Method for preparing passivation layer, solar cell and photovoltaic module

Abstract

The invention provides a method for preparing a passivation layer, a solar cell and a photovoltaic module, and belongs to the technical field of solar cells. The solar cell includes: a silicon substrate including a surface having an N-type region and a P-type region; the passivation antireflection layer is located on the surfaces, away from the silicon substrate, of the N-type region and the P-type region, the passivation antireflection layer sequentially comprises a first passivation layer and a second passivation layer in the thickness direction of the silicon substrate, the first passivation layer comprises an aluminum oxide film, and the second passivation layer comprises metal elements. According to the solar cell provided by the invention, the field passivation effect of the passivation antireflection layer can be improved, and finally, the cell performance can be improved.

Description

Technical Field

[0001] At least one embodiment of the present application relates to the field of solar cells, and in particular to a method for preparing a passivation layer, a solar cell, and a photovoltaic module. Background Art

[0002] In the process of preparing solar cells, the aluminum oxide film prepared by ALD contains hydroxyl groups (-OH groups). In the subsequent heat treatment process, the -OH groups release metastable H, which can passivate the dangling bonds on the substrate surface and reduce the surface recombination rate. However, the H released by the -OH groups under high-temperature sintering will also escape in the form of H2 or H2O, causing the passivation layer to be penetrated by the gas and destroyed. Based on this situation, how to improve the passivation performance of the passivation anti-reflection layer is an urgent problem to be solved to improve the efficiency of solar cells. Summary of the invention

[0003] In view of this, in order to at least partially solve the above-mentioned technical problems, the present application provides a method for preparing a passivation layer, a solar cell and a photovoltaic module.

[0004] According to an embodiment of one aspect of the present application, a solar cell is provided, including:

[0005] A silicon substrate comprises a surface having an N-type region and a P-type region; a passivation anti-reflection layer is located on the surface of the N-type region and the P-type region away from the silicon substrate, and along the thickness direction of the silicon substrate, the passivation anti-reflection layer sequentially comprises a first passivation layer and a second passivation layer, wherein the first passivation layer comprises an aluminum oxide film, and the second passivation layer comprises a metal element.

[0006] In some embodiments, the material of the second passivation layer includes one or more of silicon nitride, silicon oxynitride, and silicon oxide.

[0007] In some embodiments, a first atomic mass fraction of the metal element in the second passivation layer located in the P-type region is greater than a second atomic mass fraction of the metal element in the second passivation layer located in the N-type region.

[0008] In some embodiments, the difference between the first atomic mass fraction and the second atomic mass fraction is greater than or equal to 0.3%.

[0009] In some embodiments, the first atomic mass accounts for 0.3% to 1%, and the second atomic mass accounts for 0 to 0.1%.

[0010] In some embodiments, the thickness of the first passivation layer in the P-type region is greater than the thickness of the first passivation layer in the N-type region.

[0011] In some embodiments, the difference between the thickness of the first passivation layer located in the P-type region and the thickness of the first passivation layer located in the N-type region is 0.1 nm to 3 nm.

[0012] In some embodiments, the thickness uniformity of the first passivation layer is less than or equal to 5%.

[0013] In some embodiments, the thickness uniformity of the first passivation layer in the P-type region is less than or equal to 4%, and the thickness uniformity of the first passivation layer in the N-type region is less than or equal to 5%.

[0014] In some embodiments, a surface of the silicon substrate includes a plurality of P-type regions and a plurality of N-type regions alternately distributed along a first direction; a passivation contact structure, the passivation contact structure is located between the surface of the silicon substrate and the passivation anti-reflection layer;

[0015] The passivation contact structure includes a plurality of first passivation contact structures and a plurality of second passivation contact structures, the first passivation contact structure is located on a P-type region of a silicon substrate, and the second passivation contact structure is located on an N-type region of the silicon substrate; wherein the first passivation contact structure includes a first doped semiconductor layer, the second passivation contact structure includes a second doped semiconductor layer, and the thickness of the first doped semiconductor layer along a direction perpendicular to the silicon substrate is greater than the thickness of the second doped semiconductor layer along a direction perpendicular to the silicon substrate.

[0016] In some embodiments, the first surface and the second surface of the silicon substrate respectively include a plurality of P-type regions and a plurality of N-type regions distributed along a first direction; a passivation contact structure, the passivation contact structure is located between the surface of the silicon substrate and the passivation anti-reflection layer;

[0017] The passivation contact structure includes a plurality of first passivation contact structures and a plurality of second passivation contact structures, the first passivation contact structure is located on a P-type region of a silicon substrate, and the second passivation contact structure is located on an N-type region of the silicon substrate; wherein the first passivation contact structure includes a first doped semiconductor layer, the second passivation contact structure includes a second doped semiconductor layer, and the thickness of the first doped semiconductor layer along a direction perpendicular to the silicon substrate is greater than the thickness of the second doped semiconductor layer along a direction perpendicular to the silicon substrate.

