WO2024051175A1 - 一种柔性薄型单晶硅太阳电池的制备方法 - Google Patents

一种柔性薄型单晶硅太阳电池的制备方法 Download PDF

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WO2024051175A1
WO2024051175A1 PCT/CN2023/090188 CN2023090188W WO2024051175A1 WO 2024051175 A1 WO2024051175 A1 WO 2024051175A1 CN 2023090188 W CN2023090188 W CN 2023090188W WO 2024051175 A1 WO2024051175 A1 WO 2024051175A1
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silicon wafer
edge
single crystal
monocrystalline silicon
solar cell
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French (fr)
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刘文柱
刘正新
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中国科学院上海微系统与信息技术研究所
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Publication of WO2024051175A1 publication Critical patent/WO2024051175A1/zh

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor 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
    • H01L31/02—Details
    • H01L31/0224—Electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor 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
    • H01L31/02—Details
    • H01L31/0236—Special surface textures
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor 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
    • H01L31/18—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof
    • Y—GENERAL 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
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

  • the present invention relates to new energy and renewable energy technology, and more specifically to a method for preparing a flexible thin monocrystalline silicon solar cell.
  • Crystalline silicon solar cells are the most important solar photovoltaic products, with a current market share of more than 95%.
  • the main development direction of crystalline silicon solar cells is to improve conversion efficiency and reduce costs.
  • the main cost of monocrystalline silicon solar cells comes from monocrystalline silicon wafers, accounting for more than 80%.
  • the cost of monocrystalline silicon wafers mainly consists of high-purity polysilicon materials, crystal pulling, and slicing, while the cost of high-purity polysilicon materials mainly consists of reduction power consumption during the purification process. It has currently reached less than 40kWh/kg, which is close to the existing process. bottleneck, therefore, reducing the thickness of single crystal silicon wafers is an effective technical path to reduce the cost of silicon wafers.
  • single crystal silicon itself is a brittle material. Although a certain degree of bending can be achieved by reducing the thickness of the silicon wafer, since crystal silicon is an indirect band gap semiconductor, reducing the thickness of the silicon wafer will cause the current density of the battery to also decrease. Significantly reduces, thereby greatly reducing the photoelectric conversion efficiency. Moreover, due to the brittleness of monocrystalline silicon itself, even if the thickness of the silicon wafer is reduced, it is still prone to fragmentation during the bending process, especially in areas where stress is concentrated, affecting the application range of thin monocrystalline silicon solar cells. Silicon becomes more flexible.
  • the present invention provides a method for preparing a flexible thin monocrystalline silicon solar cell.
  • the method for preparing a flexible thin monocrystalline silicon solar cell according to the present invention includes the following steps: S1, providing a monocrystalline silicon wafer; S2, texturing the monocrystalline silicon wafer to produce a structure on at least one side of the monocrystalline silicon wafer. Pyramid-shaped suede anti-reflection structure; S3, smoothing the edge of the single crystal silicon wafer, which is an edge area whose distance from the edge of the single crystal silicon wafer is no more than 5mm; S4, smoothing the edge of the single crystal silicon wafer The wafers are cleaned; S5 uses smoothed and cleaned monocrystalline silicon wafers to make flexible thin solar cells.
  • the single crystal silicon wafer in step S1 is a p-type or n-type single crystal silicon wafer with a thickness of less than 120 microns.
  • step S2 KOH or NaOH alkaline solution is used, texturing additives are added, and texturing is performed at a temperature of 60-85 degrees.
  • step S3 chemical reagents are used to perform isotropic etching, or isotropic chemical vapor etching is used, or plasma is used to etch the edge portion.
  • the edge area includes edge surfaces located on the front and back of the single crystal silicon wafer and side surfaces located on the side of the single crystal silicon wafer.
  • the radius of curvature of the pyramid valley is greater than 50 nanometers.
  • the curvature radius of the edges, protrusions and grooves is greater than 25 nanometers.
  • the pyramid structure of the internal area within 5 mm of the edge on the front and back of the single crystal silicon wafer remains unchanged and the surface reflectivity is not changed.
  • step S4 the oxides and residual contaminants generated during the smoothing process are removed, and then rinsed with pure water to provide a clean surface required for solar cell production.
  • the flexible thin solar cell is a silicon heterojunction (SHJ, HJT, HIT) solar cell, a tunnel oxide passivated contact (TOPCon) solar cell, a PERC cell, or an interdigitated back contact (IBC) solar cell.
  • SHJ, HJT, HIT silicon heterojunction
  • TOPCon tunnel oxide passivated contact
  • PERC PERC cell
  • IBC interdigitated back contact
  • the following structural features are formed by rounding the edge parts: the peaks and valleys of the pyramid on the side of the silicon wafer become rounded; the protrusions and grooves on the side of the silicon wafer become rounded ; The valleys of the pyramids within 5mm of the edge of the silicon wafer become rounded; the pyramid structure in other areas on the back and front remains unchanged, without changing the surface reflectivity; thereby eliminating
  • the stress concentration area that causes the silicon wafer to break gives the thin single crystal silicon wafer a flexible structural feature and significantly improves the flexibility of the single crystal silicon wafer. At the same time, it does not change the pyramid structure and anti-reflection performance of the front and back sides of the silicon wafer.
