A heterojunction solar cell and a method for preparing the same, and a photovoltaic module

Abstract

The object of the present invention is to provide a heterojunction solar cell, a preparation method thereof and a photovoltaic module. The heterojunction solar cell comprises: a silicon substrate; a first transparent conductive layer and a first electrode are stacked on the surface of one side of the silicon substrate, and a second transparent conductive layer and a second electrode are stacked on the surface of the other side of the silicon substrate; wherein the first transparent conductive layer comprises a first laser activation region and a first non-laser activation region, and the first laser activation region is in contact with the first electrode; and / or the second transparent conductive layer comprises a second laser activation region and a second non-laser activation region, and the second laser activation region is in contact with the second electrode. The area where the TCO of the present invention contacts the electrode is a laser activation area, which can reduce the contact resistivity between the electrode and TCO and the square resistance of the transparent conductive layer, thereby achieving the purpose of reducing the series resistance Rs and improving the battery conversion efficiency.

Description

Technical Field

[0001] The invention belongs to the technical field of photovoltaics and relates to a heterojunction solar cell and a preparation method thereof and a photovoltaic module. Background Art

[0002] Silicon-based solar cells are the mainstream of the current photovoltaic industry, accounting for more than 90% of the market. Silicon-based heterojunction (HJT) solar cells have the characteristics of low recombination, high open-circuit voltage, simple structure, low-temperature process, good light stability and low temperature coefficient, making them a good candidate for realizing low-cost, high-conversion efficiency solar cells. Heterojunction (HJT) cells are mainly produced by depositing an intrinsic hydrogenated amorphous layer on the front / back side of an n-type silicon wafer, and then preparing a p-type doped silicon-containing film and an n-type doped silicon-containing film, respectively. The doped silicon-containing film is, for example, an amorphous silicon film or a microcrystalline silicon film, and then depositing a transparent conductive layer on the surface. The transparent conductive layer is also called a transparent conductive oxide film (TCO). Finally, an electrode layer is formed on the transparent conductive layer to obtain the final battery.

[0003] However, in the current battery structure design, it is difficult to reduce the contact resistance between the transparent conductive layer and the electrode in the electrode layer while taking into account the improvement of the light transmittance of the non-contact area of ​​the transparent conductive layer with the electrode, which affects the further improvement of battery efficiency. The key to improving conversion efficiency is to increase the short-circuit current Isc and reduce the series resistance Rs. The commonly used method to reduce Rs is to adjust the process parameters of hydrogenated microcrystalline silicon and transparent conductive layer (TCO).

[0004] In the heterojunction cell disclosed in the prior art, the first doped amorphous silicon inner layer has a low doping concentration, which can reduce the amorphous silicon structural distortion caused by doping, which is beneficial to improving the passivation effect of the solar cell and improving the open circuit voltage; the provision of the doped amorphous silicon oxide layer can increase the optical band gap of the main light-receiving surface of the heterojunction solar cell, reduce the absorption of incident light in the passivation film layer, and improve the short-circuit current of the solar cell; the first doped amorphous silicon outer layer has a high doping concentration, which can reduce the contact resistance between it and the first transparent conductive film, thereby reducing the series resistance of the solar cell.

[0005] Therefore, how to effectively reduce the series resistance Rs and improve the battery conversion efficiency is a technical problem that needs to be solved urgently. Summary of the invention

[0006] In view of the shortcomings of the prior art, the present invention aims to provide a heterojunction solar cell and a preparation method thereof and a photovoltaic module. In the heterojunction solar cell provided by the present invention, the area where the transparent conductive layer (TCO) contacts the electrode is a laser activated area, which can reduce the contact resistivity between the electrode and TCO and the square resistance of the transparent conductive layer, thereby achieving the purpose of reducing the series resistance Rs and improving the battery conversion efficiency.

[0007] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0008] In a first aspect, the present invention provides a heterojunction solar cell, the heterojunction solar cell comprising:

[0009] Silicon substrate;

[0010] A first transparent conductive layer and a first electrode are stacked on one surface of the silicon substrate, and a second transparent conductive layer and a second electrode are stacked on the other surface of the silicon substrate;

[0011] Wherein, the first transparent conductive layer comprises a first laser activated area and a first non-laser activated area, and the first laser activated area is in contact with the first electrode;

[0012] and / or,

[0013] The second transparent conductive layer includes a second laser activated region and a second non-laser activated region, and the second laser activated region is in contact with the second electrode.

[0014] In the heterojunction solar cell provided by the present invention, the area where the transparent conductive layer (TCO) contacts the electrode is a laser activated area, which can reduce the contact resistivity between the electrode and TCO and the TCO square resistance, thereby achieving the purpose of reducing the series resistance Rs and improving the battery conversion efficiency.

[0015] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. Through the following preferred technical solutions, the technical objectives and beneficial effects of the present invention can be better achieved and realized.

[0016] Preferably, the thickness of the first laser activated zone is 5~50nm, for example 5nm, 10nm, 15nm, 20nm, 25nm, 30nm, 35nm, 40nm, 45nm or 50nm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0017] Preferably, the thickness of the second laser activated zone is 5~50nm, for example 5nm, 10nm, 15nm, 20nm, 25nm, 30nm, 35nm, 40nm, 45nm or 50nm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0018] In the present invention, by adjusting the thickness of the first laser activated zone to 5-50 nm and / or the thickness of the second laser activated zone to 5-50 nm, the contact resistivity between the transparent conductive layer and the electrode in the laser activated area can be better reduced.

[0019] Preferably, in the region in the thickness direction of the first transparent conductive layer, the non-contact region corresponding to the first electrode is the third laser activated region.

