WO2014019340A1 - N型晶硅太阳能电池及其制作方法 - Google Patents

N型晶硅太阳能电池及其制作方法 Download PDF

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WO2014019340A1
WO2014019340A1 PCT/CN2013/000900 CN2013000900W WO2014019340A1 WO 2014019340 A1 WO2014019340 A1 WO 2014019340A1 CN 2013000900 W CN2013000900 W CN 2013000900W WO 2014019340 A1 WO2014019340 A1 WO 2014019340A1
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oxide film
silicon
film
type
solar cell
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PCT/CN2013/000900
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French (fr)
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熊景峰
杨德成
郎芳
李高非
胡志岩
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英利集团有限公司
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    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01LSEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/02Details
    • H01L31/0216Coatings
    • H01L31/02161Coatings for devices characterised by at least one potential jump barrier or surface barrier
    • H01L31/02167Coatings for devices characterised by at least one potential jump barrier or surface barrier for solar cells
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01LSEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/04Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices
    • H01L31/06Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices characterised by potential barriers
    • H01L31/068Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices characterised by potential barriers the potential barriers being only of the PN homojunction type, e.g. bulk silicon PN homojunction solar cells or thin film polycrystalline silicon PN homojunction solar cells
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02EREDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00Energy generation through renewable energy sources
    • Y02E10/50Photovoltaic [PV] energy
    • Y02E10/547Monocrystalline silicon PV cells

Definitions

  • the present invention relates to the field of solar cells, and in particular to an N-type crystalline silicon solar cell and a method of fabricating the same.
  • Monocrystalline silicon solar cells have been applied to various fields on a large scale, and their good stability and mature process flow are the basis of their large-scale application.
  • the production process of the monocrystalline silicon solar cell is shown in Figure 1. First, the silicon wafer is cleaned, and the surface of the silicon wafer is structured by chemical cleaning. Secondly, the cleaned silicon wafer is subjected to diffusion treatment, and the silicon wafer is boron-treated.
  • the diffusion process forms a pn junction; then a peripheral etching process is performed on the silicon wafer forming the pn junction to remove the conductive layer formed at the edge of the silicon wafer in the diffusion process; and then subjected to a chemical cleaning process to remove the silicon wafer during the diffusion process
  • PECVD plasma enhanced chemical vapor deposition
  • silicon nitride film In the production process of solar cells, a layer of silicon nitride film is usually deposited on the surface of the silicon wafer, which can reduce the reflection energy and improve the utilization of light energy.
  • silicon nitride is also a good passivation film because the silicon nitride film layer is rich in hydrogen, which can diffuse to the SiOx/Si interface during sintering, and the suspension at the interface.
  • the chemical passivation can effectively reduce the interface state defect density on the surface of the silicon wafer, thereby reducing the rate at which the photogenerated carriers recombine on the surface of the silicon wafer; in addition, the silicon nitride deposited on the surface of the silicon wafer contains a fixed positive Charge, the electric field generated by these positive charges can reflect the positive charges (holes) diffused to the surface, and the field effect passivation reduces the recombination of photogenerated carriers on the surface of the silicon wafer.
  • the silicon nitride film As a passivation film, if it is used to passivate the surface of the N-type silicon wafer, since the positive charge is a minority carrier, the silicon nitride film can perform a good passivation effect at this time; however, for the P-type silicon On the surface of the sheet, the negative charge is a minority carrier. If silicon nitride is used on the P-type surface, an anti-type layer is formed at the surface of the silicon wafer, which in turn increases the rate at which the photo-generated carriers recombine on the surface of the silicon wafer. .
  • the emitter is an N-type silicon wafer surface formed by phosphorus diffusion, and silicon nitride can effectively passivate.
  • the emitter is a P-type silicon surface formed by boron diffusion, and the silicon nitride loses its passivation. Therefore, the development of an effective passivation N-type solar cell boron emitter surface technology has become the key to restrict the development of N-type solar cells.
  • passivated N-type solar cells mainly use a silicon nitride/silicon oxide double-layer film to passivate the boron emitter. Although it can provide good chemical passivation performance for the silicon wafer surface, since silicon nitride has a fixed positive charge, The formation of an inversion layer on the surface of the P-type silicon wafer accelerates the probability of photo-generated carrier recombination, thereby weakening its chemical passivation performance to some extent. It can be seen that it is difficult to achieve effective inactivation of the boron emitter surface of the N-type solar cell by using the above two schemes.
