Solar cell and method for manufacturing the same

Abstract

A solar cell and a preparation method thereof, belonging to the photovoltaic field. The solar cell includes a battery substrate, a transparent conductive film located on at least one surface of the battery substrate, and an electrode located on the side of the transparent conductive film away from the battery substrate; the transparent conductive film includes a first transparent conductive film located in the electrode area and a second transparent conductive film located in the non-electrode area, and the carrier concentration of the first transparent conductive film is greater than the carrier concentration of the second transparent conductive film. The present invention reduces the contact resistance between the electrode and the first transparent conductive film by optimizing the transparent conductive film, and is combined with the carrier concentration difference in the transparent conductive film, which is beneficial to the collection of carriers and improves the battery efficiency. At the same time, the non-electrode area has a low carrier concentration, which can maintain a high light transmittance, improve the light absorption rate of the battery, and thus improve the battery efficiency. The present invention can balance the requirements of the electrode area for conductivity and the non-electrode area for light transmittance, and improve the efficiency of the battery from both electrical and optical perspectives.

Description

Technical Field

[0001] The present invention relates to the photovoltaic field, and in particular to a solar cell and a preparation method thereof. Background Art

[0002] As heterojunction cell technology (HJT) continues to advance, it is becoming more difficult to improve efficiency. Introducing a transparent conductive oxide (TCO) thin film as a conductive layer in solar cells can effectively transmit charges while maintaining high transmittance.

[0003] Existing TCO films are usually deposited using magnetron sputtering. The TCO films prepared by this method have excellent uniformity and small overall carrier concentration differences, and cannot take into account the conductivity and transmittance requirements of the electrode area and the non-electrode area.

[0004] In view of this, it is necessary to provide an improved solar cell and a preparation method thereof to solve the above technical problems. Summary of the invention

[0005] The invention provides a solar cell and a preparation method thereof, which improves carrier collection and cell efficiency by optimizing the structure of a transparent conductive film.

[0006] In order to achieve one of the above-mentioned invention objects, the present invention adopts the following technical solution:

[0007] A solar cell comprises a cell substrate, a transparent conductive film located on at least one surface of the cell substrate, and an electrode located on a side of the transparent conductive film away from the cell substrate; the transparent conductive film comprises a first transparent conductive film located in the electrode region and a second transparent conductive film located in the non-electrode region, the carrier concentration of the first transparent conductive film is greater than the carrier concentration of the second transparent conductive film, and the electrode is in contact with the first transparent conductive film.

[0008] In one embodiment, the carrier concentration of the first transparent conductive film is 2E20 / cm 3 ~4E20 / cm 3 , and / or, the carrier concentration of the second transparent conductive film is 0.2E20 / cm 3 ~2E20 / cm 3 , and / or, the transmittance of the second transparent conductive film is 85%-99%; and / or, the thickness of the transparent conductive film is 80nm-120nm.

[0009] In one embodiment, the electrode area is located within the projection of the electrode on the battery substrate along the thickness direction of the battery substrate; and / or, the first transparent conductive film is located within the projection of the electrode on the transparent conductive film along the thickness direction of the battery substrate; and / or, the projection of the electrode on the battery substrate along the thickness direction of the battery substrate covers the electrode area; and / or, the projection of the electrode on the transparent conductive film along the thickness direction of the battery substrate covers the first transparent conductive film.

[0010] In one embodiment, the first transparent conductive film is an ITO film or a VTTO film, and / or the second transparent conductive film is an ITO film or a VTTO film doped with a dopant.

[0011] In one embodiment, the dopant is a metal ion and / or a non-metal ion; wherein the metal ion is selected from a combination of at least one or more of aluminum, magnesium, potassium, sodium, calcium, strontium, barium, copper, lead, zinc, tin, cobalt, nickel, and antimony; and / or the non-metal ion is selected from a combination of at least one or more of hydrogen, boron, carbon, nitrogen, oxygen, fluorine, silicon, phosphorus, and sulfur.

[0012] In one embodiment, the battery matrix includes a silicon substrate, an intrinsic semiconductor layer located on at least one surface of the silicon substrate, and a doped semiconductor layer located on a side of the intrinsic semiconductor layer away from the silicon substrate.

[0013] In one embodiment, the silicon substrate is an N-type silicon wafer; and / or the intrinsic semiconductor layer is an intrinsic amorphous silicon layer, or an intrinsic microcrystalline silicon layer, or an intrinsic polycrystalline silicon layer; and / or the doped semiconductor layer located on the light-receiving surface of the silicon substrate is an N-type amorphous silicon layer, or an N-type microcrystalline silicon layer, or an N-type polycrystalline silicon layer, and the doping concentration is 1E20cm -3 ~1E21cm -3 ; and / or, the doped semiconductor layer located on the backlight side of the silicon substrate is a P-type amorphous silicon layer, or a P-type microcrystalline silicon layer, or a P-type polycrystalline silicon layer, and the doping concentration is 1E19cm -3 ~1E20cm -3 .

[0014] A method for preparing a solar cell comprises the following steps: forming a transparent conductive film on at least one surface of a battery substrate; forming an electrode on a surface of the transparent conductive film away from the battery substrate, wherein at least a portion of the transparent conductive film covered by the electrode constitutes a first transparent conductive film; and reducing the carrier concentration of the transparent conductive film in an area not covered by the electrode to form a second transparent conductive film.

[0015] In one embodiment, the transparent conductive film is selected from an ITO film or a VTTO film; or, the transparent conductive film is formed by a reactive plasma deposition process or a magnetron sputtering deposition process. During the deposition process, the O2 flow rate accounts for 3%~5%, the H2 flow rate accounts for 0%~4%, and the rest is Ar, and the pressure is 0.4Pa~0.7Pa.

