Heterojunction solar cell, method for manufacturing the same, and photovoltaic module

Abstract

The application relates to the field of solar cells, and discloses a heterojunction solar cell, a preparation method thereof and a photovoltaic module. The heterojunction solar cell comprises a silicon substrate, a first passivation layer, a first doped silicon layer and a first transparent conductive layer which are sequentially arranged on a light-receiving surface of the silicon substrate, wherein the first transparent conductive layer comprises a first thickness area and a second thickness area, the first transparent conductive layer is provided with a first transparent conductive sublayer on the first thickness area, the second transparent conductive layer is provided with a second transparent conductive sublayer on the second thickness area, and the thickness of the second transparent conductive sublayer is smaller than that of the first transparent conductive sublayer; the heterojunction solar cell further comprises an anti-reflection layer, the anti-reflection layer comprises a first anti-reflection sublayer, the first anti-reflection sublayer is arranged on a side surface of the second transparent conductive sublayer away from the first doped silicon layer, and the light transmittance of the first anti-reflection sublayer is higher than that of the first transparent conductive layer; and the heterojunction solar cell further comprises a first electrode, the first electrode is arranged on a side surface of the first transparent conductive sublayer away from the silicon substrate. The heterojunction solar cell can improve the absorption and utilization rate of sunlight.

Description

Technical Field

[0001] This application relates to the field of solar cell technology, and in particular to a heterojunction solar cell and its preparation method, and a photovoltaic module. Background Technology

[0002] In heterojunction solar cells, the transparent conductive layer is typically placed on the outermost layer to receive sunlight. However, the transparent conductive layer suffers from parasitic absorption, which reduces the light utilization efficiency of the heterojunction solar cell and hinders its performance improvement. Summary of the Invention

[0003] This application discloses heterojunction solar cells, their fabrication methods, and photovoltaic modules. The heterojunction solar cells of this application can reduce parasitic absorption in the first transparent conductive layer of the non-electrode region, thereby increasing the absorption capacity of sunlight and thus improving the sunlight absorption and utilization rate of the heterojunction solar cells.

[0004] In a first aspect, embodiments of this application disclose a heterojunction solar cell, the heterojunction solar cell comprising:

[0005] A silicon substrate having a light-receiving surface and a back-lighting surface disposed opposite to each other, wherein a first passivation layer and a first doped silicon layer are sequentially disposed on the light-receiving surface;

[0006] The heterojunction solar cell also includes:

[0007] A first transparent conductive layer is disposed on the side surface of the first doped silicon layer away from the silicon substrate. The first transparent conductive layer includes a first thickness region and a second thickness region. A first transparent conductive sublayer is disposed on the first thickness region, and a second transparent conductive sublayer is disposed on the second thickness region. The thickness of the second transparent conductive sublayer is less than that of the first transparent conductive sublayer.

[0008] An antireflection layer, the antireflection layer including a first antireflection sublayer, the first antireflection sublayer being disposed on the side surface of the second transparent conductive sublayer facing away from the first doped silicon layer, the light transmittance of the first antireflection sublayer being higher than that of the first transparent conductive layer;

[0009] The first electrode is disposed on the side surface of the first transparent conductive layer opposite to the silicon substrate.

[0010] Furthermore, in the second thickness region, the thickness of the second transparent conductive sublayer is greater than the thickness of the first antireflective sublayer.

[0011] Furthermore, the thickness ratio of the second transparent conductive layer in the second thickness region to the thickness of the first transparent conductive layer in the first thickness region is 1:1.4 to 1:2.

[0012] Furthermore, the thickness of the first transparent conductive sublayer is H1, the thickness of the first anti-reflection sublayer is H2, and the thickness of the second transparent conductive sublayer is H3, wherein H1, H2, and H3 satisfy: H3 + H2 > H1.

[0013] Furthermore, the thickness of the second transparent conductive sublayer is 50 nm to 70 nm; and / or,

[0014] The thickness of the first antireflection sublayer is 30 nm to 60 nm; and / or,

[0015] The thickness of the first transparent conductive layer is 70 nm to 110 nm.

[0016] Furthermore, the light transmittance of the first transparent conductive layer is 85%~88%; and / or,

[0017] The light transmittance of the first antireflective sublayer is 90%~95%; and / or,

[0018] The bandgap of the first transparent conductive layer is 3.5 eV to 4.5 eV; and / or,

[0019] The bandgap of the first anti-reflection sublayer is 4.6 eV to 5 eV; and / or,

[0020] The material of the first antireflection sublayer includes at least one of silicon oxide, silicon nitride, silicon oxynitride, and magnesium fluoride; and / or,

[0021] Along the thickness direction of the silicon substrate, the orthographic projection pattern of the first antireflective sublayer lies within the orthographic projection pattern of the second transparent conductive sublayer; and / or,

[0022] Along the thickness direction of the silicon substrate, the orthographic projection pattern of the first electrode is located within the orthographic projection pattern of the first transparent conductive sublayer.

[0023] Furthermore, the heterojunction solar cell further includes: a second passivation layer, a second doped silicon layer, a second transparent conductive layer, and a second electrode sequentially disposed on the back surface of the silicon substrate;

[0024] The second transparent conductive layer has a gap between its outline edge and the outline edge of the second doped silicon layer, so as to expose a portion of the second doped silicon layer; the antireflection layer further includes a second antireflection sublayer disposed on the exposed surface of the second doped silicon layer facing away from the silicon substrate.

[0025] Furthermore, along the thickness direction of the silicon substrate, the orthogonal projection width of any of the gaps is 0.1 mm to 0.6 mm; and / or,

[0026] The thickness of the second anti-reflection sublayer is less than the thickness of the first anti-reflection sublayer.

[0027] Furthermore, the silicon substrate includes a sidewall connecting the backlight surface and the light-receiving surface, and the antireflection layer further includes a third antireflection sublayer disposed on the sidewall of the silicon substrate.

[0028] Furthermore, the thickness of the third anti-reflection sublayer is less than the thickness of the first anti-reflection sublayer; and / or,

[0029] The first antireflection sublayer, the third antireflection sublayer, and the second antireflection sublayer are interconnected to form an integrated film.

[0030] Furthermore, the heterojunction solar cell further includes a second passivation layer, a first passivation layer, a first doped silicon layer, and a second doped silicon layer sequentially stacked between the sidewall and the third antireflection layer, wherein one of the first doped silicon layer and the second doped silicon layer is an N-type doped layer and the other is a P-type doped layer, and the second passivation layer is disposed on the sidewall.

[0031] Secondly, this application discloses a method for fabricating a heterojunction solar cell, which includes the following steps:

[0032] A first passivation layer is prepared on the light-receiving surface of a silicon substrate;

[0033] A first doped silicon layer is prepared on the first passivation layer;

[0034] A first transparent conductive layer is prepared on the first doped silicon layer; wherein the first transparent conductive layer includes a first thickness region and a second thickness region, a first transparent conductive sublayer is disposed on the first thickness region, a second transparent conductive sublayer is disposed on the second thickness region, and the thickness of the second transparent conductive sublayer is less than that of the first transparent conductive sublayer.

[0035] A first antireflection sublayer is prepared on the second transparent conductive sublayer in the second thickness region, wherein the light transmittance of the first antireflection sublayer is higher than that of the first transparent conductive layer;

[0036] A first electrode is fabricated on the first transparent conductive sublayer in the first thickness region;

[0037] Post-processing yields the heterojunction solar cell.