  • the method for preparing flexible thin monocrystalline silicon solar cells according to the present invention is suitable for preparing various thin monocrystalline silicon solar cells, and is particularly suitable for the preparation of flexible thin silicon heterojunction solar cells whose process temperature is lower than 250 degrees.
  • Figure 1 shows the basic structural information of a single crystal silicon wafer.
  • Figure 2 shows the pyramid structure formed on the front (a, c) and side (b, c) of the single crystal silicon wafer after texturing cleaning.
  • the back side of the single crystal silicon wafer has the same pyramid structure.
  • a in Figure 3 shows that the grooves between the pyramids on the surface of most of the central areas of the textured silicon wafer in Example 1 of the present invention are sharp; b shows that the grooves between the pyramids on the edge areas of the textured silicon wafer in Example 1 of the present invention are in sharp shapes. The grooves in between become a smooth structure; c shows that the small pyramids on the side of the textured silicon wafer, edge corners, and edge mechanical cutting damage in Example 1 of the present invention are all rounded into a smooth structure.
  • Figure 4 shows the results of SEM analysis. From the analysis of the fracture surface, it is found that the untreated single crystal silicon wafer (a) exhibits the brittle characteristics of a flat fracture surface. After using this inventive technology to process the edge of a 60-micron-thick single-crystal silicon wafer, it shows the flexible characteristics of multiple cleavage plane fractures. Fracture with multiple cleavage planes consumes more energy, so the silicon wafer exhibits better flexibility characteristics.
  • Figure 5 shows a molecular dynamics simulation, which is embodied in a small single crystal silicon composed of 170,000 silicon atoms.
  • the molecular dynamics simulation found that even if the sharp pyramid trench is rounded into an arc with a radius of 6.08 nanometers, the stress-strain curve has shown This treatment gives the silicon wafers better flexibility characteristics.
  • Figure 6 shows a finite element simulation. The simulation found that under the same deformation conditions, the maximum stress (von Mises stress) at the pyramid trench decreases rapidly as the radius of the rounding process increases, which has a negative impact on the flexibility of the silicon wafer. Key role.
  • Figure 7 shows a photo taken with a high-speed camera: the most fragile part of the textured silicon wafer is the edge, and fracture under stress always starts from the edge. The evidence is that some small silicon particles generated by small fractures are always the first to fly out from the edge of the fracture crack. Based on this fracture characteristic, the present invention only focuses on the edge area of the silicon wafer. Rounding.
  • Figure 8 shows that after the above processing of the textured silicon wafer in Embodiment 1 of the present invention, the 60 micron silicon wafer can be bent to a radius of 4 mm, and the silicon wafer will not break.
  • Figure 9 shows the state of bending a flexible SHJ solar cell using a single crystal silicon wafer with a thickness of 60 microns processed using the technology of this invention, which reflects the excellent flexibility characteristics.
  • the present invention provides a processing method for texturing monocrystalline silicon wafers, which makes the monocrystalline silicon wafers flexible and solves the problem of thin monocrystalline silicon wafers being fragile, thereby providing A method for preparing flexible thin single crystal silicon solar cells.
  • the method for preparing a flexible thin monocrystalline silicon solar cell according to the present invention first includes providing a monocrystalline silicon wafer 101, as shown in FIG. 1 .
  • the single crystal silicon wafer is a p-type or n-type single crystal silicon wafer with a thickness less than 120 microns.
  • the thickness of a single crystal silicon wafer is based on the calculated value of the weight of the silicon wafer divided by the density of single crystal silicon 2.33g/ cm3 and the area.
  • the method for preparing a flexible thin monocrystalline silicon solar cell according to the present invention next includes texturing the monocrystalline silicon wafer to produce a textured surface with a pyramid shape on both sides (front and back) or on one side of the monocrystalline silicon wafer. Anti-reflection structure, the sharp structure at the pyramid groove is shown as 102 in Figure 1.
  • the thickness of the single crystal silicon wafer after texturing is less than 120 microns.
  • KOH or NaOH alkaline solution is used, texturing additives are added, and texturing is performed at a temperature of 60-85 degrees.
  • the size of the pyramid is adjusted according to the solar cell process and is generally between 1.5 and 12 microns.
  • the method for preparing a flexible thin single crystal silicon solar cell according to the present invention next includes: The edges of the silicon wafer are rounded.
  • the rounding treatment can either use chemical reagents for isotropic etching, or use isotropic chemical vapor etching, or plasma can be used to etch the edge parts.
  • aqueous solutions of KOH or NaOH can selectively treat the edges of silicon wafers at a temperature of 60-80 degrees.
  • a mixed solution of HNO 3 and HF can be used to selectively treat the edges of silicon wafers at room temperature.
