Metal mesh aspect ratio optimization method based on surface modification

Abstract

The invention discloses a metal grid transverse-longitudinal ratio optimization method based on surface modification. The method comprises the following steps: acquiring a photovoltaic module comprising a front electrode; providing laser on the front electrode; protruding structures are formed at the top of the front electrode through laser induction, at least two rows of protruding structure sets form a limiting space, the width of applied liquid is limited within the distance between every two adjacent protruding structure sets, and the thickness of the applied liquid is limited within the height of formed protrusions. The inventive method induces an upwardly shaped raised structure on the top of the front electrode consisting of the material of the front electrode, which may be an irregular structure, such that the applied ink and / or paste is confined within two or more lines.

Description

Technical Field

[0001] The invention relates to the technical field of metal mesh aspect ratio optimization, and in particular to a metal mesh aspect ratio optimization method based on surface modification. Background Art

[0002] Thin-film photovoltaic modules generally consist of a back electrode, an absorber, a buffer layer / i layer, and a front electrode. In order to avoid high series resistance and the resulting high current loss, the module is usually designed as a series of monolithic interconnected cells. The specific structure is as follows Figure 1 shown.

[0003] Generally, the arrangement of batteries is as follows Figure 2 ( Figure 1 The front electrode and the back electrode in P1 and P3 are insulated, and the front electrode and the back electrode in P2 are electrically contacted, which is used for the series connection of two adjacent batteries. Since the structural areas of P1, P2, and P3 do not generate electricity, they are also called the "dead areas" of the solar cell, and the remaining areas are active units.

[0004] Figure 3 It is an integral connection of three independent batteries, and the first battery has no contact with the third battery.

[0005] In order to optimize the power conversion efficiency of solar cells, one approach often considered is to increase the transmittance of the front electrode, for example by reducing its layer thickness and increasing the generated photocurrent. However, this leads to an increase in the sheet resistance of the front electrode and, therefore, to increased conduction losses. In order to reduce such conduction losses in the front electrode, a highly conductive narrow metal grid line can be applied on the front electrode layer to increase the associated conductivity, which is known as the metallization process of photovoltaic production.

[0006] like Figure 4 As shown, since the grid line material has a lower series resistance, the application of the metal grid on the front electrode causes the charge carriers to be collected from the front electrode material, thereby concentrating the current to flow to the end of the battery. In the case of a monolithic interconnected battery, the current flowing to the end of the battery collected by the metal grid line is directly connected to the back electrode of the next battery through the P2 patterned line. Although the above metal grid structure reduces the conduction loss of the thinned front electrode, thereby offsetting the increase in series resistance. However, it also leads to an increase in the dead area due to the shadow caused by the opaque grid lines on the top of the active area.

[0007] The shaded area of ​​the absorber material below is defined by the width and length of the metal line. While the length of the metal line should not be changed to benefit from carrier collection in the metal line and a thinner front electrode (i.e., increase photocurrent without increasing series resistance), the width and thickness of the metal line can be optimized to reduce the shaded area, thereby increasing the photocurrent and efficiency of the solar cell. The relationship between the width and thickness of the metal line is called the aspect ratio.

[0008] The series resistance of a metal line is determined by the specific series resistance of its constituent materials and its cross-sectional area. Therefore, to improve the efficiency of a solar cell, the width of the metal line should be reduced to reduce light shading, while the thickness of the metal line should be increased to prevent conduction losses.

[0009] In the prior art, commercial thin-film / CIGS photovoltaic manufacturers and their related research institutions have introduced their methods for depositing metal grid structures on the front electrodes of CIGS modules. This method is called ALD (i.e. aluminum wire deposition), which is a method of mask-depositing aluminum wire structures by thermal evaporation. The resulting structure is as follows Figure 5 As shown, the various disadvantages here are:

[0010] 1) The production volume and yield of using masks are low;

[0011] 2) The cost of such special masks for producing large area modules is high;

[0012] 3) Material waste and high evaporation;

[0013] 4) The maintenance workload of the mask is high, which is most important for the efficiency of solar cells;

[0014] 5) Limitation of metal grid line width (and aspect ratio) (the mask opening is too narrow, less than a few hundred micrometers and is easily clogged during or after use).

