Gap reflective structure and solar cell

Abstract

The invention provides a gap reflective structure and a solar cell. The gap reflection structure comprises a diffuse reflection part and a directional reflection part, the directional reflection part and the diffuse reflection part are arranged in a laminated mode, and the directional reflection part is located in the middle of the gap reflection structure, or the directional reflection part is embedded in the middle of the diffuse reflection part. The overall width of the diffuse reflection part is larger than the width of the directional reflection part in at least one direction of the plane where the diffuse reflection part and the directional reflection part are located. The invention also provides a solar cell which comprises the gap reflective structure. According to the gap reflective structure, the superposition of two reflection effects is utilized, the gap light utilization efficiency of the double-sided battery can be increased to the maximum extent, the power generation efficiency of the photovoltaic module is improved, and meanwhile, obvious gaps caused by the offset of the battery string can be reduced to a certain extent.

Description

Technical Field

[0001] The present invention relates to the technical field of solar cells, and in particular to a gap reflective structure and a solar cell. Background Art

[0002] The utilization rate of light by solar cells directly determines the power generation efficiency per unit area. Therefore, in addition to increasing the light absorption and utilization of the front solar cells, it is also particularly important to make full use of the light between the cells to recycle light.

[0003] At present, the commonly used light recycling is to use the diffuse reflection effect of the white reflective glaze layer or the mirror reflection of the directional reflective film to improve the utilization rate of light energy. Among them, the white high-reflective glaze layer is a dense inorganic ceramic diffuse reflection layer that is firmly bonded to the glass through high-temperature sintering, and it needs to be constructed before the glass is tempered; the directional reflective tape is designed through the surface concave-convex structure and mirror reflection to achieve full reflection of light at a specific angle to the front of the battery cell. This solution combines the film with the glass and does not require high-temperature treatment. It can be appropriately heated to about 200°C after the glass is tempered and pasted for use. Although both have certain effects on light recycling, they still have their own disadvantages under current conditions of use:

[0004] For example, directional reflective tape can only reflect sunlight with a near vertical incident angle through the microstructure surface to the front glass surface and fully reflect the light to the front of the cell. In this case, the light energy utilization rate is relatively high, but the utilization rate of light with other incident angles is low; and due to the restrictions on the incident angle of light, the light utilization rate of directional reflective tape fluctuates greatly at different geographical locations and times, and the light utilization effect on the back of the cell is not good. Although the high-reflective glaze solution can have a good reflection effect on incident light at all angles, the utilization rate of light reflected back to the front of the cell is low due to the uncertainty of the direction of the reflected light.

[0005] Therefore, it is extremely important to consider diffuse reflection and directional reflection together and design a reflective film structure that can make full use of natural light to improve component efficiency. Summary of the invention

[0006] In order to solve the above problems, the purpose of the present invention is to provide a gap reflective structure and a solar cell. By designing the gap reflective structure, it is possible to maximize the use of natural light and comprehensively improve the utilization rate of light in the solar cell.

[0007] In order to achieve the above object, the present invention provides a gap reflective structure, which includes a diffuse reflection part and a directional reflection part;

[0008] The directional reflection part and the diffuse reflection part are arranged in the following manner:

[0009] A. The directional reflection part and the diffuse reflection part are stacked, and the directional reflection part is located in the middle of the gap reflective structure;

[0010] Or, B. the directional reflection part is nested in the middle of the diffuse reflection part;

[0011] In the above-mentioned A and B modes, along at least one direction of the plane where the diffuse reflection part and the directional reflection part are located (that is, in a direction in the same plane as the diffuse reflection part and the directional reflection part, such as Figure 3 In the x direction and / or y direction), the overall width of the diffuse reflection part is greater than the width of the directional reflection part.

[0012] In the above-mentioned gap reflective structure, when the directional reflective part is nested in the middle of the diffuse reflective part, the diffuse reflective part can be divided into several areas surrounding the directional reflective part. In this case, the overall width of the diffuse reflective part refers to the distance between two opposite edges of the diffuse reflective part ( Figure 2 d1 in the figure).

[0013] In some specific embodiments, when the directional reflection portion is nested in the diffuse reflection portion, a plane of the directional reflection portion is located at the same horizontal plane as the bottom surface of the diffuse reflection portion (e.g. Figure 2 As shown). At this time, the formation process of the gap reflective structure can be: firstly, a diffuse reflection part is formed on a substrate surface, and a space for forming a directional reflection part is reserved in the middle of the diffuse reflection part; then, a directional reflection part is formed in the reserved space to obtain the gap reflective structure. Then, a plane in the diffuse reflection part and a plane in the directional reflection part are co-located on the horizontal plane of the substrate surface. It can be understood that the above-mentioned substrate plays an auxiliary role and is not a component of the gap reflective structure.

[0014] In the above-mentioned gap reflective structure, the diffuse reflective part and the directional reflective part are combined in a stacked or nested manner to form a gap reflective structure, the directional reflective part is located in the middle of the gap reflective structure, and the diffuse reflective part is located at the edge of the gap reflective structure. In the horizontal direction, the diffuse reflective part is located on both sides of the directional reflective part (such as Figure 3 The directional reflection part can be used to reflect light with a large incident angle (such as nearly vertical incidence), and the diffuse reflection part can be used to reflect light with a small incident angle. By combining diffuse reflection and directional reflection, the reflection efficiency of the gap reflective structure for incident light can be improved.

