An anti-reflection film for a back contact solar cell, a method for manufacturing the same, and a back contact solar cell

Abstract

The application provides a back contact solar cell anti-reflection film, a preparation method thereof and a back contact solar cell. The anti-reflection film comprises a HfO2 layer, a TiO2 layer and a SiO2 layer which are sequentially stacked, the HfO2 layer is located on the side close to the silicon wafer of the back contact solar cell, and the refractive index of the SiO2 layer < the refractive index of the HfO2 layer < the refractive index of the TiO2 layer. The anti-reflection film provided by the application comprises the HfO2 layer, the TiO2 layer and the SiO2 layer which are stacked, through the design of the asymmetric refractive index gradient and the introduction of the HfO2 dense passivation layer, the super-low optical loss (the weighted average reflectivity is less than or equal to 1.8%), excellent surface passivation, higher long-term reliability and good low-temperature process compatibility are successfully realized, so that the multiple performance constraints of the anti-reflection film in the application of the BC cell are solved.

Description

Technical Field

[0001] This invention belongs to the field of solar cell technology, and relates to an anti-reflection film for a back-contact solar cell, and more particularly to an anti-reflection film for a back-contact solar cell, its preparation method, and the back-contact solar cell itself. Background Technology

[0002] In the field of back-contact solar cell (BC cell) technology, the core challenge in antireflective coating design lies in minimizing optical loss due to the absence of grid lines on the front side of the cell. Traditional antireflective coatings mainly consist of single-layer films (such as SiN...). x Traditional antireflective coatings, such as single-layer or double-layer films (e.g., MgF2 / ZnS layers), cannot simultaneously meet the four requirements of ultra-low reflectivity, high antireflection bandwidth, high surface passivation, and low-temperature process compatibility. Specifically, these four requirements correspond to stringent performance and process limitations. First, because the PN junction and metal electrodes of a BC cell are all located on the back side, the front side becomes a pure light absorption area. Any reflection loss will directly reduce the short-circuit current. Experimental data shows that when the average reflectivity in the 300nm~1200nm band exceeds 2.5%, the current density (Jsc) loss of the BC cell will be greater than 0.8mA / cm². 2 Second, the surface passivation quality of the front side, as the carrier generation region, is crucial to voltage performance. If the surface recombination current density is higher than 5 fA / cm², the voltage performance will be significantly affected. 2 This will cause the open-circuit voltage to drop by more than 20mV; third, the back of the BC battery has already undergone low-temperature metallization (silver paste sintering temperature <210℃) and is covered with a polymer encapsulation layer, so the front coating process must be controlled below 200℃ throughout, otherwise it may cause electrode delamination or aging failure of the encapsulation material.

[0003] To meet the requirements of low-temperature processes, existing technologies have developed SiO2 / TiO2 bilayer antireflective films based on low-temperature processes. This approach first achieves surface passivation by depositing an 80nm SiO2 layer (refractive index n≈1.46) via PECVD at temperatures below 180℃, and then reduces reflection by sputtering a 50nm TiO2 layer (refractive index n≈2.3). However, although this SiO2 / TiO2 bilayer antireflective film meets the requirements of low-temperature processes, it has a fundamental flaw.

[0004] The first defect is insufficient optical performance. Due to the "low-high-extremely high" refractive index ladder (1.46→2.3→3.8) formed between SiO2→TiO2→silicon substrate, a reflection peak (>6%) occurs in the 400nm~500nm short-wavelength region due to constructive interference. Meanwhile, in the 1000nm~1200nm long-wavelength region, the reflectivity rises to over 8% due to the mismatch between film thickness and wavelength. Simultaneously, the TiO2 prepared by low-temperature sputtering is in the anatase phase, exhibiting an absorption rate exceeding 15% in the 350nm~400nm ultraviolet band. Therefore, these two defects combined result in a weighted average reflectivity of only 2.8%, equivalent to a Jsc loss of 1.2 mA / cm² in the BC battery. 2 .

[0005] The second defect is the lack of a passivation mechanism. Because SiO2 itself has no fixed charge density, and the low-temperature PECVD process makes it difficult to release effective hydrogen atoms for passivation, the interface state density (Dit) is as high as 5 × 10⁻⁶. 11 eV -1 cm -2 More seriously, during TiO2 sputtering, high-energy particles bombard the silicon surface, causing lattice damage and a surge in the density of interfacial recombination centers, with measured J0s reaching 18 fA / cm². 2 This directly results in a Voc attenuation of more than 25mV, which is equivalent to an absolute loss of 0.6% in battery efficiency.

[0006] The third drawback is insufficient reliability, specifically, the density of the SiO2 thin film deposited by low-temperature PECVD is only 2.0 g / cm³. 3 (Confirmed by X-ray reflectance testing) With a porosity exceeding 10%, in a humid and hot environment (85℃ / 85%RH), water molecules penetrate along the pores to the TiO2 layer, triggering a hydrolysis reaction: TiO2 + H2O → TiO(OH)2, leading to film expansion and peeling. The measured reflectance increased by 1.2% after 96 hours. In addition, ultraviolet light stimulates the photocatalytic activity of anatase TiO2, decomposing the organic bonding materials at the interface and accelerating the aging of the component.

[0007] The fourth defect is process control failure. The sputtering process faces a significant shadowing effect on the 3μm~5μm pyramid textured surface, resulting in a film thickness uniformity deviation of >15%. At the same time, the high tensile stress of TiO2 and the compressive stress of SiO2 create stress superposition when the total thickness exceeds 150nm, which easily leads to the propagation of microcracks and ultimately causes the battery fragmentation rate to exceed 3%. In addition, the film thickness difference between the apex and the valley of the textured surface can also cause local reflectivity fluctuations, affecting the consistency of battery current.

[0008] It is evident that existing solutions sacrifice film quality to meet low-temperature requirements and introduce high-damage processes to reduce reflectivity, ultimately falling into a vicious cycle of mutual constraints between optical performance, passivation, and reliability.

[0009] CN113721310A discloses a wide-angle, broadband antireflective coating, including a substrate, a stack of alternating high / low refractive index films disposed on the substrate, and a nanostructured ultra-low refractive index film layer disposed on the top surface of the alternating high / low refractive index films. Based on mature thin-film deposition technology and a simple and rapid water etching method, this paper describes how to easily control the thickness and equivalent refractive index of the gradient refractive index film layer, combined with a multilayer film structure, to adjust the residual reflectivity over a wide band at large angles. This makes it suitable for large-area mass production, significantly reducing the cost of the antireflective coating and promising its widespread application in optical components, sensors, imaging optical systems, and solar cells.

[0010] CN108238727A discloses a method for preparing a silica / titanium dioxide nanoarray antireflection film, comprising the following steps: (1) preparing a silica suspension using silica particles and anhydrous ethanol; (2) pulling a cleaned glass substrate in the silica suspension at a certain pulling rate and annealing it to obtain a rough particle film; (3) preparing a saturated NaCl solution using a dilute hydrochloric acid solution containing TiCl3 and sodium chloride; (4) placing the obtained particle film tilted in the saturated NaCl solution and performing a hydrothermal reaction at a certain temperature. After reacting for a period of time, the film is removed to obtain a silica / titanium dioxide composite nanowire array antireflection film.

[0011] CN102222704A discloses a three-layer antireflective coating for crystalline silicon solar cells, which consists of three layers: the first layer is a silicon dioxide thin film on the surface of the silicon wafer, with a thickness of 20-30 nm and a refractive index of 1.15-1.25; the second layer is a composite film of titanium dioxide and silicon dioxide, with a thickness of 80-90 nm and a refractive index of 1.30-1.45; and the third layer is a nano-titanium dioxide thin film, with a thickness of 50-60 nm and a refractive index of 2.12-2.28. The first silicon dioxide thin film is prepared by thermal oxidation, while the second composite film and the third nano-titanium dioxide film are both prepared by sol-gel coating.

[0012] Existing antireflective coatings for back-contact solar cells all have certain drawbacks, including the difficulty in simultaneously achieving ultra-low optical loss, efficient surface passivation, and long-term environmental stability under low-temperature processing. Therefore, developing and designing a novel antireflective coating for back-contact solar cells and its fabrication method is crucial for back-contact solar cells. Summary of the Invention

[0013] To address the shortcomings of existing technologies, the present invention aims to provide an antireflective film for back-contact solar cells, its preparation method, and a back-contact solar cell. The antireflective film provided by the present invention includes stacked HfO2, TiO2, and SiO2 layers. Through asymmetric refractive index gradient design and the introduction of a dense HfO2 passivation layer, ultra-low optical loss (weighted average reflectivity ≤1.8%), excellent surface passivation, high long-term reliability, and good low-temperature process compatibility are successfully achieved, thereby solving the multiple performance constraints faced by antireflective films in BC cell applications.

