A method for preparing a solar cell, a solar cell and a photovoltaic module

Abstract

The present application relates to the field of solar cells, and in particular to a method for preparing solar cells, solar cells and photovoltaic modules. The preparation method includes: providing an initial structure of a solar cell, the initial structure of the solar cell including a silicon substrate and a dielectric layer and a first doping layer stacked on at least one side of the silicon substrate; screen printing and sintering at least one side of the initial structure of the solar cell having the first doping layer to prepare an electrode, and during the sintering process, laser injection treatment is performed on the electrode grid lines formed by screen printing to obtain a solar cell after laser injection treatment, and the sintering temperature is 650°C to 800°C; and electrical injection treatment is performed on the solar cell after laser injection treatment to obtain a solar cell after electrical injection treatment. The solar cell preparation method of the present application reduces the risk of the first doping layer being burned through during the sintering process of the passivated contact cell, while also reducing the contact resistance of the passivated contact cell.

Description

Technical Field

[0001] The present application relates to the field of solar cells, and in particular to a method for preparing a solar cell, a solar cell and a photovoltaic module. Background Art

[0002] Passivated contact cell is a solar cell based on selective carrier transport and has broad application prospects.

[0003] In recent years, the preparation process of passivated contact cells based on PECVD (Plasma Enhanced Chemical Vapor Deposition) process has begun to be applied. Compared with the traditional LPCVD (Low pressure Chemical Vapor Deposition) process, the PECVD process can reduce the thickness of the first doping layer in the passivated contact cell, thereby increasing the short-circuit current of the passivated contact cell.

[0004] However, due to the reduction in the thickness of the first doping layer, the first doping layer of the passivation contact cell is more easily burned through during the sintering process, resulting in a decrease in the cell yield. In addition, the current sintering process is prone to the formation of dense silver blocks near the emitter electrode of the passivation contact cell, resulting in an increase in the contact resistance of the passivation contact cell, thereby affecting the photoelectric conversion efficiency of the passivation contact cell. Summary of the invention

[0005] In order to solve the above technical problems, the present application discloses a method for preparing a solar cell, a solar cell and a photovoltaic module, which can improve the yield of the passivation contact cell while also improving its photoelectric conversion efficiency.

[0006] In a first aspect, the present application provides a method for preparing a solar cell, the method comprising:

[0007] Providing an initial structure of a solar cell, the initial structure of the solar cell comprising a silicon substrate and a dielectric layer and a first doping layer stacked on at least one side of the silicon substrate;

[0008] Screen printing and sintering are performed on at least one side of the initial structure of the solar cell having the first doped layer to prepare an electrode, and during the sintering process, laser injection treatment is performed on the electrode grid lines formed by screen printing to obtain a solar cell after laser injection treatment, and the sintering temperature is 650° C. to 800° C.;

[0009] The solar cell after the laser injection treatment is subjected to an electric injection treatment to obtain the solar cell after the electric injection treatment.

[0010] In one embodiment, the laser injection process includes:

[0011] During the sintering process, the electrode grid lines formed by screen printing are pulsed irradiated by laser, and a bias voltage is applied to the initial structure of the solar cell while irradiating.

[0012] In one embodiment, the power of the laser is 5W to 20W, and the wavelength is 300nm to 2000nm.

[0013] In one embodiment, the irradiation time of the pulse irradiation is 5 ms to 20 ms, and the pulse period is 1 ms to 300 ms.

[0014] In one embodiment, the process of applying the bias voltage includes:

[0015] A bias voltage having a polarity opposite to that of the PN junction of the light-receiving surface of the solar cell initial structure is applied to the solar cell initial structure.

[0016] In one implementation, the bias voltage ranges from 2V to 40V.

[0017] In one embodiment, during the electrical injection process, the voltage is 10V to 50V and the current density is 0.2A / cm 2 ~2A / cm 2 .

[0018] In one embodiment, the sintering temperature during the sintering process is 700° C. to 750° C., and the sintering time is 60 s to 120 s.

[0019] In one embodiment, during the laser injection process, the spot diameter of the laser matches the width of the electrode grid lines.

[0020] In one embodiment, the width of the electrode grid lines is 20 μm to 60 μm, and the spot diameter of the laser is 50 μm to 100 μm.

[0021] In one embodiment, the dielectric layer and the first doping layer are made by PECVD method, the dielectric layer has a thickness of 1 nm to 2 nm, and the first doping layer has a thickness of 40 nm to 80 nm.

[0022] In one embodiment, the initial structure of the solar cell includes a PN junction, and the PN junction is located on a side of the silicon substrate away from the dielectric layer. The preparation method further includes:

[0023] A first functional layer and a second functional layer are respectively prepared on the light-receiving surface and the backlight surface of the initial structure of the solar cell, wherein the first functional layer is located on the PN junction surface of the initial structure of the solar cell, and the second functional layer is located on the surface of the first doping layer.

[0024] In one embodiment, the first functional layer and / or the second functional layer is / are selected from at least one of an aluminum oxide layer, a silicon oxide layer, a silicon oxynitride layer and a silicon nitride layer.

[0025] In a second aspect, the present application provides a solar cell manufactured using the manufacturing method described in the first aspect.

[0026] In a third aspect, the present application provides a photovoltaic module, comprising the solar cell described in the second aspect.