[0015] The present invention has found that by controlling the width ratio between the directional reflection part and the gap reflective structure, the reflection efficiency of the gap reflective structure for incident light can be adjusted. When the directional reflection part is too narrow relative to the gap reflective structure (the ratio of the widths of the two is too small), the light reflection effect of the directional reflection part becomes weak, affecting the reflection efficiency of the gap reflective structure for light with a larger incident angle; when the directional reflection part is too wide relative to the gap reflective structure (the ratio of the widths of the two is too large), the area of ​​the diffuse reflection part is too small, and the reflection efficiency of the diffuse reflection part decreases, affecting the utilization rate of the gap reflective structure for incident light with a smaller incident angle. The present invention can make the gap reflective structure have a higher reflection efficiency for incident light with a larger incident angle and a smaller incident angle by controlling the width ratio of the directional reflection part to the gap reflective structure to (0.6-0.8):(1-2) (i.e., 0.3-0.8:1). In some specific embodiments, the width ratio of the directional reflection portion to the gap reflective structure can be specific values ​​such as 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, and a range with any two of the above specific values ​​as endpoints.

[0016] In the above-mentioned gap reflective structure, the geometric center line of the directional reflective portion may coincide with the geometric center line of the gap reflective structure, that is, the directional reflective portion may be located in the middle of the gap reflective structure.

[0017] In the above-mentioned gap reflective structure, the total reflectivity (the sum of diffuse reflectivity and specular reflectivity) of the diffuse reflection part in the gap reflective structure is 75%-85%. The ratio of the diffuse reflectivity to the specular reflectivity of the diffuse reflection part can be greater than or equal to 9:1. That is, the diffuse reflectivity of the diffuse reflection part accounts for more than 90% of the total reflectivity of the diffuse reflection part, and the crystal surface reflectivity of the diffuse reflection part accounts for less than 10% of the total reflectivity of the diffuse reflection part.

[0018] In the above-mentioned gap reflective structure, the hundred grid intensity of the diffuse reflection part is ≤ level 1.

[0019] In the above-mentioned gap reflective structure, the diffuse reflection part is usually a planar structure.

[0020] The present invention has no special requirements for the material of the diffuse reflection part. Any material that can form a diffuse reflection part that reaches the above-mentioned total reflectivity range, diffuse reflectivity, and specular reflectivity can be used in the present invention; further, a material that simultaneously meets the above-mentioned hundred-grid intensity range can also be selected. In some specific embodiments, the material of the diffuse reflection part in the gap reflective structure includes reflective ink. The reflective ink includes high-temperature reflective ink and / or low-temperature reflective ink.

[0021] According to a specific embodiment of the present invention, when the material of the diffuse reflection part includes high temperature reflective ink, the method of forming the diffuse reflection part using the high temperature reflective ink includes: applying the high temperature reflective ink to the surface of the substrate, drying, and tempering to form the diffuse reflection part. In this method, the drying temperature can be controlled to 150-220°C, and the drying time can be controlled to 45s-90s. The tempering temperature can be controlled to 690°C-740°C, and the tempering time can be controlled to 90s-120s.

[0022] In some specific embodiments, the high temperature ink may be ink HRC-202, whose chemical composition is composed of varnish, inorganic filler and low melting point glass powder. The varnish is composed of water-based resin, solvent and organic additive; the inorganic filler is mainly composed of titanium dioxide, barium sulfate, silicon powder and other white high temperature resistant powders, with a particle size of D100≤10um; the low melting point glass powder has a Tg≤520℃ and an expansion of 65-85×10 7 / ℃.

[0023] The preparation steps of ink HRC-202 are as follows (the amount of each reagent is calculated by weight):

[0024] 1. Preparation of organic carrier

[0025] Take three kinds of water-based resins, namely, alcohol ether resin, cellulose resin and acrylic resin, and mix them evenly in a weight ratio of 1.5:3:1.5. There are 6 parts of the above water-based resins in total. Then, slowly add them into 94 parts of ether solvent while stirring. The ether solvent is a mixture of tripropylene glycol methyl ether, diethylene glycol butyl ether and dipropylene glycol methyl ether in a weight ratio of 14:70:10. Heat the water-based resin and the ether solvent to 90°C until the system is clear and transparent to obtain an organic carrier, which is then cooled for later use.

[0026] 2. Preparation of varnish

[0027] Take 100 parts of the cooled organic carrier, add 10 parts of organic additives (including 6 parts of dispersant and 4 parts of defoamer), stir evenly to form varnish, and set aside. In some specific embodiments, the dispersant is BYK180 and the defoamer is Evonik 104E.

[0028] 3. Slurry preparation

[0029] Take 22 parts of varnish, add inorganic filler (including 20 parts of titanium dioxide, 5 parts of barium sulfate, 5 parts of silica powder, and 10 parts of sintered kaolin) while stirring; add 38 parts of low-melting-point glass powder while stirring to form a semi-finished slurry;

[0030] The semi-finished slurry is rolled using a ceramic three-roller mill until the fineness is ≤10μm, and the finished slurry is obtained by filtration.