[0014] To achieve this objective, the present invention adopts the following technical solution:

[0015] In a first aspect, the present invention provides an antireflective film for a back-contact solar cell, the antireflective film comprising an HfO2 layer, a TiO2 layer and a SiO2 layer stacked sequentially, wherein the HfO2 layer is located on the side close to the silicon wafer of the back-contact solar cell.

[0016] The refractive index of the SiO2 layer is less than the refractive index of the HfO2 layer, which in turn is less than the refractive index of the TiO2 layer.

[0017] The antireflection film of the back-contact solar cell provided by this invention employs an "asymmetric refractive index gradient," meaning that the refractive indices of the silicon wafer, HfO2 layer, TiO2 layer, and SiO2 layer are asymmetrically distributed. This design effectively eliminates the reflection peak of traditional antireflection films in the 400nm~500nm range, reducing short-wavelength reflectivity from >6% to <3%, while compressing long-wavelength reflectivity in the 1000nm~1200nm range from 8% to ≤4%. This is equivalent to designing a "gentle ramp" for light, allowing light to penetrate more easily and suppressing reflection to a very low level. Ultimately, the weighted average reflectivity across the entire 300nm~1200nm spectrum is as low as ≤1.8%. Therefore, the BC cell exhibits superior optical performance.

[0018] In the antireflection film of the back-contact solar cell provided by the present invention, the HfO2 layer, as the first film close to the silicon wafer, has a high fixed charge density and a low interface state density. It can also achieve good optical transition and passivation effects at a low temperature not higher than 200°C. This solves the problem of recombination loss on the front side of the BC cell and is compatible with the low-temperature metallization process already completed on the back side of the BC cell.

[0019] The antireflective film of the back-contact solar cell provided by this invention has a high density of HfO2 layer and an extremely low water and oxygen permeability, which can effectively block external water vapor and oxygen from corroding the internal structure of the cell. At the same time, the stable chemical properties of the HfO2 layer can suppress the performance degradation of the film layer under harsh environments such as humidity, heat, and ultraviolet radiation, thereby improving the long-term reliability of the BC cell.

[0020] The antireflective coating for the back-contact solar cell provided by this invention can be prepared using an atomic layer deposition process. The deposition rates of both the HfO2 layer and the SiO2 layer are relatively fast, which greatly improves production efficiency and reduces production costs.

[0021] In summary, the antireflective coating provided by this invention comprises stacked HfO2, TiO2, and SiO2 layers. Through asymmetric refractive index gradient design and the introduction of a dense HfO2 passivation layer, ultra-low optical loss (weighted average reflectivity ≤1.8%), excellent surface passivation, high long-term reliability, and good low-temperature process compatibility are successfully achieved, thereby solving the multiple performance constraints faced by antireflective coatings in BC battery applications.

[0022] Preferably, no intermediate layer is provided between the HfO2 layer and the TiO2 layer;

[0023] An Al2O3 transition layer is provided between the TiO2 layer and the SiO2 layer;

[0024] The surface of the SiO2 layer is a hydrophobic surface, and the contact angle of the hydrophobic surface is >105°.

[0025] In this invention, by setting an Al2O3 transition layer (refractive index 1.5~1.8) between the TiO2 layer and the SiO2 layer, and by introducing an Al2O3 transition layer with a refractive index of 1.5~1.8 as a buffer layer, and controlling the temperature to slowly cool to room temperature at a rate of 1℃ / min after deposition, the internal stress can be effectively released, thereby mitigating the risk of microcracks at the interface after cooling caused by the difference in the thermal expansion coefficient of the film.

[0026] In this invention, the surface of the SiO2 layer is hydrophobic, which helps to reduce dust adhesion to the BC battery and improve the outdoor power generation of the BC battery.

[0027] Preferably, the thickness of the Al2O3 transition layer is 2nm to 5nm, for example, it can be 2.0nm, 2.2nm, 2.4nm, 2.6nm, 2.8nm, 3.0nm, 3.2nm, 3.4nm, 3.6nm, 3.8nm, 4.0nm, 4.2nm, 4.4nm, 4.6nm, 4.8nm or 5.0nm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0028] Preferably, the thickness of the antireflective coating is 68nm~118nm;

[0029] The thickness of the HfO2 layer is 3nm~8nm;

[0030] The thickness of the TiO2 layer is 50nm~80nm;

[0031] The thickness of the SiO2 layer is 15nm~30nm.

[0032] In this invention, the thickness of the antireflective coating is 68nm~118nm, for example, it can be 68nm, 72nm, 76nm, 80nm, 84nm, 88nm, 92nm, 96nm, 100nm, 104nm, 108nm, 112nm, 116nm or 118nm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0033] In this invention, the thickness of the HfO2 layer is 3nm to 8nm, for example, it can be 3nm, 3.5nm, 4nm, 4.5nm, 5nm, 5.5nm, 6nm, 6.5nm, 7nm, 7.5nm or 8nm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable, preferably 4nm to 6nm.

[0034] In this invention, the thickness of the TiO2 layer is 50nm~80nm, for example, it can be 50nm, 52nm, 54nm, 56nm, 58nm, 60nm, 62nm, 64nm, 66nm, 68nm, 70nm, 72nm, 74nm, 76nm, 78nm or 80nm, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable, preferably 55nm~65nm.

[0035] In this invention, the thickness of the SiO2 layer is 15nm to 30nm, for example, it can be 15nm, 16nm, 17nm, 18nm, 19nm, 20nm, 21nm, 22nm, 23nm, 24nm, 25nm, 26nm, 27nm, 28nm, 29nm or 30nm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable, preferably 17nm to 23nm.

[0036] Preferably, the refractive index of the antireflective coating is 2.05-2.2;

[0037] The refractive index of the HfO2 layer is 1.9~2.1;

[0038] The refractive index of the TiO2 layer is 2.4~2.7;

[0039] The refractive index of the SiO2 layer is 1.45~1.48.

[0040] In this invention, the refractive index of the antireflective film is 2.05 to 2.2, for example, it can be 2.05, 2.06, 2.07, 2.08, 2.09, 2.10, 2.11, 2.12, 2.13, 2.14, 2.15, 2.16, 2.17, 2.18, 2.19 or 2.20, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0041] In this invention, the refractive index of the HfO2 layer is 1.9 to 2.1, for example, it can be 1.90, 1.92, 1.94, 1.96, 1.98, 2.00, 2.02, 2.04, 2.06, 2.08 or 2.10, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable. The preferred refractive index is the refractive index corresponding to a wavelength of 550 nanometers.

[0042] In this invention, the refractive index of the TiO2 layer is 2.4 to 2.7, for example, it can be 2.40, 2.42, 2.44, 2.46, 2.48, 2.50, 2.52, 2.54, 2.56, 2.58, 2.60, 2.62, 2.64, 2.66, 2.68 or 2.70, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable. The preferred refractive index is the refractive index corresponding to a wavelength of 550 nanometers.

[0043] In this invention, the refractive index of the SiO2 layer is 1.45~1.48, for example, it can be 1.45, 1.455, 1.46, 1.465, 1.47, 1.475 or 1.48, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable. The preferred refractive index is the refractive index corresponding to a wavelength of 550 nanometers.

[0044] Preferably, an Al2O3 transition layer is further provided between the TiO2 layer and the SiO2 layer.

[0045] In a second aspect, the present invention provides a method for preparing the antireflective film described in the first aspect, the method comprising:

[0046] An antireflective coating was obtained by continuously depositing HfO2, TiO2 and SiO2 layers in a single vacuum chamber using atomic layer deposition (ALD) technology.

[0047] In the method for preparing the antireflective film provided by the present invention, the HfO2 layer, TiO2 layer and SiO2 layer are deposited in the same single vacuum chamber, with no atmospheric exposure throughout the process, thus avoiding interface contamination.

[0048] Preferably, the atomic layer deposition process is carried out in a hot-wall ALD reaction chamber, with the substrate temperature controlled at 120°C to 180°C, the chamber vacuum degree ≤0.1 Torr, and the interlayer switching time ≤30 seconds.

[0049] In this invention, the atomic layer deposition process is carried out in the hot-wall ALD reaction chamber of a plate-type ALD device, which helps to ensure temperature uniformity.

[0050] In existing technologies, the back of a BC battery already has precision electrodes and a passivation layer. During coating, it is necessary to ensure that the three layers of material cover 100% only the front side. However, traditional tubular equipment causes gas to envelop the entire silicon wafer, resulting in back-side contamination and failure. Therefore, this invention uses atomic layer deposition (ALD) technology combined with an electrostatic adsorption mask scheme. By using a negatively charged mask to adsorb and shield the back of the silicon wafer, the reactive gas is vertically and directionally transported to the front of the silicon wafer, thereby achieving precise and selective deposition of the antireflection film on the front side at the atomic scale.

[0051] Preferably, in the atomic layer deposition process, a self-cleaning plasma module is integrated into the ALD equipment:

[0052] In this invention, since precursor residues (such as chlorine and carbon) can contaminate the next layer when HfO2, TiO2 and SiO2 layers are deposited consecutively, an additional step is added when switching between deposited layers: argon-oxygen mixed plasma is introduced to bombard the precursor residues from the previous layer into volatile gases and remove them.

