Method of manufacturing a photovoltaic module, photovoltaic module and solar glass module

Abstract

Method of manufacturing a photovoltaic module, comprising providing a first and a second photovoltaic sub-module, each comprising a perovskite solar cell comprising a carbon-based back electrode, arranging the first and second solar sub-modules in a back-stacking configuration, wherein the carbon-based back electrode of the first sub-module faces the carbon-based back electrode of the second sub-module, and arranging a polymeric sealant between the carbon-based back electrodes of the first and second solar sub-modules, the sealant thereby separating the sub-modules from each other and acting as a spacer between the first and second solar sub-modules.

Description

[0001] Method of manufacturing a photovoltaic module, photovoltaic module and solar glass module.

[0002] The present invention relates to a method of manufacturing a photovoltaic module. Furthermore, the present invention relates to a photovoltaic module, and a solar glass module comprising a plurality of photovoltaic modules.

[0003] Today’s development of new generation solar cell technologies is generally aimed at enhancing conversion efficiency, improving long-term stability, and reducing fabrication costs. A challenge that still exists today is to efficiently convert light into electricity under different lighting conditions, i.e., under both direct and diffuse lighting conditions.

[0004] The aim of the present invention is to provide a photovoltaic device which performs well under different lighting conditions, is stable over the long term, and can be manufactured in a cost- effective manner.

[0005] The present invention provides thereto, according to a first aspect thereof, a method of manufacturing a photovoltaic module, comprising providing a first and a second photovoltaic submodule, each comprising a perovskite solar cell comprising a carbon-based back electrode, arranging the first and second solar sub-modules in a back-stacking configuration, wherein the carbon-based back electrode of the first sub-module faces the carbon-based back electrode of the second submodule, and arranging a polymeric sealant between the carbon-based back electrodes of the first and second solar sub-modules, the sealant thereby separating the sub-modules from each other and acting as a spacer between the first and second solar sub-modules.

[0006] In a preferred embodiment of the method, the step of providing the first and a second photovoltaic sub-module comprises for each of the first and second photovoltaic sub-modules: providing a substrate which is transparent to light, depositing a transparent conducting oxide layer onto the substrate, depositing an electron transport layer on top of the transparent conducting oxide layer, depositing perovskite layer on top of the electron transport layer, and depositing a carbon-based layer on top of the perovskite layer, the carbon-based layer thereby acting as a carbon -based back electrode.

[0007] In a further preferred embodiment, the step of depositing the transparent conducting oxide layer onto the substrate comprises depositing a fluorine -doped tin oxide layer, an indium tin oxide, or an aluminum-doped zinc oxide onto the substrate.

[0008] In an alternative or further preferred embodiment, at least one of the steps of depositing the electron transport layer and depositing the perovskite absorber layer is carried out using a thin film deposition technique.

[0009] In a preferred embodiment, the thin film deposition technique comprises piezoelectric drop- on-demand inkjet printing. In a preferred embodiment, the step of depositing an electron transport layer on top of the transparent conducting oxide layer comprises depositing a compact electron transport layer onto the substrate and, optionally, depositing a mesoporous electron transport layer onto the compact electron transport layer.

[0010] In a preferred embodiment, the step of depositing a compact electron transport layer comprises inkjet printing, preferably drop-on-demand inkjet printing, a layer of a transition metal oxide, such as TiCh, SnCf or ZnO onto the substrate, and the optional step of depositing a mesoporous electron transport layer comprises inkjet printing, preferably drop -on-demand inkjet printing, a mesoporous layer of a metal oxide onto the compact electron transport layer.

[0011] In a preferred embodiment, the step of depositing the perovskite layer comprises inkjetprinting, preferably drop-on-demand inkjet printing, a layer of a perovskite precursor ink comprising metal halide perovskites of CsxMAyFAi-x-yPb(Ii-z-tBrzClt)3 structure.

[0012] In a preferred embodiment, the perovskite precursor is dissolved in at least one of dimethylformamide, dimethylsulfoxide, gamma-valerolactone and 2-methoxyethanol.

