CN117059680A - Silicon heterojunction solar cell and metallization method thereof - Google Patents

Abstract

The invention provides a silicon heterojunction solar cell and a metallization method thereof. The silicon heterojunction solar cell includes a crystalline silicon substrate. The front side of the crystalline silicon substrate is sequentially provided with a first intrinsic amorphous silicon layer, A first doped amorphous silicon/microcrystalline silicon layer, a first transparent conductive oxide layer, a first transition metal layer and a first gate line electrode, and a second intrinsic amorphous silicon substrate is sequentially provided on the back side of the crystalline silicon substrate A silicon layer, a second doped amorphous silicon/microcrystalline silicon layer, a second transparent conductive oxide layer, a second transition metal layer and a second gate line electrode. The silicon heterojunction solar cell of the present invention has a transition metal layer between the metal grid electrode and the transparent conductive oxide, which increases the adhesion between the TCO and the metal grid and is conducive to obtaining uniform, dense and hole-free The seed layer also effectively reduces the contact resistance between metal and TCO, which is beneficial to improving battery efficiency.

Description

A silicon heterojunction solar cell and its metallization method

Technical field

The present invention relates to the technical field of solar cells, and specifically to a silicon heterojunction solar cell and a metallization method thereof.

Background technique

Silicon heterojunction (HJT) solar cells use crystalline silicon wafers for carrier transport and absorption, and use amorphous or microcrystalline thin silicon layers for passivation. The top electrode consists of a transparent conductive oxide (TCO) layer and a metal gate line composition. It has excellent passivation performance and high conversion efficiency (over 26.5%), and has attracted increasing attention from the photovoltaic industry.

Silicon heterojunction solar cells require a metallization process at low temperatures due to their sensitive passivated amorphous silicon layer. Screen printing of low-temperature silver paste is currently a common metallization method for silicon heterojunction solar cells. However, the resistivity of low-temperature silver paste is much higher than that of high-temperature silver paste, more than twice as much. Therefore, in order to obtain sufficiently low line resistance, a large amount of low-temperature slurry has to be consumed, which will significantly increase the production cost of silicon heterojunction solar cells. And as the scale of solar photovoltaic production continues to expand, the demand for silver will also increase sharply. Reducing the amount of silver paste or using base metals to replace expensive silver paste is an important issue in realizing the industrialization of silicon heterojunction solar cells.

Because it can achieve lower line resistance, higher aspect ratio and lower manufacturing cost, electroplating copper technology is considered to be an effective attempt to break through the bottleneck of screen printing technology and improve carrier collection, and has become the focus of research in this field. In order to increase the lateral conductivity and reduce light reflection, the surface of the silicon heterojunction cell is covered with a TCO film, but the contact performance between the electroplated metal and the TCO film is poor. In the existing silicon heterojunction cell electroplating metallization technology, it is usually First, a seed layer is deposited using PVD technology, and then copper is electroplated on the seed layer. For example, Chinese patents CN108400175A, CN110797418A, CN113130671A, and CN113943920A disclose improving adhesion by using PVD technology to manufacture metal seed layers such as Ni, Ti, and Ta. However, this vacuum process and subsequent etching steps will significantly increase the manufacturing cost. Moreover, even if the seed layer is deposited, the contact performance between the electroplated metal and TCO is not ideal and cannot meet the requirements for large-scale industrialization. This is because the conductivity of TCO is not enough to ensure the uniformity of current distribution during electroplating. Especially when the size of the wafer increases, the adhesion between the electroplated copper gate lines and TCO is poor, which may cause problems in the subsequent battery assembly process. layering in.

Contents of the invention

In view of the shortcomings of the existing technology, the technical problem to be solved by the present invention is how to improve the contact quality between the metal gate line and the transparent conductive oxide layer, so as to realize direct electroplating of a metal seed layer on the transparent conductive oxide.

In order to solve the above problems, a first aspect of the present invention provides a silicon heterojunction solar cell, which includes a crystalline silicon substrate. The front side of the crystalline silicon substrate is sequentially provided with a first intrinsic amorphous silicon layer and a first doped layer. Amorphous silicon/microcrystalline silicon layer, first transparent conductive oxide layer, first transition metal layer and first gate line electrode, the back side of the crystalline silicon substrate is provided with a second intrinsic amorphous silicon layer, a third Two doped amorphous silicon/microcrystalline silicon layers, a second transparent conductive oxide layer, a second transition metal layer and a second gate line electrode, the composition of the first transition metal layer is the same as that of the first transparent conductive oxide layer The components of the second transition metal layer are metals and metal oxides corresponding to the components of the second transparent conductive oxide layer.

The silicon heterojunction solar cell of the present invention has a transition metal layer between the metal grid electrode and the transparent conductive oxide, which increases the adhesion between the TCO and the metal grid and is conducive to obtaining uniform, dense and hole-free The seed layer also effectively reduces the contact resistance between metal and TCO, which is beneficial to improving battery efficiency.