  • the edge part here refers to the edge area whose distance from the edge of the silicon wafer is no more than 5 mm, including the edge surfaces located on the front and back of the single crystal silicon wafer and the side surfaces located on the sides of the single crystal silicon wafer. After the edge part is rounded, the pyramid structure of the internal area within 5mm from the edge of the front and back of the single crystal silicon wafer remains unchanged, and the surface reflectivity does not change, that is, the reflectivity difference between the front and back remains at 1 under the same conditions. Within %.
  • the pyramids on the edge surface of the single crystal silicon wafer are rounded. After smoothing the pyramid structure on the edge surface, the grooves between adjacent pyramids, that is, the radius of curvature of the pyramid valley is greater than 50 nanometers. The pyramid grooves after surface treatment on the edge of the textured silicon wafer become smooth, as shown in Figure 1 As shown in 103.
  • the pyramids, edge contours, line marks left on the edge during slicing, and damage caused by mechanical vibration during the slicing process on the side surface of the single crystal silicon wafer are smoothed.
  • the grooves between adjacent pyramids that is, the curvature radius of the pyramid valley is greater than 50 nanometers.
  • the small pyramid grooves after the side surface treatment of the textured silicon wafer become smooth, as shown in the figure Shown as 104 in 1.
  • the edge contour of the side surface is rounded, the corresponding water chestnuts, spurs and grooves become rounded.
  • the curvature radius of the edges, spurs and grooves is greater than 25 nanometers.
  • the edges and corners of the textured silicon wafer become rounded after treatment, as shown in Figure As shown at 105 in Figure 1, the mechanical damage on the edge of the textured silicon wafer becomes smooth after treatment, as shown at 106 in Figure 1.
  • the preparation method of the flexible thin single crystal silicon solar cell according to the present invention next includes cleaning the single crystal silicon wafer.
  • a standard RCA cleaning process or a cleaning agent consisting of ozone plus hydrofluoric acid or hydrochloric acid is used to remove oxides and other residual contaminants generated during edge treatment, and then rinsed with pure water to provide solar Clean surfaces required for battery manufacturing.
  • the preparation method of flexible thin monocrystalline silicon solar cells according to the present invention next includes using edge-processed and cleaned silicon wafers to produce flexible thin solar cells, including but not limited to silicon heterojunction (SHJ, HJT, HIT) solar cells, tunnel Through oxide passivation contact (TOPCon) solar cells, PERC Batteries, interdigitated back contact (IBC) solar cells, etc.
  • silicon heterojunction SHJ, HJT, HIT
  • TOPCon tunnel Through oxide passivation contact
  • PERC Batteries interdigitated back contact (IBC) solar cells, etc.
  • SHJ solar cells Take flexible thin silicon heterojunction SHJ solar cells as an example.
  • the front and back structures of SHJ batteries are symmetrical, and the process temperature is below 200 degrees, making it suitable for making ultra-thin flexible batteries.
  • n-type monocrystalline silicon wafer is selected.
  • the original thickness of the silicon wafer is 180 microns.
  • the surface has not been chemically, mechanically, or chemical-mechanically CMP polished.
  • the depth of the tangent marks is about 15 microns.
  • the silicon wafer is There are also tangent marks on the edges as well as uneven areas such as thorns and grooves left by slicing.
  • Clean and texture n-type monocrystalline silicon wafers Use hydrofluoric acid, hydrochloric acid and ozone aqueous solution to clean at room temperature to remove organic pollutants on the surface. Then use the aqueous solution of KOH to add texturing additives for texturing, forming a uniform pyramid structure on the surface and back of the silicon wafer, as shown in Figure 2.
  • the size of the pyramid is 2-3 microns.
  • the pyramid structure is monotonized by the texturing liquid. Determined by the anisotropic corrosion rate of crystalline silicon, the slope of the pyramid is mainly the 111 crystal plane, and the groove between adjacent pyramids, that is, the valley of the pyramid has an acute angle of about 66 degrees, as shown in Figure 3a. Careful observation reveals that the sides of the silicon wafer also form a pyramid structure, and the size of the pyramid is similar to that of the front and back sides.
  • an aqueous solution of high concentration KOH to process the edges of the single crystal silicon wafer after texturing at a temperature of 60-80 degrees.
  • the edge of the silicon wafer is brought into contact with the solution, and the four sides and corners of the silicon wafer are processed.
  • the affinity of the solution on the surface of the silicon wafer is used to appropriately adjust the contact between the edge of the silicon wafer and the solution, so that the range of edge processing of the silicon wafer is controlled within 5 mm from the edge.
  • the structures of the edges and sides of the silicon wafer after processing are shown in Figure 3 b and c.
  • the pyramids on the sides of the silicon wafer are rounded, and the grooves, or valleys, between adjacent pyramids are rounded off from sharp corners.
  • the radius of curvature of the valley is controlled to be above 50 nm.
  • the grooves and protrusions left by the slicing and the corners of the silicon wafer are all smoothed, and preferably, the radius of curvature is controlled to be above 25nm.
  • the pyramid valleys at the edge of the silicon wafer are rounded.
  • the radius of curvature of the valleys is controlled to be above 50 nm.
  • the pyramid in the center area of the silicon wafer 5mm away from the edge is not affected. Reflection spectrometer test shows that under the same conditions, the difference in surface and back reflectance from before treatment is within 1%.