[0015] Another metallization process is screen printing to deposit metal grid lines, but the screen printing method is not suitable for large-area printing. It has a key technical limitation, that is, larger printing patterns will lead to lower deposition accuracy and poorer line shape (i.e., wider lines), especially in the middle area of ​​large-size printing areas (e.g., >1㎡). This is due to the low stiffness of the central screen of the large area (i.e., bending effect). In addition, the use of screen printing to print narrow lines requires high-quality screens (e.g., hardened and calendered stainless steel screens or knotless screens). For full-size thin-film solar cell modules (e.g., >1㎡), those high-quality large-size screens are very difficult to manufacture. Currently, no more than two suppliers in the world can do it, and it is very expensive. In addition, the screens used in the grid printing process are easily blocked and difficult to clean. Usually, for si-pv6 "x6" screens, they will be scrapped if they are not cleaned after some printing. In addition to the high cost of screen printing for large thin-film modules, it is also inflexible to change the printing pattern of the grid lines in case the production samples need to adjust the line spacing.

[0016] In addition to the traditional screen printing method, the prior art also shows an alternative rotary screen printing for conductive metal grid line deposition, but this technology is currently only applicable to SI-PV6 "x6" wafers. For the application of large-area thin-film components, the problem is similar to that of traditional screen printing. For larger printing widths such as 600-1300mm, the selected rotary tube material is difficult to maintain sufficient rigidity, which seriously affects the deposition accuracy and the related grid line width.

[0017] The electron beam evaporation process is only suitable for laboratory-scale metal grid line production and cannot be mass-produced. Therefore, a full-area coating process is required. Using this method has similar problems and limitations as using the vapor deposition method; the main ones are low production volume and high cost.

[0018] Other process methods, such as aerosol jet printing or dispensing, are new technologies for metallization processes and have strong process stability issues. The nozzles used for aerosol jetting and dispensers are easily blocked by metal particles during long-term printing, resulting in frequent process downtime. In addition, these two methods are still in the early stages of development and can only print 5 to 10 grid lines at most. For printing on large-area thin film modules, multiple printings are required, that is, the current throughput of aerosol jet printing is very low, and it is very difficult to further increase the number of nozzles used for dispensing or aerosol jetting. Therefore, the slurry / aerosol distribution in the horizontal direction in the print head is extremely challenging. Currently, the 10-nozzle technology is the bottleneck of these two technologies.

[0019] Inkjet printing is a metallization method suitable for photovoltaic modules (such as thin film PV, organic PV or silicon solar cells, etc.). The use of inkjet printing allows a variety of line shapes and forms because it is a digital printing technology. This also makes it suitable for large-scale applications, especially thin film photovoltaics. A major disadvantage of this technology is that the composition of the ink contains a small amount of metal particles and a large amount of solvent. This usually results in wide and thin lines on top of the front electrode of the solar cell. In addition, due to e.g. Figure 6 Coffee ring effect shown, where the edges of the jetted ink line are thicker than the middle of the line.

[0020] The existing proposed methods for making metal grid lines on top of the front electrode of solar cells all have a common solvent-based ink or paste, and they are all formulated according to the actual application process and vary according to the ratio of metal to solvent. The width of the metal grid line depends largely on the surface energy and wettability of the ink. This obviously limits the material used as the front electrode and / or the surface formation and / or surface treatment to obtain an optimized aspect ratio. In addition, the shape of the applied line may change after deposition because the metal grid line must be heated to remove the solvent and improve the conductivity. Simply reducing the ratio of solvent to metal, i.e. reconfiguration, may reduce the width of the line, but will always lead to clogging of the print head or the grid, respectively. Another possible way to reduce the line width by using less material or smaller droplets will also lead to thinning of the line, thereby increasing the series resistance. To overcome this problem, multi-channel solutions usually keep the line width small and increase the thickness of the metal line. However, especially for high-speed mass production with high throughput, this method has a significant disadvantage that the produced metal lines will be scattered, that is, the produced metal grid lines are not aligned.

[0021] Therefore, we provide a metal mesh aspect ratio optimization method based on surface modification to solve the above problems. Summary of the invention

[0022] In response to the problems existing in the above-mentioned prior art, the present invention provides a metal grid aspect ratio optimization method based on surface modification. The purpose of this optimization method is to apply metal grid lines with minimum width and sufficient thickness to reduce the shadow of the metal lines and ensure low series resistance. The purpose disclosed in the present invention is to optimize the aspect ratio by modifying the surface of the front electrode.

