Layer stack for thin film photovoltaic modules and method of manufacture thereof - Patents.com

Abstract

The present invention relates to a layer stack for a thin-film photovoltaic module. The layer stack is composed of a back electrode, an absorber, a buffer layer, a front electrode and an intermediate layer stacked in sequence on a corresponding substrate from bottom to top by vacuum coating deposition, the layer stack is divided by P1, P2 and P3 structural lines respectively, a conductive metal grid is embedded in the layer stack, and the metal grid is deposited on the buffer layer before or after the P2 structural line. According to the present invention, the buried grid is formed by embedding the conductive metal grid in the layer stack and depositing the metal grid on the buffer layer before or after the P2 structural line. Therefore, the front electrode and the intermediate layer can be deposited without vacuum breaking in the process sequence. Also, compared with the application of a standard thin-film photovoltaic module on the front electrode, such a buried grid shows great advantages in reducing capital expenditures and operating costs.

Description

[Technical field]

[0001] The present invention belongs to the technical field of CIGS thin-film solar cells, in particular to a layer stack for a thin-film photovoltaic module and a method for manufacturing the same. [Background technology]

[0002] As already known, continuous vacuum coating machine can greatly reduce the capital expenditure cost of vacuum coating aggregate for more subsequent layers without vacuum break. Moreover, in the process of production, more vacuum breaks lead to shorter normal operation time to reach the desired vacuum degree. However, more frequent vacuum switching will shorten the life of the vacuum turbo pump, i.e. increase the OPEX cost. Therefore, a continuous process with less vacuum break is required for thin film photovoltaic production.

[0003] In traditional thin-film photovoltaic production, vacuum coating is still a common method for depositing most layers of solar modules (e.g., back electrode, absorber, buffer layer, front electrode, intermediate layer). However, there are also some process steps, such as the solution processing of metal grid or subsequent P3 structure, that may cause process interruption during the vacuum deposition of subsequent layers. Therefore, thin-film photovoltaic production needs to maximize the combination of various vacuum coating processes to reduce costs and extend normal operation time. Thus, a new layer stack design for thin-film solar modules with metal grid needs to be designed to rearrange the metal grid printing and P3 structure in the production process sequence to reduce costs.

[0004] In the applied layer stack as shown in Figure 1, P2 needs to be accessible before the deposition of the front electrode and after the buffer layer in order to contact the back and front electrodes and connect the cells in series. Usually, it is impossible to avoid a vacuum break between the buffer layer and the front electrode. However, as shown in Figure 4, the solution processing of the metal grid and P3 structure occurs between the deposition of the front electrode and the interlayers in a standard thin film photovoltaic module layer stack. Summary of the Invention [Problem to be solved by the invention]

[0005] In order to solve the shortcomings existing in the prior art, the present invention provides a layer stack for a thin film photovoltaic module and a manufacturing method thereof. The specific technical solutions are as follows: [Means for solving the problem]

[0006] A layer stack for a thin-film photovoltaic module consists of a back electrode, an absorber, a buffer layer, a front electrode and an intermediate layer stacked in order on a corresponding substrate from bottom to top by vacuum coating deposition, and the layer stack is divided by P1 structure lines, P2 structure lines and P3 structure lines, respectively.

[0007] A conductive metal grid is embedded in the layer stack, the metal grid being deposited on the buffer layer before or after the P2 structural lines.

[0008] The layer stack further comprises a pattern region including a P1 pattern line groove where the back electrode is removed, a P2 pattern line groove close to the P1 structural line where the absorber is removed, and a P3 pattern line groove close to the P2 structural line, the metal grid being perpendicular to the P1 structural line, the P2 structural line and the P3 structural line, and the metal grid outside the pattern region being located between the buffer layer and the front electrode.

[0009] Furthermore, the metal grid is made of any of silver, copper, and aluminum.

[0010] Furthermore, the metal grids are deposited by different solution deposition methods.