[0016] In one embodiment, a plasma injection process is used to inject a dopant into the transparent conductive film in the area not covered by the electrode to form a second transparent conductive film; the dopant is a metal ion and / or a non-metal ion; wherein the metal ion is selected from a combination of at least one or more of aluminum, magnesium, potassium, sodium, calcium, strontium, barium, copper, lead, zinc, tin, cobalt, nickel, and antimony; and / or the non-metal ion is selected from a combination of at least one or more of hydrogen, boron, carbon, nitrogen, oxygen, fluorine, silicon, phosphorus, and sulfur.

[0017] In one embodiment, dopants are added to the transparent conductive film in the area not covered by the electrode by a vacuum diffusion process; or, under predetermined vacuum and predetermined temperature conditions, the battery substrate after electrode preparation is placed in a gas atmosphere of dopants to add dopants to the transparent conductive film in the area not covered by the electrode.

[0018] In one embodiment, the carrier concentration of the first transparent conductive film is 2E20 / cm 3 ~4E20 / cm 3 , and / or, the carrier concentration of the second transparent conductive film is 0.2E20 / cm 3 ~2E20 / cm 3 ; and / or, the transmittance of the second transparent conductive film is 85%-99%; and / or, the thickness of the transparent conductive film is 80nm-120nm.

[0019] In one embodiment, "preparing a battery matrix" includes the following steps in sequence: preparing a first intrinsic semiconductor layer on the backlight side of the silicon substrate; preparing a second intrinsic semiconductor layer on the light-receiving side of the silicon substrate; preparing a second doped semiconductor layer on the surface of the second intrinsic semiconductor layer away from the silicon substrate, the second doped semiconductor layer having the same doping type as the silicon substrate; preparing a first doped semiconductor layer on the surface of the first intrinsic semiconductor layer away from the silicon substrate, the first doped semiconductor layer having a doping type opposite to that of the silicon substrate.

[0020] The beneficial effects of the present invention are as follows: in the solar cell and the preparation method thereof of the present invention, the carrier concentration of the transparent conductive film located in the electrode region is greater than the carrier concentration of the transparent conductive film located in the non-electrode region, thereby reducing the contact resistance between the electrode and the first transparent conductive film, and combining the carrier concentration difference in the transparent conductive film, it is beneficial to the collection of carriers and improve the battery efficiency. At the same time, the low carrier concentration in the non-electrode region can maintain a high light transmittance, improve the light absorption rate of the battery, and thus improve the battery efficiency. The present invention can balance the requirements of the electrode region for conductivity and the non-electrode region for light transmittance, and improve the efficiency of the battery from both electrical and optical perspectives. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is a schematic structural diagram of a solar cell in one embodiment of the present invention;

[0022] Figure 2 is a schematic diagram of a transparent conductive film before and after doping with a dopant in one embodiment of the present invention;

[0023] Figure 3 is a schematic diagram of a transparent conductive film before and after doping with a dopant in another embodiment of the present invention;

[0024] Figure 4 is a flow chart of a method for preparing a solar cell in one embodiment of the present invention;

[0025] Figure 5 The present invention is a flow chart of a method for preparing a solar cell in another embodiment of the present invention.

[0026] Among them, 100-solar cell, 1-silicon substrate, 11-backlight surface, 12-light receiving surface, 2-intrinsic semiconductor layer, 21-first intrinsic semiconductor layer, 22-second intrinsic semiconductor layer, 3-doped semiconductor layer, 31-first doped semiconductor layer, 32-second doped semiconductor layer, 4-transparent conductive film, 41-first transparent conductive film, 42-second transparent conductive film, 5-electrode. DETAILED DESCRIPTION

[0027] The present invention will be described in detail below in conjunction with the specific embodiments shown in the accompanying drawings. However, these embodiments do not limit the present invention, and any structural, methodological, or functional changes made by a person skilled in the art based on these embodiments are all within the scope of protection of the present invention.

[0028] In the various drawings of the present invention, for the convenience of illustration, some sizes of structures or parts are exaggerated relative to other structures or parts, and thus, they are only used to illustrate the basic structure of the subject matter of the present invention.

[0029] Please refer to Figure 1 Combined with Figure 2 and Figure 3 As shown, a solar cell 100 according to a preferred embodiment of the present invention comprises a cell substrate, a transparent conductive film 4 located on at least one surface of the cell substrate, and an electrode 5 located on a side of the transparent conductive film 4 away from the cell substrate.

[0030] The structure of the battery substrate of the present invention is not limited, and includes all structures except the transparent conductive film 4 and the electrode 5; the preparation method of the battery substrate can also adopt any one of the prior art. At least one surface of the battery substrate includes a light-receiving surface (primary light-receiving surface) and a backlight surface (secondary light-receiving surface) arranged opposite to each other.

[0031] In one embodiment, the battery substrate includes a silicon substrate 1 , an intrinsic semiconductor layer 2 and a doped semiconductor layer 3 located on at least one surface of the silicon substrate 1 .

[0032] The silicon substrate 1 is an N-type silicon wafer with a resistivity of 0.5 Ω.cm to 3 Ω.cm and a thickness of 150 μm to 200 μm. The size is adaptively adjusted according to the size of the solar cell 100 .

[0033] The surface of the silicon substrate 1 includes a backlight surface 11 and a light receiving surface 12 which are arranged opposite to each other. The light receiving surface of the battery substrate and the light receiving surface 12 of the silicon substrate 1 are located on the same side of the silicon substrate 1, and the backlight surface of the battery substrate and the backlight surface 11 of the silicon substrate 1 are located on the same side of the silicon substrate 1.

[0034] In one embodiment, the surface of the silicon substrate 1 has a velvet structure, which can reduce the reflectivity of the surface, improve the absorption of light, and thus improve the efficiency of the battery. In one embodiment, the velvet structure is a pyramid velvet structure formed by etching with an alkali solution. The alkali solution is selected from but not limited to a potassium hydroxide solution (KOH solution), a sodium hydroxide solution (NaOH solution), or a solution of tetramethylammonium hydroxide (TMAH) plus alcohol.