[0020] Preferably, the thickness of the third laser activated zone is 70~115nm, for example 70nm, 75nm, 80nm, 85nm, 90nm, 95nm, 100nm, 105nm, 110nm or 115nm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0021] Preferably, in the region in the thickness direction of the second transparent conductive layer, the non-contact region corresponding to the second electrode is the fourth laser activated region.

[0022] In the present invention, the third and / or fourth laser activation regions are arranged along the thickness direction of the transparent conductive layer in areas not in contact with the first electrode and / or the second electrode, which is more conducive to reducing the TCO square resistance in the laser non-activation region.

[0023] Preferably, the thickness of the fourth laser activated zone is 70~115nm, for example 70nm, 75nm, 80nm, 85nm, 90nm, 95nm, 100nm, 105nm, 110nm or 115nm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0024] Preferably, in the transparent conductive layer, the carrier concentration in the laser activated region is 2E20-5E20cm -3 , for example 2E20cm -3 、2.5E20cm -3 、3E20cm -3 、3.5E20cm -3 、4E20cm -3 、4.5E20cm -3 , or 5E20cm -3 The above range is not limited to the listed values, and other values ​​not listed within the above range are also applicable.

[0025] Preferably, in the transparent conductive layer, the carrier concentration in the non-laser activated region is 1E20-4E20cm -3 , for example 1E20cm -3 、1.5E20cm -3 、2E20cm -3 、2.5E20cm -3 、3E20cm -3 、3.5E20cm -3 or 4E20cm -3The above range is not limited to the listed values, and other values ​​not listed within the above range are also applicable.

[0026] Preferably, in the transparent conductive layer, the difference between the carrier concentration in the laser activated region and the carrier concentration in the non-laser activated region is greater than or equal to 1E19 cm -3 , for example 1E19cm -3 、2E19cm -3 、5E19cm -3 、8E19cm -3 、1E20cm -3 、2E20cm -3 The above range is not limited to the listed values, and other values ​​not listed within the above range are also applicable.

[0027] Preferably, in the transparent conductive layer, the ratio of the carrier concentration in the laser activated area to the carrier concentration in the non-laser activated area is (5~20):1, for example 5:1, 8:1, 10:1, 13:1, 15:1, 18:1 or 20:1, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0028] It should be noted that the laser activation region in the present invention includes a first laser activation region, a second laser activation region, a third laser activation region and a fourth laser activation region, that is, the carrier concentration of each activation region is independently 2×E 20 ~5×E 20 cm -3 Furthermore, all differences and ratios between the laser activated area and the non-laser activated area are comparisons of areas in the same transparent conductive layer.

[0029] In the present invention, the ratio of the carrier concentration in the laser activated area to the carrier concentration in the non-laser activated area in the transparent conductive layer is regulated to be (5~20):1, which can better improve the battery performance. If it exceeds 20:1, the laser passivated TCO will turn black, resulting in only this area being able to meet the contact reduction and passivation without damage; if it is lower than 5:1, the contact resistivity will be reduced, resulting in a decrease in Rs and ultimately an increase in EFF.

[0030] Preferably, the thickness of the first transparent conductive layer is 80-120 nm, for example 80 nm, 85 nm, 90 nm, 95 nm, 100 nm, 105 nm, 110 nm, 115 nm or 120 nm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0031] Preferably, the thickness of the second transparent conductive layer is 80-120 nm, for example 80 nm, 85 nm, 90 nm, 95 nm, 100 nm, 105 nm, 110 nm, 115 nm or 120 nm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0032] Preferably, a first semiconductor layer and an n-type semiconductor layer are sequentially arranged between the silicon substrate and the first transparent conductive layer, and the first semiconductor layer is closer to the surface of the silicon substrate.

[0033] Preferably, a second semiconductor layer and a p-type semiconductor layer are sequentially arranged between the silicon substrate and the second transparent conductive layer, and the second semiconductor layer is closer to the surface of the silicon substrate.

[0034] Preferably, the first semiconductor layer and the second semiconductor layer each independently include an intrinsic semiconductor layer and / or a microcrystalline semiconductor layer.

[0035] Preferably, the n-type semiconductor layer and the p-type semiconductor layer each independently include an amorphous semiconductor layer and / or a microcrystalline semiconductor layer.

[0036] It should be noted that, in the heterojunction solar cell of the present invention, conventional semiconductor layer structures and electrode layer structures that can be used in silicon-based heterojunction solar cells are all applicable to the present invention.

[0037] In a second aspect, the present invention provides a method for preparing a heterojunction solar cell as described in the first aspect, the preparation method comprising the following steps:

[0038] After preparing a first transparent conductive layer and a second transparent conductive layer on both sides of a silicon substrate respectively;

[0039] Performing a first laser treatment on a region where the first transparent conductive layer contacts the first electrode, and / or performing a second laser treatment on a region where the second transparent conductive layer contacts the second electrode;

[0040] After the first laser treatment and / or the second laser treatment is completed, the first electrode and the second electrode are prepared to obtain the heterojunction solar cell.

[0041] In the present invention, after the first transparent conductive layer and the second transparent conductive layer are prepared, the first electrode and the second electrode are not prepared directly, but the first laser treatment and / or the second laser treatment are first performed, thereby obtaining the first laser activation area and / or the second laser activation area. Through the laser treatment, the work function of the TCO in the laser activation area is reduced, so that the work function of the TCO in the laser activation area is more matched with the work function of the electrode, thereby reducing the contact resistivity of the contact area between the transparent conductive layer and the electrode; at the same time, the carrier concentration is slightly increased, reducing the square resistance of the transparent conductive layer; the above-mentioned contact resistivity and the reduction of the square resistance of the transparent conductive layer are combined, thereby leading to a reduction in the Rs of the silicon-based heterojunction solar cell, and finally improving the conversion efficiency of the cell, which can create higher economic benefits. In addition, the preparation method is simple to operate, does not require a complicated processing process, and is suitable for large-scale production.