[0011] Further, the solution deposition method is one of inkjet printing, aerosol printing, screen printing, and electroplating.

[0012] Furthermore, the conductive ink solvent applied to the metal grid does not directly dissolve or react with the buffer layer.

[0013] Furthermore, the surface tension of the conductive ink is greater than the surface energy of the buffer layer.

[0014] Furthermore, the surface energy of the buffer layer is lower than the surface energy of the front electrode.

[0015] Moreover, the front electrode is made of a transparent conductive oxide material.

[0016] Furthermore, the front electrode is made of any of aluminum-doped zinc oxide, boron-doped zinc oxide, indium-doped zinc oxide, indium-doped tin oxide, and fluorine-doped tin oxide.

[0017] Furthermore, the intermediate layer is made of a non-conductive transparent material, the refractive index of which is between the refractive index of the glass and the laminating foil and the refractive index of the transparent conductive oxide.

[0018] Furthermore, the intermediate layer is made of either silicon nitride or aluminum oxide.

[0019] A method for manufacturing a layer stack for a thin film photovoltaic module comprises: The method includes the steps of first depositing a cell stack having a back electrode, removing the back electrode to form a cell separation of a P1 structural line, then depositing an absorber and a buffer layer, where a P2 pattern line groove next to the P1 structural line is a P2 pattern line groove formed by first removing the absorber and then depositing a metal grid perpendicular to the P1 structural line and the P2 structural line, or by first depositing a metal grid perpendicular to the P1 structural line and then removing the metal grid and the absorber, then depositing a front electrode and an intermediate layer, and removing at least a front electrode material to form a P3 pattern line groove next to the P2 structural line, such that the P1 structural line and the P3 structural line are located on different sides of the P2 structural line, and the metal grid is located vertically between the buffer layer and the front electrode.

[0020] The advantages of the present invention are as follows:

[0021] According to the present invention, a conductive metal grid is embedded in the layer stack and deposited on the buffer layer before or after the P2 structure line, forming a buried grid, so that the front electrode and intermediate layers can be deposited in the process sequence without vacuum break, and compared with the application of standard thin-film photovoltaic modules on the front electrode, such a buried grid shows great advantages in reducing capital expenditures and operating costs. [Brief description of the drawings]

[0022] [Figure 1] FIG. 1 is a schematic diagram of the layer stack of a typical thin-film solar cell. [Diagram 2] FIG. 1 is a schematic diagram showing the cell width and dead area of ​​a standard thin-film solar cell in plan view. [Diagram 3] FIG. 1 is a plan view showing the interconnection of three cells in a standard thin film photovoltaic module. [Figure 4]FIG. 1 is a cross-sectional view showing the stack-up of a thin-film solar cell having a standard metal grid structure deposited on a front electrode. [Diagram 5] FIG. 1 is a schematic diagram of a top view of a thin-film solar cell having a standard metal grid structure deposited on a front electrode. [Figure 6] FIG. 1 shows a top view of the interconnection of three cells of a thin-film photovoltaic module on a front electrode with a standard metal grid. [Figure 7] FIG. 1 is a schematic diagram of a selected production process sequence (including buffer layer, P2 construction line, front electrode, metal grid, P3 construction line, and intermediate layer) for a thin film / CIGS photovoltaic module according to an embodiment of a standard metal grid layer stack. [Figure 8] FIG. 1 is a schematic diagram of a selected production process sequence (including buffer layer, P2 construction line, front electrode, metal grid, intermediate layer, and P3 construction line) for a thin film / CIGS photovoltaic module according to another embodiment of a standard metal grid layer stack. [Figure 9] 13A-13C are cross-sectional views of a layer stack of a thin-film solar cell having a buried metal grid structure under a front electrode and an intermediate layer according to an embodiment of the buried grid process sequence of FIG. [Figure 10] 14 is a cross-sectional view of a layer stack of a thin-film solar cell having a buried metal grid structure under a front electrode and an intermediate layer according to another embodiment of the buried grid process sequence of FIG. 13. [Figure 11] FIG. 1 is a schematic diagram of a plan view of a thin-film solar cell having a buried metal grid structure deposited under a front electrode and an intermediate layer. [Figure 12] FIG. 1 is a schematic diagram of a selected production process sequence (including buffer layer, metal grid, P2 construction lines, front electrode, intermediate layer, and P3 construction lines) for a thin film / CIGS photovoltaic module according to another embodiment of an embedded metal grid layer stack. [Figure 13]FIG. 1 is a schematic diagram of a selected production process sequence (including buffer layer, P2 construction line, metal grid, front electrode, intermediate layer, and P3 construction line) for a thin film / CIGS photovoltaic module according to another embodiment of an embedded metal grid layer stack. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be described in more detail below with reference to the embodiments. It should be understood that the specific embodiments described herein do not limit the present invention, but are only used to illustrate the present invention.

