Method for introducing a photovoltaically active material into a photovoltaic module having a plurality of cells and corresponding photovoltaic module

Abstract

Method for introducing a photovoltaic absorber material into a photovoltaic module comprising a plurality of cells with a front and a rear substrate, wherein a) a photovoltaic absorber material in the solid state selected from the group consisting of semiconducting perovskites of the general form KM-A3 (K: cation, M: metal, A: anion), wherein K is selected from the group consisting of Cs + , CH3NH3 + , Li + , N / a + , K + , Rb + , Ag + , Cu + , Imidazolium cations, ammonium cations, pyridinium cations, formamidinium cations, guanidinium cations, thiourea cations, bipyridyls, Ca 2+ and Mg 2+ , M is selected from the group consisting of Pb, Sn, Bi, Fe, Mn, Cu, Co, W, Ti and Zn, and A is selected from the group consisting of I - , Cl - , F - , Br - , SCN- , BF4 - , OTf - , MnO4 - , O 2- , S 2- and SO4 2- by introducing a polar gas selected from the group consisting of primary, secondary and tertiary amines, amidines, pyridines, imidazoles, hydrogen iodine, hydrogen chloride or hydrogen bromide, ammonia and mixtures thereof, which is liquefied as a melt. b) the liquid photovoltaic absorber material is actively transported by means of pressure and / or temperature changes through an opening into a distribution channel connected to the individual cells and the individual cells, wherein reservoirs for receiving the photovoltaic absorber material are arranged at the end of each cell facing the distribution channel, c) further distribution of the photovoltaic absorber material in porous structures contained within the cells occurs passively via capillary forces from the respective reservoir and d) the polar gas causing the liquefaction is driven out of the photovoltaic absorber material.

Description

[0001] The present invention relates to a method for introducing a photovoltaically active material into a photovoltaic module comprising a plurality of cells, wherein the photovoltaically active material is first liquefied by introducing a polar gas and, in a first step, is actively transported in liquid form through an opening into a distribution channel connected to the individual cells and into the individual cells themselves by means of a pressure change, and subsequently, in a second step, further distribution of the photovoltaically active material into porous structures contained within the cells is carried out passively by means of capillary forces. The present invention also relates to a photovoltaic module manufactured in this manner.

[0002] According to current technology, the introduction of photovoltaically active material into photovoltaic cells with porous contact structures is generally carried out in liquid form. Particularly in photovoltaic cells containing organic compounds (especially perovskite solar cells), which are thermally unstable, this process must ideally take place at room temperature. This avoids the need for melting the photovoltaically active material at high temperatures.

[0003] Therefore, the photovoltaically active material has previously been dissolved in one or more solvents and crystallized in the porous substrate layer by chemical precipitation from the solvent, particularly by exceeding the solubility of the active material through solvent evaporation. For large-area photovoltaic elements (greater than or equal to 1 cm²) 2), which are enclosed between two substrate plates, uniform crystallization is not possible in this way so far, because the evaporation of the solvent from the element prevents large-area homogeneous crystallization, e.g. through uncontrolled transport processes such as diffusion of the solution containing the active material into already dried areas or re-dissolution of already crystallized areas by subsequent flow of liquid or gaseous solvent.

[0004] Furthermore, many organic solvents form complexes (e.g., MAPbl3 and DMF), which lead to unwanted inhomogeneous crystal structures when the solvent is driven off.

[0005] A method for producing a coating solution on open substrates with perovskite absorber was described by Noel et al., "A low viscosity, low boiling point, clean solvent system for the rapid crystallisation of highly specular perovskite films." Energy Environ. Sci. 2017, 10, 145-152. This method utilized the production of an absorber precursor by liquefying perovskite powder in a carrier liquid through the introduction of a polar gas. However, this procedure is problematic for solar cells sealed by two substrate plates because the absorber precursor is set in motion when the carrier liquid is expelled, leading to inhomogeneity of the absorber material within the porous structures. Furthermore, the expulsion of the solvent causes a volume change (from the liquid precursor to the solid absorber), resulting in uneven filling of the porous structures with the absorber material.