[0042] Preferably, the laser pulse width of the first laser treatment is less than 200ns, for example 50ns, 60ns, 70ns, 80ns, 90ns, 100ns, 110ns, 120ns, 130ns, 140ns, 150ns, 160ns, 170ns, 180ns, 190ns or 199ns, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0043] Preferably, the laser energy density of the first laser treatment is 0.6-2.8 J / cm 2 , for example 0.6 J / cm 2 , 0.7J / cm 2 , 0.8J / cm 2 , 0.9J / cm 2 , 1J / cm 2 , 1.1J / cm 2 , 1.2J / cm 2 , 1.3J / cm 2 , 1.4J / cm 2 , 1.5J / cm 2 , 1.6J / cm 2 , 1.7J / cm 2 , 1.8J / cm 2 , 1.9J / cm 2 , 2J / cm 2 , 2.1J / cm 2 , 2.2J / cm 2 , 2.3J / cm 2 , 2.4J / cm 2 , 2.5J / cm 2 , 2.6J / cm 2 , 2.7J / cm 2 or 2.8 J / cm2 The above range is not limited to the listed values, and other values ​​not listed within the above range are also applicable.

[0044] Preferably, the time of the first laser treatment is 1 to 60 s, for example 1 s, 5 s, 10 s, 15 s, 20 s, 25 s, 30 s, 35 s, 40 s, 45 s, 50 s, 55 s or 60 s, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0045] Preferably, the laser pulse width of the second laser treatment is less than 200ns, for example 50ns, 60ns, 70ns, 80ns, 90ns, 100ns, 110ns, 120ns, 130ns, 140ns, 150ns, 160ns, 170ns, 180ns, 190ns or 199ns, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0046] Preferably, the laser energy density of the second laser treatment is 0.6-2.8 J / cm 2 , for example 0.6 J / cm 2 , 0.7J / cm 2 , 0.8J / cm 2 , 0.9J / cm 2 , 1J / cm 2 , 1.1J / cm 2 , 1.2J / cm 2 , 1.3J / cm 2 , 1.4J / cm 2 , 1.5J / cm 2 , 1.6J / cm 2 , 1.7J / cm 2 , 1.8J / cm 2 , 1.9J / cm 2 , 2J / cm 2 , 2.1J / cm 2 , 2.2J / cm 2 , 2.3J / cm 2 , 2.4J / cm 2 , 2.5J / cm 2 , 2.6J / cm 2 , 2.7J / cm 2 or 2.8 J / cm 2 The above range is not limited to the listed values, and other values ​​not listed within the above range are also applicable.

[0047] In the present invention, the laser energy density in the first laser treatment process is 0.6-2.8 J / cm2 and / or the laser energy density during the second laser treatment is 0.6-2.8 J / cm 2 By coordinating the above numerical ranges, the activation effect of the first transparent conductive layer and the second transparent conductive layer is more excellent, so that a heterojunction solar cell structure with lower contact resistivity between the electrode and TCO and lower TCO square resistance can be obtained, thereby better improving the conversion efficiency of the battery.

[0048] Preferably, the time of the second laser treatment is 1 to 60 s, for example 1 s, 5 s, 10 s, 15 s, 20 s, 25 s, 30 s, 35 s, 40 s, 45 s, 50 s, 55 s or 60 s, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0049] In the present invention, regulating the numerical range of the preparation parameters in the first laser processing process and / or the numerical range of the parameters in the second laser processing process is more conducive to regulating the work function and carrier concentration of the transparent conductive layer TCO, thereby leading to a reduction in the TCO-electrode contact resistivity and a reduction in the TCO square resistance.

[0050] Preferably, a third laser treatment is performed on a non-contact region corresponding to the first electrode in a region in a thickness direction of the first transparent conductive layer.

[0051] In the present invention, by performing a third laser treatment, a laser activated area of ​​the first transparent conductive layer in a non-contact area with the electrode is obtained; and by adjusting the preparation parameters of the third laser treatment to be different from those of the first laser treatment process, the laser energy density in the third laser treatment process is further preferably higher than the laser energy density in the first laser treatment process, thereby increasing the carrier concentration and mobility of the TCO film layer, thereby further reducing the TCO square resistance.

[0052] Preferably, the laser pulse width of the third laser treatment is less than 200ns, for example 50ns, 60ns, 70ns, 80ns, 90ns, 100ns, 110ns, 120ns, 130ns, 140ns, 150ns, 160ns, 170ns, 180ns, 190ns or 199ns, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0053] Preferably, the laser energy density of the third laser treatment is 1.5-4.5 J / cm 2 , for example 1.5 J / cm 2 , 1.6J / cm 2 , 1.7J / cm 2 , 1.8J / cm 2 , 1.9J / cm2 , 2.0J / cm 2 , 2.1J / cm 2 , 2.5J / cm 2 , 3.0J / cm 2 、3.5J / cm 2 , 4.0J / cm 2 , or 4.5J / cm 2 The above range is not limited to the listed values, and other values ​​not listed within the above range are also applicable.