Further, the thickness of the first transition metal layer and the second transition metal layer is 10-800 nm. The transition metal layer needs to have a certain thickness to ensure good contact quality with the metal grid lines, but the thickness should not be too large, otherwise it will affect the adhesion and thus the battery efficiency.

Further, the components of the first transparent conductive oxide layer and the second transparent conductive oxide layer are selected from the group consisting of indium tin oxide (ITO), tungsten-doped indium oxide (IWO), aluminum zinc oxide (AZO), and gallium oxide. At least one of zinc (GZO) and fluorine-doped tin oxide (FTO).

Further, the first gate line electrode includes a first metal seed layer, a first copper conductive layer and a first tin protective layer, the first metal seed layer is provided on the first transition metal layer, and the first metal seed layer is disposed on the first transition metal layer. A copper conductive layer is disposed on the first copper conductive layer, the first tin protective layer covers the first metal seed layer and the surface of the first copper conductive layer, and the second gate line electrode includes a Two metal seed layers, a second copper conductive layer and a second tin protective layer, the second metal seed layer is disposed on the second transition metal layer, the second copper conductive layer is disposed on the second copper conductive layer layer, the second tin protective layer covers the surface of the second metal seed layer and the second copper conductive layer.

Further, the thickness of the first metal seed layer and the second metal seed layer is 20-2000nm, the thickness of the first copper conductive layer and the second copper conductive layer is 500-6000nm, and the thickness of the third metal seed layer is 20-2000nm. The thickness of a tin protective layer and the second tin protective layer is 500-3000nm.

A second aspect of the present invention provides a metallization method for the above-mentioned silicon heterojunction solar cell, including the following steps:

S1. Prepare quasi-heterojunction cells without metal electrodes and perform patterning processing;

S2. Use a pretreatment solution to chemically treat the transparent conductive oxide layer on the surface of the battery sheet to reduce part of the metal and metal oxide to form a transition metal layer. The surface of the battery sheet is cleaned. The pretreatment solution includes reducing solute, stabilizing Agent and pH regulator, the reducing solute is selected from one or more of potassium iodide, sodium iodide, silver iodide, copper iodide, aluminum iodide, iodine monochloride, iodine monobromide, and iodine nitrate;

S3. Electroplating and depositing a metal seed layer on the transition metal layer;

S4. Electroplating and depositing a copper conductive layer on the surface of the metal seed layer;

S5. Chemically deposit a tin protective layer on the surface of the metal seed layer and copper conductive layer;

S6. Anneal the battery slices.

The present invention uses a chemical solution method to pretreat the transparent conductive oxide, so that TCO is partially reduced to metal and its oxide, forming a transition metal layer, thereby increasing the adhesion between TCO and electroplated metal grid lines. force, a uniform, dense and hole-free seed layer can be directly electroplated on the transition metal layer, while effectively reducing the contact resistance between the metal and TCO.

Further, the stabilizer is selected from one or more of phosphoric acid, glycine, citric acid, and acetic acid, and the pH adjuster is hydrochloric acid and/or sulfuric acid. The stabilizer is used to stabilize the iodide ions in the pretreatment solution, and the pH of the solution is buffered with hydrochloric acid and/or sulfuric acid.

Further, in the pretreatment solution, the molar concentration of the reducing solute is 0.3-1 mol/L, and the molar concentration of the stabilizer is 0.2-0.8 mol/L. The reducing solute is used as a pretreatment reaction substance to reduce the transparent conductive oxide. When the solute concentration is too low, the entire reaction will be inhibited; when the solute concentration is too high, the reaction is too strong and affects the quality of the transition metal layer; the mole of the stabilizer The concentration corresponds to the reducing solute and plays a role in stabilizing iodide ions.

Further, the temperature of the pretreatment solution is 20-50°C, and the pH is 0.5-5. PH and temperature have an impact on the pretreatment effect. When the PH is too high, the reaction rate is too slow. When the PH is too low, the transition metal layer produced will be dissolved by acid, causing damage.

Further, in step S2, the pretreatment time is 1-30 minutes. The pretreatment time will affect the thickness and component ratio of the metal transition layer. Within this time range, a metal transition layer with a set thickness can be obtained.

To sum up, compared with the prior art, the present invention has the following beneficial effects:

(1) The present invention provides a transition metal layer on the surface of the transparent conductive oxide layer. The transition metal layer and the metal grid lines have high adhesion, which is conducive to the formation of a uniform, dense and hole-free seed layer by electroplating. At the same time, the contact quality between the metal gate line and the TCO is improved.

(2) The present invention uses a chemical solution method to pretreat the transparent conductive oxide to produce a uniform transition metal layer on the TCO surface, thereby enabling subsequent direct electroplating of a metal seed layer on the transition metal layer, which is consistent with the subsequent copper electroplating process. compatible and can be integrated into a single plating equipment.

(3) The present invention forms a transition metal layer after pretreatment of TCO, which is conducive to obtaining a more uniform and dense gate line in the future, so that the gate line electrode has higher conductivity, thereby effectively reducing the contact resistivity of the silicon heterojunction battery. .

