Heterojunction solar cell and preparation method thereof

Abstract

The invention provides a heterojunction solar cell and a preparation method thereof, and the method comprises the steps: sequentially arranging oxygen-containing crystalline silicon layers of a first conduction type on the surface, far away from a substrate, of a first passivation layer through employing a set deposition technology, wherein the oxygen atom doping concentration of the oxygen-containing crystalline silicon layers is gradually increased in the direction away from the substrate; on one hand, light oxygen doping is arranged at the interface of the first passivation layer, so that the dark attenuation phenomenon of a heterojunction cell is reduced, and the power off-shift problem of a photovoltaic module is further reduced; on the other hand, heavy oxygen doping is arranged on one side far away from the first passivation layer, so that the optical band gap and the short-circuit current of the crystalline silicon layer on the light receiving surface are effectively improved; and finally, oxygen-free doping is arranged at an interface adjacent to the transparent conducting layer, so that ohmic contact between the oxygen-containing crystal silicon layer and the transparent conducting layer is effectively reduced. Therefore, the comprehensive electrical performance of the heterojunction solar cell is effectively ensured and improved.

Description

Technical Field

[0001] The invention belongs to the technical field of solar cells, and in particular relates to a heterojunction solar cell and a preparation method thereof. Background Art

[0002] Heterojunction solar cells have become a new hot spot in the photovoltaic field in recent years due to their unique structure, excellent passivation mechanism and high conversion efficiency.

[0003] In the related art, hydrogenated nanocrystalline silicon oxide (nc-SiOx:H) material is used to prepare heterojunction solar cells, so as to utilize its technical advantages in increasing the optical band gap to improve the short-circuit current and photoelectric conversion efficiency of heterojunction solar cells.

[0004] However, the inventors have found that hydrogenated nanocrystalline silicon oxide materials can cause heterojunction solar cells to experience problems such as water boiling decay (i.e., the fill factor and photoelectric conversion efficiency of heterojunction solar cells are reduced under high temperature and high humidity conditions) and dark decay deterioration (i.e., the photoelectric conversion efficiency of heterojunction solar cells is reduced after long-term indoor storage), which has an adverse effect on further improving the power generation efficiency.

[0005] Therefore, it is necessary to provide a heterojunction solar cell and a preparation method thereof to effectively improve the above technical problems. Summary of the invention

[0006] In view of the above defects, the present invention provides a heterojunction solar cell and a method for preparing the same, which can enable the heterojunction solar cell to have higher photoelectric conversion efficiency and short-circuit current, while reducing the water boiling attenuation and dark decay deterioration of the heterojunction solar cell.

[0007] In a first aspect, the present invention provides a method for preparing a heterojunction solar cell, comprising:

[0008] providing a substrate having a first surface and a second surface opposite to each other;

[0009] forming a first passivation layer on the first surface of the substrate by a predetermined deposition process;

[0010] forming an oxygen-containing crystalline silicon layer of a first conductivity type on a side of the first passivation layer away from the substrate, and making the doping concentration of oxygen atoms in the oxygen-containing crystalline silicon layer gradually increase along a direction away from the substrate;

[0011] forming a first doped semiconductor layer of a first conductivity type on a side of the oxygen-containing crystalline silicon layer away from the substrate;

[0012] forming a second passivation layer on the second surface of the substrate;

[0013] forming a second doped semiconductor layer of a second conductivity type on a side of the second passivation layer facing away from the substrate;

[0014] forming transparent conductive layers on the first doped semiconductor layer and the second doped semiconductor layer respectively on a side facing away from the substrate;

[0015] Metal electrodes are formed on the side of the transparent conductive layer away from the substrate; wherein,

[0016] The first conductivity type is selected from one of a P type and an N type; and the second conductivity type is selected from the other of a P type and an N type.

[0017] In the preparation method as described above, the oxygen doping concentration in the oxygen-containing crystalline silicon layer increases continuously along the direction away from the substrate; correspondingly, the step of forming the oxygen-containing crystalline silicon layer on the side of the first passivation layer away from the substrate by using a set deposition process comprises:

[0018] A first deposition process is performed on the side of the first passivation layer away from the substrate, and while depositing to form an oxygen-containing crystalline silicon layer, the doping concentration of oxygen atoms is continuously increased to obtain the oxygen-containing crystalline silicon layer.

[0019] In the preparation method as described above, the oxygen doping concentration in the oxygen-containing crystalline silicon layer increases in a gradient along a direction away from the substrate; correspondingly, the step of forming the oxygen-containing crystalline silicon layer on the side of the first passivation layer away from the substrate by using a set deposition process comprises:

[0020] Performing a second deposition process on the first passivation layer at a side away from the substrate to sequentially form a first oxygen-containing crystalline silicon layer, a second oxygen-containing crystalline silicon layer, and a third oxygen-containing crystalline silicon layer that are stacked;

[0021] The doping concentration of oxygen atoms in the first oxygen-containing crystalline silicon layer, the second oxygen-containing crystalline silicon layer, and the third oxygen-containing crystalline silicon layer increases sequentially.