  • the present invention is directed to an N-type crystalline silicon solar cell and a method of fabricating the same, which solves the problem that the boron emitter of an N-type solar cell is difficult to be effectively passivated in the prior art.
  • an N-type crystalline silicon solar cell comprising: an N-type substrate; a boron emitter disposed on a front surface of the N-type substrate; A passivation layer is disposed on a surface of the boron emitter away from the N-type substrate, and the first passivation layer includes a silicon oxide film, an aluminum oxide film, and a silicon nitride film disposed from the inside to the outside.
  • the thickness of the first passivation film is not more than 100 nm.
  • the thickness of the silicon oxide film is within 10 nm
  • the thickness of the aluminum oxide film is within 10 nm
  • the thickness of the silicon nitride film is between 65 and 85 nm.
  • the above-mentioned N-type crystalline silicon solar cell further includes: a back field disposed on a surface of the N-type substrate away from the boron emitter side; and a second passivation layer disposed on a surface of the back field away from the side of the N-type substrate
  • the second passivation layer includes a silicon oxide film and a silicon nitride film disposed from the inside to the outside.
  • a method for fabricating an N-type crystalline silicon solar cell comprising: Sl, forming a boron emitter on a front surface of the N-type substrate; S2, and a boron emitter away from the N
  • a silicon oxide film and an aluminum oxide film are provided on the surface of the type substrate from the inside to the outside; and S3, a silicon nitride film is formed on the surface of the aluminum oxide film away from the silicon oxide film.
  • a silicon oxide film is formed on the surface of the N-type substrate away from the N-type substrate while forming the silicon oxide film.
  • the back surface of any two N-type substrates on which the silicon oxide film is formed is placed adjacent to each other, and an aluminum oxide film is formed on the surface of the silicon oxide film away from the boron emitter.
  • the above manufacturing method further includes forming a silicon nitride film on the surface of the back surface of the silicon oxide film away from the surface of the N-type substrate after step S2 or after S3.
  • the silicon oxide film is prepared by a thermal oxidation method, a plasma enhanced chemical vapor deposition method or a magnetron sputtering method; the aluminum oxide film is prepared by atomic layer deposition, sputtering, plasma enhanced chemistry. Gas phase electroplating or sol-gel method; the silicon nitride film is prepared by plasma enhanced chemical vapor deposition.
  • the aluminum oxide film on the surface of the boron emitter forms a fixed negative charge at the interface, and an electric field generated on the surface of the silicon wafer can reflect minority carriers (electrons) diffused to the surface. Going back, the number of minority carriers near the surface of the silicon wafer is greatly reduced, thereby reducing the rate at which the photogenerated carriers recombine on the surface, and can provide good field effect passivation for the surface of the silicon wafer.
  • the silicon oxide film on the surface of the boron emitter can effectively reduce the defect density of the SiO 2 /Si interface state, so that the silicon wafer surface has a good passivation effect, and the hydrogen diffusion of the silicon nitride film is rich during the sintering process.
  • the dangling bonds at the interface are passivated, providing good chemical passivation for the silicon surface. Therefore, the use of a silicon nitride/alumina/silicon oxide trilayer film to passivate the boron emitter can provide both field effect passivation and chemical passivation for better passivation.
  • FIG. 1 shows a manufacturing process flow of an N-type crystalline silicon solar cell in the prior art
  • FIG. 2 shows a schematic structural view of an N-type crystalline silicon solar cell according to the present invention
  • FIG. 3 shows Embodiments 1 and 2 A comparison diagram of the open circuit voltage test results of Comparative Examples 1 and 2.
  • an N-type crystalline silicon solar cell comprising: an N-type substrate 1, a boron emitter 2 and a first passivation layer 3, and a boron emitter 2 is disposed on the front surface of the N-type substrate 1; the first passivation layer 3 is disposed on a surface of the boron emitter 2 away from the N-type substrate 1, the first passivation layer 3 includes a silicon oxide film disposed from the inside to the outside, and is oxidized Aluminum film and silicon nitride film.
  • the aluminum oxide film on the surface of the boron emitter 2 forms a fixed negative charge at the interface, and an electric field generated on the surface of the silicon wafer can diffuse minority carriers (electrons) to the surface. Reflected back, greatly reducing the number of minority carriers near the surface of the silicon wafer, thereby reducing the rate of photo-generated carriers recombining on the surface, and providing good field effect passivation for the surface of the silicon wafer.