(4) The present invention forms a transition metal layer after pretreatment of TCO, which greatly improves the adhesion between the TCO and the gate electrode, improves the contact quality, and improves the conversion efficiency of the silicon heterojunction battery.

(5) The metallization method of the present invention is beneficial to reducing the contact resistivity after metallization of the silicon heterojunction battery and improving the adhesion to obtain higher conversion efficiency. The method has a simple process, low manufacturing cost, and is suitable for large-scale applications. large-scale industrial production.

Description of the drawings

Figure 1 is a schematic structural diagram of a silicon heterojunction solar cell in a specific embodiment of the present invention.

FIG. 2 is a flow chart of a metallization method for silicon heterojunction solar cells in a specific embodiment of the present invention.

Figure 3 is a cross-sectional morphology view of the gate line portion of the silicon heterojunction solar cell prepared in Example 1 and Comparative Example 1 of the present invention.

Figure 4 is a comparative diagram of gate line height distribution of silicon heterojunction solar cells prepared in Example 1 and Comparative Example 1 of the present invention.

Figure 5 is a comparative chart of the gate line pull-off force test results of the silicon heterojunction solar cells prepared in Example 1 and Comparative Example 1 of the present invention.

Picture description:

1-Crystalline silicon substrate, 2-First intrinsic amorphous silicon layer, 3-First doped amorphous silicon/microcrystalline silicon layer, 4-First transparent conductive oxide layer, 5-First transition metal layer , 6-The first metal seed layer, 7-The first copper conductive layer, 8-The first tin protective layer, 9-The second intrinsic amorphous silicon layer, 10-The second doped amorphous silicon/microcrystalline silicon layer , 11-the second transparent conductive oxide layer, 12-the second transition metal layer, 13-the second metal seed layer, 14-the second copper conductive layer, 15-the second tin protective layer.

Detailed ways

In order to make the above objects, features and advantages of the present invention more obvious and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be noted that the following examples are only used to illustrate the implementation methods and typical parameters of the present invention, and are not used to limit the parameter range of the present invention. Reasonable changes derived therefrom are still protected by the claims of the present invention. within the range.

It should be noted that the endpoints of ranges and any values disclosed herein are not limited to such precise ranges or values, and these ranges or values should be understood to include values approaching these ranges or values. For numerical ranges, the endpoint values of each range, the endpoint values of each range and individual point values, and the individual point values can be combined with each other to obtain one or more new numerical ranges. These values The scope shall be deemed to be specifically disclosed herein.

The specific embodiment of the present invention provides a silicon heterojunction solar cell, the typical structure of which is shown in Figure 1. The silicon heterojunction solar cell includes a crystalline silicon substrate 1. The front side of the crystalline silicon substrate 1 is sequentially stacked with a third An intrinsic amorphous silicon layer 2, a first doped amorphous silicon/microcrystalline silicon layer 3 and a first transparent conductive oxide layer 4. A first transition metal layer 5 is also provided on the first transparent conductive oxide layer 4. and a first gate line electrode, the first gate line electrode includes a first metal seed layer 6, a first copper conductive layer 7 and a first tin protective layer 8, the first metal seed layer 6 is provided on the first transition metal layer 5, The first copper conductive layer 7 is disposed on the first copper conductive layer 7, and the first tin protective layer 8 covers the first metal seed layer 6 and the surface of the first copper conductive layer 7; the back side of the crystalline silicon substrate 1 is sequentially stacked with The second intrinsic amorphous silicon layer 9, the second doped amorphous silicon/microcrystalline silicon layer 10 and the second transparent conductive oxide layer 11 are also provided with a second transition metal layer on the second transparent conductive oxide layer 11. 12 and a second gate line electrode. The second gate line electrode includes a second metal seed layer 13, a second copper conductive layer 14 and a second tin protective layer 15. The second metal seed layer 13 is disposed on the second transition metal layer 12. , the second copper conductive layer 14 is disposed on the second copper conductive layer 14, and the second tin protective layer 15 covers the surface of the second metal seed layer 13 and the second copper conductive layer 14.

The components of the first transparent conductive oxide layer 4 and the second transparent conductive oxide layer 11 are selected from indium tin oxide (ITO), tungsten-doped indium oxide (IWO), aluminum zinc oxide (AZO), gallium zinc oxide (GZO), Fluorine-doped tin oxide (FTO), etc. The composition of the first transition metal layer 5 is metal and metal oxide corresponding to the composition of the first transparent conductive oxide layer 4. If the composition of the first transparent conductive oxide layer 4 is indium tin oxide, the composition of the corresponding transition metal layer It is metal indium, tin and their oxides. Similarly, the components of the second transition metal layer 12 are metals and metal oxides corresponding to the components of the second transparent conductive oxide layer 11 . A transition metal layer is provided between the metal gate line electrode and the transparent conductive oxide, which can increase the adhesion between the TCO and the metal gate line, which is conducive to obtaining a uniform, dense and hole-free metal seed layer, and at the same time effectively reduces the The contact resistance between the gate line and the TCO is reduced, which is beneficial to improving the conversion rate of silicon heterojunction solar cells.

