WO2023237190A1

WO2023237190A1 - Method of manufacturing a photovoltaic cell, photovoltaic cell, and solar glass module

Info

Publication number: WO2023237190A1
Application number: PCT/EP2022/065563
Authority: WO
Inventors: Dimitris A. CHALKIAS; Argyroula MOURTZIKOU; Giannis KATSAGOUNOS; Elias Stathatos; Nick Kanopoulos
Original assignee: Brite Hellas S.A.
Priority date: 2022-06-08
Filing date: 2022-06-08
Publication date: 2023-12-14

Abstract

Method of manufacturing a photovoltaic cell, comprising providing a glass substrate 1, depositing an electrically conductive layer 2 onto the glass substrate, depositing a microporous electron transport layer 3 on top of the conductive layer, depositing a mesoporous electron transport layer 4 on top of the microporous electron transport layer, depositing a perovskite layer 5 on top of the microporous electron transport layer, and depositing a carbon compound layer 6 on top of the perovskite layer.

Description

METHOD OF MANUFACTURING A PHOTOVOLTAIC CELL, PHOTOVOLTAIC CELL,

AND SOLAR GLASS MODULE

The present invention relates to a method of manufacturing a photovoltaic cell, a photovoltaic cell, and a solar glass module comprising a plurality of photovoltaic cells.

A general aim in today’s development of new generation solar cell technologies is to enhance conversion efficiency and to reduce fabrication costs. Such new generation solar cell technologies include transparent assemblies of solar cells which may function as building-integrated photovoltaic windows.

In this regard, dye-sensitized solar cells (DSSCs) are considered as a promising solar cell technology, because they are made of inexpensive and nontoxic components and can be designed in a diversity of transparencies and color. However, the conversion efficiency of such solar cells is still limited.

In the last seven years, perovskite solar cells (PSC) as a DSSC development in a complete solid-state form has seen their conversion efficiency increasing at a fast rate. However, there is room for improvement in terms of conversion efficiency and long-term stability as far as existing implemented structures of PSCs is concerned. In addition, existing PSC structures’ layer uniformity and production cost effectiveness are limited.

According to a first aspect thereof, the invention provides a method of manufacturing a photovoltaic cell, comprising providing a glass substrate, depositing an electrically conductive layer onto the glass substrate, depositing a microporous electron transport layer on top of the conductive layer, depositing a mesoporous electron transport layer on top of the microporous electron transport layer, depositing a perovskite layer on top of the microporous electron transport layer, and depositing a carbon compound layer on top of the perovskite layer.

In a preferred embodiment, the step of depositing the electrically conductive layer onto the glass substrate comprises applying an electrically conductive coating onto the glass substrate.

In a preferred embodiment, the step of depositing the microporous electron transport layer on top of the conductive layer comprises inkjet -printing a printable ink solution containing at least one of tin oxide, titanium oxide and zinc oxide on top of the conductive layer. Inkjet printing is a low-cost technology, which reduces raw material waste. Instead of depositing chemical compounds on conductive substrates with conventional methods, inkjet printing enables precise patterning with limited waste of material and finally very low cost of producing photovoltaic cells. Among the most common deposition techniques, inkjet printing stands out as a deposition technique for solutionbased materials. Inkjet printing characterized for its scalability, fast material deposition with high accuracy and extremely low wastes, which also allows the formation of fine patterns of printed inks at a high resolution. Finally, inkjet printing allows for depositing a uniform, compact and smooth layer of small thickness, e.g., a nanocoating.

In a preferred embodiment, the step of depositing the mesoporous electron transport layer on top of the microporous electron transport layer comprises inkjet -printing a printable ink solution containing at least one of tin oxide, titanium oxide and zinc oxide on top of the microporous electron transport layer.

In a preferred embodiment, the mesoporous electron transport layer has a pore size of between 6 nm and 20 nm.

In a preferred embodiment, particles making up the mesoporous electron transport layer have a size of between 10 nm and 30 nm.

In a preferred embodiment, the microporous electron transport layer has a pore size of between 0,5 nm and 2 nm.

In a preferred embodiment, the step of depositing the perovskite layer on top of the mesoporous electron transport layer comprises inkjet-printing a printable ink solution containing a perovskite compound on top of the mesoporous electron transport layer. Due to the above-described advantages of inkjet printing in relation to the step of depositing the microporous electron transport layer, inkjet-printing allows for the commercialization of perovskite structures.

In a preferred embodiment, the perovskite compound comprises at least one of Cs0.05[FA0.85MA0.15]0.95Pb[I0.87Br0.83]3, (5-AVA)x(MA)(l-x)PbI3 and MAPb(Il-xClx)3, and wherein the solution is printed at a temperature of between 50 °C and 70 °C.

In a preferred embodiment, the step of depositing the carbon compound layer on top of the perovskite layer comprises inkjet-printing a printable ink solution containing carbon on top of the perovskite layer.

