Metal electrode, crystalline silicon solar cell and preparation method

Abstract

This application provides a metal electrode, a crystalline silicon solar cell, and a fabrication method thereof, relating to the field of crystalline silicon solar cell manufacturing technology. The metal electrode fabrication method mainly involves coating a positive photoresist onto the surface of a substrate, shaping and photolithographically forming grooves corresponding to the pattern; using magnetron sputtering or reactive plasma deposition technology, a seed layer and a copper electrode are sequentially formed within the grooves, with the total height of the seed layer and the copper electrode being lower than the height of the positive photoresist layer. The crystalline silicon solar cell fabrication method mainly involves forming front and back metal electrodes using the metal electrode fabrication method described above; coating negative photoresist onto the front and back metal electrodes respectively, and removing the positive photoresist layer; forming an anti-reflection film and a passivation film on the front and back of the silicon substrate, and removing the negative photoresist layer. The metal electrode fabrication method, the crystalline silicon solar cell, and the fabrication method thereof result in excellent electrode quality, high aspect ratio, and high cell efficiency.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of crystalline silicon solar cell production, in particular to a metal electrode, a crystalline silicon solar cell and a preparation method. BACKGROUND

[0002] At present, due to energy crisis and environmental crisis, countries around the world have increased the development of renewable clean energy. Among many renewable clean energies, solar energy is clean and environmentally friendly, abundant in resources and widely distributed, and thus is favored by researchers and is expected to become the most important clean renewable energy in the future; crystalline silicon solar cells, as devices for converting and utilizing solar energy, have become a research focus.

[0003] In mass production of crystalline silicon solar cells, PERC cells (Passivated Emitter and Rear Cell) account for more than 85% of the photovoltaic market. The process with a large proportion of non-silicon cost in the PERC cell is the preparation of a metal electrode, which accounts for about 45% of the total cost of the PERC cell; in the new type of solar cell HIT (Heterojunction with Intrinsic Thin-layer), the cost of silver paste accounts for 50% of the non-silicon cost. The most widely used process for preparing electrodes in the current mass production process is the screen printing process, which uses screen printing silver paste, and then forms an ohmic contact silver electrode of a semiconductor and a metal by high-temperature or low-temperature sintering to lead out photo-generated carriers.

[0004] In recent years, with the continuous decline of the production cost of solar cells, the cost of expensive silver paste in the total cost of the cell has been increasing; and the width and aspect ratio of the silver electrode are limited by the screen printing process and the physical and chemical properties of the paste, and the aspect ratio of the conventional screen printed silver electrode is 30% to 35%, which hinders the improvement of the efficiency of the crystalline silicon solar cell. In order to further reduce the cost of the solar cell and improve the efficiency of the cell, the use of wet electroplating method to make the metal electrode of the solar cell has become a research focus in mass production, and the wet electroplating method can use inexpensive nickel, copper and other metals to partially or completely replace silver to prepare electrodes to achieve cost reduction. However, the existing wet electroplating method has high chemical solution treatment cost, high quality requirement for electroplating solution, and difficult to solve the uniformity of the electroplated electrode, and the aspect ratio of the prepared electrode is still relatively small, and the efficiency of the cell is low. SUMMARY

[0005] The purpose of the embodiments of the present application is to provide a metal electrode, a crystalline silicon solar cell and a preparation method, which have excellent electrode quality, high aspect ratio and high efficiency of the cell.

[0006] In a first aspect, the embodiments of the present application provide a preparation method of a metal electrode, which mainly includes the following steps: coating a positive photoresist on a surface of a substrate by scraping, shaping the positive photoresist to form a positive photoresist layer; performing photolithography on the positive photoresist layer to form a groove corresponding to a pattern; and sequentially forming a seed layer and a copper electrode in the groove by using a magnetron sputtering technology or a reactive plasma deposition (RPD) technology, and the total height of the seed layer and the copper electrode is lower than the height of the positive photoresist layer.