In a specific embodiment, the thickness of the first transition metal layer 5 is 10-800 nm, and the thickness of the second transition metal layer 12 is 10-800 nm. The thickness of the first metal seed layer 6 is 20-2000nm, the thickness of the first copper conductive layer 7 is 500-6000nm, the thickness of the first tin protective layer 8 is 500-3000nm; the thickness of the second metal seed layer 13 is 20-2000nm. , the thickness of the second copper conductive layer 14 is 500-6000nm, and the thickness of the second tin protective layer 15 is 500-3000nm.

Preferably, the material of the first metal seed layer 6 and the second metal seed layer 13 is nickel, which is doped with one or more trace elements of phosphorus, boron, copper, tin, silver, aluminum and sulfur. The doping amount is is 0.01-5%.

As shown in Figure 2, a specific embodiment of the present invention also provides a metallization method for silicon heterojunction solar cells, which includes the following steps:

(1) Ultrasonic cleaning of quasi-heterojunction cells without front and rear metal electrodes.

(2) Pattern the front and back sides of the heterojunction cells. Patterning methods include photolithography, inkjet printing, screen printing, etc.

(3) Use a pretreatment solution to perform chemical solution treatment on the first transparent conductive oxide layer 4 and the second transparent conductive oxide layer 11 on both sides of the cell to reduce part of the metal and metal oxide to form the first transition metal layer 5 and the second transition metal layer 12. After pretreatment, weak acid and deionized water cleaning is performed.

The above-mentioned pretreatment solution includes a reducing solute, a stabilizer and a pH regulator. In specific embodiments, the reducing solute is a solute with a low redox potential that can reduce transparent conductive oxides to metals. Typical reducing solutes include potassium iodide and sodium iodide. , silver iodide, copper iodide, aluminum iodide, iodine monochloride, iodine monobromide, iodine nitrate, etc. Stabilizers are used to stabilize iodide ions in solutions, acids that do not react with reducing solutes at low concentrations, such as phosphoric acid, glycine, citric acid, acetic acid, etc. In the pretreatment solution, the molar concentration of the reducing solute is 0.3-1mol/L, and the molar concentration of the stabilizer is 0.2-0.8mol/L. The pH adjuster is used to control the pH of the pretreatment solution to maintain the pH at 0.5-5. The pH adjuster is hydrochloric acid, sulfuric acid, etc.

In specific embodiments, the temperature of the solution during the pretreatment process is controlled at 20-50°C, and the pretreatment time is 1-30 minutes. After the pretreatment, a uniform transition metal layer is formed on the surface of the transparent conductive oxide layer, so that subsequent direct treatment can be achieved. A metal seed layer is electroplated on the transition metal layer.

(4) The first metal seed layer 6 is electroplated and deposited on the first transition metal layer 5, and the second metal seed layer 13 is electroplated and deposited on the second transition metal layer 12. Double-sided electroplating can be used at the same time, or single-sided electroplating can be used. , cleaning after plating.

In specific embodiments, the electroplating deposition method of the metal seed layer includes light-induced electroplating, electric field-induced electroplating, etc., the current is set to 0.01-10mA/cm ² , the time is 1-30min, and the temperature is 20-50°C.

(5) Electroplating and depositing the first copper conductive layer 7 on the first metal seed layer 6, electroplating and depositing the second copper conductive layer 14 on the second metal seed layer 13, and cleaning after electroplating.

In specific embodiments, the deposition method of the copper conductive layer includes light-induced electroplating, electric field-induced electroplating, etc., the current is set to 0.01-10mA/cm ² , the time is 1-30min, and the temperature is 20-50°C.

(6) To remove the photoresist on the surface of the quasi-heterojunction cell, the degumming solution can be acetone or high-concentration alkaline solution such as sodium hydroxide or potassium hydroxide. After degumming, wash and dry.

(7) The first tin protective layer 8 is chemically deposited on the surface of the first metal seed layer 6 and the first copper conductive layer 7, and the second tin protective layer 15 is chemically deposited on the surface of the second metal seed layer 13 and the second copper conductive layer 14. .

In specific embodiments, the deposition method of the tin protective layer includes electrically assisted electroless plating, light-assisted electroless plating, sensitized electroless plating, etc., and the temperature of the plating solution is 20-100°C.

(8) Put the cell sheet into a tube furnace for annealing treatment, the atmosphere is nitrogen and hydrogen, the annealing treatment temperature is 100-220°C, and the reaction time is 0.2-2h, to prepare a silicon heterojunction solar cell.

The above method uses a chemical solution method to pretreat the transparent conductive oxide to produce a uniform transition metal layer on the TCO surface, followed by continuous electroplating of a metal seed layer and a copper conductive layer, and chemical tin plating of a protective layer, and finally annealing to complete the metallization process , improves the uniformity of metal grid lines, adhesion and contact resistivity of batteries. The method has simple process and low manufacturing cost, and is suitable for large-scale industrial production.

The technical solutions and effects of the present invention will be described in detail below with reference to specific embodiments. The silicon wafer substrates used in each embodiment and the comparative example are the same.