[0035] The intrinsic semiconductor layer 2 passivates the surface of the silicon substrate 1, effectively improving the open circuit voltage (Voc) and the fill factor (FF), thereby improving the efficiency of the battery. In one embodiment, the intrinsic semiconductor layer 2 includes a first intrinsic semiconductor layer 21 located on the backlight surface 11 and a second intrinsic semiconductor layer 22 located on the light-receiving surface 12.

[0036] In the present invention, the first intrinsic semiconductor layer 21 and / or the second intrinsic semiconductor layer 22 is selected from at least one or more combinations of an intrinsic amorphous silicon layer, an intrinsic microcrystalline silicon layer, or an intrinsic polycrystalline silicon layer.

[0037] In one embodiment, the first intrinsic semiconductor layer 21 and / or the second intrinsic semiconductor layer 22 includes an intrinsic amorphous silicon layer in contact with one surface of the silicon substrate 1 and an intrinsic microcrystalline silicon layer located on a side of the intrinsic amorphous silicon layer away from the silicon substrate 1. The crystallization rate of the film layer close to the silicon substrate 1 is small, which improves the passivation effect of the surface of the silicon substrate 1; while the film layer away from the silicon substrate 1 has a limited passivation effect on the silicon substrate 1, so improving its crystallization rate can improve the conductivity of the entire film layer, which is beneficial to the output and collection of carriers, thereby improving the efficiency of the solar cell 100. In addition, the combination of the intrinsic amorphous silicon layer and the intrinsic microcrystalline silicon layer does not require annealing, which reduces the production cost.

[0038] The doped semiconductor layer 3 is selected from a doped amorphous silicon layer, a doped microcrystalline silicon layer, or a doped polycrystalline silicon layer. In one embodiment, the doped semiconductor layer 3 is a first doped semiconductor layer 31 located on the backlight surface 11 and a second doped semiconductor layer 32 located on the light receiving surface 12.

[0039] In the present invention, the second doped semiconductor layer 32 located on the light-receiving surface 12 of the silicon substrate 1 is an N-type semiconductor layer. In one embodiment, the N-type semiconductor layer is a phosphorus-doped crystalline silicon layer with a doping concentration of 1E20 cm -3 ~1E21cm -3 .

[0040] The first doped semiconductor layer 31 located on the backlight surface 11 of the silicon substrate 1 is a P-type semiconductor layer. In one embodiment, the P-type semiconductor layer is a boron-doped crystalline silicon layer with a doping concentration of 1E19 cm -3 ~1E20cm -3 .

[0041] The transparent conductive film 4 is located between the doped semiconductor layer 3 and the electrode 5 , and can improve charge transfer while maintaining high light transmittance, which is beneficial to the collection and output of carriers, thereby improving the efficiency of the solar cell 100 .

[0042] The light-receiving surface and the backlight surface of the battery substrate both have an electrode area for preparing electrodes and a non-electrode area where electrodes are not required to be prepared. At least part of the electrodes 5 are in contact with the transparent conductive film 4 located in the electrode area.

[0043] In one embodiment, the electrode area is located within the projection of the electrode 5 on the battery substrate along the thickness direction of the battery substrate (or the thickness direction of the silicon substrate 1); and / or, the projection of the electrode 5 on the battery substrate along the thickness direction of the battery substrate covers the electrode area. In this design, the electrode area is not larger than the projection of the electrode 5, that is, the electrode area is consistent with the projection of the electrode 5, or the electrode area is located within the projection of the first electrode but smaller than the area where the projection of the electrode 5 is located; therefore, the area of ​​the non-electrode area not covered by the electrode 5 is maximized.

[0044] The transparent conductive film 4 includes a first transparent conductive film 41 located in the electrode region and a second transparent conductive film 42 located in the non-electrode region, and the carrier concentration of the first transparent conductive film 41 is greater than the carrier concentration of the second transparent conductive film 42. Such a design improves the conductivity of the transparent conductive film 4 located in the electrode region, reduces the contact resistance between the electrode 5 and the transparent conductive film 4, and is combined with the carrier concentration difference in the transparent conductive film 4, which is conducive to the collection of carriers and improves the battery efficiency. At the same time, the carrier concentration of the transparent conductive film 4 located in the non-electrode region is low, which can maintain a high light transmittance, improve the light absorption of the battery, and thus improve the battery effect.

[0045] like Figure 2 As shown, the first transparent conductive film 41 is located within the projection of the electrode 5 on the transparent conductive film 4 along the thickness direction of the battery substrate. And / or, Figure 3 As shown, the projection of the electrode 5 on the transparent conductive film 4 along the thickness direction of the battery substrate covers the first transparent conductive film 41. The first transparent conductive film 41 is located at the projection of the electrode 5 on the transparent conductive film 4, and the area of ​​the first transparent conductive film 41 is not greater than the area of ​​the projection of the electrode 5 on the transparent conductive film 4, so that the area of ​​the second transparent conductive film 42 is maximized, thereby improving the light transmittance of the entire film layer.

[0046] In some embodiments, the carrier concentration of the first transparent conductive film 41 is 2E20 / cm 3 ~4E20 / cm 3 , preferably 2.5E20 / cm 3 ~3.5E20 / cm 3 , maintaining a high carrier concentration and achieving ohmic contact with the electrode 5.

[0047] The carrier concentration of the second transparent conductive film 42 is 0.2E20 / cm 3 ~2E20 / cm 3, its light transmittance can be increased to 85%-99%, preferably 90%-99%, preferably 95%-99%. The second transparent conductive film 42 has better light transmittance than the first transparent conductive film 41, so that the entire transparent conductive film 4 achieves a balance between conductivity and light transmittance.