  • the most vulnerable part of the textured silicon wafer under bending stress is the edge of the silicon wafer. As shown in Figure 7, the high-speed camera found that the silicon wafer always fractures from the edge. The evidence is: the starting point of the fracture crack is always at the beginning of the fracture. Some small silicon particles flew out.
  • Figure 8 shows that a silicon wafer with a size of 156x156mm (M2 standard size) and a thickness of 60 microns can be bent to a radius of 4 mm after edge treatment.
  • the silicon wafer does not break and shows good flexibility.
  • the edge-processed monocrystalline silicon wafer is cleaned to remove surface oxides and residues generated during the treatment, so that the surface of the monocrystalline silicon meets the surface cleanliness required for SHJ solar cell preparation.
  • hydrofluoric acid, hydrochloric acid and ozone aqueous solution are used for cleaning at room temperature, and then a mixed solution of KOH and H 2 O 2 is used for cleaning at a high temperature of 60-85 degrees. After rinsing with ultrapure water, use 2% HF The aqueous solution removes surface oxides and is dried to prepare SHJ solar cells.
  • the cell structure is made according to the process flow of SHJ solar cells.
  • PECVD is used to deposit intrinsic amorphous silicon and n-type amorphous silicon thin film stacks with thicknesses of 5-10nm respectively on the front side, and then, deposit thicknesses of 5-10nm respectively on the back side.
  • PVD is used to deposit 80-100nm TCO films on the back and front respectively, and screen printing is used to make front and back metal electrodes respectively to form a thin SHJ solar cell.
  • the battery manufacturing process as the silicon wafer becomes thinner, lighter, and more flexible, the scratch and fragmentation rates caused by friction are significantly reduced, showing the advantages of flexible silicon wafers.
  • Figure 9 shows the bending of an SHJ solar cell made of silicon wafers with a thickness of 60 microns. It has been bent for more than 1,000 times without breaking or cracking. Comparison of the sun before and after bending test The battery performance is shown in Table 1 below. Within the error range, the parameters of the solar cell have not declined, showing excellent flexibility and bending performance.