Example 1

This embodiment provides a metallization method for silicon heterojunction solar energy. The process flow is as follows:

(1) Ultrasonic cleaning is performed on quasi-heterojunction cells without front and rear metal electrodes. The quasi-heterojunction cells include TCO, phosphorus-doped amorphous silicon, intrinsic amorphous silicon, and n-type stacked in sequence from the front to the back. Crystalline silicon substrate, intrinsic amorphous silicon, boron-doped amorphous silicon, TCO, and the TCO component is ITO.

(2) Use the photolithography process for patterning, and prepare the required patterned metal grid lines through the positive photoresist coating, baking, exposure, post-baking, development, fixing and film hardening processes.

(3) Perform ultrasonic cleaning on the sample, and use a pretreatment solution to chemically treat TCO on both sides. The pretreatment solution contains 0.4mol/L potassium iodide and 0.3mol/L phosphoric acid. Use sulfuric acid to adjust the pH to 3.5 and control the solution temperature. The temperature is 20°C, and the pretreatment time is 6 minutes; after pretreatment, the TCO surface consists of indium, tin and their oxide transition metal layer, which is cleaned with deionized water.

(4) Use electroplating to deposit a nickel seed layer on the transition metal layer, with a current density of 2.5mA/cm ² and an electroplating time of 4 minutes.

(5) Clean with deionized water and deposit an electroplated copper conductive layer on the nickel seed layer. The current is set to 5mA/cm ² and the electroplating time is 15 minutes.

(6) After cleaning with deionized water, use acetone to remove the photoresist, and wash and dry.

(7) Then use electroless plating to deposit a tin protective layer on the surface of the nickel seed layer and copper conductive layer. The plating bath temperature is 40°C and the electroless plating time is 15 minutes.

(8) Place the plated sample in a tube furnace and perform annealing treatment in a nitrogen and hydrogen mixed atmosphere at a treatment temperature of 160°C for 1.5 hours to prepare a silicon heterojunction solar cell.

Example 2

This embodiment provides a metallization method for silicon heterojunction solar energy. The process flow is as follows:

(1) The same quasi-heterojunction cell sheet as in Example 1 was subjected to ultrasonic cleaning.

(2) Use the photolithography process for patterning, and prepare the required patterned metal grid lines through the positive photoresist coating, baking, exposure, post-baking, development, fixing and film hardening processes.

(3) Perform ultrasonic cleaning on the sample, and use a pretreatment solution to chemically treat the ITO on both sides. The pretreatment solution contains 0.7mol/L sodium iodide and 0.5mol/L citric acid, and adjust the pH to 2 with sulfuric acid. The solution temperature is controlled to 20°C, and the pretreatment time is 6 minutes; after pretreatment, the components formed on the ITO surface include indium, tin and their oxide transition metal layers, which are cleaned with deionized water.

(4) Use electroplating to deposit a nickel seed layer on the transition metal layer, with a current density of 2.5mA/cm ² and an electroplating time of 4 minutes.

(5) Clean with deionized water and deposit an electroplated copper conductive layer on the nickel seed layer. The current is set to 5mA/cm ² and the electroplating time is 15 minutes.

(6) After cleaning with deionized water, use acetone to remove the photoresist, and wash and dry.

(7) Then use electroless plating to deposit a tin protective layer on the surface of the nickel seed layer and copper conductive layer. The plating bath temperature is 40°C and the electroless plating time is 15 minutes.

(8) Place the plated sample in a tube furnace and perform annealing treatment in a nitrogen and hydrogen mixed atmosphere at a treatment temperature of 160°C for 1.5 hours to prepare a silicon heterojunction solar cell.

Example 3

This embodiment provides a metallization method for silicon heterojunction solar energy. The process flow is as follows:

(1) The same quasi-heterojunction cell sheet as in Example 1 was subjected to ultrasonic cleaning.

(2) Use the photolithography process for patterning, and prepare the required patterned metal grid lines through the positive photoresist coating, baking, exposure, post-baking, development, fixing and film hardening processes.

(3) Perform ultrasonic cleaning of the sample, and use a pretreatment solution to chemically treat the ITO on both sides. The pretreatment solution contains 0.4mol/L silver iodide and 0.5mol/L glycine. Use hydrochloric acid to adjust the pH to 5, and control the solution temperature. The temperature is 20°C, and the pretreatment time is 10 minutes; after pretreatment, the ITO surface consists of indium, tin and their oxide transition metal layer, which is cleaned with deionized water.

(4) Use electroplating to deposit a nickel seed layer on the transition metal layer, with a current density of 2.5mA/cm ² and an electroplating time of 4 minutes.

(5) Clean with deionized water and deposit an electroplated copper conductive layer on the nickel seed layer. The current is set to 5mA/cm ² and the electroplating time is 15 minutes.

(6) After cleaning with deionized water, use acetone to remove the photoresist, and wash and dry.

(7) Then use electroless plating to deposit a tin protective layer on the surface of the nickel seed layer and copper conductive layer. The plating bath temperature is 40°C and the electroless plating time is 15 minutes.

