Heterojunction solar cell and manufacturing method therefor

Abstract

The present invention provides a heterojunction solar cell and a manufacturing method therefor. The method uses a predetermined deposition process to sequentially form an oxygen-containing crystalline silicon layer of a first conductive type on the surface of a first passivation layer distant from a silicon substrate, wherein the oxygen atom doping concentration of the oxygen-containing crystalline silicon layer gradually increases in a direction facing away from the silicon substrate. On the one hand, light oxygen doping is performed at the interface of the first passivation layer, thereby reducing dark degradation of the heterojunction solar cell, and thus mitigating power degradation of a photovoltaic module; on the other hand, heavy oxygen doping is performed on the side distant from the first passivation layer, thereby effectively increasing the optical bandgap and short-circuit current of the crystalline silicon layer on a light-receiving surface. In addition, oxygen-free doping is performed in a semiconductor layer at the interface adjacent to a transparent conductive layer, thereby effectively reducing ohmic contact between the semiconductor layer and the transparent conductive layer. The method of the present invention can effectively ensure and improve the comprehensive electrical performance of the heterojunction solar cell.

Description

Heterojunction solar cells and their fabrication methods

[0001] Cross-references to related applications

[0002] This application claims priority to Chinese patent application No. CN202411638003.8, filed on November 15, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This invention belongs to the field of solar cell technology, specifically relating to a heterojunction solar cell and its preparation method. Background Technology

[0004] Heterojunction solar cells have become a new hot topic in the photovoltaic field in recent years due to their unique structure, excellent passivation mechanism, and high conversion efficiency.

[0005] In related technologies, hydrogenated nanocrystalline silicon oxide (nc-SiOx:H) material is used to prepare heterojunction solar cells, taking advantage of its technical advantages in improving the optical bandgap to enhance the short-circuit current and photoelectric conversion efficiency of heterojunction solar cells.

[0006] However, hydrogenated nanocrystalline silicon oxide materials can cause heterojunction solar cells to suffer from problems such as water-boiling degradation (i.e., the fill factor and photoelectric conversion efficiency of heterojunction solar cells decrease under high temperature and high humidity conditions) and dark degradation (i.e., the photoelectric conversion efficiency of heterojunction solar cells decreases after long-term indoor storage), which has an adverse effect on further improving power generation efficiency.

[0007] Therefore, it is necessary to provide a heterojunction solar cell and its fabrication method to effectively improve the above-mentioned technical problems. Summary of the Invention

[0008] To address the aforementioned shortcomings, this invention provides a heterojunction solar cell and its fabrication method. This method enables heterojunction solar cells to have higher photoelectric conversion efficiency and shorter short-circuit current, while reducing water-induced degradation and dark degradation.

[0009] In a first aspect, the present invention provides a method for fabricating a heterojunction solar cell, comprising:

[0010] A silicon substrate is provided, the silicon substrate having a first main surface and a second main surface opposite to each other;

[0011] A first passivation layer is formed on the first main surface of the silicon substrate using a predetermined deposition process;

[0012] An oxygen-containing crystalline silicon layer of a first conductivity type is formed on the side of the first passivation layer away from the silicon substrate, and the oxygen atom doping concentration in the oxygen-containing crystalline silicon layer gradually increases in the direction away from the silicon substrate.

[0013] A first doped semiconductor layer of a first conductivity type is formed on the side of the oxygen-containing crystalline silicon layer opposite to the silicon substrate;

[0014] A second passivation layer is formed on the second main surface of the silicon substrate;

[0015] A second doped semiconductor layer of a second conductivity type is formed on the side of the second passivation layer opposite to the silicon substrate;

[0016] A transparent conductive layer is formed on the side of the first doped semiconductor layer and the second doped semiconductor layer that is away from the silicon substrate;

[0017] Metal electrodes are formed on the side of the transparent conductive layer opposite to the silicon substrate; wherein the first conductivity type is selected from either P-type or N-type; and the second conductivity type is selected from either P-type or N-type.

[0018] Optionally, forming an oxygen-containing silicon layer of a first conductivity type on the side of the first passivation layer away from the silicon substrate, and causing the oxygen atom doping concentration in the oxygen-containing silicon layer to gradually increase along the direction away from the silicon substrate, includes:

[0019] A first deposition process is performed on the side of the first passivation layer away from the silicon substrate, and the oxygen atom doping concentration is continuously increased while depositing the oxygen-containing crystalline silicon layer, so as to obtain an oxygen-containing crystalline silicon layer in which the oxygen atom doping concentration continuously increases in the direction away from the silicon substrate.

[0020] Optionally, forming an oxygen-containing silicon layer of a first conductivity type on the side of the first passivation layer away from the silicon substrate, and causing the oxygen atom doping concentration in the oxygen-containing silicon layer to gradually increase along the direction away from the silicon substrate, includes:

[0021] A second deposition process is performed on the side of the first passivation layer away from the silicon substrate to sequentially form a plurality of stacked oxygen-containing silicon sublayers; along the direction away from the silicon substrate, the oxygen atom doping concentration between each oxygen-containing silicon sublayer increases in a gradient.

[0022] Optionally, a second deposition process is performed on the side of the first passivation layer away from the silicon substrate to sequentially form a first oxygen-containing silicon sublayer, a second oxygen-containing silicon sublayer, and a third oxygen-containing silicon sublayer; the oxygen atom doping concentration among the first oxygen-containing silicon sublayer, the second oxygen-containing silicon sublayer, and the third oxygen-containing silicon sublayer increases in a gradient.

[0023] Optionally, the second deposition process includes the following steps:

[0024] The first oxygen-containing crystalline silicon sublayer is formed by depositing a first process gas on the side of the first passivation layer away from the silicon substrate;

[0025] The second oxygen-containing crystalline silicon sublayer is formed by depositing a second process gas on the side of the first oxygen-containing crystalline silicon sublayer away from the first passivation layer.

[0026] The third oxygen-containing silicon sublayer is formed by depositing a third process gas on the side of the second oxygen-containing silicon sublayer opposite to the first oxygen-containing silicon sublayer; wherein...

[0027] The first process gas includes CO2, H2, PH3 and SiH4, wherein the gas flow rate ratio of CO2, H2, PH3 and SiH4 is (0.0001~0.3):(5~600):(0.005~0.07):1;

[0028] The second process gas includes CO2, H2, PH3 and SiH4, wherein the gas flow rate ratio of CO2, H2, PH3 and SiH4 is (0.1~0.8):(5~600):(0.005~0.07):1;

[0029] The third process gas includes CO2, H2, PH3 and SiH4, wherein the gas flow rate ratio of CO2, H2, PH3 and SiH4 is (0.3~3):(5~600):(0.005~0.07):1.

[0030] Optionally, the step of forming the first doped semiconductor layer on the side of the oxygen-containing silicon layer opposite to the silicon substrate includes:

[0031] The first doped semiconductor layer is obtained by performing a third deposition process on the side of the oxygen-containing crystalline silicon layer away from the silicon substrate using a fourth process gas.

[0032] The fourth process gas includes H2, PH3 and SiH4, wherein the gas flow rate ratio of H2, PH3 and SiH4 is (5-600):(0.005-0.07):1.

[0033] Optionally, the first deposition process, the second deposition process, and the third deposition process each independently include: a process temperature of 170℃~230℃ and a power density of 10mW·cm³. -2 ~800mW·cm -2 The process pressure is 0.1 mbar to 8 mbar.

[0034] Optionally, forming the second doped semiconductor layer on the side of the second passivation layer opposite to the silicon substrate includes:

[0035] A fourth deposition process is performed on the side of the second passivation layer away from the silicon substrate using a fifth process gas to obtain the second doped semiconductor layer.