[0007] In the above technical solution, the metal electrode is prepared by scraping the positive photoresist and forming the groove by photolithography, and the metal electrode is composed of the seed layer and the copper electrode. The seed layer has the effect of corrosion resistance and plays the role of bonding the substrate and the copper electrode, and the copper electrode is used for collecting carriers. At the same time, the height of the metal electrode is lower than the height of the positive photoresist, so that the groove with a regular shape is not filled and has a certain spacing, which facilitates the subsequent scraping of the negative photoresist to protect the metal electrode and prevent the copper electrode grid line from being damaged in the subsequent process.

[0008] The preparation method of the metal electrode of the embodiments of the present application can solve the problem of high manufacturing cost caused by the screen printing of silver paste to prepare a silver electrode, and can also solve the problem of high wastewater treatment cost caused by the wet chemical solution electroplating technology. Most importantly, compared with the screen printing of silver electrode and the electrochemical solution electroplating of copper electrode, the preparation method of the embodiments of the present application can accurately control the height and width of the grid line, so as to prepare an electrode with excellent quality. The copper electrode has a high aspect ratio, reduces the shading area of the grid line of the front incident light, increases the luminous flux of the incident light, and corresponds to a high-efficiency battery.

[0009] In a possible implementation manner, the material of the seed layer is titanium, nickel, nickel-vanadium alloy or titanium-tungsten alloy.

[0010] In a possible implementation manner, the width of the seed layer is 10-20 μm, and the height is 2-5 μm; the width of the copper electrode is 10-20 μm, and the height is 5-15 μm.

[0011] In the above technical solution, the metal electrode composed of the seed layer and the copper electrode meets the use requirement, has a relatively low cost, and ensures that the copper electrode has a high aspect ratio.

[0012] In a possible implementation manner, the shaping method is as follows: first, the positive photoresist is scraped to have a thickness of 10-20 μm, and then soft baking is performed to realize uniform shaping of the positive photoresist. The soft baking temperature is 80-120 ℃, and the time is 60-200 s.

[0013] In a possible implementation, the method of photolithography is: using a UV light source to perform micron-level light source exposure on a region corresponding to a pattern of the positive photoresist layer, and then performing development of the exposed pattern in a developing solution, and the development time is 3-10 min.

[0014] In a second aspect, the embodiments of the present application provide a crystalline silicon solar cell, which comprises a silicon substrate, a phosphorus source doping layer, a front SiNx anti-reflection layer, and a SiO2 layer which are sequentially arranged on the front surface of the silicon substrate, an Al2O3 passivation layer and a back SiNx anti-reflection layer which are sequentially arranged on the back surface of the silicon substrate; the front metal electrode is inlaid in the front SiNx anti-reflection layer and the SiO2 layer, and the front metal electrode comprises a seed layer and a copper electrode which are sequentially arranged from inside to outside, the height-width ratio of the copper electrode is 40-50%, the seed layer is in contact with the phosphorus source doping layer, and the copper electrode extends out of the SiO2 layer; the back metal electrode is inlaid in the back SiNx anti-reflection layer and the Al2O3 passivation layer, and the back metal electrode comprises a seed layer and a copper electrode which are sequentially arranged from inside to outside, the height-width ratio of the copper electrode is 40-50%, the seed layer is in contact with the silicon substrate, and the copper electrode extends out of the back SiNx anti-reflection layer.

[0015] In the above technical solution, the crystalline silicon solar cell is a PERC cell structure, wherein the seed layer having corrosion resistance and adhesion and the copper electrode for collecting carriers jointly constitute the metal electrode, the height-width ratio of the copper electrode is high, the shadow area of incident light on the front surface of the cell is reduced, the photoelectric conversion efficiency of the cell is improved, and the manufacturing cost of the PERC cell is reduced.

[0016] In a possible implementation, the thickness of the front SiNx anti-reflection layer is 50-80 nm, and the refractive index is 2.0-2.3; the thickness of the SiO2 layer is 10-30 nm, and the refractive index is 1.6-1.8.

[0017] In the above technical solution, the SiO2 layer having a small refractive index is on the top, and the front SiNx anti-reflection layer having a large refractive index is below the SiO2 layer, the front SiNx anti-reflection layer and the SiO2 layer having certain thicknesses and refractive indexes constitute the front laminated anti-reflection film, the light flux on the front surface of the cell can be increased, the short-circuit current can be improved, and the photoelectric conversion efficiency of the cell can be ultimately improved.