[0013] In a preferred embodiment, the perovskite precursor ink is inkjet printed at a temperature between 50 °C and 100 °C.

[0014] In a preferred embodiment, for at least one of the first and second photovoltaic sub-modules, the bandgap of the material of the perovskite layer is increased by partial substituting I -ions with Br - ions.

[0015] In a preferred embodiment, the step of depositing the perovskite layer is free of any annealing step.

[0016] In a preferred embodiment, the method further comprises for at least one of the first and second photovoltaic sub-modules: depositing a hole transport layer on top of the perovskite layer before depositing the carbon-based layer and depositing the carbon-based layer on top of the hole transport layer.

[0017] In a preferred embodiment, the step of depositing a hole transport layer on top of the perovskite layer comprises inkjet printing, preferably drop -on-demand inkjet printing, a layer of an inorganic metal oxide, such as NiO, CuO or CU2O on top of the perovskite layer.

[0018] In a preferred embodiment, each of the deposition steps are carried out under ambient atmospheric conditions.

[0019] In a preferred embodiment, the step of providing a substrate which is transparent to light comprises providing a transparent glass or plastic sheet.

[0020] In a preferred embodiment, the method further comprises a step of electrically isolating parts of the transparent conducting oxide layer from each other by making scribe lines in the conducting oxide layer using laser scribing after the step of depositing the transparent conducting oxide layer onto the substrate. In a preferred embodiment, the step of depositing the carbon-based layer comprises blade coating or screen printing the carbon-based layer.

[0021] In a preferred embodiment, the step of blade coating or screen printing the carbon-based layer comprises blade coating or screen printing a paste containing at least one of graphite, carbon black, graphene, carbon nanotubes and carbon nanowires.

[0022] In a preferred embodiment, the step of arranging the polymeric sealant comprises encapsulating the first and second photovoltaic sub-modules at an ambient pressure of less than 1 bar and an ambient temperature of below 100 °C.

[0023] In a preferred embodiment, the material of the polymeric sealant is one of a thermoplastic and a thermoset polymer.

[0024] According to a second aspect thereof, the invention provides a photovoltaic module manufactured by the method according to any one of the above-described embodiments, comprising a first and a second photovoltaic sub-module, each comprising a perovskite solar cell comprising a carbon-based back electrode, wherein the first and second solar sub-modules arranged in a back- stacking configuration, wherein the carbon-based back electrode of the first sub-module faces the carbon-based back electrode of the second sub-module, and wherein a polymeric sealant is arranged between the carbon-based back electrodes of the first and second solar sub-modules, the sealant thereby separating the sub-modules from each other and acting as a spacer between the first and second solar sub-modules.

[0025] In a preferred embodiment of the photovoltaic module, one of the first and second photovoltaic sub-modules comprises a hole transport layer and the other one of the first and second photovoltaic sub-modules is devoid of a hole transport layer.

[0026] In a preferred embodiment, the carbon-based back electrodes are comprised of a paste containing at least one of graphite, carbon black, graphene, carbon nanotubes and carbon nanowires.

[0027] In a preferred embodiment, the material of the polymeric sealant is one of a thermoplastic and a thermoset polymer.

[0028] According to a third aspect thereof, the invention provides a solar glass module, comprising a plurality of photovoltaic modules according to any of the above-described embodiments.

[0029] 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.