[0054] Preferably, the time of the third laser treatment is 1 to 120 s, for example, 1s, 5s, 10s, 15s, 20s, 25s, 30s, 35s, 40s, 45s, 50s, 55s, 60s, 65s, 70s, 75s, 80s, 85s, 90s, 95s, 100s, 105s, 110s, 115s or 120s, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0055] Preferably, a fourth laser treatment is performed on a non-contact region corresponding to the second electrode in a region in a thickness direction of the second transparent conductive layer.

[0056] In the present invention, by performing a fourth laser treatment, a laser activated area of ​​the second transparent conductive layer in a non-contact area with the electrode is obtained; and by adjusting the preparation parameters of the fourth laser treatment to be different from those of the second laser treatment process, the laser energy density in the fourth laser treatment process is further preferably higher than the laser energy density in the second laser treatment process, thereby increasing the carrier concentration and mobility of the TCO film layer, thereby further reducing the TCO square resistance.

[0057] Preferably, the laser pulse width of the fourth laser treatment is less than 200ns, for example 50ns, 60ns, 70ns, 80ns, 90ns, 100ns, 110ns, 120ns, 130ns, 140ns, 150ns, 160ns, 170ns, 180ns, 190ns or 199ns, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0058] Preferably, the laser energy density of the fourth laser treatment is 1.5-4.5 J / cm 2 , for example 1.5 J / cm 2 , 1.6J / cm 2 , 1.7J / cm 2 , 1.8J / cm 2 , 1.9J / cm 2 , 2.0J / cm 2, 2.1J / cm 2 , 2.5J / cm 2 , 3.0J / cm 2 、3.5J / cm 2 , 4.0J / cm 2 , or 4.5J / cm 2 The above range is not limited to the listed values, and other values ​​not listed within the above range are also applicable.

[0059] Preferably, the time of the fourth laser treatment is 1 to 120 s, for example, 1s, 5s, 10s, 15s, 20s, 25s, 30s, 35s, 40s, 45s, 50s, 55s, 60s, 65s, 70s, 75s, 80s, 85s, 90s, 95s, 100s, 105s, 110s, 115s or 120s, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0060] It should be noted that the specific laser type of the laser processing in the present invention is not limited, for example, it can be quasi-continuous laser processing, continuous laser processing, etc.; technical personnel in this field can make adaptive selections and adjustments based on the specific processing process and parameters; and the light source wavelength in the laser processing process is a near-infrared laser of 1064nm.

[0061] Preferably, the first semiconductor layer and the n-type semiconductor are sequentially prepared on the surface of any one side of the silicon substrate, and then the first transparent conductive layer is prepared.

[0062] Preferably, the second semiconductor layer and the p-type semiconductor layer are sequentially prepared on the other side surface of the silicon substrate, and then the second transparent conductive layer is prepared.

[0063] Preferably, the preparation method of the first electrode and the second electrode comprises screen printing.

[0064] The preparation method provided by the present invention can achieve the purpose of reducing contact resistance by using conventional screen printing method without additionally adjusting the preparation process of the electrode after the transparent conductive layer is modified by laser treatment.

[0065] It should also be noted that in the preparation method provided by the present invention, except for the laser treatment process, the rest of the preparation sequence, preparation raw materials and preparation parameters are all conventional technical selections, and technical personnel in this field can make adaptive selections and adjustments based on actual needs.

[0066] Exemplarily, the present invention provides a specific preparation process of a heterojunction solar cell, and the preparation process is as follows:

[0067] (1) Silicon substrate selection.

[0068] (2) Cleaning and velveting.

[0069] The oxide layer on the surface of the silicon substrate is removed using a 4% mass fraction hydrofluoric acid solution, and the surfaces of both sides of the silicon wafer are texturized using a 3% mass fraction sodium hydroxide / potassium hydroxide solution and anisotropic etching of single crystal silicon to form a pyramid structure on the surface.

[0070] (3) Deposition of semiconductor layer.

[0071] SiH4 is introduced and deposited on one side of the silicon wafer by PECVD (plasma enhanced chemical vapor deposition) to obtain the first semiconductor layer (the first intrinsic amorphous silicon layer). Then SiH4, H2 and PH3 are introduced at the same time to deposit on the side of the intrinsic amorphous silicon layer away from the silicon wafer to obtain an n-type semiconductor layer (n-type doped amorphous silicon layer or n-type doped microcrystalline silicon layer).

[0072] SiH4 is introduced and deposited on the other side of the silicon wafer through PECVD (plasma enhanced chemical vapor deposition) to obtain a second semiconductor layer (second intrinsic amorphous silicon layer). Then SiH4, H2 and B2H6 are introduced at the same time to deposit on the side of the intrinsic amorphous silicon layer away from the silicon wafer to obtain a p-type semiconductor layer (p-type doped amorphous silicon layer or p-type doped microcrystalline silicon layer).

[0073] It should be noted that the present invention does not limit the preparation order of the p-type doped non- / microcrystalline silicon layer and the n-type doped non- / microcrystalline silicon layer. It can be that the intrinsic amorphous silicon layer and the n-type doped non- / microcrystalline silicon layer are first prepared on one side of the silicon wafer, and then the intrinsic amorphous silicon layer and the p-type doped non- / microcrystalline silicon layer are prepared on the other side of the silicon wafer; it can also be that the intrinsic amorphous silicon layer and the p-type doped non- / microcrystalline silicon layer are first prepared on one side of the silicon wafer, and then the intrinsic amorphous silicon layer and the n-type doped non- / microcrystalline silicon layer are prepared on the other side of the silicon wafer;

[0074] (4) Deposition of transparent conductive layer (TCO):

[0075] Reactive plasma deposition (RPD) or magnetron sputtering (PVD) is used to coat the surfaces of the n-type semiconductor layer and the p-type semiconductor layer, respectively. The target power is adjusted to prepare a TCO film of a certain thickness, and different proportions of argon and oxygen are introduced to adjust the carrier concentration, mobility and square resistance of the TCO film to the required range. The edge shielding (shielding by mask) is designed by the carrier plate, and the specific shielding area around is 0.8 mm, so as to obtain the first transparent conductive layer and the second transparent conductive layer.