In a preferred embodiment, the carbon compound layer comprises at least one of the following: graphite, carbon black, graphene, carbon nanotubes, carbon nanowires, a mixture of them. In a preferred embodiment, the method further comprises arranging a plain glass on top of the carbon compound layer and sealing the photovoltaic cell from the environment by applying a sealant comprising an ultraviolet curable compound around the photovoltaic cell.

According to a second aspect thereof, the invention provides a photovoltaic cell manufactured by the method according to any one of the above-described embodiments, comprising a glass substrate having an electrically conductive layer, a microporous electron transport layer on top of the conductive layer, a mesoporous electron transport layer on top of the microporous electron transport layer, a perovskite layer on top of the microporous electron transport layer, and a carbon compound layer on top of the perovskite layer.

In a preferred embodiment, the microporous electron transport layer comprises at least one of tin oxide, titanium oxide and zinc oxide.

In a preferred embodiment, the mesoporous electron transport layer comprises at least one of tin oxide, titanium oxide and zinc oxide.

In a preferred embodiment, the perovskite compound comprises at least one of Cs0.05[FA0.85MA0.15]0.95Pb[I0.87Br0.83]3, (5-AVA)x(MA)(l-x)PbI3 and MAPb(Il-xClx)3.

In a preferred embodiment, the carbon compound layer comprises at least one of the following: graphite, carbon black, graphene, carbon nanotubes, carbon nanowires, a mixture of them.

In a preferred embodiment, the photovoltaic cell further comprises a plain glass on top of the carbon compound layer, and a sealant around the photovoltaic cell, comprising an ultraviolet curable compound. According to a third aspect thereof, the invention provides a solar glass module, comprising a plurality of photovoltaic cells according to any of the above-described embodiments.

By reference to the appended drawings, which illustrate exemplary embodiments of this invention according to aspects of the invention, the detailed description provided below explains in detail various features, advantages, and aspects of this invention. As such, features of this invention can be more clearly understood from the following detailed description considered in conjunction with the following drawings. Each exemplary aspect or embodiment illustrated in the drawings is not intended to be to scale, to be comprehensive of all aspects, or to be limiting of the invention’s scope, for the invention may admit to other equally effective embodiments and aspects.

As such, the drawings are included to provide a further understanding and are incorporated in and constitute a part of this specification, wherein: figure 1 shows a cross-sectional schematic view of a photovoltaic cell according to a preferred embodiment of the present invention; figures 2A-1 and 2A-2 show top view images taken by a scanning electron microscope (SEM) of a photovoltaic cell according to a preferred embodiment of the present invention; figures 2B-1 and 2B-2 show top view images taken by an SEM of a layer of a photovoltaic cell according to a preferred embodiment of the present invention; figures 2C shows top view images taken by an SEM of another layer of a photovoltaic cell according to a preferred embodiment of the present invention; figure 3 shows a cross-sectional schematic view of a photovoltaic cell according to another preferred embodiment of the present invention; figures 4A and 4B show top view optical images of the surface of a perovskite layer after being printed on a mesoporous layer of a photovoltaic cell according to a preferred embodiment of the present invention; figures 5A, 5B and 5C show schematic top views of photovoltaic cells with different connections according to preferred embodiments of the present invention; figure 6 shows a cross-sectional schematic view of a photovoltaic cell according to another preferred embodiment of the present invention; and figure 7 shows I-V curves of a photovoltaic cell according to a preferred embodiment of the present invention. Specifically, figure 1 (FIG. 1) shows a schematic of a perovskite solar cell in cross section, comprising: 1. Substrate, 2. First electrode of conductive oxide, 3. Compact electron transport layer, 4. Mesoporous metal oxide layer, 5. Perovskite compound, 6. Second electrode of carbon compound.

Specifically, figures 2A-1 and 2A-2 (FIGS. 2A-1 and 2A-2) show SEM top views of inkjet- printed mp-TiOz layer for perovskite solar cell according to first example and second example, respectively. Figures 2B-1 and 2B-2 (FIGS. 2B-1 and 2B-2) show SEM top views of inkjet-printed perovskite compound as a layer for perovskite solar cell in high and low magnification. Figure 2C (FIG. 2C) shows a SEM top view of inkjet-printed carbon layer for perovskite solar cell.

Specifically, figure 3 (FIG. 3) shows a schematic of a perovskite solar cell in cross section, comprising: 1. Glass substrate, 2. First electrode of conductive oxide, 3. Compact electron transport layer, 4. Mesoporous metal oxide layer, 5. Perovskite compound, 6. Second electrode of carbon compound, 7. Silver contacts, 8. UV curable sealant.