[0038] Further, the step of fabricating the first transparent conductive layer on the first doped silicon layer includes:

[0039] A first portion of a transparent conductive layer is fabricated on the first doped silicon layer:

[0040] A patterned second transparent conductive layer is fabricated on the first transparent conductive layer; wherein the region without the second transparent conductive layer is the second thickness region, and the overlapping region of the first and second transparent conductive layers is the first thickness region.

[0041] Furthermore, the parameters for preparing the first transparent conductive layer include: the target material is an ITO target, the power density is 10 W / cm to 100 W / cm, the deposition rate is 0.5 nm / s to 2 nm / s, the deposition pressure is 0.5 Pa to 1.5 Pa, and the sputtering atmosphere is Ar, H2 and O2, with the partial pressure of H2 being 0% to 4% and the partial pressure of O2 being 0% to 6%.

[0042] Furthermore, the parameters for preparing the first antireflection sublayer include: the process gases are SiH4 and N2O, the flow rate of SiH4 is 1500 sccm~3000 sccm, the flow rate of N2O is 8000 sccm~11000 sccm, the ignition power is 6000 W~8000 W, and the ignition time is 20 s~100 s.

[0043] Furthermore, a second doped silicon layer is disposed on the backlight surface of the silicon substrate;

[0044] After the step of preparing a first doped silicon layer on the first passivation layer and before the step of preparing a first transparent conductive layer on the first doped silicon layer, the preparation method further includes: preparing a second transparent conductive layer on a portion of the surface of the second doped silicon layer, wherein there is a gap between the outline edge of the second transparent conductive layer and the outline edge of the second doped silicon layer, so that another portion of the second doped silicon layer is exposed.

[0045] In the step of preparing the first anti-reflection sublayer on the second transparent conductive sublayer in the second thickness region, while preparing the first anti-reflection sublayer on the second transparent conductive sublayer, a second anti-reflection sublayer is prepared on the exposed second doped silicon layer.

[0046] Furthermore, before fabricating the first passivation layer on the light-receiving surface of the silicon substrate, the fabrication method further includes: fabricating a second passivation layer on the back-lighting surface of the silicon substrate;

[0047] After the step of preparing a first doped silicon layer on the first passivation layer and before the step of preparing a first portion of a transparent conductive layer on the first doped silicon layer, the preparation method further includes: preparing a second doped silicon layer on the second passivation layer;

[0048] A second transparent conductive layer is disposed on the backlight surface of the silicon substrate, and the post-processing step includes: fabricating a second electrode on the second transparent conductive layer.

[0049] Thirdly, embodiments of this application disclose a photovoltaic module, the photovoltaic module comprising: the solar cell described in any one of the first aspects, or the solar cell prepared by the preparation method described in any one of the second aspects.

[0050] Compared with the prior art, the beneficial effects of this application are as follows:

[0051] This application provides a heterojunction solar cell and its fabrication method, as well as a photovoltaic module. The heterojunction solar cell of this application can reduce parasitic absorption of the first transparent conductive layer in the non-electrode region, improve the absorption capacity of sunlight, and thus improve the absorption and utilization rate of sunlight by the heterojunction solar cell.

[0052] The first transparent conductive layer in the heterojunction solar cell of this application includes a first transparent conductive layer located in a first thickness region and a second transparent conductive layer located in a second thickness region. A first electrode is located on the first transparent conductive layer; that is, the position of the first thickness region corresponds to the electrode region, and the position of the second thickness region corresponds to the non-electrode region. Furthermore, by further setting the thickness of the second transparent conductive layer to be less than that of the first transparent conductive layer, this application helps to significantly reduce parasitic absorption in the non-metallic regions of the second transparent conductive layer, thereby reducing the loss of absorbed light by the second transparent conductive layer. Moreover, by further setting a first antireflection layer on the second transparent conductive layer, and the light transmittance of the first antireflection layer is higher than that of the first transparent conductive layer, the absorption and utilization rate of sunlight in the non-electrode region is thus significantly improved.

[0053] In addition, the above-mentioned configuration also helps to ensure the conductivity of the first transparent conductive layer in the electrode region, thereby achieving efficient carrier transport capability through the synergistic effect of the first and second transparent conductive layers. Attached Figure Description

[0054] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0055] Figure 1 This is a schematic diagram of the structure of the first heterojunction solar cell provided in the embodiments of this application;

[0056] Figure 2 This is a schematic diagram of the structure of the first transparent conductive layer provided in the embodiments of this application;

[0057] Figure 3 This is a schematic diagram of the structure of the first transparent conductive layer and the first antireflection sublayer provided in the embodiments of this application;

[0058] Figure 4 This is a schematic diagram of the structure of the second type of heterojunction solar cell provided in the embodiments of this application;

[0059] Figure 5 This is a schematic diagram of the structure of the third heterojunction solar cell provided in the embodiments of this application;

[0060] Figure 6 This is a schematic diagram of the structure of the fourth heterojunction solar cell provided in the embodiments of this application.

[0061] Icons: 1. Silicon substrate; 1a. Light-receiving surface; 1b. Backlight-receiving surface; 11. Sidewall; 2. First passivation layer; 3. First doped silicon layer; 4. First transparent conductive layer; 4a. First thickness region; 4b. Second thickness region; 41. First transparent conductive sublayer; 42. Second transparent conductive sublayer; 5. Antireflection layer; 51. First antireflection sublayer; 52. Second antireflection sublayer; 53. Third antireflection sublayer; 6. First electrode; 7. Second passivation layer; 8. Second doped silicon layer; 9. Second transparent conductive layer; 10. Second electrode. Detailed Implementation

[0062] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0063] In this application, the terms "upper," "lower," "left," "right," "front," "rear," "top," "bottom," "inner," "outer," "middle," "vertical," "horizontal," "lateral," and "longitudinal" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are primarily for the purpose of better describing this application and its embodiments, and are not intended to limit the indicated device, element, or component to having a specific orientation, or to be constructed and operated in a specific orientation.

[0064] Furthermore, in addition to indicating location or positional relationship, some of the aforementioned terms may also have other meanings. For example, the term "above" may also be used in some cases to indicate a certain dependency or connection relationship. Those skilled in the art can understand the specific meaning of these terms in this application based on the specific circumstances.

[0065] Furthermore, the terms "first," "second," etc., are primarily used to distinguish different devices, components, or parts (which may be the same or different in specific type and construction), and are not intended to indicate or imply the relative importance or quantity of the indicated devices, components, or parts. Unless otherwise stated, "a plurality of" means two or more.

[0066] The technical solutions provided in this application will be further described below with reference to the embodiments and accompanying drawings.

[0067] The transparent conductive layer in heterojunction solar cells has both conductive and anti-reflective functions, but its high carrier concentration easily leads to free carrier absorption (mainly in the near-infrared band), while insufficient band gap causes light absorption in the ultraviolet band. The existence of these phenomena will lead to a sharp decline in the absorption and utilization rate of sunlight.

[0068] Specifically, while increasing carrier concentration helps improve the conductivity of the film, it also leads to increased reflectivity and decreased transmittance for wavelengths greater than 1000 nm, resulting in lower utilization of incident light. Furthermore, insufficient bandgap promotes intrinsic absorption due to ultraviolet light-induced electron transitions, further reducing light transmittance and the utilization of sunlight. In addition, this phenomenon causes significant loss of short-circuit current density in heterojunction solar cells, making it difficult to effectively optimize their photoelectric conversion efficiency.