[0022] The preparation method as described above, wherein the second deposition process comprises the following steps:

[0023] Using a first process gas to deposit the first oxygen-containing crystalline silicon layer on a side of the first passivation layer away from the substrate;

[0024] Using a second process gas to deposit the second oxygen-containing crystalline silicon layer on a side of the first oxygen-containing crystalline silicon layer away from the first passivation layer;

[0025] Using a third process gas to deposit the third oxygen-containing crystalline silicon layer on a side of the second oxygen-containing crystalline silicon layer away from the first oxygen-containing crystalline silicon layer;

[0026] The first process gas includes CO2, H2, PH3 and SiH4, wherein the gas flow ratio of CO2, H2, PH3 and SiH4 is (0.0001-0.3): (5-600): (0.005-0.07): 1;

[0027] The second process gas includes CO2, H2, PH3 and SiH4, wherein the gas flow ratio of CO2, H2, PH3 and SiH4 is (0.1-0.8): (5-600): (0.005-0.07): 1;

[0028] The third process gas includes CO2, H2, PH3 and SiH4, wherein the gas flow ratio of CO2, H2, PH3 and SiH4 is (0.3-3):(5-600):(0.005-0.07):1.

[0029] In the preparation method as described above, the step of forming the first doped semiconductor layer on the side of the oxygen-containing crystalline silicon layer away from the substrate comprises:

[0030] performing a third deposition process on the side of the oxygen-containing crystalline silicon layer facing away from the substrate using a fourth process gas to obtain the first doped semiconductor layer;

[0031] The fourth process gas includes H2, PH3 and SiH4, wherein the gas flow ratio of H2, PH3 and SiH4 is (5-600):(0.005-0.07):1.

[0032] The preparation method as described above, wherein in at least one of the first deposition process, the second deposition process and the third deposition process, the process temperature is 170°C to 230°C, and the power density of the power supply is 10mW·cm -2 ~800mW·cm -2 , the process pressure is 0.1mbar~8mbar.

[0033] In the preparation method as described above, the step of forming the second doped semiconductor layer on the side of the second passivation layer facing away from the substrate comprises:

[0034] performing a fourth deposition process on a side of the second passivation layer facing away from the substrate using a fifth process gas to obtain the second doped semiconductor layer;

[0035] The fifth process gas includes: CO2, H2, B2H6 and SiH4, wherein the gas flow ratio of CO2, H2, B2H6 and SiH4 is (0-4): (5-600): (0.005-0.07): 1;

[0036] In the fourth deposition process, the process temperature is 150°C to 210°C, and the power density is 10mW·cm -2 ~800mW·cm -2 , the process pressure is 0.1mbar~8mbar.

[0037] In the preparation method as described above, the step of forming the transparent conductive layer on the first doped semiconductor layer and the second doped semiconductor layer on the side away from the substrate comprises:

[0038] Using a sixth process gas, respectively perform a fifth deposition process on the first doped semiconductor layer and the second doped semiconductor layer on a side away from the substrate to obtain the transparent conductive layer;

[0039] The sixth process gas includes O2, H2, H2O and Ar, wherein the gas flow ratio of O2, H2, H2O and Ar is (0.01-0.08): (0.01-0.05): (0.0001-0.003): 1;

[0040] In the fifth deposition process, the process temperature is 80° C. to 200° C., the power supply is 1 KW to 15 KW, and the process pressure is 0.2 Pa to 2 Pa.

[0041] The preparation method as described above, wherein the oxygen-containing crystalline silicon layer comprises: 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; and / or,

[0042] 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 / or,

[0043] 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; and / or,

[0044] The thickness of the oxygen-containing crystalline silicon layer of the first conductivity type is 5nm-45nm; and / or,

[0045] The thickness of the second doped semiconductor layer is 10nm-50nm; and / or,

[0046] The thickness of the first oxygen-containing crystalline silicon layer is 0.1 nm-5 nm; and / or,

[0047] The thickness of the second oxygen-containing crystalline silicon layer is 5nm-30nm; and / or,

[0048] The thickness of the third oxygen-containing crystalline silicon layer is 0.1 nm-10 nm; and / or,

[0049] The first doped semiconductor layer of the first conductivity type has a thickness of 0.1 nm-10 nm.

[0050] In a second aspect, the present invention provides a heterojunction solar cell, comprising: a substrate having a first surface and a second surface opposite to each other;

[0051] A first passivation layer, located on a first surface of the substrate;

[0052] An oxygen-containing crystalline silicon layer of a first conductivity type is located on a side of the first passivation layer away from the substrate; the doping concentration of oxygen atoms in the oxygen-containing crystalline silicon layer gradually increases in a direction away from the substrate;

[0053] A first doped semiconductor layer of a first conductivity type, located on a side of the oxygen-containing crystalline silicon layer away from the substrate;

[0054] A second passivation layer, located on the second surface of the substrate;

[0055] A second doped semiconductor layer of a second conductivity type, located on a side of the second passivation layer away from the substrate;

[0056] A transparent conductive layer, respectively located on a side of the first doped semiconductor layer and a side of the second doped semiconductor layer facing away from the substrate;

[0057] Metal electrodes, respectively located on a side of the transparent conductive layer away from the substrate;

[0058] The first conductivity type is selected from one of P type and N type;

[0059] The second conductivity type is selected from the other of a P type and an N type.