[0036] The fifth process gas includes CO2, H2, B2H6 and SiH4, wherein the gas flow rate ratio of CO2, H2, B2H6 and SiH4 is (0-4):(5-600):(0.005-0.07):1;

[0037] The conditions for the fourth deposition process include: a process temperature of 150℃~210℃ and a power density of 10mW·cm⁻¹. -2 ~800mW·cm -2 The process pressure is 0.1 mbar to 8 mbar.

[0038] Optionally, forming the transparent conductive layer on the side of the first doped semiconductor layer and the second doped semiconductor layer facing away from the silicon substrate includes:

[0039] The transparent conductive layer is obtained by performing a fifth deposition process on the side of the first doped semiconductor layer and the second doped semiconductor layer away from the silicon substrate using a sixth process gas.

[0040] The sixth process gas includes O2, H2, H2O and Ar, wherein the gas flow rate ratio of O2, H2, H2O and Ar is (0.01~0.08):(0.01~0.05):(0.0001~0.003):1;

[0041] The conditions for the fifth deposition process include: a process temperature of 80℃ to 200℃, a power supply of 1KW to 15KW, and a process pressure of 0.2Pa to 2Pa.

[0042] In a second aspect, the present invention provides a heterojunction solar cell, comprising: a silicon substrate having a first main surface and a second main surface opposite to each other;

[0043] The first passivation layer is located on the first main surface of the silicon substrate;

[0044] An oxygen-containing crystalline silicon layer of the first conductivity type is located on the side of the first passivation layer away from the silicon substrate; the oxygen atom doping concentration in the oxygen-containing crystalline silicon layer gradually increases along the direction away from the silicon substrate;

[0045] A first doped semiconductor layer of a first conductivity type is located on the side of the oxygen-containing crystalline silicon layer opposite to the silicon substrate;

[0046] The second passivation layer is located on the second main surface of the silicon substrate;

[0047] A second doped semiconductor layer of a second conductivity type is located on the side of the second passivation layer away from the silicon substrate;

[0048] A transparent conductive layer is located on the side of the first doped semiconductor layer and the second doped semiconductor layer that is away from the silicon substrate;

[0049] Metal electrodes are respectively located on the side of the transparent conductive layer opposite to the silicon substrate;

[0050] The first conductivity type is selected from either P-type or N-type;

[0051] The second conductivity type is selected from either P-type or N-type.

[0052] Optionally, along the direction away from the silicon substrate, the concentration of oxygen atoms in the oxygen-containing crystalline silicon layer of the first conductivity type continuously increases.

[0053] Optionally, the oxygen-containing crystalline silicon layer of the first conductivity type includes a plurality of oxygen-containing crystalline silicon sub-layers stacked sequentially along the thickness direction, and the oxygen atom doping concentration between each oxygen-containing crystalline silicon sub-layer increases in a gradient along the direction away from the silicon substrate.

[0054] Optionally, along the direction away from the silicon substrate, the oxygen-containing silicon layer of the first conductivity type includes a first oxygen-containing silicon sublayer, a second oxygen-containing silicon sublayer, and a third oxygen-containing silicon sublayer stacked sequentially; the oxygen atom doping concentration among the first oxygen-containing silicon sublayer, the second oxygen-containing silicon sublayer, and the third oxygen-containing silicon sublayer increases in a gradient.

[0055] Optionally, the average oxygen doping concentration in the oxygen-containing crystalline silicon layer of the first conductivity type is 5 × 10⁻⁶. 19 atoms / cm 3 Up to 7×10 19 atoms / cm 3 .

[0056] Optionally, the material of the oxygen-containing crystalline silicon layer includes at least one of oxygen-containing microcrystalline silicon, oxygen-containing amorphous silicon, and oxygen-containing nanocrystalline silicon; and / or,

[0057] The material of the first doped semiconductor layer includes at least one of microcrystalline silicon, amorphous silicon, and nanocrystalline silicon; and / or,

[0058] The material of the second doped semiconductor layer includes at least one of oxygen-containing microcrystalline silicon, oxygen-containing amorphous silicon, and oxygen-containing nanocrystalline silicon; and / or,

[0059] The thickness of the oxygen-containing crystalline silicon layer of the first conductivity type is 5nm-45nm; and / or,

[0060] The thickness of the second doped semiconductor layer is 10nm-50nm; and / or,

[0061] The thickness of the first oxygen-containing crystalline silicon sublayer is 0.1 nm-5 nm; and / or,

[0062] The thickness of the second oxygen-containing crystalline silicon sublayer is 5nm-30nm; and / or,

[0063] The thickness of the third oxygen-containing crystalline silicon sublayer is 0.1 nm-10 nm; and / or,

[0064] The thickness of the first doped semiconductor layer is 0.1 nm to 10 nm.

[0065] Optionally, the interface between the first doped semiconductor layer and the transparent conductive layer is oxygen-free.

[0066] The heterojunction solar cell of the present invention has an oxygen-containing crystalline silicon layer of a first conductivity type with a gradually increasing oxygen atom doping concentration along the direction away from the silicon substrate. The side of this oxygen-containing crystalline silicon layer in contact with the first passivation layer is characterized by mild oxygen doping, which helps reduce dark decay in the heterojunction cell and thus reduces power drop-off issues in photovoltaic modules. The side of this oxygen-containing crystalline silicon layer away from the first passivation layer is characterized by heavy oxygen doping, which effectively improves the optical bandgap and short-circuit current of the silicon layer on the light-receiving surface. Furthermore, the semiconductor layer adjacent to the transparent conductive layer is oxygen-free, effectively reducing the ohmic contact between the semiconductor layer and the transparent conductive layer. Therefore, the heterojunction solar cell with this oxygen-containing crystalline silicon layer exhibits high photoelectric conversion efficiency, low short-circuit current, and low open-circuit voltage, as well as low water-induced degradation and dark decay, thereby effectively ensuring and improving overall electrical performance. Attached Figure Description

[0067] Figure 1 is a schematic flowchart of a method for fabricating a heterojunction solar cell according to an embodiment of the present invention;

[0068] Figure 2 is a flowchart illustrating step S30 in one embodiment of the present invention;

[0069] Figure 3 is a schematic diagram of the structure obtained after step S10 in one embodiment of the present invention.

[0070] Figure 4 is a schematic diagram of the structure obtained after step S20 in one embodiment of the present invention;

[0071] Figure 5 is a schematic diagram of the structure obtained after step S30 in one embodiment of the present invention.

[0072] Figure 6 is a schematic diagram of an oxygen-containing crystalline silicon layer (the oxygen atom doping concentration increases continuously along the direction away from the silicon substrate) provided in one embodiment of the present invention;

[0073] Figure 7 is a schematic diagram of another oxygen-containing crystalline silicon layer (the oxygen atom doping concentration increases in a gradient along the direction away from the silicon substrate) provided in one embodiment of the present invention;

[0074] Figure 8 is a schematic diagram of the structure obtained after step S40 in one embodiment of the present invention.

[0075] Figure 9 is a schematic diagram of the structure obtained after step S50 in one embodiment of the present invention.

[0076] Figure 10 is a schematic diagram of the structure obtained after step S60 in one embodiment of the present invention.

[0077] Figure 11 is a schematic diagram of the structure obtained after step S70 in one embodiment of the present invention;

[0078] Figure 12 is a schematic diagram of the structure obtained after step S80 in one embodiment of the present invention.

