Manufacturing Method of Light-Shielding Frame and Ultra-Thin Substrate Thin-Film Solar Cell

Abstract

The present invention relates to a shielding frame and a manufacturing method of an ultra-thin substrate thin-film solar cell. The shielding frame is composed of an upper frame and a lower frame which are rectangular and arranged up and down in the thickness direction. It can prevent the edge and back coating of the ultra-thin substrate, making the edge encapsulation more reliable and ensuring the reliability of long-term electronic devices. Different-sized shielding frames are used in each coating process to insulate the formed thin film layers from each other and prevent edge leakage of the device. During the coating process, the edge of the ultra-thin substrate is pressed by the shielding frame, which can prevent the four sides from warping and can heat the substrate more effectively, thus ensuring coating uniformity and improving the performance of the thin film electronic device. Using the shielding frame eliminates the edge film layer removal process in the traditional process, which not only simplifies the production process, improves production efficiency, but also avoids damage to the battery wafers that may be caused during the edge removal process.

Description

Technical Field

[0001] The present invention relates to the manufacturing technology of thin-film solar cells, specifically a shielding frame for manufacturing an ultra-thin substrate thin-film solar cell, and a manufacturing method of an ultra-thin substrate thin-film solar cell using such a shielding frame. Background Art

[0002] When the thickness of glass is lower than a certain value, such as below 0.7 mm, it will exhibit a certain flexibility, and the thinner the glass, the more obvious the flexibility. For example, the willow glass released by Corning Inc. has a thickness of 0.2 mm and can be bent arbitrarily to make flexible electronic devices, and can be attached to any curved surface.

[0003] Utilizing the flexibility of thin glass, people use thin glass as a substrate to fabricate thin-film solar cells and attach them to automotive glass with a certain curvature to form a solar power generation device for use on automobiles, such as Patent CN201310164794 and Patent CN201410132552.

[0004] Coating a film uniformly on an ultra-thin substrate is very challenging. On the one hand, the thinner the substrate, the smaller its heat capacity, and uneven local heating will cause a large temperature gradient on the substrate surface, resulting in rapid bending deformation of the substrate. The bending deformation will cause uneven film deposition on the substrate surface. On the other hand, when the thickness of the film is comparable to that of the substrate, such as when the substrate is as thin as 200 μm and the film is 2 μm thick, the mismatch in the thermal expansion coefficients of the film and the substrate will significantly change the shape of the substrate, causing the substrate to warp or arch during heating or cooling, and the larger the substrate size, the more obvious this deformation is. This phenomenon is particularly significant on thin glass or thin plastic substrates because thin glass or thin plastic has low thermal conductivity and uneven local heating is not easily transferred to other areas. Therefore, a large temperature gradient on the surface often persists, resulting in rapid warping of the four sides of the substrate at the initial stage of heating. Coating a film on such a substrate not only has poor coating uniformity but also easily forms overcoating on the back of the substrate, and there are also large differences in the thickness of the deposited film between batches, greatly affecting the performance of electronic devices on the ultra-thin substrate. To solve the problem of film coating on an ultra-thin substrate, a very uniform heating scheme is required, which is often not easily achieved on traditional film deposition equipment. At the same time, a very good device for fixing the ultra-thin substrate must be equipped to prevent its edges from warping during heating, thereby causing uneven coating or overcoating on the back.