[0027] Compared with the prior art, this application has at least the following beneficial effects:

[0028] The preparation method of the solar cell provided by the present application performs laser injection treatment on the electrode grid lines formed by screen printing during the sintering process of the solar cell, and utilizes the high energy density of the laser to assist the sintering process of the solar cell, so that the Ag in the electrode grid lines of the solar cell and the Si in the first doping layer quickly reach the Ag-Si eutectic point, and even if a lower sintering temperature is used, good metal-semiconductor contact can be achieved, and because the sintering temperature is lower than that of the prior art, the risk of the first doping layer being burned through is greatly reduced, and the yield rate of the passivated contact cell is improved; and, the present application promotes the Ag in the electrode grid lines by performing electrical injection treatment on the solar cell after the laser injection treatment. + The ions are reduced to crystalline Ag single substance, thereby forming more Ag crystals or Ag dendrites between the metal emitter and the first doped layer. More silver crystals or silver dendrites will enhance the contact performance between the metal and the semiconductor, improve the contact structure of the solar cell, and thus reduce its contact resistance. In summary, the present application reduces the risk of the first doped layer being burned through during the sintering process of the passivated contact cell through the synergistic effect of laser injection and electrical injection, while also reducing the contact resistance of the passivated contact cell, thereby making the passivated contact cell have a higher yield and a higher photoelectric conversion efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0030] Figure 1 A schematic diagram of the initial structure of a solar cell in one embodiment of the present application;

[0031] Figure 2 A schematic diagram of the initial structure of a solar cell in another embodiment of the present application;

[0032] Figure 3 This is a schematic diagram of the initial structure of a solar cell in another embodiment of the present application;

[0033] Figure 4 This is a schematic diagram of the structure of a solar cell in one embodiment of the present application;

[0034] Figure 5 This is a cross-sectional SEM (scanning electron microscope) image of the passivated contact cell of Example 1 of the present application;

[0035] Figure 6 This is a cross-sectional SEM image of the passivated contact cell of Comparative Example 1 of the present application;

[0036] Figure 7 This is a cross-sectional SEM image of the passivated contact cell of Comparative Example 2 of the present application.

[0037] Explanation of the reference numerals: silicon substrate-1, dielectric layer-2, first doping layer-3, second doping layer-4, first passivation layer-5, anti-reflection layer-6, second passivation layer-7, positive electrode-8, back electrode-9, light-receiving surface-101, backlight surface-102. DETAILED DESCRIPTION

[0038] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0039] In the present application, the terms "upper", "lower", "left", "right", "front", "back", "top", "bottom", "inner", "outer", "vertical", "horizontal", "lateral", "longitudinal" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings. These terms are mainly used to better describe the present application and its embodiments, and are not used to limit the indicated devices, elements or components to have a specific orientation, or to be constructed and operated in a specific orientation.

[0040] In addition, some of the above terms may be used to express other meanings in addition to indicating orientation or positional relationship. For example, the term "on" may also be used to express a certain dependency or connection relationship in some cases. For those of ordinary skill in the art, the specific meanings of these terms in this application can be understood according to specific circumstances.

[0041] In addition, the terms "installed", "set", "provided with", "connected", and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral structure; it can be a mechanical connection, or an electrical connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be an internal connection between two devices, elements, or components. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0042] In addition, the terms "first", "second", etc. are mainly used to distinguish different devices, elements or components (the specific types and structures may be the same or different), and are not used to indicate or imply the relative importance and quantity of the indicated devices, elements or components. Unless otherwise specified, "plurality" means two or more.

[0043] The inventors of the present application have found that although the PECVD process can reduce the thickness of the first doping layer in the passivation contact cell, the first doping layer of the passivation contact cell is more likely to be burned through during the sintering process due to the reduction in the thickness of the first doping layer, resulting in a decrease in the cell yield. In addition, the current sintering process uses high-temperature sintering above 800°C, which makes it easier for dense silver blocks to appear near the emitter electrode of the passivation contact cell. Since the silver block has poor conductivity, it will increase the contact resistance of the passivation contact cell, thereby affecting the photoelectric conversion efficiency of the passivation contact cell. Therefore, the yield and photoelectric conversion efficiency of existing passivation contact cells still need to be improved.

[0044] In view of this, the present application provides a method for preparing a solar cell, comprising the following steps:

[0045] Step A, providing an initial structure of a solar cell, wherein the initial structure of the solar cell comprises a silicon substrate and a dielectric layer and a first doping layer stacked on at least one side of the silicon substrate;

[0046] Step B, screen printing and sintering at least one side of the initial structure of the solar cell having the first doping layer to prepare an electrode, and during the sintering process, laser injection treatment is performed on the electrode grid lines formed by screen printing to obtain a solar cell after laser injection treatment, and the sintering temperature is 650° C. to 800° C.;

[0047] Step C: performing electrical injection treatment on the solar cell after the laser injection treatment to obtain the solar cell after the electrical injection treatment.

[0048] In step A of the present application, the initial structure of the solar cell includes a silicon substrate and a dielectric layer and a first doping layer stacked on at least one side of the silicon substrate. Figure 1 , the backlight surface 102 of the silicon substrate 1 has a dielectric layer 2 and a first doping layer 3 stacked in layers; in another embodiment, reference Figure 2 , the light-receiving surface 101 of the silicon substrate 1 has a dielectric layer 2 and a first doping layer 3 stacked in layers; in another embodiment, reference Figure 3 The light-receiving surface 101 and the backlight surface 102 of the silicon substrate 1 both have a dielectric layer 2 and a first doping layer 3 which are stacked.