[0079] Explanation of reference numerals in the attached figures: 100 - Silicon substrate; 210 - First passivation layer; 220 - Second passivation layer; 310 - Oxygen-containing crystalline silicon layer; 311 - First oxygen-containing crystalline silicon sublayer; 312 - Second oxygen-containing crystalline silicon sublayer; 313 - Third oxygen-containing crystalline silicon sublayer; 410 - First doped semiconductor layer; 420 - Second doped semiconductor layer; 500 - Transparent conductive layer; 600 - Metal electrode. Detailed Implementation

[0080] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0081] As shown in Figures 1, 3-5, and 8-12, in a first aspect, the present invention provides a method for fabricating a heterojunction solar cell, comprising:

[0082] S20: As shown in Figure 4, a first passivation layer 210 is disposed on the first main surface of the silicon substrate 100;

[0083] S30: As shown in Figure 5, an oxygen-containing crystalline silicon layer 310 of the first conductivity type is formed on the side of the first passivation layer 210 away from the silicon substrate 100, and the oxygen atom doping concentration in the oxygen-containing crystalline silicon layer 310 gradually increases along the direction away from the silicon substrate 100.

[0084] S40: As shown in FIG8, a first doped semiconductor layer 410 of the first conductivity type is formed on the side of the oxygen-containing crystalline silicon layer 310 facing away from the silicon substrate 100.

[0085] S50: As shown in Figure 9, a second passivation layer 220 is formed on the second main surface of the silicon substrate 100;

[0086] S60: As shown in FIG10, a second doped semiconductor layer 420 of a second conductivity type is formed on the side of the second passivation layer 220 opposite to the silicon substrate 100;

[0087] S70: As shown in FIG11, transparent conductive layers 500 are formed on the side of the first doped semiconductor layer 410 and the second doped semiconductor layer 420 away from the silicon substrate 100, respectively.

[0088] S80: As shown in Figure 12, metal electrodes 600 are formed on the side of the transparent conductive layer 500 that is away from the silicon substrate 100.

[0089] When the first conductivity type is P, the second conductivity type is N; when the first conductivity type is N, the second conductivity type is P.

[0090] The present invention provides an oxygen-containing crystalline silicon layer of a first conductivity type with an oxygen atom doping concentration that gradually increases in the direction away from the silicon substrate on the side of the first passivation layer away from the silicon substrate. This enables the heterojunction solar cell including the oxygen-containing crystalline silicon layer of the first conductivity type to have higher photoelectric conversion efficiency, short-circuit current and open-circuit voltage, while reducing the water-boiling degradation and dark degradation of the heterojunction solar cell.

[0091] This invention does not limit the shape, size, thickness, doping type, or minority carrier / resistivity ratio of the silicon substrate; it can be selected according to actual needs. In some embodiments, the silicon substrate can be getted, and then the getted silicon substrate can be texturized to obtain a substrate including a first main surface and a second main surface opposite to each other.

[0092] The first passivation layer and the second passivation layer of the present invention can be single layers or composite layers, respectively. The materials of the first passivation layer and the second passivation layer can be those well known to those skilled in the art, such as one or more of hydrogen-free intrinsic amorphous silicon, hydrogen-rich intrinsic amorphous silicon, CO2-doped intrinsic amorphous silicon, and N2O-doped intrinsic amorphous silicon.

[0093] This invention does not limit the method of preparing the first passivation layer, second passivation layer, oxygen-containing silicon layer, first doped semiconductor layer, second doped semiconductor layer, and transparent conductive layer; any method can be selected according to the actual situation. In one specific embodiment, the first passivation layer, second passivation layer, oxygen-containing silicon layer, first doped semiconductor layer, and second doped semiconductor layer can be prepared using plasma-enhanced chemical vapor deposition; the transparent conductive layer can be prepared using physical vapor deposition; and plasma-enhanced chemical vapor deposition can be performed using a plasma (VHF) power source.

[0094] In one embodiment, the silicon substrate can be treated with hydrogen plasma (HPT) before depositing the first passivation layer and / or the second passivation layer to clean the surface of the silicon substrate, promote the transformation of amorphous silicon to microcrystalline silicon on the surface of the silicon substrate, improve the microstructure of the first passivation layer and the second passivation layer on both sides of the silicon substrate, and improve the passivation quality of the interface between the passivation layer and the silicon substrate.

[0095] In one embodiment, the method of setting the metal electrode can be at least one of screen printing, laser transfer, and electroplating.

[0096] This invention improves the photoelectric conversion efficiency, short-circuit current, and open-circuit voltage of heterojunction solar cells by selecting specific fabrication processes for the oxygen-containing crystalline silicon layer. As shown in Figure 6, an oxygen-containing crystalline silicon layer with a continuously increasing oxygen atom doping concentration along the direction away from the silicon substrate can be formed on the side of the first passivation layer away from the substrate. As shown in Figure 7, an oxygen-containing crystalline silicon layer with a gradient increasing oxygen atom doping concentration along the direction away from the silicon substrate can also be formed on the side of the first passivation layer away from the substrate. This reduces the water-boiling degradation and dark degradation of heterojunction solar cells.

[0097] In one embodiment, forming an oxygen-containing silicon layer of a first conductivity type on the side of the first passivation layer away from the silicon substrate, and gradually increasing the oxygen atom doping concentration in the oxygen-containing silicon layer along the direction away from the silicon substrate, includes: performing a first deposition process on the side of the first passivation layer away from the silicon substrate, and continuously increasing the oxygen atom doping concentration while depositing and forming the oxygen-containing silicon layer, thereby obtaining an oxygen-containing silicon layer in which the oxygen atom doping concentration continuously increases along the direction away from the silicon substrate.

[0098] In another embodiment, the oxygen doping concentration in the oxygen-containing silicon layer increases in a gradient along the direction away from the substrate; the formation of a first conductivity type oxygen-containing silicon layer on the side of the first passivation layer away from the silicon substrate, and the gradual increase in the oxygen atom doping concentration in the oxygen-containing silicon layer along the direction away from the silicon substrate, includes: performing a second deposition process on the side of the first passivation layer away from the silicon substrate to sequentially form a plurality of stacked oxygen-containing silicon sub-layers, preferably 3-6 stacked oxygen-containing silicon sub-layers; the oxygen atom doping concentration between each oxygen-containing silicon sub-layer increases in a gradient along the direction away from the silicon substrate. In this disclosure, a process gas containing CO2, H2, PH3, and SiH4 can be used for the second deposition process, and the oxygen atom doping concentration can be controlled by adjusting the gas flow ratio of CO2 to SiH4 in the process gas for depositing each oxygen-containing silicon sub-layer.

[0099] In a preferred embodiment, as shown in FIG7, the formation of an oxygen-containing silicon layer of a first conductivity type on the side of the first passivation layer away from the silicon substrate, and the gradual increase of the oxygen atom doping concentration in the oxygen-containing silicon layer along the direction away from the silicon substrate, includes: performing a second deposition process on the side of the first passivation layer away from the substrate to sequentially form a stacked first oxygen-containing silicon sublayer 311, a second oxygen-containing silicon sublayer 312, and a third oxygen-containing silicon sublayer 313; wherein the oxygen atom doping concentration among the first oxygen-containing silicon sublayer, the second oxygen-containing silicon sublayer, and the third oxygen-containing silicon sublayer increases in a gradient.

[0100] As shown in Figure 2, in one specific embodiment of this disclosure, the second deposition process includes the following steps:

[0101] 1) A first oxygen-containing crystalline silicon sublayer is formed by depositing a first process gas on the side of the first passivation layer away from the silicon substrate;

[0102] 2) A second oxygen-containing crystalline silicon sublayer is formed by depositing a second process gas on the side of the first oxygen-containing crystalline silicon sublayer that is away from the first passivation sublayer;

[0103] 3) A third oxygen-containing silicon sublayer is formed by depositing a third process gas on the side of the second oxygen-containing silicon sublayer away from the first oxygen-containing silicon sublayer, resulting in an oxygen-containing silicon sublayer that sequentially includes the first oxygen-containing silicon sublayer, the second oxygen-containing silicon sublayer, and the third oxygen-containing silicon sublayer along the direction away from the first passivation layer.