[0018] According to another embodiment of the present application, a method for preparing a passivation layer is provided, comprising repeating a plurality of deposition cycles, each deposition cycle comprising:

[0019] An aluminum-containing precursor is introduced into a reaction chamber of an atomic layer deposition device, and nitrogen is introduced into the reaction chamber for an initial purge to obtain a first intermediate by-product and a first intermediate product adsorbed on a substrate; after the introduction of the aluminum-containing precursor is stopped, nitrogen is introduced into the reaction chamber for a second purge to partially remove the first intermediate by-product and unreacted aluminum-containing precursor; after the introduction of nitrogen is stopped, an oxidant is introduced into the reaction chamber, and nitrogen is introduced into the reaction chamber for a third purge to react with the first intermediate product to obtain a passivation layer monoatomic layer and a second intermediate by-product; and after the introduction of the oxidant is stopped, nitrogen is introduced into the reaction chamber for a fourth purge to partially remove the second intermediate by-product and unreacted oxidant.

[0020] In some embodiments, the initial nitrogen purge time is less than or equal to the time of introducing the aluminum-containing precursor.

[0021] In some embodiments, the time for the three nitrogen purges is less than or equal to the time for the oxidant.

[0022] According to an embodiment of another aspect of the present application, a photovoltaic assembly is provided, including a battery string, wherein the battery string includes the above-mentioned solar cell.

[0023] According to the solar cell provided by the above-mentioned embodiment of the present application, by adding metal elements to the passivation anti-reflection layer, the electric field generated by the fixed charge of the metal elements themselves is used to provide partial field passivation, thereby improving the passivation effect of the passivation anti-reflection layer, thereby reducing the recombination probability of carriers in the solar cell and improving the efficiency of the solar cell.

[0024] According to the method for preparing a passivation layer provided in the above embodiment of the present application, a through-source coordinated purging method is adopted to prepare the passivation layer. Insufficient nitrogen purging causes the raw material aluminum-containing precursor and intermediate products to remain on the surface of the prepared passivation layer, and the surface will adsorb metastable hydrogen. The passivation layer prepared by the above method is applied to solar cells, which can not only ensure the surface passivation effect, but also will not release too much H2 during the subsequent high-temperature treatment process, thereby avoiding damage to the passivation film layer and reducing the occurrence of film explosion. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings of the embodiments will be briefly introduced below. Obviously, the drawings in the following description only relate to some embodiments of the present application, rather than limiting the present application.

[0026] Figure 1 A schematic diagram of the process of preparing a passivation layer provided in an embodiment of the present application;

[0027] Figure 2 A cross-sectional schematic diagram of a back-contact solar cell provided in an embodiment of the present application;

[0028] Figure 3 The EDS test results of the back contact solar cell in the related art;

[0029] Figure 4 EDS test results of the back-contact solar cell provided in the embodiments of the present application; and

[0030] Figure 5 A cross-sectional schematic diagram of a bifacial solar cell provided in an embodiment of the present application.

[0031] Description of reference numerals:

[0032] 1-Silicon substrate;

[0033] 100-a first polarity carrier collection region;

[0034] 200-second polarity carrier collection region;

[0035] 300-Isolated area;

[0036] 2-first passivation contact structure;

[0037] 21-first interface passivation layer;

[0038] 22-a first doped semiconductor layer;

[0039] 3-second passivation contact structure;

[0040] 31- second interface passivation layer;

[0041] 32- a second doped semiconductor layer;

[0042] 4- passivation anti-reflection layer;

[0043] 41- a first passivation layer;

[0044] 42- a second passivation layer;

[0045] 5- first electrode;

[0046] 6- Second electrode. DETAILED DESCRIPTION

[0047] In order to make the purpose, technical scheme and advantages of the present application clearer, the present application is further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings. However, the present application can be implemented in different forms and should not be construed as being limited to the embodiments proposed herein. On the contrary, providing these embodiments will make the application thorough and complete, and fully convey the scope of the present application to those skilled in the art. In the accompanying drawings, for clarity, the sizes and relative sizes of layers and regions may be exaggerated, and the same reference numerals represent the same elements throughout.

[0048] The terms used herein are only for describing specific embodiments and are not intended to limit the present application. The terms "include", "comprising", etc. used herein indicate the existence of the features, steps, operations and / or components, but do not exclude the existence or addition of one or more other features, steps, operations or components.

[0049] At present, the new generation of high-efficiency solar cells use a variety of composite passivation solutions to improve the photoelectric conversion efficiency of the cells. For example, the thin oxide passive contact (TOPCon) solar cell uses low pressure chemical vapor deposition (LPCVD) to prepare the tunneling oxide layer, and plasma enhanced chemical vapor deposition (PECVD) to prepare the doped polysilicon layer to form the passivation contact structure, and atomic layer deposition (ALD) to prepare the aluminum oxide passivation layer on the passivation contact structure to achieve the passivation of high-efficiency cells.

[0050] In the related art, the aluminum oxide passivation layer is prepared by atomic layer deposition. Usually, an aluminum-containing precursor is introduced into the reaction chamber for a period of time, and after the introduction of the aluminum-containing precursor is stopped, nitrogen is purged for a period of time. Then, an oxidant is introduced for a period of time, and after the introduction of the oxidant is stopped, nitrogen is purged for a period of time.

