TWM457294U - Solar cell, module and screen printing thereof - Google Patents

Description

Solar cell, its module and printing screen

The present invention relates to a solar cell, a module thereof and a screen for printing, in particular to a twinned solar cell, a module thereof, and a screen for printing electrodes for printing a battery.

Known twinned solar cells mainly comprise: a substrate for converting light energy into electrical energy, and a front electrode and a back electrode for conducting current. The front electrode includes at least one elongated bus bar electrode and a plurality of finger electrodes laterally connected to the bus electrode. The bus electrode and the plurality of finger electrodes are manufactured by applying a conductive paste to a light receiving surface of the substrate by screen printing, and are cured by a sintering process. Wherein the screen used for printing and molding the front electrode usually comprises a mesh and a barrier layer fixed on the mesh, the barrier layer is patterned and has at least one strip and continuous a first opening, and a plurality of elongated second openings connected to the first opening, the first opening and the plurality of second openings are provided for conductive paste to pass through to form the bus electrode and the plurality of Finger electrode.

After the battery is manufactured, it must be additionally soldered (ribbon) is soldered to the bus electrode of the battery to arrange a plurality of cells in series to form a battery module. When welding, the welding bonding force between the bus electrode and the ribbon wire must be considered. If the welding bonding force between the ribbon wire and the bus electrode is not good, it is easy to cause the wire strip to fall off when the module is packaged or in subsequent use. , which in turn affects product reliability. The magnitude of the bonding force of the solder is related to the surface roughness of the bus electrode and the size of the area of the bus electrode that can be used for soldering. Moreover, because the structural design of the screen affects the shape and surface roughness of the bus electrode formed by the screen printing, how to improve the screen structure to produce a bus electrode with a large surface roughness is an important issue.

Therefore, the object of the present invention is to provide a printing screen for a structural innovation that can print a bus electrode having a high surface roughness.

Another object of the present invention is to provide a solar cell and a module thereof that can provide good solder bonding strength and improve product reliability.

Thus, the novel printing screen comprises: a mesh, and a barrier layer fixed to the mesh, the barrier layer comprising a first blocking portion and a plurality of second blocking portions. The first blocking portion has a first opening portion extending along a first direction, a plurality of second opening portions extending along a second direction different from the first direction, and a first opening portion and the first opening portion a plurality of solid portions of the region other than the second opening, and the width of the first opening is greater than the width of any of the second openings. The plurality of second blocking portions extend in the first opening portion at intervals and in parallel, each second blocking portion has a width of 20 μm to 40 μm, and the plurality of second blocking portions have a pitch of 280 μm to 840 μ. m.

The solar cell of the present invention comprises: a substrate having an opposite light receiving surface and a back surface, a front surface electrode on the light receiving surface, and a back surface electrode on the back surface. The front electrode includes a bus electrode extending in a first direction, and a plurality of finger electrodes extending in a second direction different from the first direction, the upper surface of the bus electrode having a plurality of parallel linear recesses The pitch of the plurality of linear recesses is 280 μm to 840 μm.

The solar cell module of the present invention comprises: a first plate and a second plate disposed oppositely, a plurality of solar cells arranged as described above and arranged between the first plate and the second plate, and a packaging material. The encapsulant is located between the first plate and the second plate and is wrapped around the plurality of solar cells.

The effect of the novel: through the structural improvement of the screen, a battery with structural innovation can be produced, mainly by using the plurality of second blocking portions of the screen to raise and limit the ink discharge area of the conductive paste, thereby A thicker bus electrode is formed, and the surface roughness of the printed bus electrode is improved, thereby improving the weldable area of the bus electrode and the welding bonding force, so that the welding wire can be firmly combined to improve product reliability.