Specifically, figure 4A (FIG. 4A) shows an inkjet-printed perovskite (5-AVA)_x(MA)(i-_X)Pbl3 (MAPI ) layer with lead iodide concentration of IM, whereas figure 4B (FIG. 4A) shows the inkjet- printed perovskite layer with a 1.8M lead iodide concentration after inkjet-printing deposition on TiOz film.

Specifically, figures 5A, 5B and 5C (FIGS. 5A, 5B and 5C) show top views of perovskite solar cells with different connections: (FIG. 5 A) Parallel connection (P-design); (FIG. 5B) In series connection (Z-design); (FIG. 5C) In series connection (W-design). For FIG. 5 A and FIG. 5B: active materials 21, laser scribing 22 on FTO layer and main electrical conductors 23 made of silver paste. For FIG. 5C: active materials 21, laser scribing 22 on FTO layer and main electrical conductors 23 made of silver paste.

Specifically, figure 6 (FIG. 6) shows a schematic cross-section of Carbon Perovskite solar cell in series connection (W-design).

Specifically, figure 7 (FIG. 7) shows an IV curve of 20 cm x 22 cm perovskite solar cell measured at solar light irradiation 950W/m², A.M. 1.5, T=25°C and RH=50%.

In FIG.l the basic perovskite solar glass configuration with inkjet-printed solar inks is presented. In particular, the PV glass is made according to the structure TCO/ETL/Perovskite material/Carbon. The structure of a perovskite solar cell consists of four different layers that are deposited onto a glass substrate with an electrically conductive coating. These films are inkjet- printed using different ink formulations and can be varied from electron transport layers such as transition metal oxides and perovskites where some examples may include but not limited to the general formulas Cs_xFAi _xPbl3, MAPb(Ii-_xBr_x)3, MAPb(Ii-_xCl_x)3, Cs_y|(FAPbl3)i ₁ (MAPbBrp i y Of compounds. The PV structure is briefly as follows: a compact electron transport layer such as titanium or zinc or tin dioxide is inkjet-printed onto the conductive side of glass. After that, a perovskite compound is deposited by the same method over the previous film of compact metal oxide. However, in a second aspect, before perovskite layer a mesoporous Titanium or Tin or Zinc dioxide layer can be alternatively applied by inkjet printing. To have a successful perovskite solar cell, the perovskite solution should be adsorbed in the mesoporous oxide film. Finally, a thick film of a conductive material made of carbon is screen or inkjet-printed above the previous two layers. The carbon material can be but not limited to carbon black or graphite, or graphene or mixture of them. More specifically, the previous mentioned film has a dual role as it constitutes the hole transport material (p-type semiconductor) and the cathode (positive electrode). FIG. 1 is an illustrative diagram of solar cell cross section with all independent layers described before according to an embodiment of the present invention. As shown in FIG.l in the perovskite solar cell a first electrode 2 is provided on a substrate 1 , a compact electron transport layer 3 is also provided on the top of the first electrode and a mesoporous oxide layer as layer 4. Perovskite compound layer 5 is covering the layer 4. Finally, a second electrode made of carbon 6 is provided on the top of the layer 5.

The individual layers of perovskite solar cell are described hereafter:

1. Substrate

The substrate 1 according to an embodiment of the present invention may require a sufficient level of rigidity to host the rest of the layers. Some examples of materials for the substrate 1 may include but not limited to transparent glass pane, diffused glass pane, plastic sheet, plastic membrane, poly(ethylene terephthalate) and poly(ethylene 2,6-naphthalate). The thickness of substrate 1 can be varied between 2 and 3 micrometers but not limited to this range.

2. First electrode for electron collection

The first electrode 2 according to an embodiment of the present invention, which has the role of electron collection from the solar cell, is provided on the top of substrate 1. Some examples of compounds that can be used as electrode 2 but not limited to are: Fluorine doped Tin Oxide (FTO), Indium tin Oxide (ITO), Antimony doped Tin Oxide (ATO). The thickness of the as-described compounds and layer 2 can be from 500 to 800 nm but not limited to this range.

3. Inkjet printing of compact electron transport layer (c-MOx)

The first electrode 2 according to an embodiment of the present invention is supplemented with inkjet-printed a compact layer of an electron transport layer 3. The electron transport layer 3 is preferable but not limited to be a transition metal oxide such as TiO or ZnO or SnO . The choice of the previous metal oxides does not necessarily mean the use of one of them to the construction of the solar cell but also the combination of them. The layer 3 printed on the top of electrode 2 may have a thickness ranging from 50-200 nm depending on the desired electrical performance of the solar cell. Specific example of one metal oxide ink, but not limited to, is the following: A solution of compact TiO is initially prepared by the sol-gel method by dissolving a small amount of 75% by weight of titanium diisopropoxide in isopropanol in 3.5 ml in a dilution ranging from 1/5 to 1/9 according to one embodiment of the present invention. After this, the compact coating of titanium dioxide (TiO?) is formed via inkjet printing technology on the top of the electrode 2. Specific parameters applied to the printer during the printing process according to an embodiment of the present invention are tabulated to the next Table 1.