[0049] The silicon substrate may be of a first conductivity type, the doping element of the first doping layer may be of a second conductivity type, and one of the first conductivity type and the second conductivity type may be an N type and the other may be a P type. For example, when the first conductivity type is an N type, the second conductivity type may be a P type; when the first conductivity type is a P type, the second conductivity type may be an N type.

[0050] The silicon substrate of the present application may be a pre-treated silicon substrate, and the pre-treatment process will be described later. The thickness of the silicon substrate is 100 μm to 200 μm, and the present application does not make any specific limitation as long as it can meet the purpose of the present application.

[0051] In step B of the present application, at least one side of the initial structure of the solar cell having the first doping layer may be screen printed and sintered to prepare an electrode. In one embodiment, the side of the initial structure of the solar cell having the first doping layer may be screen printed and sintered to prepare an electrode; in another embodiment, both the light-receiving side and the backlight side of the initial structure of the solar cell may be screen printed and sintered to prepare an electrode, which is conducive to further improving the photoelectric conversion efficiency of the solar cell.

[0052] Wherein, the sintering temperature is 650℃~800℃; in another optional embodiment, the sintering temperature is 700℃~750℃, and the sintering time is 60s~120s. The purpose of sintering is to make the grid lines formed by silver paste or silver aluminum paste after screen printing undergo solid phase reaction, thereby forming electrode grid lines. Compared with the existing sintering temperature greater than 800℃, the present application can make the sintering temperature lower under the premise of achieving good metal-semiconductor contact, thereby greatly reducing the risk of the first doping layer being burned through. The present application performs laser injection treatment on the electrode grid lines formed by screen printing during the sintering process of the initial structure of the solar cell, and uses the characteristics of high energy density of the laser to assist the sintering process of the solar cell, so that the Ag in the electrode grid lines of the solar cell and the Si in the first doping layer quickly reach the Ag-Si eutectic point. Therefore, even if the sintering temperature of the present application is reduced to 650℃~800℃, good metal-semiconductor contact can be achieved. Moreover, compared with the existing sintering temperature of 820°C to 850°C, the sintering temperature of the present application is lower than the existing sintering temperature, thereby greatly reducing the risk of the first doping layer being burned through and improving the yield of the passivation contact cell.

[0053] In step C of the present application, through the electrical injection treatment, electrons interact with atoms in the silicon substrate, stimulate electron-hole pairs, inject non-equilibrium carriers into the solar cell, change the quasi-Fermi level state and hydrogen charge state in the solar cell, repair the defects inside the solar cell, and promote the Ag in the electrode grid line. + The ions are reduced to crystalline Ag single substance, thereby forming more Ag crystals or Ag dendrites between the metal emitter and the first doping layer. More silver crystals or silver dendrites will enhance the contact performance between the metal and the semiconductor, improve the contact structure of the solar cell, and thus reduce the contact resistance of the solar cell. The present application has no particular restrictions on the electrical injection time, as long as the purpose of the present application can be achieved. In one embodiment, the electrical injection time is 100s to 300s; in another embodiment, the electrical injection time is 180s to 220s.

[0054] In summary, the present application reduces the risk of the first doping layer being burned through during the sintering process of the passivation contact cell through the synergistic effect of laser injection processing and electrical injection processing, while also reducing the contact resistance of the passivation contact cell, thereby making the passivation contact cell have a higher yield and higher photoelectric conversion efficiency.

[0055] In an optional embodiment, the laser injection process includes:

[0056] During the sintering process, the electrode grid lines formed by screen printing are pulsed with laser, and a bias voltage is applied to the initial structure of the solar cell while irradiating.

[0057] During the laser injection process of the present application, laser pulses are irradiated on the electrode grid lines formed by screen printing. On the one hand, the high energy density of the laser can be used to assist the sintering process of the solar cell, so that the Ag in the electrode grid lines of the solar cell and the Si in the first doping layer quickly reach the Ag-Si eutectic point; on the other hand, it can avoid laser damage to the solar cell due to irradiation to other areas of the solar cell.

[0058] The present application can control the laser irradiation to the electrode grid lines by adjusting the relevant parameters of the laser. For example, the laser scanning path can be adjusted according to the designed distribution position of the electrode grid lines on the solar cell to only irradiate the electrode grid lines without irradiating other areas of the solar cell; or, the laser spot diameter can be adjusted according to the designed width of the electrode grid lines.

[0059] In the laser injection process of the present application, since the pulse irradiation is pulsed, a bias voltage is applied to the initial structure of the solar cell while the laser irradiation is being performed, so that the application time of the bias voltage matches the pulse period of the laser. In this way, under the joint action of the pulsed laser and the bias voltage, the laser beam forms local induced carriers, and the bias voltage generates an induced current in the grid line, thereby quickly generating a hot spot. Under the synergistic action of the two, the mutual diffusion of silver and silicon is quickly induced during the sintering process, and the Ag in the grid line and the Si in the first doping layer quickly reach the Ag-Si eutectic point, thereby achieving a good metal-semiconductor contact.