(8) Place the plated sample in a tube furnace and perform annealing treatment in a nitrogen and hydrogen mixed atmosphere at a treatment temperature of 160°C for 1.5 hours to prepare a silicon heterojunction solar cell.

Example 4

This embodiment provides a metallization method for silicon heterojunction solar energy. The process flow is as follows:

(1) Ultrasonic cleaning is performed on quasi-heterojunction cells without front and rear metal electrodes. The quasi-heterojunction cells include TCO, phosphorus-doped amorphous silicon, intrinsic amorphous silicon, and n-type stacked in sequence from the front to the back. Crystalline silicon substrate, intrinsic amorphous silicon, boron-doped amorphous silicon, TCO, and the TCO component is IWO.

(2) Use the photolithography process for patterning, and prepare the required patterned metal grid lines through the positive photoresist coating, baking, exposure, post-baking, development, fixing and film hardening processes.

(3) Perform ultrasonic cleaning of the sample, and use a pretreatment solution to chemically treat TCO on both sides. The pretreatment solution contains 1 mol/L copper iodide and 0.8 mol/L acetic acid. Use hydrochloric acid to adjust the pH to 3. The solution temperature The temperature is controlled at 30°C, and the pretreatment time is 15 minutes; after pretreatment, the components formed on the TCO surface include indium and its oxide transition metal layer, which is cleaned with deionized water.

(4) Use electroplating to deposit a nickel seed layer on the transition metal layer, with a current density of 5mA/cm ² and an electroplating time of 6 minutes.

(5) Clean with deionized water and deposit an electroplated copper conductive layer on the nickel seed layer. The current is set to 8mA/cm ² and the electroplating time is 20 minutes.

(6) After cleaning with deionized water, use acetone to remove the photoresist, and wash and dry.

(7) Then use electroless plating to deposit a tin protective layer on the surface of the nickel seed layer and copper conductive layer. The plating bath temperature is 60°C and the electroless plating time is 20 minutes.

(8) Place the plated sample in a tube furnace and perform annealing treatment in a nitrogen and hydrogen mixed atmosphere at a treatment temperature of 120°C for 2 hours to prepare a silicon heterojunction solar cell.

Example 5

This embodiment provides a metallization method for silicon heterojunction solar energy. The process flow is as follows:

(1) Ultrasonic cleaning is performed on quasi-heterojunction cells without front and rear metal electrodes. The quasi-heterojunction cells include TCO, phosphorus-doped amorphous silicon, intrinsic amorphous silicon, and n-type stacked in sequence from the front to the back. Crystalline silicon substrate, intrinsic amorphous silicon, boron-doped amorphous silicon, TCO, and the TCO component is AZO.

(2) Use the photolithography process for patterning, and prepare the required patterned metal grid lines through the positive photoresist coating, baking, exposure, post-baking, development, fixing and film hardening processes.

(3) Perform ultrasonic cleaning on the sample, and use a pretreatment solution to chemically treat TCO on both sides. The pretreatment solution contains 0.5mol/L aluminum iodide and 0.4mol/L phosphoric acid. Use hydrochloric acid to adjust the pH to 4. The solution The temperature is controlled at 50°C, and the pretreatment time is 2 minutes; after pretreatment, the TCO surface forms a transition metal layer composed of aluminum, zinc and their oxides, and is cleaned with deionized water.

(4) Use electroplating to deposit a nickel seed layer on the transition metal layer, with a current density of 8mA/cm ² and an electroplating time of 2 minutes.

(5) Clean with deionized water and deposit an electroplated copper conductive layer on the nickel seed layer. The current is set to 2.5mA/cm ² and the electroplating time is 10 minutes.

(6) After cleaning with deionized water, use acetone to remove the photoresist, and wash and dry.

(7) Then use electroless plating to deposit a tin protective layer on the surface of the nickel seed layer and copper conductive layer. The plating bath temperature is 50°C and the electroless plating time is 10 minutes.

(8) Place the plated sample in a tube furnace and perform annealing treatment in a nitrogen and hydrogen mixed atmosphere. The treatment temperature is 200°C and the time is 0.2h to prepare a silicon heterojunction solar cell.

Example 6

This embodiment provides a metallization method for silicon heterojunction solar energy. The process flow is as follows:

(1) Ultrasonic cleaning is performed on quasi-heterojunction cells without front and rear metal electrodes. The quasi-heterojunction cells include TCO, phosphorus-doped amorphous silicon, intrinsic amorphous silicon, and n-type stacked in sequence from the front to the back. Crystalline silicon substrate, intrinsic amorphous silicon, boron-doped amorphous silicon, TCO, and the TCO component is GZO.

(2) Use the photolithography process for patterning, and prepare the required patterned metal grid lines through the positive photoresist coating, baking, exposure, post-baking, development, fixing and film hardening processes.

(3) Ultrasonically clean the sample, use a pretreatment solution to chemically treat TCO on both sides. The pretreatment solution contains 0.6mol/L potassium iodide and 0.4mol/L glycine. Use sulfuric acid to adjust the pH to 1 and control the solution temperature. The temperature is 20°C, and the pretreatment time is 30 minutes; after pretreatment, the TCO surface forms a transition metal layer composed of gallium, zinc and their oxides, and is cleaned with deionized water.