1‧‧‧Mesh

11‧‧‧Network cable

2‧‧‧Block layer

21‧‧‧First barrier

211‧‧‧ first opening

212‧‧‧second opening

213‧‧‧Ministry

22‧‧‧second barrier

31‧‧‧First direction

32‧‧‧second direction

4‧‧‧ first plate

5‧‧‧Second plate

6‧‧‧Solar battery

61‧‧‧Substrate

611‧‧‧Glossy surface

612‧‧‧ back

613‧‧ ‧ emitter layer

614‧‧‧Anti-reflective layer

62‧‧‧Front electrode

621‧‧‧Concurrent electrode

622‧‧‧ finger electrodes

623‧‧‧Line type recess

63‧‧‧Back electrode

7‧‧‧Package

A1, a2, w1‧‧‧ width

D1, d2, d3‧‧‧ length

P1, p2‧‧ ‧ pitch

T‧‧‧thickness

Other features and effects of the present invention will be apparent from the following description of the drawings, wherein: FIG. 1 is a top plan view of a barrier layer of a first preferred embodiment of the novel printing screen; 2 is a partial enlarged view of FIG. 1; FIG. 3 is a partial cross-sectional view of the screen for printing, the cross-sectional position of FIG. 3 is equivalent to the position of one line of FIG. 2; and FIG. 4 is a solar battery module of the present invention. 1 is a schematic partial cross-sectional view of a first preferred embodiment; FIG. 5 is a top plan view of a solar cell of the solar cell module of the first preferred embodiment; FIG. 6 is taken along line BB of FIG. Figure 7 is a partial enlarged view of Figure 5, showing a bus electrode of the solar cell having a plurality of linear recesses; Figure 8 is a partial cross-sectional view taken along line CC of Figure 7, showing the confluence The upper surface of the electrode is a rough surface with high and low undulations; FIG. 9 is a photograph of a partial portion of the solar cell taken by an optical microscope (OM), mainly taken along the length direction of the bus electrode; and FIG. 10 is a new printing net. A partial top view of a barrier layer of one of the second preferred embodiments.

Before the present invention is described in detail, it should be noted that in the following description, similar elements are denoted by the same reference numerals.

Referring to Figures 1, 2, and 3, a first preferred embodiment of the screen for printing according to the present invention comprises: a mesh 1 (Fig. 3), and a barrier layer 2 fixed to the mesh 1.

The mesh 1 includes a plurality of interlaced network cables 11, and the intersection of any two network cables 11 may be referred to as a mesh node, and the plurality of interconnected network cables 11 The holes formed between them can be called meshes. Of course, the mesh frame 1 is also provided with a frame not shown in the figure. However, since the frame and the mesh 1 are not the improvement points of the present invention, they will not be described.

The barrier layer 2 of the present embodiment is fixed to the mesh 1 and is made of a material such as a photoresist material. The barrier layer 2 includes a first barrier portion 21 with a plurality of second barrier portions 22. The first blocking portion 21 has a plurality of first openings 211 extending along a first direction 31 and spaced apart in a second direction 32 different from the first direction 31, and a plurality of extending along the second direction 32 and The second opening portion 212 of the first opening portion 211 is connected to the solid portion 213 of the region other than the plurality of first opening portions 211 and the plurality of second opening portions 212. The plurality of first openings 211 and the plurality of second openings 212 extend through the upper and lower surfaces of the barrier layer 2 and are in the form of elongated holes. In this embodiment, the first direction 31 is perpendicular to the second direction 32. Therefore, each of the first openings 211 is perpendicular to the extending direction of each of the second openings 212, but may not be vertical when implemented.

The width a1 of each of the first openings 211 of the present embodiment is greater than the width a2 of any of the second openings 212. The a1 corresponds to the length of the first opening 211 in the second direction 32, and the a2 corresponds to the length of the second opening 212 in the first direction 31.

The plurality of second blocking portions 22 of the embodiment may be divided into three groups, and the plurality of second blocking portions 22 in each group are spaced apart from each other and extend in parallel with each of the first opening portions 211, and each of the first Both ends of the two blocking portions 22 do not contact the solid portion 213 of the first blocking portion 21. The plurality of second blocking portions 22 in each of the first opening portions 211 are spaced apart along the first direction 31, Each of the second blocking portions 22 has an elongated shape and extends along the second direction 32. Therefore, the extending direction of each of the second blocking portions 22 is perpendicular to the first direction 31, but the present invention is not limited thereto. Preferably, the width w1 of each second blocking portion 22, that is, the length of the second blocking portion 22 in the first direction 31 is 20 μm~40 μm; the length d1 of each second blocking portion 22, that is, the first The length of the second blocking portion 22 in the second direction 32 is 1.0 mm to 1.4 mm. The plurality of second blocking portions 22 in the same first opening portion 211 are periodically spaced, and the pitch p1 of the plurality of second blocking portions 22 is preferably 280 μm to 840 μm, the pitch P1 refers to the distance between the same portions of any two adjacent second blocking portions 22.