[0030] 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 schematic cross-sectional side view of part of one of the sub-modules of a preferred embodiment of the photovoltaic module according to the present invention; figures 2A and 2B show top view and cross-sectional scanning electron microscopy (SEM) images, respectively, of an annealing-free inkjet-printed perovskite absorbent layer fabricated on the top of a mesoporous TiCf layer using gamma-valerolactone-based ink; figure 3 shows schematic top view of a perovskite solar sub-module of 520mm x 520mm with 70% active-to-aperture coverage, with solar stripes mutually connected in series; figure 4 shows schematic top view of a perovskite solar sub-module of 520mm x 520mm with 10% active-to-aperture coverage, with solar stripes mutually connected in series; figure 5 shows an I-V curve of a perovskite solar sub-module of 520mm x 520mm with 70% active-to-aperture coverage, with solar stripes in series connection, measured under 900W / m2solar light irradiation, an Air Mass of 1.5, a temperature of 25 °C and a relative humidity of approximately 50%; figure 6 shows an I-V curve of solar sub-module of 520mm x 520mm with 10% active-to- aperture coverage, with solar stripes in series connection, measured under 900W / m2 solar light irradiation, an Air Mass of 1.5, a temperature of 25 °C and a relative humidity of approximately 50%; figure 7 shows a schematic cross-sectional side view modules of a preferred embodiment of the photovoltaic module according to the present invention; and figure 8 shows I-V curves of a bifacial perovskite solar module of 520mm x 520mm with 70% active-to-aperture coverage, measured under 600W / m2 solar light irradiation, an Air Mass of 1.5, a temperature of 250 °C and a relative humidity of approximately 50%.

[0031] A preferred embodiment of the present invention comprises all-printed carbon-based (Cobased) bifacial perovskite solar modules with tailorable in-module transparency and power output. Bi- faciality is attained by the back-stacking integration of two independent C-based perovskite solar submodules fabricated entirely under ambient atmospheric conditions, using exclusively printing processing. The design of each of the sub-modules is optimized separately to attain high performance for either direct or diffuse light conditions, depending on the intended application.

[0032] Figure 1 presents a basic perovskite solar cell (PSC) configuration (one solar stripe) that is employed to develop the solar sub-modules. Each PSC is developed according to the structure: transparent conductive oxide (TCO)-coated substrate / electron transport layer (ETL) / perovskite active material / hole transport layer (HTL) / carbon electrode. More specifically, this architecture consists of three to five printed solar cell materials onto a TCO substrate. The majority of the solar cell materials are prepared using different ink formulations for inkjet-printing, while the prepared carbon pastes are applied using blade-coating with needle scribing. Briefly, the photovoltaic (PV) manufacturing is carried out as follows. A compact ETL, such as titanium dioxide (Ti O2) or tin dioxide (SnCf). is inkjet-printed onto the conductive side of the substrate, while, on the top of this layer, a mesoporous layer of the same materials is deposited (optionally) by the same method. Then, a thin film made of metal halide perovskites of ABX3 structure is inkjet-printed, wherein A and B are cations of different sizes and X is an anion. The term “metal halide perovskite”, as used herein, refers to a perovskite, the formula of which contains at least one metal cation and at least one halide anion. On the top of this layer, an HTL, such as an inorganic p-type semiconductor (NiO, CuO and CU2O), is deposited (optionally) again by inkjet-printing. Finally, a pm-thick film of conductive carbonaceous materials is blade-coated on the top of the aforementioned solar cell materials. The carbonaceous materials can be graphite, carbon black, graphene, carbon nanotubes or a mixture thereof.

[0033] The individual layers of the PSC are as follows:

[0034] The substrate 1 can be a transparent glass pane or plastic sheet. The thickness of substrate 1 varies between 0.125 and 4 mm. The substrate 1 thereby has a sufficient level of rigidity to host the rest of the layers.

[0035] The conductive layer 2, which functions as a charge collection layer collecting charges from the solar cell, is provided on the top of substrate 1. The conductive layer 2 is a fluorine-doped tin oxide (FTO), an indium tin oxide (ITO) or an aluminum-doped zinc oxide (AZO) layer. The thickness of layer 2 varies between 500 to 800 nm. At the limits of materials deposition, the conductive layer 2 is laser scribed to form a groove 3 to isolate a negative electrode from a positive electrode.