  • the above uses a mixed aqueous solution of hydrofluoric acid and nitric acid for rounding processing; a mixed solution of acetic acid can also be used to process the edges.
  • the alkaline solution has anisotropic corrosion characteristics for single crystal silicon wafers, and the concentration and temperature need to be controlled. Achieve good processing results.
  • KOH aqueous solution or high-concentration KOH alkaline solution can also be used. These solutions have isotropic corrosion characteristics and are controlled by adjusting the ratio of hydrofluoric acid, nitric acid and water (acetic acid). The effect of edge processing.
  • the above introduces SHJ solar cells with symmetrical structure and process temperature below 200 degrees.
  • the flexible silicon wafer processing technology of this invention can also be used for the production of asymmetric structure solar cells such as PERC, TOPCon, IBC and other high-temperature processes. It also has good Flexible.

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Abstract

本发明涉及一种柔性薄型单晶硅太阳电池的制备方法，其包括如下步骤：S1，提供单晶硅片；S2，对单晶硅片进行制绒，以在单晶硅片的至少一面制作具有金字塔形貌的绒面减反射结构；S3，对单晶硅片的边缘部分进行圆滑处理，该边缘部分为到单晶硅片的边缘的距离不大于5mm的边缘区域；S4，对单晶硅片进行清洗；S5，利用圆滑处理并清洗的单晶硅片制作柔性薄型太阳电池。根据本发明的柔性薄型单晶硅太阳电池的制备方法，消除造成硅片碎裂的应力集中产生区，使薄型单晶硅片具有柔性的结构特征，显著提高单晶硅片的柔性，工艺简单，具有广泛的应用前景和实用价值。

Description

一种柔性薄型单晶硅太阳电池的制备方法 技术领域
本发明涉及新能源的可再生能源技术，更具体地涉及一种柔性薄型单晶硅太阳电池的制备方法。
背景技术
晶体硅太阳电池是最主要的太阳能光伏产品，目前市场占有率达到95％以上。晶体硅太阳电池的主要发展方向是提高转换效率，降低成本。单晶硅太阳电池的主要成本来自单晶硅片，占80％以上。单晶硅片的成本主要由高纯多晶硅材料、拉晶、切片构成，而高纯多晶硅材料的成本主要由提纯过程中的还原电耗构成，目前已经达到40kWh/kg以下，已经接近现有工艺的瓶颈，因此，降低单晶硅片的厚度是降低硅片成本的有效技术路径。
另一方面，随着光伏应用技术和信息技术的发展，光伏的应用形态也在发生变化，各种形式的建筑一体化、车载、机载、可穿戴电子、通信节点供电等多种形态的应用方式逐步出现，除了对光电转换效率有较高的要求以外，对光伏组件的重量和安装方式提出了更高的要求，其中，对可安装于各种屋顶、车顶、便携式电源、可穿戴电子设备的柔性超薄太阳电池需求越来越多，对光伏组件的重量和柔性要求越来越高，对柔性太阳电池的需求逐渐增大，因此，急需开发出高效、稳定、无毒、柔性的太阳电池。
然而，单晶硅本身是一种脆性材料，尽管可以通过降低硅片的厚度实现一定的弯折性，但是，由于晶体硅是间接带隙半导体，降低硅片的厚度引起电池的电流密度也会显著降低，进而大大降低光电转换效率。而且，由于单晶硅本身的脆性，即使降低硅片的厚度，在弯折过程中，尤其遇到应力集中的区域仍然容易碎裂，影响薄型单晶硅太阳电池的应用范围，需要把单晶硅变得更具柔性。
发明内容
为了解决上述现有技术中由于硅片脆性导致的晶体硅太阳电池在应力作用下容易断裂的问题，本发明提供一种柔性薄型单晶硅太阳电池的制备方法。
根据本发明的柔性薄型单晶硅太阳电池的制备方法，其包括如下步骤：S1，提供单晶硅片；S2，对单晶硅片进行制绒，以在单晶硅片的至少一面制作具有金字塔形貌的绒面减反射结构；S3，对单晶硅片的边缘部分进行圆滑处理，该边缘部分为到单晶硅片的边缘的距离不大于5mm的边缘区域；S4，对单晶硅片进行清洗；S5，利用圆滑处理并清洗的单晶硅片制作柔性薄型太阳电池。