[0018] In a possible implementation, the silicon substrate is a P-type gallium-doped silicon substrate, the resistivity of the silicon substrate is 0.4-1.1 Ω·cm, the size of the silicon substrate is 156.75*156.75 mm 2 ~230*230 mm 2 , and the thickness is 80-170 μm.

[0019] In a possible implementation, the thickness of the Al2O3 passivation layer is 3-10 nm.

[0020] And / or, the thickness of the back SiNx anti-reflective layer is 90-110 nm.

[0021] In the above technical solution, the thickness of the back SiNx anti-reflective layer is greater than that of the front SiNx anti-reflective layer, which aims to reduce the damage caused by the back negative photoresist remover and surfactant.

[0022] In a third aspect, the embodiments of the present application provide a preparation method of the crystalline silicon solar cell provided in the second aspect, which includes the following steps:

[0023] The phosphorus source doping layer is formed on the front side of the silicon substrate, the front metal electrode is formed on the surface of the phosphorus source doping layer by using the preparation method of the metal electrode provided in the first aspect, and the back metal electrode is formed on the back side of the silicon substrate by using the preparation method of the metal electrode provided in the first aspect;

[0024] The negative photoresist is scraped on the front metal electrode and the back metal electrode respectively to fill the corresponding grooves, the negative photoresist layer is formed by shaping, and the whole is immersed in the positive photoresist remover to remove the positive photoresist layer;

[0025] The front SiN x anti-reflective layer and the SiO2 layer are formed on the front side of the silicon substrate, and the Al2O3 passivation layer and the back SiNx anti-reflective layer are formed on the back side of the silicon substrate;

[0026] The negative photoresist layer on the front side and the back side is respectively immersed in the negative photoresist remover to remove the negative photoresist layer.

[0027] In the above technical solution, the positive photoresist is scraped on the front side and the back side of the silicon substrate on which the emitter is formed by phosphorus source diffusion, and the grooves are formed by corresponding photoetching after the positive photoresist is uniformly shaped; the front metal electrode and the back metal electrode are prepared by using magnetron sputtering or RPD technology at the grooves, the negative photoresist is scraped at the grooves to protect the metal electrode, the positive photoresist remover is used to clean the unexposed area, the front laminated anti-reflective film and the back passivation protective film are prepared, and finally the negative photoresist on the surface of the metal electrode is removed by using the negative photoresist remover. The purpose of forming the seed layer first is to bond the silicon substrate and increase the pulling force of the copper electrode, and the second purpose is to resist the corrosion of the positive photoresist remover and avoid the formation of voids in the bonding of the silicon substrate, which causes the increase of contact resistance and affects the photoelectric conversion efficiency of the cell. The front laminated anti-reflective film includes the SiO2 layer and the front SiN x anti-reflective layer, and the SiO2 layer can protect the front SiN x anti-reflective layer, which reduces the damage of the front negative photoresist remover and surfactant; and the prepared crystalline silicon solar cell can have an excellent aspect ratio and reduce the shadow area of the front incident light.

[0028] In a possible implementation, after the removal of the negative photoresist layer, the method further comprises the step of annealing in a nitrogen atmosphere, the annealing temperature is 150-180℃, and the annealing time is 10-20min. BRIEF DESCRIPTION OF DRAWINGS

[0029] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments of the present application. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can also be obtained without creative labor on the basis of these drawings.

[0030] Figure 1 A structural schematic diagram of a crystalline silicon solar cell provided by the embodiments of the present application;

[0031] Figure 2 A structural schematic diagram in the preparation process of a crystalline silicon solar cell provided by the embodiments of the present application.

[0032] Legend: 001-silicon substrate; 002-phosphorus source doped layer; 003-seed layer; 004-copper electrode; 005-front SiNx anti-reflection layer; 006-SiO2 layer; 007-Al2O3 passivation layer; 008-back SiNx anti-reflection layer. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solutions and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application will be clearly and completely described below. The specific conditions not mentioned in the embodiments are carried out according to the conventional conditions or the conditions suggested by the manufacturers. The reagents or instruments not mentioned by the manufacturers are all conventional products that can be obtained by market purchase.