[0006] To date, no method is known for evenly distributing the active material in liquid form into the individual cells of the module via a filling structure and subsequently crystallizing the active material. Particularly with elongated photovoltaic elements (preferably 5 mm x 100 mm) with small plate spacing (preferably 10 µm), outgassing of a solvent that dissolves or dilutes the photovoltaic active material is detrimental to the uniform application of the photovoltaic active material due to the strong transport processes and subsequent re-dissolution of the active material.

[0007] Based on this, the object of the present invention was to provide a method for introducing photovoltaically active material into a module that avoids the described disadvantages of the prior art.

[0008] This problem is solved by the method with the features of claim 1 and the photovoltaic module with the features of claim 8. The further dependent claims describe advantageous embodiments.

[0009] According to the invention, a method for introducing a photovoltaically active material into a photovoltaic module comprising a plurality of cells and a front and a rear substrate is provided, comprising the following steps: a) a photovoltaic absorber material in the solid state selected from the group consisting of semiconducting perovskites of the general form KM-A3 (K: cation, M: metal, A: anion), wherein K is selected from the group consisting of Cs + , CH3NH3 + , Li + , N / a + , K + , Rb + , Ag + , Cu +, Imidazolium cations, ammonium cations, pyridinium cations, formamidinium cations, guanidinium cations, thiourea cations, bipyridyls, Ca 2+ and Mg 2+ , M is selected from the group consisting of Pb, Sn, Bi, Fe, Mn, Cu, Co, W, Ti and Zn, and A is selected from the group consisting of I - , Cl - , F - , Br - , SCN - , BF4 - , OTf - , MnO4 - , O 2- , S 2- and SO4 2- by introducing a polar gas selected from the group consisting of primary, secondary and tertiary amines, amidines, pyridines, imidazoles, hydrogen iodine, hydrogen chloride or hydrogen bromide, ammonia and mixtures thereof, which is liquefied as a melt. b) the liquid photovoltaic absorber material is actively transported by means of pressure and / or temperature changes through an opening into a distribution channel connected to the individual cells and the individual cells, wherein reservoirs for receiving the photovoltaic absorber material are arranged at the end of each cell facing the distribution channel, c) further distribution of the photovoltaic absorber material in porous structures contained within the cells occurs passively via capillary forces from the respective reservoir and d) the polar gas causing the liquefaction is driven out of the photovoltaic absorber material.

[0010] A key aspect of the present invention is that the pure photovoltaically active material can be introduced into the photovoltaic element in liquid form without the use of solvents. This is achieved by significantly lowering the melting point, particularly below room temperature, through modification of the ambient gas. The liquefied active material can then be introduced into the photovoltaic module and, unlike chemical precipitation from the melt, crystallized in pure form by significantly raising the melting point again, particularly to its original melting point, by removing the ambient gas that facilitated the liquefaction. This approach is particularly well-suited for solar cells sealed by two substrate plates, as the ambient gas can be easily adjusted during manufacturing.

[0011] According to the invention, the introduction of the photovoltaically active material into the modules takes place in two sub-processes. First, pre-filling occurs through pressure or temperature changes. For this purpose, the photovoltaically active material is distributed to the individual cells via (at least) one filling channel. This is therefore an active filling process.

[0012] In the second subprocess, the actual distribution within the individual cells takes place. This occurs passively, as the liquid photovoltaic material spreads evenly through capillary action within the porous contact structures. This process step can take longer until the liquid photovoltaic material is completely homogeneously distributed by equalizing the concentration gradients.

[0013] The module design according to the invention thus separates the introduction and distribution of the liquid photovoltaically active material.

[0014] The design and process steps are therefore chosen so that pre-filling occurs faster than distribution by capillary forces. Ultimately, the distribution channel is emptied by the stronger capillary forces.