[0023] In order to achieve the above object, the present invention adopts a metal mesh aspect ratio optimization method based on surface modification, comprising:

[0024] obtaining a photovoltaic module including a front electrode;

[0025] providing a laser on the front electrode;

[0026] A protruding structure is formed on the top of the front electrode by laser induction, and at least two rows of protruding structure groups constitute a limited space. The width of the applied liquid is limited to the spacing between two adjacent protruding structure groups, and the thickness of the applied liquid is limited to the height of the formed protrusion and the surface tension of the liquid.

[0027] In detail, the method of the present invention induces an upwardly shaped protruding structure on top of the front electrode composed of the material of the front electrode, and the protruding structure may be an irregular structure, so that the applied ink and / or paste is confined to two or more lines.

[0028] In detail, the formed protrusion structures usually have irregular shapes with heights ranging from hundreds of nanometers to micrometers, mainly depending on the thickness of the buffer layer and the front electrode, and some protrusions may have small cracks, indicating that the evaporated material has been exhausted. Their width is in the range of hundreds of nanometers.

[0029] In detail, the width of the formed protrusions is in the range of 10 μm, resulting in a minimum distance between two lines of about 10 μm.

[0030] Furthermore, the above-mentioned surface modification-based metal mesh aspect ratio optimization method can be used for single-pass technology, and can also be used for various application methods such as inkjet process, including aerosol jetting, screen printing, dispensing, etc.

[0031] In particular, the present invention helps prevent line widening due to small deviations in high-speed alignment of ink application in mass production.

[0032] As a special section of the above-mentioned metal mesh aspect ratio optimization method based on surface modification, the following discussion is made:

[0033] 1. Forming symmetrical or asymmetrical protrusion arrays:

[0034] 1) In the form of two or more lines;

[0035] 2) In the formed metal wire, the minimum distance between each protrusion structure is limited to or less than a certain range, and specifically, the range is small enough to allow capillary force to limit the applied liquid;

[0036] 3) The variation of the protrusion groups in two adjacent rows is small, that is, the applied liquid is limited to the gap formed by the two adjacent rows of protrusion arrays.

[0037] 2. The applied liquid is confined to two or more lines:

[0038] 1) In particular, the gap between two adjacent rows of protrusion groups is smaller than the width of the metal line on the untreated surface;

[0039] 2) In particular, the minimum distance between two adjacent rows of protrusion groups is 10 μm;

[0040] 3) The gap between two adjacent protrusions in the same row is small so that the capillary force can limit the applied liquid.

[0041] 3. The height of the raised structure is sufficient to confine the applied liquid:

[0042] 1) The tension aspect depends on the liquid used;

[0043] 2) Due to limiting surface tension and other aspects, the height of the protruding structure can be smaller than the final thickness of the metal grid line.

[0044] The method of producing the above-mentioned raised structure is discussed below:

[0045] 1. Use pulse laser processing.

[0046] 2. The wavelength of the laser is higher than the optical band gap of at least the upper material. It should be noted that the upper material does not absorb the laser. Generally, the upper material refers to the front electrode or buffer layer / i layer, absorber.

[0047] Further, the wavelength of the laser is lower than the optical band gap of one of the subsequent layers of material to melt / evaporate the material on the inner surface to protrude the material to the top. It should be noted that the subsequent layer of the material absorbs the laser. Generally, the subsequent layer is at the interface between the absorber and the buffer layer.

[0048] 3. Select the laser power within the range of forming the raised structure. It should be noted that if the laser power is too high, it will cause ablation, and if it is too low, it may cause the raised structure not to be formed.

[0049] 4. Generally, various thin film technologies consist of at least two layers, and it is desirable to apply lines of smaller width on top of one of the layers.

[0050] 5. Photovoltaic modules such as CIGS, CdTe and perovskite can be selected.

[0051] 6. The substrate is configured with a thin film PV module and a cover layer.

[0052] 7. Metal mesh processes that apply liquid, solvent or water-based metal wires include inkjet, aerosol jet, screen printing and dispensing.

[0053] 8. The material of the applied liquid is generally liquid, and can also be metallic ink and node ink.

[0054] 9. The liquid can be applied once and / or multiple times.

[0055] 10. The metal grid aspect ratio optimization method based on surface modification of the present invention is applicable to the metal grid line design of the front electrode and / or the back electrode (substrate or substrate structure).