[0005] On the other hand, when coating a superstrate, generally the thin film will cover the entire surface of the substrate, including the edges of the substrate, and sometimes even a small part of the peripheral area on the back of the substrate (overcoating). For electronic devices such as solar cells, these thin films usually have a certain conductivity. The thin film on the edge will become a leakage path, causing device failure, or in a humid environment, causing wet leakage that endangers safety, or the remaining thin film on the edge will become a fast channel for water vapor to enter the interior of the electronic device, resulting in long-term aging failure of the device. These situations are not allowed to occur in electronic devices. Removing the thin film deposited on the edge of the substrate to achieve the effect of edge insulation has many different methods in the industrial field, such as grinding the edge with a grinding wheel (US20090221217), removing the thin film on the edge of the substrate by sandblasting (US8569094), removing it by laser ablation (US20120015471), and there is also the lift-off method. Before coating, a material that is easy to remove is coated on the area where the thin film is not required. After the coating is completed, the above-mentioned coated material is removed, so that the film layer above is peeled off at the same time (CN102867881A). The above several methods have their respective limitations. For example, the methods of grinding the edge with a grinding wheel or sandblasting are not applicable to thin glass substrates because very thin and brittle substrates are extremely easy to break during the above mechanical edge removal process. Another example is that the lift-off method usually requires some volatile organic materials, such as photoresist. The substances volatilized by such materials during the heating process of coating are likely to affect the coating effect. Although the laser ablation method is widely used in the edge removal of thin film batteries, it requires expensive laser equipment, and there are reaction residues on the glass edge after laser ablation. The final device reliability still strongly depends on the subsequent packaging process. Patent US8071420 proposes a method for removing the thin film on the edge of the substrate during the coating process by using a shadow frame. However, since there are several layers of the solar cell film layer, the laser ablation method is still used in this patent to remove the metal film layer to ensure the edge insulation of the device and prevent edge leakage. A simple, effective, economical and practical edge removal method, avoiding expensive equipment and complex processes, is the key to manufacturing electronic devices on thin glass or other ultra-thin substrates. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a manufacturing method of an ultra-thin substrate thin film solar cell that can prevent insulation defects of the edge film layer of the thin film solar cell, and has a simple manufacturing process and low cost, as well as a shielding frame for this method.

[0007] The light-blocking frame of the present invention is composed of an upper frame and a lower frame which are rectangular and arranged up and down in the thickness direction. The size of the rectangular inner hole of the upper frame is smaller than that of the lower frame, so as to form a stepped surface on the inner wall; the size of the rectangular inner hole of the lower frame matches the size of the edge of the substrate of the thin-film solar cell to be processed; the size of the rectangular inner hole of the upper frame matches the size of the edge of the film deposition layer to be formed on the thin-film solar cell to be processed.

[0008] The manufacturing method of the ultra-thin substrate thin-film solar cell of the present invention includes the following steps:

[0009] a. Take an ultra-thin glass substrate with the thickness of the glass being 0.70 mm to 0.05 mm, and clean the ultra-thin glass.

[0010] b. Deposit a buffer layer on the ultra-thin glass substrate. This buffer layer has two functions. One is to prevent the alkali metal ions in the glass from entering the battery interior and affecting the reliability of the battery. The other is to provide a buffer between the thin glass and the front electrode, and improve the adhesion of the front electrode on the glass.

[0011] c. Continue to deposit the front electrode on the buffer layer. Before depositing the front electrode, cover the ultra-thin glass substrate with the light-blocking frame having the above structure. The lower frame of the light-blocking frame is positioned in cooperation with the edge of the ultra-thin glass substrate, and the upper frame of the light-blocking frame blocks the area at a distance D1 from the edge of the ultra-thin glass substrate. Then deposit the front electrode, so that the blocked part cannot form a film coating.

[0012] d. Continue to deposit the absorption layer on the front electrode. Before deposition, cover it with a light-blocking frame of another size. The lower frame of the light-blocking frame is positioned in cooperation with the edge of the ultra-thin glass substrate, and the upper frame of the light-blocking frame blocks the area at a distance D2 from the edge of the ultra-thin glass substrate. D1 is greater than D2, so as to form a gap between the upper frame and the side of the front electrode. Then deposit the absorption layer, so that the blocked part cannot be coated with the absorption layer, and at the same time, the absorption layer material enters the above gap and wraps the side of the front electrode.

[0013] e. Continue to deposit the back electrode on the absorption layer. Before depositing the back electrode, cover it with a light-blocking frame of a third size. The lower frame of the light-blocking frame is positioned in cooperation with the edge of the ultra-thin glass substrate, and the upper frame of the light-blocking frame blocks the area at a distance D3 from the edge of the ultra-thin glass substrate. D3 is greater than D2, preferably D3 > D1 > D2 + 2 mm; then deposit the back electrode, so that the substrate and the absorption layer of the blocked part cannot be coated with the back electrode. The back electrode is deposited above the absorption layer and does not exceed the absorption layer at the edge, so it will not contact the front electrode to cause a short circuit. At least one of the back electrode and the front electrode is an electrode transparent to sunlight, otherwise sunlight cannot enter the absorption layer to be converted into electric energy.