In this coating, the aim is to have no porous structure to avoid recombination of the electrons to the conductive substrate. The presence of compact metal oxide film helps to reduce the internal electronic leakage of the perovskite solar cell. According to an embodiment of the present invention the metal oxide film is deposited at 725.71 dpi and then thermally annealed at 500°C for lOmin to stabilize the metal oxide film 3 on the top of electrode 2. The above procedure is repeated until the required thickness of metal oxide is succeeded. As an example of the total number of metal oxide coatings, but not limited to, is about ten repetitions with intermediate annealing time periods of 10- 15 min at 500°C. During the optimization of the film, however, it is found that the reduction of the number of coatings and consequently the reduction of the annealing time periods significantly improved the value of transmittance in the integrated area of the visible spectrum (wavelength: 380nm-780nm). The percentage of this improvement was 6-9%. This improvement was accompanied by corresponding electrical efficiency and the fill factor of the perovskite solar cell. This improvement facilitates the deposition process by reducing printing and annealing time to 1/3.

4. Inkjet printing of mesoporous MO_X (mp-MO_x) layer

The first electrode 2 supplemented with inkjet-printed layer 3 according to an embodiment of the present invention is completed with inkjet-printed a layer of mesoporous metal oxide 4. The electron transport layer 4 is preferable but not limited to be a transition metal oxide such as TiO or ZnO or SnCh or WO3 or NbzO ; or combination of them. The layer 4 printed on the top of layer 3 may have a thickness ranging from 800 tol200 nm, but not limited to this range, and also to hold a porous structure with particles’ specific surface area in the range of 50-120 m²/g. Specific example of one metal oxide ink, but not limited to, is the following: A solution of mp-TiCT is prepared by the sol-gel method by dissolving a small quantity of a surfactant such as Triton X-100, or Pluronic series, or Tween series in 3 ml of different solvents. Then a small quantity of acetic acid is added to have a successful acid hydrolysis of titanium isopropoxide or titanium butoxide to form a colloidal TiO solution. The ink of mp-TiCT is inkjet-printed on layer 3 of the electrode. The created film consists of many insulating particles of a semiconductor with nanometer dimensions (10-25nm) with large energy gap 3.1-3.2 eV. The particles “fire -agglomerate” on the layer 3 at 500°C to gain electrical contact and form an extensive three-dimensional network with interconnected pores. This mesoporous film has a complex morphology, a high roughness factor and a very large surface development. The printing parameters of the inkjet printing process for depositing the mp-TiCT solution onto layer 3 are given in Table 2.

After the deposition of mp-TiCh onto layer 3, according to an embodiment of the present invention, the electrode is thermally annealed at 500 °C for 30 min to have a stabilized film. As the thickness of mp-TiCh on layer 3 is varied between 800-1200 nm the procedure of layer deposition and heating process may need to be repeated about 2-5 times on purpose of having the optimum thickness of mesoporous TiO . A top view of the film referred in the first example is appeared in FIG.2A1.

As a second example of the formation of layer 4 of m-TiO onto layer 3, according to an embodiment of the present invention, also aiming less deposition steps (1 to 3) to achieve the desired thickness of the film. According to an embodiment of the present invention, 10 g of TiO nanoparticles with average 20-30nm particle size and 60 m²/g particle specific surface are mixed with 2 ml acetic acid and 20 ml ethanol. The colloidal solution is stored in a sealed vessel at 80°C for 12 hours. The above solution is dried at 60°C for 6 hours to evaporate ethanol. Then 1 g of the above mixture were diluted in 1.2 ml of water and ultrasonicated for 2 minutes. Then 2 ml of ethanol was dispersed in the above mixture and further ultrasonicated for 2 minutes. Finally, 2 ml of ethanol in a mixture with 0.1 w% HC1 were added to the previous solution and ultrasonicated for additional 5 minutes. The final solution was diluted in methoxy-ethanol or methoxy-propanol or other solvents to be compatible with printing process in several quantities according to the desired thickness of the final layer. The printing parameters of the inkjet printing process for depositing the mp-TiO? solution onto layer 3 are given in Table 3. In an aspect of this invention the deposition of the film was done with a resolution of 1270.00 dpi and the annealing process was taken place at 500°C for 30min. According to this aspect, a top view image of mp-TiO film by inkjet printer is appeared in FIG.2A.