[0056] In order to achieve the above-mentioned object, the photovoltaic module based on surface-modified metal grid aspect ratio adopted by the present invention comprises:

[0057] front electrode;

[0058] A protrusion group is formed on the front electrode, the protrusion group includes at least two protrusion structures, at least two rows of protrusion groups form a group of protrusions, a gap is formed between two adjacent protrusion groups to limit the width of the applied liquid, and a height difference is formed between the top of the protrusion and the upper surface of the front electrode to limit the higher thickness of the applied liquid, wherein:

[0059] The protrusions are formed by the front electrode under laser induction.

[0060] In detail, the above-mentioned front electrode includes a liquid application area and a liquid leakage prohibited area, and the above-mentioned liquid application area includes liquid, front electrode, buffer layer, absorber and back electrode or liquid, front electrode and back electrode in sequence along the thickness direction, and the above-mentioned liquid leakage prohibited area includes the back electrode along the thickness direction.

[0061] In detail, the wavelength of the laser light is higher than the optical band gap of the front electrode material and the wavelength of the laser light is lower than the optical band gap of the material at the interface between the buffer layer and the absorber.

[0062] In detail, the protrusion arrangement includes parallel, staggered and random order, the distance between two adjacent rows of protrusion groups is greater than 10 μm, and the distance between two adjacent protrusion structures in the same row can be 50 nm.

[0063] In detail, the laser is a pulse laser.

[0064] The metal mesh aspect ratio optimization method based on surface modification of the present invention has the following beneficial effects:

[0065] The present invention proposes a metal grid aspect ratio optimization method based on surface modification. The purpose of this optimization method is to apply metal grid lines with minimum width and sufficient thickness to reduce the shadow of the metal lines and ensure low series resistance. The purpose of the present invention is to optimize the aspect ratio by modifying the surface of the front electrode.

[0066] The present invention proposes a photovoltaic module based on surface modification of the aspect ratio of a metal grid to modify the surface of a front electrode, especially a thin-film solar cell, so as to increase the aspect ratio of the metal grid line.

[0067] With reference to the following description and drawings, a specific embodiment of the present invention is disclosed in detail, indicating the manner in which the principle of the present invention can be adopted. It should be understood that the scope of the embodiment of the present invention is not limited thereby, and the embodiment of the present invention includes many changes, modifications and equivalents. BRIEF DESCRIPTION OF THE DRAWINGS

[0068] Figure 1 A schematic diagram of a stacked structure of a thin-film solar cell commonly used in the background art;

[0069] Figure 2 Schematic diagram of the cell width and dead zone of a standard thin-film solar cell in the background technology, and Figure 1 Top view of;

[0070] Figure 3 It is a schematic diagram of the top view of the interconnection structure of three cells of a standard thin-film PV module in the background art;

[0071] Figure 4 A schematic diagram of the current at a metal grid in a battery in the background technology;

[0072] Figure 5 A schematic diagram of an ALD (aluminum line deposition) process used in the background art;

[0073] Figure 6 a) is a schematic diagram of inkjet application of solar cell front electrode in the background technology;

[0074] Figure 6 b) is a schematic diagram of the distribution of the oil film (i.e., ink) on the top of the front electrode in the background technology;

[0075] Figure 7 a) The present invention applies pulsed laser below the band gap of the front electrode and the buffer layer at two points on the surface to cause Figure 7 b) the material protrusion of the front electrode and buffer layer on top of the solar cell surface;

[0076] Figure 8a ) is a pseudo-color grayscale 2D image taken by confocal microscopy in the present invention, showing the protrusions formed on the front electrode;

[0077] Figure 8b ) is a pseudo-color grayscale 3D image taken by a confocal microscope in the present invention, Figure 8a ) visualization;

[0078] Fig. 9 A cross-sectional image of two rows of protrusions formed on the top of the front electrode of the present invention;

[0079] Fig.10 a) applying ink between protrusions formed on the surface of the thin film solar cell;

[0080] Fig.10 b) The formed protrusions confine and evenly distribute the ink;

[0081] Fig.11 a) an array of protrusions formed in a symmetrical manner;

[0082] Fig.11b) an array of protrusions formed in a staggered manner;

[0083] Fig.11 c) a protrusion array formed in a random manner;

[0084] Fig.12 It is a bottom-up cross-sectional schematic diagram of a thin-film solar cell stack with a metal network grid in the present invention;

[0085] Fig.13 A schematic top view of the grid width and grid spacing of a thin-film solar cell having a metal network grid in the present invention;

[0086] Fig.14 Schematic diagram of top view of interconnection of three cells of the thin-film PV module with metal grid in the present invention. DETAILED DESCRIPTION

[0087] In order to make the purpose, technical solution and advantages of the present invention more clear, the present invention is further described in detail below through the accompanying drawings and embodiments. However, it should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the scope of the present invention.