[0031] In some specific embodiments, the low temperature ink may be ink HRC-201D. The preparation steps of ink HRC-201D are as follows (the amount of each reagent is calculated in parts by weight):

[0032] 1. Preparation of organic carrier

[0033] Take polyurethane modified acrylic resin and epoxy resin, mix them in a weight ratio of 4:2, and the above-mentioned water-based resin in a total of 6 parts, mix them evenly, and slowly add them into 94 parts of ether solvent while stirring. The ether solvent is a mixture of tripropylene glycol methyl ether, diethylene glycol butyl ether and dipropylene glycol methyl ether in a weight ratio of 14:70:10. Heat the water-based resin and the ether solvent to 90°C until the system is clear and transparent to obtain an organic carrier, and let it cool for later use.

[0034] 2. Preparation of varnish

[0035] Take 100 parts of the cooled organic carrier, add 10 parts of organic additives (including 6 parts of dispersant and 4 parts of defoamer), stir evenly to form varnish, and set aside. In some specific embodiments, the dispersant is BYK180 and the defoamer is Evonik 104E.

[0036] 3. Slurry preparation

[0037] Take 20 parts of varnish, add inorganic filler (including 40 parts of titanium dioxide, 10 parts of barium sulfate, 10 parts of silicon micropowder, and 20 parts of sintered kaolin) while stirring to form a semi-finished slurry;

[0038] The semi-finished slurry is rolled using a ceramic three-roller mill until the fineness is ≤10μm, and the finished slurry is obtained by filtration.

[0039] According to a specific embodiment of the present invention, when the material of the diffuse reflection part includes low-temperature reflective ink, the method of forming the diffuse reflection part using the low-temperature reflective ink includes: applying the low-temperature reflective ink to the surface of the substrate, and drying to form the diffuse reflection part. In this method, the drying temperature can be controlled to be 180-250°C, and the drying time can be controlled to be 120s-240s.

[0040] In the above solar cell, the surface of the directional reflection part has a special structural design, which can directional reflect light with a large incident angle. In some specific embodiments, the reflection angle of the directional reflection part for incident light with an incident angle of 90° is greater than or equal to 42.5°, and the reflectivity is greater than or equal to 90%. In some specific embodiments, the wavelength of the incident light can be 380nm-1200nm.

[0041] In the above-mentioned gap reflective structure, the directional reflective portion may be a directional reflective component such as a directional reflective tape.

[0042] In the above-mentioned gap reflective structure, the surface of the directional reflective tape has a directional reflective structural design. Specifically, the directional reflective tape includes a connected adhesive layer and a directional reflective layer, and the directional reflective layer has a plurality of protrusions distributed on the plane facing away from the adhesive layer, and the protrusions are triangular prisms, and the surface of the directional reflective layer facing away from the adhesive layer and exposed to the outside is aluminum-plated. In some specific embodiments, the cross-section of the triangular prism can be a triangular prism of an isosceles triangle, and the vertex angle of the isosceles triangle is preferably 120°.

[0043] In some specific embodiments, the material of the directional reflective layer can be polyethylene terephthalate (PET), and the material of the adhesive layer can be EVA.

[0044] In some specific embodiments, the structural shape of the directional reflection portion can be the same as the structure of the light redirecting reflection film in CN114788019A (application number 202080084927.1, invention name: light redirecting film) (including a hot-melt adhesive layer, a polymer layer, and an optical reflection layer). The full text of the above-mentioned patent application is introduced here for reference.

[0045] According to a specific embodiment of the present invention, the total thickness of the directional reflective layer and the adhesive layer (the thickness does not include the protrusion height of the directional reflective layer) can be 80-140 μm, for example, 120 μm. The thickness of the directional reflective layer accounts for more than 90% of the total thickness of the directional reflective layer and the adhesive layer. Since the overall thickness of the directional reflective portion is higher than the overall thickness of the diffuse reflective portion, when the directional reflective portion is nested in the middle of the diffuse reflective portion, the upper surface of the directional reflective portion protrudes upward relative to the upper surface of the diffuse reflective portion (such as Figure 2 shown).

[0046] Furthermore, the directional reflective tape further includes an insulating layer, and the insulating layer is coated on the protruding surface of the directional reflective layer.

[0047] The above-mentioned gap reflective structure provided by the present invention is suitable for bifacial cells, that is, the above-mentioned gap reflective structure can be applied in bifacial cells.

[0048] The present invention also provides a solar cell, which comprises a front panel layer, a cell layer, a back panel layer and the above-mentioned gap reflective structure provided by the present invention, wherein the cell layer is arranged between the front panel layer and the back panel layer, the gap reflective structure is arranged on the surface of the back panel layer facing the cell layer, and the surface of the directional reflection part (exposed to the outside) in the gap reflective structure faces the cell layer; the cell layer has a gap area, the position of the gap reflective structure is opposite to the position of the gap area of ​​the cell layer (that is, the projection of the gap area in the direction of the gap reflective structure is located within the surface of the gap reflective structure), and the total width of the gap reflective structure is greater than or equal to the width of the gap area of ​​the cell layer, and the width of the directional reflection part in the gap reflective structure is less than the width of the gap area of ​​the cell layer (such as Figure 6 shown).

[0049] According to a specific embodiment of the present invention, the solar cell may further include a front adhesive film and a back adhesive film, wherein the front adhesive film is disposed between the front plate layer and the battery layer, and the back adhesive film is disposed between the battery layer and the back plate layer.