(4) Use electroplating to deposit a nickel seed layer on the transition metal layer, with a current density of 3mA/cm ² and an electroplating time of 10 minutes.

(5) Clean with deionized water, and deposit an electroplated copper conductive layer on the nickel seed layer. The current is set to 6mA/cm ² and the electroplating time is 30 minutes.

(6) After cleaning with deionized water, use acetone to remove the photoresist, and wash and dry.

(7) Then use electroless plating to deposit a tin protective layer on the surface of the nickel seed layer and copper conductive layer. The plating bath temperature is 40°C and the electroless plating time is 15 minutes.

(8) Place the plated sample in a tube furnace and perform annealing treatment in a nitrogen and hydrogen mixed atmosphere. The treatment temperature is 180°C and the time is 1 hour to prepare a silicon heterojunction solar cell.

Example 7

This embodiment provides a metallization method for silicon heterojunction solar energy. The process flow is as follows:

(1) Ultrasonic cleaning is performed on quasi-heterojunction cells without front and rear metal electrodes. The quasi-heterojunction cells include TCO, phosphorus-doped amorphous silicon, intrinsic amorphous silicon, and n-type stacked in sequence from the front to the back. Crystalline silicon substrate, intrinsic amorphous silicon, boron-doped amorphous silicon, TCO, and the TCO component is FTO.

(2) Use the photolithography process for patterning, and prepare the required patterned metal grid lines through the positive photoresist coating, baking, exposure, post-baking, development, fixing and film hardening processes.

(3) Ultrasonically clean the sample, use a pretreatment solution to chemically treat TCO on both sides, the pretreatment solution contains 0.5mol/L potassium iodide and 0.3mol/L glycine, adjust the pH to 3.5 with sulfuric acid, and control the solution temperature The temperature is 25°C, and the pretreatment time is 15 minutes; after pretreatment, the TCO surface forms a transition metal layer composed of tin and its oxides, and is cleaned with deionized water.

(4) Use electroplating to deposit a nickel seed layer on the transition metal layer, with a current density of 4mA/cm ² and an electroplating time of 6 minutes.

(5) Clean with deionized water, and deposit an electroplated copper conductive layer on the nickel seed layer. The current is set to 8mA/cm ² and the electroplating time is 15 minutes.

(6) After cleaning with deionized water, use acetone to remove the photoresist, and wash and dry.

(7) Then use electroless plating to deposit a tin protective layer on the surface of the nickel seed layer and copper conductive layer. The plating bath temperature is 30°C and the electroless plating time is 12 minutes.

(8) Place the plated sample in a tube furnace and perform annealing treatment in a nitrogen and hydrogen mixed atmosphere at a treatment temperature of 160°C for 1.5 hours to prepare a silicon heterojunction solar cell.

Comparative example 1

This comparative example provides a metal method for silicon heterojunction solar energy. The process flow is as follows:

(1) The same quasi-heterojunction cell sheet as in Example 1 was subjected to ultrasonic cleaning.

(2) Use the photolithography process for patterning, and prepare the required patterned metal grid lines through the positive photoresist coating, baking, exposure, post-baking, development, fixing and film hardening processes.

(3) Use electroplating method to deposit a nickel seed layer on TCO, with a current density of 2.5mA/cm ² and an electroplating time of 4 minutes.

(4) Clean with deionized water, and deposit an electroplated copper conductive layer on the nickel seed layer. The current is set to 5mA/cm ² and the electroplating time is 15 minutes.

(5) After cleaning with deionized water, use acetone to remove the photoresist, and wash and dry.

(6) Then use electroless plating to deposit a tin protective layer on the surface of the nickel seed layer and copper conductive layer. The plating bath temperature is 40°C and the electroless plating time is 15 minutes.

(7) Place the plated sample in a tube furnace and perform annealing treatment in a nitrogen and hydrogen mixed atmosphere at a treatment temperature of 160°C for 1.5 hours to prepare a silicon heterojunction solar cell.

The cross-sectional morphology of the gate lines of the silicon heterojunction solar cells prepared in Example 1 and Comparative Example 1 is shown in Figure 1. Figure 1 a shows the silicon heterojunction solar cell of Comparative Example 1, and its metal coating and TCO The surface is loosely bonded, the coating is uneven, and there are a large number of holes; b in Figure 1 shows the silicon heterojunction solar cell of Example 1. There is a metal transition layer on the surface of the TCO, and the coating is closely combined with it. The coating is uniform and dense, without holes, and the metal grid is visible. The quality of contact between the wire and the TCO is better.

Eight silicon heterojunction solar cell samples were prepared according to the methods of Examples 1-3 and Comparative Example 1 respectively, and their grid wire pull-off force, contact resistivity, maximum height difference of grid wires at different positions and cell efficiency were tested. The results are as follows: 1 shown.