[0060] In an optional embodiment, the power of the laser is 5W to 20W, and the wavelength is 300nm to 2000nm. By adjusting the power and wavelength of the laser within the above range, the present application can not only utilize the high energy density of the laser to assist the sintering process of the solar cell, but also reduce the risk of solar cell damage caused by excessive laser power, thereby increasing the life of the solar cell.

[0061] In an optional embodiment, the irradiation time of pulse irradiation is 5ms to 20ms, and the pulse period is 1ms to 300ms; in another optional embodiment, the pulse period is 50ms to 100ms. The irradiation time of pulse irradiation refers to the irradiation time of the laser in each pulse period. The present application adjusts the irradiation time and pulse period of pulse irradiation within the above range, which is conducive to the formation of local induced carriers by the laser beam, thereby forming a local current in combination with the bias voltage, so that the Ag in the solar cell electrode grid line and the Si in the first doping layer quickly reach the Ag-Si eutectic point, thereby achieving good metal-semiconductor contact.

[0062] In an optional implementation, the process of applying the bias voltage includes:

[0063] A bias voltage having a polarity opposite to that of the PN junction of the light-receiving surface of the solar cell initial structure is applied to the solar cell initial structure.

[0064] The present application can apply a bias voltage with a polarity opposite to that of the PN junction of the light-receiving surface of the solar cell initial structure to the solar cell initial structure, and the bias voltage is less than the breakdown voltage of the solar cell. In this way, under the combined action of the pulsed laser and the bias voltage, the Ag in the electrode grid line and the Si in the first doping layer quickly reach the Ag-Si eutectic point, thereby achieving good metal-semiconductor contact.

[0065] In an optional embodiment, the bias voltage has a voltage range of 2 V to 40 V; in another optional embodiment, the bias voltage has a voltage range of 10 V to 30 V. By adjusting the bias voltage within the above range, it is beneficial to quickly make the Ag in the electrode grid line and the Si in the first doping layer reach the Ag-Si eutectic point, thereby achieving good metal-semiconductor contact.

[0066] The bias voltage of the present application refers to: applying a certain voltage to a certain point in the circuit, so that the potential of the point is shifted from the zero potential point to a predetermined positive potential or negative potential. The predetermined positive potential or negative potential can be pre-set by technicians according to actual needs.

[0067] In an optional embodiment, the voltage of the electric injection process is 10V to 50V, and the current density is 0.2A / cm 2 ~2A / cm 2 In another optional embodiment, the voltage of the electric injection process is 20V to 40V, and the current density is 1A / cm 2 ~1.5A / cm 2 By regulating the voltage and current density of the electric injection treatment within the above range, it is beneficial to stimulate electron-hole pairs and promote the Ag in the electrode grid line. + The ions are reduced to crystalline Ag single substance, which improves the contact structure of the solar cell and thus reduces the contact resistance of the solar cell.

[0068] In an optional embodiment, during the laser injection process, the spot diameter of the laser matches the width of the electrode grid line. That is, the spot diameter of the laser increases as the width of the electrode grid line increases, and decreases as the width of the electrode grid line decreases. In this way, the Ag in the electrode grid line of the solar cell and the Si in the first doping layer can quickly reach the Ag-Si eutectic point, and the solar cell can be prevented from being damaged by the laser due to the laser irradiation to other areas of the solar cell, thereby achieving good metal-semiconductor contact while reducing the risk of damage to the solar cell.

[0069] In an optional embodiment, the width of the electrode grid line is 20 μm to 60 μm, and the spot diameter of the laser is 50 μm to 100 μm. By coordinating the width of the electrode grid line and the spot diameter of the laser within the above range, it is beneficial to obtain electrode grid lines and lasers with matching widths, thereby further reducing the risk of laser damage to the solar cell due to laser irradiation to other areas of the solar cell.

[0070] In an optional embodiment, the dielectric layer and the first doping layer are prepared by PECVD, the thickness of the dielectric layer is 1nm to 2nm, and the thickness of the first doping layer is 40nm to 80nm. Exemplarily, when the width of the electrode grid line is 30μm, the spot diameter of the laser is 70μm; when the width of the electrode grid line is 40μm, the spot diameter of the laser is 80μm. By regulating the dielectric layer and the first doping layer within the above range, it is beneficial to obtain a passivated contact cell with good performance.

[0071] In an optional embodiment, the initial structure of the solar cell includes a PN junction, and the PN junction is located on a side of the silicon substrate away from the dielectric layer. The solar cell preparation method of the present application also includes:

[0072] The first functional layer and the second functional layer are respectively prepared on the light-receiving surface and the backlight surface of the initial structure of the solar cell, wherein the first functional layer is located on the PN junction surface of the initial structure of the solar cell, and the second functional layer is located on the surface of the first doping layer.

[0073] Exemplarily, a first passivation layer and an anti-reflection layer can be prepared in sequence on the light-receiving surface of the initial structure of the solar cell, and the first passivation layer and the anti-reflection layer belong to the first functional layer, wherein the first passivation layer is an aluminum oxide layer, and the anti-reflection layer is a silicon oxynitride layer, the first passivation layer plays a passivation role, and the anti-reflection layer plays an anti-reflection role; a second passivation layer can be prepared on the backlight side of the initial structure of the solar cell, the second passivation layer belongs to the second functional layer, and the second passivation layer is a silicon oxynitride layer, which plays a passivation role.