[0053] Preferably, in the atomic layer deposition process, the hafnium source used for depositing the HfO2 layer, the titanium source used for depositing the TiO2 layer, and the silicon source used for depositing the SiO2 layer are supplied independently.

[0054] In this invention, the hafnium source used for depositing the HfO2 layer, the titanium source used for depositing the TiO2 layer, and the silicon source used for depositing the SiO2 layer are delivered independently, and the valve switching accuracy is no higher than 0.1 seconds, which can avoid cross-flow and reduce the risk of cross-contamination during multi-layer deposition.

[0055] In this invention, the substrate temperature is controlled at 120°C to 180°C during the atomic layer deposition process. For example, it can be 120°C, 125°C, 130°C, 135°C, 140°C, 145°C, 150°C, 155°C, 160°C, 165°C, 170°C, 175°C, or 180°C, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable, with 145°C to 155°C being the preferred value.

[0056] In this invention, the chamber vacuum level is controlled to be ≤0.1 Torr in the atomic layer deposition process. For example, it can be 0.01 Torr, 0.02 Torr, 0.03 Torr, 0.04 Torr, 0.05 Torr, 0.06 Torr, 0.07 Torr, 0.08 Torr, 0.09 Torr, or 0.1 Torr, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0057] In this invention, the interlayer switching time in the atomic layer deposition process is controlled to be ≤30 seconds. Controlling the interlayer switching time is used to prevent interface contamination. The interlayer switching time can be, for example, 5 seconds, 10 seconds, 15 seconds, 20 seconds, 25 seconds or 30 seconds, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0058] Preferably, the method for depositing the HfO2 layer includes: reacting Hf(NMe2)4 and H2O as precursors, and using H2O plasma with a power of 40W to 60W to enhance the reaction in the first 1 to 5 deposition cycles.

[0059] In the method of depositing the HfO2 layer in this invention, the first 1 to 5 deposition cycles are enhanced by H2O plasma with a power of 40W to 60W. The power can be, for example, 40W, 42W, 44W, 46W, 48W, 50W, 52W, 54W, 56W, 58W or 60W, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable to improve the interface passivation effect.

[0060] Preferably, the method for depositing the HfO2 layer includes a first cycle of 45 to 55 cycles, in which a 0.5s to 1s Hf(NMe2)4 pulse, a nitrogen purging of ≥5s, an H2O pulse of 0.2s to 0.5s, and a nitrogen purging of ≥5s are performed sequentially in each first cycle.

[0061] In the method of depositing the HfO2 layer in this invention, the first cycle is performed 45 to 55 times, for example, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54 or 55 times, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0062] In the method for depositing the HfO2 layer in this invention, an Hf(NMe2)4 pulse of 0.5s to 1s is performed in each first cycle. For example, it can be 0.5s, 0.55s, 0.6s, 0.65s, 0.7s, 0.75s, 0.8s, 0.85s, 0.9s, 0.95s, or 1.0s, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0063] In the method of depositing the HfO2 layer in this invention, nitrogen purging is performed for ≥5s in each first cycle, for example, 5s, 6s, 7s, 8s, 9s, 10s, 12s, 15s, 18s or 20s, but not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0064] In the method of depositing the HfO2 layer in this invention, an H2O pulse of 0.2s to 0.5s is performed in each first cycle. For example, it can be 0.2s, 0.25s, 0.3s, 0.35s, 0.4s, 0.45s or 0.5s, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0065] Preferably, the method for depositing the TiO2 layer includes: reacting TiCl4 and H2O as precursors, and after every 45-55 deposition cycles, performing an oxygen plasma treatment with a power of 80W-120W and a duration of 25s-35s (to eliminate chlorine residue and reduce light absorption).

[0066] In this invention, the method for depositing the TiO2 layer involves oxygen plasma treatment after every 45-55 deposition cycles. For example, the number of cycles could be 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, or 55, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable to eliminate chlorine residue and reduce light absorption.

[0067] In this invention, during the oxygen plasma treatment of the method for depositing the TiO2 layer, the power is 80W to 120W, for example, it can be 80W, 85W, 90W, 95W, 100W, 105W, 110W, 115W or 120W, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0068] In this invention, the oxygen plasma treatment time in the method of depositing the TiO2 layer is 25s to 35s, for example, it can be 25s, 26s, 27s, 28s, 29s, 30s, 31s, 32s, 33s, 34s ​​or 35s, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0069] Preferably, the method for depositing the TiO2 layer includes a second cycle of 290 to 310 cycles, in which a TiCl4 pulse of 0.3 to 0.8 s, a nitrogen purging of ≥5 s, an H2O pulse of 0.3 to 1 s, and a nitrogen purging of ≥5 s are performed sequentially in each second cycle.

[0070] In this invention, the method for depositing the TiO2 layer involves performing a second cycle of 290 to 310 times, for example, 290, 292, 294, 296, 298, 300, 302, 304, 306, 308, or 310 times, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0071] In the method for depositing the TiO2 layer in this invention, the duration of the TiCl4 pulse in each second cycle is 0.3s to 0.8s, for example, it can be 0.3s, 0.35s, 0.4s, 0.45s, 0.5s, 0.55s, 0.6s, 0.65s, 0.7s, 0.75s or 0.8s, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0072] In the method of depositing the TiO2 layer in this invention, the nitrogen purging time in each second cycle is ≥5s, for example, it can be 5s, 6s, 7s, 8s, 9s, 10s, 12s, 15s, 18s or 20s, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0073] In the method of depositing the TiO2 layer in this invention, the duration of the H2O pulse in each second cycle is 0.3s to 1s, for example, it can be 0.3s, 0.4s, 0.5s, 0.6s, 0.7s, 0.8s, 0.9s or 1.0s, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0074] Preferably, the method for depositing the SiO2 layer includes: reacting SiH2(Net2)2 and O3 as precursors, and after the SiO2 layer is deposited, introducing fluorosilane vapor for 20-40 seconds to hydrophobize the surface of the SiO2 layer, so that the contact angle of the surface of the hydrophobized SiO2 layer is >105°.

[0075] In the present invention, in the method of depositing the SiO2 layer, after the SiO2 layer is deposited, fluorosilane vapor (such as FDTS) is introduced for 20~40s, for example, 20s, 22s, 24s, 26s, 28s, 30s, 32s, 34s, 36s, 38s or 40s, but not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0076] In the present invention, in the method of depositing the SiO2 layer, the contact angle of the surface of the hydrophobic SiO2 layer is >105°, for example, it can be 106°, 108°, 110°, 112°, 115°, 118°, 120°, 122°, 125°, 128° or 130°, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0077] Preferably, the method for depositing the SiO2 layer is performed in a third cycle several times, wherein in each third cycle, a SiH2(Net2)2 pulse of 1s to 2s, a nitrogen purging of ≥5s, an O3 pulse of 2s to 4s, and a nitrogen purging of ≥10s are performed sequentially.

[0078] In the present invention, in the method of depositing the SiO2 layer, the time for the SiH2(Net2)2 pulse in each third cycle is 1s to 2s, for example, it can be 1.0s, 1.1s, 1.2s, 1.3s, 1.4s, 1.5s, 1.6s, 1.7s, 1.8s, 1.9s or 2.0s, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0079] In the present invention, in the method of depositing the SiO2 layer, the nitrogen purging time in each third cycle is ≥5s, for example, it can be 5s, 6s, 7s, 8s, 9s, 10s, 12s, 15s, 18s or 20s, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0080] In the method for depositing the SiO2 layer in this invention, the time for the O3 pulse in each third cycle is 2s to 4s, for example, it can be 2.0s, 2.2s, 2.4s, 2.6s, 2.8s, 3.0s, 3.2s, 3.4s, 3.6s, 3.8s or 4.0s, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0081] Preferably, the ozone concentration in the O3 pulse is ≥200 g / m³, for example, it can be 200 g / m³, 220 g / m³, 240 g / m³, 260 g / m³, 280 g / m³, 300 g / m³, 320 g / m³, 340 g / m³, 360 g / m³, 380 g / m³ or 400 g / m³, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable to ensure sufficient oxidation.

[0082] Thirdly, the present invention provides a back-contact solar cell, the back-contact solar cell comprising the anti-reflection film described in the first aspect.

[0083] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0084] Compared with the prior art, the present invention has the following beneficial effects:

[0085] (1) The antireflection film of the back contact solar cell provided by the present invention adopts an “asymmetric refractive index gradient”, that is, the refractive indices of the silicon wafer, HfO2 layer, TiO2 layer and SiO2 layer are asymmetrically distributed. This design can effectively eliminate the reflection peak of the traditional antireflection film in 400nm~500nm, reduce the short-wave reflectivity from >6% to <3%, and compress the long-wave reflectivity of 1000nm~1200nm from 8% to 4%, which is equivalent to designing a “gentle ramp” for light, making it easier for light to penetrate and the reflection is suppressed to a very low level. Finally, the weighted average reflectivity of the full spectrum of 300nm~1200nm is as low as 1.8%; therefore, the BC cell exhibits superior optical performance.