The above-mentioned w1, d1 and p1 are defined, so that the second barrier portion 22 can have a function of blocking the conductive paste appropriately, so that an electrode having a sufficient surface roughness can be screen printed. The functions of the plurality of second blocking portions 22 in the screen printing process will be described later.

The thickness of the physical portion (the portion where the hole is not formed) of the barrier layer 2 of the present embodiment, that is, the thickness t of the solid portion 213 and the plurality of second blocking portions 22 is preferably 14 μm to 20 μm. This thickness defines the aforementioned structural design of the barrier layer 2 to achieve the screen printing effect required by the present invention.

The printing screen of the present invention is used for printing and manufacturing electrodes of solar cells. First, the structure of the solar cell module and the battery will be introduced, and the effect of the innovative design of the screen will be described.

Referring to FIG. 4 and FIG. 5, a first preferred embodiment of the solar cell module of the present invention comprises: a first plate 4 and a second plate 5 disposed opposite each other, and a plurality of arrays arranged on the first plate 4 and The second plate 5 The solar cells 6 and at least one package 7 between the first plate 4 and the second plate 5 and surrounding the plurality of solar cells 6.

The first plate 4 and the second plate 5 are not particularly limited in implementation, and a glass or plastic plate may be used, and the plate on one side of the light receiving surface of the battery must be permeable to light. The material of the packaging material 7 is, for example, a light-transmissive ethylene vinyl acetate copolymer (EVA), or other related materials that can be used for solar cell module packaging.

The plurality of solar cells 6 are electrically connected through ribbons not shown. The structures of the plurality of solar cells 6 are the same, and only one of them will be described below as an example. Of course, it is absolutely necessary that several batteries in a module are not identical in structure.

Referring to FIGS. 5-8, the solar cell 6 includes a substrate 61, a front electrode 62, and a back electrode 63.

The substrate 61 has an opposite light receiving surface 611 and a back surface 612. An emitter layer 613 may be disposed on the inner side of the light receiving surface 611, and an anti-reflection layer 614 may be disposed on the emitter layer 613. The substrate 61 is, for example, a germanium substrate, and one of the substrate 61 and the emitter layer 613 is an n-type semiconductor, and the other is a p-type semiconductor, thereby forming a pn junction. The anti-reflection layer 614, for example, silicon nitride material (SiN _x), can be used to reduce reflected light to increase the amount of incident light.

The front surface electrode 62 is located on the light receiving surface 611 and includes a plurality of bus electrodes 621 extending along the first direction 31, and a plurality of finger electrodes 622 extending along the second direction 32 and connecting the bus electrodes 621. The plurality of bus electrodes 621 of the embodiment are spaced apart along the second direction 32. And all are long strips. The upper surface of each of the bus electrodes 621 is a rough surface having a high and low undulation, and the upper surface of each of the bus electrodes 621 has a plurality of linear recesses 623 which are parallel to each other (the linear recess 623 is not illustrated in FIG. 5, but is enlarged in FIG. Indicate). Each of the linear recesses 623 of the present embodiment extends along the second direction 32. Therefore, the extending direction of each of the linear recesses 623 is perpendicular to the first direction 31 and also perpendicular to the extending direction of each of the bus electrodes 621, but the implementation is not limited thereto. . The pitch p2 of the plurality of linear recesses 623 is preferably 280 μm to 840 μm, and the pitch p2 is the distance between the same portions of any two adjacent linear recesses 623, and may be, for example, any two adjacent linear patterns. The distance from the same side edge of the recess 623 is the distance from the trough to the trough. Each of the bus electrodes 621 has a sufficiently large surface roughness under the above definition of p2. In addition, the length d2 of the first line 31 perpendicular to each of the linear recesses 623 is smaller than the length d3 of the first direction 31 of the bus electrode 621. Wherein d2 is also equivalent to the length of each linear recess 623 in the second direction 32; d3 corresponds to the length of the bus electrode 621 in the second direction 32, that is, the strip-shaped width of the bus electrode 621 .

It should be noted that any two adjacent linear recesses 623 have a plurality of concave and convex structures ( FIG. 8 ), which are formed by the mesh of the mesh, because the presence of the mesh affects the mesh. The flow of the conductive paste during printing is a normal phenomenon. Moreover, the recessed depth of the linear recess 623 of the present invention is greater than the recessed depth of the structure caused by the mesh.