[0074] The present application has no particular limitation on the thickness of each functional layer, as long as the purpose of the present application can be achieved. For example, the thickness of the first passivation layer is 3nm to 7nm, the thickness of the anti-reflection layer is 3nm to 7nm, and the thickness of the second passivation layer is 80nm to 100nm.

[0075] The present application has no particular restrictions on the materials of the first functional layer and the second functional layer, as long as the purpose of the present application can be achieved. For example, the first functional layer and / or the second functional layer is selected from at least one of an aluminum oxide layer, a silicon oxide layer, a silicon oxynitride layer, and a silicon nitride layer.

[0076] In an optional embodiment, the method for preparing the solar cell of the present application further includes: pre-treating the silicon substrate.

[0077] Taking N-type silicon wafer as an example, the process of pre-treating the silicon substrate includes:

[0078] 1) Texturing: providing an N-type silicon wafer as a silicon substrate, using a NaOH solution (concentration 1wt% to 3wt%) for texturing, and then using a mixture of hydrogen peroxide and NaOH solution to clean the silicon substrate, wherein the concentration of the NaOH solution in the mixture is 0.5wt% to 1wt%, and the concentration of the hydrogen peroxide is 2wt% to 3wt%;

[0079] 2) Boron diffusion: The cleaned silicon substrate is placed in a boron diffusion furnace and BCl 3 Diffusion at 900℃~1050℃ forms PN junction;

[0080] 3) Alkali polishing: Use chain HF equipment to remove borosilicate glass (BSG) on the back of the silicon substrate due to boron expansion, and then use trough wet equipment to remove the PN junction on the back and edge of the silicon substrate.

[0081] In an optional embodiment, the preparation method of the present application further comprises:

[0082] A dielectric layer, a first doping layer and a mask layer are sequentially prepared on the backlight surface of the pretreated silicon substrate. After annealing, the plated dielectric layer, the plated first doping layer and the mask layer are removed to obtain the initial structure of the solar cell. Among them, the doping element of the first doping layer has a second conductivity type, one of the first conductivity type and the second conductivity type is N-type and the other is P-type. The mask layer plays a role in protecting the first doping layer. The present application has no particular limitation on the thickness of the mask layer, as long as the purpose of the present application can be achieved. In one embodiment, the thickness of the mask layer is 5nm to 20nm; in another embodiment, the thickness of the mask layer is 8nm to 12nm.

[0083] Taking an N-type silicon substrate as an example, the preparation process of the dielectric layer, the first doping layer and the mask layer specifically includes:

[0084] Step a: Preparation of dielectric layer:

[0085] First, the furnace tube of the PECVD equipment is vacuumed and leak-checked, the pre-treated silicon substrate is placed in the PECVD equipment, and then the temperature is raised to 430℃~450℃, and then nitrous oxide (N 2 O) depositing a dielectric layer, wherein N 2 The flow rate of O is 8500 sccm to 10000 sccm, and the plasma pulse duty ratio is 20:(950 to 1150). 2 The flow rate of O can be any one of the following values: 8500sccm, 8800sccm, 9000sccm, 9200sccm, 9600sccm, 10000sccm; the plasma pulse duty ratio can be any one of the following values: 20:950, 20:1050, 20:1150.

[0086] Step b: Preparation of the first doped layer (taking phosphorus-doped amorphous silicon layer as an example):

[0087] Silane (SiH 4 ), phosphine (PH 3 ) and hydrogen (H 2 ) mixed gas, the mixed gas is ionized, and a phosphorus-doped amorphous silicon layer is deposited. 4 The flow rate is 2500sccm~3000sccm, PH 3 The flow rate is 600sccm~1000sccm, H 2 The flow rate is 6000sccm~10000sccm, and the plasma pulse duty ratio is 30:(350~600). For example, SiH 4 The flow rate can be any of the following values: 2500sccm, 2600sccm, 2700sccm, 2800sccm, 2900sccm, 3000sccm; PH 3 The flow rate can be any of the following values: 600sccm, 700sccm, 800sccm, 900sccm, 1000sccm; H 2 The flow rate can be any of the following values: 6000sccm, 7000sccm, 8000sccm, 9000sccm, 9500sccm, 10000sccm; the plasma pulse duty cycle can be any of the following values: 30:350, 30:380, 30:400, 30:430, 30:450, 30:480, 30:500, 30:530, 30:550, 30:580, 30:600.

[0088] Step c: Preparation of mask layer:

[0089] Introduce SiH into the PECVD equipment 4 and N 2 O mixed gas, depositing a mask layer on the surface of the phosphorus-doped amorphous silicon layer. 4 The flow rate is 1500sccm~2000sccm, N 2 The flow rate of O is 7000sccm to 8000sccm, and the plasma pulse duty ratio is 30:(500 to 600). 4 The flow rate can be any of the following values: 1500sccm, 1600sccm, 1700sccm, 1800sccm, 1900sccm, 2000sccm; N 2The flow rate of O can be any one of the following values: 7000sccm, 7200sccm, 7500sccm, 7700sccm, 7800sccm, 8000sccm; the plasma pulse duty ratio can be 30:500, 30:530, 30:550, 30:560, 30:580, 30:600.