[0086] (2) In the antireflection film of the back contact solar cell provided by the present invention, the HfO2 layer, as the first film close to the silicon wafer, has a high fixed charge density and a low interface state density. It can also achieve a good passivation effect at a low temperature of no more than 200°C. This solves the problem of front recombination loss of BC cell and is compatible with the low temperature metallization process already completed on the back of BC cell.

[0087] (3) In the antireflection film of the back contact solar cell provided by the present invention, the HfO2 layer has a high density and extremely low water and oxygen permeability, which can effectively block external water vapor and oxygen from eroding the internal structure of the battery; at the same time, the stable chemical properties of the HfO2 layer can suppress the performance degradation of the film layer under harsh environments such as humid heat and ultraviolet light, thereby improving the long-term reliability of the BC battery.

[0088] (4) The antireflection film of the back contact solar cell provided by the present invention can be prepared by atomic layer deposition process. The deposition rate of HfO2 layer and SiO2 layer is relatively fast, which greatly improves production efficiency and reduces production cost.

[0089] (5) The antireflection film provided by the present invention includes HfO2 layer, TiO2 layer and SiO2 layer stacked together. Through the asymmetric refractive index gradient design and the introduction of HfO2 dense passivation layer, ultra-low optical loss (weighted average reflectivity ≤1.8%), excellent surface passivation, high long-term reliability and good low temperature process compatibility are successfully achieved, thereby solving the multiple performance constraints faced by antireflection films in BC battery applications. Attached Figure Description

[0090] Figure 1 This is a schematic diagram of the back contact solar cell structure obtained by the fabrication process in Examples 1 to 11, which includes the antireflective film provided in Examples 1 to 11.

[0091] Among them, 1-HfO2 layer; 2-TiO2 layer; 3-SiO2 layer; 4-N-type single crystal silicon wafer; 5-tunneling layer; 6-boron-doped polycrystalline silicon layer; 7-phosphorus-doped polycrystalline silicon layer; 8-SiN x Film layer; 9-Metal electrode. Detailed Implementation

[0092] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0093] The "range" disclosed in this invention can be defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of the specific range. This type of range definition can include or exclude endpoints; any endpoint can be independently included or excluded, and they can be arbitrarily combined, meaning any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60~120 and 80~110 are listed for specific parameters, it is understood that ranges of 60~110 and 80~120 are also expected. Furthermore, if minimum range values ​​1 and 2 are listed, and maximum range values ​​3, 4, and 5 are also listed, then the following ranges are all expected: 1~3, 1~4, 1~5, 2~3, 2~4, and 2~5. In this invention, unless otherwise stated, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0~5" indicates that all real numbers between "0" and "5" have been listed in this article; "0~5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is described as an integer ≥2, it is equivalent to listing integers such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc. For instance, when a parameter is described as an integer selected from "2~10", it is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0094] Unless otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form new technical solutions.

[0095] The term "embodiment" as used in this invention means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment or implementation of the invention. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a mutually exclusive, independent, or alternative embodiment. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described in this invention can be combined with other embodiments.

[0096] Those skilled in the art will understand that the order in which the steps are written in the methods of the various embodiments does not imply a strict execution order. The detailed execution order of each step should be determined by its function and possible internal logic. Unless otherwise specified, all steps of the present invention may be performed sequentially or randomly, but are preferably performed sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the method may also include step (c), meaning that step (c) can be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0097] In this invention, open-ended technical features or solutions described using terms such as "comprising" do not exclude additional members beyond those listed unless otherwise specified. They can be considered as providing both closed-ended features or solutions comprised of the listed members and open-ended features or solutions that include additional members beyond the listed members. For example, A includes a1, a2, and a3. Unless otherwise specified, it may also include other members or exclude additional members. This can be considered as providing both technical features or solutions where "A is composed of a1, a2, and a3" or "A is selected from a1, a2, and a3," and technical features or solutions where "A includes not only a1, a2, and a3, but also other members."

[0098] In this invention, the terms "first aspect," "second aspect," "third aspect," "fourth aspect," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first," "second," "third," "fourth," etc., serve only as a non-exhaustive enumeration and should be understood not to constitute a closed limitation on the quantity.

[0099] Example 1

[0100] This embodiment provides an anti-reflective film for a back-contact solar cell, such as... Figure 1 As shown, the antireflective film includes an HfO2 layer 1, a TiO2 layer 2, and a SiO2 layer 3 stacked sequentially, with the HfO2 layer 1 located on the side close to the silicon wafer of the back-contact solar cell;

[0101] No intermediate layer is provided between the HfO2 layer 1 and the TiO2 layer 2;

[0102] The refractive index of the SiO2 layer 3 is less than the refractive index of the HfO2 layer 1, which is less than the refractive index of the TiO2 layer 2.

[0103] The thickness of the antireflective coating is 85 nm; the thickness of the HfO2 layer 1 is 5 nm, the thickness of the TiO2 layer 2 is 60 nm, and the thickness of the SiO2 layer 3 is 20 nm.

[0104] The antireflective coating has a refractive index of 2.15, the HfO2 layer has a refractive index of 2.0, the TiO2 layer has a refractive index of 2.5, and the SiO2 layer has a refractive index of 1.46. The refractive index is the refractive index corresponding to a wavelength of 550 nanometers.

[0105] The method for preparing the antireflective film is as follows:

[0106] (1) Take a BC battery silicon wafer with no anti-reflective coating deposited on the front side, soak it in SC1 cleaning solution (composed of ammonia water + hydrogen peroxide + water, volume ratio of 1:1:5, temperature of 70°C) for 10 minutes to remove oil and particles; then soak it in diluted hydrofluoric acid (concentration of 1%) to dissolve the thin layer of natural oxidation on the surface; then soak it in SC2 cleaning solution (composed of hydrochloric acid + hydrogen peroxide + water, volume ratio of 1:1:6, temperature of 70°C) for 10 minutes to remove metal ion residue; after soaking, rinse it with ultrapure water and blow it dry with nitrogen to obtain the cleaned BC battery silicon wafer, and then immediately send it into the vacuum ALD coating equipment;

[0107] (2) On the front side of the cleaned BC cell silicon wafer obtained in step (1), HfO2 layer 1, TiO2 layer 2 and SiO2 layer 3 are continuously deposited in a single vacuum chamber using atomic layer deposition process to obtain an anti-reflection film (since there are no metal grid lines on the front side of the BC cell, the entire surface is flat silicon, and the anti-reflection film is deposited on the front side of the BC cell silicon wafer).

[0108] The atomic layer deposition process is carried out in a hot-wall ALD reaction chamber, with the substrate temperature controlled at 150°C, the chamber vacuum degree ≤0.1 Torr, and the interlayer switching time ≤30 seconds.

[0109] The method for depositing the HfO2 layer 1 includes: reacting Hf(NMe2)4 and H2O as precursors, and using 50W H2O plasma to enhance the reaction in the first three deposition cycles; and performing 50 first cycles in the method for depositing the HfO2 layer 1, wherein each first cycle consists of a 0.8s Hf(NMe2)4 pulse (Hf(NMe2)4 adsorbed on the surface of the BC battery silicon wafer), an 8s nitrogen purging (to remove excess gas), a 0.3s H2O pulse, and an 8s nitrogen purging.

[0110] The method for depositing the TiO2 layer 2 includes: reacting TiCl4 and H2O as precursors, and performing an oxygen plasma treatment with a power of 100W and a duration of 30s after every 50 deposition cycles (approximately 10nm); and performing 300 second cycles in the method for depositing the TiO2 layer 2, wherein each second cycle consists of a 0.5s TiCl4 pulse, an 8s nitrogen purging, a 0.6s H2O pulse, and an 8s nitrogen purging.

[0111] The method for depositing the SiO2 layer 3 includes: reacting SiH2(Net2)2 and O3 as precursors; after the SiO2 layer 3 is deposited, passing fluorosilane vapor (such as FDTS) for 30s to hydrophobize the surface of the SiO2 layer 3, so that the contact angle of the surface of the hydrophobized SiO2 layer 3 is >105°; and the method for depositing the SiO2 layer 3 includes 200 third cycles, in which a 1.5s SiH2(Net2)2 pulse, an 8s nitrogen purging, a 3s O3 pulse (ozone concentration of 200 g / m³) and a 12s nitrogen purging are performed sequentially in each third cycle.

[0112] Example 2

[0113] This embodiment provides an anti-reflective film for a back-contact solar cell, such as... Figure 1 As shown, the antireflective film includes an HfO2 layer 1, a TiO2 layer 2, and a SiO2 layer 3 stacked sequentially, with the HfO2 layer 1 located on the side close to the silicon wafer of the back-contact solar cell;

[0114] No intermediate layer is provided between the HfO2 layer 1 and the TiO2 layer 2;

[0115] The refractive index of the SiO2 layer 3 is less than the refractive index of the HfO2 layer 1, which is less than the refractive index of the TiO2 layer 2.