[0088] It should be noted that when an element is referred to as being "disposed on, provided with" another element, it may be directly on the other element or there may also be a central element. When an element is considered to be "connected, connected to" another element, it may be directly connected to the other element or there may be a central element at the same time. "Fixed connection" means a fixed connection. There are many ways of fixed connection, which are not within the scope of protection of this article. The terms "vertical", "horizontal", "left", "right" and similar expressions used in this article are for illustrative purposes only and do not represent the only implementation method.

[0089] Unless otherwise defined, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs. The terms used in the specification are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0090] In order to reduce Figure 6 In view of the widening of the metal lines shown, we propose a method to shape a portion of the front electrode, namely a metal grid aspect ratio optimization method based on surface modification, the method of the present invention is used to induce an upwardly formed regular or irregular raised structure on top of the front electrode composed of the material of the front electrode, in such a way that the applied ink and / or paste is confined to two or more lines.

[0091] DETAILED DESCRIPTION OF THE EMBODIMENTS The metal mesh aspect ratio optimization method based on surface modification of the present invention is described with reference to the accompanying drawings, as shown in FIG. Figure 7 The reasons for the formation of the convex structure are as follows: Figure 7 a) shows the application of pulsed laser below the band gap of the front electrode and buffer layer at two points on the surface. Figure 7 b) Material protrusions of the front electrode and buffer layer on top of the solar cell surface. Specifically, we tested a method of applying a pulsed laser of about 15ps with a wavelength of 1064nm on a thin-film CIGS solar cell. The laser is not absorbed by the TCO and the buffer layer, because the energy of the laser is significantly lower than the band gap of the corresponding materials. Therefore, the laser passes through the upper layer and is absorbed at the interface between the absorber layer and the buffer layer, because the band gap of the absorber layer is lower than the laser energy. The absorption of a single laser pulse leads to local melting and evaporation of the absorber and buffer layer materials within the stack. The power of the laser beam must be selected in such a way that a small protrusion is formed on the surface of the front electrode. Too low a power leads to only local heating, without any limiting effect since no protrusion is produced. Too high a power leads to complete ablation of the buffer layer and the front electrode layer, which leads to widening of the line and an increase in the series resistance of the interconnect area. The thickness between the metal grid and the front electrode is greatly reduced (the ink / paste material will fill the resulting holes). It should be noted that the maximum thickness of the protrusion is the total thickness of the front electrode layer, buffer layer / i layer. The laser power used to form the desired protrusions depends primarily on the thickness of the buffer layer and the front electrode, as well as the material composition, including aspects such as hardness, stiffness, tension, adhesion, etc.

[0092] Figure 8 and Fig. 9 An image depicting this raised structure formed on top of the front electrode of a thin-film solar cell.

[0093] Specifically, FIG8 is a pseudo-color grayscale image taken by a confocal microscope. Figure 8a ) is a 2D image, Figure 8b ) is a 3D image. The constraint condition is to form two groups of protrusions on the top of the front electrode to form a limit for the applied liquid. The liquid can be ink or slurry. The structure shown is generated when the target distance is 20μm.

[0094] Fig. 9 Cross-sectional image of two rows of protrusions formed on top of the front electrode. The structure shown was generated at a target distance of 10μm. The average height of the protrusions achieved was approximately 170nm, with the maximum height value above 170nm. The width of the resulting protrusion structure was approximately in the 10μm range.

[0095] Furthermore, the formed raised structures typically have irregular shapes with heights ranging from hundreds of nanometers to micrometers, depending on the thickness of the buffer layer and the front electrode, wherein small cracks may appear in some raised structures, indicating that the evaporated material has been exhausted, and the width of the above-mentioned raised structures is in the range of hundreds of nanometers.