[0076] (5) Laser heat treatment of the first or second TCO film:

[0077] A laser is used to perform a first laser treatment on the area of ​​the first transparent conductive layer in (4) that is away from the surface of the silicon substrate where the electrode is to be printed and / or a second laser treatment on the surface of the second transparent conductive layer that is away from the silicon substrate.

[0078] (6) Printing electrodes:

[0079] After the laser treatment is completed, a layer of low-temperature conductive paste is printed on the laser-treated area on the surface of the first transparent conductive layer or the second transparent conductive layer by screen printing, and then sintered and cured to form a good ohmic contact.

[0080] Optionally, the silicon substrate is an N-type silicon wafer with a resistivity of 0.5~10Ω·cm, for example, 0.5Ω·cm, 1Ω·cm, 2Ω·cm, 3Ω·cm, 4Ω·cm, 5Ω·cm, 6Ω·cm, 7Ω·cm, 8Ω·cm, 9Ω·cm or 10Ω·cm, and a thickness of 100~150μm, for example, 100μm, 110μm, 120μm, 130μm, 140μm or 150μm, etc.

[0081] Optionally, the reaction environment temperature of the texturing treatment is 25°C~60°C, for example, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C or 60°C, and the reaction time is controlled at 3~20min, for example, 3min, 4min, 5min, 6min, 7min, 8min, 9min, 10min, 11min, 12min, 13min, 14min, 15min, 16min, 17min, 18min, 19min or 20min, etc.

[0082] Optionally, the thickness of the first semiconductor layer is 2-5 nm, for example, 2 nm, 3 nm, 4 nm or 5 nm; the thickness of the n-type semiconductor layer is 20-40 nm, for example, 20 nm, 25 nm, 30 nm, 35 nm or 40 nm.

[0083] Optionally, the thickness of the second semiconductor layer is 2-5 nm, for example, 2 nm, 3 nm, 4 nm or 5 nm; the thickness of the p-type semiconductor layer is 20-40 nm, for example, 20 nm, 25 nm, 30 nm, 35 nm or 40 nm.

[0084] Optionally, the material of the TCO film includes but is not limited to at least one of ITO, IWO, IZO or IZrO.

[0085] Optionally, the first electrode and TCO contact region and the second electrode and TCO contact region are processed by one laser process, while the first electrode and TCO non-contact region and the second electrode and TCO non-contact region are processed by another laser process.

[0086] Optionally, the conductive material in the conductive paste includes but is not limited to at least one of silver, gold, copper, aluminum or nickel.

[0087] Optionally, after the screen printing, the sintering and curing temperature is 150-220°C, for example, 150°C, 160°C, 170°C, 180°C, 190°C, 200°C, 210°C or 220°C.

[0088] In a third aspect, the present invention further provides a photovoltaic module, wherein the photovoltaic module comprises the heterojunction solar cell as described in the first aspect or the heterojunction solar cell prepared by the preparation method as described in the second aspect.

[0089] Compared with the prior art, the present invention has the following beneficial effects:

[0090] (1) In the heterojunction solar cell provided by the present invention, the area where the transparent conductive layer (TCO) contacts the electrode is a laser activated area, which can reduce the contact resistivity between the electrode and TCO and the TCO square resistance, thereby achieving the purpose of reducing the series resistance Rs and improving the battery conversion efficiency.

[0091] (2) In the present invention, after the first transparent conductive layer and the second transparent conductive layer are prepared, the first electrode and the second electrode are not prepared directly, but the first laser treatment and / or the second laser treatment are first performed to obtain the first laser activation area and / or the second laser activation area. Through the laser treatment, the work function of the TCO in the laser activation area is reduced, so that the work function of the TCO in the laser activation area is more matched with the work function of the electrode, thereby reducing the contact resistivity of the contact area between the transparent conductive layer and the electrode; at the same time, the carrier concentration is slightly increased, reducing the square resistance of the transparent conductive layer; the above-mentioned reduction in contact resistivity and the square resistance of the transparent conductive layer leads to a reduction in the Rs of the silicon-based heterojunction solar cell, and finally improves the conversion efficiency of the cell, which can create higher economic benefits. In addition, the preparation method is simple to operate, does not require a complicated processing process, and is suitable for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0092] Figure 1 This is a schematic diagram of the structure of a heterojunction solar cell provided in Example 1.

[0093] Figure 2 This is a schematic diagram of the structure of a heterojunction solar cell provided in Example 2.

[0094] Figure 3This is a schematic diagram of the structure of a heterojunction solar cell provided in Comparative Example 1.

[0095] Among them, 1-silicon substrate, 2-first semiconductor layer, 3-n-type semiconductor layer, 4-first transparent conductive layer, 41-first laser activation zone, 42-first non-laser activation zone, 43-third laser activation zone, 5-first electrode, 6-second semiconductor layer, 7-p-type semiconductor layer, 8-second transparent conductive layer, 81-second laser activation zone, 82-second non-laser activation zone, 83-fourth laser activation zone, 9-second electrode. DETAILED DESCRIPTION

[0096] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0097] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in this application are intended to cover non-exclusive inclusions.