[0116] The thickness of the antireflective coating is 68 nm; the thickness of the HfO2 layer 1 is 3 nm, the thickness of the TiO2 layer 2 is 50 nm, and the thickness of the SiO2 layer 3 is 15 nm.

[0117] The antireflective coating has a refractive index of 2.05, the HfO2 layer has a refractive index of 1.9, the TiO2 layer has a refractive index of 2.4, and the SiO2 layer has a refractive index of 1.45. The refractive index is the refractive index corresponding to a wavelength of 550 nanometers.

[0118] The method for preparing the antireflective film is as follows:

[0119] (1) Take a BC battery silicon wafer with no anti-reflective coating deposited on the front side, soak it in SC1 cleaning solution (composed of ammonia water + hydrogen peroxide + water, volume ratio of 1:1:5, temperature of 70°C) for 10 minutes to remove oil and particles; then soak it in diluted hydrofluoric acid (concentration of 1%) to dissolve the thin layer of natural oxidation on the surface; then soak it in SC2 cleaning solution (composed of hydrochloric acid + hydrogen peroxide + water, volume ratio of 1:1:6, temperature of 70°C) for 10 minutes to remove metal ion residue; after soaking, rinse it with ultrapure water and blow it dry with nitrogen to obtain the cleaned BC battery silicon wafer, and then immediately send it into the vacuum ALD coating equipment;

[0120] (2) On the front side of the cleaned BC cell silicon wafer obtained in step (1), HfO2 layer 1, TiO2 layer 2 and SiO2 layer 3 are continuously deposited in a single vacuum chamber using atomic layer deposition process to obtain an anti-reflection film (since there are no metal grid lines on the front side of the BC cell, the entire surface is flat silicon, and the anti-reflection film is deposited on the front side of the BC cell silicon wafer).

[0121] The atomic layer deposition process is carried out in a hot-wall ALD reaction chamber, with the substrate temperature controlled at 120°C, the chamber vacuum degree ≤0.1 Torr, and the interlayer switching time ≤30 seconds.

[0122] The method for depositing the HfO2 layer 1 includes: reacting Hf(NMe2)4 and H2O as precursors, and using H2O plasma with a power of 60W to enhance the reaction in the first deposition cycle; and performing 45 first cycles in the method for depositing the HfO2 layer 1, wherein in each first cycle, a 0.5s Hf(NMe2)4 pulse (Hf(NMe2)4 adsorbed on the surface of the BC battery silicon wafer), a 5s nitrogen purging (removing excess gas), a 0.2s H2O pulse, and a 5s nitrogen purging are performed sequentially;

[0123] The method for depositing the TiO2 layer 2 includes: reacting TiCl4 and H2O as precursors, and performing an oxygen plasma treatment with a power of 120W and a duration of 35s after every 45 deposition cycles (approximately 10nm) (to eliminate chlorine residue and reduce light absorption); and performing 290 second cycles in the method for depositing the TiO2 layer 2, wherein each second cycle consists of a 0.3s TiCl4 pulse, a 5s nitrogen purging, a 0.3s H2O pulse, and a 5s nitrogen purging.

[0124] The method for depositing the SiO2 layer 3 includes: reacting SiH2(Net2)2 and O3 as precursors; after the SiO2 layer 3 is deposited, passing fluorosilane vapor (such as FDTS) for 40s to hydrophobize the surface of the SiO2 layer 3, so that the contact angle of the surface of the hydrophobized SiO2 layer 3 is >105°; and the method for depositing the SiO2 layer 3 includes 150 third cycles, in which a 1s SiH2(Net2)2 pulse, a 5s nitrogen purging, a 2s O3 pulse (ozone concentration of 200 g / m³) and a 10s nitrogen purging are performed sequentially.

[0125] Example 3

[0126] This embodiment provides an anti-reflective film for a back-contact solar cell, such as... Figure 1 As shown, the antireflective film includes an HfO2 layer 1, a TiO2 layer 2, and a SiO2 layer 3 stacked sequentially, with the HfO2 layer 1 located on the side close to the silicon wafer of the back-contact solar cell;

[0127] No intermediate layer is provided between the HfO2 layer 1 and the TiO2 layer 2;

[0128] The refractive index of the SiO2 layer 3 is less than the refractive index of the HfO2 layer 1, which is less than the refractive index of the TiO2 layer 2.

[0129] The thickness of the antireflective coating is 118 nm; the thickness of the HfO2 layer 1 is 8 nm, the thickness of the TiO2 layer 2 is 80 nm, and the thickness of the SiO2 layer 3 is 30 nm.

[0130] The antireflective coating has a refractive index of 2.2, the HfO2 layer has a refractive index of 2.1, the TiO2 layer has a refractive index of 2.7, and the SiO2 layer has a refractive index of 1.48. The refractive index is the refractive index corresponding to a wavelength of 550 nanometers.

[0131] The method for preparing the antireflective film is as follows:

[0132] (1) Take a BC battery silicon wafer with no anti-reflective coating deposited on the front side, soak it in SC1 cleaning solution (composed of ammonia water + hydrogen peroxide + water, volume ratio of 1:1:5, temperature of 70°C) for 10 minutes to remove oil and particles; then soak it in diluted hydrofluoric acid (concentration of 1%) to dissolve the thin layer of natural oxidation on the surface; then soak it in SC2 cleaning solution (composed of hydrochloric acid + hydrogen peroxide + water, volume ratio of 1:1:6, temperature of 70°C) for 10 minutes to remove metal ion residue; after soaking, rinse it with ultrapure water and blow it dry with nitrogen to obtain the cleaned BC battery silicon wafer, and then immediately send it into the vacuum ALD coating equipment;

[0133] (2) On the front side of the cleaned BC cell silicon wafer obtained in step (1), HfO2 layer 1, TiO2 layer 2 and SiO2 layer 3 are continuously deposited in a single vacuum chamber using atomic layer deposition process to obtain an anti-reflection film (since there are no metal grid lines on the front side of the BC cell, the entire surface is flat silicon, and the anti-reflection film is deposited on the front side of the BC cell silicon wafer).

[0134] The atomic layer deposition process is carried out in a hot-wall ALD reaction chamber, with the substrate temperature controlled at 180°C, the chamber vacuum degree ≤0.1 Torr, and the interlayer switching time ≤30 seconds.

[0135] The method for depositing the HfO2 layer 1 includes: reacting Hf(NMe2)4 and H2O as precursors, and using H2O plasma with a power of 40W for the first 5 deposition cycles to enhance the reaction; and performing 55 first cycles in the method for depositing the HfO2 layer 1, wherein each first cycle consists of a 1s Hf(NMe2)4 pulse (Hf(NMe2)4 adsorbed on the surface of the BC battery silicon wafer), a 10s nitrogen purging (to remove excess gas), a 0.5s H2O pulse, and a 10s nitrogen purging.

[0136] The method for depositing the TiO2 layer 2 includes: reacting TiCl4 and H2O as precursors, and performing an oxygen plasma treatment with a power of 80W and a duration of 25s after every 55 deposition cycles (approximately 10nm) (to eliminate chlorine residue and reduce light absorption); and performing 310 second cycles in the method for depositing the TiO2 layer 2, wherein each second cycle consists of a 0.8s TiCl4 pulse, a 10s nitrogen purging, a 1s H2O pulse, and a 10s nitrogen purging.

[0137] The method for depositing the SiO2 layer 3 includes: reacting SiH2(Net2)2 and O3 as precursors; after the SiO2 layer 3 is deposited, introducing fluorosilane vapor (such as FDTS) for 20s to hydrophobize the surface of the SiO2 layer 3, so that the contact angle of the surface of the hydrophobized SiO2 layer 3 is >105°; and the method for depositing the SiO2 layer 3 includes 300 third cycles, in which a 2s SiH2(Net2)2 pulse, a 10s nitrogen purging, a 4s O3 pulse (ozone concentration of 210 g / m³) and a 15s nitrogen purging are performed sequentially in each third cycle.

[0138] Example 4

[0139] This embodiment provides an antireflection film for a back-contact solar cell, wherein an Al2O3 transition layer with a thickness of 3nm is provided between the TiO2 layer 2 and the SiO2 layer 3.

[0140] In step (2) of the method for preparing the antireflective film, an Al2O3 transition layer needs to be deposited between the TiO2 layer 2 and the SiO2 layer 33. The method for depositing the Al2O3 transition layer is atomic layer deposition (ALD). ALD can provide atomic-level thickness control and excellent step coverage, and is particularly suitable for preparing ultrathin transition layers.

[0141] Example 5

[0142] This embodiment provides an antireflective film for a back-contact solar cell, except that the surface of the SiO2 layer 3 is an unhydrophobic surface, and the contact angle of the unhydrophobic surface is 30°;

[0143] That is, omitting step (2) of the method for preparing the antireflective film, except for "after the SiO2 layer 3 is deposited, fluorosilane vapor (such as FDTS) is introduced for 30s to hydrophobize the surface of the SiO2 layer 3 so that the contact angle of the surface of the hydrophobized SiO2 layer 3 is >105°", the rest is the same as in Example 1.