[0069] Based on the above problems, this application provides a heterojunction solar cell and its preparation method, as well as a photovoltaic module. Using this heterojunction solar cell can effectively improve the absorption and utilization rate of sunlight.

[0070] This application discloses a heterojunction solar cell, such as... Figures 1 to 3 As shown, a heterojunction solar cell includes:

[0071] A silicon substrate 1 has a light-receiving surface 1a and a back-lighting surface 1b arranged opposite to each other. A first passivation layer 2 and a first doped silicon layer 3 are also sequentially disposed on the light-receiving surface 1a.

[0072] Heterojunction solar cells also include:

[0073] The first transparent conductive layer 4 is disposed on the side surface of the first doped silicon layer 3 facing away from the silicon substrate 1. The first transparent conductive layer 4 includes a first thickness region 4a and a second thickness region 4b. A first transparent conductive sublayer 41 is disposed on the first thickness region 4a, and a second transparent conductive sublayer 42 is disposed on the second thickness region 4b. The thickness of the second transparent conductive sublayer 42 is less than that of the first transparent conductive sublayer 41.

[0074] The antireflection layer 5 includes a first antireflection sublayer 51, which is disposed on the side surface of the second transparent conductive sublayer 42 away from the first doped silicon layer 3. The light transmittance of the first antireflection sublayer 51 is higher than that of the first transparent conductive layer 4.

[0075] The first electrode 6 is disposed on the side surface of the first transparent conductive layer 41 facing away from the silicon substrate 1.

[0076] The first passivation layer 2 is made of intrinsic silicon; the first doped silicon layer 3 is made of doped polycrystalline silicon, doped amorphous silicon, or doped microcrystalline silicon. The first antireflection layer 51 is made of at least one of silicon oxide, silicon nitride, silicon oxynitride, and magnesium fluoride. When the first antireflection layer 51 is prepared using the above materials, its absorption capacity for ultraviolet light is greater than that of the first transparent conductive layer 4, which helps to optimize the ultraviolet resistance of the heterojunction solar cell and improve the photoelectric conversion efficiency of the heterojunction solar cell. Preferably, when the first antireflection layer 51 is made of silicon oxide, silicon nitride, or silicon oxynitride, it can not only improve the absorption and utilization rate of sunlight to a higher extent, but also passivate more efficiently, passivating the contact area between it and the first transparent conductive layer 4, thereby reducing the recombination of charge carriers at the interface.

[0077] The first transparent conductive layer 4 in the heterojunction solar cell of this application includes a first transparent conductive sublayer 41 located in a first thickness region 4a and a second transparent conductive sublayer 42 located in a second thickness region 4b. The first electrode 6 is located on the first transparent conductive sublayer 41; that is, the position of the first thickness region 4a corresponds to the electrode region, and the position of the second thickness region 4b corresponds to the non-electrode region. Furthermore, by further setting the thickness of the second transparent conductive sublayer 42 to be less than that of the first transparent conductive sublayer 41, this application helps to significantly reduce the parasitic absorption of the second transparent conductive sublayer 42 in non-metallic regions, thereby reducing the loss of absorbed light by the second transparent conductive sublayer 42.

[0078] Furthermore, to improve the absorption and utilization rate of sunlight, in addition to reducing the loss of absorbed light, it is also possible to reduce the damage rate of incident light. Therefore, this application further provides a first antireflective layer 51 on the second transparent conductive layer 42, and the light transmittance of the first antireflective layer 51 is higher than that of the first transparent conductive layer 4. Thus, the presence of the first antireflective layer 51 helps to reduce reflected light at the interface, thereby improving the absorption and utilization rate of sunlight in the non-electrode region to a greater extent.

[0079] In addition, the above-mentioned arrangement also helps to ensure the conductivity of the first transparent conductive layer 41 in the electrode region, thereby achieving efficient carrier transport capability under the synergistic effect of the first transparent conductive layer 41 and the second transparent conductive layer 42.

[0080] In summary, the above-mentioned configuration of this application can effectively ensure both high absorption and utilization of sunlight and the ability of charge carriers to be transported to the first electrode 6, thereby improving the absorption and utilization of sunlight to a high extent.

[0081] Furthermore, the applicant discovered that the conductivity of the first antireflective sublayer 51 is worse than that of the first transparent conductive layer 4. Therefore, the first antireflective sublayer 51 blocks the lateral transport capability of charge carriers. Thus, this application sets the thickness of the second transparent conductive sublayer 42 to be greater than the thickness of the first antireflective sublayer 51 in the second thickness region 4b. This allows the second transparent conductive sublayer 42 to fully utilize its lateral transport capability while also giving the first antireflective sublayer 51 a higher antireflection effect. Moreover, the thermal expansion coefficients of the materials of the first antireflective sublayer 51 and the transparent conductive layer differ. Therefore, by setting a thinner first antireflective sublayer 51 on the second transparent conductive sublayer 42, the thermal stress generated in the first antireflective sublayer 51 during temperature changes is reduced, avoiding excessive stress accumulation at the interface and thus preventing a decrease in interfacial adhesion.

[0082] Furthermore, the thickness ratio of the second transparent conductive layer 42 in the second thickness region 4b to the first transparent conductive layer 41 in the first thickness region 4a is 1:1.4 to 1:2. When the ratio is within the above range, the first transparent conductive layer 41 in the first thickness region 4a and the second transparent conductive layer 42 in the second thickness region 4b have a high correlation. Specifically, the above ratio helps to reduce the parasitic absorption of the second transparent conductive layer 42 and improve the absorption and utilization rate of sunlight; and it enables the second transparent conductive layer 42 to efficiently collect charge carriers from the first doped silicon layer 3 and efficiently transport the collected charge carriers to the first transparent conductive layer 41, that is, the cooperation of the two can help to improve the transport capability of charge carriers more efficiently. For example, the thickness ratio is 1:1.4, 1:1.6, 1:1.8, 1:9, or 1:2, etc.

[0083] Further, see the return Figure 3 The thickness of the first transparent conductive sublayer 41 is H1, the thickness of the first anti-reflective sublayer 51 is H2, and the thickness of the second transparent conductive sublayer 42 is H3. H1, H2, and H3 satisfy: H3 + H2 > H1.

[0084] This application, through the aforementioned arrangement, achieves a thicker layer when the first antireflective layer 51 and the second transparent conductive layer 42 are stacked in the non-metallic region. This contributes to better optical matching, broadens the spectrum of sunlight, and allows more sunlight to be absorbed and utilized, thereby improving the absorption and utilization rate of sunlight. Furthermore, because the non-metallic region is thicker than the metallic region, it provides protection to part of the side surface of the first electrode 6, preventing reactions between the first electrode 6 and substances such as oxygen and water vapor in the air. This effectively ensures the long-term stability of the first electrode 6, enabling it to collect charge carriers more effectively.

[0085] The thickness of the second transparent conductive layer 42 is 50 nm to 70 nm. When the thickness of the second transparent conductive layer 42 is within the above range, it can effectively ensure good conductivity, which in turn helps to transport charge carriers to the first transparent conductive layer 41, and also reduces parasitic absorption, thereby further improving the absorption and utilization rate of sunlight. For example, the thickness of the second transparent conductive layer 42 is 50 nm, 55 nm, 60 nm, 65 nm, 70 nm, etc.