[0048] In an optional embodiment, the first transparent conductive film 41 is an ITO film (Indium Tin Oxide film, ITO for short) or a VTTO film (Vertical Target Tin Oxide, VTTO for short), and the film layer itself has a high carrier concentration to ensure conductivity.

[0049] The second transparent conductive film 42 is a doped ITO film or a VTTO film, and the dopant is a metal ion or a non-metal ion. The dopant improves the light transmittance of the second transparent conductive film 42, thereby improving the light absorption rate of the solar cell 100.

[0050] In an optional embodiment, the metal ions are selected from a combination of at least one or more of aluminum, magnesium, potassium, sodium, calcium, strontium, barium, copper, lead, zinc, tin, cobalt, nickel, and antimony; the non-metal ions are selected from a combination of at least one or more of hydrogen, boron, carbon, nitrogen, oxygen, fluorine, silicon, phosphorus, and sulfur.

[0051] The electrode 5 is a metal electrode, and forms a good ohmic contact with the transparent conductive film 4 and the doped semiconductor layer 3 .

[0052] In a specific embodiment, the solar cell 100 includes an N-type silicon wafer, the second intrinsic semiconductor layer 22, the second doped semiconductor layer 32, the transparent conductive film 4, and the electrode 5 located on the light-receiving surface 12 of the N-type silicon wafer, and the second doped semiconductor layer 32 is an N-type semiconductor layer; the first intrinsic semiconductor layer 21, the first doped semiconductor layer 31, the transparent conductive film 4, and the electrode 5 are located on the backlight surface 11 of the N-type silicon wafer, and the first doped semiconductor layer 31 is a P-type semiconductor layer.

[0053] Compared with the prior art, the present invention can obtain a higher short-circuit current density (Jsc) and fill factor FF gain by optimizing the optical and electrical properties of the transparent conductive film 4, thereby increasing the battery efficiency by 0.25% or more.

[0054] Please refer to Figure 2~Figure 5As shown, a method for preparing a solar cell according to a preferred embodiment of the present invention comprises the following steps: forming a transparent conductive film 4 on at least one surface of a battery substrate; forming an electrode 5 on a surface of the transparent conductive film 4 away from the battery substrate, wherein at least a portion of the transparent conductive film 4 covered by the electrode 5 constitutes a first transparent conductive film 41; and reducing the carrier concentration of the transparent conductive film 4 in an area not covered by the electrode 5 to form a second transparent conductive film 42.

[0055] In the preparation method, the electrode 5 is used as a mask to reduce the carrier concentration of the transparent conductive film 4 in the non-electrode area, so that the transparent conductive film 4 is divided into a first transparent conductive film 41 located in the electrode area and a second transparent conductive film 42 located in the non-electrode area.

[0056] All characteristic parameters of the structure, film layer, etc. described in the preparation method can refer to the above description of the solar cell 100; all characteristic parameters described in the following solar cell preparation method are also applicable to the above solar cell structure.

[0057] The structure of the battery matrix may refer to any of the above descriptions, or the battery matrix may be prepared by the following method.

[0058] In the first embodiment, preparing a battery matrix includes the following steps in sequence: preparing a first intrinsic semiconductor layer 21 on the backlight surface 11 of the silicon substrate 1; preparing a second intrinsic semiconductor layer 22 on the light-receiving surface 12 of the silicon substrate; preparing a second doped semiconductor layer 32 on the surface of the second intrinsic semiconductor layer 22 away from the silicon substrate 1, the second doped semiconductor layer 32 having the same doping type as the silicon substrate 1; preparing a first doped semiconductor layer 31 on the surface of the first intrinsic semiconductor layer 21 away from the silicon substrate 1, the first doped semiconductor layer 31 having a doping type opposite to that of the silicon substrate 1.

[0059] Specifically, an N-type silicon wafer with a resistivity of 0.5 Ω.cm to 3 Ω.cm and a thickness of 150 μm to 200 μm is selected as the silicon substrate 1, and its surface is cleaned and textured to reduce the reflectivity of the surface.

[0060] In one embodiment, a 5% by volume HF solution is used to remove the surface oxide layer and clean the silicon substrate 1. Then, a KOH solution, a NaOH solution, or a TMAH plus alcohol solution is used to form a pyramid velvet structure on the surface of the silicon wafer by utilizing anisotropic etching of single crystal silicon.

[0061] The present invention adopts a plasma enhanced chemical vapor deposition (PECVD) process to deposit the first intrinsic semiconductor layer 21 , the second intrinsic semiconductor layer 22 , the first doped semiconductor layer 31 , and the second doped semiconductor layer 32 .

[0062] The first intrinsic semiconductor layer 21 is prepared on the backlight surface 11. Silane (SiH4) gas is introduced into the vacuum chamber, and the flow rate of SiH4 gas is 50sccm-1000sccm, and a first intrinsic amorphous silicon layer and / or a first intrinsic microcrystalline silicon layer is formed on the entire area of ​​the backlight surface 11 of the silicon substrate 1 as the first intrinsic semiconductor layer 21.

[0063] Turn over and prepare the second intrinsic semiconductor layer 22 on the light receiving surface 12. Introduce SiH4 gas into the vacuum chamber with a flow rate of 50sccm-1000sccm, and form a second intrinsic amorphous silicon layer and / or a second intrinsic microcrystalline silicon layer as the second intrinsic semiconductor layer 22 on the entire area of ​​the light receiving surface 12 of the silicon substrate 1.

[0064] Then, a second doped semiconductor layer 32 is prepared on the side of the second intrinsic semiconductor layer 22 away from the silicon substrate 1. SiH4 gas, hydrogen (H2) gas and phosphine gas (PH3) are introduced into the vacuum chamber, and an N-type amorphous silicon layer and / or an N-type microcrystalline silicon layer are formed on the second intrinsic amorphous silicon layer and / or the second intrinsic microcrystalline silicon layer as the second doped semiconductor layer 32. The flow rate of SiH4 gas is 50sccm-1000sccm, the flow rate of H2 gas is 4000sccm~5000sccm, and the flow rate of PH3 gas is 50sccm~300sccm.