[0098] In the description of this application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of this application, the meaning of "plurality" is more than two, unless otherwise clearly and specifically defined.

[0099] In a specific embodiment, the present invention provides a method for preparing a heterojunction solar cell, the preparation method comprising:

[0100] (1) Selection of silicon substrate: The silicon substrate is an N-type silicon wafer with a resistivity of 0.5-10Ω·cm and a thickness of 100-150μm.

[0101] (2) Cleaning and velveting:

[0102] The oxide layer on the surface of the silicon substrate is removed using a 1-4% mass fraction hydrofluoric acid solution, and an alkali solution with a mass concentration of 1-3% (such as potassium hydroxide (KOH) and sodium hydroxide (NaOH)) is used to anisotropically etch single crystal silicon. At a reaction environment temperature of 60-80°C, both sides of the silicon wafer are textured for 3-20 minutes to form a pyramid structure on the surface.

[0103] (3) Deposition of semiconductor layer:

[0104] SiH4 is introduced and deposited on one side of the silicon wafer through PECVD (plasma enhanced chemical vapor deposition) to obtain the first semiconductor layer (the first intrinsic amorphous silicon layer with a thickness of 2~4nm). Then SiH4, H2 and PH3 are introduced at the same time and deposited on the side of the intrinsic amorphous silicon layer away from the silicon wafer to obtain an n-type semiconductor layer (n-type doped amorphous silicon layer or n-type doped microcrystalline silicon layer with a thickness of 20~40nm).

[0105] SiH4 is introduced and deposited on the other side of the silicon wafer through PECVD (plasma enhanced chemical vapor deposition) to obtain a second semiconductor layer (a second intrinsic amorphous silicon layer with a thickness of 2~4nm). Then SiH4, H2 and B2H6 are introduced at the same time and deposited on the side of the intrinsic amorphous silicon layer away from the silicon wafer to obtain a p-type semiconductor layer (p-type doped amorphous silicon layer or p-type doped microcrystalline silicon layer with a thickness of 20~40nm).

[0106] Furthermore, in the process of preparing the above-mentioned semiconductor layer, the preparation order of the p-type doped non- / microcrystalline silicon layer and the n-type doped non- / microcrystalline silicon layer is not limited. It can be that the intrinsic amorphous silicon layer and the n-type doped non- / microcrystalline silicon layer are first prepared on one side of the silicon wafer, and then the intrinsic amorphous silicon layer and the p-type doped non- / microcrystalline silicon layer are prepared on the other side of the silicon wafer; or it can be that the intrinsic amorphous silicon layer and the p-type doped non- / microcrystalline silicon layer are first prepared on one side of the silicon wafer, and then the intrinsic amorphous silicon layer and the n-type doped non- / microcrystalline silicon layer are prepared on the other side of the silicon wafer.

[0107] (4) Deposition of transparent conductive layer (TCO):

[0108] Reactive plasma deposition (RPD) or magnetron sputtering (PVD) is used to coat the surface of the n-type semiconductor layer and the surface of the p-type semiconductor layer, respectively, and the target power is adjusted to prepare a TCO film of a certain thickness (the material in the TCO film includes but is not limited to ITO, IWO, IZO or IZrO), and different proportions of argon and oxygen are introduced to adjust the carrier concentration, mobility and square resistance of the TCO film layer to the required range. The edge shielding (shielding by mask) is designed by the carrier plate, and the specific shielding area around is 0.8 mm, so as to obtain the first transparent conductive layer and the second transparent conductive layer.

[0109] (5) Laser heat treatment of the first or second TCO film:

[0110] A laser is used to perform a first laser treatment on the electrode printing area in the first transparent conductive layer away from the surface of the silicon substrate in (4) and / or a second laser treatment on the electrode printing area in the second transparent conductive layer away from the surface of the silicon substrate.

[0111] (6) Printing electrodes:

[0112] After the laser treatment, a layer of low-temperature conductive paste (the conductive material in the conductive paste includes but is not limited to silver, gold, copper, aluminum or nickel) is printed on the laser-treated area (or the surface not subjected to laser treatment) of the surface of the first transparent conductive layer or the second transparent conductive layer by screen printing, and then sintered and cured at 150-220°C to form a good ohmic contact.

[0113] Furthermore, a third laser treatment is performed on a non-contact area corresponding to the first electrode in a region in a thickness direction of the first transparent conductive layer.

[0114] And / or, a fourth laser treatment is performed on a non-contact region corresponding to the second electrode in a region in a thickness direction of the second transparent conductive layer.

[0115] The following examples were all prepared using the above-mentioned preparation method.

[0116] Example 1

[0117] This embodiment provides a heterojunction solar cell, such as Figure 1 As shown, the heterojunction solar cell comprises:

[0118] A silicon substrate 1; a first semiconductor layer 2, an n-type semiconductor layer 3, a first transparent conductive layer 4 and a first electrode 5 are stacked on the surface of one side of the silicon substrate 1, and a second semiconductor layer 6, a p-type semiconductor layer 7, a second transparent conductive layer 8 and a second electrode 9 are stacked on the surface of the other side of the silicon substrate 1.

[0119] Among them, the first transparent conductive layer 4 includes a first laser activation area 41 and a first non-laser activation area 42, the first laser activation area 41 is in contact with the first electrode 5, and the thickness of the first laser activation area 41 is 10nm; the second transparent conductive layer 8 includes a second laser activation area 81 and a second non-laser activation area 82, the second laser activation area 81 is in contact with the second electrode 9, and the thickness of the second laser activation area 81 is 10nm.