[0050] According to a specific embodiment of the present invention, the gap region of the cell layer can allow light to propagate between the front plate layer and the back plate layer. The gap region is generally located in the middle of the cell layer.

[0051] In the above solar cell, the cell layer may be a bifacial cell, the front side of the bifacial cell faces the front plate layer, and the back side of the bifacial cell faces the back plate layer.

[0052] When the interstitial reflective structure is applied to solar cells, such as Figure 6 As shown, the gap reflective structure is usually arranged in the gap area of ​​the battery layer. The directional reflective part located in the middle of the gap reflective structure can reflect the light with a large incident angle passing through the gap area of ​​the battery layer to the front plate layer, and then reflect it from the front plate layer to the front of the battery layer; the diffuse reflective part located at the edge of the gap reflective structure can diffusely reflect the light with a small incident angle, reflecting part of the light to the back of the battery layer, and reflecting the other part of the light to the front plate layer first, and then reflecting it from the front plate layer to the front of the battery layer. Through the cooperation of the diffuse reflective part and the directional reflective part, the light passing through the gap area of ​​the battery layer can reach the front and back of the battery through multiple reflections to the maximum extent, thereby improving the utilization rate of the light in the gap of the battery and improving the power of the module.

[0053] In the above solar cell, the ratio of the width of the gap reflective structure (generally the total width of the diffuse reflection part) to the width of the cell layer gap area is (1-1.5):1, for example, specific values ​​such as 1:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, and a range with any two of the above specific values ​​as endpoints, and further can be (1.1-1.5):1. The present invention has found that by controlling the width ratio of the gap reflective structure to the cell layer gap area, the power generation efficiency of the cell can be affected. Specifically, when the width of the gap reflective structure is smaller than the width of the cell layer gap area (the width ratio is less than 1:1), if displacement between cell strings occurs during the cell assembly packaging process, light leakage and the like will occur; when the gap reflective structure is too wide relative to the cell layer gap area (the width ratio is greater than 1.5:1), the gap reflective structure will cover the effective area on the back of the cell, thereby affecting the power generation efficiency of the assembly. The present invention controls the width of the gap reflective structure and the width of the gap area of ​​the battery layer to be (1-1.5):1, which can avoid light leakage on the one hand and ensure the effective area of ​​the battery cell on the other hand, thereby improving the power generation efficiency.

[0054] In the above solar cells, if the spacing between the cells is too large, the absorption of the front light will be wasted, and the cost per watt will be increased; if the spacing is too narrow, the cell strings will be offset during the packaging process, resulting in overlapping and broken pieces, etc. The width of the gap area of ​​the cell layer can be 4-10mm, for example, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm, 10mm and other specific values, and a range with any two of the above specific values ​​as endpoints; further, it can be 4-8mm.

[0055] In the above solar cell, the front plate layer may be made of a transparent material, such as glass and / or an organic transparent plate.

[0056] In the above-mentioned solar cell, the material of the backplane layer can be a transparent material, such as glass and / or an organic transparent plate. In some specific embodiments, the material of the backplane layer and the material of the diffuse reflection part can be matched with each other. For example, when the material of the backplane layer is glass, the material of the diffuse reflection part can include high-temperature reflective ink and / or low-temperature reflective ink; when the material of the backplane layer is an organic transparent plate, the material of the diffuse reflection part can be a low-temperature reflective ink.

[0057] The beneficial effects of the present invention include:

[0058] The middle position of the gap reflective structure provided by the present invention is mainly composed of a directional reflection part with a directional reflection effect, which can reflect the gap light back to the front of the battery cell in the form of directional reflection for multiple times, thereby increasing the power generation efficiency of the front side; the two side edges of the gap reflective structure are mainly composed of diffuse reflection film layers, which can not only reflect light to the front of the battery cell layer, but also reflect light to the back of the battery cell, thereby assisting in improving the power generation efficiency of the battery cell. The gap reflective structure designed by the present invention realizes the superposition of two reflection effects through the parallel or stacked design of diffuse reflection film and directional reflection film, which can maximize the utilization efficiency of the gap light of the double-sided battery, improve the power generation efficiency of the photovoltaic module, and at the same time can also reduce the obvious gap caused by the offset of the battery string to a certain extent.

[0059] The above-mentioned gap reflective structure can be used as a light recycling structure in solar cells. By selecting different reflective materials, the light reflection requirements of the glass backplane and the organic backplane can be taken into account. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Figure 1 , Figure 2 1 and 2 are side cross-sectional views of two structures of the gap reflective structure of each embodiment.

[0061] Figure 3 1 is a top view of the structure of the gap reflective structure of each embodiment.

[0062] Figure 4 Schematic diagram of the structure of the directional reflection part of each embodiment.

[0063] Figure 5 Schematic diagram of the solar cell structure of each embodiment and comparative example.

[0064] Figure 6 Schematic diagram of light propagation in solar cells of various embodiments.

[0065] Explanation of symbols: front panel layer 1, front adhesive film 2, battery cell layer 3, rear adhesive film 4, gap reflective structure 5, back panel layer 6; directional reflection part 51, diffuse reflection part 52, substrate 53, directional reflective layer 511, adhesive layer 512, insulating layer 513. DETAILED DESCRIPTION

[0066] In order to have a clearer understanding of the technical features, purposes and beneficial effects of the present invention, the technical solution of the present invention is now described in detail below, but it should not be construed as limiting the applicable scope of the present invention.