[0144] Example 6

[0145] This embodiment provides an antireflective coating for a back-contact solar cell. Except that the thickness of the HfO2 layer 1 is 1 nm, and the thicknesses of the TiO2 layer 2 and SiO2 layer 3 are increased proportionally to keep the thickness of the antireflective coating constant, the rest is the same as in Embodiment 1.

[0146] Example 7

[0147] This embodiment provides an antireflection film for a back-contact solar cell. Except that the thickness of the HfO2 layer 1 is 12nm, and the thicknesses of the TiO2 layer 2 and SiO2 layer 3 are reduced proportionally to keep the thickness of the antireflection film unchanged, the rest is the same as in Embodiment 1.

[0148] Example 8

[0149] This embodiment provides an antireflective coating for a back-contact solar cell, wherein the refractive index of the antireflective coating is 2.12 and the refractive index of the HfO2 layer is 1.6;

[0150] In step (2) of the method for preparing the antireflective film, except for adjusting the substrate temperature to 90°C during the deposition of the HfO2 layer 1, everything else is the same as in Example 1.

[0151] Example 9

[0152] This embodiment provides an antireflective coating for a back-contact solar cell. Except that the refractive index of the antireflective coating is 2.18 and the refractive index of the HfO2 layer is 2.3, all other aspects are the same as in Embodiment 1.

[0153] In step (2) of the method for preparing the antireflective film, except for the substrate temperature being adjusted to 300°C during the deposition of the HfO2 layer 1, the rest is the same as in Example 1.

[0154] Example 10

[0155] This embodiment provides an antireflection film for a back-contact solar cell. Except for step (2) of the preparation method of the antireflection film, in which "the first 1 to 5 deposition cycles are enhanced by H2O plasma with a power of 40W to 60W", the rest is the same as in Example 1.

[0156] Example 11

[0157] This embodiment provides an antireflection film for a back-contact solar cell. Except for omitting step (2) of the antireflection film preparation method, in which "after every 45-55 cycles (approximately 10 nm) of depositing the TiO2 layer 2, an oxygen plasma treatment with a power of 80W-120W and a duration of 25s-35s is performed", the rest is the same as in Example 1.

[0158] Comparative Example 1

[0159] This comparative example provides an antireflective coating for a back-contact solar cell, the antireflective coating comprising a stacked Al2O3 layer and a SiN layer. x The Al2O3 layer is located on the side of the silicon wafer that is in contact with the solar cell;

[0160] The antireflective coating has a thickness of 95 nm, the Al2O3 layer has a thickness of 15 nm, and the SiN layer has a thickness of 15 nm. x The layer thickness is 80 nm;

[0161] The antireflective coating has a refractive index of 2.1, the Al2O3 layer has a refractive index of 1.62, and the SiN... x The refractive index of the layer is 2.05;

[0162] The method for preparing the antireflective film is as follows:

[0163] First, an Al2O3 layer was prepared using atomic layer deposition (ALD) with trimethylaluminum (TMA) as the aluminum source and ozone (O3) as the oxygen source, and the deposition temperature was controlled at 220°C. Subsequently, SiN was prepared on the Al2O3 layer using plasma-enhanced chemical vapor deposition (PECVD). x The film layer uses silane (SiH4) and ammonia (NH3) as reactant gases and nitrogen (N2) as carrier gas. Plasma is excited by a high-low frequency hybrid power supply at a temperature of 400℃ for deposition, and the film properties are adjusted by controlling the gas flow ratio.

[0164] Application Example 1

[0165] This application example provides a way to... Figure 1 The fabrication process of the back-contact solar cell shown is as follows:

[0166] (1) Polishing treatment: Polish both sides of the N-type single crystal silicon wafer 4 to obtain a clean and flat initial surface; then place the polished N-type single crystal silicon wafer 4 in a high-temperature oxidation equipment and use a rapid thermal oxidation process at 850°C to grow a silicon dioxide film with a thickness of 1.5nm, thereby preparing a tunneling layer 5 on the surface of the N-type single crystal silicon wafer 4 (the core function is to allow charge carriers (electrons or holes) to pass through through the quantum tunneling effect, while perfectly passivating the silicon surface and suppressing recombination).

[0167] (2) Preparation of LP1-poly layer by LPCVD: Using a low-pressure chemical vapor deposition (LPCVD) equipment, with silane (SiH4) as the silicon source, a polycrystalline silicon layer (defined as LP1-poly) with a thickness of 80-120 nm is deposited under process conditions of 650-750℃ and 10-50 Pa. This layer is required to have uniform thickness and good crystal quality, so as to provide a basis for subsequent P-type doping.

[0168] (3) Boron and carbon diffusion: Boron and carbon diffusion is carried out by thermal diffusion process. The silicon wafer is placed in a high-temperature diffusion furnace containing borane (such as boron tribromide (BBr3) and boron trichloride (BCl3)) and carbon sources (such as methane (CH4), ethane (C2H6), tetramethylsilane (Si(CH3)4)) and oxygen sources (nitrous oxide (N2O), oxygen (O2), ozone (O3), etc.). At a temperature of 850~950℃, boron and carbon atoms are uniformly diffused into the LP1-poly layer through gaseous source diffusion to obtain boron-doped polycrystalline silicon layer 6, forming a P-type semiconductor region. By precisely controlling the diffusion time (20-40 minutes) and gas flow rate, the doping effect of the target sheet resistance of 80120Ω / □ is achieved.

[0169] (4) Laser 1 open N+gap region: The operation is performed using a DIL laser with a laser spot size of 150um×150um, a spot spacing of 30~130um, an overlap rate of 30~80%, a speed of 20000~50000mm / s, a frequency of 300~1000kHz, a power of 20~70W, a single pulse energy of 70~120uJ, and a pulse width of 0.5~1.5us;

[0170] (5) Mask removal + etching: Wet etching process is adopted, using a mixed solution of hydrofluoric acid (HF) and nitric acid (HNO3) to remove the mask layer on the front and side of the battery, while slightly etching the silicon wafer surface to remove the damaged layer and residual impurities generated during laser etching; the etching time is controlled at 3-5 minutes to ensure that the surface is clean and there is no over-etching.

[0171] (6) Second LPCVD preparation of LP2-poly layer: Using a low-pressure chemical vapor deposition (LPCVD) device, with silane (SiH4) as the silicon source, a polycrystalline silicon layer (LP2-poly) with a thickness of 80-120nm is deposited under the conditions of 650~750℃ and 10~50Pa pressure. This layer needs to have a uniform thickness and good crystal quality to ensure the uniformity of doping and provide a foundation for subsequent doping processes.

[0172] (7) Place the silicon wafer in a high-temperature diffusion furnace containing phosphorus doping source: phosphine (PH3) or phosphorus oxychloride (POCl3), carbon doping source: methane (CH4), ethane (C2H6) or tetramethylsilane (Si(CH3)4), oxygen source (nitrous oxide (N2O), oxygen (O2), ozone (O3), etc.), and perform phosphorus diffusion at a temperature of 800~900℃ to obtain phosphorus-doped polycrystalline silicon layer 7, forming an N-type semiconductor region corresponding to the boron doped region; by controlling the diffusion conditions, the sheet resistance of this region reaches 30-50Ω / □, forming a good PN junction with the P-type region;

[0173] (8) Laser 2-open P+gap region: using Dier laser operation, laser spot size 150um×150um, spot spacing 30~130um, overlap rate 20~70%, speed 40000~80750mm / s, frequency 300~807kHz, power 30~60W, single pulse energy 50~90uJ, pulse width 0.5~1.5us;

[0174] (9) A process combining wet etching and chemical texturing is adopted: First, a mixed solution of sodium hydroxide (NaOH) and isopropanol (IPA) is used for etching to remove the surface damage layer and form a pyramid-shaped textured surface structure. The etching time is 10-15 minutes, and the average height of the pyramid is controlled at 1-2 μm to improve the light absorption efficiency. Then, surface cleaning and drying are performed to ensure that the surface is clean and free of contamination.

[0175] (10) The antireflective film provided in Example 1 was prepared using the method for preparing the antireflective film provided in Example 1;

[0176] (11) PECVD coating: Plasma-enhanced chemical vapor deposition (PECVD) coating is performed on the back side, using silane (SiH4) and ammonia (NH3) as precursors to deposit SiN. x Film layer 8, with a thickness of 60~100nm, serves as passivation and anti-reflection;

[0177] (12) Electrode preparation and sintering stage: silver paste, aluminum paste, copper paste, copper-clad silver paste, tin paste, etc. are printed using screen printing process to form the metal electrode 9 of the battery;

[0178] (13) Sintering: The printed solar cells are placed in a high-temperature sintering furnace and rapidly sintered at a temperature of 750~850℃ to melt the glass powder in the electrode paste, thereby achieving a firm bond between the electrode and the silicon wafer and forming a good ohmic contact. The heating rate, peak temperature and cooling rate must be strictly controlled during the sintering process to ensure that the solar cells are not deformed and the electrodes do not fall off, thus completing the preparation of the BC solar cell.