[0086] The thickness of the first antireflective sublayer 51 is 30 nm to 60 nm. When the thickness of the first antireflective sublayer 51 is within the above range, it helps to ensure the tightness of its interface bonding with the second transparent conductive sublayer 42, and also ensures that it has a high antireflective effect. For example, the thickness of the first antireflective sublayer 51 is 30 nm, 40 nm, 50 nm, 55 nm, 60 nm, etc.

[0087] Furthermore, the thickness of the first transparent conductive sublayer 41 is 70 nm to 110 nm. A thickness within this range helps reduce the conductivity of the first transparent conductive sublayer 41, thereby facilitating carrier transport. Moreover, the thickness of the first transparent conductive sublayer 41 has a higher matching degree with the thicknesses of the first antireflection sublayer 51 and the second transparent conductive sublayer 42, further enhancing carrier transport capacity and improving the absorption and utilization rate of sunlight. For example, the thickness of the first transparent conductive sublayer 41 is 70 nm, 80 nm, 90 nm, 100 nm, 110 nm, etc.

[0088] In addition, the thickness refers to the average thickness. Taking the thickness of the first transparent conductive layer 41 as an example, it is a value obtained by calculating the thickness values ​​of the first transparent conductive layer 41 measured at multiple locations. It reflects the overall thickness level of the first transparent conductive layer 41 in the thickness direction.

[0089] Furthermore, when using an ellipsometer to test the thickness of the first transparent conductive layer 41, at least five points are taken on the first transparent conductive layer 41, and the thickness values ​​at these five points are measured respectively to obtain the average value of the measurement data. For example, an ellipsometer manufactured by Sentch GmbH, Germany, model SE-800, can be used to test the film thickness. This application does not limit the specific testing method, as long as it achieves the purpose of this application.

[0090] The first transparent conductive layer 4 has a light transmittance of 85% to 88%, and the first antireflective sublayer 51 has a light transmittance of 90% to 95%. When the light transmittance of the first antireflective sublayer 51 and the first transparent conductive layer 4 are within the above ranges, it indicates that less sunlight is reflected and scattered by the first antireflective sublayer 51. Therefore, the combined effect of the first transparent conductive layer 4 and the first antireflective sublayer 51 further helps to improve the absorption and utilization rate of sunlight by the heterojunction solar cell. For example, the light transmittance of the first transparent conductive layer 4 is 85%, 86%, 87%, 87.5%, or 88%, etc.; and the light transmittance of the first antireflective sublayer 51 is 90%, 91%, 92%, 94%, or 95%, etc.

[0091] The transmittance can be measured using an ATP9000 spectrophotometer manufactured by Aopu Tiancheng. This application does not limit the specific testing method, as long as it achieves the purpose of this application.

[0092] Furthermore, the bandgap of the first transparent conductive layer 4 is 3.5 eV to 4.5 eV; the bandgap of the first antireflective sublayer 51 is 4.6 eV to 5 eV. When the bandgap of the first transparent conductive layer 4 and the bandgap of the first antireflective sublayer 51 are within the above ranges, the higher bandgap of the first antireflective sublayer 51 helps to reduce the parasitic absorption of sunlight by the first antireflective sublayer 51. Therefore, the cooperation of the first transparent conductive layer 4 and the first antireflective sublayer 51 helps to improve the absorption and utilization rate of sunlight. For example, the bandgap of the first transparent conductive layer 4 is 3.5 eV, 3.7 eV, 3.9 eV, 4.1 eV, 4.3 eV, or 4.5 eV, etc.; the bandgap of the first antireflective sublayer 51 is 4.6 eV, 4.7 eV, 4.8 eV, 4.85 eV, or 5 eV, etc.

[0093] The bandgap width can be determined by measuring the transmittance and reflectance of the film using a Lambda 950 UV spectrophotometer manufactured by PerkinElmer, Inc., calculating the absorption from the transmittance and reflectance, and then using the Tauc Plot method (derived from UV-Vis absorption spectral data) to calculate the bandgap width. This application does not limit the specific testing method, as long as it achieves the purpose of this application.

[0094] Furthermore, along the thickness direction of silicon substrate 1 (see...) Figure 1 The orthographic projection pattern of the first antireflective sublayer 51 (in the Y direction) is located within the orthographic projection pattern of the second transparent conductive sublayer 42. The first antireflective sublayer 51 and the second transparent conductive sublayer 42 can be configured in two ways. In one optional embodiment, the area of ​​the orthographic projection pattern of the first antireflective sublayer 51 is smaller than the area of ​​the orthographic projection pattern of the second transparent conductive sublayer 42, meaning the orthographic projection pattern of the first antireflective sublayer 51 partially covers the orthographic projection pattern of the second transparent conductive sublayer 42. In another optional embodiment, the area of ​​the orthographic projection pattern of the first antireflective sublayer 51 is equal to the area of ​​the orthographic projection pattern of the second transparent conductive sublayer 42, meaning the orthographic projection patterns of the first antireflective sublayer 51 and the second transparent conductive sublayer 42 coincide. Furthermore, when their orthographic projection patterns coincide, the first antireflective sublayer 51 can function more effectively, thereby contributing to a higher level of solar energy absorption and utilization.

[0095] Furthermore, along the thickness direction of the silicon substrate 1, the orthographic projection pattern of the first electrode 6 is located within the orthographic projection pattern of the first transparent conductive sublayer 41. The arrangement of the first electrode 6 and the first transparent conductive sublayer 41 includes two implementation methods. In one optional implementation, the area of ​​the orthographic projection pattern of the first electrode 6 is smaller than the area of ​​the orthographic projection pattern of the first transparent conductive sublayer 41, meaning the orthographic projection pattern of the first electrode 6 covers a portion of the orthographic projection pattern of the first transparent conductive sublayer 41. In another optional implementation, the area of ​​the orthographic projection pattern of the first electrode 6 is equal to the area of ​​the orthographic projection pattern of the first transparent conductive sublayer 41, meaning the orthographic projection pattern of the first electrode 6 coincides with the orthographic projection pattern of the first transparent conductive sublayer 41.

[0096] Furthermore, such as Figure 4 As shown, the heterojunction solar cell further includes: a second passivation layer 7, a second doped silicon layer 8, a second transparent conductive layer 9, and a second electrode 10, which are sequentially disposed on the back surface 1b of the silicon substrate 1.

[0097] The second transparent conductive layer 9 has a gap between its outline edge and the outline edge of the second doped silicon layer 8, so that a portion of the second doped silicon layer 8 is exposed; the antireflection layer 5 also includes a second antireflection sublayer 52, which is disposed on the exposed surface of the second doped silicon layer 8 facing away from the silicon substrate 1.

[0098] Heterojunction solar cells have difficulty absorbing all incident light at once, especially low-energy light with strong penetrating power, which can easily escape through the back surface 1b of the heterojunction solar cell. Therefore, this application provides a second antireflection layer 52 in a portion of the back surface 1b. This second antireflection layer 52 can reflect the "escaped" light back into the silicon substrate 1, thereby helping to further improve the absorption and utilization rate of sunlight.

[0099] Furthermore, when the material of the second antireflection layer 52 is selected from silicon nitride, silicon oxide, silicon oxynitride, etc., the second antireflection layer 52 not only has a high reflection effect, but also has good hydrogen passivation performance, which can passivate the surface defects of the second doped silicon layer 8 and reduce the recombination of charge carriers at the interface of the second doped silicon layer 8.