[0096] Furthermore, the form of the above-mentioned protruding structure is adjusted according to the liquid used and the required width and thickness of the resulting metal grid line. The liquid includes ink or paste. In some tests, the width of the formed protruding structure is in the range of 10 μm, resulting in a minimum distance of about 10 μm between two adjacent rows of protruding groups. Fig. 9 As shown, a distance below the above will form a single protruding structure without a confined space filled with liquid.

[0097] Fig.10 It shows that the confined space formed by two or more rows of protrusion groups within a certain distance can confine and fill the liquid. Specifically, Fig.10 a) shows the application of liquid and Fig.10 b) shows the raised structures showing and evenly distributing the ink.

[0098] Fig.11 A possible embodiment of forming a raised structure using a pulsed laser is shown. Specifically, Fig.11 In the figure, the distance between two rows of protrusion groups is defined as w1, which also identifies the width of the metal grid line. The distance w2 is the spacing between two adjacent protrusion structures in the same row. The spacing setting must be small enough to ensure that the capillary force can confine the liquid within the two lines, that is, there is no leakage between two adjacent protrusion structures in the same row.

[0099] Specifically, Fig.11 a) shows a symmetrical array of protrusions, Fig.11 b) shows a staggered array of protrusions, Fig.11 c) shows a shuffled array of bumps.

[0100] It should be noted that the above-mentioned protrusion array can also be identified as a protrusion arrangement.

[0101] Furthermore, in FIG8 and Fig. 9 The example shown in , with a distance w1 of tens of microns, a distance w2 in the range of several microns, and a height of several hundred nanometers, is particularly suitable for inkjet applications, mainly because the distance w2 is small enough so that the capillary force truly confines the ink within the two generated lines, and the height is sufficient to prevent the material from overflowing the raised structure.

[0102] Of course, the above-mentioned surface modification-based metal grid aspect ratio optimization method can be applied to single-pass technology as well as multiple technologies, especially inkjet process. In particular, the present invention helps to prevent line widening due to small deviations in high-speed alignment of ink application in large-scale production.

[0103] Figure 12-14 A metal grid representation is shown, specifically, Fig.12 A cross-sectional view of a stack of thin-film solar cells having a metal grid line structure is shown. Fig.13 A schematic top view showing the grid width and grid spacing of a thin-film solar cell having a metal grid; Fig.14 A top view showing the interconnection of three cells of a thin film PV module with a metal grid.

[0104] In detail, Figure 12-14 In the figure, a metal gridline structure is applied at periodic intervals laterally to the cell or perpendicularly to P1, P2 and P3, which are continuously applied to the solar cell, and P3 interrupts the metal gridlines to prevent a short circuit between the front electrode of one cell and the front electrode of its adjacent cell.

[0105] In combination with the above, the following discussion is made as a special part of the above-mentioned metal mesh aspect ratio optimization method based on surface modification:

[0106] 1. Forming symmetrical or asymmetrical protrusion arrays:

[0107] 1) In the form of two or more lines;

[0108] 2) In the formed metal wire, the minimum distance between each protrusion structure is limited to or less than a certain range, and specifically, the range is small enough to allow capillary force to limit the applied liquid;

[0109] 3) The variation of the protrusion groups in two adjacent rows is small, that is, the applied liquid is limited to the gap formed by the two adjacent rows of protrusion arrays.

[0110] 2. The applied liquid is confined to two or more lines:

[0111] 1) In particular, the gap between two adjacent rows of protrusion groups is smaller than the width of the metal line on the untreated surface;

[0112] 2) In particular, the minimum distance between two adjacent rows of protrusion groups is 10 μm;

[0113] 3) The gap between two adjacent protrusion structures in the same row is small so that the capillary force can limit the applied liquid. It should be noted that in the case of CIGS, it is a few microns.

[0114] 3. The height of the raised structure is sufficient to confine the applied liquid:

[0115] 1) The tension aspect depends on the liquid used;

[0116] 2) Due to limiting surface tension and other aspects, the height of the protruding structure can be smaller than the final thickness of the metal grid line.

[0117] The method of producing the above-mentioned raised structure is discussed below:

[0118] 1. Use pulse laser processing.

[0119] 2. The wavelength of the laser is higher than the optical bandgap of at least the upper material. It should be noted that the upper material does not absorb the laser or absorbs only a small amount of the laser (e.g., less than 20%). Usually, the upper material generally refers to the front electrode and / or buffer layer / i layer and / or absorption layer.