[0014] f. Lead out an electrode on the above-mentioned back electrode, lead out the opposite electrode on the front electrode, and then bond and encapsulate the thin-film solar cell with a layer of glass or light-transmitting polymer through a light-transmitting adhesive material to form a solar cell structure.

[0015] In step b, the buffer layer is deposited with SiOx of 20 - 100 nm by plasma-enhanced chemical vapor deposition (PECVD). SiH4 and CO2 are used as reaction gases, the ratio of CO2 / SiH4 is between 5 - 20, and the plasma power density is between 0.03 - 0.20 W / cm2.

[0016] In step c, the front electrode is a metal or transparent conductive oxide thin film; preferably a boron-doped zinc oxide thin film with a film thickness of 1.0 - 2.0 um, a visible light transmittance greater than 80%, and a sheet resistance of 10 - 20 ohm / sq.

[0017] In step d, the absorption layer is one of the structures of a PIN structure or NIP structure of a silicon thin film, a CIGS thin-film battery, a CdTe thin-film battery structure, and an organic semiconductor thin film, or a series stack combination of two to three of them. Preferably, it is a PIN structure of an amorphous silicon thin film, which includes a P-type amorphous silicon, an intrinsic amorphous silicon, an N-type amorphous silicon deposited on the front electrode, and the transition layers between these three layers.

[0018] In step e, the back electrode is a metal or transparent conductive oxide thin film; preferably a boron-doped zinc oxide thin film with a film thickness of 1.0 - 2.0 um, a visible light transmittance greater than 80%, and a sheet resistance of 10 - 20 ohm / sq.

[0019] In step f, the polymer is one of polycarbonate (PC), polyethylene terephthalate (PET), and ethylene-tetrafluoroethylene copolymer (ETFE); the adhesive material is one of EVA, PVB, and silicone.

[0020] The advantages of the present invention are as follows: 1. By using the shielding frame, it can prevent the edges of the ultra-thin substrate and the back coating film, making the edge encapsulation more reliable and ensuring the reliability of long-term electronic devices; 2. Different-sized shielding frames are used in each coating process to insulate the formed thin film layers from each other and prevent edge leakage of the device; 3. During the coating process, the edges of the ultra-thin substrate are pressed by the shielding frame to prevent warping at the four sides, which can more effectively heat the substrate, thus ensuring coating uniformity and improving the performance of thin film electronic devices; 4. By using the shielding frame, the edge film layer removal process in the traditional process is omitted, which not only simplifies the production process, improves production efficiency, but also avoids damage to the battery chips that may be caused during the edge removal process. Description of the Drawings

[0021] Figure 1 It is a schematic cross-sectional structure diagram of the shielding border of an embodiment of the present invention;

[0022] Figure 2 is Figure 1 the top view structure diagram of

[0023] Figure 3 It is a schematic structure diagram when depositing the front electrode in the manufacturing method of an embodiment of the present invention;

[0024] Figure 4 It is a schematic structure diagram when depositing the absorption layer in the manufacturing method of an embodiment of the present invention;

[0025] Figure 5 It is a schematic structure diagram when depositing the back electrode in the manufacturing method of an embodiment of the present invention;

[0026] Figure 6 It is another schematic structure diagram when depositing the back electrode in the manufacturing method of an embodiment of the present invention. Detailed implementation manners

[0027] As Figure 1 , Figure 2 shown, the shielding border is composed of an upper frame 1 and a lower frame 2 which are rectangular and arranged up and down in the thickness direction. The inner hole size of the rectangle of the upper frame is smaller than that of the lower frame, so as to form a stepped surface on the inner wall; the inner hole size of the rectangle of the lower frame matches the edge size of the substrate m1 of the thin-film solar cell to be processed; the inner hole size of the rectangle of the upper frame matches the edge size of the layer to be coated of the thin-film solar cell to be processed.