优选地，所述步骤S1中的单晶硅片为厚度小于120微米的p型或者n型单晶硅片。
优选地，在所述步骤S2中，使用KOH或者NaOH碱性溶液，加入制绒添加剂，在60-85度温度进行制绒。
优选地，在所述步骤S3中，采用化学试剂进行各向同性腐蚀，或采用各向同性的化学蒸汽腐蚀，或采用等离子体对边缘部分进行刻蚀。
优选地，在所述步骤S3中，边缘区域包括位于单晶硅片的正面和背面的边缘表面和位于单晶硅片的侧面的侧表面。
优选地，在对边缘表面和/或侧表面的金字塔结构进行圆滑处理后，金字塔谷部的曲率半径大于50纳米。
优选地，在对侧表面的菱角、突刺和凹槽进行圆滑处理后，棱角、突刺和凹槽的曲率半径大于25纳米。
优选地，边缘部分圆滑处理后，单晶硅片的正面和背面的距离边缘5mm以内的内部区域的金字塔结构维持不变，不改变表面反射率。
优选地，在所述步骤S4中，除去圆滑处理过程中产生的氧化物以及残留污染物，然后经过纯水漂洗，提供太阳电池制作所需要的清洁表面。
优选地，柔性薄型太阳电池为硅异质结(SHJ，HJT，HIT)太阳电池、隧穿氧化层钝化接触(TOPCon)太阳电池、PERC电池、或叉指式背接触(IBC)太阳电池。
根据本发明的柔性薄型单晶硅太阳电池的制备方法，通过对边缘部分的圆滑处理，形成以下结构特征：硅片侧面的金字塔的峰和谷变圆滑；硅片侧面的突刺和凹槽变圆滑；硅片边缘5mm以内区域的金字塔的谷部变圆滑；背面和正面其他区域的金字塔结构维持不变，不改变表面反射率；从而消除 造成硅片碎裂的应力集中产生区，使薄型单晶硅片具有柔性的结构特征，显著提高单晶硅片的柔性，同时，不改变硅片正面和背面的金字塔结构和减反射性能，可广泛使用于硅异质结(HJT，SHJ，HIT)太阳电池、隧穿氧化层钝化接触(TOPCon)太阳电池、钝化发射极和背面(PERC)、叉指背接触(IBC)太阳电池等，工艺简单，具有广泛的应用前景和实用价值。根据本发明的柔性薄型单晶硅太阳电池的制备方法，适用于制备各种薄型单晶硅太阳电池，特别适合于工艺温度低于250度的柔性薄型硅异质结太阳电池的制备。
附图说明
图1显示单晶硅片的基本结构信息。
图2显示单晶硅片经过制绒清洗后在正面(a，c)和侧面(b，c)形成的金字塔结构，另外，单晶硅片的背面具有相同的金字塔结构。
图3中的a显示为本发明实施例1中制绒硅片中心大部分区域表面金字塔之间的沟槽为尖锐形状；b显示为本发明实施例1中制绒硅片边缘区域表面金字塔之间的沟槽变为光滑结构；c显示为本发明实施例1中制绒硅片侧面小金字塔、边缘棱角、边缘机械切割损伤均被圆化成光滑结构。
图4显示为SEM分析结果，从断裂面的分析发现，未经处理的单晶硅片(a)表现出平整的断裂面的脆性特性。使用该发明技术对60微米厚度的单晶硅硅片边缘进行处理后，表现为多解理面断裂的柔性特性。多解理面断裂需要消耗更多的能量，因此硅片表现出更好的柔性特征。
图5显示为分子动力学模拟，170000个硅原子组成的小单晶硅体现，分子动力学模拟发现：即使将尖锐的金字塔沟槽圆化成半径6.08纳米的圆弧，应力-应变曲线已经显示出该处理使得硅片具有更好的柔性特征。
图6显示为有限元模拟，模拟发现在相同的形变条件下，金字塔沟槽处的最大应力(von Mises stress)随着圆化处理半径的增大而迅速减小，这对硅片柔性起到关键作用。
图7显示为高速相机拍照：制绒硅片最脆弱的地方是边缘，应力作用下断裂总是从边缘开始。证据是：断裂裂痕的边缘处总是最先飞出一些小的断裂产生的小的硅粒子。基于该断裂特点，本发明仅针对硅片边缘区域进行 圆化处理。
图8显示为本发明实施例1中制绒硅片经过上述处理后，60微米的硅片可以被弯折成4毫米半径，硅片不会发生断裂。
图9示为利用该发明技术处理过的厚度60微米的单晶硅片制作柔性SHJ太阳电池弯折时的状态，体现了优良的柔性特性。
具体实施方式
以下通过特定的具体实例说明本发明的实施方式，本领域技术人员可由本说明书所揭露的内容轻易地了解本发明的其他优点与功效。本发明还可以通过另外不同的具体实施方式加以实施或应用，本说明书中的各项细节也可以基于不同观点与应用，在没有背离本发明的精神下进行各种修饰或改变。需要说明的是，本实施例中所提供的图示仅以示意方式说明本发明的基本构想，虽图示中仅显示与本发明中有关的组件而非按照实际实施时的组件数目、形状及尺寸绘制，其实际实施时各组件的型态、数量及比例可为一种随意的改变且其组件布局型态也可能更为复杂。
本发明针对单晶硅太阳电池脆性、易碎的问题，提供一种制绒单晶硅片的处理方法，使单晶硅片具有柔性特征，解决薄型单晶硅片易碎的问题，从而提供一种柔性薄型单晶硅太阳电池的制备方法。
根据本发明的柔性薄型单晶硅太阳电池的制备方法首先包括提供单晶硅片101，如图1所示。优选地，该单晶硅片为厚度小于120微米的p型或者n型单晶硅片。其中，单晶硅片的厚度以硅片的重量除以单晶硅的密度2.33g/cm3和面积的计算值为基准。
根据本发明的柔性薄型单晶硅太阳电池的制备方法接下来包括对单晶硅片进行制绒，以在单晶硅片的两面(正面和背面)或者单面制作具有金字塔形貌的绒面减反射结构，金字塔沟槽处的尖锐结构如图1中的102所示，制绒后的单晶硅片厚度在120微米以下。在优选的实施例中，使用KOH或者NaOH碱性溶液，加入制绒添加剂，在60-85度温度进行制绒。金字塔的尺寸根据太阳电池的工艺进行调节，一般在1.5至12微米之间。