5. Inkjet printing of perovskite layer

According to an embodiment of the present invention, above the layer 4 a perovskite solution is inkjet-printed in one step, being layer 5. The material of perovskite layer 5 is preferable but not limited to be between the chemical formulas Cs_xFAi _xPbl3, MAPb(Ii-_xBr_x)3, M APb(I I-_XCL)3, Csyh APbfpi , (MAPbBi ;), | i _y of compounds or combination of them. The layer 5 printed in one step on the top of layer 4 may have a thickness ranging from 800 to 2000 nm, but not limited to this range. According to the previous formulas, perovskites are consisted of hybrid organic - inorganic compounds, which preferably are dissolved at a dimethylformamide solvent (DMF) or a mixture of two or three solvents such as dimethylformamide/dimethylsulfoxide/y-Butyrolactone (DMF/DMSO/y-Butyrolactone), and as a result, many different inks with different combination of solvents and primer materials can be produced. However, it is also possible according to an embodiment of the present invention the use of organic additives in perovskite solution such as Methylamine, Phenethylamine 5-ammonium valeric acid iodide (5-AVAI), Leucine iodide, Alanine iodide during the preparation of the perovskite ink. Inkjet printing process can be quite supporting the formation of layer 5 in one step on the top of layer 4 in one step and the only requirement that should be met is the successful adsorption of perovskite ink in the porous structure of layer 4. After this step, satisfactory absorption of incident light into the perovskite solar cells (PSCs) is the key for an optimal solar to electrical energy conversion efficiency. According to an embodiment of the present invention, organometal halide perovskite absorber material MAPb(Ii- CL)3, as an example used in the inkjet printing experiments, is dissolved in dimethylformamide solvent in a concentration between 10-30 mg/ml. Besides, inkjet printing of perovskite molecules onto the semiconductor is easily succeeded since this ink is of low viscosity and with ideal surface tension for being used via inkjet printing method. For this reason, the printing of perovskite molecules on the mesoporous metal oxide layer 4 film can be easily achieved. However, the selection of the solvent is critical for the structural properties of the perovskite material and a selection between DMF, DMSO, methoxy ethanol, y-Butyrolactone has been made. According to an embodiment of the present invention for the adopted structure, the perovskite layer is initially inkjet-printed in one step, and it is dried during the printing stage at 70-120°C for 20-30 min to have full evaporation of the solvent and manage of the crystallization of the perovskite material. According to this aspect, a top view image of perovskite film by inkjet printer is appeared in FIG.2B (1) and (2) in high and low magnification, respectively. An example of the parameters used during printing process is appeared in Table 4. A critical issue to the optimum results in perovskite solar cells using inkjet printing process according to the present invention is the successful incorporation of perovskite ink into mesoporous oxide structure. In particular, the selection of the solvent in which the perovskite will be dissolved strongly affects to the quality of the printed compound. Therefore, a combination of perovskite’s solvents during the printing process is not excluded, which is directly related to the best operation of the ink in the inkjet printer. Besides, a suitable ink is stable as a function of printing time and does not affect the initial state of the printhead (e.g., nozzle clogging). The temperature of printhead and printer platen during printing as well as temperature and crystallization time seem to all affect the result, both optically and of the optimal operation of a perovskite solar cell.

6. Carbon electrode (Positive electrode)

According to an embodiment of the present invention, above the layer 5 a material based on carbon is printed as layer 6 for the integration of the perovskite solar cell. According to this, a dense solution of carbon compounds with viscosity to range between 0.1 to 20 cP is printed on the top of the layer 5 presenting benign compatibility with the perovskite. The carbon ink can be a combination of several compounds that are based on carbon such as graphite, carbon black, graphene, carbon nanotubes and carbon nanowires but not limited to them. Finally, the cell after the deposition of layers 3-6 is thermally treated in a temperature range between 50-80 °C for 15-30 h depending on the choice of the perovskite material. As an example of carbon electrode preparation, 4.5 g graphite and 1.5 g carbon black were uniformly dispersed in 20.0 g terpineol via ball milling for 2 h. Then, 1.8 ml of titanium isopropoxide and 0.3 ml glacial acetic acid were added into the mixture by ball milling for another 10 h to gain homogenized carbon ink. The printing parameters of the inkjet printing process for depositing the carbon compound onto layer 5 are given in Table 5. According to these, a top view image of carbon film by inkjet printer is appeared in FIG.2C.

Cell connections and sealing

According to an embodiment of the present invention, the completion of perovskite solar cell (FIG.3) requires the presence of silver contacts 7 and sealant 8 against any affections from the environment. According to the cross section of FIGG after the deposition of all the above-mentioned layers, we need to complete the perovskite solar cell by applying electrical contacts 7. These contacts are positioned along the two opposite sides of glass using an ultrasonic soldering station while at the same time a permanent and durable cable welding can be implemented. In a second embodiment of the present invention, silver contacts may be effectively applied on the opposite sides of the same glass by dispensing silver ink. The isolation of the perovskite solar cell from the environment according to an embodiment of the present invention can be achieved by dispensing a UV curable sealant 8 in a height equal or slightly higher than the total thickness of the layers 3-6. On the top of the layers 6 and 8 a plain glass 1 is applied isolating the layers 3-6 from ambient air.