[0100] Furthermore, along the thickness direction of the silicon substrate 1, the orthographic projection width of any gap is 0.1 mm to 0.6 mm. When the orthographic projection width of the gap is within the above range, the second transparent conductive layer 9 located between the gaps can effectively perform lateral transport, thereby significantly improving the carrier transport capacity; and it also helps to avoid leakage caused by the connection between the second transparent conductive layer 9 and the first transparent conductive layer 4, thereby significantly improving the photoelectric conversion efficiency of the heterojunction solar cell. For example, the orthographic projection width of any gap is 0.1 mm, 0.2 mm, 0.4 mm, 0.5 mm, or 0.6 mm, etc.

[0101] Furthermore, the thickness of the second anti-reflection sublayer 52 is less than the thickness of the first anti-reflection sublayer 51. Specifically, because the second anti-reflection sublayer 52 is thinner than the first anti-reflection sublayer 51, it experiences lower stress when responding to temperature changes. This helps reduce the interfacial stress between the second anti-reflection sublayer 52 and the second doped silicon layer 8, thereby ensuring a higher degree of interfacial adhesion.

[0102] Furthermore, such as Figure 5 As shown, the silicon substrate 1 includes a sidewall 11 connecting the backlight surface 1b and the light-receiving surface 1a, and the antireflection layer 5 also includes a third antireflection sublayer 53, which is disposed on the sidewall 11 of the silicon substrate 1.

[0103] When sunlight shines, it is not all perpendicular to the ground. Some of the light will shine onto the sidewall 11 of the silicon substrate 1. Therefore, this application provides a third antireflection layer 53 on the sidewall 11 of the silicon substrate 1, so that the sunlight shining onto the sidewall 11 can be fully utilized, thereby further improving the incident rate of sunlight.

[0104] In addition, when the third antireflection layer 53 is prepared using materials such as silicon oxide, silicon nitride, and silicon oxynitride, the third antireflection layer 53 can passivate the silicon substrate 1 by preventing epitaxial growth, thereby helping to reduce recombination of charge carriers at the interface of the sidewall 11 and improving the charge carrier transport capacity to a greater extent.

[0105] Furthermore, the thickness of the third anti-reflective sublayer 53 is less than the thickness of the first anti-reflective sublayer 51. Specifically, because the thickness of the third anti-reflective sublayer 53 is smaller than that of the first anti-reflective sublayer 51, it generates lower stress when responding to temperature changes, which helps to reduce the interfacial stress between the third anti-reflective sublayer 53 and the sidewall 11, thereby significantly improving the interfacial force.

[0106] Furthermore, the first antireflective sublayer 51, the third antireflective sublayer 53, and the second antireflective sublayer 52 are interconnected to form an integrated film layer. In this embodiment, the first antireflective sublayer 51, the third antireflective sublayer 53, and the second antireflective sublayer 52 are connected to form an integrated film layer, thus resulting in good effectiveness, high tightness, and fewer defects at the connection points between the various antireflective sublayers.

[0107] In one optional embodiment, the heterojunction solar cell further includes a second passivation layer 7, a first passivation layer 2, a first doped silicon layer 3, a second doped silicon layer 8, and a first transparent conductive layer 4, which are sequentially stacked between the sidewall 11 and the third antireflection layer 53, with the second passivation layer 7 disposed on the sidewall 11.

[0108] In another alternative implementation, such as Figure 6 As shown, the heterojunction solar cell also includes a second passivation layer 7, a first passivation layer 2, a first doped silicon layer 3, and a second doped silicon layer 8 sequentially stacked between the sidewall 11 and the third antireflection layer 53. One of the first doped silicon layer 3 and the second doped silicon layer 8 is an N-type doped layer, and the other is a P-type doped layer. The second passivation layer 7 is disposed on the sidewall 11. In this embodiment, since the first transparent conductive layer 4 is not disposed on the sidewall 11, it is more helpful in avoiding leakage caused by the connection between the first transparent conductive layer 4 and the second transparent conductive layer 9.

[0109] Among them, the second passivation layer 7 and the first passivation layer 2 have high passivation effect, which helps to achieve passivation effect on the sidewall 11 of the silicon substrate 1; and under the synergistic effect of the field passivation effect of the first doped silicon layer 3 and the second doped silicon layer 8 and the surface passivation effect of the third anti-reflection layer 53, it helps to improve the passivation performance of the sidewall 11 to a high extent.

[0110] In addition, the first passivation layer 2 includes a first passivation sublayer and a second passivation sublayer. The first passivation sublayer is disposed on the side surface of the second passivation layer 7 away from the silicon substrate 1. The first passivation sublayer is an oxygen-doped intrinsic amorphous silicon layer, and the second passivation sublayer is an oxygen-free intrinsic amorphous silicon layer.

[0111] This application provides a method for fabricating a heterojunction solar cell, which includes the following steps:

[0112] A first passivation layer is prepared on the light-receiving surface of a silicon substrate;

[0113] A first doped silicon layer is prepared on the first passivation layer;

[0114] A first transparent conductive layer is prepared on a first doped silicon layer; wherein the first transparent conductive layer includes a first thickness region and a second thickness region, a first transparent conductive sublayer is disposed on the first thickness region, a second transparent conductive sublayer is disposed on the second thickness region, and the thickness of the second transparent conductive sublayer is less than that of the first transparent conductive sublayer;

[0115] A first antireflection layer is fabricated on a second transparent conductive sublayer in a second thickness region, and the light transmittance of the first antireflection layer is higher than that of the first transparent conductive layer.

[0116] A first electrode is fabricated on a first transparent conductive layer in a first thickness region;

[0117] Post-processing yields heterojunction solar cells.

[0118] The first passivation layer comprises a first passivation sublayer and a second passivation sublayer stacked together. The first passivation sublayer is an oxygen-doped intrinsic amorphous silicon layer, and its preparation parameters include: process gases of SiH4 and N2O, pressure of 0.5 Torr to 0.7 Torr, ignition power of 1000 W to 2500 W, flow ratio of SiH4 to N2O of 1:1 / 20 to 1:1 / 10, and ignition time of 1 s to 5 s. The second passivation sublayer is an oxygen-free intrinsic amorphous silicon layer, and its preparation parameters include: process gases of SiH4 and H2, pressure of 0.5 Torr to 0.7 Torr, ignition power of 200 W to 2500 W, flow ratio of SiH4 to H2 of 1:0 to 1:25, and ignition time of 35 s to 55 s.

[0119] By controlling the preparation parameters within the above range, it is helpful to ensure that the prepared film layer has high quality and good contact with the silicon substrate, thereby ensuring the passivation effect of the first passivation layer.

[0120] In the step of preparing the first doped silicon layer, the preparation parameters include: the process gas includes SiH4, N2O, the first doped gas source and H2, and the flow rate ratio of SiH4, N2O, the first doped gas source and H2 is 1:(0~8):(0~8):(180~350), and the first doped gas source includes at least one of PH3, POCl3, P2O5 and P2O3.

[0121] In one alternative embodiment, the step of fabricating a first transparent conductive layer on a first doped silicon layer includes: fabricating a first transparent conductive layer in a first thickness region and a second thickness region, and then etching the first transparent conductive layer in the second thickness region to fabricate a second transparent conductive layer with a smaller thickness.