[0051] For back contact (BC) solar cells, due to their special structure, the PN junction and the composite passivation layer are both on the back surface of the cell. Since the thickness of the passivation contact structure of the P-type region and the N-type region is usually different (the P-type region and the N-type region have steps), the step effect makes the aluminum oxide passivation layer obtained by ALD deposition have poor uniformity (the step effect makes the thickness of the aluminum oxide passivation layer deposited in the P-type region and the N-type region different), which brings structural problems. On the one hand, if the local passivation layer is too thick, it will cause the passivation layer to have a film explosion problem (because the passivation layer is too thick, the surface of the passivation layer is rich in hydrogen, resulting in the phenomenon of hydrogen atoms overflowing and bursting the surface of the passivation layer after sintering, which is called film explosion), reducing the photoelectric conversion efficiency of the cell. On the other hand, if the local passivation layer is too thin, it will lead to poor passivation effect, making it difficult to balance the yield and efficiency of the product at the mass production end.

[0052] In view of this, the present application provides a method for preparing a passivation layer, a solar cell and a photovoltaic module. The prepared passivation layer is applied to the solar cell, which can improve the passivation effect of the passivation anti-reflection layer of the solar cell and reduce the risk of film explosion of the passivation anti-reflection layer of the solar cell.

[0053] Figure 1A schematic diagram of the process for preparing a passivation layer provided in an embodiment of the present application.

[0054] According to an exemplary embodiment of the present application, the present application provides a method for preparing a passivation layer, referring to Figure 1 As shown, it includes: repeating multiple deposition cycles, each deposition cycle includes: step S01 to step S04.

[0055] In step S01, an aluminum (Al)-containing precursor is introduced into a reaction chamber of an atomic layer deposition device, and nitrogen is initially purged into the reaction chamber. The aluminum-containing precursor reacts with hydroxyl groups (-OH) adsorbed on the surface to be deposited to obtain a first intermediate by-product and a first intermediate product adsorbed on the substrate.

[0056] In some embodiments, the aluminum-containing precursor is trimethylaluminium (TMA). By controlling the amount of the aluminum-containing precursor trimethylaluminium introduced, the reaction between the aluminum-containing precursor trimethylaluminium and the hydroxyl group is self-limiting. The reaction formula is shown in formula (1).

[0057] Al(CH3)3+OH=>O-Al-(CH3)2+CH4(1)

[0058] Step S02, after stopping the introduction of the aluminum-containing precursor, nitrogen is introduced into the reaction chamber for a second time for purge to partially remove the first intermediate by-product and the unreacted aluminum-containing precursor.

[0059] In an embodiment of the present application, the first intermediate product O—Al—(CH 3 ) 2 generated in step S01 is adsorbed on the surface of the substrate, and nitrogen purge is performed to partially remove CH 4 and unreacted Al(CH 3 ) 3 .

[0060] Step S03, after stopping the nitrogen purge, introducing an oxidant into the reaction chamber, and coordinating the nitrogen purge three times in the reaction chamber, the oxidant reacts with the first intermediate product to obtain a passivation layer monoatomic layer and a second intermediate by-product.

[0061] In some embodiments, the oxidant is H2O or O3.

[0062] According to an embodiment of the present application, by controlling the content of the oxidant, the reaction between the oxidant and the first intermediate product is self-limiting. The reaction formula between the oxidant and the first intermediate product is shown in Formula (2),

[0063] O-Al-(CH3)2+H2O=>O-Al-OH(2)+(O)2-Al-CH3+CH4 (2)

[0064] Step S04, after stopping the introduction of the oxidant, nitrogen is introduced into the reaction chamber for four times to purge part of the second intermediate by-product and unreacted oxidant.

[0065] In the embodiment of the present application, nitrogen gas is introduced into the reaction chamber for four times to partially remove CH4 and unreacted oxidant.

[0066] According to an embodiment of the present application, before the first deposition cycle, the reaction chamber needs to be preheated slowly, with a heating rate of less than 15°C / min, preferably 5°C / min. Multiple deposition cycles are repeated to obtain a passivation layer of a predetermined thickness, wherein the number of repetitions of the deposition cycle can be determined according to the thickness of the passivation layer to be deposited.

[0067] According to the embodiments of the present application, the atomic layer deposition equipment is not limited herein, for example, the atomic layer deposition process commonly uses Microguide's KF1800s (tubular thermal ALD), ZR5000 PEALD, Laplace, and Aiwa ALD, as long as the function of coordinated purge can be achieved through process adjustment.

[0068] In some embodiments, the initial nitrogen purge time is less than or equal to the time of introducing the aluminum-containing precursor.

[0069] In some embodiments, the time for the three nitrogen purges is less than or equal to the time for the oxidant.