[0104] In this embodiment, the first oxygen-containing crystalline silicon sublayer has a low oxygen doping concentration, which can reduce the degradation of the heterojunction solar cell (i.e., the passivation effect of hydrogen atoms in the first passivation layer is destroyed by oxygen atoms in the first oxygen-containing crystalline silicon sublayer); the second oxygen-containing crystalline silicon sublayer has a high oxygen doping concentration, which can improve the optical bandgap and short-circuit current of the oxygen-containing crystalline silicon sublayer on the light-receiving surface while maintaining a low series resistance level; the third oxygen-containing crystalline silicon sublayer has the highest oxygen doping concentration, which can further improve the light transmittance of the oxygen-containing crystalline silicon sublayer.

[0105] The present invention can also select the specific preparation process of the first oxygen-containing crystalline silicon sublayer, the second oxygen-containing crystalline silicon sublayer and the third oxygen-containing crystalline silicon sublayer. An oxygen-containing crystalline silicon sublayer with an oxygen atom doping concentration that gradually increases along the direction away from the substrate is set on the side of the first passivation layer away from the substrate, which further improves the photoelectric conversion efficiency, short-circuit current and open-circuit voltage of heterojunction solar cells, and reduces the water boiling degradation and dark decay of heterojunction solar cells.

[0106] In this disclosure, plasma-enhanced chemical vapor deposition (PECVD) can be used for the second deposition process. In this embodiment, the oxygen atoms in the oxygen-containing crystalline silicon layer mainly originate from CO2 in the process gas. CO2 decomposes in the plasma to generate oxygen atoms, thereby allowing the oxygen-containing crystalline silicon layer to be prepared by deposition.

[0107] For example, in one embodiment, the first process gas includes CO2, H2, PH3, and SiH4, wherein the gas flow rate ratio of CO2, H2, PH3, and SiH4 is (0.0001-0.3):(5-600):(0.005-0.07):1; the second process gas includes CO2, H2, PH3, and SiH4, wherein the gas flow rate ratio of CO2, H2, PH3, and SiH4 is (0.1-0.8):(5-600):(0.005-0.07):1; and the third process gas includes CO2, H2, PH3, and SiH4, wherein the gas flow rate ratio of CO2, H2, PH3, and SiH4 is (0.3-3):(5-600):(0.005-0.07):1. In this embodiment, by ensuring that the gas flow rates of each gas component in the first process gas, the second process gas, and the third process gas are within the aforementioned proportional range, the oxygen atom doping concentration among the first oxygen-containing silicon sublayer, the second oxygen-containing silicon sublayer, and the third oxygen-containing silicon sublayer in the prepared oxygen-containing silicon layer can increase in a gradient.

[0108] In one specific embodiment of this disclosure, the step of forming a first doped semiconductor layer on the side of the oxygen-containing crystalline silicon layer away from the silicon substrate includes: performing a third deposition process on the side of the oxygen-containing crystalline silicon layer away from the silicon substrate using a fourth process gas to obtain the first doped semiconductor layer.

[0109] In one specific embodiment of this disclosure, the fourth process gas includes H2, PH3 and SiH4, wherein the gas flow rate ratio of H2, PH3 and SiH4 is (5-600):(0.005-0.07):1.

[0110] The first doped semiconductor layer of the present invention is oxygen-free, that is, there is no oxygen doping at the interface between the first doped semiconductor layer and the transparent conductive layer, thereby reducing the ohmic contact between the first doped semiconductor layer and the transparent conductive layer.

[0111] In one embodiment, the conditions for the first deposition treatment, the second deposition treatment, and the third deposition treatment each independently include: a temperature of 170–230°C and a power density of 10 mW·cm³. -2 ~800mW·cm -2 The process pressure is 0.1 mbar to 8 mbar. Under the above conditions, the deposition process can obtain a uniform and dense first oxygen-containing crystalline silicon sublayer, a second oxygen-containing crystalline silicon sublayer, and a third oxygen-containing crystalline silicon sublayer stacked sequentially on the surface of the first passivation layer away from the silicon substrate. This enables the heterojunction solar cell to have higher photoelectric conversion efficiency, short-circuit current and open-circuit voltage, and lower water boiling degradation and dark decay.

[0112] In one specific embodiment of this disclosure, the step of forming a second doped semiconductor layer on the side of the second passivation layer away from the silicon substrate includes: performing a fourth deposition process on the side of the second passivation layer away from the silicon substrate using a fifth process gas to obtain the second doped semiconductor layer.

[0113] In one embodiment, the fifth process gas includes CO2, H2, B2H6 and SiH4, wherein the gas flow rate ratio of CO2, H2, B2H6 and SiH4 is (0-4):(5-600):(0.005-0.07):1, which helps to form a second doped semiconductor layer with excellent conductivity.

[0114] In one embodiment, the conditions for the fourth deposition process include: a process temperature of 150°C to 210°C and a power density of 10 mW·cm³. -2 ~800mW·cm -2 The process pressure is 0.1 mbar to 8 mbar, which can further improve the conductivity of the second doped semiconductor layer.

[0115] In one embodiment, the step of forming transparent conductive layers on the side of the first doped semiconductor layer and the side of the second doped semiconductor layer away from the silicon substrate includes: performing a fifth deposition process on the side of the first doped semiconductor layer away from the silicon substrate using a sixth process gas to obtain a transparent conductive layer on the side of the first doped semiconductor layer away from the silicon substrate; and performing a fifth deposition process on the side of the second doped semiconductor layer away from the silicon substrate to obtain a transparent conductive layer on the side of the second doped semiconductor layer away from the silicon substrate.

[0116] In one embodiment, the sixth process gas includes O2, H2, H2O and Ar, wherein the gas flow rate ratio of O2, H2, H2O and Ar is (0.01~0.08):(0.01~0.05):(0.0001~0.003):1, which can yield a transparent conductive layer with excellent transparency and conductivity.

[0117] In one embodiment, the conditions for the fifth deposition process include: a process temperature of 80°C to 200°C, a power supply of 1KW to 15KW, and a process pressure of 0.2Pa to 2Pa, which is beneficial to further improve the transparency and conductivity of the transparent conductive layer.

[0118] In a second aspect, the present invention provides a heterojunction solar cell, comprising: a silicon substrate having a first main surface and a second main surface opposite to each other;

[0119] The first passivation layer is located on the first main surface of the silicon substrate;

[0120] The oxygen-containing crystalline silicon layer of the first conductivity type is located on the side of the first passivation layer away from the silicon substrate; the oxygen atom doping concentration in the oxygen-containing crystalline silicon layer gradually increases along the direction away from the silicon substrate.

[0121] The first doped semiconductor layer of the first conductivity type is located on the side of the oxygen-containing crystalline silicon layer away from the silicon substrate;

[0122] The second passivation layer is located on the second main surface of the silicon substrate;

[0123] The second doped semiconductor layer of the second conductivity type is located on the side of the second passivation layer away from the silicon substrate;

[0124] A transparent conductive layer is located on the side of the first doped semiconductor layer and the second doped semiconductor layer that is away from the silicon substrate.

[0125] Metal electrodes are located on the side of the transparent conductive layer away from the silicon substrate.

[0126] The first conductivity type is selected from either P-type or N-type, and the second conductivity type is selected from either P-type or N-type. That is, when the first conductivity type is selected from P-type, the second conductivity type is selected from N-type, and when the first conductivity type is selected from N-type, the second conductivity type is selected from P-type.

[0127] The heterojunction solar cell of the present invention includes an oxygen-containing crystalline silicon layer with an oxygen atom doping concentration that gradually increases along the direction away from the substrate, and has high photoelectric conversion efficiency, short-circuit current and open-circuit voltage, and low water boiling degradation and dark decay.