[0015] By changing the ambient gas and / or the temperature and / or the ambient pressure, the polar gas that liquefied the photovoltaic material is eventually expelled. In contrast to solvent-based approaches, the already homogeneously distributed photovoltaic material is not set back into motion. Thus, the homogeneity is maintained. Even at the microscopic level within the pores, the uniform distribution is preserved, since this form of crystallization from the melt does not result in a significant change in the volume of the precursor.

[0016] According to the invention, in contrast to precipitation from a solvent as known from the prior art, there is no or only a slight change in volume during the transition from the liquid to the solid form, which leads to improved embedding in the porous structures and thus to higher functionality of the photovoltaic module.

[0017] The problems that arise, particularly when removing solvents, as is known from the prior art, are circumvented by introducing the photovoltaically active material into the module in the melt according to the invention, thus eliminating the need for solvents. The presented method avoids the removal of the solvent, which is detrimental to the production of a pure and homogeneous active layer, and the associated process steps, which result in longer production times and higher costs, are thereby rendered unnecessary.

[0018] Preferably, the photovoltaically active material is selected from the group consisting of organic or inorganic materials, an organic-inorganic hybrid material, or combinations thereof. These materials are photovoltaic absorber materials that can be liquefied by introducing a polar gas. Particularly preferably, they are selected from the group consisting of semiconducting perovskites of the general form KM-A3 (K: cation, M: metal, A: anion), wherein K is preferably selected from the group consisting of Cs + , CH3NH3 + , Li + , N / a + , K + , Rb + , Ag + , Cu + , Imidazolium cations, ammonium cations, pyridinium cations, formamidinium cations, guanidinium cations, thiourea cations, bipyridyls, Ca 2+ and Mg 2+, M is preferentially selected from the group consisting of Pb, Sn, Bi, Fe, Mn, Cu, Co, W, Ti and Zn, and A is preferentially selected from the group consisting of I - , Cl - , F - , Br - , SCN - , BF4 - , OTf - , MnO4 - , O 2- , S 2- and SO4 2- .

[0019] A particularly preferred example of the method according to the invention is a photovoltaically active material with perovskite crystal structure ABX3, which can be liquefied with a polar gas, e.g. the perovskite material methylammonium lead triiodide is liquefied with the gas methylamine.

[0020] Preferably in step b) the filling with the photovoltaically active material is carried out by means of negative pressure, in particular a vacuum of 100 to 800 mbar, preferably 500 to 700 mbar.

[0021] Another preferred variant provides that in step b) the photovoltaically active material is introduced at ambient pressure and then transported into the cells by applying pressure, in particular 1 to 3 bar.

[0022] According to the invention, reservoirs for receiving the photovoltaically active material are arranged at the end of each cell facing the distribution channel. These reservoirs enable the photovoltaically active material to be distributed evenly within the cells. In step c), passive distribution then occurs from the reservoir via capillary action. A further preferred embodiment provides that the reservoirs contain porous structures which then act as wicks, facilitating improved initial wetting for passive distribution via capillary action.

[0023] It is further preferred that the photovoltaically active areas, and optionally the distribution channel and / or the reservoirs, have porous structures, in particular made of a material selected from the group consisting of TiO2, SnO2, ZnO, TiN, SiN, TiC, SiC, Al2O3, ZrO2, SiO2, Fe2O3, nickel oxides, chromium oxides, cobalt oxides, glass pigments, carbon black and graphite or combinations thereof, for receiving the photovoltaically active material.

[0024] Preferably, a connecting piece with a geometry that lengthens the flow path is arranged between the distribution channel and the individual cells. This connecting piece could be, for example, meandering or zigzag-shaped. By selecting such a geometry for the connecting piece, the distribution velocity can be controlled. Furthermore, such a structure can be used to reduce the effects of ion movements that may occur under unfavorable operating conditions, thereby extending the lifetime of the photovoltaic module by increasing the path length for ions between adjacent cells.