The back surface electrode 63 is located on the back surface 612 of the substrate 61, and cooperates with the front surface electrode 62 to output electric energy generated by the battery. However, since the back surface electrode 63 is not a modification of the present invention, it will not be described.

In the method for manufacturing the solar cell 6 of the present invention, the emitter layer 613 is formed on the inner side of the light-receiving surface 611 of the substrate 61 by a diffusion process, and then can be formed on the light-receiving surface 611 by vacuum coating. The anti-reflection layer 614 may include physical vapor deposition (PVD), chemical vapor deposition (CVD), or the like. When the front surface electrode 62 and the back surface electrode 63 are formed, a conductive paste is applied onto the light receiving surface 611 and the back surface 612 by a screen printing method, and the conductive paste is cured by molding to form the conductive paste. Front surface electrode 62 and back surface electrode 63.

When the front electrode 62 is to be fabricated, it is necessary to perform screen printing in accordance with the screen of the present invention. Referring to FIGS. 2, 6, and 7, in the screen printing, since the barrier layer 2 of the screen has a specific opening pattern, the conductive paste can be coated on the anti-reflective layer 614 through the opening portion of the barrier layer 2. The conductive paste passing through the plurality of first openings 211 of the barrier layer 2 can form the plurality of bus electrodes 621 of the battery, and the conductive paste passing through the plurality of second openings 212 of the barrier layer 2 The plurality of finger electrodes 622 of the battery can be formed. Moreover, the conductive paste is a penetrating slurry, so that the emitter layer 613 can be contacted through the anti-reflective layer 614 during sintering.

Referring to FIGS. 2, 7, and 8, further illustrated, in the screen printing process, because the plurality of spaced second blocking portions 22 are disposed in the plurality of first openings 211 of the barrier layer 2 of the screen, The plurality of second blocking portions 22 can be used to raise the mesh 1 (FIG. 3) and limit the area where the ink is discharged from the slurry, so that the flow rate of the slurry corresponding to the regions of the plurality of second blocking portions 22 is small, The portion of each of the bus electrodes 621 printed corresponding to the plurality of second blocking portions 22 will The plurality of linear recesses 623 are formed, and the pitch p2 and the length d2 of the plurality of linear recesses 623 are related to the pitch p1 and the length d1 of the second blocking portion 22. Each of the bus electrodes 621 printed by the screen of the present invention has a substantially continuous strip shape, but the upper surface of the bus electrode 621 is formed by the mesh of the mesh and the design of the plurality of second blocking portions 22. Rough surface with high and low undulations. Moreover, since the linear recess 623 is further depressed with respect to other portions of the bus electrode 621, the entire surface of the bus electrode 621 is formed with a coarse structure having a large variation, so that the roughness and surface area of the bus electrode 621 can be increased, thereby enhancing the bus electrode 621. Can be used to weld the wire with the wire, thus improving the welding bond and stability, thereby improving product reliability.

It should be noted that the front electrode 62 of the battery of the present invention may also include only one bus electrode 621. Therefore, the barrier layer 2 of the screen may be provided with only a first opening portion 211, and the first opening portion 211 is A plurality of second blocking portions 22 are provided. In addition, the solid portion 213 is not connected to both ends of each second blocking portion 22 of the screen of the embodiment, so that all the opening portions of the barrier layer 2 are connected, so that the printed plurality of bus electrodes can be ensured. The 621 is connected to the plurality of finger electrodes 622 to provide a good current collecting effect.

Referring to Fig. 9, Fig. 9 is a partial photograph of the battery of the present invention taken by an optical microscope (OM), mainly a cross-sectional photograph taken along the longitudinal direction of the bus electrode 621. This photograph shows that the upper surface of the bus electrode 621 is a rough surface and has the plurality of linear recesses 623.

Referring to Table 1, Figure 2 and Figure 7, Table 1 shows the resistance of three batteries (hereinafter referred to as Experimental Examples 1, 2, and 3, respectively) produced in the present invention and a comparative example. The tensile test and the test result of the surface roughness of the bus electrode 621. The experimental examples 1, 2, and 3 of the present invention and the battery of the comparative example were all fabricated in the same manner, except that the three experimental examples of the present invention used three screens having different pitches p1 to fabricate the bus electrode 621. The battery of the comparative example was fabricated using a conventional screen (not provided with the second barrier portion 22). Among them, the tensile test is carried out by using the AIKOH-RX50 machine provided by Japan AIKOH Co., Ltd., and the test result is expressed by the tensile strength (stretching force per unit width). The surface roughness Rz was measured using a Mutitoyo SJ-210 roughness meter and the Rz roughness measurement specification of ISO 4287-1997 was used.