[0128] In this invention, the oxygen-containing crystalline silicon layer is made of at least one of oxygen-containing microcrystalline silicon, oxygen-containing amorphous silicon, and oxygen-containing nanocrystalline silicon; the first doped semiconductor layer is made of at least one of microcrystalline silicon, amorphous silicon, and nanocrystalline silicon; and the second doped semiconductor layer is made of at least one of oxygen-containing microcrystalline silicon, oxygen-containing amorphous silicon, and oxygen-containing nanocrystalline silicon. In a preferred embodiment, the oxygen-containing crystalline silicon layer includes at least one of an N-type oxygen-containing microcrystalline silicon layer, an N-type oxygen-containing amorphous silicon layer, and an N-type oxygen-containing nanocrystalline silicon layer; the first doped semiconductor layer includes at least one of an N-type microcrystalline silicon layer, an N-type amorphous silicon layer, and an N-type nanocrystalline silicon layer; and the second doped semiconductor layer includes at least one of a P-type oxygen-containing microcrystalline silicon layer, a P-type oxygen-containing amorphous silicon layer, and a P-type oxygen-containing nanocrystalline silicon layer.

[0129] In one specific embodiment of the present invention, the concentration of oxygen atoms in the oxygen-containing crystalline silicon layer of the first conductivity type continuously increases along the direction away from the silicon substrate.

[0130] In another specific embodiment of the present invention, the first conductive type of oxygen-containing crystalline silicon layer includes a plurality of oxygen-containing crystalline silicon sub-layers stacked sequentially along the thickness direction, and the oxygen atom doping concentration between each oxygen-containing crystalline silicon sub-layer increases in a gradient direction away from the silicon substrate; optionally, along the direction away from the silicon substrate, the first conductive type of oxygen-containing crystalline silicon layer includes a first oxygen-containing crystalline silicon sub-layer, a second oxygen-containing crystalline silicon sub-layer, and a third oxygen-containing crystalline silicon sub-layer stacked sequentially; the oxygen atom doping concentration between the first oxygen-containing crystalline silicon sub-layer, the second oxygen-containing crystalline silicon sub-layer, and the third oxygen-containing crystalline silicon sub-layer increases in a gradient.

[0131] In this invention, the thicknesses of the second doped semiconductor layer, the first oxygen-containing silicon sublayer, the second oxygen-containing silicon sublayer, and the third oxygen-containing silicon sublayer can vary within a wide range. In one embodiment, the thicknesses of the second doped semiconductor layer, the first oxygen-containing silicon sublayer, the second oxygen-containing silicon sublayer, and the third oxygen-containing silicon sublayer can be selected to enable the heterojunction solar cell to have better photoelectric conversion efficiency, short-circuit current, and open-circuit voltage.

[0132] In one embodiment, the thickness of the oxygen-containing crystalline silicon layer is 5 nm-45 nm; the thickness of the second doped semiconductor layer of the second conductivity type is 10 nm-50 nm; the thickness of the first oxygen-containing crystalline silicon sublayer is 0.1 nm-5 nm; the thickness of the second oxygen-containing crystalline silicon sublayer is 5 nm-30 nm; the thickness of the third oxygen-containing crystalline silicon sublayer is 0.1 nm-10 nm; and the thickness of the first doped semiconductor layer is 0.1 nm-10 nm. Within the above thickness range, the heterojunction solar cell exhibits superior photoelectric conversion efficiency, short-circuit current, and open-circuit voltage.

[0133] In this invention, the thickness of the second passivation layer is greater than the thickness of the first passivation layer. When the thickness of the second passivation layer is greater than the thickness of the first passivation layer, the parasitic absorption of light by the oxygen-containing crystalline silicon layer deposited on the surface of the first passivation layer (i.e., absorption of a large amount of incident light) can be reduced while ensuring the passivation effect of the second passivation layer, thereby improving the photoelectric conversion efficiency of the heterojunction solar cell.

[0134] In one specific embodiment of the present invention, when the thickness of the first passivation layer is 1nm-8nm and the thickness of the second passivation layer is 2nm-10nm, the passivation effect of the second passivation layer can be further improved, reducing the parasitic absorption of light by the oxygen-containing crystalline silicon layer deposited on the surface of the first passivation layer, thereby enabling the heterojunction solar cell to have higher photoelectric conversion efficiency. In some embodiments, when the thickness of the transparent conductive layer is 40nm-150nm, the light transmittance and conductivity of the transparent conductive film can be further improved.

[0135] In one specific embodiment of this disclosure, the average oxygen atom doping concentration in the oxygen-containing crystalline silicon layer of the first conductivity type is 5 × 10⁻⁶. 19 atoms / cm 3 Up to 7×10 19 atoms / cm 3 .

[0136] In one specific embodiment of the present invention, there is no oxygen doping at the adjacent interface between the first doped semiconductor layer and the transparent conductive layer, thereby effectively reducing the ohmic contact between the first doped semiconductor layer and the transparent conductive layer.

[0137] The present invention will be further described in detail below through specific embodiments.

[0138] In this invention, the doping concentration of oxygen atoms in the oxygen-containing crystalline silicon layer can be detected by mass spectrometry analysis equipment. The specific detection method is well known to those skilled in the art and will not be described in detail here.

[0139] Example 1

[0140] The method for fabricating a heterojunction solar cell provided in this embodiment includes the following steps:

[0141] 1) The surface of the silicon substrate is texturized using a texturing agent to give the silicon substrate a first main surface and a second main surface that are opposite to each other.

[0142] The silicon substrate is an N-type silicon substrate that has undergone tubular phosphorus diffusion and gettering treatment. The size of the silicon substrate is 182mm×105mm and the minority carrier / resistivity ratio is 5000.

[0143] In the texturing process, the texturing agent includes 1.5wt% NaOH solution and 0.5wt% texturing additive, the temperature is 82℃, the time is 500s, and the texturing additive is Shichuang TS53V01.

[0144] After texturing, the silicon substrate loses 0.45g in weight, and the first and second main surfaces of the silicon substrate have a pyramid structure.

[0145] The reflectivity of the first primary surface of the silicon substrate is 1.1%, the base side length of the pyramid is 1.9 μm, the height of the pyramid is 1.5 μm, and the specific surface area is 1.4 m². 2 / g, the number of pyramids per unit area is 200,000 / mm² 2 The number of pyramids per unit area on the second primary surface of the silicon substrate is 200,000 / mm. 2 ;

[0146] The second primary surface of the silicon substrate has a reflectivity of 10.1%, the base side length of the pyramid is 1.9 μm, the height of the pyramid is 1.5 μm, and the specific surface area is 1.4 m². 2 / g, the number of pyramids per unit area is 200,000 / mm² 2 The number of pyramids per unit area on the second primary surface of the silicon substrate is 200,000 / mm. 2 ;

[0147] The reflectivity is 10.1%, the length of the base of the pyramid is 1.9 μm, and the height of the pyramid is 1.5 μm.

[0148] 2) A first passivation layer is deposited on the first main surface of a silicon substrate using PECVD, and the thickness of the first passivation layer is 4 nm;

[0149] 3) A first oxygen-containing silicon sublayer is obtained by performing a second deposition process using a first process gas on the surface of the first passivation layer away from the silicon substrate using PECVD; a second oxygen-containing silicon sublayer is obtained by performing a second deposition process using a second process gas on the surface of the first oxygen-containing silicon sublayer away from the silicon substrate using PECVD; a third oxygen-containing silicon sublayer is obtained by performing a second deposition process using a third process gas on the surface of the second oxygen-containing silicon sublayer away from the silicon substrate using PECVD, thereby obtaining a third oxygen-containing silicon sublayer, and thus obtaining a first conductive type oxygen-containing silicon layer including the stacked first oxygen-containing silicon sublayer, second oxygen-containing silicon sublayer and third oxygen-containing silicon sublayer;

[0150] The first process gas includes SiH4, H2, PH3 and CO2, and the gas flow ratio of CO2, H2, PH3 and SiH4 is 0.3:200:0.04:1;

[0151] The second process gas includes SiH4, H2, PH3 and CO2, with a gas flow ratio of CO2:200:0.04:1.