[0060] The present invention arranges an oxygen-containing crystalline silicon layer of the first conductivity type whose oxygen atom doping concentration gradually increases in the direction away from the substrate on the surface of the first passivation layer away from the substrate. On the one hand, by arranging light oxygen doping at the interface of the first passivation layer, the dark decay phenomenon of the heterojunction battery is reduced, thereby reducing the power drop problem of the photovoltaic module; on the other hand, heavy oxygen doping is arranged on the side away from the first passivation layer, effectively improving the optical band gap and short-circuit current of the light-receiving crystalline silicon layer; finally, oxygen-free doping is arranged at the interface adjacent to the transparent conductive layer, effectively reducing the ohmic contact between the oxygen-containing crystalline silicon layer and the transparent conductive layer. In this way, the heterojunction solar cell including the oxygen-containing crystalline silicon layer can have higher photoelectric conversion efficiency, short-circuit current and open-circuit voltage, lower water boiling attenuation and dark decay deterioration, thereby effectively ensuring and improving the comprehensive electrical performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] Figure 1A schematic flow chart of a method for preparing a heterojunction solar cell provided in some embodiments of the present invention;

[0062] Figure 2 A schematic diagram of a flow chart of step S30 provided in some embodiments of the present invention;

[0063] Figure 3 A schematic diagram of a structure obtained after executing step S10 provided in some embodiments of the present invention;

[0064] Figure 4 A schematic diagram of a structure obtained after executing step S20 provided in some embodiments of the present invention;

[0065] Figure 5 A schematic diagram of a structure obtained after executing step S30 provided in some embodiments of the present invention;

[0066] Figure 6 A schematic structural diagram of an oxygen-containing crystalline silicon layer (the oxygen atom doping concentration continuously increases along a direction away from the substrate) provided in some embodiments of the present invention;

[0067] Figure 7 A schematic structural diagram of another oxygen-containing crystalline silicon layer (the oxygen atom doping concentration increases in a gradient along a direction away from the substrate) provided in some embodiments of the present invention;

[0068] Figure 8 A schematic diagram of a structure obtained after executing step S40 provided in some embodiments of the present invention;

[0069] Fig. 9 A schematic diagram of a structure obtained after executing step S50 provided in some embodiments of the present invention;

[0070] Fig.10 A schematic diagram of a structure obtained after executing step S60 provided in some embodiments of the present invention;

[0071] Fig.11 A schematic diagram of a structure obtained after executing step S70 provided in some embodiments of the present invention;

[0072] Fig.12 It is a schematic diagram of a structure obtained after executing step S80 provided in some embodiments of the present invention.

[0073] Description of reference numerals:

[0074] 100-substrate;

[0075] 210- first passivation layer;

[0076] 220- second passivation layer;

[0077] 310- oxygen-containing crystalline silicon layer;

[0078] 311-a first oxygen-containing crystalline silicon layer;

[0079] 312- a second oxygen-containing crystalline silicon layer;

[0080] 313 - a third oxygen-containing crystalline silicon layer;

[0081] 410-first doped semiconductor layer;

[0082] 420-second doped semiconductor layer;

[0083] 500-transparent conductive layer;

[0084] 600-Metal Electrode. DETAILED DESCRIPTION

[0085] In order to make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0086] like Figure 1 , Figure 3-Figure 5 , Figure 8-Figure 12 As shown, in a first aspect, the present invention provides a method for preparing a heterojunction solar cell, comprising:

[0087] S10: Figure 3 As shown, a substrate 100 is provided, the substrate having a first surface and a second surface opposite to each other;

[0088] S20: Figure 4 As shown, a first passivation layer 210 is disposed on the first surface of the substrate 100;

[0089] S30: Figure 5 As shown, a predetermined deposition process is used to form a first conductivity type oxygen-containing crystalline silicon layer 310 on a side of the first passivation layer 210 away from the substrate 100, and the doping concentration of oxygen atoms in the oxygen-containing crystalline silicon layer 310 gradually increases in a direction away from the substrate 100;

[0090] S40: Figure 8 As shown, a first doped semiconductor layer 410 of a first conductivity type is formed on the side of the oxygen-containing crystalline silicon layer 310 facing away from the substrate 100;

[0091] S50: Fig. 9As shown, a second passivation layer 220 is formed on the second surface of the substrate 100;

[0092] S60: Fig.10 As shown, a second doped semiconductor layer 420 of a second conductivity type is formed on the side of the second passivation layer 220 facing away from the substrate 100;

[0093] S70: Fig.11 As shown, a transparent conductive layer 500 is formed on the first doped semiconductor layer 410 and the second doped semiconductor layer 420 respectively on the side facing away from the substrate 100;

[0094] S80: Fig.12 As shown, metal electrodes 600 are formed on the side of the transparent conductive layer 500 facing away from the substrate 100;

[0095] When the first conductivity type includes a P type, the second conductivity type includes an N type; when the first conductivity type includes an N type, the second conductivity type includes a P type.

[0096] The present invention provides a first conductive type oxygen-containing crystalline silicon layer whose oxygen atom doping concentration gradually increases in a direction away from the substrate on a side of the first passivation layer away from the substrate, so that the heterojunction solar cell including the first conductive type oxygen-containing crystalline silicon layer has higher photoelectric conversion efficiency, short-circuit current and open-circuit voltage, while reducing the water boiling attenuation and dark decay deterioration of the heterojunction solar cell.

[0097] The present invention does not limit the shape, size, thickness, doping type, and minority carrier / resistivity ratio of the substrate, and can be selected according to actual needs. In some embodiments, a silicon substrate is selected as the substrate, and the silicon substrate can be doped, and then the silicon substrate after doping is textured to obtain a substrate including a first surface and a second surface opposite to each other.