It can be seen from the results of Table 1 that the surface roughness of the bus electrode 621 of the three experimental examples of the present invention is greater than 6 μm, and both of them have larger surface roughness than the comparative example, so the present invention can provide a larger welding area. Thereby increasing the welding bonding force with the welding wire, the tensile strength is large.

In summary, the novel can produce a structurally innovative battery through the structural improvement of the screen. In the present invention, the plurality of second blocking portions 22 of the screen can be used to raise and limit the ink discharge region of the conductive paste, thereby forming a thicker bus electrode 621 and enhancing the printed confluence. electrode The surface roughness of 621, in turn, improves the weldable area of the bus electrode 621 and the solder bonding force, so that the ribbon of the solder ribbon can be firmly coupled to the battery to improve product reliability.

Referring to FIG. 10, the structure of a second preferred embodiment of the novel printing screen is substantially the same as that of the first preferred embodiment, except that each second blocking portion of the barrier layer 2 of the present embodiment Both ends of 22 are connected to the solid portion 213 of the first blocking portion 21. The advantage of this structural design is that the screen printing is performed by using a doctor blade (not shown) to scrape the conductive paste so that the conductive paste passes through the screen to drop ink on the battery substrate, and the screen must have a good structure. The strength of the embodiment is such that the plurality of second blocking portions 22 are connected to the solid portion 213, so that a relatively stable connecting structure can be formed, thereby improving the structural strength and scratch resistance of the screen. It can extend the life of the screen and increase the number of times the screen is used.

The bus electrode printed using the screen of the present embodiment has an upper surface having a plurality of linear recesses respectively corresponding to the plurality of second blocking portions 22. The effect achieved by this embodiment is the same as that of the first preferred embodiment, and will not be described here.

However, the above is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention, that is, the simple equivalent changes and modifications made in accordance with the scope of the present patent application and the contents of the patent specification, All remain within the scope of this new patent.

2‧‧‧Block layer

21‧‧‧First barrier

211‧‧‧ first opening

212‧‧‧second opening

213‧‧‧Ministry

22‧‧‧second barrier

31‧‧‧First direction

32‧‧‧second direction

A1, a2, w1‧‧‧ width

D1‧‧‧ length

P1‧‧‧ pitch

Claims (8)

A screen for printing comprising: a mesh cloth and a barrier layer fixed on the mesh cloth, the barrier layer comprising: a first blocking portion having a first opening portion extending in a first direction, the number a second opening portion extending along a second direction different from the first direction, and a solid portion located in a region other than the first opening portion and the plurality of second opening portions, and the first opening portion The width is greater than the width of any of the second openings; and the plurality of second blocking portions extend in the first opening portion at intervals and in parallel with each other, and each of the second blocking portions has a width of 20 μm to 40 μm. The pitch of the two barrier portions is 280 μm to 840 μm. The screen for printing according to claim 1, wherein both ends of each of the second barrier portions of the barrier layer are connected to the solid portion. The screen for printing according to claim 1, wherein an extension direction of each of the second barrier portions of the barrier layer is perpendicular to the first direction. The screen for printing according to any one of claims 1 to 3, wherein the thickness of the solid portion of the barrier layer is 14 μm to 20 μm. A solar cell comprising: a substrate having an opposite light receiving surface and a back surface; a front electrode disposed on the light receiving surface and including a bus electrode extending in a first direction, and the plurality of edges different from the a finger electrode extending in a second direction of the first direction, the upper surface of the bus electrode has a plurality of linear recesses parallel to each other, and the plurality of linear recesses have a pitch of 280 μm to 840 μm; A back electrode is located on the back side. The solar cell of claim 5, wherein the extending direction of each of the linear recesses of the bus electrode is perpendicular to the first direction. The solar cell of claim 6, wherein the length of the vertical direction of each of the linear recesses is smaller than the length of the first electrode in the vertical direction of the bus electrode. A solar cell module comprising: a first plate and a second plate disposed oppositely; and a plurality of solar cells according to any one of claims 5 to 7 arranged on the first plate and the second plate And a package material between the first plate and the second plate and wrapped around the plurality of solar cells.