[0028] The first embodiment of the manufacturing method of the ultra-thin substrate thin-film solar cell of the present invention includes the following steps:

[0029] 1. Provide an ultra-thin glass substrate m1, the thickness of the glass is between 0.70 mm and 0.05 mm, and clean the thin glass;

[0030] 2. Deposit a buffer layer m2 on the ultra-thin glass. The buffer layer is deposited with SiOx of 20 - 100 nm by the method of plasma enhanced chemical vapor deposition (PECVD). Use SiH4 and CO2 as reaction gases, the ratio of CO2 / SiH4 is between 5 and 20, and the plasma power density is between 0.03 and 0.20 W / cm2. This buffer layer has two functions. One is to prevent the alkali metal ions in the glass from entering the battery interior and affecting the reliability of the battery. The other is to provide a buffer between the thin glass and the front electrode and improve the adhesion of the front electrode on the glass;

[0031] 3. On top of the above buffer layer, deposit the front electrode m3. The front electrode can be a metal or a transparent conductive oxide film. In this example, the front electrode is a boron-doped zinc oxide film with a film thickness of 1.0 - 2.0 μm, a visible light transmittance greater than 80%, and a sheet resistance of 10 - 20 ohm / sq. When depositing the front electrode, use a masking frame A of the first size. As shown in Figure 3 , the area at a distance D1 = 12 mm from the edge of the ultra-thin glass substrate is blocked by the masking frame A and no film is deposited;

[0032] 4. On top of the above front electrode, deposit the absorber layer m4. The absorber layer can be a PIN or NIP structure of a silicon thin film, or a CIGS thin film battery or a CdTe thin film battery structure, or an organic semiconductor thin film, or a series stacked combination of two or three of the above structures. In this example, we use a PIN structure of an amorphous silicon thin film, which includes P-type amorphous silicon, intrinsic amorphous silicon, N-type amorphous silicon deposited on the front electrode, and transition layers between these three layers. The specific deposition conditions can be found in Patent CN201210478809.6. When depositing the absorber layer, use a masking frame B. As shown in Figure 4 , the area at a distance D2 = 10 mm from the edge of the ultra-thin glass substrate is blocked by the masking frame B and no absorber layer is deposited. However, due to a 2-mm difference in the distance from the edge between the masking frames A and B, the absorber layer wraps around the side of the front electrode;

[0033] 5. On top of the above absorber layer, deposit the back electrode m5. The back electrode can be a metal or a transparent conductive oxide film. In this example, the back electrode is a boron-doped zinc oxide film with a film thickness of 1.0 - 2.0 μm, a visible light transmittance greater than 80%, and a sheet resistance of 10 - 20 ohm / sq. It should be noted that at least one of the back electrode and the front electrode must be a solar-light-transparent electrode, otherwise sunlight cannot enter the absorber layer to be converted into electrical energy. When depositing the back electrode, use a masking frame C. As shown in Figure 5 , the area at a distance D3 = 12 mm from the edge of the ultra-thin glass substrate is blocked by the masking frame C and no film is deposited. The back electrode is deposited above the absorber layer and does not extend beyond the absorber layer at the edge, so it will not contact the front electrode to cause a short circuit;

[0034] 6. Lead out an electrode on the above back electrode and an opposite electrode on the front electrode. Seal the thin-film battery on the above thin glass with another layer of glass or a light-transmissive polymer such as polycarbonate (PC), polyethylene terephthalate (PET), ethylene-tetrafluoroethylene copolymer (ETFE), etc. through a light-transmissive adhesive material such as EVA, PVB, silicone, etc. The edge can be further sealed to form a long-term reliable solar cell structure.

[0035] The steps of the second embodiment of the manufacturing method of the ultra-thin substrate thin-film solar cell of the present invention are similar to those of the first embodiment above. When plating the front electrode, the distance between the shielding frame A and the edge of the ultra-thin glass substrate is D1; when plating the absorption layer, the distance between the shielding frame B and the edge of the ultra-thin glass substrate is D2; when plating the back electrode, the distance between the shielding frame C and the edge of the ultra-thin glass substrate is D3; the only difference is that as Figure 6 , D3 > D1, that is, D3 > D1 > D2 + 2 mm.