[0025] The polar gas is preferably selected from the group consisting of • primary, secondary and tertiary amines, especially methylamine, dimethylamine, trimethylamine, • Amidines, especially formamidines, • Pyridine, • Imidazoles, • hydrogen iodine, hydrogen chloride or hydrogen bromide • Ammonia and • Mixtures thereof.

[0026] Various methods can be used to expel the polar gas from the photovoltaically active material.

[0027] A first preferred approach involves driving the polar gas out of the photovoltaically active material with another gas, in particular selected from the group consisting of air, nitrogen, argon, water vapor, or ethers or mixtures of these gases. The polar gas may optionally also contain small amounts of hydrogen iodine, hydrogen chloride, or hydrogen bromide to optimize the crystallization process by better controlling the crystallization rate and healing defects.

[0028] A second preferred option involves driving the polar gas out of the photovoltaically active material by changing the temperature.

[0029] A third preferred option involves expelling the polar gas from the photovoltaically active material by applying a negative pressure.

[0030] These three variants can be used individually or in combination.

[0031] According to the invention, a photovoltaic module is further provided which has the following features: • a front electrode comprising a front substrate and an electrically conductive electrode layer arranged on the front substrate, and a further electrode comprising a rear substrate and an electrically conductive electrode layer arranged on the rear substrate, • a plurality of photovoltaic cells arranged between the front substrate and the rear substrate, which are connected to a distribution channel, wherein reservoirs for receiving the photovoltaic absorber material are arranged at the end of each cell facing the distribution channel, • at least one porous structure arranged between the front substrate and the rear substrate, at least partially in the photovoltaically active areas, • a sealing structure arranged between the front electrode and the other electrode, comprising a multitude of glass solder bridges and • a photovoltaic absorber material selected from the group consisting of semiconducting perovskites of the general form KM-A3 (K: cation, M: metal, A: anion), homogeneously distributed within the porous structures of the cells, where K is selected from the group consisting of Cs + , CH3NH3 +, Li + , N / a + , K + , Rb + , Ag + , Cu + , Imidazolium cations, ammonium cations, pyridinium cations, formamidinium cations, guanidinium cations, thiourea cations, bipyridyls, Ca 2+ and Mg 2+ , M is selected from the group consisting of Pb, Sn, Bi, Fe, Mn, Cu, Co, W, Ti and Zn, and A is selected from the group consisting of I - , Cl - , F - , Br - , SCN - , BF4 - , OTf - , MnO4 - , O 2- , S 2- and SO4 2- , wherein at least one porous structure is free of solvents.

[0032] It should be emphasized that at least one porous structure is free of solvents.

[0033] Preferably, the photovoltaic module can be manufactured using the method described above.

[0034] The following figures are intended to describe the object according to the invention without limiting it to the specific embodiments shown here. Fig. Figure 1 shows, using a schematic representation, the process of the inventive method for introducing a photovoltaically active material into a photovoltaic module. Fig. Figure 2 shows a top view of a photovoltaic module according to the invention. Fig. Figure 3 shows different variants for the connecting piece between the distribution channel and the individual photovoltaic cells. Fig. Figure 4 shows an embodiment of a filling device for the photovoltaic module according to the invention. Fig. Figure 5 shows a top view of an exemplary module according to the invention.

[0035] In Fig. Figure 1 shows how the photovoltaic material is introduced into a photovoltaic module. First, in a first step, the perovskite powder methylammonium lead triiodide (1) is provided as the photovoltaic active material ( Fig. 1A). This is liquefied by introducing the gas methylamine (2) (3) ( Fig. 1B).

[0036] As in Fig. As shown in Figure 1C, the perovskite (3), now in liquid form, is introduced in a subsequent step into a module consisting of two substrate plates (4, 5) by applying a pressure of 2 bar through an opening for filling (6) and transported via a distribution channel (7) and a reservoir (8) to the still unfilled porous structures (9) of the individual photovoltaic cells.

[0037] Fig. 1D shows the beginning wetting of the porous structures with liquid perovskites (10) in the individual cells.