[0036] The conductive layer 2 is supplemented with an inkjet-printed compact ETL (4). The ETL 4 is a transition metal oxide, such as TiO2, SnO2 or ZnO. The selection of the previous metal oxides does not necessarily mean the use of one of them in the construction of the solar cell but also the combination of them. Layer 4, which is inkjet-printed on the top of material 2 may have a thickness ranging from 100 to 400 nm. A specific example of one metal oxide ink is the following: a solution of titanium(di-isopropoxide) bis(2,4-pentanedionate) 75% in 2-propanol diluted (1 / 9 v / v) in a mixture of terpineol and acetonitrile (2: 1 v / v). This ink is inkjet-printed to form a compact TiCL layer on the top of the material 2. The aim of using this coating is to develop a no-porous structure on the top of material 2, avoiding electrons recombination at the conductive substrate and ETL interface. The metal oxide film is deposited and then thermally treated at 500°C for 10 min to stabilize the metal oxide film 4 on top of material 2. The above procedure is repeated until the required thickness of metal oxide is succeeded. An example of the total number of metal oxide coatings is about 5 to 7 repetitions with intermediate annealing time periods of 10-15 min at 500 °C.

[0037] The conductive substrate 2 supplemented with inkjet-printed layer 4, may be completed with inkjet printing of a mesoporous layer of metal oxide 5. The electron transport layer 5 is a transition metal oxide, such as TiCL, SnCL or a combination of them. Layer 5, which is printed on top of layer 4 may have a thickness ranging from 600 to 1000 nm and holds a porous structure with particles having a specific surface area in the range of 50-120 m2 / g. The ink of mesoporous oxide can be made from a commercial product or prepared using sol-gel technology. A specific example of one metal oxide ink for the fabrication of the mesoporous layer is the following: a commercially available TiCL powder (P25 Degussa) is treated with acetic acid (1 g of powder is mixed with 2 ml of ethanol and 0.2 ml acetic acid) under 80 °C calcination for 12 h in a closed vessel, following by their drying at 60 °C for 6 h; this powder is dispersed at first in 2 ml of water, adding consecutively 2 ml of ethylene glycol monopropyl ether and 2 ml of ethylene glycol monopropyl ether (0. 1 wt% HC1); this paste is further diluted (1:3 v:v) in ethylene glycol monopropyl ether to facilitate its inkjet-printing. The particles “fire-agglomerate” on layer 4 at 550°C for 1 h 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 high specific surface area. As the thickness of each mesoporous TiCL inkjet printing deposition pass for layer 5 is varied between 100-300 nm, the procedure of layer deposition and heating process may need to be repeated about 2-5 times for the purpose of having the optimum thickness of the layer.

[0038] On top of layer 5, a perovskite precursor ink is inkjet-printed, forming layer 6. The perovskite material of layer 6 is a compound having the chemical formula CsxMAyFAi-x-yPb(Ii-z-tBrzClt)3, where MA is the methylammonium, and FA is the formamidinium. Layer 6, which is printed on the top of layer 4 or 5 (depending on the solar cell design) may have a thickness ranging from 600 to 800 nm. According to the previous formula, perovskite precursors consist of compounds, which are preferably dissolved in solvents such as dimethylformamide (DMF), dimethylsulfoxide (DMSO), gammavalerolactone (GVL) or 2 -Methoxy ethanol (EGME), and as a result, many different inks with different combination of solvents and primer materials can be produced. The inkjet printing process can support the formation of layer 6 in one-pass or multi-pass processing on top of layer 4 or 5, while the crystallization of the material can be carried out at a low temperature using only heating from the printer (heating from the print-bed and print-head). To achieve the highest quality of the inkjet-printed perovskite layer, all the printing parameters should be manipulated, such as the temperature of the print-bed and print-head, the printing frequency, the resolution, etc., to avoid manufacturing defects, such that coffee-ring defects. A specific example of one perovskite precursor ink for the fabrication of the active layer of the solar cell on the top of the mesoporous layer is the following: 0.8 M of MAI and PbL dissolved in GVL. A top-view and cross-sectional scanning electron microscopy image captured from this kind of samples are shown in figure 2. The printing parameters employed to print this ink in a Fujifilm Dimatix DMP-2850 printer employing a Dimatix Samba printhead are presented in Table 1.