[0065] Turn over, change the tray, and then prepare the first doped semiconductor layer 31 on the side of the first intrinsic semiconductor layer 21 away from the silicon substrate 1. SiH4 gas, H2 gas and diborane (B2H6) gas are introduced into the vacuum chamber, and a p-type amorphous silicon layer and / or a P-type microcrystalline silicon layer are formed on the first intrinsic amorphous silicon layer and / or the first intrinsic microcrystalline silicon layer as the first doped semiconductor layer 31. The flow rate of SiH4 gas is 50sccm-1000sccm, the flow rate of H2 gas is 4000sccm~5000sccm, and the flow rate of B2H6 gas is 50sccm~300sccm.

[0066] On the basis of the above steps, annealing can also be performed to transform the N-type amorphous silicon layer and / or the N-type microcrystalline silicon layer into an N-type polycrystalline silicon layer as the second doped semiconductor layer 32; and the P-type amorphous silicon layer and / or the P-type microcrystalline silicon layer into a P-type polycrystalline silicon layer as the first doped semiconductor layer 31.

[0067] In one embodiment, the annealing temperature is 850° C. to 1150° C., which can take into account the annealing requirements of the N-type amorphous silicon layer and / or the N-type microcrystalline silicon layer, the P-type amorphous silicon layer and / or the P-type microcrystalline silicon layer, while achieving the transformation of the crystal type and reducing the process cost.

[0068] The battery substrate obtained by the preparation method includes an N-type silicon wafer, the second intrinsic semiconductor layer 22 and the second doped semiconductor layer 32 located on the light-receiving surface 12 of the N-type silicon wafer, and the second doped semiconductor layer 32 is an N-type semiconductor layer; the first intrinsic semiconductor layer 21 and the first doped semiconductor layer 31 are located on the backlight surface 11 of the N-type silicon wafer, and the first doped semiconductor layer 31 is a P-type semiconductor layer.

[0069] In the second embodiment, the process for preparing the battery matrix is ​​different from that in the first embodiment only in the following ways:

[0070] Silane (SiH4) gas is introduced into the vacuum chamber, and the flow rate of SiH4 gas is 50sccm-1000sccm, and a second intrinsic amorphous silicon layer and / or a second intrinsic microcrystalline silicon layer are formed on the entire area of ​​the light-receiving surface 12 of the silicon substrate 1 as the second intrinsic semiconductor layer 22. Then SiH4 gas, hydrogen (H2) gas and phosphine gas (PH3) are introduced into the vacuum chamber, and an N-type amorphous silicon layer and / or an N-type microcrystalline silicon layer are formed on the second intrinsic amorphous silicon layer and / or the second intrinsic microcrystalline silicon layer as the second doped semiconductor layer 32; the flow rate of SiH4 gas is 50sccm-1000sccm, the flow rate of H2 gas is 4000sccm~5000sccm, and the flow rate of PH3 gas is 50sccm~300sccm.

[0071] Turn over, change the tray, and then introduce SiH4 gas into the vacuum chamber, the flow rate of SiH4 gas is 50sccm-1000sccm, and form a first intrinsic amorphous silicon layer and / or a first intrinsic microcrystalline silicon layer on the entire area of ​​the backlight surface 11 of the silicon substrate 1. Then introduce SiH4 gas, H2 gas and diborane (B2H6) gas into the vacuum chamber, and form a p-type amorphous silicon layer and / or a p-type microcrystalline silicon layer on the first intrinsic amorphous silicon layer and / or the first intrinsic microcrystalline silicon layer as the first doped semiconductor layer 31, the flow rate of SiH4 gas is 50sccm-1000sccm, the flow rate of H2 gas is 4000sccm~5000sccm, and the flow rate of B2H6 gas is 50sccm~300sccm.

[0072] In addition, when preparing the battery matrix, the order of the various film layers is not limited to the above two, and can be adjusted arbitrarily.

[0073] The invention adopts reactive plasma deposition (RPD) or magnetron sputtering deposition (PVD) to prepare the transparent conductive film.

[0074] During the deposition process, the edge of the surface is shielded by a mask plate designed by a carrier, and the width of the specific shielding area around is 0.6mm~0.8mm. In one embodiment, the carrier is a hollow flat plate design, and there is a convex edge of about 0.6mm~0.8mm at the edge of the hollow part to support the silicon wafer, while exposing the areas of the light-receiving surface 12 and the backlight surface 11 that need to be coated.

[0075] Take PVD deposition as an example. The PVD equipment includes at least several (such as 4) non-contaminating coating targets. If the same target material is installed on several targets, a single-component transparent conductive film can be obtained; if different target materials are installed on several targets, a multi-component mixed transparent conductive film can be obtained. The battery substrate after forming the N-type amorphous silicon layer and / or the N-type microcrystalline silicon layer, the P-type amorphous silicon layer and / or the P-type microcrystalline silicon layer is placed on a carrier, and is coated in different targets in turn to obtain an excellent transparent conductive film 4.

[0076] The O2 atmosphere is adjusted at different target positions to adjust the carrier concentration of the transparent conductive film to the concentration range required by the electrode area. In the present invention, the carrier concentration of the transparent conductive film 4 is 2 E20 / cm 3 ~4E20 / cm 3 , preferably 2.5E20 / cm 3 ~3.5E20 / cm 3 .

[0077] In an optional embodiment, the transparent conductive film is selected from a combination of one or more of an ITO film or a VTTO film, and the thickness of the transparent conductive film 4 is 70 nm to 85 nm, preferably 75 nm to 80 nm.