[0024] The prior art is described as follows:

[0025] A thin-film photovoltaic module stacked in a certain way includes, in that order, a back electrode, an absorber, a buffer layer / i-layer, a front electrode, and an interlayer, where the interlayer is an optional layer of the thin-film photovoltaic module that is configured to optimize the light coupling to the active area, adjust the color appearance for BIPV (Building Integrated Photovoltaics) applications, or improve some mechanical properties, such as adhesion in laminated glass photovoltaic modules. Due to the low voltage and large area of ​​the cells, most modules are designed with each cell interconnected in series as an individual to avoid high current losses. However, this increases the total operating voltage in the photovoltaic module.

[0026] Additionally, all layers in a cell are interconnected, as shown in Figure 1. It can be seen that the layer stack is divided by P1, P2, and P3 structural lines, respectively. Note that P1 and P3 insulate the front and back electrodes, and P2 acts as an electrical contact between the front and back electrodes, thereby connecting two adjacent cells in series. Since the P1 / P2 / P3 structural area does not generate electricity, it is usually referred to as the "dead area", as shown in Figure 2.

[0027] In order to optimize the power conversion efficiency of a solar cell, it is generally considered to increase the transmittance of the front electrode by reducing the layer thickness of the front electrode, further increasing the generated photocurrent, etc. However, this results in an increase in the sheet resistance of the front electrode, which causes conduction losses. In order to reduce such conduction losses in the front electrode, a narrow metal grid with high conductivity can be applied on the front electrode layer to improve the associated conductivity, i.e., the metallization process for photovoltaic production. Therefore, as shown in Figures 4, 5 and 6, the metal grid structure is applied to the cell laterally at periodic intervals or perpendicularly to P1 / P2 / P3. It can be seen that the grid lines are applied continuously to the solar cell. P3 prevents short circuits between the front electrode of one cell and the adjacent cell by interrupting the grid lines.

[0028] Here, Figures 7 and 8 show two examples of thin-film photovoltaic module production sequences. There is a vacuum break between the deposition of the front electrode 6 and the intermediate layer 7. Therefore, costs can be reduced if the two layers can be deposited sequentially in the same vacuum coater. The resulting layer sequence is described in the previous section (see Figure 4). Alternative layer stacks for thin-film photovoltaic devices with metallization layers, such as the present invention, have not yet been published.

[0029] Specific embodiments of the present invention are as follows.

[0030] As shown in FIG. 9 to FIG. 11, a layer stack for a thin-film photovoltaic module is composed of a back electrode, an absorber, a buffer layer, a front electrode and an intermediate layer stacked in order on a corresponding substrate from bottom to top by vacuum coating deposition, the layer stack being divided by P1 structure line, P2 structure line and P3 structure line respectively; A conductive metal grid is embedded in the layer stack, the metal grid being deposited on the buffer layer before or after the P2 structural lines.