[0090] Step d, annealing:

[0091] After the mask layer is deposited, 2 ) or oxygen (O 2 ) environment, the annealing temperature is 800°C to 980°C, and the annealing time is 20min to 50min. For example, the annealing temperature can be any one of the following values: 880°C, 900°C, 910°C, 950°C, 980°C; the annealing time can be any one of the following values: 20min, 30min, 40min, 50min.

[0092] Step e: De-plating treatment:

[0093] The light-receiving surface of the annealed silicon substrate is de-plated and cleaned to remove the plated dielectric layer, the plated first doping layer and the mask layer to obtain the initial structure of the solar cell.

[0094] The present application may use the existing de-coating process to remove the coating layers and the mask layer, as long as the purpose of the present application can be achieved, and the present application is not particularly limited. For example, a NaOH solution is used for de-coating cleaning at room temperature.

[0095] The present application has no particular limitation on the gate line paste, as long as the purpose of the present application can be achieved. For example, the gate line paste can be silver paste or silver-aluminum paste.

[0096] In a second aspect, the present application provides a solar cell produced using the solar cell production method described in any of the above embodiments.

[0097] In one embodiment, see Figure 4 The solar cell of the present application includes a silicon substrate 1, and the light-receiving surface 101 of the silicon substrate 1 has a second doping layer 4, a first passivation layer 5 and an anti-reflection layer 6 in sequence, wherein the silicon substrate 1 has a first conductivity type, the second doping layer 4 has a second conductivity type, and the second doping layer 4 forms a PN junction with the silicon substrate 1; the backlight surface 102 of the silicon substrate 1 has a dielectric layer 2, a first doping layer 3 and a second passivation layer 7 in sequence, the silicon substrate 1 has a first conductivity type, and the first doping layer 3 has a second conductivity type. In addition, a positive electrode 8 is also provided on the surface of the anti-reflection layer 6, and a back electrode 9 is also provided on the surface of the second passivation layer 7.

[0098] In a third aspect, the present application provides a photovoltaic module, wherein the photovoltaic module comprises the solar cell as described in the second aspect.

[0099] The present application also provides a photovoltaic module, which is used to convert received light energy into electrical energy and transmit it to an external load. The photovoltaic module includes: at least one battery string, which is formed by connecting a plurality of the above-mentioned solar cells; a packaging film, which is used to cover the surface of the battery string; and a cover plate, which is used to cover the surface of the packaging film away from the battery string.

[0100] The solar cell repair method, solar cell and photovoltaic module of the present application will be further described below in conjunction with more specific embodiments.

[0101] Example 1

[0102] <Preprocessing>

[0103] 1) Texturing: An N-type silicon wafer with a thickness of 130 μm is used as a silicon substrate, and a 1 wt % NaOH solution is used for texturing. After texturing, the silicon substrate is cleaned with a mixture of hydrogen peroxide and NaOH solution, wherein the concentration of the NaOH solution in the mixture is 0.5 wt %, and the concentration of the hydrogen peroxide is 2 wt %;

[0104] 2) Boron diffusion: Place the cleaned silicon substrate into a boron diffusion furnace and introduce BCl at 1000°C 3 Boron diffusion is performed to form a PN junction;

[0105] 3) Alkali polishing: Use chain HF equipment (model SC-LSS9600CS) to remove BSG on the back of the silicon substrate due to boron expansion, and then use trough wet equipment (model SC-CSZJ9600E-20F) to remove the PN junction on the back and edge of the silicon substrate.

[0106] <Preparation of dielectric layer>

[0107] The furnace tube of the PECVD equipment (model PD-520MAX) was evacuated and leak-checked to a vacuum degree of 0.1 Pa. The pretreated silicon substrate was placed in the PECVD equipment, then heated to 430 °C and N 2 O, ionized for 2 min, to obtain SiO 2 Dielectric layer. Among them, N 2 The flow rate of O2 is 9000 sccm, and the plasma pulse duty ratio is 20: 1050. The thickness of the dielectric layer is 1.6 nm.

[0108] <Preparation of the First Doping Layer>

[0109] Introduce SiH into the PECVD equipment 4 , PH 3 and H 2Mixed gas, ionized for 25 minutes, to obtain phosphorus-doped amorphous silicon layer. 4 The flow rate is 2900sccm, PH 3 The flow rate is 800sccm, H 2 The flow rate is 9500 sccm, and the plasma pulse duty ratio is 20: 500. The thickness of the first doped layer is 50 nm.

[0110] <Preparation of Mask Layer>

[0111] Introduce SiH into the PECVD equipment 4 and N 2 O mixed gas, ionized for 50s, to obtain the mask layer. 4 The flow rate is 1800sccm, N 2 The flow rate of O2 is 7800 sccm, and the plasma pulse duty ratio is 30:580. The thickness of the mask layer is 10 nm.

[0112] <Annealing treatment>

[0113] In N 2 Keep the temperature at 900℃ for 1500s.

[0114] <De-plating treatment>

[0115] The light-receiving surface of the annealed silicon substrate is de-plated and cleaned using a 5wt% NaOH solution at room temperature to remove the plated dielectric layer, the plated first doping layer and the mask layer to obtain the initial structure of the solar cell.