[0122] In another optional embodiment, the step of fabricating the first transparent conductive layer on the first doped silicon layer includes: firstly fabricating a first portion of transparent conductive layer on the first doped silicon layer, and then fabricating a patterned second portion of transparent conductive layer on the first portion of transparent conductive layer; wherein, the region without the second portion of transparent conductive layer is a second thickness region, and the overlapping region of the first portion of transparent conductive layer and the second portion of transparent conductive layer is a first thickness region. In this embodiment, the process has higher controllability, which helps to ensure the film quality of the fabricated first transparent conductive layer.

[0123] The parameters for preparing the first transparent conductive layer include: the target material is an ITO target, the power density is 10 W / cm~100 W / cm, the deposition rate is 0.5 nm / s~2 nm / s, the deposition pressure is 0.5 Pa~1.5 Pa, and the sputtering atmosphere is Ar, H2 and O2, with the partial pressure of H2 being 0%~4% and the partial pressure of O2 being 0%~6%.

[0124] By controlling the deposition pressure, power density, deposition rate, ignition time, sputtering atmosphere, and partial pressure within the above ranges, the reaction between process gases is made more complete and the reaction rate is more suitable, ensuring that the prepared film has higher density and fewer defects, thereby helping to reduce carrier recombination.

[0125] In addition, the parameters for preparing the first antireflection sublayer include: the process gases are SiH4 and N2O, the flow rate of SiH4 is 1500 sccm~3000 sccm, the flow rate of N2O is 8000 sccm~11000 sccm, the ignition power is 6000 W~8000 W, and the ignition time is 20 s~100 s.

[0126] By controlling the type and flow ratio of the process gas, the ignition power, and the ignition time within the above ranges, the reaction between the process gases is made more complete and the reaction rate is more suitable, ensuring that the prepared film has higher density and fewer defects, thereby helping to reduce carrier recombination.

[0127] Furthermore, a second doped silicon layer is disposed on the back surface of the silicon substrate;

[0128] After the step of preparing the first doped silicon layer on the first passivation layer and before the step of preparing the first transparent conductive layer on the first doped silicon layer, the preparation method further includes: preparing a second transparent conductive layer on a portion of the surface of the second doped silicon layer, wherein there is a gap between the outline edge of the second transparent conductive layer and the outline edge of the second doped silicon layer, so that another portion of the second doped silicon layer is exposed.

[0129] This application allows for the application of a photomask to be placed on the backlight surface during the fabrication of the second transparent conductive layer. The photomask's shielding effect creates a gap between the outline edge of the second transparent conductive layer and the outline edge of the second doped silicon layer, thereby helping to prevent leakage caused by the connection between the first and second transparent conductive layers. This application does not limit the specific fabrication method; any method that achieves the desired effect is acceptable.

[0130] Furthermore, in the step of preparing the first anti-reflection sublayer on the second transparent conductive sublayer in the second thickness region, the second anti-reflection sublayer is prepared on the exposed second doped silicon layer at the same time as the first anti-reflection sublayer is prepared on the second transparent conductive sublayer.

[0131] Furthermore, before fabricating the first passivation layer on the light-receiving surface of the silicon substrate, the fabrication method further includes: fabricating a second passivation layer on the back-lighting surface of the silicon substrate;

[0132] After the step of preparing a first doped silicon layer on the first passivation layer and before the step of preparing a first portion of a transparent conductive layer on the first doped silicon layer, the preparation method further includes: preparing a second doped silicon layer on the second passivation layer.

[0133] A second transparent conductive layer is provided on the backlight surface, and the post-processing steps include: fabricating a second electrode on the second transparent conductive layer.

[0134] The steps for preparing the second passivation layer include: the process gas is SiH4 and H2, the pressure is 0.3 Torr to 0.7 Torr, the ignition power is 200 W to 2500 W, the flow ratio of SiH4 to H2 is 1:(0 to 25), and the ignition time is 35 s to 85 s.

[0135] The parameters for preparing the second doped silicon layer include: the process gas includes SiH4, N2O, the second doping gas source, and H2, and the flow rate ratio of SiH4, N2O, the second doping gas source, and H2 is 1:0.1:0.2:10~1:0.5:0.8:400, and the ignition time is 220s~360s. The second doping gas source includes at least one of B2H6, BH3, BCl3, and TMB.

[0136] In addition, when preparing the first passivation layer, the second passivation layer, the first doped silicon layer, and the second doped silicon layer, the present application not only forms them on the light-receiving surface or the back-light surface of the silicon substrate, but also simultaneously forms them on the sidewalls of the silicon substrate, thereby achieving a passivation effect on the sidewalls of the silicon substrate.

[0137] The first and second electrodes can be silver electrodes or copper electrodes. When the electrodes are silver electrodes, they can be prepared using screen printing; when the electrodes are copper electrodes, they can be prepared using electroplating.

[0138] Furthermore, the third antireflective sublayer on the sidewall is also achieved simultaneously with the preparation of the first antireflective sublayer. That is, when the first antireflective sublayer is prepared, the third antireflective sublayer can be formed on the sidewall simultaneously, and the second antireflective sublayer can also be formed simultaneously in the gap of the backlight surface.

[0139] This application discloses a photovoltaic module, which includes: the solar cell described above, or a solar cell prepared by the above-described preparation method.

[0140] The technical solution of this application will be further explained below with reference to more specific embodiments and experimental test results.

[0141] Example 1:

[0142] Texturing of N-type silicon substrates.

[0143] The second passivation layer was prepared by PECVD. The process gases were SiH4 and H2, the pressure was 0.3 Torr to 0.7 Torr, the ignition power was 200 W to 2500 W, the flow ratio of SiH4 to H2 was 1:(0 to 25), and the ignition time was 35 s to 85 s. The second passivation layer was formed on the back surface and sidewalls of the silicon substrate.

[0144] A first passivation layer is prepared using PECVD, wherein the first passivation layer is formed on the light-receiving surface and sidewalls of a silicon substrate;

[0145] First, a first passivation sublayer is prepared. The process gases are SiH4 and N2O, the pressure is 0.6 Torr, the ignition power is 1500 W, the flow ratio of SiH4 to N2O is 1:0.1, and the ignition time is 3 s.

[0146] Next, a second passivation sublayer was prepared using SiH4 and H2 as process gases at a pressure of 0.6 Torr, an ignition power of 1500 W, a SiH4 to H2 flow ratio of 1:15, and an ignition time of 40 s.

[0147] A first doped silicon layer is deposited using PECVD. The second doped silicon layer is an N-type doped silicon layer. The process gases are SiH4, N2O, PH3 and H2, and the gas flow rate ratio of SiH4, N2O, PH3 and H2 is 1:(0~8):(0~8):(180~350). The first doped silicon layer is formed on the first passivation layer and the first passivation layer on the sidewall.

[0148] A second doped silicon layer, which is a P-type doped silicon layer, is deposited using PECVD. The process gases include SiH4, N2O, B2H6, and H2, with a flow rate ratio of 1:0.1:0.2:100 to 1:0.5:0.8:400. The gas pressure is 6 Torr, the ignition power is 12000 W, and the ignition time is 220 s to 360 s. The second doped silicon layer is formed on the second passivation layer and the first doped silicon layer on the sidewall.