[0152] The third process gases include SiH4, H2, PH3 and CO2, with a gas flow ratio of CO2:200:0.04:1.

[0153] The average oxygen atom concentration of the aforementioned oxygen-containing crystalline silicon layer is approximately 6.0 × 10⁻⁶. 19 atoms / cm 3 The determination was performed using secondary ion mass spectrometry.

[0154] The thickness of the first oxygen-containing crystalline silicon sublayer is 4 nm, the thickness of the second oxygen-containing crystalline silicon sublayer is 25 nm, the thickness of the third oxygen-containing crystalline silicon sublayer is 6 nm, and the total thickness of the first conductive type of oxygen-containing crystalline silicon sublayer is 35 nm.

[0155] The second deposition process was carried out at a temperature of 190℃ and a power density of 120 mW·cm⁻¹. -2 The process pressure is 3 mbar;

[0156] The first type of oxygen-containing crystalline silicon layer is the N-type oxygen-containing microcrystalline silicon layer.

[0157] 4) PECVD is used to perform a third deposition process on the surface of the oxygen-containing crystalline silicon layer of the first conductivity type away from the silicon substrate using the fourth process gas to obtain the first doped semiconductor layer of the first conductivity type, the thickness of which is 9nm.

[0158] The fourth process gas includes SiH4, H2, and PH3, with a gas flow ratio of 200:0.04:1 for H2, PH3, and SiH4. The third deposition process temperature is 190℃, and the power density is 120 mW·cm³. -2 The process pressure is 3 mbar;

[0159] The first doped semiconductor layer of the first conductivity type is an N-type microcrystalline silicon layer;

[0160] 5) A second passivation layer with a thickness of 7 nm is deposited on the second main surface of the silicon substrate using PECVD;

[0161] 6) PECVD is used to perform a fourth deposition process on the surface of the second passivation layer away from the silicon substrate using the fifth process gas to obtain a second doped semiconductor layer of the second conductivity type. The thickness of the second doped semiconductor layer of the second conductivity type is 25 nm.

[0162] The fifth process gas includes B2H6, H2 and SiH4, with a gas flow ratio of B2H6, H2 and SiH4 of 0.005:200:1;

[0163] The fourth deposition process was carried out at a temperature of 170℃ and a power density of 290 mW·cm³. -2 The process pressure is 3.5 mbar;

[0164] The second doped semiconductor layer of the second conductivity type is a P-type microcrystalline silicon layer;

[0165] 7) Physical vapor deposition is used to perform a fifth deposition process on the side of the first doped semiconductor layer and the second doped semiconductor layer of the first conductivity type away from the silicon substrate to form a transparent conductive layer.

[0166] The sixth process gas includes O2, H2, H2O and Ar, wherein the gas flow ratio of O2, H2, H2O and Ar is 0.03:0.03:0.001:1;

[0167] The fifth deposition process was carried out at a temperature of 180℃, a power density of 10kW, and a process pressure of 0.6Pa.

[0168] 8) Metal electrodes are fabricated on the side of the transparent conductive layer away from the silicon substrate by screen printing to obtain a heterojunction solar cell.

[0169] The solar cell fabricated in this embodiment includes a silicon substrate having a first main surface and a second main surface facing away from each other; a first passivation layer located on the first main surface of the silicon substrate; an N-type oxygen-containing microcrystalline silicon layer located on the side of the first passivation layer facing away from the silicon substrate; an N-type microcrystalline silicon layer located on the side of the N-type oxygen-containing microcrystalline silicon layer facing away from the silicon substrate; a second passivation layer located on the second main surface of the silicon substrate; a P-type microcrystalline silicon layer located on the side of the second passivation layer facing away from the silicon substrate; transparent conductive layers located on the sides of the N-type microcrystalline silicon layer and the P-type microcrystalline silicon layer facing away from the silicon substrate, respectively; and metal electrodes located on the sides of the transparent conductive layers facing away from the silicon substrate, respectively.

[0170] The oxygen-containing crystalline silicon layer comprises a first, second, and third oxygen-containing crystalline silicon sublayer with an increasing oxygen atom doping concentration along the direction away from the silicon substrate. SIMS analysis of the fabricated heterojunction solar cell revealed that the oxygen atom concentration in the first oxygen-containing crystalline silicon sublayer was 4 × 10⁻⁶. 19 atoms / cm 3 The oxygen atom concentration of the second oxygen-containing silicon sublayer is 6 × 10⁻⁶. 19 atoms / cm 3 The oxygen atom concentration of the third oxygen-containing silicon sublayer is 8 × 10⁻⁶. 19 atoms / cm 3 The oxygen doping concentration increases in a gradient along the direction away from the silicon substrate.

[0171] Example 2

[0172] Heterojunction solar cells were fabricated using the same method as in Example 1, except that in step 3), a first oxygen-containing crystalline silicon sublayer was obtained by performing a second deposition process using a first process gas on the surface of the first passivation layer away from the silicon substrate via PECVD; a second oxygen-containing crystalline silicon sublayer was obtained by performing a second deposition process using a second process gas on the surface of the first oxygen-containing crystalline silicon sublayer away from the silicon substrate via PECVD; a third oxygen-containing crystalline silicon sublayer was obtained by performing a second deposition process using a third process gas on the surface of the second oxygen-containing crystalline silicon sublayer away from the silicon substrate via PECVD; a fourth oxygen-containing crystalline silicon sublayer was obtained by performing a second deposition process using a fourth process gas on the surface of the third oxygen-containing crystalline silicon sublayer away from the silicon substrate via PECVD; and a fifth oxygen-containing crystalline silicon sublayer was obtained by performing a second deposition process using a fifth process gas on the surface of the fourth oxygen-containing crystalline silicon sublayer away from the silicon substrate via PECVD. This resulted in a first conductive type of oxygen-containing crystalline silicon layer comprising the stacked first, second, third, fourth, and fifth oxygen-containing crystalline silicon sublayers.

[0173] The first process gas includes SiH4, H2, PH3 and CO2, and the gas flow ratio of CO2, H2, PH3 and SiH4 is 0.2:200:0.04:1;

[0174] The second process gas includes SiH4, H2, PH3 and CO2, with a gas flow ratio of CO2:200:0.04:1.

[0175] The third process gases include SiH4, H2, PH3 and CO2, with a gas flow ratio of CO2:200:0.04:1.

[0176] The fourth process gas includes SiH4, H2, PH3 and CO2, with a gas flow ratio of CO2:200:0.04:1.

[0177] The fifth process gas includes SiH4, H2, PH3 and CO2, with a gas flow ratio of CO2:200:0.04:1.

[0178] The average oxygen atom concentration of the aforementioned oxygen-containing crystalline silicon layer is approximately 5.9 × 10⁻⁶. 19 atoms / cm 3 The determination was performed using secondary ion mass spectrometry.