[0039] On top of layer 6, a material that can transport positive charge carriers (i.e., “holes”) is deposited (optional) via the inkjet printing method. Material 7 comprises inorganic metal oxides, such as NiO, CuO or CU2O. This layer can be developed using colloids composed of surface -modified (functionalized) nanoparticles dispersed in benign-to-perovskite solvents, such as alcohols. The thickness of layer 7 can vary between 50 and 200 nm. The colloid ink for the fabrication of the HTL is fabricated as follows: at first nickel oxide nanoparticles are developed using nickel nitrate hexahydrate dissolved in deionized water under magnetic stirring (130 mg / ml); 10 M NaOH aqueous solution is then added dropwise into the above-mentioned solution until pH value is reached 10; the obtained solution is centrifuged and the precipitation is taken and washed with deionized water twice; the powder is dried at 80 °C overnight, then crystallized at 300 °C for 2 h. The obtained nickel oxide nanoparticles are treated with acetic acid (100 mg of powder is mixed with 200 pl of ethanol and 20 pl of acetic acid via calcination under 80 °C for 12 h in a closed vessel, followed by their drying at 60 °C for 6 h); this powder is dispersed into a 2-butanol-based solution (0.5 g / ml) containing 15 pl / ml methylamine 33wt. absolute ethanol. The metal oxide film is deposited by its inkjet printing using a heated print-bed at 60°C, while the temperature of the print-head is regulated at 30°C. Since the thickness of this layer is usually needed to be low, single or dual pass inkjet-printing is applied, while thermal treatment is included.

[0040] The cell is completed by the deposition of a carbon-based electrode. The carbon-based electrode, forming layer 8, is developed using printing techniques, such as blade coating with needle scribing, from viscous inks composed of carbonaceous materials and solvents that demonstrate benign compatibility with the perovskite layer. Layer 8 is developed on top of layer 6 or 7, depending on the employed solar cell architecture. The carbon paste is a combination of several compounds that are based on carbon, such as graphite, carbon black, graphene, carbon nanotubes and / or carbon nanowires. The carbon paste is a mixture of graphite micro-powder and carbon black nano-powder (3 : 1 weight ratio) milled vigorously in a mortar to attain homogenization; after that, a binder (mixture of glacial acetic acid and titanium (IV) isopropoxide (1: 100 volume ratio)) is added dropwise to the mixture scattered around the carbon powder (300 pl / g of carbon materials); finally, terpineol is used to obtain the slurry (1.7 ml / g of carbon materials).

[0041] The carbon paste is deposited by its blade-coating using a gap of 50 pm, while the solar stripes are isolated using needle scribing. After the deposition of layer 8, the cell is thermally treated at a temperature ranging between 70 and 120 °C for 20 to 60 min, depending on the composition of the carbon paste, to attain solvents evaporation and satisfactory conductivity for the operation of the solar cell.

[0042] The completion of an individual PSC (figure 1) requires the presence of silver contacts 9. The silver contacts are printed, such as dispense-printing, on TCO substrate using commercial products in the form of highly conductive silver pastes. Depending on the composition of the silver pastes and the thermal treatment needs, the procedure is applied in a different manufacturing step, such as prior to the deposition of layer 6. A specific example of silver paste used for the fabrication of the contacts of the solar cell devices is the commercial product Ag ASP-SC100-61D5, Asagi. This silver paste is dispense-printed onto the TCO substrate, while its calcination is carried out at 125 and 550 °C for 10 and 60 min, respectively. Each silver contact strip has a width of between 1 to 3 mm.

[0043] A perovskite solar sub-module in 520 mm x 520 mm indicative dimensions is presented in figure 3. The sub-module consists of 55 independent perovskite solar stripes. In this case, the solar stripes effective area is 70% of the aperture area. The perovskite solar stripes are in series connected on the top of the conductive substrate. However, an alternative case could be the partial coverage of the conductive substrate by solar stripes, where their effective area is then 10% of the aperture area. In this case, a more transparent solar sub-module can be prepared as the free space among perovskite solar stripes is enlarged (see figure 4).