Examples of perovskite solar cells Table 6 below describes some of the combination of materials that are used for the construction of perovskite solar cells but not limited to. The compounds and deposition of the inks were performed under ambient uncontrolled conditions. The temperature was varied from 20-30 °C and humidity was varied from 30-60%.

Regarding the selection of the optimal perovskite parameters, sub-cases 1 to 4 of Table 6 gave a non-uniform result after crystallization. y-Butyrolactone as a solvent did not behave positively even when the printhead temperature changed from 20°C to 60°C. The mixture of dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) in both (5-AVA)_x(MA)(i-_X)Pbl3 (MAPI) and Cso.o₅[FAo.₈₅MAo.i₅]o.95Pb[Io.₈7Bro.₈3]3 gave a uniform black shading at printhead temperature of 20°C and 60°C. Thus, TiO was combined with these two perovskites dissolved in DMF / DMSO. The crystallization temperature was set at 100°C, which is the characteristic temperature of these perovskites, and the time of crystallization was set 20min. Tests were even taken place on the gradual rise of the crystallization temperature in (5-AVA)_x(MA)(i-_X)Pbl3 (MAPI) perovskite, which did not prove to be particularly critical. In addition, the change in the concentration of lead iodide in the perovskite solution was studied and it was shown that by increasing it, a more uniform coverage is achieved during the crystallization process. As it can be seen in FIG. 4, there are white areas which are attributed to TiO . In these areas, which are observed in the left FIG.4A, carbon film will be in direct contact with TiO? film since there is no perovskite between them. This fact negatively affects the operation of the perovskite solar cell. The FIG.4B on the right has come from a higher concentration of lead iodide and specifically 1.8M, while the left one depicts the perovskite whose concentration is IM with black color, after the inkjet printing deposition. In addition, it was less prone to lesions during printing process, which took place at ambient temperature (~25°C) and relative humidity (RH ~ 25%-30%). Both FIG.4A and FIG.4B have been taken after the inkjet printing deposition and before sample is dried for 20 min at 100°C. Printing on conductive glass substrates of large dimensions requires some flexibility in terms of humidity and temperature due to the prolonged time in the deposition process and the environmental conditions that prevail in the place.

Design of internal connection of a perovskite solar module.

According to an embodiment of the present invention, the solar module can be consisted of 12-60 individual solar cells in series interconnected depending on the size of the glass and power output. The distance between the individual cells can be also varied depending on the desired visual effect. The transmittance of the solar glasses can be varied in terms of the number of solar cells used and is inversely proportional to the final power output. According to an aspect of the present invention, several distinctive designs for connecting perovskite solar cells to create perovskite modules are proposed and appear in FIG.5. Perovskite solar cells can be connected either in parallel FIG.5A or in series FIG.5B and FIG.5C connection. The parallel connection of perovskite solar cells enables the multiplication of current values while the series connection offers the capacity to multiply the value of voltage. The possible ways of connecting perovskite solar cells to create a module are summarized in FIG.5. In P-design of a module adds the values of the current of the individual perovskite solar cells while the voltage of one of them is the overall voltage of the device.

As shown above, the perovskite solar cells are at distance from each other and are completely electrically independent from each other. To collect the current along the cells there is a conductive grid, which is deposited onto glass conductive substrate. This connection is suitable for applications requiring high values of current and low values of voltage at short distances from the perovskite solar cell installation since the transmission of high values of current has significant losses. Apart from the P-design connection, there are Z-design and W-design, in which perovskite solar cells are connected in series, allowing to add the voltage of any individual perovskite solar cell at the output of the end panel. In addition, the value of the current of each individual cell is the total value of the panel. In Z-design, as in the previous case, the perovskite solar cells are electrically independent and the cells are connected through the conductive grid, which is deposited at selected points. Conversely, the W-design is simpler, without requiring the connection of solar cells in series with a conductive grid. However, it is less efficient as the active areas alternate between two conductive substrates. In Z-design, by adding silver bus bars 23 between the photovoltaic stripes (FIG.5), it is succeeded to have better collection of current and consequently higher values of it. FIG.5 is a scheme that also includes carbon layer and how it is connected with silver bus bars. This connection ends up to the positive electrode of the electrical contacts. According to an embodiment of the present invention a cross section of W connection in series is presented in FIG.6. The width of metal oxide film is varied between 0.5 to 1.0 cm and the width of carbon layer is 0.8 to 1.3 cm. The laser scribing 22 of the conductive substrate is performed, to have a monolithic perovskite solar module. The final dimensions of this device, but not limited to that, are varied between 20 cm x 22 cm to 50 cm x 50 cm. The electrical performance for a 20 cm x 22 cm presenting the current-voltage characteristic curve is given in FIG.7.