[0098] The first passivation layer and the second passivation layer of the present invention can be a single layer or a composite layer, respectively. For example, the first passivation layer and the second passivation layer can each independently include at least one of a hydrogen-free intrinsic amorphous silicon layer, a hydrogen-rich intrinsic amorphous silicon layer, a CO2-doped intrinsic amorphous silicon layer, and an N2O-doped intrinsic amorphous silicon layer.

[0099] The present invention does not limit the method for preparing the above-mentioned first passivation layer, second passivation layer, oxygen-containing crystalline silicon layer, first doped semiconductor layer, second doped semiconductor, and transparent conductive layer, and can be selected according to actual conditions. For example, the first passivation layer, the second passivation layer, the oxygen-containing crystalline silicon layer, the first doped semiconductor layer, and the second doped semiconductor can be prepared by plasma enhanced chemical vapor deposition, and the transparent conductive layer can be prepared by physical vapor deposition; plasma (VHF) power supply can be used for plasma enhanced chemical vapor deposition.

[0100] In some embodiments, before depositing the first passivation layer and the second passivation layer, the substrate can be treated with hydrogen plasma (HPT) to clean the surface of the substrate, promote the transformation of the amorphous silicon film layer to microcrystalline silicon, improve the microstructure of the first passivation layer and the second passivation layer on both sides of the substrate, and improve the interface passivation quality between the passivation layer and the substrate.

[0101] In some embodiments, the method of providing the metal electrode may be at least one of screen printing, laser transfer, and electroplating.

[0102] The present invention selects a specific preparation process for the oxygen-containing crystalline silicon layer, such as Figure 6 As shown, an oxygen-containing crystalline silicon layer whose oxygen atom doping concentration increases continuously in a direction away from the substrate can be formed on the side of the first passivation layer away from the substrate; Figure 7 As shown, an oxygen-containing crystalline silicon layer whose oxygen atom doping concentration increases gradually in a direction away from the substrate can also be formed on the side of the first passivation layer away from the substrate, thereby improving the photoelectric conversion efficiency, short-circuit current and open-circuit voltage of the heterojunction solar cell and reducing the water boiling attenuation and dark decay deterioration of the heterojunction solar cell.

[0103] In some embodiments, the oxygen doping concentration in the oxygen-containing crystalline silicon layer continuously increases in a direction away from the substrate; correspondingly, the step of forming the oxygen-containing crystalline silicon layer on the side of the first passivation layer away from the substrate includes: performing a first deposition process on the side of the first passivation layer away from the substrate, and continuously increasing the doping concentration of oxygen atoms while depositing the oxygen-containing crystalline silicon layer, to obtain the oxygen-containing crystalline silicon layer having an oxygen doping concentration that continuously increases in a direction away from the substrate.

[0104] In some embodiments, the oxygen doping concentration in the oxygen-containing crystalline silicon layer increases in a gradient along a direction away from the substrate; Figure 7 As shown, correspondingly, the step of forming an oxygen-containing crystalline silicon layer on the side of the first passivation layer facing away from the substrate includes: performing a second deposition process on the side of the first passivation layer facing away from the substrate to sequentially form a stacked first oxygen-containing crystalline silicon layer 311, a second oxygen-containing crystalline silicon layer 312 and a third oxygen-containing crystalline silicon layer 313; wherein the doping concentration of oxygen atoms in the first oxygen-containing crystalline silicon layer, the second oxygen-containing crystalline silicon layer and the third oxygen-containing crystalline silicon layer increases sequentially.

[0105] like Figure 2 As shown, according to the technical solution of the present invention, the second deposition process includes the following steps:

[0106] 1) using a first process gas to deposit a first oxygen-containing crystalline silicon layer on a side of the first passivation layer away from the substrate;

[0107] 2) using a second process gas to deposit a second oxygen-containing crystalline silicon layer on a side of the first oxygen-containing crystalline silicon layer away from the first passivation layer;

[0108] 3) Using a third process gas to deposit a third oxygen-containing crystalline silicon layer on a side of the second oxygen-containing crystalline silicon layer away from the first oxygen-containing crystalline silicon layer to form a third oxygen-containing crystalline silicon layer, thereby obtaining an oxygen-containing crystalline silicon layer including the first oxygen-containing crystalline silicon layer, the second oxygen-containing crystalline silicon layer and the third oxygen-containing crystalline silicon layer in the stacking direction.

[0109] In the present invention, the first oxygen-containing crystalline silicon layer has a lower oxygen doping concentration, which can reduce the attenuation of the heterojunction solar cell (that is, the passivation effect of the hydrogen atoms in the first passivation layer is destroyed by the oxygen atoms in the first oxygen-containing crystalline silicon layer); the second oxygen-containing crystalline silicon layer has a higher oxygen doping concentration, which improves the optical band gap and short-circuit current of the oxygen-containing crystalline silicon layer on the light-receiving surface at a lower series resistance level; the third oxygen-containing crystalline silicon layer has the highest oxygen doping concentration, which can further improve the light transmittance of the oxygen-containing crystalline silicon layer.

[0110] The present invention can also select the specific preparation process of the first oxygen-containing crystalline silicon layer, the second oxygen-containing crystalline silicon layer and the third oxygen-containing crystalline silicon layer, and set an oxygen-containing crystalline silicon layer whose oxygen atom doping concentration gradually increases in the direction away from the substrate on the side of the first passivation layer away from the substrate, so as to further improve the photoelectric conversion efficiency, short-circuit current and open-circuit voltage of the heterojunction solar cell, and reduce the water boiling attenuation and dark decay deterioration of the heterojunction solar cell.