  • the silicon oxide film on the surface of the boron emitter 2 can effectively reduce the defect density of the Si0 2 /Si interface state, thereby providing a good passivation effect on the surface of the silicon wafer, and the hydrogen rich in the silicon nitride film during the sintering process.
  • the element diffuses to the Si0 2 /Si interface, passivating the dangling bonds at the interface, providing good chemical passivation for the boron emitter 2 surface. Therefore, the use of a silicon nitride/alumina/silicon oxide trilayer film to passivate the boron emitter can provide both field effect passivation and chemical passivation for better passivation.
  • the inventors have found that since the passivation property of the aluminum oxide film has a great relationship with the silicon oxide film on the surface of the silicon wafer, the silicon oxide film on the surface of the silicon wafer has an important advantage for the aluminum oxide film thereon.
  • the thickness of the first passivation film 3 is not more than 100 nm.
  • the thickness of the silicon oxide film is within 10 nm
  • the thickness of the aluminum oxide film is within 10 nm
  • the thickness of the silicon nitride film is between 65 and 85 nm.
  • the N-type crystalline silicon solar cell having the above structure further includes a back field 4 and a second passivation layer 5, and the back field 4 is disposed on a surface of the N-type substrate 1 away from the emitter 2 side; the second passivation layer 5 is disposed at On the surface of the back field 4 away from the side of the N-type substrate 1, the second passivation layer 5 includes a silicon oxide film and a silicon nitride film which are provided from the inside to the outside.
  • the provision of the back field 4 and the second passivation layer 5 on the back side of the N-type crystalline silicon solar cell is advantageous in reducing the recombination rate of minority carriers on the back side, increasing the short-circuit current and the open circuit voltage.
  • the second passivation layer 5 and the first passivation layer 3 have the same thickness of silicon oxide film, and the second passivation layer 5 and the first passivation layer 3 have different thicknesses of silicon nitride film.
  • a method for fabricating an N-type crystalline silicon solar cell comprising: sl, forming a boron emitter on a front surface of the N-type substrate; S2, in boron A silicon oxide film and an aluminum oxide film are disposed on the surface of the emitter away from the N-type substrate from the inside to the outside; and S3, a silicon nitride film is formed on the surface of the aluminum oxide film away from the silicon oxide film.
  • Si on the surface of the P-type silicon of the boron emitter formed after boron diffusion is oxidized to form a silicon oxide film, and an aluminum oxide film is formed on the outer side of the silicon oxide film, and then a silicon nitride film is formed on the outer side of the aluminum oxide film to obtain Silicon nitride/alumina/silicon oxide three-layer passivation film structure.
  • the silicon oxide film and the aluminum oxide film may be formed in two steps or in a single step, that is, while the aluminum oxide film is prepared, the silicon of the boron emitter is formed to form silicon oxide, thereby obtaining a silicon oxide film.
  • the step S2 further includes: S21, forming a silicon oxide film on a surface of the boron emitter away from the N-type substrate; An aluminum oxide film is formed on the surface of the silicon oxide film away from the boron emitter.
  • the silicon oxide film alone can form a high-quality silicon oxide film on the boron emitter, thereby ensuring that the aluminum oxide film grown on the silicon oxide film has better uniformity and more fixed charge amount.
  • a silicon oxide film is formed on the surface of the N-type substrate away from the N-type substrate while forming the silicon oxide film.
  • the silicon oxide film on the back surface of the N-type substrate of the present invention may be prepared separately or simultaneously with the silicon oxide film on the boron emitter.
  • the step S22 further comprises: placing the back surface of any two of the N-type substrates prepared with the silicon oxide film in the process of forming the aluminum oxide, and separating the silicon oxide film from the boron emitter An aluminum oxide film is formed on the surface. Since the aluminum oxide film is formed only on the outer surface of the silicon oxide film on the boron emitter, any two N-type substrates are placed back to back in the preparation of the aluminum oxide film, and only an aluminum oxide film is formed on the front surface of the N-type substrate. , thereby simplifying the preparation method of the aluminum oxide film.
  • the silicon oxide film on the back surface of the N-type substrate of the present invention further has a silicon nitride film
  • the manufacturing method further comprises the silicon oxide film on the surface of the back field after step S2 or after S3.
  • a silicon nitride film is formed on the surface of the N-type substrate.
  • the preferred method for preparing the silicon oxide film is thermal oxidation method, plasma enhanced chemical vapor deposition method or magnetron sputtering method;
  • the preparation method of the aluminum film is an atomic layer deposition method, a sputtering method, a plasma enhanced chemical vapor deposition method or a sol-gel method; and the preparation method of the silicon nitride film is a plasma enhanced chemical vapor deposition method.