[0179] The thickness of the first oxygen-containing crystalline silicon sublayer is 3 nm, and the oxygen atom concentration is 1.8 × 10⁻⁶. 19 atoms / cm 3 The second oxygen-containing silicon sublayer has a thickness of 8 nm and an oxygen atom concentration of 3.5 × 10⁻⁶. 19 atoms / cm 3 The thickness of the third oxygen-containing silicon sublayer is 10 nm, and the oxygen atom concentration is 6.2 × 10⁻⁶. 19 atoms / cm 3 The fourth oxygen-containing silicon sublayer has a thickness of 10 nm and an oxygen atom concentration of 8.5 × 10⁻⁶. 19 atoms / cm 3 The fifth oxygen-containing silicon sublayer has a thickness of 4 nm and an oxygen atom concentration of 1.1 × 10⁻⁶. 20 atoms / cm 3 The total thickness of the oxygen-containing crystalline silicon layer of the first conductivity type is 35 nm.

[0180] Comparative Example 1

[0181] The method for preparing a heterojunction solar cell provided in this comparative example differs from that in Example 1 in that: in step 3), a single-layer N-type oxygen-containing microcrystalline silicon layer is obtained by gas deposition on the surface of the first passivation layer away from the silicon substrate.

[0182] The gases include CO2, H2, PH3, and SiH4, wherein the flow rate ratio of CO2, H2, PH3, and SiH4 is 0.3:200:0.04:1;

[0183] The deposition temperature was 190℃, and the power density was 120 mW·cm³. -2 The process pressure is 3 mbar.

[0184] Comparative Example 2

[0185] The method for preparing a heterojunction solar cell provided in this comparative example differs from that in Example 1 in that: in step 3), a single-layer N-type oxygen-containing microcrystalline silicon layer is obtained by gas deposition on the surface of the first passivation layer away from the silicon substrate.

[0186] The gases include CO2, H2, PH3, and SiH4, wherein the flow rate ratio of CO2, H2, PH3, and SiH4 is 0.6:200:0.04:1;

[0187] The deposition temperature was 190℃, and the power density was 120 mW·cm³. -2 The process pressure is 3 mbar.

[0188] Comparative Example 3

[0189] The method for preparing a heterojunction solar cell provided in this comparative example differs from that in Example 1 in that: in step 3), a single-layer N-type oxygen-containing microcrystalline silicon layer is obtained by gas deposition on the surface of the first passivation layer away from the silicon substrate.

[0190] The gases include CO2, H2, PH3, and SiH4, wherein the flow rates of CO2, H2, PH3, and SiH4 are in the ratio of 0.8:200:0.04:1.

[0191] The deposition temperature was 190℃, and the power density was 120 mW·cm³. -2 The process pressure is 3 mbar.

[0192] Performance testing

[0193] The heterojunction solar cells in the examples and comparative examples were subjected to the following performance tests, and the results are shown in Table 1.

[0194] 1) All electrical performance test data (photovoltaic conversion efficiency (Eff1), short-circuit current (Isc1), open-circuit voltage (Voc1), and fill factor (FF1)) were obtained using a Halm high-precision IV tester according to the STC standard. Test conditions: solar irradiance of 1000 W / m². 2The spectrum was AM (atmospheric mass) 1.5, and the solar panel temperature was 25°C. Using the heterojunction solar cell of Example 1 as the standard sample, the measured Eff1, Isc1, Voc1, and FF1 were set to 100%. The percentages of Eff1, Isc1, Voc1, and FF1 of the heterojunction solar cell prepared in the comparative example compared to the standard sample's Eff1, Isc1, Voc1, and FF1 were defined as Eff, Isc, Voc, and FF.

[0195] 2) 14-day dark decay: The heterojunction solar cell was placed in the workshop for 14 days and kept away from light sources. The photoelectric conversion efficiency (Eff2) of the heterojunction solar cell after 14 days of rest was tested by a Halm high-precision IV tester. The heterojunction solar cell of Example 1 was used as the standard sample, and Eff2 was set to 100%. The percentage of Eff2 of the heterojunction solar cell prepared in the comparative example compared with the Eff2 of the standard sample was defined as the 14-day dark decay Eff3.

[0196] 3) Water boiling degradation: The heterojunction solar cell was placed in hot water at 80℃±5℃ and boiled for 10 minutes. The photoelectric conversion efficiency (Eff4) of the heterojunction solar cell after boiling was tested by a Halm high-precision IV tester. The heterojunction solar cell of Example 1 was used as the standard sample, and Eff4 was set to 100%. The percentage of Eff4 of the heterojunction solar cell prepared in the comparative example compared with the Eff4 of the standard sample was defined as water boiling degradation Eff5.

[0197] Table 1. Measurement results of electrical performance of heterojunction solar cells

[0198] As shown in Table 1, the N-type oxygen-containing microcrystalline silicon layer in the heterojunction solar cells prepared in Examples 1 and 2 consists of oxygen-containing microcrystalline silicon sublayers with progressively increasing oxygen atom doping concentration, giving the heterojunction solar cells excellent resistance to dark fading and water-induced degradation. In particular, by dividing the oxygen-containing crystalline silicon layer into multiple oxygen-containing crystalline silicon sublayers, the oxygen doping concentration of the oxygen-containing crystalline silicon layer can be precisely controlled, resulting in a gradient distribution among the sublayers. This significantly improves the electrical performance of the heterojunction cell without sacrificing passivation quality. Specifically, the heterojunction solar cell prepared in Example 2 has relatively higher photoelectric conversion efficiency, short-circuit current, open-circuit voltage, and fill factor compared to the heterojunction solar cell prepared in Example 1. Its 14-day dark fading and water-induced degradation performance are comparable to that of Example 1. However, Example 2 requires more deposition reaction chambers to prepare more layers of crystalline silicon sublayers, making the process more complex than that of Example 1.

[0199] Analysis of Comparative Examples 1-3 shows that increasing the flow ratio of CO2 to SiH4 during the preparation of the N-type oxygen-containing microcrystalline silicon layer can improve the short-circuit current and cell efficiency of heterojunction solar cells, but water boiling degradation and 14-day dark decay are significantly worse.

[0200] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for producing a heterojunction solar cell, characterized by, include: A silicon substrate is provided, the silicon substrate having a first main surface and a second main surface opposite to each other; A first passivation layer is formed on the first main surface of the silicon substrate; An oxygen-containing crystalline silicon layer of a first conductivity type is formed on the side of the first passivation layer away from the silicon substrate, and the oxygen atom doping concentration in the oxygen-containing crystalline silicon layer gradually increases in the direction away from the silicon substrate. A first doped semiconductor layer of a first conductivity type is formed on the side of the oxygen-containing crystalline silicon layer opposite to the silicon substrate; A second passivation layer is formed on the second main surface of the silicon substrate; A second doped semiconductor layer of a second conductivity type is formed on the side of the second passivation layer opposite to the silicon substrate; A transparent conductive layer is formed on the side of the first doped semiconductor layer and the second doped semiconductor layer that is away from the silicon substrate; Metal electrodes are formed on the side of the transparent conductive layer that is opposite to the silicon substrate; The first conductivity type is selected from either P-type or N-type; the second conductivity type is selected from either P-type or N-type.

2. The production method according to claim 1, characterized by, The method of forming an oxygen-containing silicon layer of a first conductivity type on the side of the first passivation layer away from the silicon substrate, and such that the oxygen atom doping concentration in the oxygen-containing silicon layer gradually increases along the direction away from the silicon substrate, includes: A first deposition process is performed on the side of the first passivation layer away from the silicon substrate, and the oxygen atom doping concentration is continuously increased while depositing an oxygen-containing crystalline silicon layer, so as to obtain an oxygen-containing crystalline silicon layer in which the oxygen atom doping concentration continuously increases in the direction away from the silicon substrate.