[0149] A mask is placed on the backlight surface, and then a second transparent conductive layer is prepared on the second doped silicon layer using the PVD method, so that there is a gap between the outline edge of the second transparent conductive layer and the outline edge of the second doped silicon layer. The preparation parameters are as follows: the target material is ITO target, the power density is 60 W / cm, the deposition rate is 1 nm / s, the deposition pressure is 1.0 Pa, the sputtering atmosphere is Ar, H2 and O2, the partial pressure of H2 is 3%, the partial pressure of O2 is 3%, and the orthogonal projection width of the gap is 0.4 mm.

[0150] Remove the photomask and fabricate a first transparent conductive layer with 86% transmittance and a bandgap of 4 eV on the first doped silicon layer using the PVD method:

[0151] A first partially transparent conductive layer is prepared on a first doped silicon layer, and a patterned second partially transparent conductive layer is prepared on the first partially transparent conductive layer. The preparation parameters of the first and second partially transparent conductive layers are as follows: the target material is an ITO target, the power density is 60 W / cm, the deposition rate is 1 nm / s, the deposition pressure is 1.0 Pa, and the sputtering atmosphere is Ar, H2 and O2, with a partial pressure of 3% for H2 and 3% for O2. The thickness of the first thickness region formed by the stacking of the first partially transparent conductive layer and the second partially transparent conductive layer is 80 nm, and the thickness of the second thickness region without the second partially transparent conductive layer is 50 nm.

[0152] A first antireflection sublayer with a transmittance of 93% and a bandgap of 4.9 eV was prepared using PECVD. The process gases were SiH4 and N2O, with a SiH4 flow rate of 2000 sccm and an N2O flow rate of 9500 sccm. The ignition power was 7000 W and the ignition time was 60 s. During the preparation of the first antireflection sublayer, a third antireflection sublayer was simultaneously formed on the second doped silicon layer on the sidewall, and a second antireflection sublayer was formed at the gap of the backlight surface. The thickness of the first antireflection sublayer was 40 nm, and the thicknesses of the third and second antireflection sublayers were smaller than those of the first antireflection sublayer.

[0153] A first electrode is fabricated on a first transparent conductive layer in a first thickness region.

[0154] Post-processing involves fabricating a second electrode on the second transparent conductive layer.

[0155] Example 2:

[0156] The only difference between this embodiment and Embodiment 1 is that the thickness of the second transparent conductive sublayer and the thickness of the first antireflective sublayer are both 40 nm.

[0157] Example 3:

[0158] The only difference between this embodiment and Embodiment 1 is that the thickness of the first antireflection sublayer is 30 nm, i.e., H3 + H2 = H1.

[0159] Example 4:

[0160] The only difference between this embodiment and Embodiment 1 is that the thickness ratio of the second transparent conductive layer in the second thickness region to the first transparent conductive layer in the first thickness region is 1:2.

[0161] Example 5:

[0162] The only difference between this embodiment and Embodiment 1 is that the thickness ratio of the second transparent conductive layer in the second thickness region to the first transparent conductive layer in the first thickness region is 1:4.

[0163] Example 6:

[0164] The only difference between this embodiment and Embodiment 1 is that a second anti-reflection layer is not provided at the gap of the backlight surface.

[0165] Example 7:

[0166] The only difference between this embodiment and Embodiment 1 is that the orthographic projection width of any gap is 0.6 mm.

[0167] Example 8:

[0168] The only difference between this embodiment and Embodiment 1 is that the orthographic projection width of any gap is 0.8 mm.

[0169] Comparative Example 1:

[0170] The only difference between this comparative example and Example 1 is that this comparative example does not have a first anti-reflection layer on the second transparent conductive sublayer.

[0171] Comparative Example 2:

[0172] The only difference between this comparative example and Example 1 is that the thickness of the first transparent conductive layer and the thickness of the second transparent conductive layer in this application are the same.

[0173] Performance testing

[0174] The solar cells prepared in Examples 1 to 8 and Comparative Examples 1 to 2 were subjected to the following related tests:

[0175] This application describes the performance testing of a solar cell using a GIV-60 testing machine manufactured by Zhongsen Electric Technology Co., Ltd., covering aspects such as open-circuit voltage, short-circuit current, and fill factor. The tested solar cell has a silicon wafer size of 210 mm × 105 mm and a calibrated light intensity of 1000 ± 5 W / m². The experimental test results are shown in Table 1, which presents the performance test results of the solar cell.

[0176] Table 1 Performance test results of solar cells

[0177]

[0178] Analysis of the data from Example 1 and Comparative Example 1 shows that the photoelectric conversion efficiency of Example 1 is better than that of Comparative Example 1. It is evident that by setting the first antireflection layer on the second transparent conductive electronic layer, the first antireflection layer has higher light transmittance, thereby helping to further increase the incident rate of sunlight and thus improve the absorption and utilization rate of sunlight.

[0179] Analysis of the data from Example 1 and Comparative Example 2 shows that the photoelectric conversion efficiency of Example 2 is superior to that of Comparative Example 2. It is evident that the thickness of the second transparent conductive layer in this application is less than that of the first transparent conductive layer, resulting in less parasitic absorption in the second transparent conductive layer, thus contributing to a higher utilization rate of absorbed light. In Comparative Example 1, the thickness of the first transparent conductive layer is the same as that of the second transparent conductive layer, thereby exacerbating parasitic absorption at the second transparent conductive layer and reducing the utilization rate of absorbed light.

[0180] Analysis of the data from Examples 1 and 2 shows that the photoelectric conversion efficiency of Example 1 is better than that of Example 2. It is evident that when the thickness of the second transparent conductive layer is greater than the thickness of the first antireflective layer, the second transparent conductive layer can fully utilize its lateral transmission capability and improve light utilization; furthermore, it also ensures a tighter bond between the two layers, preventing a decrease in interfacial adhesion.

[0181] Analysis of the data from Examples 1 and 3 shows that the photoelectric conversion efficiency of Example 1 is better than that of Example 3. It is evident that when H3 + H2 > H1, this not only helps improve the absorption and utilization rate of sunlight but also enhances the structural stability of the first electrode structure, thereby further improving the carrier collection effect.

[0182] Analysis of the data from Examples 1, 4, and 5 shows that the photoelectric conversion efficiency of Examples 1 and 4 is better than that of Example 5. This indicates that the thicknesses of the first and second transparent conductive layers in Examples 1 and 4 are more suitable, and a more suitable thickness is more conducive to improving the carrier transport capability.

[0183] Analysis of the data from Examples 1 and 6 shows that the photoelectric conversion efficiency of Example 1 is better than that of Example 6. This demonstrates that by placing a second antireflective layer at the gap in the backlight surface, it is helpful to further improve the absorption and utilization rate of sunlight.

[0184] Analysis of the data from Examples 1, 7, and 8 shows that the photoelectric conversion efficiency of Examples 1 and 7 is better than that of Example 8. It is evident that the projected width of the gap in Examples 1 and 7 is more suitable. This more suitable width helps to prevent the connection between the first and second transparent conductive layers, allowing the second transparent conductive layer located between the gap to achieve a higher carrier transport capacity.