[0078] In one embodiment, the four coating targets are all ITO-based targets for depositing ITO film and / or VTTO film.

[0079] Specifically, the battery substrate is carried on a corresponding carrier, and a certain amount of energy is used to bombard the material phase in the target material, while 90% to 99% argon (Ar), 1% to 6% oxygen (O2), and 0 to 4% hydrogen (H2) are introduced. Ar is an inert protective gas, and O2 and H2 are used to dope the transparent conductive film.

[0080] For different work functions, the flow ratios of Ar, O2, and H2 are different. A decrease in the O2 flow will increase the carrier concentration of the transparent conductive film 4, while an increase in the H2 flow will have little effect on the carrier concentration of the transparent conductive film 4, but will improve the light transmittance.

[0081] In one embodiment, ITO film and VTTO film are deposited, O2 flow rate accounts for 3%~5%, H2 flow rate accounts for 0%~4%, and the rest is Ar, and the pressure is 0.4Pa~0.7Pa, which can make the carrier concentration of the transparent conductive film 2E20 / cm 3 ~4E20 / cm 3 , preferably 2.5E20 / cm 3 ~3.5E20 / cm 3 .

[0082] The present invention adopts screen printing and sintering process to prepare the electrode 5. Firstly, metal conductive paste is printed on the transparent conductive film 4 of the electrode area of ​​the light receiving surface 12 and the backlight surface 11 by screen printing, and then sintered and cured at a low temperature of 150℃ to 350℃ to form a good ohmic contact.

[0083] In an optional embodiment, the metal conductive paste is selected from but not limited to Ag, Cu, and Al. The metal conductive paste used herein includes but is not limited to low-temperature silver paste, low-temperature silver-copper paste, and low-temperature copper paste; the sintering temperature is within the range of 150°C to 350°C, and the cost is low.

[0084] After forming the electrode 5, the present invention uses the electrode 5 as a mask to process the transparent conductive film 4 located in the non-electrode area, thereby simplifying the process.

[0085] In one embodiment, the electrode 5 is used as a mask to inject dopants into the transparent conductive film 4 in the non-electrode region to reduce the carrier concentration of the transparent conductive film 4 in the non-electrode region, so that the carrier concentration of the transparent conductive film 4 in the electrode region is greater than that of the transparent conductive film 4 in the non-electrode region, which can solve the contradiction of inconsistent carrier concentration requirements between the electrode region and the light-receiving region. At the same time, the transparent conductive film 4 maintains a good light transmittance.

[0086] In an optional embodiment, the dopant is a metal ion or a non-metal ion.

[0087] The metal ions are selected from at least one or more combinations of aluminum, magnesium, potassium, sodium, calcium, strontium, barium, copper, lead, zinc, tin, cobalt, nickel, and antimony; and / or the non-metal ions are selected from at least one or more combinations of hydrogen, boron, carbon, nitrogen, oxygen, fluorine, silicon, phosphorus, and sulfur.

[0088] After ion implantation, the transparent conductive film 4 covered by the electrode 5 is not doped by the dopant, forming a first transparent conductive film 41, and the carrier concentration is 2E20 / cm 3 ~4E20 / cm 3 The transparent conductive film in the area not covered by the electrode is doped with the dopant to form a second transparent conductive film 42, and the carrier concentration is 0.2E20 / cm 3 ~2E20 / cm 3 , the transmittance is 85%-99%. After ion implantation, the carrier concentration of the TCO film is reduced, and the transmittance is also increased.

[0089] In a specific embodiment, the dopant is doped by plasma implantation. In this preparation method, during ion implantation, due to the relative disorder of plasma, when the electrode 5 is used as a mask, the transparent conductive film 4 below may form two possible situations: ① The projection of the first transparent conductive film 41 and the electrode 5 on the transparent conductive film 4 along the thickness direction of the silicon substrate 1 is consistent, such as Figure 2 ② The first transparent conductive film 41 is slightly smaller than the projection of the electrode 5 along the thickness direction of the silicon substrate 1 on the transparent conductive film 4, as shown Figure 3 shown.

[0090] In another specific embodiment, dopants are doped into the transparent conductive film 4 in the area not covered by the electrode 5 by a vacuum diffusion process.

[0091] Under predetermined vacuum and temperature conditions, the battery substrate after the electrode 5 is prepared is placed in a dopant gas atmosphere, and the dopant is doped into the transparent conductive film in the area not covered by the electrode 5 .

[0092] Specifically, the battery substrate after the electrode 5 is prepared is placed in a dopant atmosphere, and the dopant is injected into the transparent conductive film 4 in the area not covered by the electrode 5 by diffusion to form the second transparent conductive film 42 .

[0093] Taking hydrogen injection as an example, the vacuum degree is set to 0.1mbar~3mbar, the hydrogen flow rate is 10sccm~800sccm, the temperature is 160℃~250℃, and the time is 20min~120min. When injecting other dopants, hydrogen is replaced with other gases, such as methane, borane, nitrogen, oxygen, and hydrogen sulfide, and the temperature and time are also adaptively adjusted.

[0094] The solar cell 100 and the manufacturing method thereof of the present invention will be described below with reference to specific embodiments.

[0095] Example:

[0096] An N-type silicon wafer with a resistivity of 2Ω.cm and a thickness of 200 μm was selected as the silicon substrate 1. After removing the surface oxide layer with a volume fraction of 5% HF solution, a pyramid velvet structure was formed by etching with a KOH solution.

[0097] The silicon wafer is placed in a vacuum chamber, and SiH 4 gas is introduced into the vacuum chamber with a flow rate of 50 sccm-1000 sccm, so that an intrinsic amorphous silicon layer is formed on the entire area of ​​the backlight surface 11 of the silicon wafer as the first intrinsic semiconductor layer 21 .