[0179] Application Example 2

[0180] This application example provides a fabrication process for a back-contact solar cell. Except for replacing "the anti-reflection film provided in Example 1 is prepared by the method of preparing the anti-reflection film provided in Example 1" in step (10) with "the anti-reflection film provided in Example 2 is prepared by the method of preparing the anti-reflection film provided in Example 2", the rest is the same as application example 1.

[0181] Application Example 3

[0182] This application example provides a fabrication process for a back-contact solar cell. Except for replacing "the anti-reflection film provided in Example 1 is prepared by the method of preparing the anti-reflection film provided in Example 1" in step (10) with "the anti-reflection film provided in Example 3 is prepared by the method of preparing the anti-reflection film provided in Example 3", the rest is the same as application example 1.

[0183] Application Example 4

[0184] This application example provides a fabrication process for a back-contact solar cell. Except for replacing "the anti-reflection film provided in Example 1 is prepared by the method of preparing the anti-reflection film provided in Example 1" in step (10) with "the anti-reflection film provided in Example 4 is prepared by the method of preparing the anti-reflection film provided in Example 4", the rest is the same as application example 1.

[0185] Application Example 5

[0186] This application example provides a fabrication process for a back-contact solar cell. Except for replacing "the anti-reflection film provided in Example 1 is prepared by the method of preparing the anti-reflection film provided in Example 1" in step (10) with "the anti-reflection film provided in Example 5 is prepared by the method of preparing the anti-reflection film provided in Example 5", the rest is the same as application example 1.

[0187] Application Example 6

[0188] This application example provides a fabrication process for a back-contact solar cell. Except for replacing "the anti-reflection film provided in Example 1 is prepared by the method of preparing the anti-reflection film provided in Example 1" in step (10) with "the anti-reflection film provided in Example 6 is prepared by the method of preparing the anti-reflection film provided in Example 6", the rest is the same as application example 1.

[0189] Application Example 7

[0190] This application example provides a fabrication process for a back-contact solar cell. Except for replacing "the anti-reflection film provided in Example 1 is prepared by the method of preparing the anti-reflection film provided in Example 1" in step (10) with "the anti-reflection film provided in Example 7 is prepared by the method of preparing the anti-reflection film provided in Example 7", the rest is the same as application example 1.

[0191] Application Example 8

[0192] This application example provides a fabrication process for a back-contact solar cell. Except for replacing "the anti-reflection film provided in Example 1 is prepared by the method of preparing the anti-reflection film provided in Example 1" in step (10) with "the anti-reflection film provided in Example 8 is prepared by the method of preparing the anti-reflection film provided in Example 8", the rest is the same as application example 1.

[0193] Application Example 9

[0194] This application example provides a fabrication process for a back-contact solar cell. Except for replacing "the anti-reflection film provided in Example 1 is prepared by the method of preparing the anti-reflection film provided in Example 1" in step (10) with "the anti-reflection film provided in Example 9 is prepared by the method of preparing the anti-reflection film provided in Example 9", the rest is the same as application example 1.

[0195] Application Example 10

[0196] This application example provides a fabrication process for a back-contact solar cell. Except for replacing "the anti-reflection film provided in Example 1 is prepared by the method of preparing the anti-reflection film provided in Example 1" in step (10) with "the anti-reflection film provided in Example 10 is prepared by the method of preparing the anti-reflection film provided in Example 10", the rest is the same as application example 1.

[0197] Application Example 11

[0198] This application example provides a fabrication process for a back-contact solar cell. Except for replacing "the anti-reflection film provided in Example 1 is prepared by the method of preparing the anti-reflection film provided in Example 1" in step (10) with "the anti-reflection film provided in Example 11 is prepared by the method of preparing the anti-reflection film provided in Example 11", the rest is the same as application example 1.

[0199] Comparative Application Example 1

[0200] This comparative application example provides a fabrication process for a back-contact solar cell. Except for replacing "the anti-reflection film provided in Example 1 is prepared by the method of preparing the anti-reflection film provided in Example 1" in step (10) with "the anti-reflection film provided in Comparative Example 1 is prepared by the method of preparing the anti-reflection film provided in Comparative Example 1", the rest is the same as application example 1.

[0201] The back-contact solar cells obtained by the fabrication processes provided in the above application examples and comparative application examples were subjected to passivation performance tests, electrical performance tests, appearance morphology tests, PID tests, and UV aging tests.

[0202] The passivation performance testing method is as follows: photoluminescence (PL) and dark-state lifetime tests are used. The IV curve is measured under an AM1.5G solar simulator, and the minority carrier lifetime is measured using quasi-steady-state photoconductivity (QSSPC). Interface state parameters are extracted through a transmission line model (TLM) structure. The temperature is controlled at 25℃, humidity <30%RH, voltage scan rate is 10mV / s, and light intensity is 100mW / cm². 2 The interface state density, fixed charge density and surface recombination current obtained by the test are shown in Table 1.

[0203] The electrical performance testing method was as follows: The test was conducted under standard test conditions (STC), using the Wavelabs solar simulator to provide the AM1.5G spectrum, with the irradiance controlled at 1000 W / m². 2 The transverse resistance was measured using the four-probe method at a temperature of 25℃, and key parameters were obtained from the IV characteristic curve. The preheating time was controlled at 30 minutes, the scan interval at 10ms, and the voltage range at -0.5V to +1.2V. The average reflectivity, short-circuit current, and open-circuit voltage were obtained as shown in Table 2.

[0204] The method for testing the appearance morphology was as follows: a white light interferometer (accuracy 0.1 nm) and a spectrophotometer (accuracy ΔE ≤ 0.05) were used to detect the three-dimensional morphology of the film layer, and the textured surface structure characteristics were observed using a high-magnification microscope. The tests were conducted in a dust-free environment with an ambient temperature of 25℃, a relative humidity of 50%, and a light source wavelength of 550 nm. The film thickness uniformity (textured surface), surface roughness, and film transmittance color difference are shown in Table 3.

[0205] The PID test method is as follows: According to the IEC62804 standard, the back contact solar cell is placed in an environmental chamber with a temperature of 85℃ and a relative humidity of 85%, and a reverse bias voltage of 1000V is applied for 96 hours. The electrical performance parameters are measured before and after the test. The power decay and appearance failure points are shown in Table 4.

[0206] The UV aging test method is as follows: according to the IEC61215 standard, the module is subjected to a UV aging test at a wavelength of 340nm with a current of 0.76W / m. 2 The film was continuously irradiated for 500 hours, and the reflectance shift and film pulverization were tested and shown in Table 5.

[0207] Table 1

[0208]

[0209] Table 2

[0210]

[0211] Table 3

[0212]

[0213] Table 4

[0214]

[0215] Table 5

[0216]

[0217] From Tables 1 to 5, we can obtain:

[0218] (1) The back-contact solar cells obtained by the fabrication process provided in Examples 1 to 3 exhibit excellent overall performance;

[0219] (2) By comparing application example 1 and application example 4, it can be seen that in this invention, by setting an Al2O3 transition layer (refractive index 1.5~1.8) between TiO2 layer 2 and SiO2 layer 3, by introducing an Al2O3 transition layer with a refractive index of 1.5~1.8 as a buffer layer, and controlling the temperature to be slowly cooled to room temperature at a rate of 1℃ / min after deposition, the internal stress can be effectively released, thereby reducing the risk of microcracks generated at the interface after cooling caused by the difference in the thermal expansion coefficient of the film.

[0220] (3) By comparing application example 1 and application example 5, it can be seen that in this invention, the surface of SiO2 layer 3 is hydrophobic, which is beneficial to reduce dust adhesion of BC battery and improve outdoor power generation of BC battery.

[0221] (4) By comparing Application Example 1 with Application Examples 6 and 7, it can be seen that in this invention, when the thickness of HfO2 layer 1 is 3nm~8nm, the back contact solar cell exhibits better overall performance. This is because the HfO2 layer needs to reach a critical thickness of about 3nm to form a continuous, pinhole-free film, thereby uniformly exerting its high fixed negative charge passivation effect and avoiding island growth and passivation degradation due to excessive thinness. At the same time, in the range of 3nm~8nm, HfO2 can work with TiO2 layer and SiO2 layer to achieve wide-spectrum destructive interference. If it is too thick, it will destroy the phase matching and lead to enhanced reflection. Furthermore, if the film is too thick, it will destroy the stability of the multilayer film system due to excessive compressive stress.