  • the growth quality of each layer of alumina can be precisely controlled, thereby facilitating the obtaining of ultra-thin aluminum oxide film alumina having high uniformity.
  • a boron wafer having a pn junction is formed on the front surface of the silicon wafer substrate by boron diffusion.
  • a silicon oxide film having a thickness of about 5 nm is prepared by magnetron sputtering on both sides of the silicon wafer having a pn junction. , wherein the silicon oxide film is evenly distributed on the front and back surfaces of the silicon wafer; subsequently deposited by a thermal atomic layer deposition method on the silicon oxide film on the boron emitting surface to form a thick layer
  • the ultra-thin aluminum oxide film is about 3 nm.
  • the silicon wafer is placed back to back, so that the aluminum oxide film is deposited only on the boron emitter; finally, a silicon nitride film is deposited by PECVD, wherein the silicon nitride film is deposited on the silicon nitride film.
  • the thickness of the front silicon nitride film is about 80 nm
  • the thickness of the back silicon nitride film is about 70 nm.
  • a boron wafer having a pn junction is formed on the front surface of the silicon wafer substrate by boron diffusion.
  • a silicon oxide film having a thickness of about 3 nm is prepared on both sides of the silicon wafer having a pn junction by thermal oxidation.
  • the silicon oxide film is uniformly distributed on the front and back surfaces of the silicon wafer; then a layer of alumina alumina having a thickness of about 7 nm is deposited on the silicon oxide film on the boron emitting surface by PECVD; finally deposited by PECVD A silicon nitride film is formed, wherein the silicon nitride film is deposited on both front and back surfaces of the silicon wafer, the thickness of the front silicon nitride film is about 80 nm, and the thickness of the back silicon nitride film is about 70 nm.