[0070] According to the embodiments of the present application, a passivation layer is prepared by a source coordinated purging method, that is, nitrogen purging is performed simultaneously when an aluminum-containing precursor is introduced. The low-pressure nitrogen purging process allows the raw aluminum-containing precursor or the aluminum-containing precursor together with other metal element precursors and intermediate by-products to remain on the surface of the prepared passivation layer, and metastable hydrogen will be adsorbed on the surface. At the same time, in the finished battery, the metal elements will appear in the outermost passivation layer of the solar cell. The fixed charge of the metal elements can provide an electric field and provide an additional field passivation effect. When the passivation layer prepared by the above method is applied to a solar cell, it can not only ensure the surface passivation effect, but also will not release too much H2 during the subsequent high-temperature treatment process, which can avoid damage to the passivation layer and the film layer thereon due to H2 escape, thereby reducing the occurrence of film explosion.

[0071] According to an exemplary embodiment of the present application, the present application provides a passivation layer prepared by the above method.

[0072] According to an exemplary embodiment of the present application, the present application provides a solar cell, including:

[0073] A silicon substrate including a surface having an N-type region and a P-type region;

[0074] The passivation anti-reflection layer is located on the surface of the N-type region and the P-type region away from the silicon substrate, and along the thickness direction of the silicon substrate, the passivation anti-reflection layer includes a first passivation layer and a second passivation layer in sequence, wherein the material of the first passivation layer includes an aluminum oxide film, and the second passivation layer includes a metal element. The metal element includes at least one of Al, Ti, Zn, Zr, Hf, Mo, W, and Ni.

[0075] According to an embodiment of the present application, a passivation layer is prepared by a source-coordinated purging method, that is, nitrogen purging is performed simultaneously when an aluminum-containing precursor is introduced. The low-pressure nitrogen purging process allows the raw aluminum-containing precursor or the aluminum-containing precursor together with a precursor containing other metal elements, and intermediate by-products to remain on the surface of the prepared passivation layer. The surface will adsorb metastable hydrogen, and in the subsequent high-temperature treatment process, the raw aluminum-containing precursor or the aluminum-containing precursor together with a precursor containing other metal elements, and the intermediate by-products remaining on the surface will escape along with the escape of part of the hydrogen and be deposited on the surface of the second passivation layer.

[0076] According to the embodiments of the present application, the metal elements in the second passivation layer enable the second passivation layer itself to have a high density of fixed charges. The high density of fixed charges can generate a larger electric field, thereby enhancing the passivation effect of the passivation anti-reflection layer.

[0077] In some embodiments, the solar cell is, for example, a back contact solar cell, and the back contact solar cell includes but is not limited to an interdigitated back contact solar cell (IBC), a tunneling oxide passivated contact back contact solar cell (TBC), an all back contact solar cell (ABC), a heterojunction back contact solar cell (HBC), a polycrystalline silicon on oxide interdigitated back contact solar cell (POLO-IBC), a dopant-free heterojunction interdigitated back contact solar cell (DFHJ-IBC), and any one of hybrid BCs formed by hybridizing different passivation contact structures.

[0078] Figure 2 A schematic cross-sectional view of a back-contact solar cell provided in an embodiment of the present application.

[0079] According to an exemplary embodiment of the present application, the present application provides a back contact solar cell, referring to Figure 2 As shown, including:

[0080] A silicon substrate 1, wherein one surface of the silicon substrate 1 comprises a plurality of first polarity carrier collecting regions 100 and a plurality of second polarity carrier collecting regions 200 having polarities opposite to the first polarity carrier collecting regions 100, which are alternately distributed along a first direction, and an isolation region 300 is provided between adjacent first polarity carrier collecting regions 100 and second polarity carrier collecting regions 200; the first polarity carrier collecting regions 100 are P-type regions, and the second polarity carrier collecting regions 200 are N-type regions;

[0081] A passivation contact structure, the passivation contact structure comprising a plurality of first passivation contact structures 2 and a plurality of second passivation contact structures 3, the first passivation contact structures 2 being located on a P-type region of a silicon substrate, and the second passivation contact structures 3 being located on an N-type region of the silicon substrate; wherein the thickness of the first passivation contact structures 2 along a direction perpendicular to the silicon substrate is greater than the thickness of the second passivation contact structures 3 along a direction perpendicular to the silicon substrate; and

[0082] The passivation anti-reflection layer 4 is located on the surface of the first passivation contact structure 2 and the second passivation contact structure 3 away from the silicon substrate 1 . Along the thickness direction of the silicon substrate 1 , the passivation anti-reflection layer 4 includes a first passivation layer 41 and a second passivation layer 42 in sequence.

[0083] According to an embodiment of the present application, the material of the first passivation layer 41 includes an aluminum oxide film, and the surface of the second passivation layer 42 away from the silicon substrate 1 includes metal elements.

[0084] In some embodiments, the metal element includes at least one of an Al element, a Ti element, a Zn element, a Zr element, an Hf element, a Mo element, a W element, and a Ni element.

[0085] In some embodiments, the material of the second passivation layer 42 includes one or more of silicon nitride, silicon oxynitride, and silicon oxide.