[0120] Further, the wavelength of the laser is lower than the optical band gap of one of the subsequent layers of material to melt / evaporate the material on the inner surface to protrude the material. It should be noted that the subsequent layer of the material absorbs the laser, and generally, the subsequent layer is at the interface between the absorber and the buffer layer.

[0121] 3. Select the laser power within the range of forming the raised structure. It should be noted that if the laser power is too high, it will cause ablation, and if it is too low, it may cause the raised structure not to be formed.

[0122] 4. Generally, various thin film technologies consist of at least two layers, and it is desirable to apply lines of smaller width on top of one of the layers.

[0123] 5. Photovoltaic modules such as CIGS, CdTe and perovskite can be selected.

[0124] 6. The substrate is configured with a thin film PV module and a cover layer.

[0125] 7. Metal mesh processes that apply liquid, solvent or water-based metal wires include inkjet, aerosol jet, screen printing and dispensing.

[0126] 8. The material of the applied liquid is generally liquid, and can also be metallic ink and node ink.

[0127] 9. The liquid can be applied once and / or multiple times.

[0128] 10. The metal grid aspect ratio optimization method based on surface modification of the present invention is applicable to the metal grid line design of the front electrode and / or the back electrode (substrate or substrate structure).

[0129] The following examples are provided for the method of the above-mentioned raised structure:

[0130] Take CIGS with 750nmAZO and 65nmZnOS thickness as an example:

[0131] The process window is 1064nm wavelength, 15ps laser pulse, 500kHz repetition rate, 10800mm / min speed, and a beam diameter of about 20μm (2w0), with a laser power between 150mW and 250mW.

[0132] Furthermore, the photovoltaic module based on surface-modified metal grid aspect ratio adopted by the present invention comprises:

[0133] front electrode;

[0134] A protrusion group is formed on the front electrode, the protrusion group includes at least two protrusion structures, at least two rows of protrusion groups form a group of protrusions, a gap for limiting the width of the applied liquid is formed between two adjacent protrusion groups, and a height difference for limiting the thickness of the applied liquid is formed between the top of the protrusion and the upper surface of the front electrode, wherein:

[0135] The protrusions are formed by the front electrode under laser induction.

[0136] In detail, the above-mentioned front electrode includes a liquid application area and a liquid leakage prohibited area, and the above-mentioned liquid application area includes liquid, front electrode, buffer layer, absorber and back electrode or liquid, front electrode and back electrode in sequence along the thickness direction, and the above-mentioned liquid leakage prohibited area includes the back electrode along the thickness direction.

[0137] In detail, the wavelength of the laser light is higher than the optical band gap of the front electrode material and the wavelength of the laser light is lower than the optical band gap of the material at the interface between the buffer layer and the absorber.

[0138] In detail, the protrusion arrangement includes parallel, staggered and random order, the distance between two adjacent rows of protrusion groups is greater than 10 μm, and the distance between two adjacent protrusion structures in the same row can be 50 nm.

[0139] In detail, the laser is a pulse laser.

[0140] It should be noted that, in the drawings, the front electrode is marked with reference numeral 1 , the buffer layer is marked with reference numeral 2 , the absorber is marked with reference numeral 3 , and the back electrode is marked with reference numeral 4 .

[0141] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modification, equivalent substitution or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A metal mesh aspect ratio optimization method based on surface modification, characterized in that: include: obtaining a photovoltaic module including a front electrode; providing a laser on the front electrode; A convex structure is formed on the top of the front electrode by laser induction, and at least two rows of convex structure groups form a limited space, and the width of the applied liquid is limited within the spacing between two adjacent convex structure groups.

2. The metal mesh aspect ratio optimization method based on surface modification according to claim 1, characterized in that: The wavelength of the laser light is higher than the optical band gap of the front electrode material.

3. The metal mesh aspect ratio optimization method based on surface modification according to claim 2, characterized in that: The wavelength of the laser light is lower than the optical band gap of the material at the interface between the buffer layer and the absorber.

4. The metal mesh aspect ratio optimization method based on surface modification according to claim 3, characterized in that: The laser light is absorbed at the interface between the buffer layer and the absorber so that the protrusion protrudes upward from the interface between the buffer layer and the absorber and passes through the front electrode.

5. The metal mesh aspect ratio optimization method based on surface modification according to claim 4, characterized in that: At least two rows of protrusion groups form a symmetrical first protrusion array.