Claims

1. A manufacturing method of an ultra-thin substrate thin-film solar cell using an occlusion border, characterized in that, The shielding frame is composed of an upper frame and a lower frame of a rectangle arranged up and down in the thickness direction. The inner hole size of the rectangle of the upper frame is smaller than that of the lower frame, so as to form a stepped surface on the inner wall; the inner hole size of the rectangle of the lower frame matches the edge size of the substrate of the thin-film solar cell to be processed; the inner hole size of the rectangle of the upper frame matches the edge size of the layer to be coated of the thin-film solar cell to be processed. It includes the following steps: a. Take an ultra-thin glass substrate with a glass thickness of 0.70 mm to 0.05 mm, and clean the ultra-thin glass. b. Deposit a buffer layer on the ultra-thin glass substrate. In step b, the buffer layer is deposited with SiOx of 20 - 100 nm by plasma enhanced chemical vapor deposition. SiH4 and CO2 are used as reaction gases, the ratio of CO2 / SiH4 is between 5 and 20, and the plasma power density is between 0.03 and 0.20 W / cm2. c. Continue to deposit the front electrode on the buffer layer. Before depositing the front electrode, cover the ultra-thin glass substrate with the above-mentioned shielding frame. The lower frame of the shielding frame is positioned in cooperation with the edge of the ultra-thin glass substrate, and the upper frame of the shielding frame shields the area at a distance D1 from the edge of the ultra-thin glass substrate. Then deposit the front electrode, so that the shielded part cannot form a coating. d. Continue to deposit the absorption layer on the front electrode. Before deposition, cover it with a shielding frame of another size. The lower frame of the shielding frame is positioned in cooperation with the edge of the ultra-thin glass substrate, and the upper frame of the shielding frame shields the area at a distance D2 from the edge of the ultra-thin glass substrate. D1 is greater than D2, so as to form a gap between the upper frame and the side of the front electrode. Then deposit the absorption layer, so that the shielded part cannot be coated with the absorption layer, and at the same time, the absorption layer material enters the above gap and wraps the side of the front electrode. e. Continue to deposit the back electrode on the absorption layer. Before depositing the back electrode, cover it with a shielding frame of a third size. The lower frame of the shielding frame is positioned in cooperation with the edge of the ultra-thin glass substrate, and the upper frame of the shielding frame shields the area at a distance D3 from the edge of the ultra-thin glass substrate. D3 is greater than D2. Then deposit the back electrode, so that the substrate and the absorption layer of the shielded part cannot be coated with the back electrode. f. Lead out an electrode on the above back electrode, lead out the opposite electrode on the front electrode, and then bond and encapsulate the thin-film solar cell with a layer of glass or a light-transmitting polymer through a light-transmitting adhesive material to form a solar cell structure.

2. The manufacturing method of the ultra-thin substrate thin film solar cell according to claim 1, characterized in that, In step c, the front electrode is a metal or transparent conductive oxide thin film; preferably a boron-doped zinc oxide thin film, with a film thickness of 1.0 - 2.0 um, a visible light transmittance greater than 80%, and a sheet resistance of 10 - 20 ohm / sq.

3. The manufacturing method of the ultra-thin substrate thin film solar cell according to claim 1, characterized in that, In step d, the absorption layer is one of the structures of a PIN structure or an NIP structure of a silicon thin film, a CIGS thin film battery, a CdTe thin film battery structure, an organic semiconductor thin film, or a series stack combination of two to three of them.

4. The manufacturing method of the ultra-thin substrate thin-film solar cell according to claim 3, wherein, The absorption layer is a PIN structure of an amorphous silicon thin film, which includes P-type amorphous silicon, intrinsic amorphous silicon, N-type amorphous silicon deposited on the front electrode, and transition layers between these three layers.

5. The manufacturing method of the ultra-thin substrate thin film solar cell according to claim 1, characterized in that, In step e, the back electrode is a metal or a transparent conductive oxide film.

6. The manufacturing method of the ultra-thin substrate thin film solar cell according to claim 5, characterized in that The dimension D3 > D1 > D2 + 2 mm.

7. The manufacturing method of the ultra-thin substrate thin film solar cell according to claim 6, wherein, The back electrode is a boron-doped zinc oxide film with a film thickness of 1.0 - 2.0 μm, a visible light transmittance greater than 80%, and a sheet resistance of 10 - 20 ohm / sq.

8. The manufacturing method of the ultra-thin substrate thin film solar cell according to claim 1, characterized in that, In step f, the polymer is one of polycarbonate (PC), polyethylene terephthalate (PET), and ethylene-tetrafluoroethylene copolymer (ETFE); the bonding material is one of EVA, PVB, and silicone.

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