[0185] The heterojunction solar cell, its preparation method, and photovoltaic module disclosed in the embodiments of this application have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the embodiments above are only for the purpose of helping to understand the heterojunction solar cell, its preparation method, and photovoltaic module. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A heterojunction solar cell, characterized by, The heterojunction solar cell includes: A silicon substrate having a light-receiving surface and a back-lighting surface disposed opposite to each other, wherein a first passivation layer and a first doped silicon layer are sequentially disposed on the light-receiving surface, and a second passivation layer, a second doped silicon layer, a second transparent conductive layer and a second electrode are sequentially disposed on the back-lighting surface. The heterojunction solar cell also includes: A first transparent conductive layer is disposed on the side surface of the first doped silicon layer away from the silicon substrate. The first transparent conductive layer includes a first thickness region and a second thickness region. A first transparent conductive sublayer is disposed on the first thickness region, and a second transparent conductive sublayer is disposed on the second thickness region. The thickness of the second transparent conductive sublayer is less than that of the first transparent conductive sublayer. An antireflection layer, the antireflection layer including a first antireflection sublayer, the first antireflection sublayer being disposed on the side surface of the second transparent conductive sublayer facing away from the first doped silicon layer, the light transmittance of the first antireflection sublayer being higher than that of the first transparent conductive layer; The first electrode is disposed on the side surface of the first transparent conductive sublayer facing away from the silicon substrate; The second transparent conductive layer has a gap between its outline edge and the outline edge of the second doped silicon layer, so as to expose a portion of the second doped silicon layer; the antireflection layer further includes a second antireflection sublayer disposed on the exposed surface of the second doped silicon layer facing away from the silicon substrate.

2. The heterojunction solar cell according to claim 1, characterized in that, In the second thickness region, the thickness of the second transparent conductive sublayer is greater than the thickness of the first antireflective sublayer.

3. The heterojunction solar cell according to claim 1, characterized in that, The thickness ratio of the second transparent conductive layer in the second thickness region to the thickness of the first transparent conductive layer in the first thickness region is 1:1.4 to 1:

2.

4. The heterojunction solar cell according to claim 1, characterized in that, The thickness of the first transparent conductive sublayer is H1, the thickness of the first anti-reflection sublayer is H2, and the thickness of the second transparent conductive sublayer is H3. H1, H2, and H3 satisfy: H3 + H2 > H1.

5. The heterojunction solar cell according to claim 1, characterized in that, The thickness of the second transparent conductive sublayer is 50 nm to 70 nm; and / or, The thickness of the first antireflection sublayer is 30 nm to 60 nm; and / or, The thickness of the first transparent conductive layer is 70 nm to 110 nm.

6. The heterojunction solar cell according to claim 1, characterized in that, The light transmittance of the first transparent conductive layer is 85%~88%; and / or, The light transmittance of the first antireflective sublayer is 90%~95%; and / or, The bandgap of the first transparent conductive layer is 3.5 eV to 4.5 eV; and / or, The bandgap of the first anti-reflection sublayer is 4.6 eV to 5 eV; and / or, The material of the first antireflection sublayer includes at least one of silicon oxide, silicon nitride, silicon oxynitride, and magnesium fluoride; and / or, Along the thickness direction of the silicon substrate, the orthographic projection pattern of the first antireflection sublayer is located within the orthographic projection pattern of the second transparent conductive sublayer; And / or, Along the thickness direction of the silicon substrate, the orthographic projection pattern of the first electrode is located within the orthographic projection pattern of the first transparent conductive sublayer.

7. The heterojunction solar cell according to claim 1, characterized in that, Along the thickness direction of the silicon substrate, the orthogonal projection width of any of the gaps is 0.1 mm to 0.6 mm; and / or, The thickness of the second anti-reflection sublayer is less than the thickness of the first anti-reflection sublayer.

8. The heterojunction solar cell according to claim 1, characterized in that, The silicon substrate includes a sidewall connecting the backlight surface and the light-receiving surface, and the antireflection layer further includes a third antireflection sublayer disposed on the sidewall of the silicon substrate.

9. The heterojunction solar cell according to claim 8, characterized in that, The thickness of the third anti-reflection sublayer is less than the thickness of the first anti-reflection sublayer; and / or, The first antireflection sublayer, the third antireflection sublayer, and the second antireflection sublayer are interconnected to form an integrated film.

10. The heterojunction solar cell according to claim 8, characterized in that, The heterojunction solar cell further includes a second passivation layer, a first passivation layer, a first doped silicon layer, and a second doped silicon layer sequentially stacked between the sidewall and the third antireflection layer, wherein one of the first doped silicon layer and the second doped silicon layer is an N-type doped layer and the other is a P-type doped layer, and the second passivation layer is disposed on the sidewall.

11. A method for fabricating a heterojunction solar cell, characterized in that, The method for fabricating the heterojunction solar cell includes the following steps: A first passivation layer is prepared on the light-receiving surface of a silicon substrate; A first doped silicon layer is prepared on the first passivation layer; A second transparent conductive layer is formed on a portion of the surface of the second doped silicon layer on the back side of a silicon substrate, and there is a gap between the outline edge of the second transparent conductive layer and the outline edge of the second doped silicon layer, so that another portion of the second doped silicon layer is exposed. A first transparent conductive layer is prepared on the first doped silicon layer; wherein the first transparent conductive layer includes a first thickness region and a second thickness region, a first transparent conductive sublayer is disposed on the first thickness region, a second transparent conductive sublayer is disposed on the second thickness region, and the thickness of the second transparent conductive sublayer is less than that of the first transparent conductive sublayer. A first anti-reflection sublayer is prepared on the second transparent conductive sublayer, and a second anti-reflection sublayer is prepared on the exposed second doped silicon layer at the same time as the first anti-reflection sublayer is prepared. The light transmittance of the first anti-reflection sublayer is higher than that of the first transparent conductive layer. A first electrode is fabricated on the first transparent conductive sublayer in the first thickness region; Post-processing yields the heterojunction solar cell.

12. The preparation method according to claim 11, characterized in that, The step of preparing the first transparent conductive layer on the first doped silicon layer includes: A first portion of a transparent conductive layer is fabricated on the first doped silicon layer: A patterned second transparent conductive layer is fabricated on the first transparent conductive layer; wherein the region without the second transparent conductive layer is the second thickness region, and the overlapping region of the first and second transparent conductive layers is the first thickness region.

13. The preparation method according to claim 12, characterized in that, The parameters for preparing the first transparent conductive layer include: the target material is an ITO target, the power density is 10 W / cm~100 W / cm, the deposition rate is 0.5 nm / s~2 nm / s, the deposition pressure is 0.5 Pa~1.5 Pa, and the sputtering atmosphere is Ar, H2 and O2, with the partial pressure of H2 being 0%~4% and the partial pressure of O2 being 0%~6%.

14. The preparation method according to claim 11, characterized in that, The parameters for preparing the first antireflection sublayer include: the process gases are SiH4 and N2O, the flow rate of SiH4 is 1500 sccm~3000 sccm, the flow rate of N2O is 8000 sccm~11000 sccm, the ignition power is 6000 W~8000 W, and the ignition time is 20 s~100 s.

15. The preparation method according to claim 11, characterized in that, Before the first passivation layer is prepared on the light-receiving surface of the silicon substrate, the preparation method further includes: preparing a second passivation layer on the back-lighting surface of the silicon substrate; After the step of preparing a first doped silicon layer on the first passivation layer and before the step of preparing a first portion of a transparent conductive layer on the first doped silicon layer, the preparation method further includes: preparing a second doped silicon layer on the second passivation layer; A second transparent conductive layer is disposed on the backlight surface of the silicon substrate, and the post-processing step includes: fabricating a second electrode on the second transparent conductive layer.

16. A photovoltaic module, characterized in that, The photovoltaic module includes: the solar cell according to any one of claims 1 to 10, or the solar cell prepared by the preparation method according to any one of claims 11 to 15.

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