[0038] In a further step ( Fig. 1E) The liquid perovskite is further distributed within the porous structures (10) in the individual cells (). This distribution is based on capillary forces and thus enables a very homogeneous distribution of the perovskite within the porous structures.

[0039] In a final step ( Fig. 1F) The gas (2) used for liquefaction is driven out of the perovskite so that the perovskite crystallizes in the porous structures (11). For this purpose, the photovoltaic module is alternately purged with ambient air under a pressure of 2 bar and a vacuum is applied.

[0040] In Fig. Figure 2 shows a top view of a module according to the invention. A filling opening (6) is visible, which is connected to a distribution channel (7). The distribution channel is in turn connected to several photovoltaic cells in which porous structures (9) are present. A reservoir (8) serves to store the photovoltaic material, from where it is homogeneously distributed into the porous structures of the cells via capillary action.

[0041] In Fig. Figure 3 shows a top view of different options for the connection between the distribution channel and the photovoltaic cell. Here, the distribution channel (7) can be directly connected to the porous structures of the cells (9) ( Fig. 3A). Another option is the installation of a reservoir (8) ( Fig. 3B), in which the liquid active material is collected before being distributed via capillary action into the porous structures of the cells. To improve coupling to the cells, the porous structures can also be partially introduced into the reservoir. As in Fig. As outlined in Figure 3C, the speed of liquid distribution can also be controlled by having the distribution channels (7', 12) have different cross-sectional areas. In smaller channels, the flow resistance increases compared to active introduction, e.g., by changing the pressure, while the capillary forces increase for faster passive distribution. The speed of liquid flow from the distribution channel to the cells can also be achieved by lengthening the path, as shown in Figure 3C. Fig. 3D represented by a zigzag structure (13).

[0042] In Fig. Figure 4 shows a cross-section through a filling device used to fill the photovoltaic module. The cross-section shown is through a distribution channel (7) enclosed between two substrate plates (4, 5). A bell-shaped filling chamber (15) is positively fitted above the module's filling opening (6) by means of a sealing ring (14). The liquid absorber can be introduced inside the bell chamber through a connection (16). A second connection (17) allows pressure to be applied or the ambient gas to be exchanged.

[0043] Fig. Figure 5 shows a top view of an exemplary module according to the invention.

[0044] The liquid active material can be introduced into the distribution channel (7) through a filling opening (6), from where it reaches the individual cells (9).