根据本发明的柔性薄型单晶硅太阳电池的制备方法接下来包括对单晶 硅片的边缘部分进行圆滑处理。圆化处理既可以采用化学试剂进行各向同性腐蚀，也可以采用各向同性的化学蒸汽腐蚀，还可以采用等离子体对边缘部分进行刻蚀。例如，KOH或者NaOH的水溶液，在60-80度的温度下对硅片边缘进行选择性处理。又例如，HNO3和HF的混合溶液，在室温下对硅片边缘进行选择处理。
这里的边缘部分指的是到硅片边缘的距离不大于5mm的边缘区域，包括位于单晶硅片的正面和背面的边缘表面和位于单晶硅片的侧面的侧表面。边缘部分圆滑处理后，单晶硅片的正面和背面的距离边缘5mm以内的内部区域的金字塔结构维持不变，不改变表面反射率，即在同样条件下正面和背面的反射率差异维持在1％以内。
在优选的实施例中，对单晶硅片的边缘表面的金字塔进行圆滑处理。对边缘表面的金字塔结构进行圆滑处理后，相邻金字塔之间的沟槽，即金字塔谷部的曲率半径大于50纳米，制绒硅片边缘表面处理后的金字塔沟槽变得光滑，如图1中的103所示。
在优选的实施例中，对单晶硅片的侧表面的金字塔、边缘轮廓、切片时在边缘遗留的线痕以及由于切片过程中由于机械震动所造成的损伤等进行圆滑处理。对侧表面的金字塔结构进行圆滑处理后，相邻金字塔之间的沟槽，即金字塔谷部的曲率半径大于50纳米，制绒硅片侧表面处理后的小金字塔沟槽变得光滑，如图1中的104所示。对侧表面的边缘轮廓进行圆滑处理后，相应的菱角、突刺和凹槽变圆滑，棱角、突刺和凹槽的曲率半径大于25纳米，制绒硅片边缘棱角经过处理后变得圆滑，如图1中的105所示，制绒硅片边缘机械损伤经过处理后变得圆滑，如图1中的106所示。
根据本发明的柔性薄型单晶硅太阳电池的制备方法接下来包括对单晶硅片清洗。在优选的实施例中，使用标准RCA清洗工艺，或者臭氧加氢氟酸或者盐酸构成的清洗剂，除去边缘处理过程中产生的氧化物以及其他残留的污染物，然后经过纯水漂洗，提供太阳电池制作所需要的清洁表面。
根据本发明的柔性薄型单晶硅太阳电池的制备方法接下来包括利用边缘处理并清洗的硅片制作柔性薄型太阳电池，包括但不限于硅异质结(SHJ，HJT，HIT)太阳电池、隧穿氧化层钝化接触(TOPCon)太阳电池、PERC 电池、叉指式背接触(IBC)太阳电池等。
实施例1
以柔性薄型硅异质结SHJ太阳电池为例。SHJ电池的正、背面结构对称，工艺温度200度以下，适合制作超薄柔性电池。
选用n型单晶硅片，硅片原始厚度为180微米，经过切片、清洗，表面未经过化学、机械、或者化学机械CMP抛光，表面有切线痕，切线痕的深度约15微米，硅片的边缘也有切线痕以及切片留下的突刺，凹槽等不平整区域。
对n型单晶硅片进行清洗、制绒。采用氢氟酸、盐酸和臭氧水溶液在室温下进行清洗，除去表面的有机污染物。然后利用KOH的水溶液添加制绒添加剂进行制绒，在硅片的表面和背面形成均匀的金字塔结构，如图2所示，金字塔的尺寸为2-3微米，金字塔的结构由制绒液对单晶硅的各向异性腐蚀速度所决定，金字塔的斜面主要为111晶面，相邻金字塔之间的凹槽，即金字塔的谷部呈66度左右的锐角，如图3的a。仔细观察发现，硅片的侧面同样形成了金字塔结构，金字塔的尺寸和正面及背面相当。
分析发现，在硅片弯折过程中，金字塔的谷部容易由于受力不均匀而累计应力，是单晶硅片在弯折过程中碎裂的主要原因。
用天平称硅片的重量，用单晶硅的比重和硅片的面积计算出硅片的厚度为60微米。
利用高浓度KOH的水溶液对制绒后的单晶硅片边缘进行处理，温度为60-80度。处理时，使硅片的边缘与溶液接触，对硅片的四边和角部进行处理。在硅片边缘与溶液接触时，利用溶液在硅片表面亲和力，适当调节硅片边缘与溶液的接触，使硅片边缘处理的范围控制在距离边缘5mm以内的区域。
处理后硅片边缘和侧面的结构如图3的b和c所示。硅片侧面的金字塔被圆滑，相邻金字塔之间的凹槽，即谷部由尖锐的锐角变得圆滑。优选地，谷部的曲率半径控制在50nm以上。切片遗留的凹槽和突刺、硅片的菱角都变得圆滑，优选地，曲率半径控制在25nm以上。
处理后硅片边缘部分的金字塔谷被圆滑，优选地，谷部的曲率半径控制在50nm以上。距离边缘5mm以外的硅片中心区域的金字塔未受影响，经 反射光谱仪测试，在相同条件下，表面和背面反射率与处理前的差异在1％以内。
利用扫面电子显微镜对处理前后硅片的断裂面进行了观察分析，如图4所示，未经处理的硅片在外部弯折应力的作用下，断裂面呈整齐的脆性特性，而经过边缘处理的硅片，断裂面呈现多层解理面，表现出明显的柔性断裂特性，说明边缘处理使边缘和侧面的金字塔以及菱角和突刺、凹槽的曲率半径变大，有利于消除在弯折时产生应力累积，变成柔性的断裂特征，使硅片变成柔性。图5和图6的理论模拟证明了圆化处理可以显著降低应力集中，从而使得硅片在更大的应力下才会发生断裂，因此表现出更好的柔性特征。制绒硅片在弯曲应力下最脆弱的部分是硅片的边缘，如图7所示，高速相机发现硅片总是从边缘开始断裂，证据是：断裂裂痕的起点处在断裂开始时总是飞出一些碎小的硅颗粒。
图8显示，尺寸156x156mm(M2标准尺寸)、厚度60微米的硅片经过边缘处理后，可以被弯折成4毫米半径，硅片不发生断裂，表现出良好的柔性。