[0034] The metal electrode, crystalline silicon solar cell and preparation method of the embodiments of the present application will be specifically described below.

[0035] The embodiments of the present application provide a preparation method of a metal electrode, which comprises the following steps:

[0036] (1) scrape the positive photoresist on the surface of the substrate, and shape to form a positive photoresist layer; as an embodiment, the shaping method can be: first scrape the positive photoresist, the scraping thickness is 10-20μm, then perform soft baking to realize the uniform shaping of the positive photoresist, the soft baking temperature is 80-120℃, and the time is 60-200s.

[0037] (2) performing photoetching on the positive photoresist layer to form grooves corresponding to the patterns; as an embodiment, the method of photoetching is as follows: using a UV light source of an exposure machine to perform micron-level light source exposure on the regions of the positive photoresist layer corresponding to the patterns, and then performing development of the exposed patterns in a developing solution, with a development time of 3-10 min.

[0038] (3) using a magnetron sputtering technique or a reactive plasma deposition technique to sequentially form a seed layer and a copper electrode in the grooves, and the total height of the seed layer and the copper electrode is lower than the height of the positive photoresist layer, i.e., the grooves are not filled with the seed layer and the copper electrode. The material of the seed layer can be titanium, nickel, nickel-vanadium alloy or titanium-tungsten alloy; the width of the seed layer can be 10-20 μm, and the height can be 2-5 μm; the width of the copper electrode can be 10-20 μm, and the height can be 5-15 μm.

[0039] The embodiment of the present application provides a novel physical preparation scheme of a high-quality copper electrode, and the preparation method of the metal electrode is used for preparing a metal electrode including a seed layer and a copper electrode. The preparation method of the metal electrode can be used for any crystalline silicon solar cell having the metal electrode, such as a PERC cell.

[0040] Please refer to Figure 1 The embodiment of the present application provides a crystalline silicon solar cell, which belongs to a homojunction cell and is specifically a PERC cell. The crystalline silicon solar cell includes a silicon substrate 001, a phosphorus source doped layer 002, a front SiNx anti-reflection layer 005 and a SiO2 layer 006 which are sequentially and superimposed on the front of the silicon substrate 001, an Al2O3 passivation layer 007 and a back SiNx anti-reflection layer 008 which are sequentially and superimposed on the back of the silicon substrate 001; the front metal electrode is inlaid in the SiO2 layer 006 and the front SiNx anti-reflection layer 005, and the front metal electrode includes a seed layer 003 and a copper electrode 004 which are sequentially and superimposed from inside to outside, and the seed layer 003 is in contact with the phosphorus source doped layer 002, and the copper electrode 004 extends out of the SiO2 layer 006; the back metal electrode is inlaid in the back SiNx anti-reflection layer 008 and the Al2O3 passivation layer 007, and the back metal electrode includes a seed layer 003 and a copper electrode 004 which are sequentially and superimposed from inside to outside, and the seed layer 003 is in contact with the silicon substrate 001, and the copper electrode 004 extends out of the back SiNx anti-reflection layer 008.

[0041] The silicon substrate 001 can be a P-type gallium-doped silicon substrate 001, the resistivity of the silicon substrate 001 is 0.4-1.1 Ω·cm, the size of the silicon substrate 001 is 156.75*156.75 mm 2 ~230*230 mm 2 , the thickness is 80-170 μm, and the surface is cleaned and textured to form pyramids with a size of 1-5 μm.

[0042] From the front of the silicon substrate 001, the phosphorus source doping layer 002 is formed by phosphorus source diffusion on the front of the silicon substrate 001 to form a PN junction; the thickness of the front SiNx anti-reflection layer 005 is 50-80 nm, and the refractive index is 2.0-2.3; the thickness of the SiO2 layer 006 is 10-30 nm, and the refractive index is 1.6-1.8.

[0043] From the back of the silicon substrate 001, the thickness of the Al2O3 passivation layer 007 is 3-10 nm; the thickness of the back SiNx anti-reflection layer 008 is 90-110 nm.