[0111] Illustratively, in some embodiments, the first process gas includes CO2, H2, PH3, and SiH4, wherein the gas flow ratio of CO2, H2, PH3, and SiH4 is (0.0001-0.3): (5-600): (0.005-0.07): 1;

[0112] The second process gas includes CO2, H2, PH3 and SiH4, wherein the gas flow ratio of CO2, H2, PH3 and SiH4 is (0.1-0.8): (5-600): (0.005-0.07): 1;

[0113] The third process gas includes CO2, H2, PH3 and SiH4, wherein the gas flow ratio of CO2, H2, PH3 and SiH4 is (0.3-3):(5-600):(0.005-0.07):1.

[0114] According to the technical solution of the present invention, the step of forming a first doped semiconductor layer on the side of the oxygen-containing crystalline silicon layer away from the substrate includes: using a fourth process gas to perform a third deposition treatment on the side of the oxygen-containing crystalline silicon layer away from the substrate to obtain the first doped semiconductor layer.

[0115] Further, the fourth process gas includes H2, PH3 and SiH4, wherein the gas flow ratio of H2, PH3 and SiH4 is (5-600):(0.005-0.07):1.

[0116] 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.

[0117] In some embodiments, in at least one of the first deposition process, the second deposition process, and the third deposition process, the temperature is 170-230° C., and the power density of the power source is 10 W·cm -2 ~800mW·cm -2 The process pressure is 0.1mbar~8mbar, and a uniform and dense first oxygen-containing crystalline silicon layer, a second oxygen-containing crystalline silicon layer, and a third oxygen-containing crystalline silicon layer can be stacked in sequence on the surface of the first passivation layer away from the substrate, so that the heterojunction solar cell has higher photoelectric conversion efficiency, short-circuit current and open-circuit voltage, and lower water boiling attenuation and dark decay deterioration.

[0118] According to the technical solution of the present invention, the step of forming a second doped semiconductor layer on the side of the second passivation layer away from the substrate includes: using a fifth process gas to perform a fourth deposition process on the side of the second passivation layer away from the substrate to obtain the second doped semiconductor layer.

[0119] Furthermore, the fifth process gas includes: CO2, H2, B2H6 and SiH4, wherein the gas flow 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 conductive properties.

[0120] Furthermore, in the fourth deposition process, the process temperature is 150°C to 210°C, and the power density is 10 mW·cm -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.

[0121] In some embodiments, the steps of forming a transparent conductive layer on the side of the first doped semiconductor layer and the second doped semiconductor layer facing away from the substrate respectively include: performing a fifth deposition treatment on the first doped semiconductor layer using a sixth process gas to obtain a transparent conductive layer on the side of the first doped semiconductor layer facing away from the substrate; and simultaneously performing a fifth deposition treatment on the side of the second doped semiconductor layer facing away from the substrate to obtain a transparent conductive layer on the side of the second doped semiconductor layer facing away from the substrate.

[0122] Furthermore, the sixth process gas includes O2, H2, H2O and Ar, wherein the gas flow ratio of O2, H2, H2O and Ar is (0.01-0.08):(0.01-0.05):(0.0001-0.003):1, and a transparent conductive layer with excellent transparency and conductivity can be obtained.

[0123] Furthermore, in the fifth deposition treatment, the process temperature is 80° C. to 200° C., the power is 1 KW to 15 KW, and the process pressure is 0.2 Pa to 2 Pa, which is beneficial to further improve the transparency and conductivity of the transparent conductive layer.

[0124] In the present invention, 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; 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.

[0125] Furthermore, the present invention can select the thickness of the second doped semiconductor layer, the first oxygen-containing crystalline silicon layer, the second oxygen-containing crystalline silicon layer, and the third oxygen-containing crystalline silicon layer, so that the heterojunction solar cell has better photoelectric conversion efficiency, short-circuit current and open-circuit voltage.

[0126] Exemplarily, the thickness of the oxygen-containing crystalline silicon layer is 5nm-45nm, the thickness of the second doped semiconductor layer of the second conductivity type is 10nm-50nm, the thickness of the first oxygen-containing crystalline silicon layer is 0.1nm-5nm, the thickness of the second oxygen-containing crystalline silicon layer is 5nm-30nm, the thickness of the third oxygen-containing crystalline silicon layer is 0.1nm-10nm, and the thickness of the first doped semiconductor layer is 0.1nm-10nm.

[0127] In the present invention, the thickness of the second passivation layer is greater than that of the first passivation layer. When the thickness of the second passivation layer is greater than that 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 can be reduced (i.e., absorbing a large amount of incident light) while ensuring the passivation effect of the second passivation layer, thereby improving the photoelectric conversion efficiency of the heterojunction solar cell.

[0128] Furthermore, 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, and the parasitic absorption of light by the oxygen-containing crystalline silicon layer deposited on the surface of the first passivation layer can be reduced, so that the heterojunction solar cell has a higher photoelectric conversion efficiency. In some embodiments, when the thickness of the transparent conductive layer is 40nm to 150nm, the light transmittance and conductivity of the transparent conductive film can be further improved.