[0067] In the description of this specification, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0068] Example 1

[0069] This embodiment provides a gap reflective structure, such as Figures 1 to 3 As shown, the gap reflective structure includes a directional reflective portion 51 and a diffuse reflective portion 52. The present invention does not specifically limit the surface shapes of the directional reflective portion 51 and the diffuse reflective portion 52. In this embodiment, the surfaces of the directional reflective portion 51 and the diffuse reflective portion 52 are both rectangular ( Figure 3 ). Let the plane where the directional reflection part 51 and the diffuse reflection part 52 are located be the xy plane, then at least in the x direction, the overall width (d1) of the diffuse reflection part 52 is greater than the width (d2) of the directional reflection part 51, and the overall width of the diffuse reflection part 52 can represent the overall width of the gap reflective structure. Draw the center line along the same direction (x direction or y direction), and the geometric center line of the diffuse reflection part 52, the geometric center line of the directional reflection part 51 and the geometric center line of the gap reflective structure coincide. That is, the directional reflection part 51 is located in the middle of the gap reflective structure, and the edge of the gap reflective structure is the diffuse reflection part 52.

[0070] like Figure 1 As shown, the diffuse reflection part 52 and the directional reflection part 51 can be stacked; or, as shown in Figure 2 As shown, the directional reflection part 51 is nested in the middle of the diffuse reflection part 52. The width ratio of the gap reflective structure to the directional reflection part 51 is (1-2): (0.6-0.8).

[0071] The thickness of the diffuse reflection part 52 is 12-16 μm, and the thickness of the directional reflection part 51 is greater than that of the diffuse reflection part 52. Therefore, in the z direction, no matter the two are combined in a stacking manner or a nested manner, the surface of the directional reflection part 51 protrudes upward relative to the surface of the diffuse reflection part 52, such as Figure 1 and Figure 2 shown.

[0072] The directional reflective portion 51 of this embodiment is a directional reflective tape. The directional reflective tape can use a film with a directional reflective light function, and the typical feature is a multi-layer structure with a reflective film layer on the surface, and the film layer has an angle design feature. The directional reflective film is a multi-layer structure with a directional reflection angle design on the surface. Figure 4As shown, the directional reflective tape includes a connected adhesive layer 512 and a directional reflective layer 511. The surface of the directional reflective layer 511 facing away from the adhesive layer 512 is provided with a plurality of protrusions, and the protrusions are used to achieve a directional reflection angle. Each protrusion is a triangular prism, and the cross-section of the triangular prism along the z-axis direction is an isosceles triangle with a vertex angle of 120°. The surface of each protrusion is plated with aluminum. In this embodiment, the material of the adhesive layer 512 is EVA, and the material of the directional reflective layer 511 is PET.

[0073] Furthermore, the directional reflective tape further includes an insulating layer 513, and the insulating layer 513 is coated on the surface of the protrusion.

[0074] In the directional reflective tape, the sum of the thickness of the flat part (excluding the protrusions) of the directional reflective layer and the adhesive layer is 80-140 μm, specifically 120 μm.

[0075] The diffuse reflection part 52 is made of high temperature reflective ink (ink HRC202). The method of forming the diffuse reflection part 52 using the high temperature reflective ink is: the high temperature reflective ink is applied to the surface of the substrate 53 by screen printing or roller coating, dried at 150-220°C for 45s-90s, and then tempered in a furnace (690-740°C, 90s-120s) to form a dense glaze layer, which is the diffuse reflection part 52. The substrate of this experiment is backboard glass, and the backboard glass with the diffuse reflection part 52 on the surface is obtained.

[0076] The diffuse reflection part 52 is tested, and the reflectivity is tested by a spectrophotometer, the test wavelength is 550-650nm, and the incidence is vertical; the cross-cut strength is tested by a cross-cut knife, and the test method is GB / T9286-1998 "Scratching test for paint and varnish film". The test results are as follows:

[0077] The total reflectivity of the diffuse reflection part 52 on the back glass surface is 85%, of which the diffuse reflection and mirror reflection are 80.95% and 4.05% respectively (the diffuse reflection accounts for 95.2% of the total reflectivity). The 100-grid strength of the diffuse reflection part 52 is ≤ level 1, and it does not fall off when touched by hand. This shows that there is a strong bonding force between the diffuse reflection part 52 and the glass.

[0078] The back glass with the diffuse reflection part 52 is subjected to a PCT 96-hour test and a PID 192-hour test. The PCT 96-hour test is conducted using a high-pressure thermostat, and the test conditions are 121°C, 100% humidity, saturated vapor pressure, and continuous operation for 96 hours; the PID 192-hour test is to seal the glass with the glaze layer into a component through lamination, and the test conditions are 85°C, 85% relative humidity, direct current, and the voltage is set to 1500V, and continuous operation for 192 hours. In the above tests, the diffuse reflection part 52 has no failure conditions such as delamination and discoloration.