[0044] After the deposition of all the above-mentioned layers, the perovskite solar sub-modules are completed by applying electrical contacts. These contacts are positioned among the two opposite sides of the glass using an ultrasonic soldering station, while at the same time, permanent and durable cable welding is implemented. In a second embodiment of the present invention, silver contacts may be effectively applied on the opposite sides of the same conductive substrate by dispensing a low- temperature processed silver ink (compatible with the plastic substrates).

[0045] The electrical characterization of a perovskite solar sub-module with high coverage of the glass (70% of aperture area) took place at solar irradiation 900 W / m2, an Air Mass of 1.5, a temperature of 25 °C and 50% relative humidity. The corresponding I-V curve 11 is shown in figure 5. The value of current is the same for any 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 lower than 1 Ohm. Each silver strip has a length of 520 mm and a width of 3 mm. The electrical characteristics of the sub-module are presented in figure 5. The value of the overall efficiency of the effective area of the sub-module is about 12%, while it is constructed under full ambient and uncontrolled conditions.

[0046] The electrical characterization of a perovskite solar sub-module with low coverage of the glass (10% of aperture area) took place under 900 W / m2solar irradiation, an Air Mass of 1.5, a temperature of 25 °C and 50% relative humidity. The corresponding I-V curve 12 is shown in figure 6. The value of current is the same for any 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 lower than 1 Ohm. Each strip has a length of 520 mm and a width of 3 mm. However, around any of the solar cell stripes in that configuration, individual silver bus bars are additionally dispense-printed. The electrical characteristics of the sub-module are presented in figure 6. The value of the overall efficiency of the effective area of the sub-module is about 12%, while it is constructed under full ambient and uncontrolled conditions.

[0047] The perovskite solar sub-modules may consist of about 10 to 100 individual solar stripes in series interconnected depending on the size of the substrate, which can range between 500 mm x 500 mm to 1000 mm x 1000 mm area, depending on the manufacturing capability of inkjet printer. The distance between the individual cells can be varied depending on the needed transparency and power output.

[0048] To develop the bifacial C-based perovskite solar module, two solar sub-modules are placed together in a formation where carbon electrodes face one the other, making the structure of a bifacial solar module that utilizes solar light from both sides. The structure of two single perovskite solar submodules that face one other appears in figure 7, so each one of the solar stripes of the front-face submodule is exactly aligned with the corresponding solar stripes of the rear-face sub-module. The space among the solar stripes can vary at any of the perovskite solar sub-modules in a way that always the solar stripe of the front-face sub-module is exactly aligned with the corresponding solar stripe of the rear-face sub-module. The isolation of the two perovskite solar sub-modules that constitute the bifacial solar module is achieved by the use of material 10. Material 10 may be a thermoplastic membrane, such as ethylene -vinyl acetate (EVA). The encapsulation of the bifacial perovskite solar module is carried out in a lamination workstation under a pressure of 8 bar for an aperture area of 2500 cm2, under 60 °C for 15 min and 130 °C for 45 min thermal treatment. In a second embodiment, the thermoplastic sealant can be substituted by a thermoset polymer having a height ranging from 1 mm to 3 mm. The sealant is applied from one edge of the substrate to the other of the rear-face submodule to achieve isolation between the sub-modules that constitute the bifacial PV. Then, the two sub-modules are put together in a manner that carbon electrodes face one to the other, as appears in figure 7.

[0049] Device architecture engineering is applied to obtain high-performance sub-modules for either direct sunlight or diffuse light conditions. With the focus on ETL, a mesoporous design is applied for perovskite solar sub-modules that are intended to operate under high-intensity sunlight (e.g., front- face sub-module of bifacial PV) and a planar design for the corresponding devices that are intended to operate under low-intensity diffuse sunlight or indoor light (e.g., rear-face sub-module of bifacial PV).