6. The metal mesh aspect ratio optimization method based on surface modification according to claim 4, characterized in that: At least two rows of protrusion groups form a staggered second protrusion array.

7. The metal mesh aspect ratio optimization method based on surface modification according to claim 4, characterized in that: At least two rows of protrusion groups form a third random protrusion array.

8. The method for optimizing the aspect ratio of a metal mesh based on surface modification according to any one of claims 5 to 7, characterized in that: The protrusion array is at least in two rows.

9. The metal mesh aspect ratio optimization method based on surface modification according to claim 8, characterized in that: The distance between two adjacent rows of protrusion groups is greater than 10 μm.

10. The metal mesh aspect ratio optimization method based on surface modification according to claim 9, characterized in that: The distance between two adjacent protrusion structures in the same row is 50 nm.

11. The metal mesh aspect ratio optimization method based on surface modification according to claim 10, characterized in that: The photovoltaic component comprises a P1 region, a P2 region and a P3 region, and the P3 region interrupts the applied liquid.

12. The metal mesh aspect ratio optimization method based on surface modification according to claim 11, characterized in that: The P1 region includes liquid, front electrode, buffer layer, absorber and back electrode in sequence along the thickness direction; The P2 region includes a liquid, a front electrode and a back electrode in sequence along the thickness direction; The P3 region includes a back electrode along a thickness direction.

13. A photovoltaic module based on surface modification of the aspect ratio of a metal grid, characterized in that: include: front electrode; A protrusion group is formed on the front electrode, the protrusion group includes at least two protrusion structures, at least two rows of protrusion groups form a protrusion arrangement, a gap is formed between two adjacent protrusion groups to limit the width of applied liquid, and a height difference is formed between the top of the protrusion and the upper surface of the front electrode to limit the thickness of applied liquid.

14. The photovoltaic module based on surface modification of metal grid aspect ratio according to claim 13, characterized in that: The front electrode includes a liquid application area and a liquid leakage prohibition area.

15. The photovoltaic module based on surface modification of metal grid aspect ratio according to claim 14, characterized in that: The liquid application area includes liquid, front electrode, buffer layer, absorber and back electrode or liquid, front electrode and back electrode in sequence along the thickness direction; The liquid leakage prohibited area includes the back electrode in the thickness direction.

16. The photovoltaic module based on surface modification of metal grid aspect ratio according to claim 15, characterized in that: The protruding structure is formed by the front electrode under laser induction.

17. The photovoltaic module based on surface modification of metal grid aspect ratio according to claim 16, characterized in that: The wavelength of the laser light is higher than the optical band gap of the front electrode material and the wavelength of the laser light is lower than the optical band gap of the material at the interface between the buffer layer and the absorber.

18. The photovoltaic module based on surface modification of metal grid aspect ratio according to claim 17, characterized in that: The laser light is absorbed at the interface between the buffer layer and the absorber so that the protrusion protrudes upward from the interface between the buffer layer and the absorber and passes through the front electrode.

19. The photovoltaic module based on surface modification of metal grid aspect ratio according to claim 18, characterized in that: The above-mentioned protrusion arrangement includes parallel, staggered and random order.

20. The photovoltaic module based on surface-modified metal grid aspect ratio according to claim 19, characterized in that: The distance between two adjacent rows of protrusion groups is greater than 10 μm.

21. The photovoltaic module based on surface-modified metal grid aspect ratio according to claim 20, characterized in that: The above laser is a pulse laser.

22. The photovoltaic module based on surface-modified metal grid aspect ratio according to claim 21, characterized in that: The above photovoltaic modules include CIGS, CdTe and perovskite.

23. The photovoltaic module based on surface-modified metal grid aspect ratio according to claim 22, characterized in that: The above-mentioned liquid includes metallic ink or dielectric ink.

24. Application of a metal grid aspect ratio optimization method based on surface modification in inkjet process, characterized in that: Apply any one of claims 1 to 12 in an inkjet process.

25. Application of a metal mesh aspect ratio optimization method based on surface modification in aerosol jet technology, characterized in that: Apply any one of claims 1 to 12 in an aerosol spray process.

26. Application of a metal mesh aspect ratio optimization method based on surface modification in screen printing process, characterized in that: Apply any one of claims 1 to 12 in a screen printing process.

27. The application of the metal grid aspect ratio optimization method based on surface modification in the dispensing process is characterized by: Apply any one of claims 1-12 in a dispensing process.

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