[0129] In a second aspect, the present invention provides a heterojunction solar cell, comprising: a substrate having a first surface and a second surface opposite to each other;

[0130] A first passivation layer, located on a first surface of the substrate;

[0131] An oxygen-containing crystalline silicon layer of the first conductivity type is located on a side of the first passivation layer away from the substrate; the doping concentration of oxygen atoms in the oxygen-containing crystalline silicon layer gradually increases in a direction away from the substrate;

[0132] A first doped semiconductor layer of a first conductivity type is located on a side of the oxygen-containing crystalline silicon layer facing away from the substrate;

[0133] A second passivation layer, located on the second surface of the substrate;

[0134] A second doped semiconductor layer of a second conductivity type is located on a side of the second passivation layer facing away from the substrate;

[0135] A transparent conductive layer is respectively located on a side of the first doped semiconductor layer and a side of the second doped semiconductor layer facing away from the substrate;

[0136] Metal electrodes are respectively located on the side of the transparent conductive layer facing away from the substrate;

[0137] The first conductivity type is selected from one of P type and N type, and the second conductivity type is selected from the other of P type and 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.

[0138] The heterojunction solar cell comprises an oxygen-containing crystalline silicon layer whose oxygen atom doping concentration gradually increases in a direction away from the substrate, and has high photoelectric conversion efficiency, short-circuit current and open-circuit voltage, and low water boiling attenuation and dark decay deterioration.

[0139] Hereinafter, the present invention will be further described in detail through specific examples.

[0140] Example 1

[0141] The method for preparing a heterojunction solar cell provided in this embodiment comprises the following steps:

[0142] 1) performing texturing treatment on the surface of the silicon substrate using a texturing agent, so that the silicon substrate has a first surface and a second surface opposite to each other;

[0143] The silicon substrate is an N-type silicon substrate that has been treated with tubular phosphorus diffusion and gettering, the size of the silicon substrate is 182mm×105mm, and the minority carrier / resistivity ratio is 5000;

[0144] In the texturing treatment, the texturing agent includes 1.5wt% NaOH solution and 0.5wt% texturing additive, the temperature is 82°C, the time is 500s, and the texturing additive is Shichuang TS53V01;

[0145] After the texturing treatment, the weight of the silicon substrate was reduced by 0.45 g, and the first surface and the second surface of the silicon substrate had a pyramid structure;

[0146] In the first surface of the silicon substrate, the reflectivity is 10.1%, the 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 m 2 / g, the number of pyramids per unit area is 200,000 / mm 2 The number of pyramids per unit area on the second surface of the silicon substrate is 200,000 / mm 2 ;

[0147] In the second surface of the silicon substrate, the reflectivity is 10.1%, the 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 m 2 / g, the number of pyramids per unit area is 200,000 / mm 2 The number of pyramids per unit area on the second surface of the silicon substrate is 200,000 / mm 2 ;

[0148] The reflectivity is 10.1%, the side length of the pyramid is 1.9 μm, and the height of the pyramid is 1.5 μm;

[0149] 2) depositing a first passivation layer on the first surface of the silicon substrate by PECVD, wherein the thickness of the first passivation layer is 4 nm;

[0150] 3) using PECVD to allow a first gas to perform a second deposition process on a surface of the first passivation layer away from the silicon substrate to obtain a first oxygen-containing crystalline silicon layer; using PECVD to allow a second gas to perform a second deposition process on a surface of the first oxygen-containing crystalline silicon layer away from the silicon substrate to obtain a second oxygen-containing crystalline silicon layer; using PECVD to allow a third gas to perform a second deposition process on a surface of the second oxygen-containing crystalline silicon layer away from the silicon substrate to obtain a third oxygen-containing crystalline silicon layer, thereby obtaining a first conductivity type oxygen-containing crystalline silicon layer including the first oxygen-containing crystalline silicon layer, the second oxygen-containing crystalline silicon layer and the third oxygen-containing crystalline silicon layer stacked;

[0151] The first 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;

[0152] The second gas includes SiH4, H2, PH3 and CO2, and the gas flow ratio of CO2, H2, PH3 and SiH4 is 0.6:200:0.04:1;

[0153] The third gas includes SiH4, H2, PH3 and CO2, and the gas flow ratio of CO2, H2, PH3 and SiH4 is 0.8:200:0.04:1;

[0154] The thickness of the first oxygen-containing crystalline silicon layer is 4 nm, the thickness of the second oxygen-containing crystalline silicon layer is 25 nm, the thickness of the third oxygen-containing crystalline silicon layer is 6 nm, and the thickness of the first conductivity type oxygen-containing crystalline silicon layer is 35 nm;

[0155] In the second deposition process, the process temperature is 190°C and the power density is 120 mW·cm -2 , process pressure is 3mbar;

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

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

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

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

[0160] 5) depositing a second passivation layer on the second surface of the silicon substrate by PECVD, wherein the thickness of the second passivation layer is 7 nm;

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

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

[0163] In the fourth deposition process, the process temperature is 170°C and the power density is 290 mW·cm -2 , process pressure is 3.5mbar;

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

[0165] 7) using physical vapor deposition to make the sixth gas perform a fifth deposition process on the first doped semiconductor layer of the first conductivity type and the second doped semiconductor layer on a side away from the silicon substrate to form a transparent conductive layer;

[0166] The sixth 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] In the fifth deposition process, the temperature is 180°C, the power density is 10kW, and the process pressure is 0.6Pa;

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

[0169] Comparative Example 1

[0170] The method for preparing a heterojunction solar cell provided in this comparative example is different from that in Example 1 in that: in step S3, a single-layer N-type oxygen-containing microcrystalline silicon layer is obtained by performing a deposition process on the surface of the first passivation layer away from the silicon substrate by gas;

[0171] The gas includes CO2, H2, PH3 and SiH4, wherein the flow ratio of CO2, H2, PH3 and SiH4 is 0.3:200:0.04:1;

[0172] During the deposition process, the temperature was 190°C and the power density was 120 mW·cm -2 , the process pressure is 3mbar.