[0086] In some embodiments, the second passivation layer 42 is a single-layer structure of silicon nitride or silicon oxynitride, or the second passivation layer 42 is a stacked-layer structure of silicon nitride and silicon oxynitride.

[0087] In some embodiments, the thickness of the second passivation layer 42 on the P-type region is less than the thickness of the second passivation layer 42 on the N-type region.

[0088] According to an embodiment of the present application, the passivation contact types of the first passivation contact structure 2 and the second passivation contact structure 3 may be the same. For example, the first passivation contact structure 2 and the second passivation contact structure 3 are both tunneling passivation contact structures or heterogeneous contact structures. Alternatively, the passivation contact types of the first passivation contact structure 2 and the second passivation contact structure 3 may also be different. For example, one of the first passivation contact structure 2 and the second passivation contact structure 3 is a tunneling passivation contact structure, and the other of the first passivation contact structure 2 and the second passivation contact structure 3 is a heterogeneous contact structure.

[0089] In some embodiments, the first interface passivation layer 21 and the first doped semiconductor layer 22 constitute a first passivation contact structure 2, and the second interface passivation layer 31 and the second doped semiconductor layer 32 constitute a second passivation contact structure 3. For example, the first interface passivation layer 21 is a tunneling oxide layer (SiO2), the first doped semiconductor layer 22 is a doped polysilicon layer, the second interface passivation layer 31 is an intrinsic amorphous silicon layer, and the second doped semiconductor layer 32 is a doped amorphous silicon layer or a doped microcrystalline silicon layer; for another example, the first interface passivation layer 21 is a tunneling oxide layer (SiO2), the first doped semiconductor layer 22 is a doped polysilicon layer, the second interface passivation layer 31 is a tunneling oxide layer (SiO2), and the second doped semiconductor layer 32 is a doped polysilicon layer. The thickness of the first doped semiconductor layer along the direction perpendicular to the silicon substrate is greater than the thickness of the second doped semiconductor layer along the direction perpendicular to the silicon substrate.

[0090] According to an embodiment of the present application, the back-contact solar cell further includes a first electrode 5 located on the first passivation contact structure 2 , and a second electrode 6 located on the second passivation contact structure 3 .

[0091] In some embodiments, the first atomic mass fraction of the metal element on the second passivation layer 42 in the P-type region is greater than the second atomic mass fraction of the metal element on the second passivation layer 42 in the N-type region.

[0092] According to an embodiment of the present application, the atomic mass percentage of the metal element in the second passivation layer is calculated by an EDS element analyzer, and the calculation formula is shown in formula (3):

[0093] X=(C×m) / (C0×m0) (3)

[0094] Wherein, C represents the mass fraction of the metal element, m represents the relative atomic mass of the metal element, C0 represents the mass fraction of all elements in the second passivation layer, and m0 represents the sum of the relative atomic masses of all elements in the second passivation layer.

[0095] In some embodiments, the difference between the first atomic mass fraction and the second atomic mass fraction is greater than or equal to 0.3%.

[0096] In some embodiments, the first atomic mass percentage of the metal element in the second passivation layer 42 located in the P-type region is any value between 0.3% and 1%, for example, it can be 0.3%, 0.5%, 0.6%, 0.8%, 1%, but is not limited to the listed values.

[0097] In some embodiments, the second atomic mass percentage of the metal element in the second passivation layer 42 in the N-type region is any value between 0 and 0.1%, for example, 0, 0.05%, or 0.1%, but is not limited to the values ​​listed.

[0098] In some embodiments, the passivation anti-reflection layer 4 is also located on the other surface of the back contact solar cell, and along the thickness direction of the silicon substrate 1, the passivation anti-reflection layer 4 sequentially includes a first passivation layer 41 and a second passivation layer 42. The first passivation layer 41 includes an aluminum oxide film, and the second passivation layer 42 includes a metal element on a surface away from the silicon substrate 1. The metal element includes at least one of Al element, Ti element, Zn element, Zr element, Hf element, Mo element, W element, and Ni element.

[0099] In some embodiments, the first atomic mass fraction of the metal element in the second passivation layer 42 located in the P-type region is greater than the third atomic mass fraction of the metal element in the second passivation layer 42 located on the other surface of the back contact solar cell.

[0100] In some embodiments, the third atomic mass percentage of the metal element in the second passivation layer 42 located on the other surface of the back contact solar cell is any value between 0 and 0.1%, for example, it can be 0, 0.05%, 0.1%, but is not limited to the listed values.

[0101] In some embodiments, the thickness of the first passivation layer 41 in the P-type region is greater than the thickness of the first passivation layer 41 in the N-type region.

[0102] In some embodiments, the difference between the thickness of the first passivation layer 41 located in the P-type region and the thickness of the first passivation layer 41 located in the N-type region is 0.1 nm-3 nm.

[0103] In some embodiments, the thickness of the first passivation layer 41 located in the P-type region is any value between 6 nm and 10 nm, for example, 6 nm, 7 nm, 8 nm, 9 nm, and 10 nm, but is not limited to the above values.