According to an embodiment of the present invention, the completion of perovskite solar module requires the presence of silver bus bars and sealing upon any affections from the environment. According to FIG.6 after the deposition of all the compounds, each perovskite solar stripe is realized and laser scribing to isolate each stripe from the other, silver thin line of silver ink with average width 1-2 mm is dispensed across the right side of each individual perovskite solar stripe of the module. In a second embodiment of the present invention, silver contacts may be effectively applied on the opposite sides of the same glass by dispensing silver ink. The isolation of the perovskite solar module from the environment according to an embodiment of the present invention is achieved by dispensing a UV curable sealant in a height equal or slightly higher than the total thickness of the layers of the solar stripe applied all around the glass substrate. On the top of the solar module, a plain glass is applied isolating the solar stripes from ambient air. According to an embodiment of present invention the electrical characterization of a perovskite solar module was taken place at solar irradiation 950W/m², A.M. 1.5, T=25°C and RH=50% given in FIG.7. The value of current is the same for one individual strip of the active area, as well as for the whole device since the connection is in series. Carbon as a conductor is reinforced with Ag bus bars of resistance, which is lower than I . Each strip has length of 19.8cm but not limited to that length and the width is 0.55 cm but not limited to that dimension. The electrical data for a single cell or the module are presented in Table 7.

The value of overall efficiency is about 10%, while it is constructed in full ambient and uncontrolled conditions.

The present disclosure thus refers to solar cells and modules and in particular, coatings and related materials for the solar cells and modules. Specifically, it relates to perovskite solar cells and modules where all materials and methods are constructed under fully ambient air conditions with the absence of any hole transport layer while materials’ deposition method was exclusively inkjet printing. The solar cell and module in monolithic configuration include a conductive glass substrate, a first electrode provided on the substrate as electron transport layer, a perovskite compound as second layer provided on the electron transport layer and the cell is completed by the second electrode which is provided on the perovskite material, and it consists of carbon. All the materials are deposited by inkjet printing, and all are treated in ambient conditions. The present invention provides efficient solar to electrical energy conversion from nanocoatings applied with inkjet printing or any other related printing technique on the conductive surface of TCO glass (transparent conductive oxide, TCO). In particular, the present invention includes systems and methods of depositing three separate coatings namely: an electron transport layer, a perovskite layer, and a carbon layer in a monolithic configuration for the electrical energy production by solar light, prepared in completely ambient conditions.

To obtain ambient air processed, stable and highly efficient perovskite solar cells, the following technical measure were taken: Anhydrous solvents and high purity perovskite precursors, stored under inert/controlled conditions, were used.

Multi-cation mixed-halide perovskites having much higher stability in high-humidity manufacturing and thermal treatments compared to the conventional organic-inorganic perovskites, e.g., cesium-dopped, methylammonium-free, tri-halide perovskites, were developed.

High-quality perovskite crystals were obtained by solvent engineering. Specifically, appropriate volatile solvents, such as 2-methoxy ethanol (where DMF/DMSO/GBL is commonly used) and hydrophilic anti-solvents, such as Alcohols (where Chlorobenzene is commonly used) of the perovskite precursors were developed, which prevent the non-optimal crystallization kinetics of perovskites under high-humidity environment.

Highly efficient all-inorganic perovskites, such as CsPbls-x yCl_xBr_y, and 2D/3D perovskite structures, such as 4-Fluoro-Phenethylammonium iodide post-treated multi-cation mixed-halide perovskites, for higher damp-heat and light-soaking robustness, were developed.

Additives were applied in the perovskite precursor inks to regulate the crystal growth dynamics and the hydrophilicity of the perovskite material, e.g., polymers/PVP, nitrogen-containing heterocyclic compounds/TBP.

The Substrate and the perovskite precursor ink were pre-heated to eliminate the moisture effect.

Use of hydrophilic solar cell materials, e.g., LiTFSI and additives in the whole solar cell structure was avoided.

Perovskite solar cell architectures were applied that mitigate perovskite ions migration. For example, the conventional noble metal hole-transport-material-based architecture was replaced by a carbon-based hole-transport-material-free architecture.

Interfacial engineering on the solar cell architecture was applied. For example, buffer layers were introduced to favor extraction and collection of charges, as well as adjust surface wettability, such as 2-D carbon nanostructures.

Advanced encapsulation techniques were applied to obtain a hermetic enclosure of the core of the photovoltaic structure without causing degradation to the characteristics of the solar cell material. For example, prolonged high-temperature thermal treatment during device encapsulation was avoided and photo-curable resins were used. In addition, robust sealants, such as multi-layered sealants, were developed, for instance by multi-stage sealing, which prevent moisture ingress, rapid UV degradation and delamination.