[0222] (5) By comparing Application Example 1 with Application Examples 8 and 9, it can be seen that in this invention, when the refractive index of the SiO2 layer 3 is less than the refractive index of the HfO2 layer 1 and less than the refractive index of the TiO2 layer 2, and the refractive index of the HfO2 layer is further limited to 1.9~2.1, the back contact solar cell exhibits better overall performance. This is because this refractive index range makes the HfO2 layer the best "optical impedance converter" between the SiO2 layer and the TiO2 layer, achieving a smooth transition at the interface to minimize reflection. At the same time, the refractive index of 1.9~2.1 corresponds to amorphous, dense, and high-quality thin film with close stoichiometry, avoiding the thin film porosity / impurity residue implied by too low a refractive index, or the crystallization / increased oxygen vacancies implied by too high a refractive index, thereby ensuring the optimal dielectric performance and passivation characteristics.

[0223] (6) By comparing Application Example 1 and Application Example 10, it can be seen that in the present invention, when depositing the HfO2 layer 1, the first 1 to 5 deposition cycles use H2O plasma with a power of 40W to 60W to enhance the reaction, and the back contact solar cell exhibits better overall performance. This is because the process is essentially a precise "atomic-level engineering" at the silicon interface, establishing a near-perfect chemical interface in the first few atomic layers of the thin film growth, thereby laying the foundation for the subsequent growth of the entire high-quality passivation layer and avoiding the decline in battery performance due to interface quality deterioration.

[0224] (7) By comparing Application Example 1 and Application Example 11, it can be seen that in the present invention, when depositing the TiO2 layer 2, after every 45-55 deposition cycles, an oxygen plasma treatment with a power of 80W~120W and a duration of 25s~35s is performed. The back contact solar cell exhibits better overall performance. This is because this treatment, as a precise "in-situ repair and nano-annealing" process, can periodically repair film defects and optimize the structure during low-temperature growth, thereby ensuring that the final TiO2 layer has "high light transmittance" and "low defect density", avoiding the degradation of the optical and electrical performance of the battery due to the decline in film quality.

[0225] (8) By comparing Application Example 1 with Comparative Application Example 1, it can be seen that in terms of passivation performance, the film formed in Example 1 (HfO2 / TiO2 / SiO2) at 180℃ has a lower interface state density (3×10⁻⁶). 10 cm -2 ·eV -1 Comparative Example 1 (8×10) 10 cm -2 ·eV -1 The charge density is significantly reduced, and high-temperature annealing is not required; the fixed charge density (-1×10) 13 cm -2 Compared to Comparative Example 1 (+5×10) 12 cm -2 The value doubles, resulting in a stronger passivation effect; surface recombination current (4fA / cm) 2 Comparative Example 1 (8fA / cm) 2 Reduced by 50%;

[0226] In terms of electrical performance, the average reflectivity of Application Example 1 (1.80%) was significantly lower than that of Comparative Application Example 1 (4.2%), optical loss was reduced by 57%, and short-circuit current (43.6 mA / cm²) was reduced to 1.5 mA / cm². 2 The absolute gain increases the open-circuit voltage (753mV) by 6mV;

[0227] In terms of appearance and morphology, the film thickness uniformity (±3.5%) of Application Example 1 was improved by 56% compared with Comparative Application Example 1 (±8%), the surface roughness (1.8nm) was reduced by 49%, the film transmittance color difference (ΔE=0.4) was significantly improved compared with Comparative Example 1 (ΔE=2.1), and the appearance consistency was improved by 81%.

[0228] In the PID test, the power attenuation of Application Example 1 was only 0.80%, which was much lower than the 3.5% of the comparison Application Example 1, and there were no visual failure points such as yellowing at the edges.

[0229] In the UV aging test, the reflectance shift of Application Example 1 (0.20%) was much lower than that of the control Application Example 1 (1.2%), and there was no film powdering phenomenon, demonstrating excellent long-term stability.

[0230] (9) By comparing Application Example 1 with Comparative Application Example 1, it can be seen that the antireflection film of the back contact solar cell provided by the present invention adopts an "asymmetric refractive index gradient", that is, the refractive indices of silicon wafer, HfO2 layer 1, TiO2 layer 2 and SiO2 layer 3 are asymmetrically distributed. This design can effectively eliminate the reflection peak of traditional antireflection film in 400nm~500nm, reduce short-wave reflectivity from >6% to <3%, and compress long-wave reflectivity in 1000nm~1200nm from 8% to ≤4%, which is equivalent to designing a "gentle ramp" for light, making it easier for light to penetrate and reducing reflection to a very low level. Ultimately, the weighted average reflectivity of the full spectrum in 300nm~1200nm is as low as ≤1.8%. Therefore, the BC cell exhibits superior optical performance.

[0231] In the antireflection film of the back contact solar cell provided by the present invention, the HfO2 layer 1, as the first film close to the silicon wafer, has a high fixed charge density and a low interface state density. It can also achieve good optical transition and passivation effects at a low temperature of no more than 200°C. This solves the problem of recombination loss on the front side of the BC cell and is compatible with the low-temperature metallization process already completed on the back side of the BC cell.

[0232] In the antireflective film of the back contact solar cell provided by the present invention, the HfO2 layer 1 has a high density and extremely low water and oxygen permeability, which can effectively block the corrosion of the internal structure of the battery by external water vapor and oxygen; at the same time, the stable chemical properties of the HfO2 layer 1 can suppress the performance degradation of the film layer under harsh environments such as humid heat and ultraviolet radiation, thereby improving the long-term reliability of the BC battery.

[0233] The antireflection film for the back-contact solar cell provided by this invention can be prepared using an atomic layer deposition process. The deposition rates of both HfO2 layer 1 and SiO2 layer 3 are relatively fast, which greatly improves production efficiency and reduces production costs.

[0234] In summary, the antireflective film provided by this invention includes a stacked HfO2 layer 1, TiO2 layer 2, and SiO2 layer 3. Through the asymmetric refractive index gradient design and the introduction of a dense HfO2 passivation layer, ultra-low optical loss (weighted average reflectivity ≤1.8%), excellent surface passivation, high long-term reliability, and good low-temperature process compatibility are successfully achieved, thereby solving the multiple performance constraints faced by antireflective films in BC battery applications.

[0235] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. An anti-reflective film for a back-contact solar cell, characterized in that, The antireflective coating comprises an HfO2 layer, a TiO2 layer, and a SiO2 layer stacked sequentially, with the HfO2 layer located on the side close to the silicon wafer of the back-contact solar cell. The refractive index of the SiO2 layer is less than the refractive index of the HfO2 layer, which in turn is less than the refractive index of the TiO2 layer.

2. The antireflective film according to claim 1, characterized in that, No intermediate layer is provided between the HfO2 layer and the TiO2 layer; An Al2O3 transition layer is provided between the TiO2 layer and the SiO2 layer; The surface of the SiO2 layer is a hydrophobic surface, and the contact angle of the hydrophobic surface is >105°.

3. The antireflective film according to claim 1, characterized in that, The thickness of the antireflective coating is 68nm~118nm; The thickness of the HfO2 layer is 3nm~8nm; The thickness of the TiO2 layer is 50nm~80nm; The thickness of the SiO2 layer is 15nm~30nm.

4. The antireflective film according to claim 1, characterized in that, The antireflective coating has a refractive index of 2.05 to 2.2; The refractive index of the HfO2 layer is 1.9~2.1; The refractive index of the TiO2 layer is 2.4~2.7; The refractive index of the SiO2 layer is 1.45~1.

48.

5. A method for preparing the antireflective film according to any one of claims 1 to 4, characterized in that, The preparation method includes: An antireflective coating was obtained by continuously depositing HfO2, TiO2 and SiO2 layers in a single vacuum chamber using atomic layer deposition (ALD) technology.

6. The preparation method according to claim 5, characterized in that, The atomic layer deposition process is carried out in a hot-wall ALD reaction chamber, with the substrate temperature controlled at 120℃~180℃, the chamber vacuum degree ≤0.1Torr, and the interlayer switching time ≤30 seconds.

7. The preparation method according to claim 5 or 6, characterized in that, The method for depositing the HfO2 layer includes: reacting Hf(NMe2)4 and H2O as precursors, and using H2O plasma with a power of 40W to 60W to enhance the reaction in the first 1 to 5 deposition cycles.

8. The preparation method according to claim 5 or 6, characterized in that, The method for depositing the TiO2 layer includes: reacting TiCl4 and H2O as precursors, and after every 45-55 cycles (approximately 10 nm) of deposition, performing an oxygen plasma treatment with a power of 80W-120W and a duration of 25s-35s (to eliminate chlorine residue and reduce light absorption).

9. The preparation method according to claim 5 or 6, characterized in that, The method for depositing the SiO2 layer includes: reacting SiH2(Net2)2 and O3 as precursors, and after the SiO2 layer is deposited, introducing fluorosilane vapor for 20-40 seconds to hydrophobize the surface of the SiO2 layer, so that the contact angle of the surface of the hydrophobized SiO2 layer is >105°.

10. A back-contact solar cell, characterized in that, The back-contact solar cell includes the anti-reflective film according to any one of claims 1 to 4.

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