[0104] In some embodiments, the thickness of the first passivation layer 41 in the N-type region is any value between 4 nm and 8 nm, for example, 4 nm, 5 nm, 6 nm, 7 nm, and 8 nm, but is not limited to the above values.

[0105] In some embodiments, the thickness uniformity of the first passivation layer 41 is less than or equal to 5%.

[0106] In some embodiments, the thickness uniformity of the first passivation layer 41 located in the P-type region is less than or equal to 4%.

[0107] In some embodiments, the thickness uniformity of the first passivation layer 41 located in the N-type region is less than or equal to 5%.

[0108] Energy spectrum analysis and film thickness uniformity test are performed on the solar cell in the related art and the solar cell of the present application. The energy spectrum analysis test uses EDS in a scanning electron microscope to perform element analysis on a specific area, and the film thickness uniformity test performs a film thickness uniformity test on the passivation layer at the junction of the N region and the P region (such as a pad, PAD).

[0109] Figure 3 This is the EDS test result of the back-contact solar cell in the related art.

[0110] EDS test is performed on the back contact solar cell (finished cell) in the related art. Figure 3 As shown, the test results show that the surface of the passivation anti-reflection layer and the back contact solar cell in the related art has Si element, but no Al element.

[0111] Figure 4 EDS test results of the back-contact solar cell provided in the embodiments of the present application.

[0112] refer to Figure 4 As shown, the results of EDS testing of the back contact solar cell (finished cell) of the present application show that Si and Al elements exist on the surface of the passivation anti-reflection layer and the solar cell. This is because: in the process of depositing the aluminum oxide passivation layer by the atomic layer deposition process, the aluminum-containing precursor and nitrogen gas are purged together to leave more incompletely saturated aluminum-containing precursors and intermediate products on the surface of the first passivation layer. After entering the subsequent high-temperature process of annealing and sintering, the incompletely saturated aluminum-containing precursors and intermediate products remaining on the surface of the first passivation layer volatilize to the surface of the second passivation layer on the first passivation layer as hydrogen atoms in the hydrogen-rich film layer migrate and precipitate.

[0113] The full spectrum ellipsometer was used to perform film thickness uniformity tests on two randomly selected back-contact solar cells with film explosion in related technologies (sample 1 and sample 2) and two back-contact solar cells with film explosion in the present application (sample 3 and sample 4), and the test results are shown in Table 1. Among them, 5 positions (marked as N-1, N-2, N-3, N-4, N-5) on the N-type region and 5 positions (marked as P-1, P-2, P-3, P-4, P-5) on the P-type region were randomly selected from the same sample, and the film thickness of the 5 positions on the N-type region and the P-type region was measured respectively, and the average thickness of the 5 positions in the N-type region (AVG-N) and the average thickness of the 5 positions in the P-type region (AVG-P) were calculated, so as to obtain the film thickness uniformity (N uniformity) of the N-type region and the film thickness uniformity (P uniformity) of the P-type region of the sample.

[0114] Table 1

[0115] Location N-1 N-2 N-3 N-4 N-5 P-1 P-2 P-3 P-4 P-5 N uniformity P uniformity AVG-N AVG-P Sample 1 6.2 6.1 5.8 5.9 5.8 9 9.2 9 8.9 8.5 3.36% 3.92% 5.96 8.92 Sample 2 6.2 5.9 6 6.2 6.3 8.4 9 8.4 9.1 9.1 3.27% 3.98% 6.12 8.8 Sample 3 6.1 6.3 6.2 6.4 6 8.6 8.6 8.2 8.3 9 3.23% 4.68% 6.2 8.54 Sample 4 6.3 6.1 6.2 6.1 6.5 8.6 8.6 8.2 8.3 8.5 3.21% 2.37% 6.24 8.44

[0116] It should be noted that the calculation formula for film thickness uniformity is shown in formula (4):

[0117] Uniformity = (MAX-MIN) / 2 / AVG (4)

[0118] As shown in Reference Table 1, the thickness uniformity of the first passivation layer located in the N-type region of two randomly selected back-contact solar cells of the present application is 3.23% and 3.21%, respectively, both less than 4%; the thickness uniformity of the first passivation layer located in the P-type region is 4.68% and 2.37%, respectively, both less than 5%. The thickness uniformity of the passivation layer generally used in solar cells is less than 5%, which meets the thickness uniformity requirement. Compared with the first passivation layer in the related art, the thickness uniformity of the first passivation layer prepared by the method of the present application has not increased significantly, which indicates that the first passivation layer prepared by the present application has better flatness. It should be noted that the smaller the thickness uniformity, the higher the flatness of the prepared film.

[0119] According to the embodiments of the present application, Al element exists on the surface of the second passivation layer (that is, Al element exists on the surface of the finished solar cell). This is because the pressure of the nitrogen purge is reduced by the coordinated method of passing the source and purging. Compared with the original process (passing the source first and then purging), more residual aluminum-containing precursors and intermediate products are adsorbed on the surface of the battery, and metastable hydrogen will be adsorbed on the surface. The passivation layer prepared by the above method is applied to the solar cell, which can not only ensure the surface passivation effect, but also will not release too much H2 in the subsequent high-temperature treatment process, which can avoid the damage of the passivation film layer due to H2 escape, thereby reducing the occurrence of film explosion.