[0079] The surface stress of the back glass with diffuse reflection part 52 obtained in this embodiment is equivalent to the surface stress of the glass with printed ink. For example, when the thickness of the back glass is 2.0 mm, the surface stress is tested by a surface stress meter and the four-point bending is tested by a four-point bending tester. The surface stress value of the grid glass with diffuse reflection part 52 is about 70-80 MPa, and the pressure of the glass four-point bending test is greater than 130 MPa. The above results show that the diffuse reflection part 52 has no obvious effect on the load of the glass itself.

[0080] This embodiment also provides a solar cell, such as Figure 5 As shown (only used to illustrate the stacking relationship between the structures, and does not represent the actual size (including the width and thickness of each layer) and local structure (including whether there is a gap in the local area, whether the surface is protruding, etc.)), the solar cell includes a front plate layer 1, a front adhesive film 2, a battery layer 3, a gap reflective structure 5, a rear adhesive film 4 and a back plate layer 6. Among them, the front plate layer 1, the front adhesive film 2, the battery layer 3, the rear adhesive film 4 and the back plate layer 6 are stacked in sequence, and the gap reflective structure 5 is arranged between the rear adhesive film 4 and the back plate layer 6.

[0081] The materials of the front plate layer 1 and the back plate layer 6 can be glass or organic transparent plate respectively. In this embodiment, the front plate layer 1 is glass. The back plate glass used in preparing the gap reflective structure 5 is used as the back plate layer 6.

[0082] The cell layer 3 of the present embodiment is a double-sided cell, the front side of which faces the front plate layer 1 , and the back side of which faces the back plate layer 6 .

[0083] The cell layer 3 has a gap region, and the incident light reaches the surface of the backplane layer 6 through the gap region when propagating from the frontplane layer 1 to the cell layer 3 .

[0084] The gap reflective structure 5 is the above-mentioned gap reflective structure provided in this embodiment. The gap reflective structure 5 is arranged on the surface of the backplane layer 6 facing the battery cell layer 3, and the surface of the directional reflection part 51 faces the battery cell layer 3. When the directional reflection part 51 and the diffuse reflection part 52 in the gap reflective structure 5 are nested, since the thickness of the directional reflection part 51 is greater than the thickness of the diffuse reflection part 52, the directional reflection part 51 is close to the battery cell layer 3 relative to the diffuse reflection part 52; when the directional reflection part 51 and the diffuse reflection part 52 are stacked, the directional reflection part 51 is also close to the battery cell layer 3 relative to the diffuse reflection part 52. When the diffuse reflection part 52 and the directional reflection part 51 are stacked, the diffuse reflection part 52 is connected to the backplane layer 6; when the diffuse reflection part 52 and the directional reflection part 51 are nested, the surfaces of the two located on the same horizontal plane are connected to the backplane layer 6.

[0085] The position of the gap reflective structure 5 is opposite to the position of the gap region of the cell layer 3, and the width of the gap reflective structure 5 is greater than the width of the gap region (i.e., the projection of the gap region toward the gap reflective structure 5 is located within the surface of the gap reflective structure 5), so that the incident light propagating through the gap region can all reach the gap reflective structure 5. In this embodiment, the ratio of the width of the gap reflective structure 5 to the gap region is (1.1-1.5):1, and the width of the gap region is 4-8 mm.

[0086] Figure 6 Figure 1 is a schematic diagram of light propagation in a solar cell, in which the front and rear film structures are omitted. Figure 6 As shown, when light propagates inside the solar cell, the incident light first passes through the front panel layer 1 to reach the cell layer 3, and part of the incident light is reflected back to the front panel layer 1 by the cell layer 3. The light propagating to the gap area of ​​the cell layer 3 passes through the gap area to reach the gap reflective structure 5, wherein the light with a large incident angle (for example, close to vertical incidence) is mainly reflected to the front panel layer 1 by the directional reflection part 51, and is reflected once or multiple times (multiple reflections are reflections between the directional reflection part 51 and the front panel layer 1) through the path of the directional reflection part 51-front panel layer 1-cell layer 3, until all the light is reflected to the front of the cell layer 3, thereby increasing the power generation efficiency of the cell layer 3; the light with a small incident angle is mainly diffusely reflected by the diffuse reflection part 52 at the edge, and the light reflected by the diffuse reflection part 52 can be directly reflected to the back of the cell layer 3 or indirectly reflected to the front of the cell layer 3, thereby assisting in improving the power generation efficiency of the cell. The specific process of the light being indirectly reflected by the diffuse reflection part 52 to the front surface of the battery cell layer 3 is as follows: the light is first reflected by the diffuse reflection part 52 to the front plate layer 1 , and then reflected by the front plate layer 1 to the front surface of the battery cell layer 3 .

[0087] Example 2

[0088] This embodiment provides a gap reflective structure. The difference between this gap reflective structure and the gap reflective structure of Embodiment 1 is that the material of the diffuse reflection part 52 of this embodiment is changed.

[0089] Specifically, the gap reflective structure of this embodiment includes a directional reflection part 51 and a diffuse reflection part 52. The present invention does not specifically limit the surface shapes of the directional reflection part 51 and the diffuse reflection part 52. In this embodiment, the surfaces of the directional reflection part 51 and the diffuse reflection part 52 are both rectangular. Let the plane where the directional reflection part 51 and the diffuse reflection part 52 are located be the xy plane, then at least in the x direction, the overall width (d1) of the diffuse reflection part 52 is greater than the width (d2) of the directional reflection part 51. Draw a center line along the same direction (x direction or y direction), and the geometric center line of the diffuse reflection part 52 and the geometric center line of the directional reflection part 51 coincide with the geometric center line of the gap reflective structure. That is, the directional reflection part 51 is located in the middle of the gap reflective structure, and the edge of the gap reflective structure is the diffuse reflection part 52.