[0116] <Coating treatment>

[0117] ALD equipment (model KF6000) was used to first deposit an aluminum oxide layer as the first passivation layer on the light-receiving side of the initial structure of the solar cell, and then deposit a silicon oxynitride layer as an anti-reflection layer; a silicon oxynitride layer was deposited as the second passivation layer on the backlight side of the initial structure of the solar cell. The thickness of the passivation layer is 5nm, and the thickness of the anti-reflection layer is 80nm.

[0118] <Laser injection treatment>

[0119] The light-receiving surface of the initial structure of the solar cell after the coating treatment is screen-printed and sintered to prepare the electrode. During the sintering process, the electrode grid lines formed by screen printing are pulsed with laser, and a bias voltage with a polarity opposite to the PN junction of the light-receiving surface of the initial structure of the solar cell is applied to the initial structure of the solar cell while irradiating. Among them, the sintering temperature is 700℃, the sintering time is 80s; the laser power is 10W, the wavelength is 500nm, the pulse period is 3ms, the pulse irradiation time is 10ms; the bias voltage is 10V, and the solar cell after laser injection treatment is obtained.

[0120] <Electrical injection treatment>

[0121] The solar cell after laser injection treatment is subjected to electric injection treatment to obtain a solar cell after electric injection treatment. The voltage is 30V and the current density is 0.5A / cm 2 , the electrical injection time is 200s.

[0122] Embodiment 2 to Embodiment 4

[0123] Except that the sintering temperature and sintering time were adjusted as shown in Table 1 in the <Laser injection treatment>, the rest was the same as in Example 1.

[0124] Embodiment 5 to Embodiment 7

[0125] Except that the laser related parameters are adjusted as shown in Table 1 in the <Laser injection process>, the rest is the same as Example 1.

[0126] Embodiment 8-embodiment 9

[0127] Except that the bias voltage related parameters are adjusted as shown in Table 1 in the <Laser injection process>, the rest is the same as the first embodiment.

[0128] Example 10 to Example 12

[0129] Except that the voltage and current density of the electric injection treatment were adjusted as shown in Table 1 in <Electrical Injection Treatment>, the rest was the same as Example 1.

[0130] Comparative Example 1

[0131] Except that the light-receiving surface and the backlight surface of the solar cell after the winding plating are directly screen-printed and sintered to prepare electrodes, and no laser injection treatment and electric injection treatment are performed, the rest is the same as Example 1. The sintering temperature is 850°C.

[0132] Comparative Example 2

[0133] The process is the same as in Example 1 except that only laser injection treatment is performed on the solar cell, and no electrical injection treatment is performed.

[0134] Comparative Example 3

[0135] The process is the same as in Example 1 except that only electrical injection treatment is performed on the solar cells and laser injection treatment is not performed.

[0136] Table 1 Preparation parameters of each embodiment and comparative example

[0137]

[0138]

[0139] Note: In Table 1, “ / ” indicates that there is no relevant preparation parameter.

[0140] Performance Test:

[0141] Open circuit voltage, short circuit current, fill factor test:

[0142] The current (I)-voltage (V) of the solar cells of each embodiment and comparative example was measured using an IV tester (model: MX-MPVC-A20, manufacturer: Suzhou Maxwell Technology Co., Ltd.) to obtain the open circuit voltage, short circuit current and fill factor of the solar cells.

[0143] Contact resistivity test:

[0144] A TLM tester (model: TLM-SCAN, manufacturer: Shanghai Shunmiao Optoelectronics Technology Co., Ltd.) was used to perform a probe pressing test on the solar cells of each embodiment and comparative example to obtain the contact resistivity of the solar cells.

[0145] Photoelectric conversion efficiency test:

[0146] The current (I)-voltage (V) of the solar cells of each embodiment and comparative example was measured using an IV tester (model: MX-MPVC-A20, manufacturer: Suzhou Maxwell Technology Co., Ltd.) to obtain the photoelectric conversion efficiency (Eta) of the solar cells.

[0147] Solar cell yield test:

[0148] The appearance images of the solar cells of each embodiment and comparative example were obtained using a fully automatic EL (Electro Luminescence) tester (model: MX-XDL-T, manufacturer: Suzhou Maxwell Technology Co., Ltd.), and the obtained imaging images were analyzed and processed by image software to detect whether the solar cells had abnormal phenomena such as concentric circles, black spots, hidden cracks, fragments, cold solder joints, broken grids, etc. If there were, it was determined to be a defective product; if not, it was determined to be a good product. The yield rate of the solar cells was counted.

[0149] Table 2 Performance data of each embodiment and comparative example

[0150]

[0151] It can be seen from Examples 1 to 12 and Comparative Example 1 that, compared with Comparative Example 1, after laser injection and electrical injection treatment of solar cells, the Eta and yield of the solar cells are significantly improved, the contact resistivity is significantly reduced, and the open circuit voltage, short circuit current and fill factor are improved or close. This shows that the preparation method of the present application can reduce the risk of the first doping layer being burned through during the sintering process of the passivated contact cell, while also improving the yield and photoelectric conversion efficiency of the passivated contact cell, while keeping other properties unchanged or improved.