Especially, inkjet-printable perovskite precursor inks with the following characteristics were developed: environmentally friendly solvent systems such as 2-methoxy ethanol-based solvent blends instead of the commonly used toxic solvents such as DMF, DMSO and GBL; a much lower perovskite precursors content (even three times lower molarity). In this way, the toxicity (due to a lower amount of lead content) and the cost of the final active material used to develop the perovskite solar cells are greatly reduced.

As a result, the development of the perovskite active layer can be achieved by annealing- free procedures. In this way, the cost related to the energy inputs during the manufacturing of the devices is highly reduced.

Claims

CLAIMS Method of manufacturing a photovoltaic cell, comprising: providing a glass substrate; depositing an electrically conductive layer onto the glass substrate; depositing a microporous electron transport layer on top of the conductive layer; depositing a mesoporous electron transport layer on top of the microporous electron transport layer; depositing a perovskite layer on top of the microporous electron transport layer; and depositing a carbon compound layer on top of the perovskite layer. Method according to claim 1, wherein the step of depositing the electrically conductive layer onto the glass substrate comprises applying an electrically conductive coating onto the glass substrate. Method according to claim 1 or 2, wherein the step of depositing the microporous electron transport layer on top of the conductive layer comprises inkjet-printing a printable ink solution containing at least one of tin oxide, titanium oxide and zinc oxide on top of the conductive layer. Method according to any one of claims 1-3, wherein the step of depositing the mesoporous electron transport layer on top of the microporous electron transport layer comprises inkjet -printing a printable ink solution containing at least one of tin oxide, titanium oxide and zinc oxide on top of the microporous electron transport layer. Method according to claim 4, wherein the mesoporous electron transport layer has a pore size of between 6 nm and 20 nm. Method according to claim 4 or 5, wherein particles making up the mesoporous electron transport layer have a size of between 10 nm and 30 nm. Method according to any one of claims 1-6, wherein the microporous electron transport layer has a pore size of between 0,5 nm and 2 nm.

8. Method according to any one of claims 1-7, wherein the step of depositing the perovskite layer on top of the mesoporous electron transport layer comprises inkjetprinting a printable ink solution containing a perovskite compound on top of the mesoporous electron transport layer.

9. Method according to any one of claims 8, wherein the perovskite compound comprises at least one of Cso.o5CFAo.85MAo.15lo.95PbEIo.87Bro.83j3, (5-AVA)_x(MA)(i- X)Pbl3 and M APb(I i__xCl_x)3, and wherein the solution is printed at a temperature of between 50 °C and 70 °C.

10. Method according to any one of claims 1-9, wherein the step of depositing the carbon compound layer on top of the perovskite layer comprises inkjet-printing a printable ink solution containing carbon on top of the perovskite layer.

11. Method according to any one of claims 1-10, wherein the carbon compound layer comprises at least one of the following: graphite, carbon black, graphene, carbon nanotubes, carbon nanowires, a mixture of them.

12. Method according to any one of the preceding claims, further comprising: arranging a plain glass on top of the carbon compound layer; and sealing the photovoltaic cell from the environment by applying a sealant comprising an ultraviolet curable compound around the photovoltaic cell.

13. Photovoltaic cell manufactured by the method according to any one of claims 1-12, comprising a: a glass substrate having an electrically conductive layer; a microporous electron transport layer on top of the conductive layer; a mesoporous electron transport layer on top of the microporous electron transport layer; a perovskite layer on top of the microporous electron transport layer; and a carbon compound layer on top of the perovskite layer.

14. Photovoltaic cell according to claim 13, wherein the microporous electron transport layer comprises at least one of tin oxide, titanium oxide and zinc oxide. Photovoltaic cell according to claim 13 or 14, wherein the mesoporous electron transport layer comprises at least one of tin oxide, titanium oxide and zinc oxide. Photovoltaic cell according to any one of claims 13-15, wherein the mesoporous electron transport layer has a pore size of between 6 nm and 20 nm. Photovoltaic cell according to any one of claims 13-16, wherein particles making up the mesoporous electron transport layer have a size of between 10 nm and 30 nm. Photovoltaic cell according to any one of claims 13-17, wherein the microporous electron transport layer has a pore size of between 0,5 nm and 2 nm. Photovoltaic cell according to any one of claims 13-18, wherein the perovskite compound comprises at least one of Cs0.05EFA0.85MA0.15J0.95PbEI0.87Br0.83J3, (5- AVA)_x(MA)(i._x)Pbl3 and MAPb(Ii-_xCL)₃. Photovoltaic cell according to any one of claims 13-19, wherein the carbon compound layer comprises at least one of the following: graphite, carbon black, graphene, carbon nanotubes, carbon nanowires, a mixture of them. Photovoltaic cell according to any one of claims 13-20, further comprising: a plain glass on top of the carbon compound layer; and a sealant around the photovoltaic cell, comprising an ultraviolet curable compound. Solar glass module, comprising a plurality of photovoltaic cells according to any of claims 13-21.