[0090] like Figure 1 As shown, the diffuse reflection part 52 and the directional reflection part 51 can be stacked; or, as shown in Figure 2 As shown, the directional reflection part 51 is nested in the middle of the diffuse reflection part 52. The width ratio of the gap reflective structure to the directional reflection part 51 is (1-2): (0.6-0.8).

[0091] The thickness of the diffuse reflection part 52 is 12-16 μm, and the thickness of the directional reflection part 51 is greater than that of the diffuse reflection part 52. Therefore, in the z direction, no matter the two are combined in a stacked manner or a nested manner, the surface of the directional reflection part 51 protrudes upward relative to the surface of the diffuse reflection part 52.

[0092] The directional reflective portion 51 of this embodiment is a directional reflective tape. The structure of the directional reflective tape is the same as that of the directional reflective tape in the first embodiment.

[0093] The diffuse reflection part 52 is made of low-temperature reflective ink (low-temperature ink model HRC-201D). The method of forming the diffuse reflection part 52 using the low-temperature reflective ink is: the low-temperature reflective ink is applied to the surface of the substrate 53 by screen printing or roller coating, and then low-temperature drying (drying at 180-250°C for 120s-240s) forms a reflective coating, namely the diffuse reflection part 52. The substrate 53 of this embodiment is an organic transparent backplane, and an organic transparent backplane with a diffuse reflection part 52 on the surface is obtained.

[0094] The diffuse reflection part 52 was tested, the reflectivity was tested using a spectrophotometer, and the grid strength was tested using a grid knife. The test results are as follows:

[0095] The reflectivity of the diffuse reflection part 52 on the surface of the organic transparent backplane is 75%, of which the diffuse reflection and the specular reflection are 71.43% and 3.57% respectively (the diffuse reflection accounts for 95.2% of the total reflection). The hundred grid strength is ≤ level 1, and the powder will not fall off when touched by hand. This shows that there is a strong bonding force between the diffuse reflection part 52 and the organic transparent backplane.

[0096] The organic transparent backplane with the diffuse reflection part 52 was subjected to a PCT 48-hour test and a PID 96-hour test. The test method was the same as that in Example 1. It was found that the diffuse reflection part 52 had no failure conditions such as delamination and discoloration.

[0097] This embodiment also provides a solar cell, such as Figure 5 As shown, the solar cell is similar to the solar cell structure of Example 1, except that the gap reflective structure 5 of the solar cell is the gap reflective structure prepared in this embodiment. The backplane layer 6 is made of an organic transparent backplane, so that a diffuse reflection portion 52 is formed on the surface of the backplane layer 6 by coating a low-temperature reflective ink.

[0098] Comparative Example 1

[0099] This comparative example provides a gap reflective structure, which is composed of only a diffuse reflection part.

[0100] The diffuse reflection part is printed with the same high temperature reflective ink as in Example 1 (ink HRC-202), and the method of forming the diffuse reflection part with the high temperature reflective ink is the same as in Example 1.

[0101] This comparative example also provides a solar cell, the structure of which is similar to that of the solar cell in Example 1, except that the gap reflective structure is the above-mentioned gap reflective structure prepared in this comparative example (ie, it only includes a diffuse reflection part).

[0102] In this comparative example, the positions on the backplane surface corresponding to the gap regions of the cell layers are all printed with high temperature reflective ink, and a separate diffuse reflection part is used as the gap reflective structure. The structure, position and surface orientation of the diffuse reflection part are the same as those of the diffuse reflection part in Example 1.

[0103] Comparative Example 2

[0104] This comparative example provides a gap reflective structure, which is composed only of a directional reflective portion, and the directional reflective portion is a directional reflective tape, which is the same as the directional reflective tape in Example 1 and Example 2.

[0105] This comparative example also provides a solar cell, the structure of which is similar to that of the solar cell in Example 1, except that the gap reflective structure is the above-mentioned gap reflective structure prepared in this comparative example (i.e., it only includes a directional reflection part and does not include a diffuse reflection part).

[0106] In this comparative example, all positions on the backplane surface corresponding to the gap area of ​​the cell layer are affixed with directional reflective tape, and a single directional reflective portion is used as the gap reflective structure. The position and surface orientation of the directional reflective tape are the same as those of the directional reflective tape in Examples 1 and 2.

[0107] The method of fixing the directional reflective tape to the backboard layer is: heating the backboard layer to 200°C, and using equipment to stick the directional reflective tape to the surface of the backboard layer. The backboard layer with the directional reflective tape is tested in the same way as the glaze layer, both using a spectrophotometer, vertical incidence, 550-650nm reading; the reflectivity of the sample is measured to be 92%, and the reflection angle of the reflected light is greater than or equal to 42.5°.

[0108] Comparative Example 3

[0109] This comparative example provides a gap reflective structure, which is composed of a diffuse reflection part.