[0098] Turn over and introduce SiH 4 (silane) gas into the vacuum chamber with a flow rate of 50 sccm-1000 sccm to form an intrinsic amorphous silicon layer on the entire light-receiving surface 12 of the silicon wafer as the second intrinsic semiconductor layer 22 .

[0099] Then, SiH4, H2, and PH3 gases are introduced into the vacuum chamber, with a flow rate of 50sccm-1000sccm for SiH4 gas, 4000sccm~5000sccm for H2 gas, and 50sccm~300sccm for PH3 gas, to form an N-type amorphous silicon layer on the surface of the second intrinsic semiconductor layer 22 away from the silicon substrate 1.

[0100] Turn over and change the tray. Introduce SiH4, H2, and B2H6 gases into the vacuum chamber, with the flow rate of SiH4 gas being 50sccm-1000sccm, the flow rate of H2 gas being 4000sccm~5000sccm, and the flow rate of B2H6 gas being 50sccm~300sccm, to form a P-type amorphous silicon layer on the surface of the first intrinsic semiconductor layer 21 away from the silicon substrate 1.

[0101] Annealing is performed to transform the N-type amorphous silicon layer into an N-type polysilicon layer as the second doped semiconductor layer 32, and simultaneously transform the P-type amorphous silicon layer into a P-type polysilicon layer as the first doped semiconductor layer 31. The annealing temperature is 950°C.

[0102] The magnetron sputtering process is used to deposit transparent conductive films on the side where the light receiving surface 12 is located and the side where the backlight surface 11 is located. First, the ITO film is deposited with a thickness of 36nm; then the VTTO film is deposited with a thickness of 38nm. During the deposition process, the O2 flow rate accounts for 3%~5%, the H2 flow rate accounts for 1%~3%, and the rest is Ar. The pressure is 0.4 Pa~0.7Pa. The carrier concentration of the obtained transparent conductive film is 2.65E20 / cm 3 .

[0103] Prepare the electrode 5. Screen-print metal conductive paste on the electrode areas of the light-receiving surface 12 and the backlight surface 11, respectively, and sinter and solidify them at a low temperature of 220°C to form the electrode 5.

[0104] The transparent conductive film 4 located in the non-electrode area is ion-implanted. With the electrode 5 as a mask, an ion implanter is used to implant metal ions into the exposed transparent conductive film 4 not covered by the electrode 5, wherein the metal ions are aluminum. After ion implantation, the second transparent conductive film 42 located in the non-electrode area is doped with aluminum to form the second transparent conductive film 42, and the carrier concentration is 1.13E20 / cm 3 .

[0105] Comparative Example: The only difference from the embodiment is that after the electrode 5 is prepared, ion implantation is not performed on the non-electrode region, and the carrier concentration of the entire region of the transparent conductive film 4 is 2.65E20 / cm 3 .

[0106] The solar cells 100 of the above embodiment and comparative example were tested, and the results are shown in Table Figure 1 As shown. The carrier concentration of the light receiving surface 12 of the embodiment is lower, and the square resistance is further improved. Compared with the comparative example, the short-circuit current density Jsc gain of the embodiment is +0.20mA / cm 2 There is no gain in the passivation effect, the filling factor FF of the embodiment is substantially equivalent to that of the comparative example, and the efficiency Eta gain of the battery is 0.25%.

[0107] Table 1

[0108]

[0109] In summary, in the solar cell 100 and the preparation method thereof of the present invention, the carrier concentration of the first transparent conductive film 41 located in the electrode area is greater than the carrier concentration of the second transparent conductive film 42 located in the non-electrode area, which reduces the contact resistance between the electrode 5 and the first transparent conductive film 41. Combined with the carrier concentration difference in the transparent conductive film 4, it is beneficial to the collection of carriers and improves the battery efficiency. At the same time, the transparent conductive film 4 in the non-electrode area has a low carrier concentration, which can maintain a high light transmittance, improve the light absorption rate of the battery, and thus improve the battery efficiency. The present invention can balance the requirements of the electrode area for conductivity and the non-electrode area (light-receiving area) for light transmittance, and improve the efficiency of the battery from both electrical and optical perspectives.

[0110] It should be understood that although this specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each implementation mode may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

[0111] The series of detailed descriptions listed above are only specific descriptions of feasible implementation methods of the present invention. They are not intended to limit the scope of protection of the present invention. Any equivalent implementation methods or changes that do not deviate from the technical spirit of the present invention should be included in the scope of protection of the present invention.

Claims

1. A solar cell, comprising a cell substrate, a transparent conductive film (4) located on at least one surface of the cell substrate, and an electrode (5) located on a side of the transparent conductive film (4) away from the cell substrate; characterized in that: The transparent conductive film (4) comprises a first transparent conductive film (41) located in an electrode region and a second transparent conductive film (42) located in a non-electrode region; the carrier concentration of the first transparent conductive film (41) is greater than the carrier concentration of the second transparent conductive film (42); the electrode (5) is in contact with the first transparent conductive film (41); the first transparent conductive film (41) is located within the projection of the electrode (5) on the transparent conductive film (4) along the thickness direction of the battery substrate; the area of ​​the surface of the first transparent conductive film (41) in contact with the electrode (5) is consistent with the area of ​​the projection of the electrode (5) on the transparent conductive film (4); and the area of ​​the surface of the first transparent conductive film (41) in contact with the battery substrate is smaller than the area of ​​the projection of the electrode (5) on the transparent conductive film (4).

2. The solar cell according to claim 1, characterized in that: The carrier concentration of the first transparent conductive film (41) is 2E20 / cm 3 ~4E20 / cm 3 , And / or, the carrier concentration of the second transparent conductive film (42) is 0.2E20 / cm 3 ~2E20 / cm 3 , And / or, the light transmittance of the second transparent conductive film (42) is 85%-99%; And / or, the thickness of the transparent conductive film (4) is 80 nm-120 nm.