[0050] Bandgap engineering of the perovskite active layer is applied to enhance the performance of perovskite solar sub-modules under low-light and indoor-light conditions. To this purpose, wider bandgap perovskite structures are developed to capture the light from rear-face perovskite solar submodules, wherein part of T ions of the CsxMAyFAi-x-yPb(Ii-z-tBrzClt)3 structures are replaced by Br ions, increasing the bandgap of the material. A specific example of a group of perovskite structures that are developed to be employed as an active layer of rear-face perovskite solar sub-modules is the CsxMAyFAi-x-yPb(Io.85Bro.i5)3, replacing the CsxMAyFAi-x-yPbI3.

[0051] A C-based HTL-free perovskite solar sub-module architecture is applied for the front-face sub-module to attain high-efficiency and stability, while an HTL is applied in the architecture of the rear-face sub-module to increase the main PV characteristics, such as the photo-voltage and fill factor, increasing thus bifaciality.

[0052] The electrical characterization of a bifacial perovskite solar module with about 70% active -to- aperture area took place under 600 W / m2solar irradiation. The bifacial perovskite solar module was composed of two identical sub-modules. The I-V curves 13 and 14 shown in figure 8 represent the I-V characteristics of the front-face and rear-face submodules, respectively. The device was ground mounted, almost 1 m above a regular cement surface. The overall efficiency of the module was found to be higher than 15%, giving an approximate 26% increase in the power output of the device when compared to the corresponding monofacial counterpart operated under the same environmental conditions (light intensity and temperature). This number of PCE increase is considered quite high considering that the installation of the PV device was not optimized for giving an increased bifaciality factor, while the results can be even better when a rear-face sub-module is specially designed for giving high performance under diffiise / low light conditions.

[0053] The present invention is not limited to the shown embodiments but extends to other embodiments falling within the scope of protection of the appended claims.

Claims

Claims1. Method of manufacturing a photovoltaic module, comprising: providing a first and a second photovoltaic sub-module, each comprising a perovskite solar cell comprising a carbon-based back electrode; arranging the first and second solar sub-modules in a back-stacking configuration, wherein the carbon-based back electrode of the first sub-module faces the carbon-based back electrode of the second sub-module; and arranging a polymeric sealant between the carbon-based back electrodes of the first and second solar sub-modules, the sealant thereby separating the sub-modules from each other and acting as a spacer between the first and second solar sub-modules.

2. Method according to claim 1, wherein providing the first and a second photovoltaic submodule comprises for each of the first and second photovoltaic sub-modules: providing a substrate which is transparent to light; depositing a transparent conducting oxide layer onto the substrate; depositing an electron transport layer on top of the transparent conducting oxide layer; depositing perovskite layer on top of the electron transport layer; and depositing a carbon-based layer on top of the perovskite layer, the carbon-based layer thereby acting as a carbon -based back electrode.

3. Method according to claim 2, wherein the step of depositing the transparent conducting oxide layer onto the substrate comprises depositing a fluorine -doped tin oxide layer, an indium tin oxide, or an aluminum -doped zinc oxide onto the substrate.

4. Method according to claim 2 or 3, wherein at least one of the steps of depositing the electron transport layer and depositing the perovskite absorber layer is carried out using a thin film deposition technique.

5. Method according to claim 4, wherein the thin film deposition technique comprises piezoelectric drop-on-demand inkjet printing.

6. Method according to any one of claims 2 to 5, wherein the step of depositing an electron transport layer on top of the transparent conducting oxide layer comprises depositing a compact electron transport layer onto the substrate and, optionally, depositing a mesoporous electron transport layer onto the compact electron transport layer.

7. Method according to claim 6, wherein the step of depositing a compact electron transport layer comprises inkjet printing, preferably drop-on-demand inkjet printing, a layer of a transition metal oxide, such as TiCh, SnCf or ZnO onto the substrate, and wherein the optional step of depositing a mesoporous electron transport layer comprises inkjet printing, preferably drop-on-demand inkjet printing, a mesoporous layer of a metal oxide onto the compact electron transport layer.