Table 1 Performance comparison table of silicon heterojunction solar cells of Examples 1-3 and Comparative Example 1

Test results show that after TCO is pretreated, the pull-off force of the electroplated grid lines deposited on its surface increases by 2.5 to 4.5 N, the contact resistance is reduced by 4 to 18 mΩ/cm ² , and the uniformity of the grid lines is increased by 32% to 50%. , the final battery efficiency increased by 2% to 4%.

Figure 4 is a comparison chart of the gate line height distribution of the silicon heterojunction solar cells prepared in Example 1 and Comparative Example 1. It can be seen that after pretreatment, the electroplated gate line height distribution is more uniform; Figure 5 is a comparison of Example 1 and Comparative Example 1. Comparative chart of the gate line pull-off force test results of the silicon heterojunction solar cell prepared in Comparative Example 1. It can be seen that after pretreatment, the adhesion force between the electroplated gate line and TCO is greater and the contact is better.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention, but not to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: The technical solutions described in the foregoing embodiments can still be modified, or some or all of the technical features can be equivalently replaced; and these modifications or substitutions do not deviate from the essence of the corresponding technical solutions from the technical solutions of the embodiments of the present invention. scope.

Claims (10)

1. The silicon heterojunction solar cell is characterized by comprising a crystalline silicon substrate, wherein a first intrinsic amorphous silicon layer, a first doped amorphous silicon/microcrystalline silicon layer, a first transparent conductive oxide layer, a first transition metal layer and a first grid electrode are sequentially arranged on the front surface of the crystalline silicon substrate, a second intrinsic amorphous silicon layer, a second doped amorphous silicon/microcrystalline silicon layer, a second transparent conductive oxide layer, a second transition metal layer and a second grid electrode are sequentially arranged on the back surface of the crystalline silicon substrate, the components of the first transition metal layer are metal and metal oxide corresponding to the components of the first transparent conductive oxide layer, and the components of the second transition metal layer are metal and metal oxide corresponding to the components of the second transparent conductive oxide layer.

2. The silicon heterojunction solar cell of claim 1, wherein the thickness of the first transition metal layer and the second transition metal layer is 10-800nm.

3. The silicon heterojunction solar cell of claim 1, wherein the composition of the first transparent conductive oxide layer and the second transparent conductive oxide layer is selected from at least one of indium tin oxide, tungsten doped indium oxide, aluminum zinc oxide, gallium zinc oxide, fluorine doped tin oxide.

4. The silicon heterojunction solar cell of any one of claims 1-3, wherein the first gate line electrode comprises a first metal seed layer, a first copper conductive layer and a first tin protective layer, the first metal seed layer is disposed on the first transition metal layer, the first copper conductive layer is disposed on the first copper conductive layer, the first tin protective layer coats the first metal seed layer and the first copper conductive layer surface, the second gate line electrode comprises a second metal seed layer, a second copper conductive layer and a second tin protective layer, the second metal seed layer is disposed on the second transition metal layer, the second copper conductive layer is disposed on the second copper conductive layer, and the second tin protective layer coats the second metal seed layer and the second copper conductive layer surface.

5. The silicon heterojunction solar cell of claim 4, wherein the thickness of the first metal seed layer and the second metal seed layer is 20-2000nm, the thickness of the first copper conductive layer and the second copper conductive layer is 500-6000nm, and the thickness of the first tin protective layer and the second tin protective layer is 500-3000nm.

6. A method of metallizing a silicon heterojunction solar cell as claimed in any one of claims 1 to 5, comprising the steps of:

s1, preparing a quasi-heterojunction cell without a metal electrode, and performing patterning treatment;

s2, carrying out chemical solution treatment on the transparent conductive oxide layer on the surface of the battery piece by using a pretreatment solution, reducing part of metal and metal oxide to form a transition metal layer, and cleaning the surface of the battery piece, wherein the pretreatment solution comprises a reducing solute, a stabilizer and a PH regulator, and the reducing solute is one or more selected from potassium iodide, sodium iodide, silver iodide, copper iodide, aluminum iodide, iodine monochloride, iodine monobromide and iodine nitrate;

s3, electroplating and depositing a metal seed layer on the transition metal layer;

s4, electroplating and depositing a copper conducting layer on the metal seed layer;

s5, chemically depositing a tin protective layer on the surfaces of the metal seed layer and the copper conductive layer;

and S6, annealing the battery piece.

7. The method of metallizing a silicon heterojunction solar cell as claimed in claim 6, wherein the stabilizer is selected from one or more of phosphoric acid, glycine, citric acid, acetic acid, and the PH regulator is hydrochloric acid and/or sulfuric acid.

8. The method of metallizing a silicon heterojunction solar cell as claimed in claim 7, wherein the molar concentration of the reducing solute in the pretreatment solution is 0.3-1mol/L and the molar concentration of the stabilizer is 0.2-0.8mol/L.

9. The method of metallizing a silicon heterojunction solar cell as claimed in any one of claims 6 to 8, wherein the pretreatment solution has a temperature of 20-50 ℃ and a PH of 0.5-5.

10. The method of metallization of a silicon heterojunction solar cell as claimed in claim 9, wherein the pretreatment time in step S2 is 1-30min.