3. The solar cell according to claim 1, characterized in that: The electrode area is located within the projection of the electrode (5) on the battery substrate along the thickness direction of the battery substrate; and / or, the first transparent conductive film (41) is located within a projection of the electrode (5) on the transparent conductive film (4) along the thickness direction of the battery substrate; and / or, the projection of the electrode (5) on the battery substrate along the thickness direction of the battery substrate covers the electrode area; And / or, the projection of the electrode (5) on the transparent conductive film (4) along the thickness direction of the battery substrate covers the first transparent conductive film (41), and the area of ​​the first transparent conductive film (41) gradually decreases in the direction from the electrode (5) to the battery substrate.

4. The solar cell according to claim 1, characterized in that: The first transparent conductive film (41) is an ITO film or a VTTO film, and / or the second transparent conductive film (42) is an ITO film or a VTTO film doped with a dopant.

5. The solar cell according to claim 4, characterized in that: The dopant is a metal ion and / or a non-metal ion; The metal ions are selected from at least one or more of aluminum, magnesium, potassium, sodium, calcium, strontium, barium, copper, lead, zinc, tin, cobalt, nickel, and antimony; And / or the non-metal ions are selected from at least one or more combinations of hydrogen, boron, carbon, nitrogen, oxygen, fluorine, silicon, phosphorus and sulfur.

6. The solar cell according to any one of claims 1 to 5, characterized in that: The battery matrix comprises a silicon substrate (1), an intrinsic semiconductor layer (2) located on at least one surface of the silicon substrate (1), and a doped semiconductor layer (3) located on a side of the intrinsic semiconductor layer (2) away from the silicon substrate (1).

7. The solar cell according to claim 6, characterized in that: The silicon substrate (1) is an N-type silicon wafer; And / or, the intrinsic semiconductor layer (2) is an intrinsic amorphous silicon layer, or an intrinsic microcrystalline silicon layer, or an intrinsic polycrystalline silicon layer; And / or, the doped semiconductor layer (3) located on the light-receiving surface of the silicon substrate (1) is an N-type amorphous silicon layer, or an N-type microcrystalline silicon layer, or an N-type polycrystalline silicon layer, and the doping concentration is 1E20cm -3 ~1E21cm -3 ; And / or, the doped semiconductor layer (3) located on the backlight side of the silicon substrate (1) is a P-type amorphous silicon layer, or a P-type microcrystalline silicon layer, or a P-type polycrystalline silicon layer, and the doping concentration is 1E19cm -3 ~1E20cm -3 .

8. A method for preparing a solar cell, characterized in that: The steps include: forming a transparent conductive film on at least one surface of the battery substrate; An electrode is formed on the surface of the transparent conductive film away from the battery substrate, and at least a portion of the transparent conductive film covered by the electrode constitutes a first transparent conductive film; Using the electrode as a mask, dopants are injected into the transparent conductive film in the area not covered by the electrode to reduce the carrier concentration of the transparent conductive film in the area not covered by the electrode, so as to form a second transparent conductive film; the area of ​​the surface of the first transparent conductive film in contact with the electrode is consistent with the area of ​​the projection of the electrode on the transparent conductive film, and the area of ​​the surface of the first transparent conductive film in contact with the battery substrate is smaller than the area of ​​the projection of the electrode on the transparent conductive film.

9. The method for preparing a solar cell according to claim 8, characterized in that: The transparent conductive film is selected from an ITO film or a VTTO film; Alternatively, the transparent conductive film is formed by a reactive plasma deposition process or a magnetron sputtering deposition process. During the deposition process, the O2 flow rate accounts for 3% to 5%, the H2 flow rate accounts for 0% to 4%, and the rest is Ar, and the pressure is 0.4Pa to 0.7Pa.

10. The method for preparing a solar cell according to claim 8, characterized in that: Injecting dopants into the transparent conductive film in the area not covered by the electrode by a plasma injection process to form a second transparent conductive film; the dopants are metal ions and / or non-metal ions; The metal ions are selected from at least one or more of aluminum, magnesium, potassium, sodium, calcium, strontium, barium, copper, lead, zinc, tin, cobalt, nickel, and antimony; And / or, the non-metal ions are selected from at least one or more combinations of hydrogen, boron, carbon, nitrogen, oxygen, fluorine, silicon, phosphorus and sulfur.

11. The method for preparing a solar cell according to claim 8, characterized in that: doping the transparent conductive film in the area not covered by the electrode with a dopant by a vacuum diffusion process; Alternatively, under predetermined vacuum and temperature conditions, the battery substrate after the electrode is prepared is placed in a gas atmosphere of a dopant, and the dopant is doped into the transparent conductive film in the area not covered by the electrode.

12. The method for preparing a solar cell according to claim 8, characterized in that: The carrier concentration of the first transparent conductive film is 2E20 / cm 3 ~4E20 / cm 3 , And / or, the carrier concentration of the second transparent conductive film is 0.2E20 / cm 3 ~2E20 / cm 3 ; And / or, the light transmittance of the second transparent conductive film is 85%-99%; And / or, the transparent conductive film has a thickness of 80nm-120nm.

13. The method for preparing a solar cell according to any one of claims 8 to 12, characterized in that: It also includes preparing a battery matrix, and "preparing a battery matrix" includes the following steps in sequence: Preparing a first intrinsic semiconductor layer on the backlight side of the silicon substrate; preparing a second intrinsic semiconductor layer on the light-receiving surface of the silicon substrate; A second doped semiconductor layer is prepared on a surface of the second intrinsic semiconductor layer away from the silicon substrate, wherein the second doped semiconductor layer has the same doping type as the silicon substrate; A first doped semiconductor layer is prepared on a surface of the first intrinsic semiconductor layer away from the silicon substrate, wherein the doping type of the first doped semiconductor layer is opposite to that of the silicon substrate.

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