[0044] Please refer to Figure 2 The embodiment of the present application provides a preparation method of the above-mentioned crystalline silicon solar cell, which comprises the following steps:

[0045] (1) Selecting a P-type gallium-doped silicon substrate 001 with a resistivity of 0.4-1.1 Ω·cm, a size range of 156.75*156.75 mm 2 ~230*230 mm 2 , and a thickness range of 80-170 μm, first cleaning and texturing using an HF / NaOH solution to form pyramids with a size of 1-5 μm. The silicon substrate 001 is subjected to phosphorus source diffusion after texturing to form a PN junction, and wet etching is performed to remove the phosphorus source on the back of the silicon substrate 001 and the phosphorus source around the silicon wafer to prevent current leakage, thereby forming the phosphorus source doping layer 002 on the front of the silicon substrate 001.

[0046] (2) Scraping a positive photoresist on the phosphorus source doping layer 002 on the front of the silicon substrate 001, with a scraping thickness of 10-20 μm, and then soft baking at a temperature of 80-120 °C for 60-200 s to realize uniform setting of the positive photoresist and obtain a positive photoresist layer, which is used to prepare a uniform seed layer 003 and a copper electrode 004 on the front. After setting, the silicon substrate 001 is turned over by a turning wheel, and a positive photoresist is scraped on the back of the silicon substrate 001, with a scraping thickness of 10-20 μm, and then soft baking at a temperature of 80-120 °C for 60-200 s to realize uniform setting of the positive photoresist and obtain a positive photoresist layer, which is used to prepare a uniform seed layer 003 and a copper electrode 004 on the back. The specific structure is shown in part a of Figure 2 .

[0047] (3) Put the silicon substrate 001 which has been glued and shaped into the exposure machine, and use the ultraviolet light source to expose the micro-level light source to the areas corresponding to the patterns of the positive photoresist layers on the front and back surfaces respectively. Adjust the light source energy to 50-150 Kkz during the exposure of the front and back surfaces. After the exposure, develop the exposed patterns on the front and back surfaces in the developing solution for 3-10 min. The exposed areas form corresponding grid line images and regular-shaped grooves. The phosphorus-doped area under the front groove forms a heavily doped area. The specific structure is shown in part b of Figure 2 .

[0048] (4) Use the corresponding equipment of the magnetron sputtering technology or RPD technology to install the seed layer 003 target material to form the seed layer 003 in the grooves on the front and back surfaces. The width of the groove is 10-20 μm. The seed layer 003 can be nickel. The width of the seed layer 003 is 10-20 μm, and the height is 2-5 μm. The specific structure is shown in part c of Figure 2 .

[0049] (5) Again use the corresponding equipment of the magnetron sputtering technology or RPD technology to install the copper target material to prepare the copper electrode 004 on the seed layer 003 in the grooves on the front and back surfaces. The width of the copper electrode 004 is 10-20 μm, and the height is 5-15 μm. The specific structure is shown in part d of Figure 2 . The seed layer 003 and the copper electrode 004 in the front groove form the front metal electrode, and the seed layer 003 and the copper electrode 004 in the back groove form the back metal electrode. Both the front metal electrode and the back metal electrode are located in the corresponding grooves, i.e., do not fill the corresponding grooves.

[0050] (6) Scrape the negative photoresist to fill the corresponding grooves to protect the metal electrodes on the copper electrode 004 of the front metal electrode and the copper electrode 004 of the back metal electrode respectively, and shape the negative photoresist layer. The specific structure is shown in part e of Figure 2 . The negative photoresist can be purchased as a commercial product. For example, the negative photoresist is a product with the composition of 30% cyclohexane rubber, 65% xylene, and 5% crosslinking agent by mass percentage.

[0051] (7) Immersing the whole into the positive photoresist removal liquid to remove the positive photoresist layer in the unexposed areas. The negative photoresist is not soluble in the positive photoresist removal liquid, and the negative photoresist protects the metal electrodes from being affected. The specific structure is shown in part f of Figure 2 . The positive photoresist can be purchased as a commercial product. For example, the positive photoresist is a product with the composition of 73% propylene glycol monomethyl ether acetate 108-65-6, 21% cresol formaldehyde phenol formaldehyde resin 9016-83-5, and 6% 6-phycoerythrin-5,6-dihydro-5-oxo-1-naphthalene sulfonate 68510-93-0 by mass percentage.

