer 5, S5: deposit a light-absorbing porous layer 3 on the first conductive layer 4, S6: introduce a charge-conducting medium 7 into the stack 12 and the support substrate 2 until the charge-conducting medium 7 penetrates the support substrate 2 and the stack 12, S7: sealing of the solar cell. According to one aspect, the charge-conducting medium 7 is introduced into the side of the support substrate facing away from the stack 12 so that the support substrate and the stack are impregnated with the charge-conducting medium. The deposition in stages S2-S5 is carried out, for example, by a spraying or printing technique, such as inkjet printing or screen printing. An example of how step S3 can be carried out is explained in more detail below. A separating ink is prepared by mixing a powder of insulating particles with a solvent, a dispersing agent, and a binder. The solvent is, for example, water or an organic solvent. The binder is, for example, hydroxypropylcellulose. The dispersing agent is, for example, Byk 180. The mixture is stirred until the aggregated particles in the powder separate into individual particles and the particles in the ink are well dispersed. The separating ink is deposited onto the counter electrode 6 by a spraying or printing technique. The deposition of the separating ink can be repeated two, three, or more times until a sufficiently thick layer of insulating particles has been deposited on the counter electrode. Preferably, the separating ink layer is dried. MÁ / a / ZUZ J / UU { O í 4 before the next layer of separating ink is deposited over the previous layer of separating ink. It is advantageous to repeat the deposit of the separating ink two or more times since the subsequent layers of ink will repair any defects in the previous layers of insulating particles. It is important that there are no defects, such as cracks or holes, in the separating layer 5, as this would cause a short circuit between the counter electrode 6 and the first porous conductive layer 4. The solar cell in Figure 1 is infiltrated with a charge-carrying medium 7 into the pores of the light-absorbing layer 3, the pores of the first conductive layer 4, the pores of the separation layer 5, the pores of the counter electrode 6, and the pores of the support substrate 2. The charge-carrying medium forms a continuous layer within the pores of the conductive layers and between the conductive layers within the pores of the separation layer, thus enabling the transport of electrical charge between the counter electrode 6 and the working electrode, including the first conductive layer 4 and the light-absorbing layer 3. The first porous conductive layer 4 extracts electrons from the light-absorbing layer 3 and transports them to an external electrical circuit connected to the counter electrode 6 (not shown in Figure 1). The counter electrode 6 is used to transfer the electrons to the charge-carrying medium 7.The conducting medium 7 transfers electrons back to the light absorption layer 3, thus completing the electrical circuit. Depending on the nature of the charge-conducting medium 7, ions or electrons and holes can be transported between the counter electrode and the working electrode. Electrolytes in dye-sensitized solar cells are typically classified as liquid electrolytes, near-solid electrolytes, or solid electrolytes. Electrolytes can be in liquid, gel, or solid form. A large number of electrolytes of each type are described in the literature; see, for example, Chemicals Reviews, January 28, 2015, "Electrolytes in Dye-Sensitized Solar Cells." Electrolytes are an expensive component of dye-sensitized solar cells. The counter electrode is typically equipped with a catalytic substance 6b, which facilitates the transfer of electrons to the electrolyte. The charge-carrying medium exhibits a certain electrical resistance to the transport of charges. This electrical resistance increases with the distance the charge is transported. Therefore, when electrical charge is transported between the counter electrode and the light-absorbing layer, there will always be some electrical resistive loss in the conducting medium. By making the porous substrate thinner, these resistive losses can be reduced. However, as the porous substrate becomes thinner, it also becomes more mechanically brittle. The conducting medium is, for example, a conventional I / If electrolyte or a similar electrolyte, or a 17 ML / a / ZUZ J / UU { O í 4 Cu- / Co- complex electrolyte, Solid-state transition metal-based complexes or organic polymer hole conductors are known conducting media. According to some aspects, the conductive medium comprises copper ion complexes. A conductive medium that uses copper complexes as a charge carrier is a non-toxic conductive medium. The use of copper complexes as a conductive medium has been shown to produce a very high resultant photovoltage. The counter electrode 6 can, for example, be deposited onto the support substrate 2 by printing with an ink containing conductive solid particles. The conductive particles, such as metal hydride particles, can be mixed with a liquid to form an ink suitable for the printing process. The conductive particles can also be ground or otherwise treated to achieve a suitable particle size and, consequently, a desired pore size of the porous counter electrode 6. The solid particles are preferably metal-based and can be pure metals, alloys, metal hydrides, metal alloy hydrides, or mixtures thereof. The conductive layer 4 can be deposited onto the separation layer 5 in the same way that the counter electrode 6 is deposited onto the support substrate 2. The deposits can be treated by a heat treatment stage. During the heat treatment, sintering of the particles will also occur, thereby increasing the conductivity and mechanical stability of the conductive layers. The metal hydrides will be transformed into metal during the heat treatment. Heating under vacuum or with an inert gas prevents contamination of the particles and improves electrical contact between them. The terminology used herein is intended solely to describe particular aspects of the disclosure and is not intended to limit the invention. As used herein, the singular forms a, one, and the are intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms photovoltaic cell and solar cell are synonymous. Unless otherwise defined, all terms used in this description have the same meaning as commonly understood by an average person skilled in the technique to which this description pertains. The present invention is not limited to the described embodiments, but may be varied and modified within the scope of the following claims. For example, the stack of porous layers may contain other porous layers, and the order of the porous layers in the stack may be changed.