[0120] The preparation method of the present application can improve the problem of step coverage of the coating, prevent the local surface from being overly saturated with hydrogen, reduce the risk of film explosion, and is beneficial to improving the reliability of solar cells and the yield rate of battery production lines.

[0121] An aluminum oxide film is prepared by using the method for preparing a passivation layer in the related art, and the prepared aluminum oxide film is used as the first passivation layer to form a back-contact solar cell. An aluminum oxide film is prepared by using the method for preparing a passivation layer in the present application, and the prepared aluminum oxide film is used as the first passivation layer to form a back-contact solar cell. The performance comparison of the back-contact solar cell of the related art and the back-contact solar cell of the present application is shown in Table 2.

[0122] Table 2

[0123] Solar Cells First pass rate (yield) Photoelectric conversion efficiency (Eta) Open circuit voltage (Voc) Short circuit current (Isc) Fill Factor (FF) Film burst ratio Related technologies 95.87% 26.72% 0.740V 14.898A 84.50 1.3% This application 97.48% 26.73% 0.740V 14.901A 84.51 0.2%

[0124] As shown in Table 2, compared with the back-contact solar cells in the related art, the photoelectric conversion efficiency, open circuit voltage, short circuit current, fill factor and other cell performance of the back-contact solar cells of the present application remain basically unchanged, and the pass rate is increased from 95.87% to 97.48%. Without affecting the cell efficiency, the proportion of film explosion of the passivation anti-reflection layer of the back-contact solar cells of the present application is reduced from 1.3% to 0.2%, thereby improving the pass rate (also known as yield) of the solar cell production line, which is conducive to improving the cell production efficiency.

[0125] In some embodiments, the solar cell is, for example, a bifacial solar cell, and the bifacial solar cell includes but is not limited to a TOPCon solar cell.

[0126] In some embodiments, the passivation contact structure of the bifacial solar cell is discontinuous, the thickness of the passivation contact structure in the electrode area and the non-electrode area is different, the electrode area and the non-electrode area have a step effect, and the step effect makes the aluminum oxide passivation layer obtained by ALD deposition on the passivation contact structure have poor uniformity.

[0127] Figure 5 A cross-sectional schematic diagram of a bifacial solar cell provided in an embodiment of the present application.

[0128] According to an exemplary embodiment of the present application, the present application provides a double-sided solar cell, referring to Figure 5 As shown, the bifacial solar cell comprises:

[0129] A silicon substrate 1 has a first surface and a second surface opposite to each other, the first surface includes a plurality of first polarity carrier collecting regions 100, the second surface includes a plurality of second polarity carrier collecting regions 200, the first polarity carrier collecting regions 100 are P-type regions, and the second polarity carrier collecting regions 200 are N-type regions;

[0130] A passivation contact structure, comprising a plurality of first passivation contact structures 2 and a plurality of second passivation contact structures 3, wherein the passivation contact structure may cover the first surface and the second surface in whole or in part, wherein the first passivation contact structure 2 is located on a P-type region of the silicon substrate, and the second passivation contact structure 3 is located on an N-type region of the silicon substrate;

[0131] The passivation anti-reflection layer 4 is located on the surface of the N-type region and the P-type region away from the silicon substrate 1. Along the thickness direction of the silicon substrate 1, the passivation anti-reflection layer 4 includes a first passivation layer 41 and a second passivation layer 42 in sequence, wherein the first passivation layer 41 includes an aluminum oxide film, and the second passivation layer 42 includes a metal element on the surface away from the silicon substrate 1. The metal element includes at least one of Al element, Ti element, Zn element, Zr element, Hf element, Mo element, W element and Ni element.

[0132] In some embodiments, the first atomic mass fraction of the metal element on the second passivation layer 42 in the P-type region is greater than the second atomic mass fraction of the metal element on the second passivation layer 42 in the N-type region.

[0133] In some embodiments, the first passivation contact structure 2 includes a first doped semiconductor layer 22 , and the second passivation contact structure 3 includes a second doped semiconductor layer 32 . The thickness of the first doped semiconductor layer 22 along a direction perpendicular to the silicon substrate is greater than the thickness of the second doped semiconductor layer 32 along a direction perpendicular to the silicon substrate.

[0134] According to an exemplary embodiment of the present application, the present application provides a photovoltaic assembly, including a battery string, and the battery string includes the above-mentioned solar cell.

[0135] The ordinal numbers used in the specification and claims, such as "first", "second", "third", etc., to modify the corresponding elements, do not themselves mean that the elements have any ordinal numbers, nor do they represent the order of one element and another element, or the order in the manufacturing method. The use of these ordinal numbers is only used to clearly distinguish a component with a certain name from another component with the same name.

[0136] The specific embodiments described above further illustrate the purpose, technical solutions and beneficial effects of the present application. It should be understood that the above description is only a specific embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application should be included in the scope of protection of the present application.