[0031] By adopting the above technical solution, a conductive metal grid is embedded in the layer stack, and the metal grid is deposited on the buffer layer before or after the P2 structure line, forming a buried grid. Therefore, in the process sequence, the front electrode and intermediate layers can be deposited without vacuum breaking. Also, compared with the application of standard thin-film photovoltaic modules on the front electrode, such a buried grid shows great advantages in reducing capital expenditures and operating costs.

[0032] As shown in FIG. 2, the layer stack further comprises a pattern region including a P1 pattern line groove where the back electrode is removed, a P2 pattern line groove close to the P1 structure line where the absorber is removed, and a P3 pattern line groove close to the P2 structure line, the metal grid is perpendicular to the P1 structure line, the P2 structure line and the P3 structure line, and the metal grid outside the pattern region is located between the buffer layer and the front electrode.

[0033] By adopting the above mentioned technical solution, a pattern area, P1 pattern line groove, P2 pattern line groove and P3 pattern line groove are shown in the drawing.

[0034] By adopting the above technical solution, the pattern area including the P1 structure line, the P2 structure line and the P3 structure line forms a single chip serial interconnection structure in the CIGS module.

[0035] As shown in Figure 9, the P2 pattern groove does not contain metal grid material, and the metal grid outside the pattern area between the buffer layer and the front electrode is interrupted by the P2 pattern groove, so that the electrical P2 contact in the P2 pattern groove is formed as an electrode only in the order of the front electrode, then the back electrode. As shown in Figure 10, the P2 pattern groove contains metal grid material coated with the front electrode material, so that the electrical P2 contact is formed as an electrode only in the order of the front electrode, then the metal grid material, then the back electrode.

[0036] The above two sequences of electrode formation are possible options for solar module devices and have no difference in the associated advantages, it just shows that they are possible and do not pose any problems for the application of buried mesh.

[0037] Preferably, the metal grid is made of one of silver, copper and aluminium.

[0038] Preferably, the metal grid is deposited by a different solution deposition method.

[0039] Preferably, the solution deposition method is one of inkjet printing, aerosol printing, screen printing, and electroplating.

[0040] Preferably, the conductive ink solvent applied to the metal grid does not directly dissolve or react with the buffer layer.

[0041] In order to realize such a change by adopting the above technical solution, a prerequisite is that the conductive ink solvent applied to the metal grid does not directly dissolve or react with the buffer layer, otherwise, the application of the metal grid will affect the electrical properties of the buffer layer and deteriorate the interface.

[0042] Preferably, the surface tension of the conductive ink is greater than the surface energy of the buffer layer.

[0043] By adopting the above technical solution, the conductive ink to be applied needs to be selected / reformulated as a conductive ink with a surface tension much larger than the surface energy of the buffer layer, i.e., the conductive ink expected to be applied has a smaller wettability to the buffer layer. If the surface energy of the buffer layer is higher than the surface energy of the front electrode, the surface tension of the conductive ink should be increased by adding some additives. The smaller the wettability of the conductive ink used, the narrower the grid lines, i.e., the smaller the light loss due to the shadow of the grid lines.

[0044] Preferably, the surface energy of the buffer layer is lower than the surface energy of the front electrode.

[0045] By adopting the above technical solution, when the surface energy of the buffer layer is lower than that of the front electrode, the embedded grid has the advantage of a smaller grid line width compared with the standard grid on the front electrode.

[0046] Preferably, the front electrode is made of a transparent conductive oxide material.

[0047] Preferably, the front electrode is made of any of the following: aluminum doped zinc oxide, boron doped zinc oxide, indium doped zinc oxide, indium doped tin oxide, fluorine doped tin oxide.

[0048] Preferably, the intermediate layer is made of a non-conductive transparent material, the refractive index of which is between that of the glass and laminating foil and that of the transparent conductive oxide.

[0049] Preferably, the intermediate layer is made of one of silicon nitride and aluminum oxide.