  • Comparative Example 2 The open circuit voltage of an N-type crystalline silicon solar cell having a silicon nitride/silicon oxide double layer film to passivate the surface of the boron emitter was tested. The results are shown in Fig. 3.

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Abstract

一种N型晶硅太阳能电池及制造方法,N型晶硅太阳能电池包括:N型基体(1);硼发射极(2),设置在N型基体(1)的正表面上;第一钝化层(3),设置在硼发射极(2)远离N型基体(1)的表面上,第一钝化层(3)包括从内向外设置的氧化硅膜、氧化铝膜和氮化硅膜。通过在硼发射极(2)表面的氧化铝膜在界面处形成一层固定负电荷,将扩散到表面的少数载流子反射回去,减少了光生载流子在表面复合的速率,提供了场效应钝化作用;另外,在烧结过程中氮化硅膜富含的氢元素扩散到SiO2/Si界面处,钝化了界面处的悬挂键,提供了化学钝化作用。

Description

N型晶硅太阳能电池及其制作方法 技术领域 本发明涉及太阳能电池领域, 具体而言, 涉及一种 N型晶硅太 阳能电池及其制作方法。 背景技术 单晶硅太阳能电池已经被大规模应用到各个领域, 其良好的稳定性 和成熟的工艺流程是其大规模应用的基础。 单晶硅太阳能电池的生产工 艺流程如图 1 所示, 首先对硅片进行清洗, 通过化学清洗达到对硅片表 面的结构化处理; 其次将清洗后的硅片进行扩散处理, 硅片经硼扩散工 艺形成 p-n结; 之后对形成 p-n结的硅片进行周边刻蚀工艺, 以去掉在扩 散工艺中硅片边缘所形成的导电层; 然后经过化学清洗工艺, 以除去在 扩散过程中在硅片表面形成的玻璃层; 接着经 PECVD (等离子体增强化 学气相沉积法) 工艺沉积减反射膜一氮化硅膜; 最后再依次经丝网印刷 工艺、 烧结工艺等制作得到符合要求的单晶硅太阳能电池。
在太阳能电池生产过程中, 通常在硅片表面沉积一层氮化硅薄膜, 一方面可以起到减反射作用, 提高对光能的利用率。 另一方面, 氮化硅 也是一层很好的钝化膜, 这是因为氮化硅膜层富含氢元素, 这些氢可以 在烧结过程中扩散到 SiOx/Si界面处, 和界面处的悬挂键反应, 通过这种 化学钝化作用可以有效地减少硅片表面界面态缺陷密度, 从而减少了光 生载流子在硅片表面复合的速率; 另外, 硅片表面沉积的氮化硅含有固 定正电荷, 这些正电荷产生的电场可以将扩散到表面来的正电荷 (空穴) 反射回去, 通过这种场效应钝化作用, 减少了光生载流子在硅片表面的 复合。 作为钝化膜如果将其用来钝化 N型硅片表面, 由于正电荷是少数 载流子, 所以这时氮化硅膜可以起到很好的钝化效果; 然而对于 P型硅 片表面, 负电荷是少数载流子, 如果将氮化硅用于 P型表面, 则会在硅 片表面处形成一层反型层, 反而加剧了光生载流子在硅片表面复合的速 率。
对于传统的 P型太阳能电池, 其发射极是磷扩散形成的 N型硅片表 面, 用氮化硅可以有效地起到钝化作用。 然而对于 N型太阳能电池, 其 发射极是硼扩散形成的 P型硅表面, 氮化硅失去了其钝化作用。 所以发 展一种有效的钝化 N型太阳能电池硼发射极表面技术, 成为制约 N型太 阳能电池发展的关键。
目前钝化 N型太阳能电池主要使用氮化硅 /氧化硅双层膜来钝化硼发 射极, 虽然可以为硅片表面提供良好的化学钝化性能, 然而由于氮化硅 带有固定正电荷, 会在 P型硅片表面形成反型层, 反而加速了光生载流 子复合的概率, 从而在一定程度上减弱了其化学钝化性能。 由此可见, 采用上述两种方案都难以实现对 N型太阳能电池硼发射极表面的有效钝 化。 发明内容 本发明旨在提供一种 N型晶硅太阳能电池及其制作方法, 以解决现 有技术中 N型太阳能电池硼发射极难以有效得到钝化的问题。