[0173] Comparative Example 2

[0174] The method for preparing a heterojunction solar cell provided in this comparative example is different from that in Example 1 in that: in step S3, a single-layer N-type oxygen-containing microcrystalline silicon layer is obtained by performing a deposition process on the surface of the first passivation layer away from the silicon substrate by gas;

[0175] The gas includes CO2, H2, PH3 and SiH4, wherein the flow ratio of CO2, H2, PH3 and SiH4 is 0.6:200:0.04:1;

[0176] During the deposition process, the temperature was 190°C and the power density was 120 mW·cm -2 , the process pressure is 3mbar.

[0177] Comparative Example 3

[0178] The method for preparing a heterojunction solar cell provided in this comparative example is different from that in Example 1 in that: in step S3, a single-layer N-type oxygen-containing microcrystalline silicon layer is obtained by performing a deposition process on the surface of the first passivation layer away from the silicon substrate by gas;

[0179] The gas includes CO2, H2, PH3 and SiH4, wherein the flow ratio of CO2, H2, PH3 and SiH4 is 0.8:200:0.04:1;

[0180] During the deposition process, the temperature was 190°C and the power density was 120 mW·cm -2 , the process pressure is 3mbar.

[0181] Performance Testing

[0182] The following performance tests were performed on the heterojunction solar cells in the embodiment and the comparative example, and the results are shown in Table 1;

[0183] 1) All electrical performance test data (photoelectric conversion efficiency (Eff1), short circuit current (Isc1), open circuit voltage (Voc1) and fill factor (FF1)) are obtained by using a halm high-precision IV tester according to the STC standard. The test conditions are: solar irradiance of 1000W / m 2 , spectrum is AM (atmospheric mass) 1.5, and the temperature of the solar panel is 25° C. Taking the heterojunction solar cell of Example 1 as a standard sample, Eff1, Isc1, Voc1 and FF1 are set to 100%, and the percentages of Eff1, Isc1, Voc1 and FF1 of the heterojunction solar cell prepared in the comparative example compared to Eff1, Isc1, Voc1 and FF1 of the standard sample are defined as Eff, Isc, Voc and FF;

[0184] 2) 14-day dark decay: The heterojunction solar cell was placed in a workshop for 14 days away from light sources, and the photoelectric conversion efficiency (Eff2) of the heterojunction solar cell after 14 days was tested by a halm high-precision IV tester. The heterojunction solar cell of Example 1 was used as a standard sample, and Eff2 was set to 100%. The percentage of Eff2 of the heterojunction solar cell prepared in the comparative example compared to Eff2 of the standard sample was defined as the 14-day dark decay Eff3;

[0185] 3) Boiling attenuation: The heterojunction solar cell is boiled in hot water at 80°C ± 5°C for 10 minutes. The photoelectric conversion efficiency (Eff4) of the heterojunction solar cell after boiling is tested by a halm high-precision IV testing machine. The heterojunction solar cell of Example 1 is used as a standard sample, Eff4 is set to 100%, and the percentage of Eff4 of the heterojunction solar cell prepared in the comparative example compared to Eff4 of the standard sample is defined as the boiling attenuation Eff5.

[0186] Table 1 Electrical performance measurement results of heterojunction solar cells

[0187]

[0188] According to Table 1, the heterojunction solar cell prepared in Example 1 comprises an N-type oxygen-containing microcrystalline silicon layer with different oxygen atom doping concentrations, so that the heterojunction solar cell has excellent resistance to dark decay and water boiling attenuation.

[0189] Analysis of comparative examples 1-3 shows that in the preparation process of the N-type oxygen-containing microcrystalline silicon layer, increasing the flow ratio of CO2 to SiH4 can improve the short-circuit current and cell efficiency of the heterojunction solar cell, but the water boiling attenuation and 14-day dark decay deteriorate significantly.

[0190] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements 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 preparing a heterojunction solar cell, characterized in that: include: providing a substrate having a first surface and a second surface opposite to each other; forming a first passivation layer on the first surface of the substrate; Using a set deposition process to form an oxygen-containing crystalline silicon layer of a first conductivity type on a side of the first passivation layer away from the substrate, and making the doping concentration of oxygen atoms in the oxygen-containing crystalline silicon layer gradually increase along a direction away from the substrate; forming a first doped semiconductor layer of a first conductivity type on a side of the oxygen-containing crystalline silicon layer away from the substrate; forming a second passivation layer on the second surface of the substrate; forming a second doped semiconductor layer of a second conductivity type on a side of the second passivation layer facing away from the substrate; forming transparent conductive layers on the first doped semiconductor layer and the second doped semiconductor layer respectively on a side facing away from the substrate; forming metal electrodes respectively on the side of the transparent conductive layer away from the substrate; The first conductivity type is selected from one of a P type and an N type; and the second conductivity type is selected from the other of a P type and an N type.