[0110] The diffuse reflection part is printed with low-temperature reflective ink (the model of the low-temperature reflective ink is HRC-201D, which is the same as the low-temperature reflective ink in Example 2). The method of forming the diffuse reflection part with the low-temperature reflective ink is the same as that in Example 2.

[0111] This comparative example also provides a solar cell, the structure of which is similar to that of the solar cell in Example 2, except that the gap reflective structure is the above-mentioned gap reflective structure prepared in this comparative example (ie, it only includes a diffuse reflection part).

[0112] In this comparative example, the low-temperature reflective ink is printed on the entire surface of the backplane layer corresponding to the gap area of ​​the cell layer, and a separate diffuse reflection part is used as the gap reflective structure. The structure, position and surface orientation of the diffuse reflection part are the same as those of the diffuse reflection part in Example 2.

[0113] Comparative Example 4

[0114] This comparative example provides a solar cell, which does not include a gap reflective structure, and other structures are the same as those of the solar cells of Example 1 and Example 2. The back plate layer of the solar cell is a bare tempered glass.

[0115] Table 1 shows the test results of the power generation efficiency of the solar cells of Examples 1 to 2 and Comparative Examples 1 to 4. The "cell efficiency improvement" in Table 1 is based on the test results of Comparative Example 4 as a comparison benchmark.

[0116] The front panel layer, front adhesive film, cell layer and rear adhesive film used in the above embodiments and comparative examples are the same. Although the materials of the back panel layer are different, they have no obvious effect on the optical performance and power generation efficiency. Therefore, the difference in power generation performance in Table 1 mainly comes from the difference in the gap reflective structure.

[0117] Table 1

[0118]

[0119] It can be seen from Table 1 that the power generation efficiency of the solar cells of Examples 1 to 2 and Comparative Examples 1 to 3 with gap reflective structures is higher than that of Comparative Example 4 without gap reflective structures.

[0120] By comparing the results of Example 1 and Example 2 with Comparative Examples 1 to Comparative Examples 3, it can be seen that compared with using a single diffuse reflection part or a directional reflection part as the gap reflective structure, the gap reflective structure containing both a diffuse reflection part and a directional reflection part can further improve the power generation efficiency of the battery cell.

[0121] The above test results prove that the present invention, by combining the diffuse reflection part and the directional reflection part to form a gap reflective structure, can comprehensively utilize the two reflection modes of diffuse reflection and directional reflection to improve the utilization rate of light and significantly improve the power generation efficiency of the component.

Claims

1. A gap reflective structure, wherein: The gap reflective structure includes a diffuse reflection part and a directional reflection part; The directional reflection part and the diffuse reflection part are stacked, and the directional reflection part is located in the middle of the gap reflective structure, or the directional reflection part is nested in the middle of the diffuse reflection part; Along at least one direction of the plane where the diffuse reflection portion and the directional reflection portion are located, the overall width of the diffuse reflection portion is greater than the width of the directional reflection portion.

2. The interstitial reflective structure according to claim 1, wherein: The ratio of the width of the directional reflection portion to the width of the gap reflective structure is (0.6-0.8):(1-2).

3. The interstitial reflective structure according to claim 1, wherein: The geometric center line of the directional reflection portion coincides with the geometric center line of the gap reflective structure.

4. The interstitial reflective structure according to claim 1, wherein: The total reflectivity of the diffuse reflection part in the gap reflective structure is 75%-85%; the ratio of the diffuse reflection rate to the mirror reflection rate of the diffuse reflection part is greater than or equal to 9:

1.

5. The interstitial reflective structure according to claim 1, wherein: The material forming the diffuse reflection portion includes reflective ink.

6. The interstitial reflective structure according to claim 1, wherein: For incident light with an incident angle of 90°, the directional reflection portion has a reflection angle of reflected light that is greater than or equal to 42.5°, and a reflectivity that is greater than or equal to 90%.

7. The interstitial reflective structure according to claim 1, wherein: The directional reflection part includes a directional reflective tape, which includes a connected adhesive layer and a directional reflective layer. A plurality of protrusions are distributed on the surface of the directional reflective layer. The protrusions are triangular prisms, and the cross-section of the triangular prism is an isosceles triangle.

8. A solar cell, comprising a front plate layer, a cell layer, a back plate layer and the gap reflective structure according to any one of claims 1 to 7, wherein: The cell layer is arranged between the front plate layer and the back plate layer, the gap reflective structure is arranged on the surface of the back plate layer facing the cell layer, and the surface of the directional reflective part in the gap reflective structure faces the cell layer; The battery layer has a gap region, the position of the gap reflective structure is opposite to the position of the gap region of the battery layer, and the total width of the gap reflective structure is greater than or equal to the width of the gap region of the battery layer; Preferably, the solar cell further comprises a front adhesive film and a rear adhesive film, the front adhesive film is arranged between the front plate layer and the battery layer, and the rear adhesive film is arranged between the battery layer and the back plate layer.

9. The solar cell according to claim 8, wherein: The ratio of the total width of the gap reflective structure to the width of the gap area of ​​the battery layer is 1-1.5:

1.

10. The solar cell according to claim 8, wherein: The battery cell layer is a double-sided battery cell, the front side of the double-sided battery cell faces the front plate layer, and the back side of the double-sided battery cell faces the back plate layer.

11. The solar cell according to claim 8, wherein: The width of the gap area of ​​the battery layer is 4-10 mm.

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