为了实现上述目的, 根据本发明的一个方面, 提供了一种 N型晶硅 太阳能电池, N型晶硅太阳能电池包括: N型基体; 硼发射极, 设置在 N 型基体的正表面上; 第一钝化层, 设置在硼发射极远离 N型基体的表面 上, 第一钝化层包括从内向外设置的氧化硅膜、 氧化铝膜和氮化硅膜。
进一步地, 上述第一钝化膜的厚度不大于 100nm。
进一步地, 上述氧化硅膜的厚度在 lOnm 以内, 氧化铝膜的厚度在 10nm以内, 氮化硅膜的厚度在 65~85nm之间。
进一步地, 上述 N型晶硅太阳能电池还包括: 背场, 设置在 N型基 体远离硼发射极一侧的表面上; 第二钝化层, 设置在背场远离 N型基体 一侧的表面上, 第二钝化层包括从内向外设置的氧化硅膜和氮化硅膜。 根据本发明的又一方面, 还提供了一种 N型晶硅太阳能电池的制作 方法, 该制作方法包括: Sl、 在 N型基体的正表面形成硼发射极; S2、 在硼发射极远离 N型基体的表面上形成从内到外设置的氧化硅膜和氧化 铝膜; 以及 S3、 在氧化铝膜远离氧化硅膜的表面上形成氮化硅膜。
进一步地,上述步骤 S2中在形成氧化硅膜的同时在 N型基体的背场 远离 N型基体的表面上形成氧化硅膜。
进一步地, 上述步骤 S2中形成所述氧化铝的过程中, 将任意两个形 成有氧化硅膜的 N型基体的背面相靠放置后在氧化硅膜远离硼发射极的 表面上形成氧化铝膜。
进一步地, 上述制作方法在步骤 S2之后或 S3之后还包括在背场的 表面上的氧化硅膜远离 N型基体的表面上形成氮化硅膜。
进一步地, 上述氧化硅膜的制备方法为热氧化法、 等离子体增强化 学气相带电沉积法或磁控溅射法; 氧化铝膜的制备方法为原子层沉积法、 溅射法、 等离子体增强化学气相带电沉积法或溶胶凝胶法; 氮化硅膜的 制备方法为等离子体增强化学气相带电沉积法。
本发明的 N型晶硅太阳能电池, 硼发射极表面的氧化铝膜在界面处 形成一层固定负电荷, 在硅片表面产生的电场可以将扩散到表面来的少 数载流子 (电子) 反射回去, 极大减少了硅片表面附近少数载流子的数 量, 从而减少了光生载流子在表面复合的速率, 可以为硅片表面提供良 好的场效应钝化作用。 另外, 硼发射极表面的氧化硅膜可以有效地降低 Si02/Si界面态缺陷密度, 因此对硅片表面起到较好的钝化效果, 在烧结 过程中氮化硅膜富含的氢元素扩散到 Si02/Si界面处,钝化了界面处的悬 挂键, 为硅片表面提供了良好的化学钝化作用。 因此, 使用氮化硅 /氧化 铝 /氧化硅三层膜来钝化硼发射极可以同时提供场效应钝化和化学钝化, 从而获得更好的钝化效果。 同时, 发明人发现由于氧化铝膜的钝化性能 与硅片表面的氧化硅膜有极大的关系, 在硅片表面的氧化硅膜对在其上 的氧化铝膜有重要的益处。 附图说明 构成本申请的一部分的说明书附图用来提供对本发明的进一步理 解, 本发明的示意性实施例及其说明用于解释本发明, 并不构成对本发 明的不当限定。 在附图中:
图 1示出了现有技术中 N型晶硅太阳能电池的制作工艺流程; 图 2示出了根据本发明的 N型晶硅太阳能电池的结构示意图; 以及 图 3示出了实施例 1、 2和对比例 1、 2的开路电压测试结果比较示 意图。 具体实施方式 需要说明的是, 在不冲突的情况下, 本申请中的实施例及实施例中 的特征可以相互组合。 下面将参考附图并结合实施例来详细说明本发明。
在本发明一种典型的实施方式中,提供了一种 N型晶硅太阳能电池, N型晶硅太阳能电池包括: N型基体 1、 硼发射极 2和第一钝化层 3, 硼 发射极 2设置在 N型基体 1的正表面上; 第一钝化层 3设置在硼发射极 2远离 N型基体 1的表面上, 第一钝化层 3包括从内向外设置的氧化硅 膜、 氧化铝膜和氮化硅膜。
具有上述结构的 N型晶硅太阳能电池, 硼发射极 2表面的氧化铝膜 在界面处形成一层固定负电荷, 在硅片表面产生的电场可以将扩散到表 面来的少数载流子 (电子) 反射回去, 极大减少了硅片表面附近少数载 流子的数量, 从而减少了光生载流子在表面复合的速率, 可以为硅片表 面提供良好的场效应钝化作用。 另外, 硼发射极 2表面的氧化硅膜可以 有效地降低 Si02/Si界面态缺陷密度, 因此对硅片表面起到较好的钝化效 果, 在烧结过程中氮化硅膜富含的氢元素扩散到 Si02/Si界面处, 钝化了 界面处的悬挂键, 为硼发射极 2表面提供了良好的化学钝化作用。 因此, 使用氮化硅 /氧化铝 /氧化硅三层膜来钝化硼发射极可以同时提供场效应 钝化和化学钝化, 从而获得更好的钝化效果。 同时, 发明人发现由于氧 化铝膜的钝化性能与硅片表面的氧化硅膜有极大的关系, 在硅片表面的 氧化硅膜对在其上的氧化铝膜有重要的益处。 为了避免位于硼发射极 2上的第一钝化膜 3对硼发射极 2的性能造 成不利影响, 优选第一钝化膜 3的厚度不大于 100nm。