2. The preparation method according to claim 1, characterized in that: The doping concentration of oxygen atoms in the oxygen-containing crystalline silicon layer increases continuously along the direction away from the substrate; correspondingly, the step of forming the oxygen-containing crystalline silicon layer on the side of the first passivation layer away from the substrate by using a set deposition process includes: A first deposition process is performed on the side of the first passivation layer away from the substrate, and while depositing to form an oxygen-containing crystalline silicon layer, the doping concentration of oxygen atoms is continuously increased to obtain the oxygen-containing crystalline silicon layer.

3. The preparation method according to claim 1, characterized in that: The doping concentration of oxygen atoms in the oxygen-containing crystalline silicon layer increases in a gradient along a direction away from the substrate; correspondingly, the step of forming the oxygen-containing crystalline silicon layer on a side of the first passivation layer away from the substrate by using a set deposition process includes: A second deposition process is performed on the first passivation layer on a side away from the substrate to sequentially form a stacked first oxygen-containing crystalline silicon layer, a second oxygen-containing crystalline silicon layer, and a third oxygen-containing crystalline silicon layer; wherein, The doping concentration of oxygen atoms in the first oxygen-containing crystalline silicon layer, the second oxygen-containing crystalline silicon layer, and the third oxygen-containing crystalline silicon layer increases sequentially.

4. The preparation method according to claim 3, characterized in that: The second deposition process comprises the following steps: Using a first process gas to deposit the first oxygen-containing crystalline silicon layer on a side of the first passivation layer away from the substrate; Using a second process gas to deposit the second oxygen-containing crystalline silicon layer on a side of the first oxygen-containing crystalline silicon layer away from the first passivation layer; The third oxygen-containing crystalline silicon layer is formed by depositing the second oxygen-containing crystalline silicon layer on a side away from the first oxygen-containing crystalline silicon layer using a third process gas; wherein, The first process gas includes CO2, H2, PH3 and SiH4, wherein the gas flow 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 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 ratio of CO2, H2, PH3 and SiH4 is (0.3-3):(5-600):(0.005-0.07):

1.

5. The preparation method according to claim 1, characterized in that: The step of forming the first doped semiconductor layer on the side of the oxygen-containing crystalline silicon layer away from the substrate comprises: A third deposition process is performed on the side of the oxygen-containing crystalline silicon layer facing away from the 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 ratio of H2, PH3 and SiH4 is (5-600):(0.005-0.07):

1.

6. The preparation method according to any one of claims 2 to 5, characterized in that: In at least one of the first deposition process, the second deposition process, and the third deposition process, the process temperature is 170° C. to 230° C., and the power density of the power source is 10 mW·cm -2 ~800mW·cm -2 , the process pressure is 0.1mbar~8mbar.

7. The preparation method according to any one of claims 1 to 5, characterized in that: The step of forming the second doped semiconductor layer on the side of the second passivation layer facing away from the substrate comprises: A fourth deposition process is performed on the second passivation layer on a side away from the 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 ratio of CO2, H2, B2H6 and SiH4 is (0-4): (5-600): (0.005-0.07): 1; In the fourth deposition process, the process temperature is 150°C to 210°C, and the power density is 10mW·cm -2 ~800mW·cm -2 , the process pressure is 0.1mbar~8mbar.

8. The preparation method according to any one of claims 1 to 5, characterized in that: The step of forming the transparent conductive layer on the first doped semiconductor layer and the second doped semiconductor layer respectively away from the substrate comprises: A fifth deposition process is performed on the first doped semiconductor layer and the second doped semiconductor layer on a side away from the substrate using a sixth process gas to obtain the transparent conductive layer; wherein, The sixth process gas includes O2, H2, H2O and Ar, wherein the gas flow ratio of O2, H2, H2O and Ar is (0.01-0.08): (0.01-0.05): (0.0001-0.003): 1; In the fifth deposition process, the process temperature is 80° C. to 200° C., the power supply is 1 KW to 15 KW, and the process pressure is 0.2 Pa to 2 Pa.

9. The preparation method according to any one of claims 1 to 5, characterized in that: 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; and / or, 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 / or, 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; 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 layer is 0.1 nm-5 nm; and / or, The thickness of the second oxygen-containing crystalline silicon layer is 5nm-30nm; and / or, The thickness of the third oxygen-containing crystalline silicon layer is 0.1 nm-10 nm; and / or, The thickness of the first doped semiconductor layer is 0.1 nm-10 nm.

10. A heterojunction solar cell, characterized in that: The substrate comprises: a substrate having a first surface and a second surface opposite to each other; A first passivation layer, located on a first surface of the substrate; An oxygen-containing crystalline silicon layer of a first conductivity type is located on a side of the first passivation layer away from the substrate; The doping concentration of oxygen atoms in the oxygen-containing crystalline silicon layer gradually increases in a direction away from the substrate; A first doped semiconductor layer of a first conductivity type, located on a side of the oxygen-containing crystalline silicon layer away from the substrate; A second passivation layer, located on the second surface of the substrate; A second doped semiconductor layer of a second conductivity type, located on a side of the second passivation layer away from the substrate; A transparent conductive layer, respectively located on a side of the first doped semiconductor layer and a side of the second doped semiconductor layer facing away from the substrate; The metal electrodes are respectively located on the side of the transparent conductive layer away from the substrate; wherein, The first conductivity type is selected from one of P type and N type; The second conductivity type is selected from the other of a P type and an N type.

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