Claims

[1] Method for introducing a photovoltaic absorber material into a photovoltaic module comprising a plurality of cells and having a front and a rear substrate, wherein a) a photovoltaic absorber material in the solid state selected from the group consisting of semiconducting perovskites of the general form KM-A3 (K: cation, M: metal, A: anion), wherein K is selected from the group consisting of Cs + , CH3NH3 + , Li + , N / a + , K + , Rb + , Ag + , Cu + , Imidazolium cations, ammonium cations, pyridinium cations, formamidinium cations, guanidinium cations, thiourea cations, bipyridyls, Ca 2+ and Mg 2+ , M is selected from the group consisting of Pb, Sn, Bi, Fe, Mn, Cu, Co, W, Ti and Zn, and A is selected from the group consisting of I - , Cl - , F - , Br - , SCN- , BF4 - , OTf - , MnO4 - , O 2- , S 2- and SO4 2- by introducing a polar gas selected from the group consisting of primary, secondary and tertiary amines, amidines, pyridines, imidazoles, hydrogen iodine, hydrogen chloride or hydrogen bromide, ammonia and mixtures thereof, which is liquefied as a melt. b) the liquid photovoltaic absorber material is actively transported by means of pressure and / or temperature changes through an opening into a distribution channel connected to the individual cells and the individual cells, wherein reservoirs for receiving the photovoltaic absorber material are arranged at the end of each cell facing the distribution channel, c) further distribution of the photovoltaic absorber material in porous structures contained within the cells occurs passively via capillary forces from the respective reservoir and d) the polar gas causing the liquefaction is driven out of the photovoltaic absorber material. [2] Method according to claim 1, characterized by , that in step b) the negative pressure of the module for filling with the photovoltaic absorber material inside the module is caused by a temperature change by heating the module before filling and cooling it after filling. [3] Method according to any one of the preceding claims, characterized by , that in step b) the filling with the photovoltaic absorber material is carried out using negative pressure. [4] Method according to any one of the preceding claims, characterized by , that in step b) the photovoltaic absorber material is introduced at ambient pressure and then transported into the cells by applying pressure. [5] Method according to any one of the preceding claims, characterized by, that the photovoltaically active areas, and optionally the distribution channel and / or the reservoirs, have porous structures made of a material selected from the group consisting of TiO2, SnO2, ZnO, TiN, SiN, TiC, SiC, Al2O3, ZrO2, SiO2, Fe2O3, nickel oxides, chromium oxides, cobalt oxides, glass pigments, carbon black and graphite or combinations thereof for receiving the photovoltaic absorber material. [6] Method according to any one of the preceding claims, characterized by , that a connecting piece with a geometry that lengthens the flow path is arranged between the distribution channel and the individual cells. [7] Method according to any one of the preceding claims, characterized by, that the polar gas is driven out of the photovoltaically active material by another gas selected from the group consisting of air, nitrogen, argon, hydrogen iodine, hydrogen chloride, hydrogen bromide, water vapor, ethers or mixtures of these gases and / or by a change in temperature and / or by a change in ambient pressure. [8] Photovoltaic module with a front electrode comprising a front substrate and an electrically conductive electrode layer arranged on the front substrate, and another electrode comprising a rear substrate and an electrically conductive electrode layer arranged on the rear substrate, a plurality of photovoltaic cells arranged between the front substrate and the rear substrate, which are connected to a distribution channel, wherein reservoirs for receiving the photovoltaic absorber material are arranged at the end of each cell facing the distribution channel, at least one porous structure arranged between the front substrate and the rear substrate, at least partially in the photovoltaically active areas, a sealing structure arranged between the front electrode and the other electrode, comprising a multitude of glass solder bridges and a photovoltaic absorber material selected from the group consisting of semiconducting perovskites of the general form KM-A3 (K: cation, M: metal, A: anion) homogeneously distributed in the porous structures of the cells, where K is selected from the group consisting of Cs + , CH3NH3 + , Li+ , N / a + , K + , Rb + , Ag + , Cu + , Imidazolium cations, ammonium cations, pyridinium cations, formamidinium cations, guanidinium cations, thiourea cations, bipyridyls, Ca 2+ and Mg 2+ , M is selected from the group consisting of Pb, Sn, Bi, Fe, Mn, Cu, Co, W, Ti and Zn, and A is selected from the group consisting of I - , Cl - , F - , Br - , SCN - , BF4 - , OTf - , MnO4 - , O 2- , S 2- and SO4 2- , where which has at least one porous structure free of solvents. [9] Photovoltaic module according to claim 9, characterized by that the electrically conductive electrode layer arranged on the front electrode and / or the electrically conductive electrode layer arranged on the further electrode is made transparent. [10] Photovoltaic module according to one of claims 9 or 10, characterized by , that the extent of the at least two porous support layers between adjacent glass solder bridges is 3 to 10 mm and / or the thickness of all the at least two porous support layers together is 0.5 to 20 µm. [11] Photovoltaic module according to any one of claims 9 to 11, characterized by that the at least two porous support layers consist of a material selected from the group consisting of TiO2, TiN, SiN, TiC, SiC, Al2O3, ZrO2, SiO2, Fe2O3, nickel oxides, chromium oxides, cobalt oxides, glass pigments, carbon black and graphite or combinations thereof. [12] Photovoltaic module according to any one of claims 9 to 12, characterized by that the electrically conductive electrode layers consist of a material selected from the group consisting of SnO2:F, ZnO:Al and indium tin oxide or combinations thereof.

Images