把边缘部分处理过的单晶硅片进行清洗，除去表面的氧化物以及处理过程中产生的残留物，使单晶硅表面满足SHJ太阳电池制备所具备的表面洁净度。优选地，采用氢氟酸、盐酸和臭氧水溶液在室温下进行清洗，然后采用KOH和H2O2的混合溶液在60-85度的高温进行清洗，经过超纯水漂洗后，用2％HF水溶液除去表面氧化物，经过干燥后制备SHJ太阳电池。
按照SHJ太阳电池的工艺流程制作电池结构，首先利用PECVD在正面沉积厚度分别为5-10nm的本征非晶硅和n型非晶硅薄膜叠层，然后，在背面沉积厚度分别为5-10nm的本征非晶硅和p型非晶硅薄膜叠层。然后，利用PVD在背面和正面分别沉积80-100nm的TCO薄膜，利用丝网印刷分别制作正面和背面金属电极，形成薄型SHJ太阳电池。在电池的制作过程中，由于硅片变薄、重量变轻，而且具有柔性，由于摩擦产生的划伤以及碎片率明显下降，显示了柔性硅片的优势。
图9显示利用60微米厚度的硅片制作的SHJ太阳电池弯折的情形，经过1000次以上的弯折没有破碎，也没有任何隐裂。对比弯折测试前后的太阳 电池性能，如下表1所示，在误差范围内，太阳电池的各项参数均没有下降，表现了优良的柔性和弯折性能。
表1厚度60微米柔性薄型SHJ电池经过1000次弯折测试前后性能参数对比
以上采用氢氟酸和硝酸的混合水溶液进行圆化处理；也可采用醋酸混合溶液对边缘进行处理，碱性溶液对单晶硅片具有各向异性的腐蚀特性，需要对浓度和温度进行控制，达到良好的处理效果。
对单晶硅片的边缘处理，还可使用KOH水溶液，或者高浓度的KOH碱性溶液进行处理，这些溶液具有各向同性腐蚀特性，通过调节氢氟酸，硝酸和水(醋酸)的比例控制边缘处理的效果。
还可选择等离子体刻蚀等物理方法进行边缘处理，总之，该方法不限对边缘处理所采用的方法，更主要的是提供一种物理模型和最终的处理效果，研究人员可以从以上介绍的技术要点进行联想，开发更具有生产性和低成本的技术路径，实现对边缘部分的金字塔、凹槽、突刺、菱角进行圆滑处理的效果，尤其针对金字塔的谷部，突刺的凹槽等进行圆滑处理，具有以上定义的曲率半径范围，从而消除在弯折过程中产生应力累积，形成多层解理面的柔性断裂特性，使本来脆性的单晶硅片表现出柔性的特性，解决单晶硅太阳电池的易碎问题，提供一种柔性单晶硅太阳电池制作方法。
以上介绍了具有对称结构，且工艺温度低于200度的SHJ太阳电池，该发明的柔性硅片处理技术同样可用于高温工艺的PERC，TOPCon，IBC等非对称结构太阳电池制作，同样具有良好的柔性。
以上所述的，仅为本发明的较佳实施例，并非用以限定本发明的范围，本发明的上述实施例还可以做出各种变化。即凡是依据本发明申请的权利要求书及说明书内容所作的简单、等效变化与修饰，皆落入本发明专利的权利要求保护范围。本发明未详尽描述的均为常规技术内容。

Claims (10)

  1. 一种柔性薄型单晶硅太阳电池的制备方法，其特征在于，该制备方法包括如下步骤：
    S1，提供单晶硅片；
    S2，对单晶硅片进行制绒，以在单晶硅片的至少一面制作具有金字塔形貌的绒面减反射结构；
    S3，对单晶硅片的边缘部分进行圆滑处理，该边缘部分为到单晶硅片的边缘的距离不大于5mm的边缘区域；
    S4，对单晶硅片进行清洗；
    S5，利用圆滑处理并清洗的单晶硅片制作柔性薄型太阳电池。
  2. 根据权利要求1所述的制备方法，其特征在于，所述步骤S1中的单晶硅片为厚度小于120微米的p型或者n型单晶硅片。
  3. 根据权利要求1所述的制备方法，其特征在于，在所述步骤S2中，使用KOH或者NaOH碱性溶液，加入制绒添加剂，在60-85度温度进行制绒。
  4. 根据权利要求1所述的制备方法，其特征在于，在所述步骤S3中，采用化学试剂进行各向同性腐蚀，或采用各向同性的化学蒸汽腐蚀，或采用等离子体对边缘部分进行刻蚀。
  5. 根据权利要求1所述的制备方法，其特征在于，在所述步骤S3中，边缘区域包括位于单晶硅片的正面和背面的边缘表面和位于单晶硅片的侧面的侧表面。
  6. 根据权利要求5所述的制备方法，其特征在于，在对边缘表面和/或侧表面的金字塔结构进行圆滑处理后，金字塔谷部的曲率半径大于50纳米。
  7. 根据权利要求5所述的制备方法，其特征在于，在对侧表面的菱角、突刺和凹槽进行圆滑处理后，棱角、突刺和凹槽的曲率半径大于25纳米。
  8. 根据权利要求5所述的制备方法，其特征在于，边缘部分圆滑处理后，单晶硅片的正面和背面的距离边缘5mm以内的内部区域的金字塔结构维持不变，不改变表面反射率。
  9. 根据权利要求1所述的制备方法，其特征在于，在所述步骤S4中，除去圆滑处理过程中产生的氧化物以及残留污染物，然后经过纯水漂洗，提供太阳电池制作所需要的清洁表面。
  10. 根据权利要求1所述的制备方法，其特征在于，柔性薄型太阳电池为硅异质结太阳电池、隧穿氧化层钝化接触太阳电池、PERC电池、或叉指式背接触太阳电池。
PCT/CN2023/090188 2022-09-07 2023-04-24 一种柔性薄型单晶硅太阳电池的制备方法 WO2024051175A1 (zh)

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CN113013293A (zh) * 2021-02-26 2021-06-22 江苏润阳悦达光伏科技有限公司 一种异质结电池的制备方法

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