[0052] (8) The front surface of the silicon substrate 001 is sequentially formed with a front surface SiN x anti-reflection layer 005 and a SiO2 layer 006 by PECVD. x The thickness of the anti-reflection layer 005 is 50-80 nm, and the refractive index is 2.0-2.3; the thickness of the SiO2 layer 006 is 10-30 nm, and the refractive index is 1.6-1.8.

[0053] (9) The back surface of the silicon substrate 001 is sequentially formed with an Al2O3 passivation layer 007 and a back surface SiNx anti-reflection layer 008 by atomic layer deposition technology. The thickness of the Al2O3 passivation layer 007 is 3-10 nm, and the thickness of the back surface SiNx anti-reflection layer 008 is 90-110 nm. The specific structure is shown in part g of FIG. 1. Figure 2

[0054] (10) The front surface and back surface negative photoresist layer sections are infiltrated with a negative photoresist remover and a surfactant, respectively, to remove the negative photoresist layer on the metal electrode. The addition of the surfactant to the negative photoresist remover can quickly remove the negative photoresist on the surface of the metal electrode. The specific structure is shown in part h of FIG. 1. Figure 2

[0055] (11) The annealing step is performed in a nitrogen atmosphere, the annealing temperature is 150-180°C, and the annealing time is 10-20 min.

[0056] The features and performance of the present application are further described in detail below in conjunction with examples.

[0057] Example 1

[0058] The present example provides a PERC cell, which includes a silicon substrate, a phosphorus source doped layer, a front surface SiNx anti-reflection layer, and a SiO2 layer sequentially and superimposed on the front surface of the silicon substrate, and an Al2O3 passivation layer and a back surface SiNx anti-reflection layer sequentially and superimposed on the back surface of the silicon substrate. The silicon substrate is a P-type gallium-doped silicon substrate with a resistivity of 0.8 Ω·cm, a size of 230×230 mm 2 , and a thickness of 120 μm, and the surface is cleaned and textured to form pyramids with a size of 3 μm. The thickness of the front surface SiNx anti-reflection layer is 60 nm, and the refractive index is 2.2; the thickness of the SiO2 layer is 20 nm, and the refractive index is 1.7, and the refractive index of the stacked anti-reflection film composed of the front surface SiNx anti-reflection layer and the SiO2 layer reaches 2.12; the thickness of the Al2O3 passivation layer is 5 nm; and the thickness of the back surface SiNx anti-reflection layer is 100 nm.

[0059] ​​The front metal electrode is inlaid in the SiO2 layer and the front SiNx anti-reflection layer, and the front metal electrode comprises a seed layer and a copper electrode which are stacked from inside to outside, and the seed layer is in contact with the phosphorus source doped layer, and the copper electrode extends out of the SiO2 layer. The material of the seed layer is nickel, the width of the seed layer is 15 μm, and the height is 5 μm; the width of the copper electrode is 20 μm, the height is 8.6 μm, and the aspect ratio of the copper electrode on the front surface is 43%.

[0060] The back metal electrode is inlaid in the back SiNx anti-reflection layer and the Al2O3 passivation layer, and the back metal electrode comprises a seed layer and a copper electrode which are stacked from inside to outside, and the seed layer is in contact with the silicon substrate, and the copper electrode extends out of the back SiNx anti-reflection layer. The material of the seed layer is nickel, the width of the seed layer is 15 μm, and the height is 5 μm; the width of the copper electrode is 20 μm, the height is 8.6 μm, and the aspect ratio of the copper electrode on the back surface is 43%.

[0061] The PERC cell is prepared by the following steps:

[0062] (1) Select a silicon substrate, first use HF / NaOH solution to clean and form a pyramidal size, then perform phosphorus source diffusion on the surface of the silicon substrate after texturing to form a PN junction, and then perform wet etching to remove the phosphorus source on the back surface of the silicon substrate and the phosphorus source around the silicon wafer to form a phosphorus source doped layer on the front surface of the silicon substrate.