3. The production method according to claim 1 or 2, characterized by, The method of forming an oxygen-containing silicon layer of a first conductivity type on the side of the first passivation layer away from the silicon substrate, and such that the oxygen atom doping concentration in the oxygen-containing silicon layer gradually increases along the direction away from the silicon substrate, includes: A second deposition process is performed on the side of the first passivation layer away from the silicon substrate to sequentially form a plurality of stacked oxygen-containing silicon sublayers; along the direction away from the silicon substrate, the oxygen atom doping concentration between each oxygen-containing silicon sublayer increases in a gradient. Optionally, a second deposition process is performed on the side of the first passivation layer away from the silicon substrate to sequentially form a first oxygen-containing silicon sublayer, a second oxygen-containing silicon sublayer, and a third oxygen-containing silicon sublayer; the oxygen atom doping concentration among the first oxygen-containing silicon sublayer, the second oxygen-containing silicon sublayer, and the third oxygen-containing silicon sublayer increases in a gradient.

4. The production method according to any one of claims 1 to 3, characterized by, The second deposition process includes the following steps: The first oxygen-containing crystalline silicon sublayer is formed by depositing a first process gas on the side of the first passivation layer away from the silicon substrate; The second oxygen-containing crystalline silicon sublayer is formed by depositing a second process gas on the side of the first oxygen-containing crystalline silicon sublayer away from the first passivation layer. The third oxygen-containing silicon sublayer is formed by depositing a third process gas on the side of the second oxygen-containing silicon sublayer opposite to the first oxygen-containing silicon sublayer; wherein... The first process gas includes CO2, H2, PH3 and SiH4, wherein the gas flow rate ratio of CO2, H2, PH3 and SiH4 is (0.0001~0.3):(5~600):(0.005~0.07):1; The second process gas includes CO2, H2, PH3 and SiH4, wherein the gas flow rate ratio of CO2, H2, PH3 and SiH4 is (0.1~0.8):(5~600):(0.005~0.07):1; The third process gas includes CO2, H2, PH3 and SiH4, wherein the gas flow rate ratio of CO2, H2, PH3 and SiH4 is (0.3~3):(5~600):(0.005~0.07):

1.

5. The production method according to any one of claims 1 to 4, characterized by, The formation of the first doped semiconductor layer on the side of the oxygen-containing silicon layer opposite to the silicon substrate includes: A third deposition process is performed on the side of the oxygen-containing silicon layer away from the silicon substrate using a fourth process gas to obtain the first doped semiconductor layer; wherein, The fourth process gas includes H2, PH3 and SiH4, wherein the gas flow rate ratio of H2, PH3 and SiH4 is (5-600):(0.005-0.07):

1.

6. The method of any one of claims 1-5, wherein, The conditions of the first deposition process, the second deposition process, and the third deposition process each independently include a process temperature of 170 °C to 230 °C, a power density of the power source of 10 mW-cm -2 to 800 mW-cm -2 , and a process pressure of 0.1 mbar to 8 mbar.

7. The method of any one of claims 1-6, wherein, The formation of the second doped semiconductor layer on the side of the second passivation layer opposite to the silicon substrate includes: A fourth deposition process is performed on the side of the second passivation layer away from the silicon substrate using a fifth process gas to obtain the second doped semiconductor layer; wherein, The fifth process gas includes CO2, H2, B2H6 and SiH4, wherein the gas flow rate ratio of CO2, H2, B2H6 and SiH4 is (0-4):(5-600):(0.005-0.07):1; The fourth deposition process includes a process temperature of 150°C to 210°C, a power density of 10 mW·cm -2 to 800 mW·cm -2 , and a process pressure of 0.1 mbar to 8 mbar.

8. The method of any one of claims 1-7, wherein, The formation of the transparent conductive layer on the side of the first doped semiconductor layer and the second doped semiconductor layer facing away from the silicon substrate includes: The transparent conductive layer is obtained by performing a fifth deposition process on the side of the first doped semiconductor layer and the second doped semiconductor layer away from the silicon substrate using a sixth process gas; wherein, The sixth process gas includes O2, H2, H2O and Ar, wherein the gas flow rate ratio of O2, H2, H2O and Ar is (0.01~0.08):(0.01~0.05):(0.0001~0.003):1; The conditions for the fifth deposition process include: a process temperature of 80℃ to 200℃, a power supply of 1KW to 15KW, and a process pressure of 0.2Pa to 2Pa.

9. A heterojunction solar cell, characterized by include: A silicon substrate having a first main surface and a second main surface opposite to each other; The first passivation layer is located on the first main surface of the silicon substrate; An oxygen-containing crystalline silicon layer of the first conductivity type is located on the side of the first passivation layer away from the silicon substrate; The oxygen atom doping concentration in the oxygen-containing crystalline silicon layer gradually increases along the direction away from the silicon substrate; A first doped semiconductor layer of a first conductivity type is located on the side of the oxygen-containing crystalline silicon layer opposite to the silicon substrate; The second passivation layer is located on the second main surface of the silicon substrate; A second doped semiconductor layer of a second conductivity type is located on the side of the second passivation layer away from the silicon substrate; A transparent conductive layer is located on the side of the first doped semiconductor layer and the second doped semiconductor layer that is away from the silicon substrate; Metal electrodes are respectively located on the side of the transparent conductive layer opposite to the silicon substrate; wherein, The first conductivity type is selected from either P-type or N-type; the second conductivity type is selected from either P-type or N-type.

10. The heterojunction solar cell according to claim 9, characterized in that, Along the direction away from the silicon substrate, the concentration of oxygen atoms in the oxygen-containing crystalline silicon layer of the first conductivity type continuously increases.

11. The quantum dot solar cell according to claim 9 or 10, characterized in that, The first type of conductive oxygen-containing crystalline silicon layer includes a plurality of oxygen-containing crystalline silicon sub-layers stacked sequentially along the thickness direction, and the oxygen atom doping concentration between each oxygen-containing crystalline silicon sub-layer increases in a gradient direction away from the silicon substrate. Optionally, along the direction away from the silicon substrate, the oxygen-containing silicon layer of the first conductivity type includes a first oxygen-containing silicon sublayer, a second oxygen-containing silicon sublayer, and a third oxygen-containing silicon sublayer stacked sequentially; the oxygen atom doping concentration among the first oxygen-containing silicon sublayer, the second oxygen-containing silicon sublayer, and the third oxygen-containing silicon sublayer increases in a gradient.

12. The quantum dot solar cell according to any one of claims 9-11, wherein, the average dopant concentration of oxygen atoms in the oxygen-containing crystalline silicon layer of the first conductivity type is 5 x 1018 atoms / cm3 19 to 7 x 1018 atoms / cm3 3 . 19 . 3 .

13. The heterojunction solar cell according to any one of claims 9 to 12, wherein The material of the oxygen-containing crystalline silicon layer includes at least one of oxygen-containing microcrystalline silicon, oxygen-containing amorphous silicon, and oxygen-containing nanocrystalline silicon; and / or, The material of the first doped semiconductor layer includes at least one of microcrystalline silicon, amorphous silicon, and nanocrystalline silicon; and / or, The material of the second doped semiconductor layer includes at least one of oxygen-containing microcrystalline silicon, oxygen-containing amorphous silicon, and oxygen-containing nanocrystalline silicon; and / or, The thickness of the oxygen-containing crystalline silicon layer of the first conductivity type is 5nm-45nm; and / or, The thickness of the second doped semiconductor layer is 10nm-50nm; and / or, The thickness of the first oxygen-containing crystalline silicon sublayer is 0.1 nm-5 nm; and / or, The thickness of the second oxygen-containing crystalline silicon sublayer is 5nm-30nm; and / or, The thickness of the third oxygen-containing crystalline silicon sublayer is 0.1 nm-10 nm; and / or, The thickness of the first doped semiconductor layer is 0.1 nm to 10 nm.

14. The heterojunction solar cell according to any one of claims 9 to 13, characterized in that, There is no oxygen doping at the adjacent interface between the first doped semiconductor layer and the transparent conductive layer.

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