Claims

1. A solar cell, characterized in that: include: A silicon substrate (1) comprising a surface having an N-type region and a P-type region; A passivation anti-reflection layer (4) is located on the surface of the N-type region and the P-type region away from the silicon substrate (1), and along the thickness direction of the silicon substrate (1), the passivation anti-reflection layer (4) comprises a first passivation layer (41) and a second passivation layer (42) in sequence. The first passivation layer (41) comprises an aluminum oxide film, and the second passivation layer (42) comprises a metal element.

2. The solar cell according to claim 1, characterized in that The material of the second passivation layer includes one or more of silicon nitride, silicon oxynitride and silicon oxide.

3. The solar cell according to claim 1 or 2, characterized in that: The first atomic mass ratio of the metal element on the second passivation layer (42) located in the P-type region is greater than the second atomic mass ratio of the metal element on the second passivation layer (42) located in the N-type region.

4. The solar cell according to claim 3, characterized in that: The difference between the first atomic mass percentage and the second atomic mass percentage is greater than or equal to 0.2%.

5. The solar cell according to claim 3, characterized in that: The first atomic mass accounts for 0.3% to 1%. The second atomic mass accounts for 0-0.1%.

6. The solar cell according to claim 1 or 2, characterized in that: The thickness of the first passivation layer located in the P-type region is greater than the thickness of the first passivation layer located in the N-type region.

7. The solar cell according to claim 6, characterized in that: A difference between a thickness of the first passivation layer located in the P-type region and a thickness of the first passivation layer located in the N-type region is 0.1 nm to 3 nm.

8. The solar cell according to claim 1 or 2, characterized in that: The thickness uniformity of the first passivation layer is less than or equal to 5%.

9. The solar cell according to claim 8, characterized in that The thickness uniformity of the first passivation layer located in the P-type region is less than or equal to 4%, The thickness uniformity of the first passivation layer located in the N-type region is less than or equal to 5%.

10. The solar cell according to claim 1, characterized in that: A surface of the silicon substrate (1) comprises a plurality of P-type regions and a plurality of N-type regions alternately distributed along a first direction; A passivation contact structure, the passivation contact structure being located between the surface of the silicon substrate (1) and the passivation anti-reflection layer; The passivation contact structure comprises a plurality of first passivation contact structures (2) and a plurality of second passivation contact structures (3), wherein the first passivation contact structures (2) are located on the P-type region of the silicon substrate, and the second passivation contact structures (3) are located on the N-type region of the silicon substrate; The first passivation contact structure includes a first doped semiconductor layer, the second passivation contact structure includes a second doped semiconductor layer, and the thickness of the first doped semiconductor layer along a direction perpendicular to the silicon substrate is greater than the thickness of the second doped semiconductor layer along a direction perpendicular to the silicon substrate.

11. The solar cell according to claim 1, characterized in that: The first surface and the second surface of the silicon substrate (1) respectively comprise a plurality of P-type regions and a plurality of N-type regions distributed along a first direction, A passivation contact structure, the passivation contact structure being located between the surface of the silicon substrate (1) and the passivation anti-reflection layer; The passivation contact structure comprises a plurality of first passivation contact structures (2) and a plurality of second passivation contact structures (3), wherein the first passivation contact structures (2) are located on the P-type region of the silicon substrate, and the second passivation contact structures (3) are located on the N-type region of the silicon substrate; The first passivation contact structure includes a first doped semiconductor layer, the second passivation contact structure includes a second doped semiconductor layer, and the thickness of the first doped semiconductor layer along a direction perpendicular to the silicon substrate is greater than the thickness of the second doped semiconductor layer along a direction perpendicular to the silicon substrate.

12. A method for preparing a passivation layer, characterized in that: The method comprises repeating a plurality of deposition cycles, each of the deposition cycles comprising: Introducing an aluminum-containing precursor into a reaction chamber of an atomic layer deposition device, and coordinating the initial introduction of nitrogen gas into the reaction chamber to purge the reaction chamber, thereby obtaining a first intermediate byproduct and a first intermediate product adsorbed on a substrate; After the introduction of the aluminum-containing precursor is stopped, nitrogen is introduced into the reaction chamber for a second time for purging to partially remove the first intermediate by-product and the unreacted aluminum-containing precursor; After stopping the nitrogen purge, introducing an oxidant into the reaction chamber, and coordinating the nitrogen purge three times in the reaction chamber, the oxidant reacts with the first intermediate product to obtain a passivation layer monoatomic layer and a second intermediate byproduct; and After the introduction of the oxidant was stopped, nitrogen was introduced into the reaction chamber for four times to partially remove the second intermediate by-product and the unreacted oxidant.

13. The method according to claim 12, characterized in that The time for the initial nitrogen purge is less than or equal to the time for the aluminum-containing precursor.

14. The method according to claim 12, characterized in that The time for introducing nitrogen gas for three times is less than or equal to the time for introducing oxidant.

15. A photovoltaic module, characterized in that: It comprises a battery string, wherein the battery string comprises the solar cell according to any one of claims 1 to 11.

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