8. Method according to any one of claims 2 to 7, wherein the step of depositing the perovskite layer comprises inkjet-printing, preferably drop-on-demand inkjet printing, a layer of a perovskite precursor ink comprising metal halide perovskites of CsxMAyFAi-x-yPb(Ii-z-tBrzClt)3 structure.

9. Method according to claim 8, wherein the perovskite precursor is dissolved in at least one of dimethylformamide, dimethylsulfoxide, gamma-valerolactone and 2-methoxy ethanol.

10. Method according to claim 8 or 9, wherein the perovskite precursor ink is inkjet printed at a temperature between 50 °C and 100 °C.

11. Method according to claim 8, 9 or 10, wherein, for at least one of the first and second photovoltaic sub-modules, the bandgap of the material of the perovskite layer is increased by partial substituting I -ions with Br -ions.

12. Method according to any one of claims 2 to 11, wherein the step of depositing the perovskite layer is free of any annealing step.

13. Method according to any one of claims 2 to 12, further comprising for at least one of the first and second photovoltaic sub-modules: depositing a hole transport layer on top of the perovskite layer before depositing the carbon-based layer and depositing the carbon-based layer on top of the hole transport layer.

14. Method according to claim 13, wherein the step of depositing a hole transport layer on top of the perovskite layer comprises inkjet printing, preferably drop-on-demand inkjet printing, a layer of an inorganic metal oxide, such as NiO, CuO or CU2O on top of the perovskite layer.

15. Method according to any one of claims 2 to 14, wherein each of the deposition steps are carried out under ambient atmospheric conditions.

16. Method according to any one of claims 2 to 15, wherein the step of providing a substrate which is transparent to light comprises providing a transparent glass or plastic sheet.

17. Method according to any one of claims 2 to 16, further comprising a step of electrically isolating parts of the transparent conducting oxide layer from each other by making scribe lines in the conducting oxide layer using laser scribing after the step of depositing the transparent conducting oxide layer onto the substrate.

18. Method according to any one of claims 2 to 17, wherein the step of depositing the carbonbased layer comprises blade coating or screen printing the carbon-based layer.

19. Method according to claim 18, wherein the step of blade coating or screen printing the carbon-based layer comprises blade coating or screen printing a paste containing at least one of graphite, carbon black, graphene, carbon nanotubes and carbon nanowires.

20. Method according to any one of the foregoing claims, wherein the step of arranging the polymeric sealant comprises encapsulating the first and second photovoltaic sub-modules at an ambient pressure of less than 1 bar and an ambient temperature of below 100 °C.

21. Method according to any one of the foregoing claims, wherein the material of the polymeric sealant is one of a thermoplastic and a thermoset polymer.

22. Photovoltaic module manufactured by the method according any one of claims 1 to 21, comprising: a first and a second photovoltaic sub-module, each comprising a perovskite solar cell comprising a carbon-based back electrode, wherein the first and second solar sub-modules arranged in a back-stacking configuration, wherein the carbon-based back electrode of the first sub-module faces the carbonbased back electrode of the second sub-module, and wherein a polymeric sealant is arranged between the carbon-based back electrodes of the first and second solar sub-modules, the sealant thereby separating the sub-modules from each other and acting as a spacer between the first and second solar sub-modules.

23. Photovoltaic module according to claim 22, wherein one of the first and second photovoltaic sub-modules comprises a hole transport layer and the other one of the first and second photovoltaic sub-modules is devoid of a hole transport layer.

24. Photovoltaic module according to claim 22 or 23, wherein the carbon-based back electrodes are comprised of a paste containing at least one of graphite, carbon black, graphene, carbon nanotubes and carbon nanowires.

25. Photovoltaic module according to any one of claims 22 to 24, wherein the material of the polymeric sealant is one of a thermoplastic and a thermoset polymer.

26. Solar glass module, comprising a plurality of photovoltaic modules according to any of claims 22 to 25.

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