在本发明一种优选的实施例中,氧化硅膜的厚度在 10nm以内,氧化 铝膜的厚度在 10nm以内, 氮化硅膜的厚度在 65~85nm之间。 当氧化硅 膜、 氧化铝膜和氮化硅膜的厚度在上述范围之间时, 对硅片表面具有明 显的钝化效果。
具有上述结构的 N型晶硅太阳能电池还包括背场 4和第二钝化层 5, 背场 4设置在 N型基体 1远离发射极 2—侧的表面上; 第二钝化层 5设 置在背场 4远离 N型基体 1一侧的表面上, 第二钝化层 5包括从内向外 设置的氧化硅膜和氮化硅膜。 在 N型晶硅太阳能电池的背面设置背场 4 和第二钝化层 5有利于减少少数载流子在背面的复合速率, 增加短路电 流和开路电压,。 且优选第二钝化层 5与第一钝化层 3具有相同厚度的氧 化硅膜, 第二钝化层 5与第一钝化层 3具有不同厚度的氮化硅膜。
在本发明的又一种典型的实施方式中, 还提供了一种 N型晶硅太阳 能电池的制作方法, 制作方法包括: Sl、 在 N型基体的正表面形成硼发 射极; S2、 在硼发射极远离 N型基体的表面上形成从内到外设置的氧化 硅膜和氧化铝膜; 以及 S3、 在氧化铝膜远离氧化硅膜的表面上形成氮化 硅膜。
位于硼扩散之后形成的硼发射极的 P型硅表面上的 Si经过氧化作用 形成氧化硅膜, 氧化铝膜形成在氧化硅膜的外侧, 然后在氧化铝膜的外 侧形成氮化硅膜从而得到氮化硅 /氧化铝 /氧化硅三层钝化膜结构。氧化硅 膜和氧化铝膜可以分两步形成也可一步形成, 即在制备氧化铝膜的同时 氧化硼发射极的硅使其形成氧化硅, 从而得到氧化硅膜。
为了形成品质较好的氧化硅膜和氧化铝膜, 优选两者利用两步法形 成, 上述步骤 S2还包括: S21、 在硼发射极远离 N型基体的表面上形成 氧化硅膜; S22、 在氧化硅膜远离硼发射极的表面上形成氧化铝膜。 单独 制备氧化硅膜可以在硼发射极上形成高质量的氧化硅膜, 从而保证了在 氧化硅膜上生长的氧化铝膜具有较好的均匀性以及较多的固定电荷量。 在本发明一种优选的实施例中, 上述步骤 S2中在形成氧化硅膜的同 时在 N型基体的背场远离 N型基体的表面上形成氧化硅膜。 本发明的 N 型基体的背表面上的氧化硅膜可以单独制备也可以和硼发射极上的氧化 硅膜同时制备。
为了简化氧化铝膜的制备方法, 优选步骤 S22还包括中形成氧化铝 的过程中, 将任意两个制备有氧化硅膜的 N型基体的背面相靠放置后, 在氧化硅膜远离硼发射极的表面上形成氧化铝膜。 由于氧化铝膜只形成 在位于硼发射极上的在氧化硅膜的外表面上, 因此在制备氧化铝膜时将 任意两个 N型基体背对背放置, 只在 N型基体的正面形成氧化铝膜, 从 而简化了氧化铝膜的制备方法。
优选在本发明的 N型基体的背表面上的氧化硅膜的外侧还具有一层 氮化硅膜, 进而制作方法在步骤 S2之后或 S3之后还包括在背场的表面 上的氧化硅膜远离 N型基体的表面上形成氮化硅膜。
制备上述氧化硅膜、 氧化铝膜和氮化硅膜的方法有多种, 本发明优 选氧化硅膜的制备方法为热氧化法、 等离子体增强化学气相带电沉积法 或磁控溅射法; 氧化铝膜的制备方法为原子层沉积法、 溅射法、 等离子 体增强化学气相带电沉积法或溶胶凝胶法; 氮化硅膜的制备方法为等离 子体增强化学气相带电沉积法。 尤其是采用原子层沉积法制备氧化铝膜 时, 可以精确地控制每一层氧化铝的生长质量, 从而更有利于获得具有 高度均匀性的超薄氧化铝膜氧化铝。
以下将结合实施例和对比例, 进一步说明本发明的有益效果。
实施例 1
制备 N型晶硅太阳能电池:
经过硼扩散在硅片基体的正面形成硼发射极得到具有 p-n结的硅片, 首先采用磁控溅射法在具有 p-n 结的硅片正反两面各制备一层厚度在 5nm左右的氧化硅膜, 其中氧化硅膜均匀分布在硅片的正反两个表面上; 随后用热原子层沉积法在位于硼发射表面的氧化硅膜上沉积形成一层厚 度为 3nm左右的超薄氧化铝膜, 沉积过程中硅片采用背对背放置, 从而 氧化铝膜只沉积在硼发射极上; 最后使用 PECVD法沉积形成氮化硅膜, 其中氮化硅膜沉积在硅片的正反两个表面上, 正面氮化硅膜的厚度在 80nm左右, 背面氮化硅膜的厚度在 70nm左右。 测试上述 N型晶硅太阳能电池的开路电压, 结果如附图 3所示。 实施例 2