[0152] It can be seen from Examples 1 to 12 and Comparative Examples 2 to 3 that, compared with Comparative Examples 2 and 3, the present application significantly improves the Eta and yield of solar cells after laser injection and electrical injection treatment of solar cells. In addition, although the open circuit voltage, short circuit current and fill factor of Comparative Example 2 are improved compared with Comparative Example 1, the improvement of short circuit current performance is not obvious, and the contact resistivity is too large, indicating that only laser injection treatment of the passivated contact cell has limited improvement in the performance of the passivated contact cell; although the open circuit voltage, short circuit current and fill factor of Comparative Example 3 are improved compared with Comparative Example 1, the improvement of fill factor is not obvious, and the contact resistivity is too large, indicating that only electrical injection treatment of the passivated contact cell has limited improvement in the performance of the passivated contact cell. It can be seen that the preparation method of the present application can reduce the risk of burn-through of the first doping layer during the sintering process of the passivated contact cell through the synergistic effect of laser injection and electrical injection, while also improving the yield and photoelectric conversion efficiency of the passivated contact cell.

[0153] See also Figure 5 to Figure 7 From the cross-sectional SEM images of the passivated contact cells corresponding to Example 1, Comparative Example 1 and Comparative Example 2, it can be seen that Example 1 (see Figure 5 ) of silver crystals are evenly distributed on the emitter, and the size is significantly larger (the largest is about 200nm); Comparative Example 1 (see Figure 6 ) of silver crystals (spherical particles in the figure) attached to the surface of the emitter, the number of silver crystals is small, the size is small (about 90nm), and the distribution is uneven; Comparative Example 2 (see Figure 7 ) silver crystals tend to sink, the number increases, and the size becomes larger (the largest is about 100nm). This shows that the preparation method of the present application promotes the Ag in the electrode grid line + The ions are reduced to crystalline Ag single substance, thereby forming more Ag crystals between the metal emitter and the first doping layer. More silver crystals will enhance the contact performance between the metal and the semiconductor, improve the contact structure of the passivation contact battery, thereby reducing the contact resistance of the passivation contact battery, and thus improving the photoelectric conversion efficiency of the passivation contact battery.

[0154] The above is a detailed introduction to a method for preparing a solar cell, a solar cell and a photovoltaic module disclosed in the embodiments of the present application. Specific examples are used in this article to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the technical solutions and core inventions of the embodiments of the present application. At the same time, for those skilled in the art, according to the ideas of the present application, there will be changes in the specific implementation methods and application scopes. In summary, the content of this specification should not be understood as a limitation on the present application.

Claims

1. A method for preparing a solar cell, characterized in that: The preparation method comprises: Providing an initial structure of a solar cell, the initial structure of the solar cell comprising a silicon substrate and a dielectric layer and a first doping layer stacked on at least one side of the silicon substrate; Screen printing and sintering are performed on at least one side of the initial structure of the solar cell having the first doped layer to prepare an electrode, and during the sintering process, laser injection treatment is performed on the electrode grid lines formed by screen printing to obtain a solar cell after laser injection treatment, and the sintering temperature is 650° C. to 800° C.; The solar cell after laser injection treatment is subjected to electric injection treatment to obtain the solar cell after electric injection treatment. During the electric injection treatment, the voltage is 10V to 50V and the current density is 0.2A / cm 2 ~2A / cm 2 ; The laser injection process includes: During the sintering process, the electrode grid lines formed by screen printing are pulsed with laser, and a bias voltage with a polarity opposite to that of the PN junction of the light-receiving surface of the solar cell initial structure is applied to the solar cell initial structure at the same time.

2. The preparation method according to claim 1, characterized in that: The power of the laser is 5W-20W, and the wavelength is 300nm-2000nm.

3. The preparation method according to claim 1, characterized in that: The irradiation time of the pulse irradiation is 5ms to 20ms, and the pulse period is 1ms to 300ms.

4. The preparation method according to claim 1, characterized in that: The bias voltage has a voltage range of 2V to 40V.

5. The preparation method according to claim 1, characterized in that: The sintering temperature during the sintering process is 700° C. to 750° C., and the sintering time is 60s to 120s.

6. The preparation method according to claim 1, characterized in that: During the laser injection process, the spot diameter of the laser matches the width of the electrode grid lines.

7. The preparation method according to claim 6, characterized in that: The width of the electrode grid line is 20 μm to 60 μm, and the spot diameter of the laser is 50 μm to 100 μm.

8. The preparation method according to claim 1, characterized in that: The dielectric layer and the first doping layer are made by PECVD method, the dielectric layer has a thickness of 1nm-2nm, and the first doping layer has a thickness of 40nm-80nm.

9. The preparation method according to claim 1, characterized in that: The initial structure of the solar cell includes a PN junction, and the PN junction is located on a side of the silicon substrate away from the dielectric layer. The preparation method also includes: A first functional layer and a second functional layer are respectively prepared on the light-receiving surface and the backlight surface of the initial structure of the solar cell, wherein the first functional layer is located on the PN junction surface of the initial structure of the solar cell, and the second functional layer is located on the surface of the first doping layer.

10. The preparation method according to claim 9, characterized in that: The first functional layer and / or the second functional layer is / are selected from at least one of an aluminum oxide layer, a silicon oxide layer, a silicon oxynitride layer and a silicon nitride layer.

11. A solar cell, characterized in that: The solar cell is prepared by the method for preparing the solar cell according to any one of claims 1 to 10.

12. A photovoltaic module, characterized in that: Comprising the solar cell as claimed in claim 11.

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