[0063] (2) Scrape the positive photoresist (LG Chemical) on the phosphorus source doped layer on the front surface of the silicon substrate, the scraping thickness is 15 μm, then perform soft baking, the soft baking temperature is 100°C, and the time is 120 s to realize uniform setting of the positive photoresist and obtain a positive photoresist layer. After setting, flip the silicon substrate by a flipping wheel, scrape the positive photoresist on the back surface of the silicon substrate, the scraping thickness is 15 μm, then perform soft baking, the soft baking temperature is 100°C, and the time is 120 s to realize uniform setting of the positive photoresist and obtain a positive photoresist layer.

[0064] (3) Place the silicon substrate with the photoresist set into an exposure machine, and use a ultraviolet light source to perform micron-level light source exposure on the areas corresponding to the patterns on the front and back positive photoresist layers, respectively, and adjust different light source energies during front and back exposure; after exposure, develop the front and back exposure patterns in a developing solution, the developing time is 8 min, the exposed areas form corresponding grid line images and regular-shaped grooves, and the phosphorus source doped area under the front groove forms a heavily doped area.

[0065] (4) Use a corresponding equipment of a magnetron sputtering technology to install a seed layer target material, and form a seed layer in the grooves on the front and back surfaces.

[0066] (5) Using the corresponding equipment of magnetron sputtering technology, a copper target is installed to prepare a copper electrode on the seed layer in the front and back grooves. The seed layer and the copper electrode in the front groove form a front metal electrode, and the seed layer and the copper electrode in the back groove form a back metal electrode. Both the front metal electrode and the back metal electrode are located in the corresponding grooves, i.e., the corresponding grooves are not filled.

[0067] (6) The copper electrode of the front metal electrode and the copper electrode of the back metal electrode are respectively scraped to fill the corresponding grooves to protect the metal electrode, and the negative photoresist (LG Chemical) is shaped to form a negative photoresist layer.

[0068] (7) The whole is immersed in a positive photoresist removal liquid (LG Chemical) to remove the positive photoresist layer in the unexposed area.

[0069] (8) The front surface of the silicon substrate is sequentially formed with a front SiN x antireflection layer and a SiO2 layer by PECVD.

[0070] (9) The back surface of the silicon substrate is sequentially formed with an Al2O3 passivation layer and a back SiNx antireflection layer by atomic layer deposition technology.

[0071] (10) The cross sections of the front and back negative photoresist layers are respectively infiltrated with a negative photoresist removal liquid (LG Chemical) and a surfactant to remove the negative photoresist layer above the metal electrode.

[0072] (11) The annealing step is carried out in a nitrogen atmosphere, the annealing temperature is 150°C, and the annealing time is 15 min.

[0073] Example 2

[0074] This example provides a PERC cell, which is different from example 1 in that the material of the seed layer is titanium, and the aspect ratio of the front copper electrode is 45%.

[0075] Example 3

[0076] This example provides a PERC cell, which is different from example 1 in that the aspect ratio of the front copper electrode is 48%.

[0077] Example 4

[0078] This example provides a PERC cell, which is different from example 1 in that the thickness of the front SiNx antireflection layer is 80 nm, the refractive index is 2.3; the thickness of the SiO2 layer is 30 nm, the refractive index is 1.8, and the aspect ratio of the front copper electrode is 50%.

[0079] Comparative Example 1

[0080] The present comparative example provides a PERC cell, which is different from example 1 in that the metal electrode in the present comparative example is a silver electrode with a width of 45 μm and a height of 14 μm.

[0081] The performance of the above-described PERC cell was detected, and the results are shown in the following table:

[0082] Efficiency Short circuit current / A Aspect ratio Example 1 23.5％ 11.38 43％ Example 2 23.55％ 11.42 45％ Example 3 23.72％ 11.48 48％ Example 4 23.85％ 11.55 50％ Comparative Example 1 23.2％ 11.28 31％

[0083] In summary, the metal electrode, the crystalline silicon solar cell and the preparation method of the embodiments of the present application have excellent electrode quality, high aspect ratio, and high efficiency of the cell.