Claims

1. A solar cell (Ia; Ib) comprising a stack (12) of porous layers (3-6), a support substrate (2) for supporting the stack, and a charge-carrying medium (7) penetrating through the stack, wherein the stack (12) comprises: a light-absorbing porous layer (3), a first porous conducting layer (4) including conductive material for extracting photogenerated electrons from the light-absorbing layer, a porous counter-electrode (6) including conductive material, and a separation layer (5) made of electrically insulating porous material and disposed between the first conducting layer (4) and the counter-electrode (6), and wherein the first conducting layer (4) is disposed closer to the light-absorbing layer (3) than the counter-electrode (6), characterized in that the stack of porous layers (3-6) is disposed on top of the support substrate, the support substrate (2) is porous, and the charge-carrying medium (7) penetrates through the support substrate (2).

2. The solar cell according to claim 1, wherein the charge-conducting medium (7) is integrally positioned in the pores of the porous layers (3-6) and the pores of the support substrate (2), and the average size of the pores of the porous layers (3-6) is smaller than the average size of the pores of the support substrate (2), so that the capillary forces in the pores of the porous layers are stronger than the capillary forces in the pores of the support substrate.

3. The solar cell according to any of claims 1-2, wherein the size of at least 80% of the pores in the porous layers (3-6) is less than 3 pm.

4. The solar cell according to any of the preceding claims, wherein the size of at least 80% of the pores in the support substrate (2) is greater than 3 pm.

5. The solar cell according to any of the preceding claims, wherein the porosity of the support substrate (2) is at least 50%, and preferably at least 70%, and most preferably at least 80%. MA / a / ZUZ J / UU { O í 4 6. The solar cell according to any of the preceding claims, wherein the thickness of the support substrate (2) is at least 20 pm, preferably at least 30 pm, and most preferably at least 50 pm.

7. The solar cell according to any of the preceding claims, wherein the support substrate (2) comprises microfibers.

8. The solar cell according to claim 7, wherein the support substrate (2) comprises microfibers having a diameter between 0.2 pm and 10 pm, preferably between 0.2 pm and 5 pm, and most preferably between 0.2 pm and 1 pm.

9. The solar cell according to any of the preceding claims, wherein the support substrate (2) comprises woven and non-woven microfibers.

10. The solar cell according to claim 9, wherein the support substrate (2) comprises a layer (2a) of woven microfibers and a layer of non-woven microfibers (2b) disposed on the layer (2a) of woven microfibers 14.

11. The solar cell according to any of the preceding claims, wherein the support substrate (2) is flexible.

12. The solar cell according to any of the preceding claims, wherein the thickness of the separation layer (5) is between 3 pm and 50 pm, and preferably between 15 and 35 pm, and most preferably between 4 pm and 20 pm.

13. The solar cell according to any of the preceding claims, wherein the charge-conducting medium (7) is a liquid electrolyte.

14. A method for manufacturing the solar cell according to claim 1, wherein the method comprises: providing (S1) a porous support substrate (2), depositing (S2) a porous counter electrode (6) onto the porous support substrate (2), depositing (S3) a porous separation layer (5) onto the counter electrode (6), depositing (S4) a first porous conductive layer (4) onto the separation layer (5), depositing (S5) a light-absorbing porous layer (3) onto the conductive layer (4), introducing (S6) a charge-conducting medium (7) into the stack (12) and the support substrate (2) until the charge-conducting medium (7) penetrates the support substrate (2) and the stack (12), and sealing (S7) the solar cell.

15. A method according to claim 14, wherein depositing (S2) the porous counter electrode (6) comprises depositing a second porous conductive layer (6a) and a porous catalytic layer (6b) on top of the second conductive layer (6a).