[0120] The method for preparing the heterojunction solar cell is based on the above specific implementation method, and the specific process is as follows:

[0121] (1) The silicon substrate is an N-type silicon wafer with a resistivity of 5Ω·cm and a thickness of 120μm.

[0122] (2) The texturing agent is 3% sodium hydroxide solution, the texturing treatment temperature is 60°C, and the texturing time is 5 minutes.

[0123] (3) First, a first semiconductor layer and an n-type semiconductor layer are deposited in sequence on one side of the silicon wafer by a PECVD method.

[0124] The silicon wafer is turned over, the tray is changed, and the second semiconductor layer and the p-type semiconductor layer are sequentially deposited on the other side surface of the silicon wafer by the PECVD method.

[0125] (4) A first transparent conductive layer is deposited on the surface of the n-type semiconductor layer, and the deposited film thickness is 100 nm.

[0126] A second transparent conductive layer is deposited on the surface of the p-type semiconductor layer, and the deposited film thickness is 120 nm.

[0127] (5) Performing a first laser treatment on the area of ​​the first transparent conductive layer that needs to contact the first electrode, using a quasi-continuous laser at 1.9 J / cm 2 The first laser activation area is obtained by treating with near-infrared laser of 1064 nm wavelength with energy density for 45 seconds.

[0128] The second laser treatment is performed on the area of ​​the second transparent conductive layer that needs to contact the second electrode, using a quasi-continuous laser at 1.9 J / cm 2 The second laser activated area is obtained by treating with near-infrared laser of 1064 nm wavelength with energy density for 45 seconds.

[0129] (6) During the screen printing process, the conductive paste is silver paste, and the sintering and curing temperature is 200°C.

[0130] Example 2

[0131] This embodiment provides a heterojunction solar cell, such as Figure 2 As shown, the heterojunction solar cell comprises:

[0132] A silicon substrate 1; a first semiconductor layer 2, an n-type semiconductor layer 3, a first transparent conductive layer 4 and a first electrode 5 stacked in sequence on the surface of one side of the silicon substrate 1, and a second semiconductor layer 6, a p-type semiconductor layer 7, a second transparent conductive layer 8 and a second electrode 9 stacked in sequence on the surface of the other side of the silicon substrate 1.

[0133] Among them, the first transparent conductive layer 4 includes a first laser activation area 41 and a first non-laser activation area 42, the first laser activation area 41 is in contact with the first electrode 5, the thickness of the first laser activation area 41 is 10nm, and in the area in the thickness direction of the first transparent conductive layer 4, the non-contact area corresponding to the first electrode 5 is the third laser activation area 43, and the thickness is 100nm.

[0134] The second transparent conductive layer 8 includes a second laser activated area 81 and a second non-laser activated area 82. The second laser activated area 81 is in contact with the second electrode 9. The thickness of the second laser activated area 81 is 10 nm. In the area in the thickness direction of the second transparent conductive layer 8, the non-contact area corresponding to the second electrode 9 is a fourth laser activated area 83 with a thickness of 100 nm.

[0135] The difference between the preparation method in this embodiment and that in embodiment 1 is:

[0136] (5) After the first laser treatment, a third laser treatment is performed on the non-contact area corresponding to the first electrode in the thickness direction of the first transparent conductive layer, using a quasi-continuous laser with a pulse width of 150 ns and a temperature of 2.64 J / cm 2 The laser treatment was performed at a certain energy density for 20 s.

[0137] After the second laser treatment, the non-contact area corresponding to the first electrode in the thickness direction of the first transparent conductive layer is subjected to the fourth laser treatment, using a quasi-continuous laser with a pulse width of 150 ns and a pulse rate of 2.64 J / cm 2 The laser treatment was performed at a certain energy density for 20 s.

[0138] The rest of the preparation methods and parameters were the same as those in Example 1.

[0139] Comparative Example 1

[0140] This comparative example provides a heterojunction solar cell, such as Figure 3 As shown, the heterojunction solar cell comprises:

[0141] A silicon substrate 1; a first semiconductor layer 2, an n-type semiconductor layer 3, a first transparent conductive layer 4 and a first electrode 5 are stacked on the surface of one side of the silicon substrate 1, and a second semiconductor layer 6, a p-type semiconductor layer 7, a second transparent conductive layer 8 and a second electrode 9 are stacked on the surface of the other side of the silicon substrate 1.

[0142] The difference between the preparation method and Example 1 is that the first laser treatment and the second laser treatment process are not performed.

[0143] The rest of the preparation methods and parameters were the same as those in Example 1.

[0144] Table 1 and Table 2 respectively show the carrier concentration, mobility and square resistance of the transparent conductive layer in the heterojunction solar cells provided in Examples 1-2 and Comparative Example 1, and the contact resistance between the transparent conductive layer and the electrode.

[0145] Table 1

[0146]

[0147] Table 2

[0148]

[0149] The heterojunction solar cells provided in Examples 1-2 and Comparative Example 1 were tested for short-circuit current (Jsc), open-circuit voltage (Voc), fill factor (FF), conversion efficiency (EFF) and series resistance (Rs). The test results are shown in Table 3.

[0150] Table 3

[0151]

[0152] In summary, in the heterojunction solar cell provided by the present invention, the area where the transparent conductive layer (TCO) contacts the electrode is a laser activated area, which can reduce the contact resistivity between the electrode and TCO and the TCO square resistance, thereby achieving the purpose of reducing the series resistance Rs and improving the battery conversion efficiency.