[0084] The above only describes the embodiments of the present application and is not used to limit the protection scope of the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method of producing a metal electrode, characterized by, The method comprises the following steps: a positive photoresist is scraped on a surface of a substrate to form a positive photoresist layer, the substrate comprises a silicon substrate and a phosphorus source doped layer arranged on a front surface of the silicon substrate; the positive photoresist layer is subjected to photolithography to form a groove corresponding to a pattern; a seed layer and a copper electrode are sequentially formed in the groove by using a magnetron sputtering technology or a reactive plasma deposition technology, and a total height of the seed layer and the copper electrode is lower than a height of the positive photoresist layer, a width of the seed layer is 10-20 microns, and a height of the seed layer is 2-5 microns; a width of the copper electrode is 10-20 microns, and a height of the copper electrode is 5-15 microns.

2. The method of producing a metal electrode according to claim 1, wherein The seed layer is made of titanium, nickel, nickel-vanadium alloy or titanium-tungsten alloy.

3. The method of producing a metal electrode according to claim 1, wherein The method for shaping the positive photoresist layer comprises the following steps: the positive photoresist is scraped to a thickness of 10-20 microns, and then soft baking is performed to realize uniform shaping of the positive photoresist, a soft baking temperature is 80-120 DEG C, and a soft baking time is 60-200 seconds.

4. The method of producing a metal electrode according to claim 1, wherein The method for photolithography comprises the following steps: a micron-level light source is used to expose a region corresponding to a pattern of the positive photoresist layer to ultraviolet light, and then the exposed pattern is developed in a developing solution, a developing time is 3-10 minutes.

5. A method for producing a crystalline silicon solar cell, characterized by, The method comprises the following steps: A phosphorus source doped layer is formed on a front surface of a silicon substrate, a front metal electrode is formed on a surface of the phosphorus source doped layer by using the method for preparing a metal electrode according to claim 1, and a back metal electrode is formed on a back surface of the silicon substrate by using the method for preparing a metal electrode according to claim 1; A negative photoresist is scraped on the front metal electrode and the back metal electrode to fill the corresponding grooves, a negative photoresist layer is formed by shaping, and the whole is immersed in a positive photoresist removal solution to remove the positive photoresist layer; a front surface SiN x a back surface SiN anti-reflection layer; and an Al2O3 passivation layer, a back surface SiN anti-reflection layer, and a SiO2 layer are formed in sequence on the back surface of the silicon substrate. The negative photoresist layer on the front surface and the back surface is immersed in a negative photoresist removal solution to remove the negative photoresist layer.

6. The method of producing a crystalline silicon solar cell according to claim 5, wherein After the negative photoresist layer is removed, a step of annealing in a nitrogen atmosphere is further included, an annealing temperature is 150-180 DEG C, and an annealing time is 10-20 minutes.

7. The method of producing a crystalline silicon solar cell according to claim 5, wherein The front metal electrode comprises a seed layer and a copper electrode which are sequentially arranged from inside to outside, a height-width ratio of the copper electrode is 40%-50%, the seed layer is in contact with the phosphorus source doped layer, and the copper electrode extends out of the SiO2 layer; The back metal electrode comprises a seed layer and a copper electrode which are sequentially arranged from inside to outside, a height-width ratio of the copper electrode is 40%-50%, the seed layer is in contact with the silicon substrate, and the copper electrode extends out of the back SiNx anti-reflection layer.

8. The method of producing a crystalline silicon solar cell according to claim 5, wherein A thickness of the front SiNx anti-reflection layer is 50-80 nm, and a refractive index is 2.0-2.3; a thickness of the SiO2 layer is 10-30 nm, and a refractive index is 1.6-1.

8.

9. The method of producing a crystalline silicon solar cell according to claim 5, wherein The silicon substrate is a P-type gallium-doped silicon substrate, the resistivity of the silicon substrate is 0.4-1.1 ohm-cm, and the size of the silicon substrate is 156.75*156.75 mm 2 230*230 mm 2 , and the thickness is 80-170 microns; And / or, a thickness of the Al2O3 passivation layer is 3-10 nm; And / or, a thickness of the back SiNx anti-reflection layer is 90-110 nm.

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