[0050] As shown in Figures 9 to 13, a method for manufacturing a layer stack for a thin film photovoltaic module includes: The method includes the steps of first depositing a cell stack having a back electrode, removing the back electrode to form a cell separation of a P1 structural line, then depositing an absorber and a buffer layer, where a P2 pattern line groove next to the P1 structural line is a P2 pattern line groove formed by first removing the absorber and then depositing a metal grid perpendicular to the P1 structural line and the P2 structural line, or by first depositing a metal grid perpendicular to the P1 structural line and then removing the metal grid and the absorber, then depositing a front electrode and an intermediate layer, and removing at least a front electrode material to form a P3 pattern line groove next to the P2 structural line, such that the P1 structural line and the P3 structural line are located on different sides of the P2 structural line, and the metal grid is located vertically between the buffer layer and the front electrode.

[0051] By adopting the above technical solutions, the method, in cooperation with the embedded mesh of the layer stack, allows the deposition of the front electrode and the intermediate layer in a continuous vacuum coating process without vacuum breaking.

[0052] The above is only a preferred embodiment of the present invention, and is not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall fall within the protection scope of the present invention.

Claims

1. 1. A layer stack for a thin film photovoltaic module, comprising: a back electrode, an absorber, a buffer layer, a front electrode and an intermediate layer stacked in sequence on a corresponding substrate from bottom to top, said layer stack being divided by P1 structure lines, P2 structure lines and P3 structure lines, respectively; a conductive metal grid is embedded in the layer stack, the metal grid being deposited on the buffer layer before or after the P2 structural line; the layer stack further comprising a pattern region including a P1 pattern line groove where the back electrode is removed, a P2 pattern line groove proximate the P1 structural line where the absorber is removed, and a P3 pattern line groove proximate the P2 structural line; A layer stack for a thin-film photovoltaic module, wherein the metal grid is perpendicular to the P1, P2 and P3 structure lines, and the metal grid outside the pattern area is located between the buffer layer and the front electrode.

2. 10. The layer stack for a thin-film photovoltaic module of claim 1, wherein the metal grid is made of one of silver, copper, and aluminum.

3. 3. The layer stack for a thin film photovoltaic module of claim 2, wherein a conductive ink solvent applied to the metal grid does not directly dissolve the buffer layer.

4. The layer stack for a thin film photovoltaic module of claim 3 , wherein the surface tension of the conductive ink is greater than the surface energy of the buffer layer.

5. The layer stack for a thin film photovoltaic module of claim 4 , wherein the surface energy of the buffer layer is lower than the surface energy of the front electrode.

6. 10. The layer stack for a thin film photovoltaic module according to claim 1, wherein the front electrode is made of a transparent conductive oxide material.

7. 7. A layer stack for a thin film photovoltaic module according to claim 6, wherein the front electrode is made of one of the following: aluminum doped zinc oxide, boron doped zinc oxide, indium doped zinc oxide, indium doped tin oxide, fluorine doped tin oxide.

8. 2. A layer stack for a thin-film photovoltaic module according to claim 1, wherein the intermediate layer is made of a non-conductive transparent material, the refractive index of which is between the refractive index of the glass and lamination foil and the refractive index of the transparent conductive oxide.

9. 9. A layer stack for a thin-film photovoltaic module according to claim 8, wherein said intermediate layer is made of one of silicon nitride and aluminum oxide.

10. First, deposit a cell stack having a back electrode, and remove the back electrode to form a cell separation of a P1 structure line; Next, depositing an absorber and a buffer layer, where the P2 pattern line groove next to the P1 structural line is a P2 pattern line groove formed by first removing the absorber and then depositing a metal grid perpendicular to the P1 structural line and the P2 structural line, or by first depositing a metal grid perpendicular to the P1 structural line and then removing the metal grid and the absorber; Then, depositing a front electrode and an intermediate layer, and removing at least a front electrode material to form a P3 pattern line groove next to the P2 structure line, such that the P1 structure line and the P3 structure line are located on different sides of the P2 structure line, and the metal grid is located vertically between the buffer layer and the front electrode; A method for manufacturing a layer stack for a thin film photovoltaic module according to claim 1 comprising:

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