[0153] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. A heterojunction solar cell, characterized in that: The heterojunction solar cell comprises: Silicon substrate; A first transparent conductive layer and a first electrode are stacked on one surface of the silicon substrate, and a second transparent conductive layer and a second electrode are stacked on the other surface of the silicon substrate; Wherein, the first transparent conductive layer comprises a first laser activated area and a first non-laser activated area, and the first laser activated area is in contact with the first electrode; and / or, The second transparent conductive layer comprises a second laser activated region and a second non-laser activated region, and the second laser activated region is in contact with the second electrode; In the region in the thickness direction of the first transparent conductive layer, the non-contact region corresponding to the first electrode is a third laser activated region; and / or, In the region in the thickness direction of the second transparent conductive layer, the non-contact region corresponding to the second electrode is a fourth laser activated region; The preparation method comprises: Prepare a first transparent conductive layer and a second transparent conductive layer on both sides of the silicon substrate respectively; The first electrode and the second electrode are prepared by performing a first laser treatment on the area where the first transparent conductive layer contacts the first electrode, and / or performing a second laser treatment on the area where the second transparent conductive layer contacts the second electrode, performing a third laser treatment on the non-contact area corresponding to the first electrode in the area in the thickness direction of the first transparent conductive layer, and / or performing a fourth laser treatment on the non-contact area corresponding to the second electrode in the area in the thickness direction of the second transparent conductive layer, and obtaining the heterojunction solar cell.

2. The heterojunction solar cell according to claim 1, characterized in that: The thickness of the first laser activated region is 5-50 nm; And / or, the thickness of the second laser activated zone is 5-50 nm.

3. The heterojunction solar cell according to claim 1 or 2, characterized in that: The thickness of the third laser activated region is 70-115 nm; And / or, the thickness of the fourth laser activated zone is 70-115 nm.

4. The heterojunction solar cell according to claim 1, characterized in that: In the transparent conductive layer, the carrier concentration in the laser activated region is 2E20~5E20cm -3 ; And / or, in the transparent conductive layer, the carrier concentration in the non-laser activated region is 1E20~4E20cm -3 ; And / or, in the transparent conductive layer, the difference between the carrier concentration in the laser activated region and the carrier concentration in the non-laser activated region is greater than or equal to 1E19 cm -3 ; And / or, in the transparent conductive layer, the ratio of the carrier concentration in the laser activated region to the carrier concentration in the non-laser activated region is (5-20):

1.

5. The heterojunction solar cell according to claim 1, characterized in that: The thickness of the first transparent conductive layer is 80-120 nm; And / or, the thickness of the second transparent conductive layer is 80-120 nm; And / or, a first semiconductor layer and an n-type semiconductor layer are sequentially arranged between the silicon substrate and the first transparent conductive layer, and the first semiconductor layer is closer to the surface of the silicon substrate; And / or, a second semiconductor layer and a p-type semiconductor layer are sequentially arranged between the silicon substrate and the second transparent conductive layer, and the second semiconductor layer is closer to the surface of the silicon substrate; and / or, the first semiconductor layer and the second semiconductor layer each independently include an intrinsic semiconductor layer and / or a microcrystalline semiconductor layer; And / or, the n-type semiconductor layer and the p-type semiconductor layer each independently include an amorphous semiconductor layer and / or a microcrystalline semiconductor layer.

6. A method for preparing a heterojunction solar cell according to any one of claims 1 to 5, characterized in that: The preparation method comprises the following steps: Prepare a first transparent conductive layer and a second transparent conductive layer on both sides of the silicon substrate respectively; The first electrode and the second electrode are prepared by performing a first laser treatment on the area where the first transparent conductive layer contacts the first electrode, and / or performing a second laser treatment on the area where the second transparent conductive layer contacts the second electrode, performing a third laser treatment on the non-contact area corresponding to the first electrode in the area in the thickness direction of the first transparent conductive layer, and / or performing a fourth laser treatment on the non-contact area corresponding to the second electrode in the area in the thickness direction of the second transparent conductive layer, and obtaining the heterojunction solar cell.

7. The method for preparing a heterojunction solar cell according to claim 6, characterized in that: The laser pulse width of the first laser treatment is less than 200 ns, and the laser energy density of the first laser treatment is 0.6-2.8 J / cm 2 , the first laser treatment time is 1 to 60 seconds; And / or, the laser pulse width of the second laser treatment is less than 200ns, and the laser energy density of the second laser treatment is 0.6-2.8J / cm 2 , the time of the second laser treatment is 1~60s.

8. The method for preparing a heterojunction solar cell according to claim 6 or 7, characterized in that: The laser pulse width of the third laser treatment is less than 200ns, and the laser energy density of the third laser treatment is 1.5-4.5J / cm 2 , the time of the third laser treatment is 1 to 120 seconds; And / or, the laser pulse width of the fourth laser treatment is less than 200ns, and the laser energy density of the fourth laser treatment is 1.5-4.5J / cm 2 , the time of the fourth laser treatment is 1~120s.

9. The method for preparing a heterojunction solar cell according to claim 6, characterized in that: After sequentially preparing a first semiconductor layer and an n-type semiconductor on a surface of any side of the silicon substrate, preparing a first transparent conductive layer; and / or, preparing a second semiconductor layer and a p-type semiconductor layer in sequence on the other side surface of the silicon substrate, and then preparing a second transparent conductive layer; And / or, the preparation method of the first electrode and the second electrode includes screen printing.

10. A photovoltaic module, characterized in that: The photovoltaic module comprises a heterojunction solar cell as described in any one of claims 1 to 5 or a heterojunction solar cell prepared by the method for preparing a heterojunction solar cell as described in any one of claims 6 to 9.

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