经过硼扩散在硅片基体的正面形成硼发射极得到具有 p-n结的硅片, 首先采用热氧化法在具有 p-n结的硅片正反两面各制备一层厚度在 3nm 左右的氧化硅膜, 其中氧化硅膜均匀分布在硅片的正反两个表面上; 随 后用 PECVD 法在位于硼发射表面的氧化硅膜上沉积形成一层厚度为 7nm左右的氧化铝膜氧化铝; 最后使用 PECVD方法沉积形成氮化硅膜, 其中氮化硅膜沉积在硅片的正反两个表面上, 正面氮化硅膜的厚度在 80nm左右, 背面氮化硅膜的厚度在 70nm左右。
测试上述 N型晶硅太阳能电池的开路电压, 结果如附图 3所示。 对比例 1 测试具有氮化硅 /氧化铝双层膜来钝化硼发射极表面的 N型晶硅太阳 能电池的开路电压, 结果如附图 3所示。
对比例 2 测试具有氮化硅 /氧化硅双层膜来钝化硼发射极表面的 N型晶硅太阳 能电池的开路电压, 结果如附图 3所示。
由图 3可以看出, 对比例 1和对比例 2的开路电压几乎一样, 由于 开路电压直接反映了电池表面钝化效果的好坏, 因此可以判断氮化硅 /氧 化铝和氮化硅 /氧化硅这两种结构对电池硼发射极的钝化效果几乎是一 样的; 而实施例 1和实施例 2的具有氮化硅 /氧化铝 /氧化硅三层钝化膜的 电池, 其开路电压要高于仅有双层膜钝化的电池, 所以图 3 也证明了氮 化硅 /氧化铝 /氧化硅三层钝化膜具有较好的钝化效果。
以上所述仅为本发明的优选实施例而已, 并不用于限制本发明, 对 于本领域的技术人员来说, 本发明可以有各种更改和变化。 凡在本发明 的精神和原则之内, 所作的任何修改、 等同替换、 改进等, 均应包含在 本发明的保护范围之内。

Claims

权 利 要 求 书
1.一种 N型晶硅太阳能电池, 其特征在于, 所述 N型晶硅太阳能电 池包括:
N型基体 (1 );
硼发射极 (2), 设置在所述 N型基体 (1 ) 的正表面上;
第一钝化层(3 ), 设置在所述硼发射极(2)远离所述 N型基体(1 ) 的表面上, 所述第一钝化层 (3 )包括从内向外设置的氧化硅膜、 氧化铝 膜和氮化硅膜。
2.根据权利要求 1所述的 N型晶硅太阳能电池, 其特征在于, 所述 第一钝化膜 (3 ) 的厚度不大于 100nm。
3.根据权利要求 1所述的 N型晶硅太阳能电池, 其特征在于, 所述 氧化硅膜的厚度在 10nm以内, 所述氧化铝膜的厚度在 10nm以内, 所述 氮化硅膜的厚度在 65〜85nm之间。
4.根据权利要求 1所述的 N型晶硅太阳能电池, 其特征在于, 所述 N型晶硅太阳能电池还包括:
背场 (4), 设置在所述 N型基体 (1 ) 远离所述硼发射极 (2) —侧 的表面上;
第二钝化层 (5 ), 设置在所述背场 (4) 远离所述 N型基体 (1 ) 一 侧的表面上, 所述第二钝化层 (5 )包括从内向外设置的氧化硅膜和氮化 硅膜。
5.—种 N型晶硅太阳能电池的制作方法, 其特征在于, 所述制作方 法包括:
51、 在 N型基体的正表面形成硼发射极;
52、 在所述硼发射极远离所述 N型基体的表面上形成从内到外设置 的氧化硅膜和氧化铝膜; 以及 S3、 在所述氧化铝膜远离所述氧化硅膜的表面上形成氮化硅膜。
6.根据权利要求 5所述的制作方法, 其特征在于, 所述歩骤 S2中在 形成所述氧化硅膜的同时在所述 N型基体的背场远离所述 N型基体的表 面上形成氧化硅膜。
7.根据权利要求 5所述的制作方法, 其特征在于, 所述歩骤 S2中形 成所述氧化铝的过程中, 将任意两个形成有氧化硅膜的 N型基体的背面 相靠放置后, 在所述氧化硅膜远离所述硼发射极的表面上形成氧化铝膜。
8.根据权利要求 6所述的制作方法, 其特征在于, 所述制作方法在 所述歩骤 S2之后或 S3之后还包括在所述背场的表面上的氧化硅膜远离 所述 N型基体的表面上形成氮化硅膜。
9.根据权利要求 5至 8中任一项所述的制作方法, 其特征在于, 所述氧化硅膜的制备方法为热氧化法、 等离子体增强化学气相带电 沉积法或磁控溅射法;
所述氧化铝膜的制备方法为原子层沉积法、 溅射法、 等离子体增强 化学气相带电沉积法或溶胶凝胶法;
所述氮化硅膜的制备方法为等离子体增强化学气相带电沉积法。
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